ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13140.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The effect of thermally induced stress and strain on producing hackle was studied for both symmetric and asymmetric temperature distributions through the thickness of a glass plate. A relation was obtained between stress and strain and hackle for glass from 1/8 to 1/2 in. thick at 100° to –110°F. The bath temperatures used were those of ice at 32°F, a mixture of dry ice and acetone, and water at 1

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13136.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The glass composition MgO 15.5, Al2O319.5, SiO258.5, and TiO26.5 (wt%) was crystallized under controlled conditions in the range 900° to 1140°C and the electrical properties were studied. The activation energy for dc and ac conduction in the uncrystallized specimen was 32.0 and 27.4 kcal/mole, respectively; the corresponding values for the crystallized specimens were about 18.5 and 11.6 kcal/mole. X‐ray studies and color of the crystallized specimens suggested the presence of magnesium aluminum titanate crystals in which part of the titanium was reduced to the Ti3+state. These semiconducting phases were suggested as being responsible for the sharp change in the electrical properties and for the appearance of an apparent dielectric relaxation peak. Changes in the electrical properties with increasing crystallization temperature may be related to the nature, size, and shape of the cryst

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13137.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Rutile (TiO2) crystals exhibited amplitude dependent internal friction behavior characteristic of that associated with dislocation damping. The generation of excess nonstoichiometric defects decreased damping, particularly for the (1|01) [1|01|] extended dislocation system. An increase in test temperature decreased damping, suggesting that ionized defects may interact more strongly with dislocations than the defects characteristic of lower temperatures.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13138.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Viscosity and density data were obtained up to 1700°C for a series of binary aluminoborate melts that contained as much as 15 mole% (∼21 wt%) Al2O3and up to 1620°C for pure molten B2O3. Large expansion coefficient decreases and a slight activation energy increase for B2O3above 1400°C suggested a tightening of its structure. The addition of Al2O3reduced viscosity and increased activation energy. The decreased compositional dependence of molar volume (compared to SiO2additions) and the increased expansion coefficients accompanying Al2O3additions suggested a loosening of the O—B—O structure at 1600°C. Molar volume deviations from ideality were similar to but smaller than those for SiO2and GeO2additions at 1300°C. Microclustering of aluminum‐bearing polyhedra appeared to occur at slightly higher boron atom contents than with SiO2and G

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13139.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Since the difference between oxygen‐ion and cation diffusion coefficients is greater for α‐Cr2O3than for α‐Fe2O3or α‐Al2O3, a study of initial‐sintering kinetics was undertaken to show unequivocally which species is rate controlling. Fine powders of α‐Cr2O3, obtained by thermal decomposition of reagent‐grade (NH4)2Cr2O7, were lightly compacted and their isothermal rates of shrinkage were determined between 1050° and 1300°C. Resultant data follow volume‐diffusion sintering models, and calculated diffusion coefficients agree with, those measured for oxygen ions in α‐Cr2O3. There is little evidence that oxygen diffusion along grain boundaries becomes so enhanced that chromium ions are left i

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13141.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The sublimation of single‐crystal Al2O3spheres and plates in pure, dry H2was studied. The kinetics of this process are controlled by diffusion of the volatile gaseous products through the stagnant gas boundary layer adjacent to the surface. The evaporating species are probably the lower oxides of aluminum obtained by reduction of Al2O3with hydrogen. The etching of the surface by heating in dry H2was also studied. The basal planes developed most easily. The facets formed were fine steps consisting of basal and prismatic planes. Condensation of the vapors in the form of small crystallites of thin plates and whiskers of Al2O3was observed in the colder regions of the furnac

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13142.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The phase relations were established for the system silica‐sodium tetraborate. The silica liquidus curve exhibits strong upward concavity but shows no flattening. The tridymite‐cristobalite transformation occurred at 1410°± 10°C. A lowering of the α to β quartz inversion temperature of about 9°C was detected. Primary crystal habits are discussed. The region of metastable subliquidus immiscibility is also discussed and the nature of initial crystallization of the silica‐rich liqu

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13143.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The anomalously high permittivity in fine‐grained ceramic barium titanate is explained by the absence of 90° twinning within the grains, giving rise to internal stresses as the ceramic cools below the Curie temperature. Using the Devonshire phenomenological thermodynamic method and a simplified model, the stresses involved are calculated. At these stress levels, the reduced strain calculated on this model agrees well with X‐ray data for the fine‐grained material. The limitations and possible developments of the proposed model are dis

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13144.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The effect two‐dimensional pressure on the permittivity of fine‐ and coarse‐grained ceramic BaTiO3was investigated. It was shown that, unlike coarse‐grained (10° or above) barium titanate, the permittivity of the fine‐grained (1μ mean) material increased with the increase in two‐dimensional compression perpendicular to the electrode, whereas for an intermediate grain size, the permittivity was almost independent of pressure. The apparent anomalous effect of the fine grain size on the pressure coefficient of permittivity was explained satisfactorily on the basis of an internal stress model using a modified Devon‐shire thermody

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13145.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY