Effect of Critical Current Density and Critical Temperature on ac Susceptibility

Based on the flux creep equation, the effect of critical current density and critical temperature on ac susceptibility is investigated numerically in a superconducting slab immersed in an ac magnetic field. The current density dependence of the flux creep activation barrier is employed as the logarithmic law. The fundamental ac susceptibilities of the slab as a function of temperature for the same ac field have been derived in a unified picture. The results show that ac susceptibility in flux creep regime is affected by critical current density and critical temperature.     

Choice of Parameters in Morse Potential for Copper

The choice of parameters in Morse potential for copper was made by the molecular dynamics modeling. The elastic coefficients C11, C44, their temperature coefficients TC11, TC44, as well as the hydrostatic compression behaviour, i.e. pressure/volum curvs have been calculated. The choice of Morse poteotial parameters can be made by comparing the results with the experimental data. The chosen parameters are greatly different for different simulated properties.     

Effect of Laser Parameters on Sintered Powder Morphology

Selective laser sintering is a kind of rapid prototyping process whereby a three-dimensional part is built layerwise by laser scanning a powder. This process is highly inffuenced by powder and laser parameters such as laser power, scan rate, spot size and layer thickness. Therefore a study on fabricating a line with Fe-Ni-Cr powder on AISI H13 tool steel has been performed by selective laser sintering. In this study, fabrication was performed by experimental facilities consisting of a 200W fiber laser which can be focused to 0.08 mm and atmospheric chamber which can control atmospheric pressure with argon. The line was fabricated with various laser power, scan rate and layer thickness. Line width and surface quality were investigated. With power increase or layer thickness decrease, line width was decreased and line surface quality was improved with scan rate optimization.     

Evaluation of Morphology—Stable Critical Size of KNbO3 Crystals

Skeletal form of KnbO3 crystals growing in Li2B4O7 solvent was in-situ observed at 900℃ and it was found that shallow depression started to develop on the surface of KnbO3 crystals when the crystal size exceeded several micron,typically 7 micron.Based on the quantitative criterion derived by Chernov,the estimated critical size of KNbO3 crystals was 1 micron,which was consistent with the experimental measurement.The kinetic coefficients,Kcorner and Kcr,in the criterion were experimentally obtained in the diffusive-convective and diffusive-advective flow states respectively.     

Influence of Processing Parameters on Granularity Distribution of Superalloy Powders during PREP

In order to investigate the influence of processing parameters on the granularity distribution of superalloy powders during the atomization of plasma rotating electrode processing (PREP), in this paper FGH95 superalloy powders is prepared under different processing conditions by PREP and the influence of PREP processing parameters on the granularity distribution of FGH95 superalloy powders is discussed based on fractal geometry theory. The results show that with the increase of rotating velocity of the self-consuming electrode, the fractal dimension of the granularity distribution increases linearly, which results in the increase of the proportion of smaller powders. The change of interval between plasma gun and the self-consuming electrode has a little effect on the granularity distribution, also the fractal dimension of the granularity distribution changed a little correspondingly.     

Critical and Impeding Pressures of Al Evaporation during ISM Processing of NiAl

In this paper, the critical pressure pcrit and impeding pressure pimpe of the elemental evaporation were defined and studied based on the calculation of the relationship between the evaporation loss rate Nm and the chamber pressure p during melting of NiAl alloys. When the chamber pressure is lower than pcrit or higher than Pimpe Nm tends to be the maximum or minimum value and remains almost unchanged. However, declines sharply with the increase of the chamber pressure when pcrit相似文献   

Critical Behavior of 2 − Ions in Argon Gas

We measured the drift mobility of ₂ ^– ions in argon gas close to the critical point for (1.005 < T/T _c < 1.04) above T _c 150.7 K in the density range (0.025 <N/N _c< 1.733) around the bulk critical density N _c = 8.08 atoms . nm^–3. The density-normalized zero-field mobility ₀ N of the ions shows a deep minimum as a function of the gas density N as T T _c ⁺ This anomalous reduction of ₀ N occurs at a density N _m 0.76N _c. We believe that this behavior is due to the strong electrostriction exerted by the ion on the highly compressible gas. By introducing suitable contributions to the effective ion radius R due to the large gas compressibility and taking into account short-range local density and viscosity augmentation due to electrostriction, the hydrodynamic Stokes formula ₀ = e/6R, where is the gas viscosity, is in good agreement with the experimental data.     

