Preparation & application of nano-silica

Nano-silica is an inorganic chemical material, commonly known as "ultra-fine white carbon black". It is a non-toxic, odorless, and pollution-free inorganic non-metallic material and high-tech ultra-fine inorganic new material. The size is between 1~100nm, and it has a three-dimensional network structure, which is easy to agglomerate and has poor storage stability.

Preparation of nano-silica

At present, the research on nano-silica mainly uses sodium silicate and ethyl orthosilicate as raw materials, while the raw materials for industrial production are mainly low-cost sodium silicate.

• Physical method

It is mainly mechanical pulverization. The large-particle silica is ultra-finely pulverized through the combined action of impact, shear, friction and other forces generated by the ultra-fine pulverizing machine. Then, a high-efficiency grouping device is used to separate the particles of different particle sizes, so as to realize the uniformity and specificity of the particle size distribution of the nano-silica powder.

The physical production process is simple, the production volume is large, and the production process is easy to control. However, the requirements for raw materials are higher, and as the particle size decreases, the particles agglomerate due to the increase of surface energy, and it is difficult to further reduce the particle size of the powder particles.

• Chemical method

1.Chemical gas phase reaction

This method uses organosilicon compounds (such as organohalosilanes, silanes, etc.), hydrogen and oxygen or air to mix and burn. After the organosilicon compounds are burned at high temperatures, they undergo high-temperature hydrolysis in the water produced by the reaction to prepare nano-silica.

The chemical gas phase reaction method has uniform particle size, small particle size and spherical shape, high product purity and few surface hydroxyl groups. In order for this method to cause chemical reactions, heating, radiation or plasma must be used to activate the reactants into molecules. Therefore, the equipment used in this method requires high requirements, the raw materials used are expensive, and the product prices are relatively high.

2.  Precipitation

The precipitation method is to mix the reactant solution with other auxiliary agents, then add an acidifier to the mixed solution to precipitate, and the resulting precipitate is dried and calcined to obtain nano-silica.

The precipitation method has a simple process and a wide range of raw materials and has been widely studied and applied, but the problem of difficult control of its product properties has not been solved.

3.  Sol-gel method

This method generally uses silicate or silicate as the precursor to dissolve in a solvent to form a uniform solution, and then adjust the pH value to hydrolyze and polymerize the precursor to form a sol.

The sol-gel process is easy to control and has been extensively studied, and the resulting product has a larger specific surface area. However, difficulty in washing, high requirements for raw materials and too long drying time limit its use.

4.  Microemulsion method

By adding acidulant or catalyst dropwise to the microemulsion prepared from the precursor, the preparation reaction takes place in the microemulsion bubble, and the microemulsion is used to confine the nucleation, growth, coagulation, and agglomeration of the solid phase to a tiny spherical shape. In the droplet microbubbles, nano-spherical particles are formed, and further agglomeration between the particles is avoided, and it is easy to realize the controllable production of the body size.

Because of its nano-scale self-assembly ability, it is easy to realize the controllable preparation of particle size and morphology, which has attracted the interest of many researchers and has become a research hotspot in recent years. Because of its high cost, difficult to remove organic ingredients and easy environmental pollution, it has not been widely used in industry.

Surface modification of nano-SiO₂

There are a large number of active silicon light bases on the surface of nano-silica, with small size and large specific surface area, which makes it easy to agglomerate. Filled directly into organic materials, because it is difficult to infiltrate and disperse, and has poor compatibility, it is difficult to play a role, which limits its industrial application.

• Physical method

The surface coating method is a modification method in which the surface is modified and there is no chemical reaction with nano-SiO₂ , and the coating and the particles are connected by intermolecular force.

The heat treatment modification is a comprehensive process in which nano SiO₂ is placed on the back of a certain medium for heating, heat preservation and cooling, and the performance is controlled by changing the surface or internal structure of the nano SiO₂ .

• Chemical method

Fatty alcohol reacts with the hydroxyl groups on the surface of SiO₂ to remove water molecules. The hydroxyl groups on the surface of SiO₂ are replaced by alkyl groups, and alcohols are used as modifiers.

Application of Nano SiO₂

• coating

Nano-silica has a three-dimensional network structure, has a huge specific surface area, shows great activity, can form a network structure when the coating is dried, and improves the suspension of the pigment, which can keep the color of the coating without fading for a long time. In building interior and exterior wall coatings, it has excellent self-cleaning ability and adhesion.

• Adhesive/sealant field

In the field of adhesives and sealants, nano-silica is an important product with a large amount and a wide range of applications. At present, domestic high-end sealants and adhesives mainly rely on imports.

• rubber

It can improve the strength, toughness, and life of rubber products. In addition, it can also be used to make transparent rubber soles, and this type of products used to rely on imports.

• plastic

Improve the toughness, strength, abrasion resistance, aging resistance of plastics and improve the aging resistance of plastics.

• Textile field

The composite powder of the appropriate ratio of nano-silica and nano-titanium dioxide is an important additive for anti-ultraviolet radiation fibers, and can also increase the warmth retention effect and reduce the weight of clothes.

• Antimicrobial agent field/catalysis field

Nano-silica is physiologically inert and highly absorbent. It can absorb antibacterial ions to achieve antibacterial purposes. It can be used in the manufacture of refrigerator shells and computer keyboards.

• Agriculture and food

Can make the vegetables ripen earlier.

by ALPA Powder

Characteristics and application of high-purity quartz sand raw materials

Quartz sand includes ordinary quartz sand, refined quartz sand, high-purity quartz sand, and fused quartz sand. High-purity quartz sand generally refers to fine quartz powder with a SiO₂ content of more than 99.9%. It is a neutral inorganic filler and does not react with the filler. It is a very stable mineral filler.

The difference between high purity quartz sand and ordinary quartz sand

High-purity quartz sand has unique physical and chemical properties, especially its inherent crystal structure, crystal shape and crystal lattice change law, making it resistant to high temperature, small thermal expansion coefficient, piezoelectric effect, corrosion resistance, high insulation, and resonance effect And unique optical characteristics.

Chemical composition of high-purity quartz sand (μg/g)

 Particle size distribution of high purity quartz sand

 Raw material of high-purity quartz sand

• Natural Crystal

The advantages are high purity, low impurity content, less inclusions, and pure crystals can be directly used to produce electro-quartz.

The disadvantage is that the softening point is low, and a large amount of industrial production is difficult to ensure the uniformity of the mineral structure and the consistency of the internal quality and chemical content; the crystal reserves are small, and the distribution is uneven, and there are few high-grade crystals.

• Natural rock minerals (vein stone, quartz stone, etc.)

The advantage is that the raw material reserves are abundant and there are many types.

The disadvantage is that the direct extraction of ultra-pure quartz sand is currently the most advanced technology for producing ultra-pure quartz sand in the world, and only the United States, Japan, and Germany have mastered this technology.

Application of high purity quartz sand

• Quartz glass

Known as the "King of Glass", it is widely used in aerospace technology, light curing, circuit manufacturing, semiconductors, ultraviolet sterilization, laser technology, high-tech lighting sources and other fields and civilian fields.

• Electronics industry

Packaging materials, basic electronic materials, used to prepare monocrystalline silicon and polycrystalline silicon.

• Photovoltaic industry

Solar panels, semiconductor chip materials, etc.

by ALPA Powder

Nano coating preparation and application

Nano-coatings are generally made by mixing nano-materials and organic coatings. Therefore, more scientifically speaking, it should be called nano-composite coatings. It is generally believed that two conditions must be met before it can be called a nano-coating: the particle size of at least one phase in the coating is in the range of 1-100nm; the existence of the nano-phase makes the performance of the coating significantly improved or has new functions .

Nano coatings are composed of film-forming substances, pigments and fillers, additives, and solvents. Compared with ordinary coatings, nano coatings have the following characteristics: they can produce negative ions and have a health care effect on the human body; they can decompose and absorb harmful substances in the air, such as formaldehyde, etc.; have unique anti-mildew and sterilization functions; and have super self-cleaning Function; has super resistance to washing; super resistance to artificial aging; has the function of waterproof and super heat insulation.

Classification

• Nano silica coating

Silica architectural coatings do not delaminate, are thixotropic, anti-sagging, have good application performance, and greatly improve stain resistance, and have excellent self-cleaning performance and adhesion. The nano-silica coating can form a network structure when it is dried, which can improve the smoothness and anti-aging degree of the coating of vehicles and ships.

• Nano titanium dioxide coating

Nano-titanium dioxide architectural coatings can improve the weather resistance of latex paint to a new level. The application technology of the catalytic composite coating is simple and low in cost. The atmospheric environment purification coating made by the nano-titanium dioxide photocatalytic oxidation technology has a good purification effect on nitrogen oxides in the air and can also degrade other pollutants in the atmosphere.

• Nano calcium carbonate coating

Calcium carbonate is an excellent filler and white pigment with the characteristics of low price, abundant resources, good color and high grade. Application studies have shown that the flexibility, hardness, leveling and gloss of nano-calcium carbonate filled coatings are greatly improved.

Main equipment used in production

The application of nano-materials in coatings has greatly improved the performance and environmental protection of coatings, and has become the darling of the market. The main equipment for the production of nano-coatings has the following five types.

• High-speed dispersion machine

The high-speed disperser is used to pre-mix the paint and the grinding slurry.

• Ball mill

It is mainly used to grind difficult-to-disperse pigments, fillers, and coatings into color pastes or grind to the specified fineness.

• Paint mixing equipment

After dispersion, the finely ground paint slurry and some coating resins, coating additives, solvents and color pastes are mixed uniformly with paint mixing equipment, and reach the specified color, viscosity and other indicators. Some coatings also need to use a high-speed disperser to adjust the paint.

• Filter equipment

Filtering equipment is used to filter a small amount of coarse slag and other impurities in the paint after the paint is finished, so as to achieve the purpose of purification. The commonly used equipment is a vibrating screen, which is easy to operate and easy to clean.

• Filling equipment

Filling equipment is divided into manual and automatic paint filling equipment, which is used to seal the finished paint packaging of specified volume and quality.

Application field

• Nano waterproof coating

Nano-waterproof technology mainly uses nano-scale molecular organic coating materials. In a vacuum and dust-free environment, the electronic products are perfectly packaged through ultrasonic vibration to achieve the same function in the water nano-waterproof coating as in the normal state of use.

• Self-cleaning nano coating

The self-cleaning nano-coating makes it easier to keep the solar panels clean and higher working efficiency, reducing maintenance and operating costs. Utilizing the dual phobic mechanism of nanomaterials, the water in the coating can be effectively discharged, and the intrusion of external water can be prevented, so that the coating film has the performance of breathing. At the same time, the physical properties of the dual interface of nanomaterials are used to effectively discharge the intrusion of dust and oil, so that it maintains good self-cleaning properties.

• Nano coatings for optical applications

The particle size of the nano-particles is much smaller than the 400-750nm wavelength of visible light, and has a transmission effect, thus ensuring the high transparency of the nano-composite coating. Nano particles have a strong absorption effect on ultraviolet light. Add TiO₂, SiO₂ and other nanoparticles to exterior wall architectural coatings to improve weather resistance, and add TiO₂ to automotive topcoats to improve the aging resistance of automotive coatings.

• Stealth Nano Coating

Nano stealth material has excellent absorbing characteristics, and at the same time has the characteristics of good compatibility, small quality and thin thickness. The coating made of it can reduce the detection distance of the detector in a wide frequency band. Visible light, infrared and sound have a stealth effect, so they have a wide range of applications in the military.

• Nano antibacterial coating

The irradiation of light can cause the TiO₂ surface to form a wonderful super amphiphilic property where the hydrophilic and lipophilic two phases coexist in the area where the negative ions are washed and returned to the ecological protection rice. Domestically, industrially produced nano antibacterial powders have been used in coatings, and nano antibacterial coatings can be made, which can be applied to building materials, such as sanitary ware, indoor spaces, appliances, walls and floors in hospital operating rooms and wards, etc. Sterilization and cleaning effect.

Reference

Li Xunsheng et al. "Application Examples of Composite Nanomaterials in Coatings"

Ke Changmei et al. "Preparation of Nanocomposite Coatings"

Wang Zhiqiang et al. "Nano Coating and Its Preparation"

Zhang Xiaojuan. "Overview of the Development of Nano Coatings"

by ALPA Powder

Heavy calcium + superfine processing equipment

There are many types of heavy calcium grinding and processing equipment. They are combined with ultra-fine grade machines to form an ultra-fine processing system, which can generally achieve the effect of ultra-fine production. At present, the mainstream demand for heavy calcium products in heavy calcium market is 600 to 1500 mesh heavy calcium products. The value-added rate of heavy calcium products is relatively low (compared with talc, barite, kaolin, etc.), and scale is one of the main factors affecting benefits.

Heavy calcium ultra-fine processing equipment is divided into grinding equipment and grading equipment. The grinding equipment includes Raymond mill, vibration mill, dry stirring mill, ring roller mill, vertical mill, ball mill, and impeller-type ultra-fine grade machine adopts the principle of forced eddy current.

Comparison of various types of ultra-fine processing equipment

Although Raymond mills are currently commonly used equipment in heavy calcium enterprises, most of the equipment is difficult to achieve large-scale production of ultra-fine heavy calcium.

Practice has proved that in the dry large-scale production of ultra-fine heavy calcium products with more than 600 meshes, there are mainly two types of technologies and equipment suitable for the development of the industry, namely, high-fine ball mills with ultra-fine grade machines and ultra-fine vertical mills with ultra-fine mills. Subdivision level machine.

Comparison of processing systems between vertical mill and ball mill

Regarding the fluctuation of the quality (fineness) of the powder (lower grade) under the secondary classification of the vertical mill, the description is as follows: the vertical mill produces heavy calcium, and the fineness of the milled product is generally below 1000 mesh. If 1250 mesh is produced The above products must be classified twice. Similarly, the secondary classification of 800-mesh powder produced by the vertical mill results in different particle size distributions of the two lower products, which makes it difficult to define the quality of the lower products.

The use of ball mills and large classifiers makes it possible to produce single-machine heavy calcium on a large scale. The single-machine capacity of the ball mill is the largest, and its performance is more prominent when producing products with more than 1250 mesh. The superfine vertical mill has obvious energy saving effect when producing 400~1000 mesh heavy calcium products. The production of large classifiers has been very mature and reliable, producing heavy calcium powder below 2500 mesh, which greatly reduces investment costs and maintenance costs. The combined use of multiple large classifiers is an effective way to diversify products at the same time. The demand for ultrafine heavy calcium powder below 2μm is increasing rapidly, and the research on large-scale sub-micron classifiers is the main task at present.

Article source: China Powder Network

by ALPA Powder

Preparation and modification method of white carbon black

White carbon black is a general term for fine powder or ultrafine particle anhydrous and hydrated silicon dioxide or silicate. It is a white, non-toxic, amorphous fine powder or granular substance, and its silicon dioxide content is greater than 90%, the original particle size is generally 5-40nm, because the surface contains more hydroxyl groups, it is easy to absorb water and become aggregated fine particles.

White carbon black products can be divided into precipitation method white carbon black and gas phase method white carbon black according to the manufacture, and can be divided into gas phase method white carbon black, ordinary precipitated white carbon black and highly dispersed precipitated white carbon black according to the market.

The gas-phase white carbon black has small particle size (15-25nm), low impurities and high purity, superior water resistance, good dielectric properties, great flying properties, and superior reinforcement, but the process is complex and the price is high.

The precipitated silica has a large particle size (20-40nm), low purity, poor reinforcement and dielectric properties, but it can change the flexure and cracking properties of the rubber, and has good process performance and low price.

Preparation of white carbon black

The traditional method of preparing white carbon black is to use sodium silicate, silicon tetrachloride, and ethyl orthosilicate as the silicon source. Except for sodium silicate, other costs are very high. The new method uses cheap non-metallic minerals as the silicon source, which greatly reduces the production cost of white carbon black.

The use of non-metallic minerals to produce white carbon black is technically feasible and has good economic benefits. Commonly used raw materials are diatomite, serpentine, bentonite, kaolin, wollastonite, quartz sand, sepiolite, and bumps. Rod stone, fly ash, axonite, coal gangue, yellow phosphorite, etc.

Surface modification of white carbon black

The surface modification of white carbon black is to use the modifier to make the hydroxyl groups on the white carbon black surface react with the modifier through a chemical process to eliminate or reduce the silanol group on the surface to achieve the purpose of changing the surface properties.

There are three types of hydroxyl groups on the surface of white carbon: isolated and undisturbed isolated hydroxyl groups, adjacent hydroxyl groups that form hydrogen bonds with each other, and two hydroxyl groups connected to a Si atom.

The dry modification process is simple, the post-processing procedures are few, and the large-scale production is easy. The wet modification production process is simple, uses less equipment and lower production cost.

Application of white carbon black

Reinforcing agent and filler in rubber field

Carrier and filler for feed, pesticide and medicine

Matting, thickening and anti-settling of paint and ink

Friction agent and thickener for toothpaste, filling for papermaking

by ALPA Powder

Superfine production process and modification process of silicon micropowder for copper clad laminate

Copper Clad Laminate (CCL for short) is an electronic basic material made by impregnating glass fiber cloth or other reinforcing materials with a resin matrix, covering one or both sides with copper foil and hot pressing. Used in communication equipment, consumer electronics, computers, automotive electronics, industrial control medical, aerospace and other fields. The choices of fillers for CCL include silica powder, aluminum hydroxide, magnesium hydroxide, talc powder, mica powder and other materials.

Silicon micropowder has relative advantages in heat resistance, mechanical properties, electrical properties and dispersibility in the resin system. It can be used to improve heat resistance and humidity resistance, thin CCL rigidity, dimensional stability, and drilling positioning accuracy The smoothness of the inner wall, the adhesion between the layers or the insulating layer and the copper foil, and the reduction of the thermal expansion coefficient.

Types of silicon powder for copper clad laminates

At present, the silicon powder used in integrated circuit copper clad laminates mainly includes five varieties: crystalline silicon powder, molten (amorphous) silicon powder, spherical silicon powder, composite silicon powder, and active silicon powder.

• Crystalline silica powder

Started early, the process is mature and simple, and the price is relatively cheap. It has a great effect on the improvement of the rigidity, thermal stability and water absorption of the copper clad laminate.

The impact on the resin system is not optimal, the dispersibility and sedimentation resistance are not as good as the molten spherical silicon powder, the impact resistance is not as good as the molten transparent silicon powder, the thermal expansion coefficient is high, and the hardness is large, and the processing is difficult.

• Fused silica powder

White color, high purity, low linear expansion coefficient, low stress, is mainly used in large-scale and ultra-large-scale integrated circuit molding compound, epoxy castable and potting compound, especially in the application of high-frequency copper clad laminates. .

The higher melting temperature requires higher production capacity of the enterprise, complicated process and higher production cost. Generally, the dielectric constant of the product is too high, which affects the signal transmission speed.

• Spherical silica powder

The fluidity is good, the filling rate in the resin is high, the internal stress is low, the size is stable, the thermal expansion coefficient is low after being made into the plate, and it has a high bulk density and uniform stress distribution, so it can increase the fluidity and Reduce viscosity.

The price is very high and the process is complicated. At present, it has not been used on a large scale in the copper clad laminate industry, and a small amount is used in the fields of integrated circuit carrier boards and printed circuit boards.

• Compound silicon powder

Good temperature resistance, good acid and alkali corrosion resistance, poor thermal conductivity, high insulation, low expansion, stable chemical properties; moderate hardness, easy to process, reduce the wear of the drill bit in the drilling process, and reduce the dust pollution during the drilling process .

If the performance of the copper clad laminate can be guaranteed, the cost needs to be reduced.

• Active silica powder

Good temperature resistance, good acid and alkali corrosion resistance, poor thermal conductivity, high insulation, low expansion, stable chemical properties, and high hardness.

The resin systems used by copper clad laminate manufacturers are not the same. It is difficult for the silicon powder manufacturers to make the same product suitable for all users' resin systems, and the copper clad laminate manufacturers are more willing to add modifiers themselves due to their habits.

Production process of ultra-fine silicon powder

As electronic products become lighter, thinner, shorter and smaller, the use of silicon micropowder filler in copper clad laminates also requires more and more ultra-fineness. The chemical synthesis method of ultra-fine silicon powder has low yield and complex process. The physical pulverization method has low cost, simple process, and is suitable for mass industrial production. The pulverization method is divided into a dry process and a wet process.

• Dry process

The process is feeding→grinding→classification→collection→packaging. The process is simple and the production cost is low. Generally, silicon powder production enterprises choose this process.

Grinding and classification equipment is the key. The grinding equipment mainly uses ball mills. The energy consumption of the ball mill is relatively low and the production capacity is large. For some products with higher purity requirements, the jet mill can be used because the jet mill does not introduce the grinding medium, but the energy consumption of the jet mill is relatively high. Low. The classification equipment is a general air flow classifier.

• Wet process

The process is feeding→grinding→drying→deaggregation→classification→collection→packaging. Drying and deaggregation processes are required. The process is complicated and the production cost is high. Fewer companies adopt this process. The cut point is less than 5 microns and requires a surface. This process is more suitable for processing products.

In fact, for the same process, the finer the particle size of the product, the lower the cut point, the higher the energy consumption, the lower the productivity, the more serious the equipment wear, the more obvious the increase in production costs, and the higher the cost.

Surface modification of ultra-fine silicon powder

The surface modification of ultra-fine silicon powder can reduce the interaction between particles, effectively prevent particle agglomeration, reduce the viscosity of the entire system, and increase the fluidity of the system; it can enhance the compatibility of the particles with the resin matrix and make the filler particles It can be evenly dispersed in the glue.

The key to surface modification lies in how to make the modifier uniformly dispersed on the surface of the particles while ensuring the chemical bonding conditions between the modifier and the particle surface.

The dry modification process is relatively simple and the production cost is relatively low, but the effect is relatively poor. The wet process has a better modification effect, but the process is complex, requires drying and depolymerization processes, and the production cost is high.

For conventional copper clad laminates with silicon powder, dry modification is generally recommended. For 8μm cut and 6μm cut comprehensive cost and performance considerations, dry process is recommended. For products with a cut of 5μm and below, a wet process is recommended. For finer products, gas phase synthesis has been used for surface modification.

With the continuous deepening of copper clad laminate manufacturers' understanding of silicon micropowder, new requirements are also put forward for the impurities of silicon micropowder. This is mainly because the silicon micropowder impurity affects the appearance, insulation and heat resistance of the PP and substrate of CCL. Come negatively. Silicon powder impurities can be divided into two categories: magnetic impurities and non-magnetic impurities according to whether they are magnetic or not.

The key to impurity control is to ensure that the raw material impurities are sufficiently low; to prevent the environment from being introduced during the production process; to prevent the equipment and pipes from wearing out; to remove impurities during the production process (using a magnetic separator to remove magnetic impurities, which is difficult to remove non-magnetic impurities).

The future trends of fillers for copper clad laminates are as follows:

• Functionalization: Low Dk, Low Df, high thermal conductivity, flame retardant, etc.
• High filling: High filling means better performance of inorganic fillers, including low CTE, low dielectric, and high thermal conductivity.
• Particle design: Interface and agglomeration issues require continuous improvement in surface treatment technology; spherical products are the choice for high-end applications.
• Particle size distribution design: In response to the thinning, the particle size needs to be continuously reduced, but it is also necessary to prevent the difficulty of dispersion.
• Impurity control: Ultra-thin, highly reliable, and highly thermally conductive substrates expect the impurity content of the filler to be as low as possible.

Article source: China Powder Network

by ALPA Powder

Types of grinding media balls

When the ball mill is working, it relies on the impact and grinding action of the medium on the material to complete the grinding of the material. In the mechanical process of the medium’s crushing of the material, the medium is used as the energy medium to convert the external energy into the crushing work of the material. And play a role in crushing the material.

Metal grinding media ball

Since the 1980s, chromium alloy cast iron grinding balls, multi-element low alloy cast iron grinding balls, various medium and high carbon low alloy waste heat quenched steel balls, bainite air-cold forging and rolling steel grinding balls, and multiphase matrix ductile iron grinding balls have been successively developed.

Non-metal grinding media ball

• Natural ball stone grinding media

The natural ball stone grinding media mainly refers to natural materials such as silica, sea pebbles and pebbles. In recent years, with the increasing depletion of high-grade natural ball stone and the rapid development of the ceramic industry, natural ball stone grinding media has been basically replaced by artificial grinding media.

• SiO₂ grinding media ball

There are two types of SiO₂ grinding balls: natural agate balls and glass balls made of quartz. Natural agate grinding balls are expensive and difficult to use in the ceramic production industry. They are only used in experiments and some special industries, and the amount is very small. The quartz glass balls used for grinding have low density, high abrasion, low grinding efficiency, and fragile. Except for the grinding of quartz powder and some special powders, no quartz glass is used for the grinding of other ceramic powders. Grind the ball.

• AI₂O₃ grinding media ball

AI₂O₃ grinding media ball is a ceramic ball with AI₂O₃ as the main component, also called AI₂O₃ ceramic ball. Because AI₂O₃ ceramic has excellent properties such as wear resistance, corrosion resistance, high temperature resistance, impact resistance, etc., AI₂O₃ ceramic balls are widely used in the raw materials of white cement, mineral processing, ceramics, electronic materials, magnetic materials, and coatings, paints and other industries. Grinding processing is a high-quality grinding medium.

• ZrSiO₄ grinding media ball

ZrSiO₄ grinding media balls are ZrSiO₄ ceramic balls prepared with ZrSiO₄ as the main raw material, and the mass fraction of ZrO₂ is about 65% to 68% or lower. ZrSiO₄ ceramic balls are mainly used for ultrafine grinding of ZrSiO₄ raw materials, which can increase the content of ZrSiO₄, but due to high abrasion and low strength, they lack a good market prospect. It is replaced by ZrO₂ grinding media with better performance.

• ZrO₂ grinding media ball

ZrO₂ grinding media ball refers to the ZrO₂ ceramic ball with stabilizer added and the ZrO₂ content reaches more than 90%. ZrO₂ ceramic ball has the following advantages and characteristics: it has a higher density and its impact force is large, so it has a higher grinding efficiency. Product contamination can be avoided. AI₂O₃, SiO₂ and metal grinding media will contaminate the product, while ZrO₂ is chemically inert to the dispersant. The surface is smooth and hard, it has excellent roundness and reasonable size distribution, and the wear of the medium itself and the grinding lining is very small during the grinding process. Has high fracture toughness, high strength, wear resistance and chipping resistance. It is suitable for wet grinding, dispersion of high-viscosity mud and running under high-speed operating conditions. Reduce the required grinding time, have higher production efficiency and lower production costs.

Article source: China Powder Network

by ALPA Powder

Modification process of kaolin

Kaolin, also known as porcelain stone, is a kind of clay and clay rock dominated by kaolinite clay minerals. It belongs to non-metallic minerals and is an aggregate of water-containing aluminosilicates composed of multiple minerals. The pure kaolin is white, fine, soft and soft, with good plasticity and fire resistance and other physical and chemical properties.

The structural units of kaolin are stacked in layers, mainly in the form of plates, which are easy to crack along the direction parallel to the layer, and are processed into ultra-fine powder. Kaolin exists in the form of scales in nature.

Because kaolin is prone to agglomeration when its specific surface area and surface energy are too high, it cannot be uniformly dispersed when filled with organic polymer materials such as rubber and plastic, which is not conducive to the improvement of product performance. Therefore, surface modification of kaolin is needed to reduce its surface energy. After surface modification, kaolin powder can achieve the effects of being hydrophobic, reducing surface energy, improving its dispersion and compatibility with polymer-based composite materials.

The physical properties of kaolin before and after modification

The surface modification of kaolin often uses surface chemical modification methods, so modifiers are added.

The surface modification process of kaolin generally has three methods: wet method, dry method and semi-dry method.

• Wet

The wet process requires pulping, dehydration, and drying processes, and the process is more complicated, especially dehydration filtration. If the particle size is less than 1250 mesh, it will be extremely difficult and complicated.

• Dry method

The dry modification process requires relatively high technology and equipment. The process completely eliminates the dehydration and drying link, and the process is simple.

• Semi-dry

While stirring the powder in the mixer, add an appropriate amount of water modifier and additives to mix in. After heating to a certain temperature and time, the product will be in a viscous state, and then slightly dried to obtain a modified product. The process omits the dehydration process and has higher production efficiency.

Commonly used modification methods of kaolin

• Calcined modification

In the calcining modification process, the reaction is carried out at a certain temperature, and the surface activation degree is different for different reaction times.

• Surface coating modification

Through surface coating, the stability of the material structure can be enhanced, the activity of the catalyst can be increased, the agglomeration of the powder can be prevented, and the dispersion characteristics and fluidity of the powder can be improved.

The main factors affecting surface coating modification are as follows:

The properties of kaolin: The specific surface area of kaolin determines the amount of surface modification. The larger the specific surface area, the more dosage required.

The properties of the modifier: From the perspective of dispersion, the adsorption of non-ionic substances on the surface of kaolin is relatively large, but the effect is not ideal; although the adsorption of negatively charged substances is not much, the dispersion is good.

Reaction conditions: Under different temperatures and pH values, the adsorption amount of coating ions on the surface of the powder is different, which will also affect the results of surface modification.

• Intercalation modification

Kaolin intercalation methods include mechanochemical method, microwave intercalation method, liquid intercalation method, and ultrasonic intercalation method.

Kaolin intercalation nanomaterials have better plasticity, whiteness, easy dispersibility, and adsorption properties, and can give the materials optical, electrical and magnetic properties, and expand the application range of kaolin clay. The intercalation method is currently the most promising and effective technology for preparing nano-kaolin. Commonly used chemical additives include: potassium acetate, dimethyl sulfoxide, urea, formamide, hydrazine hydrate and its extensions, etc.

Kaolin itself is a very versatile and important non-metallic mineral, which is widely used in more than a dozen industries such as petroleum, plastics, coatings, refractory materials, ceramics, and papermaking.

• Application of Modified Kaolin in Coatings

Kaolin is added to white paint or paint in an appropriate amount to enhance gloss and improve its covering ability.

• Application of modified kaolin in plastics

The application of modified calcined kaolin in plastic products can make the surface smooth, improve its dimensional accuracy, deformation temperature, impact strength, chemical resistance, etc., and increase the amount of filling and reduce the cost.

• Application of modified kaolin in rubber

Adding modified kaolin powder to the rubber can improve the physical and chemical properties of the product, greatly reduce the cost, improve the product level, and increase economic benefits.

Article source: China Powder Network

by ALPA Powder

Preparation technology of barite powder

Barite is the most common mineral. Its composition is barium sulfate ( BaSO₄ ), which can be produced in low-temperature hydrothermal veins and sedimentary rocks. The chemical composition includes 65.7% BaO and 34.3% SO₃ , and there are similar substitutions of Sr, Pb and Ca in the composition. Barite is usually plate-like, granular, fibrous aggregates and crystal clusters of plate-like crystals, a few of which are dense, massive, cryptocrystalline, and soil-like, and stalactites and nodules with concentric belt-like structures are also seen. .

The pure barite is colorless and transparent, generally white, gray, light yellow, light brown, and may be light blue, pink, dark gray, etc. with impurities. Glass luster, transparent to translucent, low abrasion, good shielding, can absorb X-rays and Y-rays, chemically stable, and pure ones are hard to dissolve in water and acid.

The world is rich in barite resources, with reserves of 2 billion tons. World-famous barite producing areas include: Westmanland and Cumbria in the United Kingdom, Phils Bonny in Romania, Saxony in Germany, Tianzhu in Guizhou, China, Gongxi in Hunan, Liulin in Hubei, and Guangxi Heifenggou in Gansu, Xiangzhou, Shuiping in Shaanxi, etc.

Barite is divided into high-purity barite, ultra-fine barite, and ultra-fine active barite.

Preparation technology of high-purity barite powder

• Physical purification

Hand selection: According to the difference in color and density of barite and associated minerals, select blocky barite.

Gravity separation: According to the density difference between barite and associated minerals, the raw ore is screened, crushed, grading desliming, jigging, shaking table and other processes to obtain products with a grade of more than 88%.

Magnetic separation: It is often used to remove some iron oxide magnetic minerals and use it as the raw material of barite for collar-based drugs that require very low iron content.

• Chemical purification and whitening

Flotation: Barite with a small particle size is embedded, and physical removal of impurities is not good, and flotation is often used.

Chemical purification and whitening: through acid (or alkali) leaching, oxidation-reduction to remove carbon and iron, manganese, magnesium, nickel and other impurities in the ore.

Calcining and whitening: The hydrothermal barite undergoes heat absorption and blasting at high temperatures to volatilize the color-causing organic matter distributed in the barite crystals or gaps.

Preparation technology of ultra-fine barite powder

• Dry process

Jaw crusher, Raymond mill air classifier → baking oven → washing → dilute pickling → pulping → reaction kettle pickling reduction → filter press → washing → filter press → drying → crushing → packaging → product

• Wet process

Stirring mill, vibration mill, ball mill→modifier or precipitant→hydroxide or hydrated oxide→coating film→washing→drying→roasting→fixing→product

Preparation technology of ultrafine active barite powder

Surface chemical coating: modifier molecules are covered on the surface to obtain modified products.

Mechanochemical modification: Activate the particle surface, improve the activity of BaSO₄ and other organic matter.

Encapsulation modification: The surface of the particles is covered with a homogeneous film with a certain thickness.

High-energy modification and acid-mechanical modification: use ultraviolet, infrared, corona discharge and plasma irradiation for surface treatment.

Application of barite powder

• Chemical raw materials

Reagents and catalysts, medicaments for mineral processing and paper production, additives for oils and fats, production of plastics, pesticides, herbicides, fungicides, production of various fireworks...

• Drilling mud

Barite is usually relatively pure, soft, relatively dense, chemically friendly, and inexpensive. 80-90% of its output is used as a weighting agent for drilling mud.

• Glass material

Barite is used in glass production to make the melt uniform and improve the brightness and transparency of the glass product.

• Chemical packing

Barite powder is a general industrial filler and a good brightening agent and weighting agent. Chemically bleached barite powder is a good white pigment.

• Other applications

Barite has good properties of absorbing Y radiation, so it can be used as a shielding material; it can also be used as a getter binder for vacuum tubes such as televisions.

The development trend of barite powder preparation technology

The main preparation technologies of barite-based mineral materials include ultra-fine and surface modification, but there are not many in-depth studies on the theoretical issues of barite ultra-fine processing, mechanochemistry, interface chemistry, doping modification and other processes. Traditional barite minerals are mainly used in low value-added fields such as petrochemicals, with low product utilization and low value.

We must transfer the traditional application of barite to how to combine the mineral composition, chemical composition structure, surface properties and other related characteristics, develop simple modification processes, study relatively inexpensive, non-toxic surface modifiers, and promote The development of barite processing, the comprehensive utilization of barite, and the improvement of the competitiveness of barite ore powder.

