ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12322.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

MgO powder containing 0, 3, 5, and 10% attached H2O was hot‐pressed at 1150°C and 4000 psi. An enhanced densification rate was observed initially in the water‐containing powders, the degree of enhancement being proportional to the water percentage. Water vapor retarded the final stages of densification. Densification differences were noted between the as‐received material (5% H2O) and the “dry” powder + brucite mixtures (3 and 10% H2O). Weight loss determinations associated these differences with the dehydration characteristics of the as‐received powder and brucite. Initial enhancement was associated with “fluidized bed” particle rearrangement and final retardation with trapped water‐vapor back pressure. A final back pressure value of 1500 psi was calculated based on current h

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12323.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Clear glasses form in the system Ag2O‐B2O3up to about 35 mol% (65 wt%) Ag2O. Infrared absorption, thermal expansion, and density data indicated an analogy to the Na2O‐B2O3system. Pentaborate‐triborate group pairs appear to be formed on addition of Ag2O to B2O3up to 20 mol% Ag2O and diborate groups from 20 to 33 mol% Ag2O. This interpretation is supported by the comparison of the infrared absorption spectra of quenched and crystallized glasses. One crystallization product, Ag2O‐4B2O3, was identified previously. A new compound starts to appear at 28 mol% Ag2O. The theory that silver is generally present as a network modifier like sodium was substantiated by the comparison of the molar volume of sodium and silver borate glasses. Above 27 mol% Ag2O some atomic silver is assumed to be present; below 15 mol%, exploratory studies indicate a two‐phase structure within an immiscibility gap. A low‐temperature internal friction peak in the glasses up to 28 mol% Ag2O corresponds to the alkali peak in other glasses; a high temperature peak appearing in the 34 mol% Ag2O glass is associated with the appearance of nonbridging oxygen in

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12324.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

According to Zisman and co‐workers, in organic systems the cosine of the contact angle of a sessile drop increases with the decreasing surface tension of the drop at room temperature. The applicability of the Zisman relation to liquid metal‐ceramic systems is discussed using the systems (Al‐Mg)/graphite and (Cu‐O)/sapphire. Also discussed is the significance of the critical surface tension for spreading, γc, in the systems where the surface tension of the liquid is greater than that of the solid substrate; γcis 230 dynes/cm for graphite at 720°C and 440 dynes/cm for sapphire

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12325.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Using the method of interfacial angle equilibrium in the system UO2‐Ni, a surface energy of 754±150 ergs/cm2was determined for UO2.01at 1500°C in high‐purity Ar. The absolute interfacial energies in the system UO2‐Ni at 1500°C were also de

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12326.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The double‐cantilever‐beam technique was used to determine the effects of varying 6 factors related to specimen preparation, size, and testing conditions on the fracture toughness of polycrystalline Al2O3. Experimental design and statistical factor analysis techniques were used to investigate each factor at two levels. Direct fracture surface replication and electron microscopy provided supporting information about the fracture mode and fracture surface features for each test condition. The fracture toughness of Al2O3was higher for 30‐μm grain size than for 10‐μm grain size. Pretest annealing (900°C) and specimen width were both significant factors for 10‐μm Al2O3. The effects of variations of beam width, beam height, and test machine speed were masked by data scatter and are being studied further. The ratio of specimen width to fracture web width caused no effect in the range studied. The sensitivity of the test results to sample dimensions and surface finish is small enough that special care in cutting and measuring of samples is

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12327.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Coatings were deposited on Cu0, Ni0, and Al0anodes from aqueous solutions of NaAlO2and Na2SiO3by anodic spark deposition. Some coatings formed at constant current density (1.0 A/cm2) were characterized by scanning electron microscopy, electron beam microprobe analysis, X‐ray diffraction, and emission spectroscopy. A relation for the current decay during a multiple‐spark, constant‐voltage process was determined. This relation, which describes the behavior of most of the systems studied, iswhere φt, φ0, and φ∞are the current densities at timet, at the start of the decay (t=0), and at the steady state, respectively.Kis a constant that is voltage and system

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12328.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Uranium mononitride was studied in an automatic recording balance‐furnace system capable of high vacuum or precisely controlled gas pressure. The decomposition pressure of U2N3, which was measured at 1483° and 1607°K, agreed with values in the literature. Uranium sesquinitride compositions were substoichiometric at the U‐rich boundary, with compositions of UN1.48±0.01at 1483°K and 130 torr N2and UN1.45±0.01at 1607°K and 700 torr N2. UN has very narrow composition limits (UN0.995to UN0.997) from 1100° to 2450°K at N2pressures below 700 torr. In vacuum at 1538°K, the composition is UN0.9954±0.0001. Vaporization rates for single‐phase UN were studied by the Knudsen and Langmuir methods using temperatures from 1900° to 2860°K and N2pressures from 10‐4to 130 torr. The enthalpy of vaporization (ΔH°298) for the reaction UN(s) =U(g)+1/2N2(g) was 199±1 kcal/mol at 10‐3to 1.0 torr N2. The Langmuir data indicated an evaporation coefficient of 0.3 for U from 10‐4to 1.0 torr N2. A UN pellet (99.0% of theoretical density) was tested for spalling and cracking by repeated cycling between the UN and U2N3phase regions at 130 torr N2. At 1131°K, the nitriding rate to form U2N3was 5.2×10‐3mg/min‐cm2in 130 torr N2. After extensive nitriding and denitriding (19 cycles for times to 69 h), the bulk volume expansion of the pellet was 8.5%. The surface was not friable or powdery and the overal

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12329.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

An X‐radiographic technique was developed to obtain profiles of molten ceramic menisci and pendant drops sealed in molybdenum or tungsten capsules. The surface tension for Al2O3was calculated from the shape of the drops or menisci. Molybdenum capsules lowered the surface tension value. The density was 3.01 g/cm8at the melting poin

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12330.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The effect of impurities on the color of dense flint glass was investigated by comparing the optical absorption caused by cations in Na2O·3SiO2·2PbO glass, in Na2O·3SiO2·2PbO:1 wt% Sb2O3glass, and in Na2O·3SiO2glass; all three are colorless when of high purity. Of 11 colorants, only vanadium colored both lead glasses less intensely than the Na2O·3SiO2glass. Factors that make the lead glass more susceptible to coloration are higher oxidation states of polyvalent cations, larger absorption cross sections of polyvalent cations, and the tendency of prominent absorption bands to be closer to the wavelength at which eye sensitivity is a ma

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12331.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY