CN110055538B - Alumina slurry and preparation method thereof - Google Patents

Abstract

The invention discloses an alumina slurry, which comprises the following components in parts by weight: 5-30 parts of alumina micro powder, 1-5 parts of accelerator, 0.1-1 part of dispersant, 0.1-1 part of anti-caking agent and the balance of water. The polishing solution prepared from the raw materials has uniform particle size distribution, and has high grinding and polishing speed and polishing precision during polishing. In the preparation method of the alumina slurry provided by the invention, the content of the magnetic substance in the alumina slurry is controlled by the magnetic separator, so that the generation of scars can be inhibited in the polishing process, a grinding surface with higher precision is obtained, and the preparation method has the characteristics of high polishing speed, high polishing precision, excellent cleaning performance of a polished product and the like. The invention is suitable for the surface polishing of metal and resin lenses such as aluminum alloy, stainless steel and the like.

Description

Alumina slurry and preparation method thereof

Technical Field

The invention belongs to the field of materials, relates to an alumina slurry and a preparation method thereof, and particularly relates to an alumina slurry for polishing the surfaces of metals such as aluminum alloy, stainless steel and the like and a preparation method thereof.

Background

In recent years, metals represented by stainless steel and aluminum alloy are increasingly applied to the fields of electronic products such as mobile phone shells, computer shells, frames and the like, and in these fields, a metal blank is generally generated by cutting the metal blank into a semi-finished product with an initial shape by a cutter in a numerical control machine tool, and then performing processing technologies such as surface grinding and polishing for several steps to achieve a mirror surface effect. And a large amount of knife lines, namely macroscopic scratches, exist on the metal surface cut by the cutter. Therefore, in practical applications, it is necessary to perform surface treatment to improve the surface state thereof. Taking aluminum alloy as an example, the traditional surface polishing process is three: namely mechanical polishing, chemical polishing and electrochemical polishing. Mechanical polishing is to remove the convex part of the processed surface by cutting or generating plastic deformation on the surface of the material to obtain a smooth surface. Common mechanical polishing modes include mechanical wheel polishing, belt polishing, roller polishing, vibratory polishing, super lapping polishing and the like. Mechanical polishing can remove oil stains, scales, burrs, and the like on the surface of aluminum, but is difficult to polish parts having complicated shapes, and the mechanically polished aluminum material is prone to grain boundary corrosion and stress corrosion cracking. ② the chemical polishing can be divided into acid polishing and alkaline polishing. Common acidic polishing solutions include phosphoric acid-nitric acid, phosphoric acid-sulfuric acid-nitric acid, and the like. The "triacid" polishing system generates a large amount of nitrogen oxide gas, i.e., yellow fumes, during the polishing process. The gas has high toxicity, strong harm to human body, and serious environmental pollution. Alkaline chemical polishing is a chemical process that utilizes the selective autolysis of aluminum and aluminum alloys in alkaline solutions to smooth and polish the surface of articles to improve their surface finish. Electrochemical polishing is a metal surface treatment method using electrolyte and a direct current power supply, and is similar to electroplating except that the part to be processed is electrochemically polished as an anode, which is just opposite to electroplating. After the electrolytic bath is electrified, a layer of passive film is formed on the surface of the polished metal, metal ions are diffused through the passive film, the current density of microscopic (macroscopic) salient points and high points and burr areas at rough positions on the surface is higher than that of the rest parts of the surface, and the microscopic (macroscopic) salient points and the high points and the burr areas are dissolved at a higher speed, so that the aims of leveling and deburring are fulfilled. The three methods have respective advantages and partial defects.

For metal polishing, with the increasing requirements for global planarization and mirror effect of metal surfaces, chemical mechanical polishing is currently the only method available for mass production. Different from the traditional pure Mechanical or pure Chemical Polishing method, the Chemical Mechanical Polishing (CMP) method has the combined action of chemistry and machinery, so that the defects of surface damage caused by pure Mechanical Polishing, low Polishing speed, poor surface flatness and Polishing consistency and the like easily caused by single-purification Chemical Polishing are avoided. Alpha-alumina is widely applied to surface polishing of components such as integrated circuits, glass substrates and the like in a chemical mechanical polishing method, and has the advantages of high hardness, good stability and the like; as a chemical mechanical polishing abrasive, the shape and size of alpha-alumina directly affect the polishing effect. The smaller the particle size of the abrasive grains, the narrower the particle size distribution, i.e., the better the uniformity. Otherwise, the polishing rate of each part on the surface of the polishing sheet is not equal, so that the polishing is not uniform, the mass transfer uniformity of the polishing slurry and the distribution of pressure on the sheet are affected, the surface is seriously damaged in the polishing process, the surface roughness is large, and the polishing effect is affected by the surface defects such as polishing scratches and pits.

Some polishing agents are disclosed in the prior art, but the present polishing agents have poor particle uniformity and corresponding poor polishing effect, for example, CN1398939A "polishing composition and polishing method using the same" discloses a polishing composition comprising: (a) at least one abrasive selected from the group consisting of silica and alumina; (b) at least one organic compound selected from the group consisting of polyethylene oxide, polypropylene oxide, polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether and polyoxyalkylene addition polymer having a C-C triple bond: wherein R1-R6 are each H or C1-10 alkyl, X and Y are each ethyleneoxy or propyleneoxy, m and n are each a positive integer of 1 to 20; (c) at least one polishing accelerating compound selected from the group consisting of squaric acid, oxalic acid, tartaric acid, glycine, alpha-alanine, and histidine; (d) at least one anticorrosive selected from the group consisting of benzotriazole, benzimidazole, triazole, imidazole and tolyltriazole; (e) hydrogen peroxide; and (f) water. However, the above-mentioned method is aimed at developing a polishing composition having a suitable copper layer grinding rate, which can be used for polishing a polishing article having copper and a tantalum-containing compound coexistent without forming pits in the copper wiring portion and at the same time can reduce the chemical attack on copper. Also, the invention employs an abrasive having a particle size of preferably 10 to 100nm, which is an average particle size obtained on the surface area measured by the BET method. The method adopts nano abrasive, has high cost, and mainly aims at polishing objects with coexisting copper and tantalum-containing compounds for the semiconductor integrated circuit; the grinding material has an average particle size, the information such as the particle size distribution, the morphology and the like of the grinding agent is not mentioned, and the particle size distribution of the subsequent polishing material cannot be judged; the preparation process is complex in additive, contains dangerous chemicals such as strong oxidants, and is complex, and the harmfulness of the chemicals used in the preparation process is large.

CN1316477A "polishing composition and polishing method for manufacturing memory hard disks" discloses a polishing composition for memory hard disks, which comprises at least the following component (a) 0.1 to 50% by weight, based on the total amount of the polishing composition, of at least one abrasive selected from the group consisting of silica, alumina, ceria, zirconia, titania, silicon nitride and manganese dioxide. The above method provides a polishing composition for memory hard disks, suitable primary abrasives being selected from the group consisting of silica, alumina, ceria, iron oxide, silicon nitride, zirconia and manganese dioxide. The abrasive is not limited to any particular one of these abrasives, but silica is preferable. The particle size of alumina, zirconia, titania and silicon nitride is usually 0.01 to 1 μm, preferably 0.05 to 0.3. mu.m. The particle size is an average particle size obtained by conversion of the surface area measured by the BET method, and information such as particle size distribution and morphology of the polishing agent is not mentioned, and the particle size distribution of the subsequent polishing material cannot be judged. However, the grinding material does not refer to related information such as particle size distribution, morphology and the like, and the particle size distribution of the subsequent polishing material cannot be judged; the preparation process is complex in additive, contains dangerous chemicals such as strong oxidants, and is complex, and the harmfulness of the chemicals used in the preparation process is large. However, the application of the polishing material composition is different for different polishing articles.

CN103952084A "a method for preparing a metal polishing solution for alumina substrate" discloses a method for preparing a metal polishing solution for alumina substrate, which is characterized in that the method comprises the following steps: (1) raw material selection, (2) calcination, (3) specific surface test, (4) grinding, (5) discharging, (6) solid content test, (7) batching, and (8) detection. The method does not disclose which metal is suitable for, and the requirement on the granularity of the alumina is that the qualified granularity requirement is 1.5-2.0 mu m; although the addition of dispal leads the slurry to have better suspension property and difficult sedimentation, the dispal is not indicated; as the abrasive material, there are no mention of the relevant particle size distribution, morphology, etc.; however, whether the polishing composition is used as a powder material or a grinding material, the particle size and the distribution are indexes which must be considered, the particle size distribution is not uniform, and the surface is seriously damaged in the polishing process due to the large particles, so that the surface roughness is large, and polishing scratches are easy to occur.

Because the alumina has higher true density, the alumina is easy to precipitate in the process of storage and use, and the utilization rate of the polishing powder is lower. In order to eliminate the above-described undesirable situation, a method of adding a so-called dispersant for suppressing the sedimentation of abrasive particles in a polishing material slurry to the polishing material slurry has been adopted in recent years. Although many dispersants are currently available to disperse the polishing powder. However, since the dispersant easily causes the slurry to generate colloidal substances (gum-like) more easily during standing or use, it is inevitable during intermittent operation, and the polishing slurry becomes hard due to a large amount of colloidal substances generated at the bottom of the storage tank after standing, so that the polishing powder is difficult to stir, which results in a decrease in the effective utilization rate of the polishing powder, and the hardened colloidal substances are one of the key factors for generating scratches.

The uniform dispersion of micro-nano inorganic powder in other media has been an important research topic and an industrial problem. Dispersants are surface-active chemical species that promote dispersion of particles in suspension. The surfactant contains two chemical groups with completely different oleophilic and hydrophilic characteristics, and can be divided into ionic type and non-ionic type. The type and the proportion of the dispersing agent have great influence on the dispersibility of the polishing solution, and generally, the anionic surfactant is singly used and mainly plays a role in electrostatic stabilization; the single use of nonionic surfactant mainly plays a role in steric hindrance stabilization. Meanwhile, the selection and addition of the dispersing agent need to consider the evaluation of viscosity, rheological property and application property, including the selection of a polishing device, the mechanism of action and the like, in addition to the effects of suspension, dispersion and the like. Therefore, it is also significant to solve the problems of suspension, dispersion, and gelation (gum-like).

Therefore, the particle size distribution in the polishing material directly affects the polishing effect, and it is of great importance to study a polishing material having a uniform particle size distribution.

Disclosure of Invention

The technical problem to be solved by the invention is to provide alumina slurry and a preparation method thereof, wherein the alumina slurry has uniform particle size distribution and higher polishing precision; the preparation method is easy to operate, and the prepared alumina slurry has uniform particle size distribution.

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

the magnetic alumina slurry comprises the following components in parts by weight:

5 to 30 parts of alumina micro powder, 1 to 5 parts of accelerator, 0.1 to 1 part of dispersant,

0.1-1 part of anti-caking agent and the balance of water.

Wherein the water is deionized water, and the conductivity of the water is 10-50 us/cm.

In one embodiment of the present invention, the fine alumina powder is tabular alumina. Wherein, the polishing speed, the polishing precision and the like of the aluminum oxide with different shapes on the metal surfaces of alloy, stainless steel and the like are different. Compared with alumina with other shapes, the flat-plate alumina has the synergistic effect of the optimal polishing speed and the optimal polishing precision.

The tabular alumina of the invention has similar appearance with the flaky alumina. The flake alumina is structurally characterized in that its particles are in the shape of hexagonal flakes and have a small thickness to large aspect ratio, each particle having a ratio of at least 10: 1 ratio of diameter to thickness. The large diameter-thickness ratio is classified as sheet alumina, which shows that the diameter or thickness of alumina particles is large to obtain the large diameter-thickness ratio; the small diameter-thickness ratio is classified into plate-shaped alumina, which shows that the diameter of alumina particles is small or the thickness of the alumina particles is large, so that the diameter-thickness ratio is small; on one hand, the contact area between the aluminum oxide and a polishing device is increased in the using process of the flat-plate aluminum oxide, and on the other hand, the flat-plate aluminum oxide has small diameter-thickness ratio and large thickness with the same particle size and has the synergy of proper wear resistance, polishing speed, polishing precision and the like. Although the contact area between the alumina with a large diameter-thickness ratio and a polishing device is larger, the contact area influences the service life of the alumina slurry and is easy to break, and further the alumina with irregular morphology influences the polishing precision; alumina having a small aspect ratio has a long service life, but has poor properties such as suspension dispersion due to the specific gravity of the material. Therefore, the choice of material is very important.

As a further limitation of the above limitation, the median particle diameter D of the fine alumina powder₅₀3 to 10 μm and satisfies D₉₄/D₅₀＜1.3，D₅₀/D₃Is less than 1.5. The granularity test method of the alumina micropowder adopts a laser granularity meter to test the granularity and the distribution. Wherein D₃、D₅₀、D₉₄And the like are terms for laser granulometry to test the particle size of a material. With D₅₀For example, "D₅₀"refers to the particle size corresponding to the cumulative percent particle size distribution of a sample at 50%. Its physical meaning is that the particle size is greater than 50% of its particles and less than 50% of its particles. The particle size of the alumina micro powder can ensure good synergy of polishing speed and polishing precision in the polishing process.

As another limitation of the invention, the accelerator is one of nitric acid, hydrochloric acid, acetic acid or soluble aluminum salt, or a combination of two or more of the above. The accelerator selected by the invention has acidity in aqueous solution and has certain corrosion effect on metal; and anionic acidic and Al dissociated in aqueous solution³⁺These also have a corrosive effect on metals.

As a further limitation of the above definition, the soluble aluminum salt is one of aluminum nitrate, aluminum chloride or aluminum sulfate, or a combination of two or more thereof.

As another limitation of the invention, the dispersant is one or a combination of two or more of polyethylene glycol, sodium polyacrylate, sodium hexametaphosphate, hexadecyl trimethyl ammonium bromide or sodium dodecyl sulfate. The influence of different dispersants on the suspension and dispersion performance of the alumina is tested by the polishing performance, and the screened dispersant has better dispersion performance and can reduce the generation of colloidal substances.

As another limitation of the invention, the anti-platelet agent is one of kaolin, bentonite, montmorillonite and the like, or a combination of two or more of the kaolin, the bentonite and the montmorillonite. The anti-caking agent rapidly expands in aqueous solution to rapidly form an aluminosilicate inorganic material with a three-dimensional colloidal structure, and the material can improve the functions of suspension, dispersion, thickening, thixotropy and the like of the grinding material slurry without generating conglutination.

As a further limitation of the above definition, the particle size D of the anti-caking agent₅₀1 to 3 μm. The invention limits the granularity of the anti-board-bonding agent, promotes peptization and thixotropy of the anti-board-bonding agent in aqueous solution due to small particles, and simultaneously does not cause adverse effects such as scratches and the like in the use process of the slurry.

The invention also provides a method for preparing the magnetic alumina slurry, which comprises the following steps:

(1) dispersing of the dispersant:

adding a dispersing agent into water, and shearing and dispersing for 0.5-1 h to obtain a solution A; wherein the weight ratio of the dispersing agent to water is 0.0028-0.017: 1;

(2) and (3) dispersing the anti-board-bonding agent:

adding the anti-caking agent into the solution A, shearing and dispersing for 0.5-2.5h, and filtering to obtain slurry B; wherein the mass ratio of the anti-caking agent to the solution A is 0.0026-0.013: 1;

(3) dispersion of accelerator:

adding an accelerator into the slurry B under the stirring condition, and shearing and dispersing for 0.5-2.5h to obtain slurry C;

(4) preparing alumina slurry:

adding the alumina micro powder into the slurry C under the stirring condition, shearing and dispersing for 0.5-2.5h, and filtering to obtain slurry D;

(5) magnetic substance control:

and magnetizing the slurry D by excitation to finally prepare the magnetic alumina slurry, wherein the particle concentration of the magnetic alumina slurry is less than or equal to 5ppm by weight.

In the method, the physical and chemical properties and application properties of various materials such as a dispersing agent, a plate resistance agent, an accelerator, alumina and the like are comprehensively considered, and a reasonable process route and an adding sequence are determined; meanwhile, the invention eliminates the possibility of iron rust and other magnetic substances in the slurry in the production process of various materials and in the production process of the invention through the control of the magnetic substances, and the foreign matters are one of important factors for generating scratches in the surface quality of a polishing device in the use process of the alumina slurry; meanwhile, the method is equivalent to full detection of the slurry, and the influence of missed detection caused by the reasons that the sampling is not taken before the test or the precipitation in the test process is caused is avoided, unlike the differential alumina that limits the median particle size and the particle size distribution.

Due to the adoption of the technical scheme, compared with the prior art, the invention has the technical progress that:

the alumina slurry of the invention adopts tabular alumina micro powder as a raw material, and controls the particle size distribution of alumina, wherein the median particle diameter D of the alumina micro powder₅₀3 to 10 μm and satisfies D₉₄/D₅₀＜1.3，D₅₀/D₃Less than 1.5, the particle size distribution of the alumina micro powder ensures that the alumina slurry has uniform particle size distribution and has high grinding and polishing speed and precision during polishing; the more uniform the grain size of alumina used for polishing and the narrower the grain size distribution range, the higher the polishing precision. However, in addition, controlling the maximum particle size of the abrasive polishing powder is one of the important factors for eliminating scratches. The content of coarse particles affects the polishing ability and service life of the grinding and polishing powder, and the content of fine particles affects the quality and effect of polishing. Therefore, the particle size and the particle size distribution of the grinding and polishing powder are effectively controlled, and the method has important significance for improving the polishing capacity and the polishing effect. Meanwhile, the balance between the polishing precision and the polishing speed needs to be found by comprehensively considering the polishing object and the polishing requirement, and further, the reasonable average grain diameter and grain size distribution need to be found according to the polishing object and the polishing requirement. In addition, the added accelerator can effectively improve the grinding and polishing speed of the alumina slurry; the dispersing agent and the anti-caking agent added in the raw materials solve the problem of suspension dispersion performance of the alumina in slurry, inhibit the precipitation of alumina micropowder and avoid the generation of precipitates. In the preparation method of the alumina slurry provided by the invention, the content of the magnetic substance in the alumina slurry is controlled by the magnetic separator, so that the generation of scars can be inhibited in the polishing process, a grinding surface with higher precision is obtained, and the preparation method has the characteristics of high polishing speed, high polishing precision, excellent cleaning performance of a polished product and the like.

The invention is suitable for the surface polishing of metal and resin lenses such as aluminum alloy, stainless steel and the like.

The present invention will be described in further detail with reference to specific examples.

Drawings

FIG. 1 is an SEM photograph of a tabular alumina fine powder in example 1 of the present invention.

FIG. 2 is an SEM image of a round spheroidal alumina in a comparative example of the present invention.

Fig. 3 is an SEM image of the dumbbell-shaped alumina fine powder in the comparative example of the present invention.

Detailed Description

Example 1

The alumina slurry comprises the following components in parts by weight:

5kg of tabular alumina micropowder (SEM image is shown in figure 1), 1kg of aluminum chloride, 0.1kg of polyethylene glycol,

0.2kg of sodium polyacrylate, 0.1kg of kaolin and 93.6kg of deionized water.

Wherein the conductivity of the deionized water is 10-50 us/cm; the median particle diameter D of the tabular alumina micropowder₅₀Is 3.4 μm and satisfies D₉₄/D₅₀Is 1.2, D₅₀/D₃Is 1.4;

the method for preparing the alumina slurry comprises the following steps:

(1) dispersing of the dispersant: adding 0.1kg of polyethylene glycol and 0.2kg of sodium polyacrylate dispersant into 93.6kg of water with the conductivity of 10us/cm, and shearing and dispersing for 0.5h to obtain a solution A;

(2) and (3) dispersing the anti-board-bonding agent: adding 0.1kg of 1 mu m kaolin (the ignition loss is 10%) into the solution A, shearing and dispersing for 0.5h, and filtering by a 500-mesh wet method to obtain slurry B;

(3) dispersion of accelerator: adding 1kg of aluminum chloride into the slurry B under the stirring condition, and dispersing for 0.5h to obtain slurry C;

(4) preparing alumina slurry: adding 5kg of alumina micro powder into the slurry C under the stirring condition, dispersing for 0.5h, and filtering by a 500-mesh wet method to obtain slurry D;

(5) magnetic substance control: the slurry D was passed through a magnetic separator made of a magnetic material magnetized by excitation, and controlled to a magnetic particle concentration of not more than 5ppm by weight.

The alumina slurry prepared by the method has good suspension property and no hardening property.

A Unipol-802 polishing machine was used to polish 304 stainless steel sheets, and the alumina slurry in this example was used to test the polishing efficiency of the product and the surface quality of the polished stainless steel. Polishing efficiency is expressed in terms of relative polishing rate. The principle of the method is as follows: under the specified test conditions, the polishing erosion amount (m) of the aluminum oxide slurry to be tested on the stainless steel sheet_p) And the polishing erosion amount (m) of the aluminum oxide slurry to the stainless steel sheet is specified_p0) The ratio of. The amount of polishing erosion is expressed as weight, which is the weight of the stainless steel sheet before polishing minus the weight of the polished stainless steel sheet.

Wherein the specified test conditions are: a Unipol-802 polisher; the diameter of an object carrying block for fixing the stainless steel sheet is 80mm, and the weight of the object carrying block is 2 kg; size of 304 stainless steel sheet: 38mm by 42 mm.

The test conditions were: the rotation speed of the polishing machine is 53rpm/min, the polishing time is 10min, the flow is 3g/min, the polishing leather is polyurethane, and the polishing operation is carried out under the polishing conditions.

Wherein, the specified alumina slurry is the slurry prepared by the alumina micro powder and the pure water with the mass fraction of 5 percent in the embodiment 1.

The relative polishing speed of the alumina slurry prepared in the embodiment is 110%, and the scratch of the stainless steel surface is 0. Wherein the polishing rate of the "prescribed alumina slurry" is defined as 100% as compared with the "prescribed alumina slurry".

Examples 2 to 6

Examples 2 to 6 are an alumina slurry and a method for preparing the same, wherein the raw materials and the method for preparing the same are similar to those of example 1, but the raw materials are different only in type and amount, and the technical parameters involved in the method for preparing the same are different, as shown in the following table:

the alumina slurries obtained in examples 2 to 6 were excellent in suspensibility and free from hardening. The test performance evaluation of the alumina pastes prepared in examples 2 to 6 was the same as that of example 1, and the relevant test results are shown in the table above.

The results show that the alumina slurries of examples 2 to 6 have good suspensibility and no hardening property due to the alumina slurries; the relative polishing speed of the alumina slurry prepared by the invention is between 110 and 130 percent, which shows that the polishing speed is greatly improved. Wherein the polishing rate of the "prescribed alumina slurry" is defined as 100% as compared with the "prescribed alumina slurry". Wherein, the specified alumina slurry is the slurry prepared by the alumina micro powder and the pure water with the mass fraction of 5 percent in the embodiment 1.

Comparative example

1. Comparison experiment of different shapes of aluminum oxide

The alumina slurry is prepared by adopting alumina with different shapes, and the alumina with irregular shape, round and round-like spherical shape (the SEM image is shown in figure 2), dumbbell-shaped alumina (the SEM image is shown in figure 3) and flat-plate-shaped alumina are respectively adopted for experiments, the preparation method is the same as that of the example 1, and the experimental results are as follows:

as can be seen from the above table, the alumina slurry prepared by the same preparation method as in example 1, which contains the dispersant, the anti-caking agent, etc., has good suspension property and no hardening. But the use of flat alumina has a high relative polishing rate; the slurry prepared from the alumina with the irregular shape causes serious scratch in the using process and has slow relative polishing rate; the slurry prepared by adopting the round and round-like spherical and dumbbell-shaped alumina has no scratch but slow related polishing rate due to round and round appearance in the using process, so the alumina slurry prepared by adopting the flat-plate alumina has higher relative polishing speed and smaller scratch rate.

2. Comparison experiment by adding different dispersants and anti-caking agents

The preparation of alumina slurry was carried out using different dispersants and anti-caking agents, wherein the preparation raw materials and preparation methods were the same as in example 1 except for the kinds and amounts of the dispersants and anti-caking agents, and the results were as follows:

as can be seen from the above table, the existence of the dispersant improves the suspension property of the alumina slurry, but the hardening performance of the alumina slurry is serious, and although the relative polishing speed is improved, scratches exist; the addition of the anti-plate-bonding agent causes the prepared alumina slurry to have no suspension property and no hardening, but the relative polishing speed is slightly reduced, mainly because the addition of the anti-plate-bonding agent influences the reduction of effective grinding alumina particles in the slurry, so that the relative polishing efficiency is reduced. In the coexistence of the dispersant and the anti-caking agent, the prepared alumina slurry has good suspension dispersibility, no hardening, relative polishing speed up to 110 and no scratch by the cooperation of different additives.

3. Comparative test of demagnetization step

In the preparation process of the alumina slurry, whether the operation of the demagnetization step is performed or not has a great influence on the preparation result of the alumina slurry, referring to the preparation method in example 1, the following table shows the specific comparison:

it can be seen from the above table that the magnetic substance in various materials is reduced by the demagnetizing process, which not only does not affect the suspension performance and does not cause hardening, but also inhibits scratching.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. However, the present invention is not limited to the embodiments described above, and various modifications, changes, variations, and alterations may be made without departing from the spirit of the invention.

Claims (3)

1. An alumina slurry characterized by: comprises the following components in percentage by weight:

5 to 30 parts of alumina micro powder, 1 to 5 parts of accelerator, 0.1 to 1 part of dispersant,

0.1-1 part of anti-caking agent and the balance of water; wherein the alumina micro powder is tabular alumina; the median particle diameter D of the alumina micropowder₅₀3 to 10 μm and satisfies D₉₄/D₅₀＜1.3，D₅₀/D₃＜1.5；

Wherein the accelerator is one or the combination of two or more of nitric acid, hydrochloric acid, acetic acid or soluble aluminum salt; the soluble aluminum salt is one of aluminum nitrate, aluminum chloride or aluminum sulfate, or a combination of two or more of the aluminum nitrate, the aluminum chloride or the aluminum sulfate;

the dispersant is one or the combination of two or more of polyethylene glycol, sodium polyacrylate, sodium hexametaphosphate, hexadecyl trimethyl ammonium bromide or lauryl sodium sulfate;

the anti-caking agent is one or a combination of two or more of kaolin, bentonite, montmorillonite and the like.

2. The alumina slurry of claim 1, wherein: the granularity D of the anti-caking agent₅₀1 to 3 μm.

3. A method of preparing the alumina slurry of any one of claims 1 to 2, wherein: the method comprises the following steps:

(1) dispersing of the dispersant:

adding a dispersing agent into water, and shearing and dispersing for 0.5-1 h to obtain a solution A; wherein the mass ratio of the dispersing agent to water is 0.0028-0.017: 1;

(2) and (3) dispersing the anti-board-bonding agent:

adding the anti-caking agent into the solution A, pulping with water, shearing and dispersing for 0.5-2.5h, and filtering to obtain slurry B; wherein the mass ratio of the anti-caking agent to the solution A is 0.0026-0.013: 1;

(3) dispersion of accelerator:

adding an accelerator into the slurry B under the stirring condition, and shearing and dispersing for 0.5-2.5h to obtain slurry C;

(4) preparing alumina slurry:

adding the alumina micro powder into the slurry C under the stirring condition, shearing and dispersing for 0.5-2.5h, and filtering to obtain slurry D;

(5) magnetic substance control:

and magnetizing the slurry D by excitation to finally prepare the magnetic alumina slurry, wherein the particle concentration of the magnetic alumina slurry is less than or equal to 5ppm by weight.

Images