Papers by Keyword: Cold Pressing

Abstract: Mycelium-based composite (MBC), as a new engineering biocomposite, is receiving numerous interests due to its environmental sustainability. The study aimed to address the challenge of optimizing the physical properties of MBC for a more efficient production process. The study investigated the impact of hot or cold pressing, different pressing temperatures (120 °C, 160 °C, and 200 °C), pressing pressures (low, medium and high) and sequences (before and after drying process) on the physical properties of MBC such as density, shrinkage, moisture content and hardness. Mycelium millets were mixed with kenaf, carbon carbonate, wheat bran and wheat flour. The pressing methods and sequences significantly affected the properties of the MBC. Cold pressing had no effect on reducing shrinkage and moisture content of MBC but improved density. Hot pressing increased hardness at higher temperature and pressure, with strong mycelium-substrate bonding and less porosity observed in SEM image. The post processing sequence involving drying followed by hot pressing at 200°C exhibited higher density, hardness, less shrinkage and controllable moisture content of MBC for better dimensional stability and quality control purpose. It was crucial to optimize MBC pressing techniques for specific applications and ensure that it satisfied the demanding standards of companies looking for sustainable alternatives and cost-effective production.

Abstract: This work presents the investigation of nanopowders from magnesium aluminum spinel doped with Cr³⁺. Different synthesis conditions were used to determine the influence on lattice parameter. The following synthesis parameters varied: time of calcination, cold pressing and alternative precursor of Cr³⁺. The nanopowders properties were measured by XRD, optical transmission and EDX spectroscopy. The determined average size of synthesized nanoparticles is around 70 nm. Ceramic samples are given by hot pressing and studied by transmission spectroscopy and luminescent spectroscopy. The excitation and emission spectra demonstrates ²E - ⁴A₂ (687 nm), ⁴A₂ - ⁴T₁ (400 nm) and ⁴A₂ - ⁴T₂ (532 nm) transitions.

Abstract: The study of composites made from residual organic materials and polymeric resins, has a great projection due to the use of new raw materials and the good physical, mechanical and aesthetic characteristics these materials present in the construction industry. The manufacturing processes of these composites include the necessary pressure application to generate an efficiently compact material, where matrix and reinforcement bonding are efficient. This study defines how the compaction force influences the flexural strength of composites made from polyester resin as polymer matrix, and rice husk as reinforcement material. This is achieved by testing different series of specimens, made by applying different compaction forces in a cold process, to analyse the relationship between compaction and flexural strength. Specimens are made varying only the compaction force, from 2, 5, 8, 11, 14, and 17 tons. The results show that, when the compaction force increases, the flexural strength in the composites also increases, however, there is a pressure range where the flexural strength values are very close, conditioning the use of pressure in relation to the decrease in the specimen section.

Abstract: It is reported that alloying with Cu causes the transformation from the D0₂₂ type structure of Al₃Ti into L1₂ cubic structure. Since the lattice constant of Al_2.5Cu_0.5Ti with L1₂ structure is a = 0.3927 nm, smaller disregistry value between Al and Al_2.5Cu_0.5Ti can be achieved. In this study, novel refiner for Al cast containing Al_2.5Cu_0.5Ti intermetallic compound particles with L1₂ structure is fabricated by cold pressing. It is found that the grains of Al cast are partially refined by using the novel refiner, although microstructure of Al grain is not homogeneous. In this way, the Al_2.5Cu_0.5Ti intermetallic compound particles with L1₂ structure can become favorable heterogeneous nucleation sites for Al cast.

Abstract: There is considerable industrial potential for aluminium alloys and aluminium metal matrix composites fabricated via net shape press-and-sintering powder metallurgy using low-cost, elemental premixed powder. In this work, the compressibility and sinterability of premixed Al– 4.5Cu–0.7Si–0.5Mg powder alloy reinforced with Al2O3 particles was analyzed. The powders reinforced with increasing ceramic particle content were cold-pressed under increasing pressure and sintered at 600 oC for 40 minutes, in nitrogen atmosphere. The powders showed the typical compressibility curves and the presence of hard ceramic particles decreased the powder deformation capacity and, consequently, the powder compressibility. The sintering produced swelling of the parts, due to the poor wettability of liquid phase on the aluminium particles and to the Kirkendall effect caused by the difference in diffusivity of aluminium in copper and copper in aluminium. The presence of Al2O3 particles increased the swelling during sintering probably due to the sooner formation of liquid phase.

Abstract: Aluminium powder has been mechanically milled using different amounts of process control agent (PCA). Mechanically alloyed aluminium powder (MA Al) was prepared by attrition milling in the presence of 1.5 and 3wt.% of an EBS wax. Milling was carried out in vacuum during 10 h. Milled powders were consolidated by a press-and-sintering method. This consolidation method is not usually employed with MA Al powders. The amount of dispersed carbides formed in the Al powder increases with the percentage of PCA. These carbides restrain Al grain growth during sintering, resulting in consolidated compacts with a grain size of about 550 nm. Thus, these PM materials can be considered ultrafine grained materials. Due to grain refinement and dispersion strengthening, the tensile strength of MA Al specimens is increased remarkably.

Abstract: A lamination technique for joining ceramic green tapes fabricated from aqueous ceramic slurries via tape casting process is investigated. Monolithic pieces with varying compositions within the Al2O3 / t-ZrO2 system were fabricated by gluing the constituent tapes and pressing at room temperature. The quality of the interfaces between the different tapes in sintered specimens was evaluated by means of the fracture behavior of the pieces during the ball on three balls test. Different fracture patterns were found as a function of pressure and the characteristics of the tapes. Large scale interface defects led to delamination during fracture whereas no critical defects could be observed in the smooth fracture surfaces. Small scale interface defects were revealed by fracture.