ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11167.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The phase diagram for the system Bi2O3‐B2O3has been determined experimentally. The melting point of Bi2O3has been redetermined as 825° C with an estimated overall uncertainty of about ±3°C, and the molal heat of fusion of Bi2O3, calculated from the slope of the liquidus curve, is 2050 cal per mole. The system contains a body‐centered cubic phase of approximate composition 12Bi2O3·B2O3, which melts incongruently at 632°C. Four congruently melting compounds exist in the system: 2Bi2O3· B2O3·5B2O3, Bi2O3·3B2O3, and Bi2O3·4B2O3, with melting points, respectively, of 675°, 722°, 708°, and 715°C. The Bi2O3·4B2O3compound exhibits a sluggish transformation at 696°C. Compositions containing up to 97.5 wt% (85 mole %) Bi2O3can be partly or totally quenched to glass. Indices of the quenched glasses are greater than 1.74. A region of liquid immiscibility extends at 709°C from almost pure B2O3to 19.0 mole % Bi2O3. The extent of immiscibility theoretically calculated agrees with the experimentally determined value when 1.20 A is used for the i

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11168.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Particle‐size fractions of several Georgia kaolins, which were prepared by sedimentation procedures, were examined from the standpoint of crystallinity, cation‐exchange capacity, and surface area. Crystallinity was studied using X‐ray techniques, exchange capacities were measured using the manganese saturation method, and surface areas were determined using glycerol adsorption techniques. A linear relation was obtained between surface areas and exchange capacities when areas were increased by decreasing the particle size or by changing from well‐crystallized to poorly crystallized kaolins. In most cases, the empirically determined crystallinity ratios indicated a change in crystallinity with change in particle size, the crystallinity generally increasing with decreasing particle size in individual samples. Unlike, however, the relation noted for exchange, the crystallinity did not consistently correlate with area changes both among the various samples and within the various particle‐size fractions of a single sample. These results suggest that the relatively high cation‐exchange capacity of poorly ordered kaolins is more directly a result of high surface area with crystallinity playing, at most, a very

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11169.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

A technique has been developed for growing un‐fractured calcium titanate boules up to 25 mm long and 12 mm in diameter by flame fusion. Large untwinned sin.gle crystals have been prepared from which optical properties, density, hardness, dielectric constant, and melting point have been determine

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11170.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Equilibrium data at liquidus temperatures are presented for compositions in the quaternary system Y‐Gd‐Fe‐O in ambient atmospheres of oxygen gas (pO2, = 760 mm Hg), air (PO2, = 159 mm Hg), and CO2(pO2variable). Incongruent melting occurred in yttrium‐iron and gadolinium‐iron garnet phases and in all intermediate garnet solid solutions in the three oxygen pressure sections studied. Fractionation in the yttrium/gadolinium ratio between oxide liquid and crystalline garnet phases in the quaternary system was not observed experimentally, indicating that unzoned (Y,Gd)3Fe5O12crystals may be grown from a melt without special precautions to maintain a fixed Y

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11171.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Cubic ZrO2can be formed at 1500°C from tetragonal ZrO2and transition metals of groups V and VI or their monoxides only in the presence of TiO2. The 1500° isotherm of the pseudo‐ternary system ZrO2‐TiO2‐VO was investigated and the extent of the single‐phase cubic ZrO2region was determined. In the system Ta‐Ta2O5the lower oxides cannot be formed by reacting Ta and Ta2O5between 1450

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11172.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Observations of sphere‐to‐plate bonding of vacuum‐reduced monocrystalline rutile have been carried out over the temperature range 1200° to 1275°C. The rate law governing the interfacial growth between sphere and plate indicates that the predominant mechanism of material transport in this sintering process is volume diffusion. In the light of the reasonably satisfactory agreement between the oxygen self‐diffusion coefficients calculated from the present sintering data and those directly observed by Haul and Just utilizing an isotopic exchange technique, it is likely that oxygen ion diffusion is the rate‐determining step in the sintering experiment

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11173.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Forty‐mesh uranium carbide powders were hot‐pressed in the temperature range 500° to 1500° C under pressures varying from 10,000 to 46,000 atm. Microstructural investigations of the compacts revealed grain‐boundary sliding and fragmentation as important sintering mec

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11174.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Characteristics of temperature and field‐induced ferroelectric‐antiferroelectric phase transitions are reported as a function of composition. The ferroelectric compositions were found to exhibit remanent polarizations of the order of 30 μcoul per cm2, coupled with low dielectric constants and piezoelectric response. Evidence is presented for the existence of a polymorphic transition in the ferroelectric rhombohedral region of the system PbZrO3‐PbTiO3and the existing phase diagram modified accor

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11175.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

The role of cerium in the suppression of gamma‐ray induced coloration in glass has been found to depend on the relative concentration of Ce3+to Ce4+ions as well as on the total cerium content. In a borate glass having high ultraviolet transmission, it has been found that both Ce3+and Ce4+ions are necessary to suppress the optical absorption bands induced in the visible region. The role of cerium can be explained on the basis of a change in its oxidation state as a result of gamma irradiation. It is postulated that the cerous ions, by the reaction Ce3+→ Ce4++e, suppress the induced visible band at 2.36 ev (525 mμ), which may result from positive hole centers. High cerous ion concentration results, however, in an induced center (Ce3++e) which absorbs in the visible at about 1.9 ev (650 mμ). The presence of Ce4+ions near Ce3+prevents the formation of this center possibly by the reaction Ce4++e→ Ce3+. These induced opposite changes in the oxidation state of cerium tend to maintain a balance in the ratio of Ce3+to Ce4+ions in the glass during irradiation, and the suppression of the visible bands depends on thi

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1962.tb11176.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY