Cobalt Wire Research Articles

Fabrication of tricobalt tetraoxide thinfilm photocatalyst from cobalt nitrate deposition by a novel spark method

Tricobalt tetraoxide (Co3O4) thinfilm was successfully deposited for the first time by a novel sparking method through a two-step process, which includes cobalt nitrate deposition and subsequent thermal treatment at 300 °C. The formation mechanism of Co3O4 deposition by sparking process from highly pure cobalt wire is elucidated in detail. Deposited Co3O4 thinfilms under different spark repetition rates were intensely characterized and employed as an effective photocatalyst for degradation of organic dye. Notably, the maximum degradation of organic dye was observed for the catalytic thinfilm deposited at low repetition rate owing to its low band gap and porous morphology with smaller size grains, which may lead to the contribution of more charge carriers in the photocatalytic reaction.

Alterations in HCN1 expression and distribution during epileptogenesis in rats

BackgroundThe hyperpolarization-activated cyclic nucleotide-gated cation channel (HCN1) is predominantly located in key regions associated with epilepsy, such as the neocortex and hippocampus. Under normal physiological conditions, HCN1 plays a crucial role in the excitatory and inhibitory regulation of neuronal networks. In temporal lobe epilepsy, the expression of HCN1 is decreased in the hippocampi of both animal models and patients. However, whether HCN1 expression changes during epileptogenesis preceding spontaneous seizures remains unclear. ObjectiveThe aim of this study was to determine whether the expression of HCN1 is altered during the epileptic prodromal phase, thereby providing evidence for its role in epileptogenesis. MethodsWe utilized a cobalt wire-induced rat epilepsy model to observe changes in HCN1 during epileptogenesis and epilepsy. Additionally, we also compared HCN1 alterations in epileptogenic tissues between cobalt wire- and pilocarpine-induced epilepsy rat models. Long-term video EEG recordings were used to confirm seizures development. Transcriptional changes, translation, and distribution of HCN1 were assessed using high-throughput transcriptome sequencing, total protein extraction, membrane and cytoplasmic protein fractionation, western blotting, immunohistochemistry, and immunofluorescence techniques. ResultsIn the cobalt wire-induced rat epilepsy model during the epileptogenesis phase, total HCN1 mRNA and protein levels were downregulated. Specifically, the membrane expression of HCN1 was decreased, whereas cytoplasmic HCN1 expression showed no significant change. The distribution of HCN1 in the distal dendrites of neurons decreased. During the epilepsy period, similar HCN1 alterations were observed in the neocortex of rats with cobalt wire-induced epilepsy and hippocampus of rats with lithium pilocarpine-induced epilepsy, including downregulation of mRNA levels, decreased total protein expression, decreased membrane expression, and decreased distal dendrite expression. ConclusionsAlterations in HCN1 expression and distribution are involved in epileptogenesis beyond their association with seizure occurrence. Similarities in HCN1 alterations observed in epileptogenesis-related tissues from different models suggest a shared pathophysiological pathway in epileptogenesis involving HCN1 dysregulation. Therefore, the upregulation of HCN1 expression in neurons, maintenance of the HCN1 membrane, and distal dendrite distribution in neurons may represent promising disease-modifying strategies in epilepsy.

Development of A Potentiometric Portable Extractor for Phosphate using Water Absorbent Materials and Cobalt Wire Electrodes

Soil phosphorus is an essential nutrient in the soil and is very necessary for plants, so measuring the content of elements or their derivatives in the soil is very necessary. This study aimed to develop a portable measuring instrument for phosphate based on the potentiometric principle using cobalt electrodes. The choice of absorbent material to support portable measuring instruments is based on water absorption and the potential response of the cobalt electrode when used with an absorbent. The phosphate electrode was made from cobalt wire and Ag/AgCl as a reference electrode. A comparison of analysis results was carried out between portable extraction potentiometric and conventional potentiometric methods. The results showed that polyvinyl alcohol (PVA) was the best absorbent. Using potentiometric measurements in a portable extractor prototype with PVA as an absorbent material offers promising prospects. The comparison of measurement results between the portable extractor and conventional potentiometric had 0.8039 as the correlation coefficient. Phosphate in conventional potentiometric was measured 1.2809 times higher than portable extraction potentiometric. The potentiometric slopes were -23.69 mv/decade and -26.63 mv/decade for the portable extractor potentiometric and the traditional potentiometric methods, respectively.

Symmetry-driven half-integer conductance quantization in Cobalt–fulvalene sandwich nanowire

Precise manipulation and monitoring spin transport in one-dimensional (1D) systems is a long-sought goal in the field of nano-spintronics. Based on first-principles calculations, we report the observation of half-integer conductance quantization in the Cobalt-fulvalene sandwich nanowire. Compared with a pure monatomic Cobalt wire, the introduction of fulvalene molecules leads to three important features: Firstly, the strong coupling between the fulvalene and the Cobalt prevents the contamination of the ambient air, ensuring both chemical and physical stabilities; Secondly, the fulvalene symmetry-selectively filters out most of the d-type orbitals of the Cobalt while leaving a single d-type orbital to form an open spin channel around the Fermi level, which offers a mechanism to achieve the observed half-integer conductance; Thirdly, it maintains a superexchange coupling between adjacent Co atoms to achieve a high Curie temperature. Spin transport calculations show that this half-metallic nanowire can serve as a perfect spin filter or a spin valve device, thus revealing the potential of Cobalt-fulvalene sandwich nanowire as a promising building block of high-performance spintronics technology.

Electrical stimulation of the endopiriform nucleus attenuates epilepsy in rats by network modulation.

ObjectiveNeuromodulatory anterior thalamic deep brain stimulation (DBS) is an effective therapy for intractable epilepsy, but few patients achieve complete seizure control with thalamic DBS. Other stimulation sites may be considered for anti‐seizure DBS. We investigated bilateral low‐frequency stimulation of the endopiriform nuclei (LFS‐EPN) to control seizures induced by intracortically implanted cobalt wire in rats.MethodsChronic epilepsy was induced by cobalt wire implantation in the motor cortex unilaterally. Bipolar‐stimulating electrodes were implanted into the EPN bilaterally. Continuous electroencephalography (EEG) was recorded using electrodes placed into bilateral motor cortex and hippocampus CA1 areas. Spontaneous seizures were monitored by long‐term video‐EEG, and behavioral seizures were classified based on the Racine scale. Continuous 1‐Hz LFS‐EPN began on the third day after electrode implantation and was controlled by a multi‐channel stimulator. Stimulation continued until the rats had no seizures for three consecutive days.ResultsCompared with the control and sham stimulation groups, the LFS‐EPN group experienced significantly fewer seizures per day and the mean Racine score of seizures was lower due to fewer generalized seizures. Ictal discharges at the epileptogenic site had significantly reduced theta band power in the LFS‐EPN group compared to the other groups.InterpretationBilateral LFS‐EPN attenuates cobalt wire‐induced seizures in rats by modulating epileptic networks. Reduced ictal theta power of the EEG broadband spectrum at the lesion site may be associated with the anti‐epileptogenic mechanism of LFS‐EPN. Bilateral EPN DBS may have therapeutic applications in human partial epilepsies.

Influence of the demagnetization on the polarization of the thermal radiation emitted by hot cobalt wires

The polarization P of thermal radiation emitted by a hot cobalt wire in the temperature range from T≈400. K up to melting is studied for the first time. The radiation is linearly polarized perpendicularly to the wire. P decreases from 30%. just above room temperature down to 6.5% near melting and is continuous across the martensitic hcp−fcc transition at Tm≈700 K and across the Curie point at Tc≈1400K. However, P shows a rapid decrease for T≳1000K and, contrary to previous measurements with tungsten wires, it hysteretically behaves if the temperature change is reversed. This behavior is rationalized by accounting for the thermal demagnetization of the wire with magnetic domain size change.

P5527Unique stent design with continuous cobalt wire can avoid protruding immediately after percutaneous coronary intervention compared to classical tubed stent

P5527Unique stent design with continuous cobalt wire can avoid protruding immediately after percutaneous coronary intervention compared to classical tubed stent

Three-terminal resistive switch based on metal/metal oxide redox reactions

A solid-state three-terminal resistive switch based on gate-voltage-tunable reversible oxidation of a thin-film metallic channel is demonstrated. The switch is composed of a cobalt wire placed under a GdOx layer and a Au top electrode. The lateral resistance of the wire changes with the transition between cobalt and cobalt oxide controlled by a voltage applied to the top electrode. The kinetics of the oxidation and reduction process are examined through time- and temperature-dependent transport measurements. It is shown that that reversible voltage induced lateral resistance switching with a ratio of 103 can be achieved at room temperature. The reversible non-volatile redox reaction between metal and metal oxide may provide additional degrees of freedom for post-fabrication control of properties of solid-state materials. This type of three-terminal device has potential applications in neuromorphic computing and multilevel data storage, as well as applications that require controlling a relatively large current.

Interplay between superconductivity and ferromagnetism in crystalline nanowires

The interaction between superconductivity and ferromagnetism, which entails incompatible spin order, is one of the problems of fundamental interest in condensed-matter physics. In general, when a ferromagnet is placed in contact with a superconductor, the Cooper pairs from the superconductor are not expected to survive beyond at most a few nanometres into the ferromagnet. Here we present a systematic study of single-crystal ferromagnetic cobalt nanowires sandwiched between superconducting electrodes. Surprisingly, we find that a cobalt wire as long as 600 nm attains zero resistance at low temperatures. For even longer nanowires, the transition to incomplete superconductivity is foreshadowed by a strikingly large and sharp resistance peak near the superconducting transition temperature of the electrodes. Although the origin of the ‘critical peak’ remains mysterious, our analysis strongly points against charge or spin imbalance as its underlying cause. When a superconductor is in contact with a normal metal, Cooper pairs from the superconductor ‘leak’ into the metal, causing local superconductivity. When in contact with a ferromagnet, however, Cooper pairs do not stray very far. Therefore, the discovery that a ferromagnetic nanowire goes completely superconducting when placed between two superconducting electrodes is surprising indeed.

Characteristics of a cobalt-based phosphate microelectrode for in situ monitoring of phosphate and its biological application

The in situ monitoring of phosphate has been of great importance in many environmental applications, particularly those involving biological treatment processes and eutrophication monitoring. A microelectrode with small tip size (∼10 μm) was fabricated with cobalt wire, characterized and evaluated for in situ and in vivo environmental analysis of phosphate in biological applications. The electrochemical performance of this cobalt-based microelectrode was fully examined for its characteristics, including detection limit, response time, selectivity, reproducibility, life time, interference with pH, ions and dissolved oxygen (DO), and the stirring effect. The microelectrode showed excellent selectivity for the ortho-phosphate ions (HPO 4 2− and H 2PO 4 −) in various environmental conditions. Alkalinity and DO were found to interfere with electrode response to phosphate. The phosphate microelectrode was also evaluated with scanning electron microscopy (SEM) and cyclic voltammetry (CV). The developed microelectrode was used for in situ monitoring of phosphate in microbial flocs. Well-defined phosphate profiles across the flocs were observed under anaerobic (phosphorus release) conditions. This full characterization and successful application showed that the cobalt-based phosphate microelectrodes can be a very useful tool for in situ measurement of phosphate in various environmental conditions, including within microbial flocs.

