8 Concepts About Bentonite Clay

1. Bentonite

Bentonite, also known as "bentonite" or "bentonite", is a non-metallic mineral with montmorillonite as the main mineral component. It often contains a small amount of illite, kaolinite, zeolite, feldspar and calcite and other minerals. Montmorillonite The stone content determines the utilization value of natural bentonite.

2. Montmorillonite

Smectite is a large family of minerals with complex chemical composition. The International Clay Association has determined that Smectite is the family name, that is, the smectite family, also known as the smectite family. This group of minerals includes two subgroups, dioctahedral and trioctahedral, and more than a dozen mineral species. Bentonite usually contains minerals from the dioctahedral subgroup, such as montmorillonite, beidellite, nontronite, etc.

3. Sodium bentonite and calcium bentonite

Because part of the silicon ions and aluminum ions in the silicon-oxygen tetrahedron and aluminum-oxygen octahedron are often replaced by other low-priced cations, the montmorillonite crystal structure has a permanent negative charge. In order to balance the electricity price, the montmorillonite unit cell will adsorb exchangeable cations.

According to the type, content and crystallization chemical properties of exchangeable cations contained in bentonite, bentonite is divided into calcium bentonite, sodium bentonite, magnesium bentonite and calcium-sodium bentonite. The most common ones are the first two. .

4. Organic bentonite

Organobentonite refers to using organic ammonium cations to replace exchangeable cations in montmorillonite, covering the surface of montmorillonite, blocking the water adsorption center, causing it to lose its water absorption function, and turning into hydrophobic and lipophilic organobentonite. complex.

Organobentonite can be divided into high-viscosity organobentonite, easily dispersible organobentonite, self-activating organobentonite, and high-purity organobentonite according to functions and components.

5. Lithium bentonite

There are very few natural lithium bentonite resources. Therefore, artificial lithiation is one of the main methods for preparing lithium bentonite.

Lithium bentonite can form gel in organic solvents and replace organic bentonite. Lithium bentonite has excellent swelling, thickening and suspending properties in water, lower alcohols and lower ketones, so it is widely used in architectural coatings, latex paints, casting coatings and other products to replace various organic cellulose suspending agents.

6. Activated clay

Activated clay is made from clay (mainly bentonite) as raw material, which is obtained by inorganic acidification or salt treatment. It is a porous white-off-white powder with a microporous structure and a large specific surface area, and has strong adsorption properties. It is mainly used for decolorization and refining of petroleum processing products (lubricating oil, paraffin, petroleum jelly) and industrial animal and vegetable oils, and is used as adsorbent and catalyst carrier in the chemical industry.

7. Pillared montmorillonite

Pillared montmorillonite is a mineral material with two-dimensional pores formed by polymerized inorganic cations or organic ions (molecules) inserted into montmorillonite. It has a large specific surface area, good thermal stability, strong surface acidity and adjustable pore size. It has broad application prospects in petrochemical industry, sewage treatment, antibacterial materials and other fields.

8. Bentonite gel

Bentonite inorganic gel is a high value-added colloidal product produced with bentonite as the main raw material through purification, sodium modification, phosphating modification and gelation. The preparation process mainly includes the purification of bentonite raw ore, There are four major processes: sodium modification, phosphating modification and gelling.

Inorganic gel is a high value-added bentonite deep processing product that can be used as a thixotropic agent, thickener, dispersant, suspending agent, stabilizer, etc. It is widely used in daily chemicals, pharmaceuticals, detergents, ceramics, glass, papermaking, and casting. , battery and other industries.

by ALPA

Learn more about powders: must-know terms and concepts

Crushing/grinding/pulverizing
The process of reducing particle size.

Dry grinding
The process of crushing in air or other gaseous media.

continuous grinding
The process of continuously and evenly feeding the materials to be processed into the crushing device (or system), and at the same time, the crushed materials are discharged in time.

surface grinding
Under the action of external forces such as friction and shear, the grinding process is mainly based on surface grinding and peeling.

impact grinding
The crushing process is realized by utilizing the impact of the high-speed moving working parts of the crushing equipment on the material or the impact of the high-speed moving material and the wall.

