Papers by Keyword: Densification

Abstract: Polycrystalline yttrium aluminium garnet (YAG) ceramic has been prepared using microwave sintering. Micron-sized of Al₂O₃ and Y₂O₃ powders were mixed through in house fabrication mixer for 24 hours before calcined at 1100 °C and palletization process. The effect of sintering parameters on the microstructures was observed at various and holding times. X-ray diffraction (XRD) analysis was carried out to determine and quantify phase transformation with respect to these parameters. It was found that three phases namely YAM (Y₄Al₂O₉), YAP (YAlO₃) and YAG have been identified. While both grain sizes and density of sintered samples were found increased from 1.4 μm to 2.46 μm and 90% to 98%, respectively. Therefore, microwave sintering has a significant effect on the densification behavior of YAG.

Abstract: Biphasic Calcium Phosphate (BCP) is a ceramic material that consisting of two phases which is Hydroxyapatite (HA) and β-Tricalcium Phosphate (β-TCP). In this work, BCP and Mg-BCP (Mg Doped) was synthesized using aqueous precipitation method at standard room temperature and pressure. The synthesized powder was pressed into pellet and sintered at three consecutive temperatures of 800 °C, 900 °C, and 1000 °C. The sintered pellet was characterized using XRD to obtained the quantification analysis on phases presence and to study the crystal orientation of HA and β-TCP before and after Mg doping was introduced. FTIR was used to determine chemical constituents of synthesized powders. Diameter shrinkage analysis was performed to study the effect of temperatures on the densification of the pellet body and SEM was used to observed the morphology of each pellet. Based on the XRD result, the Mg doping is affecting the stability of the phases presence and the crystal lattice creating a distortion due to the substitution of smaller Mg ion. Analysis on the SEM morphology have shown that Mg doped BCP resulting a dense structure with less formation of porosity, necking was formed clearly at temperatures of 900 °C to 1000 °C.

Abstract: This study investigated the effect of laser power (P), scan speed (v) and hatch space (h) on densification behavior, surface quality and hardness of 18Ni300 maraging steel fabricated by selective laser melting (SLM). The results indicated that the relative density of the SLMed samples has a shape increase from 73% to 97% with the laser energy density increasing from 0.5 to 2.2 J/mm². The relative density ≥ 99% was achieved at the energy density in the range of 2.2~5.9 J/mm². The optimum process parameters were found to be laser power of 150~200 W, scan speed of 600mm/s and hatch space of 0.105mm. In addition, it was found that the hardness increased initially with the increasing relative density up to relative density of 90% and then little relationship, but finally increase again significantly. This work provides reference for determining process parameters for SLMed maraging steel and the development of 3D printing of die steels.

Abstract: The main aim of this paper is to present the research findings which come out from the experimental determination of the influence of input raw material properties and composition on the operating parameters of an injection press during the injection of biomass-plastic composites (BPC). During the injection process, important operating parameters such as injection speed, injection pressure and the temperature profile along the chamber can be recognized. In this research study, the aim was to produce BPCs of an acceptable and competitive level of quality which is determined from the final mechanical properties of BPCs. Using a variety combination of influencing variables the final quality of composites and also the operating parameters of the injection moulding press can be improved. Raw waste material variables influence, especially (a type of plastic matrix, type of biomass, particle size, moisture content) and biomass/plastic concentration ratio can be recognized during the production of composites. Their effect can be seen from the quality indicators and from the operating parameters of the injection press which has a direct impact on the production costs. The paper deals with the determination of the impact and the relationship between the input raw material variables and the operating parameters of the injection process (pressure, speed, and temperature profile). The experimental research findings were obtained using a semi-operational injection moulding press where the injection is provided by a working screw. As the input raw material, wheat straw and spruce sawdust, HDPE plastic matrix and recycled HDPE, represented by lids from PET bottles, was used. The effect of the input raw material composition was determined according to a combination and default levels of biomass/HDPE concentration ratio, using recycled HDPE instead of virgin HDPE and particle size of biomass.

Abstract: Tungsten has many excellent properties such as high melting point, high electrical conductivity, high electromigration resistance, high electron emission coefficient, high thermal stability and so on. Because of these excellent properties, high purity tungsten targets have wide applications and development prospects in the integrated circuit (IC) industry. In this paper, some manufacturing methods of tungsten targets was summarized and analyzed. The high melting point of tungsten makes powder metallurgy (PM) be the manufacturing methods of tungsten targets. After preforming of the tungsten powders, some sintering and densification processes like atmosphere pressure sintering, Hot Pressing (HP), Hot Isostatic Pressing(HIP) have been carried out. The grain size and the density of the tungsten targets is different by different manufacturing methods.

Abstract: Nowadays, one of the biggest problems is the environmental contamination, which is attributed to a great variety of factors, among which is the construction, because one of the main synthetic materials most used is concrete, artificial material consisting of portland cement, fine aggregates, coarse aggregates and water, in the production and processing of portland cement a large amount of carbon dioxide (CO₂) is generated, by 2018 approximately 8% of CO₂ emissions from the world is attributed to the cement industry. As a solution to this problem, substitutions and additions to portland cement are proposed, which will generate a reduction in consumption and processing by having a more durable and better quality material in terms of physical and mechanical characteristics. Additions of 2% are made with respect to the weight of the cement of organic additions, which do not affect the behavior of the mortar. Cubic specimens were developed for tests of pulse velocity, compressive stress and accelerated attack of sodium sulfate to determine the durability of the material, where favorable results were obtained with organic addition of corn starch.

Abstract: Nickel aluminides have shown great potential as high temperature structural materials. In this study, two classes of nickel aluminide were reinforced with 0.5wt% MWCNTs. Starting powders of nickel, aluminium and MWCNTs were ball milled together using a two stage milling regime and consolidated by spark plasma sintering. The effect of MWCNT reinforcement on the hardness of two classes of nickel aluminide was investigated. Microhardness values revealed a lack of dependence on densification for the NiAl₃ composites. The microhardness values of NiAl-CNT reduced with MWCNT addition whereas microhardness values of NiAl₃-CNT increased with MWCNT addition.

Abstract: Alumina-Y-TZP composites between 0 to 25 vol% Y-TZP content produced via conventional two-stage sintering with T₁ ranging between 1400°C and 1550°C, heating rate of 20°C/min, followed by T₂ of 1350°C and 12 hours dwelling time. The microstructure, density, Vickers hardness (H_V), Young’s modulus (E) and fracture toughness (K_IC) of the sintered samples were then evaluated. It is observed that all samples up to 10 vol% Y-TZP achieved > 98% T.D. as the T₁ increases. Samples with Y-TZP content above 10 vol% resulted in a significant decrease in density and hardness. Samples with ≤ 10 vol% Y-TZP sintered at T₁ of 1450°C was able to achieve density > 98% T.D., Vickers hardness > 18 GPa and Young’s modulus > 380 GPa and fracture toughness > 6 MPam^1/2 when compared to pure Al₂O₃ ceramics.

Abstract: A cold forging process of Mo-alloyed sintered steel was simulated by finite element method (FEM) analysis considering density change in the process. Moreover, the effect of sintering time on the behavior of the densification and the plastic deformation of it in the cold-forging process was also investigated. Using the true stress-true strain diagram obtained by the compression test with a sintered specimen, the modified true stress-true strain diagram was derived for large plastic deformation analysis with the porous material model. The result of FEM analysis for the cold compression process of the sintered specimen revealed that the analysis can simulate the shape of the excessive metal part and density change of it. Also, it was found that local deformation becomes large and thus the excessive metal part extends with increasing sintering time although the difference in the true stress-true strain diagrams is negligible.

Abstract: This paper discusses the potentials of different wood constructions for the renovation and extension of existing buildings for sustainable urban renewal. The renovation and extension of existing buildings with wood constructions can contribute significantly to sustainable urban redevelopment. The renovation of building envelopes, such as façades and roofs, with highly insulated wooden components, can reduce the transmission heat losses and related heating energy demand of existing buildings significantly. The extension of existing buildings contributes to the redensification of urban areas and can create synergies with the improvement of existing buildings’ performances. The manifold advantages of specific wooden constructions can be related to different aspects, such as construction type and material properties, building execution, design, logistic and sustainability. The results of this research discuss the architectural design and planning relevant properties of specific timber construction types, such as wood frame, cross-laminated timber (CLT), massive timber, and hybrid timber-concrete, considering the properties of different soft (such as spruce) and hard (such as beech) construction timber species. Timber constructions are compared with conventional massive constructions out of concrete and steel. The results confirm the significant advantages of timber constructions regarding all aspects.