Advanced Materials Research Vols. 217-218

Abstract: Take into account different degree of exchange-coupling interaction between soft and hard grains, the effective anisotropy and coercivity in nanocomposite permanent magnetic materials has been investigated by adopting a statistical average physical model. The calculated results show a strong dependence of effective anisotropy and coercivity on the grain size in these materials. Using this model, the serious deterioration of coercivity in experiments especially when the grain size is less then 15nm could be explained in terms of the dramatic drop of the effective anisotropy in nanocomposites.

Abstract: The pulse-laser-crystallization (PLC) technique was applied to Nd3.7Pr3.4Dy0.9Fe86B5Nb1 amorphous ribbons. After irradiation with a 248nm KrF pulse excimer laser at a fequency of 15Hz for 1 min, the Nd3.7Pr3.4Dy0.9Fe86B5Nb1 amorphous ribbons crystallized into the homogeneous Nd2Fe14B/α-Fe nanocomposite permanent magnetic materials with an average grain size around 26nm. The obtained coercivity, remanence, and (BH)max values were 6.6 K, 1.23 T, and 18.5 MGOe, respectively.

Abstract: By using the transfer matrix method studying the transmission spectra and the interior electric field distribution of symmetric structure of one-dimensional light quantum-well (AB)m(ABCBA)n(BA)m , results show that with the increase of n, (2n-1) resonance transmission peaks appear in the transmission spectra of photonic quantum-well (AB)5(ABCBA)n(BA)5, and quantization effect is obvious; strong localized electric field appear in internal field Quantum-well : when n=1, the intensity of internal localized electric field of light quantum-well (AB)m(ABCBA)1(BA)m increases with m increasing, while m=5, intensity of internal local electric field light quantum-well (AB)5(ABCBA)n(BA)5 don’t change with the change of n, but local area expanded. These optical transmission properties provide guidance for the design of new optical device of photonic crystal.

Abstract: In this study a kind of black toner, containing polymer, magnetic iron oxide pigment, and several other additives, was prepared by a suspension polymerization method. The morphology, influence factor of particle size, and glass transition of prepared toner were discussed. SEM image showed that the produced micron-sized particles have a spherical surface and the various chemicals were mixed into monomers during manufacturing of the particles. Discussion about particle formation and stability concluded that the toner particle size related with stabilizer concentration, stirrer speed, and crosslinking agent concentration. The bigger particles, resulted from droplets coalescence during polymerization process, disappeared when enough PVA stabilizer was used in the aqueous medium. .Increasing the stirrer speed corresponded to the decrease of the particles size. But any increase in stirrer speed t did not contribute to size reduction in small particles below 2μm. It was found that particle size decrease with the addition of crosslinking agent. The DSC result indicated the glass transition of polymerized toner could be effectively adjusted according to Fox equation through change the monomer ratio.

Abstract: Four series of thin films have been deposited as the precursory sources of Zn(CH3COO)2, Mg(CH3COO)2, NH4CH3COO and AlCl3 aqueous solutions using ultrasonic spray pyrolysis (USP) method. The crystalline structure, morphology images, electrical, optical properties of the films are characterized by x-ray diffraction (XRD), field emission-scan electron image (FE-SEM), Hall-effect measurement and photoluminescence (PL). From the XRD patterns and SEM images, we can see that all the films present good crystallinity and surface uniformity. Hall-effect measurement results indicate that ZnO is n-type, while N-Al codoped ZnO and N-Al codoped Zn1-xMgxO exhibit p-type conduction. Temperature dependent of electrical measurement is carried out from 300K to 500K, then the conductive mechanism and carriers scattering are analysed. Furthermore, the photoluminescence peak of Zn1-xMgxO is tuned into shorten wavelength than pure ZnO (λ＝379－352＝27nm), and also the same phenomenon of the p-type Zn1-xMgxO film exhibits blue-shifted behavior from 378nm to 356nm compared with p-type ZnO film (λ＝378－356＝21nm). In other word, the p-type Zn1-xMgxO film shifts to a shorter wavelength of 356 nm while maintaining excellent electrical performances.

Abstract: Cu-Al composite row was produced by continuous cast-rolling technique and metallurgical bonding interface was achieved. The microstructure of interface and the composite mechanism was investigated. Isolating switch was fabricated by using copper-aluminum composite row as current-carrying conductor. Main performance index and technical parameters were evaluated. The composite row shows excellent mechanical property and conductivity: overall tensile strength of 102MPa, elastic modulus of 1.5GPa, resistance rate of 0.0216Ωmm2/m and carrier density of 750A. The results present that the temperature rise, circuit resistance, mechanical life and other properties of the copper-aluminum composite row can meet the requirements of being the current-carrying conductor of isolating switch.

Abstract: When mining close-distance seams with downlink mining, in order to benefit roof maintenance and management, the decoration of lower seam roadways should try to avoid the area affected by pillar concentrated stress , using inside cross decorationg; In order to improve the recovery rate of resources, the size of protection pillar can’t be too big, when mining under pillar of upper layer and mining in pillar of upper layer with crossing. The whole lower face or some phase located under the influence of upper coal concentration stress, give roadways and working face roof maintenance a lot of difficulties. Then it appeared the conflict between security and economy, to solve this problem, we must return to the correct understanding of mine pressure behave law. In the paper, through the investigation of the typical dozen example in mining of face the coal pillar in China, to get its regular pattern of mine pressure behave, in similar conditions mining, there will be important reference and guidance.

Abstract: A new chaotic system is built which is consists of two subsystems. A subsystem is analyzed such as equilibrium, eigenvalue, Lyapunov, dimension and Lyapunov exponent. A practical circuit is designed to realize the system and the experimentation is carried out. The manifold chaotic attractor of the two subsystems is observed in the oscillograph, it is good agree with simulation.

Abstract: Hot compression tests of 7075 aluminum alloy were carried out on the Gleeble-1500 thermal simulation machine at strain rates of 0.1s-1 ，1 s-1 and at temperatures of 320°C,400°C,480°C. The compression direction are aligned at 0°，45°and 90°to the axis direction of the bar. Microstructure was studied using Optical Microscopy. The results show that the true stress of all three specimen increases with the decrease of temperature and the increase of strain rates. The true stresses rose rapidly to peak value and then held constant or decreased with the increase of the true strains at different deformation conditions. The yield strength of the specimens in 0° to the axis direction is higher than that of 90°, and 45° specimen has the lowest yield strength at different deformation conditions, which could be attributed to the elongated grain structures of the bar.

Abstract: The influences of Ce, La, Nd, Y, Sb, Zn and Mn on microstructures of Mg3Al alloys were investigated. The formation of needle-like Al-RE compounds in Mg3Al alloys added 1%RE have close relations with the type of RE element. La and Ce help the acicular phase formation in Mg3Al alloy, which mainly are Al4RE, while, granular Al2RE phases were observed in the Mg3Al alloys with 1%Nd and 1%Y. However, spherical CeSb instead of needle-like Al4RE were found in Mg3Al alloy with 1%Ce and 1%Sb addition. There were not essential differences between the microstructure of Mg3Al-1%Ce-1%Sb and AZ31-1%Ce-1%Sb alloys.