摘要:

A technique, combining photolithographic methods, ion beam etching, and hot‐pressing, has been developed, which permits the generation of a wide range of controlled pore structures. Pores in almost any number, and of almost any size and spacing, can be produced at grain boundaries with controlled misohentation. This new method has permitted the development of novel experiments, which are being used to study pore‐drag effects during grain growth, pore morphology evolution during crack healing, faceting behavior, interfacial energies, and Ostwald ripening of po

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05716.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

A commercial lithium aluminosilicate glass‐ceramic material is investigated by high‐resolution transmission electron microscopy after different heat treatments. Evidence is presented that epitaxy of β‐quartz crystals on ZrTiO4‐type crystallites is the critical step initiating silicate crystal

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05717.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Two forms of sodium cerium(III) mixed hexa‐aluminate were prepared at temperature as low as 1270°C, i.e., 300°C lower than those reported previously, and characterized by X‐ray diffraction techniques. These compounds are formed by thermal treatment, under argon, of an amorphous organometallic precursor obtained by the “citric acid method”. During the synthesis, the 3+ oxidation state of cerium is retained at all tem

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05718.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The tensile strength of two groups of fused silica optical fibers, reported by previous workers, has been analyzed in terms of a modified Weibull flaw distribution function. The function provides upper and lower strength limits and is characterized by two shape and two location parameters. The long‐length strengths predicted from this function are in close agreement with the experimental dat

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05719.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The relation between grain size and grain‐boundary microcracking during cooling in aluminum titanate ceramics was studied. Microcracking temperature was determined by the measurement of thermal contraction and expansion, which was accompanied by acoustic emission. When the ceramics were cooled at a rate of 6°C/min, stress relaxation did not occur below the sintering temperature of 1500°C. The relation between the temperature difference from the sintering temperature to the microcracking temperature and the grain size showed good agreement with the prediction based on the energy criterion of grain‐boundary microcra

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05720.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Fine‐grained polycrystalline zirconia fibers have been formed from an acetate precursor. The fibers contained a Y2O3additive, which inhibited grain growth (grain size ≤0.5 μm) and allowed the tetragonal phase to be retained at room temperature. Fibers with diameters in the range 2 to 5 μm had strengths in the range 1.5 to 2.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05721.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The oxidation kinetics of polycrystalline LaCrO3were determined by measuring the time and temperature dependence of the weight and conductivity change of reduced samples. A region of fast diffusion followed by a smaller, slower diffusion “tail” was observed in the thermogravimetric measurements. This observation can be interpreted as the rapid diffusion along the grain boundaries and subsequent diffusion into the body of the grain. The absence of the “tail” in the conductivity measurements is due to the high hole mobility along the bou

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05722.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The orientational relationship between intergrown lamellae of tetragonal (t) BaTiO3and monoclinic (m) Ba6Ti17O40was found to be (111)t||(001)m, (001)t||(101)m, and [110]t||[010]m. On the basis of this relationship a model of a topotactic boundary between these two phases was constructed.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05723.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

(111) twins are found frequently in the microstructure of BaTiO3ceramics prepared by the mixed‐oxide technique. The processing steps by which the (111) twins are formed are in question. A BaCO3‐TiO2powder mixture is milled and then Calcined at 1100°C for 2 h, where BaTiO3is formed by the release of CO2. After the powder is calcined, it is analyzed by TEM. Image and diffraction pattern data are combined to prove the presence of (111) twins in powder particles; the formation of (111) twins occurred frequently during calcination. The formation mechanism of such twins and their role during anomalous grain growth are discu

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05724.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Solid solutions of AlVO4crystallize at lower temperatures than amorphous materials between 50 and 70 mol% Al2O3prepared by the simultaneous hydrolysis of aluminum and vanadyl alkoxides. They decompose into α‐Al2O3, and V2O5, at 775° to 800°C. The compound AlVO4prepared from 50 mol% Al2O3has a triclinic unit cell with a = 0.6471 nm, b = 0.7742 nm, c = 0.9084 nm, α= 96.848°, β= 105.825°, and γ= 101.399°. The volume of the unit cell increases continuously with increases in Al2O3content. The structure contains tetrahedral AlO4, octahedral AlO6, and tetrahedral

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1987.tb05725.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY