Applied Mechanics and Materials Vol. 481

Abstract: This study aims to investigate the mechanical properties of gold nanowires using molecular dynamics (MD) simulation. The effects of the cross section size and the defects on the stress strain curves of the nanowires are examined. Moreover, the inception as well as the processing of dislocationin the nanowire is accounted by means of the centro-symmetry parameter and meanwhile, the energy variation during the dislocation is calculated. Results indicated for the pristine gold nanowire, as the cross section size increases, Youngs modulus increases, but the yielding stress decreases accordingly. Once the ultimate linear point is attained, the dislocation takes place abruptly from the nanowire surfaceand extended along the {111} planes. On the other hand, for the nanowire with defect, it was found that the dislocation is initiated from the defect which can significantlyreduce the yielding stress of the nanowires.

Abstract: Nanocrystalline ZnO thin films were manufactured by Ion Beam Assisted Pulsed Laser Deposition (IBAD PLD). The influence of technological parameters and parameters of ion assisted deposition on structural, morphological and electrical parameters of ZnO thin films were researched in the experiments. As a result it was determined that changes in the basic technological parameters of IBAD PLD (target-substrate distance, substrate temperature, energy density of the laser pulses, annealing temperature, Ar flow) are able to change properties of the thin films significant, including surface roughness in the range from 0.75±0.20 nm to 7.8±2.2 nm, resistivity in the range from 10^-3 Ohm cm to 10⁴ Ohm cm. The possibility of controlling the morphological and physical properties of ZnO nanocrystalline films obtained in the experiments has been shown.

Abstract: The effects of polyacrylic acid (PAA) as an additive on ZnO nanoparticles synthesized by precipitation method is investigated. It is found that ZnO synthesized exhibits a crystalline structure with hexagonal structure of the wurtzite. Primary size of ZnO nanoparticles synthesized can be controlled by PAA concentrations. Increasing of PAA concentration provide small particle size. Addition of 1 wt% PAA can be obtained the average primary size around 20 nm. Additionally, ZnO synthesized using PAA exhibits zeta potential value higher than ZnO synthesized without PAA. With the increasing PAA concentration, Zeta potential value increase. It indicates that ZnO synthesized using 0.5-1 wt% PAA can be well-dispersed in aqueous system and promote highly stable suspension.

Abstract: Highly dispersed ZnO nanosol, having an average particle size of about 40nm based on Particle Size Analysis (PSA), was prepared under aqueous solution without the removal of large particles by centrifugation. The ZnO nanosol was investigated on the effect of various dispersion parameters, i.e. milling time, dispersant content, pH, etc. The nanosol was effectively dispersed at 20~30 wt% of dispersant amount compared to ZnO content under ball-milling for 10 hours at pH 10. The dispersion characteristic of the nanosol was investigated into particle size and zeta potential. We discussed on the dispersion behavior of (-) charged ZnO particle surrounded by dispersant together with the variation of (-) charged dispersant's amount in aqueous medium at pH 10. The ZnO powder and nanosol were characterized by SEM, TEM, TGA, FT-IR, PSA and Zeta-potential.

Abstract: The precipitated of calcium carbonate has attractedmuch attention because of its numerous applications in various areas of plastics, textiles, rubbers, adhesives, paints and wastewater treatment. Nanosized of precipitated calcium carbonate,(PCC) will enhance the properties and give better performance. Its high purity and close controlled particle size and shape are making it the white filler of choice. Nanosized precipitated calcium carbonate particles were prepared using spraying method. The particles were prepared using three (3) different concentrations of Calcium Hydroxide,Ca (OH)₂, three (3) CO₂ flow rate and three (3) different calcinations temperature. The three (3) concentration of Calcium Hydroxide that been used are 25g/200ml, 25g/ 400ml and 25g/800ml and each of these initial solution sprayed at three (3) different CO₂ flow rate, 5l/per-minute, 7l/per-minute and 10l/per-minute. Calcium Carbonate, CaCO₃ powders were then calcined at three (3) different temperature, 1100°C,1200°C and 1300°C. Images from SEM showed morphology of the particles changed to spindle-like or prismatic when the ionic strength of the Calcium Hydroxide, Ca (OH)₂ was increased.

Abstract: In this paper, highstrength and lead-free machinable brass alloy with magnesium (Mg) and graphite (Gr) particles was fabricated via powder technology process.Mg particles were added 1.0 mass% for strengthening of brass matrix. Gr particles as machinable elements were added to the Cu-40 mass%Zn /1.0 mass% Mg (Cu-40Zn/1.0Mg) premixed powder by conventional mixing process.Spark plasma sintering process was used to consolidate the above mixed powder at 973 K.The SPSed Cu-40Zn/1.0Mg + X%Gr specimens were pre-heated at the solid solutecondition of Cu-Zn-Mg IMC, and immediately extruded.The machinability was evaluated by a drilling test using a drill tool under dry conditions.The extruded materialsexhibited fine α-β duplex phases, containing very fine precipitates of CuMgZn IMCs with 1-2μm in diameter regardless of Graddition. There was no reaction phase of reducing the machinability between brass matrix and Gr particles.Tensile properties of the extruded Cu-40Zn/1.0Mg +0.75 mass% Grmaterialwereyield strength (YS): 351 MPa, ultimate tensile strength (UTS): 539 MPa, and 18 % elongation.Average of drilling speed of Cu-40Zn/1.0Mg +0.75 Gr (N=10 times) was 0.15 mm/sthough the extruded Cu-40Zn/1.0Mg could not be drilled over 5 times.

Abstract: The morphology and intrinsic properties are important factors in determining fiber processing technology and end-use performance characteristics. In this paper, a comprehensive study on structure and fundamental properties of the Broussonetia papyrifera fibers have been carried out. Morphological characteristics of Broussonetia papyrifera fibers were investigated using biological microscope and scanning electron microscope (SEM). Crystallinity and crystal structure were investigated by X-ray diffractometer. The fibers chemical components and degree of orientation were studied using infrared spectrometer instrument. Research results show that: Broussonetia papyrifera fiber possesses smooth surface and its cross striations are similar to ramies. Macromolecular crystallinity of Broussonetia papyrifera fiber is 80.57%, which is higher than that of many other natural fibers. Broussonetia papyrifera fibers orientation (65%) is close to but slightly worse than that of several other common natural fibers.This kind of fiber is Cellulose I and has almost the same components with ramie and cotton fibers.

Abstract: This research studied ways to increase the stability of a polymer thin film with a thickness of approximately 10 nm. Our system consisted of a polystyrene (PS) thin film filled with three arm polystyrene (TAP) as additives. Formation of dewetting was investigated by atomic force microscopy and optical microscopy which showed that complete dewetting of the pure PS film occurs after being annealed at 120 oC for 5 h. The dewetting dynamics were dramatically suppressed when a small amount of TAP polymer was added into the PS thin film. We hypothesize that the nitrogen atom in the TAP polymer provides dipolarity between the polymeric thin films and the substrate followed by an increase in the interfacial interaction of the TAP/PS thin films, which in turn leads to increased film stability. However, if the concentration of TAP is too high, this leads to phase separation of the thin films. We also observed that the amount of TAP within the PS thin film largely affected the efficiency of inhibiting dewetting. This method could be utilized for the study of the mechanism in a blended polymer film.

Abstract: Patterned silicon oxide films were formed by a simple process using a dimethyl-silicone-oil as source and inks as patterning masks.After the coating of the ink, the dimethyl-silicone-oil was coated onto the substrate. The sample was heated at 150oC and ozone gas was irradiated. After the heat treatment with ozone gas, patterned silicon film was formed. The circle pattern with a diameter of 20 μm wassuccessfully formed.After the formation of the patterned silicon oxide film, the silicon oxide was hardly observed at the position where the ink coated.

Abstract: Detection for aqueous contamination of mercury is important for its risk for human and environment. We report the detection ofHg²⁺ ionswith graphene and gold in a microfluidic channel. The flow-induced voltage was measured in a microfluidic chip fabricated with a graphene and gold embedded between metal electrodes.The lowest mercury ion concentration detected by the sensor is 10^-8M with a fast response time.Our sensor can overcome the limitations of previous techniques such as portability, quick response time.