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Sodium-0-alumina hardness

Lemington H.26X., made by the General Electric Co., is a very hard borosilicate glass of high softening temperature. Tte Mg point is 780°C. It is used in high pressure mercury vapour lamps. The linear expansion coefficient is 4-6 x 10 from 20 to 580°C. Sodium and potassiiun are absent and alumina is present in quantity in this glass. [Pg.17]

Aluminium, which is also manufactured on a large scale, is produced from its ore, bauxite, from which pure alumina, the oxide, is first prepared. The alumina is dissolved in fused cryolite, a fluoride of aluminium and sodium of the formula Na3AlF6, deposits of which occur in Greenland. The aluminium sinks to the bottom of the crucible, and when a sufficient quantity accumulates it is tapped out. The flux, as the cryolite is termed, is again melted, and a further quantity of alumina is dissolved in it. The metal is fairly hard, white, susceptible of a high polish, ductile and malleable. It is also very light (about two and a half times as heavy as water), and not easily oxidised in air at the ordinary temperature, nor is it attacked by water. [Pg.9]

Geopolymers are another type of intermediate products that lie between cements and ceramics [7]. A geopolymer is made by pyroprocessing naturally occurring kaolin (alumina-rich clay) into metakaolin. This metakaolin is then reacted with an alkali hydroxide or sodium silicate to yield a rock-Uke hard mass. Thus, a chemical reaction, which is not fully understood, is employed to produce a hard ceramic-Uke product. Though this product is produced like cement, its properties are more like a sintered ceramic. It is dense and hard like a rock. [Pg.3]

Wilson et al. [25] analyzed various brands of commercial cements and specified their possible composition, properties, and microstructure. Wilson et al. report the most representative and comprehensive data on commercial porcelain dental cements. These cements consist of powdered alumina-lime-silica glass mixed with phosphoric acid that formed a hard and translucent product. The starter glass powder consists of 31.5-41.6 wt% silica, 27.2-29.1 wt% alumina, 7.7-9.0wt% calcium oxide, 7.7-11.2 wt% sodium oxide, 13.3-22 wt% fluorine and small amounts of phosphorous and zinc oxides. Often very small amounts of magnesium and strontium oxides are also present. [Pg.17]

After calcination at 450°C, hard blocks were obtained. The solid presents a 7-alumina structure and a type IV nitrogen isotherm (see Fig. 2-a), typical for mesoporous materials. The surface area was found equal to 400 50 mVg and the pore volume to 0.5 0.1 cm /g. The value of the pore diameters (centered on 5 nm) is in good agreement with SEM observations which indicate a textural mesoporosity. Many parameters of the reaction were studied. First, the composition of the initial mixture (dilution, global surfactants concentration and CTMABr/sodium palmitate ratio), secondly the procedure parameters (temperature, aging time, final pH and addition order of the chemicals) and third the nature of the chemicals (nature of the counterion of CTMA and nature of the acid) were varied. However, all the materials washed with water presented the same characteristics as described previously. [Pg.213]

It is apparent from a study of results obtained that an increase in the concentration of catalytic material will produce an increase in the yield of sodium sulfate, although the increase in yield is far less than the increase in the catalyst concentration. This is shown by Table II. Ferric oxide is effective when present in very low concentrations. Magnesium aluminate when present in greater than 0.1 mole fraction is extremely effective in converting all of the sodium chloride to sodium sulfate in relatively short intervals of time. The rate of formation of sodium sulfate with alumina as catalyst is hardly affected by a fivefold increase in the catalyst concentration. [Pg.772]

Activity for adsorption and catalytic function of alumina is revealed by partial de-hydroxylation of its surface. The variation of the density of surface hydroxyl groups is shown inf Fig. 3.34. The isoelectric point has been reported to be about 7. Proton exchange was hardly observed in the reaction of alumina in aqueous solution of sodium acetate. ... [Pg.80]


See other pages where Sodium-0-alumina hardness is mentioned: [Pg.133]    [Pg.162]    [Pg.541]    [Pg.918]    [Pg.243]    [Pg.3448]    [Pg.46]    [Pg.252]    [Pg.2]    [Pg.61]    [Pg.3447]    [Pg.162]    [Pg.248]    [Pg.1822]    [Pg.607]    [Pg.191]    [Pg.205]   


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Sodium 1-alumina

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