The lack of ductility is known to be a major drawback in the mechanical properties of amorphous alloys. A temperature impact is often used, as a factor to improve the mechanical parameters of these ...thermally unstable materials. A thick Ni
82.1
Cr
7.8
Si
4.6
Fe
3.1
Mn
0.2
Al
0.1
Cu
0.1
B
2
metallic glass ribbon was subjected to a series of one-hour anneals between 50 and 700 °C. Annealing at 250 °C revealed an increase in the density of the ribbon accompanied by structure rearrangement responsible for the
β
-relaxation process. In addition, the metallic glass demonstrated high ductility along with high tensile strength and hardness under load. Based on the analysis of transformation of excess free volume in the vicinity of the
β
-relaxation temperature, a mechanism explaining the attainment of ductility maximum realized in metallic glass under loading has been proposed.
The structure and strength of Al
x
Si–2 wt % Cu (
x =
15, 17, and 20 wt %) alloys obtained by directional solidification at a rate of 0.1 and 0.8 mm/s are investigated. It is shown that the tensile ...strength increases with an increase in the rate of solidification due to a decrease in the size of eutectic silicon and the transformation of its crystal flake into a fine-fiber one. In addition, there was an increase in tensile strength due to an increase of the share of the intermetallic phase, exceeding the reduced tensile strength due to an increase in the amount of the α-Al phase. An increase in the silicon content in the samples during solidification at a rate of 0.1 mm/s does not lead to a change in structure and strength. At a higher rate of solidification, there is a reduction of the share of eutectic and a decrease in strength.
The modes of growth of Ga
2
O
3
crystals from a solution of gallium oxide in a MoO
3
melt in the process of MoO
3
evaporation at a temperature of 1050°C have been studied. It is shown that at this ...temperature the Ga
2
O
3
crystalline phase is in equilibrium with the MoO
3
melt. As a result of the experiments, single crystals of β-Ga
2
O
3
were obtained up to 1.5 mm in cross section. The composition and structure of the crystals were studied by X-ray diffraction and electron microscopy.
The wear resistance of epitaxial layers of α- and β-polymorphs of gallium oxide grown on sapphire substrates has been considered. This is one of the first studies of the tribological properties of a ...promising wideband semiconductor crystal. As a result of tribotests conducted with the participation of a sapphire counterface in the process of dry friction in air, it has been shown that the layers of a metastable α-Ga
2
O
3
are more resistant to abrasion than the layers of the thermostable β-phase. At the same time, the obtained values of the wear coefficients allow us to attribute both polymorphs to wear-resistant materials and especially α-Ga
2
O
3
with a corundum structure. In addition, α- and β-Ga
2
O
3
demonstrate extremely low values of friction coefficients: lower than those of sapphire.
We consider a linear actuator based on a flexural force element made of a material with shape memory (SM) effect generating a useful force in one direction. A mathematical model developed for such an ...actuator makes it possible to connect its characteristics with functional properties of the material with the SM effect. The relations derived for the developed force and shaft displacement in dimensionless form describe the behavior of the force element in the form of a rod made of any material exhibiting a SM effect.
Micron-thick layers of (Cr1-xGax)2O3 solid solutions were grown by modified mist chemical vapor deposition (mist-CVD) with three different Ga concentrations. Scanning electron microscopy (SEM) and ...X-ray diffraction (XRD) methods were used to analyze the quality of the films. They showed good crystallinity, homogeneity and coalescence of the samples. Solid solution contents estimation was performed via applying Vegard’s law to XRD data and by its results the highest reached Cr:Ga ratio is approximately 1:1. Transmission spectra of solid solutions demonstrated blue-shift of the absorption edge with increase of the Ga contents. Optical bandgap increased from 3.06 eV for undoped Cr2O3 sample to 3.73 eV for the layer with the highest Ga concentration.
•High-quality micron thick crystal layers of the (Cr1-xGax)2O3 were grown by modified mist-CVD technique on the sapphire.•Cr to Ga ratio in the layers was up to 1:1 without decomposition of the solid solution in them.•Blue shift of the absorption edge and optical bandgap with higher Ga contents is observed in acquired solid solution layers.
Thick (23 µm) films of κ-Ga2O3 were grown by Halide Vapor Phase Epitaxy (HVPE) on GaN/sapphire templates at 630 °C. X-ray analysis confirmed the formation of single-phase κ-Ga2O3 with half-widths of ...the high-resolution x-ray diffraction (004), (006), and (008) symmetric reflections of 4.5 arc min and asymmetric (027) reflection of 14 arc min. Orthorhombic κ-Ga2O3 polymorph formation was confirmed from analysis of the Kikuchi diffraction pattern in electron backscattering diffraction. Secondary electron imaging indicated a reasonably flat surface morphology with a few (area density ∼103 cm−2) approximately circular (diameter ∼50–100 µm) uncoalesced regions, containing κ-Ga2O3 columns with in-plane dimensions and a height of about 10 µm. Micro-cathodoluminescence (MCL) spectra showed a wide 2–3.5 eV band that could be deconvoluted into narrower bands peaked at 2.59, 2.66, 2.86, and 3.12 eV. Ni Schottky diodes prepared on the films showed good rectification but a high series resistance. The films had a thin near-surface region dominated by Ec − 0.7 eV deep centers and a deeper region (∼2 µm from the surface) dominated by shallow donors with concentrations of ≤1016 cm−3. Photocurrent and photocapacitance spectra showed the presence of deep compensating acceptors with optical ionization energies of ∼1.35 and 2.3 eV, the latter being close to the energy of one of the MCL bands. Deep level transient spectroscopy revealed deep traps with energies near 0.3, 0.6, 0.7, 0.8, and 1 eV from the conduction band edge. The results show the potential of HVPE to grow very thick κ-Ga2O3 on GaN/sapphire templates.
The effect of H
2
, NH
3
, CO and O
2
on the electrically conductive properties of In
2
O
3
films grown by halide vapor phase epitaxy has been studied. In the temperature range of 200−550°C, In
2
O
3
...films demonstrate gas sensitivity to all considered gases, a relatively high operation speed and repeatability of cycles. The greatest response to NH
3
was obtained, which exceeded 33 arb. units at a temperature of 400°C and a gas concentration of 1000 ppm
−1
. A qualitative mechanism of gas sensitivity of In
2
O
3
films is proposed. The obtained gas-sensitive characteristics are compared with known In
2
O
3
sensors based on various materials. It is shown that the method of halide vapor phase epitaxy makes it possible to obtain indium oxide films with high gas sensitivity.
Here we report on the growth and characterisation of α- and ε-Ga2O3 epitaxial films produced by halide vapour phase epitaxy (HVPE). The films were deposited on two types of substrate: (0001) plain ...sapphire substrates and (0001) patterned sapphire substrates with regular cone-like features. In order to guarantee the same growth conditions on plain and patterned sapphire, the two substrates were used simultaneously in the same growth run. After the deposition the samples were studied by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical transmission (OT) spectroscopy, and cathodoluminescence (CL). The growth on plain sapphire substrate produced an 11 μm thick continuous α-Ga2O3 layer. The full width at half maximum (FWHM) of the (0006) XRD rocking curve is 180 arcsec, which indicates good crystallinity of the layer. In contrast, growth on the patterned sapphire substrate resulted in a layer with regular spaced faceted pyramids at the surface. XRD analysis revealed the presence of both α- and ε-phases in Ga2O3 grown on patterned sapphire substrate. The presence of the ε-Ga2O3 phase, which has narrower bandgap, was also confirmed by optical transmission measurements. SEM, TEM, and SEM CL observations revealed that α-Ga2O3 phase forms columnar structures on top of sapphire cone, and ε-Ga2O3 phase fills the valleys between the columns.
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