@article{thiagarajan_wang_bradford_zhu_yuan_2014, title={Stabilizing carbon nanotube yarns using chemical vapor infiltration}, volume={90}, ISSN={["1879-1050"]}, DOI={10.1016/j.compscitech.2013.10.008}, abstractNote={Carbon nanotube (CNT) yarns exhibit high strength, low density, and relatively good conductivity and piezoresistivity, which makes them an ideal candidate for many advanced applications such as reinforcements for multifunctional composites. However, CNT yarns usually lack the required property stability under load. In this paper a method for stabilizing CNT yarn using chemical vapor infiltration (CVI) to infiltrate and deposit pyrocarbon into CNT yarns is reported. The deposited pyrocarbon effectively binds neighboring CNTs to inhibit inter-nanotube sliding under load, which consequently stabilize the CNT yarns. Relaxation tests showed that compared to pristine CNT yarns, the stabilized yarns have higher electrical stability as well as load retention (∼93% versus ∼61%). There was also a concomitant increase in density along with improved electrical conductivity, mechanical strength and stiffness. Furthermore, under sonication the CVI treated yarns resisted disintegration, making them suitable for electrochemical applications.}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Thiagarajan, V. and Wang, X. and Bradford, P. D. and Zhu, Y. T. and Yuan, F. G.}, year={2014}, month={Jan}, pages={82–87} }
 @article{wang_ma_bliss_isler_becla_2007, title={Combining static and rotating magnetic fields during modified vertical bridgman crystal growth}, volume={21}, ISSN={["1533-6808"]}, DOI={10.2514/1.28772}, abstractNote={Static magnetic fields have been widely used to control the heat and mass transfer during crystal growth, whereas rotating magnetic fields are attracting a growing attention for crystal-growth technologies from the melt A combination of static and rotating magnetic fields can be used to control the transport phenomena during semiconductor crystal growth. This paper treats the flow of molten gallium-antimonide and the dopant transport during the vertical Bridgman process using submerged heater growth in this combination of externally applied fields. This paper investigates the effects of these fields on the transport in the melt and on the dopant distributions in the crystal.}, number={4}, journal={JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER}, author={Wang, X. and Ma, N. and Bliss, D. F. and Isler, G. W. and Becla, P.}, year={2007}, pages={736–743} }
 @article{wang_ma_2007, title={Semiconductor crystal growth by the vertical Bridgman process with transverse rotating magnetic fields}, volume={129}, ISSN={["1528-8943"]}, DOI={10.1115/1.2352790}, abstractNote={During the vertical Bridgman process, a single semiconductor crystal is grown by the solidification of an initially molten semiconductor contained in an ampoule. The motion of the electrically conducting molten semiconductor can be controlled with an externally applied magnetic field. This paper treats the flow of a molten semiconductor and the dopant transport during the vertical Bridgman process with a periodic transverse or rotating magnetic field. The frequency of the externally applied magnetic field is sufficiently low that this field penetrates throughout the molten semiconductor. Dopant distributions in the crystal are presented.}, number={2}, journal={JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME}, author={Wang, X. and Ma, N.}, year={2007}, month={Feb}, pages={241–243} }
 @article{wang_ma_2006, title={Bridgman-Stockbarger growth of binary alloyed semiconductor crystals with steady magnetic fields}, volume={20}, ISSN={["1533-6808"]}, DOI={10.2514/1.15584}, abstractNote={Single crystals of alloyed compound semiconductor crystals such as gallium‐aluminum‐antimonide are needed for optoelectronic devices. These crystals are solidified from a solution of molten gallium‐antimonide and aluminum‐antimonide in a Bridgman‐Stockbarger furnace. During the growth of alloyed semiconductor crystals, the solute’s concentration is not small so that the density differences in the melt are very large. These compositional variations drive compositionally driven buoyant convection, or solutal convection, in addition to thermally driven buoyant convection. These buoyant convections drive convective species transport, which produce nonuniformities in the concentration in both the melt and the crystal. A numerical model is presented for the unsteady transport for the growth of alloyed semiconductor crystals during the vertical Bridgman‐Stockbarger process with a steady axial magnetic field. Predictions of alloy concentration in the crystal and in the melt at several different stages during crystal growth are presented.}, number={2}, journal={JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER}, author={Wang, X and Ma, N}, year={2006}, pages={313–319} }
 @article{wang_ma_bliss_iseler_becla_2006, title={Comparing modified vertical gradient freezing with rotating magnetic fields or with steady magnetic and electric fields}, volume={287}, ISSN={["1873-5002"]}, DOI={10.1016/j.jcrysgro.2005.11.036}, abstractNote={This investigation treats the flow of molten gallium-antimonide and the dopant transport during the vertical gradient freezing process using submerged heater growth. A rotating magnetic field or a combination of steady magnetic and steady electric fields is used to control the melt motion. This paper compares the effects of these externally applied fields on the transport in the melt and on the dopant segregation in the crystal. Crystal growth in a combination of steady magnetic and electric fields produces a crystal with more radial and axial dopant homogeneity than growth in a rotating magnetic field.}, number={2}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Wang, X and Ma, N and Bliss, DF and Iseler, GW and Becla, P}, year={2006}, month={Jan}, pages={270–274} }
 @article{wang_ma_bliss_iseler_becla_2006, title={Parametric study of modified vertical bridgman growth in a rotating magnetic field}, volume={20}, ISSN={["1533-6808"]}, DOI={10.2514/1.19572}, abstractNote={Using the vertical Bridgman process, a single semiconductor crystal is grown by the solidification of an initially molten semiconductor (melt) contained in a crucible. In addition to the main Bridgman heater, a submerged heater is added that separates the melt into two zones, i.e., an upper melt and a lower melt that is continuously replenished with fluid from the upper melt to offset the rejection of species along the crystal-melt interface. As crystal growth progresses, the crucible is slowly lowered to maintain a constant lower melt depth. An externally applied rotating magnetic field produced by a synchronous motor stator is used to control the transport of the electrically conducting molten semiconductor. This paper treats the flow of a molten semiconductor and the dopant transport during the vertical Bridgman process with a submerged heater and with a transverse rotating magnetic field. This paper also investigates the effects of the crystal radius, the melt depth, the strength of the magnetic field, and the number of poles in the inductor on the dopant distributions in the crystal.}, number={3}, journal={JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER}, author={Wang, X. and Ma, N. and Bliss, D. F. and Iseler, G. W. and Becla, P.}, year={2006}, pages={384–388} }
 @article{wang_ma_bliss_iseler_2006, title={Solute segregation during modified vertical gradient freezing of alloyed compound semiconductor crystals with magnetic and electric fields}, volume={49}, ISSN={["1879-2189"]}, DOI={10.1016/j.ijheatmasstransfer.2006.03.008}, abstractNote={Single crystals of gallium–aluminum–antimonide are solidified from a solution of molten gallium–antimonide and aluminum–antimonide. Electromagnetic stirring can be induced in the melt by applying a weak electric field together with a weak axial magnetic field. This paper presents a numerical model which uses a Chebyshev spectral collocation method with a second-order implicit time integration scheme with Gauss–Lobatto collocation points. This investigation models the unsteady motion and solute transport during vertical gradient freezing by submerged heater growth with electromagnetic stirring. The radial homogeneity in the crystal improves as the solute’s concentration increases.}, number={19-20}, journal={INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER}, author={Wang, X. and Ma, N. and Bliss, D. F. and Iseler, G. W.}, year={2006}, month={Sep}, pages={3429–3438} }
 @article{wang_ma_bliss_iseler_2005, title={A numerical investigation of dopant segregation by modified vertical gradient freezing with moderate magnetic and weak electric fields}, volume={43}, number={12-Nov}, journal={International Journal of Engineering Science}, author={Wang, X. and Ma, N. and Bliss, D. F. and Iseler, G. W.}, year={2005}, pages={908–924} }
 @article{wang_ma_2005, title={Numerical model for Bridgman-Stockbarger crystal growth with a magnetic field}, volume={19}, ISSN={["1533-6808"]}, DOI={10.2514/1.13307}, abstractNote={This paper presents a model for the unsteady species transport for the growth of doped semiconductor crystals during the vertical Bridgman‐Stockbarger process with a steady axial magnetic field. This dilute species transport depends on the convective and diffusive species transport of the dopant. This convective species transport is driven by buoyant convection in the melt, which produces compositional nonuniformities in both the melt and the crystal. This transient model predicts the distribution of species in the entire crystal grown in a steady axial magnetic field. The present study presents results of concentration in the crystal and in the melt at several different stages during crystal growth. I. Introduction D URING crystal growth without a magnetic field or with a weak magnetic field, turbulent or oscillatory melt motions can produce undesirable spatial oscillations of the concentration, or microsegregation, in the crystal. 1 Turbulent or oscillatory melt motions lead to fluctuations in the heat transfer across the growth interface from the melt to the crystal. Because the local rate of crystallization depends on the balance between the local heat fluxes in the melt and the crystal, fluctuations in the heat flux from the melt create fluctuations in the local growth rate, which create microsegregation. A moderate magnetic field can be used to create a body force that provides an electromagnetic (EM) damping of the melt motion can to eliminate oscillations in the melt motion and thus in the concentration of the crystal. Unfortunately, the elimination of mixing and a moderate or strong EM damping of the residual melt motion can lead to a large variation of the crystal’s composition in the direction perpendicular to the growth direction (radial macrosegregation). On the other hand, if the magnetic field strength is so strong that the melt motion is reduced sufficiently so that it has no effect on the composition in the crystal, then this diffusion-controlled species transport can produce a radially and axially uniform composition in the crystal grown. 2 To achieve diffusion-controlled species trans�}, number={3}, journal={JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER}, author={Wang, XH and Ma, N}, year={2005}, pages={406–412} }
 @article{wang_ma_bliss_iseler_2005, title={Semiconductor crystal growth by modified vertical gradient freezing with electromagnetic stirring}, volume={19}, ISSN={["1533-6808"]}, DOI={10.2514/1.10279}, abstractNote={This paper presents a numerical model for the unsteady transport of a dopant during the VGF process by submerge d heater growth with a steady axial magnetic field and a steady radial electric current. Electromagnetic (EM) stirring can be induced in the gallium antimonide melt just above the crystal growth interface by applying a small radial electric current in the melt together with an axial magnetic field. The application of EM stirring provides a significant convective dopant transport in the melt so that the crystal solidifies with relatively good radial homogeneity. Dopant distributions in the crystal and in th e melt at several different stages during growth are presented.}, number={1}, journal={JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER}, author={Wang, XH and Ma, N and Bliss, DF and Iseler, GW}, year={2005}, pages={95–100} }
 @inproceedings{wang_ma_bliss_iseler_2005, title={Semiconductor crystal growth by modified vertical gradient freezing with electromagnetic stirring}, volume={2005-0916}, number={2005 Jan.}, booktitle={AIAA 43rd Aerospace Sciences Meeting and Exhibit, Reno, NV, Jan. 2005}, author={Wang, X.-H. and Ma, N. and Bliss, D. F. and Iseler, G. W.}, year={2005} }
 @article{holmes_wang_ma_bliss_iseler_2005, title={Vertical gradient freezing using submerged heater growth with rotation and with weak magnetic and electric fields}, volume={26}, number={5}, journal={International Journal of Heat and Fluid Flow}, author={Holmes, A. M. and Wang, X. and Ma, N. and Bliss, D. F. and Iseler, G. W.}, year={2005}, pages={792–800} }
 @article{wang_ma_2004, title={Strong magnetic field asymptotic model for binary alloyed semiconductor crystal growth}, volume={18}, ISSN={["1533-6808"]}, DOI={10.2514/1.11905}, abstractNote={We present an asymptotic model for the unsteady species transport during bulk growth of alloyed semiconductor crystals with a transverse magnetic field. During growth of alloyed semiconductors such as germanium-silicon (GeSi), the solute's concentration is not small, so that density differences in the melt are very large. These compositional variations drive compositionally driven buoyant convection, or solutal convection, in addition to thermally driven buoyant convection. These buoyant convections drive convective transport, which produces nonuniformities in the concentration in both the melt and the crystal. This transient model predicts the melt motion and the distribution of species for a crystal grown in a strong transverse magnetic field}, number={4}, journal={JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER}, author={Wang, X and Ma, N}, year={2004}, pages={476–480} }