Nickel In Samples Research Articles

In the LiCl-KCl melt at 500<sup>о</sup>С depending on the content of Li<sub>2</sub>О и LiOH

Molten alkali metal chlorides used in pyrotechnologies are aggressive corrosive agents. The high operating temperature of the process, the heterogeneity of the environment, and the significant corrosion activity of the molten salt necessitate both the search for stable structural materials and the development of methods for protecting the structural elements of high-temperature technological devices. Corrosion loss reduction techniques traditionally used in low temperature environments are not applicable at high temperatures. The article examines the influence of oxygen-containing impurities (lithium oxide and hydroxide) on the corrosion behavior of metallic nickel (grade NP1) – the main component of candidate structural alloys, a thermodynamically and structurally stable material in the melt for the process of electrolytic refining of spent nuclear fuel. A method for preparing the LiCl–KCl salt electrolyte and obtaining lithium oxide by thermal decomposition of anhydrous lithium hydroxide under vacuum is described, and the concentrations of impurities in the electrolyte and the synthesized lithium oxide are determined. An installation for conducting corrosion tests in an inert atmosphere of a glove box is presented. To assess the corrosion resistance of the material, the following were used: gravimetric analysis, X-ray diffraction analysis of the surface and cross-sectional sections, and X-ray diffraction analysis of the surface of the samples. The dependences of the corrosion rate of the material on the concentration of oxygen-containing additives Li2O and LiOH were obtained. Based on a combination of gravimetric, X-ray microspectral and X-ray phase analysis data, it was established that metallic nickel samples demonstrate high corrosion resistance in the studied melts with the introduction of Li2O and LiOH additives.

Adaptation of a Differential Scanning Calorimeter for Simultaneous Electromagnetic Measurements.

Although much information can be gained about thermally induced microstructural changes in metals through the measurement of their thermophysical properties using a differential scanning calorimeter (DSC), due to competing influences on the signal, not all microstructural changes can be fully characterised this way. For example, accurate characterisation of recrystallisation, tempering, and changes in retained delta ferrite in alloyed steels becomes complex due to additional signal changes due to the Curie point, oxidation, and the rate (and therefore the magnitude) of transformation. However, these types of microstructural changes have been shown to invoke strong magnetic and electromagnetic (EM) responses; therefore, simultaneous EM measurements can provide additional complementary data which can help to emphasise or deconvolute these complex signals and develop a more complete understanding of certain metallurgical phenomena. This paper discusses how a DSC machine has been modified to incorporate an EM sensor consisting of two copper coils printed onto either side of a ceramic substrate, with one coil acting as a transmitter and the other as a receiver. The coil is interfaced with a custom-built data acquisition system, which provides current to the transmit coil, records signals from the receive coil, and is controlled by a graphical user interface which allows the user to select multiple excitation frequencies. The equipment has a useable frequency range of approximately 1-100 kHz and outputs phase and magnitude readings at a rate of approximately 50 samples per second. Simultaneous DSC-EM measurements were performed on a nickel sample up to a temperature of 600 °C, with the reversable ferromagnetic to paramagnetic transition in the nickel sample invoking a clear EM response. The results show that the combined DSC-EM apparatus has the potential to provide a powerful tool for the analysis of thermally induced microstructural changes in metals, feeding into research on steel production, development of magnetic and conductive materials, and many more areas.

The Evaluation of Selected Trace Elements in Blood, Serum and Blood Cells of Type 2 Diabetes Patients with and without Renal Disorder.

An appropriate diet is the basis for the treatment of type 2 diabetes (T2DM). However, there are no strict recommendations regarding the content of micronutrients and their modifications in the presence of chronic kidney disease (CKD). Therefore, we decided to investigate whether T2DM patients, including those with CKD, have different levels of chromium, nickel, cobalt, magnesium, and zinc in various blood elements compared to healthy individuals. We divided our subjects into three groups: the control group (individuals without T2DM and proper renal function), those with T2DM and proper renal function, and those with T2DM and GFR < 60 mL/min/1.73 m2. We observed higher levels of chromium in all materials examined in patients with T2DM and impaired renal function. Both study groups found higher levels of nickel in samples of whole blood and red blood cells. Patients with T2DM and proper renal function had higher levels of serum manganese. Both study groups had lower levels of serum zinc. We observed higher levels of chromium in all materials examined in patients with T2DM and impaired renal function. Both study groups found higher levels of nickel in samples of whole blood and red blood cells. Patients with T2DM and proper renal function had higher levels of serum manganese. Both study groups had lower levels of serum zinc. In order to ensure effective care for patients with T2DM, it is necessary to improve the standard diet, including the content of micronutrients and their modification in patients with concomitant CKD.

Evaluation of the Pollution by the Potentially Toxic Elements in the Topsoils of a Semi-Industrial Zone, Northwestern Iran

ABSTRACT Various industries, including cement production, petrochemical processing, and power plants, exert significant environmental impacts on their surroundings. The close proximity of these industries within the study area underscores the critical need to investigate soil pollution of potentially toxic elements and elucidate possible pollution sources and associated risks. The present study involved taking 44 topsoil (0–10 cm) samples of Arsenic (As), Cadmium (Cd) Cobalt (Co), Chromium (Cr), Copper (Cu), Nickel (Ni), Lead (Pb), and Zinc (Zn) concentrations, which their mean concentration were found to be 11.29, 0.46, 15.89, 67.36, 44.36, 79.93, 8.50 and 68.27 mg kg−1, respectively. Comparison with the baseline values stated in local and international soil quality guidelines has indicated higher As, Cd, Cr, Cu, and Ni concentrations. The soil pollution indices of the geoaccumulation index, pollution index, pollution load index, and enrichment factor pollution have evaluated the pollution status of the study area to be uncontaminated to moderately contaminated, moderately polluted, polluted, deficient enrichment to moderate enrichment classes, respectively. Ecological and health risks that involved the application of the single index of ecological risk, potential ecological risk, hazard quotient, hazard index, and cancer risk have revealed that the study area was ecologically in a low-risk state with an average potential ecological risk value of 90.38, while carcinogenic (10−6-10−4) and non-carcinogenic risks (>1) were also found to be in a tolerable range for human health. Possible pollution sources were identified using multivariate statistics and further confirmed and visualized by the spatial distribution maps obtained from the deterministic interpolation method of inverse distance weighting. These analyses have suggested that the soil pollution which its existence was confirmed by the related indices and comparisons, to the potentially toxic elements of Cr and Ni can be possibly attributed to the petrochemical and power plants, to Cd could be appointed to cement plant, and to Cu could be associated with agricultural activities. It has also been found that arsenic was determined to be a common pollutant among the three main industries.

Micro-Milli Scale for the Removal of Iron and Copper by a Positively Charged Foam before Nickel Colorimetric Detection using Handy Spectrometer

Introduction: Simple alternative detection of nickel with iron and copper as interferences was proposed. The procedure was based on sampling a milligram sample and a micro-milliliter operation. Methods: The method has been applied to jewelry items. A 50 mg sample was digested by 5 mL of nitric acid with heating. The obtained solution was added with KSCN before passing through polyurethane foam (PUF) (1 cm i.d. × 8 cm length). Some metal ions-SCN complexed (e.g., Fe(III) and Cu(II)) were retained in the column while Ni(II) ions were in the eluate. A 200-500 µL aliquot was added with 4-(2-pyridylazo)-resorcinol (PAR) as the color reagent. At least 30 µL of a portion was measured for the absorbance of the color product using a handy spectrometer. Results: The positively charged foam could remove iron and copper altogether before determining nickel. A standard calibration was a plot of absorbance versus Ni(II) concentration for 1-30 mg/L: absorbance = 0.0123[Ni(II), mg/L] + 0.0435 (R2=0.9945) with a limit of detection (LOD) and limit of quantitation (LOQ) of 0.24 mg/L and 0.81 mg/L, respectively. Two bracelet samples showed the presence of nickel at 0.97 ± 0.25 and 0.27 ± 0.04 mg/g, respectively, and agreed with the reference FlameAAS method. Conclusion: The proposed method could be used to assay nickel in samples containing high levels of iron and copper, such as jewelry. This will benefit general wearers with health concerns associated with nickel, particularly in case of inexpensive accessories. The handy spectrometer used in the study might make be helpful to carry out these studies with a limited tight budget.

ANALYZING THE EXTENT OF LEACHATE FROM A MAJOR DUMPSITE WITHIN THE CRETACEOUS SEDIMENTS OF IKOM-MAMFE EMBAYMENT, SOUTHEAST NIGERIA

Groundwater resources in the region serve as a vital source of potable water for local communities and are essential for supporting various socio-economic activities. Unfortunately, the infiltration of leachate from dumpsite contributes to the dispersion of contaminants within the cretaceous sediments, posing a potential threat to groundwater quality. This study presents an exhaustive examination of leachate extent emanating from a prominent dumpsite situated within the Cretaceous sediments of the Ikom-Mamfe Embayment, Southeast Nigeria. Employing meticulous soil sampling methodologies and water collection from strategically positioned boreholes near the Ikom dumpsite, advanced techniques such as Electrical Resistivity Tomography (ERT) and Vertical Electric Sounding (VES) were utilized to scrutinize the infiltration of leachate within the site. Laboratory analyses were conducted to evaluate the concentrations of heavy metals, including Lead, Mercury, Arsenic, Nickel, Chromium, and Cadmium, in both soil and borehole water samples. The findings unveiled alarming levels of Lead and Cadmium concentrations in the soil, exceeding established regulatory thresholds, with recorded values ranging from 552.34 to 556.93 mg/kg and 11.88 to 7.46 mg/kg, respectively. Similarly, borehole water analyses in the vicinity of the Ikom dumpsite revealed elevated concentrations of Arsenic, Lead, Cadmium, and Nickel, surpassing WHO limits in specific boreholes (BH2 and BH3), indicative of potential soil porosity issues and unfavorable geological conditions prevalent in the study area. Notably, the use of ERT delineated an inverse resistivity of 5.99 Ωm at a depth of 9.26 m, pinpointing the leachate-infiltrated cretaceous sediments zone, extending laterally from 10m to 40m along the profile. The observed infiltration of leachate at 9.26 m depth underscores its penetration into the sandstone, shale, and dark gray shale strata within the dumpsite. Furthermore, the quantified thickness layer ranging from 1.41 to 4.37 affirmed leachate infiltration within the sandstone, shale, and dark gray shale strata, with implications for its movement and containment dynamics. This study underscores the critical role of layer thickness in influencing the migration and containment of leachate, with thicker layers potentially acting as barriers to its movement, while thinner layers may facilitate more rapid migration. Additionally, the assessment of aquifer protective capacity, denoted by ratings below (&lt;0.1), underscores the poor protective capacity of the aquifer system in the study area. In light of these findings, strategic management, remediation, and vigilant monitoring measures are advocated to mitigate contamination risks and safeguard water quality.

Investigations of Nernst Effect in Nickel Samples

Investigations of Nernst Effect in Nickel Samples

Hydrazine metal complexes as a single source in the mechanochemical preparation of metallic magnetic nanoparticles and investigation of their magnetic hyperthermia properties

Ferromagnetic metallic cobalt and nickel nanoparticles were synthesized by intramolecular metal-hydrazine ligand oxidation reduction reaction in basic media and the solid state. Nickel nanoparticles Ni1 and Ni2 are obtained from two complexes, Ni(N2H4)2(C2O4) and Ni(N2H4)2(HCO2)2, respectively. X-ray powder diffraction (XRD) and energy-dispersive X-ray (EDX) data show pure fcc crystal structures of nanoparticles. Scanning electron microscopy (SEM) images revealed both Ni1 and Ni2 nanoparticles have agglomerated sphere morphologies. The crystallite size estimated by using the Scherer method for Ni1 and Ni2 were 18.7 and 6.2 nm. Vibrating sample magnetometer (VSM) data show the coercivity of metallic nickel samples Ni1 and Ni2 are 50 and 153 Oe, respectively. Both nanoparticles cause an increase in the temperature of water under applied alternative magnetic field and showed specific loss power (SLP) of 70 W/g and 104.8 W/g, respectively. The same method is used in preparation of cobalt nanoparticles from two complexes, Co(N2H4)2(C2O4) and Co(N2H4)2(HCO2)2. XRD analysis data show both nanoparticles have hcp crystal structure. SEM images show nanosheet structure with sheet thickness of 10 to 30 nm. Coercivity of Co1 and Co2 nanoparticles obtained by VSM and Hc are 182 and 171 Oe, respectively. In spite of high coercivity in both Co1 and Co2 nanoparticles, the magnetic hyperthermia heating effects are not observed in practice and specific loss power (SLP) is zero.

Determination of the porosity characteristics by pycnometric methods

Data on pore size distribution in solids are obtained by pycnometric density-based methods for measuring the pore structure of materials. The results of measuring open porosity by weighing a dry sample followed by evacuation and saturation with distilled water at atmospheric pressure, impregnation with water under pressure using a hydrostat and mercury porosimetry are presented. The samples of porous nickel obtained using powder technology by sintering of the compacts from mixtures of nickel nanopowder with powder ammonium bicarbonate NH4HCO3 (a blowing agent), the volume fractions of which were 80 and 20%, respectively, were studied. A powder blowing agent with a particle size of 63 – 125, 140 – 200, and 250 – 315 μm was used. A theoretical estimation of the pore size available for the penetration of the impregnating liquid was carried out for three methods used for the determination of open porosity. It is shown that upon water saturation after evacuation the liquid can penetrate only into pores larger than 3 μm. Moreover, in porous structures with a large fraction of submicron pores, the actual values of the open porosity are significantly underestimated when using the method of saturation with distilled water after evacuation. The higher the fraction of fine pores in the material, the lower the open porosity value. The difference between the open porosity values determined by methods of water impregnation using a hydrostat and mercury porosimetry was negligible. It has been established that among three considered methods for measuring open porosity, only the method of saturation with distilled water after evacuation cannot be used in analysis of structures with submicron pores. The results obtained can be used to develop porous functional materials and products with a given porosity structure.

POOL BOILING HEAT TRANSFER CHARACTERISTICS OF POROUS NICKEL MICROSTRUCTURE SURFACES

Pool boiling is an effective heat dissipation approach in electronic cooling, battery thermal management, etc. This study used the electrochemical deposition method to fabricate one smooth nickel specimen (named Ni-smooth) and three specimens with a porous nickel-stacked structure. The three porous specimens were created with deposition current densities of 0.5 A&amp;#183;cm&lt;sup&gt;-2&lt;/sup&gt; (named Ni-0.5), 2.0 A&amp;#183;cm&lt;sup&gt;-2&lt;/sup&gt; (names Ni-2.0), and 5.0 A&amp;#183;cm&lt;sup&gt;-2&lt;/sup&gt; (named Ni-5.0), respectively. The four samples underwent microstructural characterization via scanning electron microscopy. The increasing current density led to the porous nickel surface exhibiting a more distinct pore structure, and the nickel sphere grains became more refined, developing a loose "mound-like" structure. A marked increase in the nickel film thickness was also observed. Through visual experiments, we evaluated their wettability, and through pool-boiling experiments, we tested their boiling heat-transfer properties. Our findings suggest that samples incorporating a porous nickel structure consistently outperform unmodified samples regarding heat-transfer efficiency. Specifically, sample Ni-0.5A demonstrated the most optimal boiling heat-transfer performance, evidenced by a 32.2&amp;#37; reduction in temperature at the onset of boiling, a 19.9&amp;#37; increase in critical heat flux density, and a 78.6&amp;#37; larger maximum heat-transfer coefficient compared to the smooth nickel sample. These marked improvements are intrinsically linked to the specific characteristics of the porous nickel structure. The higher performance of samples Ni-0.5 can be attributed to the presence of additional nucleation sites within the porous structure and the formation of smaller micro-crystalline dendritic constructs due to the specific current density applied during electrodeposition. Understanding this relationship between surface characteristics and electrodeposition is essential in maximizing heat-transfer efficiency.

Magnetostrictive behavior of pure nickel core: A study on the effects of annealing and magnetization using VSM and optical microscopy techniques

This study investigates the impact of annealing and magnetization on the magnetostrictive behavior of pure nickel, which is used as the core of an ultrasonic transducer. Pure metals are not commonly used as magnetic materials due to their limited magnetic and non-magnetic properties. Analyzing the effects of alloying on different characteristics of pure elements is a complex process. Improving the efficiency of magnetostrictive transducers by enhancing their properties is an area of interest for researchers. Grain size, in particular, is a significant parameter that affects the properties of ferromagnetic materials. This study reveals that exposing pure nickel and magnetized samples to an electro-polishing solution with 10 % oxalic acid for 60 s results in the appearance of grain boundaries. Furthermore, the study finds that the 90° domain wall energy is higher than the 180° domain wall energy, impacting the radial magnetostrictive force more than the longitudinal magnetostrictive force. The results show that annealing reduces the maximum output magnetic hysteresis, while magnetization has little effect. Additionally, annealing significantly reduces the coercive field, increasing the magnetostriction effect. Therefore, annealed nickel is a promising candidate for use as the core of an ultrasonic transducer for removing residual chemicals from fruits and vegetables.

