摘要:

The pressure gradient naturally effected across the cake on pressure casting can lead to pore‐character gradients and dimensional distortion if the cake is significantly compressible. The compressibilities of cakes formed on pressure slip casting of aqueous Al2O3slips defiocculated with an organic polyelectrolyte were determined for applied pressures ≤500 psi. In general the compressibility decreased with increasing pressure. Improved deflocculation of slips from which cakes were formed drastically reduced the level and pressure dependence of compressibility; cakes cast from well‐deflocculated slips were insignificantly compressible. Specific resistances determined concurrently agreed well with results obtained previously in kinetic studies. Compression‐permeability behavior can serve as a quality control test for the slip casting of technical c

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb11317.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The kinetics of the initial‐stage sintering of a UO2powder in H, were investigated over the range 600° to 1200°C by dilatometry. Decreasing green density below #40% of theoretical leads to progressively reduced rates of sintering. Initiation of the effect is related to a critical value of the ratio of pore size to particle size at which pores become stabilized and inhibit local shrinkage. Green density did not affect the sintering law or the apparent activation energy for sintering. A constant apparent activation energy for sintering of 86±8 kcal/mol was found, indicating that diffusion of the same species is rate‐controlling over this temperature range. Above 900°C, the rate‐controlling mechanism is consistent with grain‐boundary diffusion of the u

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb11318.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Nonisothermal techniques for analyzing initial‐stage sintering are reviewed. It is shown that in principle they permit the determination of all the sintering parameters (rate law, activation energy, and diffusion coefficients) normally obtained from isothermal experiments. Comparison with results from isothermal experiments performed on the same materials (UO2and ThO2gel) demonstrates the validity and accuracy of the nonisothermal technique

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb11319.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Stoichiometric NiAl2O4, CuAl2O4, and ZnAl2O4spinels were prepared and equilibrated at temperatures from 600° to 1400°C. The parametersuandx, denoting the oxygen position and fraction of divalent cations on tetrahedral sites, respectively, were determined from a detailed X‐ray diffraction analysis. In NiAl2O4,xincreased from 0.07 at 595° to 0.26 at 1391°C; in CuAl2O4,xdecreased from 0.68 at 613° to 0.64 at 1195°C; and in ZnAl2O4,xdecreased from 0.96 at 905° to 0.94 at 1197°C. The form of the temperature dependence ofxcould not be described using theoretically based equations advanced in the literature. A more general equation which allows for a non‐distributional contribution to the configurational entropy was derived and observed to properly describe the temperature dependence; the results indicate that short‐range order is of definite significance in these intermediate alum

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb11320.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The thermodynamics of a water‐vapor‐E‐glass system were studied by adsorption‐isotherm analysis. The seven isotherms completed were Brunauer type IV with permanent hysteresis. The first adsorbed water layer could not be removed by pumping, indicating permanent hydrolysis. Application of heat removed the remaining water to close the hysteresis loop. Calculation of isosteric heat of adsorption indicates that the adsorbed state is between the solid and the liquid states, equivalent to the loss of one vibrational and one translational degree of freedom. A new plot of energy vs thickness is proposed which describes the adsorption independent of surface area, as contrasted to the usual energy‐vs‐volume plot which was found to depend on surface area. A modified Clausius‐Clapeyron equation is proposed for computing the isosteric heat

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb11321.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The amorphous salicylate‐bearing product precipitated when C3A and related compounds are placed in contact with salicylic acid in aqueous solution and the residual contents of the solutions were examined by ir spectroscopy. Comparison with spectra of several aluminosalicylate complexes and crystalline aluminosalicylic acid indicated that the amorphous product is a hydroxylated chelate complex designated as Al(sal)OH, precipitated over a period of time from the cationic aluminosalicylate complex Al(sal)+, which is formed rapidly in solutio

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb11322.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Using X‐ray diffraction techniques, thermal expansion and compressibility were measured on the orthorhombic compounds HfTiO4, Hf1.26Ti0.74O4, and ZrTiO4(both quenched and cooled slowly from 1300°C). The thermal expansion of HfTiO4is highly anisotropic; the thermal expansion coefficients along the crystallographic axes are αa=+(8.7±0.5)×10−6°C−1, αb=−(5.2±0.5)×10−6°C−1, and αc=+ (5.3±0.5)×10−6°C−1. The thermal expansion of Hf1.26Ti0.74O4was similar to that of HfTiO4but that of ZrTiO4was markedly less anisotropic. The compressibilities of HfTiO4and ZrTiO4also differed markedly. All compounds investigated, however, behaved similarly in exhibiting a polymorphic transition to a high‐pressure phase having the monoclinic baddeleyite (ZrO2) structure. The polymorphism can be explained qualitatively on

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb11323.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The kinetics of reduction of 0.2 mol of –70?mesh quartz particles by 0.2 mol of graphite were determined in a batch reactor between 0.25 and 10−0torr. The effects of temperature, CO partial pressure, SiO2phase transformation, and alkali and alkaline‐earth oxide additives on the rate of reaction were studied. Increasing CO overpressure retarded carbothermal reduction. At 1400−C, addition of 5 wt% alkali oxide inhibited the reaction, whereas the same amount of alkaline‐earth oxide decreased the induction time; CaO was the best promoter. The initial reaction rate obeyed the cubic power law of nucleation growth at weight losses<15%, with an apparent activation energy of 77 kcal/mol. At higher weight losses, the Austin‐Rickett equation with an exponent near 2 was more applicable. The results are consistent with a model based on a transitory phase i

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb11324.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Experimentally determined coefficients to describe multicomponent diffusion in the system K2O‐SrO‐SiO2are compared with predictions of a simple model assuming ideal solution behavior. The agreement is satisfactory overall. On the basis of this model, it is suggested that the differences in mobilities of various ions cause deviations from the condition ΣZ4j4=0 (Z=valence,j=flux) of no space‐charge buildup. Although these deviations are small, e.g. after diffusion for 1 s, (charge flux)/(ionic flux) ≤ 10−7, the electric field caused by this deviation from electrical neutrality influences the diffusion kinetic

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb11325.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The effect of secondary phase separation on the apparent volume fraction of second phase was examined in the immiscible region of the PbO‐B2A3system. The volume fraction, V2, of the PbO‐rich phase agreed well with theoretical expressions relatingV2to density and composition, except for 0.2

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1972.tb11326.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY