Ultrafine ordered L1_(2)-Pt-Co-Mn ternary intermetallic nanoparticles as high-performance oxygen-reduction electrocatalysts for practical fuel cells

The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.

EFFECT OF ALLOYING ELEMENTS ON SENSITIVITY TO ENVIRONMENTAL EMBRITTLEMENT OF L1_2 INTERMETALLICS

The effect of Zr doping in Ni 3Al and B doping in Co 3Ti intermetallics on the sensitivity to moisture induced environmental embrittlement and on the hydrogen diffusivity was investigated. The results show that both B in Co 3Ti and Zr in Ni 3Al do not reduce the hydrogen diffusivity along the grain boundaries, therefore can not suppress the moisture induced environmental embrittlement. The above mentioned behavior of Zr in Ni 3Al and B in Co 3Ti is attributed to the fact that Zr and B are not segregated on the grain boundaries.

Influence of mechanical alloying time on the properties of Fe_3Al intermetallics prepared by spark plasma sintering

The Fe3Al-based intermetallics were prepared by mechanical alloying and spark plasma sintering （SPS）, and the influence of milling time on the properties of materials was investigated. The phase identification was investigated by X-ray, and the surface morphology and fractography were observed by scanning electron microscope （SEM）. The mechanical properties such as bending strength, strain, and microhardness were tested. The results show that Fe reacts with Al completely to form Fe3Al during short SPS processing time. The relative densities of the sintered samples were nearly 100%. The mechanical properties of the sintered samples can be improved along with the milling time. The representative values are the bend strength of 1327 MPa and the microhardness of 434.

Volta Potential Analysis of Intermetallics in 7A52 Aluminum Alloy

In order to study the effect of intermaetallics on the corrosion behaviour of 7A52 aluminum alloy, the alloy was characterized by means of SEM-EDS and scanning Kelvin probe force microscopy（SKPFM）. The experimental results indicate that there are two different intermetallics：A1-Mn-Fe and Mg2Si. Both intermetallics exhibite the negative volta potential relative to the matrix indicating an anodic behaviour. Hereby, they are easy to be dissolved and corroded under the erosive environment, and there become the corrosion initiation sites. The A1-Mn-Fe intermetallics show stronger anodic behaviour than those of Mg2Si intermetalics. It means that A1-Mn-Fe intermetalics are easier to be corroded.

Structures and Magnetic Properties of Europium-Transition Metal-Gallium Ternary Intermetallic Compounds with 1:3 Type

The crystal structures and magnetic properties of novel Eu TrGa3-r （T=Pd, It, Rh） in termetallic compounds are investigated by using powder x-ray diffraction and magnetic measurements. EuTrGa3-r crystallizes in orthorhombic structure with space group of Cmcm and Z = 4. There are four kinds of nonequivalent 4c crystal positions in EuTrGaa-r unit cell, which are occupied by 4Eu, 4GaⅠ, 4（GaⅡ, T） and 4GaⅢ, respectively. EuTrGa3-r ex- hibits the complex magnetic states in low-temperature regime, with the three-, two- and one-antiferromagnetic transitions occurring for T=Ir, T=Rh and T=Pd, respectively. It might be due to the Kondo effect： a localized antiferromagnetic interaction of the isolated impurity spins with the surrounding conduction electrons at low-temperature regime.

高速电弧喷涂Fe-Al/Cr_3C_2粉芯丝材的研制与性能研究

介绍了Fe -Al/Cr3 C2 粉芯丝材的研制过程 ,采用高速电弧喷涂技术 (HVAS) ,用Fe -Al/Cr3 C2 粉芯丝材原位合成了铁铝金属间化合物涂层 ;阐明了粉芯丝材在高速电弧喷涂技术应用中的优点 ;探讨了添加增强相Cr3 C2 对涂层氧化层的影响 ;研究了高速电弧喷涂铁铝金属间化合物涂层的性能。结果表明 ,用Fe -Al/Cr3 C2 粉芯丝材得到的高速电弧喷涂涂层具有较高的结合强度和显微硬度 ,良好的耐高温冲蚀、耐磨损性能。

金属间化物（Sm_（1－x）Y_x）_2Fe_（17）N_y结构的X射线衍射研

通过Ｘ射线衍射等手段对赝三元金屑间化物（Ｓｍ＿（１－ｘ）Ｙ＿ｘ）＿２Ｆｅ＿（１７）Ｎ＿ｙ（ｘ＝０，０．２．０．４．０．６，０．８和１．０；２＜ｙ＜３）的晶体结构及自旋磁结构进行了研究。由试验结果得出以下结论：１）当Ｙ的含量ｘ为０．４时，已出现两相共存现象，但两相中以Ｔｈ＿２Ｚｎ＿（１７）型结构相为主，Ｔｈ＿２Ｎｉ＿（１７）型结构相为次；当Ｙ的含量了达到０．６时，其晶体结构由Ｔｈ＿２Ｚｈ＿（１７）型结构变为Ｔｈ＿２Ｎｉ＿（１７）型结构；２）当Ｙ的含量ｘ在０．８～１．０的范围内，存在自旋磁结构的变化，即由易Ｃ轴各向异性变为易Ｃ平面各向异性；３）杂质相（α－Ｆｅ相）的含量随着Ｙ含量ｘ的增加而减小。

金属间化物(Sm_(1-x)Pr_x)_2Fe_(17)N_y 的各向异性机制探讨

制备了金属间化物（Ｓｍ１－ｘＰｒｘ）２Ｆｅ１７Ｎｙ（ｘ＝０，０．２，０．４，０．６，０．８，１．０；２＜ｙ＜３）的粉末样品，并通过穆斯堡尔谱等手段研究了金属间化物（Ｓｍ１－ｘＰｒｘ）２Ｆｅ１７Ｎｙ中Ｐｒ原子的替代效应，进而对其中的各向异性产生机制等方面进行了分析由实验得出以下结论：１）（Ｓｍ１－ｘＰｒｘ）２Ｆｅ１７Ｎｙ当ｘ＝０．６时发生了自旋磁结构相变，即由易Ｃ轴各向异性变为易锥面各向异性；２）金属间化物（Ｓｍ１－ｘＰｒｘ）２Ｆｅ１７Ｎｙ中Ｐｒ次格子的面各向异性较弱。

Mg-Fe-Al复合氧化物的制备及其对刚果红吸附性能的研究

通过共沉淀法制备了Mg-Fe-Al复合氧化物,并将其应用于水中刚果红的吸附研究。考察了Mg∶Fe∶Al(摩尔比)、pH、煅烧温度等因素对刚果红吸附性能的影响,并进行了吸附热力学和动力学研究。采用扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FTIR)和X射线衍射仪对Mg-Fe-Al复合氧化物进行表征。结果表明,Mg-Fe-Al复合氧化物的最佳制备条件为Mg∶Fe∶Al=2∶1∶1、pH=10、煅烧温度为500℃,并经结构表征确认,对刚果红的最大吸附量达到768.9mg/g。吸附过程符合Langmuir等温吸附方程和准二级速率方程。

Co-Ni-Al-Ti系L2_1/L1_2型双相金属间化合物合金热处理显微组织研究

对由 Ｌ２１型（Ｃｏ，Ｎｉ）２ＡｌＴｉ和Ｌ１２型（Ｃｏ，Ｎｉ）３（Ａｌ，Ｔｉ）两种有序相组成的Ｃｏ－Ｎｉ－Ａｌ－Ｔｉ系新型金属间化合物高温结构实验用合金进行了不同制度的热处理，并对相应的显微组织特征进行了分析研究，找到了控制显微组织以优化性能的热处理参数。

Effect of Trace La Addition on the Microstructure and Mechanical Property of As-cast ADC12 Al-Alloy

The effects of addition of La on the microstructure of as-cast ADC12 A1-Alloy were investigated by using optical microscope （OM）, X-ray diffraction （XRD）, scanning electron microscope （SEM）, and energy disperse spectroscopy （EDS）. The experimental results showed that the a-A1 and eutectic Si crystals were modified with the addition of 0.3 wt% La. The eutectic Si crystals showed a granular distribution. At the same time, the alloy possessed the best mechanical property. When more than 0.3 wt% La was added to ADC12 aluminum alloy, the microstructure of as-cast alloy was coarsening gradually with the increase of the content of La and the mechanical property decreased. The effect of rare earth La which was added in ADC 12 A1-Alloy for up to 0.9 wt% had been investigated in this study. The dendrites ofADC12 Al-alloy was refined obviously and the morphology of Si crystals showed a particle structure when the addition of La reached 0,3 wt%. Besides, the acicular La-rich intermetallics in the alloy deteriorated the mechanical property of alloy： To avoid this unwanted phase, the amount of added rare earth La must be less than 0.6 wt%.

First Principles Study of AI-Li Intermetallic Compounds

The structural properties, heats of formation, elastic properties, and electronic structures of four compositions of binary A1-Li intermetallics, A13Li, A1Li, A12Li3, and A14Li9, are ana- lyzed in detail by using density functional theory. The calculated formation heats indicate a strong chemical interaction between A1 and Li for all the A1-Li intermetallics. In partic- ular, in the Li-rich A1-Li compounds, the thermodynamic stability of intermetallics linearly decreases with increasing concentration of.Li. According to the computational single crystal elastic constants, all the four A1-Li intermetallic compounds considered here are mechani- cally stable. The polycrystalline elastic modulus and Poisson＇s ratio have been deduced by using Voigt, Reuss, and Hill approximations, and the calculated ratios of bulk modulus to shear modulus indicate that the four compositions of binary A1-Li intermetallics are brittle materials. With the increase of Li concentration, the bulk modulus of A1-Li intermetallics decreases in a linear manner.

