Synthesis,microstructure and mechanical properties of Cr2AlC/Al2O3 in situ composites by reactive hot pressing

Al₂O₃ particle-reinforced Cr₂AlC in situ composites were successfully fabricated from powder mixtures of Cr₃C₂, Cr, Al, and Cr₂O₃ by a reactive hot-pressing method at 1400 °C. A possible synthesis mechanism was proposed to explain the formation of the composites in which Al₂O₃ was formed by the aluminothermic reaction between Al and Cr₂O₃, meanwhile, Cr₃C₂, Al, together with Cr reacted to form Cr₂AlC in a shortened reaction route. The effect of Al₂O₃ addition on the microstructure and mechanical properties of Cr₂AlC/Al₂O₃ composites was investigated. The results indicated that the as-sintered products consisted of Cr₂AlC matrix and Al₂O₃ reinforcement, and the in situ formed fine Al₂O₃ particles dispersed at the matrix grain boundaries. The flexural strength and Vickers hardness of the composites increased gradually with increasing Al₂O₃ content. But the fracture toughness peaked at 6.0 MPa m^1/2 when the Al₂O₃ content reached 11 vol.%. The strengthening and toughening mechanism was also discussed.     

Formation of rhenium diboride via mechanochemical–annealing processing of Re and B

Rhenium diboride (ReB₂) powder was prepared by mechanochemical processing of Re–B powder mixtures with subsequent annealing at temperatures of 600 °C to 1200 °C. Reactive evolution during the synthesis was investigated; furthermore, the effects of the amount of excess B on the reactions that occurred during the synthesis were assessed. The substantial reaction of Re with B occurred at 700 °C to form Re₇B₃ with a small amount of ReB₂. At 800 °C, Re₇B₃ converted into ReB₂; this conversion was enhanced with increasing temperature and increasing amount of excess B. At 1000 °C or above, single-phase ReB₂ powder without trace quantities of Re₇B₃ was obtained for compositions with 15 wt% or greater excess B. The synthesized ReB₂ powder particles were submicrometer with the vast majority being ∼500 nm. In addition, the resulting ReB₂ powders were consolidated by hot pressing or spark plasma sintering to examine the sinterability of the powders.     

可聚合甲基丙烯酰氧丙基磷酸酯的合成

以三氯氧磷、三乙胺、丙烯酸羟丙酯(HPA)等为原料,通过多步法合成了一种磷酸酯反应型乳化剂。实验对原料配比、反应时间、反应温度等进行讨论,得到最佳工艺条件,并用红外光谱对产品进行结构表征。结果表明,合成甲基丙烯酰氧丙基磷酸酯中间体,选择n(三氯氧磷)∶n(三乙胺)∶n(HPA)=1.1∶1.3∶1,反应时间为1.5h,反应温度为25℃,第二步水解反应温度0~15℃,水解物料比为n(中间体产物)∶n(三乙胺)∶n(水)=1∶1.4∶1.2时,最终产物收率最高,可达98.80%。     

活性黄HE-4G合成研究

本文主要介绍了活性黄HE-4G的化学结构和合成过程。分析了在合成过程中2,4-二氨基苯磺酸与三聚氯氰反应的条件和控制方法。     

Adsorption of Reactive Blue 114 dye by using a new adsorbent: Pomelo peel

This paper describes the removal of Reactive Blue 114 dye from aqueous solutions by using pomelo (Citrus grandis) peel. Pomelo peel can be described as a new, low cost, abundantly available adsorbent. The optimum adsorbent mass, dye concentration, contact time and pH were determined in this study. The parameters of Langmuir, Freundlich and Temkin adsorption isotherms were also obtained using concentrations of the dyes ranging from 1.0 to 200 mg/L. Maximum adsorption capacity was obtained as 16 mg/g at pH 2 and 303 K solution temperature. The adsorption process was observed to be reaching equilibrium after about 90 min.     

Removal of acid blue 113 and reactive black 5 dye from aqueous solutions by activated red mud

Removal of acid blue 113 (AB113) and reactive black 5 (RB5) dyes from aqueous solutions by activated red mud was investigated at different reaction parameters. Activated red mud has higher removal efficiency for AB113 than that for RB5. This can be explained by a greater molecular size of RB5 than that of AB113 and by different binding affinity with the surface of the activated red mud. Equilibrium data was fitted well with Freundlich isotherm and the kinetic data followed a pseudo second-order model. Maximum adsorption capacity was 83.33 mg/g and 35.58 mg/g at pH 3 for AB113 and RB5, respectively.     

Oxidative stress mediated cytotoxicity of biologically synthesized silver nanoparticles in human lung epithelial adenocarcinoma cell line

The goal of the present study was to investigate the toxicity of biologically prepared small size of silver nanoparticles in human lung epithelial adenocarcinoma cells A549. Herein, we describe a facile method for the synthesis of silver nanoparticles by treating the supernatant from a culture of Escherichia coli with silver nitrate. The formation of silver nanoparticles was characterized using various analytical techniques. The results from UV-visible (UV-vis) spectroscopy and X-ray diffraction analysis show a characteristic strong resonance centered at 420 nm and a single crystalline nature, respectively. Fourier transform infrared spectroscopy confirmed the possible bio-molecules responsible for the reduction of silver from silver nitrate into nanoparticles. The particle size analyzer and transmission electron microscopy results suggest that silver nanoparticles are spherical in shape with an average diameter of 15 nm. The results derived from in vitro studies showed a concentration-dependent decrease in cell viability when A549 cells were exposed to silver nanoparticles. This decrease in cell viability corresponded to increased leakage of lactate dehydrogenase (LDH), increased intracellular reactive oxygen species generation (ROS), and decreased mitochondrial transmembrane potential (MTP). Furthermore, uptake and intracellular localization of silver nanoparticles were observed and were accompanied by accumulation of autophagosomes and autolysosomes in A549 cells. The results indicate that silver nanoparticles play a significant role in apoptosis. Interestingly, biologically synthesized silver nanoparticles showed more potent cytotoxicity at the concentrations tested compared to that shown by chemically synthesized silver nanoparticles. Therefore, our results demonstrated that human lung epithelial A549 cells could provide a valuable model to assess the cytotoxicity of silver nanoparticles.     

封闭空间CO2气体去除技术的研究现状与展望

阐述了国内外二氧化碳去除技术的研究现状和进展。介绍了应用于封闭空间内二氧化碳净化技术的去除原理,对一些新技术、新方法作了说明,探讨了用于封闭空间二氧化碳去除技术的研究前景。     

生态型活性粉末混凝土性能试验研究

研究了剑麻纤维活性粉末混凝土的流动度和力学性能,并在试验的基础上,就剑麻纤维对活性粉末混凝土延性和脆性的改善效果进行了量化计算。结果表明,随着剑麻纤维掺量从0增加到1.6%,活性粉末混凝土的流动度、抗压强度和抗折强度分别降低了36%、9%和13%;剑麻纤维的掺入使得混凝土的跨中位移和开口位移极限值分别增加了47%和42%,断裂能和延性指数分别提高了19%和35%。     

Application of 'waste' metal hydroxide sludge for adsorption of azo reactive dyes

The capacity and mechanism of metal hydroxide sludge in removing azo reactive dyes from aqueous solution was investigated with different parameters, such as charge amount of dyes, system pH, adsorbent particle size, and adsorbent dosage. The three anionic dyes used were CI Reactive Red 2, CI Reactive Red 120, and CI Reactive Red 141, increasing in number of sulfonic groups, respectively. Only 0.2% (w/v) of powdered sludge (<75microm) achieved color removal from 30 mg l(-1) reactive dye solutions within 5 min without pH adjustment. The larger the charge amount of the dyes, the greater the adsorption (>90%) on the metal hydroxide sludge. The system pH played a significant role in the adsorption on metal hydroxides and formation of dye-metal complexes. The optimum system pH for dye adsorption was 8-9 which was close to the pH(zpc) of the sludge while the precipitation of dye-metal complexes occurred at system pH 2. The maximum adsorption capacity (Q degrees ) of the sludge for the reactive dyes was 48-62 mg dye g(-1) adsorbent. The Langmuir and Freundlich models showed that the higher charged dyes had a higher affinity of adsorption. The smaller particle size and the greater amount of adsorbent showed the faster process, due to an increase in surface area of adsorbent. Desorption studies elucidated that metal hydroxide sludge had a tendency for ion exchange adsorption of sulfonated azo reactive dyes. Leaching data showed that the treated water was nontoxic at a system pH above 5 or a solution pH above 2.