Low-Temperature Electrochemical Synthesis of ZrO2 Films on Zirconium Substrates: Deposition of Thick Amorphous Films and in situ Crystallization on Zirconium Anode

The feasibility of synthesizing crystalline ZrO₂ films at low temperatures was evaluated using an electrochemical method. Anodization of zirconium-metal substrates in tetraethyl ammonium hydroxide (TEAOH) solutions under constant applied voltage conditions at ∼25° and ∼100°C was investigated. The chemistry and microstructure of the anodic oxide films deposited on the zirconium-metal substrates under the above conditions were characterized using X-ray diffractometry and scanning electron microscopy. The results indicated that, with sufficiently high applied voltages (in the range of 300 V) at pH ∼9.5, the initial dissolution of the zirconium anode resulted in the local saturation of the electrolyte solution with Zr⁴⁺, forming Zr(OH)⁻₅, which deposited electrophoretically on the anode as a thick, gelatinous film at 25°C. Similar treatments at 100°C resulted in an in situ crystallization of Zr(OH)₄ gel to monoclinic ZrO₂.     

Surface studies on activated and hydrided CaNi5 alloy

X-ray photoelectron spectroscopic studies on the activated pure CaNi₅ alloy as well as the hydride formed at 1 atm pressure and room temperature, CaNi₅H_4.8, showed that on activation calcium segregates to the surface and forms the oxide, whereas most of the nickel on the surface is present in the metallic form. This indicates that the coexistance of the oxide phase and the metal phase is essential for the facile hydriding behaviour of CaNi₅.     

Copper losses and thermodynamic considerations in copper smelting

A relationship between copper in slag and copper in matte during copper sulfide smelting has been derived using industrial data from 42 plants employing blast furnaces, reverberatory furnaces, flash furnaces, and Mitsubishi smelting furnaces together with the available thermodynamic equilibrium data for Cu-Fe-S-O, FeO-SiO₂, and Cu-Fe-S systems and laboratory slag-matte equilibrium information. A copper smelting diagram showing oxygen potential; sulfur potential; and copper, magnetite, and sulfur contents in slag during the smelting of different grades of copper mattes is developed for mattes containing less than 70 pct copper. The data presented can be used to determine the entrained copper losses in slag. Further, by combining the calculated value of the entrained matte with the corresponding plant data for the sulfur content of the slag, it is possible to derive the dissolved sulfur content of the slag. These calculated values were in excellent agreement with the experimentally determined sulfide capacity of fayalite slags. It is shown that there is no need to assume the presence of dissolved copper sulfide species in industrial slags. The existing equilibrium data that relate the copper content of slags to oxygen potential adequately describe the copper losses in industrial slags.     

Application and modelling of hybrid stereolithography injection mould tooling

The use of stereolithography (SL) to make injection moulding tools has been shown previously to be an efficient way of producing rapid tools for simple geometries, aiming at small lot sizes with an acceptable degree of accuracy. This paper highlights the unexplored potential of using SL inserts in hybrid tools using practical experiments and FEA mould filling models. The practical experiments reveal problems incurred by uneven flow as a result of differential thermal conductivity between dissimilar mould materials in a hybrid tool. The FEA flow models confirm that this uneven flow would be anticipated when using finite element analysis (FEA) software. A further FEA stress analysis predicts that catastrophic mould failure will be expected under some conditions and these reflect the results found in the practical experiments. The use of a homogeneous SL tool eliminates the issues caused by uneven mould filling but results in thermal distortion of the female mould. Ultimately, a SL tool backfilled with low melt point alloy provides a solution that eliminates the problems of uneven filling and thermal distortion.     

Thermal fatigue behavior of squeeze cast, discontinuous alumina-silicate fiber-reinforced aluminum alloy (A356) composite

Microstructural damage mechanisms owing to thermal cycling and isothermal exposure at elevated temperature are studied for a short alumina-silicate fiber-reinforced aluminum alloy (A356) composite produced by pressure casting. The tensile strength of the metal matrix composite is found to degrade considerably in each case. An X-ray double-crystal diffraction method is employed to study the mechanisms of recovery in the matrix. The fractal dimension of the X-ray “rocking curves” for individual grains in the composite reflects the substructure formation owing to the rearrangement of dislocations into subdomain walls. Recovery by polygonization is more pronounced in the case of thermal cycling than for equivalent isothermal exposure. The residual stresses in the matrix that provide the fiber clamping force undergo more relaxation in the case of isothermal exposure. The two competing damage mechanisms, thermally activated recovery by polygonization and relaxation of clamping stresses in the matrix, result in identical strength degradation (25%) for both thermal cycling and isothermal exposure.     

A special-purpose content addressable memory chip for real-timeimage processing

An application specific integrated circuit (ASIC) using a special-purpose content addressable memory that performs parallel search and multiple update (PSMU) operation is presented. This chip, referred to as multiple update content addressable memory (MUCAM), can search 256, 8-b-wide locations in parallel for target data and update all such locations with new data within 50 ns. MUCAM has been developed for image component labeling and merging operation in a connected component analyzer. It was fabricated using 0.9-μm CMOS technology     

The role of grain boundary diffusion in initial selective oxidation kinetics of a manganese-aluminum TRIP steel

Confocal scanning laser microscopy (CSLM) was used in real-time observation of alloy element oxidation of a manganese/aluminum transformation induced plasticity (TRIP) steel. CSLM images reveal a marked role of grain boundaries in the overall initial oxidation kinetics of the alloy and consequently in the morphology of the initial surface oxide. Changing the grain size and the oxidation temperature results in a change in the overall kinetics of selective oxidation and in the importance of oxidation at grain boundaries, respectively. Electron backscattered diffraction mapping was used to characterize the grain boundaries intersecting the surface over an area of the alloy. Subsequent CSLM observation of selective oxidation over the same area allowed quantification of oxidation kinetics as a function of individual grain boundary misorientation.