微波烧结CuTi-金刚石复合体

采用微波烧结方法制备出CuTi-金刚石复合体，并对复合体的工艺、组织和结构进行了研究．结果表明，金刚石颗粒在烧结过程中没有发生石墨化转变，CuTi-金刚石复合体中金刚石颗粒与CuTi基体间能形成良好的结合．CuTi-金刚石复合体的致密度随金刚石含量的增加出现先增加后降低的变化趋势，当金刚石含量为18.75～25vol％时达到最大值．

TiB_2/Ni coatings on surface of copper alloy electrode prepared by electrospark deposition

In order to improve the lifespan of spot-welding electrodes used for welding zinc coated steel sheets, titanium diboride was deposited onto their surface after precoating nickel as an intermediate layer. The microstructures and phase compositions of TiB2 and Ni coatings were characterized by SEM and XRD. The coating hardness was measured using a microhardness tester. The results indicate that a satisfactory TiB2 coating is obtained as a result of the intermediate nickel layer acting as a good binder between the TiB2 coating and the copper alloy substrate. Owing to its capacity of deforming, the precoated nickel layer is dense and crack free, while cracks and pores are observed in the TiB2 coating. The hardness of the TiB2/Ni coating decreases with the increase of voltage and capacitance because of the diffusion of copper and nickel and the oxidation of the coating materials. Because of the good thermal and electrical conductivities and high hardness properties of TiB2, the deformation of the electrode with TiB2/Ni coating is reduced and its spot-welding life is by far prolonged than that of the uncoated one.

Preparation and photocatalytic performance of Cu-doped TiO_2 nanoparticles

Cu-doped TiO2 nanoparticles with different doping contents from 0 to 2.0% （mole fraction） were synthesized through sol-gel method. X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and field emission scanning electron microscope （FE-SEM） were used to characterize the crystalline structure, chemical valence states and morphology of TiO2 nanoparticles. UV-Vis absorption spectrum was used to measure the optical absorption property of the samples. The photocatalytic performance of the samples was characterized by degrading 20 mg/L methyl orange under UV-Vis irradiation. The results show that the Cu-doped TiO2 nanoparticles exhibit a significant increase in photocatalytic performance over the pure TiO2 nanoparticles, and the TiO2 nanoparticles doped with 1.0% Cu show the best photocatalytic performance. The improvement in photocatalytic performance is attributed to the enhanced light adsorption in UV-Vis range and the decrease of the recombination rate of photoinduced electron-hole oair of the Cu-doped TiO2 nanoparticles.

Novel visible-light-responding InVO_4-Cu_2O-TiO_2 ternary nanoheterostructure: Preparation and photocatalytic characteristics

A novel visible-light-responding InVO4-Cu2O-TiO2 ternary nanoheterostructure was designed on the basis of the strategy of energy gap engineering and prepared through ordinary wet chemistry methods. The as-prepared nanoheterostructure was characterized by X-ray powder diffraction（XRD）, transmission electron microscopy（TEM）, high-resolution transmission electron microscopy（HRTEM） and diffuse reflectance ultraviolet-visible spectroscopy（UV-vis/DRS）. The TEM and HRTEM images of 10%InVO4-40%Cu2O-50%TiO2 confirm the formation of nanoheterostructures resulting from contact of the nanosized TiO2, Cu2O and InVO4 in the size of 5–20 nm in diameter. The InVO4-Cu2O-TiO2 nanoheterostructure, when compared with TiO2, Cu2O, InVO4, InVO4-TiO2 and Cu2O-TiO2, shows significant enhancement in the photocatalytic performance for the degradation of methyl orange（MO） under visible-light irradiation. With a 9 W energy-saving fluorescent lamp as the visible-light source, the MO degradation rate of 10%InVO4-40%Cu2O-50%TiO2 reaches close to 90% during 5 h, and the photocatalytic efficiency is maintained at over 90% after six cycles. This may be mainly ascribed to the matched bandgap configurations of TiO2, Cu2O and InVO4, and the formations of two p-n junctions by the p-type semiconductor Cu2O with the n-type semiconductors TiO2 and InVO4, all of which favor spatial photogenerated charge carrier separation. The X-ray photoelectron spectroscopy（XPS） characterization for the used 10%InVO4-40%Cu2O-50%TiO2 reveals that only a small shakeup satellite peak appears for Cu（II） species, implying bearable photocorrosion of Cu2O. This work could provide new insight into the design and preparation of novel visible-light-responding semiconductor composites.

