Effect of thermal oxidation on microstructures and mechanical properties of nanoporous coppers

Nanoporous copper oxides were formed by thermal oxidation of nanoporous copper at 150°C–270°C. The oxidation process of nanoporous copper was investigated by using XRD, SEM, nitrogen adsorption, HRTEM and nanoindentation. The variation of microstructures and mechanical properties was analyzed. The results showed that the content of copper oxides increased, the ligament gradually coarsened, and the mechanical properties of nanoporous structure were improved with the increase of oxidation temperature. When the oxidation temperature was below 210°C, the ligament surface was oxidized to Cu_2O, and the composite structure of Cu_2O@Cu was formed. The formation of CuO occurred since 220°C, and the composite structure of CuO/Cu_2 O@Cu was formed. CuO nanowires were grown on the ligament surface at 250°C; the specific surface area, elastic modulus and hardness of nanoporous structure are 1.37, 3.31 and 7.58 times that of the nanoporous copper, respectively.     

Liquid metal assisted regulation of macro-/micro-structures and mechanical properties of nanoporous copper

Nanoporous metals have received significant attention as a new class of structural and functional materials. However, the macroscopic brittle fracture under the tensile test is an impediment to their practical applications. Thus, it is of central importance to develop nanoporous materials with low cost and high tensile ductility. Herein, a nanoporous Cu film supported on a pure Cu substrate (NPC@Cu) was fabricated by utilizing a liquid Ga assisted alloying-dealloying strategy, and the thickness of NPC film can be precisely regulated by changing the mass loading of liquid Ga. In-situ X-ray diffraction was performed to further explore the alloying/dealloying mechanisms. The NPC@Cu films show good tensile mechanical properties with a minimum elongation of 13.5 %, which can be attributed to the good interface bonding and certain modulus matching between the nanoporous Cu layer and the Cu substrate. Our findings demonstrate that the design of film-substrate structure provides a feasible strategy for enhancing the mechanical properties of nanoporous metals.

     

Effects of atmospheres and precursors on MnO x /TiO2 catalysts for NH3-SCR at low temperature

The effects of atmospheres and precursors on MnO _x /TiO₂ catalysts were studied, which were prepared by the impregnation method and tested for their NO _x conversion activity in ammonia selective catalytic reduction (NH₃-SCR) reactions. Results showed that the manganese carbonate (MC) precursor caused mainly Mn₂O₃, while the manganese nitrate (MN) precursor resulted primarily in MnO₂ and the manganese sulfate (MS) precursor was unchanged. The manganese acetate (MA) precursor leaded obtaining a mixture of Mn₂O₃ and Mn₃O₄. NO _x conversion decreased in the following order: MA/TiO₂ > MC/TiO₂ > MN/TiO₂ > MS/TiO₂ > P25, with a calcination temperature of 773 K in air. Catalysts that were prepared by MA and calcined in oxygen performed strong interaction between Ti and Mn, while MnTiO₃ was observed. Compared to the catalysts calcined in nitrogen, those calcined in oxygen had larger diameter and smaller surface area and pore. Catalysts that were prepared by MA and calcined in nitrogen tended to gain higher denitration rates than those in air, since they could be prepared with significant specific surface areas. NO _x conversion decreased with calcination atmospheres: Nitrogen> Air> Oxygen. Meanwhile, amorphous Mn₂O₃ turned into crystalline Mn₂O₃, when the temperatures increased from 673 to 873 K.     

