ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14365.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The properties and composition of glasses suitable for crystallization of BaTiO3are described. The crystallization of certain glasses results in a nearly complete recovery of BaTiO3, besides the feldspar BaAl2SiO3as a minor phase. The mechanism of crystallization was investigated by thermal analysis, viscosity, and grainsize measurements as a function of the temperature whereas density data were used for evaluation of the BaTiO3content. Within the range 30 to 60% by volume of BaTiO3at about 1μ grain size, the measured dielectric constant increased from 100 to 1200. The calculated partial dielectric constant of the Titanate phase at this grain size was about 3500. As the grain size approached 0.1μ, the dielectric constant decreased and became nearly independent of the temperature because of the predominance of surface states. Other effects were attributed to special structural characteristics, such as absence of porosity and clamping of the titanate particles within the microcrystalline matrix. Data are also presented on dielectric constant and loss tangent at different frequencies, dc breakdown strength, dc resistivity, and ferroelectric properties as a function of the grain size of the crystallized materia

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14366.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Direct bonding in burned magnesite‐chrome refractories is described as a mineralogical phenomenon and as a factor governing brick properties. Hot‐load tests are recommended as a supplement to hot modulus tests to obtain a meaningful picture of high‐temperature strength. The importance of purity of ingredients is thus made more apparent. Direct‐bonded brick from open‐hearth service are shown to have a lower level of slag absorption. The result was reproduced in a unique laboratory diffusion furnace and a relation between silicate buildup and original brick purity is es

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14367.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The ionic conductivity of cubic solid solutions in the system CaO ‐Y2O3‐ZrO2was examined. Particular Y2O3‐ZrO2binary compositions were more conductive at elevated temperatures (>600°C) than either CaO‐ZrO2binary or CaO‐Y2O3‐ZrO2ternary compositions. The higher ionic conductivity appears to be related to a lower activation energy rather than to the number of oxygen vacancies dictated by composition. Those compositions of highest conductivity lie close to the cubic‐monoclinic solid‐solution phase boundary. Conductivity‐temperature data are presented that indicate a reversible order‐disorder transition for Y2O3‐ZrO2cubic solid solutions containing 20 and 25 mole % Y2O3. The transference number for the oxygen ion at 1000°C for Y2O2‐ZrO2cubic solid solut

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14368.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The system boron carbide‐silicon carbide is quasi binary and contains a eutectic of composition 70 ± 2 wt% B4C and 30 ± 2 wt% Sic at a temperature of 2300°± 20° C. The solid solubility of both B4C in Sic and Sic in B4C is less than 2 wt% at this temperature, based on metallographic and X‐ray analyses. The Sic corresponds to the hexagonal(a)allotrope when the compositions contain more than 50 wt% Sic. The cubic (p) form of Sic is stabilized in compositions which contain less than 50

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14369.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The effect of calcination and ball milling on the grain growth in Mn‐Zn ferrite is presented. Rates of grain growth and the effect of ball milling on the growth behavior were observed for ferrite powders calcined above and below the recrystallization temperature. It is shown that in addition to particle size and distribution, calcination temperature was a critical factor responsible for the growth behavior of ferrit

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14370.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Grain‐growth experiments with steep temperature gradients and with polycrystalline aggregates seeded with single crystals were carried out to explore the feasibility of growing large crystals of BaTiO3in the solid state. It is shown that both methods resulted in a large increase in size of crystals normally obtained by sintering but that the rapid grain‐boundary motion resulted in high porosity. Definite orientation dependence of grain‐boundary velocity is demonstrated, and growth in a 〈110〉 direction was found to be at least as fast as 2 mm

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14371.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The high‐temperature stability and behavior of MoSi2was studied by heating dense sintered specimens under a vacuum of 10−5mm Hg in the temperature range 1700° to 2000°C. The resulting material was examined using physical measurements, X‐ray analysis, and metallographic techniques. The decomposition of MoSi2into Mo5Si3is described. The Mo5Si3‐MoSi2eutectic temperature was determined as 1900° C, and the melting points of MoSi5and Mo5Si3were determined as 1980° and 2085° C,

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14372.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

The compounds CaSc2O4and SrSc2O4were synthesized by solid‐state reaction of the component oxides at temperatures ranging from 950° to 1400°C. Both calcium and strontium monoscandates are orthorhombic and analogous to CaFe2O4. Lattice parameters for CaSc2O4a reao= 9.461,bo= 11.122,co= 3.143 and for SrSc2O4,ao= 9.698,bo= 11.302,co= 3.185. Based on four molecules per unit cell, the X‐ray density for CaSc2O4is 3.89 g per cm3and that for SrSc2O4is 4.59 g pe

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14373.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Phase relations in the system CaO‐Al2O3‐H2O from 40° to 500°F have been determined by hydrothermal techniques. Very high purity starting materials (luminescent‐grade CaCO3) must be used if the correct phase relations for this system are to be determined. A phase diagram of the system made by using reagent‐grade CaCO3is compared with the diagram obtained from the luminescent‐grade material. The general effect of introducing foreign ions into the system is to promote the formation of the dicalcium aluminate hydrate phase. Adding various clay structures to starting mixtures had relatively little influence on the resulting phases. The action of additives on calcium aluminate cements depends on such factors as the phase relations, the nature of the hydrated alumina, and the interrelations of these factors with variable pH, foreign ions, and pressure‐temperatu

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1964.tb14374.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY