Characterization and processing of talc-magnesite from the Zinelbulak deposit

The characteristics of talc-magnesite from the Zinelbulak deposit(Uzbekistan) were investigated via X-ray diffraction, differential thermal analysis,infrared spectroscopy and optical microscopy.The mineralogical composition of the Zinelbulak talc-magnesite consists of 52 wt.%talc,43 wt.%carbonates and 5 wt.%of the iron-containing minerals magnetite,siderite and chlorite.Petrographic analysis confirmed the presence of carbonates in two forms:magnesite and breunnerite.Grindability tests revealed that talc and magnesite particles are completely separated after a grinding process carried out for 10～12 min.The distribution of the yield of talc and magnesite,as a function of the particle size,shows an irregular feature in that a comparatively coarser sample(>0.1 mm) is richer in magnesite and poor in talc while a comparatively finer sample(<0.1 mm) has a composition poorer in magnesite.The dressability of the Zinelbulak talc-magnesite was tested using conventional gravity concentration,flotation and electromagnetic separation.Gravity concentration was found to be the most economic initial process for the complete separation of magnesium carbonate and talc.Subsequent flotation and magnetic separation techniques could further increase the yield of high quality magnesite and talc.Refractory samples prepared by heating the separated magnesite at 1600℃for 2 h met the State Standards for refractory materials.

Site Selective Excitation and Energy Transfer in LiKGdF_5 Crystal Co-doped with Er^(3+) and Tb (3+)

Crystals of LiKGdF 5∶Er 3+, Tb 3+ grown by the hydrothermal synthesis technique with concentrations of 2% and 0.4% were analysed. By using site selective excitation measured at low temperature, luminescence and excitation spectra from Er 3+ and Tb 3+ ions embedded in LiKGdF 5 were clearly separated. The lifetimes of the emitting levels 4S 3/2 of Er 3+ and 5D 4 of Tb 3+ were also determined. Following the site selective spectroscopy study, the dominant energy transfer process from Tb 3+ to Er 3+ in the crystal was then investigated via transient experiments.

Cation-anionicpalladium Complexes—New Types of Antitumor, Immune Response-modulating and Radioprotective Agents

Here we report results of our investigations of new class of bioactive palladium compounds (AH n ) m [PdCl 4 ], which were discovered as a result of systematic study of correlations between composition, structure and bioactivity of different types of platinum metals coordination compounds. For the first time we demonstrated in vivoa possibility of development of palladium compounds, which exceed cisplatin in antitumor activity and do not show immunosuppressive effects, and palladium compounds with immunostimulating and radioprotective activities. Combinations of cytostatic agents or radiation with palladium complexes lead to significant synergism of their activities and high therapeutic efficiency exceeded an efficiency of their separated use.

Catalytic perfomance of rhodium chalcogen halides and rhodium chalcogenides over silica supports in methane oxidative carbonylation

The gas phase methane oxidative carbonylation was studied in the presence of molecular oxygen over silica materials including their mechanical mixtures with rhodium chalcogen chlorides obtained in non-aqueous inorganic media. The formation of Rh4SCl7, Rh4S9Cl2, Rh4SesCl3 and Rh3Se3Cl solids was confirmed by elemental analysis, IR absorption spectroscopy, XPS and X-ray diffraction. Silica, vanadium-, and molybdenum-containing mesoporous molecular sieves have been used as supports. It was found that productivity of oxygenates （methanol, methyl acetate and acetic acid） depends mainly on the method of the catalyst preparation and the type of the support.

Time course and mechanism of brain oxidative stress and damage for redox active and inactive transition metals overload

The objective of this work was to study the in vivo time course of biochemical processes of oxidative damage in the brain of Sprague-Dawley rats that received an acute overload of the redox active metals iron(Fe)and copper(Cu),and the redox inactive cobalt(Co)and nickel(Ni).Oxidative stress indicators(phospholipid and protein oxidation),glutathione(GSH),antioxidant enzymes and NADPH oxidase activities,and the plasma inflam-matory cytokine(IL-6)were measured.The results showed that in brain oxidative mechanisms for both sets of metal are different,however in both cases are irreversible.The mechanism for Fe and Cu oxidative damage is mediated by the generation of the free radical hydroxyl(Fenton reaction and homolytic cleavage of hydroperoxides).Two events of antioxidant protection prior to oxidation of phospholipids and proteins by Fe and Cu are considered.The first process is the use of GSH and the second is the increased activity of the Cu,Zn-SOD and catalase enzymes.The oxidative mechanism for metal redox inactive is the consumption of GSH,NADPH oxidase activation and inflammatory response mediated by IL-6.Co increased protein oxidation as a result of the inflammatory process.Ni produced increments of phospholipid oxidation and SOD activity.

Tetraalkylammonium Fluorosilicates as Precursors for Electrochemical Deposition of Silicon Coatings. Synthesis and Thermal Stability

Several TAAFS （tetraalkylammonium hexafluorosilicates） with different cations were synthesized. Their thermal properties were studied showing that obtained complexes are stable enough to be suitable for electrochemical deposition of silicon coatings under temperatures at least up to 200 ℃.

Tungsten Resource-Saving： Cobalt Cermets Wastes Recycling and Concentrates Extraction

Potentials range is determined in which the cobalt-tungsten alloy phase selectively dissolved in solutions of phosphoric acid to form soluble compounds of these metals, while the tungsten carbide phase remains in the precipitate. It shows that tungsten ores and concentrates are decomposed at 1,050℃-1,100℃ in sodium chloride-sodium metasilicate melts to form two immiscible phases, namely, halide-tungstate, containing 96% to 99% of tungsten, and silicate, containing 90% of the rest ore components.

Synthesis, characterization, spectroscopic and crystallographic investigation of metal complexes of N-benzyl-N-nitrosohydroxylamine

New metal complexes of N-benzyl-N-nitrosohy-droxylamine (BNHA) are isolated and characterized by elemental analysis, IR and UV-VIS spectroscopy. Spectrophotometric titration of aqueous solutions of BNHА by salts of some transition metals allowed to calculate the composition and formation constants of the metal complexes. The crystal structure of Cu (BNHА)2 is studied by X-ray diffraction. The Cu atom is coordinated by four O atoms of two bidentate ligands, which close 5-membered chelate rings. The N-O (1.306 ? - 1.320 ?) and N-N (1.274?? and 1.275? ) bond lengths indicate that π electrons are delocalized over the chelating groups. Complexes form stacks with intermolecular Cu…N contacts equal to 3.118?? and 3.306 ?.

Photostructural Changes and Electrical Switching in Amorphous Chalcogenides: Bond Waves in Thin Films

Photostructural changes and electrical switching are the well-known features of amorphous chalcogenides, also known as glassy semiconductors. Although the both phenomena were intensively studied experimentally and have a wide practical application, their nature is debated up to now. I propose a new approach that considers glass as a self-organizing system owing to characteristic instability of chemical bonding in the form of bond wave. The bond wave model is shown to be suitable for explanation of the observed effects in thin films under the action of light or electrical field, a result that opens a new way for understanding and managing the processes in glassy semiconductors.

Synthesis, Spectral Properties, Antibacterial and Antitumor Activity of Salinomycin Complexes with the Transition Metal Ions Co（ll）, Ni（ll）, Cu（ll） and Zn（ll）

SalNa （sodium salinomycin） reacts with divalent transition metal ions of Co（II）, Ni（II）, Cu（II） and Zn（II） to produce novel compounds characterized by various spectroscopic methods. The interaction of metal （II） ions with SalNa results in the formation of mononuclear complexes of a general composition of [M（Sal）2·（H2O）2] nH2O （n = 0 or 2） where the divalent cations replace Na~ ions from the cavity of initial compound. The new compounds （disalinomycinates） possess an enhanced antibacterial activity against Gram-positive microorganisms as compared to both SalNa and SalH （salinomycinic acid）, respectively. The metal （II） complexes manifest strong concentration dependent cytotoxic effect in experiments using human leukemia cell lines. The complexes of Co0I） and Cu（lI） proved to exert superior activity as compared to the Ni（II） and Zn（II） analogues and are much more cytotoxic than SalNa and SalH. Further studies should be conducted to determine the therapeutic indexes of the new compounds.

Study of impregnated cellulose thermal treatment process and properties of obtained active carbon

Single-stage process of obtaining active carbon by thermal processing of plant raw materials (mixture of different types of wood sawdust), impregnated with the mixture of phosphoric acid, urea and nitric acid salts has been developed. Active influence of impregnates on the process of carbonization and formation of carbon residue has been formed. It is established that carbon residue obtained in the interval of heating 20℃-(500℃-700℃), possesses high sorption activity to the vapors of organic compounds and has ion-exchange capacity. It has been showed that the value of carton residue depending on the impregnate used in the wood increases compared to the yield of non-treated initial raw materials by 3.1 times at 600℃ and by 4.2 times at 700℃.

LiKGdF_5∶Er^(3+),Sm^(3+)单晶的VUV光谱和量子剪裁

报道了LiKGdF_5:Er(2%),Sm(0.4%)单晶在紫外激光(三倍频Nd:YAG激光,355nm)和同步辐射真空紫外光激发下的光谱特性,讨论了不同激发下Er^(3+)离子和Sm^(3+)离子的相对发射强度及其物理机理。通过真空紫外激发光谱的测量,确定了本材料中Sm^(3+)离子的4f^45d吸收带以及Er^(3+)离子的4f^(10)5d吸收带的能量位置。实验结果表明,当激发Er^(3+)的4f^(10)5d吸收带,可以产生量子效率大于100%的量子剪裁现象,并给出了其物理模型。

Copper smelter slag treatment by ammonia solution:Leaching process optimization

The feasibility of copper smelter slag processing by ammonia solution treatment was investigated. The central composite rotatable design(CCRD) and approximation method were used to determine the optimum conditions of zinc and copper recovery to a solution. The experimental design was done at five levels of the four operating parameters which were the initial concentration of NH–3, the initial Cl ions concentration, leaching time and solid/liquid ratio. Two mathematical models describing dependence of metal recovery on the operating parameters were obtained. The models are successful in predicting the responses. It was found that optimal parameters for zinc and copper recovery are as follows(values for copper are given in brackets): initial CNH3 17.1%(19.9%), initial CCl– 160 g/L(160 g/L), leaching process duration 4.56 h(4.13 h), solid/liquid ratio 0.39(0.53). The maximum Zn and Cu recoveries to solution, obtained experimentally under the conditions, are 81.16% and 56.48%, respectively.

K_2YF_5∶Tm^(3+)单晶的光谱和能级结构

在12K的温度下,测量了水热法生长的K2YF5∶Tm3+单晶的发射和吸收光谱,分析了高掺杂样品中Tm3+离子间的交叉弛豫行为。用最小二乘法对实验能级进行拟合计算,得到了较好的均方差:18cm-1。此外,文中还给出了K2YF5∶Tm3+共振激发下1D2和1G4能级寿命的测量结果,并分析和讨论了掺杂量对能级寿命的影响。

Processing of refractory materials using various magnesium sources derived from Zinelbulak talc-magnesite

Magnesia（MgO） is widely used in the production of refractory materials due to its high melting point,high thermal shock,and excellent slag resistance.The properties of refractory materials depend upon magnesia sources and processing parameters.In this work,three different magnesium sources,namely,magnesium hydroxide concentrate,magnesium carbonate concentrate,and intermediate flotation concentrate,were obtained from the Zinelbulak talc-magnesite,Uzbekistan,by causticization-hydration and flotation processes,respectively.A series of refractory materials were prepared on the basis of these magnesium sources,and their effects on physico-mechanical properties and microstructures were investigated as a function of sintering temperature,molding pressure,and the particle size of magnesium sources.The experimental results showed that a refractory material obtained from the magnesium hydroxide concentrate at 1600℃ for 4 h demonstrated favorable parameters due mainly to a higher degree of contact among fine particles.The results obtained from X-ray diffraction and optical microscopy confirmed the presence of periclase and forsterite as the predominant phases in refractory specimens.The prepared refractory materials meet the requirements of the State Standards（Nos.4689-94 and 14832-96） for magnesia and forsterite refractories,respectively.It is,therefore,suggested herein that the use of different magnesium sources derived from the Zinelbulak talc-magnesite will offer the potential to provide economic benefits in the refractory industry.

Ultrasonic Technology for Enhanced Oil Recovery

An ultrasonic technology for enhanced oil recovery is described. For the implementation of this technology, the equipment was specially developed, taking into account the working conditions. The criteria for selections of well candidates were developed. The technology has been tested in two different regions in different geological conditions. The results of these field tests indicate the high efficiency of the proposed technology. The success rate of the method reached 90% and the increase in oil production was in the range of 40% - 100%.

Methane oxidative carbonylation catalyzed by rhodium chalcogen halides over carbon supports

Gas phase carbonylation of methane is studied in the presence of molecular oxygen over pure carbon carriers and carbon supported rhodium chalcogen halides. Activated carbons and fullerene blacks have been used as carbon supports. XPS and IR-spectroscopy data show the formation of rhodium chalcogen halides in solids prepared by different methods. We have found that the productivity of acetic acid by carbon supported rhodium chalcogen halides depends strongly on the carbon carrier and the method of the catalyst preparation. Namely, the catalyst with highest productivity for the acetic acid is prepared by synthesizing the rhodium chalcogen halide over the carbon support followed by thermal destruction. We have also found that rhodium chalcogen halides over activated carbons are more active compared with fullerene supported catalysts.

High-Density Ceramics of Al_2-xMe_x(WO₄)₃, (Me = Sc or In) Solid Solutions

Al2-xMex(WO4)3, (Me is Sc or In;x varies from 0 to 2) ceramics are sintered by two methods: 1) cold pressing with subsequent sintering at different temperatures and durations and 2) hot pressure sintering. The row materials are nanoparticles with average particle size of 20, 90 and 200 nm obtained by co-precipitation method. Density, particle size and anisometricity of the obtained ceramics are tested. The results show that optimal initial nanosized dimensions and optimal pressing conditions are needed to obtain compact ceramics. The hot pressure method provides possibilities for obtaining ceramics with a density of about 99.8%. These ceramics possess some level of transparency.

Biogenic Amorphous Silica as Filler for Elastomers

Natural products from agricultural wastes are finding importance in the polymer industry due to their many advantages such as being lightweight,low cost and environmentally friendly.In the present study the potential of the two types of rice husk ash(RHA)prepared under different conditions as fillers in natural rubber-based elastomer composites was investigated.The fillers were prepared by rice husks incineration and characterized by means of X-ray powder diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),scanning electron microscope(SEM),Brunauer-Emmett-Teller(BET)specific surface area,Hg-porosimetry and N2-adsorption.The evaluation involved determining the vulcanization characteristics of the compounds and their physical and mechanical characteristics,resistance to thermal aging as well as the dynamic properties of the vulcanizates containing RHA.It has been found that the ash from rice husk has good potential as filler in elastomers,especially as a substitute for synthetic commercially available silica.RHA improves the grip on ice and snow better than standard silica and may be used in formulations for shoe soles used for winter sports,extreme hiking footwear,ski boot soles,winter tire protectors,etc.Its quality depends on the conditions under which rice husk is incinerated.It is recommended to run the process at a temperature not higher than 800°C.In particular,cases in which the vulcanizates contain biogenic silica have very interesting characteristics like improved modulus at 300%of elongation,lower residual elongation,higher mechanical loss angle tangent at 0°C and lower at 60°C,and are superior to those of the vulcanizates containing commercially available filler Ultrasil?7000 GR.