Description:FIELD OF THE INVENTION
The present invention relates to preparation of nanophases or nanosheets of zirconium phosphate, and functionalized or modified zirconium phosphate. The present invention also discloses a composition comprising nanosheets of zirconium phosphate or modified zirconium phosphate and grease.
BACKGROUND OF THE INVENTION
Zirconium phosphate (ZP) is a layered type structure with chemical formula of Zr(HPO4)2. nH2O and paid a great attention due to their outstanding physical and chemical properties. In the structure of a-ZP, tetrahedral mono hydrogen phosphate group are attached above and below the Zr atom plane. The three-oxygen atom of each phosphate group is coordinated with three different Zr atoms and forth oxygen atom is bonded with acidic hydrogen that is perpendicular to the Zr layer. Among different crystal phase of zirconium phosphate e.g. a, ?, t, ? – ZP, due to layered structure a, and ? are widely applicable. Zirconium phosphates have extremely high ion-exchange capability, high aspect ratio, excellent thermal stability and good biocompatibility. It is widely used in different field of applications like catalysts, flame retardants, drug delivery agents, lubrication modifiers, electrolyte membranes in fuel cells, and anti-corrosive agents and so on. Layered nanomaterials show unique lubricating properties specially friction and wear reducing properties due to their nano size and layered structure. Like other 2D nano materials, zirconium phosphate is a good candidate for tribology applications. To improve the lubricating properties of nano materials, different modification has been carried out e.g. intercalation, surface functionalization etc. Most of the existing lubricants have their performance limits. And some disadvantages of other additives are like higher costs, low yield, difficulty for size control, and dark coloured material, which is a limit for its applications for lubricant additives. Zirconium phosphate is hydrophilic in nature due to attachment of –OH group with P- atom. Hydrophobic nano additive is required for lubricating application for better dispersibility in grease and lubricating oil. Long chain hydrocarbon easily attaches on the surface of ZP due to presence of –OH group at the surface of zirconium phosphate. In case of high load, zirconium phosphate shows very good lubricating properties when compared with graphite and MoS2 due to their stable and strong interlayer bonding. ZP is white color materials and it form light color when mixed with grease but in case of traditional additives like MoS2 and graphite form black color when it was mixed with grease. There was interest towards investigation and development of lubricating properties of thickness varied zirconium phosphate as well as surface functionalized layered zirconium phosphate. Some of the prior-art documents are given below:
CN103803521 relates to a method for preparing a sulfonic acid functionalized zirconium phosphate pillared layered material by using a hydrothermal fumigation technology. The method comprises the following steps: by using cetylamine-supported layered zirconium phosphate as a starting material, synergistically introducing a silicon source and a template agent between zirconium phosphate laminates through a solvent method; adjusting the pH to initiate rapid hydrolytic polycondensation of the interlayered silicon source; improving the firmness and stability of a zirconium phosphate interlayered silicon pillared structure through a hydrothermal method; filtering, drying and removing organic amine and the template agent; finally oxidizing a sulfhydryl group in a reactant by taking hydrogen peroxide as an oxidizing agent through a fumigation-oxidization technology to obtain the sulfonic acid functionalized silicon oxide pillared zirconium phosphate pillared layered material.
CN107384527A discloses a kind of bedded zirconium phosphate and the compound extreme pressure grease of molybdenum disulfide and preparation method thereof. The lubricating grease includes following components in percentage by weight:Basic lubricating grease:90 96%;The mixed powder of a bedded zirconium phosphates and molybdenum disulfide mixing composition:2.0 7.0%;Extreme pressure agent:1.0 3.0%;Antioxidant:1.0 2.0%.Preparation method comprises the following steps:Mixed powder, 1.0 3.0% extreme pressure agent, 1.0 2.0% antioxidant of the a bedded zirconium phosphates of addition 2.0 7.0% and molybdenum disulfide mixing composition in 90 96% basic lubricating greases, roll grinding 3 times with three-roll grinder, obtain grease product.
CN104552514A discloses a layered zirconium phosphate/ ammonium polyphosphate composite flame retardant and a preparation method thereof. The preparation method comprises the following steps: weighing layered zirconium phosphate and ammonium polyphosphate in a weight ratio of 1:2; dissolving the ammonium polyphosphate into water, adding the layered zirconium phosphate, and uniformly stirring to obtain the layered zirconium phosphate/ammonium polyphosphate composite flame retardant.
CN115141458A relates to a layered zirconium phosphate modified polyformaldehyde wear-resistant material for automobile parts and a preparation method and application thereof; the raw materials of the wear-resistant material comprise: polyformaldehyde, layered nano zirconium phosphate and polytetrafluoroethylene; the method comprises the following steps: mixing the anhydrous polyformaldehyde, the layered nano zirconium phosphate and the polytetrafluoroethylene to obtain a mixed material; extruding the mixed material to obtain a wear-resistant material of layered zirconium phosphate modified polyformaldehyde; the application comprises applying the wear resistant material to a plastic body panel; the lamellar zirconium phosphate with a large specific surface area is utilized, a lamellar net structure can be formed after the lamellar zirconium phosphate is added into polyformaldehyde, meanwhile, polytetrafluoroethylene has a low friction coefficient, a layer of transfer film can be formed on the friction surface of a polyformaldehyde material, and the lamellar net structure formed by the lamellar zirconium phosphate is matched, so that the abrasion of the polyformaldehyde material can be reduced, and the abrasion resistance of a formaldehyde material is effectively improved.
CN112742360A discloses a preparation method of polyethyleneimine-silicon dioxide microspheres with titanium phosphate/zirconium phosphate groups modified on the surfaces, which comprises the following steps: bonding polyethyleneimine molecules with high-density amino on the surface of the silica microsphere; converting a large amount of amino active hydrogen in a polyethyleneimine structure into phosphorous acid groups through a Mannich reaction; and (3) adsorbing titanium ions or zirconium ions by utilizing the chelation between phosphorous acid groups and metal ions, and finally preparing the polyethyleneimine-silicon dioxide microsphere with the surface modified with titanium phosphate/zirconium groups.
CN114426898A discloses a compound additive for lubricating grease and a lubricating grease composition prepared from the compound additive, wherein the compound additive for lubricating grease comprises an organic base intercalation zirconium phosphate compound and an extreme pressure agent; the organic base intercalation zirconium phosphate compound comprises one or two of organic amine intercalation zirconium phosphate, single long-chain organic ammonium intercalation zirconium phosphate or double long-chain organic ammonium intercalation zirconium phosphate. The grease composition comprises a base grease: 90.0-98.0 parts of organic base intercalation zirconium phosphate compound: 1.0-7.0 parts of extreme pressure agent: 0-3.0 parts of an antirust agent: 0.5-1.0 part; antioxidant: 0.5 to 2.0 parts.
CN103266006A provides lubricating grease containing an ion-exchange-type zirconium phosphate additive. The lubricating grease comprises the following components in parts by weight: 100.0 parts of basic lubricating grease, 1.0-10.0 parts of ion-exchange-type zirconium phosphate material, 0.05-5.0 parts of antioxidant and 0-6.0 parts of antirust agent. A preparation method of the lubricating grease comprises the following steps of: stirring and mixing the basic lubricating grease, the ion-exchange-type zirconium phosphate material and the antioxidant for 1-10 hours in the range from a room temperature to 20 DEG C, grinding and homogenizing for 0.5-3 hours by using a three-roller machine or a high-voltage homogenizer, and uniformizing the mixture to prepare the lubricating grease product.
CN115197765A discloses zirconium phosphate composite titanium-based lubricating grease and a preparation method thereof, wherein the zirconium phosphate composite titanium-based lubricating grease comprises the following components in percentage by mass: 70-95% of base oil; 4 to 25 percent of thickening agent; 1 to 5 percent of zirconium phosphate. The preparation steps mainly comprise three major parts, namely a saponification process, a hydrolysis process and a high-temperature refining process. Firstly, mixing a part of base oil with stearic acid and benzoic acid, adding isopropyl titanate, then adding deionized water, then adding residual oil and zirconium phosphate into a system, finally cooling and grinding to obtain the lubricating grease, wherein the whole process needs 7-9 h.
CN114958464A relates to the technical field of lubricating oil, and provides lubricating oil with good dispersibility and extreme pressure anti-wear property and a preparation method thereof. The lubricating oil comprises 100 parts by weight of base oil, 0.3-2 parts by weight of antioxidant, 0.5-5 parts by weight of antirust agent and 0.5-2 parts by weight of extreme pressure antiwear agent. The extreme pressure antiwear agent is phosphoramide intercalated layered zirconium phosphate, and is prepared by a two-step intercalation method, wherein 1, 6-hexamethylenediamine is used for pre-intercalation of the layered zirconium phosphate, and then phosphoramide is used for secondary intercalation.
CN106700262A provides a polypropylene wood-plastic micro-foaming compound material and a preparation method thereof. The polypropylene wood-plastic micro-foaming compound material comprises the following components in parts by weight: 40-80 parts of polypropylene, 10-50 parts of plant fiber powder, 5-20 parts of polypropylene-grafted maleic anhydride, 0.25-4 parts of an anti-aging agent, 0.5-5.0 parts of a lubricating agent and 0.1-5.0 parts of a compound foaming agent. The compound foaming agent comprises a zirconium phosphate support and azodicarbonamide loaded on the zirconium phosphate support.
CN110229708A relates to a kind of carbon nanotube/two-dimension nano materials composite materials, it is characterized in that, carbon nanotube and two-dimension nano materials obtain modified carbon nano-tube and modified two-dimension nano materials through oiliness dispersing agent is modified respectively, obtain the carbon nanotube/two-dimension nano materials composite material after loaded modified two-dimension nano materials on modified carbon nano-tube.The two-dimension nano materials are layered metal phosphates nanometer sheet, preferably bedded zirconium phosphate nanometer sheet.
CN114539655A discloses a zirconium phosphate modified UHMWPE (ultra-high molecular weight polyethylene) antifriction and wear-resistant composite material and a preparation method thereof. Firstly, utilizing silane coupling agent KH-792 to carry out organic coupling modification on the surface of a zirconium phosphate sheet layer, then mechanically blending the zirconium phosphate sheet layer with ultrahigh molecular weight polyethylene powder uniformly, putting the mixed powder into a mold, finally heating, molding, melting, solidifying and molding the mixed powder by adopting a hot-press molding method, and cooling and demolding to obtain the UHMWPE antifriction and wear-resistant composite material.
Still there was a need to prepare nanophase/nanosheets of zirconium phosphate or functionalized/modified zirconium phosphate having good tribology properties, lower costs, high yield, easy for size control, and light-coloured material.
OBJECTIVES OF THE INVENTION
The main object of the present invention is to prepare nanosheets of zirconium phosphate.
Another object of the present invention is to prepare nanosheets of functionalized or modified zirconium phosphate.
One another object of the present invention is to prepare a composition comprising nanosheets of zirconium phosphate and grease.
Yet one another object of the present invention is to prepare a composition comprising nanosheets of functionalized or modified zirconium phosphate and grease.
SUMMARY OF THE INVENTION

The present invention discloses a process for preparation of functionalized or modified zirconium phosphate, the process comprising:
a) mixing o-phosphoric acid with water to make a homogeneous solution;
b) adding zirconium oxychloride into the homogeneous solution and stirring to prepare a homogeneous white gel.
c) transferring the homogeneous white gel to a teflon-lined auto clave and keeping the homogeneous white gel at 180-220 °C for 12-24 hours in a hot air oven to prepare a milky white precipitate;
d) washing and drying the milky white precipitate to obtain zirconium phosphate;
e) adding the zirconium phosphate into water and sonicating the mixture of zirconium phosphate and water for 1-2 hours;
f) adding sebacic acid or sodium dodecyl benzene sulfonate or oleic acid or dodecyl amine or triethoxy(octyl)silane, into the mixture of zirconium phosphate and water, and stirring the mixture for 2-4 hours to form a solution;
g) transferring the solution into a teflon-lined auto clave and keeping the solution at 130-180 °C for 2-4 hours in a hot air oven to prepare a solid white product or refluxing the solution at 80-100 oC for 4-12 hours to prepare a solid white product;
h) washing and drying the solid white product with water to obtain the functionalized or modified zirconium phosphate.
In an embodiment of the present invention, the o-phosphoric acid is in an amount in a range of 70-90 wt% and zirconium oxychloride is in an amount in a range of 10-30 wt%.
In an embodiment of the present invention, the zirconium phosphate is in an amount in a range of 80-90 wt% and sebacic acid or sodium dodecyl benzene sulfonate or oleic acid, or dodecyl amine, or triethoxy(octyl)silane is in an amount in a range of 10-20 wt%.
In an embodiment of the present invention, the water is deionized water.
The present invention also discloses a composition, comprising:
- zirconium phosphate or functionalized or modified zirconium phosphate in an amount of 0.01 to 3wt%; and
- grease in an amount of 97 to 100wt%.
BRIEF DESCRIPTION OF DRAWINGS / FIGURES
Figure 1 illustrates FESEM images of (a) ZP-1, (b) ZP-2, (c) ZP-3, (d) ZP-4, (e) ZP-5, and (f) TEM images of ZP.
Figure 2 illustrates XRD spectra of ZP sample.
Figure 3 illustrates (a) Coefficient of friction curves of different functionalized ZP sample, (b) average coefficient of friction of functionalized ZP samples (c) Average WSD plots of blank grease, pure ZP sample and functionalized ZP samples, and d) percentage reduction in CoF and WSD with respect to blank grease.
DETAILED DESCRIPTION OF THE INVENTION
In an aspect of the present invention, the present invention discloses a process for preparation of zirconium phosphate, the process comprising:
a) mixing o-phosphoric acid with water to make a homogeneous solution;
b) adding zirconium oxychloride into the homogeneous solution and stirring to prepare a homogeneous white gel.
c) transferring the homogeneous white gel to a teflon-lined auto clave and keeping the homogeneous white gel at 180-220 °C for 12-24 hours in a hot air oven to prepare a milky white precipitate;
d) washing and drying the milky white precipitate to obtain zirconium phosphate.
In another aspect of the present invention, the present invention discloses a process for preparation of functionalized or modified zirconium phosphate, the process comprising:
a) adding zirconium phosphate into water and sonicating the mixture of zirconium phosphate and water for 1-2 hours;
b) adding sebacic acid into the mixture of zirconium phosphate and water, and stirring the mixture for 2-4 hours to form a solution;
c) transferring the solution into a teflon-lined auto clave and keeping the solution at 130-180 °C for 2-4 hours in a hot air oven to prepare solid white product;
d) washing and drying the solid white product with water to obtain the functionalized or modified zirconium phosphate.
In another aspect of the present invention, the present invention discloses a process for preparation of functionalized or modified zirconium phosphate, the process comprising:
a) adding zirconium phosphate into water and sonicating the mixture of zirconium phosphate and water for 1-2 hours;
b) adding sodium dodecyl benzene sulfonate or oleic acid or dodecyl amine or triethoxy(octyl)silane into the mixture of zirconium phosphate and water, and stirring the mixture for 2-4 hours to form a solution;
c) refluxing the solution at 80-100 oC for 4-12 hours to prepare a solid white product;
d) washing and drying the solid white product with water to obtain the functionalized or modified zirconium phosphate.
In one another aspect of the present invention, the present invention discloses a process for preparation of functionalized or modified zirconium phosphate, the process comprising:
a) mixing o-phosphoric acid with water to make a homogeneous solution;
b) adding zirconium oxychloride into the homogeneous solution and stirring to prepare a homogeneous white gel.
c) transferring the homogeneous white gel to a teflon-lined auto clave and keeping the homogeneous white gel at 180-220 °C for 12-24 hours in a hot air oven to prepare a milky white precipitate;
d) washing and drying the milky white precipitate to obtain zirconium phosphate;
e) adding the zirconium phosphate into water and sonicating the mixture of zirconium phosphate and water for 1-2 hours;
f) adding sebacic acid into the mixture of zirconium phosphate and water, and stirring the mixture for 2-4 hours to form a solution;
g) transferring the solution into a teflon-lined auto clave and keeping the solution at 130-180 °C for 2-4 hours in a hot air oven to prepare solid white product;
h) washing and drying the solid white product with water to obtain the functionalized or modified zirconium phosphate.
