CN110003797B

CN110003797B - Sapphire rough polishing solution and preparation method thereof

Info

Publication number: CN110003797B
Application number: CN201910320946.9A
Authority: CN
Inventors: 左海珍
Original assignee: Kunming Soft Communication Technology Co Ltd
Current assignee: Kunming soft Communication Technology Co., Ltd
Priority date: 2019-04-21
Filing date: 2019-04-21
Publication date: 2020-11-10
Anticipated expiration: 2039-04-21
Also published as: CN110003797A

Abstract

The invention provides a sapphire rough polishing solution which contains an alpha-alumina abrasive medium, an oxidant, a preservative, a Ti ion complexing agent, a Fe ion complexing agent, deionized water and a pH regulator, wherein alpha-alumina particles are obtained by purifying kaolinite, the purity of the alumina particles is more than 99 wt%, the Mohs hardness is 9.1, the particle size is concentrated on 0.5 +/-0.25 mu m, and the average removal amount of sapphire in 2-20 minutes reaches 40-80 mu m.

Description

Sapphire rough polishing solution and preparation method thereof

Technical Field

The invention relates to an alumina polishing solution and a preparation method thereof, in particular to a sapphire rough polishing solution prepared by using alpha-alumina obtained by kaolinite purification as a raw material and a preparation method thereof.

Technical Field

With the rapid development of optoelectronic technology and the increasing demand of LED optoelectronic product materials, there are many substrate materials that can be used for GaN wafer LEDs, but the number of substrate materials that can be actually used for commercialization is still small, and there are only two kinds of substrate materials, namely sapphire and SiC, and there is no third substrate for the commercial production of GaN LEDs. Compared with sapphire, SiC is a very important substrate material, is a low-resistance material, can be used for manufacturing electrodes, has a lattice constant and a thermal expansion coefficient which are closer to those of a GaN material, is easy to dissolve, has a blue light emitting characteristic, but has the defects that the difference between the thermal expansion coefficient and the GaN is large, cracks of an epitaxial GaN layer are easily caused, the epitaxial GaN layer is not suitable for being used in a large amount, and the price is relatively high. Sapphire substrates are currently the best and most commonly used substrate material.

Sapphire crystal (alpha-A1)₂O₃) It is a high-quality optical functional material with high-temp. resistance, wear resistance, corrosion resistance and wide light-transmitting wave band, and it has the hexagonal close-packed type identical to that of group III nitride, and is a good material formed from three unique combinations of physical, mechanical and chemical properties. In the field of optical communications, sapphire crystals are used not only as short-wavelength active devices but also as passive devices for polarized light in the field of microelectronics, and sapphire can be used as a substrate for a new generation of semiconductor substrate SOI (on insulator), and due to the excellent blocking effect of sapphire, the capacitance effect of a transistor can be reduced, and the operation speed thereof can be made faster and the power consumption thereof can be made lower. In the field of optoelectronics, sapphire crystals are the substrate material of choice for fabricating GaN Light Emitting Diodes (LEDs). Before growing a thin film on a sapphire substrate, scratches, pits, stress regions, and the like generated during slicing are first removed, and then surface roughness is reduced. The greater the roughness of the surface, the more dangling bonds of the surface, the easier it is to adsorb other impurities, and there is a poor lattice match with the overlying film. The traditional pure mechanical polishing is to use polishing powder to continuously grind the surface of a polished material, which is easy to generateDeep scratching. In CMP (chemical mechanical polishing), chemical reactants are removed by mechanical action under the environment of chemical action, so that the removal rate of materials is improved, and good surface morphology is obtained.

The chemical composition and concentration of the polishing solution, the type, size, shape and concentration of the abrasive, the viscosity, pH, flow rate and flow path of the polishing solution all have an influence on the removal rate. The properties of the abrasive particles directly influence the polishing effect of the polishing solution, and play a vital role in removing redundant parts and improving the smoothness of a polishing sheet. The abrasive particles of the slurry are also different for each different device global polishing process. The commonly used oxide polishing liquid abrasive is SiO₂、Al₂O₃、CeO₂Wherein SiO is₂The polishing solution has good selectivity and dispersibility, good mechanical wear performance, active chemical property, and easy post-cleaning treatment, and has the disadvantages of easy gel generation during the polishing process, low polishing rate to hard substrate material, and CeO₂The polishing solution has the advantages of high polishing rate and high material removal rate, and has the disadvantages of high viscosity, easy scratching, poor selectivity and difficult subsequent cleaning, A1₂0₃The polishing solution has the disadvantages of low selectivity, poor dispersion stability, easy agglomeration and the like, but has an excellent removal rate for a sapphire substrate and the like which are hard substrates. With the development of the LED industry, the demand of sapphire substrate is increasing, A1₂0₃The application of polishing solutions in CMP is becoming more important. In recent years, the research on alumina polishing solutions mainly focuses on the preparation method of alumina, and as for the preparation method of alumina, the following methods are mainly focused: (1) the aluminum ammonium sulfate pyrolysis method, the improved Bayer method, the explosion method and the like in the solid-phase method are relatively mature preparation methods, the flow of the solid-phase method for preparing the ultrafine powder is simple, no solvent is needed, the yield is high, but the generated powder is easy to agglomerate, the granularity is not easy to control, and high-quality nano powder with small grain diameter and uniform distribution is difficult to obtain; (2) gas phase method: the gas phase method mainly comprises chemical vapor deposition, wherein the material form is changed by heating, etc., the reaction is carried out in the gas state, and then the reaction is carried out in the cooling processThe method has the advantages of controllable reaction conditions, easy product refining, good particle dispersibility, small particle size, narrow distribution, low yield and difficult powder collection; (3) liquid phase methods such as hydrolysis, spray drying, sol-gel, emulsification, etc.; in detail, the hydrolysis method is to add an alcohol solution of isopropyl sec-butyl alcohol or aluminum isopropoxide into water for hydrolysis, control the size of particles generated by controlling the polycondensation process of hydrolysis products, and prepare nano aluminum oxide by high-temperature calcination; the spray drying method is to spray a metal salt solution into a high-temperature environment in a mist form, evaporate and thermally decompose metal to separate out a solid phase, and directly obtain nano aluminum oxide; the sol-gel method is a method in which a metal alkoxide is dissolved in an organic solvent, the alkoxide is hydrolyzed and polymerized by distillation to form a sol, and water is added to the sol to form a gel. Drying the gel at low temperature in a vacuum state to obtain loose xerogel, and then calcining at high temperature to obtain nano alumina powder; the emulsion method is a method in which one of two mutually incompatible solutions is dispersed in the form of droplets in the other phase to form an emulsion, and then an oxide or hydroxide is produced by reaction in the fine droplets.

China kaolin mineral resources rank the front of the world, a mineral producing area at 267 has been proved, and the reserve is proved to be 29.10 hundred million tons, wherein: the method is characterized in that kaolin is built in non-coal in China, the resource reserves occupy the fifth place in the world, the ascertained reserves are 14.68 hundred million tons and mainly and intensively distributed in the Guangdong, Shaanxi, Fujian, Jiangxi, Hunan and Jiangsu provinces, and account for 84.55 percent of the total reserves in China; the reserve of kaolin (kaolinite rock) containing coal for construction accounts for the first place in the world, the proven reserve is 14.42 hundred million tons, and the reserve is mainly distributed in great identity in Shanxi, Huanyu, inner Mongolian Junger, Wuda, Anhui Huai Bei, Shanxi Hancheng and the like, wherein the resources of the inner Mongolian Junger coal field are the most. Kaolin is an industrial mineral with excellent performance and is widely applied to the fields of ceramics, papermaking, rubber, plastics, petroleum, chemical industry and the like. The kaolin is mainly composed of kaolinite group minerals, and the main component of the kaolin is Al₂O₃And Si0₂Part of Fe ₂0₃, Ti0₂Small amount of CaO, MgO, K ₂0,Na₂O, and the like. In addition, although kaolin is directly ground to prepare polishing powder, the difficulty of the preparation process is mainly concentrated on the aspects of particle size distribution, roasting process and product whiteness, the components of the polishing powder are not complicated and varied due to the rough preparation process, the cutting force is unstable, and the use dimension and the use direction of the product are finally influenced.

In view of one or more of the above problems in the prior art, the present invention provides an alumina rough polishing solution for sapphire substrates.

A sapphire rough polishing solution, comprising: abrasive media: alumina particles, 8-15 wt.%; oxidizing agent: t-butyl peroxy, 2-5 wt.%; preservative: one or more of methylisothiazolinone or isothiazolinone, 0.1-0.5 wt.%; ti ion complexing agent: 1, 2-cyclohexanediaminetetraacetic acid, 0.1-1 wt.%; (ii) a Fe ion complexing agent: EDTA, 0.05-0.1 wt.%; deionized water: 75-90 wt.%; pH regulator: one or more of citric acid or tartaric acid, and adjusting the pH =3.5-5, wherein the alumina particles are obtained by purifying kaolinite, and the Al is₂O₃The crystalline phase of (a) is alpha-alumina.

Further, the alumina particles have a purity of greater than 99wt.%,

further, the Mohs hardness of the alumina particles is 9.1,

further, the particle size is centered at 0.5. + -. 0.25. mu.m, D₉₇≤1μm

Further, the average removal amount of the rough polishing solution to the sapphire is 40-80 μm within 2-20 minutes.

Further, the alumina particles contain titanium oxide or iron oxide, and the ratio of titanium oxide to iron oxide is as follows: alumina is less than or equal to 0.1 wt.%.

A preparation method of the sapphire rough polishing solution as set forth in claims 1-6, comprising the following steps:

(1) pulping and grading to obtain magnetic separation materials, gradient magnetic separation for removing iron and titanium, roasting for whitening, high-temperature calcification, purifying alumina, obtaining alpha-alumina powder abrasive medium, and placing a proper amount of abrasive medium into a dispersion cylinder of a reaction kettle;

(2) adding deionized water into the dispersion cylinder of the reaction kettle, and mechanically stirring for 5-10min at the rotating speed of 50-20000 r/min;

(3) continuously adding one or more oxidants of tert-butyl peroxide, aluminum nitrate and hydrogen peroxide into the dispersion cylinder, and mechanically stirring for 1-2min at the rotation speed of 50-20000 r/min;

(4) and (2) sequentially adding one or more preservatives of methylisothiazolinone or isothiazolinone, a1, 2-cyclohexanediamine tetraacetic acid Ti ion complexing agent and a Fe ion complexing agent EDTA into the dispersion cylinder, continuously stirring for 2-10min, adding one or more pH regulators of citric acid or tartaric acid at a rotation speed of 50-20000r/min (5), and adjusting the pH =3.5-5 of the polishing solution to obtain the sapphire rough polishing solution.

Further, the magnetic separation material obtained by pulping and grading is obtained by performing coarse grinding, slurry preparation and sand removal and particle size grading treatment on the kaolinite in a cyclone, wherein the mass ratio of the prepared slurry is that the kaolinite after coarse grinding: dispersing agent: water = (0.05-0.15): (0.001-0.01): 1, mixing and stirring speed is 500-; the parameters of the gradient magnetic separation for removing iron and titanium are as follows: background magnetic field strength 1.5 x 10⁴Oe, the flow rate is 1-2 cm/s; magnetization period 3-8min, such that titanium content is below 0.3wt.% and iron content is below 0.2 wt.%; the roasting whitening process comprises the following steps: dehydration, drying, roasting at 800-^oC, rate of temperature rise 10^oC/min, keeping the temperature for 2-3h after the roasting temperature is reached, and roasting the oxygen-nitrogen mixed gas O in the atmosphere₂/N₂= 5-8 wt.%, and Al with whiteness of more than 90% is obtained₂O₃ ^.xSiO₂And (3) material, wherein X is more than or equal to 1.

Further, high-temperature calcification is carried out to the above-mentioned Al₂O₃ ^.xSiO₂Adding CaO powder into the materials, uniformly stirring, and heating to 1200-1300 DEG C^oC, reacting for 1-2h to obtain CaO^.SiO₂With CaO^.Al₂O₃Cooling the mixture to 80-90 deg.C^oC。

Further, the alumina is purified by adding 30-40wt.% Na into the product after high-temperature calcification₂CO₃An aqueous solution of a carboxylic acid and a carboxylic acid,stirring and reacting for 2-4h, filtering for multiple times, collecting filtrate, adding 5-20 wt.% of HCl aqueous solution into the filtrate, reacting for 0.5-1h, slowly adding 2-5wt.% sodium hexametaphosphate, adjusting the pH value by using 2-5wt.% ammonia water, slowly stirring to obtain white precipitate, filtering, alternately washing with deionized water and ethanol solution for multiple times, drying at normal temperature, and 1350-^oC roasting to obtain alpha-Al with the purity of more than 99 wt%₂O₃And (3) alumina powder.

The beneficial technical effects are as follows:

(1) the alumina particles are uniform in size, with the particle size centered at 0.5 + -0.25 μm, D₉₇Less than or equal to 1 mu m and stable and good polishing effect.

(2) The Mohs hardness of the alumina is 9.1, the polishing efficiency is high, and the average removal amount of the sapphire reaches 40-80 mu m within 2-20 minutes.

(3) The polishing solution has long shelf life and can be free from the interference of bacteria or fungi.

(4) The complexing agent has good complexing ability on titanium ions and iron ions, and can effectively complex titanium and iron impurities in alumina and titanium and iron ions in sapphire.

The attached drawings of the specification:

FIG. 1 is a process flow diagram for obtaining alumina particles from kaolinite purification;

FIG. 2 is a graph showing a distribution of the particle size of alumina in the rough polishing solution;

FIG. 3 XRD patterns of alumina in polishing solutions of example 1 and example 2;

FIG. 4 is an SEM image of alumina in the rough polishing solution.

Detailed Description

The specific implementation steps of the invention are shown in fig. 1, and are specifically described as follows:

firstly, the dispersant used in the slurry preparation process is a mixture of sodium hexametaphosphate, sodium polyacrylat and sodium oxalate, the compound dispersant has obvious improvement on the dispersion stability of the prepared slurry, and the sodium hexametaphosphate and the sodium polyacrylate can effectively improve the dispersion stability of the slurry. The sodium hexametaphosphate is attached to the surface of the mineral after being dissociated, so that the negative charge of the surface of the mineral is increased, mineral particles are separated due to static electricity, meanwhile, the ultra-large molecular group of the sodium hexametaphosphate is attached to the surface of the mineral to generate a strong steric hindrance effect so as to enhance the dispersion effect, sodium oxalate is introduced to enhance the adsorption and the negative ion of the surface characteristic of the mineral, so that the surface potential is changed to be negative, the isoelectric point is reduced, and the addition of the sodium polyacrylate is beneficial to the dispersion and the separation of compound minerals, namely the use of the dispersing agent is beneficial to subsequent sand removal, particle size classification, gradient magnetic separation and whitening, so that the purity of kaolin purification is effectively improved, and the kaolin purification is more uniform and thorough.

The main impurity minerals in the ore sample are iron-containing titanium minerals, wherein the titanium-containing minerals are mainly anatase and rutile, a small amount of brookite, ferrotitanium rutile and ilmenite, the iron-containing minerals are mainly limonite, hematite, tourmaline and the like, in addition, Fe and Ti are dyeing elements which need to be removed in the CMP polishing process so as to avoid pollution to a polishing substrate, coloring elements such as iron and titanium and organic carbon in kaolin are main factors influencing the whiteness of a polishing material, and the current method for removing the ferrotitanium mainly comprises the following steps: (A) flotation: the method is to separate the coloring matter such as anatase, tourmaline and the like from the kaolin suspension dispersed in water by utilizing the characteristic that the oleophylic energy of the coloring matter enters organic liquid such as fatty acid, benzene, carbon tetrachloride and the like, and the industrial application of the method is mainly limited by the cost at present. The main defects of iron and titanium removal by a flotation method are that the amount of residual medicament adsorbed on the surface of kaolin particles is large, dehydration is difficult, and the whole process is complex; (b) chemical reduction: the iron is removed by direct acid leaching or reduction bleaching, the factors influencing the bleaching effect by chemical reduction are many, such as the characteristics, temperature, pH value, medicament dosage, ore pulp concentration, bleaching time, stirring strength and the like of the ore, and if the ore contains high organic substances and impurities, the bleaching effect is poor, and the whiteness is not greatly improved. (c) The microbiological method comprises the following steps: the microorganism method is to use some microorganisms (malt, azotobacter and aspergillus niger) to oxidize or reduce impurity iron (pyrite, iron oxide ore and the like) into soluble iron to achieve the aim of removing iron impurities in kaolin, but the microorganism oxidation method has large floor area and long treatment period, has different fungus treatment efficiencies for different types of clay, and is subject to further research and optimization. Through high-gradient magnetic separation on kaolin, the content of titanium is reduced from 4-5.5 wt.% to 0.3wt.%, and the content of iron is reduced from 3-4 wt.% to 0.2wt.%, so that the effect is obvious.

In addition, factors influencing whiteness include organic carbon, and organic matters are easy to burn at high temperature, so that calcination is the most economical and effective method for removing organic carbon in kaolin powder, the calcination atmosphere has great influence on carbon removal in the calcination process, the oxidation atmosphere is favorable for burning removal of carbon, and the reduction atmosphere is unfavorable for carbon removal. Under the reducing or weak oxidizing atmosphere, the organic carbon in the kaolin powder can be converted into CO, and when the ventilation is poor and the temperature is low, the CO is decomposed into CO₂And dispersed carbon, which is the function of low-temperature carbon deposition. For this reason, when the calcination temperature is low and the oxidizing atmosphere is weak, the surface of the product is gray. The oxygen-nitrogen mixed gas O of the roasting atmosphere of the invention₂/N₂= 5-8 wt.%, and Al with whiteness of more than 90% is obtained₂O₃ ^.xSiO₂The material can also have simple phase change in the roasting process to generate Al₂O₃ ^.xSiO₂And (3) feeding.

High temperature calcification is used to form CaO which can react with an aqueous solution of sodium carbonate^.Al₂O₃Generating sodium tetrahydroxy chlorate and CaO which does not react with the sodium carbonate aqueous solution^.SiO₂And further realize CaO^.Al₂O₃And CaO^.SiO₂To obtain CaO^.SiO₂The grain diameter of the powder is less than 1mm, CaO^.SiO₂SiO in powder₂The content is more than 97 wt.%.

Then, 5-20 wt.% of HCl aqueous solution is added into the filtrate to react to form AlCl₃Adding a dispersing agent sodium hexametaphosphate in advance, then slowly adding 2-5wt.% of ammonia water to obtain white precipitated aluminum hydroxide, and using ethanol and ethanolMultiple alternate filtering and washing, normal temperature drying, 1350-^oRoasting C to obtain alpha Al with purity of more than 99 wt%₂O₃Alumina powder with particle size below 1 μm, mainly concentrated at 0.5 + -0.25 μm, as shown in figure 2 and figure 4, in which Na, Ca, Cl ions are almost completely washed.

In addition, in a polar aqueous solution, the alumina particles are agglomerated under the action of electrostatic force and the like, so that flocculation, delamination and other phenomena are easy to occur, and the dispersibility and stability of the polishing solution are damaged. The large-particle agglomerates generated by the agglomeration of abrasive particles are a main cause of scratches occurring on the surface of a substrate during chemical mechanical polishing, and thus a dispersant, sodium hexametaphosphate, should be added in advance before precipitation due to the formation of uniform alumina.

In addition, the hardness of the polished alumina particles is required to be higher than that of the workpiece to be polished to achieve an abrasive effect. The general calcining temperature of the high-temperature alumina is 1350-1450 ℃. The conversion rate is disregarded. The higher the temperature of calcination, the higher the hardness and vice versa.

As shown in figure 3, the crystal form of the carrier after high-temperature roasting is alpha-Al₂O₃(JCPDS number 46-1212), and the diffraction peak is very strong and sharp, which indicates that the alumina has a perfect crystal structure. In the whole diffraction angle, γ -Al was not found₂O₃Or diffraction peaks of other crystalline phases.

The conversion rate is closely related to the calcining process, and the higher the conversion rate is, the higher the purity of the alumina is. Namely, the higher the content of the alpha-alumina, the grinding effect and the wear resistance are obviously improved.

The grain size of the alumina determines the brightness of the surface of the workpiece being polished. The smaller the particle the higher the brightness. In addition, the brightness of the polished alumina surface is related to the hardness of the alumina. The finer the alumina micropowder particles of the same hardness, the higher the brightness. However, the lower the hardness of the same size of polished alumina, the higher the brightness, and the Mohs hardness of the alpha alumina used in the invention is 9.1, which meets the industry standard.

In addition, after high-gradient magnetic separation, the content of alumina is reduced from 36.75 to 32.02, and 12% of alumina is lost, wherein the loss rate of the alumina is obviously higher than that of the silica. This is caused by the fact that the magnetic mineral iron titanium is closely related to the aluminum-containing mineral such as diaspore, and they are often associated with intergrowth and like phases and are difficult to disperse, so that part of the alumina is magnetically separated from the titanium-containing iron mineral, and the recovery rate of the final silica is 91.99% and the recovery rate of the alumina is 81.27%.

The following explanation is made with respect to the composition of the sapphire rough polishing liquid:

(1) pH value: in the case of using deionized water as the dispersion medium of the abrasive medium, the isoelectric point of the alumina particles in water is determined, and the isoelectric point of the α -alumina particles in water is measured to be about pH =4, which helps to determine the dispersion effect of the suspension. In deionized water, alpha-Al₂O₃The sedimentation volume of the suspension is minimum in the acidic range (pH = 3.5-5), and is higher in the neutral and alkaline regions₂O₃The optimal pH value of the particles dispersed in the deionized water is within the range of 3.5-5, and in the pH range, the alumina particles have proper zeta potential and are well dispersed through electrostatic repulsion action generated by an electric double layer, so that a small sedimentation volume is generated. In addition, the citric acid or tartaric acid organic acid is used as an acid regulator, and simultaneously, metal ions are not introduced into the polishing solution, and the Ti or Fe complexing agent can be effectively assisted to complex the metal ions, so that the influence of the metal ions on the polishing performance is reduced.

(2) Content of abrasive medium: generally speaking, the higher the content of the abrasive medium in the polishing solution, the higher the average removal amount thereof, for example, due to the increase of the concentration of the abrasive in the polishing solution, the number of particles participating in mechanical grinding in the polishing process is increased, the corresponding number of effective particles is also increased, and under a certain particle size, the increase of the number of effective particles enhances the mechanical grinding force, thereby increasing the polishing rate. But in the practical application process, the problems of abrasive agglomeration, abrasive precipitation and use cost must be considered, and the content of the alumina particles is optimized to be 8-15 wt.%.

(3) Metal complexing agent: the complexing agent added during the preparation of the polishing solution is mainly used for complexing metal ions generated in the polishing solution, and the metal ions generally come from the polishing solution, a reactant of a material to be polished and a reactant ground by a metal grinding disc of a polishing agent. In the invention, Ti ions and Fe ions are inevitably present in the solution due to the defects of the silicon oxide dispersion solution, and the presence of the ions can generate precipitate particles in the polishing process, influence the polishing effect of the polishing solution and even destroy a polished workpiece in severe cases, so that a metal complexing agent is added into the polishing solution, which can promote the formation of a polished film and further improve the polishing rate. The method can balance the mechanical removal rate and the dissolution rate of reactants in the polishing solution, reduce the re-precipitation rate of reaction products on the surface when the dissolution rate is low, and solve the problem of poor flatness caused by excessive material removal when the solubility is high. It can also form stable complex with metal ion to prevent surface contamination or adsorption. Among them, there are the targeted selection of EDTA with good complexing performance for Fe ions (although the complexing effect of disodium EDTA is usually better, the complexing agent introduces secondary pollution of sodium ions and is irretrievable) and the selection of 1, 2-cyclohexanediamine tetraacetic acid with good complexing performance for Ti ions, and in addition, the above citric acid and tartaric acid are also good technical complexing agents, so in the CMP field, the selection of a proper amount of complexing agent has become one of the indispensable components of the polishing solution.

(4) The oxidizing agent can form an oxide film on the surface of the polishing workpiece, the oxide film on the convex part of the polishing workpiece is ground off by mechanical action, and the oxide film on the concave part is prevented from being further corroded, so that the subsequent mechanical polishing is facilitated, and the polishing efficiency and the surface flatness are improved. In the invention, one or more of tert-butyl peroxy, aluminum nitrate and hydrogen peroxide are used, wherein in terms of effect, tert-butyl peroxy' hydrogen peroxide > aluminum nitrate;

(5) preservative: because organic substances or grease are inevitably adhered in the polishing process, a certain breeding environment is provided for the propagation of bacteria and fungi, the pH of the polishing solution can be obviously changed by biological acid generated in the propagation process, the polishing effect of the polishing solution is further reduced, even scratches or scars are formed on the surface of the alumina sapphire, and finally the product is discarded.

(6) The invention is a rough polishing solution, namely after rough polishing, a subsequent fine polishing process can be added according to the requirements of actual manufacturers, so that the rough polishing solution can effectively polish sapphire without adding a corrosion inhibitor, a passivating agent and a surfactant, and the average removal amount of the sapphire in 2-20 minutes is 40-80 mu m, which is far higher than the standard of the market that the removal amount is 10-30 mu m in 8 minutes of processing time.

The processes for preparing the rough polishing solution in examples 1 to 3 of the present invention are as follows:

(1) pulping and grading to obtain magnetic separation materials: carrying out coarse grinding, slurry preparation and sand removal and particle size classification treatment on kaolinite in a swirler, wherein the mass ratio of slurry preparation is kaolin subjected to coarse grinding: dispersing agent: and (3) water = (0.1): (0.005): 1, the stirring speed of the prepared slurry is 650r/min, the stirring time is 2 hours, and the content of the kaolin with the granularity of less than 3mm is more than 90 percent, so that the magnetic separation raw material is obtained.

(2) Gradient magnetic separation for removing iron and titanium: background magnetic field strength 1.5 x 10⁴Oe, flow rate 1.5 cm/s; magnetization period 5.5min, resulting in titanium content below 0.3wt.% and iron content below 0.2 wt.%.

(3) Baking whitening and simple phase transition: dehydrating, drying, and calcining at 950 deg.C^oC, rate of temperature rise 10^oC/min, keeping the temperature for 2.5h after the roasting temperature is reached, and roasting the oxygen-nitrogen mixed gas O in the atmosphere₂/N₂=6.5wt.%, Al having a whiteness of more than 90% is obtained₂O₃ ^.xSiO₂And (3) material, wherein X is more than or equal to 1.

(4) High-temperature calcification: to the above Al₂O₃ ^.xSiO₂Adding CaO powder into the materials, stirring uniformly, heating to 1250^oC, reacting for 1.5h to obtain CaO^.SiO₂With CaO^.Al₂O₃Cooling the mixture to 85 deg.C^oC。

(5) Purifying the alumina: to the above mixture was added 35wt.% Na₂CO₃Stirring and reacting the aqueous solution for 3 hours, filtering the aqueous solution for multiple times, collecting filtrate, adding 12.5wt.% of HCl aqueous solution into the filtrate, reacting the mixture for 0.75 hour, slowly adding 3.5wt.% of sodium hexametaphosphate, adjusting the pH value by using 3.5wt.% of ammonia water, slowly stirring the mixture to obtain white precipitates, filtering the mixture by using a 180-mesh filter membrane, alternately washing the mixture by using deionized water and an ethanol solution for multiple times, drying the mixture at normal temperature, and 1400 drying the mixture at 1400 normal temperature^oC roasting to obtain alpha-Al with the purity of more than 99 wt%₂O₃And (3) alumina powder.

Further, the number of the alternate washing was 3.

Further, the pH value ranges from 10.

Further, the dispersing agent is a mixture of sodium hexametaphosphate, sodium polyacrylat and sodium oxalate in a mass ratio of 0.35:1:1, and the pH value of the prepared slurry is adjusted by using ethylamine, wherein the pH value is = 9.5.

Placing the obtained alpha alumina as a raw material in a reaction kettle, adding deionized water into a dispersion cylinder of the reaction kettle, and mechanically stirring for 5-10min at a rotation speed of 50-20000 r/min; continuously adding one or more oxidants of tert-butyl peroxide, aluminum nitrate and hydrogen peroxide into the dispersion cylinder, and mechanically stirring for 1-2min at the rotation speed of 50-20000 r/min; sequentially adding methylisothiazolinone or one or more preservatives of isothiazolinone, a1, 2-cyclohexanediamine tetraacetic acid Ti ion complexing agent and a Fe ion complexing agent EDTA into the dispersion cylinder, and continuously stirring for 2-10min at a rotation speed of 50-20000 r/min; adding a proper amount of one or more pH regulators of citric acid or tartaric acid, and adjusting the pH =3.5-5 of the polishing solution to obtain the sapphire rough polishing solution.

Example 1

A sapphire rough polishing solution, comprising:

abrasive media: alumina particles, 8 wt.%;

oxidizing agent: 2wt.% of t-butyl peroxide

Preservative: methylisothiazolinone, 0.1wt. -%)

Ti ion complexing agent: 1, 2-cyclohexanediaminetetraacetic acid, 0.1-1 wt.%;

fe ion complexing agent: EDTA, 0.05-0.1 wt.%;

deionized water;

and adjusting the pH of the polishing solution to be 3.5 by using citric acid.

Example 2

A sapphire rough polishing solution, comprising:

abrasive media: alumina particles, 11.5 wt.%;

oxidizing agent: t-butyl peroxy, 3.5wt. -%)

Preservative: methylisothiazolinone, 0.3wt. -%)

Ti ion complexing agent: 1, 2-cyclohexanediaminetetraacetic acid, 0.5 wt.%;

fe ion complexing agent: EDTA, 0.075 wt.%;

deionized water;

and mixing citric acid and tartaric acid, and adjusting the pH of the polishing solution to be 4.5.

Example 3

A sapphire rough polishing solution, comprising:

abrasive media: alumina particles, 15 wt.%;

oxidizing agent: t-butyl peroxy, 5wt. -%)

Preservative: isothiazolinone, 0.5wt. -%)

Ti ion complexing agent: 1, 2-cyclohexanediaminetetraacetic acid, 1 wt.%;

fe ion complexing agent: EDTA, 0.1 wt.%;

deionized water;

tartaric acid adjusted the slurry pH = 5.

The embodiments of the present invention have been described in detail, but the embodiments are merely examples, and the present invention is not limited to the embodiments described above. Any equivalent modifications and substitutions to those skilled in the art are also within the scope of the present invention. Accordingly, equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered by the present invention.

Claims

1. A preparation method of sapphire rough polishing solution is characterized by comprising the following steps:

wherein, the pulping and grading obtain magnetic separation materials: carrying out coarse grinding, slurry preparation and sand removal and particle size classification treatment on kaolinite in a swirler, wherein the mass ratio of slurry preparation is that after coarse grinding, the kaolinite is: dispersing agent: water (0.05-0.15) = (0.001-0.01): 1, mixing and stirring speed is 500-;

wherein the parameters of the gradient magnetic separation iron and titanium removal are as follows: background magnetic field strength 1.5 x 10⁴Oe, the flow rate is 1-2 cm/s; magnetization period 3-8min, such that titanium content is below 0.3wt.% and iron content is below 0.2 wt.%;

wherein the roasting whitening process comprises the following steps: dehydration, drying, roasting at 800-^oC, rate of temperature rise 10^oC/min, keeping the temperature for 2-3h after the roasting temperature is reached, and roasting the oxygen-nitrogen mixed gas O in the atmosphere₂/N₂= 5-8 wt.%, and Al with whiteness of more than 90% is obtained₂O₃ ^.xSiO₂Materials, X is more than or equal to 1;

(3) continuously adding tert-butyl peroxide into the dispersion cylinder, and mechanically stirring for 1-2min at the rotation speed of 50-20000 r/min;

(4) sequentially adding methylisothiazolinone or one or two preservatives of isothiazolinone, 1, 2-cyclohexanediamine tetraacetic acid Ti ion complexing agent and Fe ion complexing agent EDTA into the dispersion cylinder, and continuously stirring for 2-10min at the rotating speed of 50-20000 r/min;

(5) adding appropriate amount of one or two pH regulators of citric acid or tartaric acid, adjusting pH =3.5-5 to obtain sapphire rough polishing solution,

the rough polishing solution comprises:

abrasive media: alumina particles, 8-15 wt.%;

oxidizing agent: t-butyl peroxy, 2-5 wt.%;

preservative: one or both of methylisothiazolinone or isothiazolinone, 0.1-0.5 wt.%;

ti ion complexing agent: 1, 2-cyclohexanediaminetetraacetic acid, 0.1-1 wt.%;

fe ion complexing agent: EDTA, 0.05-0.1 wt.%;

deionized water: 75-90 wt.%;

pH regulator: one or two of citric acid and tartaric acid, and adjusting the pH = 3.5-5.

2. The method according to claim 1, wherein the high temperature calcification is performed to the Al₂O₃ ^.xSiO₂Adding CaO powder into the materials, uniformly stirring, and heating to 1200-1300 DEG C^oC, reacting for 1-2h to obtain CaO^.SiO₂With CaO^.Al₂O₃Cooling the mixture to 80-90 deg.C^oC。

3. The method of claim 2, wherein the alumina is purified by adding 30-40wt.% Na to the product after high-temperature calcification₂CO₃Stirring and reacting the aqueous solution for 2-4h, filtering for multiple times, collecting the filtrate, adding 5-20 wt.% of HCl aqueous solution into the filtrate, reacting for 0.5-1h, slowly adding 2-5wt.% sodium hexametaphosphate, adjusting the pH value by using 2-5wt.% ammonia water, slowly stirring to obtain white precipitate, filtering, alternately washing the deionized water and the ethanol solution for multiple times, drying at normal temperature, 1350-^oC roasting to obtain alpha-Al with the purity of more than 99 wt%₂O₃And (3) alumina powder.

4. The method according to claim 1, wherein the alumina particles have a mohs hardness of 9.1.

5. The method of claim 1, wherein the particle size is centered at 0.5 ± 0.25 μm, D₉₇≤1μm。

6. The method according to claim 1, wherein the rough polishing solution has an average sapphire removal amount of 40-80 μm within 2-20 minutes.

7. The method according to claim 1, wherein the alumina particles comprise titanium oxide and iron oxide, and the mass ratio of titanium oxide and iron oxide to alumina is less than or equal to 0.1%.