Failure mechanism of cemented tungsten carbide dies in wet drawing process of steel cord filament

Cemented tungsten carbide die has been used in wire drawing for almost a century. A combination of strength and wear resistance has made this material widely accepted in the steel wire industry, particularly in drawing steel cord filament. Used cemented tungsten carbide dies, collected from different sources where different lubricants were applied in the wet drawing process, were dissected with high speed diamond saw and examined by using scanning electron microscopy. Failure modes of cemented tungsten carbide dies were classified. Electrochemical properties of pure cobalt wire and cemented tungsten carbide were examined by anodic and cyclic polarization measurements to investigate the corrosion resistance of cobalt and cemented tungsten carbide in wire drawing lubricants. Results show that binding agent (cobalt) in cemented tungsten carbide might be selectively leached in certain lubricants, and the leaching rate increased as oxygen concentration decreased in the lubricants and pH was lowered inside the crevice. Contact of steel wire on the cemented carbide die due to the mismatch of slip during drawing could be the original source of stress. Synergic effect of stress and leaching could be the answer for the severe cracking of cemented carbide dies in the wet drawing process.

The unilateral cobalt wire model of neocortical epilepsy: a method of producing subacute focal seizures in rodents

In the course of experiments on focal epilepsy in rats, we have recognized that there are no adequate models of subacute focal epilepsy in rodents. We have, therefore, reevaluated a previously described rat model that reliably generates subacute seizures over 2–3 weeks. After implantation of a short length of cobalt wire into the left motor cortex, the animals are monitored by standard EEG over the next 3 weeks. They develop three seizure types: 1. Simple partial seizures with contralateral clonic jerks, lasting 17.9 ± 46.4 min; these seizures were characterized by repetitive single spikes; 2. Secondarily generalized seizures, lasting 34.5 ± 19.0 s; and 3. Complex partial seizures with a paroxysmal EEG, lasting 39.6 ± 55.5 s. Post mortem brains were imaged using standard magnetic resonance techniques, after removal of the ferromagnetic cobalt wire. There was a localized loss of the MR signal that differed by pulse sequence, indicating spread of the ferromagnetic cobalt into the brain tissue. The image disruption caused by the cobalt was quite abrupt, indicating a sharp cobalt concentration gradient. However, we saw no evidence of widespread cerebral injury. The unilateral cobalt wire model generates less frequent, but more persistent seizures than seen in most acute, focal models. The ferromagnetic signal present, even after wire removal, indicates that metallic cobalt leaches into the cortex and may be responsible for generating the seizures. This model should be useful for testing new therapies for neocortical epilepsy.

Surface characterization of tungsten and tungsten carbide–cobalt probe materials for a fine‐pitch four‐point probe by variable excitation XPS using synchrotron radiation

AbstractIn the course of the development of a new fine‐pitch four‐point probe, surface oxide layers of the probe material were characterized by a non‐destructive depth profiling analysis with a variable excitation XPS using synchrotron radiation. The high surface sensitivity of this technique has allowed us to measure the ultra‐thin thickness of the oxide layer on the probe material without damage. The XPS of W 4f of the tungsten metal was measured in the excitation x‐ray energy range 100–1200 eV at the Photon Factory (BL‐13C), Tsukuba, Japan and analysed by the simulation of attenuation in the layer models using the values of inelastic mean free path (IMFP) and effective attenuation length (EAL) calculated by the National Institute of Standards and Technology (NIST) database programs 71 and 82, respectively. The values of practical EAL at 1 nm depth were smaller than the IMFP by 20–40% and resulted in a smaller thickness of the surface oxide layer than for that of IMFP by about 20%. The result showed that the thickness of the surface oxide layer of the tungsten metal was 1.0 nm ‘as received’ and 0.5 nm after polish. The XPS of W 4f of the superfine grain (grain size < 0.5 µm) tungsten carbide–cobalt wires with 0.45 mm diameter, which is a probe size of conventional four‐point probes, were measured and the results indicated that the thickness of the surface oxide layer of the tungsten carbide–cobalt was 0.4 nm ‘as received’, and the thickness of the oxide layer was increased to 0.5 nm after polish. The XPS of W 4f of the tungsten carbide–cobalt wire with 0.05 mm diameter of an actual probe for a new fine‐pitch four‐point probe system was also measured and the results indicated that the thickness of the surface oxide layer was 0.6 nm. The XPS of W 4f also indicated the existence of an intermediate thin layer of WO2 between W and WO3. Copyright © 2004 John Wiley & Sons, Ltd.

Oscillatory behaviour during the partial oxidation of methane over cobalt wires and foils

The oscillatory behaviour over cobalt wire and foil catalysts was examined at atmospheric pressure under various reaction temperatures and argon/methane/oxygen feed gas compositions for the partial oxidation of methane. Rough and porous oxide layers on the catalyst surface were confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The results obtained from the experimental studies indicated that the oscillatory behaviour exhibited during methane oxidation was related to the behaviour of the catalyst surface switching back and forth from the reduced state to the oxidised state. The reduction of the oxide layer followed by the almost immediate re-oxidation of the metal can be accounted for only if the oxide layer formed by oxidation is different from the oxide layer existing during reduction.

Heat transfer characteristics of liquid nitrogen for cyclic heating

Bubble formation and the critical heat flux to transit to boiling state for cyclic heat inputs have been investigated using a platinum - 0.5at% cobalt (Pt-Co) wire and a silver sheathed Bi-2223 tape, in order to evaluate the cooling stability for superconducting AC power apparatus. Sinusoidal cyclic heat inputs ranging from 2 to 150 Hz were applied to a horizontal thin wire immersed in a pool of saturated liquid nitrogen under normal atmospheric pressure. A high-speed video camera with a frame speed of 1000 frames/s has been used to observe bubble formation around the wire. The bubble frequency and the critical heat flux to transit to boiling state have been measured for each frequency. As a result, it has been found that the bubble frequency and the critical heat flux have depended on the heating frequency. The same experiment has been performed on a silver sheathed Bi-2223 tape, however, the mechanism of bubble formation is different. The dependence of the critical heat flux on the heating frequency has been also observed.

Brillouin investigation of the dynamic properties of cobalt wire arrays

We have investigated the long-wavelength spin waves in 400 Å thick cobalt wires with various width/period ratios: 0.5/1, 1/1.5, and 2/3 μm, using Brillouin light scattering. All of them show a new low-frequency line which is absent in the unpatterned films: it is attributed to modes originating from the uniform bulk mode of the infinite layer which give rise to a measurable Brillouin intensity only when both anisotropy and patterning are present in the sample. The variations of the frequency of the magnetostatic surface mode (the so-called Damon–Eshbach mode) were studied versus a magnetic-field H applied parallel or perpendicular to the axis of the wires. Compared with unpatterned layers, the Brillouin frequencies are higher when H lies along the wire axis; they are not found to be significantly sensitive to the width or to the separation of the wires. We interpret this result in terms of a slight reduction of the magnetic anisotropy for the wires. For H perpendicular to the wire axis, the spin wave frequencies are reduced by the shape- and orientation-dependent demagnetizing field Hd. The experimental determinations of Hd agree with our calculations of its mean value assuming a uniform magnetization and taking into account the interaction between the wires.

A metallic cobalt electrode for the indirect potentiometric determination of calcium and magnesium in natural waters using flow injection analysis

A flow injection analysis of Ca 2+ and Mg 2+ using indirect potentiometric detection in natural waters is proposed, where Ca 2+ or Mg 2+ are injected into a buffer carrier containing phosphate, resulting in the formation of Ca 3(PO 4) 2 or Mg 3(PO 4) 2. The consequent reduction in free phosphate in the carrier solution is detected using a metallic cobalt wire electrode. Indirect electrode response was used and the experimental conditions affecting electrode response were optimized. Responses were linear in the concentration range 5×10 −4 to 5×10 −3 M with a detection limit of 1×10 −5 M in 20 mM phosphate buffer at pH 8.0. The relative standard derivation at 1 mM of Ca 2+ and Mg 2+ were 3.9 and 3.7% ( n=10), respectively. EGTA and 8-hydroxyquinoline were used as the masking agents for Ca 2+ and Mg 2+, respectively. Concentrations of Ca 2+ and Mg 2+ in natural waters were successfully determined by the proposed method.

Direct determination of phosphate in soil extracts by potentiometric flow injection using a cobalt wire electrode

A system is described for the direct potentiometric flow injection analysis of phosphates using a cobalt wire electrode. It is proposed that the electrode response to phosphate is a result of Co 3(PO) 2 precipitate formation at the electrode surface. The electrode response to phosphate was found to be depend on the phthalate concentration, carrier pH, flow rate and injected volume. A linear response with a slope of −41±0.5 mV/decade was obtained in the concentration range of 1.0×10 −5 – 5.0×10 −3 M with a detection limit of 1×10 −6 M, using a carrier solution containing 25 mM potassium hydrogen phthalate at pH 4.0. The proposed method was used for the determination of soil extracts with a fast analysis, low cost, high sensitivity and selectivity.

Flow injection potentiometric determination of phosphate in waste waters and fertilisers using a cobalt wire ion-selective electrode

Flow injection potentiometric (FIP) determinations of dihydrogenphosphate (H2PO4–) in fertilisers and waste waters were undertaken using a cobalt wire phosphate ion selective electrode (ISE). The cobalt wire electrode was used in the FIP determination of phosphate in a carrier containing 4 × 10–2 mol l–1 potassium hydrogenphthalate at pH 5. The FIP technique was validated for fertiliser and waste water samples against standard spectrophotometric methods of analysis. The experimental data demonstrated that FIP is a highly selective and accurate technique for the determination of phosphate in fertilisers [i.e., the FIP and spectrophotometric data compare to within a few per cent (relative)]. A significant chloride interference occurs in waste water samples; however, this problem can be eradicated by using the chloride selectivity coefficient, and chloride concentrations determined independently using ion-selective electrode potentiometry. The discrepancy between corrected FIP and spectrophotometric data for phosphate in waste waters is generally ±5% (relative). X-ray photoelectron spectroscopic and electrochemical impedance spectroscopic (EIS) results suggest that the cobalt oxide surface film of the electrode is dissolved in phosphate media, facilitating the corrosion process that regulates the response of the cobalt wire electrode. It has been found that the EIS response of the cobalt wire electrode is dependent on both the pH and phosphate content of the solution. A charge-transfer reaction mechanism, and accompanying Nernst equation, have been proposed to explain the phosphate response of the cobalt wire electrode.

Potentiometric oxygen sensor based on mixed potential of cobalt wire electrode

A novel and simple potentiometric oxygen sensor suitable for the measurement of partial pressure of oxygen ( P o 2 ) in flowing blood is described. The sensor is based on measuring a steady-state mixed potential that originates at the surface of a cobalt wire electrode. This mixed or corrosion potential arises from the slow oxidation of cobalt and simultaneous reduction of oxygen at the electrode surface, and changes as a function of sample P o 2 levels. The probe is fabricated with an outer gas permeable silicone rubber tubing (1.06 mm o.d.), which contains an internal buffer solution (25.0 mM potassium hydrogen phthalate, pH 4.0, containing 1.0 mM KCl), a cobalt wire (0.1 mm o.d.) as the working electrode and an Ag/AgCl wire as the reference electrode. The sensor characteristics (slope, detection limits, linear range, drift rates, etc.) along with the response mechanism based on mixed potential are discussed in detail. In vitro evaluation of catheter forms of the sensors performed in a blood loop indicate that the proposed sensor design can closely follow P o 2 changes induced in blood during 2–3 h of continuous monitoring.