Range Of Applied Voltages Research Articles

A Na3V2(PO4)3 cathode material for use in hybrid lithium ion batteries

A NASICON-structure Na3V2(PO4)3 cathode material prepared by carbothermal reduction method is employed in a hybrid-ion battery with Li-involved electrolyte and anode. The ion-transportation mechanism is firstly investigated in this complicated system for an open three-dimensional framework Na3V2(PO4)3. Ion-exchange is greatly influenced by the standing time, for example, the 1 hour battery presents a specific capacity of 128 mA h g(-1) while the 24 hour battery exhibits a value of 148 mA h g(-1) with improved rate and cycling performances over existing literature reported Li-ion batteries. In the hybrid-ion system, an ion-exchange process likely takes place between the two Na(2) sites in the rhombohedral structure. NaLi2V2(PO4)3 could be produced by ion-transportation since the Na(+) in the Na(1) site is stationary and the three Na(2) sites could be used to accommodate the incoming alkali ions; Li(x)Na(y)V2(PO4)3 would come out when the vacant site in Na(2) was occupied depending on the applied voltage range. The reported methodology and power characteristics are greater than those previously reported.

Low-threshold UV light-emitting diodes realized from ZnO/MgZnO quantum-well-based metal-insulator-semiconductor structures

ZnO/MgZnO quantum-well (QW)-based light-emitting diodes using the metal–insulator–semiconductor (MIS) structure have been demonstrated and characterized in this study. ZnO near-band-edge UV emission peaked at ∼372 nm is observed at room temperature and the average energy conversion efficiency is obtained about 0.51%. Current–voltage analysis reveals a typical phenomenon of space-charge-limited current conduction in the applied voltage range of 0.9<V<2.0 V. The carrier transport and recombination mechanisms are investigated and discussed in terms of photoluminescence and energy band alignment diagram. In particular, the emission threshold voltage is obtained as low as 2.5 V, indicating the great potential of the QW-based MIS structure in low-voltage solid state lighting applications.

Interface-related switching behaviors of amorphous Pr0.67Sr0.33MnO3-based memory cells

The resistive switching properties in amorphous Pr0.67Sr0.33MnO3 films deposited by pulsed laser deposition are investigated. Reproducible and bipolar counter-8-shape and 8-shape switching behaviours of Au/Pr0.67Sr0.33MnO3/F:SnO2 junctions are obtained at room temperature. Dramatically, the coexistence of two switching polarities could be reversibly adjusted by an applied voltage range. The results allocated those two switching types to areas of different defect densities beneath the same electrode. The migration of oxygen vacancies and the trapping effect of electrons under an applied electric field play an important role. An interface-effect-related resistance switching is proposed in an amorphous Pr0.67Sr0.33MnO3-based memory cell.

Physical characterizations of semi-conducting conjugated polymer-CNTs nanocomposites

Carbon nanotubes (CNTs) were prepared using Alcholic Catalyst Chemical Vapor Deposition (ACCVD) technique in order to investigate the effects of their addition on the optical, electrical and mechanical properties of Poly(3-octylthiophene-2,5-diyl) (P3OT) matrix. The absorption spectra of the prepared CNTs and CNT-P3OT nanocomposites were measured in the spectral range 200 nm–3,000 nm at room temperature. The optical energy gap was determined from the obtained UV/Vis absorption spectrum. Optical results reveal that the prepared CNTs are almost single walled. Besides, the addition of CNTs to P3OT polymer matrix will decrease the optical energy gap and enhance the optical absorbance of P3OT matrix. On the other hand, the addition of CNTs to P3OT matrix will increase the electrical conductivity of P3OT matrix up to four orders of magnitude above the percolation threshold (0.44 wt% CNTs). Additionally, I–V characteristics indicate that the conduction mechanism is Ohmic at low applied voltage range while it is due to the trap charge limited at high applied voltage range. Furthermore, the behavior of dc conductivity with temperature was also investigated and the obtained results reveal that the activation energy decreases with CNTs content. Finally, mechanical results reveal that the elastic modulus values increase with the increasing of CNTs content in P3OT matrix.

