FORM 2
THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See section 10, rule 13) 1. Title of the invention: LUBRICANT WITH LAYERED NANOSTRUCTURE ADDITIVES
2. Applicant(s)
NAME NATIONALITY ADDRESS
HINDUSTAN PETROLEUM Indian Petroleum House, 17, Jamshedji
CORPORATION LIMITED Tata Road, Churchgate, Mumbai
Maharashtra, 400020, India
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it
is to be performed.

TECHNICAL FIELD
[0001] The present subject matter relates, in general, to additives for
lubricants and, in particular, to layered nanostructure additives for lubricants.
BACKGROUND
[0002] Friction and wear between moving mechanical components of
machines and automobiles often result in energy and material losses. Lubricants are substances which are introduced between surfaces in mutual contact to reduce friction between them. In automobiles, lubricants keep surfaces of moving components separated, thus reducing friction and wear, and thereby increasing mechanical durability, energy efficiency of various components of the automobile, and longevity of the components. Lubricants also act as coolants to remove heat produced by friction. They also coat surfaces of moving mechanical components and protect them from wear and corrosion. In order to provide these functions, lubricants typically comprise one or more additives or property modifiers in addition to base oil. These additives can be, for example, antioxidants, detergents, anti-wear substances, anti-foaming agents, viscosity index improvers, and the like.
BRIEF DESCRIPTION OF DRAWINGS
[0003] The detailed description is described with reference to the
accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components. For simplicity and clarity of illustration, elements in the figures are not necessarily to scale.

[0004] Fig. 1 illustrates a method for preparing layered nanostructure
additive based lubricants, in accordance with an implementation of the present subject matter.
[0005] Fig. 2 graphically illustrates HR-SEM images of the layered
nanostructure additives, in accordance with an implementation of the present subject matter.
[0006] Fig. 3(a) illustrates wear test results for the layered nanostructure
additive based lubricant with diesel engine oil as the lubricating fluid at a load of 40 kgf, in accordance with an implementation of the present subject matter.
[0007] Fig. 3(b) illustrates wear test results for the layered nanostructure
additive based lubricant with diesel engine oil as the lubricating fluid at a load of 60 kgf, in accordance with an implementation of the present subject matter.
[0008] Fig. 3(c) illustrates wear test results for the layered nanostructure
additive based lubricant with petrol engine oil as the lubricating fluid at a load of 40 kgf, in accordance with an implementation of the present subject matter.
[0009] Fig. 3(d) illustrates wear test results for the layered nanostructure
additive based lubricant with petrol engine oil as the lubricating fluid at a load of 60 kgf, in accordance with an implementation of the present subject matter.
[0010] Fig. 3(e) illustrates wear test results for the layered nanostructure
additive based lubricant with gear oil of GL 4 grade and viscosity SAE 80W90 as the lubricating fluid at a load of 40 kgf, in accordance with an implementation of the present subject matter.
[0011] Fig. 3(f) illustrates wear test results for the layered nanostructure
additive based lubricant with gear oil of GL 4 grade and viscosity SAE 80W90 as the lubricating fluid at a load of 80 kgf, in accordance with an implementation of the present subject matter.
[0012] Fig. 3(g) illustrates wear test results for the layered nanostructure
additive based lubricant with gear oil of GL 4 grade and viscosity EP140 as the

lubricating fluid at a load of 40 kgf, in accordance with an implementation of the present subject matter.
[0013] Fig. 3(h) illustrates wear test results for the layered nanostructure
additive based lubricant with gear oil of GL 4 grade and viscosity EP140 as the lubricating fluid at a load of 80 kgf, in accordance with an implementation of the present subject matter.
[0014] Fig. 4(a) graphically illustrates friction test results indicating the
variation in coefficient of friction of the layered nanostructure additive based lubricant with diesel engine oil as the lubricating fluid, in accordance with an implementation of the present subject matter.
[0015] Fig. 4(b) graphically illustrates seizure load results indicating the
variation in seizure load of the layered nanostructure additive based lubricant with diesel engine oil as the lubricating fluid, in accordance with an implementation of the present subject matter.
[0016] Fig. 4(c) graphically illustrates friction test results indicating the
variation in coefficient of friction of the layered nanostructure additive based lubricant with petrol engine oil as the lubricating fluid, in accordance with an implementation of the present subject matter.
[0017] Fig. 4(d) graphically illustrates seizure load results indicating the
variation in seizure load of the layered nanostructure additive based lubricant with petrol engine oil as the lubricating fluid, in accordance with an implementation of the present subject matter.
[0018] Fig. 4(e) graphically illustrates friction test results indicating the
variation in coefficient of friction of the layered nanostructure additive based lubricant with gear oil of GL 4 grade and viscosity SAE 80W90 as the lubricating fluid, in accordance with an implementation of the present subject matter.
[0019] Fig. 4(f) graphically illustrates seizure load results indicating the
variation in seizure load of the layered nanostructure additive based lubricant with

gear oil of GL 4 grade and viscosity SAE 80W90 as the lubricating fluid, in accordance with an implementation of the present subject matter.
[0020] Fig. 4(g) graphically illustrates friction test results indicating the
variation in coefficient of friction of the layered nanostructure additive based lubricant gear oil of GL 4 grade and viscosity EP140 as the lubricating fluid, in accordance with an implementation of the present subject matter.
[0021] Fig. 4(h) graphically illustrates seizure load results indicating the
variation in seizure load of the layered nanostructure additive based lubricant with gear oil of GL 4 grade and viscosity EP140 as the lubricating fluid, in accordance with an implementation of the present subject matter.
[0022] Fig. 5(a) graphically illustrates extreme pressure (EP) test results
indicating the variation in Load wear index (LWI) of the layered nanostructure additive based lubricant with gear oil of GL 4 grade and viscosity SAE 80W90 as the lubricating fluid, in accordance with an implementation of the present subject matter.
[0023] Fig. 5(b) graphically illustrates the extreme pressure (EP) test
results indicating the variation in weld load of the layered nanostructure additive based lubricant with gear oil of GL 4 grade and viscosity SAE 80W90 as the lubricating fluid, in accordance with an implementation of the present subject matter.
[0024] Fig. 5(c) graphically illustrates the extreme pressure (EP) test
results indicating the variation in Load wear index (LWI) of the layered nanostructure additive based lubricant with gear oil of GL 4 grade and viscosity EP140 as the lubricating fluid, in accordance with an implementation of the present subject matter.
[0025] Fig. 5(d) graphically illustrates the extreme pressure (EP) test
results indicating the variation in weld load of the layered nanostructure additive based lubricant with gear oil of GL 4 grade and viscosity EP140 as the lubricating fluid, in accordance with an implementation of the present subject matter.

[0026] Fig. 6 graphically illustrates characterization of worn out balls
using a scanning electron microscope with X-ray diffraction attachment for the layered nanostructure additive based lubricant, in accordance with an implementation of the present subject matter.
[0027] Fig. 7 graphically illustrates variations in brake thermal efficiency
of the layered nanostructure additive based lubricant in a diesel engine test rig, in accordance with an implementation of the present subject matter.
[0028] Fig. 8 graphically illustrates variation in total fuel consumption of
the layered nanostructure additive based lubricant, in accordance with an implementation of the present subject matter.
DETAILED DESCRIPTION
[0029] Generally, on fractional distillation of crude oil, different base oils
separate out as distillates. Examples of base oils are petroleum distillates, mineral oils, vegetable oils, esters, polyolefin, etc. Typically, formulations of lubricants comprise base oil and additives.
[0030] Nanoparticles have been tested for use as additives in the base oils
for lubricants in automobile and other industrial applications. These nanoparticles may be metallic, non-metallic, or salts of metals and non-metals having an average particle diameter upto 100 nm. Studies have shown that nanoparticle based lubricants exhibit better tribological properties as compared to ordinary lubricants without nanoparticles due to their nano size. Their small size also enables them to penetrate into wear crevices. Nanoparticles have a high surface to volume ratio which imparts high surface affinity and chemical reactivity to the nanoparticles. They can also form a thin coating with the thickness of just one or two molecules to separate surface asperities of the moving components of a machine. Thus, nano particles are emerging as suitable additives for industrial lubricants, such as, lubricating engine oils, greases, dry film lubricants, and forging lubricants.

[0031] Several types of nanoparticles have been studied as potential
additives for lubricants, including metal oxides of silicon, titanium, nickel, tin, aluminium, and zinc; fluorides of metals such as cerium, lanthanum, and calcium; and zinc, tin, and lead sulfides, and metals, such as nickel, zinc, tin, and silver, and non-metals like carbon nanotubes. Nanoparticles may also be of different types based on their structure, for example, nanospheres, nanoplatelets, and nanoflowers. Nanoplatelets have a layered nanostructure which comprise of stacks of nanomaterial, predominantly nanosheets. The stacks vary in thickness from 1-15 nm and have an average diameter of 1-100 micrometer. Nanoflowers also comprise a layered nanostructure and have a flower-like morphology when visualized under a microscope.
[0032] As both nanoplatelets and nanoflowers comprise stacks that are
bound to each other by weak Vander Waal’s force, these stacks tend to slide over each other. This provides ready partial cleavage of the stacks under rubbing conditions, providing high resistance to friction and wear and extended lifetime in vacuum.
[0033] Lubricating properties of fully formulated lubricating fluids may be
enhanced by dispersing these layered nanostructure additives, such as nanoplatelets and nanoflowers, in lubricating fluid, for example, petrol engine oil of SM grade, diesel engine oil of CI 4 grade, and gear oil GL 4 grade. These lubricating fluids include base oils and other additives, such as, detergents, anti-foaming agents, antioxidants, and the like, that have different property modifying effects which make them suitable for use as lubricants.
[0034] However, these layered nanostructure additives in fully formulated
lubricants tend to agglomerate due to the presence of other additives, such as antioxidants, detergents, and the like, which are already present in the lubricant. Agglomeration caused by the other additives tends to destabilize the dispersion making the lubricant unsuitable and causing potential damage to moving components. Moreover, the other additives in the lubricating fluid tend to cause shearing of the stacks in the layered nanostructure further leading to

destabilization of the nanostructures in the lubricating fluid. Therefore, the challenge is to obtain a layered nanostructure additive based lubricant which has a uniform dispersion of the layered nanostructure additives in the fully formulated lubricating fluid and which does not agglomerate or settle over an extended period of time.
[0035] The present subject matter provides a method for preparing a
lubricant with layered nanostructure additives. The method comprises the steps of contacting the layered nanostructure additives with a surfactant and a solvent to obtain a first mixture, evaporating the solvent from the first mixture to obtain surface modified layered nanostructure additives, and dispersing the surface modified layered nanostructure additives in a lubricating fluid to obtain the lubricant. The lubricating fluid comprises base oil in a range of 90-99% by weight of the lubricating fluid and other additives in a range of 1-10% by weight of the lubricating fluid. The layered nanostructure additives dispersed in the lubricating fluid are selected from the group consisting of nanoplatelets, nanoflowers, and a combination thereof and the weight ratio of the surfactant to the layered nanostructure additives is in a range of 1.2:1 to 1.5:1.
[0036] The method provides a stable suspension of layered nanostructure
additives, namely nanoplatelets and nanoflowers, in the lubricating fluid. The lubricant obtained by the method also shows improved performance characteristics, such as anti-wear, anti-friction, and extreme pressure characteristics when compared to lubricants without the layered nanostructure additives as will be explained later with test results. Thus, layered nanostructure additives can be dispersed in a stable manner in lubricating fluids comprising base oil and additives, to form the layered nanostructure additive based lubricant.
[0037] These and other advantages of the present subject matter will be
described in greater detail in conjunction with the figures as illustrated. It should be noted that the description and figures merely illustrate the principles of the present subject matter and in no way limit the present subject matter to the description and figures illustrated herein.

[0038] Fig. 1 illustrates a method 100 for preparing a lubricant with
layered nanostructure additives, in accordance with an implementation of the present subject matter. The method 100 includes contacting the layered nanostructure additives with a surfactant and a solvent to obtain a first mixture, at block 102. The layered nanostructure additives may have different morphologies. For instance, the layered nanostructure additives may be nanoplatelets and nanoflowers. The nanoplatelets and nanoflowers of the present subject matter have a thickness varying between 5-10 nm. It has been tested that the nanoplatelets and nanoflowers with thickness over the mentioned range exhibit optimal lubricating properties, as will be explained later. Layered nanostructure additives having greater thickness may be subject to shearing which adversely affects the stability of the lubricant. In an example implementation, the layered nanostructure additives used for the method 100 may be selected from one of transition metal disulphides, graphene, inorganic graphene analogues, and combinations thereof. In an example implementation, the transition metal disulphides are selected from the group consisting of molybdenum disulphide, tungsten disulphide, and combination thereof.
[0039] At block 102, the layered nanostructure additives are contacted
with the surfactant and the solvent to obtain a first mixture. In one implementation, the solvent is selected from the group consisting of hexane, iso-octane, n-heptane, toluene, and the like. For stability in a fluid medium, the surface of the layered nanostructure additives needs to be suitably modified with the surfactant. The surfactants include compounds that lower the surface tension between two liquids or a liquid and a solid and may be used as detergents, anti-foaming agents, and dispersants. When the surfactants are mixed with the layered nanostructure additives, one end of the surfactant molecule attaches to the surface of the layered nanostructure additives through chemical bonds. The other end of the surfactant molecule is free and extends into the lubricating fluid forming reverse micelles. Thus, the surfactants generate an effective repulsive force between layered nanostructure additives due to steric repulsion between the surfactant molecules attached to the surface of the nanostructures, thereby

preventing agglomeration. The effective repulsive force between the layered nanostructure additives coated with the surfactant results in a stable mixture of the layered nanostructure additives in the lubricating fluid. In one implementation, the surfactant is selected from the group consisting of sorbitan monooleate (SPAN 80), cetyl trimethylammonium bromide (CTAB), and a combination thereof. In an implementation, the weight ratio of the surfactant to the layered nanostructure additives is in a range of 1.2:1-1.5:1. It has been tested that this weight ratio of the surfactant to the layered nanostructure additives did not increase the foaming tendency of the lubricant, as will be explained later. In one implementation, a mixture of the layered nanostructure additives and the surfactant is dissolved in the solvent to form the first mixture.
[0040] The method 100, at step 104 includes, evaporating the solvent from
the first mixture to obtain the surface modified layered nanostructure additives. Evaporating the solvent from the first mixture improves enhancement of reverse micelle formation by improving surface bonding of the surfactants to the layered nanostructure additives. In an example implementation, the method comprises sonicating the first mixture prior to evaporating the solvent. The first mixture can be sonicated in an ultrasonic probe sonicator at 50 % amplitude in pulse mode for 30 minutes followed by sonication in continuous mode for 30 minutes for thorough mixing, formation, and bonding of reverse micelles to the surface of the layered nanostructure additives. The sonication of the first mixture prior to evaporating the first mixture causes the reverse micelles to properly bond to the surface of the layered nanostructure additives, thereby increasing stability of layered nanostructure additives in the lubricating fluid.
[0041] Evaporating the solvent, at block 102, includes stir heating on a
magnetic stirrer. In an implementation, the stir heating is conducted on the magnetic stirrer at a speed of 500-600 rpm and at a temperature range of 60-70oC. The stir heating helps in removing any excess solvent molecules trapped in the nanostructure of the layered nanostructure additives and also superficially modifies the surface of the layered nanostructure additives by one of

chemisorption and functionalization, thereby increasing lipophilicity of the layered nanostructure additives. This further increases stability of the layered nanostructure additives when dispersed in the lubricating fluid. The surface modified layered nanostructure additives obtained from evaporating the solvent, at block 102, may be cooled and dried to obtain a fine powder of the surface modified layered nanostructure additives which may be packed and stored or dispersed in the fully formulated lubricating fluid.
[0042] The method 100, at step 106, includes dispersing the surface
modified layered nanostructure additives in the lubricating fluid to obtain the lubricant. The lubricating fluid comprises base oil in a range of 90-99% by weight of the lubricating fluid and other additives in a range of 1-10% by weight of the lubricating fluid. The additives present in the lubricating fluid may include corrosion inhibitors often used in engine coolant like boron, alkaline or detergent additives, such as magnesium and calcium used to neutralize acids which form during a combustion process in an engine, a friction-reducer and anti-oxidant, such as molybdenum, an anti-foaming agent, such as silicon, and an anti-oxidant and anti-wear agent, such as Zinc dialkyl dithio phosphate (ZDDP). The lubricating fluid contains the above mentioned elements as additives for functioning under severe conditions.
[0043] At step 106, dispersing the surface modified layered nanostructure
additives in the lubricating fluid includes contacting the surface modified layered nanostructure additives with the lubricating fluid to form a first suspension and sonicating the first suspension to obtain the lubricant. In an example implementation, sonicating the first suspension includes ultra sonicating, in an ultrasonic probe sonicator, for a time period of 8-12 minutes at 50% amplitude under a pulse mode of 0.5 seconds. This is followed by sonication in continuous mode for 30 – 40 minutes. For optimal stability of the layered nanostructure additives in the lubricant, sonicating the first suspension comprises ultra sonicating, in an ultrasonic probe sonicator, for a time period of 10 minutes at 50% amplitude under a pulse mode of 0.5 seconds followed by sonication in

