Initial micro-galvanic corrosion behavior between Mg_(2)Ca and α-Mg via quasi-in situ SEM approach and first-principles calculation

The initial micro-galvanic corrosion behavior of Mg-30wt%Ca alloy only containing Mg_(2)Ca andα-Mg was studied by immersion testing in a 0.9%Na Cl solution at 37°C.The quasi-in situ SEM and TEM results show that Mg_(2)Ca corroded easier thanα-Mg,indicating that Mg_(2)Ca acted as an anode.The work function(Φ)for Mg_(2)Ca calculated by first-principles is significantly lower compared to that forα-Mg.The Volta potential measured by a scanning Kelvin probe force microscope reveals that the Mg_(2)Ca had a relatively low Volta potential(ψ)value.The lowerΦandψvalues for Mg_(2)Ca indicate a lower electrochemical nobility,which is consistent with the experimental phenomenon.

Galvanic corrosion of AZ31B joined to dual-phase steel with and without Zn layer by ultrasonic and friction stir welding

Galvanic corrosion of AZ31B joined with bare or Zn-coated DP590 steel by ultrasonic spot welding or linear friction stir welding was quantitatively studied by pre-defining anode and cathode in the lap joint samples. Corrosion volume and depth from Mg anode surfaces exposed to 0.1 M sodium chloride solution was analyzed as functions of cathode surface type and welding method. Characterization of as-welded joints was performed to identify any microstructural feature of the bonding zone that could impact galvanic corrosion behavior.COMSOL modeling with modified user subroutine was conducted to simulate the progression of Mg corrosion in the same joint and electrode configurations used for the corrosion experiments. The experimental results indicated that Zn-coated cathode surface can reduce Mg galvanic corrosion significantly as galvanic polarization and cathodic current on Zn-coated surface remained relatively low for Mg in the weld joints.COMSOL modeling described the growth of Mg galvanic corrosion in a reasonable manner but showed limitation by underestimating the corrosion volume as it did not capture self-corrosion.

Galvanic反应原位制备多金属氢氧化物用于OER催化

采用镍氨和钴氨为电解液电沉积金属钴镍,提高材料的比表面积和导电性,再通过Galvanic反应快速合成了金属钴镍复合钴镍铁氢氧化物(CoNi/CoNiFe H)催化剂用于OER催化,采用XRD、SEM、XPS对材料的结构、形貌进行了表征,并研究了其电化学性能。结果表明:在1 M KOH溶液中,电流密度为10 mA·cm^(-2)时,过电位仅有250 mV,Tafel斜率为29 mV·dec^(-1),且具有良好的稳定性。这为制备廉价的多金属复合材料用于高效OER催化提供了新的方法。

A study on vestibular-evoked myogenic potentials via galvanic vestibular stimulation in normal people

Objectives: The aim of our study is to examine vestibular-evoked myogenic potentials(VEMPs) elicited by the galvanic vestibular stimulation in the sternocleidomastoid muscle(SCM) in healthy subjects for clinical applications of auditory neuropathy or vestibular neuropathy in the future.Methods: We enrolled sixteen healthy subjects to record the average responses of SCM to galvanic vestibular stimulation(GVS) [current 3 mA;duration 1 ms] by electromyography(EMG). SPSS 18.0 software was used to analyze the obtained data for mean and standard deviation.Results: In all healthy subjects mastoid-forehead galvanic vestibular stimulation produced a positive-negative biphasic EMG responses on SCM ipsilateral to the cathodal electrode. The latency of p13 was 11.7 ± 3.0 ms. The latency of n23 was 17.8 ± 3.4 ms. The amplitude of p13-n23 was147.0 ± 69.0 μV. The interaural asymmetry ratio(AR) of p13, n23 latency and the amplitude was respectively 0.12 ± 0.09, 0.08 ± 0.08 and0.16 ± 0.10.Discussions: Galvanic vestibular stimulation could elicit biphasic EMG responses from SCM via the vestibular nerve but not from the otolith organs. Galvanic stimulation together with air conducted sound(ACS) or bone conducted vibration(BCV) can elicit VEMPs and may enable the differentiation of retrolabyrinthine lesions from labyrinthine lesions in vestibular system.

GALVANIC CORROSION BETWEEN GRAPHITE EPOXY COMPOSITE MATERIALS AND LY12CZ ALUMINUM ALLOY

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Galvanic Corrosion Behaviour of HE 20 / MDN 138 ＆ HE 20 /MDN 250 Alloys in Natural Seawater

In view of their excellent mechanical properties, workability and heat treatment characteristics, MDN 138 & MDN 250 have been widely used in missile, rocket and aerospace industries. With light weight and high performance characteristics HE 20 aluminium alloy acts as an important material in defence and aerospace applications. The galvanic corrosion behaviour of the metal combinations HE 20 / MDN 138 and HE 20 / MDN 250, with 1:1 area ratio, has been studied in natural seawater using the open well facility of CECRI's Offshore Platform at Tuticorin for a year. The open circuit potentials of MDN 138, MDN 250 and HE 20 of the individual metal, the mixed potential and galvanic current of the couples HE 20 / MDN 138 and HE 20 / MDN 250 were periodically monitored throughout the study period. The calcareous deposits on MDN 138 and MDN 250 were analysed using XRD. The results of the study reveal that that HE 20 has offered required amount of protection to MDN 138 & MDN 250.

GALVANIC INTERACTION OF CONTACTING SULFIDE PARTICLE AND ITS EFFECT ON FLOTATION

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Galvanic Interactions of HE15 / MDN138 & HE15 / MDN250 Alloys in Natural Seawater

HE15 is a heat treatable high strength alloy with excellent machinability find wide applications in aerospace and defence industries. In view of their excellent mechanical properties, workability, machinability, heat treatment characteristics and good resistance to general and stress corrosion cracking, MDN138 & MDN250 have been widely used in petrochemical, nuclear and aerospace industries. The galvanic corrosion behaviour of the metal combinations HE15 / MDN138 and HE15 / MDN250, with 1:1 area ratio, has been studied in natural seawater using the open well facility of CECRI's Offshore Platform at Tuticorin for a year. The open circuit potentials of MDN138, MDN250 and HE15 of the individual metal, the galvanic potential and galvanic current of the couples HE15 / MDN138 and HE15 / MDN250 were periodically monitored throughout the study period. The calcareous deposits on MDN138 and MDN250 in galvanic contact with HE15 were analyzed using XRD. The electrochemical behaviors of MDN138, MDN250 and HE15 in seawater have been studied using an electrochemical work station. The surface characteristics of MDN138 and MDN250 in galvanic contact with HE15 have been examined with scanning electron microscope. The results of the study reveal that HE15 offered required amount of protection to MDN138 & MDN250.

Multi-physics analysis of the galvanic corrosion of Mg-steel couple under the influence of time-dependent anisotropic deposition film

The anisotropic deposit film formed during the galvanic corrosion can impede the mass transfer of the involved species,thereby affecting the electro-chemical behavior and the evolution of galvanic corrosion.The limitations of experimental studies in the spatial-temporal scales restrict a deeper understanding of the corrosion mechanism,which can be complemented by numerical simulation.A multi-physics coupled model is proposed in this work to systematically investigate the temporal and spatial evolution of galvanic corrosion of the Mg-steel couple with the growing anisotropic deposition layer.By utilizing the multi-physics field coupled technique,various coupled physical-chemical processes underlying the corrosion behavior are built into the model,including chemical reactions,ionic mass transfer in the bulk solution and the deposition layer,interfacial reaction,deposition of corrosion products as well as the morphological transitions caused by metal dissolution and deposition.In particular,the anisotropic deposit film is considered to be a porous layer with a porosity varying in time and space as the corrosion evolves.The predicted corrosion morphology by this model is better than the previous models.The coupled relationship between the electrochemical behavior(e.g.,electrode reaction kinetics,current density,surface potential)and the physical processes(e.g.,ionic transport,geometric evolution of metal surface and film interface)is revealed.The results indicate that a porous deposition layer with a denser inner layer and a loose outer layer is generated,leading to more significant inhibition of mass transfer in the inner layer than the outer layer.The anisotropism of the deposition layer results in a non-uniform conductivity distribution and a discontinuous current density distribution in the electrolyte.The current density on the electrode surface is inhibited by the deposition layer and the variation in the cathode/anode area ratio during the corrosion process.The competition between the transport process and the electrochemical reaction determines the spatial-temporal evolution of the ion concentration.

Morphology-dependent structures and catalytic performances of Au nanostructures on Cu_2O nanocrystals synthesized by galvanic replacement reaction

Au nanostructures were prepared on uniform Cu_2O octahedra and rhombic dodecahedra via the galvanic replacement reaction between HAu Cl4 and Cu2O. The compositions and structures were studied by Scanning Electron Microscope(SEM), Transmission Electron Microscope(TEM), High-Resolution Transmission Electron Microscope(HRTEM), X-Ray Diffraction(XRD), X-Ray Absorption Spectroscopy(XAS), X-ray Photoelectron Spectroscopy(XPS) and in-situ DRIFTS spectroscopy of CO adsorption. Different from the formation of Au–Cu alloys on Cu_2O cubes by the galvanic replacement reaction(Chem Nano Mat 2(2016)861-865), metallic Au particles and positively-charged Au clusters form on Cu_2O octahedra and rhombic dodecahedra at very small Au loadings and only metallic Au particles form at large Au loadings. Metallic Au particles on Cu_2O octahedra and rhombic dodecahedra are more active in catalyzing the liquid phase aerobic oxidation reaction of benzyl alcohol than positively-charged Au clusters. These results demonstrate an obvious morphology effect of Cu_2O nanocrystals on the liquid–solid interfacial reactions and prove oxide morphology as an effective strategy to tune the surface reactivity and catalytic performance.

Retro-labyrinthine Lesion Site Detected by Galvanic Vestibular Stimulation Elicited Vestibular-evoked Myogenic Potentials in Patients with Auditory Neuropathy

Objective Auditory neuropathy(AN)is a unique pattern of hearing loss with preservation of hair cell function.The condition is characterized by the presence of otoacoustic emissions(OAE)or cochlear microphonic(CM)responses with severe abnormalities of the auditory brainstem response(ABR).The vestibular branches of the VIII cranial nerve and the structures innervated by it can also be affected.However,the precise lesion sites in the vestibular system are not well characterized in patients with AN.Methods The air-conducted sound(ACS)vestibular-evoked myogenic potentials(VEMPs)and galvanic vestibular stimuli(GVS)-VEMPs were examined in 14 patients with AN.Results On examination of VEMPs(n=14,28 ears),the absent rates of ACS-cervical VEMP(cVEMP),ACS-ocular VEMP(oVEMP),GVS-cVEMP,GVS-oVEMP and caloric test were 92.9%(26/28),85.7%(24/28),67.9%(19/28),53.6%(15/28),and 61.5%(8/13),respectively.Impaired functions of the saccule,inferior vestibular nerve,utricle,superior vestibular nerve,and horizontal semicircular canal were found in 25.0%(7/28),67.9%(19/28),32.1%(9/28),53.6%(15/28)and 61.5%(8/13)patients,respectively.On comparing the elicited VEMPs parameters of AN patients with those of normal controls,both ACS-VEMPs and GVS-VEMPs showed abnormal results in AN patients(such as,lower presence rates,elevated thresholds,prolonged latencies,and decreased amplitudes).Conclusion The study suggested that patients with AN often have concomitant vestibular disorders.Retro-labyrinthine lesions were more frequently observed in this study.GVS-VEMPs combined with ACS-VEMPs may help identify the lesion sites and facilitate detection of areas of vestibular dysfunction in these patients.

Computational design of Mg alloys with minimal galvanic corrosion

Formation of galvanic cells between constituent phases is largely responsible for corrosion in Mg-based alloys.We develop a methodology to calculate the electrochemical potentials of intermetallic compounds and alloys using a simple model based on the Born-Haber cycle.Calculated electrochemical potentials are used to predict and control the formation of galvanic cells and minimize corrosion.We demonstrate the applicability of our model by minimizing galvanic corrosion in Mg-3wt%Sr-x Zn alloy by tailoring the Zn composition.The methodology proposed in this work is applicable for any general alloy system and will facilitate efficient design of corrosion resistant alloys.

Galvanic effects on electrochemical behaviors of bare surface of 304 stainless steel

The bare surface of 304 stainless steel is produced by the fast fracture method. The influence of the surface galvanic cell on the electrochemical behaviors of bare surface of 304 stainless steel has been investigated in H 2SO 4 solutions with different concentrations. The results show that the solution corrosivity level and the area ratio influence the surface galvanic effects caused by the inhomogeneity between the free film surface of alloy and the passive surface. The surface galvanic effects can speed up the dissolution rate of the bare surface of the alloy and will change the electrochemical behavior of bare surface. With the increase of the area ratio between passive surface and fractured surface, the galvanic potential becomes more positive and, in the range of passive potential, both galvanic current and the peak fracture current increase evidently.

Study of galvanic corrosion and mechanical joint properties of AZ31B and carbon-fiber–reinforced polymer joined by friction self-piercing riveting

A new testing methodology was developed to quantitively study galvanic corrosion of AZ31B and thermoset carbon-fiber–reinforced polymer spot-joined by a friction self-piercing riveting process.Pre-defined areas of AZ31B in the joint were exposed in 0.1 M NaCl solution over time.Massive galvanic corrosion of AZ31B was observed as exposure time increased.The measured volume loss was converted into corrosion current that was at least 48 times greater than the corrosion current of AZ31B without galvanic coupling.Ninety percent of the mechanical joint integrity was retained for corroded F-SPR joints to 200 h and then decreased because of the massive volume loss of AZ31B。

Water Resources Management and Wastewater Treatment in the Democratic Republic of Congo (D.R.C): Application of Galvanic Treatment, Results and Prospectives

The rapid industrial development and population growth increase the utilization of fresh water resulting in an increase of the amount of wastewater. Several Countries face a double challenge with regard to water resources, namely meeting the growing need for water for the population and treating the wastewater generated for application. The toxicity found in these water streams threatens the environment and human health. Hence the urgent need is to treat wastewater. The DRC is not immune from this threat. Its average population growth rate has exceeded the 3% and the number of industries it hosts continues to increase. The wastewater generated by this increasing pressure from urbanization and industrialization must be treated as required in the Congolese legal arsenal. Various factors need to be considered prior choosing the water treatment method. The choice must take into account the imperatives of the moment which are: modernization (local context) and sustainable development (international context). There are several wastewater treatments that are widely used for the removal of toxic elements such as ion exchange, reverse osmosis, chemical precipitation and electro-coagulation just to name a few. The most recent studies have shown that the galvanic technique can be used in the purification of water from domestic and industrial origin to meet drinking water standards. Various researchers have used this technique at laboratory and pilot scale demonstrating its cost-effectiveness as it uses no chemical reagents, consumes less energy and occupies only a small space for processing large flows. However, there are very few studies demonstrating the success of this treatment on an industrial scale. Therefore, this work seeks to understand and master the mechanisms that take place in the galvanic treatment. In addition, this study focuses on the development of a robust prototype that is adaptable to the needs of various users while at the same time being relatively cheap to meet the national needs.

On the Galvanic Modification of Seawater

Chemical properties of seawater are studied at forced shifting of Fermi level εF? in the band gap of liquid water due to deviation of its composition H2O1−z ( |?z|−13 ) from the stoichiometric one ( z = 0 ). It is shown that the hypo-stoichiometric state ( z > 0 ) of seawater emerges when Fermi level is shifted to the local electron level ?εH3O of hydroxonium H3O+ in galvanic cell with the strongly polarized anode and the quasi-equilibrium cathode. Then, each εH3O is occupied by electron and hydroxonium radicals [H3O]? together with hydroxide anions [OH−]?form in seawater hydrated electrons [(H2O)2−] . The opposite hyper-stoichiometric state ( z εOH for removing electron from each hydroxide ion OH−and forming hydroxyl radicals [OH] as strong oxidizers. It turned out that the ions of sodium and chlorine are connected into hydrates of sodium hypochlorite NaClO in this case.

On Diffusive Confining a Galvanic Crystallization out of Molten Salts

The electron-energy band structure of electric Double Layer (DL) between a molten salt and metal electrode (an anode or cathode) is studied for the electrodepositing crystallization process when the width of DL metal part is less than the one in the molten salt. It is shown that just the molten-salt part of the double layer confines a rate of electrodepositing process. The reason of this is a neutralization of depositing ions into the molten-salt near the electrode and hence their diffusively confined motion in a density gradient field. It is important to minimize the electrodepositing potential for effective component crystallization out of the molten salt and its exchange process including selective extracting of salt components by their crystallization on electrodes of galvanic circuit. It is shown that this can be carried out by means of fine and controllable variation of reduction-oxidation (RedOx) potential of the non-stoichiometric salts. A possible application of a potentiometer for monitoring and managing the salt composition is considered. For this, one uses precise methods of electric-motion-force and coulometer titration by solid electrolyte(for example, M+–β ”–Al2O3) of the basic salt metal (M。) as a reduction agent in the molten-salt solution.

The Effect of Novel Low Energy Pulsed Light Combined with Galvanic Energy for Home-Use Hair Removal of Dark Skin

Background and Objectives: Permanent reduction of unwanted hair on skin types V and VI is the most challenging procedure among all hair removal technologies based on selective absorption of light or laser. The objective of this study is to evaluate the safety and efficacy of a low energy pulsed-light device combined with galvanic energy, intended for home-use hair removal on dark skin. Materials and Methods: Fifteen women with skin types V and VI and dark terminal hair in axillaarea self-administrated 6 treatments at 2 week intervals, using a hand-held IPL combined with galvanicenergy device, using HPL (Home Pulsed Light) technology. Hair count and photographs were performed pre-treatment and 1 and 3 months after the last sixth treatment. Adverse events and subject satisfaction scores were recorded. Results: All patients showed a positive clinical response to treatment, with reduction of unwanted hair. Hair counts were significantly reduced by 57.3% 1 month following last treatment and by 44.5% 3 months following last treatment. No adverse events were recorded. Subject satisfaction scores of the device usability and the treatment outcome were high. Conclusions: Low energy pulsed light combined with galvanic energy may be applied safely and effectively for at-home hair removal for people with dark skin types V and VI.

Studies of Grinding Media Corrosion from Galvanic Interaction on Galena Flotation

This study has been done to determine the galvanic interaction between five types of grinding media (mild steel, cast iron, 10% chromium, 20% chromium, and ceramic media) and galena, in situ of the mill. The ceramic media has a significantly not galvanic interaction with galena and high chromium media has a significantly weaker galvanic interaction with galena, and produces a very much lower amount of oxidize iron species in the mill discharge than mild steel medium. The investigation of the various reactions occurring on the galena surface was investigated by ethylene diamine-tetra acetic acid disodium salt (EDTA) extraction and X-ray photoelectron spectroscopy (XPS) measurements. The floatability of galena is dependent on the galvanic current between grinding media and galena during grinding because the current is relative to the amount of iron oxidation species and the reduction rate on galena. Iron oxidation species depressed galena flotation. The optimum galena flotation was achieved by selecting grinding conditions that enabled iron oxidation to be controlled.

Galvanic Skin Response—Extinction Biofeedback Training for Psychogenic Abdominal Pain: A Validation Protocol

Abdominal and pelvic pain of psychogenic origin is a widespread, disabling, difficult to identify, and often inadequately treated medical condition. This condition is often associated with poor quality of life due to high pain interference with daily activities. Cognitive behavioral psychological therapy and neuromodulation with biofeedback are validated therapies for the treatment of this condition. Aim of the present research work is the validation of a therapeutic protocol that involves the use of both techniques in combination. 20 patients diagnosed with psychogenic abdominal pain, of both sexes, aged between 18 and 60 years who had not benefited from pharmacological therapies were enrolled. 10 patients were randomly assigned to the control group (psychological treatment only), another 10 patients were assigned to the study group (neuromodulation with biofeedback-Galvanic skin response-extinction in combination with psychological therapy). For both groups, the pain score, interference of pain with daily living activities, pain relief, and the share of anxiety associated with the pain condition were evaluated (pre- and post-treatment). The patients who underwent the combined treatment achieved statistically significant better scores than patients in the control group, respectively −4.9 ± 0.9 vs −1.0 ± 0.4 for Pain;−5.1 ± 1.1 vs −0.9 ± 0.3 for Interference with life;−7.2 ± 3.7 vs −2.2 ± 2.1 for HAMA;4.6 ± 1.2 vs 1.1 ± 0.6 for Relief.