Jin Feng Leng

Structure and Photoelectric Properties of Cu3N Thin Films by Reactive Magnetron Sputtering

Cu3N thin films can potentially be used for development of optical storage devices and integrate circuit of semiconductor. In this study the Cu3N films were deposited on glass substrate successfully by reactive direct current magnetron sputtering at different N2/(N2+Ar) flow ratio. The results showed that the nitrogen partial pressure affected the preferring orientation of the thin films when the sputtering power and substrate temperature was fixed. With increasing N2/(N2+Ar) flow ratio from 10% to 90%, Cu3N(111) orientation with rich-copper changed to Cu3N(100) orientation with rich nitrogen, the transmittance of the thin films improved gradually, and the corresponding optical band gap (Eg) increased from 1.10 eV to 1.21eV. The resistivity of copper nitrogen films changed from 5.62Ω.cm to 3.00×103Ω.cm at the scope of 10%~90% of N2/(N2+Ar) flow ratio.

Influence of Sputtering Power on the Structure, Optical and Electric Properties of Cu3N Films

The Cu3N films were deposited successfully by reactive direct current magnetron sputtering, the films were comprehensively and systematically characterized by X-ray diffraction analyzer (XRD), UV-Visible spectrophotometer, four-probe resistance tester and other instruments. Results showed that under low deposition power (80W~100W), crystal orientation increased, which is attributed to higher energy under higher power. When sputtering power exceeded the value, excessive energy led to anti-sputtering hindering the process of further nucleation and growth of films. The transmittance of the films deposited under 100W reached the peak value of 78% on the scope of near-infrared light, and optical band gap (Eg) of 1.35ev. The resistivity of Cu3N films increased from 9.68×102Ω.cm to 2.12×103 Ω.cm with increasing in sputtering power up to 100W.

Preparation of Graphene and Graphene/Al Composites

Metal matrix composites reinforced by graphene particles exhibit physical and mechanical property and are developed and qualified for use in aerospace structure, bioengineering, energy storage material and photoelectric device. In the present paper, graphene was fabricated by modify Hummers method, and then was surface modified by chemical plating copper. The graphene/Al composites were fabricated by powder metallurgic method. Morphology characterization of graphene and composites were detected by XRD and SEM,the fabrication parameters of composites were optimized by testing harness and density. The volume fraction of graphene particles was 3%, the density of composites was maximum of 96.5%. The hardness had a maximum of HB 42.6, and the hardness of graphene/Al composites increased by 33.5%.

Effects of Rare Earth Y Addition on Microstructural and Properties of Pure Copper

The effects of rare earth Y addition on microstructure and properties of pure copper were investigated. Mechanical test, electrical test, oxidation resistance test, metalloscope, scanning electronic microscope (SEM) and X-ray difffraction (XRD) were performed to study the properties, microstructure and constitution. The results showed that both the hardness and antioxidant properties obviously increased with the increase of Y, confirmed the successful refinement role of Y. A small amount of Y (less than 0.5 wt.%) could improve the electrical conductivity of pure copper. When the Y content reached 0.2 wt.%, pure coppers obtained optimum electrical conductivity which is 96.8% IACS. However, over-added Y (>0.5 wt.%) resulted in second phase of Cu7Y coarsening and non-homogeneous microstructures forming, which reduces the conductivity of copper. In addition, Y can effectively purify the organization of molten copper.

Aging Behavior of A356.2 with Yb Modified

The effect of aging treatment on the aging hardening of 0% Yb and 0.4% Yb modified A356.2 alloy was investigated by hardness measurements and optical microscope. In this work, A356.2 was first subjected to 535°C for 5h and then subjected to 150°C, 180°C for 2h-12h hours. Results show that during aging process, there was a hardness peak along the increasing of aging temperature and time. With increasing aging progress, the morphology of Si phases became shorter and spherical. After optimum time, Si phases was coarse and the dendritic grain was broken. The peak-aged of unmodified alloys was 150°C for 10h and 180°C for 6h，and corresponding hardness values were 62.35HB and 77.10HB, respectively. With Yb addition, the hardness reached 87.58HB and 98.28HB on peak aging of 150°C/8h and 180°C/ 6h, respectively. The greatest degree of hardness was increased by 40.46% and 27.47%, combined with no Yb addition. XRD shows the interplanar crystal spacing of A356.2 with 0.4% Yb addition, which was larger than fresh A356.2 alloy. When adding 0.4%Yb under 180°C for 6h aging progress, the ultimate tensile strength was 284 MPa 12.7% increasing compared with former work.

Processing and Electrical Properties of Nano-Al2O3/Cu Composites

Copper matrix composites (CMCs) are widely used in electrical equipment and electrical contact materials due to their excellent electrical properties. Al2O3 powders are widely used as a reinforcing agent to enhance mechanical properties of MMCs. The xAl2O3/Cu (x =0, 0.2, 0.5, 0.7, and 1.0wt. %) composites were prepared via vacuum arc melting method. The mechanical and electrical properties were obtained by measuring the hardness and conductivity. The morphology of copper and Al2O3/Cu composites was characterized by optical microscopy (OM) and scanning electron microscopy (SEM). With the addition of Al2O3 from 0.2 wt. % to 1.0 wt. %, the relative densities of composites decreased from 98.5% to 97.0%. The hardness of the composites increased with increase in the Al2O3 powders content. The hardness of 1.0Al2O3/Cu composites was 57.9 HB, which was higher than that of pure Cu by 18.6%.. With the addition of Al2O3, the IACS% of Al2O3/Cu composites decreased from 88.97 to 86.16.

Influence of Yb Modification on the Microstructure and Mechanical Properties of A356.2 Aluminum Alloy

A356.2 aluminum alloy (Al–7Si–0.35Mg) has been widely used in automotive and aircraft industries. Previous studies found that the metamorphism effect of rare earth is better than other type of elements because of long modification time and good stability. The influence of Yb addition (0%, 0.2%, 0.4% and 0.6%) and T6 heat treatment on A356.2 alloy has been investigated in this work. The microstructures and mechanical properties of the specimen after T6 treatment were examined by optical microscope, scanning electronic microscope and tensile tests. Experimental results showed that Yb could reduce the size of α-Al and change the Si morphology from needle-like to fine spheroidal particles. With the increase of Yb content, the ultimate tensile strength increased gradually. When adding 0.4%Yb, the alloy achieved the highest ultimate tensile strength (252 MPa) and hardness (97.3HB), 10.12% and 37.66% higher than the alloy with no Yb addition. Tensile fracture analysis showed that the fracture mechanism for A356.2 aluminum alloy after T6 treatment is transgranular/intergranular mixed mode of fracture.

Microstructure of As-Cast 7085 Aluminum Alloy by Homogenization

7085 aluminum alloy has been widely used in aviation and aerospace because of high fracture toughness, high strength, slow quench sensitivity and low density. In the as-cast microstructure, it is not avoidable for massive un-dissolved secondary phases and dendritic segregation. The microstructure of as-cast high strength 7085 aluminum alloy after two-stage homogenization was studied by optical microscopy (OM), X-ray diffractometer (XRD), scanning election microscopy (SEM), energy dispersive spectrometer (EDS) and differential scanning calorimeter (DSC). It was found that the severe dendritic segregation exists in as-cast 7085 aluminum alloy and a small amount of Al7Cu2Fe exists in the as-cast 7085 alloy. The evolution of primary eutectic structure of 7085 alloy consists of three processes: the dissolution of non-equilibrium eutectic phase α (Al) + Mg (Zn)2, the transformation from Mg (Zn)2 to Al2CuMg and the dissolution of new phase Mg (Zn)2. A suitable two-stage homogenization scheme for as-cast 7085 aluminum alloy is 300°C/8 h + 465°C/24 h.

Influence of Substrate Temperature on the Al and Zr Co-Doped ZnO Thin Films Prepared by RF Magnetron Sputtering

ZnO doped Al2O3 and ZrO2 (ZAZO) thin films were deposited by the radio frequency magnetron sputtering on substrate temperature with 100°C, 150°C, 200°C, 250°C and 300°C. The surface morphology and electrical properties of the films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and four-probe tester. The results showed that the substrate temperature obviously influenced the grain size of ZAZO films. The ZnO thin film had the largest crystallization orientation for the (002) peak and the smallest FWHM value at substrate temperature of 250°C. As the temperature increasing, the resistance of films gradually decreased till reaching a minimum at 250°C and then rised. Due to the increasing of Al and Zr concentrations into ZnO lattice, the Al ions created an abundance number of free electrons in the ZnO lattice, and in turn, the electrical conductivity increased. In addition, the improvement of film in the crystalline state results in the film resistivity decreases.

Effect of Sputtering Power on Photocatalytic Activity of Thin TiO2 Films

TiO2 thin films with outstanding photocatalysis can potentially be used for photocatalysis device in the field of environmental protection. TiO2 thin film (99.99%) was fabricated successfully by power metallurgy. The effect of sputtering power on TiO2 thin films by radio frequency magnetron sputtering was investigated. The results show that the higher sputtering power is beneficial for the growth of Rutile structure with superior photocatalysis. With the increasing of sputtering power, the rate of methyl orange degradation increases under UV light irradiation. The degradation rate of TiO2 thin film under sputtering power 75W and 165W is 40% and 80% respectively. This is attributed to the increase of the rutile phase with many defects and dislocation network under higher sputtering power.