Density aluminum nitride

Carr and his co-workers [86C01, 87C01] have shown that transmission electron microscopy is a powerful tool in characterizing linear and higher-order defect configurations and their densities on shock-modified rutile, alumina, aluminum nitride, and zirconia [84H02]. The principal impediment to detailed characterization of shock-formed defects is their very high concentrations, which prevent identification of specific deformation features except in... 

Aluminum nitride powder synthesized by high-temperature routes can be sintered to a density of more than 97% of the theoretical density by adding calcium or yttrium compounds as sintering aids [52-54]. Therefore, new processing routes to aluminum nitride predominantly aim at powders with lower quantities of cationic impurities. In addition, the formation of aluminum nitride coatings [55-58] or fibers [59] has become subject of extensive research. 

The research results from the effects of nitrogen pressure in the reactor, density of initial mixture, sample diameter, and aluminum additive on the acid—alkah balance of the washing water (pH), combustion temperature, and burning rate for obtaining of aluminum nitride are given. 

Aluminum nitride (AIN) is a covalent-bonded compound and has a hexagonal wurtzite-type crystal structure and a density of 3.26 gcm . Pure AlN is translucent and colorless (white in powder form), and a stable compound in inert atmospheres at temperatures up to 2000 °C. 

Density of Cubic Boron Nitride. The c-BN structure, with its tetrahedral bonding, is isotropic and, except on the (111) plane, is more compact than that of h-BN (with its sjp anisotropic structure and wide interlayer spacing). Consequently c>BN has higher theoretical density than h-BN (3.43 g/cm vs. 2.34 g/cm ). It should be pointed out that the diamond-like structure of cubic boron nitride is similar to those of the other two refiactory covalent nitrides, i.e., aluminum nitride and silicon nitride, as weU as silicon carbide (see Ch. 7, Sec. 3.0). 

Substrates made by the multilayer process from tape cast alumina have received considerable attention in recent years for multichip module (MCM) applications. An MCM consists of an array of closely packed chips on an interconnect board several inches on a side. Cofired ceramic is attractive relative to organic laminates because its thermal conductivity is almost 2 orders of magnitude higher, an important consideration in high-density circuitry. In addition both alumina and aluminum nitride ceramics are more closely matched to silicon in CTE than are organic boards. For similar reasons, alumina and AIN are attractive for ball grid array (EGA) mounting of chips. ... 

ALUMINUM NITRIDE. AIN. Mol. wt. 40.99 density 3.26 g/cm CTE 4.6 X IQ-S/oc 2200°C under 4 atm. Nj, sublimes at 1 atm. White, hexagonal crystal structure. Powder hydrolyzes on contact with water or water vapor. Water-resistant powders that allow aqueous processing are commercially available. Stable against... 

The reinforcing fibers are usually CVD SiC or modified aluminum oxide. A common matrix material is SiC deposited by chemical-vapor infiltration (CVI) (see Ch. 5). The CVD reaction is based on the decomposition of methyl-trichlorosilane at 1200°C. Densities approaching 90% are reported.b l Another common matrix material is Si3N4 which is deposited by isothermal CVI using the reaction of ammonia and silicon tetrachloride in hydrogen at 1100-1300°C and a total pressure of 5 torr.l" " ] The energy of fracture of such a composite is considerably higher than that of unreinforced hot-pressed silicon nitride. 

Most structural PMCs consist of a relatively soft matrix, such as a thermosetting plastic of polyester, phenolic, or epoxy, sometimes referred to as resin-matrix composites. Some typical polymers used as matrices in PMCs are listed in Table 1.28. The list of metals used in MMCs is much shorter. Aluminum, magnesium, titanium, and iron- and nickel-based alloys are the most common (see Table 1.29). These metals are typically utilized due to their combination of low density and good mechanical properties. Matrix materials for CMCs generally fall into fonr categories glass ceramics like lithium aluminosilicate oxide ceramics like aluminnm oxide (alnmina) and mullite nitride ceramics such as silicon nitride and carbide ceramics such as silicon carbide. 

Four examples were given in the patent, all using supercritical propane with polysilane and aluminum isopropoxide, so-called precursor ceramic materials. In one instance scanning electron microscopy was used to demonstfate that polysil me was deposited as a smooth surtace film on the alumina fibers and fine silicon nitride whiskers. A silicon carbide material with internal pore openings as small as 10 microns was penetrated by supercritical propane laden with aluminum isopropoxide. Weight gains of up to 43% can be obtained depending on the density of the initial host ceramic. 

Alumina 9- lu-m9-n9 [NL, fr. L alumin-. alumen alum] (1801) (corundum) n. The oxide of aluminum, AI2O3, very refractory and next to diamond and boron nitride in hardness, obtained by the calcinations of bauxite. Alumina powder is used as a fire-retardant filler in plastics and, over the past two decades, alumina fibers have enjoyed increasing use as reinforcements for plastics, metals, and even ceramics. Its density is 3.965 g/cm. ... 

The three covalent nitrides are low-density materials with melting points which are higher than those of their parent elements boron, aluminum, and silicon. Of the three, boron nitride has the highest melting point... 

---