Abrasive tool making process – material – or composition – With inorganic material – Clay – silica – or silicate
Reexamination Certificate
2002-08-20
2004-01-06
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With inorganic material
Clay, silica, or silicate
C051S307000, C051S309000, C051S295000, C051S293000
Reexamination Certificate
active
06673132
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an abrasive for polishing and, more particularly, to an SiO
2
/Al
2
O
3
composite abrasive. The present invention also relates to a method for producing the composite abrasive.
2. Related Prior Art
As an important material for polishing, Al
2
O
3
abrasives can be applied to the surface treatments of metal, glass, optical lens, compact disks etc. The Al
2
O
3
abrasive usually provides high polishing rates to obtain a flat surface, however, the roughness increases as well. One way to solve such a problem is to modify the Al
2
O
3
abrasive into a composite material by mixing with other materials. Additionally, for conventional Al
2
O
3
abrasives, the polishing slurry has to be maintained at a low pH value, usually about 4, so that the Al
2
O
3
abrasives can be well dispersed in water.
U.S. Pat. No. 6,261,476 mentioned a method to promote the polishing effect by simply blending abrasives of different sizes, which is adopted for chemical mechanical polishing (CMP) by most users now.
Mutsuo Sando, et al. mentioned another method in Funtai Kogaku Kaishi (1992, 29(10), 755-761), in which an SiO
2
layer is provided on an &agr;-Al
2
O
3
abrasive surfaces. Unfortunately, the surface potential of this composite abrasive drops instantly when the pH value of the solution is higher than 5. That is, such composite material cannot be used in high-pH solutions.
Therefore, it is desirable to provide an improved polishing abrasive to mitigate and/or obviate the aforementioned problems.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a modified SiO
2
/Al
2
O
3
composite abrasive, which has positive surface charges when dispersed in an alkaline solution.
Another object of the present invention is to provide a method for producing the modified SiO
2
/Al
2
O
3
composite abrasive.
The modified SiO
2
/Al
2
O
3
composite abrasive of the present invention can be used for polishing in an alkaline solution because of the positive surface charges, and exhibits good polishing rates because of the Al
2
O
3
cores. The SiO
2
layer coated on the Al
2
O
3
core usually has a thickness ranging from 1 nm to 100 nm.
The method for producing the SiO
2
/Al
2
O
3
composite abrasive of the present invention is to mix an Al
2
O
3
abrasive and a precursory material in an alcohol. The mixture is then reacted with an acidic solution.
The precursory material aforementioned can be a silicide with an alkoxy group, for example, tetraethoxysilane. The alcohol can be C
1-4
alkyl alcohol, preferably isopropanol. The acidic solution can be inorganic, for example, sulfuric acid and hydrochloric acid; or organic, for example, acetic acid.
REFERENCES:
patent: 6258137 (2001-07-01), Garg et al.
patent: 2002/0042210 (2002-04-01), Mandal et al.
Chang Sung-Chun
Liu Ru-Shi
Bacon & Thomas PLLC
Everlight USA, Inc.
Marcheschi Michael
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