Local segregation in Cu-In precursors and its effects on microstructures of selenized CuInSe2 thin films

Local segregation in Cu-In precursors and its effects on the element distribution and microstructures of selenized CuInSe₂ thin films were investigated. Cu-In precursors with an ideal total mole ratio of Cu to In of 0.92 were prepared by middle frequency alternating current magnetron sputtering with Cu-In alloy target, then CuInSe₂ absorbers for solar cells were formed by selenization process in selenium atmosphere. Scanning electron microscope and energy dispersive X-ray spectroscope were used respectively to observe the surface morphologies and determine the compositions of both Cu-In precursors and CuInSe₂ thin films. Their microstructures were characterized by X-ray diffractometry and Raman spectroscope. The results show that Cu-In precursors are mainly composed of Cu₁₁In₉ phase with In-rich solid solution. Stoichiometric CuInSe₂ thin films with a homogeneous element distribution and single chalcopyrite phase can be synthesized from a segregated Cu-In precursor film with an ideal total mole ratio of Cu to In of 0.92. CuInSe₂ thin film shows P-type conductivity and its resistivity reaches 1.2×10³ Θ·cm. Foundation item: Project(2004AA513023) supported by the National High Technology Research and Development Program of China     

Preparation and mechanical behavior of Mg-based bulk metallic glasses and their matrix composite

Mg87-xCuxDy13(x=22,27,32) bulk metallic glasses (BGMs) with a diameter of 6-8 mm and in-situ Mg phase reinforced Mg70Cu17Dy13 BMG matrix composite with a diameter of 3 mm have been prepared by copper mould casting. The glass forming ability (GFA) of Mg-Cu-Dy alloys have been investigated by differential scanning calorimetry (DSC) and X-Ray diffraction (XRD) and tne mechanical properties have been measured. Results show that Mg87-xCuxDy13(x=22,27,32) alloys in the Mg-Cu-Dy alloy system exhibit excellent GFA, and Mg60Cu27Dy13 alloy has the largest GFA among these alloys. And In-situ Mg phase reinforced Mg70Cu17Dy13 BMG matrix composite exhibits some work hardening and a high fracture compressive strength of 702.38 MPa and some plastic strain of 0.81%. The improvement of the mechanical properties is attributed to the fact that the Mg phase distributed in the amorphous matrix of the alloy has some effective load bearing and plastic deformation ability to restrict the expanding of shear bands and cracks and produce its own plastic deformation.     

Highly sensitive glucose sensor based on hierarchical CuO

The fabrication of high performance CuO based glucose sensors remains a great challenge due to the "trade-off effect" between sensitivity and linear range. In this study, a hierarchical CuO nanostructure with a great number of firecracker-shaped nanorods along the ligament and three-dimensional interconnected nanoporous is obtained by dealloying and post oxidation process of Al-33.3 wt% Cu eutectic alloy ribbons. Because of the precise structural design, not only the number of active sites for glucose electro-oxidation is significantly increased but also the glucose diffusion under high concentration is greatly accelerated, leading to a high sensitivity of 1.18 mA cm~(-2) mM~(-1) and a wider linear range up to 5.53 mM for glucose detection. This work provides a potential approach to design hierarchical nanostructure for other metal oxides with desirable properties for electrocatalytic applications.     

Crystallization kinetics and magnetic properties of Fe73.5Si13.5B9Cu1Nb1V2 nanocrystalline powder cores

Amorphous ribbons of the alloy Fe_73.5Si_13.5B₉Cu₁Nb₁V₂ were prepared by the standard single copper wheel melt spinning technique in the air atmosphere. The crystallization kinetics of amorphous ribbons was analyzed by non-isothermal differential scanning calorimetry (DSC) measurements. The crystallization activation energies of amorphous ribbons calculated by using Kissinger model were 364 and 337 kJ/mol for the first and the second crystallization, respectively. The Avrami exponent n was calculated from the Johnson-Mehl-Avrami (JMA) equation. The value of the Avrami exponent showed that the crystallization mechanism in the non-isothermal primary crystallization of amorphous ribbons was all shapes growing from small dimensions controlled by diffusion at decreasing nucleation rate. The variation of soft magnetic properties of nanocrystalline Fe_73.5Si_13.5B₉Cu₁Nb₁V₂ alloy powder cores as a function of milling times has been investigated. It is found that the effective permeability of the cores shows high frequency stability and decreases with the increase of milling times. The quality factor increases with increasing frequency in lower frequency range, and reaches a maximum at the frequency of 80 kHz then decreases gradually with increasing frequency.     

Interfacial characteristics of high frequency induction brazed Cu and pre-metalized graphite joints

Oxygen-free copper and pre-metalized graphite were brazed using CuNiSnP braze alloy by high frequency induction heating method. Interfacial microstructures and reaction phases were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The strength and resistance of the joints were tested. It is found that when the brazing parameters are optimized, the structures of the joints are graphite/(Cu,Ni)/Ni(s.s)+Ni _x P _y /Cu₃P+Cu(s.s) (including Sn)+eutectic structures (Cu₃P+Ni₃P+Cu(s.s)/Cu (s.s)/Cu). When the temperature increases to 750 °C or the holding time prolongs to 300 s, the eutectic structures disappear and the amount of Cu₃P increases. The maximum shear strength of the joints is 5.2 MPa, which fracture at the interface of graphite and metallization. The resistance of the joints is no more than 5 mΩ.     

Zr41 Ti14 Ni12.5 Cu10 Be22.5非晶合金冲击压缩行为理论与实验研究

为研究Zr_(41)Ti_(14)Ni_(12.5)Cu_(10)Be_(22.5)非晶合金的冲击压缩响应及物态方程,利用平板冲击试验,测试了受到速度为350 m/s～550 m/s的铜板冲击时,非晶合金试样的自由面粒子速度;采用阻抗匹配法得到了材料的雨贡纽参数,并利用理想混合物模型对材料的雨贡纽参数进行预估,分析对比了理论计算结果与实验结果;将求材料格林艾森物态方程转化为非线性最优化问题,提出了基于模拟退火算法的材料格林艾森物态方程计算方法,设计了退火参数表,并采用解析法计算了材料的布里希-默纳罕物态方程和三项式物态方程,对比研究了三种物态方程与实验结果.理论和实验结果表明,5～10 GPa压力范围内,Zr_(41)Ti_(14)Ni_(12.5)Cu_(10)Be_(22.5)非晶合金的零压体积声速为4 267 m/s,D-u曲线斜率为4.376,曲线斜率远大于一般金属材料,其雨贡纽极限强度为5.60 GPa左右;理想混合物模型仅适用于计算高压区Zr基非晶合金的雨贡纽参数,低压区理论计算结果与实验结果误差较大;在5～10 GPa压力范围内,格林艾森物态方程、三项式物态方程与实验结果吻合度较高,而布里希-默纳罕物态方程误差较大,不适用于计算材料状态参量.     

Resource assessment of copper deposits in China

Copper-bearing deposits of China are statistically analyzed in terms of ore grade, metal amount and ore tonnage. Each of grade and metal amount shows more or less a lognormal distribution. Analysis gives 10 copper metallogenic districts, each having specific densities of deposit numbers and copper reserves larger than 3. Based on the ratio of copper in ore value (R _Cu), Chinese copper deposits are classified into two groups: mainly copper-producing deposits (MC: R _Cu⩾0.5) and accessorily copper-producing deposits (AC: R _Cu<0.5). The grade-tonnage relation of MC deposits can be combined by two exponential functions approximating high grade (>3.0%) and low grade (<2.0%) parts. The critical copper grade, which is obtained from the low grade part of the relation, is 0.34%. Chinese copper resources are concluded to become pessimistic, because some mines are working with grades close to this critical value. Taking account of the fact that many copper deposits are actually polymetallic, Cu-equivalent grades, which are converted from ratios of metal prices to the copper price, are also introduced. The critical Cu-equivalent grade of MC deposits (0.43%) also suggests that Chinese copper resources are pessimistic.     

Properties of Al-doped Copper Nitride Films Prepared by Reactive Magnetron Sputtering

Cu3N and Al Cu3N films were prepared with reactive magnetron sputtering method. The two films were deposited on glass substrates at 0.8 Pa N2 partial pressure and 100 ℃ substrate temperature by using a pure Cu and AI target, respectively. X-ray diffraction （XRD） measurements show that the un-doped film was composed of Cu3N crystallites with anti-ReO3 structure and adopted [111] preferred orientation. XRD shows that the growth of Al-doped copper nitride films （AlxCu3N） was affected strongly by doping AI, the intensity of [111] peak decreases with increasing the concentration of Al and the high concentration of Al could prevent the Cu3N from crystallization. AFM shows that the surface of AlCu3N film is smoother than that of Cu3N film. Compared with the Cu3N films, the resistivities of the Al-doped copper nitride films （AlxCu3N） have been reduced, and the microhardness has been enhanced.     

Structural Properties and Energy Analysis of ZrxCu90-xAl10Ternary Metallic Glasses

Classical molecular dynamics(MD) were conducted to study the structure and energy distribution of Zr_xCu_90-xAl₁₀(x=20, 30, 40, 50, 60, 70) ternary alloys. When the Zr composition is 30%, the glass transition temperature reaches the maximum value and the Zr₃₀Cu₆₀Al₁₀ owns high glass forming ability(GFA). Analysis of the short-range structure shows that there are more low-energy Zr-centered polyhedron with high coordination number(CN...     

Fabrication and characterization of porous mullite ceramics from pyrolysis of alumina powders filled silicone resin

Porous mullite ceramics were fabricated from pyrolysis of nanometer alumina powders filled silicone resin. At 1573 K, the mixture of nanometer γ-Al2O3 and silicone resin can be entirely transformed to mullite in air. The effects of shaping pressure on microstructure and mechanical property were investigated. Increasing shaping pressure leads to decrease in open porosity and average pore size, narrower pore size distribution, and improvement in flexural strength. With a shaping pressure of 43 MPa, nanoporous mullite ceramics with an average pore size of 50 nm can be obtained, showing 33% in open porosity and 42 MPa in flexural strength. The microstructure of porous mullite ceramics consists of dense region and loose region.     

Effect of Cu seed on the synthesis and characterization of FeCo alloy nano-particles by using polyol method

Fine metal particles with uniform shape, narrow size distribution and high purity are increasingly needed for specific uses in high tech industrial application. We report the direct chemical synthesis of FeCo alloy particles using the mixture of FeCl2·4H2O, Co (Ac)2·4H2O (Ac: acetate) and NaOH in ethylene glycol, and then obtained FeCo alloy particles better dispersed by adding the polyvinylpyrrolidone (PVP) and also the size could be controlled by adding copper. The prepared nano-particles were characterized using FESEM, XRD and VSM. The mean diameter of these particles was varied in the range of sub- mi- crometer to nanometer with metal-ion concentration. FeCo particles showed the typical soft magnetic properties.     

Effect of Porous Copper Pore Density on Joint Interface: Microstructure and Mechanical Analysis

The effect of the pore density of porous copper (Cu) on brazed Cu/porous Cu was investigated. A filler with a composition of Cu-9.0Sn-7.0Ni-6.0P (Sn: Tin; Ni: Nickel; P: Phosphorus) and porous Cu with pore densities of 15 pores per inch (PPI), 25 PPI, and 50 PPI were employed. The joint strength of Cu/porous Cu was evaluated with shear tests at different brazing temperatures. Characterizations of the joint interface and fractured surface were achieved with scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The micro-hardness test of Cu/porous Cu joint interface showed a high hardness value (HV) for 50 PPI porous Cu. This result was in line with its low shear strength. It was proved that the joint strength of Cu/porous Cu is dependent on the pore density of the porous Cu structure and brittle phases of Cu₃P and Ni₃P in the brazed interface.     