continuous mode for 30 minutes. Sonicating improves dispersion of the layered nanostructure additives in the lubricant and increases stability of layered nanostructure additive based lubricant.
[0044] The present subject matter also provides a lubricant dispersed with
surface modified layered nanostructure additives. The lubricant comprises the lubricating fluid comprising about 90% to 99% base oil and about 1% to 10% additives and surface modified layered nanostructure additives from about 0.05 weight % to 0.2 weight % dispersed in the lubricating fluid. The layered nanostructure additives are selected from the group consisting of nanoplatelets, nanoflowers, and a combination thereof. The layered nanostructure additives are fabricated from a material selected from the group consisting of transition metal disulphides, graphene, inorganic graphene analogues, and combinations thereof.
[0045] The following discussion is directed to various examples of the
present subject matter. Although certain methods and compositions have been described herein as examples, the scope of coverage of this patent application is not limited thereto. On the contrary, the present subject matter covers all methods and compositions fairly falling within the scope of the claims either literally or under the doctrine of equivalents.
[0046] Certain terms are used throughout the description to refer to certain
components and are to be construed as being mentioned by way of example and for purposes of explanation and not as limiting.
[0047] The term “viscosity index” as used in the examples refers to
change in viscosity of a lubricant with change in temperature. The lower the viscosity index, the greater is the change of viscosity of a lubricant with temperature. Thus, the higher the viscosity index, the better is the quality of the lubricant. A viscosity index value greater than 90 is preferred for the lubricant.
[0048] The term “American Society for Testing and Materials (ASTM) D
445” as used in the examples refers to a test method that specifies a procedure for determination of kinematic viscosity of the lubricant by measuring the time for a

volume of liquid to flow under gravity through a calibrated glass capillary viscometer.
[0049] The term “total acid number” (TAN) ASTM D 664 as used in the
examples determines ability of lubricant to resist additive depletion, acidic contamination and oxidation of lubricant under automotive environment. The TAN is the amount of potassium hydroxide in milligrams required to neutralize the acids in one gram of the lubricant. The TAN value indicates potential corrosiveness of the lubricant. A TAN value lesser than 3 indicates that the lubricant is stable.
[0050] The term “total base number” (TBN) as used in the examples refers
to effectiveness of the lubricant in controlling acid formation during combustion process. The higher the TBN, the more effective the lubricant is in suspending wear-causing contaminants and reducing the corrosive effects of acids over an extended period of time. A TBN value higher than 5 indicates that the lubricant has good control over acid formation during the combustion process.
[0051] The term “ASTM D 2896” as used in the examples refers to a test
method for determination of the TBN of the lubricant by potentiometric titration with perchloric acid in glacial acetic acid.
[0052] The term “ASTM copper strip corrosion standard as per ASTM D
130” as used in the examples refers to a standard used for representing corrosion protection of the lubricant. The standard has classification numbers from 1 to 4 for various color and tarnish levels of a copper strip immersed in the lubricant. A classification number of 1a indicates excellent corrosion protection, 1b indicates good corrosion protection, and 1c indicates sufficient corrosion protection of the lubricant.
[0053] The term “copper strip corrosion test” as used in the examples
refers to a test used for determining the classification number of the lubricant. The test involves immersion of a polished copper strip in the lubricant at elevated

temperature for a period of time and testing the color and tarnish levels of the copper strip.
[0054] The term “four-ball wear test machine” as used in the examples
refers to a machine used for testing various performance characteristics of the lubricant. The machine comprises of a ball pot in which three balls are clamped together and thereby kept stationary or fixed in one position. These balls are then covered with the lubricant. A fourth ball is pressed against a cavity formed by the three stationary balls and the fourth ball is rotated.
[0055] The term “wear scar diameter” as used in the examples refers to
diameter of wear scars on the three stationary balls tested on the four-ball wear test machine. The larger the wear scar, the poorer is the lubricating ability of the lubricant.
[0056] The term “ASTM D 4172” as used in the examples refers to a test
method for evaluation of the anti-wear properties of the lubricants in sliding contact by means of the Four-Ball Wear Test Machine.
[0057] The term “seizure load” as used in the examples refers to a load at
which a sudden increase in coefficient of friction value occurs. The higher the seizure load, the better the anti-friction property of the lubricant.
[0058] The term “ASTM D 5183” as used in the examples refers to a test
method for determining coefficient of friction of the lubricant by means of the Four-Ball Wear Test Machine. Initially, a load is applied which gradually increased at regular time intervals until the lubricant undergoes seizure.
[0059] The term “friction test” as used in the examples refers to a test
performed for determining the seizure load and the coefficient of friction of the lubricant. The seizure load refers to the load at which there is a sharp rise in fractional torque characterized on a graph while the machine is running. The coefficient of friction is determined by considering the loads between initial load and the seizure load.

[0060] The term “ASTM D 2783” as used in the examples refers to a test
method for determination of the load-carrying properties of lubricating fluids. The following two determinations are made using ASTM D 2783: 1. Load-wear index, and 2. Weld load by means of the four-ball extreme-pressure tester.
[0061] The term “load-wear index” as used in the examples refers to an
extreme pressure (EP) property of the lubricant calculated using the four-ball wear test machine. Here the speed of rotation is maintained at 1760 RPM and the whole test procedure is done under room temperature. A series of tests of 10-s duration are carried out with increasing loads during each tests until 4 balls weld under extreme pressure. The load at which weld occurs is called the weld load. The first run is made at an initial load of 40 kgf and the additional runs are carried out at consecutively higher loads until and the 4 balls weld under extreme pressure. A total of 10 readings are considered in the test and the corrected load is calculated for all ten readings. The load wear index is calculated from the corrected load. The corrected load is calculated as follows:
Corrected load=LDh/X;
where L is the applied load in kgf, Dh is hertz scar diameter in mm, and
X is average scar diameter in mm.
Hertz scar diameter is the average diameter, in mm, of an indentation caused by deformation of the balls under static load before application of the load. It may be calculated from the equation Dh = 8.73X10-3 (P)1/3.
[0062] The term “endurance test” as used in the examples refers to a test
conducted on an engine by subjecting it to varying loads and varying speeds for a continuous period of 80 hours without stoppage. This is used to determine the engine wear & tear and fuel consumption over a period of time.
[0063] The term “bench test” as used in the examples refers to a test
performed on the engine at a particular load and a particular speed to determine the efficiency of the engine at that particular load and speed.

[0064] The term "petrol engine rig" as used in the examples refers to a test
rig consisting of petrol engine connected to a dynamometer for applying speed and loads to an engine.
[0065] The term "diesel engine rig" as used in the examples refers to test
rig consisting of diesel engine connected to dynamometer for applying speed and loads to an engine.
EXAMPLES
EXAMPLE 1: PREPARATION OF LUBRICANT WITH LAYERED NANOSTRUCTURE ADDITIVES USING THE METHOD OF THE PRESENT SUBJECT MATTER
[0066] In an example implementation, the layered nanostructure additive
includes nanoplatelets of molybdenum disulphide, tungsten disulphide, and graphene. It is to be understood that nanoplatelets and nanoflowers of other transition metals and graphene analogues may be used. The nanoplatelets have a thickness ranging from 5-10 nm. At this range, the nanoplatelets used in the lubricant provide optimal results. A High Resolution-Scanning Electron Microscope (HR-SEM) analysis of the nanoplatelets was conducted. Fig. 2 depicts the HR-SEM images obtained by analysis of the nanoplatelets, in accordance with an implementation of the present subject matter. In Fig. 2, 200a depicts HR-SEM image of molybdenum disulphide nanoplatelets, 200b depicts the HR-SEM image of tungsten disulphide nanoplatelets, and 200c depicts the HR-SEM image of the graphene nanoplatelets.
[0067] The surface of the nanoplatelets was modified using a surfactant to
prevent agglomeration of the nanoplatelets and to obtain a uniform dispersion of the nanoplatelets in the lubricating fluid. In an example implementation, sorbitan monooleate is selected as the surfactant for surface modification of the nanoplatelets. The nanoplatelets are coated with the sorbitan monooleate surfactant to form the surface modified nanoplatelets. As a result of the surface modification, reverse micelles of the surfactant are formed on the surface of the nanoplatelets which increase stability of the lubricant by preventing

agglomeration of the nanoplatelets. In the example implementation, the surface modified nanoplatelets from about 0.05 weight % to 0.2 weight % were dispersed in the lubricating fluid to obtain the lubricant. Dispersing the surface modified nanoplatelets at the mentioned range provides optimal results of lubrication. Beyond the above mentioned range of weight % of the surface modified layered nanostructure additives there may be an increase in wear effects on mechanical moving components of an engine where the layered nanostructure additive based lubricant is being used. This may be due to overcrowding of the surface modified layered nanostructure additives at interfaces between the mechanical moving components of the engine in relative motion.
[0068] In the example implementation, the sodium monooleate (SPAN 80)
surfactant and the nanoplatelets in ratio of 1.5:1 was mixed in approximately 50.0 ml of n-hexane solvent to form a first mixture. The first mixture was sonicated in an ultrasonic probe sonicator for a time period of 1 hour at 50% amplitude under a continuous mode followed by evaporation. Evaporation was achieved by stir heating the sonicated first mixture on a magnetic stirrer at a speed of 500-600 rpm and at a temperature range of 60-70oC to obtain the surface modified nanoplatelets. The surface modified nanoplatelets were cooled and dried prior to dispersing in a lubricant. The surface modified nanoplatelets were contacted with the lubricant to form a first suspension and sonicated in an ultrasonic probe sonicator, for a time period of 10 minutes at 50% amplitude under a pulse mode of 0.5 seconds to obtain the lubricant. The surface modified nanoplatelets were dispersed in lubricating fluids, such as GL-4 grade, SM grade, and CI-4 grade lubricants. Compositions of the lubricating fluids are as illustrated in Table 1. It is to be understood that any other lubricating fluid comprising base oil in a range of 90-99% by weight of the lubricating fluid and additives in a range of 1-10% by weight of the lubricating fluid may be used.
Table 1: Additive composition in HP GL-4, Racer 4, and HP CI 4 lubricants

Grade


HP GL -4 Racer 4 HP CI 4
a b c d e f g h Calcium, mg/Kg ASTM D5185 <10 1700 to 1900 3000 to 4000

Zinc , mg/Kg ASTM D5185 <10 800 to 1200 1000 to 1500

Phosphorous, mg/Kg ASTM D5185 100 to 200 700-1000 1000 to 1500

Sulfur, Wt% ASTM D4951 1 to 4 0.1 to 0.5 0.1 to 0.75

Magnesium , mg/Kg ASTM D5185 <10 <10 <10

Molybdenum, mg/Kg ASTM D5185 <10 <10 <10

Boron, mg/Kg ASTM D5185 <10 <10 <10

Sodium, mg/Kg ASTM D5185 5 – 20 10-16 10-20
[0069] In an example implementation, the layered nanostructure additive based
lubricant described herein can be used for lubrication in vehicles in the automotive industry. Thus, to determine the suitability of the layered nanostructure additive based lubricant in the automotive industry evaluation of physico-chemical properties of the layered nanostructure additive based lubricant becomes necessary. The physico-chemical properties of lubricants include viscosity index, total acid number, total base number, and the like, that determine the suitability of lubricant for use in vehicles, such as in engines of two-wheelers and four-wheelers. The physico-chemical properties of the layered nanostructure additive based lubricants were evaluated to investigate the suitability of the surfactant and the surface modification process to the automotive environment.

EXAMPLE 2: EVALUATION OF PHYSICO-CHEMICAL PROPERTIES OF THE LUBRICANT COMPRISING SURFACE MODIFIED LAYERED NANOSTRUCTURE ADDITIVES
[0070] In an example implementation to analyze the physico-chemical
properties of the layered nanostructure additive based lubricant, different tests such as foaming tendency test, Kinematic viscosity test, total acid number test, total base number test, and copper strip corrosion test were performed.
EXAMPLE 2.1: FOAMING TENDENCY TEST
[0071] Generally, lubricants comprise foaming additives. These foaming
additives keep the engine and other components clean by producing foam. However, excessive foam can result in loss in lubrication which eventually leads to mechanical failure of the engine and its components.
[0072] Surfactants used for surface modification of layered nanostructure
additives often generate foam and can increase the amount of foam produced by the lubricant. Therefore, the foaming tendency of the layered nanostructure additive based lubricant was tested to assess effect of the surface modified layered nanostructure additives on the foaming tendency of the lubricant.
[0073] The foaming tendency was tested as per ASTM D 892 and was
performed in two stages. During the first stage, 200ml of a sample of the layered nanostructure additive based lubricant was maintained at a temperature of 24oC in a 1000ml beaker. Air was constantly blown through the sample at a constant rate of 95 mL/min for 5 minutes. The sample was allowed to rest for 10 mins. Volume of foam was measures at the end of blowing of air and after the sample was allowed to rest. During the second stage, a sample of the layered nanostructure additive based lubricant was maintained at a temperature of 93.5oC. Air was constantly blown through the sample at a constant rate of 95 mL/min for 5 minutes. The sample was allowed to rest for 10 mins. Volume of foam was measured at the end of blowing of air and after the sample was allowed to rest. The volume of foam generated for layered nanostructure additive based lubricant

for different ratios of surfactant to layered nanostructure additives is as illustrated in Table 2.1.
Table 2.1: Results of foaming tendency test

Sample (Racer 4 as base oil-200mL) Ratio of
Surfactan
t to the
layered
nanostru
cture additives Foam Volume (ml)

First stage at 24 oC Second stage at 93.5 oC

At the end of
5 min
blowing
period At the end of 10 min settling period At the end of
5 min
blowing
period At the end of 10
min settling
period
Base oil 0 5 Nil 30 Nil
Base oil
+0.05 WS2
(CTAB) 1.5:1 5 Nil 30 Nil
Base oil + 0.05% WS2 (SPAN 80) 1.5:1 5 Nil 32 Nil
Base oil
+0.05 MoS2
(CTAB) 1.5:1 6 Nil 30 Nil
Base oil +
0.05% MoS2
(SPAN 80) 1.5:1 5 Nil 32 Nil
Base oil
+0.05 WS2
(CTAB) 3:1 12 5 52 14
Base oil + 0.05% WS2 (SPAN 80) 3:1 14 5 55 15
Base oil
+0.05 MoS2
(CTAB) 3:1 15 8 52 12
Base oil +
0.05% MoS2
(SPAN 80) 3:1 15 7 53 12
Base
oil+0.05
graphene(CT
AB) 1.5:1 4 nil 25 Nil
Base
oil+0.05
graphene(SP
AN 80) 1.5:1 5 Nil 30 nil
[0074] The critical limit of foam produced according to ASTM D 892 is
• At 24oC: Maximum of 10mL after blowing air and nil after allowing to rest.

• At 93.5oC: Maximum of 40mL after blowing air and nil after allowing to rest.
[0075] Based on limits set by ASTM D 892 and Table 2.1, it was observed
that ratio of surfactant to layered nanostructure additives during surface modification of layered nanostructure additives beyond 1.5:1 increased foaming tendency of the lubricant significantly. It was also observed that ratio of surfactant to layered nanostructure additives during surface modification of layered nanostructure additives limited by 1.5:1 did not alter foaming tendency of lubricant significantly.
EXAMPLE 2.1: KINEMATIC VISCOSITY TEST
[0076] Viscosity of the lubricant is closely related to its ability to reduce
friction. Viscosity index is a parameter that indicates the variation of viscosity with temperature. The effect of surface modified layered nanostructure additives on the viscosity index of the lubricant was calculated as per ASTM D 445 standard by measuring viscosity of the layered nanostructure additive based lubricant at 40oC and 100oC. According to ASTM D 445, a high value (normally > 90) of the viscosity index indicates that the layered nanostructure additive based lubricant has good lubricating properties.
[0077] Table 2.2.1 depicts results of kinematic viscosity test for layered
nanostructure additive based lubricant where the lubricant is the SM grade oil. Table 2.2.2 depicts results of kinematic viscosity test for layered nanostructure additive based lubricant where the lubricant is CI 4 grade oil.
Table 2.2.1: Results of kinematic viscosity test (SM grade oil)

Sample (SM grade oil: Racer 4 (20W40) Viscosity at
0
40 C (cSt) Viscosity at
0
100 C (cSt) Viscosity index
Racer 4 (20W40) 137.18 15.68 119
Racer 4 (20W40)+0.2 % WS2 (CTAB) 144.31 16.28 119

Racer 4 (20W40)+0.2 % 143.28 16.11 118
MoS2 (SPAN 80)
Racer 4 (20W40)+0.2 % 144.22 16.23 119
graphene (CTAB)
Table 2.2.2: Results of kinematic viscosity test (CI 4 grade oil)

Sample (CI 4 grade oil: HP CI 4 (15W40)) Viscosity at
0
40 C (cSt) Viscosity at
0
100 C (cSt) Viscosity index
HP CI 4 (15W40) 123.14 14.62 120
HP CI 4 (15W40)+0.2 % WS2 (CTAB) 125.22 14.81 120
HP CI 4 (15W40) +0.2 % MoS2 (SPAN 80) 124.88 14.34 119
HP CI 4 (15W40) +0.2 % graphene (CTAB) 125.34 14.78 120
[0078] As can be seen from Table 2.2.1 and Table 2.2.2, viscosity index of
layered nanostructure additives based lubricants is comparable with viscosity index of lubricant not comprising the surface modified layered nanostructure additives.
EXAMPLE 2.3: TEST FOR TOTAL ACID NUMBER (TAN)
[0079] Total Acid Number (TAN) is a measure of presence of acids within
the nano suspension lubricant. The Total Acid Number is the amount of potassium hydroxide in milligrams that is needed to neutralize the acids in one gram of the nano suspension lubricant. The TAN value indicates potential corrosiveness of the nano suspension lubricant. Thus, maintaining a low TAN value is essential to maintain and protect components of engines. Generally, a low TAN value (< 3) gives an indication that the lubricant is non-corrosive.
[0080] Tests were conducted to assess the effect of surface modified
layered nanostructure additives on TAN of lubricants. The table below illustrates

the TAN values of layered nanostructure additive based lubricants prepared using the method of the present subject matter. Table 2.3.1 depicts TAN of layered nanostructure additive based lubricants where the lubricant is the SM grade oil. Table 2.3.2 depicts TAN of layered nanostructure additive based lubricants where the lubricant is the CI 4 grade oil.
Table 2.3.1: Measured TAN (SM grade oil)