Article source: China Powder Network

by ALPA Powder

Production and modification process of heavy calcium carbonate

Heavy calcium carbonate, also known as ground calcium carbonate, or heavy calcium for short, is made by processing natural carbonate minerals as raw materials. It has high chemical purity, high inertness, good thermal stability, will not decompose below 400℃, high whiteness, low oil absorption, low refractive index, soft, dry, free of crystal water, low hardness, low abrasion value, non-toxic , Tasteless, odorless, good dispersion and other advantages.

As a functional inorganic filler, calcium carbonate is mainly used in papermaking, plastics, paint and coatings, rubber and other industries. From a global perspective, calcium carbonate for papermaking accounts for 60% of the consumption structure.

As a functional filler, heavy calcium carbonate, its mesh number, whiteness and calcium carbonate content determine its application areas. 325 mesh, whiteness 95%, calcium carbonate content 98% can be used for paper making; 325 mesh, whiteness 95%, calcium carbonate content 98.5% can be used for artificial marble; 325 mesh, whiteness 90%, calcium carbonate content 98% Can be used for construction; 400 mesh, whiteness 93%, 96% calcium carbonate content can be used for rubber; 400 mesh, whiteness 95%, calcium carbonate content 99% can be used for plastics; 400 mesh, whiteness 95%, carbonic acid 98.5% calcium content can be used for floor tiles.

With the development of grinding and grading equipment, the production and demand of ultrafine heavy calcium powder has increased significantly. Among them, the use of 2500-6500 mesh heavy calcium powder in high-end papermaking has also increased.

Production of heavy calcium carbonate

The raw materials are carbonate minerals such as shells, calcite, marble, limestone, chalk and dolomite.

Common heavy calcium processing methods include dry, wet, and dry-wet process combination methods. Dry processing is conducive to the realization of industrial scale and a certain degree of product refinement; wet processing is conducive to achieving a higher degree of product refinement and functional production; dry and wet process combination is conducive to making up for the dry process in high-end products The insufficiency.

From a practical point of view, products with D97=2500 mesh or less are generally produced by dry method; products with D97=2500~6500 mesh (or higher content of 2μm) are usually produced by wet method.

• Dry process

The main equipment of dry process is Raymond mill, ball mill, jet mill, ring roller mill, vibration mill, vertical mill, and high-speed mechanical impact mill.

At present, the dry processing of large-scale enterprises in the world mostly uses vertical mill processing equipment and technology. The large-scale and fine-grained benefits of vertical mill dry powder production are the most obvious. It has become one of the main research directions in the refined processing technology of heavy calcium powder in recent years.

• Wet process

The wet method is used to process refined and functional heavy calcium powder, the mesh number is above 3000, and the equipment mostly uses stirring mills. Adding pulverizing aids in the fine media mill can prepare sub-micron or even nano ultra-fine powder.

Wet grinding mainly produces products above 3000 mesh, and dry grinding mainly produces products below 2500 mesh. The particle size distribution of heavy calcium produced by wet method is narrow, which is unimodal or bimodal; the particle size distribution of heavy calcium produced by dry method is broad, and the distribution is bimodal or multimodal.

The particles of wet grinding products are generally spherical or quasi-spherical; dry products are mostly indeterminate and have obvious edges and corners.

• Dry and wet process combination

The dry-wet integrated process of vertical mill + secondary classification + tertiary classification and multi-stage wet grinding can be used to produce 325~800 mesh products to meet the basic needs of the market, and use super-subdivision equipment for secondary and tertiary The graded production of medium and high-end fine powders of 800 to 2500 meshes meets the needs of the medium and high-end markets. The lower product adopts wet grinding and other fine grinding and functional development, and produces 2500~6500 mesh ultra-fine functional powder to meet the high-end market demand.

The dry-wet integrated process of vertical mill + secondary classification + tertiary classification combined with multi-stage wet grinding not only realizes the large-scale industrialization of heavy calcium, refined and functional products, but also improves the product structure, which is the future of heavy carbonic acid An integrated demonstration process for the in-depth development of calcium industry transformation and upgrading.

Modification of heavy calcium carbonate

The minerals of heavy calcium carbonate dissociate during the crushing process, and unsaturated particles Ca²⁺ and CO₃^2- will be exposed. Unsaturated particles will hydrate with surface water, making the surface of heavy calcium carbonate particles hydrophilic and oleophobic. The active points on the surface of heavy calcium carbonate can be used for physical and chemical modification to change its hydrophilic and oleophobic properties.

Modification methods include: physical coating modification, surface deposition modification, surface chemical modification (coupling agent modification, composite coupling agent modification, polymer coating modification, organic matter modification), mechanochemical modification High-energy surface modification (irradiation, plasma, ultrasonic).

Optimize the effect of surface modification, the size of modified heavy calcium carbonate is nano-sized, green and environmentally friendly, and the conversion of calcium carbonate modification to special type, functional type and high value-added type is the development trend of heavy calcium surface modification.

Article source: China Powder Network

by ALPA Powder