Key Engineering Materials Vols. 531-532

Abstract: The Pd/Sn catalytic coating on graphite electrode had been synthesized by chemical plating in this paper. Scanning electron microscope(SEM)and Electrochemical workstation(EW)were used to analyze the coating surface topography and electro-catalytic properties of modified graphite electrode with and without the coating. Results show that Pd and Sn are in the form of spherical particle and completely cover the surface of graphite electrode includes concave defects. Most Pd and Sn particles are dispersive ones of size of about 70 nm and few of which are polymerized in island forms. The peak value of current density increases with scanning speed, which goes positive potential scanning. Further more, the peak current increases with the concentration of NaOH solution, which shows nonlinear relationship between peak current and solution concentration, The peak current increases more rapidly with solution concentration increases in low NaOH concentration solution than that in high NaOH concentration solution.

Abstract: Metamaterials are artificial composite structures or composite materials, which possess supernormal physical properties that natural materials don’t have. Through orderly designing the structures in the critical physical size of materials, we can render the materials to break through some restriction in some certain apparent natural laws. Electromagnetic metamaterials, which have the unusual electromagnetic property of controlling the transmission of electromagnetic wave, are discussed in this paper. Also, forming condition of the metamaterials is testified in theory. In metamaterials, electromagnetic wave could come up to be bending around certain boundary, but its transmission characteristics have no change. According to the superiority of the metamaterials, the metamaterials have the unique military value in the aspect of stealth. And if metamaterials are realized in militarily, it’s no doubt that the possessors will have predominance.

Abstract: A New Complex Crystal [Co(Hdmg)₂(Him)₂]·(ClO4) (H2dmg = Dimethylglyoxime,Him = Imidazole) Had Been Synthesised in Aqueous Solution and Was Characterized by X-ray Diffraction and IR Spectrum. the Complex Crystallizes in Triclinic Space Group with Cell Constants a= 20.868(7)Å, B=11.408(4)Å, C=15.816(4)Å, α=90.00°, β=116.97(2)°, γ= 90.00°, V= 3355.8(17) Å3, Z=4, F(000)=1732. the Coordination Environment of Cobalt Atom Is a Slightly Distorted Octahedron. the Four Equatorial Donors Are Four Nitrogen Atoms from Two Bidentate Chelate Hdmg Anion Ligands. the Apex Points Are Occupied by Two Nitrogen Atoms from him Ligands. the Co-N(Him) Distance Is 1.930Å, and the Co-N(dmg) Distances Are Varying in the Range from 1.886Å to 1.993Å which Are in Agreement with Corresponding Reported in a Number of other Structurally Related Copper(II) Complexes.

Abstract: Diverse nanostructural materials including spheres, nanorods, vesicles, and large compound vesicles have been created via formation of amphiphilic ABA triblock copolymers, self-assembling and morphology transition in the reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization. The polymerization of styrene (St) was performed in a selective solvent, methanol, using S,S′-bis(α,α′-dimethyl-α′′-acetic acid)-trithiocarbonate terminated poly(N,N-dimethylacrylamide) (PDMAa-TC) as macro chain transfer agent and stabilizer, and 1H NMR, and TEM were used to monitor the polymerization.

Abstract: CoCrAlY bond coat(BC) and top ceramic coating(TCC) were fabricated on the GH99 super alloy by air plasma spray(APS), before TCC fabrication, BC was treated by sand blasting with different blasting parameters (blasting pressure, blasting speed). The roughness Ra of BC surface was obtained by orthogonal experiment design. Then, cross section morphology of TCC/BC interface were investigated by scanning electron micrograph(SEM), meanwhile TCC/BC interface stresses were analyzed based upon ABAQUS software using finite element method (FEM). The results show that, the roughness of bond coat surface increase first with increasing blasting pressure and speed, then decrease finally becomes stable. Both maximum tensile stress and compressive stress appear in TCC/BC interface area which is bigger in BC layer than that in TCC layer; With the increase of amplitude of interface triangle, the TCC/BC interface stress increase first then decrease until 7μm amplitude, then there appears a decrease of the interface stress.

