Aluminum sintering

K. A. Schwetz, A. Lipp, The effect of boron and aluminum sintering additives on the properties of dense sintered otSiC, Science of Ceramics 10, Berchtesgaden Sept. 1979, H. Hausner (Ed.), Verlag Deutsche Keramiske Ges 1980, pp. 149-158. 

Sol—Gel Sintered Aluminum Oxide. A new and much more versatile sintered alumina abrasive is now produced from aluminum monohydrate, with or without small additions of modifiers such as magnesia, by the sol—gel process (see Sol-gel technology). The first modified sol—gel abrasive on the market, Cubitron, was patented (27) and produced by the 3M Corporation for products such as coated belts and disks. The success of this material promoted intensive research into sol—gel abrasives. 

In 1990, appioximately 66,000 metric tons of alumina trihydiate [12252-70-9] AI2O2 3H20, the most widely used flame retardant, was used to inhibit the flammabihty of plastics processed at low temperatures. Alumina trihydrate is manufactured from either bauxite ore or recovered aluminum by either the Bayer or sinter processes (25). In the Bayer process, the bauxite ore is digested in a caustic solution, then filtered to remove siUcate, titanate, and iron impurities. The alumina trihydrate is recovered from the filtered solution by precipitation. In the sinter process the aluminum is leached from the ore using a solution of soda and lime from which pure alumina trihydrate is recovered (see Aluminum compounds). 

Brinell Tests of Steel Products Comparison Hardness Tester Practice Rockwell Test on Cemented Carbides Rockwell Test for Sintered Materials Knoop Test for Electrodeposited Coatings Webster Hardness Gauge Barcol Test of Aluminum Alloys... 

Miscellaneous Methods. Powdered metals such as aluminum, chromium, nickel, and copper, along with various aHoys, can be appHed to parts by electrostatic deposition. The metal strip containing the attached powdered metal must be further processed by cold rolling and sintering to compact and bond the metal powder. 

Porous parts and bearings are made by both the press and sinter techniques, whereas filters are made by loose powder sintering. The metals most commonly used for P/M porous products are bron2e, stainless steel (type 316), nickel-base alloys (Monel, Inconel, nickel), titanium, and aluminum. 

Dispersions of flake aluminum powders having surface oxide up to 14 wt % Al O have been pressed, sintered, and worked to a material known as sintered aluminum powder (SAP). This product exhibits high strength at elevated temperatures. Nickel containing small additions of thoria, known as TD-nickel, is also a high temperature cermet. 

Aluminum resinate particles, ie, size precipitate, are attracted to the fiber surfaces because of a difference in charge and thus are retained (45,46,54). In general, the particles of size precipitate are small and are distributed fairly uniformly over the sheet. However, on drying, there is some sintering of the particles which helps to redistribute them on the fibers. 

Rotational Molding. Hodow articles and large, complex shapes are made by rotational mol ding, usuady from polyethylene powder of relatively low viscosity (57—59). The resin is in the form of a fine powder. A measured quantity is placed inside an aluminum mold and the mold is heated in an oven and rotated at low speed. The resin sinters and fuses, coating the inside of the mold. The mold is then cooled by water spray and the part solidifies, dupHcating the inside of the mold. 

Aluminum hydroxides are technically the most widely used members of the alurnina chemicals family. The most important source of aluminum hydroxides is the bauxite refining plant for alurnina production. A small amount of somewhat purer aluminum hydroxide is produced by the Sinter process. 

Commercial production of bayerite is relatively small and employs CO2 neutralization of caustic aluminate Hquor obtained from either Bayer or sinter processes. The product obtained is about 90% crystalline bayerite having small amounts of gibbsite, pseudoboehmite, and amorphous aluminum hydroxides. 

Calcium Aluminate Cements. Low purity calcium aluminate [12042-78-3] cements are obtained by sintering or fusing bauxite and lime in a rotary or shaft kiln. A high purity calcium aluminate cement, 2CaO 5AI2O2, capable of withstanding service temperatures of 1750°C can be prepared by the reaction of high purity lime with calcined or hydrated alumina (see Aluminum compounds). 

Aluminum babbitt has been a U.S. alternative (6,20). On cooling this molten material, 8% lead separates from the aluminum as globules at the surface for improved antiscoring properties. More recendy, a sintered lead—alurninum containing 8.5% lead, 4% siUcon, 1.5% tin, and 0.5% copper has been developed for automotive use. 

Metals such as copper, iron, or a combination of the two, usually modified with tin, bismuth, and/or lead ate used as binders of sintered friction materials where deformation under the high forming pressure is requited to lock together the property modifiers within a matrix. Metals such as copper, iron, zinc, aluminum, and occasionally lead are also used as friction modifiers. 

The predominate role of the 2inc and aluminum oxides in the ICI catalyst is to reduce the rate of sintering and loss of metallic copper surface area, which, in addition to poisoning, is one of the modes of activity loss with time for this catalyst. 

---