scholarly journals Effects of Carbon Doping and Annealing Temperature on Magnetic MnAl Powders and MnAl Polymeric Composites

2021 ◽  
Vol 11 (5) ◽  
pp. 2067
Author(s):  
Wannisa Thongsamrit ◽  
Thanida Charoensuk ◽  
Panissa Saetang ◽  
Pongsakorn Jantaratana ◽  
Chesta Ruttanapun ◽  
...  
Keyword(s):  
Magnetic Separation ◽  
Remanent Magnetization ◽  
Annealing Temperature ◽  
Carbon Doping ◽  
Induction Melting ◽  
Powder Form ◽  
Domain Wall Pinning ◽  
Oxide Phases ◽  
Solution Route ◽  
C Doping

Process parameters leading to magnetic polymer composites, an essential ingredient in the additive manufacturing of rare-earth-free magnets, are investigated. The induction melting of manganese (Mn) and aluminum (Al), and subsequent annealing at 450, 500, or 550 °C for 20 min, gave rise to ferromagnetic τ–MnAl phase, as well as other phases. The nonmagnetic Al4C3 and oxide phases were then removed by the magnetic separation. Magnetic powders from the magnetic separation were incorporated in polylactic acid (PLA) matrix via a solution route. The remanent magnetization as high as 4.3 emu/g in the powder form was reduced to 2.3–2.6 emu/g in the composites. The reduction in coercivity was minimal, and the largest value of 814 Oe was obtained when the powder annealed at 450 °C was loaded in the composite. The phase composition and hence magnetic properties were even more sensitive to the carbon (C) doping. Interestingly, the addition of 3% C led to coercivity as high as 1445 Oe in MnAl–C powders without further annealing. The enhanced coercivity was attributed to the domain wall pinning by the AlMn3C phase, and magnetizations are likely increased by this phase.

scholarly journals Bottom-Up Synthesis of Porous NiMo Alloy for Hydrogen Evolution Reaction

2017 ◽  
Author(s):  
Kailong Hu ◽  
Samuel Jeong ◽  
Mitsuru Wakisaka ◽  
Jun-ichi Fujita ◽  
Yoshikazu Ito
Keyword(s):  
Catalytic Activity ◽  
Hydrogen Production ◽  
Water Splitting ◽  
Hydrogen Evolution Reaction ◽  
Annealing Temperature ◽  
Hydrogen Atmosphere ◽  
Porous Electrodes ◽  
Bottom Up ◽  
Annealing Temperatures ◽  
Oxide Phases

Bottom-up synthesis of porous NiMo alloy reduced by NiMoO4 nanofibers was systematically investigated to fabricate non-noble metal porous electrodes for hydrogen production. The different annealing temperatures of NiMoO4 nanofibers under hydrogen atmosphere reveal that the 950 °C annealing temperature is a key to produce bicontinuous and monorhinic porous NiMo alloy without oxide phases. The porous NiMo alloy as cathodes in electrical water splitting demonstrates not only almost identical catalytic activity with commercial Pt/C, but also superb stability for 12 days.

scholarly journals Bottom-Up Synthesis of Porous NiMo Alloy for Hydrogen Evolution Reaction

2017 ◽  
Author(s):  
Kailong Hu ◽  
Samuel Jeong ◽  
Mitsuru Wakisaka ◽  
Jun-ichi Fujita ◽  
Yoshikazu Ito
Keyword(s):  
Catalytic Activity ◽  
Hydrogen Production ◽  
Hydrogen Evolution Reaction ◽  
Electrode Potential ◽  
Annealing Temperature ◽  
Hydrogen Atmosphere ◽  
Porous Electrodes ◽  
Bottom Up ◽  
Annealing Temperatures ◽  
Oxide Phases

Bottom-up synthesis of porous NiMo alloy reduced by NiMoO4 nanofibers was systematically investigated to fabricate non-noble metal porous electrodes for hydrogen production. The different annealing temperatures of NiMoO4 nanofibers under hydrogen atmosphere reveal that the 950 °C annealing temperature is a key to produce bicontinuous porous NiMo alloy without oxide phases. The porous NiMo alloy as cathodes in electrical water splitting demonstrates not only almost identical catalytic activity with commercial Pt/C in 1.0 M KOH solution, but also superb stability for 12 days at an electrode potential of −200 mV (v.s. RHE).

Rutile nanotubes by electrochemical anodization

RSC Advances ◽  
2016 ◽  
Vol 6 (78) ◽  
pp. 74510-74514 ◽  
Author(s):  
Rangasamy Savitha ◽  
Ravikrishna Raghunathan ◽  
Raghuram Chetty
Keyword(s):  
Titanium Dioxide ◽  
Annealing Temperature ◽  
Electrochemical Anodization ◽  
Powder Form ◽  
Titanium Dioxide Nanotubes ◽  
Rutile Titanium Dioxide

We present a facile method to synthesize rutile titanium dioxide nanotubes (R-TiNT), directly in powder form through rapid breakdown electrochemical anodization by modifying the post anodization processing and annealing temperature.

Influence of C-Doping on the B-11 and N-14 Quadrupole Coupling Constants in Boron-Nitride Nanotubes: A DFT Study

2007 ◽  
Vol 62 (1-2) ◽  
pp. 56-60 ◽  
Author(s):  
Mahmoud Mirzaei ◽  
Nasser L. Hadipour ◽  
Mohammad Reza Abolhassani
Keyword(s):  
Boron Nitride ◽  
Density Functional ◽  
Computational Study ◽  
Boron Nitride Nanotubes ◽  
Coupling Constants ◽  
Carbon Doping ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Quadrupole Coupling ◽  
C Doping

A computational study at the level of density functional theory (DFT) was carried out to investigate the influence of carbon doping (C-doping) on the 11B and 14N quadrupole coupling constants (CQ) in the (6,0) single-walled boron-nitride nanotube (BNNT). To this aim, a 10 Å length of BNNT consisting of 24 B atoms and 24 N atoms was selected where the end atoms are capped by hydrogen atoms. To follow the purpose, six C atoms were doped instead of three B and three N atoms as a central ring in the surface of the C-doped BNNT. The calculated CQ values for both optimized BNNT systems, raw and C-doped, reveal different electrostatic environments in the mentioned systems. It was also demonstrated that the end nuclei have the largest CQ values in both considered BNNT systems.

Effect of Deformation and Annealing on Microstructure and Properties of Composite Cu-10Fe-3Ag Wire

2010 ◽  
Vol 150-151 ◽  
pp. 673-679
Author(s):  
Yong Li ◽  
Dan Qing Yi ◽  
Rui Qing Liu ◽  
Shun Ping Sun
Keyword(s):  
Thermal Stability ◽  
Electron Microscope ◽  
Annealing Temperature ◽  
Induction Melting ◽  
Ductile Rupture ◽  
In Situ Composite ◽  
Transmission Electron ◽  
Effects Of Aging ◽  
Thermal Stability Of

A Cu–10Fe–3Ag alloy was produced by means of induction melting. The effects of aging processes on microhardness and conductivity of Cu–10Fe–3Ag alloy were studied. The microstructure of the alloy was examined using transmission electron microscope (TEM). The results show that: presence of Ag can accelerate γ-Fe precipitation from in the Cu matrix, but also reduces the thermal stability of Fe fibers. As the annealing temperature increasing, the microhardness and conductivity of Cu-10Fe-3Ag in-situ composite increase at first and then decrease. Annealed at 475 for 6h, the alloy has an excellent combination of microhardness and conductivity, the microhardness and conductivity reach 209HV and 58.4% IACS, respectively. The Fractures of the alloy are all ductile rupture and the dimples are smaller with the annealing temperature increasing.

Effects of carbon doping on structure and magnetocaloric properties of Mn1.25Fe0.7P0.5Si0.5 alloys

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jimei Niu ◽  
Zhigang Zheng
Keyword(s):  
Magnetic Field ◽  
Entropy Change ◽  
Type Structure ◽  
Carbon Doping ◽  
Sintering Process ◽  
Arc Melting ◽  
Magnetocaloric Properties ◽  
C Doping ◽  
Room Temperature Magnetic Refrigeration ◽  
P Type

Abstract (Mn,Fe)2(P,Si)-basedmaterials are promisingly applied in the room-temperature magnetic refrigeration field. In this study, Mn1.25Fe0.7P0.5Si0.5Cx (x = 0, 0.01, 0.03 and 0.05) alloys were prepared by arc-melting and then a two-stage sintering process. The effects of C doping on the crystal structure and magnetocaloric behavior are discussed. Results indicate that the Fe2P-type structure (space group of P62 m) was crystallized for all samples with weakened first-order magnetic transitions (FOMT). The Curie temperature could be altered from 223.5 K to 278.5 K with the large magnetocaloric effect (MCE) remaining by C doping. In the applied magnetic field of 5 T, the peak value of magnetic entropy change (–ΔS M) increased by 7.3% to reach 25.1 J × kg–1 × K–1. The temperature-induced entropy change (ΔS DSC) derived from DSC was slightly larger than ΔS M induced by the magnetic field. The Mn1.25Fe0.7P0.5Si0.5 alloys with large MCE can be effectively tuned by C doping because C atoms prefered to share the substitute and occupy the interstitial sites in hexagonal Fe2P-type structure.

