ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13317.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

It is proposed as a working hypothesis that the many so‐called microplastic effects produced by pressure of hard, sharp points on glasses do not occur by plastic flow, but by densification. An interferometric technique is illustrated, by means of which the existence of densification can readily be demonstrated and its magnitude estimated. It is concluded that the “hardness” number of glasses is best interpreted as a measure of the critical stress for yield by densification; that the hardness number has no necessary relation to tensile strength; and that the technology of glass cutting is dependent on residual stresses associated with densific

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13318.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Initial sintering equations are shown to depend as much on possible particle shape variations in powder systems as on the mechanism of material transport. Also, competing mechanisms, such as surface diffusion, may alter the generally assumed relations between neck growth and shrinkage and so may affect the sintering kinetics. When shrinkage occurs by volume diffusion, both effects may be overcome by measuring the size of the interparticle boundary as well as the shrinkage during sintering. When grain boundary diffusion is the mechanism of shrinkage, both the cross‐sectional area and the radius of curvature of the neck must be measured during sintering. The usefulness of simultaneous measurements of neck growth and shrinkage is demonstrated with literature data for coppe

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13319.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

The range of existence of the cubic phase in the system CaO‐ZrO2was determined at temperatures from 1300° to 1700°C, using the lattice parameter method. This technique could not be used at higher temperatures because of anomalous changes in the lattice parameter. The possibility of the existence of a compound, CaZr4O9, occurring at 20 mole % CaO, was inferred from X‐ray data. The (hypothesized) compound appeared to undergo a phase transformation at about 1650°C. The cubic field was widened when CaCO2was substituted for CaO as a reagent, probably because of the formation of an intermediate active oxide. This widening of the field may shed light on some of the discrepancies in the lite

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13320.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Hot‐pressed magnesium oxide was deformed in compression at stresses from 1000 to 6500 psi and at temperatures from 1200° to 1500°C. Steady state creep rates from 0.001 to 0.8%/hr were measured. The thermal activation energy was 105 ± 12 or 111 ± 12 kcal/mole, depending on the method of stress compensation used. A power law analysis for stress gave an exponent of 2.6 ± 0.6, and a stress activation analysis yielded a constant of (7.6 ± 1.4) × 10‐4psi‐1. The statistical significance of all the constants is high. Deformations as large as 40% occurred, and no change in grain shape was detected. None of the available models for creep mechanisms are completely applicable to t

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13321.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Diffusion of radioactive133Xe in single crystals of CsI was measured using two techniques for introducing Xe: a homogeneous doping method in which133Xe was introduced through the decay of homogeneously distributed133I, and a recoil doping technique in which133Xe was recoiled into the specimen from an external fissionable source. The results for both techniques were consistent with a classical diffusion model and with each other. The diffusion coefficient was given by:whereD0= 0.57 ± 2.30 cm2/sec, andQ= 1.01 ± 0.04 ev. The results show that classical gas diffusion applies in simple systems under ideal conditions, in contrast to the complex behavior frequently observed in fission gas diffusion studies with nuclear reactor fuels. The results also show that the recoil doping method may be a valid technique for the study of rare gas diffusion in nonfissionable solids, and that diffusion does not appear to be enhanced along the fission fragment trac

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13322.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

The eutectic and solidus temperatures of the PbTiO3‐KF binary system were investigated by DTA for four compositions. Optical studies of crystal habit as a function of crystallization conditions were used to determine favorable conditions for growing PbTiO3crystals from a KF flux. Results of X‐ray studies of these crystals agree closely with those of earlier studies. Interferometric measurements of thermal expansion confirmed the ferroelectric transition at 490° C. Specific heat studies indicated a transition energy of about 1550 cal/mole with an entropy change of 2.055 cal/mole °C. Spontaneous polarization was calculated as 66 μcoulom

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13323.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Contact angles of aluminum drops on sapphire measured under vacuum conditions from 660° to 1250°C generally fell into three ranges. Large obtuse contact angles indicating interfacial energies greater than either of the two surface energies were obtained up to about 900°C; van der Waals bonding then existed at a compound interface. In the intermediate range, contact angles were 90° or slightly greater indicating a common interface with an energy,sγl, greater thansγgbut less than lγg. Acute contact angles indicating asγlless thansγgand greater thanlγgoccurred above about 950°C because of the formation of a high temperature complex surface structure withsγg>lγg. A hydroxylated sapphire surface has a lowersγgwhich increases with gradual dehydroxylation and conversion to the high temperature surface structure with a corresponding change in contact angle through the three ranges. Chemical bonding existed in the latter two ranges. Reactions occurred between Al and the sapphire surface to form volatile species at contact angles less than 90°. Molten Al normally has an oxide coating the effect of which appears to be removed a

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13324.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Mass spectrometric investigations of the high temperature equilibrium vapor species over the solids Li2SO4, Na2SO4, K2SO4, Rb2SO4, and Cs2SO4have shown that the products of thermal decomposition are M(g), where M = Li, Na, K, Rb, or Cs, SO2(g), and O2(g). In addition, molecules like K2SO4(g), Rb2SO4(g), and Cs2SO4(g) were observed, and the results show that sublimation as molecules becomes increasingly important for the heavier alkali metal sulfates. The equilibrium constants at several temperatures and heats for the decomposition reactionwere determined for Li2SO4, Na2SO4, and K2SO4. Calculated values of the heats of decomposition for Na2SO4and K2SO4, for which thermodynamic data are available, were in agreement with the measured quantities. The heats and entropies of sublimation to monomeric molecules for K2SO4(s), Rb2SO4(s), and Cs2SO4(s) were ΔH02,1154°K= 72.8 ± 2.0 kcal mole‐1and ΔS0S1554°K= 29.2 ± 1.8 eu; ΔH0S,1123°K= 69.7 ± 1.0 kcal mole‐1and ΔS0S, 1123°K= 27.4 ± 0.8 eu; and ΔH0S, 1081°K= 63.9 ± 1.7 kcal mole‐1and ΔS0S, 1081°K= 26.2

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13325.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

The TiO2‐rich side of the system PbO‐TiO2was investigated by X‐ray diffraction techniques, and a new compound PbTi3O7was found. It has a bimolecular monoclinic unit Cell witha= 10.732 A,b= 3.812 A, c = 6.578 A, and β= 98° 05′. The PbTi3O7decomposes into PbTiOsand rutile at temperatures above 850°C. The overall decomposition proceeds according to first‐order kinetics with an apparent activation energy of about 170

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13326.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY