规则螺旋碳纳米管的制备及其结构的研究

以钛片为催化剂，通过乙炔气体在７５０℃下热解制备了规则螺旋的碳管，这些规则的螺旋碳管直径约为２００ｎｍ，规则螺旋碳管的形成与钛片的预处理有关，在盐酸处理过的钛片表面上所生长的碳管几乎都是规则螺旋形状的。     

Ti-V合金及其氢化物结构的研究

介绍了3种组成的Ti-V合金(Ti0.76V0.24、Ti0.51V0.49和Ti0.25V0.75)及其氢化物的晶体结构确定方法.通过XRD分析和理论计算,确定这3种合金为bcc结构,它们的纯β相氢化物是fcc结构,并测得了这两类结构的晶胞参数.研究发现,Ti-V合金吸氢性能比金属V有所改善,H原子数与合金原子数之和的比大于1.0才能发生α相氢化物向β相氢化物的转变.     

Structure and Electrical Resistivities of Liquid Al and Ga Metals and Their Binary Alloys

The ionic and electronic properties of liquid Al and Ga metals and Al_1-x Ga _x alloys have been investigated self-consistently. Partial structure factors have been calculated from the solution of the Ornstein–Zernike equation with the hybridized mean spherical approximation closure, and the transferable electron–ion potential of Fiolhais et?al. has been used as the input pseudopotential. Two different formulas are used in the electrical resistivity calculation, namely, the Faber–Ziman formula and the modified Ziman’s formula suggested by Ferraz–March. The results are compared with each other and experimental values.     

Effect of Electropolishing of Metals and Alloys in a Deep Eutectic Solvent on Their Corrosion Characteristics

Materials Science - It is shown that the electrochemical anodic treatment of alloys (stainless steels, Al–Mg alloys, and bronzes) in Ethaline (eutectic mixture of choline chloride and...     

Changes in the Crystal Structure of Metals in the Course of Their Laser Processing

Journal of Engineering Physics and Thermophysics - By the x-ray diffractometry method, the authors found a change in the crystal structure of a number of metals in the zone of exposure of their...     

The Wettability of Copper-Manganese Alloys on Alumina and Their Potential as Direct Brazing Filler Metals

The wetting and spreading of copper-manganese alloys on alumina was studied using a sessile drop technique. The contact angle, solid-liquid interfacial energy and the work of adhesion values were calculated based on the experimentally measured spreading radius in the temperature range of 1100 to 1300°C. Using an in situ measurement technique, the spreading radius could be continuously monitored as a function of time.

The results were compared to similar work on the copper-titanium/alumina system. Similar spreading behavior was observed for both systems and it is proposed that spreading occurs by the same interfacial reaction product nucleation and growth mechanism. While the maximum work of adhesion was lower for copper-manganese alloys on alumina relative to that for copper-titanium alloys on alumina (1425 versus 2800 mJ.m²), the copper-manganese/alumina adhesion values are sufficient for many direct bonding applications. The potential for improving interlayer mechanical properties for alumina brazed with copper-manganese alloys is also discussed.     

金属在液固两相流中的冲刷腐蚀

液固两相流体的冲刷腐蚀行为较单相流体更为复杂,在相同液相介质的情况下,其冲刷腐蚀对材料的破坏程度更为严重。综述了国内外对液固两相流的冲刷腐蚀体系开展的研究,对冲刷腐蚀的过程有了进一步的认识,对冲刷腐蚀的影响规律和危害性进行了论述,从而为材料的选用提供一定的参考依据。     

金属在两相流动水体中的冲刷腐蚀

水体对金属的冲刷行为会加剧金属的腐蚀 ,影响金属的使用寿命 ,冲刷行为的腐蚀机理很复杂 ,不同的环境介质和不同的金属材料其腐蚀机理亦不同。弄清楚冲刷腐蚀的机理有利于金属的防腐蚀设计。为此 ,对冲刷腐蚀的特征、影响因素、研究方法及腐蚀机理进行了论述     

Synthesis and Study of Binary Actinide and Lanthanide Compounds: XXIV. Curium-Cobalt Alloys

Two microsamples of ²⁴⁴Cm-Co alloys prepared by high-temperature condensation of curium metal vapor onto flat cobalt supports were studied. Both samples contained two intermetallic compounds with hexagonal lattices: Co17Cm2 and Co₅Cm. The existence of Co₂Cm or Co₂(Cm,Th) intermetallic compound with a cubic lattice was assumed. It was found that Cm is insoluble in - and -Co at room temperature and at heating.     

Trends in Superconductivity of Heavy-Electron Metals

Superconductivity in metals with electrons exhibiting a strongly enhanced effective mass may still be considered as an exotic phenomenon. In various cases, convincing evidence for unconventional superconducting states has been found and it seems quite conceivable that superconductivity in these materials is not triggered by the usual electron–phonon interaction. We briefly review the present state of knowledge and also discuss a few recent developments.     

Specific Features of the Temperature Dependence of the Mechanical Properties of Some Transition Metals and Their Alloys

On the basis of the results of theoretical investigations confirmed by the experimental data, it is established that, at certain temperatures and strain rates, the interstitial atoms in transition metals and alloys based on these metals participate in the dynamic interaction with dislocations, which facilitates the process of hardening of these metals. We compute the temperatures of dynamic interaction for hydrogen, nitrogen, oxygen, and carbon in two modifications of iron and metals from the VA group. It is shown that these effects can be significant after holding in environments. Dynamic strain aging is also typical of alloys based on the investigated metals.     

Mechanisms of Corosion and Oxidation of Metals and Alloys

Selected topics in field of the study of the mechanisms of corrosion and of oxidation of metals or alloys are presented. The first part reports a new model for the mechanism of the breakaway oxidation of ferritic stainless steels in water vapour. The second part is devoted to the physico‐chemical aspects of oxidation and presents experimental methods useful in the kinetic modelling applied to two alloys, the zircalloy‐4 and an AlMg5 % in the liquid state. In the third part the physical and numerical modelling of the stress corrosion cracking behaviour in face‐centered cubic (fcc) alloys is detailed, which enables the study of the influence of macroscopic parameters (such as the temperature or hydrogen activity) on the fracture process.     

Interaction of Hexafluoroacetylacetone with Metals and Their Alloys in the Medium of Supercritical Carbon Dioxide in the Processes of Equipment Decontamination

In the course of treatment of stainless steel with supercritical CO₂ containing -diketones in combination with pyridine and water, these agents react mainly with the oxide films. Therefore, in industrial use of such media, e.g., for decontamination of the equipment, the corrosion is expected to be low. Under these conditions, uranium does not dissolve from the surface of metallic uranium, and iron does not dissolve from the surface of pure metallic iron. In treatment of a copper or nickel surface with supercritical CO₂ containing -diketons and modifiers, both the oxide film and metals are involved in the reaction. It is presumed that water facilitates ionization of the complexing agent, and pyridine (or another amine with pK _a 5-6) creates a medium favorable for complexation. Furthermore, pyridine molecules may be incorporated in the complex as additional ligands.     

Uniaxial Ratcheting Behaviors of Metals with Different Crystal Structures or Values of Fault Energy: Macroscopic Experiments

The uniaxial ratcheting behaviors of several metals with different crystal structures or values of fault energy were observed by the stress-controlled cyclic tests at room temperature. The prescribed metals included 316L stainless steel, pure copper, pure aluminum, and ordinary 20# carbon steel. The effects of applied mean stress, stress amplitude and stress ratio on the uniaxial ratcheting were also investigated. The observations show that different crystal structures or values of fault energy result in more or less di?erent ratcheting behaviors for the prescribed metals. The different ratcheting behaviors are partially caused by the variation of dislocation mobility.     

High Damping Alloys and Their Application

Damping alloys show prospective applications in the elimination of unwanted vibrations and acoustic noise. The basic definitions and characterization methods of damping capacity are reviewed in this paper. Several physical mechanisms controlled by the alloy microstructure are responsible for the damping behavior in the damping alloys. Composite, dislocation, ferromagnetic and planar defect types are commonly classified for the alloys, which show the different damping behavior against temperature, frequency of vibration,amplitude of vibration and damping modes. Development of practically applicable damping alloys requires the higher mechanical properties and adequate workability, besides the high damping capacity. A new Mn-Cu damping alloy, named as M2052 alloy, is recently developed with possible industrial applications.