摘要:

An empirical extension of conformal ionic solution theory is presented which describes the solution behavior of a class of reciprocal molten salt systems, the A+qA, B+qB∥C‐qC, D‐qDcharge‐asymmetric systems. The thermodynamic properties of such ternary systems can be calculated from data on the standard free energy change for the metathetical reaction between the 4 pure constituents and solution data on the 4 binary subsystems. Calculated liquidus phase diagrams for the systems Na,Sr∥Cl,NO3; Na,Ba∥Cl,NO3; Li,K∥Cl,CrO4; Li,K∥Br,CrO4; and Na,Ca∥F,Cl agree well with measurements within experimental uncertainties. These systems are illustrative of a wide range of values of the thermodynamic quantities used in the calculations. The equations developed should prove useful as a test of the self‐consistency of reported phase diagrams, as a means of calculating Liquidus temperatures in experimentally inaccessible regions, and as an aid in constructing phase diagrams from a minimum num

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1975.tb18968.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Oxidation on the 2 crystal faces of SiC platelets was studied. The oxidation of the C face followed a simple parabolic law and was oxide‐diffusion controlled, whereas that of the opposite crystal face exhibited a linear growth rate which was surface‐reaction controlled. Previous investigators, who studied the oxidation of Sic by measuring weight change, found that the oxidation rate follows a simple parabolic law. At high temperatures and long reaction times, there is an increase in the oxidation rate which has previously been attributed to a change in the state of the oxide. The present investigation, however, indicates that this change occurs as the linear oxidation rate becomes domin

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1975.tb18969.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Isothermal sintering experiments were combined with measurements of crystallite size distribution and BET surface area in a study of the sintering mechanisms in thoria gel. The results suggest that crystallites in the gel have a coordination number of ∼5 and sinter together by a grain‐boundary diffusion mechan

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1975.tb18970.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The failure strengths of soda‐lime glass rods exposed to 9 liquids with polarities from 30.9 to 63.1 kcal/mol were determined experimentally in flexure. The fracture strength clearly decreased with increasing polarity. The necessity of maintaining a high degree of purity in the environmental fluids to obtain meaningful results was illustrated by tests in which controlled amounts of a highly polar liquid (methanol) were introduced into puren‐hexane. Traces as small as 0.004% reduced the strength significantly whereas a 0.05% addition reduced it to that in pure metha

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1975.tb18971.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The high‐temperature chemical stability of hot‐pressed Si3N4was studied between 600° and 1450°C. Reactions were followed by X‐ray diffraction and scanning electron microscopy. In air, this material begins to oxidize at 700° to 750°C; a distinct amorphous siO2surface layer results after 24 h at 750°C‐Concomitant formation of cristobalite occurs, depending on exposure time, and is enhanced as temperature is Increased. Magnesium and calcium magnesium silicates form above 1000°C. The data suggest that impurities, e.g. Mg, Ca, and Fe, greatly lower the oxidation resistance o

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1975.tb18972.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The disappearing‐phase method was used to determine the extent of the solid‐solution region of the PLZT system for conventionally sintered ceramics prepared at 1100° and 1300°C in a PbO atmosphere provided by pbZrO3. A decrease in the firing temperature from 1300° to 1100°C lowers the solubility limit by 5 to 8 at.% La. Beyond the limits of solubility, additional La forms La2Zr2O7and/or La2Ti2O7. The limit determined by the disappearing‐phase method (1300°C firing) is compared to values determined by the parametric method. The Curie temperature is stabilized at 5 at.% La for modified PbZrO3(1300

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1975.tb18973.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The conductivity of thin poly crystalline Sn oxide films prepared by spraying solutions of Sn(IV) compounds onto glass or quartz substrates was studied. Conductivity was decreased by increasing the temperature or prolonging the time of heating after hydrolysis, by substituting SnBr4for SnCl4, and by substituting O2for N2during spraying. These effects are explained in terms of nonstoichiometry of the sample and the presence of residual halogens in the crystal lattice as detected by ion‐probe analysi

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1975.tb18974.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Changes in the dimensions and heat content of hydrated cement specimens were determined as a function of temperature and concentration of deicing agent in cooling‐warming cycles between +15° and ‐ 70°C. The concentration of the polar deicer (NaCl) solution varied from 0 to 26% and that of the nonpolar (urea) solution from 0 to 40%. TheW/Cratios were 0.4,0.6, and 0.8 plain and 0.5 air‐entrained. Experiments were also conducted to clarify the effect of cooling rate and sample size. The observations can be explained by the mechanism previously proposed for phase transitions of adsorbates. In the presence of salts, freezing and melting of liquid exuded from the pores on cooling proceed according to the bulk phase diagram, producing double peaks in the thermograms except at extreme concentrations. The detrimental effect of deicers is attributed mainly to the high degree of saturation, a consequence of the low vapor pressure of the solutions. A beneficial aspect is the widening of the temperature range in which transitions occur. These opposing effects result in the worst conditions at a low deicer concentration (5% NaCl) and optimum conditions at a moderately high concentration (13% NaCl). Since the effect of deicers is physical, it should be common to all chemicals. Air entrainment, although beneficial in most circumstances, can be detrimental. The best protection against “salt scaling” appears to be reduction

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1975.tb18975.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Polycrystalline Al2O3fabricated into plates or shapes by hot‐working techniques exhibits high in‐line transmittance from 0.4 to 5.5 μm. Examination of the product by an inverse pole figure technique demonstrated a strong {0001} texture normal to the pressing direction for both equiaxed and textured microstructures. The crystallographic texture was attributed to the dominance of basal slip in deformation. A comparison of transmissivity in the 2 principal directions of a forged plate strongly suggested that a reduction of birefringence resulting from the crystallographic texture was partially responsible for the high transmissivity. The absorption coefficient at 4.5 μm was 0.15 mm‐1, ∼ that for sintered Al2O3and 5 times that fo

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1975.tb18976.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Powdered premelted end‐member glasses were mixed in equimolar quantities to yield the composition 0.5Li2O· 0.5K2O·2SiO2. The pristine strength of glass rods drawn from melts of this mixture showed the same relation to melting history and to microphase size as that of the glass melted from batch as reported in Part I of this paper. No conclusive differences in strength were found when alkali nitrates were used instead of alkali carbonates. Bubbling dry O2into the melt increased the strength, as did melting in dry O2, but much more rapidly. Although bubbling with dry Ar increased the strength rapidly at first, a very drastic and sharp decrease follo

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1975.tb18977.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY