Controlling the Electrical Properties of Reactively Sputtered High Entropy Alloy CrFeNiCoCu Films

2021 ◽  
Author(s):  
J. Mayandi ◽  
T. G. Finstad ◽  
M. Stange ◽  
G. C. Vásque ◽  
M. F. Sunding ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Weak Localization ◽  
High Entropy Alloy ◽  
X Ray Diffraction ◽  
High Entropy ◽  
Alloy Scattering ◽  
Relative Contribution ◽  
Effective Resistivity ◽  
Wide Range ◽  
Hall Effect Measurements

AbstractOxide-containing films were made by reactively sputtering a high-entropy alloy target of CrFeCoNiCu. We report on a wide range of changes to the electrical properties made by different heat treatments in oxidizing and reducing atmospheres, respectively. We combine temperature-dependent Hall effect measurements down to 10 K to study the transport mechanisms and correlate that with structural measurements by x-ray diffraction and scanning electron microscopy. The measured/effective resistivity could be varied between 1.3 × 10−4 Ω cm and 1.2 × 10−3 Ω cm by post-deposition processing. The temperature coefficient of resistivity could be varied between − 1.2 × 10−3 K−1 through 0 and to + 0.7 × 10−3 K−1. The key to the variation is controlling the morphology and topology of the film. The conduction of charge carriers is dominated by the relative contribution of weak localization and alloy scattering by varying the degree of disorder in the metallic high-entropy alloy and its topology.

scholarly journals A Study of Thin Film Resistors Prepared Using Ni-Cr-Si-Al-Ta High Entropy Alloy

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Ruei-Cheng Lin ◽  
Tai-Kuang Lee ◽  
Der-Ho Wu ◽  
Ying-Chieh Lee
Keyword(s):  
Annealing Temperature ◽  
Phase Evolution ◽  
Amorphous Structure ◽  
High Entropy Alloy ◽  
X Ray Diffraction ◽  
Temperature Coefficient Of Resistance ◽  
X Ray ◽  
High Entropy ◽  
Transmission Electron ◽  
Thin Film Resistors

Ni-Cr-Si-Al-Ta resistive thin films were prepared on glass and Al2O3substrates by DC magnetron cosputtering from targets of Ni0.35-Cr0.25-Si0.2-Al0.2casting alloy and Ta metal. Electrical properties and microstructures of Ni-Cr-Si-Al-Ta films under different sputtering powers and annealing temperatures were investigated. The phase evolution, microstructure, and composition of Ni-Cr-Si-Al-Ta films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Auger electron spectroscopy (AES). When the annealing temperature was set to 300°C, the Ni-Cr-Si-Al-Ta films with an amorphous structure were observed. When the annealing temperature was at 500°C, the Ni-Cr-Si-Al-Ta films crystallized into Al0.9Ni4.22, Cr2Ta, and Ta5Si3phases. The Ni-Cr-Si-Al-Ta films deposited at 100 W and annealed at 300°C which exhibited the higher resistivity 2215 μΩ-cm with −10 ppm/°C of temperature coefficient of resistance (TCR).

scholarly journals Influence of Aluminum and Molybdenum on the Microstructure and Corrosion Behavior of Thermally Sprayed High-Entropy Alloy Coatings

2021 ◽  
Author(s):  
Martin Löbel ◽  
Thomas Lindner ◽  
Maximilian Grimm ◽  
Lisa-Marie Rymer ◽  
Thomas Lampke
Keyword(s):  
Corrosion Resistance ◽  
Protective Coatings ◽  
Base Alloy ◽  
Alloy System ◽  
High Entropy Alloy ◽  
Oxide Content ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Structural And Functional Properties ◽  
Wide Range

AbstractHigh-entropy alloys (HEAs) have shown a wide range of promising structural and functional properties. By the application of coating technology, an economical exploitation can be achieved. The high wear and corrosion resistance of HEAs make them particularly interesting for the application as protective coatings. Especially for alloys with a high chromium content, a high corrosion resistance has been revealed. For the current investigations, the equimolar HEA CrFeCoNi with a single-phase face centered cubic structure is considered as a base alloy system. To increase the corrosion resistance as well as the hardness and strength, the influence of the alloying elements aluminum and molybdenum is analyzed. For the current investigations, the high kinetic process high-velocity oxygen fuel thermal spraying (HVOF) has been considered to produce coatings with a low porosity and oxide content. Feedstock is produced by inert gas atomization. The influence of the alloy composition on the microstructure, phase formation and resulting property profile is studied in detail. A detailed analysis of the corrosion resistance and underlying mechanisms is conducted. The pitting and passivation behavior are investigated by potentiodynamic polarization measurements in NaCl and H2SO4 electrolyte. A distinct improvement of the corrosion resistance can be achieved for the alloy Al0.3CrFeCoNiMo0.2.

An X-ray Diffraction Investigation of Tin Oxide Deposition and Annealing

2001 ◽  
Vol 666 ◽  
Author(s):  
Joshua J. Robbins ◽  
Yen-Jung Huang ◽  
Mailasu Bai ◽  
Tyrone Vincent ◽  
Colin A. Wolden
Keyword(s):  
Electrical Properties ◽  
Tin Oxide ◽  
Structural Changes ◽  
Chemical Vapor ◽  
Transparent Conductor ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxide Deposition ◽  
Hall Effect Measurements ◽  
Bombardment Energy

ABSTRACTTin oxide thin films were deposited by plasma-enhanced chemical vapor deposition (PECVD) for applications as a transparent conductor. X-ray diffraction (XRD) and atomic force microscopy (AFM) were used to quantify the crystal structure and morphology of these films both as-deposited and after annealing conditions. Annealing was performed in an argon environment as a function of time and temperature. Although annealing was found to significantly improve electrical properties, the structure as measured by XRD remained largely unchanged. Hall effect measurements show that the improvements in resistivity are due to increases in carrier concentration. XRD did reveal that films deposited on the powered electrode had a film orientation that was distinctly different than films deposited on the grounded electrode. These changes suggest the importance of ion bombardment energy. The structural changes were correlated with improved electrical properties.

scholarly journals Design and Production of a New FeCoNiCrAlCu High-Entropy Alloy: Influence of Powder Production Method on Sintering

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4342
Author(s):  
Eduardo Reverte ◽  
Monique Calvo-Dahlborg ◽  
Ulf Dahlborg ◽  
Monica Campos ◽  
Paula Alvaredo ◽  
...  
Keyword(s):  
Atomic Radius ◽  
Production Method ◽  
High Entropy Alloy ◽  
X Ray Diffraction ◽  
Vacuum Sintering ◽  
High Entropy ◽  
Powder Production ◽  
Production Techniques ◽  
Fcc Phase ◽  
Domain Iii

The structure of FeCoNiCrAl1.8Cu0.5 high-entropy alloys (HEA) obtained by two different routes has been studied. The selection of the composition has followed the Hume–Rothery approach in terms of number of itinerant electrons (e/a) and average atomic radius to control the formation of specific phases. The alloys were obtained either from a mixture of elemental powders or from gas-atomised powders, being consolidated in both cases by uniaxial pressing and vacuum sintering at temperatures of 1200 °C and 1300 °C. The characterization performed in the sintered samples from both types of powder includes scanning electron microscopy, X-ray diffraction, differential thermal analysis, and density measurements. It was found that the powder production techniques give similar phases content. However, the sintering at 1300 °C destroys the achieved phase stability of the samples. The phases identified by all techniques and confirmed by Thermo-Calc calculations are the following: a major Co-Ni-Al-rich (P1) BCC phase, which stays stable after 1300 °C sintering and homogenising TT treatments; a complex Cr-Fe-rich (P2) B2 type phase, which transforms into a sigma phase after the 1300 °C sintering and homogenising TT treatments; and a very minor Al-Cu-rich (P3) FCC phase, which also transforms into Domain II and Domain III phases during the heating at 1300 °C and homogenising TT treatments.

scholarly journals Data-Driven Discovery and Synthesis of High Entropy Alloy Hydrides with Targeted Thermodynamic Stability

2021 ◽  
Author(s):  
Matthew Witman ◽  
Gustav Ek ◽  
Sanliang Ling ◽  
Jeffery Chames ◽  
Sapan Agarwal ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Data Driven ◽  
High Entropy Alloy ◽  
Hydrogen Storage Materials ◽  
Equilibrium Pressure ◽  
High Entropy ◽  
Storage Materials ◽  
Composition Space ◽  
Wide Range ◽  
Selection For

Solid-state hydrogen storage materials that are optimized for specific use cases could be a crucial facilitator of the hydrogen economy transition. Yet the discovery of novel hydriding materials has historically been a manual process driven by chemical intuition or experimental trial-and-error. Data-driven materials' discovery paradigms provide an alternative to traditional approaches, whereby machine/statistical learning (ML) models are used to efficiently screen materials for desired properties and significantly narrow the scope of expensive/time-consuming first-principles modeling and experimental validation. Here we specifically focus on a relatively new class of hydrogen storage materials, high entropy alloy (HEA) hydrides, whose vast combinatorial composition space and local structural disorder necessitates a data-driven approach that does not rely on exact crystal structures in order to make property predictions. Our ML model quickly screens hydride stability within a large HEA space and permits down selection for laboratory validation based not only on targeted thermodynamic properties, but also secondary criteria such as alloy phase stability and density. To experimentally verify our predictions, we performed targeted synthesis and characterization of several novel hydrides that demonstrate significant destabilization (70x increase in equilibrium pressure, 20 kJ/molH<sub>2</sub> decrease in desorption enthalpy) relative to the benchmark HEA hydride, TiVZrNbHfH<sub>x</sub>. Ultimately, by providing a large composition space in which hydride thermodynamics can be continuously tuned over a wide range, this work will enable efficient materials selection for various applications, especially in areas such as metal hydride based hydrogen compressors, actuators, and heat pumps.

scholarly journals Effect of V and Ti on the Oxidation Resistance of WMoTaNb Refractory High-Entropy Alloy at High Temperatures

Metals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 41
Author(s):  
Shuaidan Lu ◽  
Xiaoxiao Li ◽  
Xiaoyu Liang ◽  
Wei Yang ◽  
Jian Chen
Keyword(s):  
Oxidation Resistance ◽  
High Temperatures ◽  
Elevated Temperatures ◽  
Early Stage ◽  
Mass Gain ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Entropy

Alloying with V and Ti elements effectively improves the strength of WMoTaNb refractory high entropy alloys (RHEAs) at elevated temperatures. However, their effects on the oxidation resistance of WMoTaNb RHEAs are unknown, which is vitally important to their application at high temperatures. In this work, the effect of V and Ti on the oxidation behavior of WMoTaNb RHEA at 1000 °C was investigated using a thermogravimetric system, X-ray diffraction and scanning electron microscopy. The oxidation of all alloys was found to obey a power law passivating oxidation at the early stage. The addition of V aggravates the volatility of V2O5, MoO3 and WO3, and leads to disastrous internal oxidation. The addition of Ti reduces the mass gain in forming the full coverage of passivating scale and prolongs the passivation duration of alloys.

Microstructure and Properties of TiB2/AlFeNiCoCr Composites by Spark Plasma Sintering

2020 ◽  
Vol 842 ◽  
pp. 83-89
Author(s):  
Dai Hong Xiao ◽  
Min Dong Wu
Keyword(s):  
Spark Plasma Sintering ◽  
Phase Evolution ◽  
High Entropy Alloy ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
Alloy Matrix ◽  
High Entropy ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Temperature And Pressure

TiB2/AlFeNiCoCr high-entropy-alloy-matrix composites were fabricated by spark plasma sintering. Effects of SPS process on microstructure and mechanical properties of 0.5 vol.% TiB2/AlFeNiCoCr composites were studied using X-ray diffraction, density testing, scanning electron microscopy, mechanical property testing. It is shown that increasing of sintering temperature and pressure can improve the relative density and compressive properties of 5 vol. %TiB2/AlCoCrFeNi composites. During the spark plasma sintering, there is phase evolution in the composites. The 5 vol. % TiB2/AlCoCrFeNi composite after sintering at 1200 °C and 30 ~ 45 MPa is composed of phases BCC, B2, FCC, σ and TiB2.

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