Advanced Materials Research Vols. 378-379

Abstract: Reactive compatibilization between high-density polyethylene(HDPE) and wood-flour was achieved via direct reactive extrusion of glycidyl methacrylate(GMA), initiator, HDPE and wood-flour. Impact rupture surface of the composite was observed by scanning electron microscope(SEM), and its load deformation temperature(HDT) and mechanical properties were tested. Effect of GMA dosage and extrusion temperature on reactive compatibilization of the composite was analysed. The result indicated that the anchoring strength of interface in the composite was obviously strengthened, and its HDT, tensile strength, flexural strength, notched impact strength and elongation at break of the composite were distinctly improved due to the addition of GMA and dicumyl peroxide(DCP). When the composite was extruded at 180°C, the peak values of its HDT, tensile strength, flexural strength, elongation at break and notched impact strength respectively were 84°C, 40Mpa, 45Mpa, 11% and 6.6KJ.m-2, which respectively increased by 17°C, 74%, 36%, 83% and 69% than that of the composite without reactive compatibilization, and when the composite was extruded at 190°C, the peak values of its HDT, tensile strength, flexural strength, elongation at break and notched impact strength respectively were 84°C, 40Mpa, 44Mpa, 11% and 6.6KJ.m-2, which respectively increased by 20°C, 60%, 26%, 83% and 83% than that of the composite without reactive compatibilization. When GMA usage increased, the HDT and mechanical properties of the composite increased first, then descended, and the optimum usage of GMA was 1wt%-3wt%.

Abstract: A low cost and substrate-independent method has been established to synthesize vertically aligned ZnO nanowires (NWs) on iron oxide films coated silicon substrates via low pressure Chemical Vapor Deposition (CVD) method at 650oC. In this study, Si substrates were dipped into the iron (III) nitrate nonahydrate solution prior to the synthesis process. This oxidized iron film facilitated the growth of highly oriented (002) ZnO seed layer, which allowed subsequent vertically aligned ZnO NWs to be grown on top of it during the synthesis. This approach has provided a good alternative to grow vertically aligned ZnO NWs without the need of considering the epilayer relationship between the ZnO and the material to be used as substrate.

Abstract: Cast IN738LC alloy mainly consists of primary gamma matrix, gamma prime precipitates, and carbides. SEM-EDS analysis results suggested that most of the carbides are MC type ones that possess high Ti or Ta contents. MC carbides were partly dissolved into the matrix during the solid solution treatment, and the morphology and size of carbides were influenced by the solid solution treatment temperature. Characteristics of gamma prime precipitates were also significantly affected by the solid solution treatment conditions. Single or duplex size distributions of gamma prime precipitates were obtained depending on the solid solution treatment condition. Higher tensile strength was obtained in the case of finer precipitation size and in the case of single size distribution as compared with that of duplex size distribution.

Abstract: Four-wave mixing (FWM) phenomenon can be produced by using a different refractive index of the optical fiber in an erbium doped fiber laser system. In our study, we used a 20 meter length of Photonics crystal fiber (PCF) to generate multiwavelength signals. Variable optical attenuator is employed in the setup to study its effect on the output signals. Results show that uniform signals were obtained by using the VOA to suppress other modes of wavelengths which occurred before placing the VOA. New lasing wavelength at 1530.445 nm, 1531.450 nm, 1531.960 and 1532.415 nm were produced uniformly.

Abstract: This paper presents an overview of the work undertaken by Rolls-Royce to introduce Hot Isostatically Pressed (HIP) large bore, austenitic stainless steel pipework into a safety critical application - a Nuclear Reactor plant. It describes the advantages of using HIP product forms to combine separate sections of straight pipe and elbows and, in so doing, reducing the number of structural plant welds.

Abstract: Water proofing is an obvious problem in developing successful underwater robots. In previous research, most underwater robots have used a mechanical seal for water proofing. However, this kind of seal has not proved reliable because of friction and wear between the stationary parts and moving parts. This paper presents a method to seal the moving parts in underwater robots, especially robot fish. The proposed seal for under water robots is developed using Magneto Rheology (MR) fluid. MR fluid is a kind of smart material, of which the viscosity varies with the external magnetic field. This fluid is composed of silicon oil and small magnetic particles, which are micrometer sized, and when an external magnetic field is applied to the fluid, the small particles align with the magnetic flux line. The arrays of magnetic particles in the fluid inhibit the fluid flow, which changes the viscosity of fluid. Taking advantage of this phenomenon, we devised a seal with a permanent magnet and MR fluid. Our analysis demonstrates the performance of the developed seal. The magnetic equivalent circuit method and FEM (Finite Element Method) are used to calculate the magnetic field and the analysis results show that the developed seal can sustain 10 atm pressure.

Abstract: In order to investigate the influence of the traps which exist in the multi-quantum-well (MQW) of GaN-based light-emitting diodes (LEDs), we analyzed the output current fluctuation known as random telegraph noise (RTN) at reverse-biased region. We could find the two-level current fluctuations at two samples (S1, S2) and the low-level average time (τlow) is larger than the high-level average time (τhigh) at both samples, which means that the energy level of the trap is located below the mid-gap of used material. With increasing a reverse bias voltage, in case of S1, τhigh becomes higher and τlow becomes lower as the energy level of the trap becomes relatively higher in reference to quasi Fermi level, EFn. On the contrary, the τhigh becomes lower and the τlow becomes higher at S2 as the energy level of the trap becomes relatively lower in reference to quasi Fermi level, EFp.

Abstract: Gate oxide shorts (GOS) defect is a critical factor in influencing yield or reliability of the wafer. Due to the conventional test vehicles are not appropriate to collect mass of testing data for GOS defect densities detection and have different manufacture process from the normal transistors resulting in the high testing cost. In this paper, a novel pseudo transistor matrix (PTM) is proposed for GOS density extraction which has almost the same structure as normal transistor. By assuming that GOS are completely independent, the defect density of GOS is extracted from the layout attributes and yield with PTM as a test vehicle to collect mass of testing data. Experimental results show that the extracted GOS defect density is in a good agreement with inline e-test data.

Abstract: Since Ronan Point tower local collapse in UK in 1968, progressive collapse phenomenon in structures attracted more attention for civil engineers all over the world so there were no useful researches and manual codes related to progressive collapse designing before. Progressive collapse occurs when loading pattern, boundary condition and resisting path changed, so critical elements undergo excessive unpredicted loading. We cannot omit reason of collapse as well as prevention of distribution of it that cause progressive collapse. Also, we cannot predict exact location of collapse beginning, so we should generalized design guides to whole or part of structures elements based on risk analyzing. Also we can use load carrying element removal scenario for critical elements. To prevent progressive collapse, structural systems require to having a well-distributed, redundant lateral load resisting system and ductile connections capable of undergoing large inelastic rotations without failing. There are some new guides and criteria for elements and connections to be designed to resist progressive collapse. Depends on required accuracy, importance of the buildings and acceptable risk level, the analysis methodologies ranged from linear to nonlinear with static and dynamic approaches. In this paper, codes and researches recommendations to resist progressive collapse for steel structures are presented, classified and compared. Also, applicable design methods based on codes and some retrofitting methods are summarized.

Abstract: Landfills come with a cover barrier which includes a compacted silty clay liner essential to safety on site. However this barrier encounters problems, especially those related to the differential settlement, which may cause stress in the clay layer leading to the development of cracks. Generally speaking, tensile stress damage and shearing are observed on the cap cover. Due to the weak mechanical performance of the clay layer it was proposed to add polypropylene fibre reinforcement. Direct tensile tests and compression tests under low confinement were carried out on unreinforced and reinforced soils. An improvement in soil resistance and in the brittleness index of fibre-reinforced clay was characterised. The proposed solution, technically feasible, enabled an optimization of the thickness of the mineral barrier.