Abstract: The formation mechanisms of horizontal wrinkles and water wave wrinkles on steel casting surface have been investigated in this study. The horizontal wrinkles, which are the traces of rising steel flow overlapping, are caused by low pouring temperature and slow molten steel flow rising rate. The water wave wrinkles are resulted from the use of an alcohol-based refractory coating with poor permeability and strong penetration behavior. This coating may penetrate deeply into the pores of sand mold and are not easy to be dried by flame combustion. When pouring the alcohol containing in the coating will volatilize and generate a large amount of gas, forming a gas cushion at steel-mold interface. With the gas escapes gradually, the gas cushion disappears, leaving a gap between the steel and the mold, the solidifying casting surface layer will freely fall down and creep in this gap under gravity itself, resulting in casting surface wrinkling.

Abstract: In this study, Zn0.99Co0.01Al0.015O thin film has been prepared by sol-gel method. The structural and magnetic properties of the sample were investigated. X-ray diffraction spectroscopy analyses indicate that the Co and Al codoping can not disturb the structure of ZnO. No additional peaks are observed in the Zn0.99Co0.01AlxO and Al3+ and Co2+ substitute for Zn2+ without changing the wurtzite structure. The resistance measurements confirm that Al ions increase the free carriers concentration. Based on the above experiments we think the ferromagnetic behavior of the sample could not originate from Co nanoclusters. The presence of free carriers and localized d spins is a prerequisite for the appearance of ferromagnetism. As the result, the carriers generated by Al doping is considered a main factor to induce the ferromagnetic phenomenon.

Abstract: Natural silk fibers were used as the template to synthesis biomorphic ZnO fibers. Silk fibers were first immersed into a Zn(NO3)2 solution and then sintered in air at high temperatures to produce the final ZnO fibers. Their microstructures, phases, and synthesis process were analyzed. The results show that these synthesized fibers retained the morphologies of silk faithfully. The sintering temperatures had the effect on the continuity of the biomorphic fibers. The crystallite sizes of these biomorphic ZnO are in nano scale. The fabrication process of biomorphic ceramic included the formation of ZnO and removal of their silk templates. The ZnO formed before the removal of the silk-template, so that the fibrous morphology of the silk could be retained to this ZnO. The method of using bio-template could provide a new idea for the design of oxide fiber.

Abstract: Er3+, Na+-co-doped CaF2 transparent ceramics with Er3+ dopant concentration of 5at% and Na+ of 0, 0.5, 1.0 and 1.5at% were fabricated by the vacuum hot pressing method. Absorption spectra, emission spectra and fluorescence lifetimes were measured at room temperature to study the effects of Na+ on the spectral properties of Er3+: CaF2 transparent ceramic. The results showed that after introducing Na ion into Er3+: CaF2 transparent ceramics, charge-neutralized Er3+-Na+ structure formed which prevented Er3+ from clustering, the absorption intensity of ceramics decreased with the increase of Na+ concentration, but the spectroscopy and photoluminescence properties of Er3+ in CaF2 transparent ceramic could be modulated by adjusting the concentration of Na+. Co-doping Na+ to increase fluorescence lifetime should have an optimal value.

Abstract: Ti2SC has been synthesized using Ti/TiS2/2TiC as initial materials. Combining X-ray diffaraction analysis with thermodynamic calculations, a reaction path is proposed for the intermediate phase TiS and Ti2SC formation. TiS was more possible to be obtained from TiS2 and Ti rather than the decomposition of TiS2. TiC was the main impurity phase in Ti2SC and was difficult to eliminate. The high pressure technology using can help improve the purity of the sample. Scanning electron microscopy (SEM) shows the typically layer structure of the material. Thermogravimetry (TG) and differential scanning calorimetry (DSC) are also to be used to investigate the reaction mechanism，indicating that it would be useful for the formation of more purity sample by adjusting the content of TiS2.