K. Salama

University of Houston, Houston, Texas, United States

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Publications (240)393.75 Total impact

  • Sameer Ghalsasi · Goran Majkic · Kamel Salama
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    ABSTRACT: We present results of a study aimed at understanding the formation of BaZrO<sub>3</sub> (BZO) precipitates in YBCO using the TFA-MOD process, as well as optimizing the BZO concentration with respect to the flux pinning performance. A reference YBCO sample containing no BZO, as well as three samples containing 4, 5 and 6% BZO were made and characterized with respect to in-field critical current ( IC ) performance and angular field IC dependence. Furthermore, the samples were analysed using transmission electron microscopy to identify the morphology of pinning precipitates and correlate it to the flux pinning behavior. The introduction of BZO does not result in formation of c-axis peaks in the angular field IC behavior, but rather in considerable widening of the ab-plane peaks in the field angular IC behavior with increasing BZO content, as well as in decreased field-angular anisotropy of IC . This behavior is analysed and correlated to the underlying microstructure of pinning precipitates.
    No preview · Article · Jul 2011 · IEEE Transactions on Applied Superconductivity
  • K. Zhang · Y. L. Yang · A. J. Jacobson · K. Salama
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    ABSTRACT: The effects of microstructure on the oxygen permeation in SrCo0.8Fe0.2O3-δ(SCFO) and La0.2 Sr0.8 Fe0.8Cr0.2 O3 (LSFCO) was investigated using disc samples fabricated under different processing conditions. The microstructure of LSFCO remained unchanged when the sintering temperature was increased from 1300 to 1450 °C, but the average grain size of SCFO increased considerably when the sintering temperature was increased from 930 to 1200 °C. The change in grain size was found to have a strong effect on the oxygen permeation flux in SCFO, which increased considerably as the grain size was decreased. This indicates that the contribution of the grain boundary diffusion to the steady state oxygen flux in SCFO is substantial and grain boundaries provide faster diffusion paths in oxygen permeation through the samples.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
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    ABSTRACT: Dc magnetic field, temperature, and magnetic history dependencies of the millimeter-wave surface resistance have been measured in high quality grain-aligned and in polycrystalline YBa2Cu3Ox bulk material. The measurements were carried at 75 GHz using the endplate of the cavity replacement method. The data is interpreted in terms of the presence of intra- and inter-grain types of weak links. The values of characteristic critical fields of the bulk and the weak link junctions are determined and discussed.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • K. Salama · S. Sathyamurthy · M. Mironova
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    ABSTRACT: In this paper, the feasibility of applying solution deposition processes for the fabrication of coated conductors has been explored. The crystal and chemical compatibility of the buffer layers processed using metallorganic decomposition with the Y123 deposition using the trifluoroacetate process has been studied. Two buffer layer materials have been used, namely, barium zirconate and strontium titanate. The measured superconducting properties of these conductors were correlated with the microstructure observed on these samples using SEM and cross-sectional TEM. In case of barium zirconate buffer layers, though there exists a very good structural and chemical compatibility between the buffer layer and the Y123, the presence of surface defects in the buffer layer causes compositional heterogeneity and randomly oriented grains in the Y123 film. This leads to poor superconducting properties. In case of strontium titanate buffer layers, due to the excellent crystal and chemical compatibility, and the absence of surface defects, high critical current densities (of the order of 106 A/cm2 at 77K and self field) were obtained. However, TEM cross section studies reveals the presence of a significant portions of a-oriented Y123 crystallites which could lead to lower critical current densities. Further studies of the TFA process is required to eliminate the occurrence of a-oriented Y123 in the microstructure. This could lead to further improvements in the properties.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • Yu X. Zhou · Wai Lo · Tong B. Tang · Kamel Salama
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    ABSTRACT: Levitation force and magnetic field trapping are the most important properties of YBCO large grain materials. They are dependent on the pinning force exerting on the magnetic flux lines by various crystal defects in YBCO. In this paper, Ga-doped bulk YBCO samples were fabricated by SmBCO seeded melt-growth process. The levitation force and trapped field were enhanced by the introduce of nanometer scale week superconducting regions which are formed by the Ga partially substituting for Cu on the Cu-O chain.
    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • V. Selvamanickam · K. Salama

    No preview · Article · Jan 2011 · MRS Online Proceeding Library
  • N. Chennoufi · G. Majkic · Y. C. Chen · K. Salama
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    ABSTRACT: We present a method for spark plasma sintering (SPS) with reduced thermal and electrical losses compared to all-graphite SPS. Relative to the all-graphite configuration, the present design significantly reduces both the required power input and total current for the same synthesis temperature (e.g., 7.5 vs 0.6 kW and 1530 vs 350 A at 900 oC). These reductions allow for significantly smaller power source and process chamber, drastic reduction in energy consumption, easier thermal management, and enhanced synthesis/homogenization by eliminating die “leakage” currents, allowing for maximization of current density and its intrinsic effect on homogenization by diffusion. A finite element (FE) model solution for temperature and current distributions, as well as thermal losses for both the present and the all-graphite SPS setups, is presented and compared to experimental results.
    No preview · Article · Oct 2009 · Metallurgical and Materials Transactions A
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    ABSTRACT: Combined twist and tensile loading states are expected in many applications of YBCO coated conductors. Wire twist is introduced due to winding on complex shapes or for AC loss reduction, while tensile loading originates from sources such as differential thermal expansion and inertial forces. In this study, we analyse the electromechanical behavior of an IBAD/MOCVD YBCO coated conductor configuration with the superconducting layer deposited on hastelloy substrate and encapsulated by copper. The effect of pre-applied twist on degradation of current carrying capability as a function of tensile stress was studied via experimental measurements on tapes with 1 micron thick YBCO layer and 50 micron thick hastelloy substrate at 77 K. In addition, the stress states under pure torsion are modeled using continuum mechanics. Both numerical and approximate analytical solutions are presented, and the stress and strain distributions as a function of applied twist angle are analysed.
    No preview · Article · Jul 2009 · IEEE Transactions on Applied Superconductivity
  • Jin Chen · Yuxiang Zhou · S. Ghalsasi · I. Rusakova · Kamel Salama
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    ABSTRACT: This paper describes a promising route to introduce columnar defects into YBCO films by chemical doping process. A series of Y<sub>2</sub>O<sub>3</sub> and BaZrO<sub>3</sub> doped YBCO films were fabricated by a TFA_MOD process. The J<sub>c</sub> of Y<sub>2</sub>O<sub>3</sub> doped YBCO film was found to be larger than that of pure YBCO film at all fields though no columnar defects were observed. On the other hand, high density nanoscale Zr enriched columnar defects were successfully achieved in Zr-doped YBCO. The size of these defects was as small as 10 nm. Effects of heat treatment temperatures (760<sup>deg</sup>C ~ 820<sup>deg</sup>C), dwell times (0.5 h ~ 3 h) and partial pressures of oxygen (0 ~ 1%) on defects formation in BaZrO<sub>3</sub> doped YBCO were investigated. It was found that the formation of columnar defects depends on process conditions. Films with such nanoscale columnar defects exhibited a significant enhancement of J<sub>c</sub> at all fields. Maximum pinning force density exceeding 8 GN m<sup>-3</sup> was obtained in 5% BZO-doped YBCO films.
    No preview · Article · Jul 2009 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: The effects of thermal neutron irradiation and excess oxygen on the properties of Ti-sheathed MgB<sub>2</sub> wires were investigated separately in this paper. No significant influence was observed when thermal neutron irradiation with fluence levels of 1.23 times 10<sup>14</sup> and 5.75 times 10<sup>14</sup> cm<sup>-2</sup> were applied on the sample, while fluence level of 3.16 times 10<sup>15</sup> cm<sup>-2</sup> provided a strong suppression of in-field critical current density. Excess oxygen in sample preparation process had negative effect on the properties of the MgB<sub>2</sub> wires. The samples prepared in air possessed lower critical temperature and in-field current carrying capability in comparison with the sample prepared in glove box.
    Full-text · Article · Jul 2009 · IEEE Transactions on Applied Superconductivity
  • Source
    Hui Fang · M. Alessandrini · C. Hoyt · G. Liang · B. Lv · K. Salama
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    ABSTRACT: Ti-sheathed MgB<sub>2</sub> wires doped with different amount of TiC nanoparticles were investigated. X-ray diffraction pattern suggested the existence of TiC<sub>0.59</sub> phase and carbon incorporation into MgB<sub>2</sub> lattice to form Mg(B<sub>1-x</sub>C<sub>x</sub>)<sub>2</sub>. Strong enhancement of in-field current carrying capability was observed on 2.5% TiC doped sample. The temperature effect was also studied. It was found that 850<sup>deg</sup>C was the optimized annealing temperature.
    Full-text · Article · Jul 2009 · IEEE Transactions on Applied Superconductivity
  • Sameer V. Ghalsasi · Y.X. Zhou · J. Chen · I. Rusakova · B. Lv · Kamel Salama
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    ABSTRACT: Fabrication of thick YBa<sub>2</sub>Cu<sub>3</sub>O<sub>y</sub> (YBCO) films with high critical current densities(J<sub>c</sub>) has remained one of the major challenges in the coated conductor development process. In this work, we report successful fabrication of several multi-layer YBCO films with thicknesses ranging from 0.1 micrometers to 1.2 micrometers. The films were deposited on a single crystal substrate by using a multi-layer TFA-MOD technique. The effect of variation in the thickness of an individual layer in a multi-layer film on the overall properties of the film was studied by processing multi-layer films with individual layers of 0.1 micrometers, 0.2 micrometers and 0.5 micrometers. The J<sub>c</sub> value for the 0.1 micrometers thick single-layer film was as high as 7 MA/cm<sup>2</sup>, and the J<sub>c</sub> for 6-layer1.2 micrometers thick film was 1 MA/cm<sup>2</sup> at 77 K and self field. XRD, SEM and TEM were used to study the dependence of J<sub>c</sub> on the orientation, texture and microstructure of the film. It was found that the texture, connections between the two successive layers, porosity, and the crack formation affect the J<sub>c</sub> of the film. In addition, we report a multi layer fabrication route with a shorter duration of the pyrolysis reaction according to the number of coats.
    No preview · Article · Jul 2009 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: In order for superconducting coil applications to operate safely at high current densities, thermal stability of the wire must be addressed in terms of quench development and protection. In this study, we investigate quench propagation in stacks of commercially available MgB<sub>2</sub> superconducting wire taking into account both longitudinal heat transfer along the wire and transverse heat transfer across the insulation to adjacent wire segments. We present a two-dimensional Finite Element Method model, to simulate quench propagation. Wires and insulation layers are explicitly modeled as separate subdomains, where the wire domain takes into account the composite nature of these tapes. We report results for Minimum Quench Energy and Quench Propagation Velocity as a function of operating temperature and applied magnetic field. We also present a comparison of the behavior of the present model to alternative formulations where layers of tape and insulation are treated as a homogeneous single domain with lumped properties.
    No preview · Article · Jul 2009 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: We analyze the effect of Mn addition to Gd-substituted YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-delta</sub>(YBCO) on transport current and behavior under applied magnetic field. The high-temperature superconducting tapes were manufactured by ion-beam assisted deposition and metal organic chemical vapor deposition on hastelloy substrates. The field dependence measurements as a function of Mn concentration were performed in applied magnetic fields up to 1.5 T at 77 K. The dependence of critical current on the field angle was measured in the plane perpendicular to the sample longitudinal axis (current axis). The effect of Mn concentration on critical temperature is also reported. The results are characterized and discussed.
    No preview · Article · Jul 2009 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: The thermal stability of superconducting wires is one of the important issues for wire applications. We present a numerical study on the effect of the wire design parameters on the quench behavior of superconducting MgB2 wire employed in coils. The model considers a stack of MgB2 wires of rectangular cross section separated by insulation layers and subjected to a thermal disturbance. The problem is solved on a two-dimensional domain and employs the current sharing concept in the transition between superconducting and normal states. The effects of three design parameters in wire manufacturing are investigated. Quench behavior is compared for wires having different filling factor of superconducting filaments, different volume of copper stabilizer, and different residual resistivity ratio (RRR) values for copper. The results indicate that the quench propagation velocity (QPV) at 1.5 T is weakly affected by changes in the volume and electrical properties of copper, whereas the minimum quench energy (MQE) is strongly dependent on the RRR value of copper and can increase by a factor of nearly 2 with the RRR varying from 30 to 150. Both the MQE and QPV change remarkably by varying the MgB2 filling factor. The MQE drops by a factor of 6 and the QPV increases by a factor of 2 with the filling factor varying from 10.5% to 25%.
    No preview · Article · Feb 2009 · Superconductor Science and Technology
  • Phil T. Putman · Kamel Salama
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    ABSTRACT: In a coaxial magnetic brake, the changing field produced by movement of a solenoidal magnet induces a current in the wall of a conductive tube. The interaction of the field and current leads to a repulsive force that slows the motion of the magnet. We have tested the performance of this type of brake by firing a projectile carrying a permanent magnet into an aluminum tube. The results were compared to a model based on published theoretical results. The model was then used to predict braking distance for speeds and masses of interest in hypervelocity research, and it was found that brakes incorporating presently available superconducting materials are capable of stopping projectiles in practical distances. In addition, a new means of centering the projectile in the catch tube is presented, accompanied by a calculation of the centering force on the projectile, and high-speed photographs showing the alignment of a projectile with the brake tube.
    No preview · Article · Feb 2009 · IEEE Transactions on Magnetics
  • M. S. Bhuiyan · M. Paranthaman · K. Salama
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    ABSTRACT: The authors regret that text in sections 1 (Introduction) and 2 (Processing of CSD film) (pp R1-R7) in the above review article was reproduced from references 11 and 12 (Schwartz R W 1997 Chem. Mater. 9 2325 and Schwartz R W, Schneller T and Waser R 2004 C. R. Chim. 7 433) without the permission of the authors or the publishers. The primary author, a postdoctoral research associate, mistakenly thought that referencing the reproduced text and figures was sufficient; however, all authors take responsibility for failing to catch this error and obtain copyright permission from the publishers. We regret this unfortunate incident and we sincerely apologize to the authors, Dr Schneller, Dr Schwartz and Dr Waser; the publishers and readers for any inconvenience arising from this error.
    No preview · Article · Jan 2009 · Superconductor Science and Technology
  • Source
    Mina Hanna · Shufang Wang · Joan M Redwing · X X Xi · Kamel Salama
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    ABSTRACT: A study was performed to examine the Jc behavior as a function of thickness in MgB2 films fabricated by ex situ annealing at 840 °C of boron films, grown by chemical vapor deposition, in Mg vapor. The film thicknesses range between 300 nm and 10 µm. The values of Jc range from 1.2 × 107 A cm−2 for 300 nm to 1.9 × 105 A cm−2 for 10 µm film thicknesses at 20 K and self-field. The study shows that the critical current density (Jc) in MgB2 films decreases with increasing film thickness, similar to that observed in YBCO-coated conductors. Moreover, our study shows that critical current (Ic) reaches its maximum value of 728 A cm−1 width at ~1 µm thick MgB2 films at 20 K and self-field, which is, interestingly, the same thickness of pulsed-laser-deposited YBCO-coated conductors at which Ic reaches its maximum value. The high Jc values carried by our films show that the ex situ fabrication method can produce high quality MgB2 films at low processing temperatures, which is promising for RF cavity applications and coated-conductor wires and tapes.
    Full-text · Article · Dec 2008 · Superconductor Science and Technology
  • P.T. Putman · K. Salama
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    ABSTRACT: In a coaxial magnetic brake, the changing field produced by movement of a solenoidal magnet induces a current in the wall of a conductive tube. The interaction of the field and current leads to a repulsive force that slows the motion of the magnet. We have tested the performance of this type of brake by firing a projectile carrying a permanent magnet into an aluminum tube. The results were compared to a model based on published theoretical results. The model was then used to predict braking distance for speeds and masses of interest in hypervelocity research, and it was found that brakes incorporating presently available superconducting materials are capable of stopping projectiles in practical distances. In addition, a new means of centering the projectile in the catch tube is presented, accompanied by a calculation of the centering force on the projectile, and high-speed photographs showing the alignment of a projectile with the brake tube.
    No preview · Conference Paper · Jul 2008
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    ABSTRACT: Magnesium diboride has a great potential for magnet applications in many areas such as high energy physics, MRI, and space-related projects. The main goal of our ongoing research effort is to study magnet design, winding process, and magnet testing. Last year, in a 14 cm bore solenoid we reached a central magnetic flux density of 1 tesla at 16 K with almost 500 m of commercial multifilament tape. In order to design appropriate quench detection and protection systems, it is important to define the quench propagation characteristics in solenoids made with this superconductor. In this work we show our experimental activity, from winding to testing, with a 14 cm bore solenoid made with commercial multifilament MgB<sub>2</sub> tape. In particular we address a quench propagation study on a coil made with 2 m of the same tape.
    No preview · Article · Jul 2008 · IEEE Transactions on Applied Superconductivity

Publication Stats

4k Citations
393.75 Total Impact Points

Institutions

  • 1986-2011
    • University of Houston
      • • Department of Mechanical Engineering
      • • Texas Center for Superconductivity
      Houston, Texas, United States
  • 2009
    • Sam Houston State University
      • Department of Physics
      Хантсвилл, Texas, United States
  • 2008
    • Pennsylvania State University
      • Department of Physics
      University Park, Maryland, United States
  • 2002
    • University of Cambridge
      Cambridge, England, United Kingdom
  • 1998
    • Oak Ridge National Laboratory
      • Chemical Sciences Division
      Oak Ridge, Florida, United States
  • 1995
    • University of Wisconsin, Madison
      • Department of Materials Science and Engineering
      Mississippi, United States
  • 1990-1995
    • University of Texas Health Science Center at Houston
      Houston, Texas, United States
  • 1993
    • United States Naval Research Laboratory
      Washington, Washington, D.C., United States