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1.
The nanocrystalline La0.8Sr0.2MnO3 (LSM) is prepared by varying the revolutions per minute and milling time of planetary monomill during the mechanochemical
method. The LSM forms in a relatively shorter milling time with an increase in the milling speed from 250 to 600 rpm. The
structural phase transition from orthorhombic to rhombohedral phase in the LSM prepared by ball milling at the speed 250 rpm
for 36 h is seen due to sintering it at 700 °C for 4 h. The crystallite size reduces with the increase in both the milling
speed and the milling time individually or combined. The microhardness (HV) and sintered density increase with the reduction
in the crystallite size. The temperature-activated transition temperature is suppressed by reducing the grain size in the
nanometer range. The electrical dc conductivity increases with the reduction in the grain/crystallite size. 相似文献
2.
Nanocrystalline CuAlS2 chalcopyrite has been mechanosynthesized at room temperature for the first time by ball milling the stoichiometric mixture
of elemental of Cu, Al, and S powders under argon atmosphere. Initially, the CuAlS2 phase is formed by solid state reaction of elemental powders within 15 min of milling and in the course of milling crystallite
size decreases slowly to ~5 nm within 10 h of milling. Microstructure characterization and phase transformation kinetics of
the elemental powders toward the chalcopyrite phase formation has been made by employing the Rietveld analysis using X-ray
diffraction data of unmilled and ball-milled samples. 相似文献
3.
M. Takeguchi M. Shimojo K. Furuya 《Applied Physics A: Materials Science & Processing》2008,93(2):439-442
Electron beam induced deposition was performed using a Pt(PF3)4 precursor gas. Self-standing nanowires were produced on the edge of a molybdenum film, followed by two post-deposition processes;
electron beam irradiation at room temperature and heating at about 400 K in vacuum. The as-deposited nanowires were composed
of an amorphous phase, of which the dominant composition was platinum but containing a small amount of phosphorus impurity.
After irradiating with a 300 keV electron beam, the amorphous nanowires were transformed to crystalline ones. By heating,
the as-deposited nanowires became single-crystal platinum with a large grain size and the phosphorus content disappeared. 相似文献
4.
G. V. Kalinnikov R. A. Andrievski V. N. Kopylov D. Louzguine 《Physics of the Solid State》2008,50(2):374-378
Nanostructured and x-ray-amorphous films in the TiB2-B4C system are prepared by nonreactive magnetron sputtering in the absence and presence of an additional external magnetic field with inductions of up to 0.3 T. The properties of the deposited films, such as the grain size, phase composition, dominant texture, roughness, and hardness, are investigated using transmission electron microscopy, microdiffraction, x-ray powder diffraction, atomic force microscopy, and microdurometry. The specific features of the phase diagram as applied to films and the effect of application of the magnetic field on their properties are discussed. 相似文献
5.
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
6.
Yu. A. Kotov V. V. Osipov O. M. Samatov M. G. Ivanov V. V. Platonov A. M. Murzakaev E. I. Azarkevich A. I. Medvedev A. K. Shtolts O. R. Timoshenkova 《Technical Physics》2004,49(3):352-357
The characteristics (phase composition, grain shape, grain size distribution, and specific surface area) of Ce0.78Gd0.22O2-δ nanopowders produced by exposing the target to pulsed CO2 laser radiation are reported. Reasons for a threefold increase in the output of the experimental powder-preparation unit
(up to 60 g/h) with the characteristic grain size (≈10 nm) remaining unchanged are discussed. 相似文献
7.
Vasily Lavrentiev Jiri Vacik Hiroshi Naramoto Kazumasa Narumi 《Applied Physics A: Materials Science & Processing》2009,95(3):867-873
The structure transformation occurring in fullerene film under bombardment by 50 keV C60+ cluster ions is reported. The Raman spectra of the irradiated C60 films reveal a new peak rising at 1458 cm−1 with an increase in the ion fluence. This feature of the Raman spectra suggests linear polymerization of solid C60 induced by the cluster ion impacts. The aligned C60 polymeric chains composing about 5–10 fullerene molecules have been distinguished on the film surface after the high-fluence
irradiation using atomic force microscopy (AFM). The surface profiling analysis of the irradiated films has revealed pronounced
sputtering during the treatment. The obtained results indicate that the C60 polymerization occurs in a deep layer situated more than 40 nm below the film surface. The deep location of the C60 polymeric phase indirectly confirms the dominant role of shock waves in the detected C60 phase transformation. 相似文献
8.
Pyrochlore-structured materials are very important materials due to their structural and conducting properties. These properties
can be further modified by changing processing conditions. In the present study, pyrochlore (Y2Ti2O7) is synthesized using high-energy ball milling. During various stages of ball milling, the ball-milled powder is taken for
investigating the structural and thermal properties. The replacement of Ti2O3 by TiO2 in nominal composition leads to lower ball milling duration to form Y2Ti2O7. Differential thermal analysis showed the single exothermic peak below 800 °C, which indicates formation of disordered pyrochlore
phase. The as prepared powders (40-h ball milled) were compacted and heat treated at 1,450 °C for 12 h. The conductivity of
sintered sample is found to be one order higher than earlier reported pure Y2Ti2O7 pyrochlore. 相似文献
9.
The double perovskite Sr2NiMoO6 powders and ceramics were prepared by two different (conventional and precursor) solid-state reaction methods. The phase
structure was characterized by XRD and TEM techniques. It has been indicated that single-phase perovskite powders were obtained
when calcined in air at 1300°C. However, nano-particles of the size 30–60 nm have been found in powders prepared with the
precursor method, while those from the conventional route exhibit large irregular shaped particles with aggregation. The dielectric
properties (ε
r
and tanδ) were also examined in the sintered ceramics. The results showed the transition point at 280°C for conventional route, while
no clear phase change was observed in ceramics from the precursor route. These observations clearly indicate that the different
starting processes affected the phase formation behavior and the electrical properties of Sr2NiMoO6 ceramics. 相似文献
10.
P. Tiberto L. Boarino F. Celegato M. Coisson E. Enrico N. de Leo F. Vinai P. Allia 《Journal of nanoparticle research》2011,13(9):4211-4218
Array of dots have been designed by assembling a monolayer of polystyrene nanospheres (PN) on sputtered thin films having
Ni80Fe20 and Co composition with different thickness, ranging in the interval 20 ÷ 80 nm. Subsequently the films are nanopatterned
using the nanospheres as a mask during sputter etching with Ar+ ions. A Reactive Ion Etching (RIE) process before sputter etching is used to control the final diameter of the magnetic dots
that thus can be tailored as desired (typically ranging in the interval 250 ÷ 400 nm depending on the PN starting diameter).
In addition, electron beam lithography has been exploited to obtain arrays of dots in Ni80Fe20 thin films having approximately the same mean size and dot distance as in self-assembled samples. All films have been routinely
characterized by SEM and AFM microscopy to evaluate the microstructure. Magnetic domain patterns at magnetic remanence and
in the demagnetised state have been imaged by MFM microscopy technique. Room-temperature hysteresis properties have been measured
by an alternating gradient force magnetometer. In general, the magnetization process in all patterned films has been observed
to have features typical of a vortex whose nucleation field depends on sample thickness and mean dot dimension. A comparison
between magnetic arrays of Ni80Fe20 dots prepared by self-assembling of polystyrene nanospheres and electron beam lithography is presented to rule out the role
of microstructure (i.e., order, size, and mutual distance of the magnetic dots) on magnetic properties. 相似文献
11.
Al<Subscript>2</Subscript>O<Subscript>3</Subscript> plasma production during pulsed laser deposition
F. Caridi L. Torrisi A. M. Mezzasalma G. Mondio A. Borrielli 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):467-472
A Nd:YAG laser operating in second harmonic (532 nm), 3 ns pulse duration, 150 mJ pulse energy, and 10 Hz repetition rate,
is employed to irradiate Al2O3 target placed in high vacuum. The produced plasma is investigated by an ion collector used in time-of-flight configuration
and by a mass quadrupole spectrometer, in order to determine the equivalent plasma temperature and the atomic and molecular
composition. Pulsed laser deposition technique has been used to produce thin films on different substrates placed close to
the target. Different surface analyses, such as energy dispersive X-ray fluorescence (EDXRF), X-ray photoelectron spectroscopy
(XPS) and surface profilometry are employed to characterize the produced films. Measurements of ablation yield, plasma equivalent
temperature, acceleration voltage and characterization of grown thin films are presented and discussed. 相似文献
12.
High-energy ball milling has been shown to be a promising method for the fabrication of rare earth—transition metal nanopowders.
In this work, NdCo5 nanoflakes and nanoparticles have been produced by a two-stage high-energy ball milling (HEBM), by first using wet HEBM to
prepare precursor nanocrystalline powders followed by surfactant-assisted HEBM. NdCo5 flakes have a thickness below 150 nm and an aspect ratio as high as 102–103; the nanoparticles have an average size of 7 nm. Both the nanoparticles and nano-flakes exhibited high coercivities at low
temperatures, with values at 50 K of 3 and 3.7 kOe, respectively. The high values of coercivity can be attributed to the large
surface anisotropy of nanoparticles that leads to an effective uniaxial-type of behavior in contrast to the planar anisotropy
of the bulk samples. Angle-dependent magnetization measurements at different temperatures were used to determine the spin
reorientation transitions in the nanopowders and nanoparticles. The nanoparticles showed spin reorientation temperatures,
T
SR1 = 276 and T
SR2 = 237 K which are lower when compared with the values of 290 and 245 K, respectively for bulk. 相似文献
13.
F. Bensebaa C. Durand A. Aouadou L. Scoles X. Du D. Wang Y. Le Page 《Journal of nanoparticle research》2010,12(5):1897-1903
A new preparation method for CuInS2 and CuInSe2 nanoparticles synthesis is described without using any organic solvent. Heating Cu, In, and S/Se precursors dissolved in
water for 30 min in a microwave oven in the presence of mercapto-acetic acid leads to monodispersed chalcopyrite nanoparticles.
No precipitation of these nanoparticles is observed after several months at room temperature. These new materials have been
thoroughly characterized to confirm their compositions, sizes, and structure without any filtration. Transmission electron
microscopy (TEM) confirmed particle sizes below 5 nm. Energy dispersive X-ray analysis (EDXA) confirmed the chemical composition
of these samples. X-ray diffraction (XRD) showed a chalcopyrite-type structure with crystallite size of about 2 nm. No difference
has been observed between batch and continuous synthesis processes. Cu
x
InS2 and Cu
x
InSe2 nanoparticles, with x < 1, have been also synthesized and identified. Simulation using a commercial software confirmed the difference between copper
poor (Cu
x
InS2) and copper rich (CuInS2) chalcopyrite structures. Conventional spray deposition techniques have been used to form relatively thin films on solid
substrates. 相似文献
14.
Tingyin Ning Cong Chen Yueliang Zhou Heng Lu Dongxiang Zhang Hai Ming Guozhen Yang 《Applied Physics A: Materials Science & Processing》2009,94(3):567-570
CaCu3Ti4O12 (CCTO) thin films were successfully prepared on LaAlO3 substrates by pulsed laser deposition technique. We measured the nonlinear optical susceptibility of the thin films using
Z-scan method at a wavelength of 532 nm with pulse durations of 25 ps and 7 ns. The large values of the third-order nonlinear
optical susceptibility, χ
(3), of the CCTO film were obtained to be 2.79×10−8 esu and 3.30×10−6 esu in picosecond and nanosecond time regimes, respectively, which are among the best results of some representative nonlinear
optical materials. The origin of optical nonlinearity of CCTO films was discussed. The results indicate that the CCTO films
on LaAlO3 substrates are promising candidate materials for applications in nonlinear optical devices. 相似文献
15.
K. Kumar K. Ramamoorthy P. M. Koinkar R. Chandramohan K. Sankaranarayanan 《Journal of nanoparticle research》2007,9(2):331-335
A novel route to the growth of thin films of ZnAl2O4 in nano-scale order was developed and nano-thin films of ZnAl2O4 are grown. The variation of grain size with solution concentration is reported. The thin film was deposited by modified liquid-phase
deposition (LPD) technique using a novel acid based chemical reaction for the first time to ternary system. This modified
LPD is based on a novel reaction that favours the formation of nanostructures during the treatment of a precursor (here ZnO)
and a metal foil (Al) in diluted HF acid. The acid serves both as a solvent and catalyst. Usually, in wet process synthesis
of binary systems, the metal foil will act as F− ion scavenger. In this method, formation of a ternary compound as well as growth of thin film nanostructures of that compound
was achieved by the same chemical reaction at room temperature. The role of acid concentration in the nanostructure formation
is discussed. The relationship between HF concentration and grain size were also graphically enumerated. Structural, compositional
and surface morphological properties of thin films were studied using Philips, Xpert-MPD: X-ray diffractometer and Philips,
ESEM-TMP + EDAX, Nanoscope-III: AFM. The technique is a novel, simple and low cost route for the growth of nano-thin films
of ternary oxide material. 相似文献
16.
S. V. Komogortsev R. S. Iskhakov P. A. Kuznetsov A. I. Belyaeva G. N. Bondarenko L. A. Chekanova 《Physics of the Solid State》2010,52(11):2287-2290
The structural properties and parameters of ferromagnetic resonance have been studied for Fe73.5CuNb3Si13.5B9 nanocrystalline alloys produced from the initial amorphous state via annealing under different conditions. The dependence
of the linewidth of the ferromagnetic resonance on the grain size ΔH ∼ D
6 has been found. The result is discussed within the framework of the random magnetic anisotropy model. 相似文献
17.
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
18.
Thin films of Sb2Te3 and (Sb2Te3)70(Bi2Te3)30 alloy and have been deposited on precleaned glass substrate by thermal evaporation technique in a vacuum of 2?×?10?6 Torr. The structural study was carried out by X-ray diffractometer, which shows that the films are polycrystalline in nature. The grain size, microstrain and dislocation density were determined. The Seebeck coefficient was determined as the ratio of the potential difference across the films to the temperature difference. The power factor for the (Sb2Te3)70 (Bi2Te3)30 and (Sb2Te3) is found to be 19.602 and 1.066 of the film of thickness 1,500 Å, respectively. The Van der-Pauw technique was used to measure the Hall coefficient at room temperature. The carrier concentration was calculated and the results were discussed. 相似文献
19.
Preferential growth of different crystal planes in layered Bi2Te3 thin films with each layer <40 nm has been achieved by a simple magnetron co-sputtering method. The preferential growth of
(015) plane or (001) was achieved at special depositing conditions due to the more sufficient growth along the in-plane direction
induced by the enhanced diffusion of atoms and lower deposition rate. The Bi2Te3 film with preferential growth of (001) plane possesses about two times higher electrical conductivity and Seebeck coefficient
as compared to the film with preferential growth of (015) plane, due to the greatly enhanced carrier mobility. Furthermore,
the thermal conductivity has been suppressed due to more phonon scattering at grain boundaries, compared with ordinary Bi2Te3 alloys and films. 相似文献
20.
The phase composition and the temperature dependence of the magnetization of the Er0.45Ho0.55Fe2 compound in coarse-grained, microcrystalline, and submicrocrystalline states are investigated experimentally. It is found
that, upon heating under vacuum, the Er0.45Ho0.55Fe2 microcrystalline powder with a crystalline grain size of ∼1 μm undergoes decomposition into pure iron and rare-earth (erbium
and holmium) oxides and nitrides at a temperature of 500 K. The changes observed in the phase composition of the microcrystalline
powder due to annealing are confirmed by x-ray diffraction analysis. Heating of the Er0.45Ho0.55Fe2 submicrocrystalline sample leads to a partial change in the phase composition. The phase composition of a large crystal (∼1
mm in size) remains unchanged upon heating to 1080 K. It is shown that the thermal stability of the Er0.45Ho0.55Fe2 compound depends on the crystalline grain size.
__________
Translated from Fizika Tverdogo Tela, Vol. 44, No. 6, 2002, pp. 1060–1063.
Original Russian Text Copyright ? 2002 by Mulyukov, Sharipov, Korznikova. 相似文献