CN110759719A

CN110759719A - Diamond ceramic microcrystalline abrasive and preparation method thereof

Info

Publication number: CN110759719A
Application number: CN201910615771.4A
Authority: CN
Inventors: 薛冰; 叶现军; 刘海红; 陈泽秋
Original assignee: Qingdao Hanxing Environmental Protection Technology Co Ltd
Current assignee: Qingdao Hanxing Environmental Protection Technology Co Ltd
Priority date: 2019-07-09
Filing date: 2019-07-09
Publication date: 2020-02-07

Abstract

The invention discloses a diamond composite ceramic microcrystalline abrasive which comprises alumina crystals and silicon carbide particles existing among the alumina crystals, and comprises the following components of seed crystal particles of α -alumina formation of 1.50-3.50, SiC of 1.50-3.50 and ZrO of 0.05-0.30₂Or TiO₂Molar equivalents of at least one alkali metal oxide; and 92.1 to 96.48 wt% of Al₂O₃(ii) a Wherein the abrasive is based on theoretical oxides of each componentThe sum of the contents of all components in the particles is 100, the silicon carbide particles are introduced into the ceramic microcrystal abrasive material, the unique microstructure of the ceramic microcrystal abrasive material cannot be changed, and the hardness of the obtained product is greatly improved, so that the problem of hardness reduction caused by a modifier is solved, and the obtained product maintains high toughness and high hardness.

Description

Diamond ceramic microcrystalline abrasive and preparation method thereof

Technical Field

The invention relates to the technical field of abrasives, in particular to a diamond ceramic microcrystalline abrasive and a preparation method thereof.

Background

The ceramic microcrystal abrasive belongs to a sintered abrasive, is different from the traditional fused corundum abrasive, and leads the artificial abrasive to show the trend of developing towards high toughness and high hardness. The sol-gel method is adopted for preparation, so that the product has a unique microstructure, and the final product has good self-sharpening property. Therefore, the bonded or coated abrasive tool made of the ceramic abrasive has the advantages of high grinding efficiency, long service life and the like, and can process difficult-to-grind materials, and the like, and the bonded or coated abrasive tool is widely researched and produced in recent years.

α -alumina is widely used as an abrasive in the abrasives industry, it can be used in pure form or more preferably in the form of an alumina containing additives to enhance its abrasive properties β -alumina is a form of alumina in which metal ions other than aluminum and oxygen are contained in the crystal lattice β -alumina generally exhibits inferior properties as an abrasive compared to α -alumina many commercially important α -alumina abrasive particles are derived from sol-gel precursors made by preparing a dispersion (e.g. a sol) comprising water, α -alumina precursors such as alumina monohydrate (boehmite) and optionally a peptizing agent such as an acid such as nitric acid, then gelling the dispersion, drying the gelled dispersion, crushing the dried dispersion into particles, calcining the particles to remove volatiles, and sintering the calcined particles at temperatures below the melting point of α -alumina-in many cases, the dispersion further comprises one or more oxide modifiers (e.g. Rare Earth Oxides (REO), Cr2O 38, CoO 2O, NiO 582, NiO O, NiO 6326, NiO

Common ceramic microcrystalline abrasives in the market at present comprise SG abrasives of Saint-gobain company and CUBITRON abrasives of 3M company, wherein white SG abrasives of Saint-gobain have the characteristics of ultrahigh hardness, fine crystals and good self-sharpening property, and although the toughness is obviously superior to that of common fused corundum abrasives, the toughness is still obviously different from that of CUBITRON of 3M; the modifier is added into the 3M CUBITRON product to generate a two-phase structure, the toughness of the product is remarkably improved, but the purity of alumina is reduced due to the addition of the modifier, so that the hardness of the product is obviously reduced and is only equivalent to the microhardness of brown corundum.

Disclosure of Invention

The invention aims to solve the technical problem of providing a diamond ceramic microcrystalline abrasive and a preparation method thereof, and aims to solve the problem that the high microhardness and the high toughness of the ceramic microcrystalline abrasive in the prior art cannot be simultaneously met.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a diamond-shaped composite ceramic microcrystalline abrasive comprising alumina crystals and silicon carbide particles present between said alumina crystals, comprising,

1.50 to 3.50 seed crystal particles of an α -alumina formation, 1.50 to 3.50 SiC;

0.05 to 0.30 ZrO₂Or TiO₂Molar equivalents of at least one alkali metal oxide;

and 92.1 to 96.48 wt% of Al₂O₃；

Wherein the sum of the contents of the components in the abrasive particles is 100 based on the theoretical oxides of the components

Preferably, the alumina crystals have interconnected lamellar structures.

As a preferred technical scheme, the density of the abrasive is more than 4.5g/cm³What is, what isThe microhardness of the abrasive is 23GPa, and the grain size of the alumina crystal is not more than 3 um.

