Electron Wire Research Articles

Pillaring Electronic Nano-Wires to Slice T-Nb2O5 Laminated Particles for Durable Lithium-Ion Batteries.

T-Nb2O5 characterized by the pronounced intercalation pseudocapacitance effect, is regarded as a promising and alternative anode for fast-charging Li-ion batteries. However, its electrochemical kinetics are still hindered by the absence of sufficient and homogenous conductive wiring inside active microparticles. Herein, an in situ pillaring strategy of electronic nano-wires is proposed to slice T-Nb2O5 laminated particles for the development of durable and fast-charging anodes for Li-ion batteries. A micro-level layered structure consisting of nano-carbon-inserted T-Nb2O5 composite flakes is designed and enabled by successive ion exchange, slice exfoliation, in situ polymerization, and carbonization processes. The pillared carbon interlayer (derived from polyaniline) can serve as in-built conductive wires to promote and homogenize electron transfer inside the micro-level particles. The porous structure (formed by the self-assembly of exfoliated flakes) contributes to the improved electrolyte immersion and enhanced lithium migration. Benefitting from the kinetically favorable effects, the modified T-Nb2O5 anode achieves the high-rate capability (108.4 mAhg-1 at 10 Ag-1) and ultralong cycling durability (138 mAhg-1 at 1.0 Ag-1 after 8000 cycles, with an average capacity decaying rate as small as 0.043‰). This work provides an effective strategy of electron wire pillaring with the slicing effect for laminated electrode materials with high tap density.

Microstructure and Properties of Ti-6Al-4V Articles 3D-Printed with Co-axial Electron Beam and Wire Technology

Advanced additive manufacturing technology of direct energy deposition type called x Beam 3D Metal Printing was employed for manufacturing of articles of various size and shape using titanium Ti-6Al-4V alloy wire as a feedstock material. The key distinctive feature of this process is applying of the hollow conical electron beam generated by low-voltage (< 20 kV) gas-discharge electron beam gun for heating and melting of the substrate and wire, which ensures precisely controllable liquid metal transfer from the wire end to the substrate, specific temperature gradients at the fusion area and heat flow from liquid metal pool. Such conditions of heating, melting and cooling during deposition of molten additive material provide controllable microstructure formation, including grain size and material texture. Influence of processing parameters and cooling conditions on fusion, crystallization, grain growth and intragrain structure of manufactured “chunky” Ti-6Al-4V blocks was discussed. The post-processing heat treatment was used to relieve residual stresses formed during article manufacturing. Tensile and fatigue testing has been performed for samples cut in various directions of produced articles to investigate the material uniformity. Optimization of processing parameters allowed production of 3D printed articles from Ti-6Al-4V with isotropic microstructure and mechanical characteristics which met standard requirements for Ti-6Al-4V material.

A review on post processing techniques of additively manufactured metal parts for improving the material properties

Metal additive manufacturing (AM) processes are used to produce metal parts with greater design freedom and no material wastage from a CAD model, using powder or wire as feedstock with a layer by layer joining of materials by a high intensity energy source such as laser or electron beam. These processes include selective laser melting (SLM), electron beam melting (EBM) and wire arc additive manufacturing (WAAM) techniques which has wide usage in fabricating metal alloys such as aluminum and titanium for the aerospace and automotive applications. However, these AM parts show many limitations in the as built state like poor surface finish and high tensile residual stress, which will affect the mechanical properties and surface integrity because of the usage of high intensity energy-based melting for the fabrication of parts. This give rise to the need for post processing techniques such as heat treatment and additional machining and polishing operations such as shot peening (SP), laser shock peening (LSP), abrasive flow machining(AFM), friction stir processing (FSP) and hot isostatic pressing (HIP) to improve its surface finish, fatigue life and other material properties. This review paper aims to understand the defects of as built AM parts and focus on the post processing techniques employed by the researchers and its effects on the improvement of AM components.

Microstructure and Properties of 3D Ti-6Al-4V Articles Produced with Advanced Co-axial Electron Beam &amp; Wire Additive Manufacturing Technology

Ti-6Al-4V articles were produced with advanced additive manufacturing technology of Direct Energy Deposition (DED) type using profile electron beam and wire as feedstock material. The key distinctive feature of this additive manufacturing process is the applying of the hollow conical electron beam generated by low-voltage (&lt;20kV) gas-discharge EB gun for heating and melting of the substrate and co-axially fed wire. Such configuration ensures precisely controllable liquid metal transfer from the wire end to the substrate, specific temperature gradients at the fusion area and heat flow from liquid metal pool. Such conditions of heating, melting and cooling during 3D manufacturing processing provide the ability for controllable microstructure formation, including grain size and material texture. Influence of processing parameters and cooling conditions on crystallization, grain formation and intragrain structure of solidified material is discussed. Optimization of processing parameters allowed production of 3D Ti-6Al- 4V articles with isotropic microstructure and mechanical properties which met standard requirements for Ti-6Al-4V alloy.

Effect of the Fermi Surface Anisotropy on the Electrical Conductivity of a Thin Inhomogeneous Metal Wire

The high-frequency electrical conductivity of a thin inhomogeneous metal wire with a dielectric core is calculated using the kinetic approach. The Fermi surface of a metal is assumed to be an ellipsoid of revolution with the rotational axis coinciding with the wire axis. In the investigated case of isotropic electron scattering, the volume relaxation time does not depend on either the energy or the direction of electron scattering. No limitations are imposed on the ratio between the conduction’s electron free path and wire radius. The dependences of the absolute value and argument of the dimensionless conductivity on the dimensionless transverse effective mass, dimensionless wire radius, dimensionless electric field frequency, and ratio between the wire and dielectric core radii are analyzed.

A new 3D printing method based on non-vacuum electron beam technology

Electron beam freeform fabrication (EBF3) is one the of rapid manufacturing methods, which produces metal parts using an electron beam and wire feed unit in a layer additive fashion without need of mold or jigs. The main disadvantage of EBF3 is that the process is carried out in a chamber, which not only takes a lot of time to evacuate but also limits the size of the part being printed. Non-vacuum electron beam (NVEB) welding is widely used in industry field as a reason for its high production volumes. So a NVEB 3D printing device based on a non-vacuum electron beam welding machine from SST is designed. A serial of experiments is carried out to get a deep understand of 3D printing processing procedure using non-vacuum electron beam system and find a suitable process window. Result shows that droplet transfer mode is one of the most important parameters which determines the quality of the deposition.

Synthesis and utilization of carbon nanotubes for fabrication of electrochemical biosensors

This review summarizes the most recent contributions in the fabrication of carbon nanotubes-based electrochemical biosensors in recent years. It discusses the synthesis and application of carbon nanotubes to the assembly of carbon nanotube-based electrochemical sensors, its analytical performance and future expectations. An increasing number of reviews and publications involving carbon nanotubes sensors have been reported ever since the first design of carbon nanotube electrochemical biosensors. The large surface area and good electrical conductivity of carbon nanotubes allow them to act as “electron wire” between the redox center of an enzyme or protein and an electrode's surface, which make them very excellent material for the design of electrochemical biosensors. Carbon nanotubes promote the different rapid electron transfers that facilitate accurate and selective detection of cytochrome-c, β-nicotinamide adenine dinucleotide, hemoglobin and biomolecules, such as glucose, cholesterol, ascorbic acid, uric acid, dopamine pesticides, metals ions and hydrogen peroxide.

Structural Analysis of Respirasomes in Electron Transfer Pathway of Acidithiobacillus ferrooxidans: A Computer-Aided Molecular Designing Study

Acidithiobacillus ferrooxidans obtains its metabolic energy by reducing extracellular ferrous iron with either downhill or uphill electron transfer pathway. The downhill electron transfer pathway has been substantially explored in recent years to underpin the mechanism of iron respiration but, there exists a wide gap in our present understanding on how these proteins are organized as a supercomplex and what sort of atomic level interactions governs their stability in the iron respiratory chain. In the present study, we aimed at unraveling the structural basis of supermolecular association of respirasomes using protein threading, protein-protein docking, and molecular dynamics (MD) simulation protocols. Our results revealed that Phe312 of outer membrane cytochrome c plays a crucial role in diffusing electrons from heme C group to Asp73 of rusticyanin. In line with the previous experimental results, His143 of rusticyanin was found to have a stable interaction with Glu121 of periplasmic cytochrome c4. Cytochrome c4 interacts with subunit B of cytochrome c oxidase through Lys146 and Thr148 of the conserved hydrophobic/aromatic motif 145-WKWTFSY-151 to attain stability during simulation. Phe468 of cytochrome c oxidase was found indispensable for stabilizing heme aa3 during MD simulation. Taken together, we conclude that the molecular interactions of charged and hydrophobic amino acids present on the surface of each respirasome form a hypothetical electron wire in the iron respiratory supercomplex of A. ferrooxidans.