Hydrogen-Sensing Characteristics of a Pd/GaN Schottky Diode With a Simple Surface Roughness Approach

Hydrogen-sensing characteristics of a Pd/GaN Schottky diode with a simple surface roughness approach are studied and demonstrated. A high sensing response Sr of 2.05 × 105 and a large Schottky barrier height variation ratio (ΔφB/φair) of 36.3% upon exposure to a 1% H2/air gas at 303 K are found. They could be attributed to the presence of more adsorption sites caused by the employed surface plasma treatment. The increase in series resistance due to the decrease in sensing response under the applied voltage range from 0.5 to 1 V is found. Based on the kinetic analysis and transient-state behavior measurement, at 523 K, the studied device shows a faster adsorption time of 2.9 s and a higher initial rate of 968 μA/s. Consequently, the studied structure provides a promise for high-performance GaN-based Schottky-diode-type hydrogen sensor applications.

Direct fabrication and morphology of metallic micropatterns by pulsed jet nanoelectrospraying of silver nano-ink

A pulsed jet nanoelectrospray technique was applied to direct fabrication of silver micropatterns. The deposition of a commercial organic silver nano-ink was performed in a fully voltage-controlled fashion by voltage pulses ranging from 550 to 800 V with variable durations. By using 15 μm nozzles, patterns with 100-μm-sized features were locally freeformed on a silicon substrate with a spraying distance of 250 μm. An energy-dispersive X-ray spectrum confirmed metallic silver was developed in all the patterns after heat treatment at 220°C. The size and microstructural evolution of silver films was observed to strongly depend on the deposition volume and material flow over substrate surface. A good linear relationship between the deposition volume and pulse duration was exhibited over the applied voltage range in the cone-jet mode, demonstrating a drop-on-demand capability. By fitting, the deposition volume rate was estimated to be in the range of 0.38–0.59 pL/ms and was shown to increase with the applied voltage.

Blood cell capture in a sawtooth dielectrophoretic microchannel

Biological fluids can be considered to contain information-rich mixtures of biochemicals and particles that enable clinicians to accurately diagnose a wide range of pathologies. Rapid and inexpensive analysis of blood and other bodily fluids is a topic gaining substantial attention in both science and medicine. One line of development involves microfluidic approaches that provide unique advantages over entrenched technologies, including rapid analysis times, microliter sample and reagent volumes, potentially low cost, and practical portability. The present study focuses on the isolation and concentration of human blood cells from small-volume samples of diluted whole blood. Separation of cells from the matrix of whole blood was accomplished using constant potential insulator-based gradient dielectrophoresis in a converging, sawtooth-patterned microchannel. The channel design enabled the isolation and concentration of specific cell types by exploiting variations in their characteristic physical properties. The technique can operate with isotonic buffers, allowing capture of whole cells, and reproducible capture occurred at specific locales within the channel over a global applied voltage range of 200-700 V.

Participation of Oxygen in Charge/Discharge Reactions in Li1.2Mn0.4Fe0.4O2: Evidence of Removal/Reinsertion of Oxide Ions

We have investigated the charge-discharge mechanism in the first cycle and the origin of its high charge–discharge capacity for Li1.2Mn0.4Fe0.4O2 (0.5Li2MnO3·0.5LiFeO2) positive electrode material of lithium ion batteries. Results reveal that oxygen loss occurs in the entire region of the Li1.2Mn0.4Fe0.4O2 particles composed of Mn-rich (Fe-substituted Li2MnO3) and Fe-rich (Mn-substituted LiFeO2) nanodomains during the first charge. Nanodomains of Mn-Li ferrites with a spinel structure start to be formed along the particle surfaces. During the first discharge, the extracted oxygen is partially reinserted preferentially into the Fe-rich nanodomains as oxide ions rather than in the Mn-rich nanodomains, and the proportion of the spinel nanodomains decreases. The origin of the high charge–discharge capacity might be ascribed to the participation of the oxide ions and neutral oxygen species in charge compensation by incorporation of the LiFeO2 component into Li2MnO3. Irreversible capacity at the first cycle can be caused by the irreversible loss of oxygen during the charge and irreversible structural changes throughout the cycle: the movements of transition metal ions inducing random cation-site occupation throughout the cycle, associated with the formation and incomplete disappearance of the spinel ferrite nanodomains which is almost electrochemically-inactive under the applied voltage range.

