FXR discharges at various pressures

The formation period time, current rise time, and photon energy of FXR discharges have been investigated at initial pressures of 5×10^?6 to 1×10^?2Torr. It has been found that the parameters studied are almost constant between 5×10^?6 and 1×10^?3Torr. The results obtained indicate that the upper limit of the interelectrode breakdown pressure is about 10^?3 Torr when the initial pressure is 10^?6 Torr.     

Performance of a combined magnetron pump-gauge at ultrahigh vacuum

This paper reports experimental results on 3 magnetron pump-gauges designed to combine the properties of UHV magnetron pumps and magnetron gauges into a single device with a portable (battery operated) power supply. The pump-gauges had a renewable cathode of Ti and were useful in the pressure range 7 × 10^?9 to 1.5 × 10^?4 Pa. As gauges, the sensitivities were about 1.5 × 10^?2 A Pa^?1. As pumps, the speeds were about 0.15 litre s^?1 for Kr.     

Effects of damage rate on Cu precipitation in Fe–Cu model alloys under neutron irradiation

The formation of Cu precipitates and point defect clusters was investigated in two Fe–Cu binary model alloys, Fe–0.3Cu and Fe–0.6Cu, irradiated at 573?K at three different damage rates, namely 3.8?×?10^?10, 1.5?×?10^?8 and 5?×?10^?8?dpa (displacements per atom)/s, up to about 1.6?×?10^?2?dpa. Results of positron annihilation experiments indicated that Cu precipitates were formed in these irradiations with different damage rates. The growth of Cu precipitates does not increase monotonously with increasing irradiation dose, but it rather depends on the nucleation and growth of microvoids. It is also clear that the nucleation and growth of microvoids are influenced by the irradiation dose rate.     

The high pressure structures and the phase transitions of K2[Pt(CN)4]Br0.3·3H2O

The lattice constants of KCP were determined by single crystla X-ray diffraction experiments up to 3 × 10⁹Pa. The pressure dependence of the compressibilities is anomalous around 7 × 10⁸Pa and 2 × 10⁹Pa. The platinum chains are shortened abruptly at 7 × 10⁸ Pa, where the compressibility perpendicular to the platinum chain is normal. The other anomaly around 2 × 10⁹Pa was found in the compression along the direction perpendicular to the platinum chain. The crystal structure analyses showed that the pressure-induced displacement of a water molecule is coupled with the shortening of the Pt chains observed at 7 × 10⁸Pa. The other anomaly at 2 × 10⁹Pa is associated with the transformation of the molecular structure of the tetracyanoplatinate complex anions.     

A simple opposed-anvil apparatus for high pressure and temperature experiments above 10 GPa

A new opposed-anvil high pressure and temperature apparatus was developed based on the Drickamer-type apparatus. Various improvements were made to increase the sample volume and to generate high pressure and temperature stably and easily. By optimizing components such as the anvil, heater, and gasket, large sample volumes of about 4?mm³ (～10³ times more than that previously obtained with our previous apparatus) were achieved, with compact and light apparatus (outer diameter ? 40?mm; height 31?mm; weight 300?g). Pressures and temperatures up to about 15?GPa and 1700?K can routinely and stably be achieved by using this assembly. In order to extend the pressure range further, sintered diamond was used as an anvil material. As a result, pressures and temperatures of around 38?GPa and 1400?K were achieved, although the sample volume was decreased to about 1.3×10^?1?mm³.     

Diffusion of titanium in slightly reduced rutile

The self-diffusion of ⁴⁴Ti in slightly reduced rutile. TiO_2?δ, was measured along the c axis over the temperature range of 1000–1100°C between 0.2 and 1 × 10^?18atm. oxygen pressure. These measurements enabled the determination of the defect structure of TiO_2-δ for 0.02 ?gd ? 0.001. For oxygen pressures between 1 × 10^?13 and 1 × 10^?16atm. at 1058.4°C random tetravalent titanium atoms are the predominant defects evident from self-diffusion. The enthalpy of motion was determined as ΔH_m = 57.03 ± 4.9% kcal/mole. From the activation energy at 1.69 × 10^?16atm., the enthalpy of formation for tetravalent titanium interstitials was determined as ΔH_f = 276 ± 15.6% kcal/mole.For oxygen pressures less than 1 × 10^?16atm. at 1058.4°C, the tracer diffusion coefficient shows a continuous decline as the oxygen pressure is lowered. Comparisons with thermogravimetric studies and consideration of the similarity in structure between nonstoichiometric point defect phases and the first homologous series phase indicate that the order-disorder transition retains a considerable degree of short range order below the critical concentration in the form of Wadsley defects.     

Volume properties and compressibility of the graphite-potassium-mercury compounds

Abstract

The volume properties of graphite intercalation compounds (GIGS) C4KHg and of the initial intermetallic compounds KHg and KHg₂ have been investigated in the piston-cylinder apparatus, using the direct volumetric technique, under pressures up to 25 kbar. The compounds, average compressibility K₊, was determined to be 3.8×10^?3 kbar^?1 for C₄KHg, 3.0×10^?3 kbar-^?1 for C₈KHg, 4.8×10^?1 kbar^?1 for KHg, and 4.0 ×10^?1 kbar^?1 for KHg₂ at pressures of 0-20 kbar. The compressibility of the “two-dimensional” KHg layer in the GIC under various pressure conditions has been estimated. These estimates permit comparison of KHg properties in the “three dimensional” and “quasi-two dimensional” states. It was concluded that the influence of the graphite matrix on the intercalant is insignificant for this type ternary GIC.     

Absolute coverage and isostemc heat of adsorption of deuterium on Pt(111) studied by nuclear microanalysis

The absolute coverage (θ) of deuterium adsorbed on Pt(111) in the ranges 180< T<440 K and 5 × 10^?6 < P < 5 × 10^?2 Pa D₂ has been determined by nuclear microanalysis using the D(³He, p)⁴He reaction. From these data, the isosteric heat of adsorption (E_a) has been determined to be 67 ± 7 kJ mol^?1 at θ ? 0.3. This heat of adsorption yields values of the pre-exponential for desorption (10^?5 to 10^?2 cm² atom^?1 s^?1) that lie much closer to the normal range for a second order process than those determined from previous isosteric heat measurements. The E_a versus θ relationship indicates that the adsorbed D atoms are mobile and that there is a repulsive interaction of 6–8 kJ mol^?1 at nearest neighbour distances. At 300 K the coverage decreases to ? 0.05 monolayer (? 8 × 10¹³ D atoms cm^?2) as P→ 0, apparently invalidating a recent model of site exchange in the adsorbed layer.     

SrB4O7:Sm2+: an optical sensor reflecting non-hydrostatic pressure at high-temperature and/or high pressure in a diamond anvil cell

A systematic investigation on the fluorescent spectra of SrB₄O₇:Sm²⁺ was performed in detail at high-temperature up to 623?K and/or high pressure up to 23.2?GPa with different pressure-transmitting media (PTMs), respectively. Combined with experiment data of previous research, the change of the ⁷D₀–⁵F₀ line (0–0 line) full width at half maximum (FWHM) of SrB₄O₇:Sm²⁺ under different pressure environments was specifically discussed. The results indicate that the FWHM of 0–0 line is sensitive to the non-hydrostatic pressure environment in 2-propanol, and methanol and ethanol mixture (ME) PTMs at ambient temperature. The first-order and the second-order derivation of the temperature dependence of 0–0 line FWHM at ambient pressure are 1.48(±0.21)?×?10^?4?nm/K and 9.63(±0.63)?×?10^?7?nm²/K² below 623?K. The 0–0 line FWHM is also sensitive to the non-hydrostatic pressure environment in ME at high-temperature and high pressure simultaneous, the non-hydrostatic transition pressures are 9.6?GPa at 323?K, 11.0?GPa at 373?K, 14.4?GPa at 423?K, respectively. SrB₄O₇:Sm²⁺ is recommended as an optical sensor to reflect the change of pressure environment in liquid media at high-temperature and/or high pressure.     

Pressure dependent oxidation of Al(111): A photoemission and surface exafs study

The initial oxidation of Al(111) has been studied with photoemission and surface EXAFS for single crystal surfaces. We find that the oxidation is pressure dependent and that at pressures below 2×10^?7 Torr molecular oxygen chemisorbs while at pressures above 1×10^?6 Torr the chemisorption is disassociative. These results are discussed in the context of other LEED and surface EXAFS studies.     

Preparation and characterization of zirconium sulfophenyl phosphate-doped sulfonated poly(phthalazinone ether sulfone) composite proton exchange membrane

Polymer composite membranes based on sulfonated poly(phthalazinone ether sulfone) (SPPES) and zirconium sulfophenyl phosphate (ZrSPP) were prepared. Three ZrSPP concentrations were used: 10, 20, and 30 wt%. The membranes were characterized by infrared spectroscopy (IR), X-ray diffraction spectroscopy, thermal gravimetric analysis, and scanning electron microscopy (SEM). The IR results indicated the formation of intense hydrogen bonds between ZrSPP and SPPES molecules. The SEM micrographs showed that ZrSPP well dispersed with SPPES and form a lattice structure. The proton conductivity of the SPPES (degree of sulfonation (DS) 64 %)/ZrSPP (10 wt%) composite membrane reached 0.39 S/cm at 120 °C 100 % relative humidity and that of the 30 wt% of SPPES (DS 16.1 %)/ZrSPP composite membrane reached 0.18 S/cm at 150 °C. The methanol permeabilities of the SPPES/ZrSPP composite membranes were in the range of 2.1?×?10^?8 to 0.13?×?10^?8?cm²/s, much lower than that of Nafion®117 (10^?6?cm²/s). The composite membranes exhibited good thermal stabilities, proton conductivities, and good methanol resistance properties.     

Continuously transferring cold atoms in caesium double magneto-optical trap

We have established a caesium double magneto-optical trap (MOT) system for cavity-QED experiment, and demonstrated the continuous transfer of cold caesium atoms from the vapour-cell MOT with a pressure of ～ 1×10^-6 Pa to the ultra-high-vacuum (UHV) MOT with a pressure of ～ 8×10^-8 Pa via a focused continuous-wave transfer laser beam. The effect of frequency detuning as well as the intensity of the transfer beam is systematically investigated, which makes the transverse cooling adequate before the atoms leak out of the vapour-cell MOT to reduce divergence of the cold atomic beam. The typical cold atomic flux got from vapour-cell MOT is ～2×10⁷ atoms/s. About 5×10⁶ caesium atoms are recaptured in the UHV MOT.     

Thermionic cathode parameters versus pressure in a sustained argon arc

Experimental data on the influence of the argon pressure on the performance of a rodlike thoriated-tungsten cathode in a sustained arc discharge are reported for the first time. The integral parameters of the cathode, namely, the electron work function, temperature, current density, and specific surface area of erosion at currents of 20–150 A in the pressure range 2.66 × 10³?1.00 × 10⁵ Pa, are measured. Taken together, these parameters provide comprehensive information about the operating conditions of the activated cathode. A significant influence of the pressure on the specific erosion of the cathode is noted.     

Surface microstructure and morphology study of thin films produced from volatile fluorine-containing rare-earth β-diketonate complexes and their adducts

We present the results of a surface microstructure and morphology study of thin films produced from volatile fluorine-containing rare-earth β-diketonate complexes and their adducts. Films 0.2–0.4 μm in thickness were synthesized in vacuum by means of thermal deposition of the parent substances at a pressure of 5 × 10^?4?1 × 10^?3 Pa and a deposition rate of 3 × 10^?3 μm s^?1 (for NaNd(FOD)₄ films, the deposition rate was 8 × 10^?2 μm s^?1). The microstructure of films depends on the deposition conditions. The films of [NaNd(PTFA)₄] and [NaNd(FOD)₄] complexes and Ln(PTFA)₃ · S₁ adducts have an amorphous structure. The [NaNd(PTFA)₄(Phen)] and Nd(PTFA)₃ · S₂ films are characterized by a more ordered polycrystalline structure with the grain size ranging from 0.2 to 1.5 μm.     

Benzoylferrocene-modified carbon nanotubes paste electrode as a voltammetric sensor for determination of hydrochlorothiazide in pharmaceutical and biological samples

The electrooxidation of hydrochlorothiazide (HCT) at the surface of a benzoylferrocene modified multi-walled carbon nanotube paste electrode was studied using electrochemical approaches. Under the optimized conditions (pH 7.0), the square wave voltammetric peak current of HCT increased linearly with HCT concentration in the ranges of 6.0?×?10^?7 to 3.0?×?10^?4 M. The detection limit was 9.0?×?10^?8 M HCT. The diffusion coefficient (D?=?1.75?×?10^?5 cm²/s) and electron transfer coefficient (α?=?0.45) for HCT oxidation were also determined. The proposed sensor was successfully applied for the determination of HCT in human urine and tablet samples.     

The reaction of nitrous oxide with rhodium

A clean rhodium filament at room temperature is highly reactive towards nitrous oxide. The oxygen atom of the N₂O molecule is adsorbed with a sticking probability of 0.45 whilst the nitrogen atoms appear in the gas phase as molecular nitrogen. The room temperature uptake of oxygen is about 5 × 10¹⁴ atom cm^?2 and is independent of nitrous oxide pressure in the range 3.5 × 10^?8 to 1.1 × 10^?6 torr. The adsorption curve is of typical form with an initial region of essentially constant sticking probability. For the first 80% of adsorption at room temperature the shape is satisfactorily accounted for if molecules are able to visit 4–5 adsorption sites whilst held in a weakly-bonded precursor state.     

Selective determination of catecholamine in the presence of ascorbic acid or uric acid on the membrane of silver nanoparticles/poly l-phenylalanine

The silver ions and l-phenylalanine were co-deposited and formed a hybrid membrane on the surface of glassy carbon electrode by cyclic voltammetry. The membrane had good properties for catalyzing the redox of catecholamine neurotransmitters, including epinephrine (EP), norepinephrine (NE), and dopamine (DA). The electrochemical behaviors of these neurotransmitters were studied on this modified electrode. and therefore, an assay for each of them is set up and the detection limits for EP, NE, and DA are 7.2?×?10^?9, 6.4?×?10^?9, and 8.5?×?10^?9 mol L^?1, respectively. The proposed method can effectively eliminate the interference of the ascorbic acid and uric acid. The conditions which influenced the analyses were optimized. Using this method to determine the content of EP, NE, and DA in injections, the results were satisfactory.     

Spectral and nonlinear studies of an aniline blue dye in liquid and solid media

Solid-state dye-doped polymers are an attractive alternative to conventional liquid dye solutions. In this paper, the spectral characteristics and nonlinear properties of the Aniline Blue dye has been studied. The third-order nonlinear optical properties of the Aniline Blue dye in ethanol and a dye-doped polymer film were measured by the Z-scan technique using a 632.8-nm He-Ne laser. This material exhibits a negative optical non-linearity. The dye at a 0.4-mM concentration exhibited a nonlinear refractive coefficient (n ₂ = ?4.02 × 10^?8 and ?4.41 × 10^?8 cm²/W in liquid and solid media, respectively), a nonlinear absorption coefficient (β = ?9.7 × 10^?4 and ?11.63 × 10^?4 cm/W in liquid and solid media, respectively), and susceptibility (x ⁽³⁾ = 1.844 × 10^?6 and 2.028 × 10^?6 esu in liquid and solid media, respectively). These results show that the Aniline Blue dye has potential applications in nonlinear optics.     

Evaluation of carbon-supported copper phthalocyanine (CuPc/C) as a cathode catalyst for fuel cells using Nafion as an electrolyte

Carbon-supported copper phthalocyanine (CuPc/C) nanoclusters, as a novel suitable cathode catalyst in polymer electrolyte membrane fuel cells, have been synthesized via a combined solvent impregnation and milling procedure along with high-temperature treatment. For optimizing the electrocatalytic activity of the catalyst obtained, the electrode with varying Nafion ionomer contents in the catalyst layer was screened by cyclic voltammetry and linear sweep voltammetry employing a rotating disk electrode technique to investigate the effect of Nafion ionomer as for alkaline electrolyte. For comparative purposes, electrode with various contents of available anion-ionomer was also investigated. The results revealed that the content of Nafion ionomer can affect the oxygen reduction reaction activity of the CuPc/C catalyst and an optimal content of Nafion ionomer was around 3.5?×?10¹?μg?cm^?2, which corresponds well with the electrode prepared using available anion-ionomer. The electrode prepared using Nafion ionomer can produce a comparable performance to that of using available anion-ionomer, giving an onset potential at 0.1 V with a half-wave potential of ?0.03 V. Furthermore, Koutechy–Levich analysis showed that the value of electron transfer number is in the range of 3.40 to 3.74 when using electrode with varying Nafion ionomer contents from 2.5?×?10¹ to 1.6?×?10²?μg?cm^?2. The membrane electrode assembly fabricated with the CuPc/C cathode catalyst with a loading of 3.6 mg?cm^?2 and a Nafion membrane immersed in 3 M KOH for 48 h produced a power density of 3.8 mW?cm^?2 at room temperature.     

DX-Like behavior of Se-impurity centers in gasb under hydrostatic pressure

Abstract

Hall coefficient (R_H) and electrical resistivity measurements have been performed as a function of temperature (between 77 K and 300 K) and under hydrostatic pressures (up to 15 kbar) on a set of Se-doped GaSb samples with impurity concentrations in the range 8×10¹⁷ cm^?3 - 1×10¹⁸ cm^?3. With increasing pressure at 300 K, the electrons are strongly trapped into a resonant impurity level. The pressure induced occupation of this level leads to time-dependent effects at T<120 K. The activated thermal electron emission over a potential barrier E<sb>B = 300×30 meV gives clear evidence for a large lattice relaxation around the impurity centers characteristic for DX-like behavior.