The hardness of cerium oxide is only 6 (silicon dioxide is 7, alumina is 9), only from a mechanical point of view, with low hardness cerium oxide to polish silica based materials, such as silicate glass, quartz glass, etc., is not technically feasible, but at present cerium oxide polishing powder is the preferred polishing powder based on silicon dioxide or even silicon nitride materials. It can be seen that cerium oxide polishing powder also has other functions in addition to mechanical effects.

The soft texture of CeO2 can significantly reduce the scratch on the polished workpiece surface, and the conversion of variable valence particle ion Ce4+/Ce3+ in CeO2 can improve the chemical reactivity between CeO2 and the polished workpiece, and significantly improve the polishing rate. Oxygen vacancy usually occurs in the CeO2 lattice to change its physical and chemical properties. It is generally believed that CeO2 can form Ce-O-Si chemical bond with the surface of the polished workpiece, and polish the polished workpiece with the fracture of the Ce-O-Si bond. The chemical-mechanical polishing rate is influenced by both the rate of Ce-O-Si bond formation and the rate of Ce-O-Si fracture in the polished workpiece.

The purpose of cerium oxide polishing is to remove the concave and convex layer and crack layer generated on the surface of the workpiece in the future, make the surface of the workpiece transparent and smooth, achieve the specified surface grade, and accurately correct the surface geometry to achieve the specified surface shape accuracy. In the initial stage of polishing, it is the process of CeO2 removing the convex and convex layer on the surface of the glass, so that the glass exposes the fresh surface. At the same time, since the main group of silicate glass is divided into SiO2, and the remaining components are alkali metal oxides, they will be hydrolyzed during the polishing process, resulting in water-containing silica gel layer and silica gel layer on the glass surface, making the glass surface softened and easy to be removed.

Reasonable selection of polishing fluid can make the surface of the processed workpiece bright and beautiful, bright and dazzling, but also can prevent the corrosion of the workpiece, maintain and improve the luster of the workpiece surface, and play the role of cleaning pieces and abrades. Remove oil, soften the surface of the workpiece to accelerate wear, reduce the impact of the grinding tool on the workpiece, improve the workpiece conditions. It has non-toxic, no corrosion, not easy to deteriorate and other properties.

There are many types of polishing fluid, which should be selected according to the processing conditions. In the finishing efficiency, grinding quality of work, polishing finish and so on. The polishes all show their unique effects.

The pH of the alumina polishing liquid is the pH value of the polishing liquid. When the pH value of the polishing liquid is 9.6, the mechanical effect of the polishing liquid is much greater than the chemical effect, and the removal rate is relatively large, resulting in a high damage layer on the surface of the polished sheet after polishing, and the roughness is relatively large.

When the pH value of the polishing liquid is increased to 10.84 ~ 11.34, when the mechanical action and chemical action reach an equivalent state, the uniformity of the chemical action is good, so that the surface tension is small, the consistency of the quality treatment is good, and the surface polishing effect can be obtained.

When the pH value is greater than 11.67, SiO2 hydrosol generates water-soluble ammonia silicate under the action of strong alkali, so that SiO2 particles in the silica sol cannot play the role of grinding and become transparent liquid. At this time, the mechanical action basically fails, and the polishing is mainly based on chemical action, and the surface corrosion pits increase, making the surface roughness increase again.

Generally speaking, the larger the particle size of the polishing powder, the greater the grinding force, the more suitable for harder materials, it should be noted that all the particle size of the polishing powder has a distribution problem, the average particle size or the size of the median diameter D50 only determines the speed of the polishing speed, and the maximum particle size Dmax determines the polishing accuracy. Therefore, in order to obtain high precision requirements, the maximum particle size of the polishing powder must be controlled. The reason why ordinary polishing powder has scratches is that there are large particles. Therefore, nano-polishing powder with narrow particle size distribution is generally selected. The concentration of the slurry in the polishing process determines the polishing speed, and the higher the concentration, the higher the polishing speed. When using small particle polishing powder, the slurry concentration is appropriately lowered to obtain the appropriate fluidity, and it is generally recommended to be 7-10%. In addition, the appearance of alumina is also an important factor affecting the polishing effect:

① When the alumina used in the slurry is spherical (especially for ultra-fine powder), the removal rate is high, the polishing speed is fast, the polishing surface is not easy to produce fine scratches, and the finish is high, which can be used for the processing of high-precision products such as semiconductor single crystal, quartz crystal and precision optical devices.

② When the slurry is used in flakes of alumina, because of its good dispersion stability and parallel alignment, the upper and lower surfaces of the flakes of alumina can be basically parallel to the surface of the polished material, to avoid the damage under the surface of the material to the maximum extent, so that the polished surface is smooth like a mirror, which can be used for the polishing of ceramics and the polishing of glass surfaces such as optical microscopy.

1, Na2O influence α-Al2O3 phase transition Na2O at high temperature (above 1400℃) calcination with Al2O3 reaction to form high aluminate Na2O·11Al2O3, also known as β-Al2O3, at high temperature his structure is stable, will coexist with α-Al2O3, In the calcination process, it greatly reduces the conversion rate and conversion rate of α-Al2O3, and will also coarser the grain of alumina, reduce the specific surface area, and the crystal shape is irregular.

2, Na2O affects the mechanical strength and electrical conductivity of products In the field of wear-resistant products and ceramic applications, sodium oxide has a great impact on the mechanical strength and electrical conductivity of alumina products. Under normal circumstances, the higher the content of Na2O, the higher the conductivity, the worse the electrical insulation performance of alumina ceramics and wear-resistant products, and the mechanical strength will be reduced.

1) In the military field - used for aircraft turbine blades, shafts and other precision casting machine parts, ordnance, all kinds of spring gear hydraulic parts surface strengthening treatment, eliminate internal stress.

2) In the civil field - used for titanium alloy and stainless steel workpiece and products (stainless steel tableware, kitchen utensils), textile machinery parts, stamping abrading tools, machine abrading tools, medical equipment and other metal products of tool cleaning, surface finishing and surface pretreatment, in addition to oxidation, rust, deburring, strengthening, polishing treatment. Cleaning of glass processing, tire manufacturing and plastic molding tools.