Sample (Lubricant Used: SM grade oil-Racer 4) Total Acid number
Racer 4 (20W40) <2
Racer 4 + 0.2 % WS2 (CTAB) <2
Racer 4+0.2 % MoS2 (SPAN 80) <2
Racer 4 +0.2 % graphene (CTAB) <2
Table 2.3.2: Measured TAN (CI 4 grade oil)
[0081] As can be seen from Table 2.3.1 and Table 2.3.2, TAN value of the
layered nanostructure additive based lubricant is comparable with TAN value of lubricant not comprising the surface modified layered nanostructure additives. Therefore, dispersing the lubricant with the surface modified layered nanostructure additives does not affect TAN and, in consequence, is non-corrosive.
EXAMPLE 2.4: TEST FOR TOTAL BASE NUMBER
[0082] Lubricants are required to prevent acidic corrosion within the
combustion chamber of a running engine and should protect different engine components, such as, piston rings, cylinder liner and piston crown from damage

by sulphur or nitrogen containing acids. Total Base Number (TBN) of the lubricant determines how effectively acids formed during combustion process of the engine are reduced. The higher the TBN (typically > 5), the more effective the lubricant is in suspending wear-causing contaminants and reducing the corrosive effects of acids over an extended period of time.
[0083] The TBN of the layered nanostructure additive based lubricants
was tested to assess the effect of surface modified layered nanostructure additives on the TBN of lubricants. The TBN was measured by the ASTM D 2896 standard potentiometric titration with perchloric acid. Table 2.4.1 depicts measured TBN where the lubricant was the SM grade oil. Table 2.4.2 depicts measured TBN where the lubricant was CI 4 grade oil.
Table 2.4.1: Measured TBN (SM grade oil)

Sample (Lubricant Used: SM grade oil-Racer 4) Total Base number
HP CI 4 oil >10
HP CI 4 +0.2 % MoS2 (CTAB) >10
HP CI 4 +0.2 % WS2 (SPAN 80) >10
HP CI 4 +0.2 % graphene (CTAB) >10
Table 2.4.1: Measured TBN (CI 4 grade oil)

Sample (Lubricant used: SM grade oil-Racer 4) Total Base number
Racer 4 >6
Racer 4+0.2 % WS2 (CTAB) >6
Racer 4+0.2 % MoS2 (SPAN 80) >6
Racer 4 +0.2 % graphene (CTAB) >6
[0084] As can been from Table 2.4.1 and Table 2.4.2, the TBN of layered
nanostructure additive based lubricant is comparable with TBN of lubricant not comprising the surface modified layered nanostructure additives.
EXAMPLE 2.5: COPPER STRIP CORROSION TEST
[0085] The Copper Strip Corrosion Test is carried out to assess the
relative degree of corrosiveness of a number of petroleum products, including

aviation fuels, automotive gasoline, lubricating oils and other products. In the test, a polished copper strip is immersed in 30mL of the lubricant at elevated temperature of about 100oC for about 3 hours. After the test period, the copper strip is removed, washed and the color and tarnish level assessed against the ASTM Copper Strip Corrosion Standard. A classification number from 1-4 is assigned based on a comparison with the ASTM Copper Strip Corrosion Standards. A value of 1a denotes excellent protection, 1b denotes good protection, and 1c denotes sufficient.
[0086] The copper strip corrosion test was performed to assess the effect
of surface modified layered nanostructure additives on the degree of corrosiveness of the lubricant. The lubricant used for the test was SM 4 grade oil and SM 4 grade oil dispersed with the surface modified layered nanostructure additives to form the layered nanostructure additive based lubricant. Table 2.5 depicts results of copper strip corrosion test.
Table 2.5: Results for Copper Strip Corrosion Test

Sample (Lubricant used: SM 4 grade oil-Racer 4) Copper strip corrosion result
Racer 4 1a
Racer 4+ 0.2 % WS2 (CTAB/SPAN 80)) 1a
Racer 4+ 0.2 % MoS2 (CTAB/SPAN 80) 1a
Racer 4+ 0.2 % MoS2 (other surfactants) 1b
Racer 4 +0.2 % WS2 (other surfactants) 1b
Racer 4 +0.2 % graphene (CTAB/SPAN 80) 1a
[0087] As can be seen from Table 2.5, layered nanostructure additives
surface modified with CTAB and sodium monooleate (SPAN 80) are better suitable for automotive environment. Also, it can be observed that layered

nanostructure additive based lubricant dispersed with layered nanostructure additives surface modified with CTAB and sodium monooleate (SPAN 80) provide corrosion resistance comparable with the lubricant not comprising the surface modified layered nanostructure additives.
EXAMPLE 3: EVALUATION OF TRIBOLOGICAL PROPERTIES
[0088] In this example, tribological properties of lubricants, such as wear
resistance, friction resistance, and the like, was compared with tribological properties of layered nanostructure additive based lubricants.
EXAMPLE 3.1: FOUR BALL WEAR TEST
[0089] The Four Ball Wear Test determines the wear protection properties
of a lubricant. The wear tests were conducted for each of petrol engine oil and diesel engine oil as the lubricating fluid at 40 kgf load and 60 kgf load. The wear tests on gear oils of GL 4 grade were conducted at 40 kgf and 80 kgf loads. The wear scar diameters (WSD) on the stationary balls were measured using a Metallurgical microscope. The effect of surface modified layered nanostructure additives on wear resistance of lubricant was assessed by comparing wear resistance of the layered nanostructure additive based lubricants with wear resistance of lubricants not comprising layered nanostructure additives.
[0090] Fig.(s) 3(a)-3(h) illustrate the wear test results for the layered
nanostructure additive based lubricants with the surface modified layered nanostructure additives dispersed in different lubricating fluids, according to an example implementation. In the graphs illustrated in the Fig.(s) 3(a)-3(h), the y-axis depicts the wear scar diameter and the x-axis depicts different compositions of the layered nanostructure additive based lubricant with different lubricating fluids, such as diesel engine oil, petrol engine oil, and gear oil. The wear scar diameter is represented in microns.
[0091] The graph 300(a) illustrated in Fig. 3(a) depicts the wear test
results of the layered nanostructure additive based lubricant having diesel engine

oil of CI 4 grade as the lubricating fluid at 40 Kgf load, according to an example implementation. It may be noted from the graph 300(a) that the wear scar diameter of layered nanostructure additive based lubricant is lesser than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it. Addition of surface modified layered nanostructure additives to the lubricant to obtain the layered nanostructure additive based lubricant reduces the wear scar diameter substantially.
[0092] The graph 300(b) illustrated in Fig. 3(b) depicts the wear test
results of the layered nanostructure additive based lubricant having diesel engine oil of CI 4 grade as the lubricating fluid at 60 Kgf load, according to an example implementation. It may be noted from the graph 300(b) that the wear scar diameter of layered nanostructure additive based lubricant is lesser than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it. Addition of surface modified layered nanostructure additives to the lubricant to obtain the layered nanostructure additive based lubricant reduces the wear scar diameter substantially.
[0093] The graph 300(c) illustrated in Fig. 3(c) depicts the wear test
results of the layered nanostructure additive based lubricant having petrol engine oil of SM grade as the lubricating fluid at 40 Kgf load, according to an example implementation. It may be noted from the graph 300(c) that the wear scar diameter of layered nanostructure additive based lubricant is lesser than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it. Addition of surface modified layered nanostructure additives to the lubricant to obtain the layered nanostructure additive based lubricant reduces the wear scar diameter substantially.
[0094] The graph 300(d) illustrated in Fig. 3(d) depicts the wear test
results of the layered nanostructure additive based lubricant having petrol engine oil of SM grade as the lubricating fluid at 60 Kgf load, according to an example implementation. It may be noted from the graph 300(d) that the wear scar diameter of layered nanostructure additive based lubricant is lesser than the

lubricant not comprising the surface modified layered nanostructure additives dispersed in it. Addition of surface modified layered nanostructure additives to the lubricant to obtain the layered nanostructure additive based lubricant reduces the wear scar diameter substantially.
[0095] The graph 300(e) illustrated in Fig. 3(e) depicts the wear test
results of the layered nanostructure additive based lubricant having gear oil SAE 80W90 of GL 4 grade as the lubricating fluid at 40 Kgf load, according to an example implementation. It may be noted from the graph 300(e) that the wear scar diameter of layered nanostructure additive based lubricant is lesser than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it. Addition of surface modified layered nanostructure additives to the lubricant to obtain the layered nanostructure additive based lubricant reduces the wear scar diameter substantially.
[0096] The graph 300(f) illustrated in Fig. 3(f) depicts the wear test results
of the layered nanostructure additive based lubricant having gear oil SAE 80W90 of GL 4 grade as the lubricating fluid at 80 Kgf load, according to an example implementation. It may be noted from the graph 300(f) that the wear scar diameter of layered nanostructure additive based lubricant is lesser than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it. Addition of surface modified layered nanostructure additives to the lubricant to obtain the layered nanostructure additive based lubricant reduces the wear scar diameter substantially.
[0097] The wear properties of the layered nanostructure additive based
lubricants having gear oil of GL 4 grade as the lubricating fluid was also tested. The gear oil of GL 4 grade having two different viscosity grades, such as EP 140 and SAE 80 W 90 were used for the tests. The graph 300(g) illustrated in Fig. 3(g) depicts the wear test results of the layered nanostructure additive based lubricant having gear oil EP 140 of GL 4 grade as the lubricating fluid at 40 Kgf load, according to an example implementation. It may be noted from the graph 300(g) that the wear scar diameter of layered nanostructure additive based lubricant is

