共查询到20条相似文献,搜索用时 31 毫秒
1.
A. V. Semirov D. A. Bukreev A. A. Moiseev V. A. Lukshina E. G. Volkova S. O. Volchkov G. V. Kurlyandskaya 《Technical Physics》2011,56(3):395-399
The temperature dependences of the magnetic properties and the magnetoimpedance effect of soft magnetic nanocrystalline Fe73.5Si16.5B6Nb3Cu1 alloy ribbons are studied in the temperature range 24–160°C. A high temperature sensitivity of the impedance and the magnetoimpedance
effect of the ribbons are detected in the ac frequency range 0.1–50 MHz. At an ac frequency of 50 MHz, the change in the impedance
reaches 0.2 Ω/°C (0.5%/°C) in the temperature range 85–160°C. When the temperature increases, a monotonically decreasing character
of the dependence of the magnetoimpedance effect on the applied magnetic field changes into a dependence having an increasing
initial segment. The effect of temperature on the magnetoimpedance properties of the soft magnetic nanocrystalline ribbons
is shown to result from temperature-induced changes in their electrical conductivity, magnetization, and effective magnetic
anisotropy. 相似文献
2.
O. M. Fedorova V. F. Balakirev Yu. V. Golikov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(8):1153-1154
The solubility ranges of Er2O3 and Mn3O4 oxides and ErMn2O5 manganite in ErMnO3 ± δ are determined for the temperature range 900–1400°C. 相似文献
3.
Monika Aggarwal M. Husain Samina Khan Zishan H. Khan 《Journal of nanoparticle research》2007,9(6):1047-1055
Carbon nanotubes (CNTs) are synthesized by the catalytic decomposition of acetylene using low pressure chemical vapour deposition
method (LPCVD) at 800 °C and at a chamber pressure of 10 Torr over a supported catalyst film of Fe70Pd30. Morphology of these CNTs is studied using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and
High Resolution Transmission Electron Microscopy (HRTEM). From HRTEM image of these multi-walled carbon nanotubes (MWNTs),
it is clear that these MWNTs do not possess a co-axial cylindrical structure, but are composed of imperfect and broken graphite
cylinders of different sizes. The average diameter and length of the nanotubes varies between 20–70 nm and 5–60 μm respectively.
Electrical transport measurements of these MWNTs are studied over a temperature range of 298–4.2 K. The results have been
interpreted in terms of variable-range hopping (VRH) over the entire temperature range of 298–4.2 K. Three-dimensional variable-range
hopping (VRH) is suggested for the temperature range (298–125 K), while two-dimensional VRH is observed for the temperature
range (125–4.2 K). 相似文献
4.
Zhe Zheng Yunzhong Chen Zexiang Shen Jan Ma Chorng-Haur Sow Wei Huang Ting Yu 《Applied Physics A: Materials Science & Processing》2007,89(1):115-119
We report the synthesis of single-crystalline α-Fe2O3 nanoflakes from a simple Fe–air reaction within the temperatures range of 260–400 °C. The nanoflakes synthesized at the lowest
temperature (260 °C) in this work show an ultra-sharp morphology: 5–10 nm in thickness, 1–2 μm in length, 20 nm in base-width
and around 5 nm at the tips; successfully demonstrate the promising electron field emission properties of a large-scaled α-Fe2O3 nanostructure film and exhibit the potential applications as future field-emission (FE) electron sources and displays (FEDs).
The formation and growth of α-Fe2O3 nanostructures were discussed based on the surface diffusion mechanism.
PACS 79.60.Jv; 79.70.+q; 77.84.Bw 相似文献
5.
Banarji Behera Pratibindhya Nayak Ram N. P. Choudhary 《Central European Journal of Physics》2008,6(2):289-295
A polycrystalline sample of KCa2Nb5O15 with tungsten bronze structure was prepared by a mixed oxide method at high temperature. A preliminary structural analysis
of the compound showed an orthorhombic crystal structure at room temperature. Surface morphology of the compound shows a uniform
grain distribution throughout the surface of the sample. Studies of temperature variation on dielectric response at various
frequencies show that the compound has a transition temperature well above the room temperature (i.e., 105°C), which was confirmed
by the polarization measurement. Electrical properties of the material have been studied using a complex impedance spectroscopy
(CIS) technique in a wide temperature (31–500°C) and frequency (102–106 Hz) range that showed only bulk contribution and non-Debye type relaxation processes in the material. The activation energy
of the compound (calculated from both the loss and modulus spectrum) is same, and hence the relaxation process may be attributed
to the same type of charge carriers. A possible ‘hopping’ mechanism for electrical transport processes in the system is evident
from the modulus analysis. A plot of dc conductivity (bulk) with temperature variation demonstrates that the compound exhibits
Arrhenius type of electrical conductivity.
相似文献
6.
Elemental mixtures of Al, Cu, Fe powders with the nominal composition of Al70Cu20Fe10 were mechanically alloyed in a planetary ball mill for 80 h. Subsequent annealing of the as-milled powders were performed
at 600–800°C temperature range for 4 h. Structural characteristics of the mechanically alloyed Al70Cu20Fe10 powders with the milling time and the heat treatment were investigated by X-ray diffraction (XRD), differential scanning
calorimeter (DSC) and differential thermal analysis (DTA). Mechanical alloying of the Al70Cu20Fe10 did not result in the formation of icosahedral quasicrystalline phase (i-phase) and a long time milling resulted in the formation
of β-Al(Cu,Fe) solid solution phase (β-phase). The i-phase was observed only for short-time milled powders after heat treatment above 600°C. The β-phase was one of the major phases in the Al70Cu20Fe10 alloy. The w-Al7Cu2Fe1 phase (w-phase) was obtained only after heat treatment of the short-time milled and unmilled samples. The present investigation
indicated that a suitable technique to obtain a large amount of quasicrystalline powders is to use a combination of short-time
milling and subsequent annealing. 相似文献
7.
SiO2-TiO2 films [Si:Ti = 1:(0.06–2.3)] are obtained by the sol-gel method. The structural and photoluminescent properties of the films
and powders heat-treated at different temperatures are studied. It is shown that after 700°C the composite consists of TiO2 crystallites that are structurally similar to anatase and distributed in an amorphous SiO2 matrix. The photoluminescence spectra have maxima at 450–500 nm. The photoluminescence intensity depends on the treatment
temperature and TiO2 content.
__________
Translated from Zhurnal Prikladnoi Spektroskopii Vol. 74, No. 3, pp. 357–361, May–June, 2007. 相似文献
8.
The electrophysical properties and structure of the nonstoichiometric high-temperature superconductor YBa2Cu3O
y
restored at T = 930–950°C after low-temperature decomposition (T = 200°C) into phases different in the oxygen content have been studied. It has been shown that, unlike heat treatments at
T ≤ 900°C, the superconducting properties are almost completely restored for 3–5 h during grain recrystallization, which is
impossible at lower temperatures. After short-term annealing at T = 930–950°C (for 1–2 h), the ceramic material still contains a significant number of structural defects, most likely, in
cation sublattices. These defects can contribute to the pinning of magnetic vortices, which substantially increases the critical
current density in magnetic fields up to 2 T as compared to ceramic materials produced by the conventional technology. 相似文献
9.
Nanoscale yttrium–barium–copper oxide (Y2BaCuO5, Y211) particles were synthesized using the emulsion method and the solution method. The basic water-in-oil (w/o) emulsion
system consisted of n-octane (continuous oil phase), cetyltrimethylammonium bromide (cationic surfactant), butanol (cosurfactant) and water. The
composition of the emulsion system was varied and characterized by measuring the conductivity of the solutions and droplet
size. The droplet size of emulsion was determined by using the dynamic light scattering method. The water content, cosurfactant
content, and surfactant/n-octane ratio affected the droplet size which was in the range of 3–8 nm, and hence the w/o emulsion system was referred to
as a nano-emulsion system. A model was used to verify the droplet size. The influence of salt (Y2(NO3)3) content on the droplet size was investigated and the addition of salt reduced the droplet size. The effects of reaction
time and temperature on the Y211 particle sizes were also investigated. The particles were characterized using the TEM, SEM,
and XRD. Nanoparticles produced by the nano-emulsion method were calcined at 850°C to form the Y211 phase as compared to solid
state processing temperature of 1050°C. Based on the TEM analysis, the average diameter of the Y211 particles produced using
the nano-emulsion method was in the range of 30–100 nm. The effect of adding 15% Y211 nanoparticles to the superconductor
YBCO-123 as flux pinning centers, was investigated, and the transition temperature was reduced by 3 K. 相似文献
10.
Yu. M. Shul’ga E. N. Kabachkov D. V. Matyushenko E. N. Kurkin I. A. Domashnev 《Technical Physics》2011,56(1):97-101
TiO2 nanopowder is produced by the low-temperature hydrolysis of TiCl4. The phase composition of the sample is found to form at a hydrolysis temperature of 30–38°C. Low-temperature annealing (up
to 440°C) increases the degree of crystallinity of the phases present in the sample (anatase, brookite) and only weakly affects
their ratio. At 500°C, the sample consists of three phases: rutile is detected apart from anatase and brookite. Brookite begins
to fail at 600°C; at 700°C, crystalline brookite fails completely. 相似文献
11.
We have synthesized nanosized La0.67Ca0.33MnO3 by a simple low-cost novel synthesis route without calcination at high temperature. The study of these nanoparticles indicates
excellent properties similar to colossal magnetoresistance (CMR) materials sintered at ∼1600°C for 20 h. The resulting particle
size is in the range of 50–160 nm as determined by scanning electron microscopy. Resistivity measurement has been carried
out down to 12 K. The sample shows metal-to-insulator (M–I) transition at 205 K.
相似文献
12.
C. Masingboon S. Maensiri T. Yamwong P.L. Anderson S. Seraphin 《Applied Physics A: Materials Science & Processing》2008,91(1):87-95
Nanocrystalline CaCu3Ti4O12 powders with particle sizes of 50–90 nm were synthesized by a simple method using Ca(NO3)2·4H2O, Cu(NO3)2·4H2O, titanium(diisoproproxide) bis(2,4-pentanedionate) and freshly extracted egg white (ovalbumin) in aqueous medium. The synthesized
precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found
to be at above 400 °C. The precursor was calcined at 700 and 800 °C in air for 8 h to obtain nanocrystalline powders of CaCu3Ti4O12. The calcined CaCu3Ti4O12 powders were characterized by XRD, FTIR, SEM and TEM. Sintering of the powders was conducted in air at 1100 °C for 16 h.
The XRD results indicated that all sintered samples have a typical perovskite CaCu3Ti4O12 structure and a small amount of CuO, although the sintered sample of the 700 °C calcined powders contained some amount of
CaTiO3. SEM micrographs showed the average grain sizes of 12.0±7.8 and 15.5±8.9 μm for the sintered CaCu3Ti4O12 ceramics prepared using the CaCu3Ti4O12 powders calcined at 700 and 800 °C, respectively. The sintered samples exhibit a giant dielectric constant, ε′ of ∼ 1.5–5×104. The dielectric behavior of both samples exhibits Debye-like relaxation, and can be explained based on a Maxwell–Wagner model.
PACS 77.22.Gm; 81.05.Je; 81.07.Wx; 81.20.Ev 相似文献
13.
Phan Van Cuong Joonghoe Dho Hyo Yeol Park Do-Hyung Kim 《Applied Physics A: Materials Science & Processing》2009,95(2):567-571
This paper reports on the sonochemical-assisted synthesis of La0.7Sr0.3MnO3 (LSMO) nanoparticles (NPs) which have a single-crystalline perovskite structure. The average particle size of LSMO NPs was
controlled from about 40 to 120 nm by changing the annealing temperatures from 750 to 1050°C. The particle size, electrical
resistivity, and ferromagnetic transition temperature of LSMO NPs were strongly dependent on the annealing temperature. A
substantial decrease in resistivity and an enhancement in the insulator–metal transition temperature were found on increasing
the annealing temperature. Furthermore, the enhancement in magnetization and paramagnetic–ferromagnetic (PM–FM) transition
temperatures was observed as the annealing temperature increases. 相似文献
14.
There has been an increasing interest towards the incorporation of nanosize ceramic fillers in polymer electrolytes. Solid
polymer electrolytes based on polyvinylidene fluoride (PVDF), silver triflate (AgCF3SO3), and x wt% of aluminum oxide (Al2O3) nanopowders (where x = 1, 3, 5, and 10, respectively) have been prepared using solution casting technique. The structural characteristics of these
thin film specimens were studied using Fourier transform infrared (FTIR) and X-ray diffraction (XRD) patterns at room temperature.
The appearance of new absorption bands and gradual shifts observed in some characteristic peaks confirmed the complex formation
between polyvinylidene fluoride and silver triflate. Furthermore, the addition of nanosized filler Al2O3 has also indicated the interaction of the filler with the polymer salt complex. The XRD patterns obtained for all these samples
in the 2θ range 10° to 70° showed the amorphous nature of these samples.
Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, December 7–9,
2006. 相似文献
15.
L. M. Kubalova I. A. Sviridov V. I. Fadeeva 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(8):1033-1035
The solid-phase interaction of cobalt with boron during high-energy ball milling of Co80B20 and Co60B40 mixtures was studied. It was found that Co3B boride forms during the mechanical alloying of components in the presence of both modifications of Co with a reduction in
the size of blocks of up to 7–15 nm. The transformation of the metastable Co3B phase into stable Co2B and CoB borides is observed in the temperature range of 590–700°C. 相似文献
16.
Pigment-grade anatase TiO2 particles (160 nm) were passivated using ultra-thin insulating films deposited by molecular layer deposition (MLD). Trimethylaluminum
(TMA) and ethylene glycol (E.G) were used as aluminum alkoxide (alucone) precursors in the temperature range of 100–160 °C.
The growth rate varied from 0.5 nm/cycle at 100 °C to 0.35 nm/cycle at 160 °C. Methylene blue oxidation tests indicated that
the photoactivity of pigment-grade TiO2 particles was quenched after 20 cycles of alucone MLD film, which was comparable to 70 cycles of Al2O3 film deposited by atomic layer deposition (ALD). Alucone films would decompose in the presence of water at room temperature
and would form a more stable composite containing aluminum, which decreased the passivation effect on the photoactivity of
TiO2 particles. 相似文献
17.