Growth and Studies of Li (Mn, Co) Oxides for Battery Electrodes

1999 ◽  
Vol 606 ◽  
Author(s):  
S. Nieto-Ramos ◽  
M.S. Tomar ◽  
R.S. Katiyar
Keyword(s):  
Spin Coating ◽  
Annealing Temperature ◽  
Lithium Ion ◽  
Rechargeable Batteries ◽  
Rechargeable Battery ◽  
Oxide Materials ◽  
Synthetic Route ◽  
X Ray Diffraction ◽  
X Ray ◽  
Solution Route

AbstractThere is interest in lithium intercalation oxide materials for cathodes in rechargeable batteries. We have synthesized LiMOx, (where M = Mn, Co) by a less expensive solution route. Reagent grade acetates or hydroxides as precursors for lithium, manganese, and cobalt, respectively, with methoxy ethenol and acetic acid as solvents were used. Powders with different compositions were achieved at annealing temperature below 700 °C. Thin films were deposited by spin coating. X-ray diffraction, Raman spectroscopy, and impedance spectroscopic results are presented. These studies indicate that this synthetic route is suitable to produce good quality lithium-based oxides useful for cathode in lithium-ion rechargeable battery.

Carbon Doping of GaAs by OMVPE Using CC14: A Comparison of Gallium and Arsenic Precursors

1991 ◽  
Vol 240 ◽  
Author(s):  
W. S. Hob Son
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Hole Concentration ◽  
Carbon Doping ◽  
Carbon Incorporation ◽  
C Doping ◽  
Van Der Pauw ◽  
Secondary Ion ◽  
Dopant Source ◽  
Very High

ABSTRACTThe carbon doping properties of GaAs with carbon tetrachloride as the dopant source were examined using trimethylgallium (TMGa) or triethylgallium (TEGa) as the gallium precursors and arsine or tertiarybutylarsine (TBAs) as the arsenic precursors. Secondary ion mass spectrometry (SIMS) and Hall measurements (van der Pauw method) were used to characterize the epitaxial GaAs:C layers. Very high C-doping concentrations (∼1020 cm−3) could be obtained with either TMGa and TEGa. The use of TBAs instead of AsH3 led to a significant reduction in carbon incorporation, by approximately a factor of 5–10 per mole of As precursor, over the temperature range examined (520°C - 700°C). Hydrogen at significant concentrations (0.5 – 6 × 1019 cm−3) was detected by SIMS in GaAs:C layers grown at ≤550°C utilizing all four combinations of Ga/As precursors and suggested the presence of electrically inactive C-H complexes. A post-growth anneal under helium at 550°C for 60s of these samples resulted in a 50–100% increase in hole concentration by driving out the hydrogen.

scholarly journals Crystallization Kinetics Analysis of the Amorphouse Mg72Zn24Ca4 Alloy at the Isothermal Annealing Temperature of 507 K

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2815
Author(s):  
Janusz Lelito
Keyword(s):  
Metallic Glass ◽  
Crystallization Kinetics ◽  
Rate Constant ◽  
Crystallization Process ◽  
Annealing Temperature ◽  
Isothermal Annealing ◽  
Avrami Exponent ◽  
Induction Melting ◽  
Transformation Rate ◽  
Transformation Rate Constant

This paper presents tests of metallic glass based on Mg72Zn24Ca4 alloy. Metallic glass was made using induction melting and further injection on a rotating copper wheel. A differential scanning calorimeter (DSC) was used to investigate the phase transformation of an amorphous ribbon. The tests were carried out at an isothermal annealing temperature of 507 K. The Kolmogorov-Johnson-Mahl-Avrami-Evans model was used to analyze the crystallization kinetics of the amorphous Mg72Zn24Ca4 alloy. In this model, both Avrami’s exponent n and transformation rate constant K were analyzed. Both of these kinetic parameters were examined as a function of time and the solid fraction. The Avrami exponent n value at the beginning of the crystallization process has value n = 1.9 and at the end of the crystallization process has value n = 3.6. The kinetic constant K values change in the opposite way as the exponent n. At the beginning of the crystallization process the constant K has value K = 9.19 × 10−7 s−n (ln(K) = −13.9) and at the end of the crystallization process has the value K = 6.19 × 10−9 s−n (ln(K) = −18.9). These parameters behave similarly, analyzing them as a function of the duration of the isothermal transformation. The exponent n increases and the constant K decreases with the duration of the crystallization process. With such a change of the Avrami exponent n and the transformation rate constant K, the crystallization process is controlled by the 3D growth on predetermined nuclei. Because each metallic glass has a place for heterogeneous nucleation, so called pre-existing nuclei, in which nucleation is strengthened and the energy barrier is lowered. These nuclei along with possible surface-induced crystallization, lead to rapid nucleation at the beginning of the process, and therefore a larger transformed fraction than expected for purely uniform nucleation. These sites are used and saturated with time, followed mainly by homogeneous nucleation. In addition, such a high value of the Avrami exponent n at the end of the crystallization process can cause the impingement effect, heterogeneous distribution of nuclei and the diffusion-controlled grain growth in the Mg72Zn24Ca4 metallic glassy alloy.

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