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1.
Bimetallic PdAu nanoparticles on SiO2 substrate were produced by a sequential room-temperature sputtering deposition method. By the atomic force microscopy technique
we studied the nanoparticles self-organization mechanisms in various conditions. First, Pd nucleation and growth proceeds
at the substrate defects and the Pd nanoparticles density increase rapidly. During the second sputtering deposition, Au atoms
adsorb on the SiO2 and diffuse toward Pd nanoparticles without forming new nuclei. The Au atoms are trapped by the preformed Pd nanoparticles,
forming PdAu bimetallic nanoparticles which size increases. Furthermore, fixing the amount of deposited Pd and increasing
the amount of deposited Au, we analyzed the evolution of the PdAu film surface morphology: we observe that the PdAu grows
initially as three-dimensional islands; then the PdAu film morphology evolves from compact three-dimensional islands to partially
coalesced worm-like structures, followed by a percolation morphology and finally to a continuous and rough film. The application
of the interrupted coalescence model allowed us to evaluate the critical mean island diameter R
c ≈ 2.8 nm for the partial coalescence process. The application of the dynamic scaling theory of growing interfaces allowed
us to evaluate the dynamic growth exponent β = 0.21 ± 0.01 from the evolution of the film surface roughness. Finally, fixing the amount of deposited Pd and Au we studied
the self-organization mechanism of the PdAu nanoparticles induced by thermal processes performed in the 973–1173 K temperature
range. The observed kinetic growth mechanism is consistent with a surface diffusion-limited ripening of the nanoparticles
with a temperature-dependent growth exponent. The dependence of the growth exponent on the temperature is supposed to be linked
to the variation with the temperature of the characteristics of the PdAu alloy. The activation energy for the surface diffusion
process was evaluated in 0.54 ± 0.03 eV. 相似文献
2.
Vladimir V. Tatarchuk Anastasiya P. Sergievskaya Irina A. Druzhinina Vladimir I. Zaikovsky 《Journal of nanoparticle research》2011,13(10):4997-5007
The kinetics of the growth of gold nanoparticles during the reduction of tetrachloroauric acid by hydrazine in dispersed aqueous
solution encapsulated by reverse micelles of Triton N-42 surfactant (with decane as dispersion medium) was studied by means
of spectrophotometry. According to DLS data, at a set value of solubilization capacity V
s/V
o = 0.005 initial micelles have an aqueous core hydrodynamic diameter d
c = 3.6±0.2 nm. The final particles obtained after full reduction of AuIII have a metallic core of defect-free single-crystalline gold with a narrow size distribution and average core diameter d
Au = 7.7 ± 1.4 nm as shown by TEM. The rate of the particle growth is limited by the rate of gold reduction. The process kinetics
corresponds to the model consisting of two stages of reduction AuIII → AuI → Au0. The stages involve the formation and redox decay of the intermediate complexes Au(N2H4)Cl3 and Au(N2H4)Cl, and each stage proceeds via two routes: (1) homogeneous in the dispersed aqueous phase, and (2) heterogeneous on the
particle surfaces. Reactions taking route (2) are autocatalytic because they proceed with participation of the surface atoms
of particles as the final products of AuIII reduction. The dependencies of observed rate constants on reagent concentrations, temperature, and solubilization capacity
of the micellar solution are studied. 相似文献
3.
T. C. He C. S. Wang X. Pan C. Z. Zhang G. Y. Lu 《Applied physics. B, Lasers and optics》2009,94(4):653-659
A novel azobenzene-containing fluorinated polyimide was synthesized. The nonlinear optical property and photoinduced birefringence
of a polyimide thin film were investigated. Large third-order nonlinear refraction (n
2=−4.49×10−11 cm2/W) was observed in the polyimide thin film by carrying out Z-scan measurement. The polyimide thin film exhibited larger nonlinear
refraction than that of a mono-azo dye doped PMMA thin film (n
2=−1.63×10−12 cm2/W). The photoinduced birefringence of the polyimide thin film (▵
n∼10−2) under different pump intensities was investigated; it was much larger than that of the mono-azo dye doped PMMA thin film
(▵
n∼10−3). Moreover, the time constants for birefringence growth and relaxation processes were determined. 相似文献
4.
Electrical resistance measurements are reported on the binary liquid mixtures CS2 + CH3CN and CS2 + CH3NO2 with special reference to the critical region. Impurity conduction seems to be the dominant mechanism for charge transport.
For the liquid mixture filled at the critical composition, the resistance of the system aboveT
c follows the relationR=R
c−A(T−T
c)
b
withb=0·6±0·1. BelowT
c the conductivities of the two phases obey a relation σ2−σ1=B(T
c−T)β with β=0·34±0·02, the exponent of the transport coefficient being the same as the exponent of the order parameter, an equilibrium
property. 相似文献
5.
M. O. Vlasova N. D. Galanina V. S. Demidov A. A. Nedosekin A. Ya. Ostapchuk V. A. Sadykov N. A. Khaldeeva A. L. Endalov M. A. Martem’yanov A. K. Ponosov F. M. Sergeev M. Yu. Tel’nov 《JETP Letters》1996,64(4):258-262
The polarization of the leading Λ hyperons produced on carbon and lead target nuclei by 4–10 GeV neutrons in the angle range
Θ<8.5° with respect to the beam and with only neutral-particle accompaniment is measured: 〈Π〉=−0.096±0.018 for C and 〈Π〉=−
0.128±0.047 for Pb. The dependence of the polarization on the transverse momentum and the Feynman variable is measured. The
normalized invariant cross section as a function of p
⊥
2
is found to be approximated by the function A exp(−Bp
⊥
2
), where the parameter B is independent of the kind of nucleus (B=8.71±0.09 (GeV/c)−2 for carbon and B=8.83±0.18 (GeV/c)−2 for lead).
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 4, 237–240 (25 August 1996) 相似文献
6.
The electron paramagnetic resonance study of Cu2+-doped bis(l-asparaginato)Mg(II) is performed at room temperature. Two magnetically non-equivalent sites for Cu2+ are observed. The spin-Hamiltonian parameters evaluated by fitting spectra to the crystalline field of rhombic symmetry are
as follows: g
x
= 2.0420 ± 0.0002, g
y
= 2.0808 ± 0.0002, g
z
= 2.3600 ± 0.0002, A
x
= (99 ± 2) × 10−4 cm−1, A
y
= (108 ± 2) × 10−4 cm−1, A
z
= (140 ± 2) × 10−4 cm−1. The ground state wave function of Cu2+ is also determined. The g-anisotropy is estimated and compared with the experimental value. Further, with the help of optical study the nature of bonding
of a metal ion with different ligands in the complex is discussed. 相似文献
7.
We have theoretically investigated the thermal characteristics of double-channel ridge–waveguide InGaAs/InAlAs/InP quantum
cascade lasers (QCLs) using a two-dimensional heat dissipation model. The temperature distribution, heat flow, and thermal
conductance (G
th) of QCLs were obtained through the thermal simulation. A thick electroplated Au around the laser ridges helps to improve
the heat dissipation from devices, being good enough to substitute the buried heterostructure (BH) by InP regrowth for epilayer-up
bonded lasers. The effects of the device geometry (i.e., ridge width and cavity length) on the G
th of QCLs were investigated. With 5 μm thick electroplated Au, the G
th is increased with the decrease of ridge width, indicating an improvement from G
th=177 W/K⋅cm2 at W=40 μm to G
th=301 W/K⋅cm2 at W=9 μm for 2 mm long lasers. For the 9 μm×2 mm epilayer-down bonded laser with 5 μm thick electroplated Au, the use of InP
contact layer leads to a further improvement of 13% in G
th, and it was totally raised by 45% corresponding to 436 W/K⋅cm2 compared to the epilayer-up bonded laser with InGaAs contact layer. It is found that the epilayer-down bonded 9 μm wide BH
laser with InP contact layer leads to the highest G
th=449 W/K⋅cm2. The theoretical results were also compared with available obtained experimentally data. 相似文献
8.
《The European Physical Journal C - Particles and Fields》2007,50(3):535-538
We report on the observation of a KSp resonance signal at a mass of 1765 ± 5 MeV/c
2, with intrinsic width Γ = 108 ± 22 MeV/c
2, produced inclusively in Σ--nucleus interactions at 340 GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region xF>0.7, in this region its production cross section rises approximately linearly with (1-xF), reaching BR(X→KSp)dσ/dxF=(5.2±2.3)μb per nucleon at xF=0.8. The hard xF spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a Σ*+ state. No corresponding peaks were observed in the K-p and Λπ± mass spectra.
PACS 25.80.-e; 13.60.Rj; 14.20.Jn 相似文献
9.
R. Yu. Abdulsabirov I. I. Antonova S. L. Korableva N. M. Nizamutdinov V. G. Stepanov N. M. Khasanova 《Physics of the Solid State》1997,39(3):423-425
The orientational dependences of the EPR spectra of Fe3+-doped LiCaAlF6 single crystals (space group P31c, Z=2), grown at the Laboratory of Magnetic Radio Spectroscopy at Kazan’ State University, have been investigated in detail.
The spectrum is described by a trigonal spin Hamiltonian with the following parameters: B
20=40.072×10−4 cm−1, B
40=−5.799×10−4 cm−1, B
43=−4.281×10−4 cm−1, A
s=24.33±1, A
p=6.13±1, g
∥=g
⊥=2.00217±0.0003. A theoretical calculation of the hyperfine structure parameters shows that they are described quite well
when allowance is made for the overlapping of the wave functions of the paramagnetic center and the ligands (F−).
Fiz. Tverd. Tela (St. Petersburg) 39, 488–490 (March 1997) 相似文献
10.
Detailed measurements of magnetization and ac susceptibility at low temperatures of 1% Zr-substituted Y9Co7 are presented. All results are indicative of itinerant weak ferromagnetism withT
c
∼ 9.5 K. The zero-field magnetizations followT
2 orT
4/3 behaviour as in the Ni-substituted system. The estimated critical exponents areβ=0.38±0.03,γ=1.16±0.05. It is argued that the main effect of the non-magnetic Zr-substitution in Y9Co7 is to stabilize the ferromagnetic ordering by suppressing the ‘hopping’ of Co atoms along thec-axis sites of the hexagonal structure. 相似文献
11.
The values of the insulator gap Δ in one-dimensional systems of interacting bosons described by the Hubbard Hamiltonian are
calculated at low temperatures by the quantum world-line Monte Carlo algorithm. The dependence of Δ on the size of the system,
the temperature, and the parameters of the model is investigated. It is shown that a chain with N
a=50 sites is already sufficient to estimate the thermodynamic value of the critical quantity (t/U)c for which a transition from the insulator into the superfluid state occurs in a commensurate system. To within the computational
error, this value, (t/U)c=0.300±0.005, agrees with the value (t/U)c=0.304±0.002 obtained previously by the combined “exact diagonalization + renormalization-group analysis” method. The characteristic
Kosterlitz-Thouless behavior of the insulator gap is demonstrated near the critical region: Δ∼exp[−b(1−t/t
c)−1/2].
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 2, 92–96 (25 July 1996) 相似文献
12.
Performance of the backward wave oscillator (BWO) is greatly enhanced with the introduction of plasma. Linear theory of the
dispersion relation and the growth rate have been derived and analysed numerically for plasma-filled rippled wall rectangular
waveguide driven by sheet electron beam. To see the effect of plasma on the TM01 cold wave structure mode and on the generated frequency, the parameters used are: relativistic factor γ = 1.5 (i.e. v/c = 0.741), average waveguide height y
0 = 1.445 cm, axial corrugation period z
0 = 1.67 cm, and corrugation amplitude ε = 0.225 cm. The plasma density is varied from zero to 2 ×1012 cm − 3. The presence of plasma tends to raise the TM01 mode cut-off frequency (14 GHz at 2 ×1012 cm − 3 plasma density) relative to the vacuum cut-off frequency (5 GHz) which also causes a decrease in the group velocity everywhere,
resulting in a flattening of the dispersion relation. With the introduction of plasma, an enhancement in absolute instability
was observed. 相似文献
13.
Y. K. Gupta Jitendra Kumar Pratibha 《International Journal of Theoretical Physics》2012,51(10):3290-3302
A class of well behaved charged analogues of Schwarzchild’s interior solution has been obtained using a particular electric intensity. The solutions of this class are utilized to depict a superdense star model with surface density 2×1014 g cm−3. The solution obtained is new and the pressure (p), density (c 2 ρ), velocity of sound and (p/(c 2 ρ)) are monotonically decreasing towards the pressure free interface. Moreover the adiabatic constant is found to be more than (4/3) which is necessary for stability under radial perturbation. Also the electric intensity increases monotonically towards the surface. The well behaved model has the maximum mass M=1.740793M Θ , Radius 12.130308 km. The redshift at the center and on the surface is given by z 0=0.384261 and z a =0.292489. Out of the models of superdense star obtained couple of models represent Vela Pulsar for (i) α 2=1.03, b=0.33, , Radius=10.8566 km, M=1.18331M Θ , I=0.642601×1045, (ii) α 2=1.1, b=0.3, , Radius=11.197533 km, M=1.311438M Θ , I=0.774508×1045. All the solutions mentioned above are reducible to Schwarzchild interior solution in the absence of charge. 相似文献
14.
Lorenzo Iorio 《General Relativity and Gravitation》2011,43(6):1697-1706
The strategy followed so far in the performed or proposed tests of the general relativistic Lense-Thirring effect in the gravitational
field of the Earth with laser-ranged satellites of LAGEOS type relies upon the cancelation of the disturbing huge precessions
induced by the first even zonal harmonic coefficient J
2 of the multipolar expansion of the Newtonian part of the terrestrial gravitational potential by means of suitably designed
linear combinations of the nodes Ω of more than one spacecraft. Actually, such a removal does depend on the accuracy with
which the coefficients of the combinations adopted can be realistically known. Uncertainties of the order of 2 cm in the semimajor
axes a and 0.5 milliarcseconds in the inclinations I of LAGEOS and LAGEOS II, entering the expression of the coefficient c
1 of the combination of their nodes used so far, yield an uncertainty δc
1 = 1.30 × 10−8. It gives an imperfectly canceled J
2 signal of 10.8 milliarcseconds per year corresponding to 23% of the Lense-Thirring signature. Uncertainties of the order
of 10–30 microarcseconds in the inclinations yield δc
1 = 7.9 × 10−9 which corresponds to an uncanceled J
2 signature of 6.5 milliarcseconds per year, i.e. 14% of the Lense-Thirring signal. Concerning a future LAGEOS-LAGEOS II-LARES
combination with coefficients k
1 and k
2, the same uncertainties in a and the less accurate uncertainties in I as before yield δk
1 = 1.1 × 10−8, δk
2 = 2 × 10−9; they imply a residual J
2 combined precession of 14.7 milliarcseconds per year corresponding to 29% of the Lense-Thirring trend. Uncertainties in the
inclinations at ≈ 10 microarcseconds level give δk
1 = 5 × 10−9, δk
2 = 2 × 10−9; the uncanceled J
2 effect is 7.9 milliarcseconds per year, i.e. 16% of the relativistic effect. 相似文献
15.
Roth CB Pound A Kamp SW Murray CA Dutcher JR 《The European physical journal. E, Soft matter》2006,20(4):441-448
We have used transmission ellipsometry to measure the glass transition temperature, Tg, of freely-standing films of atactic and syndiotactic poly(methyl methacrylate) (PMMA). We have prepared films with different
molecular weights, MW, (159×103 < M
w < 1.3×106) and film thicknesses, h, ( 30nm < h < 200 nm). For the high-MW ( M
w > 509×103) atactic PMMA films, we find that Tg decreases linearly with decreasing h, which is qualitatively similar to previous results obtained for high-MW freely-standing polystyrene (PS) films. However,
the overall magnitude of the Tg reduction is much less (by roughly a factor of three) for the high-MW freely-standing PMMA films than for freely-standing
PS films of comparable MW and h. The observed differences between the freely-standing PMMA and PS film data suggest that differences in chemical structure
determine the magnitude of the Tg reduction and we discuss the possible origins of these differences. Our analysis of the MW-dependence of the Tg reductions suggests that the mechanism responsible for the MW-dependent Tg reductions observed in the high-MW freely-standing films is different than that responsible for the MW-independent Tg reductions observed in the low-MW freely-standing and supported films. 相似文献
16.
《Journal of Macromolecular Science: Physics》2013,52(3):695-709
Abstract Films of high‐molecular‐weight amorphous polystyrene (PS, M w = 225 kg/mol, M w/M n = 3, T g‐bulk = 97°C, where T g‐bulk is the glass transition temperature of the bulk sample) and poly(methyl methacrylate) (PMMA, M w = 87 kg/mol, M w/M n = 2, T g‐bulk = 109°C) were brought into contact in a lap‐shear joint geometry at a constant healing temperature T h, between 44°C and 114°C, for 1 or 24 hr and submitted to tensile loading on an Instron tester at ambient temperature. The development of the lap‐shear strength σ at an incompatible PS–PMMA interface has been followed in regard to those at compatible PS–PS and PMMA–PMMA interfaces. The values of strength for the incompatible PS–PMMA and compatible PMMA–PMMA interfaces were found to be close, both being smaller by a factor of 2 to 3 than the values of σ for the PS–PS interface developed after healing at the same conditions. This observation suggests that the development of the interfacial structure at the PS–PMMA interface is controlled by the slow component, i.e., PMMA. Bonding at the three interfaces investigated was mechanically detected after healing for 24 hr at T h = 44°C, i.e., well below T g‐bulks of PS and PMMA, with the observation of very close values of the lap‐shear strength for the three interfaces considered, 0.11–0.13 MPa. This result indicates that the incompatibility between the chain segments of PS and PMMA plays a negligible negative role in the interfacial bonding well below T g‐bulk. 相似文献
17.
The third-order elastic constants of single crystal GaSb are determined using ultrasonic pulse interferometer at 10 MHz. The
constants at 300°K, in units of 1011 N.m.−2, are Cl11 = ™ 4 ·75 ± 0·06 C144 = + 0·50 ± 0·25 C113 = ™ 3 ·08 ± 0·02 C166 = ™ 2·16 ± 0·13 C123 = ™ 0 ·44 ± 0·29 C456 = ™ 0·25 ± 0·15 These constants are used to evaluate the three anharmonic first and second neighbour force constants based
on modified Keating’s model. The constants are (in units of 1011 N.m−2)γ=− 2·406;δ=0·407;ε=−0·222. 相似文献
18.
《The European Physical Journal C - Particles and Fields》2007,50(2):315-328
The inclusive production cross sections of the strange vector mesons K*0, K̄*0, and φ have been measured in interactions of 920 GeV protons with C, Ti, and W targets with the HERA-B detector at the HERA
storage ring. Differential cross sections as a function of rapidity and transverse momentum have been measured in the central
rapidity region and for transverse momenta up to pT = 3.5 GeV/c. The atomic number dependence is parametrised as σpA=σpN*Aα, where σpN is the proton–nucleon cross section. Within the phase space accessible, α(K*0)=0.86±0.03, α(K̄*0)=0.87±0.03, and α(φ)=0.96±0.02. The total proton–nucleon cross sections, determined by extrapolating the differential measurements
to full phase space, are σpN→K*0=(5.06±0.54) mb, σpN→K̄*0=(4.02±0.45) mb, and σpN→φ=(1.17±0.11) mb. For all resonances the Cronin effect is observed; compared to the measurements of Cronin et al. for K± mesons, the measured values of α for φ mesons coincide with those of K+ mesons for all transverse momenta, while the enhancement for K*0/K̄*0 mesons is smaller. 相似文献
19.
Colloidal synthesis of BaF2 nanoparticles and their application as fillers in polymer nanocomposites
Sathyamurthy Srivatsan Tuncer Enis More Karren L. Gu Baohua Sauers Isidor Paranthaman M. Parans 《Applied Physics A: Materials Science & Processing》2012,106(3):661-667
Nanoparticles of pure and Eu-doped BaF2 have been prepared through sol-gel colloidal synthesis. In addition, BaF2-filled PMMA polymer nanocomposites were fabricated and dielectric properties were measured. The as-synthesized pure and Eu-doped
BaF2 nanoparticles were analyzed by both X-ray diffraction and transmission electron microscopy and consisted of crystalline BaF2 particles with an average diameter of 13.6 nm with a standard deviation of about ±2.4 nm. The photoluminescence properties
of the pure and Eu-doped (2%, 4% and 8%) nanoparticles showed characteristic emission of Eu3+ (5D0→7F
J
(J=1–4) transitions). We also measured significantly enhanced dielectric breakdown strength of up to 30% for BaF2 nanocomposites over the unfilled PMMA polymer. This study thus offers some promise of sol-gel synthesis of nanocomposite
dielectrics with great potential for use as electrical insulation materials in cryogenic high-voltage applications. 相似文献
20.
The interaction of three common herbicides, paraquat, acifluorfen and alachlor, with spinach chloroplast photosystem II (PS II) was investigated by measuring1H nuclear magnetic resonance spin-lattice relaxation rates, transient nuclear Overhauser effect (NOE) and NOE spectroscopy (NOESY) spectra. Binding to PS II was detected by (i) the enhancement of single-selective relaxation rates and (ii) the decrease in the optimal mixing time providing maximal cross-peak intensity in NOESY spectra. Titration of relaxation enhancements was used to calculate the dissociation constants (K d) from the bound state for paraquat (K d = 292 ± 71 μM−1) and acifluorfen (K d = 311 ± 58 μM−1). A similarK d was apparent for alachlor. Double-selective relaxation rates allowed the isolation of dipolar relaxation terms between selected proton pairs wherefrom dynamic features of the bound state were evaluated. In all cases the motional correlation time of bound herbicide (τc = 0.1−0.4 ns at 300 K) was found two orders of magnitude slower than in the free-solution state. In the case of alachlor the E and Z isomers were observed to bind differently to PS II and a change in conformation could be hypothesized. 相似文献