Grinding and modification of ultrafine mica powder
With the development of industry, downstream application companies have increasingly higher requirements for the quality of mica powder. Currently, muscovite powder with a D90 of about 45 μm is mainly used in papermaking, latex paint, rubber and other industries, while high-end coatings, pearlescent mica and other products are The particle size of mica powder has put forward higher requirements, and the preparation of micro-nano-level ultra-fine mica powder is urgent.
During the grinding process, muscovite can still be tightly combined along the fresh surface after interlayer cleavage. It is one of the more difficult minerals to grind. Currently, micro-nano-level muscovite ultrafine powder is difficult to prepare using conventional grinding equipment. Many domestic mica manufacturers will mine high-quality muscovite and simply coarsely grind it for export. Others will be made into muscovite products with D90 particle size of about 45μm or even coarser, resulting in a waste of resources and reducing product competitiveness.
Mica ultrafine grinding preparation
At present, the ultra-fine grinding process of mica is divided into two grinding methods: dry method and wet method. Among them: the main equipment for dry ultra-fine grinding include high-speed mechanical impact mill, airflow mill, cyclone or cyclone flow autogenous grinding machine, etc. and the corresponding dry airflow classifier; the production equipment for wet grinding sericite powder includes sand mill, grinding machine, etc. Flaking machines and colloid mills are the main ones, while wet fine classification uses hydrocyclone classification technology.
The high-speed planetary roller mill can effectively perform dry and wet grinding of mica. The median diameter of the particles after grinding can reach 10 μm or less; the mica material stays in the grinding for a very short time, generally 5-10s. ; By adjusting the roller structure, mica powder with the required diameter-thickness ratio can be obtained. Under wet grinding conditions, mica powder can obtain a diameter-thickness ratio in the range of 20-60.
The stirring mill adopts special grinding media, which has good application effect in ultra-fine peeling of mica powder without damaging the surface of mica, and can make the diameter-thickness ratio of mica powder >60.
Mica powder surface coating or modification
The surface coating or modification of mica powder can prepare pearlescent mica and colored mica pigments to improve their corresponding properties in materials such as rubber and coatings. There are also many related studies.
Mica is surface-coated to prepare pearlescent mica and colored mica pigments. Currently, the liquid phase deposition method is mainly used. Common methods include alkali addition, thermal hydrolysis, buffering, etc. Commonly used coating agent titanium sources in industry are titanium tetrachloride and titanyl sulfate.
Application of mica powder
Mica powder can be used in fields such as electrical insulation materials, functional coating fillers, rubber fillers, plastic fillers, cosmetics and welding materials.
Using silicon nitride ceramics as raw material for mobile phone backplanes
As smartphone technology continues to develop and competition intensifies, mobile phone manufacturers have launched various new designs and innovations to attract more consumers, and ceramic backplanes are one of the tricks. Its emergence began in 2012 when Sharp launched a smartphone with a ceramic backplane. However, due to technical and cost issues, ceramic backplanes were only used in a few high-end brands at that time. However, with the development of processing technology, the application range of ceramic backplanes is becoming wider and wider.
In the field of ceramic backsheets, the protagonists are almost all zirconia ceramics, but recently researchers seem to have begun to think about silicon nitride. Compared with zirconia, silicon nitride is considered by researchers to be a superior and promising mobile phone backplane material, especially whisker-toughened silicon nitride ceramics. The reasons are as follows:
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(1) Silicon nitride ceramics have higher impact toughness, are not easily broken, are not easily damaged during machining, and have a higher yield;
(2) Silicon nitride ceramic has high thermal conductivity, which is more than 10 times that of zirconia ceramic, and it is easier to dissipate heat. Therefore, the heat generated when the mobile phone is running at high speed or the battery is charging and discharging is easy to dissipate, which is beneficial to the normal operation of the mobile phone. Avoid slowdowns and other phenomena;
(3) The dielectric loss of silicon nitride ceramics is two orders of magnitude lower than that of zirconia, making it more transparent to mobile phone signals and making it easier to communicate smoothly in environments with weak signals;
(4) Silicon nitride ceramic has higher hardness and lower density than zirconia, which can effectively reduce the quality of the fuselage, and its cost is close to that of zirconia;
(5) Silicon nitride ceramic is a colorless ceramic, which is relatively easy to color and has good coloring effect. It also has a jade-like texture and is suitable for use in, for example, mid-to-high-end mobile phone casings.
Therefore, the use of silicon nitride ceramic materials as communication device mobile phone backplane materials can, to a certain extent, make up for the shortcomings of current zirconia mobile phone backplane materials, and does have certain prospects.
Although there are not many reports on silicon nitride mobile phone backplane materials, it has been used as a structural ceramic for a long time and has fully proven its application stability and reliability in harsh environments such as automobile engines. If silicon nitride is used as a new mobile phone backplane material, it not only has the same excellent mechanical properties as zirconia, but also has the advantages of good texture, light weight, and more sensitive signals. It is a new mobile phone backplane material with great potential.
At present, the key to breakthrough lies in how to optimize the process to make Si3N4 ceramics not only easy to dissipate heat and rich in color, but also the preparation process can be simple and reliable, and the cost becomes acceptable. If the above difficulties can be overcome, perhaps one day in the future we will be able to see Si3N4 on smartphone backplanes and smart wearable devices.
7 Major Application Of Ultrafine Talc Powder
The nature of ultrafine talc powder is that it is a natural hydrated magnesium silicate mineral. It is inert to most chemical reagents and does not decompose when in contact with acids. It is a poor conductor of electricity, has low thermal conductivity and high thermal shock resistance. It can be heated when heated. It does not decompose even at high temperatures of 900°C. These excellent properties of talc make it a good filler. Today, we will sort out the application fields of ultrafine talc powder.
Application of talc powder in coating industry
Because talc has excellent physical and chemical properties such as lubricity, anti-adhesion, flow aid, fire resistance, acid resistance, insulation, high melting point, chemical inactivity, good covering power, softness, good gloss, and strong adsorption.
As a filler, the application of talc powder in coatings is mainly reflected in:
1. High whiteness, uniform particle size and strong dispersion;
2. Can serve as a skeleton;
3. Reduce manufacturing costs;
4. Improve the film hardness of the paint;
5. It can increase the stability of product shape;
6. Increase tensile strength, shear strength, bending strength, and pressure strength, and reduce deformation, elongation, and thermal expansion coefficient.
Application of talc powder in plastics industry
◆ Application in polypropylene resin
Talc is commonly used to fill polypropylene. Talc powder has the characteristics of lamellar structure, so talc powder with finer particle size can be used as a reinforcing filler for polypropylene.
◆ Application in polyethylene resin
Talc is natural magnesium silicate. Its unique micro-scale structure has certain water resistance and high chemical inertness, so it has good chemical resistance and sliding properties. Polyethylene filled with it can be used as engineering plastics. It has good chemical resistance and fluidity and can compete with ABS, nylon, and polycarbonate.
◆ Application in ABS resin
ABS resin is an amorphous polymer with excellent molding processability like polystyrene; it has good impact strength, low temperature resistance, high tensile strength and good creep resistance.
Application of talc powder in preparation industry
◆ Used as a dispersant for volatile oils
Talcum powder has a certain adsorption capacity, so it can adsorb volatile oil to the surface of its particles and disperse it evenly, increasing the contact area between volatile oil and liquid medicine, thereby increasing the solubility of volatile oil.
◆ Covered with powder coat layer
In sugar coating, talc powder can be used to coat the powder coating layer. White talc powder that passes through a 100-mesh sieve is suitable.
◆ Used as lubricant
Since talc has a layered structure that easily breaks into scales, it can be used as a lubricant to improve the compression moldability and fluidity of pharmaceutical powders.
◆ Used as filter aid
Talcum powder is not easy to react with drugs and has certain adsorption capacity, so it can be used as a filter aid.
Application of talc powder as pharmaceutical excipients
◆ Used as a disintegrant for hydrophobic drugs
Talcum powder is a hydrophilic substance. When added as an excipient to a drug, it can improve the hydrophilicity of the entire drug, making it easier for water to penetrate into the drug and making it easier to disintegrate.
◆ Used as anti-adhesive agent
Stickiness problem is a common problem in the coating process. It will lead to slow coating speed, longer production cycle, pellet sticking, reduced yield, film damage, affecting drug release and other problems.
◆ Increase the critical relative humidity of drugs
Application of talc powder in paper industry
The addition of talcum powder in the papermaking industry helps to increase filler retention and improve paper transparency, smoothness and printability, and makes the paper more ink absorbent.
Application of Talcum Powder in Cosmetics Industry
Talcum powder is a high-quality filler in the cosmetics industry. Due to its high silicon content, it can block infrared rays and enhance the sun protection and anti-infrared ray properties of cosmetics.
Application of talc powder in ceramic industry
In the ceramic industry, talcum powder plays an important role. The reason for the different colors of ceramics is that talcum powder is added to them. Different proportions and different ingredients can make ceramics display different colors, and at the same time, they can also make ceramics display different colors. After ceramic calcination, the density is uniform, the surface is smooth and the gloss is good.
Application of talc powder in textile industry
Ultra-finely ground talcum powder is often used as filler and bleaching agent in certain textiles, such as waterproof cloth, fireproof cloth, wheat flour bags, rope nylon, etc., which can enhance the density of the fabric and enhance heat and acid and alkali resistance. performance.
Application of ultrafine powder technology to develop edible resources
With the development of modern technology, the process has put forward higher and higher requirements for the particle size of powder. Many materials need to be crushed to the sub-micron level or nano-level, which cannot be achieved by traditional crushing technology and equipment. Ultrafine powder technology is developed based on this and involves the preparation and application of ultrafine powders and related new technologies. Its research content includes ultrafine powder preparation technology, classification technology, separation technology, and drying technology. , conveying mixing and homogenizing technology, surface modification technology, particle composite technology, detection and application technology, etc.
With the reduction of land, food will become a scarce commodity in the next century, and developing new food sources is a serious problem facing mankind. Ultra-fine powder technology can break cell walls, improve taste, and enhance digestion and absorption, thereby improving the bioavailability of edible resources and promoting the body's absorption of inedible parts of animals and plants. Therefore, it is widely used in the food industry. Been very widely used.
1 Grain processing
During the ultrafine milling process of flour, the glycosidic bonds may be broken and easily hydrolyzed by α-amylase, which is beneficial to fermentation. As the flour particles become smaller, their surface area becomes larger, which improves the adsorption, chemical activity, solubility and dispersibility of the material, thus causing changes in the macroscopic physical and chemical properties of flour. Wu Xuehui et al. proposed that flour with different particle sizes can be used to obtain flour with different protein contents to meet the needs of different products. The taste and absorption and utilization rate of the flour processed by ultra-fine powder are significantly improved. Wheat bran powder, soybean micron powder, etc. are added to flour to transform inferior flour into high-fiber or high-protein flour.
2 Deep processing of agricultural and sideline products
In recent years, plant-based green foods have become a focus of concern around the world, and edible plant-based foods are important resources for human survival. This situation can be improved by using ultra-fine powder technology. For example, the first step in the deep processing of edible plant stems and fruits is to control the crushing fineness to achieve different degrees of cell wall breaking and component separation.
3 Functional health food
Generally speaking, the high-tech means of ultrafine crushing are used to crush health food raw materials into ultrafine products with a particle size of less than 10 μm, which is called ultrafine health food. It has a large specific surface area and porosity, so it has strong adsorption and high activity. After ultra-fine processing of food, the nutrients in the food that are indispensable to the human body but difficult to eat can be fully absorbed by the human body, thereby maximizing the bioavailability and health care efficacy of the food.
4 Aquatic products processing
The ultrafine powder processed through ultrafine crushing of spirulina, kelp, pearls, turtles, shark cartilage, etc. has some unique advantages. The traditional method of processing pearl powder is ball milling for more than ten hours, and the particle size reaches several hundred meshes. However, if pearls are instantly crushed under low temperature of about -67°C and strict purification air flow conditions, ultrafine pearl powder with an average particle size of 1.0 μm and a D97 of less than 1.73 μm can be obtained. In addition, the entire production process is pollution-free. Compared with traditional pearl powder processing methods, the active ingredients of pearls are fully retained, and its calcium content is as high as 42%. It can be used as a medicinal diet or food additive to make calcium-supplementing nutritious foods.
Ultrafine powder technology is widely used in the food industry and plays a very important role in developing new edible resources and improving product quality.
The difference between quartz powder, silica powder, microsilica powder and white carbon black
Quartz powder and silica powder both refer to crystalline SiO2 powder. Simply put, they break stones into powder. Quartz powder is relatively coarse, while silica powder is relatively fine. Quartz powder is a powder obtained by crushing quartz raw ore through different processing equipment. Microsilica powder is an ultra-fine powder obtained by grinding quartz ore that has reached a certain purity, or a silica fine powder obtained by chemical means. However, their physical properties, chemical composition and application areas are different.
Microsilica fume is an industrial by-product, also called silica fume. Through the collection of smoke from smelting and incineration plants, fine dust containing high silica content is found.
Differences in properties between silica powder and quartz powder
1. Physical properties of silica powder and quartz powder
Microsilica powder and quartz powder are both fine powder materials, and their particle sizes are very small, usually less than 1 micron. However, their physical properties differ. Microsilica powder is usually light, loose, and low in density; quartz powder is relatively dense and high in density.
2. Chemical composition of silica powder and quartz powder
Microsilica and quartz powder are also chemically different. Silica powder is a type of silica (SiO2). Its crystal structure is similar to quartz, but due to its small size, it is usually an amorphous structure with many active groups on the surface. Quartz powder is made by crushing and finely grinding large crystal quartz minerals, and its chemical composition is SiO2.
3. Application fields of silica powder and quartz powder
Microsilica powder and quartz powder are widely used in industry, but their application fields are different. Microsilica powder is usually used in electronics, optics, ceramics, cosmetics, coatings, plastics and other fields. It is mainly used to increase the stability of materials, reduce material costs and improve the processing performance of materials. Quartz powder is mainly used in glass, ceramics, cement, building materials, metal surface spraying and other fields. Its high hardness and chemical stability make it an important component of many functional materials.
The effect of common minerals on plastic filling modification
Filling modification of plastics refers to a type of composite technology that adds low-cost fillers to resin to reduce the cost of polymer products. Its primary purpose is often to reduce costs. But since it is filling modification, it is also possible to improve certain properties after filling.
In thermoplastics, filling can improve the heat resistance, rigidity, hardness, dimensional stability, creep resistance, wear resistance, flame retardancy, smoke elimination and degradability of composite products, and reduce the molding shrinkage rate to improve Product accuracy; in thermosetting plastics, in addition to the aforementioned performance improvements, some resins are essential reinforcing materials in processing, such as unsaturated resins, phenolic resins and amino resins, which all need to be filled and reinforced.
Common modification properties of fillers
① Improve the rigidity of composite materials: specifically reflected in performance indicators such as flexural strength, flexural modulus, and hardness. The higher the silica content in the filler, the more obvious the rigidity modification effect will be. The order of rigidity modification of various fillers is silica (increase by 120%) > mica (increase by 100%) > wollastonite (increase by 80%) > barium sulfate (increase by 60%) > talc (increase by 50%) > Heavy calcium carbonate (increased by 30%) > light calcium carbonate (increased by 20%).
② Improve the dimensional stability of composite materials: specifically reflected in reducing shrinkage, reducing warpage, reducing linear expansion coefficient, reducing creep, and increasing isotropy. The order of dimensional stability effects is spherical fillers > granular fillers > flaky fillers >Fibrous filler.
③Improve the heat resistance of composite materials: The specific performance index is the heat deformation temperature. For example, the heat deformation temperature increases with the increase of talc powder content.
④ Improve the thermal stability of composite materials: Inorganic powders can absorb and promote analyte substances to varying degrees, thereby degrading the degree of thermal decomposition. In addition, inorganic fillers can also improve the wear resistance and hardness of composite materials.
Special modified properties of fillers
The reason why it is called the special modifying properties of fillers is that some fillers have and some do not have these modifying functions. The same filler may or may not have modifying functions under different conditions.
① Improve the tensile and impact properties of composite materials: Inorganic powder cannot always improve the tensile and impact properties of composite materials. It can only be improved when special conditions are met, and the improvement is not large. After the inorganic filler reaches a certain fineness, the tensile strength and impact strength of the composite material can be improved if the filler surface is well coated and a compatibilizer is added to the composite system.
② Improve the fluidity of composite materials: Most inorganic powders can improve the fluidity of composite materials, but talc powder reduces the fluidity of composite materials.
③ Improve the optical properties of composite materials: Inorganic powder can improve the covering, matting and astigmatism of composite materials. For example, titanium dioxide is a typical inorganic pigment with strong covering power.
④Improve the environmentally friendly combustion performance of composite materials: First, inorganic powder materials can make composite materials burn thoroughly, because cracks will occur during combustion and increase the oxygen contact area; second, inorganic powder materials can absorb some toxic gases when composite materials burn, Reduce toxic gas emissions; third, inorganic powder improves the thermal conductivity of composite materials, making combustion faster and shortening combustion time.
⑤ Promote the flame retardancy of composite materials: Not all inorganic powders are helpful for flame retardancy. Only inorganic powders containing silicon elements can help improve the flame retardancy and can be used as flame retardant synergists. The specific reason is that when silicon-containing materials are burned, a barrier layer can be formed on the surface of the combustion material to reduce the probability of oxygen contacting the material surface.
⑥ Optimize other properties of composite materials: nucleating agent function. When the particle size of talc powder is less than 1 μm, it can act as an inorganic nucleating agent in PP. To block infrared rays, inorganic powders containing silicon such as talc, kaolin, and mica all have good infrared and ultraviolet blocking properties.
Spherical Alumina Filler Market Overview
Because spherical alumina powder has good thermal conductivity and excellent cost performance, it is a thermally conductive filler used in large quantities and with a high proportion of thermal interface materials on the market.
The morphology of spherical alumina shows a regular spherical structure, and the particle size is usually in the range of a few microns to dozens of dimensions. It is mainly prepared through liquid phase precipitation, high-temperature plasma, spray pyrolysis and other routes.
When spherical alumina is used as a filler, the higher the sphericity of the particles, the smaller the surface energy and the better the surface fluidity. It can be more uniformly mixed with the polymer matrix, and the mixed system has better fluidity. After film formation, The prepared composite material has better uniformity.
High energy-consuming fields such as new energy vehicles and 5G promote the application of spherical alumina in the field of thermal management. The demand for spherical alumina increases and the market continues to expand. In addition to being a thermal conductive material, spherical alumina is also widely used in advanced ceramics, catalysis, grinding and polishing, composite materials, etc., and has broad market prospects.
According to QYResearch statistics, the global spherical alumina filler market size will be approximately US$398 million in 2023, and is expected to reach US$68.5 billion in 2029, with a CAGR of 9.5% in the next few years.
Globally, major manufacturers of spherical alumina fillers include Denka Co., Ltd., Baitu High-tech, Yaduma, Showa Denko, Nippon Steel & Sumitomo Metal, Sibelco, Tianjin Zexi Minerals, Lianrui New Materials, Daehan Ceramics, One Shitong, Kaisheng Technology, Dongkuk R&S, Yixin Mining Technology and Suzhou Jinyi New Materials, etc.
Currently, global core manufacturers are mainly located in Japan, South Korea and China. In terms of output value, Japan and China account for more than 80% of the market share. From 2018 to 2021, Japan is the main producing area, with an average share of 50%. By 2023, China's output value share will exceed 45%. In the next few years, China will occupy the main market share.
In terms of product types, 30-80μm is currently the most important segmented product, accounting for approximately 46% of the market share.
In terms of product type, thermal interface materials TIM is currently the main source of demand, accounting for approximately 49%. When used as thermal interface materials, spherical aluminum fillers can be used in thermal pads, thermal grease, thermal potting glue, thermal gel, etc.
At present, the terminal applications driving demand for spherical alumina are mainly photovoltaic cells, new energy vehicle power batteries, 5G communications/high-end electronic products, chip packaging, etc. At the same time, the future development trend of spherical alumina is mainly high purity and low radioactivity.
10 major changes after ultrafine crushing of powder materials
The various changes that occur to the crushed materials during the crushing process are insignificant compared to the coarse crushing process, but for the ultra-fine crushing process, due to reasons such as high crushing intensity, long crushing time, and large changes in material properties, it is seems important. This change in the crystal structure and physical and chemical properties of the crushed material caused by mechanical ultrafine crushing is called the mechanochemical effect of the crushing process.
1. Changes in particle size
After ultrafine grinding, the most obvious change in the powder material is the finer particle size. According to different particle sizes, ultrafine powders are usually divided into: micron level (particle size 1 ~ 30 μm), submicron level (particle size 1 ~ 0.1 μm) and nano level (particle size 0.001 ~ 0.1 μm).
2. Changes in crystal structure
During the ultrafine crushing process, due to the strong and lasting mechanical force, the powder material undergoes lattice distortion to varying degrees, the grain size becomes smaller, the structure becomes disordered, amorphous or amorphous substances are formed on the surface, and even Polycrystalline conversion. These changes can be detected by X-ray diffraction, infrared spectroscopy, nuclear magnetic resonance, electron paramagnetic resonance, and differential calorimetry.
3. Changes in chemical composition
Due to the strong mechanical activation, the materials directly undergo chemical reactions under certain circumstances during the ultrafine crushing process. Reaction types include decomposition, gas-solid, liquid-solid, solid-solid reaction, etc.
4. Changes in solubility
Such as the dissolution of powdered quartz, calcite, cassiterite, corundum, bauxite, chromite, magnetite, galena, titanium magnetite, volcanic ash, kaolin, etc. in inorganic acids after fine grinding or ultra-fine grinding Both speed and solubility are increased.
5. Changes in sintering properties
There are two main types of changes in thermal properties of materials caused by fine grinding or ultra-fine grinding:
First, due to the increased dispersion of materials, solid-phase reactions become easier, the sintering temperature of the products decreases, and the mechanical properties of the products are also improved.
The second is that changes in crystal structure and amorphization lead to a shift in crystal phase transition temperature.
6. Changes in cation exchange capacity
Some silicate minerals, especially some clay minerals such as bentonite and kaolin, have significant changes in cation exchange capacity after fine or ultra-fine grinding.
7. Changes in hydration performance and reactivity
Fine grinding can improve the reactivity of calcium hydroxide materials, which is very important in the preparation of building materials. Because these materials are inert or not active enough for hydration. For example, the hydration activity of volcanic ash and its reactivity with calcium hydroxide are almost zero at the beginning, but after fine grinding in a ball mill or vibrating mill, they can be improved to almost those of diatomaceous earth.
8. Electrical changes
Fine grinding or ultra-fine grinding also affects the surface electrical and dielectric properties of minerals. For example, after biotite is impacted, crushed and ground, its isoelectric point and surface electrokinetic potential (Zeta potential) will change.
9. Changes in density
After grinding natural zeolite (mainly composed of clinoptilolite, mordenite and quartz) and synthetic zeolite (mainly mordenite) in a planetary ball mill, it was found that the density of these two zeolites changed differently.
10. Changes in properties of clay suspensions and hydrogels
Wet grinding improves the plasticity and dry flexural strength of clay. On the contrary, in dry grinding, the plasticity and dry bending strength of the material increase in a short period of time, but tend to decrease as the grinding time increases.
In short, in addition to the properties of raw materials, feed particle size and crushing or activation time, factors that affect the mechanochemical changes of materials also include equipment type, crushing method, crushing environment or atmosphere, crushing aids, etc. It is undoubtedly necessary to pay attention to the combined influence of these factors in the study of mechanochemistry.
Silicon nitride ceramics—the “leader” in four major fields
Silicon nitride (Si3N4) is a covalently bonded compound composed of silicon and nitrogen. It was discovered in 1857 and was mass-produced as a ceramic material by 1955. Silicon nitride ceramics have many advantages that metal materials and polymer materials do not have, such as high temperature resistance (bending strength can reach more than 350MPa at 1200°C), acid and alkali corrosion resistance, self-lubrication, etc., and are widely used in aerospace, national defense and military industries. , widely used in the mechanical field.
Mechanical field
Silicon nitride ceramics are mainly used in the machinery industry as valves, pipes, classifying wheels and ceramic cutting tools. The most widely used silicon nitride ceramic bearing balls are silicon nitride ceramic bearing balls.
Silicon nitride bearing balls can rotate up to 600,000 revolutions per minute during use. They are mainly used in precision machine tool spindles, high-speed bearings for electric spindles, aerospace engines, automobile engine bearings and other equipment bearings.
Silicon nitride ceramic bearing balls have outstanding advantages compared with steel balls: low density, high temperature resistance, self-lubricating, and corrosion resistance. As a high-speed rotating body, the ceramic ball generates centrifugal stress, and the low density of silicon nitride reduces the centrifugal stress on the outer ring of the high-speed rotating body. Dense Si3N4 ceramics also exhibit high fracture toughness, high modulus properties and self-lubricating properties, and can excellently resist a variety of wear and endure harsh environments that may cause other ceramic materials to crack, deform or collapse, including extreme temperatures, large temperature differences, Ultra high vacuum. Silicon nitride bearings are expected to find wide application in various industries.
Wave-transparent materials field
Porous silicon nitride ceramics have relatively high flexural strength and lower density, which is one of the key factors for their application in aerospace. It is also creep-resistant (compared to metals), which improves the structure's stability at high temperatures. This material has a variety of additional properties, including hardness, electromagnetic properties and thermal resistance, and is used as a wave-transparent material to make radomes and antenna windows. With the development of the national defense industry, missiles are developing towards high Mach number, wide frequency band, multi-mode and precision guidance. Silicon nitride ceramics and their composite materials have excellent properties such as heat protection, wave transmission, and load-bearing, making them one of the new generation of high-performance wave-transparent materials studied.
Semiconductor field
In addition to excellent mechanical properties, silicon nitride ceramics also exhibit a range of excellent thermal conductivity properties, making them suitable for use in the demanding semiconductor field. Thermal conductivity is the inherent ability of a material to transfer or conduct heat. Due to the unique chemical composition and microstructure of silicon nitride, it has excellent comprehensive properties compared with alumina ceramics and aluminum nitride ceramics.
Bioceramics field
As a new generation of bioceramic materials, silicon nitride ceramics not only have the excellent qualities of ceramic materials, but also have good radiographic properties, anti-infection properties, biocompatibility properties and osseointegration properties.
The above-mentioned excellent properties of silicon nitride ceramics make it an ideal biomaterial, and it is used in biosensors, spine, orthopedics, dentistry and other implants.
How to choose a suitable ultra-fine grinding process for pigment production?
Pigments, as a colorant, are widely used in various fields: such as paints, inks, plastics, fabrics, cosmetics, food, etc. We can roughly divide colorants into two types: insoluble pigments and soluble dyes. Due to the insolubility of pigments, their coloring strength and color will be directly affected by the size and morphology of the pigment particles. Therefore, choosing a suitable and efficient ultra-fine grinding and pulverization process will significantly enhance the coloring performance of the pigment on the matrix material. In addition, pigment particles of a certain size and shape can change the absorption and scattering of light of different spectra, thereby changing the color and giving the surface of the base material a specific appearance.
Impact grinding
Mechanical impact mills can be used for fine grinding of soft to medium hard materials. Typical fineness ranges for median particle size are 20 to 500 μm. A choice of rotor types ensures stable temperatures during grinding. These characteristics of the mills make them suitable for deagglomerating pigment particles after drying. In addition, the easy-to-operate and clean design allows you to quickly switch between different materials. At the same time, the wide variety of grinding tools that can be installed on the mill means that they can be used to process a variety of different products and achieve different material finenesses.
Impact grinding machine with classifier
This type of classifying mill offers the possibility of achieving both grinding and classifying functions in one system. The CSM classifier is a combination of a fine impact classifier and a guide wheel classifier. Using two independent motor drives, one for the grinding disc and the other for the grading wheel, the CSM can precisely adjust the grading wheel speed to obtain a wide range of final product fineness from d97=9μm to 200μm. By utilizing the geometry of the classifier impeller and the air seal between the classifier wheel and the machine top cover, precise control of the upper limit of the particle size of the grinding material is ensured, thereby achieving fine classification.
Fluidized bed jet mill
This jet mill is suitable for ultra-fine crushing of materials of various hardnesses (soft to extremely hard). In the grinding area, the particles are driven by high-speed airflow to collide and grind with each other. There are no additional grinding parts. The dynamic classifier controls the maximum particle size. The air flow velocity at the nozzle outlet in the grinding chamber can reach 500 to 600 m/s. Because high grinding energy and impact speed can be generated in the fluidized bed, it is possible to achieve a D50 fineness of 1 to 5 μm.
If the products being ground are organic pigments, special attention needs to be paid to characteristic values that may cause dust explosions. This mainly involves critical energy, critical temperature and Kst value. Based on these data, adequate protection must be provided when limit values are exceeded. The first solution is to build a pressure shock-resistant device in the factory, including special elements such as explosion protection valves and rupture discs. The second solution is to operate under inert gas and reliably control the oxygen content of the plant.
Using a suitable ultra-fine grinding process can produce high-quality pigments with special flow characteristics and achieve the fineness and quality required for the final product. This optimized ultra-fine grinding and crushing process also increases the value of the product and reduces energy consumption and other production costs.