Transition metal complexes of thiosemicarbazones with quinoxaline hub: an emphasis on antidiabetic property

New transition metal complexes of quinoxaline–thiosemicarbazone ligands were prepared and characterised by spectroanalytical techniques. The ligands L1H2 and L2H2 were obtained by the reaction of quinoxaline-2.3(1,4H)-dione with methyl and phenyl thiosemicarbazide, respectively. All the complexes are found to be monomeric in nature and have tetrahedral geometry. The copper complexes have shown redox responses in the applied voltage range, whereas the ligands and other complexes are electrochemically innocent. The ligands, copper and zinc complexes are explored for antidiabetic activity in the diabetes-induced Wister rats. Evaluation of antidiabetic activity was done by blood-glucose test and oral glucose tolerance test; few compounds have exhibited significant antidiabetic activity and posses low toxicity with a high safety profile.

Determining Ultrafine Particle Collection Efficiency in a Nanometer Aerosol Sampler

The Nanometer Aerosol Sampler (NAS, Model 3089) manufactured by TSI Incorporated (Minnesota, USA) is commonly used to collect ultrafine particles (UFPs, diameter < 100 nm) for off-line analysis. However, the UFP collection efficiency for this instrument has only been reported for polystyrene latex (PSL) particles at a flow rate of 1 L· min–1 and a voltage of 10 KV. To expand the applicability of the NAS and determine the optimal conditions for collecting the greatest amount of UFPs for a given time, three types of UFPs (PSL, candle smoke particles, and diesel exhaust particles) were collected across a flow rate range of 1–4 L· min–1 and an applied voltage range of 1.0 to 9.3 KV. The experimental results indicate that at identical conditions, the PSL particle collection efficiency in the TSI instrument manual (43% to 8%) was lower than the measured efficiency of candle smoke particles (99.5% to 39%) and diesel exhaust particles (99% to 32%). Decreasing the flow rate and increasing the voltage increased the collection efficiency, with the highest efficiency obtained at 1 L· min–1 and 9.3 KV. However, the NAS collected the greatest amount of UFPs at 4 L· min–1 and 9.3 KV, since the voltage had more of an impact on UFP collection efficiency than did the flow rate. After modifying a well-established electrostatic precipitator (ESP) model by introducing a factor F, which is a function of the electric Peclet number and the flow rate, agreement with the experimental results was obtained.

Abnormal bipolar-like resistance change behavior induced by symmetric electroforming inPt/TiO2/Pt resistive switching cells

Abnormal bipolar-like resistive changes are reported inTiO2 thin films sandwiched between Pt top and bottom electrodes. The abnormal behavior isshown relying on the applied voltage range. That is, normal bipolar switching is also shownin the same sample with the optimized voltage range. In the abnormal mode, both set- andreset-like changes in resistance take place under the same polarity of the applied voltage.This abnormal behavior is considered to be due to symmetric electroforming which isassumed to activate electrochemical reactions involving oxygen vacancies at bothPt/TiO2 interfaces. We analyze the abnormal behavior in terms of the interfacial resistive switchingtaking place on both interfaces nearly simultaneously.

CCNR type high field instability in Ti4+-substituted Mn–Zn ferrites

Polycrystalline samples of the spinel ferrite system Zn0.3Mn0.7+xTixAl0.1Fe1.9−2xO4 (x = 0.0–0.3) have been studied for electrical switching in the temperature range from 300 to 700 K and applied voltage range from 0 to 400 V. High electric field induced resistance switching of nearly 200% has been observed for all the compositions. The dependence of temperature and applied electric field strength on switching has been examined. The electric field and temperature required for switching increase with increase in Mn–Ti concentration. The results have been interpreted considering previous models and have been ascribed to the existence of space charge limiting current in the system. The switching observed, is of current-controlled negative resistance (CCNR)-type.

Time dependent breakdown characteristics of parylene dielectric in metal–insulator–metal capacitors

In this work, we present reliability results of MIM (Metal–Insulator–Metal) capacitors fabricated with parylene as the dielectric, deposited at room temperature. We have evaluated the time dependent dielectric breakdown (TDDB) of parylene-based MIM capacitors as a function of constant DC voltage stress, area and dielectric thickness of the capacitor. Mean-time-to-failure (MTTF) of parylene evaluated at different stress voltages shows a power law distribution over the applied voltage range and device area, with MTTF driven by the number of defects. Defect density in the parylene capacitors is also reported and is calculated to be ∼1.2 × 10 3 defects/cm 2.

Biohydrogen production via biocatalyzed electrolysis in acetate-fed bioelectrochemical cells and microbial community analysis

Hydrogen was efficiently produced via acetate oxidation using a two-chambered bioelectrochemical cell (BEC), a modified microbial fuel cell (MFC), in which a cathode was kept free of oxygen and the thermodynamic barrier overcome by augmenting the electrochemical potential achieved by bacteria with the addition of a small external voltage. The production of hydrogen gradually increased with increasing applied voltage from 0.1 to 1.0 V, reaching its maximum efficiency of 52.5% at 0.8 V, corresponding to a hydrogen yield of 2.1 mol per 1 mol acetate. The anodic loss of electrons was more detrimental compared to that of cathodic loss, especially with the higher applied voltage range. The cathode headspace gas consisted mainly of hydrogen (>96.6%), but with minor methane (2.5%) and carbon dioxide (0.9%) impurities diffused from the anode chamber. To maintain the purity or prevent the loss of the hydrogen produced, much concern is required for the control of CO 2 and CH 4 because these gases diffuse more readily through a Nafion 117 membrane than H 2. To produce hydrogen, the continuous augmentation of the circuit by an external voltage had no harmful effect on the bacterial viability but resulted in a remarkable change in the bacterial community. There was a substantial decrease in species diversity with a single emergent Pelobacter propionicus-like species in the BEC. Interestingly, Geobacter-like species were integral members of the bacterial consortia in an MFC and BEC.

Electrical Characteristics of n-ZnO/p-Si Heterojunction Diodes Grown by Pulsed Laser Deposition at Different Oxygen Pressures

Heterojunction diodes of n-type ZnO/p-type silicon (100) were fabricated by pulsed laser deposition of ZnO films on p-Si substrates in oxygen ambient at different pressures. These heterojunctions were found to be rectifying with a maximum forward-to-reverse current ratio of about 1,000 in the applied voltage range of −5 V to +5 V. The turn-on voltage of the heterojunctions was found to depend on the ambient oxygen pressure during the growth of the ZnO film. The current density–voltage characteristics and the variation of the series resistance of the n-ZnO/p-Si heterojunctions were found to be in line with the Anderson model and Burstein-Moss (BM) shift.

Electric Field-induced Charge Transfer of (Bu4N)2[Ru(dcbpyH)2-(NCS)2] on Gold, Silver, and Copper Electrode Surfaces Investigated by Means of Surface-enhanced Raman Scattering

The potential-induced charge transfer of the dye (Bu4N)2[Ru(dcbpyH)2-(NCS)2] (N719) on Au, Ag, and Cu electrode surfaces has been examined by surface-enhanced Raman scattering (SERS) in the applied voltage range between 0.0 and ?0.8 V. N719 is assumed to have a relatively perpendicular geometry with its bipyridine ring on the metal surfaces. A strong appearance of the carboxylate band at ~1370 cm-1 indicates that the carboxyl group will likely be deprotonated on the metal surfaces. As the electric potential is shifted from ?0.8 to 0.0 V, the ν (NCS) band at ~2100 cm-1 on the electrode surfaces appears to undergo a shift in frequency and intensity change. This indicated that the charge transfer between the dye and metal electrode surfaces had occurred. Electric-field-dependent charge transfer differs somewhat depending on the type of metal surfaces as suggested from the dissimilar frequency positions of the ν (NCS) band.

Electric field-induced adsorption change of 1,3,5-benzenetricarboxylic acid on gold, silver, and copper electrode surfaces investigated by surface-enhanced Raman scattering

The potential-induced adsorption structure of 1,3,5-benzenetricarboxylic acid (trimesic acid TMA) on Au, Ag, and Cu electrode surfaces has been examined by means of surface-enhanced Raman scattering (SERS) in an applied voltage range between −0.6 and 0.6 V. Spectral analyses indicate that TMA is assumed to have a perpendicular geometry with its benzene ring on Au, Ag, and Cu surfaces. The carboxylate band’s strong appearance at ∼1390 cm −1 indicates that TMA should bind to the metal surfaces via its carboxylate group. As the electric potential is shifted from 0.6 to −0.6 V, the adsorption of TMA onto the electrodes’ surfaces appears to change, as indicated by the frequency shift or the change in the vibrational bands’ intensity. As previously reported [B. Han, Z. Li, S. Pronkin, Th. Wandlowski, Can. J. Phys. 82 (2004) 1481], depending on the applied electric field, it seems possible that TMA may form several distinctly different adlayer structures on an Au surface between 0 and 0.4 V. Such a potential-dependent adsorption change depending on the applied electric field is not found to occur on Ag and Cu under our potential region.

Noise-rejection techniques for impedance and dielectric spectrometers using ubiquitous test and measurement equipment

This work encompassed the development for a frequency-domain impedance and dielectric spectrometer using ubiquitous test and measurement equipment, i.e., signal generators and digital oscilloscopes. Various methods of amplification, noise rejection, and computations were employed to achieve the desired goals. The frequency range of 100 mHz-1 MHz was tested using air capacitors of 3.7 and 14.5 pF and an applied voltage range of 10-300 mV. The multichannel instrument produced a stable and reproducible dual-phase (real and imaginary or magnitude and phase) current sensitivity of 250 fA with an average phase stability of less than 0.5 degrees (tan delta<10(-2)) and a single-phase (magnitude only) current sensitivity of 60 fA.

Two kinds of hexagon emission patterns with different spatio-temporal symmetry in dielectric barrier discharge

Two kinds of emission hexagonal patterns with different spatio-temporal symmetry are observed in lower and higher applied voltage range respectively by using a dielectric barrier discharge device with water electrodes. The spatial wavelength and filament diameter of the hexagon in higher applied voltage range are larger than that in lower voltage range. The hexagon in higher applied voltage range has a brighter background，while no background exists in the hexagon in lower applied voltage range. The spatio-temporal dynamics of the two kinds of hexagon patterns is investigated. It is found that the hexagonal pattern in lower voltage range is an interlacing of two rectangular sublattices, which have a time sequence inversion behavior. The filaments in the hexagon in higher voltage range discharge simultaneously. The influence of the wall charges on the spatio-temporal dynamics of the emission patterns is discussed.

Carrier conduction in heterojunction of hydrogenated nanocrystalline silicon with crystal silicon

Phosphorus-doped hydrogenated nanocrystalline silicon (n-type nc-Si:H) film was deposited by plasma enhanced chemical vapor deposition technique on heavy doped p-type crystalline silicon ((p +)c-Si) substrate to form heterojunction of (n)nc-Si:H/(p +)c-Si. In electrical experiments, both negative resistance in forward current–voltage ( I–V) measurements and current staircases in reverse I–V experimental data were observed from this structure of (n)nc-Si:H/(p +)c-Si at 77 K, which reveals it as a semiconductor heterojunction tunnel diode. The forward current is assigned to interband tunneling, excess and thermionic emission component, respectively. Within reverse bias voltage range from 0 to around − 13 V, the reverse current can be ascribed to minority carriers instead of majority carriers tunneling across the depletion layer in heterojunction. Cross reverse applied voltage range from − 13 to about − 37 V, the reverse current can be attributed to injection of electrons via sequent resonant tunneling through Si nanocrystals into substrate. As further increasing reverse applied voltage, the reverse current can be allocated to carrier avalanche multiplication within amorphous buffer layer region to enhance electron resonant tunneling in nc-Si:H layer.