Applied Mechanics and Materials Vols. 117-119

Abstract: High-quality Cu nanowires (CuNWs) were synthesized in high yield by an improved liquid-phase reduction method. In each synthesis, both length and diameter of CuNWs could be controlled by changing water bath temperature and the concentrations of reagents. Furthermore, magnetron sputtering technology and spin-coating method were combined to fabricate a kind of Cu NWs/thin-film structure. Optical testing results showed that such composite structure exhibited an abnormal absorption at the wavelength of about 656nm, which might have potential applications in surface plasmon resonance based fields.

Abstract: Monodispersed SiO₂/Ag core-shell nanoparticles have been synthesized successfully via a facile and fast route. Morphology of the product was investigated by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) technique. It has been revealed that the diameter of SiO₂/Ag compostie was ca. 220 nm and the shell of Ag nanoparticle are homogeneous and monodispersed. The antibacterial activities of SiO₂/Ag core-shell nanoparticles were tested by means of minimal inhibitory concentration (MIC) and viable cell counting method. The results showed that the SiO₂/Ag presents a good antibacterial performance against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans), which indicated its potential applications as antibacterial material for microbiocides.

Abstract: A new method was developed to synthesize high active TiO₂ nanocrystals by the hydrolysis of titanium (IV) chloride in water at 40-80°C, employing nanocrystal cellulose (NCC) as morphology controlling agent. The obtained samples were characterized with transmission electron microscopy (TEM), X-ray diffraction (XRD), and ultraviolet-visible spectrophotometer. TEM investigations revealed that the crystals synthesized at 40-60°C were flower-like which was composed of nanoneedles, and when the temperature rose up to 70-80°C, cubic nanocrystals with an edge length of 100-200 nm were observed. XRD results showed that the crystalline phase of the nanocrystals had a strong dependence on the temperature and aging time, and the content of rutile phase increased with increasing either the temperature or the aging time. The photocatalytic activities of the samples were tested by the degradation of methyl orange in aqueous solution under high pressure mercury lamp. The experimental results revealed that cubic nanocrystals showed much higher photoactivity than flower-like ones.

Abstract: Heat transfer coefficient, temperature of cooling water and casting speed have definitely influence for the mould thermal state, especially with the high temperature. The coupled visco-elasto-plastic FEM models have been presented for thermal process analysis of steel shell and the mould copper plates. It is shown that, the heat transfer coefficient and the temperature of cooling water have little influence to the maximum equivalent mises stress and equivalent strain of the mould; but the casting speed has a great influence, with the increasing casting speed from 1.0 to 1.6 m/min, equivalent mises stress creasing rate is reached to 8.7%, and the equivalent strain is also getting smaller.

Abstract: Damage behavior of composite stiffened plates of structure I and structure II at different positions and under different impact energy subjected to low-velocity impact testing was studied in this paper. Visual observation and ultrasonic C-scanning were also employed to inspect the damage size. The results showed that damage behavior of composite stiffened plates was not only related to damage behavior of laminates, but also related to damage between stringer and laminate and damage of stringer itself. It was found that the mechanism of absorbing energy varies with the impact position, as well as the damage behavior. When the impact position was near stringer, partial energy was absorbed by stringer to make stringer and laminate disengage and damage area of laminates was smaller. Damage behavior of composite stiffened plates varies with the structure. Damage area of samples of structure II was smaller than that of samples of structure I. It was estimated preliminarily that design of structure II was better than that of structure I.

Abstract: This paper reports a novel colorimetric sensor for pymetrozine based on p-aminobenzenesulfonic acid functionalized silver nanoparticles (p-ABSA-modified Ag NPs), which were characterized by IR spectroscopy, ultraviolet–visible spectroscopy (UV–vis), and transmission electron microscopy (TEM). The newly synthesized p-ABSA-modified Ag NPs are yellow in color due to the intense surface plasmon absorption band centered at 400nm. In the presence of pymetrozine, the yellow p-ABSA-modified Ag NPs solution turns to dark green, with a dramatic surface plasmon absorption band centered at 660nm. Moreover, high selectivity for pymetrozine was approved by the comparative experiments with an absorption ratio of A660/A400 more than 0.7. This highly sensitive sensor allows a direct and rapid quantitative assay of pymetrozine with a colorimetric limited detection concentration of 0.01mg/L.

Abstract: High frequency longitudinal guided waves were used to inspect the anchored rock bolts. Experiments were conducted to find the optimal frequencies for the bolt testing. A broad-band signal was excited at the top end of the bolt, and the power spectral density(PSD) analysis of the bolt end reflected waves was made. Base on that the frequency component of the bolt end reflected waves could be obtain, and the frequencies with higher power spectral density values are the optimal ones. At optimal frequencies, the guided wave attenuates more slightly than it is at other frequencies and the bolt end reflected waves can be clearly acquisitioned. Experimental results show that the optimal frequencies of guided wave in a free bolt and in an anchored bolt are quite the same, and they are mainly affected by the bolt instead of the anchor media. Conclusions can be drawn that the propagation velocities of guided wave at optimal frequencies in a free bolt are close to those in the embedded section of the bolt. As a result, the bolt length and the position of flaw in the anchored bolt can be determined by the guided wave velocity in a free bolt and the reflected wave from the bolt end and from the flaw, respectively.

Abstract: The spherical tungsten powder was prepared by chemical reaction with ammonium tungstate and strong acids under ultrasonic and mechanical agitation. After precipitation reaction, the precipitate was dried and grinded, and then reduced into tungsten powder with hydrogen. The effects of acid kinds and dispersant on the fine tungsten powder were studied in this paper. The result shows that the acid kinds and its addition amount have great effect on the shape of tungsten particles. The tungsten powder with uniform particle size and spherical could be prepared by adding 17ml sulfric acid into 100ml ammonium tungstate. The tungsten particles can be finer and more dispersive, and have a spherical with addition of dispersant SDS (Sodium dodecyl sulfate). The particle size is about 1.5 micrometer.

Abstract: Cutting force experiments in turning aluminum-silicon alloy ZL104 are carried out with cement carbide tool YG8. The influence of cutting parameters on cutting force is obtained based on single factor experiments. The results indicate that depth of cut and feed rate have great influence on cutting force while cutting speed provides just little impact.

Abstract: This paper describes the materials and the methods used to make a tensile test of composite materail. The experimental study is conducted to observe the crashing behavior of composite material using different types of material namely; glass/epoxy carbon/epoxy and jute/epoxy specimens. Then, the behavior of the composite specimens is observed to determine the best material that produced the highest mechanical properties to be used as a material for a straight bevel gear in robotic arm application. The experimental work has been divided into two stages. The first stage is the experimental process, which involves fabrication of the specimens for the tensile test. The second stage is the preparation of specimens for the tensil test.