Alumina is the most mature of the engineering ceramics, offering excellent electrical insulation properties together with high hardness and good wear resistance but relatively low strength and fracture toughness.
                                                            

During the prodcution, small amounts of silica (SiO2), magnesia (MgO) and zirconia (ZrO2) may be added to alumina ceramics. The applications vary with the purity of Alumina.99% Alumina Ceramics are mostly used for high temperature crucibles, kiln furniture, special abrasion resistant parts, such as ceramic bearings, ceramic sealings or faucet discs; 95% Alumina Ceramics are usually applied for corrosion-resitant components or wear proof parts; 85% Alumina Ceramis can be metallized with metals like molybdenum, niobium, tantalum to use for electric vacuum devices.

                                                              
Properties of Alumina Ceramics
Alumina has a high melting point, high hardness and high mechanical strength, although mechanical strength is reduced at temperatures above 1000°C. Due to the relatively large coefficient of thermal expansion, thermal shock resistance is reduced. Alumina is an electrically insulating material, with a high electrical resistivity, increasing with purity.Good chemical stability of alumina, leads to a high corrosion resistance. It is insoluble in water and only slightly soluble in strong acid and alkaline solution.

                                                          
Various Application of Alumina Ceramics
1.Seal rings
2.Medical prostheses
3.Laser tubes
4.Electronic substrates
5.Ballistic armour
6.Thermocouple tubes
7.Electrical insulators
8.Grinding media
9.Threadguides
10.Wear components

                                                              

Characteristics	Unit	95 Al2O3	99 Al2O3	ZrO2	GPSi3N4	BN	Glass Ceramic
Crystal Structure	-	hexagonal	hexagonal	tetragonal	hexagonal	hexagonal	-
Color	-	white	ivory	white	gray	white	white
Density	g/cm3	3.65	3.88	5.95	3.22	2.26	2.55
Water Absorption	%	0	0	0	0	0.0-1.0	0
Young's Modulus	Gpa	280	350	205	295	670	65
Vickers Hardness	Gpa	14	20	12	18-20	-	-
Flexural Strength	Mpa	280	300	900	650	51	100
Compressive Strength	Mpa	2000	2500	2200	2200	230	500
Thermal Conductivity	W/(m·k)	18-25	30	2.2	25	20	1.7
Thermal shock resistance	Δ(℃)	220	180-200	280-350	450-650	>1500	25-100
Max. Working Temperature	℃	1500	1700	850	1200	960	800
Volume Resistivity	Ω·cm	>10^15	>10^14	>10^12	>10^14	10^13	10^16
Dielectric Constant (1 MHz )	-	9.5	9.8	26	8.2	4.08	6.02
Dielectric Strength	kV/mm	16	22	-	16	375	40

                                                                    
About UniPreTec
UniPreTec provides high-performance ceramic products in Alumina, Zirconia, Zirconia Toughened Alumina, Silicon Carbide, Silicon Nitride and  further special materials. Along with these materials, we offer several machining from which to choose such as cutting, drilling, sawing, turning, grinding, polishing etc.. Furthermore, our technologies and equipments allow us to provide various and flexible forming processes, like dry pressing, isostatic pressing, extrusion, injection moulding and slip casting.