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1.
The single crystals with stoichiometry close to 1:1:2 of CuInTe2 (CIT) have been grown by chemical vapor transport (CVT) technique using iodine as the transporting agent at different growth temperatures. Single crystal X-ray diffraction studies have confirmed the chalcopyrite structure for the grown crystals and the volume of unit cell is found to be the same for the crystals grown at different conditions. Energy dispersive X-ray (EDAX) analysis of CIT single crystals grown shows almost the same stoichiometric compositions. Scanning electron microscope (SEM) analysis reveals kink, step and layer patterns on the surface of CIT single crystals depending on the growth temperatures. The optical absorption spectra of as-grown CIT single crystals grown at different conditions show that they have same band gap energies (1.0405 eV). Raman spectra exhibit a high intensity peak of A1 mode at 123 cm?1. Annealed at 473 K in nitrogen atmosphere for 40 h CIT single crystals have higher hole mobility (105.6 cm2V?1s?1) and hole concentration (23.28 × 1017 cm?3) compared with values of hole mobility (63.69 cm2 V?1 s?1) and hole concentration (6.99 × 1015 cm?3) of the as-grown CIT single crystals. 相似文献
2.
This paper reported a simple and rapid route to large-scale synthesis of nanostructured SiC powders using rice husk as the precursor. Rapid carbothermal reduction reactions were achieved in a 2.45 GHz microwave field in an argon atmosphere. The XRD patterns revealed that complete carbothermal reduction of silica was achieved at 1300 °C for 60 min or at 1500 °C for only 15 min by microwave heating, resulting in β-SiC formation. The FE-SEM images showed that the β-SiC powders were mixtures of particles and whiskers. The β-SiC particles had diameters of 60–130 nm and the β-SiC whiskers, which were several to tens of micrometers in length, had diameters of 110–170 nm. The β-SiC powder synthesized at 1500 °C for 15 min showed the highest BET surface area of 12.2 m2/g. Compared to the conventional heating method, the microwave heating method proved to be an efficient approach for synthesis of SiC in terms of energy and time saving, as well as for fabrication of nanostructured SiC. 相似文献
3.
《Science and Technology of Advanced Materials》2001,2(2):381-388
Impurity tracer diffusion of 59Fe, 51Cr and 57Co in CVD β-SiC has been studied in the temperature range between 973 and 1873 K. The temperature dependence of the volume diffusion coefficients of iron and chromium can be expressed by linear Arrhenius equations. The preexponential factor and the activation energy are estimated to be 8.7×10−15 m2 s−1 and 111 kJ mol−1 for iron, respectively, and 9.5×10−15 m2 s−1 and 81 kJ mol−1 for chromium, respectively. The diffusion coefficients of iron and chromium are much higher than those of the self-diffusion in β-SiC. Furthermore, the activation energies for the diffusion of iron and chromium are about one-tenth of those for carbon and silicon in β-SiC. Therefore, it seems that an interstitial mechanism is predominant for the diffusion of iron and chromium in β-SiC. On the other hand, the diffusion coefficient of cobalt above 1673 K is higher than that of iron, while at lower temperatures it is much lower than that of iron. The difference in the diffusion coefficients at 1173 K is more than three orders of magnitude. Thus, the temperature dependence of the diffusion coefficients of cobalt shows a strongly curved Arrhenius relation. This suggests that cobalt atoms diffuse by an interstitial mechanism at higher temperatures and by a substitutional mechanism at lower temperatures. From the deeper regions of the penetration profiles of iron, chromium and cobalt the dislocation diffusion coefficients of them have been estimated. 相似文献
4.
《Advanced Powder Technology》2014,25(4):1205-1211
This study is concerned with a common class of problem involving two phase separation of a dispersed gas flow from a continuous liquid flow under extreme processing conditions. Relatively fine spherical bubbles of order 500 μm were generated in the presence of a surfactant under a high shear rate within a rectangular, multi-channeled, cuboidal downcomer. Liquid fluxes, as high as 176 cm/s through each channel of the downcomer, sheared bubbles from a sintered surface mounted flush to the channel wall before disengaging the downcomer flow into a vertical vessel. Both high feed fluxes, up to 15 cm/s, and high gas fluxes, up to 5.5 cm/s, ensured a high gas holdup beneath the downcomer and the hindered rising of the bubbles. Enhanced bubble–liquid segregation was achieved using an arrangement of parallel inclined channels incorporated below the main vertical chamber. This novel device, referred to as the Reflux Flotation Cell, prevented the entrainment of bubbles to the underflow, and significantly reduced the liquid flux to overflow, even in the absence of a conventional froth zone. Extreme upward bubble surface fluxes of up to 600 s−1 were achieved, while counter-current downward liquid fluxes reached 14.4 cm/s, arguably four times the bubble terminal rise velocity. Hence successful phase separation was achieved while operating well beyond the so-called flooding condition arising from extreme levels of gas and feed fluxes. This hydrodynamic arrangement should find application in increasing surfactant extraction rates in foam fractionation and ion flotation, gas absorption, and even particulate flotation. 相似文献
5.
Small bubbles can be observed in both sapphire and Ti-sapphire bulk crystals grown by Czochralski technique (Cz). Various thickness of wafers cut from the grown ingots were studied by optical microscopy. Bubbles distribution has different regulation in sapphire and Ti-sapphire crystals. All bubbles are spherical and have a diameter range from 2 μm to 5 μm in sapphire crystals while 10–45 μm in Ti-doped sapphire crystals. Some adjacent bubbles congregated into defects present various sizes and shape. The bubbles density increases as a function of pulling rate and rotation rate. The effect of bubbles on optical characterizations of Ti-sapphire crystals has been studied. 相似文献
6.
There have been studied single crystals of undoped and doped Bi12TiO20 with two concentrations of W5+ (2.62 × 1017 cm−3 and 2.62 × 1018 cm−3). There have been obtained absorption spectra in the energy range of 10,482–15,408 cm−1 by classical measurements. There have been determined the cross-section (σa) of the impurity absorption and the oscillator strength of d–d transitions. There have been calculated the refractive index of doped crystals and the concentration of Ti3+ ions in an undoped sample through an experiment. 相似文献
7.
《Materials science & engineering. C, Materials for biological applications》2006,26(5-7):805-808
Crystal structure of β-SiC nanowires was investigated using Raman spectroscopy, FT-IR, XRD, transmission electron microscopy and selected area electron diffraction. Cubic β-SiC nanowires were synthesized by heating NiO catalyzed Si substrates with WO3 and graphite mixed powders in the growth temperature of 1000–1100 °C. HRTEM image showed atomic arrangements of the grown SiC nanowires with a main growth direction of [111]. Raman spectra showed two characteristic peaks at 796 cm− 1 and 968 cm− 1, which are corresponding to transversal optic mode and longitudinal optic mode of β-SiC, respectively. Also, FT-IR absorption spectroscopy showed a SiC characteristic absorption band at ∼792 cm− 1. 相似文献
8.
The potential nonlinear optical material of Terbium (Tb3+) ion doped l-Histidine hydrochloride monohydrate (LHHC) single crystals were successfully grown. Tb3+:LHHC crystals of 7 mm × 5 mm × 3 mm and 59 mm length and 15 mm diameter have been grown by the slow solvent evaporation and Sankaranarayanan-Ramasamy (SR) techniques respectively. The grown crystals were characterized by single crystal X-ray diffraction analysis to confirm the crystalline structure and morphology. High resolution X-ray diffraction (HRXRD) studies revealed that the SR grown sample shows relatively good crystalline nature with 9″ full-width at half-maximum (FWHM) for the diffraction curve. Functional groups were identified by Fourier transform infra-red spectroscopy (FTIR). The optical transparency and band gaps of grown crystals were measured by UV–Vis spectroscopy. Thermogravimetric and differential thermal analysis (TG/DTA) studies reveal that the crystal was thermally stable up to 155 °C in SR grown crystal. Surface morphology of the growth plane was observed using scanning electron microscopy (SEM). The incorporation of Tb ion was estimated by EDAX. The frequency-dependent dielectric properties of the crystals were carried out for different temperatures. Vickers hardness study carried out on (1 0 0) face at room temperature shows increased hardness of the SR method grown crystal. Second harmonic generation efficiency of SEST and SR grown crystals are 3.2 and 3.5 times greater than that of pure KDP. The Photoluminescence (PL) studies of Tb3+ ions result from the radiative intra-configurational f-f transitions that occur from the 5D4 excited state to the 7Fj (j = 6, 5, 4, 3) ground states. The decay curve of the 5D4 level of emission was observed with a long life time of 319.2041 μs for the SR grown Tb3+:LHHC crystal. 相似文献
9.
H.T. Shaban 《Materials Chemistry and Physics》2010,119(1-2):131-134
TlGaSe2 single crystals were grown by modified Bridgman method. The crystals were identified structurally by X-ray diffraction. Measurements of electrical conductivity and Hall effect were performed in the range (200–492 K) and (163–602 K) for thermoelectric power (TEP) measurements. Anisotropic nature of the layered TlGaSe2 crystal was investigated. Hall effect and thermoelectric power measurements revealed the extrinsic p-type conduction in the low temperature range of the study. The analysis of the temperature-dependent electrical conductivity and carrier concentration reveal that the acceptor level is located at 0.2 eV above the valence band of TlGaSe2. From the obtained experimental data, the main characteristic parameters of the crystals have been estimated. Energy gap and acceptor concentration were 2.23 eV and 9.6 × 1013 cm?3 respectively. 相似文献
10.
《Materials Research Bulletin》2006,41(3):547-552
In this paper, (Ca + Yb)- and (Ca + Sr)-stabilized α-SiAlON powders were fabricated by combustion synthesis. The influence of Ca2+ incorporation on the phase composition and grain morphology of combustion products was discussed. The experimental results showed that with the incorporation of Ca2+ well-developed rod-like (Ca + Yb) α-SiAlON crystals could be produced. It was also found that, when only Sr2+ was used as stabilizing cation, the reaction product was (α + β)-SiAlON composite, in which β-SiAlON was the predominant phase and the relative content of α-SiAlON was low. With the incorporation of Ca2+, however, both the relative content and the lattice parameters of α-SiAlON were clearly increased. These results indicated that the incorporation of Ca2+ could assist Sr2+ into the α-SiAlON lattice structure. 相似文献
11.
High-quality Ag2In2SiSe6 and Ag2In2GeSe6 single crystals have been successfully grown by the vertical Bridgman–Stockbarger method and the horizontal gradient freeze technique, respectively. For pristine and Ar+ ion-irradiated surfaces of the single crystals under study, X-ray photoelectron core-level and valence-band spectra have been measured. Results of these studies allow for concluding that the Ag2In2SiSe6 and Ag2In2GeSe6 single crystal surfaces are sensitive with respect to Ar+ ion-irradiation. In particular, Ar+ ion-bombardment with energy of 3.0 keV during 5 min at an ion current density of 14 μA/cm2 has induced some modification in top surface layers leading to an increase of content of In atoms in the layers. Comparison on a common energy scale of the X-ray emission Se Kβ2 bands representing energy distribution of the Se 4p states and the X-ray photoelectron valence-band spectra reveal that the main contribution of the valence Se p states occur in the upper portion of the valence band, with also their significant contributions in other valence band regions of the Ag2In2SiSe6 and Ag2In2GeSe6 single crystals. In addition, for the single crystals under consideration, temperature dependences of specific dark conductivity and spectral distributions of photoconductivity have been explored. It has been established that the Ag2In2SiSe6 and Ag2In2GeSe6 single crystals are high-resistance semiconductors with value of the specific electrical conductivity σ ≈ 1.67 × 10–9 Ω–1 сm–1 (at Т = 300 K). The both compounds are materials with p-type conductivity. 相似文献
12.
P. Unifantowicz S. Vaucher M. Lewandowska K.J. Kurzydłowski 《Materials Characterization》2010,61(6):648-652
The subject of this work is focused on characterization of the microstructures and orientations of SiC crystals synthesized in diamond–SiC–Si composites using reactive microwave sintering. The SiC crystals grown on the surfaces of diamonds have either shapes of cubes or hexagonal prisms, dependent on crystallographic orientation of diamond. The selection of a specified plane in diamond lattice for the TEM investigations enabled a direct comparison of SiC orientations against two types of diamond facets. On the {111} diamond faces a 200 nm layer of 30–80 nm flat β-SiC grains was found having a semi-coherent interface with diamond at an orientation: (111)[112]SiC║(111)[110]C. On the {100} diamond faces β-SiC forms a 300 nm intermediate layer of 20–80 nm grains and an outer 1.2 µm layer on top of it. Surprisingly, the SiC lattice of the outer layer is aligned with the diamond lattice: (111)[110]SiC║(111)[110]C. 相似文献
13.
《Advanced Powder Technology》2014,25(4):1212-1219
Ions of inorganic salts are known to affect bubble coalescence via ion size, charge density and polarizability. In this paper, a systematic study of the effect of monovalent anions (F−, Cl−, Br− and I−) and cations (Li+, Na+ and K+) on the lifetime of liquid films between two bubble surfaces is carried out by applying the thin film interferometry method. To mimic realistic conditions of bubble coalescence in a bubble column, drainage and stability of saline water films driven by different interface approach speeds (10–300 μm/s) using a nano-pump was investigated. The results show significant effects of interface approach speed on transient film thickness and radius, film stability and rupture, and lifetime of saline water films. The experiments also indicate that there is a critical approach speed of 35 μm/s for pure deionised water above which the water films instantly coalesce, i.e., no water film can be obtained. High interface approach speed creates corrugation on saline water film surfaces, which rapidly increases the rates of film radial expansion and drainage, and shortens the film lifetime. There is a critical salt concentration above which the saline water film lifetime abruptly increases. This critical concentration is independent of the interface approach speeds of 10–300 μm/s. Our experimental results show a decreasing trend of film lifetime with increasing the size of either the cation or anion (NaF > LiCl > NaCl > NaBr > NaI). The order of the critical concentrations is the opposite of the order of lifetimes. The experimental results highlight the ion-specific effect of salt ions on the water structure and hence the behavior of saline liquid films. These results are relevant to a number of chemical engineering processes taking place in saline water, including mineral separation by flotation using air bubbles in saline water. 相似文献
14.
Urchin-like α-Fe2O3 superstructures have been deposited on Si substrate using thermal decomposition FeCl3 solution at 200–600 °C in the oven. The morphologies and structures of the synthesized urchin-like superstructures have been characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results show that urchin-like α-Fe2O3 superstructures were a polycrystal with the rhombohedral structure and typical diameters of 16–20 nm and lengths up to 1.0 μm. The as-prepared α-Fe2O3 superstructures have a high Brunauer–Emmett–Teller (BET) surface area of about 60.24 m2/g. The photoluminescence spectrum of the urchin-like α-Fe2O3 superstructures consists of one weak emission peak at 548 nm (2.26 eV). A possible new mechanism for the formation of the urchin-like superstructures was also preliminarily discussed. 相似文献
15.
《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2007,571(3):699-703
The effect of neutron irradiation on a lithium tetraborate (Li2B4O7, LBO) single crystal has been investigated. The crystals of high optical quality are found to be quite stable under high neutron fluence. This study shows that LBO crystals can be used as a proportional counter for neutron fluxes of the order 109 cm−2 s−1 and higher. The detectors fabricated were found to have a sensitivity of ∼3×10−18 A (nv)−1. 相似文献
16.
The presented study reports on the spectroscopic characteristics of a new high performance scintillation material KCaI3:Eu. The growth of ∅ 17 mm boules using the Bridgman–Stockbarger method in fused silica ampoules is demonstrated to produce yellow tinted, yet transparent single crystals suitable for use in spectroscopic applications due to very promising performance. Scintillation light yield of 72,000 ± 3000 ph/MeV and energy resolution of 3% (FWHM) at 662 keV and 6.1% at 122 keV was obtained from small single crystals of approximately 15 mm3. For a much larger 3.8 cm3 detector, 4.4% and 7.3% for the same energy. Proportionality of the scintillation response to the energy of ionizing radiation is within 96% of the ideal response over an energy range of 14–662 keV. The high light yield and energy resolution of KCaI3:Eu make it suitable for potential use in domestic security applications requiring radionuclide identification. 相似文献
17.
TbVO4 (TV) single crystals with dimensions of 18 × 18 × 16 mm3 were grown by Czochralski method under different atmosphere. XPS studies revealed the presence of V4+ and Tb4+ in TV crystal grown at 99.9% N2 atmosphere, which caused a wide absorption peak centered at 950 nm in the transmission spectrum. TV crystal grown at 80% N2 + 20% CO2 mixed atmosphere has high transmittance at 600–1500 nm waveband. Faraday rotation spectra of TV crystal were measured. TV crystal has a larger Faraday rotation than terbium gallium garnet (TGG) crystal at 500–1500 nm waveband. 相似文献
18.
Gong-yi Li Xiao-dong Li Hao Wang Xin Xing Yong Yang 《Materials Science and Engineering: B》2010,166(1):108-112
β-SiC nanowires are a novel type of photocatalysts. However, they tend to be entangled together especially at high concentrations when dispersed in water, which may reduce the photocatalytic activity. It is reasonable to expect that β-SiC nanowires would provide better photocatalytic activity if they are grown on activated carbon. In the letter we report the successful synthesis of quantities of β-SiC nanowires grown on the surfaces of the activated carbon by pyrolysis of polycarbosilane at 1300 °C. The nanowires, with the diameters of 50–100 nm and the length of tens of micrometers, are composed of single crystal β-SiC along the 〈1 1 1〉 direction. Both the VLS and the VS mechanisms were employed to interpret the nanowires growth. 相似文献
19.
《Materials Research Bulletin》2006,41(7):1337-1344
The new phases α-NaSbP2S6 and β-NaSbP2S6 were synthesized by ceramic and reactive flux methods at 773 K. The structures of α-NaSbP2S6 and β-NaSbP2S6 were determined by the single-crystal X-ray diffraction technique. α-NaSbP2S6 crystallizes in the monoclinic space group P21/c with a = 11.231(2) Å, b = 7.2807(15) Å, c = 11.640(2) Å, β = 108.99(3)°, V = 900.0(3) Å3 and z = 4. β-NaSbP2S6 crystallizes in the monoclinic space group P21 with a = 6.6167(13) Å, b = 7.3993(15) Å, c = 9.895(2) Å, β = 92.12(3) °, V = 484.10(17) Å3 and z = 2.The α- and β-phases of NaSbP2S6 are closely related, the main difference lies in the stacking of the [Sb[P2S6]]nn− layers. The structure of α-NaSbP2S6 consists of two condensed layers (MPS3 type) to give an ABAB… sequence with Na+ cations located in the interlayer space. The packing of β-NaSbP2S6 is formed by monolayers of [Sb[P2S6]]nn− stacked in an AA… fashion separated by a layer of Na+ cations. Both phases are derivates of the M1+M3+P2Q6 family.The optical band gaps of α-NaSbP2S6 and β-NaSbP2S6 were determined by UV–vis diffuse reflectance measurements to be 2.17 and 2.25 eV, respectively. 相似文献
20.
We report a study on the optical properties of 40 keV Xe+ implants with a dose of 5 × 1016 ions/cm2 into p-type conducting CuInSe2 single crystals using the phase resolved method of the photoacoustic spectroscopy (PAS) technique. Photoacoustic spectra have been measured in the photon energy range 0.7 < hν < 1.4 eV prior and after implantation at various phase angles using a high resolution fully computerized spectrometer. Once the spectra separation is carried out, an analysis on the impact of Xe+ on the defect structure of CuInSe2 is presented. The results obtained here are discussed in the light of current reported literature. 相似文献