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Enneti R.K.,Global Tungsten and Powders Corporation | Park S.J.,Pohang University of Science and Technology | German R.M.,San Diego State University | Atre S.V.,Oregon Nanoscience and Microtechnologies Institute
Materials and Manufacturing Processes | Year: 2012

Developing a rapid and efficient method for removing polymers (termed binders) from a shaped powder component, know as a green body, is important to forming defect-free metal, ceramic, and cermet structures. The rapid growth in powder injection molding to form complex shapes at high precision in large quantities has increased the need for faster, cleaner, and cheaper polymer removal processes. Binder removal using controlled heating of the component in gaseous atmosphere is the most popular method. This thermal debinding or burnout process is a delicate process, since it is easy to crack, blister, slump, or otherwise damage the component with an improperly designed cycle. To avoid these issues, often long heating cycles are used to remove the binder, but with a loss of productivity. Considerable progress has been made over the past several decades in understanding various phenomena during polymer burnout, resulting in substantial reduction in the thermal debinding time. This article provides an overview of the research carried out on thermal debinding process (primarily from powder injection molded samples) with major emphasis on progress reported over the last fifteen years. This review article proposes a model to predict the formation of defects during all stages of thermal debinding and suggests future research direction in the field. © 2012 Copyright Taylor and Francis Group, LLC.

Park K.,Dongduk Womens University | Tuttle G.,Oregon State University | Sinche F.,Oregon State University | Harper S.L.,Oregon State University | Harper S.L.,Oregon Nanoscience and Microtechnologies Institute
Archives of Pharmacal Research | Year: 2013

The stability of citrate-capped silver nanoparticles (AgNPs) and the embryonic developmental toxicity were evaluated in the fish test water. Serious aggregation of AgNPs was observed in undiluted fish water (DM-100) in which high concentration of ionic salts exist. However, AgNPs were found to be stable for 7 days in DM-10, prepared by diluting the original fish water (DM-100) with deionized water to 10 %. The normal physiology of zebrafish embryos were evaluated in DM-10 to see if DM-10 can be used as a control vehicle for the embryonic fish toxicity test. As results, DM-10 without AgNPs did not induce any significant adverse effects on embryonic development of zebrafish determined by mortality, hatching, malformations and heart rate. When embryonic toxicity of AgNPs was tested in both DM-10 and in DM-100, AgNPs showed higher toxicity in DM-10 than in DM-100. This means that the big-sized aggregates of AgNPs were low toxic compared to the nano-sized AgNPs. AgNPs induced delayed hatching, decreased heart rate, pericardial edema, and embryo death. Accumulation of AgNPs in the embryo bodies was also observed. Based on this study, citrate-capped AgNPs are not aggregated in DM-10 and it can be used as a control vehicle in the toxicity test of fish embryonic development. © 2013 The Pharmaceutical Society of Korea and Springer Science+Business Media Dordrecht.

Moeck P.,Oregon Nanoscience and Microtechnologies Institute | Rouvimov S.,Oregon Nanoscience and Microtechnologies Institute
Zeitschrift fur Kristallographie | Year: 2010

The foundations of precession electron diffraction in a transmission electron microscope are outlined. A brief illustration of the fact that laboratory-based powder X-ray diffraction fingerprinting is not feasible for nano-crystals is given. A procedure for structural fingerprinting of nanocrystals on the basis of structural data that can be extracted from precession electron diffraction spot patterns is proposed. © Oldenbourg Wissenschaftsverlag, München.

Enneti R.K.,Global Tungsten and Powders Corporation | Bothara M.G.,Oregon Nanoscience and Microtechnologies Institute | Park S.-J.,Pohang University of Science and Technology | Atre S.V.,Oregon Nanoscience and Microtechnologies Institute
Ceramics International | Year: 2012

Field assisted sintering (FAST) or spark plasma sintering (SPS) has emerged as a promising technology for densification of ultra high temperature ceramics like HfB 2-20SiC at relatively low temperatures and shorter times. In the present study the concepts of master sintering curve (MSC) was applied to model the densification behavior of HfB 2-20SiC during FAST process. An activation energy of 300 kJ/mol was estimated for field assisted sintering of HfB 2-20SiC. The densification curves at various heating rates merged for activation energy of 300 kJ/mol confirming the applicability of MSC concepts to FAST process. The developed master sintering curves can be used to design sintering cycles and predict the densification of HfB 2-20SiC during FAST process. © 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Atkins R.,University of Oregon | Atkins R.,Oregon Nanoscience and Microtechnologies Institute | Wilson J.,University of Oregon | Wilson J.,Oregon Nanoscience and Microtechnologies Institute | And 5 more authors.
Chemistry of Materials | Year: 2012

A modification of the modulated elemental reactants synthetic technique was developed and used to synthesize eleven members of the [(SnSe) 1.15]m(TaSe2)n family of compounds, with m and n equal to integer values between 1 and 6. Each of the intergrowth compounds contained highly oriented intergrowths of SnSe bilayers and TaSe 2 monolayers with abrupt interfaces perpendicular to the c-axis. The c-lattice parameter increased 0.579(1) nm per SnSe bilayer and 0.649(1) nm per Se-Ta-Se trilayer (TaSe2) as m and n were varied. ab-plane X-ray diffraction patterns and transmission electron microscope images revealed a square in-plane structure of the SnSe constituent, a hexagonal in-plane structure for the TaSe2 constituent, and rotational disorder between the constituent layers. Temperature dependent electrical resistivity, measured on several specimens, revealed metallic behavior, and a simple model is presented to explain the differences in resistivity as a function of m and n. © 2012 American Chemical Society.

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