共查询到20条相似文献,搜索用时 15 毫秒
1.
Photostimulated degradation of the reflectivity of white anodic-oxide coatings on Al alloy (Al-AOCs) that are used as thermal-regulating
coatings of space vehicles is investigated by spectroscopy of diffuse reflection in the region of 0.5–6 eV. It is established
that irradiation in vaccum when λ≤300 nm leads to the appearance in diffuse-reflection spectra of the absorption bands at
4.0 and ∼4.6 eV that are similar to these induced by vacuum heating for T≥350 K. A growth in the absorption bands is accompanied
by gas release from the coatings. These processes have a common excitation spectrum, basic kinetic regularities, and a thermoactivated
character. UV irradiation in vacuum is assumed to initiate Al-AOC destruction with the formation of color centers. This process
is accompanied by the desorption of molecular products.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 801–806, November–December, 1997. 相似文献
2.
The diffuse reflection spectroscopy technique was used to investigate the color centers (CC) in the products of thermolysis
and photolysis of disperse Al(OH)3 in a vacuum. The spectra were recorded in situ in the region of 2.5–6.0 eV and 4000–12,000 cm−1. It was found that in thermolysis of Al(OH3) production of Al is accompanied, by transformation of the IR spectra of the compound and overtone vibrations of OH groups
and by the appearance of an absorption band (AB) at 4.0 eV with a shoulder at 4.4 eV. A similar AB is induced by UV irradiation
of Al(OH)3 in a vacuum. In the position of the maximum and shape, the AB at 4.0 eV in aluminum oxide produced by thermolysis of Al(OH)3 coincides with the AB of CC responsible for light- and temperature-stimulated degradation of white anode oxide coatings on
Al(Al-AOC). This suggests that in Al-AOC, CC are formed in decay of structural OmHn groups. In Al oxide and in Al-AOC, their nature is discussed with the use of data on optical absorption of radiation-induced
defects in Al2O3.
Research Institute of Physics at St. Petersburg State University, St. Petersburg 1, Ul’yanovskaya St., Petrodvorets St. Petersburg,
198904, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 400–404, May–June, 1998. 相似文献
3.
The absorption edge of the perovskite La0.9Sr0.1MnO3, determined using the diffuse reflection coefficient spectra, shifts by the giant amount 0.4 eV in the direction of lower
energies as the temperature decreases from the Curie point (155 K) to 141 K.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 4, 303–306 (25 August 1999) 相似文献
4.
B. P. Aduev D. R. Nurmukhametov A. V. Puzynin 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(3):452-456
The temperature dependence of the probability of the explosion of pentaerythritol tetranitrate (PETN) with an admixture of
NiC particles (0.3 wt %) initiated by laser pulses (1064 nm, 20 ns) was studied over the temperature range 295–450 K. At 295–350
K, a weak temperature dependence was observed. The determining contribution to explosion initiation was made by the absorption
of laser radiation by nanoparticles. The threshold of explosive decomposition at 295 K decreased by ∼40 times compared with
samples free of NiC nanoparticles. Over the temperature range 400–450 K, the threshold of the explosive decomposition of samples
containing NiC nanoparticles decreased with the activation energy ∼0.4 eV. A decrease in the threshold of explosive decomposition
with a ∼0.4 eV activation energy over the temperature range 340–440 K was also observed for laser action on PETN samples not
containing NiC. A hypothesis was suggested according to which the absorption of a light quantum caused the transfer of an
electron from the valence band of the crystal to a level in the forbidden band with subsequent thermal positive ion dissociation
to the carbocation and NO3 radical. 相似文献
5.
Rammo I. Kerikmyaé M. Lepist M. Matizen L. Pung L. Ritslaid K. 《Journal of Applied Spectroscopy》1997,64(4):560-562
We investigate the impurity absorption of SrS−Ce phosphors. For this purpose, we measure the spectra of diffuse reflection
of powder phosphors. It is established that the introduction of Ce simultaneously with a coactivator gives rise to a strong
absorption band at 2.88 eV, and the introduction of a coactivator (NH4F, NH4Cl, NH4Br, NH4I, LiCl, NaCl or KCl), to an absorption band at about 2.36 eV. We assume that the absorption band at 2.88 eV is caused by
that portion of Ce introduced that forms the center of luminescence of Ce3+.
Tartu University, Estonian, Republic, 18, Yulikooli St., Tartu, EE2400, Estonia. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 64, No. 4, pp. 542–544, July–August, 1997. 相似文献
6.
Three kinds of Al–Ti nanoparticles (7.7, 27.8, and 42.6 at.% Ti) have been prepared from Al–65, Al–85, and Al–88 at.% Ti master
alloys by hydrogen plasma-metal reaction, with average particle sizes of 30, 25, and 80 nm, respectively. The higher evaporation
rate of Al than Ti resulted in the low Ti contents in the nanoparticles than those in the master alloys. Microscopy observation
revealed that the primary nanoparticles are spherical in shape, and occur as chain aggregates of several individual nanoparticles
due to the faster collision rate than the coalescence rate. All the Al–Ti nanoparticles contain amorphous alumina layers of
about 2–3 nm in thickness surrounding the crystalline core. AlTi intermetallic nanoparticles were successfully produced for
Al–27.8 at.% Ti, with a single crystal of AlTi in one chain aggregate. The composite nanoparticles of Al together with some
Al3Ti phases are prepared for Al–7.7 at.% Ti, with each phase in the individual particle of one chain aggregate. The composite
nanoparticles of AlTi with some AlTi3 were produced for Al–42.6 at.% Ti, with each phase in the individual particle of one chain aggregate. The formation mechanism
of Al–Ti nanoparticles was interpreted in terms of phase transition and the effect of hydrogen. 相似文献
7.
A method for preparing thin films of CsPbI3 and Cs4PbI6 complex compounds has been developed. Their absorption spectrum is investigated in the energy range of 2–6 eV at temperatures
from 90 to 500 K. It is found that the CsPbI3 compound is unstable and passes to the Cs4PbI6 phase upon heating at T ≥ 400 K. 相似文献
8.
A program has been developed for separating the spectrum of radiation-induced absorption in powdered zinc oxide and reflective
coatings based on it into individual components which includes calculations of the parameters of the bands arising from intrinsic
point defects, bands from chemisorbed gases, and nonelective absorption by free electrons. Experimental results on the changes
in the diffuse reflection spectra of ZnO powder and reflective coatings after the action of various forms of radiation have
been found. The experimental spectra have been decomposed into individual components.
Tomsk Polytechnic University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 106–112, September,
1997. 相似文献
9.
Ch. B. Lushchik E. A. Vasil'chenko I. A. Kudryavtseva M. M. Kirm A. Ch. Lushchik 《Russian Physics Journal》1996,39(11):1029-1040
The paper discusses the phenomenon of electron-excitation multiplication that arises when alkali halide crystals are exposed
to 12–32 eV photons, with absorption of one photon followed at 8 K by the appearance of two or three electron excitations.
Measurement of the spectrum of F-center generation by 6.5–32 eV photons showed that at 200–300 K, when vacancies and interstitials
are mobile, the formation of stable defects is especially efficient when radiation creates a mixture of electron-hole pairs
and excitons. Certain mechanisms of creation and stabilization of defects at various stages in electron-excitation multiplication
are discussed.
Institute of Physics of Estonia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 30–44, November,
1996. 相似文献
10.
A. V. Kabyshev F. V. Konusov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(2):327-334
The optical absorption of leucosapphire and polycrystalline corundum (polycor) upon coimplantation of iron and chromium ions
and subsequent annealing in vacuum is studied. The structure of the states localized in the band gap induced by radiation
defects exhibits a higher stability to annealing as compared to implantation of other types of ions into aluminum oxide and
to separate irradiation with iron and chromium ions. The governing contribution to the exponential and interband absorption
is made by substitutional defects of either type, their clusters, and impurity-vacancy complexes. The effect of incorporated
iron ions on the population of levels of chromium-containing defect clusters, on their recharge, and on interaction with intrinsic
radiation and biographical defects is revealed. Mixed clusters of substitutional defects are optically active in a spectral
range of 2.0–4.0 eV after annealing at a temperature of 1300–1600 K. 相似文献
11.
M. M. Michailov A. N. Lapin S. P. Andriets N. V. Dedov 《Russian Physics Journal》2009,52(10):1036-1042
Comparative analysis of the diffuse reflectance spectra (300–2100 nm) and of the integrated absorption factor of coatings
based on micropowders, nanopowders, and micropowders modified with Al2O3 nanopowders has been performed. In addition, the changes in the spectra resulting from electron irradiation of the powders
with energies of 30 keV at a fluence of up to 3∙16 cm–2 have been analyzed. It has been found that the diffuse reflectance decreases in order of coatings based on micro-powders,
nano-powders and modified powders, while radiation resistance increases in order of coatings based on nano-powders, modified
and micropowders. 相似文献
12.
B. C. Anusionwu G. A. Adebayo C. A. Madu 《Applied Physics A: Materials Science & Processing》2009,97(3):533-541
The surface properties of Al–Ga and Al–Ge liquid alloys have been theoretically investigated at a temperature of 1100 K and
1220 K respectively. For the Al–Ga system, the quasi chemical model for regular alloy and a model for phase segregating alloy
systems were applied, while for the Al–Ge system the quasi chemical model for regular and compound forming binary alloys were
applied. In the case of Al–Ga, the models for the regular alloys and that for the phase segregating alloys produced the same
value of order energy and same values of thermodynamic and surface properties, while for the Al–Ge system, the model for the
regular alloy reproduced better the thermodynamic properties of the alloy. The model for the compound forming systems showed
a qualitative trend with the measured values of the thermodynamic properties of the Al–Ge alloy and suggests the presence
of a weak complex of the form Al2Ge3. The surface concentrations for the alloys show that Ga manifests some level of surface segregation in Al–Ga liquid alloy
while the surface concentration of Ge in Al–Ge liquid alloy showed a near Roultian behavior below 0.8 atomic fraction of Ge. 相似文献
13.
Data presented on the influence of the temperature in the range 80–650 K on the spectral kinetics of the luminescence and
transient absorption of unactivated CsI crystals under irradiation by pulsed electron beams (〈E〉=0.25 MeV, t
1/2=15 ns, j=20 A/cm2). The structure of the short-wavelength part of the transient absorption spectra at T=80–350 K exhibits features, suggesting that the nuclear subsystem of self-trapped excitons (STE’s) transforms repeatedly
during their lifetime until their radiative annihilation at T⩾80 K, alternately occupying di-and trihalide ionic configurations. It is established that a temperature-induced increase
in the yield of radiation defects, as well as F and H color centers, and quenching of the UV luminescence in CsI occur in the same temperature region (above 350 K) and are characterized
by identical thermal activation energies (∼0.22 eV). It is postulated that the STE’s in a CsI crystal can have a trihalide
ionic core with either an on-center or off-center configuration; the high-temperature luminescence of CsI crystals is associated
with the radiative annihilation of an off-center STE with the structure (I−(I0I−
e
−))*.
Fiz. Tverd. Tela (St. Petersburg) 40, 640–644 (April 1998) 相似文献
14.
Y. J. Wu Y. Q. Lin S. P. Gu X. M. Chen 《Applied Physics A: Materials Science & Processing》2009,97(1):191-194
La0.5Bi0.5MnO3 ceramics with a single phase were prepared by a solid-state reaction method, and their dielectric properties were characterized.
Two dielectric relaxations with a giant dielectric constant were identified in the temperature range from 125 to 350 K. The
electron hopping between Mn3+ and Mn4+ was found to be the origin of the dielectric relaxation at low temperatures (125–200 K) with an activation energy of 0.18 eV.
The high temperature (200–350 K) dielectric relaxation can be attributed to the conduction. 相似文献
15.
A. D. Korotaev D. P. Borisov V. Yu. Moshkov S. V. Ovchinnikov Yu. P. Pinzhin V. M. Savostikov A. N. Tyumentsev 《Russian Physics Journal》2008,51(11):1178-1187
Peculiar relationship between the composition and fine structure and the variations in strength properties of nanostructured
and nanocomposite, high-carbon, high-oxygen Ti–Al–Si–N films are investigated using Auger spectroscopy, electron microscopy,
X-ray structural analysis and hardness measurements. It is shown that a TiN-based phase can form in these films, which exhibits
nanocrystalline or two-level grain structure distributed in the x-ray amorphous phase whose volume fraction is 20–50%. The
grain-structure character can be deliberately changed by incorporating aluminum or silicon into the films. It is found out
that irrespective of their structural state and composition the films demonstrate high thermal stability of superhardness
and microstructure up to the temperatures Т ≈ 1173 K. Hardness is seen to decrease at Т ≥ 1273 K as a result of dislocation recovery, stress relaxation and early recrystallization. It is suggested that the high
strength properties demonstrated by these films are due to the presence of dislocation substructure and high shear resistance
of the x-ray amorphous phases along nanocrystallite boundaries.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 57–65, November, 2008. 相似文献
16.
A. V. Mudryi A. I. Patuk V. M. Trukhan I. A. Shakin S. F. Marenkin 《Journal of Applied Spectroscopy》1998,65(1):155-159
An investigation is made of the low-temperature (4.2–78 K) photoluminescence of single crystals of cadmium diarsenide grown
from the gas phase and by the Bridgman method. Radiation near the fundamental absorption edge is detected, which is attributed
to annihilation of free excitons with simultaneous emission of phonons (the lines 1.0029 and 0.9840 eV at 4.2 K). The optical
width of the forbidden band is estimated at 4.2 K.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 149–152, January–February, 1998. 相似文献
17.
A. Ya. Khairullina T. V. Ol’shanskaya O. N. Kudanovich D. S. Filimonenko 《Journal of Applied Spectroscopy》2010,77(5):700-707
We have established a correlation between diffuse reflection of nickel oxide-based composites in the red region of the spectrum
and the nanostructural properties of the roughness profile of the composite. We present calculations of the absorption spectra
for samples of nanostructured nickel oxide of thickness 0.25–0.35 μm on aluminum oxide substrates from diffuse reflection
and transmission of the layers by multiple scattering methods, taking into account the luminescence of the samples in the
weak absorption region. Using a special optical system, we have determined the selective sensitivity to carbon monoxide exposure
of a nanostructured nickel oxide composite at room temperature. The result is of fundamental importance for development of
optical selective gas sensor technology in the visible region of the spectrum. 相似文献
18.
LiCoO2 thin films were prepared by electron beam evaporation technique using LiCoO2 target with Li/Co ratio 1.1 in an oxygen partial pressure of 5 × 10−4 mbar. The films prepared at substrate temperature T
s < 573 K were amorphous in nature, and the films prepared at T
s > 573 K exhibited well defined (104), (101), and (003) peaks among which the (104) orientation predominates. The X-ray photoelectron
spectroscopy (XPS) and inductively coupled plasma (ICP) data revealed that the films prepared in the substrate temperature
range 673–773 K are nearly stoichiometric. The grain size increases with an increase of substrate temperature. The Co–eg absorption bands, are empty and their peak position lies at around 1.7 eV above the top to the Co–t2g bands. The fundamental absorption edge was observed at 2.32 eV. The films annealed at 1,023 K in a controlled oxygen environment
exhibit (104) out plane texture with large grains.
Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006 相似文献
19.
N. K. Tsenev V. N. Perevezentsev M. Yu. Shcherban’ A. N. Tsenev 《Technical Physics》2010,55(6):822-826
The annealing-induced evolution of the structure and microhardness of submicro-and nanocrystalline Al—3% Mg and Al 1570 alloys
produced by torsional severe plastic deformation are studied. Annealing of the Al-3% Mg alloy at 373–423 K and annealing of
the Al 1570 alloy at 373–473 K are shown to result in the relaxation of internal stresses and subsequent normal grain growth.
As the annealing temperature increases, the microhardness decreases. At higher temperatures (473 K for the Al—3% Mg alloy
and 573 K for the Al 1570 alloy), anomalous grain growth takes place. This growth is accompanied by the appearance of numerous
grains with a high dislocation density, a high concentration of impurity atoms in grain boundaries, and an increase in the
microhardness. These effects are explained. 相似文献
20.
Ablation of pentafluorophenylazide (FPA) in an Ar matrix at 8–10 K was carried out upon irradiation with ns-pulsed UV lasers
in a vacuum. The plume of ablated products was monitored by a time-resolved imaging/spectroscopic technique using a gated
and intensified CCD camera system. A large amount of pentafluorophenylnitrene (FPN) having a high kinetic energy (≈6 eV) was
ejected as fragments from the matrix film during ablation. A quantitative formation of triplet FPN from the photolysis of
the FPA was observed by spectroscopic measurements in the IR and UV-visible regions, and was confirmed by a theoretical IR
spectrum calculated according to density functional theory. A FPN beam is useful for chemical surface modification of organic
materials, such as aromatic polyester and alkylthiol. A surface analysis of these materials by X-ray photoelectron spectroscopy
and Fourier transform infrared reflection absorption spectroscopy showed that the FPN was immobilized onto the surface through
chemical bonds. This technique for the chemical surface modification of materials is made possible by a pulsed beam of reactive
fragments with a high density in the laser ablation process.
Received: 14 June 1999 / Accepted: 18 June 1999 / Published online: 21 October 1999 相似文献