Advanced Materials Research Vols. 295-297

Abstract: We studied coherent phonon dynamics in Co-Mo-catalyst grown single-walled carbon nanotubes by using sub-5-fs visible pulses. Vibrational wave-packets corresponding to radial breathing mode for four chiral systems, (6,4), (6,5), (7,5) and (8,3), can be separately observed and achieved exact chirality assignments without ambiguity in coherent phonon spectra. Coherent phonon generation of radial breathing modes is in-depth studied by analyzing the probe energy dependent amplitude profiles, which indicates that the real and imaginary parts of the third-order susceptibility can both contribute to the modulation of the probed difference absorbance.

Abstract: In this paper the diesel engine exhaust noise in petroleum well workplaces has been measured, the peak values scatters mainly in the low-frequency range, and the top value has reached 123dB. Based on transfer matrix method, this paper analyzes six kinds of silencing elements and establishes optimizing calculation procedure for diesel engine exhaust muffler. According to optimizing calculation procedure and exhaust noise frequency spectrum characteristic of diesel engine, we have designed a new large amount resistance muffler for G12V190 type diesel engine. After petroleum well scene experiment, the insertion loss of exhaust muffler has reached 33dB.

Abstract: In this paper, semi-solid slurry was prepared by power ultrasonic on flowing A356 melts. A simple device of ultrasonic treatment was made and the method of applying power ultrasound from the top of ingot was adopted. we investigated the influence of the experimental parameters impact on the size and morphology of the primary phase α-Al in A356 slurry, which included the power of the power ultrasound, treatment temperature and the distance between ultrasonic source and the melts ( here refer to from vibration head to the bottom of melt channel in this paper). The regularity of ultrasonic influence on grain refinement and morphology spheroidizing of primary phase α-Al in A356 alloy were obtained. The results show that when the loading power range from 800W to 1000W, the grain refinement effect goes more obviously with the increasing power of ultrasonic, howerer, when the power is up to 1500W, the effect goes worse; and the best primary phase is obtained at 615 oC among the four treatment temperature (645 °C, 630 °C, 615 °C, 600 °C); with the increase of the distance, among the four groups data (7mm, 9mm, 12mm, 15mm), the microstructure of A356 alloy goes more coarse and the segregation is more serious, the average grain size and form factor of the best primary phase α-Al was 29.47um and 0.78, respectively in this study.

Abstract: Martensitic transformation is the most important phase transformation strengthening the 30CrNi3MoV ultra-high-strength steel during heat treatment process. Characteristics of the martensitic transformation in the 30CrNi3MoV steel were investigated by means of dilatometric measurements and microstructural observations. The results showed that the starting and finishing martensitic transformation temperatures of the 30CrNi3MoV explored steel are 317°C and 167°C respectively, which are hardly influenced by the cooling rate from austenite region. Such a wide temperature range of martensitic transformation in the 30CrNi3MoV steel results into the diversity of martensite microstructures. The microstructures in all the quenched 30CrNi3MoV samples are composed of mixture of lath and acicular martensite, corresponding to low-carbon and high-carbon martensite respectively. The transformation rate of acicular martensite is much slower than that of lath martensite, which can be attributed to the stabilization of the rest high-carbon austenite after the formation of lath martensite.

Abstract: High-strength sheet including 2MnB5 Boron and magnesium alloy sheet is the material commonly used in modern machinery, which is easy to induce problems such as excessive rebound, cracking, forming force increase, easy mould wear and the like. The heat analysis of 2MnB5 Boron and magnesium alloy sheet hot stamping forming process and experiments indicate that the transition process from Austenite to Martensite by controlling the sheet heating and cooling temperature is the foundation of heat forming. Only when the cooling rate reaches or surpasses the critical cooling rate, Austenite can be transformed to Martensite directly. Critical cooling rate of sheet is related to the elements of critical water flow rate, mould cooling system design, cooling medium, dented mould medium and the like. Under the condition that the elements of mould structure, cooling system, cooling medium and the like are defined, critical cooling rate is a constant value. As a result, through controlling critical water flow rate, hot forming transition process and hot forming requirements can be guaranteed to overcome the excessive rebound, cracking, forming force increase, easy mould wear and the like in hot forming process.

Abstract: The calculation and application of alloy design for DM6S and DM8B high carbon alloy steels with ultra-fine caebides were introduced in this paper. On the basis of carbides transformation orderliness in Cr-W-Mo-V high carbon alloy steel at different temperature, the structure and composition of the phases and its transformation orderliness in the steels at different temperature were estimated by phase-equilibrium thermodynamic calculation for Fe-Cr-W-Mo-V-Si-Mn-Ni-C system. The rational heat treatment technics were concluded on the basis of the matrix composition at different austenitizing temperature, and the hardness of quenching and secondary hardening was doped out. The yield strength and the toughness can be forecasted on the basis of average cohesive-energy of martensit matrix by the calculation at electronic and atomic scale. The practice of two new steels DM6S and DM8B shows that the prospective objective can be obtained by theoretic design adding a small quantity of technical tests.

Abstract: High purity ZrSiO₄ powders were prepared using zirconium oxychloride and tetraethoxysilane as raw materials by the microwave hydrothermal (M-H) method, in which NaF was added as mineralizer to promote the crystallization of zircon. The results show that the microwave-hydrothermal method greatly reduces the starting crystallization temperature of ZrSiO₄ powders to 160~200 °C in 30 minutes, the characteristics of the microwave hydrothermally synthesized powders are superior to that synthesized by conventional hydrothermal in stability, purity and morphologies. And the XRD analysis shows that all peaks of the former powders are abnormal broadness except the (200) and (220) peaks, and the crystallization of powders can be improved by adding seed crystals of ZrSiO₄. The ZrSiO₄ particles are disk-like platelets which are monocrystal and have a trend of Single crystal to polycrystalline transition. The synthesis mechanism of ZrSiO₄ by microwave hydrothermal (M-H) process is discussed.

Abstract: The composite shear wall system with permanent thermal-insulation wall form of glazed hollow bead is a new kind of energy-saving building. the experimental study on the seismic performance of composite shear wall structure was proposed. Through the tests of the walls with different shear-span ratio and axial compression ratio under vertical force and low cyclic horizontal load, the seismic behaviors of slitted shear walls under low cyclic load tests were studied. Through the expemental study, the calculation methods for load-bearing capacity of walls with different shear-span ratio were obtained. And then the laws for the energy dissipation and ductility feature were revealed. Besides, the comparison analysis were made on the seismic behaviors between composite shear walls and common shear walls.The study could provide a foundation for the designing evaluating on the performance for the new structure.

Abstract: Graft copolymerization of diethylenetriamine onto bagasse celluloses was investigated with ammonium ceric nitrate as initiator in an aqueous medium. The condition of the graft copolymerization initiator concentration, the mass ratio of monomer/cellulose, reaction temperature, reaction time based on the experiment is optimized according to the zeta potential. The results showed the relative optimum process conditions were: the concentration of initiator at 36.98mmol/L, the mass ratio of the monomer and cellulose at 1:1, the reaction temperature at 70°C, and the reaction time by 3h. In addition, the graft copolymers were characterized by Fourier transform infrared spectra (FT-IR), X-ray diffraction analysis (XRD). The results showed that bagasse celluloses could be grafted with diethylenetriamine in aqueous medium.

Abstract: Based on the experimental results of three steel fiber reinforced high-strength concrete frame exterior joint under the low cycle loading, the numerical simulation by nonlinear finite element method was adopted to analyze their behaviors and to explore the influence of axial compressive ratio on seismic capacity of the joint. The results indicate that the increase of the axial compressive ratio enhances the restriction role to the joint core area concrete, slows down the degeneration degree of shearing-resistance capacity and stiffness, enhances the shearing-resistance capacity of the core area, the joint ductility and the energy dissipation capacity. The finite element analysis coincides well with the experimental results. In finite element analysis, steel fiber was equated with micro-reinforcement, and then put evenly into the concrete unit. Compared with the test results, the method of taking the steel fiber and concrete as a holistic model was thus validated.