Advanced Materials Research Vols. 284-286

Abstract: Polyurethane elastomers (PUE) were prepared by casting method using the prepolymer and the chain extender. In here, the prepolymer synthesized by using poly(tetramethylene glycol ether) (PTMG) and toluene diisocyanate (TDI), the chain extender was a mixture of 3,5-dimetylthio toluene diamine (E-300) and triethanolamine. The effects of the NCO concentration in prepolymer, the molar ratio of E-300/triethanolamine, and the chain extension coefficient of NCO/NH₂ on the mechanical properties of the prepared PUE were studied. The results showed that the prepared PUE possesses excellent mechanical properties which can meet the drum scraper’s application requirements when the NCO concentration in prepolymer was 5.06% and the molar ratio of composite chain extender was 0.92/0.08.

Abstract: In order to establish a suitable heat treatment process after forging for the heavy forgings to prevent “grain inheritance”, a heat treatment process including pretreatments, pre-heating, normalization, super-cooling and dehydrogenation is proposed. The heavy forgings with the ratio 1.3 of largest diameter 1700mm to its length 1260mm are manufactured by two times upsetting and elongating process. The results show that the heavy forgings treated according to the forging process and the heat treatment process are all qualified and up to the standards of supersonic inspection.

Abstract: The interaction between self-synthesized fluorescent probe 2-(2'- Chloro phenyl)- 5- (2'- hydroxyl phenyl)1,3,4-oxadiazole (HOXD) and Calf thymus DNA was studied using UV absorption spectra and fluorescence quenching spectra．The data of fluorescence quenching of HOXD by DNA were analyzed according to Stern-Volmer equation and Lineweaver-Burk double-reciprocal equation．The results indicated that the fluorescence quenching of HOXD might be static one attributed to the formation of adduct from HOXD and DNA, which was confirmed by the data of temperature effect experiment. Further results presented in the paper showed that intercalation binding might be the interaction mode between HOXD and DNA.

Abstract: Copper nanoparticles were fabricated in poly(vinyl alcohol)/polyacrylamide interpenetrating polymer networks (PVA/PAAm IPNs) by reduction of copper ions with sodium hypophosphite in aqueous solutions. The PVA/PAAm IPNs hydrogels were synthesized in terms of a simultaneous interpenetrating route in the presence of glutaraldehyde and N,N'-methylene-bis-acrylamide. The swelling and mechanical properties of the resulting PVA/PAAm/Cu nanocomposite hydrogels were investigated by a gravimetric method and compression stress-strain test. The results indicated that the copper nanoparticles were assembled in the PVA/PAAm IPN hydrogels in a spherical shape, and were well dispersed and stabilized by the polymer networks, with a size range from 10 to 20 nm. The complexation of PVA and PAAm with Cu²⁺ in PVA/PAAm IPNs played an important part in avoiding the aggregation of copper nanoparticles, and providing particle size and size distribution controllability and stability. The nanocomposite hydrogels exhibited slightly lower swelling, but better compression mechanical properties than that of the control PVA/PAAm IPNs. These properties can be easily tuned by changing the component ratios to meet the requirements of the specific applications such as drug controlled release or tissue engineering.

Abstract: Pd catalyst is very active in Suzuki reaction. As a heterogeneous catalyst, SWNTs/Pd shows highly catalytic ability with Suzuki reaction. We will demonstrate the effect of catalyst’s amount, the reaction time and temperature on Suzuki reaction in this work. In comparison, a control experiment used commercial Pd/C as catalyst in Suzuki reaction has been done. An optimum reaction condition of about reacting 60 min at 50°C with 5% (mass%) catalyst is confirmed finally, and a better catalytic ability of SWNTs/Pd than commercial Pd/C is also observed.

Abstract: FA high-precision drive, namely cycloid driving speed reducer with three cycloid gears, adopts the new driving structure of three cycloid gears at eccentric angle of 120 between each other. The paper analyzes the force of cycloid gear and pin gear at three supporting points of gear pin mainly by analysis, and compares the force of cycloid gear of the speed reducers with two cycloid gears.

Abstract: In this paper, nano-Ti₃SiC₂/MoSi₂ composite, whose second phase was 20-150nm, was in situ prepared by mechanical activation (MA) and SPS process with the quaternary powers of Mo, Si, Ti, and C. The results showed that: (1) matrix MoSi₂ has strong repulsion to other elements, which leads to more second-phase particles inside the matrix rather than on the matrix surface; (2) matrix MoSi₂ has strong restriction on the growing of the second phase, which makes the particle diameter of the second phase inside the matrix only in 200 nm around, while that over the surface reaches to 800 nm around.

Abstract: In order to research the colloidal and thixotropic performance of the inorganic gel prepared by high purity montmorillonite, this study uses the moderate grade bentonite ores from Weifang (China) as raw material. Two-stage hydrocyclone classification was applied to obtain the high purity montmorillonite with its content of 94.8 per cent. In contrast to other methods of montmorillonite purification, two-stage purification by hydroclone has the advantages of larger throughput and easily achieving auto-control in industry, and products with different montmorillonite content can be obtained by this method. And then the inorganic gel was prepared by the prepared high purity montmorillonite , its colloidal and thixotropic performances were further studies. Research results show that the inorganic gel belongs to plastic body liquidity, the viscosity decreases with the increase of the shear rate, the static and dynamic shearing stress values are 33.98 Pa and 91.89 Pa respectively, and the thixotropic value is 95.2 dyne·s/cm², which indicates that it has preferable colloidal and thixotropic performance. Montmorillonite inorganic gel prepared by bentonite with high montmorillonite content and low- layer charge has better gel performance. The application result of inorganic gel in dentifrice and medicine shows that it has excellent effect.

Abstract: Through the analysis of manufacture methods on molybdenum substrate target at home and abroad, method of powder metallurgy is put forward. Some factors affecting compound pressing are studied and discussed, among which, selective standards and requests of powder properties, compaction pressure, lubricant agents are detailed illuminated respectively. Demands for green compact densities of tungsten and molybdenum are brought forward after compound pressing in order to guarantee interfacial level-off and organic combination.

Abstract: The denitrogenation technology and mechanism of a new kind of Ni-base superalloy during vacuum induction melting (VIM) were studied. The nitrogen content could be reduced from 0.0005% to 0.0002% by this technology. The calculated interaction coefficient of Ti with N () is about -0.38, and the activity coefficient of N () is 0.714. The denitrogenation mechanism was discussed through the calculation of the reaction ratio constants and .