ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11155.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

It has been found that yttrium‐iron garnet can be grown from solutions of yttrium‐iron garnet and molten BaO·xB2O3. This solvent possesses none of the undesirable properties of the usual solvents in that it is noncorrosive, nonvolatile, and has a specific gravity less than that of yttrium‐iron garnet. These properties make the solvent useful for the usual slow‐cooling growth methods and for controlled growth on seeds. The replacement of Ba with Na, K, Pb, Ca, and Sr will yield yttrium‐iron garnet as will the replacement of B2O3with V2O5. A definite relation exists between the amount of B2O3in the solvent and the amount of iron in the crystallized phase; namely, the percentage of iron in the crystallized phase is higher with increased B2O3concentration in the solvent. The use of this type of phase equilibrium information makes possible an orderly method of selecting solvents for crys

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11156.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

A non‐steady‐state method of measuring thermal diffusivity is described. The method has been used for measurements on glasses, ceramics, and refractories up to 1000°C with satisfactory results. The choice of a non‐steady‐state method permits simplification of the equipment and the specimen preparation required. In addition, only temperature differences, times, and specimen thickness need to be known. The temperature rise of a flat heating element and that of a heat sink in the medium are measured. For a given thickness and time, the diffusivity is a function of the ratio of the foregoing two temperatures. The applications and limitations of the method are d

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11157.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Magnesium oxide single crystals were coated with copper, cobalt, nickel, aluminum, iron, and gold to determine what effect, if any, altering the surface would have on the mechanical strength of the MgO. The coated crystals were given various heat treatments to allow a metal oxide to form on the MgO surface. The specimens were bent, using a three‐point loading machine to determine the flow stress. These geld strengths were then compared. It was found that the iron, nickel, and cobalt oxide layers decidedly lowered the yield strength whereas aluminum, gold, and copper had no effec

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11158.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The linear thermal expansion of single‐crystal and polycrystalline aluminum oxide and poly‐crystalline thorium oxide was measured from 100° to 1100° K with an interferometric technique. For each substance the results are well described by Gruneisen's equation using a Nernst‐Linde‐mann energy

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11159.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The system Li2O‐Al2O3‐SiO2contains several compounds and solid solutions which are important commercially and which are also of interest from a structural point of view. In addition to the interesting polymorphic modifications exhibited by spodumene and eucryptite, the solid solutions between spodumene and eucryptite and more particularly the solid solutions between spodumene and silica (the so‐called silica‐O series) constitute a group of materials quite suitable for studying the applicability of infrared methods for structural interpretations. The infrared spectra of all the compounds and some typical solid solutions have been obtained and the relations between these spectra and the structures as determined by X‐ray methods are

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11160.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The binary system CaO‐Nb2O5has been shown to include three compounds: CaO·Nb2O5, which melts congruently at 1560°C; 2CaO·Nb2O5, which melts congruently at 1576°C; and 3CaO·‐Nb2O5, which melts incongruently at 1560°C. Three eutectic compositions occur at 6% CaO (1362°C), 23% CaO (1492°C), and 34% CaO (1535°C). These results were obtained by the cone‐fusion technique. The compound 3CaO‐Nb2O5has been shown to exist in two forms: type I, face‐centered cubic with a = 7.978 A, having a superlattice with a = 23.934 A, and type II, orthorhombic (pseudotetragonal, distorted cubic) with a = 11.51 A, b = 11.10 A, c = 15.98 A, having a pseudocell with a = 5.754 A, b = 5.551 A, and c = 7.990 A. The conditions controlling the formation of these two forms were not determinable from the exp

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11161.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Stress‐strain curves and stress‐relaxation curves were determined at various temperatures (1° to 70°C) and concentrations (16 to 22 wt%) for attapulgite suspended in water. Stress‐relaxation experiments were conducted under different conditions on samples which were relaxed for various durations of time between successive cyclic deformations. The flow properties are given in terms of rheopexy and thixotropy. The flow curve (for shear rates 0 to 700 per second versus shear stress) shows, first, a rheopectic hysteresis loop which changes on repeated shearing to a reversible and reproducible non‐Newtonian flow curve. After resting the system for about 12 hours, the resulting flow curve shows a thixotropic loop. Viscosity as a function of pH shows an inversion at pH ⋍ 6.3. A model for explaining the observed facts is proposed. The script S type of looped‐over flow curves showing both rheopectic and thixotropic characteristics is explained in terms of breakage of “logjammed” and crystalline bundles. A plot of the yield‐point viscosities versus the reciprocal of temperature for the rheopectic and thixotropic curves shows activation energies of about 1 and 2 kcal respectively. An autographic rotational viscom‐eter was designed and utilized to obtain the data reported so that the objectionable effects of frictional heating in the sample were minimized. The calibration response of the viscometer to a glycerol standard shows good agreement with pub

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11162.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The mechanisms of the sintering of ZnS were determined by measurement of the rate of growth of the necks between polycrystalline spheres. In vacuum (10−6mm Hg) at temperatures higher than 600° C the mechanism of sintering is that of volume diffusion with coefficient Dv, = 1.06 × 10−2exp (‐26,400/RT); below 600°C surface diffusion predominates, with coefficient D3, = 9.14 × 10‐3exp (‐5700/RT). In Zn vapor (10−2mm Hg) between 550° and 650°C the predominating mechanism of sintering is surf ace diffusion, D3, = 7.06 × 10−2exp (‐8600/RT). It has been found that in an argon atmosphere the diffusion coe

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11163.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The mechanism of reaction sintering was studied in mixtures of uranium‐uranium sesquinitride and uranium‐silicon. Refractory uranium mono‐nitride of high density may be prepared by hot pressing mixtures of uranium and uranium sesquinitride at 1000°C. Steps of the process are (1) densification of the uranium metal into a continuous uranium matrix and (2) reaction of the uranium sesquinitride with the uranium matrix. On the contrary, during hot pressing uranium‐silicon mixtures react before any densification of the uranium occurs. The pressing temperature required for a given density is then practically the same as for unreacted powders and the previously formed compound. Densification stages of the prereacted compounds may be described by the equations y = aot2/5+ b0, y = a1log t + b1, and y = a2t−1/2+ b2, where y is the shrinkage and t is the time. The first stage is absent during densification of the powde

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11164.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY