Engineering Commons^™

Inferring Mechanical Resonances In Micro - And Nanocantilevers Using The Harmonic Detection Of Resonance (Hdr) Method To Develop A Novel Sensing Platform, Gayatri Keskar

All Dissertations

During the past two decades, advances in microelectromechanical systems (MEMS) have spurred efforts worldwide to develop sensing platforms based on smart microcantilevers. A microcantilever beam is one of the simplest MEMS structures which forms the basis for portable, fast and highly sensitive schemes that are capable of measuring small deflections in static or dynamic response due to changes in external parameters such as mass, pressure, charge, etc.
In this dissertation, I mainly focus on MEMS sensors with transducers in the form of microcantilevers. Variations in the microcantilever's response such as resonant frequency, amplitude, phase and quality factor when exposed to …

High Temperature Wetting And Multilayer Adsorption In Oxide Systems, Haijun Qian

All Dissertations

The primary objective of this thesis research is to greatly advance the knowledge of the formation mechanism and thermodynamic stability of a unique class of surficial amorphous films (SAFs) and analogous intergranular films (IGFs) via critical experiments and modeling. These quasi-liquid IGFs and SAFs films exhibit the following distinct characteristics: 1) self-regulating (equilibrium) thicknesses on the order of 1 nm, 2) structures and compositions that are neither found nor stable as bulk phases, and 3) thermodynamic stability below the bulk solidus lines.
The first part of this study examines anisotropic wetting of ZnO single crystals by Bi2O3-rich liquid with and …

Some Problems In Statistical Mechanics With Applications To Materials Science, Ethan Ballard

All Dissertations

In this work, some problems in statistical mechanics related to condensed matter physics and of general interst in materials science, physics, chemistry and polymer science are considered. In chapters 1-4, the work by E.M. Lifshitz on the group-theoretical refinements of the Landau theory of phase transitions is brought to completion. Based on mathematical results obtained by Yamabe, Osgood, Phillips, Sarnak, and Kholodenko analytical results for determinants were developed which allows for prediction of the symmetry of the phase after a phase transition provided that the symmetry prior to the phase transition is known. Numerical results are presented which are in …

Raman Studies Of 1,3,5,7 Cyclooctatetraene At High Pressure, Martin Galley, Ed Romano, Sergey Tkachev, Michael Pravica

Undergraduate Research Opportunities Program (UROP)

We performed Raman spectroscopic studies of 1,3,5,7-cyclooctatetraene at elevated pressures up to 10 GPa with the aim of examining possible planarization of the molecule and further studying two prior-discovered phases of the solid with pressure. The Raman excitation source was a Krypton-ion laser operating at 674.1 nm (give wavelength).

1,3,5,7 Cyclooctatetraene has an octagonal formation however it is not aromatic or anti-aromatic (not a subject to the 4n+2 Huckel’s rule) [1]. As a result, its adopts a somewhat reactive tub shape. Upon the addition or removal of one to two electrons under ambient conditions, the molecule planarizes and becomes aromatic …

Structural Studies Of Crsi2 At High Pressures And Temperatures, Weldu Gabrimicael, Ravhi S. Kumar, Andrew Cornelius

Undergraduate Research Opportunities Program (UROP)

It is of extreme importance to develop new potential energy sources to reduce dependence on fossil fuels. As a result of this, the study of thermoelectric materials, capable of changing heat into electrical energy, has become a field of great interest regarding fundamental properties. To help better understand these materials, facilities for the measurement of relevant properties at high pressure have been developed, but lack the ability to characterize the materials at high temperature and pressure. Therefore, this project has the goal of developing a heater arrangement to be used in conjunction with the high pressure capabilities already developed to …

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 …

Microstructural Characterization Of Diode Laser Deposited Ti-6al-4v, Tian Fu, Zhiqiang Fan, Syamala R. Pulugurtha, Todd E. Sparks, Jianzhong Ruan, Frank W. Liou, Joseph William Newkirk

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Laser Direct Metal Deposition (DMD) is an effective approach to manufacturing or repairing a range of metal components. The process is a layer-by-layer approach to building up a three dimensional solid object. The microstructure influences mechanical properties of the deposited parts. Thus, it is important to understand the microstructural features of diode laser deposited parts. This paper presents a microstructure analysis of a diode laser deposited Ti-6Al-4V onto a Ti-6Al-4V substrate. laser deposited parts. This paper presents a microstructure analysis of a diode laser deposited Ti-6Al-4V onto a Ti-6Al-4V substrate.

Design And Fabrication Of Piezoelectric Micro Generator Using Laser Micromachining And Mems Technique, Hyunuk Kim

Material Science and Engineering Theses - Archive

An energy harvesting device based on PbPb(Zr0.52Ti0.48)O3-Pb(Zn1/3Nb2/3)O3 ceramics was fabricated by using laser micromachining technique. It was found that the laser machining process did not have a significant effect on electrical properties of piezoelectric material. The device was found to generate continuous power of 1.13 μW at. 870Hz across a 288.5 kΩ load with power density of 301.3 μW/cm3. The characterization was conducted in low frequency regime of 50-1000Hz at the constant force of 8g(where g=9.8m/s2) In order to fabricate a lead free MEMS device, BaTiO3 was selected as the piezoelectric material. BaTiO3 gel was synthesized by aqueous process using …

Nanoparticulate Composites Of Melt Textured Yba2cu3o7−X Superconductors, Oratai Jongprateep, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

It has been shown that Nd1+xBa_2−xCu₃O_7−x could exhibit a pronounced Jc(H) peak effect, which results in an enhancement of the critical current density under the medium range magnetic field. Additions of small quantities of Nd₂O₃ into Pt-doped YBa₂Cu₃O_7−x (Y123) resulted in the formation of nanosized (30–60 nm) secondary phases which are expected to have a significant effect on superconducting properties of melt textured Y123 single crystals. By considering of solidification kinetics, effect of neodymium oxide and platinum addition on processing parameters of melt textured Y123 superconductors are …

The Role Of Silicon Content On Environmental Degradations Of T91 Steels, Ajit K. Roy, D. Maitra, Pankaj Kumar

Mechanical Engineering Faculty Research

T91 grade steels showed a gradual enhancement in tensile ductility at ambient temperature due to an increase in Si content from 0.5 to 2.0 weight percent (wt.%). However, the ultimate tensile strength was reduced only above 1.5 wt.% Si. The corrosion potential became more active in an acidic solution with increasing temperature. The cracking susceptibility in a similar environment under a slow-strain-rate (SSR) condition was enhanced at higher temperatures showing reduced ductility, time to failure, and true failure stress. Cathodic potentials applied to the test specimens in SSR testing caused an enhanced cracking tendency at 30 and 60°C, suggesting hydrogen …

Tensile Deformation Of A Nickel-Base Alloy At Elevated Temperatures, Ajit K. Roy, Anand Venkatesh, Vikram Marthandam

Mechanical Engineering Faculty Research

The results of tensile testing involving Waspaloy indicate that the failure strain was gradually reduced at temperatures ranging between ambient and 300 °C. Further, serrations were observed in the engineering stress versus strain diagrams in the temperature range of 300-600 °C. The reduced failure strain and the formation of serrations in these temperature regimes could be the result of dynamic strain aging of this alloy. The extent of work hardening due to plastic deformation was reduced at temperatures above 300 °C. A combination of ductile and intergranular brittle failures was seen at temperatures above 600 °C. γ′ was detected at …

The Role Of Crystallographic Relationships Between Alpha(Α) And Beta(Β) Phases On The Elevated Temperature Isothermal Phase Transformation Kinetics In Timetal Lcb (Ti-6.5mo-4.5fe-1.5al), Basak Kokuoz

All Theses

This investigation has examined the mechanisms controlling the precipitation of various alpha (α) phase morphologies which form during the elevated temperature beta(β)beta(β)+alpha(α) phase transformations in TIMETAL LCB (Ti-6.8Mo-4.5Fe-1.5Al, in wt.%).
Alpha (α) phase precipitation was promoted by aging the TIMETAL LCB specimens in the α+β two phase region. The temperature range considered was between 700-745oC.The specimens were isothermally aged for successively increasing times, starting at 30 seconds until the equilibrium microstructure was achieved. Solution treated and aged TIMETAL LCB specimens were investigated using x-ray diffraction (XRD), optical (OM) and scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and quantitative image …

50th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 50th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-endorsed by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Breckenridge, Colorado, July 27-31, 2008.

Glass And Glass-Ceramic Sealant Compositions, Richard K. Brow, Signo Tadeu Dos Reis, Glen Benson

Materials Science and Engineering Faculty Research & Creative Works

A glass composition for use as a sealant or otherwise bonded to a fuel cell component, including from about 40 mol % to about 60 mol % RO; from about 2 mol % to about 10 mol % M₂O₃; and from about 35 mol % to about 45 mol % SiO₂. R is selected from the group including strontium, calcium, magnesium and zinc and combinations thereof. M is selected from the group including aluminum, boron, lanthanum, iron and combinations thereof. The glass includes at least about 5 mol % ZnO. Upon heat treatment, the …

Diffusion Bonding Of Stainless Astm A240 Grade 304 In Double Side Flux Cored Arc Welding, S Pitaknorachon, B Poopat

Journal of Metals, Materials and Minerals

Double side flux cored arc welding (DS-FCAW) has been developed from conventional flux cored arc welding (FCAW). DS-FCAW, dual torches are used by placing an opposite to each other and welding on both sides simultaneously. The objective of this research paper is to investigate diffusion bonding effect due to DS-FCAW. Stainless steel ASTM A240 Grade 304 was studied. Other welding parameters were set constant except welding current and voltage. Diffusion bonding was observed even though weld profiles from macro inspection showed lack of penetration by weld metal in all experiments. It can be concluded that, at certain conditions, the welds …

Improvement Of Mechanical Properties For En Aw 6082 Aluminium Alloy Using Equal-Channel Angular Pressing (Ecap) And Post-Ecap Aging, M Fujda, T Kvačkaj, K Nagyová

Journal of Metals, Materials and Minerals

The mechanical properties and microstructure of EN AW 6082 aluminium alloy subjected to severe plastic deformation and aging treatment were compared with those of the extruded and artificially aged state (initial state). The initial state of alloy subjected to solution annealing and quenching was severely deformed at ambient temperature by equal channel angular pressing (ECAP) following route C up to three passes. Polyedric microstructure of initial state was considerably changed by the repetitive ECA-pressing. Deformation bands with different density of slip lines were observed in microstructure of ECAPed and aged states, which indicated non-uniform deformation across the cross-section of ECAPed …

A Longitudinal Study Of The Ethical Development Of Engineering And Non-Engineering Students At A National Research University, Cynthia J. Finelli, Janel A. Sutkus, Donald D. Carpenter, Trevor S. Harding

Materials Engineering

No abstract provided.

Surface Modification Of Bricks By Chitosan Coatings, S Nilpairach, S T. Dubas

Journal of Metals, Materials and Minerals

Bricks were successfully modified by application of a chitosan coating in order to provide their surface with a water repellant character. The chitosan coating was prepared by depositing solutions of variable chitosan concentration (1% or 2.5% w/w) onto the brick surface and let to dry under ambient condition. In order to improve the water repellant property, the films were cross-linked with a 1% solution of sodium citrate, sodium sulfate or sodium tri - polyphosphate. The effect of the chitosan concentration on the morphology of the coating at the brick surface was observed by scanning electron microscope (SEM). It was found …

Current Status Of Nanotechnology Consumer Products And Nano-Safety Issues, N Chuankrerkkul, S Sangsuk

Journal of Metals, Materials and Minerals

This paper is divided into 2 parts to present a review on nanotechnology consumer products ('Nanotech' products) and a current status on 'Nano-Safety' issue. The first part focuses on up-to-date information of 'Nanotech' products that were already on the market as reported by Project on Emerging Nanotechnologies of the Woodrow Wilson International Center for Scholars. There are more than 500 products for a variety of applications, among which health and fitness products are the largest category. The products in this group consist of clothing, cosmetics and sunscreens. Silver is the most commonly used material, followed by carbon in the forms …

Effect Of Limestone Dust On The Properties Of Thai Pottery Sintering At Low Temperature, S Sangsuk, S Khunthon, S Saenapitak, S Nilpairach

Journal of Metals, Materials and Minerals

Limestone dust from a limestone crushing plant was used as an additive in pottery clay for this experiment. After the limestone dust was sieved through a 35 mesh stainless steel sieve, it was mixed with Angthong pottery clay at various contents. Samples with and without limestone dust were sintered at 600, 700, 900, and 1000o C. Because of limestone blowing for samples with limestone dust sintered at 900 and 1000o C, physical property measurement was performed only for samples sintered at 600 and 700o C. While sintering at low temperatures (600 and 700o C), physical properties of samples with limestone …

Morphology Controlled Calcium Ortho Phosphates Induced By Chemical Additions Under Hydrothermal Reaction, D P. Kashima, E Kongkul, T Daopradubwon

Journal of Metals, Materials and Minerals

Morphology controlled calcium orthophosphates under hydrothermal reaction was achieved using saturated solution of monocalcium phosphate monohydrate (MCPM) as a starting material. MCPM saturated solution was hydrothermally treated at 180°C for 4 and 12 hrs. Citric acid as a chelating agent and a mixed solution of NaNO3 and NaF were individually added into the reactor. The morphologies, phases and microstructures of the obtained products were characterized by optical microscope (OM), X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. Irregular shape crystals were obtained when a saturated solution of MCPM was autoclaved at 180°C for 4 hrs. Though citric acid was …

Calcium Phosphate Film Coating On Titanium Substrate By Electrochemical Deposition, D P. Kashima, A Rakngarm

Journal of Metals, Materials and Minerals

Calcium phosphate film on titanium substrate was achieved by electrochemical method in four different kinds of electrolyte. The pure titanium metal (99.99%) with 0.8 cm in width and 2 cm in length was used as a substrate and it was subsequently etched by 2M HF for 1 minute before electrochemical deposition. Calcium phosphate film could form at a different current density for each kind of electrolyte as follows: 10 mA/cm2 for MCPM based aqueous solution, 20 mA/cm2 for MCPM based aqueous solution with ions addition, 10 mA/cm2 and 20 mA/cm2 for MCPM based 20%V/V ethanol and 50%V/V ethanol solution, respectively. …

Improved L-929 Cell Growth From Self Assembled Pdadmac/Gelatin Thin Films, P Kittitheeranun, P Potiyaraj, T Bunaprasert, N Sanchavanakit, S T. Dubas

Journal of Metals, Materials and Minerals

This article demonstrates the advantages of using PDADMAC/gelatin over chitosan/gelatin multilayer thin films to improve L-929 mouse fibroblast growth. Although chitosan-based materials are often preferred in cell culture, we put in evidence the problematic low stability and decomposition of chitosan based film under physiological pH. Two kinds of coating were assembled using either chitosan or Poly(diallyldimethylammonium chloride) (PDADMAC) as polycationic polyelectrolyte and gelatin as the anionic counterpart. The non-toxic nature of each coating was confirmed by MTT assay for cell viability and cell proliferation. Using optical microscopy, it was observed that the L-929 fibroblast spread preferentially on the PDADMAC/gelatin surface …

Effects Of Tin Powder On Properties Of Sintered Stainless Steels, N Tosangthum, P Muangtong, O Coovattanachai, M Morakotjinda, T Yodkaew, P Wila, R Krataitong, B Vetayanugul, R Tongsri

Journal of Metals, Materials and Minerals

It was found that addition of 4 wt.% of gas-atomized tin (Sn) powder to stainless steel powders could alter sintered properties of P/M stainless steels. For stainless steel series 300 powders, Sn powder addition resulted in improved tensile properties and hardness. It was speculated that the liquid Sn, formed during sintering process, acted as either a sintering activator or a solvent for nickel (Ni) dissolution. Sintering activation existed because the liquid Sn acted as a diffusion path for powder particle constituent atoms. Dissolution of Ni in Sn was simply due to diffusion of Ni atoms from stainless steel series 300 …

Sintered Properties Of 409l Powder Compacts Influenced By Metal Powder Additives, O Coovattanachai, T Yodkaew, M Morakotjinda, N Tosangthum, R Krataitong, A Daraphan, B Vetayanugul, R Tongsri

Journal of Metals, Materials and Minerals

Sintering of powder compacts, prepared by admixing of 409L powder with 2-6 wt.% of copper and nickel powders was investigated. It was observed that the strength of the 409L-Cu specimens increased with increasing Cu content. In contrast, sintered density and elongation decreased with increasing Cu content due to swelling effect. When 2 wt.% of Ni powders were added, sintered density and strengths were maximized. When Ni contents higher than 2 wt.% , the decrease of sintered density and strengths were attributed to the number of pores left by the original sites of Ni powder particles.

Sintered Fe-Al2o3and Fe-Sic Composites, T Yodkaew, M Morakotjinda, N Tosangthum, O Coovattanachai, R Krataitong, P Siriphol, B Vetayanugul, S Chakthin, N Poolthong, R Tongsri

Journal of Metals, Materials and Minerals

The presence of non-reactive (Al2O3) and reactive (SiC) hard particles affected properties of sintered Fe-base composites. With the same compacting and sintering conditions, addition of Al2O3 particles caused reduction of sintered densities. Tensile strengths, elongation and hardness of the sintered Fe-Al2O3 materials decreased with increasing Al2O3 particle amounts. The presence of Al2O3 particles prohibited compacting and sintering processes of the Fe powder. In contrast, addition of SiC particles resulted in reaction between Fe and SiC particles. Sintered density of the sintered Fe-SiC composites was significantly lower than that of the sintered Fe-Al2O3 materials. However, tensile strengths and hardness, except elongation, …

Sintered Materials Prepared From Stainless Steel Series 300 And 400 Powders, M Morakotjinda, N Kuljittipipat, N Poolthong, N Tosangthum, P Wila, R Krataitong, T Yodkaew, O Coovattanachai, B Vetayanugul, R Tongsri

Journal of Metals, Materials and Minerals

Some sintered materials were prepared from mixtures of stainless steel series 300 and series 400 powders. The sintered stainless steels consisted of both austenitic and ferritic phases so they were designated as sintered duplex stainless steels (SDSSs). Microstructures and properties of the SDSSs were characterized and tested. Most SDSSs, except the 310L powder-base SDSSs, showed improved tensile strengths and hardness but exhibited inferior ductility, compared to those of the sintered stainless steels series 300. The 304L-410L SDSS showed promising mechanical properties. This SDSS were further investigated by varying weight ratio of 304L and 410L powders. It was found that sintered …

Effects Of Yttria Concentration And Microstructure On Electric Breakdown Of Yttria Stabilized Zirconia, O Jongprateep, V Petrovsky, F Dogan

Journal of Metals, Materials and Minerals

Ceramic materials have great potentials for capacitor application. However, low breakdown strength of the materials remains a key challenge for development of high performance capacitors. In this study, yttria stabilized zirconia (YSZ) were fabricated and tested for breakdown strength. YSZ samples with 3, 8, and 10 mol% yttria were carefully processed to control grain size and porosity level. Experimental results revealed that breakdown strength as high as 2 MV/cm could be achieved. The breakdown strength was not significantly affected by porosity level, but it was by yttria concentration. Relationship among yttria concentration, residual porosity and breakdown strength is discussed in …

Nano-Size Hydroxyapatite Powders Preparation By Wet-Chemical Precipitation Route, N Monmaturapoj

Journal of Metals, Materials and Minerals

In this study, wet-chemical process was performed to prepare nano-size hydroxyapatite (HA) powders (≈10 nm) by varying concentration (low, medium and high) of the starting solutions in order to increase the amount of as-dried HA powders with different process conditions. Particle sizes and density were analyzed and differential thermal analysis was used to determine the glass transition (Tg) and the onset crystallization (Tc) temperatures. XRD and SEM were performed to identify phases and microstructure. The wet-chemical precipitation using low concentration of starting solution under reflux environment could be the optimize process to induce the formation of hydroxyapatite rather than tricalcium …

Reflection High-Energy Electron Diffraction Studies Of Indium Phosphide (100) And Growth On Indium And Indium Nitride On Silicon (100), Mohamed Abd-Elsattar Hafez

Electrical & Computer Engineering Theses & Dissertations

Study of the effects of atomic hydrogen exposure on structure and morphology of semiconductor surfaces is important for fundamental properties and applications. In this dissertation, the electron yield of a hydrogen-cleaned indium phosphide (InP) surface was measured and correlated to the development of the surface morphology, which was monitored by in situ reflection high-energy electron diffraction (RHEED). Atomic hydrogen treatment produced a clean, well-ordered, and (2x4)-reconstructed InP(100) surface. The quantum efficiency, after activation to negative electron affinity, and the secondary electron emission were shown to increase with hydrogen cleaning time. RHEED patterns of low-index InP(100) surface were modified by the …