lesser than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it. Addition of surface modified layered nanostructure additives to the lubricant to obtain the layered nanostructure additive based lubricant reduces the wear scar diameter substantially.
[0098] The graph 300(h) illustrated in Fig. 3(h) depicts the wear test
results of the layered nanostructure additive based lubricant having gear oil EP 140 of GL 4 grade as the lubricating fluid at 80 Kgf load, according to an example implementation. It may be noted from the graph 300(h) that the wear scar diameter of layered nanostructure additive based lubricant is lesser than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it. Addition of surface modified layered nanostructure additives to the lubricant to obtain the layered nanostructure additive based lubricant reduces the wear scar diameter substantially.
[0099] The Four Ball Wear Test was also used to determine the wear
protection properties of a lubricant with different concentrations of the surface modified layered nanostructure additives. Different weight concentrations, namely 0.05%, 0.1%, 0.2%, and 0.4% of the layered nanostructure additives of WS2, MoS2, and graphene were taken in base oil. The wear scar diameter for each concentration was averaged. The average wear scar diameter for each concentration of the surface modified layered nanostructure additives as obtained using the Four Ball Wear Test are as shown in Table 3.1.1-Table 3.1.4.
Table 3.1.1: Average wear scar diameter at each concentration of the surface modified layered nanostructure additives in diesel engine oil

CI 4 plus grade engine oil analysis at 40 kgf load
Sample Average wear scar diameter at each concentration of different surface modified layered nanostructure additives (microns)
Diesel engine oil+0 % surface modified layered nanostructure additives 398.74

Diesel engine oil+0.05 surface modified layered nanostructure additives 397.16
Diesel engine oil+0.1 % surface modified layered nanostructure additives 389.5
Diesel engine oil+0.2 % surface modified layered nanostructure additives 370.05
Diesel engine oil+0.4 % surface modified layered nanostructure additives 412.54
Table 3.1.2: Average wear scar diameter at each concentration of the surface modified layered nanostructure additives in petrol engine oil

SM grade engine oil analysis at 40 kgf load
Sample Average wear scar diameter at each concentration of different surface modified layered nanostructure additives (microns)
Petrol Engine oil+0% surface modified layered nanostructure additives 389.6
Petrol engine oil+0.05 surface modified layered nanostructure additives 389.43
Petrol engine oil+0.1 % surface modified layered nanostructure additives 370.64
Petrol engine oil+0.2 % surface modified layered nanostructure additives 358.31
Petrol engine oil+0.4 % surface modified layered nanostructure additives 443.64
Table 3.1.3: Average wear scar diameter at each concentration of the surface modified layered nanostructure additives in gear oil (GL4 (SAE 80W90))

GL4 (SAE 80W90 ) grade Gear oil analysis at 40 kgf load
Sample Average wear scar diameter at each concentration of different surface modified layered nanostructure additives (microns)
Gear oil+0% surface modified layered nanostructure additives 355.95
Gear oil+0.05 surface modified layered nanostructure additives 354.19
Gear oil+0.1 % surface modified layered nanostructure additives 338.9
Gear oil+0.2 % surface modified layered nanostructure additives 313.49
Gear oil+0.4 % surface modified layered nanostructure additives 412.916
Table 3.1.4: Average wear scar diameter at each concentration of the surface modified layered nanostructure additives in gear oil (EP 140 GL4)

EP 140 GL4 grade Gear oil analysis at 40 kgf load
Sample Average wear scar diameter at each concentration of different surface modified layered nanostructure additives (microns)
Gear oil+0% surface modified layered nanostructure additives 332.59
Gear oil+0.05 % surface modified layered nanostructure additives 330.5
Gear oil+0.1 % surface modified layered nanostructure additives 320.4

Gear oil+0.2 % surface modified layered nanostructure additives 314.06
Gear oil+0.4 % surface modified layered nanostructure additives 436.65
[00100] From Table 3.1.1-3.1.4, it can be seen that wear scar diameter of
lubricant comprising the surface modified layered nanostructure additives in a weight concentration in the range of 0.05%-0.2% was lower than wear scar diameter of the lubricant not comprising the surface modified layered nanostructure additives.
EXAMPLE 3.2: FRICTION TEST
[00101] The friction test was conducted to determine the effect of surface
modified layered nanostructure additives on coefficient of friction of the lubricant. The test was conducted under the following prescribed test conditions using the ASTM 4 Ball wear tester. The test was conducted under the following test conditions:
• Temperature 75±2°C
• Speed 600 RPM
• Duration 10 min at each load starting from 10 kgf
• Load 98.1 N (10 kgf) per 10 min increment to a load that indicates
incipient seizure, i.e., sudden increase in friction force value over steady
state on the friction trace.
[00102] The measured coefficient of friction and seizure load are shown in Fig.(s) 4(a)-Fig. 4(h). In the graphs illustrated in the Fig.(s) 4(a), 4(c), 4(e) and 4(g), the y-axis depicts the measured friction coefficient and the x-axis depicts different compositions of the layered nanostructure additive based lubricant with different lubricating fluids, such as diesel engine oil, petrol engine oil, and gear oil. Similarly, in the graphs illustrated in Fig.(s) 4(b), 4(d), 4(f), and 4(h), the y-

axis depicts the seizure load and the x-axis depicts different compositions of the layered nanostructure additive based lubricant with different lubricating fluids, such as diesel engine oil, petrol engine oil, and gear oil.
[00103] The graph 400(a) and 400(b) illustrated in Fig. 4(a) and Fig. 4(b)
depicts the friction coefficient and seizure load results of the layered nanostructure additive based lubricant having diesel engine oil of CI 4 grade as the lubricating fluid, according to an example implementation. It may be noted from the graph 400(a) that the friction coefficient of layered nanostructure additive based lubricant is lesser than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it. Also, it may be noted from the graph 400(b) that the seizure load of layered nanostructure additive based lubricant is higher than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it.
[00104] The graph 400(c) and 400(d) illustrated in Fig. 4(c) and Fig. 4(d)
depicts the friction coefficient and seizure load results of the layered nanostructure additive based lubricant having petrol engine oil of SM grade as the lubricating fluid, according to an example implementation. It may be noted from the graph 400(c) that the friction coefficient of layered nanostructure additive based lubricant is lesser than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it. Also, it may be noted from the graph 400(d) that the seizure load of layered nanostructure additive based lubricant is higher than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it.
[00105] The graph 400(e) and 400(f) illustrated in Fig. 4(e) and Fig. 4(f)
depicts the friction coefficient and seizure load results of the layered nanostructure additive based lubricant having gear oil SAE 80W90 of grade GL 4 as the lubricating fluid, according to an example implementation. It may be noted from the graph 400(e) that the friction coefficient of layered nanostructure additive based lubricant is lesser than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it. Also, it may be noted

from the graph 400(f) that the seizure load of layered nanostructure additive based lubricant is higher than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it.
[00106] The graph 400(g) and 400(h) illustrated in Fig. 4(g) and Fig. 4(h)
depicts the friction coefficient and seizure load results of the layered nanostructure additive based lubricant having gear oil EP 140 of grade GL 4 as the lubricating fluid, according to an example implementation. It may be noted from the graph 400(g) that the friction coefficient of layered nanostructure additive based lubricant is lesser than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it. Also, it may be noted from the graph 400(h) that the seizure load of layered nanostructure additive based lubricant is higher than the lubricant not comprising the surface modified layered nanostructure additives dispersed in it.
[00107] From the graphs 400(a)-400(h) it can be seen that addition of the
surface modified layered nanostructure additives to the lubricant decreases the friction coefficient of the lubricant and increases the seizure load. This indicates that the layered nanostructure additive based lubricant of the present subject matter provides better anti-friction properties as compared to the lubricant not comprising the surface modified layered nanostructure additives.
[00108] Effect of different weight concentrations on the friction coefficient
and seizure load was also studied. Different weight concentrations, namely 0.05%, 0.1%, 0.2%, and 0.4% of the layered nanostructure additives of WS2, MoS2, and graphene were taken in base oil. The friction coefficient and seizure load for each concentration was averaged. The average value of friction coefficient and seizure load for different concentration of the layered nanostructure additives was as shown in Table 3.2.1-3.2.4
Table 3.2.1: Average friction coefficient and seizure load at each concentration of layered nanostructure additives in diesel engine oil

Friction coefficien grade oils) t and seizure load of CI 4 plus oils (CI 4 (SAE 15W40)

Sample Avg. seizure load at each concentration Avg. coefficient of friction at each concentration
Diesel engine oil+0 % surface modified layered nanostructure additives 110 0.0835
Diesel engine oil+0.05 % surface modified layered nanostructure additives 110 0.08153
Diesel engine oil+0.1 % surface modified layered nanostructure additives 120 0.0757
Diesel engine oil+0.2 % surface modified layered nanostructure additives 140 0.0724
Diesel engine oil+0.4 % surface modified layered nanostructure additives 100 0.0918
Table 3.2.2: Average friction coefficient and seizure load at each concentration of layered nanostructure additives in petrol engine oil

