Materials Science Forum Vols. 773-774

Abstract: The optimum condition for preparing a highly efficient activated carbon has been investigated in this work. The effects of different activation temperatures on the pore structure and surface morphology of highly efficient activated carbon (AC) derived from waste palm shell by chemical activation method using phosphoric acid as activating agent were studied. For activation, different activation temperatures in the range of 550 °C-650 °C were carried out. Activated carbon with well developed pore size were produced at activation temperature of 600 °C for 2 hours. At this temperature the Brunauer , Emmett and Teller (BET) surface areas are 1287 m²g^-1, the total pore volume for adsorption and desorption are 0.742 cm³ g^-1. Scanning Electron Microscope also confirmed the porosity of the highly efficient activated carbon. Finally it was tested in vitro to determine its adsorbing capacity for paraquat as a toxin. For optimum adsorption ability of activated carbon for paraquat, 0.9% NaCl solution is the most suitable solvent. The paraquat preferentially adsorbed onto the activated carbon in NaCl solution. The adsorption ability of the activated carbon (the amount adsorbed) for paraquat observed to be 99.9 mg g^-1.

Abstract: Aluminum foams are porous metallic materials which possess an outstanding combination of physical and mechanical properties such as: a high rigidity with a very low density. In this present research work, a study on the upsetting of an aluminum foam (with a density = 0.73 g/cm³) is carried out by employing different compression velocity values. From the results obtained, it is possible to determine the material flow stress for its subsequent use in finite element simulations (FEM). Once the material flow stress has been determined, it will be employed in order to analyze the conformability of several parts by FEM.

Abstract: This work is motivated by the need to efficiently machine the edges of ophthalmic polymer lenses for mounting in spectacle or instrument frames. The polymer materials used are required to have suitable optical characteristics such high refractive index and Abbe number, combined with low density and high scratch and impact resistance. Edge surface finish is an important aesthetic consideration; its quality is governed by the material removal operation and the physical properties of the material being processed. The wear behaviour of polymer materials is not as straightforward as for other materials due to their molecular and structural complexity, not to mention their time-dependent properties. Four commercial ophthalmic polymers have been studied in this work using nanoindentation techniques which are evaluated as tools for probing surface mechanical properties in order to better understand the grinding response of polymer materials.

Abstract: In this work fibres and complex three-dimensional scaffolds of a covalently linked graphene-polycaprolactone composite were successfully extruded and printed using a melt extrusion printing system. Fibres with varying diameters and morphologies, as well as complex scaffolds were fabricated using an additive fabrication approach and were characterized. It was found that the addition of graphene improves the mechanical properties of the fibres by over 50% and in vitro cytotoxicity tests showed good biocompatibility indicating a promising material for tissue engineering applications.

Abstract: Fibre metal laminates are sandwich materials comprised of a fibre-reinforced composite and a metal alloy. These advanced materials offer superior properties compared to the monolithic constituents; primarily, improved specific strength and stiffness compared to metals and improved impact and fatigue resistance when compared to composite materials. The use of these advanced materials is currently restricted to specialised applications where the superior properties justify the high cost of manufacturing. The formability of a fibre metal laminate based on a glass fibre reinforced polypropylene and an aluminium alloy is investigated in this study using techniques developed for the evaluation of metallic materials. Specimens of varying geometry were stretched over a hemispherical punch and an open die configuration was used to facilitate the acquisition of the strain using a using an optical measurement system. The experimental results were used to determine a forming limit diagram and to elucidate the safe forming limits of the material. In addition, the effect of specimen geometry on deformation behaviour was investigated by analysing the evolution of strain on the surface of the specimens. A significant finding of this study is that advanced materials such as fibre metal laminates can be formed in a similar manner to monolithic metals.

Abstract: Creep Age Forming (CAF) is an effective forming technique combined forming and heat treatment, based on creep and age hardening characteristics of some aluminum alloys. It has been widely used to manufacture large integral panels with airfoil sections and complex curvatures of high strength aluminum alloy. The aim of this paper is to study the influence of element types on springback prediction of creep age forming of aluminum alloy integral panel. Firstly, the finite element models are built by 3D-solid elements and Shell elements separately. And then a set of creep aging constitutive equations of 7055 aluminum alloy are implemented into the commercial FE solver MSC.MARC through user defined subroutine. Finally, springback values predicted by 3D-solid elements model and Shell elements model respectively are compared under different height to width ratios. Some important conclusions were drawn. For the reinforcing panel with the height to width ratio is more than 5:1, shell elements should be used to get more accurate springback prediction result. If the height to width ratio is less than 5:1, solids elements should be used. Above conclusions provide theoretical basis for the study of CAF of the aluminum alloy integral panel by finite element simulation method.

Abstract: To save energy, the heavy machinery industries are encountering the challenge of reducing the equipment weight. The paper introduced a 550 MPa grade steel plate to replace the traditional 345 MPa grade steel for heavy machinery manufacturing. The niobium and vanadium micro-alloyed steel plate is characterized as bainite microstructure with high toughness, improved welding performance, and good fatigue resistance. A comparison between the present 550 MPa grade steel plate and a Ni, Mo, Cu bainite steel was studied. The developed steel plate shows competitiveness for a high performance and low cost. The 15% of weight reduction is achieved in a 50 ton digger at a typical engineering machinery plant.

Abstract: This study developed a precise hybrid optical lens (PHOL) that included polymer and glass materials. Although glass offers superior anti-thermal, anti-environmental, anti-scraped corrosion resistance and optical properties than polymer materials, it is difficult to fabricate glass materials. Therefore, it is difficult to obtain a high-accuracy aspheric glass lens. This paper presents the fabrication of a PHOL that combined aspheric polymer and glass bases using a glass-molding technique. The PHOL can be used to reduce aberration errors in optical systems using two materials. The PHOL maintains the advantages of glass materials, and the cost of aspheric polymer is lower than that of the aspheric glass layer. Thermosetting polymer was used as the aspheric part in this study. Compared to UV-curable polymer, thermosetting polymer has higher thermal stability, and the molds are not limited by glass materials, which must be transmissible by UV light. First, a glass sphere lens was used as a base of the PHOL. Subsequently, the ultra-precise diamond turning technique was used to fabricate the mold with an aspheric profile. During the molding process, the thermosetting polymer was formed into an aspheric layer and covered on the glass base. The PHOL of 11.2 mm in diameter was obtained using controlled cooling. Finally, the surface accuracy (PV) of the PHOL was less than 0.5μm, has been successfully fabricated in this study.

Abstract: In the present work an investigation on primary processing of CuZr based shape memory alloys is proposed. In particular, the study addresses the effect of hot rolling process on the properties of CuZr shape memory alloys, in which the addition of some elements, such as Cr, Co and Ni, is taken into account. These alloys are produced by means of vacuum arc melting furnace under non contaminating conditions. Considering the high reactivity of these alloys, due to Zr element, hot working was undertaken after sealing the ingot cigars in a stainless steel protective can. The characterization of the rolled alloys is performed using DSC in terms of evolution of martensitic transfor-mation temperatures. The analysis is completed with mechanical and the microstructure investigations by means of microhardness and scanning electron microscopy (SEM) observations, respectively. The main result of this work is the evaluation of hot workability property of this system, which can be improved by adding metallic elements to the binary CuZr intermetallic system. Moreover, interesting characteristics, such as high transformation temperatures, thermal stability and reduced thermal hysteresis, can be also improved by means of the addition of Ni and Co at the same time.

Abstract: The composite materials with 2, 4 and 6 % Cu were developed using a noble stir casting method. Tensile test was conducted using universal tensile test machine according to ASTM-2002 (E8M-01) standard and the fracture surface was analysed using scanning electron microscope (SEM). The result showed that the ultimate tensile strength (UTS) was increased due to the percentage increment of Cu in the Al-Cu matrix. A significant change in UTS was observed from 2 to 4 % Cu whereas slight improvement was seen from 4 to 6 % Cu addition. The SEM micrograph of the fracture surface reveals that the cracks were propagated in the fibrous zone resulting from the initiation of micro voids between the matrix and particle interfaces. The number and size of dimples for 2% Cu were considerably lower and the facet features were noticeably higher than higher Cu content composition, whereas, the dimple and facet size and number for the 4% Cu are very close to the 6% Cu content composite which may play important role in the improvement of tensile strength. These findings tinted for the potential application of SiC_p reinforced Cu influenced Al-Cu-SiCp composite for automotive engine components and other similar applications as well.