汽车尾气用催化剂载体研究现状及展望

汽车尾气催化净化器中，催化剂载体是实现高效尾气净化的一个关键因素。本文综述了对尾气净化催化剂载体的要求和研究现状。并提出导电型复合陶瓷是今后尾气净化载体材料研究和发展的一个新型方向。     

Microstructure and mechanical properties of TiC0.7N0.3-HfC cermet tool materials

TiC_0.7N_0.3-HfC cermet tool materials were fabricated by hot-press sintering. Effects of different metal additives (Ni, Co, Ni-Co and Ni-Mo), sintering temperature and holding time on the microstructures and mechanical properties of TiC_0.7N_0.3-HfC cermets were investigated. Results showed that Ni-Mo or Ni-Co as metal additives was better for the mechanical properties of TiC_0.7N_0.3-HfC cermets than only Ni or only Co as the metal additives and Ni-Mo better than Ni-Co. HfC particle dispersion existed in these four cermets and only in the TiC_0.7N_0.3-HfC-Ni-Mo cermet the core-rim structure obviously existed. TiC_0.7N_0.3-HfC-Ni-Mo cermet had significantly smaller grains than the other three cermets because Ni-Mo can significantly refine the grain. With the sintering temperature increasing from 1450?°C to 1650?°C, grains grew gradually; Vickers hardness and flexural strength decreased gradually and the fracture toughness increased firstly and then decreased. With the holding time increasing from 15?min to 60?min, grains grew gradually; Vickers hardness, flexural strength and the fracture toughness increased firstly and then decreased. TiC_0.7N_0.3-HfC-Ni-Mo cermets sintered at 1450?°C with 30?min holding time had the better comprehensive mechanical properties with flexural strength of 1346.41?±?31?MPa, fracture toughness of 8.46?±?0.23?MPa?m^1/2 and Vickers hardness of 22.91?±?0.22?GPa.     

Flexural behavior of metallic fiber-reinforced adhesively bonded single lap joints

Incorporation of additives into the adhesive layer in adhesively bonded joints can improve the stress distriution in the adhesive layer and increase adhesive toughness. In this paper, the geometric and material parameters of metal fibers utilized for strengthening adhesively bonded single lap joints under flexural loading were investigated by using experimental investigations and finite element modeling. According to the experimental results, incorporating metal fibers in the adhesive layer of a bonded joint can have a significant impact on the flexural load bearing of the joint. This was in relationship with the numerical results foreseeing enhanced stress distributions of the adhesive layer, when the metal fibers were added to the adhesive layer. Some important parameters in the design of metal fiber-reinforced adhesive joints include the volume fraction (the distance between the fibers and the fiber diameter), orientation, and mechanical properties of the fibers. It was concluded that the peak normal stresses in the adhesive layer can be reduced, and consequently the load bearing of the joint can be improved by reducing the distance between the fibers, increasing the fiber diameter and choosing a stiffer material for the fibers in the longitudinal direction.     

Polyol-Derived Alkoxide/Hydroxide Base Catalysts II: Transesterification Reactions

Biodiesel, fatty acid methyl ester (FAME), was produced by transesterification of canola oil with methanol in the presence of a series of alkoxide/hydroxide base catalysts produced from glycerol, 1,2-propanediol, 1,3-propanediol, xylitol, or sorbitol produced by dehydration reaction of sodium hydroxide in the presence of polyols. Transesterification reactions proceeded efficiently in the presence of sodium alkoxide catalysts prepared at three different mole ratios of sodium hydroxide to glycerol (1:1, 2:1, and 3:1). The production of methyl ester during the course of the reaction was determined repeatedly and the reaction progress was compared with that achieved in a reaction catalyzed by freshly prepared anhydrous sodium methoxide as a standard catalyst. Sodium alkoxide/hydroxide catalysts activity during the first 2 min of the reaction was in the order of: sorbitol < xylitol < sodium methoxide < 1,2-propanediol < 1,3-propanediol < glycerol regardless of the mole ratio of sodium hydroxide to glycerol. All catalysts showed a higher methyl ester accumulation at higher ratios of sodium hydroxide to polyol and had the following order 1:1 < 2:1 < 3:1 (sodium hydroxide:glycerol). Several of these catalysts were as powerful as sodium methoxide in catalyzing the transesterification reaction at the same mole concentration. All alkoxide/hydroxide catalysts resulted in a high FAME accumulation (>95 wt%) in a single transesterification batch reaction.     

氯化铁浸出废金属回收海绵铜的工艺研究

采用氯化铁选择性浸出工艺对废金属进行综合利用,制备氯化铁及海绵铜。主要考察了废金属浸出、海绵铜洗涤工艺的可行性,并确定浸出工艺的最佳条件。结果表明:在搅拌速度150 r/min、氯化铁溶液质量分数29.91%、浸出剂量为理论量105%、反应温度60℃、反应时间1.0 h的条件下,铁浸出率为94.86%,铜浸出率为3.57%。浸出渣经盐酸溶液洗涤,能有效提高海绵铜的品质。     

2205双相不锈钢的焊接工艺研究

在2205双相不镑钢焊接过程中,通过对焊缝金属和焊接热影响区内金属相变的分析研究,总结出了合理的焊接工艺。     

Reforming of methane and coalbed methane over nanocomposite Ni/ZrO2 catalyst

Nanocomposite Ni/ZrO₂-AN catalyst consisting of comparably sized Ni metal and ZrO₂ nanoparticles is studied in comparison with zirconia- and alumina-supported Ni catalysts (Ni/ZrO₂-CP and commercial Ni/Al₂O₃-C) for steam reforming of methane (SRM) and for combined steam and CO₂ reforming of methane (CSCRM). The reactions are performed under atmospheric pressure with stoichiometric amounts of H₂O and CH₄ or (H₂O + CO₂) and CH₄ at 1073 K. Under a wide range of methane space velocity (gas hourly space velocity of methane GHSV_CH4 = 12,000–96,000 ml/(h g_cat.), the nanocomposite Ni/ZrO₂-AN catalyst always shows higher activity and stability for both SRM and CSCRM reactions. The two supported Ni catalysts (Ni/ZrO₂-CP and Ni/Al₂O₃-C) exhibit fairly stable catalysis under low GHSV_CH4 but they are easily deactivated under high GHSV_CH4 and become completely inactive when they are reacted for ca.100 h at GHSV_CH4 = 48,000 ml/(h g_cat.). The CSCRM reaction is carried out with different H₂O/CO₂ ratios in the reaction feed while keeping the molar ratio (H₂O + CO₂)/CH₄ = 1.0, the results prove that the nanocomposite Ni/ZrO₂-AN catalyst can be highly promising in enabling a catalytic technology for the production of syngas with flexible H₂/CO ratios (ca. H₂/CO = 1.0–3.0) to meet the requirements of various downstream chemical syntheses.     

Electro-oxidation of coal on NiO and/or Co3O4 modified TiO2/Pt electrodes

A TiO₂/Pt based electrode exhibited better activity for the oxidation of coal in a basic system compared to Ti/Pt, TiO₂–Cu/Pt and pure metal electrodes. The surface morphologies and composition of the electrodes were studied by SEM and XRD, respectively. Linear sweep voltammetry was employed to investigate the catalytic effects of electrodes, and the product of coal oxidization was determined by a gas collection test. The TiO₂/Pt electrodes that were modified with NiO and/or Co₃O₄ exhibited higher average currents and a lower decrease in mass during electrolysis compared to the other electrodes; this finding indicated that NiO and Co₃O₄ play important roles as catalysts.     

绿色环保型金属切削液研究进展

绿色环保型切削液的研究是未来金属切削液的发展趋势,主要从基础油和添加剂两方面综述了绿色环保型金属切削液的研究现状和发展趋势,对于从事金属切削液的相关专业人员具有一定的参考价值。     

Synthesis,characterization and photocatalytic activity study of aluminium doped BiSbO4 microflakes

Metal oxides have an extraordinary ability to generate charge carriers with significant importance in environmental remediation. For the degradation of different dyes, a one-step hydrothermal method was adopted to synthesize Al-doped BiSbO_4. While bismuth antimonate composite with reduced graphene oxide was synthesized by the simple ultra-sonication method. To investigate the structural confirmation, X-ray diffraction (XRD) was used. For studying morphology, scanning electron microscopy (SEM) was conducted. UV–Visible spectroscopy (UV) and Fourier transform infrared spectroscopy (FTIR) were used to observe the optical properties and vibrational modes of the as-synthesized BiSbO₄ nanoparticles and doped Al–BiSbO₄. The above-mentioned studies verify the formation of nanoparticles of Al-doped BiSbO₄. The synthesized composite was used to degrade the organic dyes such as methylene blue and crystal violet. The degradation efficiency of doped, undoped and composite is studied and compared. The results indicate the extraordinary efficiency of BiSbO₄/rGO composite to doped and bare samples for the degradation of dyes. It is confirmed by the degradation of different dyes that the BiSbO₄/rGO composite shows the best catalytic efficiency.