1. A mixed liquid crystal lubricant is characterized in that the mixed liquid crystal lubricant is selected from biphenyl compounds or the combination of dibenzyl ester compounds and phenyl biphenyl acetylene compounds,

the biphenyl compounds are selected from the following formulas:

wherein R is¹，R²，R³The radicals are all selected from alkyl, alkeneAlkyl, alkynyl, alkoxy, H, F, Cl, CF₃，OCF₃Any one or combination of more of CN;

the dibenzyl ester compounds are selected from the following formulas:

wherein R is⁴，R⁵，R⁶，R⁷，R⁸，R⁹The groups are all selected from alkyl, alkenyl, alkynyl, alkoxy, H, F, Cl and CF₃，OCF₃Any one or combination of more of CN;

the phenyl biphenyl acetylene compound is selected from the following formulas:

wherein R is^a，R^b，R^c，R^dThe groups are all selected from alkyl, alkenyl, alkynyl, alkoxy, H, F, Cl and CF₃，OCF₃And any one or combination of more of CN.

2. The hybrid liquid crystal lubricant of claim 1, wherein R is¹，R²，R³，R⁴，R⁵，R⁶，R⁷，R⁸，R⁹，R^a，R^b，R^c，R^dThe group is selected from alkyl, alkenyl, alkynyl, alkoxy including straight or branched chain alkyl, alkenyl, alkynyl, alkoxy.

3. The hybrid liquid crystal lubricant of claim 2, wherein R is¹，R²，R³，R⁴，R⁵，R⁶，R⁷，R⁸，R⁹，R^a，R^b，R^c，R^dThe number of carbon atoms in the group selected from alkyl, alkenyl, alkynyl and alkoxy is C1-C7.

4. The mixed liquid crystal lubricant as claimed in claim 1, wherein the biphenyl compounds or dibenzyl ester compounds account for 50-90% of the mixed liquid crystal by mass, and the balance is phenyl biphenyl acetylene compounds.

5. Use of the mixed liquid crystal lubricant according to any one of claims 1 to 4 as a lubricant for matching silicon nitride and polyimide materials.

6. A ultra-smooth system matched with silicon nitride/polyimide under liquid crystal lubrication is characterized in that: the ultra-slip system is silicon nitride/polyimide as a friction pair and the mixed liquid crystal lubricant of claim 1 as a lubricant.

7. The ultra-smooth liquid crystal lubricated silicon nitride/polyimide mating system of claim 6, wherein: the polyimide is a 6FDA-ODA type polyimide material.

8. The ultra-smooth liquid crystal lubricated silicon nitride/polyimide mating system of claim 6, wherein: the coefficient of friction of the ultra-smooth system is of the order of 0.001.

Background

Friction is an inevitable phenomenon in daily life and industrial production, and is accompanied by abrasion when friction occurs. Energy waste caused by friction and abrasion accounts for about 30% of global disposable energy, and the loss caused by the energy waste accounts for about 2-7% of GDP of each country every year. The use of advanced lubrication techniques is an effective way to solve this problem. The ultra-smooth is a revolutionary technology with friction energy consumption and wear rate expected to be reduced by several orders of magnitude, and due to the excellent characteristics of ultra-low friction coefficient and near-zero wear rate, the ultra-smooth friction material provides important support for future industrial progress and social development.

Silicon nitride (Si)₃N₄) The inorganic matter is an atomic crystal, is an important structural ceramic material, has the characteristics of high strength, high temperature resistance, high hardness, good comprehensive mechanical property, thermal shock resistance, high-temperature oxidation resistance, self-lubrication, wear resistance, corrosion resistance and the like, and is widely used in the field of mechanical industry for manufacturing mechanical components such as bearings, gas turbine blades, mechanical seal rings, permanent molds and the like; in the chemical industry, as wear-resistant, corrosion-resistant parts, such as ball valves, pump bodies, combustion carburetors, filters, etc.; in the field of metallurgical industry, because silicon nitride ceramics are high temperature resistant, have small friction coefficient and self-lubricating property, and are stable to most metals and alloy solutions, the silicon nitride ceramics can be used for manufacturing dies for processing metal materials, such as pipe-pulling core rods, extrusion dies, wire-pulling dies, rollers, conveying rollers, heating body clamps, thermocouple sleeving, metal heat treatment supporting members, crucibles, aluminum liquid guiding bags, aluminum bag linings and the like. Meanwhile, as a ceramic material, the ceramic material has wide application in the aspects of electronics, military and nuclear industries. Because silicon nitride has the characteristics of wear resistance, corrosion resistance, high temperature resistance, oxidation resistance, thermal shock resistance, low specific gravity and the like which are difficult to compare with common metal materials, the silicon nitride can bear the severe working environment which is difficult to be met by metal or high polymer materials, becomes a key basic material for supporting the prop industry in the 21 st century after the metal materials and the high polymer materials, becomes one of the most active research objects, and is considered as a candidate material with the most application potential in high-temperature structural ceramics.

