ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14396.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The thermal conductance of insulating firebrick was measured in gas atmospheres other than air. The effect of using insulating firebrick in gases of thermal conductivity higher or lower than that of air was correlated with porosity. Curves are presented that permit direct computation of the thermal conductance of these brick in any gas atmosphere of known thermal conductivity. An equation is given for estimating the thermal conductance of a clay‐based brick using only its porosity and thermal conductance in ai

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14397.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

A general principle for the preparation of semiconducting oxide glasses is presented. Some borates, phosphates, and germanates were prepared. The mechanism of electrical conduction was demonstrated to be electronic rather than ionic by (a) the absence of electrolysis, (b) the absence of electromotive force when the glass was used as an electrolyte, and (c) the magnitude of the activation energies for conduction.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14398.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

This paper is a brief review of the physical and chemical methods of strengthening glass, in particular that due to the large for small ion exchange resulting from treatment in molten salt at temperatures below the annealing range for the glass. Abrasion of treated glass is shown to reduce markedly the strength of experimental alkali‐lime‐silica glasses as well as commercial glasses of this and other types. Treated alkali‐alumina‐silica and alkali‐zirconia‐silica glasses, however, are less affected by abrasion. Strength after abrasion increases with alumina or zirconia content, reaching 117,000 psi for cane of a 35% alumina glass. The explanation for the aluminum or zirconium effect may involve an unusual ionic environment caused by their presence in

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14399.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

This paper is Part IT of a two‐part series reviewing the present understanding of space charge and electrode polarization in glass and the interrelations of these concepts with the usually measured electrical properties of glass. Emphasis is placed on a theory describing the distribution of static space charge in material having only a single mobile charge carrier. Charge dissociation and recombination are considered and the carriers are assumed to move under diffusion and conduction. The charge distributions predicted by the theory are discussed and are compared with the results of experiments which were undertaken specifically to verify essential features of the predictions. The theory is confirmed qualitatively by the observed charge distribution shapes and asymmetries. Quantitative confirmation is also shown in computed values of mobility, diffusion constant, and contact potential ratios. This theory has here been expanded to include a linearized ac treatment, and the phenomena predicted by this treatment fit the known data semi‐quantitatively. A large low‐frequency relaxation mechanism is predicted. Previous theory and experiment were briefly reviewed in Part I. In Part I1 the predicted and observed space charges are conceptually related to various phenomena such as conduction, electrode polarization, dielectric absorption, and dielectric loss. Needed improvements in the present theory and a number of ideas for more experiments are outlined in order to stimulate efforts to acquire a more detailed understanding of these phen

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14400.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Experiments on the system Al2SiO5at high temperatures and pressures with the belt apparatus indicate that kyanite melts incongruently above about 1500°C at 25,000 bars to Al2O3(corundum) plus liquid. The pressure‐temperature curves obtained by starting with either a 1/1 Al2O3/SiO2gel or with kyanite are essentially identical but differ considerably from the results with andalu‐site and sillimanite. The structure of the starting material has considerable influence on the kinetics of the reaction and the metastable formation of corundum in this system. An “equilibrium” curve based on the andalusite‐sillimanite data is described byP= 33.8 × 10‐3T ‐ 26.4 (Pi

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14401.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The effect of various gaseous atmospheres (nitrogen, hydrogen, and water vapor) on the fracture strength of single‐crystal and poly‐crystalline A1203 was investigated. Sapphire specimens exposed to hydrogen and nitrogen at elevated temperatures and subsequently tested at room temperature did not become brittle or lose strength. Sapphire specimens exposed to moisture in a specific temperature range showed a definite impairment of strength in subsequent room‐temperature bend tests. The strength was recovered when the moisture‐exposed specimens were heated to 400°C. It is suggested that the loss of strength and the recovery are due to the formation and decomposition of a surface precipitate, presumably a hydrate of some type. Polycrystalline alumina (Lucalox) did not show any significant loss in strength when exposed to

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14402.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The thermal decomposition of the ammonium sul‐fate, carbonate, nitrate, oxalate, and sulfate salts of praseodymium, neodymium, and samarium was investigated thermogravimetrically in the temperature range 25° to 1400° C. Each salt was decomposed at a heating rate of 2.5° C per minute. The pyrolytic sequences have been identified, and the temperatures of formation of intermediates and of the sesquioxides have been determined. The sesquioxide formation temperatures increased in the order samarium, neodymium, and praseodymium irrespective of the anion. The nonstoichiometric ranges between Pr6O11and Pr2O3and the extent of these ranges have been determined for oxides derived from the carbonate, nitrate, and oxalate salts of praseodymium. The nonstoichiometric oxides of praseodymium were not observed in the decomposition of the alum and sulfate s

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14403.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Most of the known oxides of lead including the intermediate oxides Pb12O19and Pb2O3have been prepared under equilibrium conditions. Precise X‐ray powder data have been obtained for the intermediate oxide phases. Solid‐vapor equilibrium data have been obtained for reactions in the system lead‐oxygen over the range 200° to 900° C and 3 to 1400 bars Po2. Pressure‐temperature univariant equilibrium curves are presented for the reactions PbO2⇋ Pb12O19+ oxygen, Pb12O19⇋ Pb3O4+ oxygen, and Pb3O4⇋ PbO + oxygen. The enthalpies of reaction are, respectively, 26.8, 34.6, and 33.7 kcal per mole. Eutectic melting between PbO and Pb3O4occurs at 875° C and 124 bars. A stability field for Pb2O3exists above 1000 bars PO2at 600° C. Approximate resistivity d

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14404.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Experimental measurements have been made on the rate of dissolution of sapphire, dense poly‐crystalline alumina, mullite, fused silica, and anorthite in a 20A12O3‐4OCaO‐40SiO2slag at 1350° to 1500° C under conditions of free and forced convection. Dissolution rates and their temperature dependence were found to be controlled by transport within the liquid boundary layer. At low temperatures alumina is by far the most corrosion resistant; at higher temperatures differences between the refractories tested are less pro

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14405.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY