The beauty of metal powder

May 30, 2021

Hello everyone! I am aluminum powder. "Silver gray metal, light weight, highly flammable, and excellent thermal conductivity" are all my attribute labels. I am a very popular material variety on the earth. I can be seen in many places, do you think Know me, don't worry, please listen to me slowly.
1、Metal aluminum pigment "silver powder, silver powder"
Metal aluminum pigments can be used in solvent-based coatings, powder coatings, plastics, printing, inks and other fields, and are important members of the metal pigment family. The aluminum powder particles used for pigments are usually scaly, and the ratio of the flake diameter to the thickness is about (40:1)-(100:1). It is precisely because of this scaly particle state that aluminum pigments have Dazzling silver metallic luster and physical shielding function. In addition to the beautiful decorative properties, one of the most important characteristics of aluminum pigments is its high reflectivity. In addition to visible light, aluminum pigments can also reflect infrared and ultraviolet light waves.
There are currently two main preparation methods for these scaly aluminum powder particles: dry production and wet production. Dry production is to use atomized aluminum powder and surface treatment agent to directly grind aluminum powder in an inert gas. In wet production, kerosene or solvent gasoline is used as a protective agent to add a coating agent, dispersant, brightener, anti-settling agent and other additives to ball mill the atomized aluminum powder into a specific scaly particle structure. The wet method is mostly used in the industry. The production of silver cars relies heavily on these scaly aluminum powder particles.
2、Firework luminous agent

Aluminum powder is highly flammable and emits dazzling white light and super heat. Using this feature, aluminum powder can be used as a luminous agent for fireworks, emitting a nearly white flashing effect in the dark sky, and the heat released can make other chromogen ions in the fireworks emit colored light (this principle is derived from metal Flame reaction of ions). The use of aluminum powder can emit dazzling white light characteristics. When technology is not so advanced, aluminum powder can also act as a flashlight.
3、Rockets and missile fuel

Metal combustion agents are one of the important components of modern solid propellants. Metal combustion agents can increase the explosive heat and density of the propellants. At the same time, the solid metal oxide particles generated by combustion play a role in suppressing oscillating combustion. The available metal combustion agents are: Lithium, beryllium, boron, magnesium, aluminum, etc. The easy availability of aluminum powder and its high reactivity and flammability mean that when used as a solid fuel, it can provide a large amount of thrust at a relatively low cost, so there is no doubt that aluminum powder can be used as an additive for energy materials. Missile and rocket fuel are reused.
The ignition delay and slow combustion kinetics of ordinary aluminum powder and micron aluminum powder limit its use in rocket propellants. The aluminum powder of the above size condenses into large "agglomerates" on the combustion surface of the propellant, prolonging the burning time. The typical large droplet size is 20-50μm, and it takes 10-100ms to burn completely. The use of nanometer aluminum powder can increase the energy released per unit volume of the propellant, increase the specific impulse, increase the burning rate and stabilize the dye. Therefore, when used as a propellant, people attach great importance to the size of aluminum powder. At the same time, because the propellant cannot be prepared and used immediately, and the aluminum powder is extremely sensitive to the environment, in addition to studying how to prepare small particles of nano aluminum powder, its activity control and stability research work is also extremely important.
4、Used for directional blasting

Utilizing the strong reducibility of aluminum powder and the ability to release a lot of heat when aluminum is converted into aluminum oxide, aluminum powder is commonly used in industry to reduce some oxides. This type of reaction is called thermite reaction (aluminum and some metal oxides reaction). In reality, this reaction is often used to weld metals, such as rail connections, and can be used to connect ceramics and metals.
Reaction formula: 2Al+Fe2O3→2Fe+Al2O3
Due to the large amount of heat released by the reaction, the replaced iron flows out in a molten form, allowing the molten iron to flow into the cracks in the rails, and after cooling, the rails are firmly bonded together.
Since it can be welded, it can of course be blown. The modern directional blasting technology used to remove old buildings is the fusing technique using thermite reaction. The high-temperature fusing steel bars produced by the aluminothermic reaction are the directional collapse of old buildings or illegal buildings.
Approximate operation steps: Calculate the thickness of the channel steel, estimate the amount of thermite, dig a groove in the reinforced concrete, protect the surrounding with fine sand, place the thermite, the temperature generated by ignition is as high as 2500-3500 ℃, which is enough to make the channel steel Fuse.
5、Used for fingerprint display

There is always only one truth, and fingerprints at the crime scene often become the key to solving crimes. However, many fingerprints are not directly visible to the naked eye. Detectives use various physical or chemical techniques to bring the truth to the surface. Whether it is Sherlock Holmes, Detective Conan or Li Changyu, they are definitely good at physics or chemistry. Dust developing method is a common method. Its operation method is to sprinkle a layer of very fine powder on the fingerprint area first, and then carefully remove the surface powder, the fingerprint can be revealed. Aluminum powder is a very effective fingerprint powder. It can be used on glass. It can provide good contrast on the surface of most colors except silver. In theory, the smaller the particle size, the better.
6、Solar cells

Aluminum powder is also used to make a thick paste, which is applied to the back of photovoltaic solar cells. Aluminum paste is a conductive electronic paste that acts as a back field and electrode on the solar cell.
The fine particles of aluminum powder are more active than the surface and the aluminum powder itself is active. It is a flammable and explosive hazardous chemical. A little carelessness or mismanagement will easily cause accidents such as combustion and explosion. Therefore, in the process of its production, use, storage, transportation, equipment maintenance, etc., it is necessary to "knowledge" the properties of aluminum powder and take precautions to control it.