Nevertheless, the direct use of silicon nitride as a self-lubricating wear-resistant material still has the problems of excessive friction and high friction coefficient, and still has important significance in realizing the ultra-smooth technology of a silicon nitride material operation system.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the ultra-smooth system of the silicon nitride/polyimide matching pair under the liquid crystal lubrication, the ultra-smooth system takes liquid crystal as a lubricant to be used in a moving system of the silicon nitride and polyimide matching pair, the friction between friction pairs can be effectively reduced, the friction coefficient is up to 0.001 magnitude, and the ultra-smooth phenomenon occurs.

The technical scheme provided by the invention is as follows: a liquid crystal lubricant is a mixed liquid crystal selected from the combination of biphenyl compounds or dibenzyl ester compounds and phenyl biphenyl acetylene compounds.

The biphenyl compound in the liquid crystal lubricant is selected from biphenyl compounds shown in the following formula:

further, said R¹，R²，R³The group is selected from alkyl, alkenyl, alkynyl, alkoxy including straight or branched chain alkyl, alkenyl, alkynyl, alkoxy, H, F, Cl, CF₃，OCF₃And any one or combination of more of CN.

The dibenzyl ester compounds in the liquid crystal lubricant are selected from the dibenzyl ester compounds shown in the following formula:

further, said R⁴，R⁵，R⁶，R⁷，R⁸，R⁹The group is selected from alkyl, alkenyl, alkynyl, alkoxy including straight or branched chain alkyl, alkenyl, alkynyl, alkoxy, H, F, Cl, CF₃，OCF₃And any one or combination of more of CN.

The phenyl biphenyl acetylene compounds in the liquid crystal lubricant are selected from phenyl biphenyl acetylene compounds shown in the following formula:

further, said R^a，R^b，R^c，R^dThe group is selected from alkyl, alkenyl, alkynyl, alkoxy including straight or branched chain alkyl, alkenyl, alkynyl, alkoxy, H, F, Cl, CF₃，OCF₃And any one or combination of more of CN.

Further, said R¹，R²，R³，R⁴，R⁵，R⁶，R⁷，R⁸，R⁹，R^a，R^b，R^c，R^dThe number of carbon atoms in the group selected from alkyl, alkenyl, alkynyl and alkoxy is C1-C7.

The liquid crystal lubricant is used as a lubricant under the matching of silicon nitride and polyimide materials.

Further, the liquid crystal lubricant is used as a lubricant of a component of the mixed liquid crystal, the biphenyl compound or the dibenzyl ester compound accounts for 50-90% of the mixed liquid crystal by mass, and the balance is the phenyl biphenyl acetylene compound.

The ultra-smooth system is characterized in that silicon nitride/polyimide is used as a friction pair, and the mixed liquid crystal lubricant is used as a lubricant.

Further, the polyimide material is a 6FDA (4,4'- (hexafluoroisopropanol) dicarboxylic anhydride) -ODA (4,4' -oxybisbenzzenamine) type polyimide material.

The invention provides a super-slip system which takes liquid crystal under a series of silicon nitride and polyimide matching pairs as a lubricant, the system takes mixed liquid crystal prepared by biphenyl compounds or dibenzyl ester compounds and phenyl biphenyl acetylene compounds as the lubricant, silicon nitride and 6FDA-ODA type polyimide materials are matched, the friction coefficient of the motion system is as low as 0.001 magnitude, and the stable super-slip phenomenon is realized.