Simultaneous electrogenerative leaching of chaicopyrite concentrate and MnO2

In order to enhance the electrogenerative leaching rate of chalcopyrite concentrate reasonably, the principle of generative process was applied to simultaneous leaching of chalcopyrite concentrate and MnO2. The results show that Cu^2＋ and Mn^2＋ in addition to electrical energy could be acquired in the simultaneous electrogenerative leaching process. The leaching cell has the open circuit potential of about 1.0 V and gains quantity of electricity of about 700 C. The optimum leaching rates of Cu^2＋ and Mn^2＋ are 23.10% and 22.1%, respectively after electrogenera- tive leaching for about 10 h under the present conditions.     

Influence of nano-scaled dispersed second phase on substructure of deformed dispersion strengthened copper alloy

The deformation behavior of dispersion strengthened copper alloy Cu-Al₂O₃ was studied by TEM. The results show that nano-scaled dispersed second phase not only increases dislocation density in matrix, but also has an important influence on the dislocation substructure. The presence of fine dispersed Al₂O₃ particles results in a uniform and random dislocation distribution in matrix copper and causes the difficulty in formation of dislocation cell structure and the decrease in the amount of cell structure during deformation. Deformation gives rise to much more dislocations and dislocation cells form more difficultly and the decrease in the cell size with the increase of dispersion degree. Foundation item: Project (2002AA302505) supported by the National Advanced Materials Committee of China     

Structure relaxation of Mg65Cu25Gd10 metallic glass and its effect on strength

To identify the re-arrangement of constituent atoms of an amorphous Mg₆₅Cu₂₅Gd₁₀ alloy happened with annealing, structure relaxation of the alloy was investigated as a function of annealing time at 373 K through extended X-ray absorption fine structure (EXAFS) analysis procedures. To understand the effect of structure relaxation on strength, compression tests were conducted for both the as-cast and the annealed Mg₆₅Cu₂₅Gd₁₀ samples. It is found that short range order around Cu and Gd atoms exhibits different variation trends with increasing annealing time at 373 K, though the structure of the alloy still remains to be amorphous. Based on the fact that the strength of the alloy first exhibits a reduction and then a recovery with annealing time, it is suggested that the enhancement of short range order around Cu should be responsible for the strength reduction, while the enhancement of short range order around Gd should be responsible for the strength recovery. Funded by National ‘863’ Program (No. 2003AA305071)     

Experimental Analysis of Dynamic Stiffness Coefficient of the New Mn Cu Alloy Annular Parts

Based on excitation-resonance mass testing principle, a proper experiment testing system is designed for annular parts. The dynamics characters of the axis sleeve, which is made of a new Mn-Cu alloy and used as a vibration reductor in high acceleration rotary testing machine for fusee, is investigated. The relationship between stiffness coefficient and utilizing frequency is obtained, and the simplified dynamics model of crystal is established. From the viewpoint of crystal microstructure of the Mn-Cu alloy, the experiment result is analyzed by the viscoelastic theory, and the characters of stress and strain in the condition of high frequency are discussed. The results indicate that the Mn-Cu alloy annular parts are fit to be used on the high accleration rotary testing machine for fusee.     

Chemieal Synthesis and Magnetie Properties of Nanocrystalline （La0.67-XGdx）Sr0.33MnO3 Using Amorphous Molecular Alloy as Precursors

A new route to synthesize nanosized crystalline of （La0.67-xGdx）Sr0.33MnO3 （X=0.05, 0.10, 0.15, 0.20） perovskite-type complex oxides at calcination temperature of 600-1000℃ using the amorphous molecular alloy as precursors was reported. The precursor could be completely decomposed into complex oxide at temperature below 500℃ according to the TGA and DTA results. XRD demonstrates that the decomposed species is composed of perovskite-type structure at calcination temperature of 600℃ for 2 h. The particle size that depends on the calcination temperature of the precursor is in a range of 30-120 nm as determined by transmission electron microscopy （TEM）. This method is effective and can be easily quantitatively controlled to synthesize nanosized perovskite-type complex oxides. The magnetic properties of （La0.67 xGdx）Sr0.33MnO3 nanocrystalline were preliminary studied.