Application of coal gangue in the field of dense ceramic materials
Coal gangue is the rock trapped in the coal seam, and it is also the waste in the process of coal mining and coal washing. At present, the accumulated coal gangue in the country is as high as several billion tons, which has caused serious damage to the ecological environment. As a recyclable resource, coal gangue has been widely used in many fields.
Through research, it is found that the main components in coal gangue are alumina and silica, and these compounds are commonly used raw materials for ceramic production. Coal gangue itself also has a large number of micropores and a high specific surface area. Therefore, coal gangue can be used to prepare ceramics and other materials with excellent properties such as high mechanical strength, acid and alkali corrosion resistance, and long life.
1. Dense mullite and its composite materials
Mullite (3Al2O3·2SiO2) is a high-quality refractory material with the characteristics of high density, good thermal shock resistance, good creep resistance, low expansion coefficient and stable chemical composition. In my country, there are few natural mullite reserves, and most of the mullite is artificially synthesized. Generally, kaolin and alumina powder are used as raw materials, and mullite materials are prepared by sintering or electrofusion. Since the content of kaolinite in coal gangue can generally reach more than 90%, mullite and mullite composite materials with excellent performance can be prepared by mixing gangue with auxiliary materials such as Al2O3 and calcination at high temperature. my country has also made some progress in the preparation of mullite and its composite materials from coal gangue.
Using high-alumina bauxite as the main raw material, together with coal gangue and a small amount of Al2O3 to prepare mullite clinker, the research found that mullite clinker with excellent performance can be fired at 1700 °C, and its apparent porosity is less than 25 %, bulk density ≥ 2.75g/cm3.
The pickled coal gangue was used as the main raw material, which was evenly mixed with alumina, and mullite was prepared by solid-state sintering. It will first increase and then decrease slightly, so the holding time for preparing mullite should be controlled within 2h.
Using bauxite and coal gangue as main raw materials, vanadium pentoxide (V2O5) and aluminum fluoride (AlF3) as additives, a crystal whose main crystal phase is mullite phase was prepared by solid state reaction. The research shows that: when aluminum When bauxite and silicon-alumina in coal gangue are mixed at a molar ratio of 2:3.05, the strength and hardness of the prepared mullite material have been significantly improved, and the performance is the best. Its volume density is as high as 2.3g/cm3, the apparent porosity is 23.6%, the water absorption rate is 10.55%, and the flexural strength is 114MPa.
The mullite-high silica glass composite material was successfully synthesized by using coal gangue and kaolin as raw materials and adding potassium feldspar. The study found that the sintering temperature of the mixture without adding potassium feldspar is above 1590°C, while the sintering temperature of the mixture with K2O ratio of 1.5% and adding potassium feldspar can be reduced to 1530°C. Therefore, adding a certain amount of potassium feldspar to the mixture can reduce the sintering temperature.
Using coal gangue as raw material, the gangue is activated by impurity removal, calcination and other processes, and the nano-mullite composite powder material is prepared by hydrothermal crystallization. The results show that the nano-mullite composite phase was prepared from the activated coal gangue powder under the conditions of a concentration of 2-4mol/L sodium hydroxide solution, a stirring temperature of 80-90°C, a heat preservation of 3h, and a liquid-solid ratio of 10mL/g. Powder, nano-mullite composite powder has a good crystallization effect, most of which are columnar crystals, the grain length is 50nm, and the average aspect ratio reaches 3.5.
2. Dense sialon and its composite materials
Using high-alumina coal gangue, iron concentrate powder, and coke powder as raw materials, the Fe-Sialon composite dense material was prepared by carbothermal reduction nitriding method at 1400-1550°C for 4 hours. It was found that the coke content exceeded 10% 1. The Fe-Sialon dense material prepared at 1500℃ for 4 hours has the most uniform grain distribution and the best performance.
Using coal gangue and natural clay as the main raw materials, the colloidal molding process was used to shape the green body, and the β-Sialon/SiC composite dense ceramic material was successfully synthesized by the carbothermal reduction nitriding process. The study found that the optimized process of colloidal molding can be used to produce a green body with a density as high as 1.12g/cm3, and a dense β-Sialon/SiC composite material can be produced after sintering.
Effect of Modified Tourmaline Powder on Properties of ABS Composites
Tourmaline is used in water purification, medical treatment and other fields due to its piezoelectricity, far-infrared properties and the ability to release air negative ions. However, its raw material is a single tourmaline material, which limits its application and cannot meet people's requirements for modern materials. Therefore, new functional composite materials obtained by blending tourmaline and other materials have become a current research hotspot.
ABS resin is a graft copolymer composed of three monomers of acrylonitrile, butadiene and styrene. It has high strength and high toughness, strong corrosion resistance to acid, alkali and salt, and good molding processability. Well, the finished product has the characteristics of smooth surface, easy dyeing and electroplating, etc., and has been widely used in various fields.
The surface of tourmaline powder was modified with sodium stearate and titanate, and the modified tourmaline was blended with ABS resin to prepare tourmaline/ABS composite material. The results showed that:
(1) The tourmaline powder was successfully modified by sodium stearate and titanate, which reduced its hydrophilicity and improved its interface binding force with ABS resin.
(2) With the increase of the amount of modified tourmaline in ABS resin, the tensile strength and impact strength of tourmaline/ABS composites first increased and then decreased. Compared with the ABS resin without added tourmaline, when the amount of modified tourmaline was 2%, the tensile strength of the composite material increased by 11.30%; when the amount of modified tourmaline was 3%, the impact strength of the composite material The strength increased by 38.18%. The composite material can also release negative ions. When the amount of modified tourmaline is 3%, the negative ion release amount of the composite material is 456.5/cm2, which expands the application range of ABS resin.
Application and characteristics of talcum powder in food grade grease
Food safety has always been the focus of people's attention. There are many factors affecting food safety, among which the pollution caused by the leakage of lubricating materials in food equipment is one of the important reasons. Food-grade grease is widely used in key transmission parts of food processing equipment such as bearings, chains and guide rails, and the lubricating performance of grease mainly depends on the additives used.
In view of the guarantee of the safety of food-grade grease, non-toxic and harmless are the primary considerations when selecting additives. As a food additive, food-grade talc powder is often used in food flow aids and mold release; because of its good lubricating properties, it also has certain applications in the field of tribology, such as coating talc powder on protective clothing to Reduce skin damage of medical staff during COVID-19; in addition, talc powder in lubricating oil has excellent anti-friction properties, which can better reduce the wear of cast iron equipment.
The composite aluminum-based grease was prepared by white oil and thickener, and the effect of the mass fraction of food-grade talcum powder on the tribological properties of the grease was investigated. The results showed that:
(1) Talc powder can improve the thermal stability of the composite aluminum-based grease, and the extensional decomposition temperature of the base grease is significantly lower than that of the grease containing talc powder;
(2) Talc powder can improve the tribological properties of composite aluminum-based grease, that is, improve the stability of the friction process, reduce the friction coefficient and wear volume; When the mass fraction of talcum powder is 1.0%, the average friction coefficient and wear volume are the smallest; Polishing plays an effective anti-friction and anti-wear effect;
(3) The lubricating grease with 1.0% talc powder is most likely to be applied to food equipment and other fields.
(4) Talc powder is a layered silicate, which can be adsorbed on the surface of the friction pair during the friction process, which is equivalent to the sliding of a "sliding bearing", thereby reducing friction and reducing wear.
(5) From the perspective of the thermal stability of the grease, when the degradation termination temperature is reached, the remaining weight of the grease sample containing talcum powder is higher than that of the base grease. This is because the main components of talc powder are MgO and SiO2, and the heat of SiO2 Good stability, can improve its thermal stability. Since a large amount of heat is easily generated during the friction process, SiO2 with better thermal stability tends to stay in the gap of the friction pair. Due to the roughness of the surface of the steel plate, the real contact area between the steel ball and the steel plate is small, and it bears high contact stress at the beginning of the friction process, which is easy to generate large friction and creates grooves on the surface of the wear scar, so some talc powder (mainly SiO2) can repair the gully produced on the surface of the wear scar during the friction process, thereby increasing the contact area between the friction pairs and reducing the contact stress between the friction pairs; at the same time, SiO2 is a commonly used polishing material, so a small amount of SiO2 can A micro-polishing effect is produced on the surface of the friction pair, thereby achieving the effect of reducing friction and reducing wear.
Application of metal powder materials in the pharmaceutical industry
Solid pharmaceutical preparations account for about 70% to 80% of pharmaceutical products. The dosage forms containing solid pharmaceuticals include powders, granules, capsules, tablets, powder injections, and suspensions, such as the ibuprofen we used to cure the new crown disease Sustained-release capsules, ibuprofen suspensions, Ganmao granules, etc., are actually closely related to powder materials. The production processes involved include crushing, grading, mixing, granulation, etc. Some solid pharmaceutical preparations need to be modified during the preparation process to improve the powder properties, so as to meet the needs of product quality and powder operation. In addition to the above-mentioned solid pharmaceutical preparations which need to be crushed and processed, the preparation of some raw materials also needs to rely on the catalytic reduction of metal powders.
The application of metal powders in medicine also involves different shape control. Among them, spherical powders are mostly prepared by liquid phase and gas phase methods, and flake powders are mostly prepared by solid phase methods. The particle size, purity and mass fraction of trace elements of metal powder play a decisive role in the yield and pass rate of medicine. The development and application of powder preparation technology and metal powder materials are important to the preparation process and preparation quality of the pharmaceutical industry. influences.
In traditional Chinese medicine preparations and synthetic medicines, traditional Chinese medicine biological powder materials and metal powders have been widely used. At present, for mineral medicines, precious medicines and traditional Chinese medicines with special properties, hammering and ball milling methods are generally used in China. Make the drug reach a certain particle size, and can maintain the inherent pharmacodynamic basic substance of traditional Chinese medicine.
The particle size, quality difference, mixing uniformity, and tablet strength of traditional Chinese medicine are mostly related to the powder. For the medicinal materials processed by ultrafine powder technology, the fluidity, filling and compression molding properties of the solid preparation can be controlled. To achieve the purpose of controlling the quality of solid preparations, and its disintegration, dissolution and bioavailability are related to the powder properties of each material in the drug prescription.
The smaller the particle size of the powder material for traditional Chinese medicine, the better. The powder material of traditional Chinese medicine with a median particle size of about 15 μm has a high cell wall breaking rate, which is beneficial to the release and absorption of the drug; During the process, the homogenization of each active ingredient is conducive to retaining biologically active ingredients and improving the efficacy of the drug; it is easy to shape and apply, which is conducive to exerting the efficacy of the drug and improving the utilization rate of the drug.
When synthesizing western medicine, metal powder materials with a median particle size of about 75 μm are generally used for chemical reactions such as catalysis, reduction and oxidation. In recent years, with the current upsurge of modernization of Chinese and Western medicine and the development of nanotechnology, powder technology also has a broader development space, which provides new methods and approaches for the research of modern drug delivery systems, and also significantly improves the human body’s ability to respond to various diseases. Components Absorption rate and absorption capacity of active ingredients.
As an important industry in the field of fine chemicals, medicine has become the focus of development and competition in the past ten years. The synthesis of modern medicine depends on the production of new and high-quality pharmaceutical intermediates, so more and more people pay attention to powder technology and powder materials; Put forward higher and newer requirements. Among metal powder materials, zinc powder is most widely used in medicine because of its preparation process, physical and chemical properties, good catalytic reduction effect on pharmaceutical intermediates or synthetic drugs, and high product yield. With the increasing safety and environmental protection requirements, powder technology and powder materials will continue to develop, and the development of new alternative technologies and materials has always been promoting the continuous progress of the pharmaceutical industry.
Application of jet pulverization equipment in the production of titanium dioxide
1. The principle of jet crushing
Jet milling equipment includes jet mill, jet mill or fluid energy mill, which uses the energy of high-speed airflow or superheated steam to make particles impact, collide, and rub against each other to achieve ultrafine pulverization or depolymerization. The general principle of jet milling: the dry and oil-free compressed air or superheated steam is accelerated into a supersonic airflow through the Laval nozzle, and the high-speed jet ejected drives the material to move at a high speed, causing the particles to collide and rub against each other and be crushed. The crushed materials arrive at the classification area with the airflow, and the materials that meet the fineness requirements are finally collected by the classifier, and the materials that do not meet the requirements are returned to the crushing chamber to continue crushing.
2. Classification of jet milling equipment
The jet mills used in industry mainly include the following types: flat jet mill, fluidized bed jet jet mill, circulating tube jet mill, counter jet jet mill, and target jet mill. Among these types of jet mills, flat jet mills, fluidized bed jet mills, and circulating tube jet mills are widely used.
2.1 Counter jet jet mill
After the material enters the crushing chamber through the screw feeder, the impact energy of the high-speed airflow is sprayed out by several relatively set nozzles, and the rapid expansion of the airflow forms the collision and friction generated by the suspension and boiling of the fluidized bed to crush the material. Coarse and fine mixed powder is driven by the negative pressure airflow through the turbine classification device installed on the top. The fine powder is forced to pass through the classification device and is collected by the cyclone collector and bag filter. The coarse powder is thrown away by gravity and the centrifugal force generated by the high-speed rotating classification device. It goes to the four walls and settles back to the crushing chamber to continue crushing.
2.2 Flat jet mill
The high-pressure airflow as the crushing kinetic energy enters the pressure-stabilized air storage bag on the periphery of the crushing chamber as an air distribution station. The airflow is accelerated into a supersonic airflow through the Laval nozzle and then enters the crushing chamber, and the material is accelerated into the crushing chamber through the Venturi nozzle. Perform simultaneous crushing. Since the Laval nozzle and the crushing chamber are installed at an acute angle, the high-speed jet stream drives the material to circulate in the crushing chamber, and the particles collide, collide, and rub against each other as well as with the wall of the fixed target plate to be crushed. Driven by the centripetal airflow, the fine particles are introduced into the central outlet pipe of the pulverizer and enter the cyclone separator for collection, while the coarse powder is thrown to the surrounding wall of the pulverization chamber under the action of centrifugal force for circular motion and continues pulverization.
2.3 Circulating tube jet mill
The raw material is fed into the crushing chamber through the Venturi nozzle, and the high-pressure air is sprayed into the runway-shaped circulating tubular crushing chamber with unequal diameter and variable curvature through a group of nozzles, accelerating the particles to collide, collide, rub and crush each other. At the same time, the swirling flow also drives the crushed particles upwards into the classification area along the pipeline, and the dense material flow is shunted under the action of the centrifugal force field in the classification area, and the fine particles are discharged after being classified by the louver type inertial classifier in the inner layer. Coarse particles return along the downpipe in the outer layer and continue to be pulverized in a circular manner.
2.4 Fluidized bed jet mill
Jet mill (fluidized bed jet mill) is the compressed air that is accelerated by the Laval nozzle into a supersonic airflow and then injected into the crushing area to make the material fluidized (the airflow expands to form a fluidized bed that suspends and boils and collides with each other). Therefore every particle has the same motion state. In the pulverization zone, the accelerated particles collide with each other and pulverize at the junction of each nozzle. The crushed material is conveyed to the classification area by the updraft, and the fine powder meeting the particle size requirement is screened out by the classifying wheels arranged horizontally, and the coarse powder not meeting the particle size requirement is returned to the crushing area for further crushing. Qualified fine powder enters the high-efficiency cyclone separator with the airflow to be collected, and the dusty gas is filtered and purified by the dust collector and then discharged into the atmosphere.
Application of jet pulverization equipment in the production of titanium dioxide
1. Titanium dioxide requirements for crushing
Titanium dioxide used as a pigment has excellent optical properties and stable chemical properties. Titanium dioxide has very high requirements on particle size, particle size distribution and purity. Generally, the particle size of titanium dioxide is based on the wavelength range of visible light, that is, 0.15m ~ 0.35m. And as a white basic pigment, it is very sensitive to the increase of impurities, especially iron impurities, and the increase is required to be less than 5 ppm when pulverized. In addition, titanium dioxide is also required to have good dispersibility in different coating systems. Therefore, the general mechanical crushing equipment is difficult to meet the requirements, so the final crushing of titanium dioxide (finished product crushing), at present, jet mills are used at home and abroad.
2. The choice of jet mill for titanium dioxide production
According to the crushing requirements of titanium dioxide: narrow particle size distribution, less increase in inclusions, good dispersibility, etc., and the material characteristics of titanium dioxide: high viscosity, poor fluidity, fine particle size and easy wall attachment, etc., currently titanium dioxide manufacturers all choose self-grading function The flat (also known as horizontal disc) airflow mill is used as the final crushing equipment for titanium dioxide;
And use superheated steam as crushing tool. Because the steam is easy to get and cheap, the pressure of the steam working medium is much higher than that of the compressed air and it is also easy to increase, so the kinetic energy of the steam is larger than that of the compressed air. At the same time, the cleanliness of superheated steam is higher than that of compressed air, with low viscosity and no static electricity. Moreover, while crushing, it can eliminate the static electricity generated by material collision and friction, and reduce the secondary cohesion of powdered materials. In addition, crushing at high temperature can improve the application dispersibility of titanium dioxide and increase the fluidity of titanium dioxide. The energy consumption of superheated steam is low, which is only 30% to 65% of that of compressed air.
3. Development of jet milling
With the rapid development of titanium dioxide industry, the requirements for equipment are getting higher and higher. On the premise of meeting the process conditions and quality requirements, the large-scale and systematization of equipment is particularly important, and jet milling is also constantly improving along with the development of titanium dioxide. The production capacity of the gas powder machine has also changed from the initial 1.2t/h to 1.5 t/h to 2.5 t/h to 3.5 t/h now, and the production capacity of the gas powder system has also changed from 10,000 t/h for a single line a. Up to now, the single line is 20,000 t/a, and the collection method has also changed from the relatively backward wet collection to the advanced dry collection, which greatly improves the primary yield and reduces waste.
Learn more about the benefits of fluidized bed jet mills
Since the advent of jet milling and grading equipment in the 1930s, the types have been continuously updated and the structure has been continuously improved. Bed (on-spray) jet mill, etc.
The fluidized bed jet mill is a new model developed and put into use by a German company in the late 1970s and early 1980s. It has the characteristics of low energy consumption, light wear, low pollution, low noise, fine particle size and relatively uniform distribution of products, etc. Resins, phenolic resins, PVC, pigments and dyes, powder coatings, couplers, pharmaceuticals, cosmetics, advanced ceramics, magnetic powders, abrasives, metal powders, food, fragrances, stearic acid, fats, waxes, mineral powders, and pesticides and wettability It is widely used in the production of powder and so on.
Main Advantage
(1) Change the line and surface impact crushing of the traditional jet mill to the three-dimensional impact crushing of the space, and make full use of the high-speed airflow generated by the jet impact in the flow of materials in the crushing chamber, so that the crushing area is similar to a fluidized state Excellent gas-solid crushing and graded circulation flow effect, which improves the efficiency of impact crushing and the comprehensive utilization of energy. Compared with other traditional methods, the energy consumption is reduced by 30-40% on average;
(2) Since the impact crushing area and the gas-solid flow belt are placed in the middle space of the crushing chamber, the impact and abrasion of the materials driven by the high-speed airflow on the wall of the crushing chamber are avoided, and the most serious wear problem in jet impact crushing is improved, and greatly reduced. the potential for the material to be contaminated;
(3) Protective gases such as high-purity nitrogen or argon are used as the working medium to prevent oxidation, and the closed-loop operation has low gas consumption and reduces costs;
(4) There is no dust flying during the complete closed-loop operation, no pollution to the environment, and no harm to the human body;
(5) After jet milling, the activity of the powder increases. The energy of the high-speed jet flow in the jet mill crushing and classification process can not only cause the particles to be impacted and crushed, but also change the internal structure of the particles, especially the surface state, to a certain extent. The energy of the gas flow removes atoms or ions from the particle lattice, causing a mechanical loss of the crystalline structure. In this way, while the powder material is ultrafinely pulverized, the surface energy or internal energy of the particles increases, and the activity of the particles increases. The increase in the activity of the particles is not only beneficial to the chemical reaction, but also beneficial to the adsorption and coating of the particles.
(6) The particle size of the product is fine, the output is large, and it is suitable for large-scale production; the particle size classification accuracy is high, so the particle size distribution of the product is narrow, and the particle size of the product is also easy to adjust.
The fluidized bed jet mill has many advantages such as low energy consumption, small wear and high classification accuracy, and it is widely used in the current ultrafine grinding equipment. However, because there is no specific theoretical guidance, engineering practice is often used to design the structure of the fluidized bed jet mill.
People have done a lot of research on the nozzle, but the research on the flow field inside the fluidized bed jet mill is still limited to theoretical analysis. There are many applications for the pulverization of fluidized bed jet mills, but in the process of jet milling, they often rely on experience to adjust process parameters, lacking the support and guidance of theoretical research.
Therefore, it is necessary to further deepen the applied basic research of the fluidized bed jet mill jet milling process, and strengthen the understanding and knowledge of the fluidized bed jet mill pulverization mechanism. With the continuous development of fluidized bed jet mill pulverization technology and the widening of its application range, fluidized bed jet mill pulverization technology will play an increasingly important role.
Main beneficiation and purification technologies and characteristics of kaolin
The purpose of purifying kaolin is to remove harmful dyeing impurities such as iron minerals, titanium minerals and organic matter to improve the whiteness of the product; on the other hand, to remove sandy minerals such as quartz and feldspar to improve Improve the quality of kaolin products, and then expand the breadth and depth of its application, and obtain better economic benefits while making full use of kaolin resources.
At present, the purification process of kaolin mainly includes gravity separation, magnetic separation, flotation, leaching, chemical bleaching and roasting.
1. Re-election
The gravity separation purification process mainly uses the difference in density and particle size between kaolin and gangue minerals to remove light organic matter and high-density impurities containing elements such as iron, titanium and manganese, so as to achieve the purpose of purifying kaolin and reduce or remove impurities. Negative impact on its whiteness.
2. Magnetic separation
The magnetic separation process is used to remove weak magnetic dyeing impurities such as hematite, siderite, pyrite and rutile in kaolin. Magnetic separation does not require the use of chemicals and has no pollution to the environment, so it is widely used in the purification process of non-metallic ores. The removal of weakly magnetic impurity particles in kaolin requires a high magnetic induction intensity and magnetic field gradient, and the development of magnetic separation technology and equipment upgrades have enabled the magnetic separation and purification of kaolin and other non-metallic minerals to be effectively realized.
3. Flotation
The flotation purification process can effectively remove iron, titanium and carbon impurities in kaolin, and realize the recovery and reuse of low-grade kaolin resources such as coal series kaolin. Kaolin has finer particles and is more difficult to float than gangue minerals. Therefore, reverse flotation is often used in the kaolin flotation purification process to achieve a better effect of removing impurities, such as reverse flotation carbon removal, desulfurization and iron removal. Kerosene is used as a collector, pine oil is used as a foaming agent, and water glass is used as an inhibitor. The flotation purification process is mostly used to treat kaolin raw ore with more impurities and lower whiteness, so as to realize the comprehensive utilization of low-grade kaolin resources.
4. Leaching
Leaching is a method of selectively dissolving and removing certain impurity components in kaolin through appropriate leaching agents, such as acid leaching and microbial leaching using hydrochloric acid or sulfuric acid. The leaching process is simple, energy-saving, can reduce production costs, and has good development potential. Using sulfuric acid with a concentration of 25% to acid-leach hard kaolin with high iron content for 5 hours, the iron removal rate can reach 37.67%. Because most of the iron in the raw ore exists in the form of pyrite, in order to achieve a better iron removal effect, oxidative acid leaching is carried out with H2O2 as the oxidizing agent. Coal series kaolin contains impurities such as pyrite, limonite and hematite. During the calcination process, pyrite will be oxidized into dark brown iron oxides, which will reduce the whiteness of kaolin. Thiobacillus ferrooxidans can decompose pyrite through catalytic oxidation, so it can be used to remove pyrite from kaolin.
5. Chemical bleaching
Ferric ions and their oxides are the main dyeing impurities that reduce the whiteness of kaolin. The method of removing these harmful impurities through chemical reagents is called chemical bleaching. The chemical bleaching method of kaolin is divided into oxidation method, reduction method and oxidation-reduction combined method.
The principle of the oxidation bleaching method is to oxidize the harmful coloring impurities in the reduced state into soluble substances, and then remove them. For example, oxidize pyrite into soluble ferrous sulfate, and then oxidize the organic matter and remove it by washing with water. Commonly used strong oxidants include sodium hypochlorite, potassium permanganate and hydrogen peroxide. The bleaching effect is affected by pH value, temperature, chemical dosage, pulp concentration and bleaching time.
The principle of the reduction bleaching method is to reduce the insoluble ferric oxide to soluble ferrous salt, so that the harmful element iron is converted into a soluble phase for dissolution, and then removed through the washing process. Commonly used reductive bleaching agents include sodium dithionite (Na2S2O4) and thiourea dioxide (HO2SC(NH)NH2).
6. Roasting
Roasting is also an important purification process to improve the whiteness of kaolin. Kaolin can remove carbon-containing impurities in it through roasting process, such as removing magnetic impurities through magnetization roasting and magnetic separation, and removing certain metal impurities through chlorination roasting.
Low-temperature roasting can remove surface and interlayer hydroxyl groups without destroying the kaolinite structure, and at the same time effectively decompose carbon-containing organic matter, so that the low-grade coal-measure kaolin can meet the requirements of glass fiber raw materials, and effectively realize the low-grade coal-measure kaolin resources. use.
Magnetization roasting converts iron-containing impurities in kaolin into strong magnetic or strong magnetic iron-containing minerals, and then removes impurities by magnetic separation. The purification effect of magnetization roasting on kaolin is better than that of traditional chemical bleaching methods.
Chlorination roasting is the addition of chlorinating agents during kaolin roasting to convert certain metal oxides and sulfide impurities into volatile chlorides to achieve the purpose of removing the metal elements.
7. Combined purification technology
It is difficult to obtain high-quality kaolin products by a single purification process, especially when dealing with low-grade coal-measure kaolin with large reserves in my country and kaolin with complex mineral composition. Different types of kaolin treatment processes are different, among which soft kaolin treatment process includes crushing, pulping, cyclone, selective flocculation, bleaching, centrifugation, peeling, magnetic separation; hard kaolin treatment process includes crushing, pulping, Cyclone, centrifuge, flaking, bleaching or crushing, roasting, pulping, cyclone, flaking, centrifuge; sandy kaolin treatment process includes pulping, spiral classifier, sedimentation, centrifuge, flaking, bleaching or raw ore , Pulping, Gravity Desanding, Blending, Flotation.
8. Stripping
Peeling is divided into mechanical peeling and chemical peeling, which is an important process of deep processing technology. It is necessary to peel kaolin into extremely thin sheets, and then go through magnetic separation to remove iron and bleach to meet the requirements of low wear and high whiteness. It is widely used in papermaking, Cosmetics, medicine, etc.
5 types of electronic communication function filling materials and market demand
Electronic communication functional filler is a kind of functional filler with excellent performance. It is filled in the packaging materials of electronic chips and electronic printed circuit boards. It can meet the signal transmission requirements of high frequency, high speed, low delay, low loss and high reliability. It is widely used In electronics, advanced communications (5G), storage computing, artificial intelligence, autonomous driving, satellite positioning, aerospace, high-speed railway and other fields.
