TEM and Raman scattering investigation of carbon in annealed Co/C soft X-ray multilayers

The structures of the carbon sublayers in the annealed Co/C soft X-ray multilayers fabricated by using a dual-facing-target sputtering system have been characterized by transmission electron microscopy (TEM) and Raman spectroscopy (RS). The results suggest that the structural variations in the carbon layers can be roughly divided into three stages, i.e. ordering, crystalline and grain growth stages. At the ordering stage with annealing temperatures below 400°C, the amorphous carbon layers change from ones of bond-angle disorder and fourfold-bonding only to ones of threefold-bonding. At the crystalline stage, the amorphous carbon layers in the as-deposited multilayers crystallize to graphite crystallites in the annealing temperature range of 500–600°C. At the grain growth stage, the specimens are annealed at temperatures higher than 700°C. A growth in the graphite crystallite dimensions is observed, which is consistent with the TEM results. Project supported by the National Natural Science Foundation of China and Beijing Zhongguancun Associated Center of Analysis and Measurement.     

Ag/Si multilayers with nanometer sized particles of silver during annealing process

Thein situ low angle X-ray diffraction and transmission electron microscopy were used to monitor the interdiffusion characteristics as well as the microstructure in Ag/Si multilayers with modulated wavelength 7. 64 nm when annealing from 323 to 573 K. The interdiffusion mechanism of Ag/Si multilayers with immiscibility is different from that of other metal/Si multilayers which are miscible. Phase separation takes place at 323 K, then silicon atoms diffuse into silver sublayers through silver grain boundaries and separate silver sublayers into nanometer sized silver particles gradually at higher temperature. The mean size of silver particles is about 5 nm. The activation energy and frequency factor are determined to be 0.24 eV and 2.02 x⁻²⁰m²/s, respectively. An erratum to this article is available at .     

Thermal expansion of ferroelectrics

Using the interference method the thermal expansion of lithium hydrazinium sulphate [Li(N₂H₅)SO₄] has been investigated in the temperature range ?170° C. to +220° C. The principal expansion coefficients along the crystallographic axes have been determined and at room temperature (25° C.) the values ofa _a,a _b anda _c are respectively 17·7, 13·5, and 43·0, ×10^?6 (°C.)^?1. The expansion coefficients are found to vary nonlinearly, and, in particular, along thec-axis the thermal expansion shows an anomalous behaviour between ?160°C. and ?60°C. and also in the neighbourhood of +130°C. These anomalies are explained as due to homomorphous transitions in which there is a reorientation of the ?NH ₊ ³ group about the N-N axis or a re-alignment of the ?NH₂ group.     

Transition phenomena at saturation temperature conductance study of alkali halides in formamide in the presence of nonelectrolytes

The interaction between alkali halide ions and organic nonelectrolytes in formamide solutions was followed by conductance measurements. A saturated solution of the nonelectrolyte (sucrose and mannitol) containing a known amount of the alkali halide salt was prepared at 50.0 ±0.05° C. Crystals were separated by contrifugation at the same temperature. Conductance of the centrifugate was measured at different temperatures between 30° and 70° C. Plots of — logk vs. 1/T showed a break at the saturation temperature where two straight lines appeared to intersect. This transitional behaviour has been explained on the basis of (i) the change in solvent structure, (ii) hydrogen bonding, and (iii) ion solvation.     

Positron annihilation in annealed and quenched teflon and in sulphur

The value (τ₂) and the intensity (I₂) of the delayed component in the lifetime spectra of positrons annihilating in annealed and quenched teflon and in sulphur and crystex (polymer sulphur), at room temperature and at 77° K are reported. These data and the X-ray diffraction patterns for these materials are discussed in terms of the free volume model for the formation and quenching of positronium atoms in molecular materials.     

Properties of GaAs single crystals grown by molecular beam epitaxy at low temperatures

Properties of GaAs single crystals grown at low temperatures by molecular beam epitaxy (LTMBE GaAs) have been studied. The results show that excessive arsenic atoms of about 10²⁰ cm⁻³ exist in LTMBE GaAs in the form of arsenic interstitial couples, and cause the dilation in lattice parameter of LTMBE GaAs. The arsenic interstitial couples will be decomposed, and the excessive arsenic atoms will precipitate during the annealing above 300°C. Arsenic precipitates accumulate in the junctions of epilayers with the increase in the temperature of annealing. The depletion regions caused by arsenic precipitates overlap each other in LTMBE GaAs, taking on the character of high resistivity, and the effects of backgating or sidegating are effectively restrained.     

Transition phenomena at saturation temperature studies on electrolytic conductance of alkali halides in aqueous systems

A plot of negative logarithm of the electrical conductance (K)vs reciprocal of the absolute temperature (T) shows the existence of the transition in the systems ‘Electrolyte-Sucrose-water’, ‘Electrolyte-Mannitol-water’, and ‘Electrolyte-Xylose-water’. A saturated solution of sucrose/mannitol/xylose containing a known amount of an electrolyte was prepared at a temperature of 50·0±0·05° C and the crystals were separated by centrifugation at the same temperature. The conductance of the centrifugate was measured in a tubular conductivity cell at different temperatures in the range between 30° C to 70° C. The plot of ?log₁₀ Kvs 1/T showed a break at the saturation temperature, the point where two straight lines appeared to intersect. The transition can be explained on the basis of change in the water structure due to the presence of ‘structure-breaking’ and/or ‘structure-making’ ions. These sucrose, xylose, and mannitol molecules due to the presence of a number of hydrogen bonding sites contribute largely toward the build up of big structures in the supersaturated state. These structures crumble as the system undergoes the transition at the saturation temperature. Different electrolytes produced more or less similar effect.     

Magneto-optical Kerr effect in CoxAg1-x nanostructured granular films

A series of Co_xAg_{1 - x} nanostructured granular films have been prepared by ion beam sputtering and annealed at 100, 250, 400, 500°C. The optical constants, the complex dielectric function and magneto-optical Kerr parameters were measured at room temperature. For the samples having low Co compositions, the strong Kerr effect enhancement is observed around the Ag plasma edge. With an increase in annealing temperature, the resonance-like peaks appear in the Kerr rotation, and the peak positions are shifted toward the low photon energy region. From the analysis of the numerical calculations, it is concluded that the magneto-optical Kerr effect enhancement (MOKE) is due to the presence of the steep plasma edge.     

Magneto-optical Kerr effect in Co x Ag1-x nanostructured granular films

A series of Co_xAg_{1 - x} nanostructured granular films have been prepared by ion beam sputtering and annealed at 100, 250, 400, 500°C. The optical constants, the complex dielectric function and magneto-optical Kerr parameters were measured at room temperature. For the samples having low Co compositions, the strong Kerr effect enhancement is observed around the Ag plasma edge. With an increase in annealing temperature, the resonance-like peaks appear in the Kerr rotation, and the peak positions are shifted toward the low photon energy region. From the analysis of the numerical calculations, it is concluded that the magneto-optical Kerr effect enhancement (MOKE) is due to the presence of the steep plasma edge.     

Modelling of ultrasound therapeutic heating and numerical study of the dynamics of the induced heat shock response

In this presentation we consider hyperthermia, a procedure of raising the temperature above 43 °C, as a treatment modality. To this purpose, a numerical model of in vivo soft tissue ultrasound heating is proposed by extending a previously presented in vitro model. Based on the numerical simulations, a heating scheme satisfying some constraints related to potential clinical applications is established, and the resulting temperature time-course profile is composed with the temperature-dependent protein denaturation formula of a recently published mathematical model for the eukaryotic heat shock response. The obtained simulation results of the combined models are discussed in view of potential application of ultrasound soft tissue heating in clinical treatment.     

Microwave spectrum of trichloroacetonitrile

The microwave spectra of different isotopic species of trichloroacetonitrile—CCl ₃ ³⁵ CN, CCl ₂ ³⁵ Cl³⁷CN, CCl³⁵Cl ₂ ³⁷ CN and CCl ₃ ³⁷ CN—in the region 20,000–40,100 Mc./sec. have been studied both at room temperature and at low temperature. From the measurements of B₀ values of the symmetric tops, assuming the C-C and C-N bond distances, the other two parameters are determined. They are: C-Cl=1·771 A, C-C-Cl=108° 52′.     

The crystal and molecular structure of 3, 4-dihydroxy L-phenyl-alanine

The molecule crystallizes in spacegroup P2₁ with two molecules per unit cell. The unit cell dimensions area = 6.044 Å,b = 13.607 Å,c = 5.311 Å,γ = 97.55°. The density was calculated to be 1.512 g.ml.^?1 and found to be 1.51 g.ml.^?1 The major atoms were located by the reliable image method and the hydrogen atoms were located from a difference electron density map. Full-matrix least squares refinement of the parameters yielded an unweighted residual indexR of 0.088. The bond lengths and angles of the amino acid grouping are consistent with values in other amino acids. The structural parameters of the aromatic system are very similar to those of noradrenaline and dopamine hydrochlorides. The crystal structure is dominated by a three-dimensional intermolecular hydrogen bonding system. The molecular conformation is different from that displayed by any other aromatic amino acid or peptide whose crystal structure is known.     

Magnetic properties and microstructure of HDDR isotropic Nd-Dy-Fe-Co-B bonded magnets with high coercivity

The effect of small amount of Co and Dy addition on the magnetic properties of HDDR isotropic Nd-Dy-Fe-Co-B bonded magnets was investigated. The experimental results show that the intrinsic coercivity H_cj and the reversible temperature coefficient of remanence of (Nd_0.65 Dy_0.35)_12.5-(Fe_0.9Co_0.1)₈₁B_6.5 magnet were 1.53 MA·m^-1(19.3 kOe) and -0.059%/°C (25–155°C), respectively. The high coercivity and low temperature coefficient of the magnet are due to the enhanced anisotropy field, increased Curie temperature and improved microstructure by Dy and Co addition.     

Synthesis and surface reactivity of phosphide nanocrystals

Gap and InP nanocrystals were synthesized from Na₃P and GaCI₃ at low temperature (80–100°C) and atmospheric pressure. The samples were characterized by XRD and TEM measurements. The surface reactivity of Gap nanocrystals was studied by heating in N₂. The weight of the nanocrystals increased at the temperature between 370°C and 480°C. It can be concluded that N, molecule was absorbed and reactivated on the surface of Gap nanocrystals. Keywords: gallium phosphide, indium phosphide, nanocrystal, surface reactivity.     

On the role of finite,hereditarily normal spaces and maps in the genesis of compact Hausdorff spaces

We consider how properties of the bonding maps of the inverse spectrum determine properties of the inverse limit. Specifically, we study the limits of inverse spectra of finite T₀-spaces with bonding maps which are either chaining or normalizing. We will show that if the bonding maps are normalizing, then the inverse limit is a normal T₀-space, and therefore, its Hausdorff reflection is its subset of specialization minimal elements. If the maps are chaining, then the inverse limit is a completely normal spectral space; such spaces have been studied since they include the real spectra of commutative rings [C.N. Delzell, J.J. Madden, J. Algebra 169 (1994) 71], and the prime spectrum of a ring of functions, Spec(C(X)). The existence and importance of this class of non-Hausdorff, normal topological spaces was extremely surprising to us. Further, each of these results is reversible; if the inverse limit is normal, then each space in the spectrum is preceded by one whose bonding map to it is normalizing. By way of contrast, the inverse limit of finite T₀-spaces with separating bonding maps need not be a normal topological space (Example 3.8(a)) and furthermore, if the spaces of the inverse spectrum are normal, then the Hausdorff reflection of the limit must be zero-dimensional (Theorem 3.15).     

Thermal study of some manganese oxide and hydrous oxide minerals

The minerals manganite, pyrolusite, ramsdellite, cryptomelane, psilomelane, braunite, lithiophorite and woodruffite from Sandur manganese ore deposits, Bellary District, Mysore State, which have been investigated by microscopic, chemical and X-ray methods (Naganna, 1963) are subjected to thermal study through differential thermal analysis and gravimetric thermal analysis. The hydrous oxides of manganese undergo dehydration below 400° C. and subsequent changes follow later. Most of the minerals containing MnO₂ thermally react in two stages, one at about 600° C. and the other beyond 800° C. The thermal behaviour of pyrolusite is seen to be similar to that ofβ MnO₂, while the thermal behaviour of ramsdellite is found to be similar to those ofα orγ MnO₂. Further the study suggests that ramsdellite may change over to pyrolusite below 500° C.     

The near ultraviolet absorption spectra ofortho- andmeta-thiocresols

The absorption spectra ofortho- andmeta-thiocresols have been studied in the present investigation. The ortho-thiocresol spectrum consists of about forty-five bands of rather a diffuse nature and in general low intensity in the region from 2873 Å to 2600 Å. The maximum number of bands is obtained by using a path length of 330 cm. for absorption, the temperature of the bulb being maintained at 14°C. Several of these bands are assigned as due tov-v-transitions. The (0, 0) band is chosen at 35386 cm.^?1 which is the strongest band on the longer wavelength side. Vibrational frequencies in the excited state have values 729, 957 and 1159 and combinations and overtones of these are present. Themeta-thiocresol spectrum consists of about forty bands of rather a diffuse nature and very weak intensities in the region from 2900 Å to 2590 Å. The maximum number of bands is obtained by using a path length 200 cm. for absorption and by keeping the temperature of the bulb at 20° C. The (0, 0) band is chosen to be that at 34793 cm.^?1 which is the strongest band on the longer wavelength side. Vibrational frequencies in the excited state have values 492, 611, 720, 845, 965, 1016 and 1155 cm.^?1 and combinations and overtones of these are present.     

Variation of the piezo-electric constants of α-quartz with temperature

The method of finding the piezo-electric constants with the help of the variations of bond distances and bond angles on strain has been utilised in finding the variations of the piezo-electric constants ε₁₁ and ε₄₁ of α-quartz with temperature. It is found that the variations of ε₁₁ with temperature can be explained on the basis of the change of co-ordinates with temperature. At 558° C. the silicon atoms are found to occupy the same positions as they do in β-quartz. As the transition temperature is reached, the longitudinal coefficient ε₁₁ drops to zero, while the transverse coefficient ε₄₁ decreases by only 15%. The piezo-electric constant of β-quartz has been similarly determined and its value comes out to be 1·05×10⁴ for a non-ionic crystal (k=·724) and 1·45×10⁴ for an ionic crystal (k=1).     

Experimental Investigation of thermal convection in an inclined narrow gap II

In the past decade the development in micro technology has experienced great progress, what made the knowledge of the flow behavior in small cavities fundamentally interesting. Our experimental contribution describes the measured temperature and velocity fields in a fluid containing inclined cavity with the dimensions 17 × 6 × 24 mm³ (w × d × h). Using PIV/T, we can determine the velocity and temperature distribution in the cavity simultaneously. The chamber is illuminated with a white light sheet of 1 mm. A 20% glycerin-water mixture is examined. The lower side is heated to 46.2°C, while the upper side has a constant temperature of 26°C. In this work we present the measured velocity and temperature fields of the fluid at different angles of the cavity orientation with respect to the direction of gravity in the stationary state. This is a continuation of last years presentation [1] in the sense that the temperature difference has been substantially increased. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Microstructure and photoluminescence of a-SiO x :H

Two strong photoluminescence (PL) bands in the spectral range of 550–900 nm have been observed at room temperature from a series of a-SiO _x :H films fabricated by plasma-enhanced chemical vapor deposition (PECVD) technique. One is composed of a main band in the red-light region and a shoulder; the other is located at about 850 nm, only found after 1170°C annealing in N₂ atmosphere. In conjunction with infrared (IR) and micro-Raman spectra, it is thought that the two PL bands are associated with a-Si clusters in the SiO _x network and nanocrystalline silicon in SiO₂, respectively. Project supported by the National Natural Science Foundation of China (Grant No. 69576025).