Materials Science and Engineering Faculty Publications and Presentations Copyright (c) 2013 Boise State University All rights reserved. http://scholarworks.boisestate.edu/mse_facpubs Recent documents in Materials Science and Engineering Faculty Publications and Presentations en-us Wed, 08 May 2013 01:36:04 PDT 3600 Oxidation Investigation of NBG-18 Nuclear-Grade Graphite http://scholarworks.boisestate.edu/mse_facpubs/155 http://scholarworks.boisestate.edu/mse_facpubs/155 Mon, 06 May 2013 11:00:55 PDT The oxidation kinetics of NBG-18 nuclear graphite was investigated between 500 and 775°C with oxygen partial pressures ranging from 10 to 40 kPa. Using a phenomenological shrinking-core model, reaction rates normalized to the reactive surface area were determined. In addition, a more rigorous, mechanism-based model is proposed for the reaction rate of nuclear graphites based on observed spill-over of the carbon-oxygen surface intermediate onto the graphite basal plane. This mechanistic model suggests the reaction is controlled simultaneously by the dissociative chemisorption of oxygen and the desorption of reactive surface intermediates to form CO(g) and CO2(g). The activation energies for these processes were approximated as180±10, 260±10 and 190±10 kJ/mol, respectively.

]]> Joshua Kane et al. Characterization of the Fabrication Process of Rolled LTCC Structures http://scholarworks.boisestate.edu/mse_facpubs/154 http://scholarworks.boisestate.edu/mse_facpubs/154 Fri, 03 May 2013 09:18:14 PDT This work focuses on the fabrication and assembly of cylindrical plasma containment tubes using DuPont's 951 low temperature co-fired ceramics (LTCC) for use in miniature electrostatic thrusters. The tube is used to contain argon plasma, which is generated by a spiral inductively coupled plasma antenna, which is also fabricated in LTCC. The tube also interfaces with two electrically biased grids on the opposite end, which accelerate the plasma out of the tube. These interfaces are highly dependent on the dimensions and tolerances of the containment tube. The development of the fabrication process will be presented for the incorporation of the tubes and grids onto the base as a single structure. This includes constructing the antenna base, shaping the “rolled” LTCC containment tube using a jig and isostatic press, and integrating the tube and antenna base during the firing. Following the fabrication, measurements will be taken to determine tube circularity and hermeticity of the seal at the interface between the tube and the antenna base. The results will be presented and characterized to evaluate the effectiveness of the structure as well as the documentation of the development of a rolled LTCC tube structure integrated with a planar LTCC antenna base.

]]> Kelci Parrish et al. Compositional Tuning of Structural Stability of Lithiated Cubic Titania via a Vacancy-Filling Mechanism under High Pressure http://scholarworks.boisestate.edu/mse_facpubs/153 http://scholarworks.boisestate.edu/mse_facpubs/153 Tue, 30 Apr 2013 10:27:16 PDT Experimental and theoretical studies on the compositional dependence of stability and compressibility in lithiated cubic titania are presented. The crystalline-to-amorphous phase transition pressure increases monotonically with Li concentration (from ∼17.5  GPa for delithiated to no phase transition for fully lithiated cubic titania up to 60 GPa). The associated enhancement in structural stability is postulated to arise from a vacancy filling mechanism in which an applied pressure drives interstitial Li ions to vacancy sites in the oxide interior. The results are of significance for understanding mechanisms of structural response of metal oxide electrode materials at high pressures as well as emerging energy storage technologies utilizing such materials.

]]> Hui Xiong Investigation of NaY Zeolite with Adsorbed CO<sub>2</sub> by Neutron Powder Diffraction http://scholarworks.boisestate.edu/mse_facpubs/152 http://scholarworks.boisestate.edu/mse_facpubs/152 Thu, 04 Apr 2013 09:39:10 PDT The crystal structure of dehydrated NaY zeolite (Na-FAU structure type) with and without adsorbed CO2 has been determined at 4 K and at room temperature (RT) using neutron powder diffraction techniques. The CO2-containing sample was prepared at 195 K and 0.1 MPa pCO2 (dry ice sublimation conditions). Neutron diffraction data provides direct evidence that adsorption of CO2 results in significant migration of the extraframework Na cations in the zeolite structure. At 4 K, 45 of the apparent 76 CO2/cell were located in two crystallographically independent sites bonding to the Na cations (Na10) in the supercage site II. While the CO2 molecule in the first site has a linear configuration interacting with Na10 via one terminal oxygen, the CO2 molecule in the second site appears to have a bent O–C–O configuration (148.3(3)°), with both oxygen atoms coordinating to two symmetry-related Na10. Using DFT total energy calculations we found that the Na–CO2 interaction slightly facilitates the bending motion for CO2 by decreasing the energy cost for the 148.3(3)° bond angle by ≈0.2 eV/CO2. However, this Na–CO2 interaction is not enough to cause a 32° bond angle distortion in CO2 (the energy cost of ≈0.66 eV/CO2). We propose that rotational disorder plays a significant role in the appearance of the bent CO2, while a small bending is possible. Our studies will help to provide a basis for interpreting CO2 adsorption phenomena in NaY and related zeolites.

]]> W. Wong-Ng et al. Suppression of Fe<sub>Li</sub> Antisite Defects in Fluorine-Doped LiFePO<sub>4</sub> http://scholarworks.boisestate.edu/mse_facpubs/151 http://scholarworks.boisestate.edu/mse_facpubs/151 Wed, 03 Apr 2013 10:22:18 PDT We report on the suppression of FeLi antisite defects in LiFe(PO4)1−xF3x with 0 ⩽ x ⩽ 0.4 prepared by sol–gel and hydrothermal methods. Evidence for a systematic suppression of antisite defects upon fluorine doping in LiFePO4 is inferred from Fourier transform infrared spectra, wherein a noticeable red shift in the symmetric P–O stretching vibrational mode of (PO4)3− polyanion from 970 to 957 cm−1 was observed. We report detailed structural and compositional studies of LiFe(PO4)1−xF3x, and discuss the implications for the performance of LiFePO4 cathodes in lithium ion batteries.

]]> A. V. Radhamani et al. Novel Smart Stannate Based Coatings of Self-Healing Functionality for AZ91D Magnesium Alloy http://scholarworks.boisestate.edu/mse_facpubs/150 http://scholarworks.boisestate.edu/mse_facpubs/150 Thu, 28 Mar 2013 14:53:33 PDT Smart stannate based coatings were used for improving the corrosion resistance of AZ91D alloy. The proposed coatings characterize with their safety compared with the process involving toxic chromate. They are also industrially applicable and economically attractive where only two steps are needed for the coating preparation and the chemicals used are just a diluted tin-oxide solution. The electrochemical behavior and the self-healing characteristics due to stannate coatings on Mg substrate has been evaluated in 3.5% NaCl solution. Polarization measurements, electrochemical impedance spectroscopy, SEM–EDS analyses were performed to assess the performance of the coatings in NaCl and to determine the optimum conditions for self-healing ability. Results showed that stannate coatings improve the resistance to localized corrosion and micro-cracks due to formation of tin oxide-rich magnesium hydroxide layer. It was confirmed that stannate are promising coatings provide a self-healing functionality for Mg substrate that heal the pitting zones and auto-repair the micro-cracks.

]]> Abdel Salam Hamdy et al. An Oxygen Transfer Model for High Purity Graphite Oxidation http://scholarworks.boisestate.edu/mse_facpubs/149 http://scholarworks.boisestate.edu/mse_facpubs/149 Thu, 28 Mar 2013 14:45:41 PDT An intrinsic mathematical model is developed for the investigation of the gas-solid reaction kinetics of high-purity graphite and oxygen. This model is based upon the oxygen transfer mechanism and uses physically meaningful parameters that are directly comparable to the experimental and theoretical literature of the carbon-oxygen reaction system. The model was used to extract reaction parameters for NBG-18 polycrystalline graphite for oxygen/nitrogen mixtures with a total pressure of 100 kPa. Experimental temperatures ranged from 500 to 850°C for oxygen partial pressures of 1, 5, 10, 20, and 40 kPa. The optimized model parameters are in good agreement with previously reported literature values.

]]> Joshua Kane et al. Texture and Training of Magnetic Shape Memory Foam http://scholarworks.boisestate.edu/mse_facpubs/147 http://scholarworks.boisestate.edu/mse_facpubs/147 Mon, 04 Feb 2013 13:47:34 PST Magnetic shape memory alloys display magnetic-field-induced strain (MFIS) of up to 10% as single crystals. Polycrystalline materials are much easier to create but display a near-zero MFIS because twinning of neighboring grains introduces strain incompatibility, leading to high internal stresses. Pores reduce these incompatibilities between grains and thus increase the MFIS of polycrystalline Ni–Mn–Ga, which after training (thermo-magneto-mechanical cycling) exhibits MFIS as high as 8.7%. Here, we show that this training effect results from a decoupling of struts surrounding pores in polycrystalline Ni–Mn–Ga during the martensitic transformation. To show this effect in highly textured porous samples, neutron diffraction measurements were performed as a function of temperature for phase characterization and a method for structure analysis was developed. Texture measurements were conducted with a magnetic field applied at various orientations to the porous sample, demonstrating that selection of martensite variants takes place during cooling.

]]> Cassie Witherspoon et al. Characterization of Mineral Ores from Northern and Northwest Pakistan http://scholarworks.boisestate.edu/mse_facpubs/146 http://scholarworks.boisestate.edu/mse_facpubs/146 Wed, 30 Jan 2013 12:45:07 PST Pakistan is home to many varieties of minerals, some of which make it prominent in the mineral world. The exploration of Pakistan’s mineral wealth is far from complete and has rarely been conducted in the north and northwest of the country. This article presents the newest exploration and examination of minerals from an unexploited area in Pakistan. Several materials characterization techniques were carried out to examine and identify the phase and structure of the minerals, including x-ray diffraction, energy dispersive x-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy. In this study, several commonly found minerals are identified, including calcite, dolomite, quartz, talc, and fluorapatite.

]]> Yaseen Iqbal et al. Transformation Volume Strain in Ni-Mn-Ga Thin Films http://scholarworks.boisestate.edu/mse_facpubs/145 http://scholarworks.boisestate.edu/mse_facpubs/145 Fri, 18 Jan 2013 14:39:42 PST The temperature dependences of the lattice parameters and residual stress have been measured for a fine-grained Ni52.2Mn26.8Ga21.0 (at. %) thin film fabricated by sputter deposition onto a heated silicon wafer with SiNx buffer layer. The transformation volume strain in the film was found to be a lattice expansion during the forward martensitic transformation which is opposite to a volume contraction exhibited by bulk Ni-Mn-Ga alloys. This unusual effect can be explained by the substrate-induced residual stresses in the film and the difference in the elastic modulus of austenite and martensite.

]]> I. R. Aseguinolaza et al. A Preliminary Study on the Development of La<sub>2</sub>O<sub>3</sub>-Bearing Nanostructured Ferritic Steels via High Energy Ball Milling http://scholarworks.boisestate.edu/mse_facpubs/144 http://scholarworks.boisestate.edu/mse_facpubs/144 Mon, 03 Dec 2012 11:54:30 PST Elemental powder mixture of Fe-Cr-Ti-Mo and La2O3 were ball milled for different milling times in a high energy shaker mill. Effects of ball milling time on crystallite size, particle size and hardness were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and microhardness tester. After 10 hours of ball milling, the smallest crystallite size and highest hardness were ∼24 nm and ∼970 HV, respectively. Transmission electron microscopy (TEM) studies have revealed nanoscale features 2-5 nm in diameter present in the milled powder. Local atom probe tomography studies have shown that these nanoscale features were possibly nanoclusters enriched in La, TiO and O.

]]> Somayeh Pasebani et al. A Magnetic Shape Memory Micropump: Contact-Free, and Compatible with PCR and Human DNA Profiling http://scholarworks.boisestate.edu/mse_facpubs/143 http://scholarworks.boisestate.edu/mse_facpubs/143 Wed, 28 Nov 2012 14:25:23 PST Magnetic shape memory (MSM) Ni–Mn–Ga elements are relatively new materials with a variety of remarkable properties. They respond to changes in magnetic fields by elongating and shortening up to 6%. We have constructed a micropump which consists principally of a single component, the MSM element. The pump can be driven by the rotation of a diametrically magnetized cylindrical magnet or by an electrical rotation of the magnetic field; it is reversible, and can be effectively operated by hand without any electrical power. The MSM element does not inhibit the polymerase chain reaction. We demonstrate that it is compatible with forensic applications and show that it does not inhibit human DNA profiling. This novel pump is suitable for lab-on-a-chip applications that require microfluidics.

]]> K. Ullakko et al. Oxidation Studies on NBG-18 Grade Nuclear Graphite http://scholarworks.boisestate.edu/mse_facpubs/142 http://scholarworks.boisestate.edu/mse_facpubs/142 Thu, 08 Nov 2012 13:54:17 PST In this work we focus on the oxidation of grade NBG-18 nuclear graphite in oxygen/nitrogen atmospheres. NBG-18 was chosen because of its potential use in high dosage regions of the pebble bed concept VHTR.

]]> J. Kane et al. Corrosion Protection Performance of Nano-Particles Thin-Films Containing Vanadium Ions Formed on Aluminium Alloys http://scholarworks.boisestate.edu/mse_facpubs/141 http://scholarworks.boisestate.edu/mse_facpubs/141 Tue, 30 Oct 2012 15:00:58 PDT Purpose – The paper seeks to find out new eco-environmentally friendly surface treatments based on vanadate compounds as alternatives to the process involving toxic chromates for the corrosion protection of aluminium alloys.

Design/methodology/approach – A treatment process in which the surface was etched prior to vanadia treatment is being proposed. The process involves cleaning, etching in potassium hydroxide followed by treatment in vanadia prepared by sol-gel method. The effect of surface preparation prior to vanadia treatment on the corrosion resistance of AA6061 T6 in 3.5 per cent NaCl solution was measured using AC impedance spectroscopy and DC polarization techniques. Surface examination was performed by scanning electron microscopy (SEM), energy dispersive X-ray (EDS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM).

Findings – It has been shown that the etching process prior to vanadia treatment enhanced formation of a uniformly distributed compact surface V-rich Al-oxide film of smooth appearance and inhibited the active surface sites and thereby preventing localized corrosion.

Originality/value – Vanadate conversion coatings seem very promising as alternatives to toxic chromating for the corrosion protection of aluminium alloys in NaCl solution.

]]> Abdel Salam Hamdy et al. Environmentally Compliant Silica Conversion Coatings Prepared by Sol-Gel Method for Aluminum Alloys http://scholarworks.boisestate.edu/mse_facpubs/140 http://scholarworks.boisestate.edu/mse_facpubs/140 Tue, 30 Oct 2012 14:38:39 PDT Chromate conversion coatings have been widely applied for the corrosion protection of aluminum alloys. However, the waste containing Cr6+ has many limitations due to environmental considerations and health hazards. Silicates are among the proposed alternatives to chromating. A series of specimens were prepared under the following conditions: (a) as polished, (b) directly treated with silica, (c) etched, (d) oxide thickened and, (e) etching followed by oxide thickening. After surface preparation, the specimens were dipped in two different silica solution prepared via the sol–gel method. Electrochemical impedance spectroscopy (EIS) and polarization measurements have been used to evaluate the coating performance in 3.5% NaCl. The optimum conditions under which silica treatments can provide good corrosion protection to the aluminum substrate were determined. The surface preparation prior to silica treatment was found to have a marked effect on the corrosion protection of AA6061 T6. Generally, silica treatments improve the corrosion resistance due to formation of protective oxides that act as a barrier to oxygen diffusion to the metal surface. According to the EIS and polarization measurements, a combination between etching and oxide thickening prior to silica treatment plays an important role in the corrosion protection mechanism.

]]> Abdel Salam Hamdy et al. Grain Boundary and Triple Junction Chemistry of Silicon Carbide with Aluminum or Aluminum Nitride Additive http://scholarworks.boisestate.edu/mse_facpubs/139 http://scholarworks.boisestate.edu/mse_facpubs/139 Fri, 26 Oct 2012 15:02:50 PDT Edgardo Pabit et al. Joining of Ion Transport Membranes Using a Novel Transient Liquid Phase Process http://scholarworks.boisestate.edu/mse_facpubs/138 http://scholarworks.boisestate.edu/mse_facpubs/138 Fri, 26 Oct 2012 14:48:04 PDT A novel transient liquid phase (TLP), or partially transient liquid phase (PTLP) ceramic-ceramic joining process has been developed that leaves behind no interfacial phase, enabling the fabrication of complex systems of components. The process can be used to join and manifold components and reduce the sintering temperatures of ion transport membranes. This process has been tested in the joining of high temperature perovskite ion transport membranes. Utilizing metal oxides mixed at low melting point compositions of their respective systems, then combined with a more refractory compound, the process has resulted in a strong joint with low porosity that is hermetic to helium.

]]> Darryl P. Butt et al. Synthesis and Pyrolysis of Novel Polysilazane to SiBCN Ceramic http://scholarworks.boisestate.edu/mse_facpubs/136 http://scholarworks.boisestate.edu/mse_facpubs/136 Fri, 26 Oct 2012 13:12:10 PDT A novel synthesis route was developed to produce exceptionally thermal stable SiBCN-based ceramics. This route turns out to be cheaper, simpler and faster than the conventional route. The SiBCN-based preceramic polymer was synthesized by using three monomers, trichlorosilane (HSiCl3), boron trichloride (BCl3), and hexamethydisilazane (HMDZ), at a molar ratio of about 1:1:4. The product becomes an amorphous structure with crosslinked bonds during the elimination of (CH3)3SiCl. An intermolecular condensation with the loss of HMDZ occurs in a second stage without the addition of crosslinking agents. In the final pyrolysis stage, hydrogen-rich species such as CH4 are lost. The chemical structure and composition of the obtained polymer were investigated using IR, MAS-NMR, TGA, DSC, XRD, EA, AA, ICP, and EDS. Through the pyrolysis of preceramic polymers, the mechanisms of the structural and compositional changes at a high temperature were also examined. A preceramic polymer useful for nuclear application can be formed, which provides hydrothermal stability under autoclave test.

]]> Jongsang Lee et al. Novel Anti-Corrosion Nano-Sized Vanadia-Based Thin Films Prepared by Sol-Gel Method for Aluminum Alloys http://scholarworks.boisestate.edu/mse_facpubs/134 http://scholarworks.boisestate.edu/mse_facpubs/134 Fri, 26 Oct 2012 12:55:10 PDT Chromate conversion coatings have been widely applied for the corrosion protection of aluminum alloys. However, the waste containing Cr6+ has many limitations due to the environmental consideration and health hazards. Vanadates are among the proposed alternatives to chromating. Series of specimens were prepared under the following conditions: (a) as polished, (b) directly treated with vanadia, (c) etched, (d) oxide thickened, and (e) etching followed by oxide thickening. After surface preparation, the specimens were dipped in vanadia solution prepared via sol gel method. Electrochemical impedance spectroscopy (EIS) and polarization measurements have been used to evaluate the coating performance in 3.5% NaCl. The optimum conditions under which vanadia treatments can provide good corrosion protection to the aluminum substrate were determined. The surface morphologies of the treated samples were investigated using SEM and EDS. Optical microscope was also used to investigate the occurrence of pitting corrosion. The surface preparation prior to vanadia treatment was found to have a marked effect on the corrosion protection of AA6061 T6. Generally, vanadia treatments improve the corrosion resistance due to formation of highly protective vanadium oxides. According to the EIS and polarization measurements, a combination between etching and oxide thickening prior to vanadia treatment plays an important role on the corrosion protection mechanism.

]]> Abdel Salam Hamdy et al. Kinetics of Hydrothermally Induced Transformation of Yttria Partially Stabilized Zirconia http://scholarworks.boisestate.edu/mse_facpubs/133 http://scholarworks.boisestate.edu/mse_facpubs/133 Fri, 26 Oct 2012 12:49:11 PDT Yttria-stabilized zirconia undergoes tetragonal to monoclinic phase transformation under hydrothermal conditions in the temperature range of 150–350 °C. Phase transformation accompanied by volume change in bulk yttria partially stabilized zirconia (YPSZ) leads to micro-cracking, loss of mechanical integrity and ultimately disintegration. The mechanical properties of the bulk YPSZ material deteriorate with the amount of the phase transformation and in some cases catastrophic failure are observed. The phase transformation is analyzed using macroscopic and microscopic techniques. X-ray diffraction data is used to quantify the phase transformation in bulk material. Kinetics of the phase transformation is studied at various temperatures.

]]> J. J. Payyapilly et al.