scholarly journals Peculiar Magnetic Features and Superconductivity in Sulfur Doped Amorphous Carbon

2016 ◽  
Author(s):  
Israel Felner
Keyword(s):  
Amorphous Carbon ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Magnetic Behavior ◽  
Protective Atmosphere ◽  
Zero Field ◽  
Magnetic Studies ◽  
High Tc ◽  
Two Phases ◽  
Magnetic States

We report on magnetic studies of inhomogeneous commercial and synthesized amorphous carbon (a-C) and a-C doped with sulfur (a-CS) powders which exhibit (i) peculiar magnetic behavior and (ii) traces of two superconducting (SC) phase ~ Tc=33 and at 65 K. (i) The temperature dependence of zero-field-cooled (ZFC) curves measured up to room temperature show a well distinguish elusive peaks around 50-80 K, their origin is not yet known. These peaks are totally washed-out in the second ZFC sweeps and in the FC branches as well. As a result, in the vicinity of the peaks, the FC curves lie below the ZFC peaks (FC<ZFC), a phenomenon which is rarely observed. These magnetic anomalies are intrinsic properties of a-C and a-CS materials (ii) SC was observed in three different a-C sources: (a) The commercial a-C powder contains 0.21% of sulfur and it is suggested that two different a-CS phases (at 33 and 65 K) are the origin of the two SC states observed. The compositions of these two phases are not yet unknown. The small SC volume fractions of the 33 K phase can be enhanced by a solid reaction with additional sulfur at 250 ºC. (b) The synthesized a-C powder (obtained from decomposition of sucrose) is not SC. However, when mixed with sulfur and heated at 400 ºC under a protective atmosphere, the a-CS powder obtained also show traces of a SC phase at TC= 42 K. (c)The same occurs in a-C thin films. The as-grown films are not SC but a SC phase at Tc = 34 K emerges after the films were reacted with sulfur at elevated temperatures. It is concluded therefore, that all SC phases observed are due to different unknown a-CS phases. Since the a-C and a-CS powders possess SC and magnetic states, we believe that these powders resemble the high TC curates and Fe-As based systems in which the SC and the magnetic states are closed related to each other.

scholarly journals Magnetic studies of 0.7(Fe2O3)/0.3(ZnO) nanocomposites in nanopowder form and dispersed in polymer matrix

2016 ◽  
Vol 34 (2) ◽  
pp. 286-296 ◽  
Author(s):  
Janusz Typek ◽  
Kamil Wardal ◽  
Grzegorz Zolnierkiewicz ◽  
Anna Szymczyk ◽  
Nikos Guskos ◽  
...  
Keyword(s):  
Polymer Matrix ◽  
Magnetic Behavior ◽  
Magnetic Studies ◽  
Static Magnetization ◽  
Interparticle Interactions ◽  
Neat Polymer ◽  
Two Samples ◽  
Poly Ethylene ◽  
Two Phases ◽  
Average Size

AbstractMagnetic properties of 0.7(Fe2O3)/0.3(ZnO) nanocomposite synthesized by traditional wet chemistry method and containing only two phases: ZnO (nonmagnetic) and ZnFe2O4 (magnetic, with nanocrystallites of average size 12 nm, but forming large agglomerates, up to 100 nm in size) were studied by DC magnetization and ferromagnetic resonance (FMR). The investigated nanocomposite was either in a form of nanopowder or dispersed at concentration of 0.1 wt.% in poly(ethylene naphthalate-block-tetramethylene oxide) PTMO-b-PEN polymer matrix. Similarities and differences in magnetic behavior of these two samples revealed by the study of static magnetization and FMR spectra have been discussed relative to different morphologies and the associated variation of interparticle interactions. Moreover, thermal and thermo-oxidative stability of the nanocomposite and the neat polymer have been studied by thermogravimetric method.

Diffusion and Adhesion of Cu/Parylene

1990 ◽  
Vol 203 ◽  
Author(s):  
G. Yang ◽  
S. Dabral ◽  
L. You ◽  
H. Bakhrut ◽  
J. F. McDonald ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
Integrated Circuit ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Unit Length ◽  
High Vacuum ◽  
Diffusion Barriers ◽  
Cu Metallization ◽  
Dry Adhesion ◽  
Diffusion Characteristics

ABSTRACTThe combination of Cu and parylene (poly-p-xylylene) for metallization and insulator in integrated circuit or packaging multilayer interconnection systems gives one of the lowest resistance and capacitance values per unit length. In this paper we present a detailed study of the diffusion characteristics of Cu in parylene-n (PA-n) substrates. PA-n was vapor-deposited and Cu metallization performed at room temperature using the Partially Ionized Beam (PIB) technique. Rutherford Backscattering (RBS) technique has been used to study the diffusion of Cu in PA-n substrate after annealing the samples to elevated temperatures in vacuum. We found no sign of Cu diffusion after the Cu/PA-n sample was annealed at 300°C for 6 hours. Diffusion occurs at 350 °C. However, preannealed PA-n substrate prior to Cu deposition can prevent the diffusion even at a temperatures above 350°C. Also we found that amorphous carbon and chromium are good diffusion barriers of Cu on PA-n. The dry adhesion between PA-n deposited on Al, Cu and Ag was found to be good. The adhesion of these PIB deposited metals on PA-n in high vacuum was also very good.

Magnetic Behavior of Nanocomposites Prepared in a Vitreous Alumina Gel

1990 ◽  
Vol 206 ◽  
Author(s):  
R. D. Shull ◽  
J. J. Ritter ◽  
A. J. Shapiro ◽  
L. J. Swartzendruber ◽  
L. H. Bennett
Keyword(s):  
Magnetic Susceptibility ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Bulk Material ◽  
Magnetic Behavior ◽  
Subsequent Treatment ◽  
Ferric Nitrate ◽  
Fe Content ◽  
Alumina Gel ◽  
Aqueous Aluminum

ABSTRACTHomogeneous gelled composites of iron and vitreous alumina containing 10-40% Fe have been prepared by room temperature polymerization of aqueous aluminum alkoxide solutions containing ferric nitrate and nitric acid at low pH. Scanning electron microscopy, x-ray diffraction, and Mossbauer spectroscopy demonstrated that this bulk material is comprised of nanometer-sized regions of iron compounds embedded in a vitreous alumina gel matrix. Magnetization data showed that in the as-cured condition these nanocomposites are paramagnetic at room temperature and become either superparamagnetic or ferromagnetic on cooling to 10 K. The magnetic susceptibility increased with the Fe content and with decreasing temperature. Analysis of the temperature dependence of the magnetic susceptibility indicated the magnetic moment per Fe atom was 1.87 µB for the 10% Fe nanocomposite and that it increased linearly with composition to 1.96 µB for the 40% Fe material. Mössbauer effect data showed that subsequent treatment of these materials in a gaseous environment of hydrogen at elevated temperatures (T<400 C) changed the form of the iron in the magnetic regions. These results are compared to that observed for similar nanocomposites prepared using a silica gel matrix.

Thermal properties of nanocrystalline Al composites reinforced by AlN nanoparticles

2009 ◽  
Vol 24 (1) ◽  
pp. 24-31 ◽  
Author(s):  
Y.Q. Liu ◽  
H.T. Cong ◽  
H.M. Cheng
Keyword(s):  
Thermal Properties ◽  
Room Temperature ◽  
Significant Contribution ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
High Tc ◽  
Percolation Behavior ◽  
Potential Applications ◽  
Electronic Packaging Material

To explore potential applications of nanocomposites for microelectronic packaging, the thermal properties were investigated on newly developed nanocrystalline Al composites reinforced by AlN nanoparticles. It was found that the thermal conductivity (TC) is reduced with increasing AlN volume fraction (Vp), since connectivity of Al matrix is decreased by introduction of the nanoparticles. Although AlN nanoparticles introduce thermal resistance, they still have significant contribution to the TC of the composite as high-TC inclusion. Particularly, a percolation behavior of AlN nanoparticles is thought to occur with the threshold at 23–30%. Measurements at elevated temperatures (∼500 °C) show almost no distinct degradation of TC relative to room temperature. Moreover, the coefficient of thermal expansion (CTE) is remarkably lowered as Vp increases, e.g., from 26 × 10−6 to 13.9 × 10−6 K−1, by raising Vp to 39%. Therefore, the nanocomposites may be applicable as electronic packaging material, due to the combination of acceptable TC and low CTE.

Off-Axis Electron Holography of Self-Assembled Co Nanoparticle Rings

2007 ◽  
Vol 1026 ◽  
Author(s):  
Takeshi Kasama ◽  
Rafal E. Dunin-Borkowski ◽  
Michael R. Scheinfein ◽  
Steven L. Tripp ◽  
Jie Liu ◽  
...  
Keyword(s):  
Room Temperature ◽  
Phase Image ◽  
Objective Lens ◽  
Electron Holography ◽  
Zero Field ◽  
Transmission Electron ◽  
Out Of Plane ◽  
Self Assembled ◽  
Magnetic States

AbstractWe use off-axis electron holography in the transmission electron microscope (TEM) to study magnetic flux closure (FC) states in self-assembled nanoparticle rings that each contain between five and eleven 25-nm-diameter Co crystals. Electron holograms are acquired at room temperature in zero-field conditions after applying chosen magnetic fields to the samples in situ in the TEM by partially exciting the conventional microscope objective lens. Mean inner potential contributions to the phase shift are determined by turning the samples over, and subsequently subtracted from each recorded phase image to obtain magnetic induction maps. Our results show that most nanoparticle rings form FC remanent magnetic states, and occasionally onion-like states. Although the chiralities (the directions of magnetization) of the FC states are determined by the shapes, sizes and positions of the constituent nanoparticles, reproducible magnetization reversal of each ring can be achieved by using an out-of-plane magnetic field of between 1600 and 2500 Oe.

Co-DOPED ZnO NANOWIRES GROWN BY VAPOR–LIQUID–SOLID METHOD: STRUCTURAL, OPTICAL AND MAGNETIC STUDIES

NANO ◽  
2012 ◽  
Vol 07 (04) ◽  
pp. 1250028 ◽  
Author(s):  
BAPPADITYA PAL ◽  
SOUMEN DHARA ◽  
P. K. GIRI
Keyword(s):  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Visible Region ◽  
Magnetic Behavior ◽  
Hexagonal Structure ◽  
Zno Nanowires ◽  
Magnetic Studies ◽  
Microscopy Imaging ◽  
Doped Zno ◽  
Co Doped

We report on the growth of Co -doped ZnO nanowires (NWs) on Si substrate using a self-catalytic vapor deposition method from a Co -doped ZnO nanopowder source and study its structural, optical and magnetic properties for the as-grown and rapid thermal annealed samples. Co (5%)-doped ZnO ( ZnCoO ) nanoparticles (NPs) are used as source material for the growth process. Electron microscopy imaging clearly reveals the formation of long ZnO NWs with uniform diameter. X-ray diffraction analysis confirms the single crystalline hexagonal structure of Co -doped ZnO NWs without impurities of metallic cobalt or other phases. Micro-Raman studies of doped samples show doping/disorder induced additional modes as compared to the undoped ZnO . Room temperature photoluminescence spectra of the doped ZnO NWs show strong emission band at ~380 nm and no significant emission was observed in the visible region indicating low defect content in the NWs. The field dependent magnetization (M–H curve) measured at room temperature exhibits paramagnetic nature for the NWs with the magnetic moment in the range 2–3.7 milli-emu/cm2 for the applied field of 2 Tesla, while the source ZnCoO NPs exhibit room temperature ferromagnetism with saturation magnetization ~6 emu/g. Possible mechanism of alteration in magnetic behavior in doped NWs are discussed based on the growth conditions and role of defects.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Spherulite Structures in a Melt Spun Fe-Ni Austenitic Steel

1985 ◽  
Vol 43 ◽  
pp. 52-53
Author(s):  
G. M. Michal ◽  
T. K. Glasgow ◽  
T. J. Moore
Keyword(s):  
Austenitic Steel ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Large Range ◽  
Amorphous Structure ◽  
Nucleation And Growth ◽  
Ni Alloys ◽  
Melt Spun ◽  
Crystal Fibers ◽  
Rapidly Solidified

Large additions of B to Fe-Ni alloys can lead to the formation of an amorphous structure, if the alloy is rapidly cooled from the liquid state to room temperature. Isothermal aging of such structures at elevated temperatures causes crystallization to occur. Commonly such crystallization pro ceeds by the nucleation and growth of spherulites which are spherical crystalline bodies of radiating crystal fibers. Spherulite features were found in the present study in a rapidly solidified alloy that was fully crysstalline as-cast. This alloy was part of a program to develop an austenitic steel for elevated temperature applications by strengthening it with TiB2. The alloy contained a relatively large percentage of B, not to induce an amorphous structure, but only as a consequence of trying to obtain a large volume fracture of TiB2 in the completely processed alloy. The observation of spherulitic features in this alloy is described herein. Utilization of the large range of useful magnifications obtainable in a modern TEM, when a suitably thinned foil is available, was a key element in this analysis.

FANSTEEL 85 METAL

Alloy Digest ◽  
1981 ◽  
Vol 30 (6) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Creep Strength ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Base Alloy ◽  
Heat Treating ◽  
Good Combination ◽  
Bend Strength ◽  
Temperature Performance

Abstract FANSTEEL 85 METAL is a columbium-base alloy characterized by good fabricability at room temperature, good weldability and a good combination of creep strength and oxidation resistance at elevated temperatures. Its applications include missile and rocket components and many other high-temperature parts. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, tensile properties, and bend strength as well as creep. It also includes information on low and high temperature performance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Cb-7. Producer or source: Fansteel Metallurgical Corporation. Originally published December 1963, revised June 1981.

Strong Coupling: Polariton Bose Condensation

2017 ◽  
Author(s):  
Alexey V. Kavokin ◽  
Jeremy J. Baumberg ◽  
Guillaume Malpuech ◽  
Fabrice P. Laussy
Keyword(s):  
Strong Coupling ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Dissipative System ◽  
Bose Condensation ◽  
Einstein Condensation ◽  
Strong Coupling Regime ◽  
Stimulated Scattering ◽  
Exciton Polaritons ◽  
Bose Einstein

In this Chapter we address the physics of Bose-Einstein condensation and its implications to a driven-dissipative system such as the polariton laser. We discuss the dynamics of exciton-polaritons non-resonantly pumped within a microcavity in the strong coupling regime. It is shown how the stimulated scattering of exciton-polaritons leads to formation of bosonic condensates that may be stable at elevated temperatures, including room temperature.

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