3D characterization of abnormal grain growth in nanocrystalline nickel

AbstractAbnormal grain growth, a pervasive phenomenon witnessed during the annealing of nanocrystalline metals, precipitates a swift diminution of the distinctive properties inherent to such materials. Historically, conventional transmission electron microscopy has struggled to efficiently procure comprehensive five‐parameter crystallographic information from a substantial number of grain boundaries in nanocrystalline metals, thus inhibiting a deeper understanding of abnormal grain growth behavior within nanocrystalline materials. In this study, we utilize a high‐throughput characterization method—three‐dimensional orientation mapping in the TEM (3D‐OMiTEM) to characterize the crystallographic five‐parameter character of grain boundaries with an area of over 3.4 × 106 nm2 in an abnormally grown nanocrystalline nickel sample. When coupled with existing theoretical simulation results, it is discerned that the grain boundary population shows a relatively large scatter when it is correlated to the calculated grain boundary energy; the grain boundaries of abnormally grown grains exhibit lower grain boundary energy compared to those that have not undergone abnormal growth. Merging high‐throughput grain boundary information obtained from three‐dimensional orientation mapping data with grain boundary properties derived from high‐throughput theoretical calculations following the concept of materials genome engineering will undoubtedly facilitate further advancements in comprehending and discerning the interfacial behaviors of crystalline materials.

Wire Electrochemical Etching of Superhydrophobic Nickel Surfaces with Enhanced Corrosion Protection

Superhydrophobic nickel surfaces have significant advantages in the field of corrosion protection compared with traditional nickel corrosion protection methods which need a toxic chemical corrosion inhibitor. Electrochemical etching, an ideal method for fabricating superhydrophobic nickel surfaces, was also limited by low current density, resulting in low processing efficiency. To overcome this limitation, we proposed a new method to fabricate a superhydrophobic nickel surface using a wire electrochemical etching method. The wire electrochemical etching method accomplished the etching process by sweeping a controlled wire cathode across the surface of the anode nickel plate in an environmentally friendly neutral electrolyte, NaCl. The superhydrophobic nickel sample with a contact angle of 153° and a rolling angle of 10° could be fabricated by wire electrochemical etching and modification. Additionally, the optimal parameters of the wire electrochemical etching and the principle of superhydrophobic surface formation had also been systematically investigated, respectively. Moreover, the superhydrophobic nickel surface had self-cleaning performance, antifouling performance, corrosion protection, and abrasion resistance. Wire electrochemical etching improves the current density of processing, which means that this method improves the processing efficiency for fabricating a superhydrophobic nickel surface. This work is expected to enrich the theory and technology for fabricating superhydrophobic nickel surfaces to improve the corrosion protection of nickel.

Determination of Ag in high-purity solutions of copper and nickel by high-resolution continuum-source electrothermal atomic absorption spectrometry (HR-CS-ETAAS)

A need to control the silver content in high-purity copper and nickel samples is attributed to the deterioration of the technical characteristics of materials when the presence of such impurities exceeds the permissible levels. In this study, modes for the determination of Ag in copper and nickel by high-resolution electrothermal atomic absorption spectrometry with a continuum source at a content of 10–6 – 10–5 % have been developed. The optimal temperature regimes of the atomizer program and the amount of chemical modifier introduced were developed proceeding from the results of studying the regularities of atomic absorption measurements of silver in matrix solutions of Cu and Ni (with a concentration of 10 g/liter each). To construct calibration dependences, aqueous standard solutions of the analyte (determination in copper) and aqueous standard solutions of the analyte with the addition of nickel nitrate 10 mg/liter (determination in nickel) were used. The atomization temperature was chosen to be 1600°C. The dosing volume of the solutions in the graphite furnace was always 20 μl. When determining Ag in high-purity copper, different temperatures of the pyrolysis stage were used for measurements with dosing of standard analyte solutions (600°C) and for measurements with dosing of the analyzed copper solution (800°C). In the determination of silver in nickel solutions, the temperature of the pyrolysis stage was 800°C. The developed conditions for the determination of silver were tested in the analysis of high-purity samples of copper and nickel (standard solutions of Inorganic Ventures, USA with a concentration of 10 g/liter) using spiked tests. The maximum value of the relative error of determinations does not exceed 13%. The detection limits for silver were: 1.8 × 10–6 % in copper and 3.2 × 10–6 % in nickel.

