Modeling of the Effect of pH on the Calcite Dissolution Kinetics

The kinetics and mechanism of calcite dissolution at various pH are investigated. A scheme of the ion distribution in various states of the medium is presented. The kinetic curves of dissolution are modeled, taking into account the structure of the electrical double layer and the acid-base characteristics of calcite.     

Multicharged ion source based on Penning-type discharge with electron cyclotron resonance heating by millimeter waves

We suggest a Penning-type discharge as a trigger discharge for fast development of pulsed electron cyclotron resonance plasma. The Penning-type discharge glows at a low pressure as needed. Gyrotron radiation (75 GHz, 200 kW, 1 ms) was used for plasma heating. Fully striped helium ions were demonstrated, average charge of ions in the plasma was ≈ 2. Experiment and calculations show that high charge states of heavier gases require lower initial pressure and longer development time. Only moderate charge states are achievable in this pulsed scheme.     

Dislocations in manganese-doped InSb

Electron probe X-ray microanalysis data for quenched InSb〈Mn〉 samples demonstrate that most of the manganese goes to doping of dislocations in the semiconductor lattice. The manganese-doped dislocations in InSb determine the magnetic and electrical properties of the material at room temperature and above. According to magnetic measurements, this is accompanied by the formation of several magnetic phases. Codoping of InSb with manganese and zinc with the aim of neutralizing one of the magnetic phases allowed us to obtain a ferromagnetic semiconductor with a Curie temperature of 320 K.     

Topographic analysis of the surface of the GaSb〈Mn〉 magnetic semiconductor

We have studied the formation of magnetic properties on the impurity–dislocation magnetism principle in a sample of a manganese-doped gallium antimonide compound semiconductor prepared by melt quenching. It has been shown using X-ray diffraction, optical microscopy, and scanning electron microscopy that the generation of dislocations and their motion during quenching play a key role in determining the microstructure of the GaSb〈Mn〉 magnetic semiconductor.     

Influence of copper on the structure and mechanical properties of pearlitic steels

The structure and mechanical properties of pearlitic steels, which contain ~0.6% carbon and copper in the amount of 1.25 and 1.4%, have been studied in the states immediately after the pearlitic transformation (with different rates of cooling) and after tempering at 500°C. It has been established that tempered pearlitic steel with copper is 10–15% stronger than the steel of similar composition without copper. The strengthening of copper-containing pearlitic steel after tempering is caused by the precipitation of copper particles 5–20 nm in size in the ferritic regions of pearlite and in grains of free ferrite.     

Interaction between Copper(II) Oxide and Aqueous Ammonia in the Presence of Ethylenediaminetetraacetic Acid

The interaction of copper(II) oxide with aqueous ammonia containing ethylenediaminetetraacetic acid (H₄L) is analyzed in terms of formal heterogeneous kinetics and the fractal dimension of the dissolving space. It is shown experimentally that, in the presence of H₄L, the dissolution rate of CuO grows with increasing ammonia concentration. At a fixed ammonia concentration, the dissolution rate of CuO passes through a maximum at an H₄L concentration of 8 × 10^–3mol/l. Two mechanisms of dissolution are suggested, namely, an adsorption and a redox mechanism. The adsorption mechanism involves four intermediate species and implies that the dissolution rate is a fractional rational function of the EDTA concentration. The redox mechanism takes into account the oxide/electrolyte interfacial potential. The role of the CuOHL^3–ion is elucidated, and the kinetic parameters of dissolution are derived.     

A microstructural study of a quenched InSb ingot

Samples cut from a quenched ingot of the compound semiconductor InSb have been characterized by precision X-ray diffraction. The results show that the central and top parts of the ingot have [110] texture, whereas its bottom part is polycrystalline, which is interpreted in terms of the heat removal geometry during quenching. The texture plane coincides with the easy cleavage plane (110), typical of the III–V compound semiconductors and due to dislocation pile-ups. The microstructure of the quenched InSb ingot includes characteristic microcracks, dotted with dislocation outcrops on the polished surface. The observed increase in the unit-cell parameters of quenched InSb is tentatively attributed to the high dislocation density in the quenched ingot.