V. Singh S. Watanabe T. K. Gundu Rao I.-J. Lee 《Applied physics. B, Lasers and optics》2011,104(4):1019-1027
Tricalcium aluminate doped with Eu3+ was prepared at furnace temperatures as low as 500°C by using the convenient combustion route and examined using powder X-ray
diffraction, scanning electron microscope and photoluminescence techniques. A room-temperature photoluminescence study showed
that the phosphors can be efficiently excited by UV/Visible region, emitting a red light with a peak wavelength of 616 nm
corresponding to the 5D0–7F2 transition of Eu3+ ions. The phosphor exhibits three thermoluminescence (TL) peaks at 195°C, 325°C and 390°C. Electron Spin Resonance (ESR)
studies were carried out to study the defect centres induced in the phosphor by gamma irradiation and also to identify the
defect centres responsible for the TL process. Room-temperature ESR spectrum of irradiated phosphor appears to be a superposition
of three distinct centres. One of the centres (centre I) with principal g-value 2.0130 is identified as O− ion while centre II with an axially symmetric principal values g
∥=2.0030 and g
⊥=2.0072 is assigned to an F+ centre (singly ionized oxygen vacancy). O− ion (hole centre) correlates with the TL peak at 195°C and the F+ centre (electron centre), which acts as a recombination centre, is also correlated to the 195°C TL peak. F+ centre further appears to be related to the high temperature peak at 390°C. Centre III is also assigned to an F+ centre and seems to be the recombination centre for the TL peak at 325°C. 相似文献
18.
Using an ordinary ceramic fabrication technique, we fabricated lead-free (1-x)(K0.5Na0.5)NbO3-xBa(Ti0.95Zr0.05)O3 ceramics with CuO sintering aid . Ba(Ti0.95Zr0.05)O3 diffuses into (K0.5Na0.5)NbO3 to form a new solid solution. The ceramics with perovskite structure possess orthorhombic phase at x≤0.04 and become tetragonal
phase at x≥0.06. Both the paraelectric cubic–ferroelectric tetragonal and the ferroelectric tetragonal–ferroelectric orthorhombic
phase transition temperatures decrease with increasing the concentration of Ba(Ti0.95Zr0.05)O3. The doping of CuO effectively promotes the densification of the ceramics. The coexistence of the orthorhombic and tetragonal
phases at 0.04<x<0.06 and the improvement in sintering performances of the ceramics significantly enhance the piezoelectric
and dielectric properties at room temperature. The ceramics with x=0.04–0.06 and y=0.75–1.50 possess excellent properties:
d33=119–185 pC/N, kP=37–44%, kt=35–49%, ε=341–1129, cosδ=0.7–4.4% and Tc=312–346 °C.
PACS 77.65.-j; 77.84.Dy; 77.84.-s 相似文献
19.
The photovoltaic characteristics of a photoelectrochemical cell of ITO/TiO2/PVC-LiClO4/graphite are reported. This paper is concerned with the influence of light intensity and temperature on short-circuit current
density, Jsc and open-circuit voltage, Voc of the device. The photoelectrochemical cell material was a screen-printed layer of titanium dioxide onto an ITO-covered
glass substrate, which was used as a working electrode of the cell. The solid electrolyte was polivinylchloride-lithium perchlorate.
The graphite film serves as a counter electrode of the cell. The current density–voltage characteristics of the device under
an illumination of 20, 40, 60, 80 and 100 mW cm−2 light from a tungsten halogen lamp were recorded at 40 °C as well as under an illumination of 100 mW cm−2 at 30, 35, 40, 45 and 50 °C, respectively. It was found that the short-circuit current density, Jsc of the device increases with both light intensity and temperature. The Jsc obtained at 100 mW cm−2 was 1.0 μAcm−2 and that at 50 °C was 0.7 μAcm−2. 相似文献
20.
The [N(CH3)4][N(C2H5)4]ZnCl4 compound has been synthesized by a solution-based chemical method. The X-ray diffraction study at room temperature revealed
an orthorhombic system with P21212 space group. The complex impedance has been investigated in the temperature and frequency ranges 420–520 K and 200 Hz–5 MHz,
respectively. The grain interior and grain boundary contribution to the electrical response in the material have been identified.
Dielectric data were analyzed using the complex electrical modulus M
* for the sample at various temperature. The modulus plots can be characterized by full width at half height or in terms of
a non-exponential decay function ϕ(t) = exp[(−t/τ)
β
]. The detailed conductivity study indicated that the electrical conduction in the material is a thermally activated process.
The variation of the AC conductivity with frequency at different temperatures obeys the Almond and West universal law. 相似文献