Advanced Materials Research Vols. 557-559

Abstract: Additive-free bulk Si-B-N-C ceramics were prepared by pyrolysis of preceramic precursor (PBS-Me), which mainly involves cross linking, warm-pressing and pyrolysis. The density of crack-free bulk ceramic attains 1.94 g/cm³ when Calcined at 1300 °C. The shaped workpieces exhibit amorphous structure even be pyrolysised at 1400°C in N₂, and there are some pores existing in the green body derived from warm-pressing and the resulting Si-B-N-C ceramic body, and these pores allow the gaseous byproducts be expeled from bodies. The pyrolyzed samples were studied by high temperature thermo gravimetric analysis, it shows that the Si-B-N-C body had an excellent high temperature resistance.

Abstract: Modified silicon-containing arylacetylene resins (DMSEPE-OMPS) were prepared from poly(dimethylsilyleneethynylenephenyleneethynylene) (DMSEPE) and Octa(maleimidophenyl)- silsesquioxane (OMPS). The curing reaction of DMSEPE-OMPS resin was studied by FT-IR and DSC techniques. Thermal stability and dielectric properties of cured DMSEPE-OMPS resins were determined. FT-IR and DSC analyses indicate that thermal polymerization of DMSEPE-OMPS resin occurs in the curing process. Thermal stabilities of cured DMSEPE-OMPS resins under N₂ and air atmosphere decrease gradually with the increment of OMPS components. The incorporation of OMPS can obviously reduce dielectric constant of DMSEPE-OMPS resins.

Abstract: The ductility loss and the failure of cladding tubes due to oxidation are considered as a threat to the safety of the nuclear. In this study, oxidation behaviors and the effect of oxide layer on the mechanical properties of Zr-1Nb-0.7Sn-0.1Fe alloy cladding tubes with a lower tin content (<1 wt. %) were investigated. The drastic increase of the oxidation rate at 700oC suggests the change in the nature of the oxide layer with increase of temperature. The acceleration of the oxidation rate for Zr-1Nb-0.7Sn-0.1Fe alloy tubes at 700oC suggests the increased volume fraction of less protective porous oxide, supported by the presence of oxide cracks even before mechanical testing. The ductility increased after oxidation at 600oC, suggesting softening due to recovery and recrystallization is predominant over the ductility loss caused by oxidation. The ductility began to decrease significantly after oxidation at 700oC and cladding tubes exhibited the brittle fracture.

Abstract: Cu-Ni-Zn/Cu-Zr/Cu-Ni-Zn three layered clad plates were prepared by high pressure torsioning (HPT) at room temperature and theirmicrostructural and mechanical analyses wereperformed. No intermetallic compounds were observed at Cu-Zr/Cu-Ni-Zn interfaces in the as-HPTed and heat-treated Cu/Ni-Zn/Cu-Zr/Cu-Ni-Zn clad plates. The strength of as-HPTed clad plate reached up to 610 MPa with the ductility of 14%. After heat treatment at 500oC, Cu-Ni-Zn/Cu-Zr/Cu-Ni-Zn clad plate exhibited the strength up to 490 MPa and the ductility of 28 %. The clad plate fractured all together at the same time without discontinuous drop of the stress until final fracture. The excellent mechanical reliability and the good interfacialbonding strength can be attributed to the absence of detrimental interfacial reaction compounds between Cu-Ni-Zn and Cu-Zr.

Abstract: The melt-spinning technique is applied to the preparation of the nanocrystalline and amorphous Mg2Ni-type alloys with nominal compositions of Mg₂₀Ni_10-xMn_x (x=0, 1, 2, 3, 4). The microstructures of the as-cast and spun alloys were characterized by XRD and HRTEM. The electrochemical performances of the as-spun alloys are measured by an automatic galvanostatic system. The results show that the as-spun Mg₂₀Ni₁₀ alloy displays an entire nanocrystalline structure, whereas the as-spun Mg20Ni6Mn4 alloy exhibits a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni facilitates the glass formation in the Mg₂Ni-type alloy. And the amorphization degree of the as-spun alloys substituted by Mn increases with the growing of the spinning rate. The substitution of Mn for Ni and the melt spinning ameliorate electrochemical hydrogen storage characteristics of the alloys substantially. The electrochemical discharge capacity and cycle stability of the alloys are considerably enhanced by increasing the amount of Mn substitution and the spinning rate. The high rate discharge ability (HRD) of the alloys first augments and then falls with the growing of the Mn content and the spinning rate.

