Papers by Keyword: Powder Technology

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Authors: Tian Hong Guo, Juan Li, Yong Cai Zhang, Zhan Jun Yang
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.
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Authors: Mehdi Estili, Kenta Takagi, Akira Kawasaki
Abstract: Capability of multiwalled carbon nanotubes (CNTs) to create in-depth gradients in properties and functionalities of conventional materials has been investigated for the first time. Functionally graded material (FGM) concept has also been employed for the first time to bridge conventional materials to their advanced nanocomposites containing a high concentration of CNTs, which is promising for unexplored yet novel structural, electronic and biomaterial applications. In this study, α-alumina ceramics considered as the most challenging case has been used as the matrix. Bulk, layered, nanostructure-controlled, CNT-based, functionally graded α-alumina ceramics have been fabricated employing a recently established powder processing technology. In-depth gradients in microstructure, grain size and hardness have been successfully achieved in alumina ceramic without cracking, delamination or warping, after homogeneous and gradual incorporation of the CNTs within the alumina ceramic matrix. The FGM approach showed promise to successfully bridge conventional ceramics to their nanocomposites containing a high concentration of CNTs.
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Authors: Jessica Osorio-Ramos, Mario Romero-Romo, Elizabeth Refugio-García, Eduardo Terres-Rojo, Enrique Rocha-Rangel
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.
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Authors: Hermann Riedel, Torsten Kraft
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Authors: Luis Antonio C. Ybarra, Afonso Chimanski, Gilberto J. Pereira, Izabel Fernanda Machado, Humberto Naoyuki Yoshimura
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, KIc, determined by an indention fracture method using Shetty equation, remained constant at around 9.1 MPa.m1/2.
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Authors: Martin Zarbov, David Brandon, Assaf Thon, Nissim Cohen
Abstract: For the past 10 years Cerel has been engaged in the development of prototype, EPDprocessed, micro-components, primarily for the microelectronics industry. In this contribution we summarize some of the problems of integrating EPD into the production process, and discuss the parameters that need to be considered and controlled. Suitable dispersion media and additives can usually be found for powder of any chemical composition to be deposited by EPD, providing the particle size and size distribution, and their surface to volume ratio are suitable. So it is the geometrical requirements and the dimensional tolerances of the product that often limit the EPD process. We give three examples: the EPD embedding of passive components in a punched ceramic tape, the production of porous capacitor anodes by EPD, and the EPD formation and printing of narrow conducting lines on a ceramic tape substrate. In each case the production process parameters have been chosen to satisfy the engineering requirements while minimizing the the formation of process defects. Defects include: variations in particle packing density; loss of adhesion and deposit cracking, and surface roughness or thickness variations.
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Authors: Jie Cheng, Jian Zhang Li, Jun Bo Zhong, Wei Hu
Abstract: Paralled flaw precipitation method has been employed to synthesize nanostructured ZnO. The prepared photocatalyst was characterized by BET, XRD. The paper reveals that Methyl Orange (MO) can be decolorized effectively in ZnO suspension system under UV irradiation. The optimal loading of photocatalyst in our experimental condition for the decolorization of MO is 1g/L. The present study, on the base of Langmuir-Hinshelwood mechanism, illustrates that the decolorization reaction is a pseudo first order kinetic model with the limiting rate constant of 8.48×10-2 mgL-1min-1 and equilibrium adsorption constant 0.335 L/mg, respectively.
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Authors: Dun Pu Zhang, Dan Xu, Chun Hua Lu, Ya Ru Ni, Zhong Zi Xu
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.
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Authors: M. Ohyanagi, T. Tsujikami, S. Sugahara, Makoto Koizumi, E.A. Levashov, I.P. Borovinskaya
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Authors: Jing Li, Wei Sun, Wei Min Dai, Yong Cai Zhang
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.
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