Influence of Cu（II） on Ag（I） Recovery by Photocatalytic Reduction Method with TiO2 Suspension

Photocatalytic reduction method using TiO2 suspension for removal as well as possibly recovery of silver （Ag（I）） in the presence of Cu（II） is examined. The photocatalytic reduction was performed by batch technique in a closed reactor equipped with UV lamp. The concentration of unreduced Ag（I） was analyzed by atomic absorption spectrophotometry method. The research results indicate that Ag（I） in the solution can be removed and recovered effectively as silver metal Ag（0） deposited on the surface of TiO2 for photocatalytic reduction. In addition, the presence of Cu（II） ion with increasing concentration leads to a proportional decline in Ag（I） photoreduction due to the prominent competition in the adsorption on the surface of TiO2. The effectiveness of Ag（I） ion photoreduction in the presence of Cu（II） ion is strongly influenced by solution pH and the highest photoreduction is obtained at pH 5 - 8, which is related with the speciation ofAg（I）, TiO2 surface as well as Cu（II） in the solution.

Effect of Ti content on corrosion behavior of Cu-Ti alloys in 3.5% NaCl solution

The corrosion behavior of the Cu-Ti alloys with different Ti contents in 3.5%(mass fraction)NaCl solution was investigated using electrochemical measurements,immersion tests,mass loss measurements and SEM observation.The results show that Ti dissolved in the Cu matrix changes the corrosion process of the alloys.Pure Cu sample exhibits a typical active–passive-transpassive corrosion behavior.The anodic polarization current densities of the Cu-Ti alloys steadily increase with increasing applied potential,indicating that active dissolution of copper proceeds due to the potential difference in the galvanic coupling of Cu and Ti.The increase of Ti content decreases the corrosion resistance of the Cu-Ti alloys.

Octahedral Cu_2O-modified TiO_2 nanotube arrays for efficient photocatalytic reduction of CO_2

A photocatalyst composed of TiO 2 nanotube arrays（TNTs） and octahedral Cu2 O nanoparticles was fabricated,and its performance in the photocatalytic reduction of CO2 under visible and simulated solar irradiation was studied. The average nanotube diameter and length was 100 nm and 5 μm,respectively. The different amount of octahedral Cu2 O modified TNTs were obtained by varying electrochemical deposition time. TNTs modified with an optimized amount of Cu2 O nanoparticles exhibited high efficiency in the photocatalysis,and the predominant hydrocarbon product was methane. The methane yield increased with increasing Cu2 O content of the catalyst up to a certain deposition time,and decreased with further increase in Cu2 O deposition time. Insufficient deposition time（5 min） resulted in a small amount of Cu2 O nanoparticles on the TNTs,leading to the disadvantage of harvesting light. However,excess deposition time（45 min） gave rise to entire TNT surface being most covered with Cu2 O nanoparticles with large sizes,inconvenient for the transport of photo-generated carriers. The highest methane yield under simulated solar and visible light irradiation was observed for the catalysts prepared at a Cu2 O deposition time of 15 and 30 min respectively. The morphology,crystallization,photoresponse and electrochemical properties of the catalyst were characterized to understand the mechanism of its high photocatalytic activity. The TNT structure provided abundant active sites for the adsorption of reactants,and promoted the transport of photogenerated carriers that improved charge separation. Modifying the TNTs with octahedral Cu2 O nanoparticles promoted light absorption,and prevented the hydrocarbon product from oxidation. These factors provided the Cu2O-modified TNT photocatalyst with high efficiency in the reduction of CO2,without requiring co-catalysts or sacrificial agents.

Preparation of hierarchical CuO@TiO_2 nanowire film and its application in photoelectrochemical water splitting

A new kind of self-standing CuO@TiO2 nanowires (NWs) film with hierarchical feature was prepared by a three-step protocol consisting of hydrothermal reaction, electroless plating, and branched growth processes. This heterostructured CuO@TiO2 NWs film demonstrates the favorable physical properties in the photoelectrochemical cell (PEC) water splitting, such as the hierarchical surface, the extended optical absorption range, and the rapid interface charge transfer kinetics. Under the illumination of the simulated solar light, the pristine TiO2 NWs film only attains a photocurrent density of 0.12 mA/cm2 at 1.0 V versus reversible hydrogen electrode (RHE). Significantly, the CuO@TiO2 NWs film can yield a dramatically increased photocurrent density of 0.56 mA/cm2 at the same applied voltage. Furthermore, amperometric I?t tests of the CuO@TiO2 NWs film reveal satisfactory stability. All the above characteristics of this heterostructured CuO@TiO2 NWs film indicate its great potential in the water splitting applications with solar visible light.

Selective hydrogenolysis of furfuryl alcohol to 1,5-and 1,2-pentanediol over Cu-LaCoO_3 catalysts with balanced Cu^O-CoO sites

Selective hydrogenolysis of biomass‐derived furfuryl alcohol(FFA)to 1,5‐and 1,2‐pentanediol(PeD)was conducted over Cu‐LaCoO3 catalysts with different Cu loadings;the catalysts were derived from perovskite structures prepared by a one‐step citrate complexing method.The catalytic performances of the Cu‐LaCoO3 catalysts were found to depend on the Cu loading and pretreatment conditions.The catalyst with 10 wt%Cu loading exhibited the best catalytic performance after prereduction in 5%H2‐95%N2,achieving a high FFA conversion of 100%and selectivity of 55.5%for 1,5‐pentanediol(40.3%)and 1,2‐pentanediol(15.2%)at 413 K and 6 MPa H2.This catalyst could be reused four times without a loss of FFA conversion but it resulted in a slight decrease in pentanediol selectivity.Correlation between the structural changes in the catalysts at different states and the simultaneous variation in the catalytic performance revealed that cooperative catalysis between Cu0 and CoO promoted the hydrogenolysis of FFA to PeDs,especially to 1,5‐PeD,while Co0 promoted the hydrogenation of FFA to tetrahydrofurfuryl alcohol(THFA).Therefore,it is suggested that a synergetic effect between balanced Cu0 and CoO sites plays a critical role in achieving a high yield of PeDs with a high 1,5‐/1,2‐pentanediol selectivity ratio during FFA hydrogenolysis.

Vacuum Brazing of TiAl Based Alloy with 40Cr Steel

The vacuum brazing of TiAl based alloy with 40Cr steel was investigated using Ag-Cu-Ti filler metal. The experimental results show that the Ag, Cu, Ti atoms in the filler metal and the base metal inter-diffuse toward each other during brazing and react at the interface to form an inter-metallic AlCu 2Ti compound which joins two parts to produce a brazing joint with higher strength.

A Numerical Investigation of Nanocomposite of Copper and Titanium Dioxide in Water Based Fluid Influenced by Instigated Magnetic Region

Presence of external electrical field plays a vital role in heat transfer and fluid flow phenomena. Keeping this in view present article is a numerical investigation of stagnation point flow of water based nanoparticles suspended fluid under the influence of induced magnetic field. A detailed comparative analysis has been performed by considering Copper and Titanium dioxide nanoparticles. Utilization of similarity analysis leads to a simplified system of coupled nonlinear differential equations, which has been tackled numerically by means of shooting technique followed by Runge-Kutta of order 5. The solutions are computed correct up to 6 decimal places. Influence of pertinent parameters is examined for fluid flow, induced magnetic field, and temperature profile. One of the key findings includes that magnetic parameter plays a vital role in directing fluid flow and lowering temperature profile. Moreover, it is concluded that Cu-water based nanofluid high thermal conductivity contributes in enhancing heat transfer efficiently.