Correlation between impact strength and fracture surface fractal dimension of ABS filled with hollow glass beads

The hollow glass bead (HGB) filled poly(acrylonitrile–butadiene–styrene) copolymer (ABS) composites were prepared by means of a twin‐screw extruder. The HGB surface of was treated using a silane coupling agent, and the filler volume fraction was range from 0 to 15%. The impact strength (σ_I) of the ABS/HGB composites was measured at room temperature. On the basis of the impact fracture surface SEM photograph, the impact fracture surface fractal dimension (D_s) of the composites was measured, respectively, by means of the pixel‐covering method and projective‐covering method and an image processing software, to investigate the relationship between the D_s and σ_I of the composites. The results showed that the σ_I was related closely to D_s: σ_I increased with an increase of D_s, and the relationship between them could be described by an exponential function. Furthermore, the D_s measured by the pixel‐covering method were from 1.6232 to 1.7313, while those measured by the projective‐covering method were from 2.5174 to 2.5752. Copyright © 2010 John Wiley & Sons, Ltd.     

Evaluation of Gibbs free energy for the transfer of a highly hydrophilic ion from an acidic aqueous solution to an organic solution based on ion pair extraction

A method to determine the standard Gibbs free energy for the transfer, ΔG°_tr, of a highly hydrophilic metal ion from an aqueous solution, W, in the presence of high concentration of H⁺ to an organic solution, O, was proposed based on the theoretical consideration of the distribution process of ions between W and O. The usefulness of the proposed method was verified experimentally by comparing ΔG°_tr of Mg²⁺ determined by the method with that obtained by voltammetry for the ion transfer at the W|O interface. The O examined were nitrobenzene (NB) and 1,2-dichloroethane (DCE). By applying the proposed method, ΔG°_tr of NpO₂⁺, UO₂²⁺, NpO₂²⁺ and PuO₂²⁺ from an acidic W to NB were determined.     

Electrocatalytic Oxidation of Methanol and Related Chemical Species on Ultrafine Pt and PtRu Particles Supported on Carbon

Well-homogenized PtRu/C electrocatalysts possessing high specific activity for methanol electro-oxidation were prepared by a co-impregnation method from carbon black and ethanolic solutions of Pt(NH₃)₂(NO₂)₂ and RuNO(NO₃) _x . The specific activity for methanol electro-oxidation increased with an increase in the PtRu particle size. A similar size effect was observed for Pt/C electrocatalysts. The size effect was discussed by considering a model catalyst method.     

Photoelectrochemical Detection of Glucose by Using an Enzyme‐Modified Photoelectrode

A new photoelectrochemical method for the determination of glucose based on the photoelectrochemical effect of poly(thionine) photoelectrode to hydrogen peroxide (H₂O₂) was reported. The H₂O₂‐sensitive photoelectrode was fabricated by electropolymerizing thionine on the surface of ITO electrode. And then glucose oxidase was immobilized on the photoelectrode via the aid of chitosan enwrapping, forming an enzyme‐modified photoelectrode. The photoelectrode was employed as an electron acceptor; H₂O₂ from the catalytic reaction of enzyme was employed as an electron donor, developing an analytical method of glucose without hydrogen peroxidase. In the paper, the photoelectrochemical effects of photoelectrode to H₂O₂ and glucose were studied. The effects of the bias voltage and the electrolyte pH on the photocurrent were investigated. The linear response of glucose concentrations ranged from 0.05 to 2.00 mmol/L was obtained with a detection limit of 22.0 µmol/L and sensitivity of 73.2 nA/(mmol·L^?1). The applied feasibility of method was acknowledged through monitoring the glucose in practical samples.     

Na2O掺杂C12A7材料的结构及其抗菌性能

本文利用溶胶-凝胶方法制备了Na2O掺杂的C12A7(12CaO.7Al2O3-Na2O)材料,通过X-射线衍射(XRD)、电子顺磁共振(EPR)、电感等离子体耦合-原子发射光谱(ICP-AES)和飞行时间质谱(TOF-MS)研究了材料结构与性能。选用金黄色葡萄球菌和大肠杆菌为受试菌种,研究了C12A7-Na2O的抗菌性能。结果表明,Na2O掺杂对C12A7的晶体结构以及材料中的氧负离子的浓度没有显著的影响,且C12A7-Na2O材料具有较高的抗菌性能。利用扫描电镜(SEM)对杀菌前后的金黄色葡萄球菌和大肠杆菌的菌体形态进行了观测,初步探讨了C12A7-Na2O的抗菌机理。     

Selective oxidation of methane to formaldehyde by oxygen over silica-supported iron catalysts (Special column of methane transformation, Article)

FeO_x-SiO₂ catalysts prepared by a sol-gel method were studied for the selective oxidation of methane by oxygen. A single-pass formaldehyde yield of 2.0% was obtained over the FeO_x-SiO₂ with an iron content of 0.5 wt% at 898 K. This 0.5 wt% FeO_x-SiO₂ catalyst demonstrated significantly higher catalytic performances than the 0.5 wt% FeO_x/SiO₂ prepared by an impregnation method. The correlation between the catalytic performances and the characterizations with UV-Vis and H₂-TPR suggested that the higher dispersion of iron species in the catalyst prepared by the sol-gel method was responsible for its higher catalytic activity for formaldehyde formation. The modification of the FeO_x-SiO₂ by phosphorus enhanced the formaldehyde selectivity, and a single-pass formaldehyde yield of 2.4% could be attained over a P-FeO_x-SiO₂ catalyst (P/Fe = 0.5) at 898 K. Raman spectroscopic measurements indicated the formation of FePO₄ nanoclusters in this catalyst, which were more selective toward formaldehyde formation.     

Synthesis of Pb8Pr2(GeO4)4(VO4)2 and refinement of its crystal structure

The conditions of synthesis of lead praseodymium vanadatogermanate Pb₈Pr₂(GeO₄)₄(VO₄)₂ with an apatite structure were determined by X-ray powder diffraction. The elemental composition and homogeneity of the synthesized sample were verified by scanning electron microscopy. The crystal structure was refined by the Rietveld method.     

A simplified version of the total kjeldahl nitrogen method using an ammonia extraction ultrasound-assisted purge-and-trap system and ion chromatography for analyses of geological samples

The total Kjeldahl nitrogen (TKN) method was simplified by using a manifold connected to a purge-and-trap system immersed into an ultrasonic (US) bath for simultaneous ammonia (NH₃) extraction from many previously digested samples. Then, ammonia was collected in an acidic solution, converted to ammonium (NH₄⁺), and finally determined by ion chromatography method. Some variables were optimized, such as ultrasonic irradiation power and frequency, ultrasound-assisted NH₃ extraction time, NH₄⁺ mass and sulfuric acid concentration added to the NH₃ collector flask. Recovery tests revealed no changes in the pH values and no conversion of NH₄⁺ into other nitrogen species during the irradiation of NH₄Cl solutions with 25 or 40 kHz ultrasonic waves for up to 20 min. Sediment and oil free sandstone samples and soil certified reference materials (NCS DC 73319, NCS DC 73321 and NCS DC 73326) with different total nitrogen concentrations were analysed. The proposed method is faster, simpler and more sensitive than the classical Kjeldahl steam distillation method. The time for NH₃ extraction by the US-assisted purge-and-trap system (20 min) was half of that by the Kjeldahl steam distillation (40 min) for 10 previously digested samples. The detection limit was 9 μg g⁻¹ N, while for the Kjeldahl classical/indophenol method was 58 μg g⁻¹ N. Precision was always better than 13%. In the proposed method, carcinogenic reagents are not used, contrarily to the indophenol method. Furthermore, the proposed method can be adapted for fixed-NH₄⁺ determination.     

Comparison of oxidation polymerization methods of thiophene in aqueous medium and its mechanism

Precipitation method of oxidation polymerization for preparing polythiophene was carried out as well as dispersion and emulsion methods in aqueous medium by using (NH₄)₂S₂O₈ and CuCl₂ as the oxidant and catalyst, respectively. In precipitation method, ethanol was served as an auxiliary solvent to water. The effective conjugated length (ECL) of the obtained polythiophene was demonstrated to be evaluated by the UV absorption spectrum. The ECL of the polythiophene gradually increases with the rise of the content of ethanol in the mixed solvent in precipitation polymerization, and it was higher comparing to the ECL of the product prepared by aqueous dispersion or emulsion method. An electron transition mechanism of the oxidation polymerization of thiophene was suggested.     

The leaching of V(V) with PO4 in the speciation analysis of soil

The leaching of V(V) from soil by two phosphate reagents, viz. (NH₄)₂HPO₄ and Na₃PO₄ has been studied. (NH₄)₂HPO₄ (1 M) and Na₃PO₄ (0.01 M) were efficient enough to extract all V(V) species from samples. The results were compared with that extracted by Na₂CO₃. Statistical evaluations show that the proposed method is similar to the established method utilizing Na₂CO₃.The method was applied in the analysis of soil samples from contaminated area of the vanadium mine where many grazing cattle died.Validation of the method was also done by comparing the sum of V(IV) and V(V) and the total vanadium obtained from the samples by an independent method. It was found that the sum of V(V) and V(IV) is in good agreement with the total content of vanadium in all samples after HF-H₂SO₄-HClO₄ digestion. From the results of the investigation, it follows that the use of phosphate fertilizers in V(V)-rich soil may enhance the mobility and availability of V(V) to plants. The plants, in turn, are consumed by animals that may die depending on the level of poisoning.     

Magnetic graphene nanocomposite as an efficient catalyst for hydrogenation of nitroarenes

Graphene-Fe₃O₄ nanocomposite（G-Fe₃O₄） was synthesized by a chemical co-precipitation method which was used as an efficient catalyst for the reduction of nitroarenes with hydrazine hydrate.The method has been applied to a broad range of compounds with different properties and the yields were in the range of 75%-92%.The G-Fe₃O₄ catalyst can be readily recovered and reused 5 times without significant loss of the catalytic activity.     

Synthesis and Characterization of H3PW12O40 and H3PMo12O40 Nanoparticles by a Simple Method

In this study H₃PW₁₂O₄₀·9H₂O and H₃PMo₁₂O₄₀·6H₂O (HPA) particles were changed into nano forms by heat-treatment in an autoclave as a simple, repaid, inexpensive and one step method. The particle size of these nanoparticles was around 25 nm. The as-synthesized nanostructures were characterized by dynamic light scattering, X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and inductively coupled plasma analyzer. Thermal stability of nanoparticles was surveyed by thermal gravimeter analyse. Acidity of prepared nanoparticles was investigated by pyridine adsorption method. Results showed rising acidity by declining particle size of HPA.     

Electrical properties of the CuCr2O4 spinel catalyst

Electrical resistivity of CuCr₂O₄ spinel obtained by a coprecipitation method was measured at various temperatures from 350 to 923K in air. Oxidation of its surface chromium ions at various temperatures was determined by an iodometric method. The temperature dependence of resistivity and the presence of higher-valent chromium ions at higher temperatures indicated CuCr₂O₄ to be an extrinsic semiconductor. Log ? vs $\text{1}\text{T}$ plots yielded straight lines in the whole temperature range with two breaks, one around 550K and the other around 730K. The first break was attributed to the saturation of the surface with higher-valent chromium, while the second break was attributed to tetragonal-to-cubic phase transition in CuCr₂O₄. Log ? vs $\text{1}\text{T}$ plots obtained while cooling exhibited hysteresis near the second break, confirming this break to be due to a first-order diffusionless transition.     

Mössbauer emission spectroscopy of an unsupported cobalt-molybdenum hydrodesulfurization catalyst

A new internal standard method coupled with the standard addition method for PIXE analysis has been developed. In its basic principle, this method is characterized by that a suitable element present initially in the sample is used as an internal standard, and further the comparative standard is prepared by applying the standard addition method to the duplicated sample. When a sample contains W_a g of trace element A to be determined together with an element B which is usable as an internal standard, and when the comparative standard is prepared by adding an exactly known amount of element A, W _a ^* g, to the duplicated sample, the absolute concentration of W_a can easily be determined by the following equation even if the above sample and comparative standard are irradiated separately by a different number of protons W_a=W _a ^* /[(R^*/R)-1] where R and R^* are ratios of net photopeak counts due to the characteristic X-rays from the element A and B in the irradiated sample and comparative standard, respectively. The usefulness of the method was examined through determination of Cu, Zn, Rb and Sr in two biological materials, such as spinach and orchard leaves. As a result, this method was demonstrated to be sensitive, highly reproducible and reasonably accurate.     

A new internal standard method for activation analysis and its application. Determination of Co,Ni, Rb,Sr in pepperbush by means of photon activation

A new internal standard method for activation analysis has been developed. This method is characterized by that a suitable element present originally in the sample is used as an internal standard and the comparative standard is prepared by applying the standard addition method to the duplicated sample. When a sample under examination contains W_ag of trace element A to be determined together with a known amount of element B which is usable as an internal standard, and when the comparative standard is prepared by adding W _a ^* g of accurately known small amount of the element A to the duplicated sample, even if the sample and comparative standard are irradiated separately by particles with different fluxes, W_a can be determined, easily by using the following equation: W_a=W _a ^* /[(A _R ^* /A_R)-1] Where A_R and A _R ^* are counting ratios of gamma-rays emitted by two radioactive nuclides produced from the element A and B in the sample and comparative standard, respectively. Neither correction of the inhomogeneities of flux between the sample and comparative standard, nor that of, the self-shielding effects are necessary for the present method. The usefulness of the method was examined through the determination of Co, Ni, Rb and Sr in pepperbush by means of photon activation, and the precision and accuracy of the method were proved to be valid.     

磁性Fe3O4/石墨烯Photo-Fenton催化剂的制备及其催化活性

采用共沉淀法制备磁性Fe3O4/GE(石墨烯)催化剂,实现Fe3O4纳米颗粒生长和氧化石墨烯还原同步进行,采用FTIR、XRD、TEM及低温氮吸附-脱附等对Fe3O4/GE纳米催化剂的物相、颗粒粒径及比表面积进行了表征。在H2O2存在条件下,以亚甲基蓝为目标降解物,考察了在模拟太阳光下Fe3O4/GE的催化活性,当氧化石墨烯与Fe3O4的质量比为1∶10时,经过2 h催化反应,在pH=6条件下,对亚甲基蓝的降解率达到98.7%,经过10次循环使用后对染料溶液的降解率仍保持在95.7%以上,明显优于纯的Fe3O4。     

离子交换-双氧水氧化法制备纳米CeO2晶体

以99.995% Ce(NO₃)₃和强碱性阴离子交换树脂为原料，采用离子交换-双氧水氧化法合成制备出纳米CeO₂晶体。并就离子交换反应中的Ce³⁺浓度、树脂加入速度和离子交换温度及H₂O₂加入速度等条件对CeO₂粒径的影响进行了探讨，得出了离子交换-双氧水氧化法制备纳米CeO₂晶体的最佳工艺条件。FTIR、TEM分析表明，离子交换法无需对合成的Ce(OH)₃溶胶进行洗涤即可去除NO₃^-、CO₃^2-等阴离子杂质，并用H₂O₂将该溶胶氧化，经真空干燥可制得粒径分布均匀，平均晶粒尺寸约3 nm，高纯度的CeO₂粉体。     

Influence of In on the activity of zinc in liquid (tin + zinc + indium)

The activity of Zn in low-melting {(1−x₁−x₂)Sn+x₁Zn+x₂In}alloys has been determined by the method of equilibrium saturation with metal vapour at T=750 K. The total mole fraction of Zn and In was less than 0.25. As the method of equilibrium saturation is a comparative one, it is necessary to have an appropriate reference mixture. The {(1−x)Sn−xZn}alloy was taken as the reference mixture. The interaction parameter ε_Zn^In was determined by a least-squares method. The experimental value of ε_Zn^In was compared with the calculated value on the basis of a model of relative difference of ionic volumes.     

The development of an evaluation method for capture columns used in two-dimensional liquid chromatography

Capture columns are important interface tools for on line two-dimensional liquid chromatography (2D-LC). In this study, a systematic method was developed to evaluate and optimize the capture ability of capture columns by off-line method. First, the parameter Δt_R (Δt_R = t₂−t₁−t₀−W) was introduced to quantitatively represent the capture ability of the capture column by connecting a capture column behind the first dimensional column. Based on the value of Δt_R, an appropriate capture column was selected after the first dimensional column was fixed. Then, the capture ability of the selected column was promoted by adjusting the mobile phase of the first dimensional column. Capture ability was also optimized using complex sample analysis software system (CSASS) software. Second, the elution mode of the trapped compounds on the capture column was investigated by connecting the capture column before the second dimensional column. More specifically, in mode I, capture column was connected to the second dimension without changing the flow rate direction and the trapped compounds must pass through the capture column and be eluted into the second dimensional column. The contrary connection mode was mode II. It was found that mode I is more suitable method for 2D-LC. Finally, an off-line reversed-phase/hydrophilic interaction liquid chromatography two-dimensional liquid chromatography (RP/HILIC 2D-LC) system with a C18 capture column was developed to demonstrate the practical application of this method.     

Peak parking method for measurement of molecular diffusivity in liquid phase systems

The combination of series of measurements of band broadening made with the peak parking (PP) method, using successively an open capillary tube and a HPLC column, gives a convenient procedure for the measurement of the molecular diffusivity (D_m) of compounds in solutions, of their axial dispersion coefficient (D_ax,m) in chromatographic columns, and of the tortuosity or obstructive factor of the column bed. The molecular diffusivity measured for benzene in methanol was in excellent agreement with literature data. The ratio of the axial dispersion coefficient to this diffusivity gives the obstructive factor (γ_m) of the packed bed, which was 0.74 for the column used. The values of D_m in other solutions were obtained from the D_ax,m values measured by the PP method, by correcting the D_ax,m values with the γ_m value. The D_m values determined by this method were in good agreement with those previously reported or estimated using literature correlations. These results showed that the PP method is effective for the experimental measurement of D_m.