Journal of the American Ceramic Society

TIEN, T.‐Y.; CARLSON, W. G.

doi: 10.1111/j.1151-2916.1962.tb11060.xpmid: N/A

The effect of additives on the properties of lead titanate was investigated. The additives employed were selected on the basis of potential solid solution or liquid formation with PbTiO3 during sintering. Most of these additives aided sintering and produced dense polycrystalline specimens of PbTiO3 with densities in the range 89 to 95% of theoretical. The dielectric constant and dissipation factor were found to vary considerably, depending on the additive employed. Some poled specimens exhibited a piezoelectric coefficient, d33, as high as 130 × 10−12 coulombs per newton with a dielectric constant of about 160 at room temperature. The microstructure of some of the specimens was also studied and a texture similar to that of barium titanate was observed for those specimens which gave the higher piezoelectric response.

TIEN, T.‐Y.; SUBBARAO, E. C.; HRIZO, J.

doi: 10.1111/j.1151-2916.1962.tb11061.xpmid: N/A

The formation of a complete series of solid solutions in the system PbTiO3‐KNbO3 was established by X‐ray and dielectric studies. The room‐temperature symmetry of the entire system was tetragonal except for compositions containing more than 96 mole % KNbO3, which had orthorhombic symmetry. The axial ratio, c/a, and the ferroelectric Curie temperature decreased from both the end‐members. The lowest Curie temperature observed in the system was 175°C for the composition with 80 mole % KNbO3. A generalization has been made on the variation of ferroelectric Curie temperatures with compositions in binary systems of perovskitetype solid solutions with and without a common cation.

SUCOV, EUGENE W.

doi: 10.1111/j.1151-2916.1962.tb11062.xpmid: N/A

The general method of determining the stress in an infinite half‐plane elastic solid due to indentation by a rigid punch (originated by Sned‐don) is extended to include elastic, deformable indenters by measuring and introducing the equation of the deformed contour. This is an improvement over Hertz's method since, in addition to the elastic constants of the materials, which Hertz used, the deformed contour of the material while under load is available. The mathematics of the method is reviewed, and the tensile stress is calculated for a contour of the form uz(r) = A°+A2r4+A4r2 A description is given of the interferometric technique that was used to measure the indented contour in glass. The results of the calculation show that, for the specific case of a steel ball indenting a glass plate with moderate load, the simple Hertz theory is adequate. Application of this method to other materials and shapes is discussed briefly.

DAY, DELBERT E.; RINDONE, GUY E.

doi: 10.1111/j.1151-2916.1962.tb11063.xpmid: N/A

An X‐ray fluorescence technique has been used to study the coordination number of the aluminum ions in soda aluminosilicate glasses. The fact that the emission wavelength of the Kα line of aluminum is slightly different for aluminum ions in different coordination states is utilized in this technique. Using this small difference in wavelength, it is shown that, depending on the Al/Na ratio, the soda aluminosilicate glasses contain aluminum ions in either fourfold and/or sixfold coordination. The X‐ray fluorescence measurements are shown to support the structural model which has been proposed for the soda aluminosilicate glasses to explain the behavior of some of their physical properties.

RAHN, H. N.; MAYER, E. H.; FRAME, J. W.

doi: 10.1111/j.1151-2916.1962.tb11064.xpmid: N/A

Changes in residual alloy concentration, particularly increases in copper and nickel, which take place in pickling were found to be due to the formation of a pickling film through galvanic plating of these elements dissolved in the acid. Before pickling, the steel surface was actually higher in copper and nickel than was the interior, owing to preferential oxidation of iron during mill processing. Pickling film buildup (such as surface copper) was found to have no direct telation to adherence. Slow pickling steels, however, on which adherence was less easily obtained, built up more copper on the surface; hence, an apparent correlation existed. Fast pickling steels, which gave good adherence with less metal removal than was required for slow pickling steels, showed much more surface roughening for the same amount of metal removal. This increased roughening is felt to be a contributing factor toward good direct‐on adherence.

SCOTT, WILLIAM D.

doi: 10.1111/j.1151-2916.1962.tb11065.xpmid: N/A

A modified Bridgman‐Stockbarger method was used to grow single crystals of MgF2 weighing about 200 g. The purity of the charge material was critical. Purification was achieved by first drying technical‐grade MgF2 and then vaporizing in vacuum. Spectral transmission of the single crystals was measured; in comparison with CaF2, MgF2 was slightly less transparent in the infrared region and had about the same transparency in the ultraviolet region. Modulus‐of‐rupture values were also obtained in several orientations. No plastic flow was observed.

PHILLIPS, BERT; MUAN, ARNULF

doi: 10.1111/j.1151-2916.1962.tb11066.xpmid: N/A

Equilibrium relations in isothermal sections through the system MgO‐FeO‐Fe2O3 have been determined in the temperature range 1400° to 1800°C. Oxide mixtures prepared from reagent‐grade chemicals were equilibrated and subsequently quenched to room temperature while sealed in 80Pt20Rh tubes. The data obtained for the isothermal sections are used to infer equilibrium relations existing along the liquidus surface of the system.

PASK, JOSEPH A.; FULRATH, RICHARD M.

doi: 10.1111/j.1151-2916.1962.tb11067.xpmid: N/A

The sessile‐drop method for the evaluation of wetting is discussed in terms of forces acting on the liquid drop. For acute angles, or wetting of the solid, the driving force is the lowering of the solid‐gas surface energy by the liquid. Contact angles of approximately 25° and less, obtained under appropriate conditions, appear to be associated with interfacial conditions that lead to the development of a strong chemical bond (an interchange or sharing of electrons) and to good adherence. A theory is proposed whereby chemical bonding depends on the development of a balance of bond energies across the metal‐glass interface. The factors that lead to this condition are discussed. A modified Dupre's equation to take into account a strain factor and a contact coefficient is developed. Bonding of Na2Si2O5 molten glass to platinum, gold, and iron and oxidized iron in several atmospheres is discussed.

CHESSIN, HENRY; TURKDOGAN, E. T.

doi: 10.1111/j.1151-2916.1962.tb11068.xpmid: N/A

Calcium diferrite has been prepared at 1220°C in air. The lattice constants at 25° C of calcium diferrite have been determined by X‐ray powder data and have been based on the hexagonal system. They are a= 5.992 ± 0.004 A and co = 31.121 ± 0.008 A. The coefficients of thermal expansion were evaluated by X‐ray methods between‐130° and 25°C to be α1= 9.2 × 10−6 per°C and 3= 23 × lop6 per °C, where a3 is along the principal axis and α is perpendicular to it. The diferrite is ferromagnetic with a Curie point of 135°C. Comparison of the results obtained from the present work with those of some recent studies shows that the X‐ray data given by previous workers on compounds claimed to be Ca3FeleO15, Ca4Fe17O29, and Ca4Fe4O25 are for calcium diferrite. The present work, however, also indicates that when mixtures of calcium diferrite plus ferrous oxide (up to 6 wt%) are heat‐treated at 1220°C, a new phase appears together with the diferrite.

SEGNIT, E. R.

doi: 10.1111/j.1151-2916.1962.tb11069.xpmid: N/A

Equilibrium relations in part of the quaternary system CaO‐ZnO‐Al2O3‐SiO2 have been investigated by the quenching method. Liquidus surfaces and primary‐phase fields have been determined in planes containing respectively 8, 10, and 15% A12O3, as well as six quaternary invariant points. The minimum melting point in the system is 1030°± 5°C at a composition of 18.5% CaO, 22.5% ZnO, 8.2% A12O3, and 50.8% SiO2,. At this point the condensed phases in equilibrium are tridymite, willemite, melilite, anorthite, and liquid. The results have a bearing on reactions occurring in lead blast‐furnace slags, in some ceramic glazes, and in certain zinc‐bearing rocks and ores.