Crystal Chemistry of Hydrous Calcium Silicates: I, Substitution of Aluminum in Lattice of Tobermorite

Mixtures of 0.8 moles of CaO per mole of SiO₂ plus Al₂O₃ were prepared from lime, kaolin, and tripoli (microcrystalline quartz); the amounts of SiO₂ to Al₂O₃ were varied to give from 0.2 to 20.7% Al₂O₃ by weight of dry solids. After hydrothermal treatment (170° to 175°C.), the products were examined by differential thermal analysis and by X-ray diffraction. A homogeneous solid identified as the mineral tobermorite (4CaO.5SiO₂.5H₂O) and containing up to 4 or 5% Al₂O₃ was obtained. Increasing the amount of Al₂O₃ in the raw mixture above about 5% resulted in the formation of the hydrogarnet 3CaO.Al₂O₃.SiO₂.4H₂O as a second phase. Allowing for the Al₂O₃ combined in this solid, it was indicated that slightly more Al₂O₃ was substituted in the tobermorite as the amount was increased in the raw mixture. It is suggested that the Al³⁺ ions probably assume tetrahedral coordination when substituting for the Si⁴⁺ ions.     

ACTUARIAL, NAIVE CLINICAL, AND SOPHISTICATED CLINICAL PREDICTION OF PATHOLOGY FROM FIGURE DRAWINGS.

87 PAIRS OF FIGURE DRAWINGS, 37 BY NORMALS AND 50 BY PSYCHIATRIC PATIENTS, WERE GIVEN TO 27 CLINICAL STUDENTS AND 6 EXPERIENCED CLINICIANS, ALONG WITH A COMPLETE ACCOUNT OF THE PERTINENT RESEARCH FINDINGS OF HILER AND NESVIG. SS WERE ASKED TO JUDGE WHETHER THE DRAWINGS WERE NORMAL OR PATHOLOGICAL. THE STUDENTS WERE SUPERIOR TO THE CLINICIANS IN THE TASK, AND 23% OF THEM WERE SUPERIOR TO AN ACTUARIAL FORMULA THAT HAD BEEN CONSTRUCTED PREVIOUSLY. DATA WERE INTERPRETED TO SUPPORT THE RELATIVE SUPERIORITY OF SOPHISTICATED OVER NAIVE CLINICAL PREDICTION AND THE POSSIBILITY THAT IN SOME CIRCUMSTANCE IT MAY BE SUPERIOR TO ACTUARIAL FORMULAS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decorated Dislocations in Magnesia Crystals

Diffusion of iron ions into magnesia single crystals at 1350° C in a moist atmosphere produces a host lattice of magnesiowüstite. Spinel dissolved in the lattice at this temperature precipitates on dislocations during cooling. The precipitates are large enough to be viewed with a transmission microscope. Reheat treatment of the crystals containing decorated dislocations in atmospheres of CO₂-H₂ results in rather gross dendritic voids through the reduction of the ferric ion. Chemically induced vacancies were found to result in the formation of helical and prismatic loop dislocation arrangements typical of vacancy condensation mechanisms. The spacing of rows of prismatic loops was found to be in agreement with the values predicted by the equations of Bullough and Newman if one assumes a critical shear value of 5(10)⁻⁶μ for magnesiowüstite at 1350°C.     

Magnetic Ceramics: I, General Methods of Magnetic Ferrite Preparation

Various methods of preparing the technically important ferrospinels are discussed; particular attention is given to the reactivity and homogeneity of the final mixture. The reactivity and intimacy of mixing of the initial components may be improved by the use of chemical methods of comminution and mixing, viz., thermal decomposition of the mixed chemicals, chemical precipitation of the components, or ignition of the components in a fine state of division. The use of controlled partial pressures of oxygen (CO₂-CO mixtures) for the preparation of magnetite and manganese ferrite is discussed. The feasibility of the application of these methods on a commercial scale is outlined.     

Determination of Biaxial Compressive Strength of a Sintered Alumina Ceramic

The compressive strength of commercial high-density alumina was measured in several compressive biaxial stress states. The compressive strength was only slightly affected by the magnitude of the intermediate principal stress. The average value of the compressive strengths measured in all stress states, excluding the equibiaxial and the near-uniaxial compressive stress states, was 528 ksi. The average of the coefficients of variation was 3%. The tensile strength measured for the material indicates that the ratio of compressive strength to tensile strength is ∼ 18.     

Inhomogeneity-Packing Density Relations in Binary Powders—Experimental Studies

The purpose of this investigation was to determine if the bulk specific volume of inhomogeneous binary powder mixtures, with a large size ratio, corresponds to the theoretical values calculated from known compositional inhomogeneity data. The theoretical calculations are based on the assumption that the body packs according to the Furnas model on a local scale. To minimize the effects of particle geometry, experiments were performed with glass microbeads.     

Magnetic Ceramics: V, Magnetic Properties of Square Loop Ferrites Within the System MgO-MnO-Fe2O3

Thirteen compositions within the center of the system MgO-MnO-Fe₂O₃ were investigated because of their rectangular hysteresis-loop characteristic. Initial permeabilities were measured, and B_m, B_T, H_c , and R_8m were obtained from quasi-static hysteresis loops. High MgO content was found to be detrimental to the magnetic properties and to impair the loop rectangularity. The highest hysteresis-loop squareness ratio, R, _8m , was found in a composition with high Fe₂O3 content, and the lowest coercive force, H_c , was found in a composition with high MnO content.