微铬渣作水泥混合材的研究

本文对微铬渣的矿物组成 ,胶凝性和用微铬渣作混合材生产的水泥的力学性能、保水性及压蒸安定性进行了研究。结果表明 :微铬渣的主要矿物组成为 α′- C2 S、β- C2 S、γ- C2 S、Mg O、C3A和微量 Cr、Cr2 O3等 ,它具有一定的胶凝性 ,并且 ,硫酸盐激发剂能显著提高其水化活性。微铬渣作水泥混合材能够改善水泥的保水性 ,但考虑安定性因素 ,微铬渣在水泥中的掺量应控制在 30

用堆底法加回渣引弧生产微铬的试验

介绍了用堆底法加回渣引弧生产微铝合金的试验情况，分析了试验降碳未达预期目的原因，指出热兑法还是目前生产微铬合金的好方法。

Fretting wear and friction oxidation behavior of 0Cr20Ni32AlTi alloy at high temperature

The fretting wear behavior of 0Cr20Ni32AlTi alloy was investigated with crossed cylinder contact under 80 N at 300 and 400 °C.Wear scar and debris were analyzed systematically by scanning electron microscopy and X-ray photoelectron spectroscopy.The results show that the friction logs are mixed fretting regime and gross slip regime with the magnitudes of displacement of 10 and 20 μm,respectively.Severe wear and friction oxidation occur on the material surface.A large number of granular debris produced in the fretting process can be easily congregated and adhered at the contact zone after repeated crushes.The resultant of friction oxidation is mainly composed of Fe3O4,Fe2O3,Cr2O3 and NiO.Temperature and friction are the major factors affecting the oxidation reaction rate.The fretting friction effect can enhance the oxidation reaction activity of surface atoms of 0Cr20Ni32AlTi alloy and reduce the oxidation activation energy.As result,the oxidation reaction rate is accelerated.

“波伦法”液态硅铬合金热兑生产实践探讨

介绍了“波伦法”热兑中的理论及实际过程,指出热兑是生产微铬合金的重要方法,运用这种方法降成本有实效。

Characteristics of Inconel Powders for Powder-Bed Additive Manufacturing

In this study, the flow characteristics and behaviors of virgin and recycled Inconel powder for powder-bed additive manufacturing （AM） were studied using different powder characterization techniques. The results revealed that the particle size distribution （PSD） for the selective laser melting （SLM） process is typically in the range from 15 μm to 63 μm. The flow rate of virgin Inconel powder is around 28 s·（50 g）^-1. In addition, the packing density was found to be 60%. The rheological test results indicate that the virgin powder has reasonably good flowability compared with the recycled powder. The inter-relation between the powder characteristics is discussed herein. A propeller was successfully printed using the powder. The results suggest that Inconel powder is suitable for AM and can be a good reference for researchers who attempt to pro- duce AM powders.

Effect of the chelating agents on bio-sorption of hexavalent chromium using Agave sisalana fibers

The current work is focused on the study of the bio-sorption of hexavalent chromium from aqueous solution using sisal natural fiber(Agave sisalana) treated by various chelating agents(ligands) such as urea(UR),thiocarbamide(TC), ethylenediaminetetraacetic acid(EDTA), and diphenyl carbazide(DCZ). The fiber treatments were investigated using Fourier Transform Infrared Spectroscopy(FTIR) and Scanning electron microscope(SEM). The kinetics of chromium bio-sorption was studied in batch presses under the effect of some physicochemical factors such as the nature of chelating agent(F@UR, F@TC, F@DCZ, and F@EDTA),adsorbent dose(2–10 g·L^(-1)), chromium initial concentration(100–500 mg·L^(-1)), solution pH(1–6), and batch temperature(20 ℃–50 ℃). This study resulted in an optimum adsorption at a chromium initial concentration of 100 mg·L^(-1), at pH 2, and at 20 ℃. The obtained results showed clearly that the treatment with chelating agent boosts the adsorptive capacity of A. sisalana fibers Cr(VI) 10.9 mg·g^(-1) to 58.6 mg·g^(-1). The modeling study showed that the adsorption kinetics obey the pseudo-second-order model, with an R2 in the range of 0.991 and 0.999. The bio-sorption isotherms followed the Langmuir model; the maximum uptake capacity of(F@N, F@UR,F@TC, F@DCZ, and F@EDTA) was found to be respectively, 12.3 mg·g^(-1), 25.33 mg·g^(-1), 28.73 mg·g^(-1),42.54 mg·g^(-1), and 61.45 mg·g^(-1). The determined adsorption thermodynamics parameters such as enthalpy,free energy, and entropy showed that the adsorption process is exothermic, spontaneous, and has a stable configuration.

Biosorption of Chromium from Aqueous Solution Using Chitosan

Adsorption experiment from aqueous solutions containing known amount of Cr （chromium） using chitosan was explored to evaluate the efficiency of chitosan as sorbent for Cr. Some variable parameters such as pH, reaction time and chitosan dosage were optimized. Under the optimum experiment condition, the effect of common ions on the adsorption of Cr （i.e., Na^＋, K^＋, Mg^2＋, Ca^2＋ for Cr（Ⅲ）, and Cl^-, NO3^-, SO4^2- for Cr（Ⅵ）） was also investigated. Furthermore, the sorption mechanism of Cr by chitosan was investigated by applying Langmuir and Freundlich isotherm equations to the data obtained. In addition, to confirm the characteristics of the chitosan, the surface morphology of the biomass was determined by SEM （scanning electron microscope） and specific surface area analyzer （N2-BET （Brunaeur, Emmet and Teller））. Consequently, the following matters have been mainly clarified： （1） chitosan can be an efficient sorbent for Cr （both Cr（Ⅲ） and Cr（Ⅵ））; （2） the effect of common ions on the adsorption ofCr （Cr（Ⅲ） and Cr（Ⅵ）） was not significant under this experimental conditions; （3） adsorption isotherms using the chitosan can be generally described by Langmuir isotherm more satisfactorily for Cr. The adsorption may have occurred mainly by monolayer reaction; （4） the rates of adsorption were found to conform to pseudo-second order kinetics.

Joint effects of microwave and chromium trioxide on root tip cells of Vicia faba

The mutagemc effects of microwave and chromium trioxide （CrO3） on Vicia faba root tip were studied. Micronucleus assay and chromosomal aberration assay were used to determine the mitotic index, the micronucleus frequency and chromosomal aberration frequency of Vicia faba root tip cells induced by microwave and CrO3. The results showed that the micronucleus frequency decreased, and that the mitotic index and chromosomal aberration frequency showed linear dose responses to CrO3, in treatment of microwave for 5 s. In microwave of 25 s, the mitotic index decreased, the micronucleus frequency and chromosomal aberration frequency increased with increase of CrO3 concentration. We concluded that microwave and CrO3 had antagonistic effect on the mitotic index of Vicia faba root tip cells, but had synergetic effect on micronucleus frequency and chromosomal aberration frequency of Viciafaba root tip cells.

Photocatalysts of Cr Doped TiO2 Film Prepared by Micro Arc Oxidation

A series of Cr doped TiO2 films were prepared by micro arc oxidation （MAO） using an electrolyte of Na3PO4＋K2Cr2O7. X-ray diffraction and scanning electron microscopy revealed that the films mainly consisted of anatase phase with a porous surface morphology. The films have an excellent photocatalytic effect for degradation of methylene blue and decomposition of water under visible light illumination. This arises from the formation of Cr3＋/Cr4＋ and oxygen vacancy energy levels owing to Cr doping. The former reduces the electron-hole recombination chance, while the latter generates a new gap between the conduction band （CB） and valence band （VB） of TiO2, which lowers the photo energy of the excited electron in the VB to the oxygen vacancy states. The mechanisms for film synthesis during the MAO process are also presented.

Purification of Organic Wastewater Containing Cu^(2+) and Cr^(3+) by a Combined Process of Micro Electrolysis and Biofilm

A complex process of micro electrolysis and biofilm was developed to continuously treat organic wastew-aters containing heavy metal ions such as Cu2+ and Or3+, and the relevant purifying mechanism was also addressed. In detail, organic materials in wastewater could be consumed as nutritious source by biofilm composed of aerobes and anaerobes. However, for heavy metal ions (Cu2+, Cr3+), part was removed by electrodeposition, and some was adsorbed on biofilm. In order to compare with the combined process of micro electrolysis and biofilm, the experimental data of micro electrolysis process (intermittent) or biofilm process (continuous) were provided, and the kinetic data of C6H12O6 (glucose) biodegradation by cultured microbes or acclimated microbes were also obtained. These experimental results indicated that for wastewater initially consisted of CeH12O6 (500mg-L-1), Cu2+ and Cr3+ (10mg-L-1), after treatment, its concentrations of C6H12O6, Cu2+ and Cr3+ were lowered to the level of 55-65mg.L^1, and less than 1mg-L-1, respectively. And the industrial reused water standards could be met by treated wastewater.

Microwave-assisted Fenton-like decolorization of methyl orange solution using chromium compounds

Azo dyes discharged in the environment are persistent organic pollutants （POPs）, which are very difficult to remove. We developed a microwave-assisted Fenton-like process to degrade methyl orange （MO）, an azo dye, with hydrogen peroxide （H2O2） catalyzed by chromium compounds coexisting with MO in the solution. Comparison between the Cr（Ⅲ）-H2O2 and Cr（Ⅵ）-H2O2 systems shows＂ that Cr（Ⅵ） has a stronger and more stable catalytical activity than Cr（Ⅲ）, and Cr（Ⅲ） is more susceptible to a change in the acidity or alkalinity of the reaction system. With a Cr（Ⅵ） concentration of 10 mmol L^-1 or a Cr（Ⅲ） concentration of 12 mmol L^-1 in the solution under the microwave irradiation of a power larger than 300 W for 3 min, 10 mmol L^-1 H2O2 can degrade more than 95% of 1 000 mg L^-1 methyl orange; when the microwave power is increased to 700 W, the same amount of H2O2 can degrade all methyl orange in the solution with the same amount of Cr（Ⅵ ） catalyst. Ultraviolet-visible spectrography indicates the cleavage of the azo bond in methyl orange after treatment, suggesting the potential o of this Fenton-like process to degrade azo dye POPs. Reusing waste chromium compounds coexisting with dyestuff in wastewater to catalyze the degradation of azo dyes could be a cost-effective technique for azo dyes and chromate manufacturers and/or users to treat their wastewater and prevent POPs from endangering the environment. This is of particula importance to controlling the water quality of the Three Gorges Reservoir.

Formation of nanocrystalline microstructure in arc ion plated CrN films

Applying negative bias voltages caused significant microstructure changes in arc ion plated CrN films. Nanocrystalline microstructures were obtained by adjusting the negative bias voltage. Structural characterizations of the films were carried out using X-ray diffractometry (XRD) and high-resolution transmission electron microscopy (HR-TEM). The results indicated that increasing ion bombardment by applying negative bias voltages resulted in the formation of defects in the CrN films, inducing microstructure evolution from micro-columnar to nanocrystalline. The microhardness and residual stresses of the films were also affected. Based on the experimental results, the evolution mechanisms of the film microstructure and properties were discussed by considering ion bombardment effects.

Heavy metal contamination, physico-chemical and microbial evaluation of water samples collected from chromite mine environment of Sukinda, India

Water samples from chromite mine quarry of Sukinda and its adjacent areas were analyzed for their heavy metal contamination along with physico-chemical and microbial contents. The chromite mine water samples possessed high concentrations of heavy metals in the order of Cr〉Fe〉Zn〉Ni〉Co〉Mn while ground water did not show any heavy metal contamination except Fe. Physico-chemical parameters of mine water samples showed deviation from those of normal water. Mine water harboured low microbial populations of bacteria, fungi and actinomycetes in comparison with mine adjacent water samples. The correlation of data between metals with physico-chemical parameters showed both positive and negative responses while that of metal and microbial population exhibited negative correlation. Bacterial strains isolated from chromite mine water exhibited high tolerance towards chromium and other heavy metals as well as antibiotics which could be used as an indicator of heavy metal pollution.

Carburization of ferrochromium metals in chromium ore fines containing coal during voluminal reduction by microwave heating

Chromium ore fines containing coal (COFCC) can be rapidly heated by microwave to conduct the voluminal reduction, which lays a foundation of getting sponge ferrochromium powders with a lower content of C. Under the conditions of COFCC with n(O)-n(C) (molar ratio) as 1.00-0.84 and n(SiO2)-n(CaO) as 1.00-0.39, the samples were heated by 10 kW microwave power to reach the given temperatures and held for different times respectively. The results show that the low-C-Cr ferrochromium metal phase in the reduced materials forms before the high-C-Cr ferrochromium metal phase does. With increasing temperature the C content of ferrochromium metals is in a positive correlation with the content of Cr. The C content of ferrochromium metal in reduced materials is 0-10.07% with an average value of 4.68%. With the increase of holding time the Cr content in ferrochromium metals is in a negative correlation with the content of C, while the content of Fe changes in the contrary way. In the microwave field the kinetic conditions of carburization are closely related with the temperature of microwave heating, holding time and carbon fitting ratio.

Removal of chromium (Ⅵ) from aqueous solutions using quaternized chitosan microspheres

In this study, quaternized chitosan microspheres （QCMS） were prepared and its Cr （VI） removal potential was investigated. Batch experiments were conducted to examine kinetics, adsorption isotherm, pH effect, and thermodynamic parameters. Equilibrium was attained within 50 rain and maximum removal of 97.34% was achieved under the optimum conditions at pH 5. Adsorption data for Cr （VI） uptake by the QCMS were analyzed according to Langmuir, Freundlich, and Temkin adsorption models. The maximum uptake of Cr （VI） was 39.1 mg.g-a. Thermodynamic parameters for the adsorption system were determinated at 293 K, 303 K, 313 K and 323 K. （AH° = 16.08 kJ.mol- 1;AG° = -5.84 to -8.08 kJ.mo1-1 and AS° = 74.81 J.K-1 .tool-l）. So the positive values of both A/-F and AS° suggest an endothermic reaction and increase in randomness at the solid-liquid interface during the adsorption. AG° values obtained were negative indicating a spontaneous adsorp- tion process. The kinetic process was described by a pseudo-second-order rate equation very well. The results of the present study indicated that the QCMS could he considered as a potential adsorbent for Cr （V1） in aqueous solutions.

Mutagenic effects of chromium trioxide on root tip cells of Vicia faba

In this study on the mutagenic effects of different concentrations of chromium trioxide (CrO3) on Vicia faba root tip, micronucleus assay and chromosome aberration assay were used to determine the mitotic indexes, micronucleus rate and chromosome aberration rate of Vicia faba root tip cells. The results showed that the effects of CrO3 concentration on the mitotic indexes were complicated. CrO3 increases the micronucleus rate of Vicia faba root tip cells. It was found that within certain range of CrO3 concentration the micronucleus rate increased systematically with increased concentration of CrO3, but that the micronucleus rate decreased at higher level of CrO3 and that CrO3 also caused various types of chromosome aberration at a rate which increased systematically with increased concentration of CrO3. We concluded that CrO3 has significant mutagenic effect on Vicia faba root tip cells.

Synthesis of PGMA Microspheres with Amino Groups for High-capacity Adsorption of Cr(VI) by Cerium Initiated Graft Polymerization

Abstract A novel polyglycidylmethacrylate （PGMA） microspheres with high adsorption capacity of Cr（VI） was prepared by cerium（IV） initiated graft polymerization of tentacle-type polymer chains with amino group on polymer microspheres with hydroxyl groups. The micron-sized PGMA microspheres were prepared by a dispersion polym erization method and subsequently modified by ring-opening reaction to introduce functional hydroxyl groups. The polymer microspheres were characterized by scanning electron microscopy （SEM） and Fourier transform infrared spectroscopy （FTIR）. The results indicated that the polymer microspheres had an average diameter of 5 m with uniform size distribution. The free amino group content was determined to be 5.13 mmol·g^-1 for g;PGMA-NH2 microspheres by potentiometric and conductometric titration methods. The Cr（VI） adsorption results indicated that the graft polymerization of tentacle-type polymer chains on the polymer microspheres could produce adsorbents with high adsorption capacity （500 mg-g-l）. The polymer microspheres with grafted tentacle polymer chains have potenial application in large-scale removal of Cr（VI） in aqueous solution.

EXPRESSION OF CYCLOOXYGENASE-2 IN MALIGNANT PHEOCHROMOCYTOMAS AND ITS RELATIONSHIP WITH MICROVESSEL DENSITY

Objective To investigate the expression of cyclooxygenase-2 （ Cox-2 ） and microvessel density （MVD） in benign and malignant pheochromocytomas, and the relationship between Cox-2 and MVD. Methods Specimens and clinical data from 38 patients （ 21 benign and 17 malignant pheochromocytomas ） were studied. Slides of normal adrenal glands in nephrectomy specimens from another 20 patients with benign renal tumors were used as control. Irnmunohistochemical technology was performed to detect the Cox-2 and MVD in all specimens. Results Expression of Cox-2 was observed in 5 of the 21 benign pheochromocytomas （23. 8% ） , and in 14 of the 17 malignant （82.4%）. No expression of Cox-2 was observed in control slides. There were significant differences of Cox-2 expression between benign and malignant pheochromocytomas, as well as between malignant pheochromocytomas and control （ P 〈0. 05）. Expressions of MVD were 36. 41 ±13. 00, 21.43 ±8. 05, and 13. 36 ±4.34 in malignant, benign pheochromocytomas, and in control, respectively. Conclusion Cox-2 may contribute to the invasive characteristics of malignant pheochromocytomas and be used as a marker to distinguish malignant from benign pheochromocytomas. Expression of MVD in malignant pheochromocytomas was directly correlated with Cox-2.

Electrochemical Synthesis of Chromium Silicides from Molten Salts

Electrochemical synthesis of chromium silicides from NaCl-KCl-K2SiF6-CrF3 system has been investigated by cyclic voltammetry and DC （direct current） electrolysis at 850℃. The process of Cr and Si joint electroreduction in chloride-fluoride melt proceeds in one stage in a kinetic mode. The cathode product was analyzed using XRD （X-ray diffraction） method. XRD data have confirmed that CraSi is the dominant phase. SEM （scanning electron microscopy） results have shown that Cr3Si powder samples consist of 50-150 lain particles and that tungsten silicide was formed at the surface of tungsten cathode after chrome-free system electrolysis.

Detoxification of chromium-containing slag by Achromobacter sp.CH-1 and selective recovery of chromium

Based on the principle of bacterial leaching and bacterial metallurgy,a novel technology for the detoxification of chromium-containing slag by Achromobacter sp.CH-1 and chromium recovery was proposed.Strain CH-1 cell morphology before and after Cr(Ⅵ) reduction was observed with a scanning electron microscope(SEM),and the reduction product is found to adhere to terminals of CH-1 cells.Energy-dispersive X-ray(EDX) and electron paramagnetic resonance(EPR) analyses reveal that the main component of the reduction product is Cr(Ⅲ).Furthermore,small and large-scale demonstration projects reveal that Achromobacter sp.can be used to detoxify chromium-containing slag and to selectively recover chromium by using this novel technique.Chromium recovery rate increases with decreasing particle sizes of chromium-containing slag and slagheap height.Chromium recovery rates in 10 t/batch and 20 t/batch of on-site demonstration projects for chromium-containing slag detoxification are more than 90%.