Today, speaking of 3D printing, we have already introduced many applications of 3D printing, such as printing houses, Bridges, and so on. Today, we will talk about a relevant material used in 3D printing -- metal powder.

Titanium alloy, aluminum alloy, stainless steel, can be used for 3D printing

Metal powder materials printing consumables widely used in 3D printing mainly include four types in the form: liquid photosensitive resin materials, thin materials, low melting point silk materials, and powder materials. In terms of composition, it almost covers all kinds of stuff in current production and life, including polymer materials such as plastic, resin, wax, metal and alloy materials, ceramic materials, and so on. Among them, cutting edge and the most potential is the metal powder 3 d printing, according to consultancy SmarTech predicts that by 2024 the world used in metal powder material made in increasing the size of the market will reach $11 billion.

Currently, 3d-printed metal powder materials include stainless steel, die steel, nickel alloy, titanium alloy, cobalt-chromium alloy, aluminum alloy and bronze alloy.

Iron base alloy is one of the most important. The dosage of the most significant engineering metal materials, for the formation of a more complex structure, such as 3 d printing stainless steel, compared with the traditional casting forging technology, it has high strength, excellent resistance to high temperature, wear resistance, corrosion resistance, and other physical, chemical and mechanical properties, and has high dimensional precision and material utilization. In the aerospace, automotive, shipbuilding, machinery manufacturing, and other industries are widely used.

Titanium alloys have excellent strength and toughness, combined with corrosion resistance, low specific gravity, and biocompatibility, making them ideal for many high-performance engineering applications in aerospace and automotive racing. They are also used in the production of biomedical implants with high strength, low modulus, and high fatigue resistance.

Cobalt-chromium alloys are commonly used in surgical implants such as alloying artificial joints, knees, and hips, as well as in engine components, wind turbines, and many other industrial components due to their high wear resistance, excellent biocompatibility and nickel-free (nickel content <0.1%).

Aluminum alloy is one of the most widely used nonferrous metal structural materials in the industry. The research shows that the aluminum alloy used in 3D printing can make the parts compact and small in structure, and its mechanical properties are comparable to or even better than casting parts. Its quality can be reduced by 22% compared with traditional process parts, but the cost can be reduced by 30%. 

Copper alloys have excellent thermal conductivity and electrical conductivity. Copper with excellent thermal conductivity in thermal management applications can combine design degrees of freedom to produce complex internal structures and flexible cooling channels.

How is the metal powder for 3D printing made?

The preparation methods of metal powder can be divided into a reduction method, electrolysis method, grinding method, atomization method, etc. At present, argon atomization and rotating plasma electrode are the two most advanced powder making processes in China.

1. Argon atomization

Argon atomization powder is a powder making method that the metal liquid is crushed into fine particles by the rapid flow of argon gas and then condensed into solid powder.

2. Plasma rotating electrode method

The fourth state plasma is known as the material and plasma rotating electrode atomization method (PREP) milling process can be described as follows: the metal or droplet atomized indoor inert gas (argon or helium) friction, further broken under the alloy consumable electrode, the power consumption of extreme in coaxial plasma arc heat source melt formed under the action of liquid membrane, liquid membrane under the effect of rotating centrifugal force formed by high-speed throw droplets, molten action of a shear stress, then drop under the effect of surface tension, fast cooling solidification into spherical powder.

The metal powder produced by the plasma rotating electrode method has the following advantages:

(1) High sphericity, smooth surface, good fluidity, steep loose packing density, so

(2) Powder size is small, particle size distribution is narrow, the oxygen content

is low, printing less/no spherification and agglomeration phenomenon, melting effect

is good, product surface finish is high, and the consistency and uniformity of printing can be fully guaranteed;

(3) There are no hollow powders and satellite powders, and there are no air gap, trainability, and exhalation porosity, cracks, and other defects caused by hollow spheres in the printing process.

What are the requirements of 3D printing on the properties of

metal powders?

We've just mentioned several metal powders that can be used in 3D printing, so what does a metal powder need to satisfy to meet the material requirements of 3D printing?

1. Purity

Ceramic inclusions will significantly reduce the performance of the final product, and these inclusions generally have a high melting point, it is difficult to sintering, so there must be no ceramic inclusions in the powder.

Besides, oxygen and nitrogen content also need to be strictly controlled.

Currently used in metal powder preparation technology of 3 d printing mainly atomization method, powder has a large specific surface area, natural oxidation, in particular applications, such as aerospace customer index requirements more stringent, such as oxygen levels in the high-temperature alloy powder is 0.006% - 0.018%, oxygen content of titanium alloy powder was 0.007% - 0.013%, stainless steel powder oxygen content of 0.010% to 0.025%.

2. Distribution of powder size

Different 3D printing equipment and forming process have different requirements on powder size distribution. At present, the commonly used powder size range of metal 3D printing is 15-53 cm (fine powder) and 53-105 cm (coarse powder), which can be extended to 105-150 cm (coarse powder) in some cases.

The selection of metal powder particle size for 3D printing is mainly divided according to the metal printers with different energy sources. The printer with laser as the energy source is suitable for using 15-53 m powder as the consumable material because of its beautiful focusing spot and easy melting of fine powder. With electron beam as the energy source, the duster printer has a slightly thick focusing place,which is more suitable for melting duster and is mainly suitable for using duster of 53-105 m. For coaxial powder feeder printers, powder with a particle size of 105-150 m can be used as consumables.

3. Morphology of powder

The morphology of the powder is closely related to the preparation method of the dust. Generally, when the metal gas or molten liquid is transformed into the earth, the shape of powder particles tends to be spherical. When the solid is converted into the soil, the powder particles are mostly of irregular shape, while the powder prepared by aqueous solution electrolysis is mostly dendritic.

In general, the higher the sphericity, the better the fluidity of the powder particles. The sphericity of 3D printed metal powder is required to be more than 98%, which makes it easier to lay and send powder for printing.

The table above shows the morphology of metal powders corresponding to different powder preparation methods. It can be seen that, except for aerosol and rotating electrode methods, the morphology of powders prepared by other means is non-spherical. Therefore, aerosol and rotating electrode methods are the primary preparation methods of high-quality 3D printing metal powders.

4. Powder fluidity and loose packing density

The powder fluidity directly affects the uniformity of powder spreading and the stability of powder feeding in the printing process.

The fluidity is related to the powder morphology, particle size distribution, and loose packing density. The larger the powder particle is, the more regular the particle shape is, and the smaller the proportion of fine powder in the particle size composition is, the better the fluidity is. The particle density remained unchanged, the relative density increased, and the powder fluidity increased. Besides, the adsorption of water and gas on the surface of particles will reduce the fluidity of the powder.

Apparent density powder sample is naturally full of container, unit volume of powder quality, in general, the more coarse powder particle size, the larger the apparent density, thickness of collocation powder can obtain higher apparent density, visible density effects on metal printing density of the final product is uncertain, but apparent density increased, can improve the liquidity of powder.

For the past few years, China has actively explored 3 d printing metal powder preparation technology and has many advanced milling equipment applications. But, in general, there is still a gap between pulverizing technology at home and abroad. The current high-end alloy powder and the manufacturing equipment is still mainly relied on imports, in promoting the local 3 d printing with metal powder preparation technology on the development of China is still a long way to go.

What is the hardest substance worldwide? Every person thinks typically about rubies. But you never believe that porcelains might likewise be the hardest compound in the world. Here we present to you silicon nitride ceramics (Si3N4 ceramics), which have high toughness, specifically hot-pressed silicon nitride porcelains, which is among the hardest materials in the world. It has high strength, low thickness, and also high-temperature resistance.

Silicon nitride ceramics is an inorganic material that does not shrink during sintering. Silicon nitride has high strength, especially hot-pressed silicon nitride, which is one of the hardest substances in the world. It has high strength, low density, and high-temperature resistance.

Silicon nitride ceramic is a kind of covalent bond compound, the basic structural unit for [SiN4] tetrahedron, silicon atom is located in the center of the tetrahedron, there are four nitrogen atoms around it, which located in tetrahedral four vertices, then to every three tetrahedra Shared in the form of an atom, the three-dimensional space form a continuous and strong network structure.

Numerous residential or commercial properties of silicon nitride result from this structure. Pure Si3N4 is 3119 and also has two crystal structures, α, and β, both of which are hexagonal crystals. The decomposition temperature is 1800 ° C in air and 1850 ° C in 110MPa nitrogen. Si3N4 has a low thermal expansion coefficient and high thermal conductivity, so its thermal shock resistance is excellent. The hot-pressed sintered silicon nitride will not crack even after being heated to 1000 ° C. At a not too high temperature, Si3N4 has higher strength and impact resistance. Still, it will break with the increase of the service time above 1200 ℃, which will reduce its power. It will be more prone to fatigue damage above 1450 ℃, so Si3N4 The operating temperature generally does not exceed 1300 ° C. Because the theoretical density of Si3N4 ceramics is low, it is much lighter than steel and engineering super heat-resistant alloy steels. Therefore, it is appropriate to replace Si3N4 ceramics with alloy steels in those places that require materials with high strength, low density, and high-temperature resistance. But that's it.

As an excellent high-temperature engineering material, Si3N4 ceramic material has the most advantages in its application in high-temperature fields. It is incredibly resistant to high temperatures, and its strength can be maintained up to 1200 ° C without decreasing. It will not melt into melt after being heated. It will not decompose until 1900 ° C. It has extreme chemical resistance and can withstand almost all Inorganic acid and caustic soda solution below 30% can also resist the corrosion of many organic acids; it is also a high-performance electrical insulation material.

The future development direction of Si3N4 ceramics is:

1. Make full use of the excellent characteristics of Si3N4 itself;

2. Research and control the best composition of existing flux when Si3N4 powder is sintered;

3. Improve the milling, forming and sintering processes;

4. Develop composites of materials such as Si3N4 and SiC to make more high-performance composite materials.

Silicon nitride ceramics uses silicon powder as a raw material. It is first formed into the desired shape by ordinary molding methods. Initial nitriding is performed in nitrogen at a high temperature of 1200 ° C, and a part of the silicon powder reacts with nitrogen to form silicon nitride. At this time, the entire body has a particular strength. Then a second nitriding is performed in a high-temperature furnace at 1350 ° C to 1450 ° C to react to form silicon nitride. Hot-pressing sintering can be used to produce silicon nitride with a theoretical density of 99%.

Si3N4 ceramic has the characteristics of lightweight and robust hardness, which can be used to make ball bearings. It has higher accuracy than metal bearings, generates less heat, and can operate in higher temperatures and corrosive media. It has higher efficiency than metal bearings, generates less heat, and can work in higher temperatures and corrosive media. The steam nozzle made of Si3N4 ceramic has the characteristics of wear resistance and heat resistance, and it has no visible damage after being used in a 650 ℃ boiler for several months, while other heat-resistant and corrosion-resistant alloy steel nozzles can only be used for 1-2 months under the same conditions. The Si3N4 ceramic glow plug developed by Chinese scientists solves the problem of cold starting of diesel engines and is suitable for direct injection or non-direct injection diesel engines. This glow plug is the most advanced and ideal ignition device for diesel engines today. Japanese researchers have successfully developed a new rough pump with a rotor in the pump casing consisting of 11 Si3N4 ceramic rotors. Because the shoe uses a Si3N4 ceramic rotor with a small thermal expansion coefficient and precision air bearings, it can operate normally without lubrication and cooling media. If this pump is combined with an ultra-vacuum pump such as a turbo molecular pump, a vacuum system suitable for use in a nuclear fusion reactor or semiconductor processing equipment can be formed.

The above are just a few application examples of Si3N4 ceramics as structural materials. It is believed that with the improvement of Si3N4 powder production, molding, sintering, and processing technology, its performance and reliability will continue to improve, and silicon nitride ceramics will be more widely used. Due to the improvement of the purity of Si3N4 ceramic raw materials, the rapid development of molding technology and the sintering technology of Si3N4 ceramic powder, and the continuous expansion of the application field, Si3N4 is taking an increasingly important position in the industry as a structural engineering ceramic. Si3N4 ceramic has excellent comprehensive properties and abundant resources, is an ideal high-temperature structural material, has a wide application field and market, and countries around the world are racing to research and development. Ceramic materials have the characteristics of wear resistance, corrosion resistance, high-temperature resistance, oxidation resistance, thermal shock resistance, and low specific gravity, which are incomparable for general metal materials. It can withstand the harsh working environment where metal or polymer materials are incapable and have a wide range of application prospects. It has become the critical primary material to support the pillar industry of the 21st century after metal materials and polymer materials. It has become one of the most active research fields. Today, countries around the world attach great importance to their research and development. As an essential member of the high-temperature structural ceramic family, Si3N4 ceramics have better mechanical properties, thermal properties, and chemical stability than other high-temperature structural ceramics such as oxide ceramics and carbide ceramics. Therefore, it is considered to be the most promising material in high-temperature structural ceramics.

It can be predicted that with the continuous progress of basic research and new technology development of ceramics, especially the increasingly sophisticated technology for the preparation of complicated and broad parts, Si3N4 ceramic materials will be more widely used as engineering materials with excellent performance.

Ceramic materials have been applied to various aspects of our lives. Ceramic materials are a class of inorganic non-metal materials made of natural or synthetic compounds after being shaped and sintered at high temperatures. It has the advantages of high melting point, high hardness, high abrasion resistance, oxidation resistance, etc.. It can be used as structural materials, tool materials, etc. Since ceramic also has some unique properties, it can also be used as a functional material. With the progress of society, people have higher and higher requirements for materials, and this performance is not only reflected in the field of science but also the area of people's lives. The progress of materials has mostly promoted the development of society, which in turn has helped the growth of materials science. In the case of ceramic materials, ceramic materials have penetrated the history of human development. They have continued to develop with the progress of history, temporarily emerging in the field of materials science.

Ceramic materials can be divided into ordinary ceramic materials and unique ceramic materials. Everyday ceramic materials are sintered from natural materials such as feldspar, clay, and quartz, and are conventional silicate materials. Ordinary ceramics have rich sources, low cost, and mature technology. This ceramic material can be divided into daily-use ceramics, building ceramics, electrical insulation ceramics, and chemical ceramics according to their performance characteristics and uses. Unique ceramic materials are made of high-purity synthetic raw materials, formed by precise control technology and sintered, and generally, have specific unique properties to meet various needs. According to their raw material components, they can be divided into carbide ceramics, oxide ceramics, nitride ceramics, and cermets. Unique ceramics have select mechanical, acoustic, optical, electrical, magnetic, thermal, and other properties, and they are also widely used.

Let us focus on the carbide ceramic materials. Carbide ceramics are ceramics containing carbon, poorly soluble compounds as the main component. One is a metal-like carbide such as titanium carbide, zirconium carbide, tungsten carbide, etc .; one is a non-metal carbide, such as carbon tetraboride, silicon carbide, and the like. Carbide is a high-temperature resistant material. Many of these carbides have melting points above 3000 ° C. Most carbides are more resistant to oxidation than carbon and graphite. Many carbides have high hardness and excellent chemical stability. Carbide ceramics also have unique properties such as high heat resistance and high hardness. Carbide ceramics are widely used as heat-resistant materials and super hard tools.

Among the high-temperature carbide structure, ceramic materials, silicon carbide ceramics, boron carbide ceramics, and titanium carbide ceramics are the three most important materials and are used most widely.

1. Silicon carbide has a diamond crystal structure and has strong covalent bonds. Silicon carbide ceramic has high hardness, good strength, high thermal conductivity, and excellent oxidation resistance. It can be used in high temperature, high pressure, strong acid, strong alkali, and high-temperature oxidation environments. It is widely used in the petroleum industry, chemical industry, and energy industry. It is also used in the fields of machinery, mining, papermaking, steelmaking, nuclear sector, microelectronics industry, and lasers.

2. The hardness of boron carbide is second only to diamond and cubic boron carbide in nature. In particular, the nearly constant high-temperature hardness is unmatched by other materials, so it has become an essential member of the superhard material family. Boron carbide has a high melting point, high hardness, high modulus, small capacity, abrasion resistance, acid, and alkali corrosion resistance, etc., and has good neutron and oxygen absorption capabilities, has a lower coefficient of expansion, excellent thermoelectric properties, is A relevant structural ceramic material. Boron carbide ceramic is an advanced excellent grinding material, which can be used for grinding, grinding, drilling, and polishing of hard materials such as gems, ceramics, tools, bearings, hard alloys, etc. Boron carbide ceramics are the first choice for industrial ceramic materials, Widely used in sandblasting machinery, electronics, information, aerospace, automotive and other industries; boron carbide ceramics have large thermal neutron capture cross-sections, have excellent neutron absorption and radiation resistance, and can be used as shielding and control materials Is the safety guarantee of the nuclear industry; boron carbide ceramics have high strength and small specific gravity, and are particularly suitable for use in bullet-proof armor, such as the protection of aircraft, vehicles, ships, and human bodies; boron carbide ceramics have the characteristics of anti-oxidation and high-temperature resistance. As advanced shaped and amorphous refractories are widely used in metallurgical fields; boron carbide ceramics have stable chemical properties, do not react with acids and alkalis, and have high synthetic positions, so they are widely used in the production of other boron-containing materials, such as bosonization Titanium, zirconium boride, etc .;

3. Titanium carbide ceramic has high strength, good thermal conductivity, high hardness, excellent chemical stability, no hydrolysis, good high-temperature oxidation resistance, and does not react with acids at room temperature. Titanium carbide ceramics are essential raw materials for hard alloys; transparent titanium carbide ceramics are right optical materials; porous titanium carbide ceramics can be used as high-temperature-resistant materials and used to make filters and photocatalytic materials when the porosity of titanium carbide ceramics is 50%, Great for artificial bones.

In most countries in the north, the rainy and snowy weather in winter is likely to cause snow in the road area to be frozen, so that the adhesion of the vehicle tires to the ground is reduced, the danger of driving is also increased, and the smooth traffic is also severely affected. According to statistics, 15%~30% of winter traffic accidents are related to road area snow icing. In order to solve the severe traffic safety problems caused by snowy roads, people actively explored and tried many methods.

With the development of science and technology and the continuous discovery of new materials, some scientists have boldly imagined that if the road is paved with conductive concrete, when the ice and snow pile up, as long as the road is energized and heated, it can quickly melt the ice and snow and solve the problem of road slippery. Keep traffic safe and smooth.

In 1980, some developed countries began to explore the feasibility of conductive concrete and studied its preparation technology. In the 1970s, the United States and the Nordic countries introduced the research and application of conductive concrete in order to solve the problem of road and bridge concrete corrosion caused by deicing salt. In the late 1990s, the study of conductive concrete began to be gradually applied in practice. In 1998, China tried to incorporate graphite into cement paste to make indoor heating floors, which was very satisfactory. In 2003, the United States applied conductive concrete to the deck of the Roca Spur Bridge, using its thermoelectric effect to deicing snow. These research results show that conductive concrete has solid prospects, and it is extremely feasible to apply to melt ice and snow.

Graphite is a relatively easy-to-obtain inorganic material that has not only good electrical and thermal conductivity but also has excellent chemical inertness. Studies have shown that the electrical resistivity of conductive commercial concrete can vary from 10-1 to 106 Ω·cm with the change of graphite content. However, it is necessary to make the commercial concrete have good conductivity when the content is high, and the graphite powder The water demand is significant, and it is necessary to increase significantly the water consumption of the commercial concrete mixture, which will cause the strength of the commercial concrete to decrease as the amount of graphite powder increases rapidly. When the content of graphite exceeds 12%, the increase of electrical conductivity is not apparent, while the compressive strength decreases sharply with the increase of graphite content. When the amount of graphite is more than 20%, the compressive strength is less than 10MPa, and the resistivity is less than 10MPa. Less than 50 Ω·cm.

The incorporation of graphite powder makes the workability of the concrete mixture worse, but it can meet the requirements of engineering construction. As the amount of graphite powder is increased, the strength of conductive concrete decreases; the fineness of graphite powder has little effect on the strength of conductive concrete. The electrical resistivity of the conductive concrete decreases with the increase of the fineness and the amount of the graphite powder. After continuous energization, it has an excellent electrothermal effect and a power generation effect. Conductive concrete with excellent workability, strength, and electrical conductivity can be prepared by using graphite powder. The conductive concrete is mixed into ordinary concrete, and the concrete is transformed into a new composite material with specific conductivity. After the power is turned on, the concrete is energized and heated. As the temperature of the road surface rises, the snow and ice are melted by heat. Conductive concrete can melt snow in a timely and efficient manner, ensure smooth traffic and safety, reduce national economic losses caused by ice and snow disasters, be green, and meet the requirements of sustainable development. As a new type of composite functional concrete, it not only has the superior mechanical ability of ordinary concrete, but also has good electrical conductivity and thermal conductivity; it can effectively avoid the traffic accident risk caused by snow and ice in winter road area and can solve the deicing salt. The economic and environmental problems brought about have good application prospects.

Black graphite can be transformed into expensive ornate diamonds. Is this transformation a physical or chemical change? We can answer this question from the analysis of the following aspects.

1. Analysis from the characteristics of chemical changes

We know that chemical changes are often called chemical reactions. Chemical shifts are the formation of other substances when they change. Materials are transformed into new elements of entirely different nature through chemical reactions, which are characteristic of chemical changes. When graphite, a pure substance composed of carbon, becomes diamond under certain conditions, although diamond is also a pure substance composed of carbon, the properties of diamond are quite different from those of graphite (the chemical properties of graphite are more active than diamond); Another element of carbon. This shows that the diamond is a new substance that turns from graphite during the change. Changes in the formation of new materials are not physical changes.

2. From the perspective of crystal structure

When graphite is converted into diamond, the graphite crystal structure is destroyed, the weak bonding force between the graphite layer and the layer is broken or changed, or the chemical bond and bonding mode between the carbon atoms in the hexagonal plane is also significantly improved. The combination between them is regularly combined into a vertical structure according to the form and requirements of the diamond. That is, the layered structure of graphite is transformed into a regular tetrahedral structure of diamond. According to the fact that the same substance has only one structure, graphite and diamond are two materials with different crystal structures. Since the process of change changes from one element to another, it is not a physical change. It can be seen that the transformation of matter from one structure to another is a chemical change process.

3. Analysis from the perspective of thermal effects

This transition is an exothermic reaction. The form in which energy is converted into heat during a chemical reaction during this transition is illustrated. When graphite turns into a diamond, it is a chemical reaction that absorbs heat. Therefore, the conversion of graphite to diamond under certain conditions is not a physical change.

4. From the perspective of catalyst

The transformation of graphite into diamond must be carried out under high temperature and high pressure. Even at a temperature of 2000 ° C to 4000 ° C and a weight of 60,000 to 120,000 atmospheres, the transformation rate is still low, and chromium, iron, and platinum are required as catalysts. Depending on the principle that the enzyme can only change the price of the chemical reaction, the catalyst cannot change the rate of physical change. When graphite is converted to diamond, the catalyst is used to accelerate the reaction rate. If this shift is a material change, does it make sense to use the catalyst? It can be seen that this change is not physical.

In summary, the mutual transformation of diamond and graphite under certain conditions is a chemical change. The mutual transformation of allomorphs under certain conditions is a chemical change. Some people say that the mutual transformation of diamond and graphite under certain conditions is a physical change process. This is not true. A shift in energy often accompanies a chemical reaction. This energy change can be expressed in the form of light energy, electrical energy, mechanical energy, or thermal energy. It is often shown in the form of heat, sometimes releasing heat and sometimes absorbing heat.

Similar to lead-based and nickel-based batteries, lithium ions use a positive electrode (cathode), a negative electrode (anode), and an electrolyte as a conductor. The positive wire is a metal oxide, and the negative electrode is composed of porous graphite. During discharge, lithium ions move from the negative electrode to the positive electrode through the electrolyte and the separator; during charging, lithium ions flow from the positive electrode to the negative electrode in opposite directions.

When the battery is charged and discharged, Li+ shuttles between the positive and negative electrodes, during discharge, the anode oxidizes, loses electrons, and the cathode is reduced to obtain particles; when charging, the charge moves in the opposite direction.

There are many types of lithium-ion batteries, depending on the electrode material. But when you choose different materials, the battery performance will vary greatly.

The positive electrode materials all contain Li+. Common lithium cobalt oxide (lithium cobalt oxide), lithium manganese oxide (also known as spinel or lithium manganate), lithium iron phosphate, nickel cobalt manganese ternary material (NMC) [3] and lithium nickel cobalt Aluminum oxide (NCA). All of these materials have a theoretical upper energy limit (lithium-ion has a theoretical capacity of about 2000 kWh, which is more than ten times the specific energy of a commercial lithium-ion battery).

Sony's original lithium-ion battery uses coke (a coal product) as a harmful electrode material. Since 1997, most lithium-ion battery manufacturers, including Sony, have converted anode materials to graphite, resulting in a flat discharge curve. Graphite is a form of carbon that is used in pencils. It can store lithium ions well during charging and has a long cycle and excellent stability. Of the carbon materials, graphite is the most common, followed by hard carbon and soft carbon. Other carbons, such as carbon nanotubes, have not yet found their commercial use. The figure below compares the voltage discharge curves of a modern lithium-ion battery with graphite as the negative electrode and a lithium-ion battery with an old coke negative electrode.

In the normal operating discharge range, the battery should have a flat voltage curve, which is better than the former coke.

Anode materials are also evolving, and researchers are continually experimenting with new materials, including silicon-based alloys. In this alloy, six carbon atoms are bonded to one lithium-ion, and one silicon atom can bond four lithium ions. This means that the negative silicon electrode can theoretically store ten times the energy of the graphite material. At present, silicon materials have increased by 20%-30% in specific capacity at the cost of reducing load potential and cycle life. However, the problem is that during the charging process, lithium ions are easily expanded in volume after being embedded in the silicon-based material (growing to more than four times the initial size).

The nanostructured lithium titanate salt has good cycle life and load capacity, excellent low-temperature performance, and functional safety performance as a harmful electrode material. Still, its specific function is low, and the cost is high.

P-test-butyl benzoic acid (PTBBA) is a colorless needle crystal or crystalline powder. It is an important organic synthesis intermediate widely used in chemical synthesis, cosmetics, flavors, and fragrances, etc., such as alkyd resin. Improvers, cutting oils, lubricant additives, food preservatives, stabilizers for polyethylene.

The synthesis method of p-test-butyl benzoic acid, at present, the existing synthesis method is oxidative synthesis, mainly including solventless oxidation method, nitric acid oxidation method, liquid-phase catalytic oxidation method, potassium permanganate oxidation method, microwave synthesis method High-temperature gas phase oxidation method. These methods are all based on p-test-but toluene.

Use of p-test-butyl benzoic acid:

P-test-butyl benzoic acid is an important organic synthesis intermediate. Its main applications are:

1. Used as a modifier for the production of alkyd resins;

2. Used as cutting oil and lubricating oil additive; used as polypropylene nucleating agent;

3. Used as a food preservative;

4, p-tert-butyl benzoic acid can be used as a regulator of polyester polymerization;

5. The phosphonium salt, sodium salt, zinc salt and the like of p-test-butyl benzoic acid can be used as a stabilizer for polyethylene;

6, p-tert-butyl benzoic acid can also be used as an additive for automotive deodorants, an outer film of oral drugs, alloy preservatives, lubricating additives, polypropylene nucleating agents, polyvinyl chloride heat stabilizers, metalworking cutting fluids, anti- Oxygen agents, alkyd resin improvers, fluxes, dyes, and new sunscreens;

7. P-test-butyl benzoic acid is also used in the production of methyl p-test-butyl benzoate, which is widely used in chemical synthesis, cosmetics, flavors, and fragrances.

Storage of p-test-butyl benzoic acid:

Storehouses storing p-test-butyl benzoic acid should be kept ventilated and dried at low temperatures; they must be stored separately from strong oxidants and strong bases.

First-aid measures using p-test-butyl benzoic acid:

1. This product is moderately toxic. The oral LD50 of rats is 568 mg/kg.

2. If inhaled, move the patient to fresh air. If breathing stops, perform artificial respiration. Seek medical attention promptly.

3. In case of skin contact, rinse with soap and plenty of water. Immediately take the patient to the hospital. Seek medical attention quickly.

4. In case of eye contact, rinse thoroughly with plenty of water for at least 15 minutes and seek medical advice immediately.

5. If you misuse it, don't give anything to the unconscious person through the mouth. Rinse with water. Seek medical attention immediately.

Potential health effects of p-test-butyl benzoic acid:

1. Inhalation of p-test-butyl benzoic acid is harmful to health and may cause respiratory irritation.

2, swallowing and swallowing p-tert-butyl benzoic acid is detrimental to the human body.

3, p-tert-butyl benzoic acid contact with the skin if absorbed by the skin will be toxic, may cause skin irritation.

4. P-test-butyl benzoic acid causes eye irritation.