Materials Science and Engineering Commons^™

Scandia And Ceria Stabilized Zirconia Based Electrolytes And Anodes For Intermediate Temperature Solid Oxide Fuel Cells: Manufacturing And Properties, Yan Chen

Electronic Theses and Dissertations

Mesoscale optical phenomena occur when light interacts with a number of different types of materials, such as biological and chemical systems and fabricated nanostructures. As a framework, mesoscale optics unifies the interpretations of the interaction of light with complex media when the outcome depends significantly upon the scale of the interaction. Most importantly, it guides the process of designing an optical sensing technique by focusing on the nature and amount of information that can be extracted from a measurement. Different aspects of mesoscale optics are addressed in this dissertation which led to the solution of a number of problems in …

Preparation And Characterization Of Highly Filled Graphite-Based Polybenzoxazine Composites, A. Pengdam, S. Rimdusit

Journal of Metals, Materials and Minerals

This research aims to study suitable preparation methods and to characterize highly filled graphite composites using polybenzoxazine as a matrix. The high loading of graphite filler was attained in the range of 40 to 80% by wt. due to the very low a-stage viscosity of the benzoxazine resin (BA-a) used. The suitable condition for the compression molding of the highly filled graphite-polybenzoxazine (PBA-a) composites was at temperature of 200°C, and pressure of 15 MPa in the hydraulic hot-press machine for 3 hours to assure a fully cured specimen. The densities of the obtained composites were found to be in a …

Freeze-Form Extrusion Fabrication Of Functionally Graded Material Composites Using Zirconium Carbide And Tungsten, Ang Li, Aaron S. Thornton, Bradley K. Deuser, Jeremy Lee Watts, Ming-Chuan Leu, Greg Hilmas, Robert G. Landers

Materials Science and Engineering Faculty Research & Creative Works

Ultra-high-temperature ceramics are being investigated for future use in aerospace applications due to their superior thermo-mechanical properties, as well as their oxidation resistance, at temperatures above 2000⁰C. However, their brittleness makes them susceptible to thermal shock failure. As graded composites, components fabricated as functionally-graded materials (FGMs) can combine the superior properties of ceramics with the toughness of an underlying refractory metal. This paper discusses the grading of two materials through the use of a Freeze-form Extrusion Fabrication (FEF) system to build FGM parts consisting of zirconium carbide (ZrC) and tungsten (W). Aqueous-based colloidal suspensions of ZrC and W were developed …

The Influence Of Heterogeneous Meninges On The Brain Mechanics Under Primary Blast Loading, Linxia Gu, Mehdi S. Chafi, Shailesh Ganpule, Namas Chandra

Department of Mechanical and Materials Engineering: Faculty Publications

In the modeling of brain mechanics subjected to primary blast waves, there is currently no consensus on how many biological components to be used in the brain–meninges–skull complex, and what type of constitutive models to be adopted. The objective of this study is to determine the role of layered meninges in damping the dynamic response of the brain under primary blast loadings. A composite structures composed of eight solid relevant layers (including the pia, cerebrospinal fluid (CSF), dura maters) with different mechanical properties are constructed to mimic the heterogeneous human head. A hyper-viscoelastic material model is developed to better represent …

Effect Of Copper Addition On Mechanical Properties And Electrical Conductivity Of Pp/C-Cu Bipolar Plate Composites, Anne Zulfia, Taufik Abimanyu, Verina Warga Dalam

Makara Journal of Technology

Effect of Copper Addition on Mechanical Properties and Electrical Conductivity of PP/C-Cu Bipolar Plate Composites. Bipolar plate is a major component in PEM fuel cell which possess main function of collecting and removing electrons from anode to cathode. Therefore, materials for bipolar plates produced must have high electrical conductivity. To obtain bipolar plate materials which is cheap, lightweight and high conductivity, so it is developed bipolar plates material based on PP/C-Cu composite. PP/C-Cu composites has been made by mixing all materials then compounding, rheomix, hot blending and hot press. Cu (Copper) has been used various from 0.1 wt%, 1 wt% …

Medium Density Fibreboard Made Of Acetylated Sludge From Paper Mill, Luthfi Hakim, Evalina Herawati, I Nyoman Jaya Wistara

Makara Journal of Technology

Medium Density Fibreboard Made of Acetylated Sludge from Paper Mill. Research of using sludge as raw material for making medium density fibreboard (MDF) was useful to create additional value of sludge. The objective of the research was to evaluate physical properties, mechanical properties, and durability of MDF from acetylated sludge in 4 levels of acetate anhydride (0%, 3%, 5%, and 7%) with 3 replicates. The MDF was made using dry process. After materials were mixed with adhesives, they were pressed using hotpress under 170 oC temperature and 45 Pa pressure for 25 minutes. The size of the MDF sample was …

Effect Of Particle Size, Binder Content And Heat Treatment On Mechanical Properties Of 13-93 Bioactive Glass Scaffolds, Krishna C. R. Kolan, Ming-Chuan Leu, Greg Hilmas, Mariano Garcia Velez

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Particle size, binder content and the post-processing schedule are important parameters that affect the microstructure, and, hence, the mechanical properties of parts produced using the indirect selective laser sintering process. 13-93 bioactive glass, with mean particle sizes ranging from 10 μm to 44 μm, is mixed with different amounts of stearic acid binder to fabricate green scaffolds. Through the design of the post-processing schedule, the time required for postprocessing the green scaffolds is reduced from the initial 80 hrs to 12 hrs. The compressive strength varies from 41 MPa for a part with~60% porosity to 157 MPa for a part …

A Study On The Combined Effect Of Forging And Aging In Mg-Y-Re Alloy, S. K. Panigrahi, W. Yuan, R. S. Mishra, R. Delorme, B. Davis, R. A. Howell, K. Cho

Materials Science and Engineering Faculty Research & Creative Works

The combined effect of forging and aging on microstructural evolution and mechanical properties of a Mg-Y-RE alloy was studied in the present work by employing hardness measurements, tensile tests, optical microscopy (OM), scanning electron microscopy (SEM) and electron back scattered diffraction (EBSD) analysis. the -F temper treated bulk Mg-Y-RE alloy samples were subjected to forging for microstructural refinement and subsequent aging to maximize the strength-ductility combination. the forged samples combined with peak aging treatment (60 h at 180 °C) exhibited an excellent combination of high strength (388 MPa) and high ductility (23%). the combined effect of grain refinement, work hardening, …

Effect Of Sintering On Microstructure And Properties Of Hydroxyapatite Produced By Different Synthesizing Methods, N Monmaturapoj, C Yatongchai

Journal of Metals, Materials and Minerals

The aim of this study is to investigate the effect of the sintering schedule on microstructure and properties of hydroxyapatite which is produced by different synthesizing methods. Hence, wet-chemical precipitation and solid-state reaction were performed to prepare nano-sized hydroxyapatite (HA) powders. Powders were then uniaxially pressed and sintered by varying temperatures and times. XRD and SEM were used to identify phases and morphology. Density and porosity of the sintered sample were determined using the Archimedes technique. Flexural strength was measured by a universal testing machine. The results show that density and strength could be improved by increasing the sintering temperature …

Optimizing The Mechanical Properties Of Partially Yttria Stabilized Zirconia With Alumina Additions, Ramanaganapathy Kandaswamy

All Theses

Zirconia is one of the extensively studied solid oxide ceramics with respect to its use in various industrial applications like electrolyte in fuel cells, sensors, refractories and exhaust chamber in automobile industry. It can be found from the literature 1-4 that are contradictory results on the mechanical properties when alumina is added. There are several factors like microstructure, phase composition and method of processing that affects the mechanical properties of the material. The focus of this research is to examine how hardness, tensile strength and other properties varies with alumina content and deduce the optimal amount of alumina that is …

Freeze Extrusion Fabrication Of 13-93 Bioactive Glass Scaffolds For Bone Repair, Tieshu Huang, Nikhil D. Doiphode, M. N. Rahaman, Ming-Chuan Leu, B. Sonny Bal, D. E. Day

Materials Science and Engineering Faculty Research & Creative Works

There is an increasing demand for synthetic scaffolds with the requisite biocompatibility, internal architecture, and mechanical properties for the bone repair and regeneration. In this work, scaffolds of a silicate bioactive glass (13-93) were prepared by a freeze extrusion fabrication (FEF) method and evaluated in vitro for potential applications in bone repair and regeneration. The process parameters for FEF production of scaffolds with the requisite microstructural characteristics, as well as the mechanical and cell culture response of the scaffolds were evaluated. After binder burnout and sintering (60 min at 700°C), the scaffolds consisted of a dense glass network with interpenetrating …

Performance Of Nevada’S Aggregates In Alkali-Aggregate Reactivity Of Portland Cement Concrete, Mohammad Shahidul Islam

UNLV Theses, Dissertations, Professional Papers, and Capstones

Alkali-aggregate reaction (AAR) is a form of distress that occurs in concrete and results in serviceability problems, cracks, spalling, and other deterioration mechanisms. There are two categories of AAR, namely, alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR). Alkali-silica reaction is one of the most recognized deleterious phenomena in concrete, and has been a major concern since its discovery in the 1940s. The reaction which occurs between reactive silica or silicates present in some aggregates and alkalis of Portland cement produces an alkali-silica gel that expands in the presence of moisture resulting in concrete cracks. ACR is also a chemical reaction …

Mechanical Properties Of Ramie Fiber Reinforced Epoxy Lamina Composite For Socket Prosthesis, Tresna P. Soemardi, Widjajalaksmi Kusumaningsih, Agustinus Purna Irawan

Makara Journal of Technology

Mechanical properties of ramie fiber reinforced epoxy lamina composite for socket prosthesis. This paper presents an investigation into the application of natural fiber composite especially ramie fiber reinforced epoxy lamina composite for socket prosthesis. The research focuses on the tensile and shear strength from ramie fiber reinforced epoxy lamina composite which will be applied as alternative material for socket prosthesis. The research based on American Society for Testing Material (ASTM) standard D 3039/D 3039M for tensile strength and ASTM D 4255/D 4255M-83 for shear strength. The ramie fiber applied is a fiber continue 100 % Ne14'S with Epoxy Resin Bakelite …

Freeform Fabrication Of Zirconium Diboride Parts Using Selective Laser Sintering, Ming-Chuan Leu, Erik B. Adamek, Tieshu Huang, Greg Hilmas, Fatih Dogan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Using the Selective Laser Sintering (SLS) process, both flexural test bars and 3D fuel injector components have been fabricated with zirconium diboride (ZrB₂) powder. Stearic acid was selected as the binder. Values of SLS process parameters were chosen such that the green parts could be built with sharp geometrical features and that the sintered parts could have good mechanical properties. After binder burnout and sintering, the SLS fabricated ZrB₂ test bars achieved 80% theoretical density, and the average flexural strength of the sintered samples was 195 MPa. These values demonstrate the feasibility of the SLS process for …

Microstructure And Mechanical Properties Of En Aw 6082 Aluminium Alloy Prepared By Equal-Channel Angular Pressing, M Fujda, T Kvačkaj

Journal of Metals, Materials and Minerals

The mechanical properties and microstructure of EN AW 6082 aluminium alloy subjected to severe plastic deformation (SPD) and natural ageing are compared with those of extruded and artificially aged state (initial state) and quenched state of alloy after solution annealing. Quenched state of alloy was deformed at room temperature by equal channel angular pressing (ECAP) following route C up to three passes. Polyedric microstructure of quenched state was considerably changed by SPD. Deformation bands with different amount of deformation were observed in microstructure of ECAPed state, which indicated non-uniform deformation across the cross-section of ECAPed specimen. Ultimate tensile strength (UTS) …

Effect Of Solution Annealing Temperature On Structure And Mechanical Properties Of En Aw 2024 Aluminium Alloy, M Fujda, R Mišičko, L Rusňáková, M Sojko

Journal of Metals, Materials and Minerals

The effect of solution annealing temperature on the change of microstructural and mechanical properties of EN AW 2024 aluminium alloy was investigated using a metallographic analysis, Vickers hardness measurement and tensile test. An intensive growth of solid solution grains was the result of the increase of solution annealing temperature by the finely dispersed particles dissolved during applied annealing process. The role of these finely dispersed particles was to inhibit the recrystallization process and grain growth of solid solution matrix through its pinning effect on the migrated solid solution grain boundaries. Observed changes of the microstructure involved the strength decline and …

Titanium Alloyed With Boron, Seshacharyulu Tamirisakandala, Daniel B. Miracle, Raghavan Srinivasan, Jay S. Gunasekera

Mechanical and Materials Engineering Faculty Publications

Small additions of boron to conventional titanium alloys have been found to produce significant changes to the microstructures and associated properties. Grain refinement and improved strength and stiffness are first-order effects, which lead to possibilities for developing novel and affordable processing methodologies and to enhance performance over conventional titanium alloys. In this article, we introduce this new class of titanium alloys and describe unique formability benefits achieved via engineering microstructures.

Drawing Quality Steel Sheet Under Tension And Bending Condition, M Mihaliková, M Buršák

Journal of Metals, Materials and Minerals

The paper analyzes the influence of the loading rate in the interval from 1 to 1000 mm/min on the mechanical properties of drawing quality steel sheet with the gauge of 1 mm, used for the manufacturing of automotive parts, under tension and bending conditions. It describes the aspects of material characteristics under tension and bending conditions, while bending tests were made on notched specimens (a modified impact bending test). The paper presents knowledge that using a modified notch toughness test. It is possible to achieve the pressability (formability) characteristics corresponding to dynamic strain rates even under the static loading.

Kinetics Of Carbonisation, Microstructure And Properties Of Al-Al4c3 System Prepared By Mechanical Alloying, M Besterci

Journal of Metals, Materials and Minerals

The method of mechanical alloying process is described. Carbon transformation to carbide Al4C3 is characterised within different heat treatment schedules and nine commercial carbon powders are tested. The micromechanism of carbon incorporation into the metallic powder, and the compacting of it are described. The influence of dispersed carbides on mechanical properties is evaluated together with the influence of deformation on microstructure and properties.

Synthesis, Processing And Characterization Of Nanocrystalline Titanium Dioxide, Shipeng Qiu

Electronic Theses and Dissertations

Titanium dioxide (TiO2), one of the basic ceramic materials, has found a variety of applications in industry and in our daily life. It has been shown that particle size reduction in this system, especially to nano regime, has the great potential to offer remarkable improvement in physical, mechanical, optical, biological and electrical properties. This thesis reports on the synthesis and characterization of the nanocrystalline TiO2 ceramic in details. The study selected a simple sol-gel synthesis process, which can be easily controlled and reproduced. Titanium tetraisopropoxide, isopropanol and deionized water were used as starting materials. By careful control of relative proportion …

Behavior Of Ductile Materials Under Impulsive Loading, M. Y. Brunner

Tanzania Journal of Engineering and Technology (TJET)

Ductile materials under dynamic loading are known to be able to absorb energy and thereby delay or even prevent structural failure. This paper is concerned with such behaviour in the case of impulsive loads of short duration. It is shown that even when the feared, unstable, labile condition is attained, failure may not necessarily occur. This behaviour is particularly impressive for structures with large mass, because it is essentially the mass which slows down the attainment of the failure strains. If the impulsive load dies away quickly enough, the constant plastic resistance will be adequate to bring the increasing deformations …

Effect Of The Variations Of The Mobile Dislocation Density On The Thermally Activated Cyclic Deformation Behavior, J. S. Mshana

Tanzania Journal of Engineering and Technology (TJET)

The application of the transition state theory of rate processes to describe tension-tension, strain controlled cyclic deformation BEHAVIOUR was extended to describe the effect of the variations of the mobile dislocation density on the cyclic deformation BEHAVIOUR. It was shown from the derived constitutive relation that due to the net increase in the mobile dislocation density during strain controlled cyclic deformation the stress change per cycle (or in function of time) increases.

Materials Testing And Consultancy For The Tanzanian Industry, H. Fallenbach

Tanzania Journal of Engineering and Technology (TJET)

Abstract