Jet pulverizing
The high-speed jet formed by the expansion and acceleration of compressed gas through the nozzle causes impact, collision and friction between particles and between particles and the wall, thereby realizing the crushing process.

Crushing ratio/ratio of size reduction
The ratio of the characteristic particle diameters of the feed material and the discharge material during the crushing operation indicates the degree to which the particle size of the material is reduced after crushing.

grinding efficiency
The output rate of qualified products per unit energy consumption per unit time.

grinding balance
During the crushing process, the particle size of the powder material no longer continues to decrease and the specific surface area no longer continues to increase.

mechano-chemistry
Structural or physical and chemical changes induced by mechanical forces during the material crushing process.

grinding media
It is an object that is loaded in the mill and uses the impact, collision, shearing, grinding and peeling effects generated during its movement to crush the material.

Grinding aid
Additional additives to improve crushing and grinding efficiency.

Dispersant/dispersing agent
It is an additive that directional adsorbs on the surface of the treated particles to prevent them from aggregating with each other and maintain the stability of the particles within a certain period of time.

classification
The process of dividing a material into two or more particle size distribution levels.

Sieving
The process of grading using sieves.

fluid classification
The process of classifying liquid or gaseous media.

Dry classification/wind classification (dry classification)
The process of classification in air or other gaseous media.

gravity classification
The process of classifying particles based on the difference in their final settling velocity in liquid or gaseous media.

centrifugal classification
The process of grading based on the different trajectories of particles in the centrifugal force field.

Cut size
According to the particle size, the material is divided into coarse and fine particles and the separation limit particle size of the product.

classification efficiency
The degree of separation of coarse and fine grade products during the classification process is usually expressed by the ratio of the mass of the fine-grained material after classification to the mass of the graded material smaller than the cutting particle size. It is a measure of the quality of the grading operation. an important indicator.

surface treatment
A general term for processes such as particle shaping, surface modification, and surface coating.

particle functional design
The process of changing the morphology, structure and characteristics of particles for the purpose of material functionalization.

Particle shape modification
A process that changes the shape of particles.

sphericity
The process of processing irregularly shaped particles into spherical or approximately spherical particles.

Degree of sphericity
The particle shape is close to a sphere.

surface modification
The process of changing the surface properties of particles through the adsorption, reaction, coating or coating of surface modifiers on the particle surface.

wet modification
The process of surface modification of materials in a slurry with a certain solid-liquid ratio or solid content.

Dry modification
The process of surface modification of dry or dried powder materials.

physical coating
The process of surface modification using physical methods.

mechano-chemical modification
The process of surface modification is achieved with the help of strong mechanical force in the crushing process.

encapsulation modification
The process of surface modification by covering the surface of particles with a homogeneous and certain thickness film.

high energy surface modification
The process of surface modification using irradiation or radiation.

Surface modifying agent
Substances that modify the surface of particles.

surface coating
The process of forming inorganic coatings on the surface of particles.

by ALPA

Pigment powder ultrafine crushing equipment

Particle size is one of the important indicators of pigments. Generally, pigment particles are required to have stable physical form, uniform particle size, and good dispersion, without agglomeration or precipitation.

​Iron oxide pigment is a pigment with good dispersion, excellent light resistance and weather resistance. It mainly refers to the four types of iron oxide red, iron yellow, iron black and iron brown coloring pigments based on iron oxides. Among them, iron oxide red is the main one.
Precipitated (wet) iron oxide pigments are very fine, but during the filtration and drying processes, due to factors such as van der Waals forces, hydrogen bonds, charges, etc., the micro-aggregates aggregate into large aggregates and cannot be directly used in high-end coatings. For coloring, ultrafine crushing is necessary. Jet milling uses the energy of high-speed airflow or superheated steam to ultrafinely grind solid materials. It is one of the most commonly used ultrafine grinding methods.

At present, in the pigment production industry, the application range of airflow crushing is becoming more and more extensive, which mainly comes from the following two factors:

First, the safety of mechanical crushing is poor, because if hard metal falls on the high-speed rotating mechanical teeth, it is easy to produce an open flame, which is very dangerous in a dusty pigment production workshop, but airflow crushing does not have this question;

Second, airflow crushing belongs to ultra-fine crushing. In the production of some special pigments, the fineness of the pigments is required to be higher.

1. Iron oxide pigment

During the filtration and drying process of iron oxide pigments, due to van der Waals forces, hydrogen bonds, charges and other factors, micro-aggregates aggregate into large aggregates, which cannot be deaggregated through general mechanical action. Using a fluidized bed or disc-type jet mill to process iron oxide pigments, the Hagermann fineness can reach: iron oxide red 5.5 to 7.0, the darker the color, the better the fineness; iron oxide yellow 7.5; iron oxide black 7.0 .

After ultra-fine crushing, the iron oxide pigment is depolymerized from large aggregates into small aggregates. When producing paint, it only takes a short time of high-speed stirring process to achieve the required fineness, thereby saving costs and the small size of the pigment. The aggregates are difficult to coarsen into large aggregates, thus ensuring the quality of the paint.

2. Black high temperature resistant manganese ferrite pigment

The fine particles of manganese ferrite pigment that have been surface-coated, surface-modified, dried, and pulverized are flocculated again into coarse particles of varying degrees, and cannot effectively exert the pigment properties of manganese ferrite.

After deep processing and grinding using a fluidized bed or disc-type jet mill, the Hagermann fineness of the manganese ferrite pigment is approximately 7 to 7.5. It has good dispersion and can give full play to its optical and pigment properties.

3. Brown ceramic pigment

The brown ceramic pigment is ultrafinely pulverized using a flat jet mill. When the air pressure is 7.5×105Pa and the feeding speed is 100kg/h, the product d50 is 4.55μm and the maximum particle size is 9.64μm.

At present, common ultra-fine grinding equipment includes jet mill, mechanical impact ultra-fine grinder, stirring ball mill, sand mill, vibration mill, colloid mill, high-pressure jet grinder, planetary ball mill, pressure roller mill, and ring roller mill. etc.

by ALPA

Production technology of high-quality calcium hydroxide

Calcium hydroxide, commonly known as hydrated lime, has a chemical formula of Ca(OH)2. Generally in powder form, it will lose water and become calcium oxide (quicklime) at 580°C under normal pressure. Calcium hydroxide is slightly soluble in water, and its solubility decreases as the temperature increases. The colorless and transparent solution obtained by dissolving in water is commonly known as clear lime water. A milky suspension composed of calcium hydroxide and water is called milk of lime.

Dry calcium hydroxide production process: qualified quicklime is crushed by a jaw crusher. It is sent into the lime silo via bucket elevator and bin-type vibrating conveyor. The lime in the silo is quantitatively added to the hydrated lime pre-digester through star-shaped feeding, and is initially digested under strong stirring by the stirring rod, and then enters the digester to complete the digestion process. The digested lime is input into the slaked lime silo by the slaked lime elevator and the inlet screw conveyor, and then the qualified refined slaked lime is obtained by the ash adding spiral air separator. The refined slaked lime is unloaded into the finished slaked lime silo and then packaged according to user needs. During the dry digestion reaction, the organizational structure changes, causing Ca(OH)2 to form a loose powder, with the volume increasing to 1.5 to 2.0 times the original volume. The product and raw materials have better fluidity, so the dry digestion process can be used in water. The high conversion rate reaction of quicklime can be achieved under the condition of low ash ratio (mass ratio of water to lime).

Calcium hydroxide applications

(1) Flame retardant materials

Calcium hydroxide powder is widely used as a filler in polymer materials. Adding calcium hydroxide to polymer materials can improve the thermal stability and flame retardant properties of composite materials; calcium hydroxide is alkaline and can react with hydrogen chloride (HCl) released when PVC is thermally decomposed, eliminating the degradation of PVC by hydrogen chloride. The autocatalytic effect of the process has a certain thermal stabilization effect.

(2) Degradable polymer materials

Calcium hydroxide can be used as an auxiliary agent for environmental absorption of plastics. It has dechlorination, cracking and alkaline degradation effects on the decomposition of plastics.

(3) Wastewater treatment

The role of calcium hydroxide in wastewater can be basically summarized into four aspects: neutralizing free acids in wastewater, neutralizing acid salts in wastewater, reacting with metal ions to produce water-insoluble precipitates, and adjusting the pH of wastewater. value.

(4) Desulfurizer

In the calcium hydroxide-gypsum wet desulfurization process, the flue gas comes into contact with the Ca(OH)2 absorption liquid over a large area, so that the SO2 in the flue gas dissolves in water and reacts with the calcium hydroxide slurry to form calcium sulfite, which is then blown in Under the condition of a large amount of air, calcium sulfite is oxidized to generate CaS (V2H2O), thereby achieving the purpose of reducing SO2 in the flue gas. In the calcium desulfurization process, calcium ions are actually involved in the sulfur fixation. Calcium carbonate, calcium oxide, and calcium hydroxide can all be used as desulfurization agents.

(5) Medical and health care

Calcium hydroxide is used for disinfection in a variety of places, such as scientific research, laboratories, medicine, factories, etc. It has a long history of use in clinical medicine.

(6) Food processing

Adding a certain amount of food-grade calcium hydroxide to milk powder can not only adjust the pH value of the milk powder and promote the rapid dissolution of the milk powder in water, but also supplement calcium.

by ALPA

4 key points for choosing powder surface modifiers

There are many types of powder surface modifiers on the market with various functions and of course different prices. How to choose the most suitable modifier?

Practice has shown that when selecting surface modifier varieties, the main considerations include: the properties of the powder raw materials, the use or application field of the product, as well as technology, price and environmental protection.

1. Properties of powder raw materials

The properties of powder raw materials are mainly acid, alkalinity, surface structure and functional groups, adsorption and chemical reaction characteristics, etc. Surface modifiers that can chemically react or chemically adsorb with the surface of powder particles should be selected as much as possible, because physical adsorption on It is easy to desorb under strong stirring or extrusion during subsequent applications.

For example, the surfaces of acidic silicate minerals such as quartz, feldspar, mica, and kaolin can bond with silane coupling agents to form stronger chemical adsorption; however, silane coupling agents generally cannot bond with alkaline carbonates. Minerals undergo chemical reactions or chemical adsorption, while titanate and aluminate coupling agents can chemically adsorb with carbonate alkaline minerals under certain conditions and to a certain extent.

2. Product use

The purpose of the product is the most important consideration in selecting a surface modifier. Different application fields have different technical requirements for powder application performance, such as surface wettability, dispersion, pH value, hiding power, weather resistance, gloss, antibacterial properties, UV protection, etc. This means that surface modification should be selected according to the purpose. One of the reasons for the variety of sexual agents.

For example, inorganic powders (fillers or pigments) used in various plastics, rubbers, adhesives, oily or solvent-based coatings require good surface lipophilicity, that is, good affinity or compatibility with the organic polymer base material. , which requires the selection of surface modifiers that can make the surface of inorganic powders hydrophobic and oleophilic; for inorganic pigments used in ceramic blanks, they are not only required to have good dispersion in the dry state, but also require affinity with the inorganic blanks. Good compatibility and can be evenly dispersed in the blank; for surface modifiers of inorganic powders (fillers or pigments) used in water-based paints or coatings, the dispersion and sedimentation stability of the modified powder in the water phase are required. Good compatibility.

For inorganic surface modifiers, they are mainly selected based on the functional requirements of powder materials in the application field. For example, to make titanium dioxide have good weather resistance and chemical stability, SiO2 and Al2O3 must be used for surface coating (film) , in order to make the muscovite pigment have a good pearlescent effect, it is necessary to use TiO2 for surface coating (film).

At the same time, different application systems have different components. When selecting a surface modifier, you must also consider the compatibility and compatibility with the application system components to avoid the functional failure of other components in the system due to the surface modifier.

3. Modification process

The modification process is also one of the important considerations in selecting surface modifiers, such as temperature, pressure and environmental factors. All organic surface modifiers will decompose at a certain temperature. For example, the boiling point of silane coupling agents varies between 100 and 310°C depending on the type. Therefore, it is best to select a surface modifier with a decomposition temperature or boiling point that is higher than the processing temperature of the application.

The current surface modification process mainly adopts dry method and wet method. There is no need to consider the water solubility of the dry process, but the water solubility of the surface modifier must be considered for the wet process, because only if it is soluble in water can it fully contact and react with the powder particles in a wet environment.

Therefore, for surface modifiers that are not directly water-soluble and must be used in a wet environment, they must be saponified, ammonized or emulsified in advance so that they can be dissolved and dispersed in aqueous solutions.

4. Price and environmental factors

Finally, when selecting surface modifiers, price and environmental factors must also be considered. On the premise of meeting application performance requirements or optimizing application performance, try to choose cheaper surface modifiers to reduce the cost of surface modification. At the same time, attention should be paid to selecting surface modifiers that do not pollute the environment.

by ALPA

5 Major Types of Surface Modification Methods For Carbon Fiber

Carbon fiber (CF), as a new type of composite reinforced material, has been widely used in various industries and has attracted much attention. However, the surface of CF is relatively smooth and has no active groups. The fiber surface is chemically inert, so the fiber has poor hydrophilicity and poor adhesion to the matrix, and is easy to fall off. Therefore, it is necessary to improve the interface between CF and matrix reinforcement.

So far, the common surface modification methods of carbon fiber mainly include coating modification, surface graft modification, oxidation modification, plasma modification and joint modification, among which oxidation treatment and surface grafting treatment are more popular. Methods. These modification methods improve the fiber's wettability, chemical bonding, and mechanical interlocking with the matrix to form a transition layer, promote uniform stress transmission, and reduce stress concentration.

The surface of carbon fiber is smooth, has few active groups, and does not adhere firmly to the matrix. In normal applications, it is necessary to improve the adhesion rate. One method is to roughen the smooth carbon fiber surface through physical effects, creating grooves or small holes to increase the contact area with the matrix material. Polymers or nanoparticles can be filled in the fiber. In the grooves on the surface, the fiber and polymer can be mechanically locked together through the rough shape of the fiber surface after curing, resulting in an obvious mechanical interlocking effect between the fiber and the matrix, which is beneficial to improving the interface strength.

1. Coating modification

Carbon fiber coating modification can cover a variety of materials, such as metal salts, metal alloys, carbon nanomaterials, etc., through spraying, physical or chemical deposition, polymers, sol-gel methods and coating processes. After coating, the surface of CFs has different properties.

2. Surface grafting

Carbon fiber surface grafting is a bottom-up, extensively studied CFｓs modification method. Compared with surface oxidation and coating methods, surface grafting can give the grafted polymer better adhesion to the CF surface. Through radiation or chemical reaction, the grafting reaction is triggered on the surface of CFs, and polymers with functional groups are introduced on the surface of CFs, which improves the interface strength of the composite material.

3. Oxidation treatment

Carbon fiber oxidation treatment is a simple modification method that not only increases the pore distribution and pore size on the CF surface, but also introduces different concentrations of oxygen-containing functional groups, which has a significant impact on the material interface adhesion and immobilization efficiency (IE). Influence.

4. Plasma treatment

Plasma treatment is a prominent and successful treatment method for a variety of materials, including carbon materials. High enough energy plasma is used to hit the CF surface, causing the chemical bonds to break and reorganize on the surface, thereby improving the surface structure and performance of the carbon fiber to achieve good adhesion between CF and the matrix material. Plasma treatment has the advantages of simple operation, high efficiency, green and environmental protection.

5. Joint modification

The above-mentioned single modification methods have more or less defects. For example, coating-modified CF has low adhesion between the coating and CF, requires the use of solvents during the manufacturing process, has low preparation efficiency, and is difficult to produce continuously; investment in plasma treatment equipment is expensive; in wet chemical oxidation and electrolysis Some liquid contamination is inevitable during chemical treatment, and the modification conditions should be precisely controlled in gas-phase oxidation to prevent excessive oxidation from destroying the internal structure of CF, and the use of nanomaterials or grafted polymers to modify the surface of carbon fibers is complex.