Friction coefficient and seizure load of SM grade oils (SM (SAE 15W40) grade oils)
Sample Avg. seizure load at each concentration Avg. coefficient of friction at each concentration
Petrol Engine oil+0% surface modified layered nanostructure additives 130 0.099
Petrol Engine oil+0.05% Surface modified layered nanostructure additives 130 0.09763
Petrol Engine oil+0.1% Surface modified layered nanostructure additives 130 0.0876
Petrol Engine oil+0.2% Surface modified layered nanostructure additives 140 0.0774

Petrol Engine oil+0.4% Surface modified layered nanostructure additives 120 0.0113
Table 3.2.3: Average friction coefficient and seizure load at each concentration of layered nanostructure additives in gear oil (GL 4 (SAE 80W90))

Friction coefficient and seizure load of GL 4 (SAE 80W90) oils
Sample Avg. seizure load at each concentration Avg. coefficient of friction at each concentration
Gear oil (SAE 80W90)+0% surface modified layered nanostructure additives 130 0.0891
Gear oil (SAE 80W90)+0.05 % Surface modified layered nanostructure additives 186.67 0.0879
Gear oil (SAE 80W90)+0.1 % Surface modified layered nanostructure additives 206.67 0.0854
Gear oil (SAE 80W90)+0.2 % Surface modified layered nanostructure additives 220 0.0725
Gear oil (SAE 80W90)+0.4 % Surface modified layered nanostructure additives 170 0.1097
Table 3.2.4: Average friction coefficient and seizure load at each concentration of layered nanostructure additives in gear oil (GL 4 (EP 140))

Friction coefficient and seizure load of GL 4 (EP 140) oils
Sample Avg. seizure load at each concentration Avg. coefficient of friction at each concentration
Gear oil (EP 140)+ 0% surface modified layered nanostructure additives 220 0.0911

Gear oil (EP140)+0.05 % Surface modified layered nanostructure additives 233.33 0.0901
Gear oil (EP140)+0.1 % Surface modified layered nanostructure additives 246.67 0.0834
Gear oil (EP140)+0.2 % Surface modified layered nanostructure additives 273.33 0.0685
Gear oil (EP140)+0.4 % Surface modified layered nanostructure additives 200 0.1163
[00109] From Table 3.2.1-3.2.4 it can be observed that weight concentration of layered nanostructure additives in the range of 0.05%-0.2% in lubricant provided higher seizure load and lower friction coefficient than lubricant not comprising the surface modified layered nanostructure additives.
EXAMPLE 3.4: EVALUATION OF EXTREME PRESSURE PROPERTIES OF GEAR OILS
[00110] Extreme pressure lubricants, such as gear oils are designed for use in severe applications across a variety of conditions, including high load, moisture and a wide range of operating speeds and loads. Thus, effect of surface modified layered nanostructure additives on extreme pressure (EP) properties of the gear oil as the lubricating fluid was tested.
[00111] In EP test, generally, two parameters, such as Load-wear index and Weld load are evaluated to determine EP properties. Higher the value of the load wear index and weld load for a lubricant, the lubricant may be understood to have better EP properties.
[00112] The EP tests were carried out on the layered nanostructure additive based lubricants and lubricants not comprising the surface modified layered nanostructure additives. Gear oils of GL4 grade of viscosity grade SAE 80 W 90 and EP 140 were used as the lubricants.
[00113] Fig.(s) 5(a)-5(d) graphically illustrates the variation of extreme pressure (EP) properties of the layered nanostructure additive based lubricant, according to

an example implementation. In the graphs illustrated in the Fig.(s) 4(a), and 4(c), the y-axis depicts the load wear index and the x-axis depicts different compositions of the layered nanostructure additive based lubricant with different gear oils. Similarly, in the graphs illustrated in Fig.(s) 4(b) and 4(d), the y-axis depicts the weld load and the x-axis depicts different compositions of the layered nanostructure additive based lubricant with different gear oils.
[00114] The graph 500(a) and 500(b) illustrated in Fig. 5(a) and Fig. 5(b) depicts the load wear index and weld load results of the layered nanostructure additive based lubricant having gear oil SAE 80W90 of grade GL 4 as the lubricating fluid, according to an example implementation. It may be noted from the graph 500(a) and 500(b) that the load wear index and weld load of layered nanostructure additive based lubricant is higher than that of the lubricant not comprising the surface modified layered nanostructure additives dispersed in it.
[00115] The graph 500(c) and 400(c) illustrated in Fig. 5(b) and Fig. 5(c) depicts the load wear index and weld load results of the layered nanostructure additive based lubricant having gear oil EP140 of grade GL 4 as the lubricating fluid, according to an example implementation. It may be noted from the graph 500(c) and 500(d) that the load wear index and weld load of layered nanostructure additive based lubricant is higher than that of the lubricant not comprising the surface modified layered nanostructure additives dispersed in it.
[00116] From graphs 500(a), 500(b), 500(c), and 500(d), it can be observed that the load wear index and weld load is higher in layered nanostructure additive based lubricant indicating better EP properties.
EXAMPLE 3.5: METALLOGRAPHIC STUDIES ON WORN SURFACE OF BALLS
[00117] To determine the wear characteristics of the layered nanostructure additive based lubricant, metallographic studies of worn out metallic balls used in the wear test was performed. The scar area of the worn out metallic balls after the wear test were magnified in a Scanning Electron Microscope (SEM) and observed for deposition of particles on the worn out surface of the balls. On viewing the

balls in the SEM deposition of the layered nanostructure additives on the surface of the worn out balls can be seen. Fig. 6 illustrates characterization of the worn out balls on scanning electron microscope with X-ray diffraction attachment, according to an example implementation.
[00118] The graph 602 in Fig. 6 depicts the deposition of particles on the worn out balls when the lubricating fluid, such as gear oil GL 4 grade was used. The graph 604 depicts the deposition of particles on the worn out balls when the lubricating fluid, such as gear oil of GL 4 grade was mixed with 0.2 weight % of the surface modified WS2 nanoplatelets. The graph 606 depicts the deposition of particles on the worn out balls when the lubricating fluid, such as gear oil GL 4 grade was mixed with 0.2 weight % of the surface modified MoS2 nano platelets were used. The y-axis of the graphs 602, 604, and 606 depict the amount of deposition of the layered nanostructure additives on the worn out balls and the x-axis depicts the energy of the x-ray radiation used by the SEM. The energy of the x-ray radiation is represented in Kilo electron volts (Kev). In the graph 604, a peak is seen corresponding to tungsten (W) and sulphide (S) indicating that surface modified WS2 nanoplatelets were deposited on the worn surface of the balls and thereby provided wear resistance. Similarly in the graph of 606, a peak is seen corresponding to molybdenum (Mo) and sulphide (S) indicating that surface modified MoS2 nanoplatelets were deposited on the worn surface of the balls and thereby provided wear resistance.
EXAMPLE 3.5: PERFORMANCE TESTING ON A DIESEL ENGINE TEST RIG
[00119] The performance test with lubricating oil was carried out on a diesel engine by means of a specially designed test rig. The petrol engine test rig consisted of a 1200 cc 4 cylinder, four stroke, turbocharged CRDI diesel engine connected to an eddy current dynamometer. The specification of the engine used for the performance test is as shown in Table 3.5.1.
Table 3.5.1: Specification of diesel engine for performance testing

Type 4 Cylinder, 4 stroke, CRDI engine
Ignition microprocessor based engine management

system(ECU),
Displacement 1250 cc
Bore and stroke Bore 69.6 mm, stroke 82 mm
Maximum Power 55 kW @ 4000 rpm
Maximum Torque 190 Nm @ 2500 rpm
Lubricant SAE 15 W40 oil (factory recommended)
[00120] The Morse test is generally used to determine brake power or power available at a crank shaft of the engine and various efficiencies of an engine. Morse test is carried out at different speeds and loads to determine various efficiencies of the engine with lubricants.
[00121] Fig. 7 illustrates graphical representations of variations in brake thermal efficiency of layered nanostructure additive based lubricants in the diesel engine test rig, according to an example implementation. The graph 700 illustrated in Fig. 7 depicts the variation of brake thermal efficiency with brake power at 2500 RPM speed of the engine and the graph 702 illustrated in Fig. 7 depicts the variation of brake thermal efficiency with brake power at 4000 RPM speed of the engine. In the graphs 700 and 702 the y-axes depicts the brake thermal efficiency (ηbrake thermal) and the x-axes depicts the brake power. The brake power is represented in kilowatts. From the graphs 700 and 702, an improvement in the brake thermal efficiency at lower as well as higher speeds of the engine is observed with the layered nanostructure additive based lubricant.
EXAMPLE 3.6: ENDURANCE TEST FOR WEAR AND LIFE OF ENGINE
[00122] The wear performance of layered nanostructure additive based lubricant was compared to the lubricant not comprising the surface modified layered nanostructure additives. The wear performance was tested by subjecting the engine lubricated with the layered nanostructure additive based lubricant to 80 hour test under cyclic loading on a test rig. The engine test rig consists of a 100 cc single cylinder petrol engine connected to an alternating current dynamometer. The specification of the engine used for testing wear performance is as shown in Table 3.6.1.

