Thinner Wires Research Articles

Characterization of the frictional losses and heat transfer of oscillatory viscous flow through wire-mesh regenerators

In this paper, new relations for calculating heat transfer and pressure drop characteristics of oscillatory flow through wire-mesh screen regenerator such as Darcy permeability, Forchheimer’s inertial coefficient, and heat transfer area per unit volume, as a function of the wire diameter are presented. According to the derived relations, thinner wires have higher pressure drop and higher heat transfer rate. The relations are applicable for all regenerative cryocoolers. Embedding the new relations into a numerical model, three Stirling-type orifice pulse tube cryocoolers with three regenerators different in length and diameter but same volume in a variety of wire diameters, have been modeled. The results achieved by the model reveal that the local heat transfer coefficient decreases with increase of the wire diameter and the length-to-diameter ratio. In addition, it was shown that the mean absolute gas–solid wire temperature difference is a linear function of wire diameter in the range investigated. The results show that for larger length-to-diameter ratios, Forchheimer’s effect will dominate frictional losses, and the variations of the frictional losses are proportional to the inverse of the wire diameter. Wire diameter has been optimized to maximize the coefficient of performance of the cryocooler. Shorter regenerators have thinner optimum wires.

Limits to Metallic Conduction in Atomic-Scale Quasi-One-Dimensional Silicon Wires

The recent observation of ultralow resistivity in highly doped, atomic-scale silicon wires has sparked interest in what limits conduction in these quasi-1D systems. Here we present electron transport measurements of gated Si:P wires of widths 4.6 and 1.5 nm. At 4.6 nm we find an electron mobility, μ(el)≃60 cm²/V s, in excellent agreement with that of macroscopic Hall bars. Metallic conduction persists to millikelvin temperatures where we observe Gaussian conductance fluctuations of order δG∼e²/h. In thinner wires (1.5 nm), metallic conduction breaks down at G≲e²/h, where localization of carriers leads to Coulomb blockade. Metallic behavior is explained by the large carrier densities in Si:P δ-doped systems, allowing the occupation of all six valleys of the silicon conduction band, enhancing the number of 1D channels and hence the localization length.

Strain induced peculiarities in transport properties of Bi nanowires

We report results on the effect of strain on the thermopower and electrical resistance of glass-coated individual Bi nanowires. Here, we show that there is a critical diameter of wires below which the contribution of holes to the charge transport in pure Bi nanowires is more significant than that of electrons. The properties of Bi nanowires are examined in the light of a strain induced electronic topological transition. At low temperatures, the thermopower dependences on strain exhibit a non-monotonic behavior inherent in thinner wires, where the thermopower is dominated by the diffusion transport mechanism of holes. The hole-dominated transport can be transformed into electron-dominated transport through a smooth manipulation with the phonon spectrum and Fermi surface by applying a uniaxial strain. A fairly high value of the thermoelectric power factor (S2/ρ = 89 μW cm−1 K−2) was found in the temperature range of 80–300 K, where the dominant mechanism contributing to the thermopower is diffusive thermoelectric generation with electrons as the majority carrier.

Mechanism Analysis and Dairy Filtration Experimental Research on Porous 1Cr18Ni9 Stainless Steel Components

Cool-drawn 1Cr18Ni9 stainless steel wires of 0.1~0.5 mm can be woven and punched to prepare porous metal filters. There is certain amount of connected micron pores in the transformable components. Filtration mechanism of this porous material is investigated and three series of samples with different diameter of wires, porosities and filtrating ranges are prepared. Filtration performances compares experiments are carried out on a kind of chocolate milk with the brand of Sanyuan. Three-dimensional microscopy, KEYENCE VHX-600, is applied to investigate the diaphragms before and after filtrating. Portable contamination analysis kit, HPCA-2, is chosen to identify the degree of contaminating. Results indicate that these kind of porous metal filters have valid solid/fluid separating effects. Wires diameters and other preparation parameters will identify the porosity. Thinner wires contribute to more and tinier porous and will block particles effectively. Thickness of filters plays the similar role of filtration layer. Higher porosity will increase the cleanliness of the passing fluid and decrease the filtering efficiency. The data in this paper provide technical support to the application in dairy filtration industry.

Open-coil orthopedic traction spring: An innovative approach for force delivery with face-mask therapy

Facemask therapy/reverse pull headgear is the popular method for maxillary protraction in maxillary deficient adolescence cases. Furthermore, various protraction methods and appliances have been developed, and evaluated extensively for their clinical efficiency. Their effectiveness enhanced with optimum orthopedic force magnitude and low-load deflection rate (LDR) and force constancy over a period of time. With the advent of NiTi springs or springs prepared from thinner wires, force decay has been markedly reduced. For use of NiTi, clinician has to depend upon prefabricated closed coil springs, which are expensive. Open-coil orthopedic traction spring (OCOTS) is developed utilizing 0.012 Australian stainless steel wire for orthopedic traction. This paper describes fabrication and clinical application of OCOTS, with numerous advantages. It sustains low LDR with optimum force magnitude. Its design is adjustable for desired length and force level. It is fail-safe for both activation and deactivation (i.e., it cannot be overstretched or over activated, and decompression limit of open-coil is also controlled by the operator).

Challenge to Development of Functional Multi-Wire EDM Slicing Method Using Wire Electrode with Track-Shaped Section

Brittle materials, such as silicon, silicon carbide and sapphire have been conventionally sliced for wafers by a multi-wire saw method with slurry in industrial fields. Recently, the multi-wire saw method with a fixed diamond abrasive wire has been available as a commercial product at acceptable cost, and the high slicing performance is expected compared with the normal multi-wire saw method with slurry. However, there still remain some problems such as bad working environment with abrasives, cleaning cost of sliced wafers, crack generation on the sliced surface and a large kerf loss against a wafer thickness. On the other hand, the developed multi-wire EDM slicing method would accomplish the high performance slicing of silicon and silicon carbide with a narrow kerf width under a clean process environment. However, the thinner wire is challenging process with a normal round shape wire electrode. Therefore, the new wire electrode with track-shaped section was proposed in order to satisfy both the narrow kerf width and the high wire tension even in the case of thin wire electrode. In this study, the running control of wire electrode with a track-shaped section was experimentally investigated, and the possibility of proposed process was discussed.

Torsion in Strain-Gradient Plasticity: Energetic Scale Effects

We study elasto-plastic torsion in a thin wire within the framework of the strain-gradient plasticity theory elaborated by Gurtin and Anand in 2005. The theory in question envisages two material scales: an energetic length-scale, which takes into account the so-called “geometrically-necessary dislocations” through a dependence of the free energy on the Burgers tensor, and a dissipative length-scale. For the rate-independent case with null dissipative length-scale, we construct and characterize a special class of solutions to the evolution problem. With the aid of such characterization, we estimate the dependence on the energetic scale of the ratio between the torque and the twist. Our analysis confirms that the energetic scale is responsible for size-dependent strain-hardening, with thinner wires being stronger. We also detect, and quantify in terms of the energetic length-scale, both a critical twist, after which the wire becomes fully plastified, and two boundary layers near the external boundary of the...

Microstructure and Superconductive Property of MgB2/Al Composite Materials

MgB2has the higher critical temperature of superconducting transition (TC: 39K) among the intermetallic compound superconductive materials, however, MgB2is hard for practical use because of its unworkable and lower critical current density (JC) in a high magnetic field than Nb-based superconductive materials. We have developed the original method of three-dimensional penetration casting (3DPC) to fabricate the MgB2/Al composite materials. In the composite material we made, MgB2particles dispersed to the matrix uniformly. Thus, these composite materials can be processed by machining, extrusion and rolling. TheTCwas determined by electrical resistivity and magnetization to be about 37～39K. In this work, we made composite material with ground MgB2particle with the purpose of extruding thinner wires of composite material, successfully produced φ1mm wire and changed the matrix from pure Al to Al-In alloy.JCof composite materials with the matrix of Al-In alloy was calculated from the width of the magnetic hysteresis based on the extended Bean model. The result was better than that of MgB2/Al composite material without Indium. Microstructures of these samples had been confirmed by SEM observation.

Atomistic calculation of the thermal conductance of large scale bulk-nanowire junctions

We have developed a stable and efficient kernel method to compute thermal transport in open systems, based on the scattering-matrix approach. This method is applied to compute the thermal conductance of a junction between bulk silicon and silicon nanowires with diameter up to 10 nm. We have found that beyond a threshold diameter of 7 nm, transmission spectra and contact conductances scale with the cross section of the contact surface, whereas deviations from this general trend are observed in thinner wires. This result allows us to predict the thermal resistance of bulk-nanowire interfaces with larger cross sections than those tractable with atomistic simulations, and indicate the characteristic size beyond which atomistic systems can in principle be treated accurately by mean-field theories. Our calculations also elucidate how dimensionality reduction and shape affect interfacial heat transport.

Photoabsorption Properties in InAs Wire Structures Investigated by Dual Light Illumination Method in Scanning Tunneling Microscopy

The photoabsorption properties of InAs wire structures have been investigated through photoinduced current (PIC) measurements by a dual light illumination method in scanning tunneling microscopy. On InAs wires with a width of around 50 nm, the dependences of the PIC signal on incident photon energy and on a light polarization were examined. A steplike shape in the photoabsorption spectrum, obtained from the photon energy dependence, as well as weak polarization dependence indicate that this wire structure behaved like a quantum well because of a weak lateral confinement effect. On the other hand, apparent polarization dependence was observed on the InAs wires with a width of around 25 nm, which is attributable to an enhancement of structural anisotropy in the thinner wire.

Growth and properties of tin oxide nanowires and the effect of annealing conditions

Luminescence data obtained in the visible region from the SnO2 nanowires are used to determine the defect levels within the bandgap responsible for the strong orange emission, and a shift in the orange luminescence is seen at low temperatures. Temperature-dependent photoluminescence (PL) in the UV region shows the merging of the various emission lines at low temperature into a single broad UV peak with increasing temperatures. Investigations of PL and transmission electron microscope-energy dispersive x-ray spectroscopy (TEM-XEDS) from wires of different diameters show that the luminescence in the gap originates from surface states and thinner wires have more oxygen vacancies compared to thicker ones. Nanowires post rapid thermal annealing in two different ambients viz. oxygen and nitrogen are compared, using Raman, photoluminescence (PL) and x-ray photoelectron spectroscopy (XPS) as characterization tools. Our data demonstrate that annealing in oxygen improves the crystalline quality of the nanowires due to the decrease in the oxygen vacancies.

Wavelength Sensitivity of Single Nanowire Excitation Polarization Anisotropies Explained through a Generalized Treatment of Their Linear Absorption

We investigate the excitation polarization anisotropy of individual semiconductor nanowires (NWs) by monitoring their band edge emission above 680 nm in order to clarify the origin of their strong polarization response. Samples studied include both CdSe and CdSe/CdS core/shell nanowires grown using solution chemistry as well as analogous wires made via chemical-vapor-deposition (CVD). In the limit of optically thick wires, with radii above ∼25 nm, we find NW optical responses consistent with the interaction between strong dielectric contrast influences and the onset of bulk-like behavior. Namely, a sizable wavelength dependence of the excitation polarization anisotropy (ρ(exc)) exists when NW diameters become comparable to the wavelength of light inside the wire. As a consequence, pronounced ρ(exc) rolloffs occur at short wavelengths. By contrast, thinner wires do not exhibit such wavelength dependencies, in agreement with earlier studies. We quantitatively explain observed wavelength sensitivities by modeling the NW as an absorbing dielectric cylinder under plane wave excitation. A comparison of predicted ρ(exc)-values to experimental numbers shows good agreement and confirms the existence of wavelength-dependent ρ(exc)-values in optically thick wires. Additional results of the model include generalized expressions for NW linear absorption cross-sections under parallel, perpendicular, and circularly polarized excitation. This study therefore adds to a growing body of knowledge about NW polarization anisotropies, specifically, their response in a size regime where dielectric contrast effects compete with the onset of bulk-like behavior.

Failure analysis of flexible metal hose at compressor discharge

Flexible hoses are sometimes placed at compressor discharge to minimize the effect of vibrations on piping and vessels. Doing well for this purpose, these elements can suffer dynamic loads from gas pulsation and fail. The root cause of the failure of a flexible connection at the discharge of an oil distillery propane alternating compressor is investigated. The connection is a 150 mm stainless steel corrugated metal hose with an external braid. The failure took place by overload of the braid, after wear of the wires. The fractures in the wires were consequence of fatigue crack propagation in previously worn areas. It was found that the flexible connection was under a larger working pressure than the maximum allowable as defined by the manufacturer. The failed flexible had thinner wires and different braid design than those previously used by the user. Recommendations include procedures to verify dimensions previous to assembly and to increase the inspection frequency of these elements, as well as to verify vibration levels of the connected machines. An elastomer material placed between corrugated and braid would diminish the rate of wear caused by vibrations.

Preparation of Fe and Co based amorphous wires by in-water quenching process

The investigation addresses the effect of in-water quenching process parameters on the magnetic properties of Fe and Co based amorphous wires. The in-water quenching process parameters such as water drum speed, crucible nozzle orifice diameter, crucible nozzle to water level separation and gas pressure for melt ejection were found to be critically important to obtain continuous and ductile wires. The thinner wires with a diameter of ∼124 μm revealed superior soft magnetic properties with coercivities as low as ∼5˙63 A m–1 (70˙8 mOe) which was attributed to their high amorphous nature and consequent isotropy. This was also manifested from their surface morphology as observed by scanning electron microscopy. The Fe77˙5Si7˙5B15 and Co72˙5Si12˙5B15 (at.-%) wires in their as prepared state revealed high fracture strength, above 3000 MPa, and high microhardness ∼1200 HV (Vickers pyramid number).

Chip-Level Performance Maximization Using ASIS (Application-Specific Interconnect Structure) Wiring Design Concept for 45 nm CMOS Generation

A novel interconnect design concept named (Appilication-specific Interconnect Structure) is presented for 45 nm CMOS performance maximization. Basic scheme of ASIS is that corresponding to applications, such as high-performance, low-power, or high reliability, interconnect structure as well as metal thickness is individually optimized in order to maximize chip-level performance matched to the application. Our investigation shows that for low-power application, the increased resistivity of scaled-down Cu-wire is not a main issue, so that thinner wire is more advantageous. For high-performance application, partially double pitch structure for local and intermediate layers is advantageous. For high-reliability requirement, Cu-Al alloy or CoWP cap-metal is quite effective for boosting reliability.

The effect of Pd and Cu in the intermetallic growth of alloy Au wire

This is the new wire evaluation work for the reliability of the wire-bonding process. There is a trend for the plastic integrated-circuit package to function at higher junction temperature with thinner wire. New alloy Au wires have been developed to meet the reliability requirements. Two types of alloy Au wires, Au-Pd and Au-Cu, were evaluated in this study. These samples were aged between 155°C and 205°C under air from 0 h to 3,000 h. According to this study, the phase-formation sequence of Au2Al, Au5Al2, and Au4Al intermetallic is similar to the pure Au wire. There is a Pd-rich layer working as a diffusion barrier to slow down the growth rate of intermetallic phases in the Au-Pd wire. The Au-Cu wire also slowed down the growth rate with a different mechanism. Both wires have better reliability based on the microstructure examination. The reliability test results show longer working life at higher temperatures in comparison with the regular Au wire.

Strength and ductility of thin Cu wires

Abstract The stress–strain behavior of thin copper wires in the range 20–250 μm diameter and various purities (3N, 5N) have been investigated. The wires were subjected to a recrystallization heat treatment and tensile properties were determined. Tensile testing was performed using a microtensile testing machine equipped with a non-contacting laser-optical speckle correlation sensor adapted for high-resolution strain measurement. The fracture elongation of all specimens exhibited lower values than that of bulk Cu with a decreasing trend for thinner wires. High-purity wires with a pronounced bamboo structure showed a size dependence of the yield strength which increased with decreasing wire diameter. Surface topography and fracture surfaces of the specimens were examined. The microstructural investigations were performed to arrive at an understanding and interpretation of our experimental results.

Optical coherent transient effects in a magnetized semiconductor quantum wire

Effects of an external magnetic field on free induction decay (FID) and the Stark effect in GaAs/GaAlAs quantum wires have been investigated analytically. Our results show that both FID and the Stark effect become enhanced due to the presence of a magnetic field. We have also seen that the magnetic field plays an important role in wider wires while in thinner wires, the geometric confinement dominates over the magnetic effects. The results are found to be in good qualitative agreement with that available in the literature.

Microchannel Networks for Nanowire Patterning

Microchannel Networks for Nanowire Patterning

Plasmons and the quantum limit in semiconductor wires

We report on the observation by Raman scattering of one-dimensional plasmons in deep-etched wires with lateral sizes w down to 30 nm. We determine the dispersion of these collective excitations down to 45 nm, well beyond the transition to a single one-dimensional subband occupancy $(w\ensuremath{\sim}60\mathrm{nm}),$ and demonstrate that they can be well described both within the random-phase approximation and the L\"uttinger liquid theory. In thinner wires, the Raman spectra reduce to a single undispersive low-energy line which we attribute to a plasmon localized by longitudinal disorder in the external potential.