In one another aspect of the present invention, the present invention discloses a process for preparation of functionalized or modified zirconium phosphate, the process comprising:
a) mixing o-phosphoric acid with water to make a homogeneous solution;
b) adding zirconium oxychloride into the homogeneous solution and stirring to prepare a homogeneous white gel.
c) transferring the homogeneous white gel to a teflon-lined auto clave and keeping the homogeneous white gel at 180-220 °C for 12-24 hours in a hot air oven to prepare a milky white precipitate;
d) washing and drying the milky white precipitate to obtain zirconium phosphate;
e) adding the zirconium phosphate into water and sonicating the mixture of zirconium phosphate and water for 1-2 hours;
f) adding sebacic acid or sodium dodecyl benzene sulfonate or oleic acid or dodecyl amine or triethoxy(octyl)silane, into the mixture of zirconium phosphate and water, and stirring the mixture for 2-4 hours to form a solution;
g) transferring the solution into a teflon-lined auto clave and keeping the solution at 130-180 °C for 2-4 hours in a hot air oven to prepare a solid white product or refluxing the solution at 80-100 oC for 4-12 hours to prepare a solid white product;
h) washing and drying the solid white product with water to obtain the functionalized or modified zirconium phosphate.
In yet another aspect of the present invention, the present invention discloses a composition, comprising:
- zirconium phosphate or functionalized or modified zirconium phosphate in an amount of 0.01 to 3wt%; and
- grease in an amount of 97 to 100wt%.
In a feature of the present invention, the o-phosphoric acid is in an amount in a range of 70-90 wt% and zirconium oxychloride is in an amount in a range of 10-30 wt%.
In a feature of the present invention, the zirconium phosphate is in an amount in a range of 80-90 wt%; and sebacic acid or sodium dodecyl benzene sulfonate or oleic acid, or dodecyl amine, or triethoxy(octyl)silane is in an amount in a range of 10-20 wt%.
In a feature of the present invention, the water is deionized water.
Synthesis of Zirconium phosphate:
Zirconium phosphate nanosheet was synthesized by a simple one step hydrothermal reaction using zirconium oxychloride and o-phosphoric acid. In this method, thickness of the sheet was varied by changing the water content in the reaction mixture and keeping unaltered the mole ratio of zirconium and phosphorous. The Table-1 shows the sample name with thickness and the mole ratio of zirconium, phosphorous and water.
Table 1: Samples codes with mole ratios and thickness
Sample Name Mole ratio of
Zr : P
in reaction mixture Mole ratio of
H2O : (Zr + P) Thickness
ZP-1 1:12 27.15 : 1 12-17
ZP-2 1:12 11.4 : 1 45-75
ZP-3 1:12 6.14 : 1 50-130
ZP-4 1:12 2.64 : 1 120-170
ZP-5 1:12 0.885 : 1 230-350

Synthesis of zirconium phosphate (ZP-1):
In this methods, 10 mL of 85% o-phosphoric acid was mixed with 75 mL of DI water to make homogeneous solution. After that 4.0 g of zirconium oxychloride was added slowly into the mixture and stirred until homogeneous white gel was formed. The gel was then transferred to Teflon-lined auto clave and kept it at 200 °C for 24 hours in hot air oven. After the completion of the reaction, milky white precipitate was washed with deionised water until pH of solution become 7 and dried at 60°C. and the sample named as ZP-1.
Synthesis of zirconium phosphate (ZP-2):
10 mL of 85% o-phosphoric acid was mixed with 30 mL of DI water to make homogeneous solution. After that 4.0 g of zirconium oxychloride was added slowly into the mixture and stirred until homogeneous white gel was formed. The gel was then transferred to Teflon-lined auto clave and kept it at 200 °C for 24 hours in hot air oven. After the completion of the reaction, milky white precipitate was washed with deionised water until pH of solution become 7 and dried at 60°C. and the sample named as ZP-2.
Synthesis of zirconium phosphate (ZP-3):
10 mL of 85% o-phosphoric acid was mixed with 15 mL of DI water to make homogeneous solution. After that 4.0 g of zirconium oxychloride was added slowly into the mixture and stirred until homogeneous white gel was formed. The gel was then transferred to Teflon-lined auto clave and kept it at 200 °C for 24 hours in hot air oven. After the completion of the reaction, milky white precipitate was washed with deionised water until pH of solution become 7 and dried at 60°C. and the sample named as ZP-3.
Synthesis of zirconium phosphate (ZP-4):
10 mL of 85% o-phosphoric acid was mixed with 5 mL of DI water to make homogeneous solution. 4.0 g of zirconium oxychloride was then added slowly into the phosphoric acid mixture and stirred until homogeneous white gel was formed. The gel was then transferred to Teflon-lined auto clave and kept it at 200 °C for 24 hours in hot air oven. After the completion of the reaction, milky white precipitate was washed with deionised water until pH of solution become 7 and dried at 60°C. and the sample named as ZP-4.
Synthesis of zirconium phosphate (ZP-5):
4.0 g of zirconium oxychloride was slowly added to 10 mL of 85% o-phosphoric acid and mixed untilled white homogeneous gel was formed. The white gel was then transferred to Teflon-lined auto clave and kept it at 200 °C for 24 hours in hot air oven. After the completion of the reaction, milky white precipitate was washed with deionised water until pH of solution become 7 and dried at 60°C. and the sample named as ZP-5.
Synthesis of functionalized zirconium phosphate:
Functionalized zirconium phosphate was prepared by different molecule like oleic acid, dodecyl amine, sodium dodecyl benzene sulfonate, triethoxy(octyl)silane, sebacic acid, Ethylene diamine tetra acetic acid etc. at the surface of nanosheet by simple hydrothermal and reflux method.
Synthesis of ZP-Sb:
0.5 g of as-synthesized zirconium phosphate was added in to 40 mL of DI water and sonicated for 1 hour. After that 0.8 g of sebacic acid was added into it and stirred it for another 3 hours. Then the solution was transferred into Teflon-lined auto clave and kept it at 150 °C for 3 hours in hot air oven. After completion of the reaction, the solid white product was washed with DI water and dried at 60? in hot air oven. The sample is named as ZP-Sb.
Synthesis of ZP-SDBS:
0.5 g of as-synthesized zirconium phosphate was added in to 20 mL of DI water and sonicated for 1 hour. Next, 2.4 g of sodium dodecyl benzene sulfonate was dissolved in 20 mL DI water. The aqueous solution of sodium dodecyl benzene sulfonate was added drop wise into the dispersed zirconium phosphate solution and stirred it for 3 hours. The solution was then transferred into Teflon-lined auto clave and kept it at 150 °C for 3 hours in hot air oven. After the completion of reaction, the solid white product was washed with DI water and dried at 60 °C in hot air oven. The sample is named as ZP-SDBS.
Synthesis of ZP-DA:
0.5 g of as-synthesized zirconium phosphate was added in to 20 mL of ethanol and sonicated for 1 hour. Next, 1.5 g of dodecyl amine was dissolved in 10 mL ethanol. The solution was then added drop wise into the dispersed zirconium phosphate solution and reflux at 90 °C for 12 hours in nitrogen atmosphere. After the completion of reaction, the solid white product was washed with ethanol and dried at 60 °C in hot air oven. The sample is named as ZP-DA.
Synthesis of ZP-OA:
0.5 g of as-synthesized zirconium phosphate was added in to 20 mL of ethanol and sonicated for 1 hour. Next, 10 mL of oleic acid was then added into the dispersed ethanolic zirconium phosphate solution and reflux at 100 °C for 12 hours in nitrogen atmosphere. After the completion of reaction, the solid white product was washed with ethanol and dried at 60 °C in hot air oven. The sample is named as ZP-OA.
Synthesis of ZP-OS:
0.5 g of as-synthesized zirconium phosphate was added in to 40 mL of ethanol and sonicated for 1h. Next, 1.0 mL of triethoxy(octyl)silane was then added into the dispersed ethanolic zirconium phosphate solution and reflux at 80 °C for 2 hours in nitrogen atmosphere. After the completion of reaction, the solid white product was washed with ethanol and dried at 60 °C in hot air oven. The sample is named as ZP-OS.
Characterization:
FESEM and TEM analysis:
We have characterized our as-synthesized zirconium phosphate nanosheets by SEM and TEM analysis. From SEM images hexagonal nanoplate like morphology of zirconium phosphate was found. It is also seen that thickness of zirconium phosphate nanosheet was increased from 12 nm to 350 nm with decreasing the water content in the reaction mixture. The typical thickness for all sample are found in the range of 12-17 nm for ZP-1, 45-75 nm for ZP-2, 50- 130 nm for ZP-3, 120-170 nm for ZP-4, 230-350 nm for ZP-5. The SEM and TEM images for zirconium phosphate are shown in Figure 1.
XRD analysis:
The zirconium phosphate nano sheets are characterized by XRD analysis (Figure 2) and it is seen that all ZP sample shows same XRD pattern and peak appeared at 11.7, 19.7, 24.8, 33.9, 37.0, 42.7, 44.1, 44.6, 48.3, 51.1, 51.6, 55.35, 55.9, 57.3, 60.4 ° which was well matched with JCPDS data. The peak at 11.7, 19.7, 24.8 and 33.9 corresponds to (002), (110), (112), (020) which confirmed the formation orthorhombic phase of zirconium phosphate.
Inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis:
The chemical formula of zirconium phosphate is Zr(HPO4)2.nH2O. The mole ratio of zirconium to phosphorus in ZrP is 1:2. Further, ICP-OES carried out to check the mole ratio and wt % of zirconium and phosphorus in as-synthesized zirconium phosphate. The weight percentage of zirconium and phosphorus of corresponding sample are shown in Table 2. From, ICP-OES, it is found that Zr : P mole ratio is nearly 1:2 for all sample.
Table 2: ICP-OES data
Sample Code Weight percentage of Phosphorous Weight percentage of Zirconium Calculated Mole ratio of Zr : P
ZP-1 15.9 21.8 1 : 2.1
ZP-2 18.9 29.6 1 : 1.9
ZP-3 19.4 29.7 1 : 1.97
ZP-4 18.0 29.5 1: 1.91
ZP-5 18.6 28.0 1 : 1.96

Tribological Properties:
Tribological performances (Coefficient of friction (CoF) and wear scar diameter (WSD)) of grease and grease composite were performed as per ASTM 4172 (Test Conditions: Load = 392 N (40 Kg), Temperature = 75 °C, Speed (rpm) = 1200, Duration = 1 hour) on DUCOM, India four-ball tester WO-1786. The SS balls having the diameter of 12.7 mm were used. The balls were cleaned with acetone or isopropanol before doing the experiments.

Optimization of the size dependence of nanomaterial was done by tribological evaluation as illustrated in Table 3. As the thickness of the nanomaterial increases, the coefficient of friction (CoF) and wear scar diameter (WSD) was reducing. Achieved an excellent performance for the ZP-5 nanomaterial with 16 and 32% of reduction in CoF and WSD compared to blank grease.

Mixing process of nanomaterial with grease: The following is the mixing process: Clean all the equipment with acetone or isopropanol to ensure there are no impurities. 1 wt% of the synthesized nanomaterial was added to the grease and the mixture was stirred manually then by overhead stirrer at ~1000 rpm. Followed by the grinding the greases two-three times by three-roller grinder for uniform and even dispersion of nanomaterial in the grease. The same process was followed for the blank grease (without the nanomaterial).

Table 3: Coefficient of friction and wear scar diameter values of grease with and without nanomaterial.
Sample CoF % Reduction of CoF WSD (µm) % Reduction of WSD
Blank grease 0.1724 - 838 -
Grease + 1 wt% ZP-1 0.1722 0.12 790 5.7
Grease + 1 wt% ZP-2 0.1651 4.23 744 11.2
Grease + 1 wt% ZP-3 0.1593 7.60 724 13.6
Grease + 1 wt% ZP-4 0.1545 10.38 591 29.5
Grease + 1 wt% ZP-5 0.1447 16.07 566 32.4

Optimization of the concentration of the ZP-5 was performed. As the concentration of the ZP-5 was increases from 1 to 3 wt%, there is an increase in the both CoF and WSD. The increase in the CoF and WSD was due to the agglomeration of the nanomaterial, thereby which itself acts as a friction. Therefore, the concentration of the ZP-5 was optimized to the 1 wt%, with 16 and 32% reduction in the CoF and WSD respectively.
Table 4: Optimization of loading concentration of ZP-5. Coefficient of friction and wear scar diameter ZP-5 at different concentrations.
% Loading of ZP-5 CoF % Reduction of CoF WSD (µm) % Reduction of WSD
1.0 0.1447 16.07 566 32.4
1.5 0.1506 12.65 580 31
2.0 0.1563 9.34 603 28
2.5 0.1627 5.63 671 20
3.0 0.1626 5.68 702 16.2

For the improvement and better dispersibility of the ZP additive, surface modification was performed over ZP nanomaterial with different types of surfactants having different functional groups such as sebacic acid (SA), sodium dodecyl benzene sulfonate (SDBS), triethoxy(octyl)silane (OS), dodecyl amine (DA), oleic acid (OA). With all the surface modifications, observed an enhancement in reduction of CoF and WSD. Amine functional surface modification showed highest reduction in CoF and WSD.