Table 3.6.1: Specification of engine for testing wear performance

Type Single Cylinder, 4 stroke, Twin spark
Displacement 100cc
Bore x stroke 50mm x 49.5mm
Compression Ratio 8.8:1
Maximum Power 7.8bhp @ 7500 rpm
Maximum Torque 8 Nm @ 4500 rpm
Ignition System Digital Electronic Ignition
Engine Start Electric/Kick
[00123] The alternating current dynamometer was used for loading the engine. The speed of dynamometer, voltage & current developed by dynamometer, fuel consumption and temperature of exhaust gases were measured. The cyclic loading was conducted with 16 cycles of 5 hrs cyclic loading. The cyclic loading of 2 ½ hour was done as per the sequence given in Table 3.6.2.
Table 3.6.2: Sequence of cyclic loading
Test hours Test Conditions
2hr 75% of full load at declared max speed
2hr 100% load at speed to maximum torque
10 min Idling
50 min 100% load at declared max speed.
Test hours Test Conditions
2hr 75% of full load at declared max speed
2hr 100% load at speed to maximum torque
10 min Idling
50 min 100% load at declared max speed.
[00124] After the completion of the endurance test, the engine was dismantled and the conditions of the aforementioned design features, such as the cylinder liner of the engine and the piston rings were inspected for possible wear and tear. The wear of the cylinder liner was measured in terms of increase in diameter of the cylinder liner. The readings of diameter of the cylinder liner before and after the test were noted down and the difference was reported as wear loss of the cylinder liner. The wear loss was reported is as shown in Table 3.6.3.
Table 3.6.3: Results of wear of the cylinder liner at different positions of the
cylinder
| | Engine liner wear in \xm |

Lubricant
Position
from
TDC in cm RACER 4 RACER 4+0.2 % WS2 platelets RACER 4+0.2 % MoS2 platelets
2 5.0 4.2 4.33
4 6.5 4.65 4.71
4 7.5 4.66 5.54
8 7.55 3.05 5.81
Mean Wear in |j,m 6.64 4.14 5.18
[00125] Wear of the piston rings in the engine was also determined. The wear of the piston rings were reported in terms of weight loss of the piston rings. The test results for weight loss of the piston rings are as shown in Table 3.6.4.
Table 3.6.4: Results for weight loss of the piston rings and gudgeon ring in 80 hr test

Oil RACER 4 RACER 4+0.2 %
WS2
nanoplat elets RACER 4+0.2 %
MoS2
nanoplate lets RACER 4+0.2 % graphene
nano platelets
Piston rings. Serial Weigh t loss mg
Compression ring 1 1IP 2 1 1.1 1.3
Compression ring 1 2IP 18 9.5 11.5 10.8
Expanding ring E1 2 1 1.4 1.5
Oil ring 1 1SR 7 3.5 4.8 4.4
Oil ring 2 2SR 5 1.8 2.4 2.1
Total weight loss, mg 34 16.8 21.2 20.1
Gudgeon pin wear, mg 11 7 8.2 7.2
[00126] From Table 3.6.3 and 3.6.4, it can be observed that the layered nanostructure additive based lubricant having the surface modified layered nanostructure additives dispersed therein have substantially reduced the wear in

the piston rings and the cylinder liners of the engine. Thus, the layered nanostructure additive based lubricant of the present subject matter provide better endurance to the engine than lubricants that do not comprise the surface modified layered nanostructure additives.
[00127] The fuel consumption was measured during the endurance test at an interval of 2 hours to assess the fuel efficiency of the layered nanostructure additive based lubricant. The fuel consumption at instant and total fuel consumption were recorded. Fig. 9 graphically illustrates variation in total fuel consumption for the layered nanostructure additive based lubricant, according to an example implementation. The y-axis of the graph 800 illustrated in Fig. 8 depicts the total fuel consumption and the x-axis depicts the time duration of the test. The time duration is expressed in hours and the total fuel consumption is expressed in Kg/hr. As may be observed from the graph 800 the fuel consumption with the layered nanostructure additive based lubricant reduced as compared to the lubricating fluid without having the surface modified layered nanostructure additives.
[00128] Based on the endurance test it can be observed that the layered nanostructure additive based lubricants exhibit a reduction in the wear of the components of the engine and improvement in the mileage of the engine. Further, the stability test, tribological tests, bench tests, and endurance tests, it can be observed that layered nanostructure additive based lubricants provide comparable or better results than lubricants not comprising the surface modified layered nanostructure additives.
[00129] Other embodiments of the present subject matter will be apparent from consideration of the present specification. It is intended that the present specification and examples be considered as illustrative only and as encompassing the equivalents thereof.

I/We Claim:
1. A method (100) for preparing a lubricant with layered nanostructure additives,
the method (100) comprising:
contacting the layered nanostructure additives with a surfactant and a solvent to obtain a first mixture;
evaporating the solvent from the first mixture to obtain surface modified layered nanostructure additives; and
dispersing the surface modified layered nanostructure additives in a lubricating fluid to obtain the lubricant, wherein the lubricating fluid comprises base oil in a range of 90-99% by weight of the lubricating fluid and additives in a range of 1-10% by weight of the lubricating fluid,
wherein the weight ratio of the surfactant to the layered nanostructure additives is in a range of 1.5:1 to 2:1.
2. The method (100) as claimed in claim 1, wherein the layered nanostructure additives are fabricated from a material selected from the group consisting of transition metal disulphides, graphene, inorganic graphene analogues, and combinations thereof.
3. The method (100) as claimed in claim 2, wherein the transition metal disulphides are selected from the group consisting of molybdenum disulphide, tungsten disulphide, and a combination thereof.
4. The method (100) as claimed in claim 1, wherein the solvent is selected from the group consisting of hexane, iso-octane, n-heptane, toluene, and combinations thereof.

5. The method (100) as claimed in claim 1, wherein the surfactant is selected from the group consisting of sorbitan monooleate, cetyl trimethylammonium bromide (CTAB), and a combination thereof.
6. The method (100) as claimed in claim 1, wherein the method comprises sonicating the first mixture prior to evaporating the solvent.
7. The method (100) as claimed in claim 6, wherein sonicating comprises ultra sonicating, in an ultrasonic probe sonicator, for a time period of 30 minutes at 50% amplitude under a pulse mode followed by ultra sonicating for a time period of 30 minutes at 50% amplitude under a continuous mode.
8. The method (100) as claimed in claim 1, wherein the evaporating comprises stir heating on a magnetic stirrer.
9. The method (100) as claimed in claim 8, wherein the stir heating is conducted on the magnetic stirrer at a speed of 500-600 rpm and at a temperature range of 60-70oC.
10. The method (100) as claimed in claim 8, wherein the stir heating provides a dry powder of the surface modified layered nanostructure additives.
11. The method (100) as claimed in claim 1, wherein dispersing the surface modified layered nanostructure additives in the lubricating fluid comprises:
adding the surface modified layered nanostructure additives to the lubricating fluid to form a first suspension; and
sonicating the first suspension to obtain the lubricant.

12. The method (100) as claimed in claim 11, wherein the sonicating the first suspension comprises ultra sonicating, in an ultrasonic probe sonicator, for a time period of 8-12 minutes at 50% amplitude under a pulse mode of 0.5 seconds amplitude followed by ultra sonicating in continuous mode for 30-40 minutes at 50% amplitude.
13. The method (100) as claimed in claim 11, wherein the sonicating the first suspension comprises ultra sonicating, in an ultrasonic probe sonicator, for a time period of 10 minutes at 50% amplitude under a pulse mode of 0.5 seconds followed by ultra sonicating in continuous mode for 30 minutes at 50% amplitude.
14. The method (100) as claimed in claim 1, wherein the surface modified layered nanostructure additive comprises the layered nanostructure additive coated with the surfactant.
15. The method (100) as claimed in claim 1, wherein the layered nanostructure additives are selected from the group consisting of nanoplatelets, nanoflowers, and a combination thereof.
16. A lubricant dispersed with surface modified layered nanostructure additives comprising:
a lubricating fluid comprising about 90% to 99% base oil and about 1% to 10% additives; and
surface modified layered nanostructure additives from about 0.05 weight % to 0.2 weight % dispersed in the lubricating fluid, wherein the layered nanostructure additives are selected from the group consisting of nanoplatelets, nanoflowers, and a combination thereof.

17. The lubricant as claimed in claimed in claim 16, wherein the layered nanostructure additives are fabricated from a material selected from the group consisting of transition metal disulphides, graphene, inorganic graphene analogues, and combinations thereof.
18. The lubricant as claimed in claimed in claim 17, wherein the transition metal disulphides are selected from the group consisting of molybdenum disulphide, tungsten disulphide, and a combination thereof.