ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1959.tb14075.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

The effect on alkali ion mobility of compositional changes in simple glasses was investigated by observing the dielectric loss behavior in a number of ternary glass systems, formed by adding increasing amounts of various third components to potassia‐silica and soda‐silica base glasses. Oxides of barium, strontium, calcium, cadmium, lead, magnesium, zinc, aluminum, boron, tin, zirconium, titanium, and silicon were introduced. Tan δ values were determined at room temperature and at a frequency of 1 kc. per second. Na+ion mobility was found to be profoundly influenced by the type and amount of third component present. RO oxides decreased tan δ by amounts which appear to bear some relation to the size of the cation introduced. Tan δ curves for the MgO and ZnO series were unique in that each was characterized by a pronounced minimum and maximum. Curves for SnO2, Al2O3, and ZrO2additions passed through a minimum and in the latter two cases rose to tan δ values greater than that of the base glass itself. Curves for the series containing B2O3and TiO2continued to lower values throughout the range of compositions studied. The characteristic shapes of the loss curves are discussed with reference to the roles assumed by the introduced

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1959.tb14076.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Areas of glass formation were determined in the system Li2O‐CaO‐Al2O3‐SiO2at different levels from 0 to 30 weight%CaO. Thermal, chemical, optical, and electrical properties also were determined. Some of the glasses, especially those at the higher CaO levels, may find commercial applic

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1959.tb14077.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Single‐crystal X‐ray and electron‐diffraction studies show the existence in one polymorph of 4CaO.Al2O3. 13H2O of a hexagonal structural element with α= 5.74 a.u.,c= 7.92 a. u. and atomic contents Ca2(OH)7‐ 3H2O. These structural elements are stacked in a complex way and there are probably two or more poly‐types as in SiC or ZnS. Hydrocalumite is closely related to 4CaO.A12O3.13H2O, from which it is derived by substitution of CO32‐for 20H‐+ 3H2O once in every eight structural elements; similar substitutions explain the existence of compounds of the types 3CaO Al2O3.CaY2‐ xH2O and 3CaO Al2O3CaYxH2O. On dehydration, 4CaO.Al2O3.13H2O first loses molecular water and undergoes stacking changes and shrinkage along c. At 150° to 250°C., Ca(OH)2and 4CaO.3Al2O3.3H2O are formed and, by 1000°C., CaO and 12CaO.7Al2O8. The dehydration of hydrocalumite follows a similar course, but no 4CaO.3A

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1959.tb14078.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Chemical and physical analyses have shown that hydrous titanium dioxide, prepared from titanium sulfate solution, consists of flocculates of small anatase crystals. Water and sulfur trioxide appear to be present as adsorbed layers and in capillaries between and within the flocculates. During heating, loss of water occurs at about 150°C., loss of sulfur trioxide at about 650°C., crystallite and particle‐size growth at about 600°C., and the transformation of anatase to rutile in the range 700° to 950°C., depending on the method of preparing the samples. The kinetics of the transformation were found to be first order, following an induction time which appeared to depend on a nucleation process. Activation energies were of the order of 100 kcal. per mole and frequency factors of the order of 1020to 1022hr.‐1. Precision X‐ray diffraction studies showed that the anatase lattice expanded slightly before the transformation and that the initial rutile formed wa

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1959.tb14079.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

An apparatus for obtaining the X‐ray powder diffraction pattern of a sample while its temperature is increasing at a constant controlled rate has been developed. This equipment is described in enough detail to permit duplicate construction. The program controller is continuously sensitive to the sample temperature and controls the amount of power supplied to the sample heater. Complete schematic details of the electronic circuitry are included, and mechanical details of the program generator are illustrated photographically. The dehydration of clays and related minerals is discussed to illustrate the use of this versatile apparatus. The first order diffraction maxima of water‐wet vermiculite and monoionic sodium, calcium, and magnesium montmorillonites are recorded while the sample temperature is increased at the rate of 5°C. per minute. This is then repeated with ethylene glycol substituting for the water. The temperatures of dehydration and of deglycolation depend on the nature of the exchange cation and are shown to increase in the order sodium

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1959.tb14080.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

The effect of firing temperature and time on the weight loss, fired porosity, and dielectric properties of lead metaniobate was investigated. The amount of lead oxide lost was found to be a linear function of firing time and in addition increased rapidly as the firing temperature was increased. Specimens fired for 30 minutes at temperatures below 1275°C. had weight losses of less than 1% based on the amount of available PbO present, whereas specimens fired for the same length of time at temperatures greater than 1275°C. had weight losses up to 3.5%. Both a minimum and a maximum point were found in the fired porosity curve of lead metaniobate in the temperature range 1200° to 1350°C. When firing for 30 minutes, the minimum point occurred at about 1225°C. with a porosity value of 8% and the maximum point at 1300°C. with a porosity of 18%. The effect of porosity and weight loss on the dielectric properties of lead metaniobate is presented. The effect of replacing up to 0.7 mole fraction of the lead ion in lead metaniobate by cadmium was investigated. Cadmium additions lowered the Curie temperature and diluted the ferroelectric properties of lead metani

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1959.tb14081.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

The formation of ferrous iron in the system MgO‐Fe2O3MgFe2O4is of interest in connection with its deleterious effect on the microwave performance of magnesium ferrite, MgFe2O4. The partial reduction of ferric iron in the system at relatively low temperatures is discussed in terms of the preferential diffusion of iron, and its partial stabilization as ferrous iron from lattice energy consideration

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1959.tb14082.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

A study was made of the resistance to thermal fracture of four ceramic coatings of the cobalt‐bearing ground‐coat type applied to enameling‐grade iron specimens. The study was made of coated‐metal systems in the unsteady state, symmetrically cooled, and in the absence of viscous or plastic flow. Determinations were made of the elastic characteristics of the coating‐metal composites, the effective coefficient of linear expansion, the temperature at which the coating and base metal were at dimensional equilibrium, and the temperature differential sufficient to induce coating fracture when water quenched. Coating‐metal thickness ratios were correlated with the maximum specimen temperature withstood in water quenching without coating fracture. Studies indicated that ceramic coatings, after receiving a given thermal treatment, fracture when subjected to a thermal shock by a critical temperature differential. When no residual coating stress is present, thermal shock resistance is inversely related to the thermal expansion characteristics of the coating. The critical stress at which coating fracture occurs may be expressed as the sum of thermal and residual stresses developed in annealed systems in which viscous or plastic flow does not occur. Residual compressive stress in a coating is a major factor in improved thermal shock resistance. Increased thermal shock resistance is gained by decreased coatin

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1959.tb14083.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Europium oxide of 99.7% purity was compacted into small bars and pellets which were fired at temperatures from 1050° to 1700°C. for 2 to 120 hours in atmospheres that were oxidizing, mildly reducing (open furnace), or strongly reducing. It was found that (1) europium oxide compacts fired in oxygen for 2 hours at 1500°C. bad attained a density of 90% of theoretical and were stable in boiling water, (2) compacts fired under mildly reducing conditions at 1500°C. for 2 hours had attained a density of 84% of theoretical and disintegrated in boiling water, and (3) those fired similarly in a hydrogen atmosphere began to fuse at 1500°C. The linear thermal expansion of the compacts fired at 1500°C. in the open furnace was 10.5 x 10‐6in. perin. per°C. between 0° and 1000 °C. and their molar specific heat between 0° and 800°C. was 33.3 cal. Careful investigation of the structural changes occurring in europium oxide with rising temperature revealed that (1) the low‐temperature (body‐centered cubic) form inverts slowly to the high‐temperature form at approximately 1050°C., (2) the high‐temperature form has monoclinic symmetry, and (3) it does not revert readily to the cubic form; its theoretical density was calculated to

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1959.tb14084.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY