Diameter Tungsten Wire Research Articles

Measurements of Temperature Distribution in Thermal Boundary Layer and Quenching Distance at Combustion Chamber of Internal Combustion Engine

The thermal boundary layer near the combustion chamber wall of internal combustion engine has the important key to decrease in the cooling loss. And it is thought that the pollutant emission such as unburnt hydrocarbons exists near the wall because combustion flame is quenched when it approaches the wall. Therefore, the thickness and temperature distribution in the boundary layer are important. Then, resistance wire thermometer with tungsten wire of 5μm diameter is developed for the purpose of measuring boundary layer temperature directly. The measurement of temperature distribution of boundary layer is carried out, by using a rapid compression-expansion machine (RCEM). The nitrogen gas is used in order to oxidation prevention of tungsten wire. The measurement of the various positions in the combustion chamber is possible to make the measurement position movable in the vertical direction to wall. As a result of experiment, thermal boundary layer thickness in compression stroke was 0.5mm in maximum. Next, we try to measure a quenching distance of the combustion flame in homogeneous charged compression ignition engine of a mixture of di-methyle ether and air. The quenching distance is shorter than the thermal boundary layer thickness of non-combustion conditions.

Surface Micro-Structuring Using Polymer Elongation

High-aspect structures are fabricated by photo-polymer elongation using a template. The template, tungsten wire of sub-mm diameter, makes SU-8 film locally stretched and deformed in long and fine fibrous geometry. The aspect ratio of fabricated structure becomes over 8, while the finest diameter is less than 10μm. Both of surface tension and viscosity of SU-8 film determines the yield of fibrous micro-structure. The wire diameter and drawing distance allow one to obtain desired profile of structure. Fibrous structures can be hexagonally aligned utilizing appropriate template with specific diameter and pitch of wire designed based on an analysis of surface energy.

Continuously manufacturing of bulk metallic glass-coated wire composite

Continuously processing is developed for producing a novel bulk metallic glass (BMG)-coated wire composite. The process here yields wire composite coil with the wire diameter of several hundred microns. This paper shows Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 (VIT1) BMG-coated tungsten wire of 200μm and 250μm diameter as examples. The thickness of BMG coating is controllable from several to tens of microns. The amorphous structure of BMG coating is proved by using X-ray diffraction and differential scanning calorimeter (DSC) measurement. The interface is studied by using nano-indentation. Results show that the interface bonding between the tungsten wire and VIT1 BMG coating is excellent. The tension property of the wire composite is illustrated as ultimate fracture strength of 2233MPa and elongation of 1.1%. These data are similar to the mechanical properties of the tungsten wire.

Reproducible Fabrication of Scanning Tunneling Microscope Tips

La fabricacion reproducible de puntas de barrido para microscopios de efecto tunel es demostrada usando un metodo electroquimico. Las puntas son hechas a partir de alambre de tungsteno de 0.5 mm de diametro. Controlando las condiciones de fabricacion: la inmersion en la solucion electrolitica, rangos de voltaje-corriente y duracion del proceso se logra realizar puntas con relaciones de aspecto de 0.68 y radios de punta de 330 nm en el mejor caso

Energy Efficiency of Corona Discharge Reactor Driven by Inductive Energy Storage System Pulsed Power Generator

Characteristics of a pulse corona reactor driven by an inductive energy storage (IES) pulsed power generator are described in this paper with focusing on the influence of streamer-to-glow transition on NO removal efficiency. A pulsed high voltage with a short rise time of under 30 ns is employed to generate streamer discharges homogeneously in whole the discharge region. Fast recovery diodes are used as semiconductor opening switch (SOS) to shorten the rise time. The various resistors are employed as dummy load to clarify a suitable circuit parameter such as the capacitance of a primary energy storage capacitor and/or the inductance of a secondary energy storage inductor. The energy transfer efficiency of the pulsed power generator has a maximum value of 50% at 714 Omega dummy load resistance. A co-axial cylinder type discharge chamber was used as the corona discharge plasma reactor driven by the IES pulsed power generator. The pulsed power generator supplies 30 kV pulse with 300 pps repetition rate. The co-axial cylinder plasma reactor consists of 1 mm diameter tungsten wire and 19 mm i.d. copper tube with 30 cm length. NO removal from the simulated diesel engine exhaust gas (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> :O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> =9:1, Initial NO concentration=200 ppm) increased with input energy into the reactor. The energy efficiency for NO removal was obtained to be 25 g/kWh at 30 % removal in gas flow rate of 2 L/min. However, the energy efficiency decreased to 5 g/kWh with increasing capacitance of the primary capacitor from several hundreds pF to several nF. This decrease was caused by a streamer-to-glow transition. The efficiency was affected by oxygen concentration in the gas mixture.

Electrical explosion of conductors in the high-pressure zone of a convergent shock wave

The effect of the environmental pressure on the electrical explosion of a conductor (fine tungsten wire of diameter 30 μm) in an insulating liquid (distilled water) is studied. The pressure in the water is produced by exploding a multiwire array with the test conductor on its axis. Along with the experiment, the magnetohydrodynamic simulation of the explosion is carried out. It is shown that a high pressure produced in the explosion zone retards the electrical explosion of the conductor and, consequently, increases the explosion energy.

SOSダイオードを用いたパルスパワー電源によるNOx除去におけるストリーマ&amp;mdash;グロー転移の影響

Influence of streamer-to-glow transition in NOx removal from a simulated diesel exhaust gas using pulse streamer discharge (PSD) reactor is described in this paper. A co-axial cylinder type discharge chamber was used as the PSD reactor which was driven by inductive energy storage (IES) pulse power generator with semiconductor opening switch (SOS). The pulsed power generator supplies both polarity of 30 kV pulse with 300 pps repetition rate and 25 ns pulse width. The co-axial cylinder plasma reactor consists of 1 mm diameter tungsten wire and 19 mm i.d. copper tube with 30 cm length. NO removal from the simulated gas (N2:O2=9:1, Initial NO concentration=200 ppm) increased with input energy into plasma reactor. The energy efficiency for NO removal was obtained to be 25 g/kWh at 30 % removal in gas flow rate of 2 L/min. However, the energy efficiency decreased to 4.6 g/kWh with increasing capacitance of the primary capacitor from several hundreds pF to several nF. This decrease is caused with streamer-to-glow transition.

Fabrication of nanoelectrodes for neurophysiology: cathodic electrophoretic paint insulationand focused ion beam milling

The fabrication and characterization of tungsten nanoelectrodes insulated with cathodic electrophoreticpaint is described together with their application within the field of neurophysiology. The tip of a127 µm diameter tungsten wire was etched down to less than 100 nm and then insulated withcathodic electrophoretic paint. Focused ion beam (FIB) polishing was employed to removethe insulation at the electrode’s apex, leaving a nanoscale sized conductive tip of100–1000 nm. The nanoelectrodes were examined by scanning electron microscopy (SEM)and their electrochemical properties characterized by steady state linear sweepvoltammetry. Electrode impedance at 1 kHz was measured too. The ability of a 700 nmtipped electrode to record well-isolated action potentials extracellularly from single visualneurons in vivo was demonstrated. Such electrodes have the potential to open newpopulations of neurons to study.

Copper ring–disk microelectrodes: fabrication, characterization, and application as an amperometric detector for capillary columns

A novel approach to the fabrication of metal ring–disk (RD) microelectrodes is presented that employs flexible chemical vapor deposition (CVD) and electrode modification techniques. Specifically, the development of a copper ring–disk microelectrode is described utilizing a combination of CVD coating, electroetching, and electroplating. Initially, a 25 μm diameter tungsten wire is concentrically coated by CVD with an insulating layer of silica, a layer of tungsten metal, and finally, a second outer layer of silica. The copper surface was prepared by first creating micrometer cavities by electrochemical etching the tungsten in hydroxide solutions followed by electrodeposition of copper from aqueous solutions of Cu(II). Each step of the process was characterized by scanning electron microscopy, optical microscopy, and cyclic voltammetry, demonstrating the preparation of a viable metal-based dual ring–disk microelectrode system. For the purpose of demonstrating the concept of introducing specific selectivity into the device, amperometric detection of galactose in 0.1 M NaOH was performed at +0.60 V in bulk solution and after flow injection analysis in a capillary column.

Diagnostic studies of a low-pressure inductively coupled plasma in argon using a double Langmuir probe

The electron temperature and electron number density of a laboratory-built low-pressure inductively coupled plasma (LP-ICP) were measured using a double Langmuir probe. The probe was composed of two 0.5 mm diameter tungsten wires and a magnesia sleeve shielding the wires that could be linearly moved in the central channel of the plasma by a vacuum linear-motion feedthrough. The role of parameters was studied at a height of 25 mm above the load coil, which yielded an electron temperature of 3–6 eV and an electron number density of 2.5–5 × 1013 cm−3. Less dependence on operating factors was noticed at higher observation heights, and when water loaded on the low-pressure plasma was increased, the electron temperature and electron number density were reduced, unlike with an atmospheric ICP.

Development of Metal-Based Microelectrode Sensor Platforms by Chemical Vapor Deposition

A novel approach to the fabrication of metal mircoelectrodes is described that employs chemical vapor deposition (CVD) techniques and electrode modification strategies. Two specific examples for the fabrication of copper and silver microelectrodes are described, which utilize a combination of CVD coating, electroetching and electroplating. Initially, a 25 μm diameter tungsten wire is concentrically coated with an insulating layer of silica with excellent adhesion between the two surfaces. Tungsten metal is then readily removed by electrochemical etching in hydroxide solution to afford a well-defined microcavity at the electrode tip. For the purpose of demonstrating the concept of introducing specific selectivity into the device as well as fabricating well-defined metal microelectrodes, copper and silver were electrodeposited into the microcavity from aqueous solutions of the respective cations. Both modified electrodes were characterized by electrochemistry and microscopy, and subsequently used as electrochemical sensors for the detection of glucose and chloride ions. This methodology offers a facile approach to the development of highly selective microsensors with well-defined electrode sensing elements.

The effect of strain rate on the tensile deformation of Ti-6Al-4V/SiC composites

Department of Materials Science. Polytechnic University of MadridE. T. S. de Ingenieros de Caminos. 28040 Madrid, Spain(Received November 2, 2000)(Accepted in revised form January 15, 2001)Keywords: Composites; Mechanical properties; Strain rate; FractureIntroductionThe search for lighter, stiffer and stronger materials has led to the reinforcement of light alloys withceramic fibers. In this respect, Ti alloys reinforced with SiC monofilaments stand out as the materialswith the best performance in term of specific stiffness and strength at intermediate temperatures (300°C to 700 °C). They were mainly aimed at gas turbine engines for aerospace vehicles, and significantprogress has been achieved over the last ten years, although their future is still dubious due to cost andother considerations (1–2). The effect of temperature and loading conditions (static or cyclic) on themechanical behavior of these composites has been extensively analyzed, but there is no informationavailable on their performance at high strain rates, so this investigation is focussed on this question.Apart from of its scientific interest, the response of fiber-reinforced Ti-alloy composites to thoseconditions is important from the practical viewpoint, as gas turbine components are often subjected tohigh strain rate and impact loading.Material and Experimental TechniquesThe composite material analyzed in this investigation was a Ti-6Al-4V alloy uniaxially reinforced with35 vol. % Sigma 11401 SiC fibers. Composite panels of 1.35 mm in thickness were manufactured byDERA (UK) by the foil-fiber-foil method. The panels were consolidated in vacuum at 940°C during 1hour under 30 MPa of pressure. The matrix filled completely the spaces between the fibers, whosecenters formed an imperfect hexagonal array. The Sigma 11401 fibers were processed by chemicalvapor deposition of b-SiC on a 15mm diameter tungsten wire, and a carbon coating of ’ 4 mm wasfinally deposited by the same method.Dog-bone specimens of 15 mm gage length and 3 mm width were machined with the fibers orientedin the loading direction using a water-jet. Tensile tests were carried out in a servo-hydraulic testingmachine with nominal cross-head speeds of 0.08 mm/min and 9 mm/min, which correspond to averagestrain rates of approximately 2 10

Z-pinch discharges in aluminum and tungsten wires

A series of experiments on Z-pinch plasmas, driven by a pulsed power generator that delivers 160 kA with a rise time (10%–90%) of 65 ns are reported. Tungsten wires of various diameters were used and results are compared with 15 μm diameter aluminum wire. The expansion of the pinch is studied as a function of wire diameter and material. Schlieren observations show that the coronal plasma of various diameters of tungsten wires expands with the velocity of (9.4±1.0)×103 m/s. The aluminum pinch expands at least a factor of 2 faster. The m=0 perturbations appear at about 8 ns for the aluminum compared with 20 ns for the tungsten pinch. The wavelength and diameter of the perturbations increase with time for both types of wires, and relatively faster for the aluminum pinch. The short wavelength perturbations (∼200 μm) persist for a longer time for larger diameter tungsten wires. Bright spots are seen to appear after 60 ns from the current start for tungsten wires, whereas for aluminum wires, bright spots appear after 40 ns. The decay time of bright spots is 40 ns for the smallest diameter tungsten wire compared with only a few nanoseconds for larger diameter wires. Hard x-ray emission above 6 keV was observed from tungsten wire pinches, but it was not observed from either bright spots or the plasma column for the aluminum pinch. However, hard x-ray emission from the anode due to an electron beam was observed for wires of both materials.

Three-dimensional tomography using a soft X-ray holographic microscope and CCD camera.

The depth resolution of a soft X-ray hologram is much worse than its transverse resolution because a single soft X-ray hologram has a small numerical aperture. To obtain a three-dimensional image, in-line holograms of a specimen were recorded from various directions and reconstructed to obtain two-dimensional projection data. Then, a three-dimensional reconstruction was performed by back-projection of these reconstructed holograms. Three-dimensional images of a tungsten wire of diameter 10 micro m and a fossil of a diatom were obtained.

Diamond fibre microheaters

Free standing diamond fibres with 125 μm diameter tungsten wire or carburised steel cores coated by chemical vapour deposition with ∼ 35 μm thick diamond were heated by passing an electric current through the cores. Tungsten wire cored fibres were heated to 1000°C in a vacuum without any visible change in the fibres. In air the diamond oxidised above ∼550°C. The diamond fibres with the carburised steel core reached a maximum temperature of ∼ 200°C before melting at a local hot spot. This core was also ferromagnetic and thus the fibre had a unique combination of properties. Oxidation produced a large increase in the diamond surface area and this effect might be used to enhance heat transfer in diamond fibre sensors and in diamond fibre-metal matrix composite thermal conductors.

An experimental study of plasma density determination by a cylindrical Langmuir probe at different pressures and magnetic fields in a cylindrical magnetron discharge in heavy rare gases

This article presents an experimental study that contributes to the problem of interpretation of cylindrical Langmuir probe data obtained in a non-isothermal low-temperature plasma in magnetic field. A discussion on the influence of positive ion - neutral collisions on the charged particle density estimation is also given and the effect is demonstrated on the experimental data. A Maxwellian electron energy distribution is assumed throughout the present study. The Langmuir probe data are obtained in a cylindrical magnetron discharge in argon at pressures from 1.5 to 6 Pa and magnetic fields between 100 and 500 G. The radially movable Langmuir probe was made of either m or m diameter tungsten wire in order to investigate the effect of the probe dimensions on the estimated plasma density. The electron density is calculated from the electron current at the space potential (used as a reference) and from the OML collisionless theory. The ion density is calculated by using ABR - Chen theory without and with the correction due to the collisions of positive ions in the probe sheath. Also, the recent collisional positive-ion-collection-theory is used for comparison. The resulting numerical values of plasma density are compared over more than one order of magnitude change in the plasma density given by its radial dependence in the cylindrical magnetron discharge. Optical measurements were made in order to quantitatively assess the neutral gas temperature in the discharge and the density of particles in excited states that could induce secondary electron emission from the probe surface and thus apparently enhance the positive-ion density estimated from the probe positive-ion current. The effect of secondary electron emission from the probe surface on the probe data interpretation has been found small compared to the experimental error limits and consequently not substantial for our experimental conditions. In the range of our experimental conditions the ABR - Chen theory with the collisional correction gives the best agreement of the estimated numerical values of ion and electron densities in the whole range of its investigated change. Also from our results it follows that the effect of the magnetic field on the thinner-probe-electron-current at the space potential and hence on the reference-electron-density-estimation is negligible within the experimental uncertainties up to a magnetic field strength of 500 G which was the maximum used in our experimental study.

Confinement of injected beam ions in a Kingdon trap

Ions from a 2 keV hydrogen beam (a few nA current) were captured into an electrostatic ion trap (Kingdon trap) and stored for as long as 100 ms. The containment time was limited by the chamber pressure. The trap was made of an Al cylinder, 4 in. in diameter by 6 in. long, with a central tungsten wire of diameter 0.0025 in. Fast (100 ns fall time), high voltage pulses (1.9 kV → 0 V) with various durations of up to 100 ms were fed to the wire to turn the trap on and off. The cylinder was held at a constant potential ≈ 1.9 kV. The ions were dumped at the end of each storage interval and a fraction of them was measured by a microchannel plate. A signal to background ratio of 10 was achieved. The number of ions was found to decrease exponentially with a time constant of 60 ms due to collisions with the residual gas. The technique is being extended to slow, highly-charged ions and lower pressures.

The recrystallization mechanism of doped tungsten wire

In the earlier literature, studies on the nucleation and growth mechanism of primary recrystallization and the mechanism of secondary recrystallization were very few. This letter reports some of our work concerning these aspects. The samples were K-Al-Si-doped tungsten wire of diameter 0.39 mm

Dual collector cycloidal mass spectrometer for precision analysis of hydrogen isotopes

The cycloidal mass spectrometer design of Andrew (1) has been adapted to dual ion collection for hydrogen isotope analysis. Difficulties experienced by Andrew with thermal expansion of the wire used to produce uniform electric fields were overcome by using 0.05 mm diameter tungsten wire. The focal lengths for ion beams M/e = 2 and 3, are 2 and 3 cm respectively. The sensitivity is about two orders of magnitude higher than for magnetic sector mass spectrometers of similar size. Under normal operating conditions the H 3 + production is 10% of the total ion current HD + and H 3 +, and the reproducibility of δD measurements is better than ±0.5 per mil. Increase of the resolving power to 600 for separation of 3He + from HD + and H 3 + ions appears feasible.

Self-emissive probes

A high-density magnetized plasma is seen to heat small diameter tungsten wire probes to electron emission. The use of these self-emissive probes to determine the plasma potential in a tandem mirror plasma is investigated. A simplified model is presented and comparison is made with conventional emissive probe behavior.