Scholarly Works, Materials Science and Engineering (MSE)

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An acoustic position sensor
Dong, Shuxiang; Bai, Feiming; Li, Jiefang; Viehland, Dwight D. (AIP Publishing, 2003-11-01)
This article presents an acoustic method-the resonance acoustic field sensor or piezoelectric-sound-resonance cavity (PSRC)-for object position detection. This method utilizes the change of acoustic radiation impedance as a sensing mechanism. The PSRC both generates and detects a resonance acoustic field, along both the axial and transverse directions. We have discovered that an inserted object or an object motion in the sound radiation field results in changes in both the voltage and phase of the PSRC. Results have shown that a minimum object displacement of <10 mum can be detected in the axial direction (and <100 mum in the transverse) by this method. (C) 2003 American Institute of Physics.
Adaptive ferroelectric states in systems with low domain wall energy: Tetragonal microdomains
Jin, Y. M.; Wang, Yu. U.; Khachaturyan, Armen G.; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2003-09-01)
Ferroelectric and ferroelastic phases with very low domain wall energies have been shown to form miniaturized microdomain structures. A theory of an adaptive ferroelectric phase has been developed to predict the microdomain-averaged crystal lattice parameters of this structurally inhomogeneous state. The theory is an extension of conventional martensite theory, applied to ferroelectric systems with very low domain wall energies. The case of ferroelectric microdomains of tetragonal symmetry is considered. It is shown for such a case that a nanoscale coherent mixture of microdomains can be interpreted as an adaptive ferroelectric phase, whose microdomain-averaged crystal lattice is monoclinic. The crystal lattice parameters of this monoclinic phase are self-adjusting parameters, which minimize the transformation stress. Self-adjustment is achieved by application of the invariant plane strain to the parent cubic lattice, and the value of the self-adjusted parameters is a linear superposition of the lattice constants of the parent and product phases. Experimental investigations of Pb(Mg1/3Nb2/3)O-3-PbTiO3 and Pb(Zn1/3Nb2/3)O-3-PbTiO3 single crystals confirm many of the predictions of this theory. (C) 2003 American Institute of Physics.
Additive Friction Stir-Enabled Solid-State Additive Manufacturing for the Repair of 7075 Aluminum Alloy
Griffiths, R. Joey; Petersen, Dylan T.; Garcia, David; Yu, Hang Z. (MDPI, 2019-08-23)
The repair of high strength, high performance 7075 aluminum alloy is essential for a broad range of aerospace and defense applications. However, it is challenging to implement it using traditional fusion welding-based approaches, owing to hot cracking and void formation during solidification. Here, the use of an emerging solid-state additive manufacturing technology, additive friction stir deposition, is explored for the repair of volume damages such as through -holes and grooves in 7075 aluminum alloy. Three repair experiments have been conducted: double through-hole filling, single through-hole filling, and long, wide-groove filling. In all experiments, additive friction stir deposition proves to be effective at filling the entire volume. Additionally, sufficient mixing between the deposited material and the side wall of the feature is always observed in the upper portions of the repair. Poor mixing and inadequate repair quality have been observed in deeper portions of the filling in some scenarios. Based on these observations, the advantages and disadvantages of using additive friction stir deposition for repairing volume damages are discussed. High quality and highly flexible repairs are expected with systematic optimization work on process control and repair strategy development in the future.
Affect of annealing on uniform and nonuniform strains in a sputtered Mo film on Si
Adler, Thomas; Houska, Charles R. (American Institute of Physics, 1979)
Sputtered films of 1.5 μm of Mo deposited on (111) ‐oriented Si failed either by blistering or localized eruptions after various thermal treatments. Investigations were carried out to determine the amount of strain in the film associated with this unstable mechanical behavior. Two types of measurements were employed. One employs macroscopic interferometer measurements to measure deflection and the other x‐ray diffraction. A separation is made of intrinsic and thermally induced strains. The intrinsic strains are believed to be due mainly to Ar atoms embedded during sputtering which remain throughout annealing treatments. These atoms also introduce a broadening of the diffraction lines because of the special constraints associated within films. This effect is separated from the usual line broadening due to dislocations and small particle size. Annealing treatments reconfirm that dislocation mechanisms are not as effective in relieving nonuniform microstrain in films as they are in cold‐work filings of the same material.
Aging and slow dynamics in SrxBa1-xNb2O6
Chao, L. K.; Colla, Eugene V.; Weissman, Michael B.; Viehland, Dwight D. (American Physical Society, 2005-10-10)
The uniaxial "relaxor" ferroelectric SrxBa1-xNb2O6 (SBN) is found to crossover from holelike to cumulative aging as it is cooled into the frozen relaxor regime. The cumulative aging contrasts sharply with the behavior of cubic relaxors, supporting ideas that the spin-glasslike aging in cubic relaxors is connected with polarization components orthogonal to the net ferropolarization. In the relaxor regime, small dc fields are found to suppress much of the dissipative response, similar to long-time aging. Pyroelectric currents are measured, along with limits on pyroelectric noise, allowing limits to be set on dynamically coherent domain sizes. Large nonlinear susceptibilities are found near the freezing transition.
Aging associated domain evolution in the orthorhombic phase of < 001 > textured (K0.5Na0.5)Nb0.97Sb0.03O3 ceramics
Yao, Jianjun; Li, Jiefang; Viehland, Dwight D.; Chang, Y. F.; Messing, G. L. (AIP Publishing, 2012-03-01)
Aging effect due to domain evolution in (K-0.5,Na-0.5)Nb0.97Sb0.03O3 < 001 > textured ceramics was investigated by piezoresponse force microscopy. We find that aging effect is pronounced in the orthorhombic single phase field. A more uniform and finer domain structure on the order of several hundred nanometers was observed after aging and is believed to originate from defect-migration. After poling, large domains (similar to 10 mu m) with smooth boundaries were found in the aged condition due to the more readily redistribution of uniform and finer domain structures after aging. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3698154]
Alternating and direct current field effects on the structure-property relationships in Na0.5Bi0.5TiO3-x% BaTiO3 textured ceramics
Ge, Wenwei; Maurya, Deepam; Li, Jiefang; Priya, Shashank; Viehland, Dwight D. (AIP Publishing, 2013-06-01)
The influence of alternating (ac) and direct current (dc) fields on the structural and dielectric properties of [001](PC) textured Na0.5Bi0.5TiO3-7%BaTiO3 (NBT-7%BT) ceramics has been investigated. X-ray diffraction measurements revealed that the depolarization at temperature T-d in poled samples resulted from a tetragonal -> pseudo-cubic transition on heating. Moderate ac drive and dc bias had opposite influences on T-d: ac drive decreased the T-d, whereas dc bias increased it. These investigations suggested an effective method to expand the working temperature range of NBT-x%BT textured ceramics to a high temperature. (C) 2013 AIP Publishing LLC.
Anatomy of vertical heteroepitaxial interfaces reveals the memristive mechanism in Nb2O5-NaNbO3 thin films
Li, Linglong; Lu, Lu; Wang, Zhiguang; Li, Yanxi; Yao, Yonggang; Zhang, Dawei; Yang, Guang; Yao, Jianjun; Viehland, Dwight D.; Yang, Yaodong (Springer Nature, 2015-03-18)
Dynamic oxygen vacancies play a significant role in memristive switching materials and memristors can be realized via well controlled doping. Based on this idea we deposite Nb2O5-NaNbO3 nanocomposite thin films on SrRuO3-buffered LaAlO3 substrates. Through the spontaneous phase separation and self-assembly growth, two phases form clear vertical heteroepitaxial nanostructures. The interfaces between niobium oxide and sodium niobate full of ion vacancies form the conductive channels. Alternative I-V behavior attributed to dynamic ion migration reveals the memristive switching mechanism under the external bias. We believe that this phenomenon has a great potential in future device applications.
Anhysteretic field-induced rhombhohedral to orthorhombic transformation in <110>-oriented 0.7Pb(Mg1/3Nb2/3)O-3-0.3PbTiO(3) crystals
Viehland, Dwight D.; Li, Jiefang (American Institute of Physics, 2002-12-15)
The electric-field induced polarization (P-E) and strain (epsilon-E) characteristics of <110>(c)-oriented 0.7Pb(Mg1/3Nb2/3)O-3-0.3PbTiO(3) crystals have been investigated, under both unipolar and bipolar drive. A field-induced transformation was observed below saturation. Under unipolar drive, the P-E and epsilon-E loops were anhysteretic even at the transformation point, demonstrating complete reversibility between ferroelectric rhombohedral and orthorhombic phases. The results show that "polarization rotation" can occur between <111>(c) and <110>(c), where the polarization is confined to the (100)(c) in a monoclinic M-b type symmetry. (C) 2002 American Institute of Physics.
Anisotropic hydrogen diffusion in alpha-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations
Zhang, Yongfeng; Jiang, Chao; Bai, Xianming (Springer Nature, 2017-01-20)
This report presents an accelerated kinetic Monte Carlo (KMC) method to compute the diffusivity of hydrogen in hcp metals and alloys, considering both thermally activated hopping and quantum tunneling. The acceleration is achieved by replacing regular KMC jumps in trapping energy basins formed by neighboring tetrahedral interstitial sites, with analytical solutions for basin exiting time and probability. Parameterized by density functional theory (DFT) calculations, the accelerated KMC method is shown to be capable of efficiently calculating hydrogen diffusivity in alpha-Zr and Zircaloy, without altering the kinetics of long-range diffusion. Above room temperature, hydrogen diffusion in alpha-Zr and Zircaloy is dominated by thermal hopping, with negligible contribution from quantum tunneling. The diffusivity predicted by this DFT + KMC approach agrees well with that from previous independent experiments and theories, without using any data fitting. The diffusivity along < c > is found to be slightly higher than that along < a >, with the anisotropy saturated at about 1.20 at high temperatures, resolving contradictory results in previous experiments. Demonstrated using hydrogen diffusion in alpha-Zr, the same method can be extended for on-lattice diffusion in hcp metals, or systems with similar trapping basins.
Annealing twins in nanocrystalline fcc metals: A molecular dynamics simulation
Farkas, Diana; Bringa, Eduardo M.; Caro, Alfredo (American Physical Society, 2007-05-23)
We report fully three-dimensional atomistic molecular dynamics studies of grain growth kinetics in nanocrystalline Cu of 5 nm average grain size. We observe the formation of annealing twins as part of the grain growth process. The grain size and energy evolution was monitored as a function of time for various temperatures, yielding an activation energy for the process. The atomistic mechanism of annealing twin formation from the moving boundaries is described.
Application of Sapphire-Fiber-Bragg-Grating-Based Multi-Point Temperature Sensor in Boilers at a Commercial Power Plant
Yang, Shuo; Homa, Daniel S.; Heyl, Hanna; Theis, Logan; Beach, John; Dudding, Billy; Acord, Glen; Taylor, Dwyn; Pickrell, Gary R.; Wang, Anbo (MDPI, 2019-07-21)
Readily available temperature sensing in boilers is necessary to improve efficiencies, minimize downtime, and reduce toxic emissions for a power plant. The current techniques are typically deployed as a single-point measurement and are primarily used for detection and prevention of catastrophic events due to the harsh environment. In this work, a multi-point temperature sensor based on wavelength-multiplexed sapphire fiber Bragg gratings (SFBGs) were fabricated via the point-by-point method with a femtosecond laser. The sensor was packaged and calibrated in the lab, including thermally equilibrating at 1200 °C, followed by a 110-h, 1000 °C stability test. After laboratory testing, the sensor system was deployed in both a commercial coal-fired and a gas-fired boiler for 42 days and 48 days, respectively. The performance of the sensor was consistent during the entire test duration, over the course of which it measured temperatures up to 950 °C (with some excursions over 1000 °C), showing the survivability of the sensor in a field environment. The sensor has a demonstrated measurement range from room temperature to 1200 °C, but the maximum temperature limit is expected to be up to 1900 °C, based on previous work with other sapphire based temperature sensors.
Behavior of Random Hole Optical Fibers under Gamma Ray Irradiation and Its Potential Use in Radiation Sensing Applications
Alfeeli, Bassam; Pickrell, Gary R.; Garland, Marc; Wang, Anbo (MDPI, 2007-05-24)
Effects of radiation on sensing and data transmission components are of greatinterest in many applications including homeland security, nuclear power generation, andmilitary. A new type of microstructured optical fiber (MOF) called the random hole opticalfiber (RHOF) has been recently developed. The RHOFs can be made in many differentforms by varying the core size and the size and extent of porosity in the cladding region.The fibers used in this study possessed an outer diameter of 110 _m and a core ofapproximately 20 _m. The fiber structure contains thousands of air holes surrounding thecore with sizes ranging from less than 100 nm to a few _m. We present the first study ofthe behavior of RHOF under gamma irradiation. We also propose, for the first time to ourknowledge, an ionizing radiation sensor system based on scintillation light from ascintillator phosphor embedded within a holey optical fiber structure. The RHOF radiationresponse was compared to normal single mode and multimode commercial fibers(germanium doped core, pure silica cladding) and to those of radiation resistant fibers (puresilica core with fluorine doped cladding fibers). The comparison was done by measuringradiation-induced absorption (RIA) in all fiber samples at the 1550 nm wavelength window(1545 25 nm). The study was carried out under a high-intensity gamma ray field from a 60Co source (with an exposure rate of 4x104 rad/hr) at an Oak Ridge National Laboratory gamma ray irradiation facility. Linear behavior, at dose values less than 106 rad, was observed in all fiber samples except in the pure silica core fluorine doped cladding fiber which showed RIA saturation at 0.01 dB. RHOF samples demonstrated low RIA (0.02 and 0.005 dB) compared to standard germanium doped core pure silica cladding (SMF and MMF) fibers. Results also showed the possibility of post-fabrication treatment to improve the radiation resistance of the RHOF fibers.
Bias-field effect on the temperature anomalies of dielectric permittivity in PbMg1/3Nb2/3O3-PbTiO3 single crystals
Raevski, I. P.; Prosandeev, S. A.; Emelyanov, A. S.; Raevskaya, S. I.; Colla, Eugene V.; Viehland, Dwight D.; Kleemann, W.; Vakhrushev, S. B.; Dellis, J. L.; El Marssi, M.; Jastrabik, L. (American Physical Society, 2005-11-16)
In contrast to ordinary ferroelectrics where the temperature T-m of the permittivity maximum monotonically increases with bias field E in (1-x)PbMg1/3Nb2/3O3-(x)PbTiO3 (0 <= x <= 0.35) single crystals, T-m was found to remain constant or to decrease with E up to a certain threshold field E-t, above which T-m starts increasing. The threshold field E-t decreases with increasing x, tending toward zero at approximately x=0.4. We explain this dependence in the framework of models which take into account quenched random fields and random bonds. For crystals with 0.06 <= x <= 0.13, the E-T phase diagrams are constructed. In contrast to PMN, they exhibit an additional, nearly field-independent boundary, in the vicinity of the Vogel-Fulcher temperature. We believe this boundary to correspond to an additional phase transition and the appearing order parameter is likely to be nonpolar.
Bridging domain mechanism for phase coexistence in morphotropic phase boundary ferroelectrics
Rao, W. F.; Wang, Yu. U. (AIP Publishing, 2007-04-01)
Computer modeling and simulation reveals a bridging domain mechanism that explains the phase coexistence commonly observed around the morphotropic phase boundaries of ferroelectric solid solutions. The simulation takes into account the important role of coupled ferroelectric and ferroelastic domain microstructures in phase coexistence phenomenon. It shows that minor domains of metastable phase spontaneously coexist with and bridge major domains of stable phase to reduce total system free energy, including bulk free energy, domain wall energy, and long-range electrostatic and elastostatic energies. The existence of bridging domains also explains the enhanced piezoelectric response in the vicinity of morphotropic phase boundaries. (C) 2007 American Institute of Physics.
Broadening of x‐ray diffraction lines from small subgrains containing gradients of spacing
Houska, Charles R. (American Institute of Physics, 1978)
Recent data on subgrain size and spacing gradients in the Cu‐Ni system allow a more critical examination of a technique currently used to obtain the composition profiles of small diffusion zones. These data support the assumption that the broadening from individual subgrains need not include a spacing gradient term when volume diffusion is predominant. However, care should be taken in the interpretation of the earliest stage of diffusion where grain boundaries,surface, and other defects may introduce large spacing gradients.
Calculation of x‐ray intensity from a rough sample based on a statistical model
Hwang, Bing; Houska, Charles R. (American Institute of Physics, 1988-06-01)
An x‐ray intensity correction is developed which begins with a roughness model that is often used to describe real surfaces. This is based upon a normal distribution of surface asperities relative to a mean plane. Pair correlation between absorbing elements along x‐ray paths either entering or leaving the sample with respect to the signal producing element is accomplished by means of an exponential autocorrelation function. This allows the degree of roughness to be varied on a local scale to fit specific surfaces using statistical data. Equations are developed to describe x‐ray fluorescence and diffraction signals for symmetric and asymmetric beam optics. Theory is compared with experiment using a roughened, fully stabilized zirconia sample.
Carrier capture delay and modulation bandwidth in an edge-emitting quantum dot laser
Asryan, Levon V.; Wu, Y. C.; Suris, R. A. (AIP Publishing, 2011-03-01)
We show that the carrier capture from the optical confinement layer into quantum dots (QDs) can strongly limit the modulation bandwidth omega(-3) dB of a QD laser. As a function of the cross-section sigma(n) of carrier capture into a QD, omega(-3) dB asymptotically approaches its highest value when sigma(n) -> infinity the case of instantaneous capture). With reducing sigma(n), omega(-3) dB decreases and becomes zero at a certain nonvanishing sigma(n)(min). The use of multiple-layers with QDs significantly improves the laser modulation response-omega(-3) dB is considerably higher in a multilayer structure as compared to a single-layer structure at the same dc current. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3571295]
Characterization and elimination of dry etching damaged layer in Pt/Pb(Zr0.53Ti0.47)O-3/Pt ferroelectric capacitor
Lee, J. K.; Kim, T. Y.; Chung, Ilsub; Desu, Seshu B. (AIP Publishing, 1999-07-01)
The damage of Pb(Zr0.53Ti0.47)O-3 thin film due to dry etching process was characterized in terms of the microstructure and electrical properties. The damaged layer seems to be amorphous and the thickness of the damaged layer is about 10 nm. The existence of such a layer in Pt/Pb(Zr0.53Ti0.47)O-3/Pt ferroelectric capacitor tends to increase the coercive voltage and the leakage current. The damaged layer was not fully reverted to perovskite phase by the thermal annealing. With the wet cleaning treatment, however, the damaged layer was successfully removed thereby revealing significantly improved electrical properties. (C) 1999 American Institute of Physics. [S0003-6951(99)00529-X].
Characterization of magnetoelectric laminate composites operated in longitudinal-transverse and transverse-transverse modes
Dong, Shuxiang; Li, Jiefang; Viehland, Dwight D. (American Institute of Physics, 2004-03-01)
Magnetostrictive and piezoelectric laminate composites of terfenol-D and Pb(Zr1-xTix)O-3 have been studied. The magnetoelectric (ME) coefficients have been characterized for the different operational modes: (i) a longitudinally magnetized and transversely polarized longitudinal transverse (LT) mode, and (ii) a transversely magnetized and transversely polarized transverse-transverse (TT) mode. The results demonstrate that the (LT) magnetoelectric mode has dramatically higher ME coefficients than the TT one. The LT magnetoelectric coefficient is up to 5-7 times larger than the TT one, when operated in low magnetic bias ranges. (C) 2004 American Institute of Physics.

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