Investigation of the Thermal Conductivity of Methanol–n-Hexanol Mutual Solutions at High Parameters of State

The thermal conductivity of methyl and normal hexyl alcohols and of methanol–n-hexanol solutions in wide ranges of temperature and pressure are measured in a facility implementing the regular regime method. The regularity of variation of the thermal conductivity of binary solutions with concentration is found.     

Metal sorption by biomass of melanin‐producing fungi grown in clay‐containing medium

The sorption of toxic metals by fungal mycelia grown in clay‐containing medium is reported in this work. Biomass of melanin‐producing microfungi of the genus Cladosporium (C cladosporioides, C resinae and C herbarum) and Aureobasidium pullulans, clay minerals and fungal mycelia grown in clay‐containing medium were compared for their equilibrium Cu and Cd uptake from pH‐buffered solutions using experimental sorption isotherms. Bentonite (Cherkassy) in the natural form was shown to be the best Cu sorbent compared with the other clays and clay minerals tested. Cu sorption isotherms fitted the Langmuir sorption model for all cases. Comparison of Cu and Cd uptake for biomass and bentonite showed a lower biomass uptake capacity but a considerably higher affinity of the biosorbent for the solute. The presence of kaolinite and palygorskite in the medium generally reduced both Cu and Cd sorption capacity and the metal‐binding ability of the fungal–clay mixtures. In contrast, addition of bentonite into the medium did not appreciably alter the Cd sorption ability but increased the sorption of Cu by A pullulans and C cladosporioides grown in this medium. A common feature for all fungi grown in the presence of bentonite was an increase in the Cu sorption capacity (Q_max) of the biomineral sorbents and a reduction in their affinity (Langmuir parameter b) compared with control biomass. A difference between predicted and experimental data obtained for biomass grown on bentonite medium was also observed. The connection between the sorption capacity of biomass grown in clay‐containing medium, mycelial morphology and the structure of fungal pellets is discussed and a mechanism for the changed sorption capacity of the combined biomineral sorbents is proposed which involves blocking or modification of binding sites on biotic and abiotic components of the ‘biomineral’ association. © 2002 Society of Chemical Industry     

The Gilbert-Holland FDTD thin slot model revisited: an alternative expression for the in-cell capacitance

This paper proposes an alternative expression for the in-cell capacitance of a photoelectrical cell (PEC)-mounted slot, which is the conceptual cornerstone of the Gilbert-Holland subcell finite difference time domain (FDTD) model. By treating a slightly modified electrostatic problem, the extraneous charge singularity on the PEC edges touching the cell, which is characteristic of the originally proposed model, is removed. The latter offers better physical grounds for a new expression of the capacitance and the effective permittivity used in the update equations. High resolution standard FDTD simulation results are presented in support of the new expression.     

Optical properties of Nd-doped Ca3(VO4)2 single crystal fiber

Optical absorption and photoluminescence of Ca₃(VO₄)₂ single crystal grown by a floating-zone technique and containing Nd³⁺ ions were investigated. High absorption coefficients and broadening of most absorption bands are present at 300 K, while substructures in some of the same bands can be evidenced at 12 K. Most features of measured spectra are characteristic of random occupation of more than a single Ca²⁺ site by the Nd³⁺ ion and of distortions provoked by different charge compensation mechanisms involving oxygen vacancies promotion in the crystal lattice. Nd³⁺ optical properties were studied by using the Judd-Ofelt theory to calculate the spectral parameters relevant for laser applications.     

X-ray-based measurement of composition during electron beam melting of AISI 316 stainless steel: Part II. Evaporative processes and simulation

An energy dispersive X-ray (EDX) detector mounted on a laboratory scale electron beam furnace (30 kW) was employed to assess the potential use of X-rays as a means of on-line composition monitoring during electron beam (E B) melting of alloys. The design and construction of the collimation and protection systems used for the EDX are described in Part I. In Part II, a mathematical simulation of the heat, mass, and momentum transfer was performed for comparison to the EDX and vapor deposition results. The predicted flow patterns and evaporation rates are used to explain the differences between the two experimental methods. For the EDX spectra measured, the X-rays generated were from the center of the hearth where fluid flow rising from the bulk of the pool is sufficient to maintain the bulk composition despite the high evaporative flux from the surface. The flow moves radially outward from the center of the pool, with the volatile species being depleted. The vapor deposition technique measures the entire region, giving an average surface composition, and it therefore differs from the EDX results, which gave a near bulk composition. This combined study using in-situ EDX measurements and numerical simulations both provided an insight into the phenomena controlling the evaporation in an EB-heated system and demonstrated the viability of using EDX to measure the bulk composition during EB melting processes.     

Kinetics of BaTiO3 and PbTiO3 Formation from Metallo-organic Precursors

Kinetics of BaTiO₃ and PbTiO₃ formation from metalloorganic precursors were studied. The fine grain size of the decomposed product and the greater degree of mixing led to very rapid kinetics of compound formation. The kinetics data were fitted to the Carter model for a diffusion-controlled process. Formation of PbTiO₃ was modeled as a two-stage process with a single activation energy, and the formation of BaTiO₃ as a single-stage process.