Tellurium Corrosion of Type 304/304L Stainless Steel, Iron, Chromium, and Nickel in High-Temperature Liquid Sodium.

Investigating tellurium (Te) corrosion on structural materials is crucial for sodium-cooled fast reactors (SFRs) due to radionuclide presence and knowledge gaps. In this study, Type 304/304L stainless steel (SS304), chromium (Cr), iron (Fe), and nickel (Ni) samples were immersed in low-oxygen environments with Te in liquid sodium at 773 K for 30 days. At 10 ppm oxygen, SS304 showed multiple oxide layers, including a compact NaCrO2 interlayer and porous Na-Fe-Ni-O outer layers. Tellurium penetrated through the porous layers but was hindered by the NaCrO2 interlayer. At 0.01 ppm oxygen, Cr had no oxide layer, while Fe and Ni had unstable ones. Tellurium-induced pitting was deeper in Fe and Ni compared to Cr. Oxygen levels and Cr composition are critical factors affecting stable oxide compound layer formation and mitigating Te-induced pitting.

Comparative analysis of the structural, magnetic, and magnetocaloric properties of Gd0.5Dy0.5Mn0.5X0.5O3 (X = Ni, Fe, and Co) nanoparticles

Depending on the type of dopant used, materials can exhibit notably different structural, magnetic, and magnetocaloric properties of Gd0.5Dy0.5Mn0.5Ni0.5O3 (GDM_Nickel), Gd0.5Dy0.5Mn0.5Fe0.5O3 (GDM_Iron), and Gd0.5Dy0.5Mn0.5Co0.5O3 (GDM_Cobalt) magnetic nanoparticles have been examined experimentally. These samples were made using the well-known sol–gel technique. The structure of the systems was ascertained using both X-Ray Diffraction patterns and Scanning Electron Microscopic studies confirming the synthesis of nano-sized perovskites. With the presence of spin-glass and charge-ordering tendencies, magnetic studies revealed that these systems had a variety of magnetic states ranging from ferrimagnetic, antiferromagnetic to paramagnetic behaviors. The presence of Griffiths phase is also detected in both GDM_Nickel and GDM_Cobalt systems. The maximum entropy changes of the GDM_Nickel sample reached the highest value with 14.187 J Kg−1 at 7 T and 326 J kg−1 as a relative cooling power.

Morphological investigation and electrochemical performance evaluation of novel porous Ni–Pt produced by Al-deposition/dissolution in molten salts for hydrogen and oxygen evolution reaction

A two-step electrolytic deposition of Ni and Pt from aqueous solutions formed a porous Ni–Pt alloy surface. A nickel sample with a thin layer of platinum covered by a nickel electrode coating was used in the electrolysis of aluminium from molten salts at 900°. The molten salt was a mixture of 48.25 mol% NaCl, 48.25 mol% KCl and 3.5 mol% AlF3. Deposition of Al on Ni and Pt samples was carried out at a potential of −1.8 V, respectively. Al and the resulting intermetallic phases were dissolved at −0.5 V to produce porous Ni–Pt alloy foams. It was found that a porous Ni–Pt alloy layer is formed due to an intense reaction between liquid Al and solid Ni, which propagates deep into the solid material. The high temperature of the molten salts allows the metallic Pt to penetrate deep into the porous structure. It makes it possible to obtain a uniform Pt distribution in the electrode volume. The fabricated porous Ni–Pt alloy was tested in cathodic and anodic polarisation measurements in an aqueous solution of 10 wt% KOH to assess their electrocatalytic activity. During constant-voltage electrolysis, a solid-electrolyte hydrogen sensor was coupled to the experimental system and allowed the in-situ hydrogen production efficiency to be measured. The promising electrochemical performance of porous Ni–Pt alloys as electrode materials for hydrogen and oxygen release in alkaline solutions was confirmed by measuring the partial pressure of hydrogen in electrolysis at constant voltage. Due to the large amount of highly active surface area, the porous Ni–Pt alloys showed a significantly higher current density than untreated samples in hydrogen evolution reactions. Based on cyclic voltammetry measurements, it was demonstrated that the electrochemically active surface area was highest for the modified Ni–Pt electrode. The Pt-modified sample with Al deposition at −1.8 V and a molten salt temperature of 900 °C generated the highest amount of hydrogen (9.38 mL).

