Electrochemical study on new polymer composite for zinc corrosion protection

Galvanostatic electrodeposition mode was employed for the synthesis of new polyaniline and polypyrrole-based composite coatings (PANI/PPY) onto pure zinc electrode. Potentiodynamic polarization, open circuit potential measurements and Electrochemical Impedance Spectroscopy (EIS) were employed to assess the ability of these composite coatings to provide an effective barrier to corrosion in chloride environment. Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM) observations were employed to characterize the structure and morphology of the modified electrodes. The coatings deposited galvanostatically at lower current density showed the best quality in terms of protection ability towards aggressive medium. It was found that the new PANI/PPY composite coatings had significantly better properties than single polymer coatings regarding the corrosion protection.     

High-temperature tensile and creep deformation of cross-weld specimens of weld joint between T92 martensitic and Super304H austenitic steels

The high-temperature mechanical behavior of cross-weld specimens prepared from a dissimilar weld joint between T92 martensitic and Super304H austenitic heat-resistant steels incorporating Ni-based weld metal was evaluated at temperatures up to 650 °C. For both high temperature tensile and creep tests, failure took place in T92 due to its faster degradation with temperature increase. The heat-affected zone of T92 played a critical role during creep deformation, resulting in type IV failure under the long-term creep condition. For the creep specimens, the location of failure shifted from the base metal region to the fine-grained heat-affected zone as the creep duration time increased from the short-term to the long-term condition. The massive precipitation of Laves phase on the grain boundaries of the fine-grained heat-affected zone during creep deformation was observed and found to be responsible for the accelerated void formation in the area leading to the premature failure.     

A new method for manufacturing graded refractories by localized hot uniaxial pressing

In this study, a cylinder of fine-grained carbon-bonded alumina was pressed uniaxially at high temperatures in an argon atmosphere. The resulting changes in mechanical properties, physical properties and microstructure were described with various techniques. The porosity of the material was found to have decreased significantly, leading to higher density, higher dynamic Young's modulus, higher strength and increased hardness. Additionally, gradients in porosity and hardness were observed that resulted from inhomogeneous temperature distribution during compression. Possibilities and conditions for the production of graded refractory materials can be deduced from the results.     

Numerical analysis of carbon saving potential in a top gas recycling oxygen blast furnace

Aiming at the current characteristics of blast furnace(BF)process,carbon saving potential of blast furnace was investigated from the perspective of the relationship between degree of direct reduction and carbon consumption.A new relationship chart between carbon consumption and degree of direct reduction,which can reflect more real situation of blast furnace operation,was established.Furthermore,the carbon saving potential of hydrogen-rich oxygen blast furnace(OBF)process was analyzed.Then,the policy implications based on this relationship chart established were suggested.On this basis,the method of improving the carbon saving potential of blast furnace was recycling the top gas with removal of CO_2 and H_2O or increasing hydrogen in BF gas and full oxygen blast.The results show that the carbon saving potential in traditional blast furnace(TBF)is only 38-56kg·t~(-1) while that in OBF is 138kg·t~(-1).Theoretically,the lowest carbon consumption of OBF is 261kg·t~(-1)and the corresponding degree of direct reduction is 0.04.In addition,the theoretical lowest carbon consumption of hydrogen-rich OBF is 257kg·t~(-1).The modeling analysis can be used to estimate the carbon savings potential in new ironmaking process and its related CO_2 emissions.     

Surface coating with poly(trifluoroethyl methacrylate) through rapid expansion of supercritical CO2 solutions

Rapid expansion of supercritical solutions (RESS) of poly(trifluoroethyl methacrylate), poly(TFEMA), was performed to produce ultrafine particles for spray coating application to improve the hydrophobicity of moisture-sensitive biodegradable materials. Carbon dioxide (CO₂) was used as the RESS solvent. Thermoplastic starch/poly(butylene adipate-co-terephthalate) (TPS/PBAT, 60:40 wt/wt) blend was used as the coating substrate. The objectives of this work were to determine the capacity of the RESS process for coating TPS-based material with poly(TFEMA), and to investigate the effect of RESS parameters – i.e. pre-expansion pressure and temperature (P_pre, T_pre) and poly(TFEMA) concentration – on the surface morphology and hydrophobicity of the coated materials. It was found that RESS produced poly(TFEMA) particles precipitated onto the surface of the TPS/PBAT substrate, with particle sizes ranging from 30 nm to several microns, depending on processing parameters. Rapid expansion of fluoropolymer solutions (0.3–1.0 wt%) with P_pre of 331 bar initiated from unsaturated conditions produced nanoparticles with a narrow size distribution of ∼30–70 nm; whereas larger particles with broader size distributions and a lower degree of agglomeration were obtained when supersaturated solutions were expanded with P_pre of 172 bar, especially at T_pre (80 °C) – higher than the glass transition temperature (73 °C) of poly(TFEMA). The surface coverage by the fluoropolymer increased with increasing P_pre and poly(TFEMA) concentration, but decreased with increasing T_pre. In addition, the hydrophobicity of the coated substrate, determined by water contact angle and water vapor transmission rate measurements, increased with increasing surface coverage.     

Dislocation slip and twinning in Ni-based L12 type alloys

We report theoretical results on dislocation slip and twinning in Ni₃ (Al, Ti, Ta, Hf) compositions with L1₂ crystal structures utilizing first-principles simulations. The lattice parameters of Ni₃Al, Ni₃Al_0.75Ta_0.25, Ni₃Al_0.5Ta_0.5, Ni₃Ta, Ni₃Ti and Ni₃Al_0.75Hf_0.25 are calculated, and the crystal structures with lower structural energies are determined. We established the Generalized Stacking Fault Energy (GSFE) and Generalized Planar Fault Energy (GPFE), and calculated stacking fault energies APB (anti-phase boundary) and CSF (complex stacking fault) matched other calculations and experiments. Based on the extended Peierls–Nabarro model for slip and the proposed twin nucleation model, we predict slip and twinning stress and the results show a general agreement with available experimental data. The results show that in the studied intermetallic alloys, twinning stress is lower than slip stress; Ta and Hf ternary addition are substantial to increase flow stress in Ni₃Al. The models proposed in the paper provide quantitative understanding and guidelines for selecting optimal precipitate chemistry and composition to obtain higher mechanical strength in Shape Memory Alloys.     

Preparation of novel ceramics with high CaO content from steel slag

Steel slag, an industrial waste discharged from steelmaking process, cannot be extensively used in traditional aluminosilicate based ceramics manufacturing for its high content of calcium oxide. In order to efficiently utilize such solid waste, a method of preparing ceramics with high CaO content was put forward. In this paper, steel slag in combination with quartz, talcum, clay and feldspar was converted to a novel ceramic by traditional ceramic process. The sintering mechanism, microstructure and performances were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) techniques, combined experimenting of linear shrinkage, water absorption and flexural strength. The results revealed that all crystal phases in the novel ceramic were pyroxene group minerals, including diopsite ferrian, augite and diopsite. Almost all raw materials including quartz joined the reaction and transformed into pyroxene or glass phase in the sintering process, and different kinds of clays and feldspars had no impact on the final crystal phases. Flexural strength of the ceramic containing 40 wt.% steel slag in raw materials can reach 143 MPa at sintering temperature of 1210 °C and its corresponding water absorption, weight loss, linear shrinkage were 0.02%, 8.8%, 6.0% respectively. Pyroxene group minerals in ceramics would contribute to the excellent physical and mechanical properties.     

Graphene aerogels as a highly efficient counter electrode material for dye-sensitized solar cells

Graphene aerogels (GAs) prepared with an organic sol–gel process, possessing a high specific surface area of 814 m²/g and a high electric conductivity of 850 S/m, are applied as a counter electrode material for dye-sensitized solar cells (DSSCs). The performance of the GA as the counter electrode material is found to be dependent on its film thickness, with thicker films offering more surface areas for the involved catalytic reduction reaction but at the same time increasing the charge and mass transport resistances. At an optimum GA film thickness of 4.9 μm, a power conversion efficiency of 96% of that achieved with a Pt counter electrode based DSSC is obtained. In addition, a thinner GA film of 1.7 μm, when loaded with Pt of 1 mol% through a photo-reduction process, achieves a power conversion efficiency of 98% of that obtained with a Pt counter electrode based DSSC. The excellent performances of the GA-based counter electrodes are manifested with electrochemical impedance analyses and cyclic voltammetry based catalytic activity analyses.     

Al-Zn-Mg-Cu合金多尺度第二相粒子与性能关系研究

介绍了Al-Zn-Mg-Cu合金多尺度第二相粒子与性能关系的研究。涉及的多尺度第二相粒子包括微米尺度的金属间化合物、亚微米尺度的弥散相、纳米尺度的晶内析出相和晶界析出相;涉及的相关性能为强度、断裂韧性以及腐蚀性能。结合相关文献与作者的研究工作,可以得出以下结论:金属间化合物会影响合金的断裂韧性和腐蚀抗力;弥散相通过抑制基体再结晶的方式影响合金的强度、断裂韧性以及腐蚀抗力;晶界析出相会影响合金的断裂韧性和腐蚀抗力;晶内析出相影响合金的强度和断裂韧性。     

Cu熔体中氧化夹杂在超重力场下的运动规律

对超重力场条件下Cu熔体中的氧化夹杂进行受力分析,建立夹杂颗粒沿超重力方向上的运动速度与运动距离方程,并通过理论计算分析重力系数、夹杂物特性(尺寸、种类、含量)以及熔体温度对夹杂物在超重力场中运动行为的影响。计算结果表明,超重力场能强化Cu熔体中氧化夹杂的定向分离过程,其中重力系数、夹杂物尺寸、夹杂与熔体之间密度差(固液密度差)对夹杂颗粒运动行为影响较大。较大的重力系数、夹杂物尺寸以及固液密度差均有利于夹杂物的上浮去除。