Advanced Materials Research Vols. 821-822

Abstract: The magnetic field interference was studied by numerical simulation and experimental examination during dual-ingot low-frequency electromagnetic casting process. By using ANSYS software package to mesh and compute, the magnetic field distribution of semi-continuous casting mold region was simulated. The calculated results were verified with the experimental ones and the effects of current direction, shield, silicon sheet and the coil distance on the distribution of magnetic field and ingot were observed. The result indicated that: regardless of current direction, the magnetic field interference among coils appears and the magnetic flux density weakens in the neighbor part of coils. When the current direction of adjacent coils is opposite, the magnetic intensity in ingots is stronger than that of in the same direction. As the distance between coils increases, the magnetic field reduction generated by interference decreases. The magnetic field interference can be alleviated by setting silicon steel sheets or shield.

Abstract: Electro-spark deposition (ESD) is a microwelding process that utilizes short duration of electrical pulses to deposit electrode materials to a metallic substrate. In this paper, taking TA2 bar as electrode, a deposition layer of thickness up to 40μm was built up to on 7075 aluminum alloy substrate by means of ESD. The deposition layer is metallurgical bonded to the substrate. The microstructure, phase composition, and micro-hardness of TA2 coating were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and micro-hardness test. The microstructure of the coating was mainly composed of TiN phase, Al3Ti phase, AlN phase and Al phase. Its micro-hardness reached 295 HV0.05, about 2 times as high as that of the substrate. The hardness at the cross-section of the entire deposition layer showed a gradient distribution.

Abstract: The influences of different pouring temperature and mold temperature on solidified structure of superalloy K4169 under low-voltage pulsed magnetic field (LVPMF) were investigated in the paper. The experimental results show that solidified structure of superalloy K4169 under LVPMF can be refined greatly with appropriate cooling rate of the alloy. The dendrite growth is restrained and the microstructure is changed from larger dendrite grains to smaller equiaxed grains. When the pouring temperature is at 1380 °C-1530 °C or the mold temperature is at 1000 °C-1300 °C, the increase of pouring temperature or mold temperature enhances the refinement effect of LVPMF processing. With the increase of the pouring temperature or the mold temperature, average grain size of the alloy decreases and the primary phase degrades from developed dendrites into equiaxed crystals under the LVPMF.

Abstract: For the purpose of investigating the influence of different process condition on alkali reduce rate and mass increase rate, the techniques of polyester fiber pretreatment, electroless copper plating, and electroless silver plating were carefully analyzed and compared. It was found that the best coursing condition was: 5.5 mol/L concentration, 65°C temperature, 30 minutes reaction time, 1:200 bath ratio. Under these conditions, the alkali reduction rate was 11.38%. As for copper plating liquid concentration of 0.08 mol/L, pH value 9.5, 80°C temperature, liquid silver plated concentration 0.02 mol/L, the coating weight gain rate was 52.1%. Microcosmic morphology on coating surface and surface resistance test show that the fabric was evenly coated with Cu, Ag, metal ions, which resulting in excellent electric conductivity and good electromagnetic shielding performance.

Abstract: In this paper, a kind of electromagnetic shielding fabric was introduced. The fabric was woven by composite yarns made of stainless steel fibers, cotton and polyester filaments. Using the tracer fiber technology, the internal structure of yarns and fabrics was observed through the optical microscope. Electromagnetic shielding effectiveness of the fabric was tested by FY800 electromagnetic radiation tester according to the standard of ASTM D4935-10. The optical microscope photographs show that the yarns and fabrics have many different sizes of metal grids internally. Research results show that with the increase of arrangement proportion of metallic yarns, fabric thickness and content of metallic fibers, electromagnetic shielding effectiveness of the fabric has a rising trend.

Abstract: Electromagnetic (EM) shielding effectiveness of fifteen woven fabrics which use different yarns as raw materials were evaluated and compared in this paper. Test samples were obtained through the change of yarn structure, the content of stainless steel filaments and process parameters. Fabric electromagnetic shielding effectiveness (SE) was analyzed in terms of the content of stainless steel filaments,fabric density and fabric tightness .The mechanism of electromagnetic shielding of worsted fabric with stainless steel filaments was further studied at different frequencies. The result has certain directive significance on developing high-performance woolen fabrics against electromagnetic radiation.

Abstract: Titanium dioxide nanoparticles have the unique properties of optic character and can be used in textile region. In this paper, the application status, prepare methods of physical method and chemical method, application method of exhaustion, pad-dry-cure and coating methods in textile modification of titanium dioxide nanoparticles are introduced. The prepared mechanisms are then analysis. It is shown that titanium dioxide nanoparticles can provide ultraviolet-resistance fuction, anti-bacterial activity, infrared effects, anti-static eclectricity function, anti-aging function and Self-cleaning effect in textile modification. As last, the existed problems and tend to development are analysized.

Abstract: A new microwave imidization method was used to prepare polyimide (PI) film in this paper. FT-IR spectrum and ultraviolet absorption spectrum are measured to study the chemical structure and optical properties of this film. The FT-IR spectrum shows that the characteristic imide groups are observed at the peaks of 727.18 cm^-1, 1379.67 cm^-1 and 1776.51 cm^-1, which confirmed imide formation. The ultraviolet absorption spectrum reveals that optical band gap of the PI is about 2.64 eV.

Abstract: A novel fluorescence probe was obtained by click reaction based on the materials of etraphenylethylene (TPE) and 8-hydroxyquinoline, which were used as fluorescent group and accepter group respectively. It displays high selectivity and sensitivity towards Ag⁺ and Fe³⁺ in THF-H₂O(2:3, v/v) as they can form stable 2:1 metal-ligand complexes.

Abstract: Nb⁵⁺-doped SrTiO₃ (STO) particles were synthesized by a simple hydrothermal reaction at 150 °C for 4h. It was found that the main diffraction peaks of Nb⁵⁺-doped STO samples with different dosage of dopants shifted gradually to low angles, indicating the little lattice parameter expansions which result from the partial substitution of Ti⁴⁺ (0.061 nm) by Nb⁵⁺ (0.064 nm) in perovskite structure. From the lattice parameters, the max Nb⁵⁺ dopant concentration is about 2 mol%, and the particles obtained were 200 nm-sized and monodispersed.