Device for measuring the Seebeck coeffi cient of thermoelectric materials in the temperature range 300–800 K

The problem of identifying patterns that are associated with the features of the structure and phase composition of new thermoelectric materials obtained by self-propagating high-temperature synthesis is considered. A measuring device has been developed to determine the Seebeck coefficient (thermoelectric motive force) of thermoelectric materials in the temperature range of 300–800 K in argon, air or vacuum. The design of the measuring device is described in detail, the capabilities of the device and the measurement error (less than 5 %) are discussed. The thermoelectromotive force of reference nickel samples in the temperature range of 300–800 K in an argon medium was measured by a differential method. Negative values of the Seebeck coefficient of the nickel sample were obtained throughout the studied temperature range, which indicates the predominance of electrons as the main charge carriers in the sample material. At room temperature, the measured value of the Seebeck coefficient is –19.05 mkV/K and decreases to a value of –25.71 mkV/K with an increase in temperature to 515 K. With a further increase in temperature to 640 K, the Seebeck coefficient monotonically increases to a value of –19.60 mkV/K. At temperatures above 640 K, the Seebeck coefficient continuously decreases and at 824 K reaches a value of –24.12 mkV/K. The Curie point is 644 K. The obtained values of the Seebeck coefficient for nickel in the temperature range 300–800 K are comparable with the data given in the literature. When calculating the Seebeck coefficient of the material, equations are used using the Seebeck coefficient values for the positive and negative thermocouple paths, which eliminates the need for additional measuring probes and contacts to measure the thermoelectric voltage on the sample. The set-up can also be used to make electrical resistance measurements using the standard 4-point method.

Impact of an Aluminization Process on the Microstructure and Texture of Samples of Haynes 282 Nickel Alloy Produced Using the Direct Metal Laser Sintering (DMLS) Technique.

In this study, we examined the effects of an aluminization process on the microstructure and texture of Haynes 282 nickel samples fabricated using the direct metal laser sintering technique. The aluminization process involved the use of chemical vapor deposition with AlCl3 vapors in a hydrogen atmosphere at a temperature of 1040 °C for 8 h. Following the 3D printing and aluminization steps, we analyzed the microstructure of the Haynes 282 nickel alloy samples using light microscopy and scanning electron microscopy. Additionally, we investigated the texture using X-ray diffractometry. A texture analysis revealed that after the process of direct laser sintering of metals, the texture of the Haynes 282 nickel alloy samples developed a texture typical of cast materials. Then, in the aluminization process, the texture was transformed-from foundry-type components to a texture characteristic of recrystallization.

Recombination of oxygen atoms on the surface of oxidized polycrystalline nickel—temperature and pressure dependences

The recombination of neutral oxygen atoms in the ground state on the oxidized nickel samples was studied experimentally in the range of pressures where the maximum density occurs in weakly ionized low-pressure oxygen plasma, i.e. between 40 and 200 Pa. The recombination coefficient was determined in the flowing afterglow. The source of oxygen atoms was plasma sustained in a quartz tube of inner diameter 4.7 mm by a microwave discharge in the surfatron mode. The recombination coefficient was determined in the afterglow chamber, which was a Pyrex tube with an inner diameter of 36 mm. The density of oxygen atoms in the afterglow chamber was varied by adjusting the discharge power, the gas flow, the pressure, and the position of a recombinator. Such flexibility of the experimental system enabled adjustment of the temperature of the oxidized nickel samples independently from the O-atom density in its vicinity or other parameters. The density of oxygen atoms in the afterglow chamber at various system parameters was determined by the Šorli method, which is reliable, and has an accuracy of about 20%. The recombination coefficient was determined by calorimetry. The coefficient was inversely proportional to the square root of the pressure and exponentially to the sample temperature. Systematic measurements performed at various pressures and temperatures enabled empirical formula, which were explained qualitatively by recombination kinetics.