Abstract: From facile preparation method and available low-cost raw materials, we have synthesized a novel kind of aniline-based organodisulfide bis(2-aminobenzyl) disulfide (OABD) and its homopolymer (POABD). The polymer POABD was characterized by Fourier transform infrared spectroscopy (FT-IR) and cyclic voltammetry. The cyclic voltammetry tests reveal that the redox of the S-S bonds behavior in the anodic and cathodic peak potentials differences for poly(bis(2-aminobenzyl) disulfide) is 70 mV. The results indicated that poly(bis(2-aminobenzyl) disulfide) has an excellent electrochemical reversibility.

Abstract: This paper describes the basic analytical technique used in characterizing bio-oil into various components in terms of function groups as well as assessing its thermal behaviour. Pyrolysis, being one of the most widely used techniques in converting biomass was employed to get bio-oil from empty palm fruit bunches (EPFB).The bio-oil obtained was characterized using Fourier Transform Infrared (FTIR) while the thermal behaviour were assessed using Thermogravimetric analysis (TGA) and Differential Scanning Calometry (DSC). The results showed a great range of functional groups of phenol, alcohols, ketones, aldehydes, carboxylic acids, alkanes, alkenes and aromatic in the FTIR spectrum. The onset thermal temperature of thermal decomposition from TGA result is 32°C corresponding to about 13.4281 mg and the amount of residue was found to be 3.9969mg which shows that the bio-oil losses weight very fast; a characteristic of lighter product which strongly support combustion. The stages on DTG curve, in the degradation, which occurred at temperature range between 70-90°C, correspond to the removal of light hydrocarbons (such as aldehydes, alcohols and carboxylic acids) and moisture content in the bio-oil. The glass transition temperature, Tg, was found to be 53.63°C indicating that the bio-oil tested is less rigid and hence requires less force delivery. The characterization results indicate that the bio-oil obtained from oil palm EFB can be a potentially valuable source of fuels and chemicals feedstocks. Utilization of bio-oil for fuels and chemicals manufacture can significantly reduce or eliminate the harmful effects of fossil based products on the environment.

Abstract: carbon foams were prepared using a medium rank bituminous coal in this paper. The influence of foaming temperature, foaming pressure and time of releasing pressure on open porosity, bulk density and pore morphology of carbon foam were discussed, respectively. The bulk density and true density were tested. The texture of the carbon foams was characterized by scanning electron microscopy. The results show that the pores diameter of carbon foam derived from coal is more uniform, which is in range of 100μm-200μm. Nevertheless, there are a spot of irregular large holes. Foaming temperature is key fact and the suitable foaming temperature must be near to the maximum fluidity temperature of coal. With the foaming pressure increasing, the open porosity reduces, the bulk density increases and the pores diameter gets smaller and more regular.

Abstract: Novel polymeric form-stable phase change material (SMA-g-PEG) was synthesized by the reaction of styrene-maleic anhydride copolymer (SMA) with polyethylene glycol (PEG). The phase transition behaviors and crystalline morphology were investigated by DSC and WAXD, and thermal stability was analyzed by TGA. The results indicated that the SMA-g-PEG has suitable transition temperature, high transition enthalpy and good thermal stability. The heat storage mechanism of SMA-g-PEG is the transfer between crystalline and amorphous states of the hanging segment PEG. And SMA, serving as ‘polymeric bone’, restricts the molecular chain of the hanging segment’s free movement at high temperature, so, SMA-g-PEG can keep its solid state in the transition processing.

Abstract: The goal of this study was to investigate the sintering mechanism of Si powder, with the particle size of Si, sintering temperature, and sintering environment as the variables. The use of a crucible, by controlling the vapor atmosphere at certain temperatures, coarsened the silicon powder. Experiment of data show that by avoiding the vapor pressure of crucible a sintering at 1380°C causes the silicon powder easily to sinter to high density, without the use of any doping addition. Therefore it is to our advantage to discover the microstructure phenomenon of silicon powder and reveal its nature. The crystalline structure of the heat-treated samples was studied with Scanning electron microscopy (SEM) to explain the resultant of contamination that causes the densification.