Papers by Keyword: Powder Technology

Abstract: This paper evaluated the use of the pitcher, a ceramic waste obtained through the quality process of a sanitary ware industry, in the development of a material for usage in the manufacture of sintered parts. The pitcher was obtained through powder technology and is composed, according to the chemical analysis obtained by X-ray fluorescence spectrometry, of clayey minerals (clay and kaolin), quartz, and feldspar, which may include ceramic rocks such as granite, pegmatite and phyllite; that is, it has proved to be a potential raw material due to the minerals that can still be reused. The pitcher passed through a granulometry-based selection process, sieving about 20kg using the following sieve sequence: 18 MESH, 25 MESH, 30 MESH, 120 MESH and 400 MESH; with around 70% of the residue being retained in the sieves of 120 and 400 MESH, which were selected to be used in the evaluation. The samples were compacted in a manual press with different pressures, between 300 and 1000 kgf, and after were sintered at a temperature of 1100oC in a resistive furnace. To characterize the material, the apparent and green density, as well as the compressibility curve, were determined to identify the best compression pressure. The microstructure of the test specimen and the pitcher homogeneity were evaluated using Scanning Electron Microscopy (SEM). Both particle sizes presented the typical compressibility curve, in which the density increases with increasing compaction pressure, while the curve slope decreases with increasing pressure. The density increase with the increasing compaction pressure indicates a good densification for the temperatures, independent of the sample granulometry. The sintering porosity decreased proportionally to the particle size in the sintered samples. The analysis showed that the particle size of 400 MESH sintered at 1100oC obtained more porous surfaces, thus indicating a promising future for the manufacture of parts using powder technology, especially for the development of filters.

Abstract: This research aimed to prepare (Fe-Ni) alloy by powder technology method for its technological and commercial importance. Iron and Nickel powders were tacking then their powders mixed and blended together with percent (63% Fe-37% Ni), then the powders compacted isostatic cold pressure at (6 ton). Laser surface treatment was done for the samples with different energies (0, 200, 260, 300) mJ and pulse time (10 sec) At a distance (100 cm). The X-ray diffractions test indicated that all samples have Face Center Cubic (F.C.C), and the samples at 300 mJ has best properties which include increase of phases intensity and decrease of grain size according to Debye-Scherrer equation. The Atomic Force Microscope (AFM) also shows better properties with increase laser energy. Where increased soft-ness of surface, homogeneity surface and decrease in grain size with increase laser energy. The laser analysis resulted that melting all surface molecules which led to improvement in the structural properties.

Abstract: Cobalt is widely used to produce WC-Co hard metals, but this binder has problems of shortage and unstable price. In this work, cobalt was replaced by an iron aluminide intermetallic binder. WC-10%(Fe₃Al-3%B) composite was prepared by vibration milling of WC, Fe, Fe-B, and Al powders and sintered by spark plasma sintering (SPS) at 1150 °C for 8 min under 30 MPa. The milling time was 0.17, 12, 25 and 50 h. The SPS was efficient to consolidate the composite resulting in relative density of ~98% or higher. With increasing milling time, Vickers hardness (HV₃₀) of composite increased from 12 to 14 GPa due to the enhanced homogeneity of microstructure, while the fracture toughness, K_Ic, determined by an indention fracture method using Shetty equation, remained constant at around 9.1 MPa.m^1/2.

Abstract: Aimed by reducing the total cost of products, powder metallurgy (PM) processing of Ti is a subject of high interest. However, using of conventional PM techniques presents difficulties due to the intrinsic characteristics of Ti, like low strain ability, and high reactivity, which lead to low compressibility. Moreover, Ti powders with small particle size are difficult to process by conventional PM techniques as they present a lower compressibility and also a poor flowability. On the other hand, the colloidal processing has been used for long in ceramics to achieve green bodies with high densities, complex shapes and homogeneous microstructures, but they are rarely used to shape metal powders because of its high density and high surface reactivity. However, the possibility to process fine particles makes these techniques interesting for metals with low density like Ti.The colloid-chemistry control of metallic powders in aqueous slurries is proposed as a way to prepare Ti porous parts with small particle size, throughout the formulation of aqueous slurries with solid contents as high as 50 vol.%. The chemical and chemical-physic stability of Ti powders 10 μm in size was determined by measuring the zeta potential as a function of pH, and dispersant concentration, while the later optimization of Ti slurries and their adequation for the use of different colloidal techniques, were studied in terms of rheology and the addition of the processing additives, such as gel or foaming agents. Techniques such as thermal gelling, foaming, and impregnation of exo-templates or robocasting were used to build Ti parts with random and/or tailored macroporosity. The shaped pieces made on Ti were sintered in vacuum at 1100 oC for 30 minutes, and their microstructure and mechanical properties were determined and compared with dense materials shaped by combining PM and colloidal techniques in previous works

Abstract: Thepresent research analyzes the effect induced through addition of two zinc concentrations to composites based on recycled PET (polyethylene terephthalate), as a polymer matrix. Prior to mechanical assessment, the optimum grinding time was determined, namely, where the smaller particle size was generated (PET–420mm and Zn-5mm), that was 3 h. Subsequently, a comparison was done between two different blends, changing the zinc concentration 10 or 30 wt. %, from which the necessary test specimens for isothermal sintering were prepared and exposed at 256°C for 10, 15 and 20 minutes periods. These preliminary specimens permitted to value, for each zinc concentration, theirdensity, hardness (shore D) and water absorption. The best results were obtained with the samples sintered for the intermediate periods. The flexion and compression toughness were evaluated, where the blend with the higher toughness contained 30 wt. % Zn.

Abstract: TiO₂/SnS₂ nanocomposite was synthesized via hydrothermal treatment of tin (IV) chloride pentahydrate, thioacetamide and TiO₂ nanotubes in deionized water at 150 °C for 3 h. The structure, composition and optical property of the as-synthesized nanocomposite were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy and UV-vis diffuse reflectance spectra, and its photocatalytic property was tested in the reduction of aqueous Cr⁶⁺ under visible-light (λ > 420 nm) irradiation. It was observed that TiO₂ nanotubes exhibited no photocatalytic activity, whereas TiO₂/SnS₂ nanocomposite exhibited photocatalytic activity in the reduction of aqueous Cr⁶⁺ under visible-light (λ > 420 nm) irradiation.

Abstract: TiN-coated aluminum pigments were prepared by nanoparticle-bonding technology of high-energy ball milling. The effect of ball milling on the morphology and evolution of the composite powders was investigated via field-emission scanning electron microscopy, transmission electron microscopy, and particle size distribution analysis. Results show that the TiN nanoparticles bonded to the surface of aluminum microflakes under the action of a mechanical force but in the absence of any binder. A uniform nanoparticle coating formed on the surface of the flake aluminum microparticle. The optical reflectance of the TiN/Al composites was measured within 200 nm to 2500 nm wavelength. The reflectance gradually decreased as the milling time was prolonged.

Abstract: Parallel flow precipitation has been employed to prepare nanostructured SnO₂. It is found that the specific surface areas and photocatalytic performance of SnO₂ has a strong dependence on the kind of precipitant. The prepared photocatalysts were characterized by BET, XRD, UV-Vis diffuse reflectance and SEM. The results show that SnO₂ prepared by NH₃·H₂O + (NH₄)₂CO₃ has the highest BET surface area and the smallest crystal average size. SnO₂ prepared by NH₃·H₂O + (NH₄)₂CO₃ exhibits the best photocatalytic activity. The results of further experiments show that the specific surface area plays an important role in promotion of photocatalytic activity of SnO₂ prepared by NH₃·H₂O + (NH₄)₂CO₃.

Abstract: An in situ thermal oxidation strategy was proposed for synthesizing different SnO2 nanostructures, using our homemade SnS2 nanoplates as a precursor. The characterization results from X-ray diffraction, energy dispersive X-ray spectroscopy, and field emission scanning electron microscope revealed that the heating temperature played an important role in the microstructure and composition of the resultant products. By heating the SnS2 nanoplates in air at 400, 600 and 800 °C for 5 h, nanoplates, a mixture of nanoplates and nanoparticles, and nanoparticles of SnO2 were synthesized, respectively. The residual S was about 2.2 mol % in the product synthesized at 400 °C, while no residual S was detected in the products synthesized at 600 and 800 °C.

Abstract: This study dealt with the processing, microstructure and wear behavior of vanadium carbide reinforced iron matrix composite. Powder technology combined with in situ synthesis was used to successfully fabricate the composite. The microstructure of the composite was characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope. The microstructural study reveals that the round VC particles are distributed uniformly in the iron matrix, the interface between the iron matrix and VC is clean, and no interface precipitates is found. Dry-sliding wear behavior of VC-Fe composite was tested using MM-200 wear testing machine. The results indicate that the composite has excellent wear resistance, and microploughing and grooving are the dominant wear mechanisms for the composite. Hardness and bend strength of the composite are 62HRC and 990.1MPa, respectively.