Papers by Keyword: Fabrication

Abstract: The aim of this research was to study the feasibility for applications related to powder metallurgy in EDM electrode fabrication by combination of the percentage Cu-C-Ni element. The experiment was performed by comparing preliminary distribution results of particle size before and after the grinding of metal powders. The work-piece was pressed at a pressure of 200 Psi using a uniaxial press machine. The pressed green compact work-piece was then baked in a furnace. The gas inside the furnace that was used to control the temperature during the cold press procedure had a mixture gas ratio between argon and hydrogen of 95:5 (common grade) at 1030 ^oC and a soaking time of one hour. The results were examined by comparing the electric resistivity property, apparent density, bulk density as well as the porosity percentage inside the work piece material. The results revealed that the optimum combination of percentage Cu-C-Ni element was Cu92-C3-Ni5 (%wt), leading to the satisfactory Copper distribution in most of the structure. The size of sub sieve powder after grinding was found to be 22-31 micron with an electric resistivity of 1.45829E-05 k-ohm*cm. The minimum porosity percentage was found to be 2.19 %. Therefore, the element properties were found to be suitable for using as an electrode in EDM work when compared to that of the electrode prototype (EDM C3).

Abstract: Renewable energy attracts many researchers as the non-renewable one has negative environmental impacts and limited availability. One of the main types of renewable energy is the blue energy where electricity is generated by water waves using triboelectric nanogenerators (TENGs). Thin films play an important role in the performance and therefore the efficiency of TENGs as they represent the electrodes between which electrons move producing electricity. In order to increase the generated electricity from TENGs, the properties of these electrodes should be modified. Therefore, in this paper, nano- and micro-size thin films are fabricated and characterized by measuring the geometrical parameters and electrical properties. Thin films are fabricated using aluminum with thicknesses 0.5 μm and 1.5 μm on acrylic substrate and 0.5 μm copper film on different types of dielectric materials including PVC and polystyrene. Atomic force microscopy is used to measure the geometrical parameters of the fabricated films including thickness and surface roughness. Also, Gwyddion software is used for the grain size evaluation. On the other hand, Keithley is used for measuring the electrical properties including electrical conductivity and sheet resistance. It is found that the electrical conductivity of aluminum films is inversely proportional to the thickness. The corresponding measured values of the electrical conductivity of the fabricated thinner and thicker aluminum films equal 1.7 x 10⁷ (Ω.m)^-1 and 1.4×10⁷ (Ω.m)^-1, respectively. Whereas, the electrical conductivity of the fabricated copper film equals 8.8×10⁷ (Ω.m)^-1. In addition, the temperature effects on the electrical conductivity are studied. Finally, simulation of a TENG using COMSOL software is accomplished in order to evaluate the electrical outputs of potential, charge, and energy.

Abstract: Friction stir processing (FSP) is emerging as a singular solid-state surface engineering technique to fabricate surface composites (SC) since its adaption from Friction Stir Welding (FSW) from the early 90s. FSP is a promising technique to overcome the barrier of magnesium being a poor material in terms of wear and corrosion resistant without adding much on the processing cost and thus, widen its applications.The targeted property enhancement by forming surface composites via FSP are strength, ductility, hardness, wear resistance, toughness, fatigue life, formability, corrosion resistance, etc. Although, a decade of research work has been carried out on FSP for different metal alloys, the advantages of the process particularly on magnesium alloys is yet to be understood clearly. The present review is focused on understanding the response of magnesium alloys for friction stir processing to fabricate surface composites. The available literatures have been thoroughly reviewed to present the microstructure evolution during processing and the mechanism of strengthening; the works on magnesium has been summarized to understand the effect of various processing parameters such as tool speed (rotation and traverse), number of passes, etc. and the tool geometry on the resulting properties. Also, details regarding the selection of suitable tool material and reinforcing particles to achieve optimum properties for specific magnesium alloys is included. Important suggestions and scope for further research regarding fabrication of surface composites on magnesium alloy are provided.

Abstract: Having a robust non-destructive evaluation (NDE) technique for friction stir welded (FSWed) joints is of interest to the processing community. Such a technique has to be sensitive to the different types and shapes of internal weld defects and has to be applicable for both similar and dissimilar material FSW joints. Investigated was the ability of ultrasonic guided waves to detect and assess the quality of FSW joints. The fundamental anti-symmetric (A₀) mode was selected to detect the flaws in FSW joints. Guided waves were excited (using PZT wafers) and received (using a laser Doppler vibrometer, LDV). Implemented was the frequency-wavenumber filtering technique to separate forward propagating wave from any back propagating reflected wave due to the welded joint. Identified was the reflection of the A₀ mode caused by the presence of the interface and/or defects within the joint. The findings indicate little sensitivity to the presence of material interface suggesting this technique to have a promising potential among guided-wave-based techniques in the qualitative and quantitative assessment of FSW joints.

Abstract: Bioreactor systems for cultivating cells in Life Sciences have been widely used for decades. Recently, there is a trend towards miniaturization, disposables and even micro platforms that fulfill increasing demands strongly aiming for production and testing of novel pharmaceutical products. Miniaturized bioreactors allow low power consumption, portability and reduced space requirements and utilize smaller volumes of reagents and samples [1,2]. A recursive strategy is necessary for optimizing the design and the manufacture of such miniaturized bioreactors. For the fabrication of these prototypes utilized micro-milling. Micro milling is a mechanical process which is commonly applied to create micro-structures in metals, e.g. aluminum and steel, or polymers, e.g. poly carbonate substrates. The structures and geometries are generated by utilizing computer aided design. By means of computer-aided manufacturing, the machining operations are implemented and then transferred to the machine tool. The machine tool moves the cutting tools with certain speeds, feeds and traverse ranges to the substrate. Micro milling has the advantage that the materials are generally not degraded by chemical substances, heating procedures or electromagnetic radiation.

Abstract: Modern medical science delivers through innovative chemical or mechanical/physical means new strategies to treat patients mildly and fight diseases accurately. In line with this development a screening procedure for tissue samples under usage of the electronic speckle pattern interferometry is developed at the University of Applied Science Wildau. The paper at hand provides the corner stone for such a procedure in form of an incubation system that is adapted to the properties of an electronic speckle pattern interferometer and allows the incubation as well as study of samples over time. As a result the developed system can regulate its own temperature and is constructed for use in an electronic speckle pattern interferometry (ESPI) setup. Its design allows a simple modular approach for further development

Abstract: This research aims to fabrication and evaluation the properties of cement reinforcement made from Panicum repens. The research is divided into two parts are as follows; to determined the optimal ratio selection, and to compare the properties of Panicum repens reinforced cement, and without grasses by using the optimal ratio. The raw materials used in this research were cut in length of 2.0-2.5 cm. In this research was determined the properties of Panicum repens reinforced cement in terms of bulk density, water absorption, and compressive strength. The influence of fibers soaked with 5% of sodium hydroxide concentration was also conducted in this research. The surface structure and chemical characteristics of fibers used to produce reinforced cement were observed by using scanning electron microscope (SEM), and energy dispersive x-ray spectrometer (EDS), respectively. Moreover, relationships of information collected from this research were concerned. Furthermore, the addition of Panicum repens fibers could improve the flexural strength of composite materials.

Abstract: In the present work, the neat epoxy and different orientations [0°, 45°, 90°, (45°/-45°/45°) s, (±45°/0°/90°) s] of unidirectional carbon/epoxy composites are experimentally studied under tensile and impact loading. The notched impact tests are performed using the Izod impact machine to obtain the energy absorption of neat epoxy and different CFRP composites which is required for effective design of bullet proof jackets and military vehicles. The micro mechanical analysis is employed to determine the shear properties of a matrix using the tensile properties. Using classical laminate theory [CLT], the theoretical tensile properties are determined. The SEM fractography analysis is used to observe the damage mechanisms of neat epoxy and different orientations of CFRP composites subjected to tension and impact loading.

Abstract: Tuning the bandgap of superlattice structures creates devices with unique optical, electronic and mechanical properties. Designing solar cells with superlattice structures increases the range of light energy absorbed from the solar spectrum in the device. A superlattice is a nanostructure composed of alternating thin layers of two materials. The thickness of the constituent materials alters the optical bandgap of the superlattice. This paper discusses a mathematical model which computes the effective bandgap of a CdTe/PbTe superlattice based on a given thickness of the CdTe and PbTe films. The output of this model is verified by fabricating superlattices with different thickness and measuring their effective bandgaps. The electrochemical atomic layer deposition method is used to fabricate the superlattice structures. The advantage of this method over other vacuum techniques is that it is inexpensive and operates at room temperature. This paper also discusses a method to mitigate the lattice mismatch between the substrate and the superlattice. The optical bandgaps, crystallinity, grain size and chemical composition of the structures are measured using a spectrometer, diffractometer, transmission electron microscope and scanning electron microscope, respectively. The bandgaps of the fabricated superlattices were in agreement with the simulated values. This model can be used for designing the bandgaps of superlattices which can be incorporated in solar cells.

Abstract: Light weight as a primary factor in combination with strength and durability properties of aluminium alloys brings financial benefits accruing not only from material procurement but along the whole chain of production, manufacturing, delivery and installation, maintenance and even disposal. A significant contribution in the quest to deliver more value has been the development in the last decade of harmonized design and execution standards, the Eurocodes, National Annexes and adapted codes or recommendations for specific applications. The sustainability issue can be dealt with in a more reliable way due to the comprehensive data tools and comparative analyses available nowadays. Experience with growing numbers of applications also delivers benchmark values for initial cost and maintenance requirements.