Functional Dissection of the Multi-Domain Di-Heme Cytochrome c550 from Thermus thermophilus

In bacteria, oxidation of sulfite to sulfate, the most common strategy for sulfite detoxification, is mainly accomplished by the molybdenum-containing sulfite:acceptor oxidoreductases (SORs). Bacterial SORs are very diverse proteins; they can exist as monomers or homodimers of their core subunit, as well as heterodimers with an additional cytochrome c subunit. We have previously described the homodimeric SOR from Thermus thermophilus HB8 (SORTTHB8), identified its physiological electron acceptor, cytochrome c 550, and demonstrated the key role of the latter in coupling sulfite oxidation to aerobic respiration. Herein, the role of this di-heme cytochrome c was further investigated. The cytochrome was shown to be composed of two conformationally independent domains, each containing one heme moiety. Each domain was separately cloned, expressed in E. coli and purified to homogeneity. Stopped-flow experiments showed that: i) the N-terminal domain is the only one accepting electrons from SORTTHB8; ii) the N- and C-terminal domains are in rapid redox equilibrium and iii) both domains are able to transfer electrons further to cytochrome c 552, the physiological substrate of the ba 3 and caa 3 terminal oxidases. These findings show that cytochrome c 550 functions as a electron shuttle, without working as an electron wire with one heme acting as the electron entry and the other as the electron exit site. Although contribution of the cytochrome c 550 C-terminal domain to T. thermophilus sulfur respiration seems to be dispensable, we suggest that di-heme composition of the cytochrome physiologically enables storage of the two electrons generated from sulfite oxidation, thereof ensuring efficient contribution of sulfite detoxification to the respiratory chain-mediated energy generation.

Electrical Properties of ZnO Film Prepared by Thermal Oxidation Method

Zn films were deposited on Al2O3 tube with Au electron and Pt wire by direct current magnetron sputtering, then ZnO films were synthesized by thermal oxidation in different temperature using resistance furnace. Surface topography of films was investigated by atomic force microscope. The resistance of ZnO films in air and other atmosphere was tested in a gas sensor test system. Results showed that the films surface morphology changed significantly during thermal oxidation growth. ZnO film synthesized at 1000 0C for 3 minutes has the smallest grain (32.6nm), the biggest roughness (60.9nm). Resistance of ZnO films declined with the increasing of heater power. The resistance of the ZnO layers depends dramatically on the sputtering time (direct proportion to the film thickness). The resistance of ZnO films in 10 minutes sputtering time is one order of magnitude higher than that in 80 minutes.

Two-photon chemistry in ruthenium 2,2'-bipyridyl-functionalized single-wall carbon nanotubes.

Ruthenium polypyridyl complexes are widely used as light harvesters in dye-sensitized solar cells. Since one of the potential applications of single-wall carbon nanotubes (SWCNTs) and their derived materials is their use as active components in organic and hybrid solar cells, the study of the photochemistry of SWCNTs with tethered ruthenium polypyridyl complexes is important. A water-soluble ruthenium tris(bipyridyl) complex linked through peptidic bonds to SWCNTs (Ru-SWCNTs) was prepared by radical addition of thiol-terminated SWCNT to a terminal C=C double bond of a bipyridyl ligand of the ruthenium tris(bipyridyl) complex. The resulting macromolecular Ru-SWCNT (approximately 500 nm, 15.6% ruthenium complex content) was water-soluble and was characterized by using TEM, thermogravimetric analysis, chemical analysis, and optical spectroscopy. The emission of Ru-SWCNT is 1.6 times weaker than that of a mixture of [Ru(bpy)(3)](2+) and SWCNT of similar concentration. Time-resolved absorption optical spectroscopy allows the detection of the [Ru(bpy)(3)](2+)-excited triplet and [Ru(bpy)(3)](+). The laser flash studies reveal that Ru-SWCNT exhibits an unprecedented two-photon process that is enabled by the semiconducting properties of the SWCNT. Thus, the effect of the excitation wavelength and laser power on the transient spectra indicate that upon excitation of two [Ru(bpy)(3)](2+) complexes of Ru-SWCNT, a disproportionation process occurs leading to delayed formation of [Ru(bpy)(3)](+) and the performance of the SWCNT as a semiconductor. This two-photon delayed [Ru(bpy)(3)](+) generation is not observed in the photolysis of [Ru(bpy)(3)](3+); SWCNT acts as an electron wire or electron relay in the disproportionation of two [Ru(bpy)(3)](2+) triplets in a process that illustrates that the SWCNT plays a key role in the process. We propose a mechanism for this two-photon disproportionation compatible with i) the need for high laser flux, ii) the long lifetime of the [Ru(bpy)(3)](2+) triplets, iii) the semiconducting properties of the SWNT, and iv) the energy of the HOMO/LUMO levels involved.

Enalapril Treatment Alters the Contribution of Epoxyeicosatrienoic Acids but Not Gap Junctions to Endothelium-Derived Hyperpolarizing Factor Activity in Mesenteric Arteries of Spontaneously Hypertensive Rats

Reduction in endothelium-derived hyperpolarizing factor (EDHF)-mediated dilatory function in large, elastic arteries during hypertension is reversed after blood pressure normalization. We investigated whether similar mechanisms occurred in smaller mesenteric resistance arteries from aged Wistar-Kyoto (WKY) rats, spontaneously hypertensive rats (SHRs), and SHRs treated with the angiotensin-converting enzyme inhibitor, enalapril, using immunohistochemistry, serial-section electron microscopy, electrophysiology and wire myography. Unlike the superior mesenteric artery, EDHF relaxations in muscular mesenteric arteries were not reduced in SHRs, although morphological differences were found in the endothelium and smooth muscle. In WKY rats, SHRs and enalapril-treated SHRs, relaxations were mediated by small-, large-, and intermediate-conductance calcium-activated potassium channels, which were distributed in the endothelium, smooth muscle, and both layers, respectively. However, only WKY hyperpolarizations and relaxations were sensitive to gap junction blockers, and these arteries expressed more endothelial and myoendothelial gap junctions than arteries from SHRs. Responses in WKY rats, but not SHRs, were also reduced by inhibitors of epoxyeicosatrienoic acids (EETs), 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE) and miconazole, although sensitivity to EET regioisomers was endothelium-independent in all rats. Enalapril treatment of SHRs reduced blood pressure and restored sensitivity to 14,15-EEZE, but not to gap junction blockers, and failed to reverse the morphological changes. In conclusion, the mechanisms underlying EDHF in muscular mesenteric arteries differ between WKY rats and SHRs, with gap junctions and EETs involved only in WKY rats. However, reduction of blood pressure in SHRs with enalapril restored a role for EETs, but not gap junctions, without reversing morphological changes, suggesting a differential control of chemical and structural alterations.

Altered EDHF‐mediated dilation in spontaneously hypertensive rats following enalapril treatment

Endothelium derived hyperpolarising factor (EDHF) plays a prominent role in resistance arteries via a variety of different mechanisms. We examined these mechanisms in first order mesenteric arterial branches from Wistar‐Kyoto (WKY), spontaneously hypertensive rats (SHR) and age‐matched SHR with blood pressure normalized by enalapril (30 mg/kg/day, 8 wks), using serial section electron microscopy and wire myography in the presence of L‐NAME (100 microM) and indomethacin (10 microM). EDHF‐mediated dilations to acetylcholine (ACh) were sensitive in all three groups to the combination of BKCa, IKCa and SKCa channel inhibitors, iberiotoxin (100 nM), apamin (500 nM) and TRAM‐34 (500 nM). However, only responses in WKY were sensitive to the combined gap junction antagonists, 37,43gap 27, 40gap 40 and 43gap 26 (100 microM each), while responses in both WKY and enalapril treated SHR were sensitive to the selective inhibitor of epoxyeicosatrienoic acid derivatives (EETs), 14,15‐EEZE (10 microM). Electron microscopy showed significantly fewer myoendothelial gap junctions (MEGJs) in SHR than in WKY and no change following enalapril treatment. In conclusion, responses in WKY are dependent on EETs, MEGJs and BKCa, while responses in SHR are dependent on BKCa but independent of EETs or gap junctions. Reduction in angiotensinII with enalapril restores the involvement of EETs but not gap junctions.

Insight into Molecular Stability and Physiological Properties of the Diheme Cytochrome CYC41from the Acidophilic BacteriumAcidithiobacillus ferrooxidans

The cyc1 gene encoding the soluble dihemic cytochrome c CYC(41) from Acidithiobacillus ferrooxidans, an acidophilic organism, has been cloned and expressed in Escherichia coli as the host organism. The cytochrome was successfully produced and folded only in fermentative conditions: this allowed us to determine the molecular basis of the heme insertion at extreme pH. Point mutations at two sequence positions (E121 and Y63) were introduced near the two hemes in order to assign individual redox potentials to the hemes and to identify the interaction sites with the redox partners, rusticyanin and cytochrome oxidase. Characterization of mutants E121A, Y63A, and Y63F CYC(41) with biochemical and biophysical techniques were carried out. Substitution of tyrosine 63 by phenylalanine alters the environment of heme B. This result indicates that heme B has the lower redox potential. Interaction studies with the two physiological partners indicate that CYC(41) functions as an electron wire between RCy and cytochrome oxidase. A specific glutamate residue (E121) located near heme A is directly involved in the interaction with RCy. A docking analysis of CYC(41), RCy, and cytochrome oxidase allowed us to propose a model for the complex in agreement with our experimental data.

Thermodynamic characterization of a tetrahaem cytochrome isolated from a facultative aerobic bacterium, Shewanella frigidimarina: a putative redox model for flavocytochrome c3.

The facultative aerobic bacterium Shewanella frigidimarina produces a small c-type tetrahaem cytochrome (86 residues) under anaerobic growth conditions. This protein is involved in the respiration of iron and shares 42% sequence identity with the N-terminal domain of a soluble flavocytochrome, isolated from the periplasm of the same bacterium, which also contains four c -type haem groups. The thermodynamic properties of the redox centres and of an ionizable centre in the tetrahaem cytochrome were determined using NMR and visible spectroscopy techniques. This is the first detailed thermodynamic study performed on a tetrahaem cytochrome isolated from a facultative aerobic bacterium and reveals that this protein presents unique features. The redox centres have negative and different redox potentials, which are modulated by redox interactions between the four haems (covering a range of 8-56 mV) and by redox-Bohr interactions between the haems and an ionizable centre (-4 to -36 mV) located in close proximity to haem III. All of the interactions between the five centres are clearly dominated by electrostatic effects and the microscopic reduction potential of haem III is the one most affected by the oxidation of the other haems and by the protonation state of the molecule. Altogether, this study indicates that the tetrahaem cytochrome isolated from S. frigidimarina (Sfc) has the thermodynamic properties to work as an electron wire between its redox partners. Considering the high degree of sequence identity between Sfc and the cytochrome domain of flavocytochrome c(3), the structural similarities of the haem core, and that the macroscopic potentials are also identical, the results obtained in this work are rationalized in order to put forward a putative redox model for flavocytochrome c(3).

Long-wavelength instability in a double-electron-quantum-wire structure

We investigate theoretically the possibility of finding a charge-density-wave (CDW) instability in a zero-temperature double-electron-quantum-wire structure. Intrawire and interwire correlations are treated on the same footing within the self-consistent-field approximation of Singwi and co-workers. To check for the CDW instability, the static density susceptibility is calculated over a wide range of wire parameters (electron number density, wire size, and wire spacing). We find that the double-quantum-wire structure may become unstable against a long-wavelength CDW instability for sufficiently low electron density and narrow wire size, in the close proximity of two wires.

Coupled phonon-ripplon modes in a single wire of electrons on the liquid-helium surface

The coupled phonon-ripplon modes of the quasi-one-dimensional electron chain on the liquid helium sutface are studied. It is shown that the electron-ripplon coupling leads to the splitting of the collective modes of the wire with the appearance of low-frequency modes and high-frequency optical modes starting from threshold frequencies. The effective masses of an electron plus the associated dimple for low frequency modes are estimated and the values of the threshold frequencies are calculated. The results obtained can be used in experimental attempts to observe the phase transition of the electron wire into a quasi-ordered phase.

Reliability assessment of a plastic encapsulated RF switching device

In this study the degradation and reliability of a plastic encapsulated RF switching device were assessed by comparing several lots of a device that came directly off the assembly line to several other lots which had been subjected to accelerated stress testing. Comparisons of the structure, die and wirebonds were based on the results of examinations using optical microscopy, X-ray analysis, scanning acoustic microscopy, environmental scanning electron microscopy and wire bond pull tests.

Compressible and incompressible stripes in a narrow electron channel

The capacitance of a single-electron wire at high quantizing magnetic fields is studied. We demonstrate that the capacitance spectroscopy allows us to study the formation of compressible and incompressible stripes directly. The electron wire is field induced in a metal insulator semiconductor heterostructure beneath a center gate. The electrostatic potential defining the wire edge is controlled by a tuning-fork-shaped electrode that encloses the center gate. It is found that the capacitance spectra are very sensitive to the wire edge potential and show a clear asymmetry of the capacitance minimum at filling factor n52. The experimental results are well described by a simple model considering the contribution of compressible and incompressible stripes in the electron channel, to the capacitance signal. The capacitance minima are thus determined in our experiments by the geometry of the compressible and incompressible stripes in the channel and not by the defect-induced density of states. @S0163-1829~96!02143-1#

Multimetal DTAB packages for a 125-MHz computer

In this study the degradation and reliability of a plastic encapsulated RF switching device were assessed by comparing several lots of a device that came directly off the assembly line to several other lots which had been subjected to accelerated stress testing. Comparisons of the structure, die and wirebonds were based on the results of examinations using optical microscopy, X-ray analysis, scanning acoustic microscopy, environmental scanning electron microscopy and wire bond pull tests.