共查询到20条相似文献,搜索用时 218 毫秒
1.
Naofumi Ohtsu Bun Tsuchiya Masaoki Oku Tatsuo Shikama Kazuaki Wagatsuma 《Applied Surface Science》2007,253(16):6844-6847
The initial oxidation of hafnium hydride was studied by X-ray photoelectron spectroscopy (XPS). The clean surface of hafnium hydride was obtained by fracturing the specimen in an XPS measurement chamber under a background pressure of 2.7 × 10−6 Pa. The fractured surface was oxidized in situ with the exposure to high-purity oxygen and the residual gases in an ultra-high vacuum chamber. The XPS spectra for the oxidized surfaces had the shoulder due to the oxidation, and the shoulder grew up with increase in exposure time even in the ultra-high vacuum. The factor analysis for the XPS spectra of the oxidized surface showed that the oxide formed in the chamber consists of only the hafnium dioxide, and no suboxide states are contained. The result corresponded to the oxide observed on hafnium hydride fractured in air. 相似文献
2.
Zirconium dioxide ZrO2 and hafnium dioxide HfO2 are investigated using high-temperature Raman spectroscopy in the temperature range 300–2080 K, including the regions of the monoclinic-tetragonal phase transitions revealed in these materials. An analysis is made of the specific features observed in the evolution of the high-temperature Raman spectra of both the monoclinic (m) and tetragonal (t) modifications of ZrO2 and HfO2 with variations in the temperature. The polarized Raman spectra of the metastable tetragonal phases in solid solutions based on zirconia and hafnia are used to identify the symmetry of vibrations in the spectra of the tetragonal modifications of pure zirconium and hafnium dioxides, which exist at high temperatures. 相似文献
3.
M. Forker L. Freise D. Simon H. Saitovitch P. R. J. Silva 《Hyperfine Interactions》1987,35(1-4):829-832
The electric quadrupole interaction (QI) at the site of181Ta in different hafnium hydrides HfHx has been investigated as a function of temperature by TDPAC measurements. Below 300 K the QI is static within a 300 nsec
time window. Above 300 K a dynamic QI related to the diffusion of hydrogen atoms leads to relaxation effects in the TDPAC
spectra. The average residence time between hydrogen jumps, evaluated on the basis of the theory of stochastic perturbations,
ranges from 100 nsec at 400 K in the ɛ-phase to 1 nsec at 700 K in the α-phase of the hafnium-hydrogen system. The activation
energy for hydrogen jumps was found to be independent of the hydrogen concentration: Ea=0.53(12) eV. 相似文献
4.
X-ray photoelectron spectroscopy has been used to determine the Auger parameters in elemental hafnium and in hafnium oxide (HfO2). The zirconium Lα line has been used as a source of excitation to study the 3d core levels of hafnium, the 1s core level of oxygen, and the X-ray excited MNN Auger region of hafnium and KVV Auger region of oxygen. The Auger parameters for hafnium and oxygen have been determined from these spectral data. In case of oxygen, the Auger parameter has been compared with the corresponding value in water. The change in the Auger parameter is observed to be negative for hafnium and positive for oxygen. We have shown that the opposite signs of the Auger parameters in binary systems can be utilized to determine the direction of charge transfer between the constituents. This is consistent with the chemical shift due to charge transfer. This chemical shift in the core level has been evaluated by subtracting the relaxation shift from the experimentally observed core level shift. It is found to be positive for the 3d5/2 core level of hafnium in the oxide indicating a charge transfer from hafnium to oxygen in the oxide. The observations are consistent with Pauling’s electronegativity criterion. 相似文献
5.
Andrew P. Purdy Rebecca Sorber Albert Epshteyn Katherine A. Pettigrew Joel B. Miller 《Journal of nanoparticle research》2011,13(10):5435-5448
Hafnium tetrachloride was reduced in organic solvents with lithium powder, sodium–potassium alloy, or lithium hydride/Et3B. All reductions required sonochemical agitation to proceed at an appreciable rate, with the notable exception of the reaction
of HfCl4 with Li in diethyl ether. Activation of C–H bonds occurred in all reactions, which resulted in carbon-containing products.
HfCl4 was reduced on a 50-g scale with LiH/Et3B, and a 10-g scale with Li powder in pentane. All the solid products from the reductions were converted to nanomaterials
by annealing under vacuum from 500 to 1,000 °C, which also resulted in the sublimation of the alkali metal salts. The nanomaterials
contain a mixture of products with the α-Hf (hexagonal) structure (crystallite size 8–250 nm) and the HfC (FCC) structure
(crystallite size 3–80 nm), with the amount of hafnium in the bulk annealed product varying from 88 to 99 wt%. When toluene,
pentane, or triethylamine solvents were used, the presence of amorphous graphitic or carbonaceous material was also detected
by solid state 13C NMR. Thermally annealed products were additionally characterized by electron microscopy and thermal analysis under Ar/O2, and have BET surface areas ranging from 2.7 to 155 m2/g. 相似文献
6.
In this paper, we report the first-ever isotropic Compton profile of hafnium measured at an intermediate resolution, with
661.65 keV γ-radiation. To compare our experimental data, the theoretical computations have also been carried out within the
framework of pseudopotential using CRYSTAL03 code and the renormalized-free-atom (RFA) model. It is found that the present
experimental profile is in better agreement with the RFA calculations if the outer electronic configuration is chosen as 5d3.26s0.8. The cohesive energy of Hf is also deduced from the experimental data and is compared with the available data.
On leave from Hindu College, Sonepat 131 001, India 相似文献
7.
Optical characterization of sol gel TiO<Subscript>2</Subscript> monoliths doped with Brilliant Green
S. A. Tomás O. Zelaya R. Palomino R. Lozada O. García J. M. Yáñez A. Ferreira da Silva 《The European physical journal. Special topics》2008,153(1):255-258
Amorphous titanium dioxide monoliths doped with brilliant green (BG) were synthesized by the sol-gel process. The optical
properties of the monoliths were characterized by Photoacoustic Spectroscopy and Photoluminescence Spectroscopy. The absorption
spectra for the BG-doped TiO2 monoliths exhibited two well defined absorption regions: a band below 400 nm corresponding to TiO2 absorption and three absorption bands centered at 424 nm, 588 nm, and 632 nm due to brilliant green. While the undoped TiO2 monoliths showed no luminescence, the doped samples showed a strong luminescence band at 673 nm, which increased its intensity
for increasing organic dye doping. 相似文献
8.
M. M. Mikhailov 《Journal of Applied Spectroscopy》2006,73(1):79-84
The diffuse reflectance (DR) spectra and the cathodoluminescence (CL) spectra in the range 0.34–2.10 μm and changes in the
spectra after bombardment by accelerated electrons have been studied as a function of the specific surface area and the grain
sizes of titanium dioxide (rutile) powders of different grades (P1, P2, P02, R10). It has been established that the diffuse
reflection coefficient and the luminescence band intensity increase as the specific surface area decreases and the grain size
of the powder increases. A smaller specific surface area of the powders means lesser initial flareup and subsequent “quenching”
of the CL bands as a function of electron fluence. It has been shown that history-related differences between powders of different
grades is a less significant factor than the specific surface area in determining the diffuse reflectance and luminescence
and also the radiation resistance of the powders.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 73–77, January–February, 2006. 相似文献
9.
XPS spectra are presented from films of different stoichiometry: HfN1.0 made by CVD and reactive sputtering and HfN1.09 made by ion plating. They support the existing theoretical calculations where the valence band comprises a strong Hf 5d band immediately below EF and a band of mainly N 2p character some 6 eV below EF. The core levels are shifted to larger binding energies by about 1.5 eV indicating electron transfer from hafnium to nitrogen. The effect of substoichiometry on the spectra is very small. 相似文献
10.
V. I. Yukhvid D. E. Andreev V. N. Sanin N. V. Sachkova 《Russian Journal of Physical Chemistry B, Focus on Physics》2017,11(5):815-819
The production of hafnium aluminides from mixtures of hafnium or its oxide with aluminum in the combustion mode is impossible because of a near-zero thermal effect. The present study is aimed at stimulating autowave chemical transformation with the help of energetic formulations and producing cast hafnium aluminides by means of combustion methods. The characteristics of the autowave synthesis and the conditions for producing cast hafnium aluminides are determined, and their composition and structure are investigated. 相似文献
11.
U. Köster O. Arndt R. Catherall J. G. Correia B. Crepieux R. Eichler P. Fernier L. M. Fraile S. Hennrich K. Johnston S. Lukic J. Neuhausen B. S. Nara Singh B. Pfeiffer E. Siesling 《The European physical journal. Special topics》2007,150(1):293-296
The production of ISOL beams of hafnium is described.
Radioactive Hf isotopes were produced at ISOLDE by 1.4 GeV proton-induced spallation
in Ta and W foils. Chemical evaporation in form of HfF4 and mass separation in the
molecular sideband HfF3+ after electron impact ionization provided intense
and pure beams.
Beams of 158-185Hf and short-lived isomers down to 1.1 s 177mHf were
observed, but the method could be extended to reach even more exotic isotopes:
down to about 154Hf (N=82) on the neutron-deficient side and up to
neutron-rich 188Hf. 相似文献
12.
E. I. Slobozhanina N. M. Kozlova L. P. Kas’ko M. V. Mamontova E. A. Chernitskii 《Journal of Applied Spectroscopy》1998,65(6):988-991
Absorption and luminescence excitation and emission spectra of the amniotic fluid from females with a normal course of pregnancy
and with fetation anomalies are investigated. It is shown that the amniotic fluid manifests, in addition to an intense UV
luminescence, a luminescence in the range of 380–650 nm. The first luminescence peak with λmax = 430–450 nm is most likely due to the presence of NADH2 and hormones in the amniotic fluid, whereas the peak located at longer wavelengths with λmax = 520–540 nm is due to pigments (bilirubin, etc.). Differences in absorption spectra of the amniotic fluid in the case of
the normal course of pregnancy and upon its pathologies are established. Luminescence emission and excitation spectra of the
amniotic fluid in cases of intrauterine fetation pathologies are shifted toward the longwave region compared to normal pregnancy
cases. It is concluded that the spectral-luminescent analysis of the amniotic fluid can be used as an additional rapid test
for monitoring of intrauterine fetal pathologies.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 939–942, November–December, 1998. 相似文献
13.
O. M. Bordun I. I. Kukharskii V. V. Dmitruk V. G. Antonyuk V. P. Savchin 《Journal of Applied Spectroscopy》2008,75(5):681-684
Luminescence photoexcitation spectra of α-Bi2O3 ceramics are investigated. Luminescence spectra were deconvoluted into fundamental components using the Alentsev-Fok method.
It is established that the luminescence spectra of α-Bi2O3 ceramics consist of three fundamental bands with maxima at 2.75, 2.40, and 1.97 eV. A comparison of the results with those
from an investigation of luminescence of various modifications of bismuth oxide and bismuth germanates suggests that luminescence
of these compounds is caused by radiation processes that occur in structural complexes that contain the bismuth ion in a nearest
oxygen environment.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 672–676, September–October, 2008. 相似文献
14.
V. I. Solomonov A. V. Spirina S. F. Konev S. O. Cholakh 《Optics and Spectroscopy》2014,116(5):793-797
An analysis of the electron spin resonance (ESR) spectrum of transparent ceramics composed of yttrium oxide with zirconium and hafnium additives has revealed the presence of signals (with similar parameters) from Zr3+ and Hf3+ ions, which have a similar electron configurations of the ground states: [Kr]4d 1 and [Xe]5d 1, respectively. It is shown that the pulsed cathodoluminescence spectra of these ions consist of two bands peaking at λ ≈ 818 and 900 nm. 相似文献
15.
Sc2O3 luminescence spectra are studied. The spectra are separated into elementary bands by the Alentsev–Fock method. It is established
that the luminescence spectra consist of a number of overlapping bands with maxima at 3.5; 3.05; 2.65; 2.35, and 2.05 eV.
The band at 3.5 eV is interpreted as emission of self-localized excitons, and the other bands, as defect-center recombination.
L’vov State University, 50, Dragomanov St., L’vov, 290005, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol.
64, No. 6, pp. 776–778, November–December, 1997. 相似文献
16.
E. M. Shishonok L. Trinkler S. V. Leonchik B. Berzinya 《Journal of Applied Spectroscopy》2008,75(4):567-575
Under high pressure and temperature conditions, we have obtained samples of thulium-activated cubic boron nitride in the form
of micropowders, ceramics, and polycrystals activated by thulium in the presence of aluminum. We studied the cathodoluminescence
(CL), photoluminescence (PL), and photoluminescence excitation spectra of the samples. In the luminescence spectra we observe
structured bands with maxima at ∼370, ∼475, ∼660, and ∼ 800 nm, assigned to electronic transitions in the triply charged thulium
ions. We have established that the most efficient method for excitation of “blue” luminescence at ∼475 nm for thulium ions
in cBN is excitation by an electron beam. The cBN samples synthesized in the presence of Al have photoluminescence spectra
with a more complex structure compared with samples not containing Al, with the band of dominant intensity at about 660 nm.
Hypothetically, this is a consequence of incorporation of thulium ions into the crystalline phases cBN and AlN, which are
equally likely to be formed during synthesis. The observed photoluminescence spectrum of the indicated samples is the superposition
of the photoluminescence spectra of the Tm3+ ions located in the crystal fields of cBN and AlN of different symmetries. The presence in the photoluminescence excitation
spectra (at 450, 490, and 660 nm) of structure, with features at wavelengths shorter than the excited photoluminescence, suggests
a nonresonant mechanism for its excitation. We have established that luminescence of Tm3+ ions is less intense than for other rare earth elements incorporated into cubic boron nitride.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 547–555, July–August, 2008. 相似文献
17.
Hao Wang Y. Wang J. Feng C. Ye B. Y. Wang H. B. Wang Q. Li Y. Jiang A. P. Huang Z. S. Xiao 《Applied Physics A: Materials Science & Processing》2008,93(3):681-684
High-k gate dielectric hafnium dioxide films were grown on Si (100) substrate by pulsed laser deposition at room temperature. The
as-deposited films were amorphous and that were monoclinic and orthorhombic after annealed at 500°C in air and N2 atmosphere, respectively. After annealed, the accumulation capacitance values increase rapidly and the flat-band voltage
shifts from −1.34 V to 0.449 V due to the generation of negative charges via post-annealing. The dielectric constant is in
the range of 8–40 depending on the microstructure. The I–V curve indicates that the films possess of a promising low leakage
current density of 4.2×10−8 A/cm2 at the applied voltage of −1.5 V. 相似文献
18.
Experimental data on the magnetic susceptibility of nonstoichiometric hafnium carbide HfCy(0.6< y<1.0) are presented. Anomalies are found in the temperature dependences of the magnetic susceptibility of the carbides HfC0.71, HfC0.78, and HfC0.83 in the temperature range 870–930 K. These anomalies are due to the formation of a superstructural short-range order in their
nonmetallic sublattice. It is shown that the short-range order in the carbides HfC0.71 and HfC0.78 corresponds to the ordered phase Hf3C2, while in the carbide HfC0.83 it corresponds to the ordered phase Hf6C5. It is found that the magnetic susceptibility of the carbide HfC0.78 in the temperature interval 910–980 K is zero.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 4, 296–301 (25 February 1999) 相似文献
19.
L. A. Mendoza-Zélis A. G. Bibiloni M. C. Caracoche A. R. Lopéz-García J. A. Martínez R. C. Mercader A. F. Pasquevich 《Hyperfine Interactions》1977,3(1):315-320
The electric field gradient EFG in hafnium pyrovanadate has been measured at Hf sites at different temperatures with the time-differential perturbed angular correlation method. The results obtained show the existence of a phase transition around 110°C. 相似文献
20.
Yu. M. Smirnov 《Journal of Applied Spectroscopy》1997,64(6):715-720
Detailed information about excitation cross-selections of spectral lines of titanium, zirconium, and hafnium atoms obtained
using extended crossed beams are used for calculation of the excitation cross-sections of the3G0-levels of these atoms. Results are compared with cross-sections calculated in Born’s approximation. For titanium: it is found
that theoretical predictions agree well with experimental data. Differences found for zirconium are explained by the single-configuration
approximation used in the calculation.
Moscow Power Institute, Russia, 14 Krasnokazarmennaya St., 111250, Moscow E-250, Russia. Translated from Zhurnal Prikladnoi
Spektroskopii, Vol. 64, No. 6, pp. 707–710, November–December, 1997. 相似文献