As a preferred technical scheme, the method for manufacturing the diamond-shaped composite ceramic microcrystalline abrasive comprises the following steps:

1) mixing deionized water, superfine α -alumina particles, zirconia sol, titania sol, nano iron oxide or/and metal nitrate, and uniformly stirring to obtain a solution A;

2) adding boehmite rubber powder into the solution A, and stirring for 10-30 minutes to obtain gel B;

3) adding silicon carbide particles into the gel B, and stirring for 10-30 minutes to obtain a plastic body C;

4) removing air in the plastomer C obtained in the step 3) to obtain an embryo body D;

5) drying and crushing the embryo body D obtained in the step 4) at the temperature of not higher than 120 ℃ to obtain crushed particles;

6) sequentially carrying out low-temperature calcination and high-temperature sintering on the crushed particles obtained in the step 5), wherein the low-temperature calcination temperature is 700-900 ℃, and the high-temperature sintering temperature is 1250-1500 ℃;

7) screening the abrasive particles sintered at high temperature in the step 6).

As a preferable technical scheme, the weight of the boehmite rubber powder is 60-90% of the weight of the deionized water.

According to a preferable technical scheme, the weight of the silicon carbide particles is 10% -60% of that of the deionized water.

As a preferable technical scheme, the weight of the ultrafine α -alumina particles or the nano iron oxide is 1 to 1.8 percent of the weight of the boehmite rubber powder.

As a preferable technical scheme, the weight of the zirconia sol or the titania sol is 1.8 to 2.5 percent of the weight of the boehmite rubber powder.

As a preferable technical scheme, the weight of the metal nitrate is 2-8% of the weight of the boehmite rubber powder.

By adopting the technical scheme, the silicon carbide particles are introduced into the composite ceramic microcrystalline abrasive, the unique microstructure of the ceramic microcrystalline abrasive is not changed, and the hardness of the abrasive product is greatly improved due to the microhardness of the silicon carbide, which is about 29GPa-30GPa, so that the problem of hardness reduction caused by a modifier is solved, and the obtained product not only maintains high toughness, but also maintains high hardness.

Detailed Description

The following further describes the embodiments of the present invention. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1

A preparation method of a diamond ceramic microcrystalline abrasive comprises the following steps:

step 1, mixing deionized water and a sintering modification auxiliary agent and uniformly stirring to obtain a solution A;

step 2, adding boehmite rubber powder into the solution A, and stirring for 10-30 minutes to obtain gel B;

step 3, adding silicon carbide particles into the gel B, and stirring for 10-30 minutes to obtain a plastic body C;

step 4, removing air in the plastomer obtained in the step 3 to obtain an embryo D;

step 5, drying and crushing the embryo body in the step 4 at the temperature of not higher than 120 ℃ to obtain crushed particles;

step 6, sequentially carrying out low-temperature calcination and high-temperature sintering on the crushed particles obtained in the step 5, wherein the low-temperature calcination temperature is 700-900 ℃, and the high-temperature sintering temperature is 1250-1500 ℃;

and 7, screening the abrasive particles sintered at high temperature in the step 6.

The sintering modification auxiliary agent comprises superfine α -alumina particles, zirconia sol, titania sol, nano iron oxide or/and metal nitrates, wherein the metal nitrates comprise magnesium nitrate, zinc nitrate, cobalt nitrate, chromium nitrate, gadolinium nitrate, lanthanum nitrate, neodymium nitrate, ytterbium nitrate and the like.

The superfine α -alumina particles and nano-iron oxide can be used as seed crystal materials, the aim is to reduce the sintering temperature to obtain compact abrasive particles at a lower sintering temperature, the zirconia sol and the titania sol can change the grain boundary characteristics of the microcrystal of the product and prevent the microcrystal from rapidly growing up in a high-temperature process to cause the quality reduction of the product, and the seed crystal materials can be used independently or can be used together with the zirconia sol and the titania sol.

This example will be described in detail below by taking as an example the use of the seed material ultrafine α -alumina fine particles in combination with a zirconia sol.

20KG of deionized water dispersion containing ultrafine α -alumina particles is added into a vacuum kneader with the capacity of 100L, and the preparation method of the dispersion comprises the steps of loading boehmite rubber powder into an alumina crucible, placing the alumina crucible into a muffle furnace, heating to 1250 ℃, preserving the temperature for 1h to obtain α -alumina particles, cooling, adding 150g of ultrafine α -alumina particles and 20KG of deionized water into a vibration grinder (wherein the grinding medium of the vibration grinder is alumina balls), and grinding for 24h to finally obtain the deionized water dispersion of the ultrafine α -alumina particles.

Wherein, the boehmite rubber powder is a powdery material obtained by drying and grinding boehmite sol.