1. Common filling materials for electronic communication functions
At present, the mature electronic communication functional filling materials on the market mainly include high-performance silica powder materials, spherical alumina materials and boehmite, high-performance silica powder materials include high-purity silica, crystalline silica , spherical silica and fused silica.
(1) High-purity silica
It is made of natural quartz sand through processes such as airflow crushing, surface coating, and impurity removal. It has the characteristics of high purity and concentrated particle size distribution, and can reduce the release of α particles from packaging materials, thereby reducing the occurrence of integrated circuits. The probability of soft errors is filled in epoxy molding compound as a functional filling material, and is widely used in chip packaging in the fields of electronic communication, storage computing, and artificial intelligence.
(2) Crystalline silica
Using natural quartz sand as raw material, it is processed through impurity removal, grading, airflow crushing and other processes. It has the characteristics of concentrated particle size distribution, precise control of large particles, and less magnetic foreign matter. It can improve the performance of downstream related products in terms of electrical properties and other aspects. Physical properties, silicone rubber products prepared from it as raw materials can be used as composite materials in electronic communications, aerospace, high-speed railways, LED lighting and other fields.
(3) Fused silica
It is made of crystalline silica as raw material through high-temperature melting, jet milling and other processes. It has the characteristics of low electrical conductivity, excellent insulation performance, and low magnetic foreign matter. At the same time, the dielectric constant, dielectric loss, and linear expansion coefficient are also high. Lower than crystalline silica, it is used as a functional filler in high-frequency and high-speed copper clad laminates in the fields of advanced communications (5G), autonomous driving, and artificial intelligence.
(4) Spherical silica
It is made of high-purity silica powder material through spheroidization treatment, jet milling and other processes. It has uniform particle size, high spheroidization rate, high fluidity, good insulation performance, low magnetic foreign matter, low dielectric A series of excellent characteristics such as electrical constant, low dielectric loss, and small linear expansion coefficient are mainly used as functional filling materials for high-frequency and high-speed copper clad laminates, as well as functional filling materials for epoxy molding compounds in chip packaging materials, etc., used in aerospace, high-speed High-frequency high-speed copper clad laminates and high-end chip materials for high-end railways.
(5) spherical alumina
Alumina is used as raw material, and it is prepared through airflow crushing, spherification, surface coating, impurity removal and other processes. It has easy dispersibility, controllable particle size and uniform particle size, high spheroidization rate, low content of magnetic foreign matter, It has the characteristics of good thermal conductivity and high volume filling rate. It is mainly used as a filling material in epoxy resin and silicone to produce thermal interface materials.
The Effect of Sugar Substances on the Crystallization of Nano-CaCO3
Nano-calcium carbonate is an important new nano-material, which is widely used in coatings, rubber, paper and other fields. The preparation of different types of nano-calcium carbonate particles has always been the focus of research.
At present, metal salts, organic acids, inorganic acids, polyvinyl alcohol, amino acids, and surfactants are often used as crystal form control agents for nano-calcium carbonate. By using different crystal form control agents, different sizes, shapes, and crystal forms can be obtained. Nano-calcium carbonate particles, and can change the agglomeration of nano-calcium carbonate particles, so as to realize the controllable synthesis of nano-calcium carbonate.
Nano-calcium carbonate was synthesized by carbonization method, and glucose, sucrose and soluble starch were used as crystal form control agents respectively. The influence of the addition of non-crystal form control agents and different sugar substances on the conductivity and pH changes during the reaction process was analyzed in detail. the result shows:
(1) By adding sucrose, glucose, and soluble starch with the same mass fraction to the reaction system, relatively regular cubic calcite-type nano-calcium carbonate crystals were obtained, which may be due to the existence of polar —OH groups in the sugar structure, Moreover, O in the molecule has a lone pair of electrons, which has high electronegativity, and can coordinate with Ca2+ through charge matching, which inhibits the growth of nano-calcium carbonate crystals.
(2) Adding sugar additives before the carbonization reaction can promote the nucleation reaction, reduce the surface energy of calcium carbonate crystal nuclei, enable smaller crystal nuclei to exist stably, inhibit the aggregation and growth of calcium carbonate crystal nuclei, and generate cubic nano calcium carbonate particles.
(3) The carbonization process is controlled by using sugar as a crystal form control agent, and the obtained product has relatively good dispersibility.
Material Application of Tourmaline Mineral
Tourmaline mineral material is a material with special functions that is processed and prepared from natural tourmaline mineral as the main raw material. Tourmaline mineral materials mainly include ultrafine tourmaline powder and modified ultrafine tourmaline powder, as well as tourmaline ceramics, tourmaline fibers, tourmaline coatings, and tourmaline composites prepared from ultrafine tourmaline powder or modified ultrafine tourmaline powder. materials etc.