Drawings

FIG. 1 is a molecular structural formula of biphenyl compounds in the mixed liquid crystal lubricant of the present invention;

FIG. 2 is a molecular structural formula of a dibenzyl ester compound in the mixed liquid crystal lubricant of the present invention;

FIG. 3 is a molecular structural formula of phenyl biphenyl acetylene compounds in the mixed liquid crystal lubricant of the present invention;

FIG. 4 is a molecular structural formula of a 6FDA-ODA type polyimide material used in the present invention;

FIG. 5 is a molecular structural formula of 5CB liquid crystal used in the present invention;

FIG. 6 is a structural diagram of a liquid crystal molecule of 3UTPP2 used in the present invention;

FIG. 7 is a 5CB-3UTPP2 mixed liquid crystal lubricated Si of the present invention₃N₄A plot of friction coefficient versus time for the/6 FDA-ODA couple;

FIG. 8 is a structural formula of a 3PEP5 liquid crystal molecule used in the present invention;

FIG. 9 is a structural diagram of a liquid crystal molecule of 3UTPP4 used in the present invention;

FIG. 10 is a 3PEP5-3UTPP4 mixed liquid crystal lubricated Si of the present invention₃N₄A plot of friction coefficient versus time for the/6 FDA-ODA couple;

FIG. 11 is a 5CB-3UTPP4 mixed liquid crystal lubricated Si of the present invention₃N₄A plot of coefficient of friction versus time for the/6 FDA-ODA couple, a)5CB (75%) +3UTPP4 (25%), b)5C (80%) +3UTPP4 (20%);

FIG. 12 is a view of the present invention of Si without lubricant₃N₄A plot of friction coefficient versus time for the/6 FDA-ODA couple;

FIG. 13 shows a biphenyl molecular liquid crystal 5CB lubricating Si of the present invention₃N₄A plot of friction coefficient versus time for the/6 FDA-ODA couple;

FIG. 14 shows the dibenzyl ester molecular liquid crystal 3PEP5 lubricating Si of the present invention₃N₄A plot of friction coefficient versus time for the/6 FDA-ODA couple;

FIG. 15 is a liquid crystal molecular structural formula of 2UTPP3 of the present invention;

FIG. 16 is a liquid crystal molecular structural formula of 4UTPP3 of the present invention.

Detailed Description

The technical solution of the present invention will be clearly and completely described below with reference to the specific embodiments and the accompanying drawings.

In the following examples, a micro-friction test was carried out using a UTM-3 type micro-friction tester (Bruker, Germany). In the test, a silicon nitride ball (diameter: 4.45mm) produced by Shanghai research institute was used as a static test piece, a 6FDA-ODA type polyimide material was attached to a fixed disk as a disk test piece in rotational motion, and the disk test piece was rotated at 50rpm with a radius of the circular friction path of 8.5 mm. The test load was applied vertically through the center line of the ball specimen and the test was conducted in a point-surface contact mode. Under the load condition of 5N, 0.1 to 0.2ml of liquid crystal was dropped or no liquid crystal was added as a lubricant between the silicon nitride spheres and the 6FDA-ODA type polyimide material, and the test was carried out at room temperature. During the test, the coefficient of friction (COF) was automatically recorded by a computer, and then the average coefficient of friction was calculated by software.

Example 1

Mixed liquid crystal lubricants formulated with 5CB monomolecular liquid crystal (75 wt.%) as shown in FIG. 5 and 3UTPP2 monomolecular liquid crystal (25 wt.%) as shown in FIG. 6 as Si₃N₄The lubricant of the sports system under the/6 FDA-ODA pair is tested for 1h, and the friction coefficient of the lubricant changes along with time is shown in figure 7. The average friction coefficient of the process is 0.006635, and the motion system is in a stable ultra-smooth state.

Example 2

Mixed liquid crystal lubricants formulated with 3PEP5 monomolecular liquid crystal (90 wt.%) as shown in FIG. 8 and 3UTPP4 monomolecular liquid crystal (10 wt.%) as shown in FIG. 9 as Si₃N₄The lubricant of the sports system under the 6FDA-ODA pair is tested on the same friction pair for 3 periods of 1h, and the time-dependent change of the friction coefficient is shown in figure 10, wherein 5N- (3PEP5-3UTPP4) - (6FDA-ODA)/SI is shown in the figure₃N₄- (1), 3PEP5-3UTPP4 mixed liquid crystal lubrication, Si under 5N load₃N₄5N- (3PEP5-3UTPP4) - (6FDA-ODA)/SI, a graph of the coefficient of friction over time in the first test period with a 6FDA-ODA accessory₃N₄-(2)，5N-(3PEP5-3UTPP4)-(6FDA-ODA)/SI₃N₄- (3), and so on.

The average coefficient of friction for this process is reported in table 1. The system was in a super-slippery state during the test.

TABLE 13 PEP5-3UTPP4 liquid crystal lubricated Si₃N₄Average of each test cycle under a/6 FDA-ODA pairingCoefficient of friction

Example 3

Mixed liquid crystal lubricants formulated with 5CB monomolecular liquid crystal (75 wt.%) as shown in FIG. 5 and 3UTPP4 monomolecular liquid crystal (25 wt.%) as shown in FIG. 9 as Si₃N₄The lubricant of the motion system under the/6 FDA-ODA pair is tested on the same friction pair for 1h in 3 cycles, and the time-dependent change of the friction coefficient is shown in a graph of FIG. 11-a, wherein the graph is illustrated as example 2. It can be observed from fig. 11-a that in the first test cycle, the kinematic system enters a stable super-slip state after 1000 s. Also the locomotor system was in a stable super-slippery state throughout the second and third test cycles.

The average coefficient of friction for this process is reported in table 2.

Table 25 CB-3UTPP4 liquid crystal (5CB (75 wt.%) +3UTPP4(25 wt.%)) lubricating Si₃N₄Average coefficient of friction per test period for the 6FDA-ODA couple

Example 4

Mixed liquid crystal lubricants formulated with 5CB monomolecular liquid crystal (80 wt.%) as shown in FIG. 5 and 3UTPP4 monomolecular liquid crystal (20 wt.%) as shown in FIG. 9 as Si₃N₄The lubricant of the motion system under the/6 FDA-ODA pair is tested on the same friction pair for 4 cycles of 1h, and the time-dependent change of the friction coefficient is shown in a graph of fig. 11-b, wherein the graph is illustrated as example 2. The average coefficient of friction for this process is reported in table 3. From FIG. 11-b and Table 3, it can be observed that in the first test cycle, the motilesThe stable super-slippery state is entered after 1650s, although the average coefficient of friction for this period is slightly over the order of 0.001. The exercise system is always in a stable super-slippery state during the second, third and fourth test cycles.

Table 35 CB-3UTPP4 liquid crystal (5CB (80 wt.%) +3UTPP4(20 wt.%)) lubricous Si₃N₄Average coefficient of friction per test period for the 6FDA-ODA couple

Comparative example 1

Without liquid crystal lubrication, Si₃N₄The 1h test is carried out under a 6FDA-ODA accessory, the friction coefficient of the process is always large along with the time change graph shown in figure 12, the average friction coefficient is far larger than 0.001 order of magnitude, and the motion system is not in a super-slip state.

Comparative example 2

Using monomolecular liquid crystal 5CB (shown in FIG. 5) as Si₃N₄The lubricant of the motion system under the/6 FDA-ODA pair is tested on the same friction pair for 1h in 3 cycles, and the time-dependent change of the friction coefficient is shown in figure 13, wherein the curve is shown in example 2. The average coefficient of friction for this procedure is reported in table 4. As shown in fig. 13 and table 4, the locomotion system was not in the super-slippery state.

TABLE 4 liquid Crystal 5CB lubricating Si₃N₄Average coefficient of friction per test period for the 6FDA-ODA couple

Comparative example 3

Monomolecular liquid crystal 3PEP5 (shown in FIG. 8) was used as Si₃N₄The lubricant of the motion system under the/6 FDA-ODA pair is tested on the same friction pair for 1h in 3 cycles, and the time-dependent change of the friction coefficient is shown in a graph as example 2 in figure 14. Average friction of the processThe coefficients are reported in table 5. As shown in fig. 14 and table 5, the locomotion system was not in the super-slippery state.

TABLE 5 liquid Crystal 3PEP5 Lubricant Si₃N₄Average coefficient of friction per test period for the 6FDA-ODA couple

The experimental results show that: without liquid crystal lubrication, Si₃N₄When the/6 FDA-ODA is matched, the friction coefficient does not reach 0.001 order of magnitude, and the ultra-smooth phenomenon is not realized; using monomolecular liquid crystals as lubricant, Si₃N₄When the/6 FDA-ODA type polyimide material is matched, the ultra-smooth behavior of 0.001 order of magnitude is not realized, and the mixed liquid crystal provided by the invention is used as a lubricant, and Si₃N₄When the/6 FDA-ODA type polyimide material is matched with a pair, the friction between friction pairs can be effectively reduced, the friction coefficient in a stable motion state is all as low as 0.001 order of magnitude, and the ultra-smooth behavior of a system is realized.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.