Then, 280g of zirconia sol (wherein the solid content of the zirconia sol is 10% and the particle size is 5nm-10nm) is added into the dispersion liquid, a vacuum kneader is started to stir to obtain a solution A, 20kg of boehmite rubber powder is added to mix and stir for 30min to obtain a gel B, 4.2kg of silicon carbide particles are added into the gel B to mix for 30min, and then the material becomes a plastic body with high viscosity.

The silicon carbide particles can be from fine-grained micropowder granular silicon carbide produced in the traditional silicon carbide abrasive industry, and can also be from submicron-diameter fibrous or submicron-thickness flaky silicon carbide synthesized by a new process, the addition of the silicon carbide can obviously improve the hardness of the abrasive particles, the addition amount of the silicon carbide particles is 5-70% of the weight of the rubber powder, in the embodiment of the invention, the silicon carbide particles are granular silicon carbide particles, and the particle size requirement of the silicon carbide particles is less than 0.7 um.

After the preparation of the plastic body is completed, the air in the body needs to be extruded, in the examples of the invention, this is to be eliminated: the plastic body is transferred into a vacuum pug mill, the vacuum pug mill can remove air in the plastic body, and due to kneading and extruding effects of the screw on the pug, the directional structure of the pug is improved, the components are more uniform, and the fine mixing of the high-viscosity pug is completed. Continuously pugging twice to obtain a blank.

In the embodiment of the invention, the template can be additionally arranged at the discharge port after the second mud is connected, and the template is provided with different cross-sectional shapes, so that continuous strip-shaped blanks with various cross-sectional shapes can be prepared, the surface area of the blank can be increased, and the drying time and the energy consumption can be saved. The particles can be preliminarily molded in advance and used in combination with later-stage crushing equipment, so that the particles with sharp shapes more suitable for grinding can be obtained. For example, a common cross-sectional shape may be provided as: circular or rectangular. The sheet-shaped mud blank can be extruded, the thickness of the sheet is generally less than 1mm, the sheet-shaped mud blank is favorable for quick drying, the drying period is shortened, the energy consumption is saved, the sheet-shaped blank naturally cracks into fragments during drying, the larger fragments need to be crushed again in a crusher, and the crushed fragments are still sheet-shaped particles with reduced appearance.

In the embodiment of the invention, the template is provided with an elongated hole, and the cross section of the hole has the following dimensions: 10mm 1 mm. After the pugging is finished, a sheet-shaped continuous blank can be extruded from the template.

The embryo body is then dried to convert the embryo body from an aqueous plastic body to a brittle particle for later further extrusion or comminution into smaller particles, in embodiments of the invention, the embryo body is dried by: and (3) putting the stainless steel disc with the sheet blank into a hot air circulation oven or microwave drying equipment, setting the temperature to be 100 ℃, and taking out after 3 hours to obtain the dried discontinuous brittle fragments.

Then putting the brittle fragments into a disc crusher with the diameter of 250 to be crushed, discharging the materials to pass through a 14-mesh screen (namely the aperture of the screen is 1400um), and returning the particles with the overlarge particle size on the screen to be crushed again to finally obtain crushed particles.

The crushed particles need to be calcined, and the purpose of calcination is that the boehmite rubber powder in the mixing section and the sintering modification auxiliary agent contain water which is chemically combined water and can be volatilized at higher temperature. In addition, part of the sintering modification aid is decomposed at high temperature and finally becomes an oxide. The water and decomposition products need to be slowly released under a controllable temperature rising curve so as not to cause excessive cracks inside the particles to break and pulverize, and therefore, low-temperature calcination and high-temperature sintering are required to be sequentially carried out.

In the examples of the present invention, the calcination is carried out by: low-temperature calcination: loading the crushed particles into a sagger, feeding the sagger into a roller kiln for calcination, and setting temperature parameters as follows: uniformly heating from 0 ℃ for 1h to 300 ℃, uniformly heating from 300 ℃ for 1h to 500 ℃, uniformly heating from 500 ℃ for 1h to 800 ℃, and then preserving heat at 800 ℃ for 1 h; then carrying out high-temperature sintering: setting temperature at 1360 deg.C, maintaining for 30min, selecting high temperature sintering equipment such as roller kiln, pushed slab kiln, rotary furnace, etc., and various kilns capable of reaching sintering temperature can be adopted to obtain final density of 3.74g/cm³Abrasive particles having a microhardness of 25 GPa.

And finally, screening the abrasive particles sintered at high temperature: the sintered abrasive grains are screened by a proper screen to form the grain size composition required by the bonded and coated abrasive tools respectively specified in national standards GB/T9258.2-2008 and GB/T2481.1-1998 respectively. The screening equipment can be a linear screen, a circular vibrating screen, a shaking plate screen and the like, and the screen can be a national standard stainless steel net or a non-standard stainless steel net or a silk net for screen printing. The stainless steel net is required to be uniform in size, the silk net holes are good in elasticity and not easy to block, and the screening efficiency of the semi-finished product is high.

Example 2

The embodiment provides another preparation method of a diamond ceramic microcrystalline abrasive: adding 20kg of deionized water into a 100L vacuum kneader, then adding 650g of magnesium nitrate hexahydrate, 900g of neodymium nitrate hexahydrate and 60g of cobalt nitrate hexahydrate, then adding 280g of zirconia sol (same as example 1), starting the machine to stir for 5min to obtain solution A, adding 20kg of boehmite rubber powder to mix for 30min to obtain gel B, adding 4.2kg of granular silicon carbide micro powder (the grain size of the silicon carbide micro powder is less than 0.7um) into the gel B to mix for 30min, and changing the material into a plastic body with high viscosity.

After the preparation of the plastomer is completed, the air in the plastomer is removed: the plastic body is transferred into a vacuum pugging machine, mud is continuously connected for two times, a discharge hole after mud is continuously connected for the second time is additionally provided with a template, different section shapes are arranged on the template, and continuous strip-shaped blanks with various section shapes can be manufactured. 10mm 1 mm. After the pugging is finished, a sheet-shaped continuous blank can be extruded from the template.

The crushed particles need to be calcined, which in the examples of the invention is done by: low-temperature calcination: loading the crushed particles into a sagger, feeding the sagger into a roller kiln for calcination, and setting the same temperature parameters as those in the example 1; then carrying out high-temperature sintering: setting the temperature at 1400 deg.C, maintaining the temperature for 30min, selecting high temperature sintering equipment such as roller kiln, pushed slab kiln, rotary furnace, etc., and allowing various kilns to reach sintering temperature to obtain final density of 3.73g/cm³Abrasive grains having a microhardness of 22 GPa.

Example 3

This example provides another method for preparing a diamond-shaped ceramic microcrystalline abrasive, which includes adding 20kg of deionized water into a 100L vacuum kneader, adding 280g of zirconia sol (same as example 1), starting the machine to stir for 5min to obtain solution a, adding 20kg of boehmite rubber powder, mixing for 30min to obtain gel B, adding 1.4kg of silicon carbide nanowires (the diameter of the silicon carbide nanowires is 100nm-600nm, the length of the silicon carbide nanowires is 50um-100um) into the gel B, and mixing for 30min to obtain a plastic with high viscosity.

The crushed particles need to be calcined, which in the examples of the invention is done by: low-temperature calcination: loading the crushed particles into a sagger, feeding the sagger into a roller kiln for calcination, and setting the same temperature parameters as those in the example 1; then carrying out high-temperature sintering: setting the temperature at 1450 deg.C, maintaining the temperature for 30min, selecting high-temperature sintering equipment such as roller kiln, pushed slab kiln, rotary furnace, etc., and allowing various kilns to reach sintering temperature to obtain final density of 3.82g/cm³Abrasive grains having a microhardness of 24 GPa.

The embodiments of the present invention have been described in detail, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, and the scope of protection is still within the scope of the invention.

Claims

1. A diamond-shaped composite ceramic microcrystalline abrasive comprising alumina crystals and silicon carbide particles present between said alumina crystals, characterized by comprising the following components:

and 92.1 to 96.48 wt% of Al₂O₃；

Wherein the sum of the contents of the components in the abrasive particles is 100 based on the theoretical oxides of the components.

2. The diamond-shaped composite ceramic microcrystalline abrasive according to claim 1, wherein: the aluminum oxide crystals also have interconnected lamellar structures.

3. The diamond-shaped composite ceramic microcrystalline abrasive according to claim 1, wherein: the density of the abrasive is more than 4.5g/cm³The microhardness of the abrasive is 23GPa, and the grain size of the alumina crystal is not more than 3 um.

4. A method of making the diamond-shaped composite ceramic crystallite abrasive according to any one of claims 1 to 3, characterized in that: the method comprises the following steps:

5. The method of claim 4, wherein: the weight of the boehmite rubber powder is 60% -90% of the weight of the deionized water.

6. The method of claim 5, wherein: the weight of the silicon carbide particles is 10% -60% of the weight of the deionized water.

7. The method of claim 6, wherein the weight of the ultrafine α -alumina particles or nano iron oxide is 1-1.8% of the weight of the boehmite rubber powder.

8. The method of claim 6, wherein: the weight of the zirconia sol or the titania sol is 1.8 to 2.5 percent of the weight of the boehmite rubber powder.

9. The method of claim 6, wherein: the weight of the metal nitrate is 2-8% of the weight of the boehmite rubber powder.