ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12030.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The wetting of AlN and TiC by liquid Ag and liquid Cu was investigated by the sessile drop technique at 10−6torr or less. An empirical relation was established between the cosine of the contact angle and the temperature or surface tension of the liquid drop. The critical surface tension for spreading and its physical significance are discussed. A method for estimating the surface energies of ceramics is proposed. The surface tension of TiC is estimated to be 1242±158 dynes/cm and that of AlN 990±110 dynes/cm. The surface tension of liquid Ag followed the equation γLv(Ag) (dynes/cm) = 1092–0.14T (°C) and that of liquid Cu γLV(Cu) (dynes/cm) = 1462–

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12031.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Thermal expansion of tetragonal PbO, investigated by high‐temperature X‐ray diffraction in vacuum, is nearly isotropic, with the coefficient in thec0direction only slightly greater than that in thea0direction. Volume thermal expansion is only slightly greater than in massicot. Retardation of the litharge‐massicot transformation is tentatively interpreted as the result of very low oxygen partial pressures caused by catastrophic oxidation of the stainless‐steel sample holder and resulting oxygen scavenging by lea

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12032.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The compounds CaTe2O5, SrTe2O5, and CdTe2O5were obtained as mica‐like plates by slowly cooling their melts. Dielectric properties were similar to those of mica. Optical and infrared spectra showed appreciable transmittance from 0.33 to 7 μm on with a cutoff at 10 μm. The compounds have refractive indices greater than 2. X‐ray diffraction studies showed that only the calcium and cadmium compounds are isomorphous; tentative structures, accounting for the marked cleavage, are proposed for these materials on the basis of the geometric distribution of X‐ray sca

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12033.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

A unique method was developed for mechanical testing of brittle materials to create an unlimited number of stress ratios in the tension‐tension and tension‐compression quadrants. The stress states are achieved by internal and external pressurization of tubular specimens in a special pressure vessel. Failure envelopes were determined for polycrystalline alumina and fine‐grained isotropic graphite. The modified maximum strain energy and Coulomb‐Mohr theories fit the data best; these theories should be plotted as bands representing probability of failure. The biaxial tensile strengths of alumina and graphite are lower than their uniaxial tensile strengths; the tensile strengths decrease as the compressive stress in the orthogonal directions in

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12034.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Theoretical analysis of the strength of materials consisting of particles joined along contact areas small in relation to particle size resulted in the modelwherepdenotes strength,Dparticle size, γ surface energy, d linear extent of the contact area,Emodulus of elasticity for the particles, and θ porosity. The first factor has the same form as the Griffith model except that particle size is substituted for crack size; it shows that strength increases inversely with the square root of particle size. The model can be used as a guide in the design of materials such as mortars with low cement content, sand‐lime bricks, soil stabilizers, and sintered products. The strengths of mortars made from finely ground quartz and cement and cured at high temperatures were 4 to 40 times higher than those of normal mortars with the same cement/water ra

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12035.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Initial sintering of several materials was studied by measuring powder compact densification at constant rates of heating (CRH). The CRH technique was extremely sensitive to the particle size distribution and other characteristics of the compacts. Although the CRH method circumvents several problems encountered in isothermal studies, it cannot be used to identify the mechanism of diffusion. Using the method on carefully prepared alumina powder compacts and assuming a grain‐boundary diffusion mechanism, an activation energy of 115±10 kcal/mol was obtained. Zirconia (yttria‐stabilized) and titania also exhibited a single densification mechanism with diffusion coefficients which correlate well with values obtained by isothermal measurem

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12036.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Thermal expansion of CeO2, Ho2O8, and Lu2O3was determined from 100° to 300°K by a back‐reflection X‐ray technique. The variation of thermal expansion with temperature is the same as that of specific heat for CeO2and Ho2O3; these oxides obey the Grueneisen model of thermal expansion in the temperature range st

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12037.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Conventional thermogravimetry, differential thermal analysis, and evolved gas analysis were used to study the thermal decomposition of reagent‐grade FeSO4·7H2O and of freeze‐dried FeSO4·H2O in oxidizing and inert atmospheres. The mechanism depends on the atmosphere but is the same for the freeze‐dried and conventional materials. In oxygen, iron(II) is converted to iron(III) before the sulfate ion decomposes, whereas in nitrogen this conversion occurs simultaneously with the first step of the sulfate decomposition. The presence of moisture lowers the decomposition temperature. Moess‐bauer spectroscopy, X‐ray diffraction data, and surface area measurements substantiated the proposed decomposit

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12038.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Kinetic equations for initial sintering were obtained by combining the conventional kinetic equation with an empirical expression for grain growth in the initial stage. The equations describe the isothermal shrinkage of ZnO in O2at 80 torr and 800° to 950°C. The equation also successfully analyzed the sintering of powder compacts of Al2O3studied by other worker

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12039.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY