Effect of Ratio of Surface Area to Volume on Oxygen Self-Diffusion Coefficients Determined for Crushed MgO-Al2O3 Spinels

Oxygen self-diffusion coefficients for single-crystal MgO-Al₂O₃ spinels previously determined for crushed particles were recalculated using the microscopic suface area of the sample, as was done for alumina. The corrected results agree well with those of Reddy and Cooper .     

Preparation and characterization of stable dispersions of carbon black and nanodiamond in culture medium for in vitro toxicity assessment

Stable dispersions of carbon black and nanodiamond in culture medium were prepared by adding a pre-mixed dispersion of commercial carbon black or nanodiamond in aqueous bovine serum albumin (BSA) solution to culture medium. Dynamic light scattering revealed that carbon black and nanodiamond dispersions prepared in both NaCl solution and culture medium were highly stable. From DLVO theory and the results of zeta potential measurements, the theoretical effect of the electrostatic interactions between adsorbed BSA molecules was found to be minimal. The asymmetric flow field-flow fractionation measurements revealed that 0.05 or 0.56 mg/mL of BSA molecules were adsorbed on 0.11 or 1.09 mg/mL of carbon black, respectively, indicating 1:2 complexation of BSA with the colloidal particles. In the case of nanodiamond, 0.06 or 0.60 mg/mL of BSA molecules were adsorbed on 0.10 or 1.05 mg/mL of nanodiamond, respectively, indicating 1:2 complexation of BSA, which is the same ratio as in the case of carbon black. The adsorbed BSA molecules served as an effective stabilizing agent for the carbon black and nanodiamond, ensuring dispersion stability for at least 1 week. The preparation of the dispersions can be easily carried out by other researchers for toxicity studies.     

Oxygen Self-Diffusion in Single-Crystal Y2O3

Self-diffusion coefficients of the oxygen ion in single-crystal Y₂O₃ were determined by the gas-solid isotope exchange technique. The results in the range 1100° to 1500°C are described by D=7.3 X 10^-6 exp [-19l(kJ/mol)/RT] cm²/s. Comparison of the results with those for oxides with the fluorite-type structure indicates that the regularly arranged vacant anion sites in the C-type structure do not contribute eflectively to oxygen ion diffusion .     

Deformation characteristics of ultra-thin liquid film considering temperature and film thickness dependence of surface tension

Thermocapillary deformations of an ultra-thin liquid film caused by temperature distribution were three-dimensionally analyzed using the unsteady and linearized long wave equation considering the temperature and film thickness dependence of surface tension. The temperature and film thickness dependence equation for the surface tension of a liquid was firstly established. The temperature dependence of the surface tension was obtained experimentally using a surface tensiometer and the film thickness dependence was obtained theoretically from the corrected van der Waals pressure equation for a symmetric multilayer system. Time evolutions of depression and groove of the ultra-thin liquid film caused by local heating were obtained quantitatively.     

Optimal initial production control period based on a quality growth model

The initial production phase of new products or the initial installation phase of new manufacturing facilities is often unstable because of inexperienced workers and many defective products. An initial production process control, in which the defects in design, production technologies and products are fully fixed and removed, is switched to a normal process control whenever it is ready for actual mass production. This paper discusses a method of deciding the optimal initial production control period, based on a quality growth model. It is determined by the number of products with the minimum expected total quality control cost. Finally a penalty cost due to unattainable loss to the quality goal is introduced in the quality control cost: the realized stabilization level of the initial production process control is lower than the original quality objective. Numerical illustrations of the optimal policy are also presented. Copyright © 1999 John Wiley & Sons, Ltd.     

Dynamic flying characteristics of an air bearing slider over a disk with grooves and distribution of material properties

Bit-patterned media (BPM) consisting of land parts for read/writing and grooves, which are almost filled with non-magnetic materials to prevent magnetic interference between recording bits, are considered to be promising media for achieving ultrahigh density recording. A flying head slider flying over a BPM disk suffers from variations in both the spacing and van der Waals (vdW) attractive forces, which induce slider vibrations and spacing fluctuations. In the present study, we considered that BPM disks not only have a groove depth distribution, but that they also have a distribution of material properties (e.g., refractive index), which gives rise to a distribution in the vdW force. In the dynamic responses of sliders with small groove depths and a small variation in the refractive index, spacing fluctuations are found to be a superposition of fluctuations due to slider behaviors (1) over a disk with transverse grooves in a uniform material with a uniform refractive index (Case 1) and (2) over a flat disk with a refractive index distribution (Case 2). When the effects of Cases 1 and 2 cancel each other, the spacing fluctuations for the two cases cancel each other, reducing the total spacing fluctuation.     

Formation of Alkoxy-Derived lead Niobates in the PbO-Rich Region

The formation of lead niobates in the PbO-rich region is studied using powders prepared by the simultaneous hydrolysis of lead and niobium alkoxides. Cubic 3PbO·2Nb_2PO₅ solid solutions crystallize at low temperatures from amorphous materials having concentrations of 58 to 75 mol% PbO. The lattice parameter a increases linearly from 1.0544 to 1.0708 nm with increasing PbO. At higher temperatures the solid solutions made with 66.67 and 71.43 mol% PbO transform into 2PbO·Nb₂O₅ (monoclinic) and 5PbO·2Nb₂O_s (monoclinic), respectively. Monoclinic 5PbO·2Nb₂O₅ transforms into a new modification at = 3850° to = 3900°C. It has a rhombohedral unit cell with a = 0.7461 nm and c = 4.8092 nm ( a = 1.6599 nm, a = 25.97°). In the presence of excess lead, monoclinic 5PbO·2Nb₂O₅ transforms into tetragonal 3PbO·Nb₂O₅.     

Theoretical analyses of surface interaction stresses considering two-dimensional periodic material distributions

Microsystem Technologies - The interaction stresses (pressure and shear stress) for the (001) surface between a half-space consisting of a homogeneous material and a half-space with a spatially...     

Effects of Na2SiO3 on anodization of Mg-Al-Zn alloy in 3 M KOH solution

The anodic behavior of Mg-Al-Zn alloy (AZ91D) under low potential electrolysis in 3 M KOH solutions was studied with and without addition of 0.5-5 M Na₂SiO₃. Anodic films incorporating silicon were formed during electrolysis, and the films formed under constant potential electrolysis at 4 V in 3 M KOH solution with Na₂SiO₃ were uniform and thicker than the films formed without Na₂SiO₃. A few at% of silicon was present as Mg₂SiO₄ in the films, although the main compound was Mg(OH)₂. The corrosion resistance of the films formed in solutions with Na₂SiO₃ increased in an anodic polarization test in 0.1 M KCl solution.