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Articles 241 - 249 of 249

Full-Text Articles in Materials Science and Engineering

Laser-Assisted Synthesis And Optical Properties Of Bismuth Nanorods, Jason Reppert Aug 2007

Laser-Assisted Synthesis And Optical Properties Of Bismuth Nanorods, Jason Reppert

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Bismuth in the bulk form is a semimetal with a rhombohedral structure. It has a small band overlap between the conduction and valence bands and a highly anisotropic electron effective-mass tensor. Thermoelectric materials, in which one of the three dimensions is in the nanometer regime, exhibit unique quantum confinement properties and have generated much interest in recent years. Theoretical investigations have suggested that nanowires with diameters <10 nm will possess a figure-of-merit ZT>2. Prior to this research, it has been shown by the Dresselhaus group at MIT that Bi nanowires with small enough diameters (~50 nm), prepared via the template-method, undergo a transition from a semimetal …


Development And In Vitro Examination Of Materials For Osseointegration, Sahil Jalota May 2007

Development And In Vitro Examination Of Materials For Osseointegration, Sahil Jalota

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Bone is a connective tissue with nanosized particles of carbonated apatitic calcium phosphate dispersed in a hydrated collagen matrix. With the ageing of the baby boomer population, an increasing number of people sustain bone fractures and defects. Hence, efforts are underway to develop materials to hasten the healing and repairing of such defects. These materials are termed as artificial bone substitutes.
This study represents innovative techniques for development of bone implant materials and improving the existing substitute materials. Emphasis was on three different kinds of materials: Metals (titanium and alloys), Ceramics (calcium phosphates), and Polymers (collagen). The bioactivity of titanium …


Study Of Structure Development During Melt Spinning Of Isotactic Polypropylene Fibers Using Raman Spectroscopy And Wide Angle X-Ray Diffraction Simultaneously , Dushyanth Pandana Jan 2007

Study Of Structure Development During Melt Spinning Of Isotactic Polypropylene Fibers Using Raman Spectroscopy And Wide Angle X-Ray Diffraction Simultaneously , Dushyanth Pandana

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ABSTRACT
Isotactic polypropylene (iPP) fibers have a wide variety of applications. Specific end-use applications require specific properties, which are dependent on the polymer morphology produced during processing. Therefore, the final properties of a material are dependent on the processing parameters. iPP fibers are produced mainly by melt spinning. The important processing parameters in the melt spinning process include, the extrusion temperatures, the throughput and shear rates, the rate of cooling, and the feed and draw roll take-up velocities. An understanding of how the morphology develops along the spinline, and the effect of processing parameters on the morphology is crucial in …


Synthesis And Photocatalysis Study Of Brookite Phase Titanium Dioxide Nanoparticles, Radhika Bhave Jan 2007

Synthesis And Photocatalysis Study Of Brookite Phase Titanium Dioxide Nanoparticles, Radhika Bhave

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Titanium dioxide is used in variety of applications like photocatalysis, self-cleaning coatings, fog proof glass and water purifier. A lot of research is being done in synthesis and applications of TiO2. Titanium dioxide or TiO2 mainly exists in three phases namely anatase, brookite and rutile. Current studies relate to synthesis of brookite phase TiO2 nanoparticles by ambient condition sol (ACS) process and characterization of these particles for phase purity, morphology and surface area analysis. The photoactivity of these particles was investigated and absorption in the visible light region was detected. This implies brookite to have good potential to be used …


Optimizing Production Methods For Artifical Silk Proteins Through Bioreactor And Purification Studies Of Recombinant Proteins Expressed From Pichia Pastoris, Aaron Ramey Dec 2006

Optimizing Production Methods For Artifical Silk Proteins Through Bioreactor And Purification Studies Of Recombinant Proteins Expressed From Pichia Pastoris, Aaron Ramey

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Advancements in the field of biomaterials are being made to produce an artificial silk fiber. A gene was constructed which utilized components from both the dragline silk of Nephila clavipes and nematode collagen. For this engineered protein, the yeast strain Pichia pastoris was chosen to be the host organism. Previous research has shown P. pastoris to have comparatively low amounts of specific protein productivity. Therefore, this problem must be compensated for by obtaining extremely high cell densities. The main focus of this study was to optimize the fermentation parameters of transgenic yeast cultures within a bioreactor in order to increase …


Influence Of Temperature And Polymer/ Mold Surface Interactions On Micro-Feature Replication At Ambient Pressure In Micro Injection Molding, Varun Thakur Dec 2006

Influence Of Temperature And Polymer/ Mold Surface Interactions On Micro-Feature Replication At Ambient Pressure In Micro Injection Molding, Varun Thakur

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This study assesses micro-feature replication at elevated mold temperature and ambient pressure using a variety of polymers. Moldings were made on the surface of stainless steel and silicon wafers containing features as small as 130 nm under isothermal conditions in a heated chamber by allowing polymer to spread over the features at ambient pressure. Feature replication was analyzed via AFM and SEM. Polymer behavior was characterized via melt contact angle and melt viscosity. While feature detail was well replicated, the moldings exhibited poor dimensional accuracy due to shrinkage. In general, polymers with low viscosity and surface tension comparable to the …


Dielectric Properties And Method Of Characterizing Ceramic Powders And Multiphase Composites, Ravi Kiran Kota Dec 2006

Dielectric Properties And Method Of Characterizing Ceramic Powders And Multiphase Composites, Ravi Kiran Kota

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Barium Titanate was the first developed ferroelectric ceramic material and even today it is widely used. It is also a well-known material used for capacitors. The only reason behind a wide range of applications is that barium titanate boasts of high dielectric properties. A phase transition from cubic to tetragonal at normal working temperatures provides enhanced dielectric properties in this electronic material. For any application and design, the most inquired property is the dielectric constant. Predicting the dielectric constant is very much required as it is the pre-requisite. This is the major objective of the present work. To estimate the …


Theoretical And Empirical Investigation Into Polymer Blend Morphology In Fiber Spinning, Ajay D. Padsalgikar Aug 1996

Theoretical And Empirical Investigation Into Polymer Blend Morphology In Fiber Spinning, Ajay D. Padsalgikar

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A promising way of developing new fiber forming materials is by utilization of polymer blends. The morphology of polymer blends has a significant effect on the properties of the resultant fiber. Morphological studies have shown that immiscible additives remain dispersed in the matrix as suspended droplets and that the droplets are elongated into fibrils under the action of shear or extensional forces during processing. The deformability of the dispersed phase is a controlling factor in deciding the resultant morphology and thereby the fiber properties. We report the results of a study of droplet deformation in uniaxial elongational flow under non …


Study Of Parameters Affecting Performance Of Automotive Transmission Filters, Debra Cauthen Aug 1991

Study Of Parameters Affecting Performance Of Automotive Transmission Filters, Debra Cauthen

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Modified isocyanate binders have been introduced as a possible alternative to phenolic resins for bonding nonwovens in automatic transmission filtration. The Occupational Safety and Health Administration (OSHA) and the American Conference of Governmental Industrial Hygienists (ACGIH) have placed restrictions on worker exposure to phenol-formaldehyde due to toxicological and ecological concerns. Modified isocyanates are unproven for bonding needlefelts in this application.