Calculation of Scattering Parameters for Ultracold K–Cs Elastic Collisions

A theoretical study of elastic scattering properties in a mixture of ³⁹K and ¹³³Cs atoms at cold and ultracold temperatures is reported in this paper. Based on the new constructed accurate singlet X ¹∑⁺ and triplet a ³∑⁺ states interatomic potentials for ³⁹K¹³³Cs mixture, the interspecies s-wave scattering lengths and the p-wave scattering volumes are calculated by the variable phase method and the semiclassical method, respectively. Good agreement between two methods is obtained. The mass dependence of the scattering data by considering all isotopomers is explored, and the numbers of bound states supported by the molecular potentials for each isotopomer are also calculated.     

X-Ray and Neutron Diffraction Studies on Thermal Parameters of Thalous Bromide

Thermal parameters of TIBr were determined using both X-ray and neutron diffraction techniques. The data was analysed by Rietveld profile refinement procedure. From the neutron diffraction data, due to weak odd-order reflections, it was not possible to determine the individual thermal parameters. The X-ray diffraction measurements yielded BT1=0.296(5)nm2 and BBr=0.162(5) nm2. The overall isotropic value, J9 was 0.252(7) nm2 which is in good agreement with B=0.230(8) nm2 obtained from present neutron diffraction measurements. The present values are also in good agreement with theoretical estimates obtained from the shell models.     

Influence of Experimental Parameters on Reactive Magnetron Sputtering CN_x Thin Films

Carbon nitride thin films were deposited on Si(001) using unbalanced magnetron sputtering at different experimental parameters. The effects of nitrogen partial pressure, substrate temperature and substrate bias on the deposition rate and nitrogen content are discussed.     

Critical phenomena of liquid4He in the vicinity of the upper λ point

We determinedC _p along six isobars near T in the vicinity of the upper superfluid transition point (upper point) from measurements ofC _v and (P/T) _v along six isochores.C _p was analyzed with the functionC _p =(A/)^–(1+D^–)+B for T>T, and the same function with primed coefficients for T, whereD denotes the strength of the effect of the irrelevant variable. The present work clarified the effect of the pressure (irrelevant variable) on the critical behavior of ⁴ He near T, that is, the correction term due to the irrelevant variable increases with pressure even in the small range 3×10^–3. This indicates that the pressure depresses the true critical region. The universality of the amplitude ratioA/A was confirmed even in the vicinity of the upper point by specific heat measurements. With constraints ==–0.02, ==–0.5, andB=B the pressure-independent amplitude ratiosA/A=1.088±0.007 andD/D=0.85±0.2 were obtained.AD/AD=0.93±0.2 implies that the pressure has a similar effect onC _p in the normal fluid and superfluid regions, within experimental errors.     

Critical behavior of the free surface of liquid 4He near the λ point

The noncriticality of the free surface of liquid ⁴He near the point and the finite-size scaling postulate are combined to show that the surface tension can have two singularities, one due to rounding and another due to shifting. The rounding singularity can be reduced, via a further scaling assumption, to that previously suggested by Sobyanin and Hohenberg. Results from calculations based on continuous symmetry models and experiments on topologically 2D ⁴He films are used to argue that the shift singularity is ¦t¦^1–, which is consistent with the leading singularity observed by Magerlein and Sanders.     

Effect of Processing Parameters on Microstructures of Melt—Spun Al—In Immiscible Alloys

Melt spinning rapid solidification technique was employed to fabricate homogeneous Al-In immiscible alloys and their final microstructures and morphologies were investigated.There existed a transition of columnar Al grain→equiaxed grain for the thicker ribbon,but only columnar Al grain for the thinner ribbon throughout the thickness.In the columnar grain field,most of the fine In particles was distributed within the cells,but a minority of bigger In particles or short rods was perpendicularly distributed at the grain boundaries.In the equiaxed grain field,the fine In particles were located in Al grains and coarser particles were situated at the boundaries.The average particle size increased with increasing distance from the chilled surface throughout the ribbon.At the same wheel speed (same cooling rate),the average particle size increased with raising In content.At the same composition condition,the average particle size decreased with increasing wheel speed and/or decreasing ejection temperature.     

Influence of Temperature‐Time Parameters of Heat Treatment on the Process of Planarization of the Surface Relief of Microelectron Structures

The authors consider the process of fusion of phosphorosilicate and borophosphorosilicate glasses in planarization of the surface of integrated microcircuits under the conditions of both isothermal and pulse heat treatment. An expression for calculating the angle of fusion of the relief step as a function of the concentration of doping impurities in a glass and the time and temperature of heat treatment is obtained.     

Critical properties of4He in aerogel near the λ-line

We measured the superfluid fraction _s/ and the isobaric thermal expansion coefficient _P of⁴He confined in an aerogel. Data were obtained near the -line along several isobars. Powerlaw fits to the results for _s/ as a function of tT/T_c–1 (T_c is the transition temperature) give a pressure—independent exponent =0.755 when a confluent singular term is included. Fits to the _P data of power laws yield the specific-heat exponents –0.6 and –1.0 above and below T_c respectively. When an analytic background term a×t is included in the fit, the pressure-independent value =–0.59 is permitted, but the amplitude ratio A/A is found to be near zero and the coefficient of the analytic term is large. The measured values for and or are inconsistent with hyperscaling in three dimensions.     

Burnout at Large Subcoolings and Near‐Critical Pressures of Toluene

The results of experimental investigation of a burnout of toluene at subcoolings t = 50–270°C at the tube inlet and pressures P/P _cr = 0.70–0.94 are given. The critical heat fluxes as functions of the mass velocity of the liquid and its subcooling to the saturation temperature are established. The results obtained are compared to the data for water.     

Variance of Critical Current Density with Microstructure by a Special Process

A promising method —“powder in tube”technique was used to fabricate Ag-sheathed Bi-2223superconductive tapes with high critical current density.After a combination processing of pressingand subsequent heat treatment,we obtained tapes with high degree of texture,good compactionand uniform properties.At 77 K in zero field,J_C was higher than 1×10~4 A/cm~2 while the highestJ_C was 1.69×10~4 A/cm~2.SEM and XRD was used to detect the tapes texture,and the relationship be-tween J_C and the degree of texture is discussed.In addition,the reason for obstacling the improvementof J_C is also investigated.     

Growth of skyrmionic MnSi nanowires on Si： Critical importance of the SiO2 layer

MnSi in the B20 structure is a prototypical helimagnet that forms a skyrmion lattice, a vortex-like spin texture under applied magnetic field. We have systematically explored the synthesis of single crystal MnSi nanowires via controlled oxide-assisted chemical vapor deposition and observed a characteristic signature of skyrmion magnetic ordering in the MnSi nanowires. The thickness of the SiO2 layer on the Si substrate plays the key role in obtaining a high yield of B20 MnSi skyrmion nanowires. A growth mechanism was proposed that is consistent with the existence of an optimum SiO2 thickness. A growth phase diagram was constructed based on the extensive studies of various growth conditions for various MnSi nanostructures. The persistence of both the helicoidal and skyrmion magnetic ordering in the one-dimensional wires was directly revealed by ac and dc magnetic measurements.     

Effects of Sintering on the Microstructure and Critical Current Density of Ag-sheathed BiPbSrCaCuO Superconducting Tapes

The effects of sintering on the microstructure and the critical current density of Ag-sheathedBiPbSrCaCuO (2223) superconducting tapes prepared by the powder-in-tube technique were in-vestigated. The microstructure of oxide layer and the J_C at 77 K were strongly dependent on thesintering condition. The optimum sintering temperature, time and cooling rate to maximize J_C valueswere in the range about 840-850℃, 100-200 h and 50-100℃/h, respectively.