JPH05156238A - Abrasive for mechanochemical grinding and method of grinding material piece - Google Patents

Abstract

PURPOSE: To provide an inexpensive abrasive which does not selectively wear off surface particles of a hardened product and does not cause surface roughness by mixing an aqueous slurry of colloidal silica with water and a specified mechanical abrasive.

CONSTITUTION: This agent comprises 13-99.2 wt.% aqueous slurry of colloidal silica having a pH of above 7, 0.7-85 wt.% water and 0.07-2.0 wt.% mechanical abrasive having a particle diameter of 0.1-10 μn and selected from one or more of the materials in the group consisting of Fe₂O₃, Fe₃O₄, MgO, BaCO₃, CaCO₃, MnO₂, CeO, SiO₂, CeO₂, Cr₂O₃ and Al₂O₃.

COPYRIGHT: (C)1993,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is a mechanochemical polishing abrasive for use in polishing hard substrates, such as ceramics, crystalline materials, glass and similar materials, which require highly polished surfaces. is there.

The economics of polishing and finishing ceramics are often the most expensive part of the ceramic manufacturing process. Economically considering the polishing of ceramics,
Both the time used and the consumables used are involved. In the final polishing of ceramics, diamond abrasives are uneconomically used.
The polishing process, which is expensive and uses diamond abrasives, is time consuming.

On the contrary, ceramic finishes are extremely susceptible to damage. Unlike metal finishes that are ductile,
Ceramics are generally extremely brittle. The brittle nature of ceramics makes them extremely fragile below the surface.
This subsurface damage adversely affects important physical properties of the ceramic. Such physical properties adversely affected by the finish reduce the strength of the ceramic, alter the magnetism of the ceramic, and even alter the electrical properties of the ceramic.

Advantageous ceramic finishes have traditionally been
Achieved with hard abrasives such as diamond or silicon carbide. Although this hard abrasive produced an acceptable surface under certain circumstances, it still left some surface and subsurface damage with this compound. The use of softer abrasive abrasives, such as colloidal silica, has been tested for advantageous ceramic finishes. Colloidal silica was found to polish alumina, silica and silicone.

In fact, colloidal silicic acid is uneconomically used for polishing silicone chips. However, the use of colloidal silicic acid to polish the preferred ceramic tends to produce a preferred polished ceramic product having substantial step irregularities. This irregularity is believed to be due to the chemical decomposition of selective particles on the preferred ceramic by colloidal silicic acid.

[0006]

The use of colloidal silicic acid for polished silicone surfaces, metals, glasses, garnets and sapphires has been described by H. S. W. Gutsche and
J. W. "Polishing of" by Moody
Sapphirewith Colloidal Sil
ica ”, J. Electrical Chemical
l Soc. 125, No. 1, 136-138,
(1978). This publication discloses that colloidal silicic acid has a chemical effect on hard sapphire materials which allow colloidal silicic acid to polish sapphire. This publication makes no mention of combining colloidal silicic acid with another abrasive to polish the cured material.

CaC as a polishing agent for mechanochemical polishing
Using O ₃ , BaCO ₃ and MgO is described in H. B
ora and R. J. Stokes, Study
of Mechanochemical Machi
Ning of Ceramics and the
Effect on Thin Film Behav
ior, United States Goverme
nt Report N00014-80-C-0437
-1 (April 30, 1981) published in the Official Gazette. This official gazette contains M by various abrasives including rock salt, calcite, fluorite and various other abrasives including window glass.
It details the polishing of thin layers of gO, Al ₂ O ₃ and Si. It has been found that the three compounds described above are mechanochemically polishable to one or more of the above materials. None of the mechanochemical abrasives used were combined with colloidal silicic acid.

Mechanochemical polishing of sapphire, silicone and quartz crystal plates is described in N. Yasunaga, U .;
Tarumi, A .; Obara, “Mechanis
mand application of the M
echanochemical Polishing
Method Using Soft Powder "
The Science of Ceramic Ma
chinig and Surface Finish
ing II, NBS special public
ation 562, U.S.A. S. Government P
printing Office, Washingto
n, D. C. , Pp. 171-183 (1979). Sapphire, silicone and quartz were polished using wet and dry mechanochemical media. The mechanochemical medium is BaCO ₃ , Fe ₃ O ₄ , CeC
_{O 2, SiO 2, CeO 2} , including a diamond and MnO _2. The first focus of this publication is the description of the composition of crystalline silicic acid in mixed powder abrasives during material polishing.
The crystalline material was produced by grinding the above hard material at high temperature and high pressure with mixed powder. This publication does not disclose the use of colloidal silicic acid in any method for mechanochemical polishing.

[0009]

The present invention has the above-mentioned problems.

[0010]

The object of the present invention is to provide an inexpensive mechanochemical polishing abrasive which is capable of abrading hardened material pieces without selectively abrading the surface particles of the hardened material pieces. Is to provide.

Another object of the present invention is to provide a method for polishing hardened material pieces with inexpensive mechanochemical abrasives. The present invention relates generally to mechanochemical abrasives. Mechanochemical abrasives
It consists of a slurry of colloidal silica containing one or more mechanical abrasives.

In a variant of this embodiment, the invention relates to a slurry of colloidal silicic acid, Fe ₂ O ₃ , Fe ₃ O ₄ ,
MgO, BaCO ₃ , CaCO ₃ , MnO ₂ , CeO, S
A mechanochemical abrasive consisting of a mechanical abrasive selected from one or more substances of the group consisting of iO ₂ , CeO ₂ , Cr ₂ O ₃ and Al ₂ O ₃ .

In a preferred embodiment, the present invention is a mechanochemical composition comprising from about 13 to about 99.3 wt% of a colloidal silicic acid base slurry and from about 0.7 to about 2.0 wt% mechanical abrasive. It is an abrasive for polishing. The mechanical abrasive has a particle size of about 0.1 micron to about 10 microns. Mechanical abrasives include Fe ₂ O ₃ , Fe ₃ O ₄ , MgO, BaCO ₃
, CaCO ₃ , MnO ₂ , CeO, SiO ₂ , CeO ₂
, Cr ₂ O ₃ and Al ₂ O ₃ are selected from one or more substances.

In another embodiment, the present invention is a method of polishing one or more pieces of material with a mechanochemical polishing abrasive. Abrasives for mechanochemical polishing include aqueous slurry of colloidal silicic acid, Fe ₂ O ₃ , Fe ₃ O ₄ ,
MgO, BaCO ₃ , CaCO ₃ , MnO ₂ , CeO,
Consisting of _{SiO 2, CeO 2, Cr 2} O 3 and Al ₂ O ₃ - mechanical polishing agent selected from one or more substances of the group consisting of. The piece of material is used with a mechanochemical polishing abrasive, either directly or with the piece, and the polishing device is contacted with the one or more pieces of material for a time sufficient to polish the surface of the piece of material. It is polished by.

The present invention relates to a mechanochemical polishing abrasive and a method of polishing a piece of material with the mechanochemical polishing abrasive. The mechanochemical polishing abrasive according to the present invention comprises a colloidal silicate material combined with a mechanical abrasive.

The colloidal silicate material containing the mechanochemical polishing abrasive reacts, according to the present invention, with the various surface components that make up the hardened material strip being abraded with the mechanochemical polishing abrasive. .. The exact chemical reaction that occurs between colloidal silicic acid and the elements and molecules on the surface of the piece of material is not completely understood. However, it is believed that the colloidal silicic acid reacts with the cured piece of material to produce a surface material of the piece of material that is softer than the mechanical abrasive. For the reasons mentioned above, one drawback with colloidal silicic acid is that when it acts on the described particles on the surface of the hardened support, so that the material surface is chemically modified by the colloidal silicic acid, it becomes uneven. It is clear that the surface finish of the can occur.

Colloidal silicic acid is typically supplied in an aqueous (hydrous) slurry composed of up to 50% or more of colloidal silicic acid. One important feature of colloidal silicic acid slurries is that colloidal silicic acid does not precipitate out of the slurry even after extended periods of time. Colloidal silicic acid is generally included in an aqueous slurry that is combined with water. However, for the purpose of the abrasive for polishing according to the present invention, the colloidal silicic acid need not be a slurry with water, and, in some cases, should not be a slurry with water, although alcohols and organic solvents or It may be some other liquid, such as a similar material.
Water is not desirable in all cases as a slurry of material, since water can adversely react with some pieces of hardened material to produce a useless product.

The preferred colloidal silicic acid is an aqueous slurry of colloidal silicic acid. The content of colloidal silicic acid in the aqueous slurry in% by weight is not critical. However, it is advantageous for the colloidal silicic acid to be in the range of about 15-50% by weight or more in the aqueous slurry.

Other properties of the colloidal silicic acid slurry, such as pH, particle size, etc., are of no importance to the usefulness of the colloidal silicic acid slurry in its chemical reaction with the surface of the cured piece of material. However, p of colloidal silica slurry
It is advantageous if H is about 7 or more. PH above 7
It has been found that the colloidal silicic acid slurries having ## STR4 ## are base slurries and react more efficiently with the surface of materials that can be abraded using the mechanochemical abrading agent of the present invention.

Advantageous aqueous slurries of colloidal silicic acid may be the known colloidal silicic acid slurries. Generally, colloidal silicic acid is stabilized within a pH range of about 8-14 and especially about 9-11. The preferred colloidal silica has a pH in the range of about 9.8 to 10.2 and an average particle size of about 0.06 micron. In addition, the mechanochemical abrasive abrasive contains a mechanical abrasive. Mechanical abrasives are generally softer than the material from which the piece of material is made. However, mechanical abrasives are generally harder than the surface material of a piece of material obtained by a chemical reaction between the colloidal silicic acid component of the abrasive abrasive and the hardened piece of material. The purpose of the mechanical abrasive is to polish the softer reacted material from the surface of the hardened piece of material that remains behind the surface of the smoothed piece of material. By polishing a softer reaction product consisting of the surface of the cured piece of material, the mechanical abrasive continuously exposes the cured surface to colloidal silicic acid which chemically reacts with the exposed surface. In this way, the highly abraded, hardened support surface area can be reduced to a minimum by the selective reaction of colloidal silicic acid with various selective particles on the surface of the hardened material strip.

The mechanical abrasive useful in the mechanochemical abrasive according to the present invention may be any material or compound of materials known in the art useful as a mechanical abrasive material. Mechanical abrasives are not as hard as the material of which the piece of material is made and are typically softer. Mechanical abrasive material, for example, be selected from one or more of the following _{components: Fe 2 O 3, Fe 3} O 4, MgO, BaCO 3, C
aCO ₃ , MnO ₂ , CeO, SiO ₂ , CeO ₂ , C
r ₂ O ₃ and Al ₂ O ₃ . An advantageous mechanical abrasive is Fe
₂ O ₃ . Mechanical abrasives from about 0.1 micron to about 1
It is also advantageous to have an average particle size of 0 micron and particularly preferably about 0.5 to 5.0 micron.

As mentioned above, the abrasive for mechanochemical polishing according to the present invention comprises a slurry of colloidal silica and 1
One or more mechanical abrasives. The mechanochemical polishing abrasive according to the present invention comprises about 0.1 grams of a powdered mechanical abrasive having 100 ml of colloidal silicic acid to enough colloidal silicic acid to convert the mechanochemical polishing abrasive into a viscous slurry. And an amount of mechanical abrasive in combination with. The amount of mechanical abrasive required to convert the mechanochemical abrasive abrasive into a viscous slurry varies depending on the mechanical abrasive used and the silicic acid content of the colloidal silicic acid.

Water or another diluent material such as alcohol, solvent, etc. may be added to the mechanical abrasive / colloidal silica mixture to modify the viscosity of the mechanochemical abrasive. Low viscosity mechanochemical abrasives are conveniently used on material strips. It covers the piece of material evenly and generally has good flowability and polishing properties.

Advantageously, the mechanochemical abrasive according to the present invention comprises a powdered mechanical abrasive of about 0.07 to about 2.0.
% By weight, about 13 to about 99.2% by weight colloidal silicic acid and about 0.7 to about 85% by weight water. Advantageously, the water is deionized water.

The mechanochemical abrasive according to the present invention is useful for polishing the surface of many different hardened material pieces. An abrasive for mechanochemical polishing according to the present invention,
It may be used to polish the surface of any material that can chemically react with a colloidal silica slurry. Examples of such materials are silicone (eg silicone wafer), sapphire, metal, glass, alumina, silicone nitride (Si ₃ N ₄ ), gallium arsenide (GaAs),
Includes magnesium oxide (MgO), zirconia and other hardened ceramic and non-ceramic materials.

The mechanochemical polishing abrasive according to the present invention may be used for polishing hardened material strips by any polishing apparatus known in the art for polishing hardened material strips. The polishing may be carried out by any polishing equipment, including by hand using pads and mechanochemical polishing abrasives or by mechanically using the liquid mechanochemical polishing abrasives according to the present invention. Pad is
Advantageously, it is connected to a machine for polishing a piece of material which has been hardened with the polishing abrasive according to the invention. The abrasive abrasive is applied to the pad or piece of material and then frictionally contacts at least one side of the piece of material covered by the abrasive during the polishing process. The piece of material is polished for a time sufficient to polish the surface of the piece of material for the desired finish.

The polishing environment, including pressure and temperature, affects the material polishing rate. However, abrasives are effective over a wide range of pressures and temperatures when polishing material pieces. Certain pressures and temperatures are not necessary for mechanochemical abrasives because the mechanochemical abrasives are effective.

Some advantageous examples according to the invention are set out below. However, many other examples are within the scope of the invention.

[0029]

Examples Example 1: The alumina (Al ₂ O ₃ ) in this example was polished with various abrasives, including mechanical abrasives, chemical abrasives and mechanochemical abrasives according to the invention. The abrasives were evaluated for their ability to remove surface material from the pieces of alumina material over time.

The surface of the piece of alumina material was worked by rubbing a composite plate having 30 micron diamond particles on the hard polymer and subsequently rubbing a composite plate having 6 micron diamond particles on the soft polymer. After processing the surface of alumina, Knoop hardness (Knoop
Indent) was made into a piece of cured material with a load of 5 kg and was indented at a loading of 70 microns / second with a loading time of 15 seconds. Material removal was obtained by measuring the decrease in Knoop hardness over the length of the diagonal over time. Both a vibration sander and a semi-automatic sander were used.
Vibratory polishing was used to minimize mechanical strain. The test was monitored for 24 hours. A semi-automatic sander was used to provide the added mechanical strain.

The polishing treatment was carried out on a polishing cloth TEXMET® sold by Buehler.

The outline of the polishing results for alumina material piece is in Table 1 below: first table Labs milling rate how Research friction agent (microns / h) vibration Fe ₂ O ₃ 0.002 Lab Polished colloidal silicic acid 0.042 Fe ₂ O ₃ + (colloidal silicic acid) 0.125 (micron / sec) Mechanical Fe ₂ O ₃ 0 Rotary colloidal silicic acid 0.26 Polished 1/4 micron diamond 0 3 micron diamond 0.21 Fe ₂ O ₃ + (colloidal silicic acid) 0.35 When both vibration polishing and mechanical rotary polishing are used,
A mechanochemical polishing abrasive according to the present invention, consisting of a colloidal silicic acid slurry in combination with a mechanical abrasive, Fe ₂ O ₃ , has a higher polishing rate than both colloidal silicic acid or Fe ₂ O ₃ alone. Alumina can be polished. Additionally, the polishing rate for colloidal silicic acid / Fe ₂ O ₃ abrasives is significantly higher than that of the combination of colloidal silicic acid and Fe ₂ O ₃ (0.125 micron / h for vibration polishing). 0.044 micron / h and 0.3
5 micron / sec vs. 0.26 micron / sec for rotary polishing).

This example clearly shows that the mechanochemical polishing abrasives according to the invention surprisingly have superior polishing rates compared to colloidal silicic acid or mechanical abrasives alone or in combination. It was

EXAMPLE 2 Samples showing Knoop hardness of alumina, silicone nitride and zirconia were prepared using the same vibration polishing method as described above, colloidal silicic acid, various mechanical abrasives and various mechanochemicals according to the invention. Polished with an abrasive. Mechanochemical polishing medium is Al ₂ O ₃ , C
1 l of a solution consisting of 490 ml of aqueous colloidal silicic acid with either 20 g of eO ₂ , Cr ₂ O ₃ or Fe ₃ O _2.
Composed of. The aqueous colloidal silicic acid has a pH of about 10.0, an average particle size of about 0.05 to 0.07 micron, and a specific gravity of 1.390.
And contained 50% solids. Deionized water 5
ml was added to the mixture to complete the formulation.

Vibration polishing was used to polish various samples for 24 hours. The polishing rate of each abrasive at micron / h was measured. The results of vibration polishing of three samples are given in Table 2 below: Table 2 Mechanochemical polishing rate (microns / h) polishing medium Alumina Silicon Nitrido Zirconia Al ₂ O ₃ + colloidal silica 0.045 0.04. 163 0.173 Ce ₂ O ₃ + colloidal silicic acid 0.027 0.300 0.1875 Ce ₂ O ₃ 0.006 0.135 ------ Fe ₂ O ₃ + colloidal silicic acid 0.125 0.300 0 .448 Fe ₂ O ₃ 0.003 0.042 0.173 Cr ₂ O ₃ + colloidal silica 0.148 0.188 0.233 Cr ₂ O ₃ 0.00 0.058 0.00 (CS) colloidal silica 0 0.044 ------ 0.058 The colloidal silicic acid used above is the same colloidal silicic acid used in the mechanochemical polishing abrasive. No water was added to the colloidal silicic acid before it was used for testing purposes. A slurry consisting of each of the mechanical abrasives was used in the test by adding 5 ml of deionized water to about 20 g of powdered mechanical abrasive.

The polishing pressure and temperature were not critical to the results, but were kept constant during the test, whenever possible. The polishing temperature was maintained at about 25 ° C. while maintaining the polishing pressure at about 50 g / cm ² .

In many cases, the mechanochemical polishing abrasives according to the present invention polished their respective materials at a higher rate than when colloidal silica or mechanical abrasives were used alone or in combination. Only Ce ₂ O ₃ plus colloidal silicic acid showed a lower polishing rate when polishing alumina than when colloidal silicic acid was used alone.

Claims (6)

[Claims] 1. An abrasive for mechanochemical polishing, comprising:
An aqueous slurry of colloidal silicic acid having a pH of greater than about 7, about 13 to about 99.2 wt%, water about 0.7 to about 85 wt%, and mechanical having a particle size of about 0.1 micron to about 10 microns. contain from about 0.07 to about 2.0 wt% abrasive, the mechanical abrasive this case, Fe ₂ O _3, Fe
₃ O ₄ , MgO, BaCO ₃ , CaCO ₃ , MnO ₂ , Ce
_{O, SiO 2, CeO 2,} Cr 2 O 3 and Al _2, characterized in that the one or more substances of the group consisting of O ₃ are those selected, mechanochemical polishing for abrasive. 2. The mechanochemical polishing abrasive of claim 1 wherein the colloidal silicic acid has a pH greater than 7. 3. The mechanochemical abrasive abrasive of claim 1, wherein the mechanical abrasive has a particle size of from about 0.1 micron to about 10 microns. 4. The abrasive for mechanochemical polishing according to claim 1, wherein the mechanical abrasive is Fe ₂ O ₃ . 5. A method of polishing a piece of material, comprising: an aqueous slurry of colloidal silicic acid, Fe ₂ O ₃ , Fe ₃ O ₄ , Mg.
O, BaCO ₃ , CaCO ₃ , MnO ₂ , CeO, Si
1 of the group consisting of O ₂ , CeO ₂ , Cr ₂ O ₃ and Al ₂ O _3.
When a mechanochemical polishing abrasive consisting of a mechanical polishing material selected from two or more substances is used, the mechanochemical polishing abrasive is used for a pad installed in a mechanical polishing apparatus, and the material is A method of polishing a piece of material, which comprises frictionally contacting at least one surface of the piece of material with a pad of a mechanical polishing device for a time sufficient to polish the surface of the piece. 6. The polishing method according to claim 5, wherein the polishing agent for mechanochemical polishing is used in a polishing apparatus.