Papers by Keyword: Uniaxial Pressing

Abstract: This paper presents a method for fabricating a porous Ni-Al₂O₃-Al compact using uniaxial double-action pressing, which was subsequently infiltrated with molten aluminium. Al₂O₃ ceramic particles primarily serve to create porosity within the composite compact. Due to the difficulty pressing hard metal powders, aluminium powder was introduced into the Ni+Al₂O₃ mixture to act as a plasticizer, improving the material's compressibility. Experiments indicated that the optimal infiltration temperature was 750 °C with an infiltration duration of 300 seconds. To evaluate the reaction extent among the initial components, a subset of infiltrated samples underwent annealing at 800 °C for 3 hours under an inert argon atmosphere. Both annealed and reference samples were subjected to thermal cycling. The microstructure and thermal stability of the resulting composite materials were analyzed and characterized using scanning electron microscopy with energy-dispersive spectroscopy, respectively.

Abstract: This work reports the influence of chemical composition and sintering schedule on the properties of sintered bodies of hydroxyapatite (HA) bioceramic. The method of preparing sintered bodies by solid state reaction and uniaxial pressing. The raw material used calcium carbonate (CaCO₃) and ammonium dihydrogen phosphate (NH₄H₂PO₄) powder as precursors. These powders were mixed at CaCO₃: NH₄H₂PO₄ mass ratio of 1:0.697, 1:0.692, 1:0.689, 1:0.685 and 1:0.68, respectively. The compositions in the temperatures range of 800-1300 °C for 3 hour. The sintered bodies were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). Properties including phase, microstructures, porosity and bending strength of the samples. The results show that green bodies can be sintered at 1150 °C for 3 hours. This temperature found that crystals growth, highest of HA phase content in sintered bodies, good density and high efficiency strength properties.

Abstract: Alumina-zirconia composite is an engineering material with a great potential to be develop for application as high temperature resistance structural material. In this research, zirconia toughness alumina (ZTA) was produced by physical interaction between Al₂O₃ powder and Y₂O₃-ZrO₂ powder. Two composition of powder with different Al₂O₃: Y₂O₃-ZrO₂ ratio was used, 70:30 and 80:20 by weight. Two different compaction methods, i.e. uniaxial pressing and cold isostatic pressing (CIP) with a maximum load of 150 MPa were used in this research to investigate the differences in properties of composites. Sintering process was done at four different temperatures with the heating rate is 5 o C/ min with a soaking time of five hours. Mechanical testing, i.e. compressive strength and hardness was performed to all samples. The microstructure analysis using a Scanning Electron Microscope SEM was also studied. From the result, the composite with the ratio of 70:30 showed better mechanical properties as compared to 80:20 composite. Addition of zirconia in the composite gave an increased in toughness due to transformation toughening mechanism of tetragonal to monoclinic phase. As a conclusion the composites produced high compaction green density will improved the sintering process, resulting in improved mechanical properties.

Abstract: Investigations carried out referred to obtaining material based on the high-speed steel and non-alloy steel. The conventional powder metallurgy method was used for manufacturing these materials, consisting in compacting the powder in the closed die and sintering it next, the isostatic pressing method, and the modern pressureless forming powder metallurgy. Forming methods were developed during the investigations for high-speed and non-alloy steel powders, making it possible to obtain materials with three layers in their structure. Investigations included determining the sintering conditions, and especially the temperature and treatment cycle, as well as examining the selected mechanical properties. It was found out, basing on the comparison of structures and properties of test pieces made with the pressureless forming method, as well as with the isostatic pressing and pressing in the closed die, with further sintering, that in structures of all examined test pieces in the sintered state fine carbides occurred distributed homogeneously in the high-speed steel layer. It was noticed, that increase of the sintering temperature, regardless of the manufacturing method, results in the uncontrolled growth and coagulation of the primary carbides and melting up to forming of eutectics in layers consisting of the high-speed steel. It was found out basing on the microhardness tests that hardness of test pieces both those pressureless formed, compacted in the closed die, and isostatically cold pressed and sintered grows along with the sintering temperature. It was also noted that the sintering temperature range is bigger in case of the pressureless formed materials.

Abstract: The main goal of this work is to demonstrate that the use of recycled material originated from SiC ceramics is viable. These ceramics were produced by commercial starch consolidation process. Before calcination stage, surplus of these materials always appears. This surplus is rich in SiC and starch. Samples were made by material previously milled in automatic mortar and sieved (100 Tyler). Later, 10% of distilled water was added to the material and the mixture was pressed at 40 MPa. In order to characterize the ceramic, three point flexural test were made, according to the ASTM C1161/94 norm. The results were analyzed by Weibull statistical method. Apparent density and porosity measures also were made, according to ASTM C20/87 norm. A verification of the surface was made in the fracture area by the depth from focus method and SEM image analysis. The results showed that the recycling process is fully viable, being a good economic option and reduce possible pollutant effect to the environment.