Alumina Density and Properties

Alumina (Al2O3) is an advanced ceramic material with numerous useful properties. It’s hard and wear-resistant, capable of withstanding extreme temperatures, an electrical insulator, and completely chemically inert.

Alumina can be found in many forms, from powder to pellets and pieces for sputtering targets, and fabrication processes include uniaxial and isostatic pressing, injection molding, slip casting and green and biscuit machining techniques.

Hardness

Hardness is an integral characteristic of alumina ceramic that makes it suitable for many diverse applications. Alumina ceramic has a Mohs hardness rating of 9, making it much harder than stainless steel or diamond, providing exceptional resistance against abrasion – used widely in textile guides, pump plungers, chute linings, discharge orifices, etc.

Alumina stands up well against abrasion due to its hardness, and can withstand high-temperature environments without losing strength or structural integrity. Furthermore, it features a low coefficient of friction which limits wear from other surfaces; making alumina an ideal material in environments where abrasion is an ongoing concern.

Alumina’s hardness helps it resist chemical attacks from acids and alkalis, making it an excellent choice for applications requiring high temperature refractories such as electrical and voltage insulators, metallurgical laboratory equipment, seal rings for gas laser tubes, laboratory instrumentation.

Alumina not only boasts excellent refractory properties, but it is also highly mechanical. Alumina offers exceptional strength, stiffness, and toughness with high tensile strength and impact resistance making it useful in applications such as industrial machinery components, refractory lined vessels, ballistic body armour as well as ballistic body armour. Furthermore, its exceptional abrasion and corrosion resistance makes it the ideal material to use for demanding processing applications.

Due to its hardness, alumina can be difficult to machine, but standard tools made of carbide or titanium can easily cut it and polish it for finishing purposes. Because alumina is chemically inert and does not react with most chemicals used in manufacturing applications – dental crowns, surgical implants and stents made from this material will not contaminate patients while it also works well for telecom components automotive components and process equipment components.

Density

Alumina is a relatively soft material which allows it to be bent into various forms, making it suitable for manufacturing many different products and structures, including aircraft parts. Due to this flexibility, Alumina can be easily formed into various products and structures such as aircraft parts. Alumina’s strength and toughness also makes it suitable as industrial abrasives, insulators and refractory materials; in addition it has great electrical and thermal conductivity as well as excellent chemical resistance properties which makes it suitable as electrical conductors and thermal conductive elements making Alumina highly versatile as a good conductor as an electrical conductor while giving electrical and thermal conductor with good chemical resistance qualities; additionally its thin aluminium oxide coating protects it from corrosion making it impervious against air and water surfaces alike.

Alumina can be produced from various raw materials, but the most popular source is bauxite. Bauxite is an ore rich in aluminium that is mined and processed using caustic soda to form an aqueous solution called “bauxite alumina”, then pumped into precipitator tanks where solid aluminium hydroxide crystals form that are then collected and filtered off, ready for further use as alumina.

Density variations for alumina vary greatly depending on its production method, with lower-void ceramics having greater densities that ultimately determine suitability for particular applications.

Note that many of alumina’s outstanding properties can be enhanced through variations in manufacturing and additives. At FEECO Innovation Center, our team has experience working with an array of alumina formulations and can develop and test these products on a batch scale to determine whether they will suit an application.

High purity alumina ceramics, which can be tailored to specific particle size and distribution specifications, make an excellent material choice for industrial applications that demand uncompromised materials. Resistant to corrosion from various chemicals including hydrofluoric acid and molten alkalis as well as their vapors, they remain hard and stiff even under radiation and elevated temperature exposure – perfect for ceramic-to-metal feedthroughs, X-ray component feedthroughs and high voltage bushings as well as special refractory products like stress relief beads and sputtering targets.

Thermal Conductivity

Alumina is an extremely hard, dense material with excellent wear- and corrosion-resistance, boasting high thermal conductivity (about 30 to 35 W/mK) for an oxide ceramic material.

These properties make alumina an invaluable material in industrial settings, such as aluminum metal production and as refractories. Alumina can also be combined with other elements to impart different properties – for instance reducing its reactivity or increasing its strength – or used as the foundation for other advanced ceramics such as boron nitride and zirconia production.

Produced from bauxite ore using the Bayer process, in which caustic soda combined with heat and pressure is combined with caustic soda to dissolve aluminum-bearing minerals. After crystallization in a rotary kiln to remove bound water and sodium aluminate crystals, creating pure alumina which can then be calcined to transform it into its alpha phase, preferred form for various applications.

Alpha alumina’s strong ionic and covalent bonds contribute to its outstanding physical and chemical properties, giving this high-performance ceramic excellent physical and chemical characteristics. This material can even withstand attacks from powerful inorganic acids like orthophosphoric and hydrofluoric acids! Alpha alumina structure boasts high strength, hardness and refractoriness with excellent electrical insulation properties as well as dielectric characteristics; furthermore it is highly resistant to corrosion and abrasion resistance.

Alumina is non-toxic and less toxic than other industrial materials. Studies conducted on laboratory animals and humans have confirmed this fact and revealed no ill effects from inhaling high concentrations of alumina dust; studies on humans do not appear to cause lung fibrosis or worsen existing silicosis symptoms either.

Alumina can be easily machined in its green and biscuit states, and can be sinter-formed into tight tolerance parts with little difficulty. Production of fully densified components requires special tools in order to account for shrinkage during sintering; for the best results the best quality diamond tools should be used during this process in order to avoid damaging material and achieve desired geometry.

Electrical Conductivity

Alumina stands out among oxide-based engineering ceramics with its relatively high electrical conductivity, making it a useful insulator in high voltage electric power transmission lines such as an AC system that supplies power to homes. Furthermore, capacitors and transformer coils often employ this material. To enhance its conductivity further, zirconia or carbon nanotubes may need to be added.

Alumina’s electrical conductivity is affected by oxygen and other impurities that reduce its crystal lattice energy, while bulk conductivity is determined by electron hopping at Co2+ and Co3+ ions. Ionic conductivity depends on diffusion coefficient n, concentration of ions, distance between them and chemical potential difference; estimated from diffusion equation using Nernst-Einstein relation whereby conductivity, D diffusion coefficient, concentration, valence z of the ions, elementary charge, Boltzmann constant Kb and temperature T are all variables.

Multiple studies have demonstrated that breathing powdered alumina particles can cause respiratory irritation and lung damage, including lipoid pneumonia. Overexposure has also been linked to coronary artery disease and renal disease.

Studies of the rheological behavior of alumina-based composites under DC electrical fields of various strengths were performed using oscillatory shear mode. G'(o)/o increased significantly with field strength. G'(o) increased due to ionic polarization of alumina particles and their dipole moments being activated within the natural rubber XL matrix. This causes chain free movement to cease, leading to stiffer chains with an increase in elastic modulus of nearly two orders of magnitude. Alumina-based composites exhibit excellent electrical conductivity for use in medical, industrial, and automotive applications as well as having lower melting points than pure alumina for easier machineing processes.