Co-Ni-Al-Ti系L2_1/L1_2型双相金属间化合物合金的显微组织和力学行为研究

对于由 L2 1 型 ( Co,Ni) 2 Al Ti和 L12 型 ( Co,Ni) 3( Al,Ti)两种有序相组成的 Co- Ni- Al- Ti系新型金属间化合物高温结构用合金 ,经热处理后获得不同显微组织的高温压缩和室温断裂等力学行为进行了分析研究 ,确立了合金成分、显微组织和机械性能之间的关系 ,找到了进一步提高高温强度和室温塑性的途径。

Phase equilibria of Mg-rich corner in Mg Zn Al ternary system at 300 °C

The phase equilibria and compositions in Mg-rich comer at 300℃ were determined in the Mg-Zn-A1 ternary system through the equilibrated alloy method by using X-ray diffraction （XRD） and scanning electron microscopy （SEM） assisted with energy dispersive spectroscopy of X-ray （EDS）. The results show that there exist three three-phase regions consisted of a-Mg＋Mg17A112（7）＋A15Mg11Zn4（φ）, a-Mg＋Mga2（Al, Zn）49（r）＋A15MgllZn4（φ） and a-Mg＋MgZn＋Mg32（A1, Zn）49（r）, respectively. The intermetallic compounds in equilibrium with a-Mg phase all have large composition ranges, not appear to be linear. At the same time, both zinc and aluminum are soluble in the a-Mg solid solution, with which the compounds are in equilibrium.

Highly dispersed L1_(0)-PtZn intermetallic catalyst for efficient oxygen reduction

Highly active and durable electrocatalysts with minimal Pt usage are desired for commercial fuel cell applications.Herein,we present a highly dispersed L1_(0)-PtZn intermetallic catalyst for the oxygen reduction reaction(ORR),in which a Zn-rich metal–organic framework(MOF)is used as an in situ generated support to confine the growth of PtZn particles.Despite requiring high-temperature treatment,the intermetallic L1_(0)-PtZn particles exhibit a small mean size of3.95 nm,which confers the catalysts with high electrochemical active surface area(81.9 m^(2)g_(Pt)^(-1))and atomic utilization.The Pt electron structure and binding strength between Pt and oxygen intermediates are optimized through ligand effect and compressive strain.These advantages result in ORR mass activity and specific activity of 0.926 A mg_(Pt)^(-1) and 1.13 mA cm^(-2),respectively,which are 5.4 and 4.0 times those of commercial Pt/C.The stable L10structure provides the catalysts with superb durability;only a halfwave potential loss of 11 mV is observed after 30,000 cycles of accelerated stress tests,through which the structure evolves into a more stable PtZn-Pt core-shell structure.Therefore,the development of a Zn-based MOF as a catalyst support is demonstrated,providing a synergy strategy to prepare highly dispersed intermetallic alloys with high activity and durability.

Synthesis and characterization of FeAl nanoparticles by flow-levitation method

The synthesis of high purity intermetallic FeAI nanoparticles using the flow-levitation （FL） method was reported. Iron and aluminium droplets were levitated stably at about 2 230℃. The morphology, clystal structure and chemical composition of FeAI nanoparticles were investigated by transmission electron microscopy （TEM）, high-resolution TEM, X-ray diffraction and energy dispersive spectrometry. The results show that the average particle size of these nanoparticles is about 34.5 nm. Measurements of the d-spacing from X-ray diffraction and electron diffraction studies confirm that the intermetallic nanoparticles have the same crystal structure （B2） as the bulk FeA1. A thin oxidation coating is formed around the particles when being exposed to air. Based on the XPS measurements, the surface coating of the FeAI nanoparticles is composed of Fe2O3 and FeAl2O4. Besides, hysteresis curve reveals that saturation magnetization （Ms） of FeA1 is 1.66 A/m2, and the coercivity is about 1.214×10^3 A/re.

Inverse identification of constitutive parameters of Ti_2AlNb intermetallic alloys based on cooperative particle swarm optimization

Ti_2AlNb intermetallic alloy is a relatively newly developed high-temperature-resistant structural material, which is expected to replace nickel-based super alloys for thermally and mechanically stressed components in aeronautic and automotive engines due to its excellent mechanical properties and high strength retention at elevated temperature. The aim of this work is to present a fast and reliable methodology of inverse identification of constitutive model parameters directly from cutting experiments. FE-machining simulations implemented with a modified Johnson-Cook（TANH） constitutive model are performed to establish the robust link between observables and constitutive parameters. A series of orthogonal cutting experiments with varied cutting parameters is carried out to allow an exact comparison to the 2 D FE-simulations. A cooperative particle swarm optimization algorithm is developed and implemented into the Matlab programs to identify the enormous constitutive parameters. Results show that the simulation observables（i.e., cutting forces, chip morphologies, cutting temperature） implemented with the identified optimal material constants have high consistency with those obtained from experiments,which illustrates that the FE-machining models using the identified parameters obtained from the proposed methodology could be predicted in a close agreement to the experiments. Considering the wide range of the applied unknown parameters number, the proposed inverse methodology of identifying constitutive equations shows excellent prospect, and it can be used for other newly developed metal materials.