Therefore, when modifying the surface of carbon fiber, joint modification using multiple modification methods can avoid the shortcomings of using them alone and combine the advantages with each other. This is the main direction of carbon fiber surface modification treatment in the future.

by ALPA

What are the differences between white talc, black talc and hydrotalcite?

At present, the products related to "talc" on the market mainly include white talc, black talc, hydrotalcite, etc. Although they are all called talc, their ingredients, uses, prices, etc. are very different.

1. White talc

Talc is a hydrous magnesium silicate mineral, most commonly found in white, which is white talc. Look at China for the world's talc. The white talc supplied in the international market mainly comes from China. The advantages of Chinese talc are not only reflected in reserves and output, but more importantly, in the extraordinary quality of white talc, especially high-purity white talc.

White talc has high electrical insulation, heat insulation, high melting point and strong adsorption of oil. It is widely used in papermaking, chemical industry, medicine, rubber, ceramics, paint, cosmetics and other industries.

2. Black talc

Black talc is a 2:1 type (T-O-T) magnesium-rich silicate clay mineral. It is soft, has a flaky structure and a slippery feel. It does not contain water between the layers, is odorless and tasteless, has stable chemical properties, small particles, and a large specific surface area. Black talc is gray to black because it contains organic carbon. Its chemical composition, mineral composition and mineral deposit origin are similar to white talc. The main ore components are usually composed of talc, quartz, organic carbon, etc.

At present, most black talc is processed into white talc through whitening technology and then used in the traditional ceramic industry and basic fillers. The research directions are mainly high-efficiency whitening and ultra-fine processing technology.

3. Hydrotalcite

Hydrotalcite is divided into natural hydrotalcite and synthetic hydrotalcite. Since natural hydrotalcite is difficult to mine and its purity is not high, the market supply of hydrotalcite is dominated by synthetic hydrotalcite.

Synthetic hydrotalcites (LDHs) are a class of anionic layered compounds with broad application prospects, mainly composed of hydrotalcite (HT), hydrotalcite-like (HTLC for short) and their intercalation chemical products pillared hydrotalcite (Pillared LDH) constitute.

Synthetic hydrotalcite is a non-toxic dihydroxy compound with a special layered structure. It has physical and chemical properties such as charging properties, anion exchangeability, adsorption properties, catalytic properties, etc. It has a wide range of applications in the field of polymer resin materials. Mainly used as heat stabilizer for polyvinyl chloride (PVC) production and halogen absorber for polyolefin resin production.

The main finished product categories of synthetic hydrotalcite include general synthetic hydrotalcite, highly transparent synthetic hydrotalcite and flame-retardant synthetic hydrotalcite.

by ALPA

6 Types of Modification Methods for Coal Gangue

In order to solve the problem of coal gangue accumulation, find ways to extract the additional utilization value of coal gangue, and "turn waste into treasure" to the maximum extent, many researchers have modified coal gangue to increase its activity, making it a material with various high Value-added environmentally friendly materials solve the problem of coal gangue pollution from the root cause and achieve the purpose of waste resource recycling and environmental protection.

At present, the modification methods of coal gangue mainly include traditional acid or alkali treatment, mechanochemical method, surface organic modification method, calcination modification method, hydrothermal modification method and composite modification method.

1. Mechanical modification method

Mechanical grinding is a common physical method for modifying materials. Grinding coal gangue will increase its specific surface area and thereby improve the adsorption activity of solid particles. It will also change the crystal structure and crystal particle size of coal gangue, and the raw materials are in When the particles are refined, micro-homogenization is obtained, and the reactivity will be greatly improved.

2. Acid or alkali modification method

Acid modification is to dissolve acid-soluble metal ions such as Al, Fe, and Ca in the coal gangue through acid leaching, improve the pore size distribution, number of holes, and specific surface area inside the coal gangue, and change the crystal structure and surface properties of the coal gangue; in addition In addition, acid modification can also increase the active sites of coal gangue to make its adsorption performance stronger.

3. Surface organic modification method

Surface modification of coal gangue refers to grafting a layer of organic modifiers on the surface of coal gangue through chemical or physical methods to change the surface charge, hydrophilicity, dispersion and other properties of coal gangue, and perform modification and activation to give coal gangue its unique properties. Adsorption characteristics, enhance the repair and activation ability of coal gangue, and broaden the application scope of coal gangue.

4. Calcination modification method

Calcination modification refers to the process of transforming low surface activity kaolinite in coal gangue into highly active metakaolinite through high-temperature roasting. The porosity and crystal structure of coal gangue can be changed through calcination. The degree of calcination modification of coal gangue is mainly affected by the calcination temperature and calcination time. The difference between these two main factors will cause different phases of kaolin in coal gangue. Changes will lead to performance differences in the calcined modified coal gangue.

5. Hydrothermal modification method

Hydrothermal modified coal gangue refers to a certain degree of physical or chemical modification of coal gangue under a certain temperature and pressure to obtain a more complete material. In particular, the supercritical hydrothermal method has many unique properties. It can not only improve the reactivity of coal gangue, but also change the internal structure of coal gangue to a certain extent. When used to prepare zeolite molecular sieves, it can obtain high cleanliness and complete crystal form. New Materials.

6. Compound modification method

Composite modification is generally based on thermal modification, using mechanical modification or chemical modification to stimulate the activity of coal gangue. Composite modification can integrate the advantages of a single modification method to a certain extent, make up for its inherent defects, and produce synergistic effects. The comprehensive performance of composite modified coal gangue is obviously better than that of coal gangue modified by a single process, and it can also meet various needs. Industrial needs. Moreover, the composite process can greatly improve the activation efficiency of coal gangue, obtain coal gangue composite materials with better performance, and promote the efficient utilization of mineral resources in coal gangue, so it is widely used.

by ALPA

Stirring mill, jet mill, sand mill, how to choose?

Ultra-fine grinding equipment uses mechanical force to grind materials to the micron level and classify them. Due to its good processing performance, it is widely used in high-end coatings, food, medicine, chemicals, building materials, medicinal materials, mining and other industries. With the rapid development of the global economy, my country's powder industry is booming, and powder equipment, especially ultra-fine crushing equipment, plays a key role in this.

Mixing mill

A stirrer grinder (stirrer mill) refers to a type of ultra-fine grinding equipment consisting of a stationary cylinder filled with grinding media and a rotating agitator. The cylinder of the mixing grinder is generally made with a cooling jacket. When grinding materials, cooling water or other cooling media can be passed into the cooling jacket to control the temperature rise during grinding. The inner wall of the grinding barrel can be lined with different materials according to different grinding requirements, or a fixed short shaft (rod) can be installed and made into different shapes to enhance the grinding effect. The agitator is the most important part of the mixing mill, and there are types such as shaft-rod type, disc type, perforated disc type, cylindrical type, ring type, spiral type, etc. Among them, spiral and rod stirrer mills are mainly vertical, while disc stirrer mills come in two types: vertical and horizontal.

Jet mill

The particle size of the finished product of airflow mill is in the range of 1~30μm, and the particle size of the processing feed is strictly controlled below 1mm under normal circumstances. It can be widely used in materials such as rare earths, various hard marbles, kaolin, talc and other medium-hard non-metallic minerals. of ultra-fine processing.

Flat airflow pulverizer: Flat airflow pulverizer is also called horizontal disc airflow mill. When the equipment is working, high-pressure airflow is ejected from the nozzle at ultra-high speed, and the material is accelerated by the Manchuri nozzle and then sent to the crushing chamber for high-speed circular motion, where it is crushed through impact, collision, and friction. Under the action of centrifugal force, coarse particles are thrown towards the wall of the crushing chamber for circular crushing, and fine particles overflow with the airflow and are collected. The advantages of this equipment are simple structure and easy operation.

Fluidized bed air jet mill: commonly used for ultra-fine crushing, breaking up and shaping of materials in ceramics, chemical raw materials, refractory materials, battery materials, pharmaceuticals and other industries. When the equipment is working, high-pressure air is sprayed into the crushing chamber at high speed through several nozzles. The fed materials are accelerated by the high-pressure airflow in the crushing chamber. They are crushed through collision and friction at the intersection of each nozzle, and then enter the classification chamber with the airflow to complete classification. The coarse material settles back to the crushing area to continue crushing, and the overflow of qualified products is collected by the cyclone separator.