Table 5: Coefficient of friction and wear scar diameter values of grease with 1 wt% of modified ZP
Grease + Functionalized ZP COF % Reduction of COF WSD (µm) % Reduction of WSD % Reduction of WSD w.r.t. ZP-5
Grease + 1 wt% ZP-SA 0.1293 25.00 522 37.7 7.8
Grease + 1 wt% ZP-SDBS 0.1351 21.64 546 35 3.5
Grease + 1 wt% ZP-OS 0.1247 26.67 533 36.4 5.8
Grease + 1 wt% ZP-DA 0.1237 28.25 510 39 10
Grease + 1 wt% ZP-OA 0.1290 25.2 518 38.2 8.5

EP load analysis as per ASTM D 2783 using ZP materials in grease:
The tester is operated with one steel ball under load rotating against three steel balls held stationary in the form of a cradle. The rotating speed is 1770 ± 60 rpm. Lubricating greases are brought to 27 ± 8°C (80 ± 15°F) and then subjected to a series of tests of 10-s duration at increasing loads until welding occurs.
Test Conditions: Load = Varies, Temperature = 25 °C, Speed (rpm) = 1760 rpm, Duration = 10 sec.
Samples ZP-2, 4 and 5 additives showed better OK and weld load properties in base grease.
Table 6: OK load and weld load of grease with and without nanomaterial.

Sample EP load
OK load (Kg) Weld load (Kg)
Base Grease 100 126
Grease + 1 wt% ZP-1 126 160
Grease + 1 wt% ZP-2 160 200
Grease + 1 wt% ZP-3 126 160
Grease + 1 wt% ZP-4 160 200
Grease + 1 wt% ZP-5 160 200

Advantages of the present invention:
• Simple one step hydrothermal method.
• Scalable synthesis with high percentage of yield.
• Tuning thickness of zirconium nanoplate by changing the water content only without changing the precursors concentration.
• Modification of the surface of zirconium phosphate by different carbon chain molecule such as oleic acid, dodecyl amine, sodium dodecyl benzene sulfonate, triethoxy octyl silane using simple condensation method.
• Improved dispersion of zirconium phosphate into grease matrix by functionalization technique.
• Light color lubricating agent for grease.
• Tribology study (anti-friction, anti-wear and extreme pressure) with respect to thickness and functionalized zirconium phosphate nanoplate. , Claims:1. A process for preparation of functionalized or modified zirconium phosphate, the process comprising:
a) mixing o-phosphoric acid with water to make a homogeneous solution;
b) adding zirconium oxychloride into the homogeneous solution and stirring to prepare a homogeneous white gel.
c) transferring the homogeneous white gel to a teflon-lined auto clave and keeping the homogeneous white gel at 180-220 °C for 12-24 hours in a hot air oven to prepare a milky white precipitate;
d) washing and drying the milky white precipitate to obtain zirconium phosphate;
e) adding the zirconium phosphate into water and sonicating the mixture of zirconium phosphate and water for 1-2 hours;
f) adding sebacic acid or sodium dodecyl benzene sulfonate or oleic acid or dodecyl amine or triethoxy(octyl)silane, into the mixture of zirconium phosphate and water, and stirring the mixture for 2-4 hours to form a solution;
g) transferring the solution into a teflon-lined auto clave and keeping the solution at 130-180 °C for 2-4 hours in a hot air oven to prepare a solid white product or refluxing the solution at 80-100 oC for 4-12 hours to prepare a solid white product;
h) washing and drying the solid white product with water to obtain the functionalized or modified zirconium phosphate.
2. The process as claimed in claim 1, wherein the o-phosphoric acid is in an amount in a range of 70-90 wt% and zirconium oxychloride is in an amount in a range of 10-30 wt%.
3. The process as claimed in claim 1, wherein the zirconium phosphate is in an amount in a range of 80-90 wt% and sebacic acid or sodium dodecyl benzene sulfonate or oleic acid, or dodecyl amine, or triethoxy(octyl)silane is in an amount in a range of 10-20 wt%.
4. The process as claimed in claim 1, wherein the water is deionized water.
5. A composition, comprising:
- zirconium phosphate or functionalized or modified zirconium phosphate in an amount of 0.01 to 3wt%; and
- grease in an amount of 97 to 100wt%.