Tourmaline gems are mainly dominated by attributes such as aesthetics, durability, rarity, and non-toxicity, while tourmaline mineral materials mainly emphasize their functional attributes, such as spontaneous polarization, pyroelectricity, infrared radiation, and adsorption properties. Tourmaline mineral material is a functional material obtained by reprocessing tourmaline mineral according to human will in order to realize some functional application properties of tourmaline.
1. Water treatment materials
The spontaneous polarization of tourmaline makes it have an electrostatic field around it, and has strong adsorption, which can effectively adsorb metal ions and acid radical ions in the solution, and crystallize from the surface of tourmaline, thereby purifying water. Therefore, tourmaline is a good environmental material for water pollution control, and as an excellent raw material for preparing adsorbents, it has a very good application prospect.
Because it is difficult for metal ions to enter the crystal structure of tourmaline, the adsorption of tourmaline to ions is mainly surface adsorption. There is an electrostatic field around tourmaline particles, and its surface adsorption is mainly complex adsorption and electrostatic adsorption, and can simultaneously adsorb anions and cations, and the adsorption amount is not limited by the ion exchange amount. In the solution, positive and negative ions are gathered at the two poles of the tourmaline crystal, and the ions are precipitated after reaching the saturated adsorption concentration.
2. Health care textiles
The number of negative oxygen ions in the air is one of the important criteria for evaluating air quality, because negative oxygen ions can reduce the content of dust and harmful gases in the air. Water in the air can be electrolyzed by tourmaline, thereby increasing the number of negative oxygen ions in the air. In addition, tourmaline can produce infrared radiation absorbed by the human body, produce thermal effects, increase the temperature of local tissues of the human body, expand blood vessels, accelerate blood flow, improve local blood circulation, and play a role in health care and physical therapy. Therefore, tourmaline can be used in textile manufacturing to make clothing and accessories with health care functions.
In the 1990s, Japan began to use tourmaline as the main raw material to produce negative ion textiles, and used post-finishing technology to carry out negative ion modification treatment on natural fibers (such as cotton and wool). The treatment solution containing ultra-fine tourmaline powder is fixed and attached to the surface of the fabric by padding and drying processes, so that the fabric has anion function. The felt is modified with negative ions by using the treatment solution prepared by 5-15 μm tourmaline powder, anionic dispersant, binder and water, and the treated felt has a good negative ion generating effect.
3. Coating additives
Tourmaline mineral materials can be used as additives in negative ion coatings. Coatings added with ultrafine tourmaline powder can meet the requirements of general coatings on color perception, texture and scrub resistance, and can also release a certain concentration of negative ions to achieve a certain sterilization effect. Some negative ion coatings produced in Japan and South Korea have been sold domestically, and their prices are much higher than ordinary coatings.
4. Photocatalytic materials
TiO2 is a highly active photocatalytic material with good thermal stability and strong photooxidation resistance. However, the recombination rate of photoelectrons and holes produced by TiO2 is high, and the photocatalytic efficiency is low, which affects the industrial application of TiO2. Tourmaline has the properties of spontaneous polarization and infrared radiation, and the composite material of tourmaline and TiO2 can not only improve the photocatalytic activity of TiO2, but also have the advantages of both materials.
5. Fuel activation
Tourmaline has a high infrared radiation emissivity in the 3-6.2μm band, which is conducive to the absorption of radiation by the human body and produces thermal effects, so tourmaline mineral materials have health care and physiotherapy functions. At the same time, the excellent infrared radiation performance of tourmaline mineral materials can also be used to improve fuel combustion efficiency.
Fuel oil is a liquid mixture composed of a series of alkanes, olefins, naphthenes, aromatic hydrocarbons, polycyclic aromatic hydrocarbons and additives. The study found that the C-C bond resonance in fuel oil can absorb radiation with a wavelength of 3.2-3.6 μm, and the C=C and C≡C bonds absorb radiation with a wavelength of 4.4-4.7 μm and 5.8-6.2 μm, respectively. When the fuel molecule is activated by the infrared radiation material, it absorbs the radiation released by the infrared radiation material and stores the energy inside the fuel molecule. When the fuel enters the combustion chamber, the stored energy will be released in the form of explosive kinetic energy, thereby increasing the internal energy of the fuel molecules, so only a small amount of heat energy can be provided during combustion to break the carbon-carbon covalent bonds in the fuel molecules, thereby improving combustion efficiency and improved power performance.
Tourmaline mineral materials have a high infrared radiation rate in the 3-6.2μm band, so using tourmaline mineral materials to activate fuel oil can improve the energy-saving and emission-reduction effects of fuel vehicles.