Counter-jet airflow pulverizer: Counter-jet airflow pulverizer is also called collision airflow mill and reverse jet mill. When the equipment is working, two accelerated materials and high-speed airflow meet at a certain point on the horizontal straight line and collide to complete the crushing. The solid particles that enter the classification chamber with the airflow are under the action of the classification rotor, and the coarse particles remain on the outer edge and are crushed. Return to the crushing chamber for re-crushing, and the fine particles that meet the particle size requirements continue to rise, and after flowing out, they become products through gas-solid separation.

Sand mill

A sand mill is another form of stirrer or bead mill, so named because it originally used natural sand as the grinding media. Sand mills mainly rely on the high-speed rotation between grinding media and materials to perform grinding work. They can be divided into open and closed types, and each can be divided into vertical and horizontal types.
Generally speaking, the difference between a horizontal sand mill and a vertical sand mill is that the horizontal sand mill has a larger sand capacity, higher grinding efficiency, and is relatively easy to disassemble and clean. In terms of application, sand mills are widely used in coatings, dyes, paints, inks, medical drugs, nanofillers, magnetic powder, ferrite, photosensitive film, pesticides, papermaking, cosmetics and other fields for efficient grinding of nanopowders.

No matter how the powder industry develops, ultrafine impact grinding has always been one of the main means to obtain ultra-fine powder.

by ALPA

Using powder metallurgy to prepare high thermal conductivity copper and diamond composite materials

In fields such as electronic packaging and aerospace, metal-based heat dissipation devices have been developed for decades. As the power density of devices continues to increase, higher requirements are placed on the thermal conductivity of electronic packaging materials. By compounding diamond with high thermal conductivity (2 200 W/(m·K)) and low thermal expansion coefficient ((8.6±1)×10-7/K) with metals such as copper and aluminum, high thermal conductivity can be integrated , a "metal + diamond" composite material with an adjustable thermal expansion coefficient and high mechanical properties and processing properties, thereby meeting the stringent requirements of different electronic packaging, and is regarded as the fourth generation of electronic packaging materials.

Among various metal materials, compared with other metals such as aluminum, copper has a higher thermal conductivity (385~400 W/ (m·K)) and a relatively low thermal expansion coefficient (17×10-6/K). By simply adding a smaller amount of diamond reinforcement, the thermal expansion coefficient can match that of semiconductors and it is easy to obtain higher thermal conductivity. It can not only meet the stringent requirements of today's electronic packaging, but also has good heat resistance, corrosion resistance and chemical stability. It can meet the requirements of extreme service conditions such as high temperature and corrosive environment to a greater extent, such as nuclear power projects, acid-base and dry, wet, cold and hot atmospheric environments.

How to prepare?

There are currently many methods for preparing diamond/copper composite materials, such as powder metallurgy, chemical deposition, mechanical alloying, spray deposition, casting, etc. Among them, powder metallurgy has become one of the most commonly used preparation methods because of its simple preparation process and excellent performance of the prepared composite materials. In this way, Cu powder and diamond particles can be mixed evenly through ball milling, etc., and then sintering and molding can be used to prepare a composite material with a uniform microstructure. As the most critical step in powder metallurgy, sintering molding is related to the final quality of the finished product. Commonly used sintering processes currently used in the preparation of Cu/diamond composite materials include: hot press sintering, high temperature and high pressure sintering, and discharge plasma sintering.

Hot press sintering
The hot pressing sintering method is a diffusion welding forming method. As a traditional method for preparing composite materials, the main process is to mix the reinforcement and copper powder evenly, put them into a mold of a specific shape, and place them in the atmosphere, vacuum or protected environment. In the atmosphere, pressure is applied in the uniaxial direction while heating, so that forming and sintering proceed simultaneously. Since the powder is sintered under pressure, the powder has good fluidity and the material has a high density, which can discharge the residual gas in the powder, thereby forming a stable and strong interface between diamond and copper. , improve the bonding strength and thermophysical properties of composite materials

by ALPA