Zn Metal Powder Research Articles

Fabrication of solid-state symmetrical supercapacitor device based on constructed novel Gr-Cu-MoO2 disk electrodes based on Co-replacement reactions

The use of graphite-based substrates has attracted the attention of many researchers due to their high-performance capacitive behavior. Graphite Disk (GD) electrodes due to being more robust and capacity than graphite sheets can be used on an industrial scale. In this research, for the first time, by using the co-replacement method as a straightforward and without wasting energy method, MoO2 and Cu nanostructures with particular morphology were in-situ co-replaced on GD substrates based on commercial graphite and Zn-metal powder. The results of the scanning electron microscopy analysis clearly showed the MoO2–Cu nanosheet formed on the porous GD (PGC) electrode, which has caused a tremendous increase in the capacitance and cyclic stability due to the augment in the surface area and synergistic effect of MoO2–Cu nanostructure. Also, different characterization analysis results confirmed the co-replacement of MoO2 and Cu nanostructures onto the PGD electrode. Electrochemical investigation exhibited that this electrode has an extraordinary capacity of 28526 mF/cm2 at 2 mA/cm2 in 1M H2SO4. The investigation of the capacitive behavior of the MoO2–Cu/PGD supercapacitor device showed that the fabricated supercapacitor device has an astonished capacitance of 4916.98 mF/cm2 (145.27 F/g), power of 18017.34 mW/cm2, and energy density of 4154.84 mWh/cm2 at 1 mA/cm2.

Synthesis of nanocrystalline zinc powder: Investigating the influence of crystallite size and lattice strain on Debye-Waller factors

In this investigation, nano-sized zinc particles were synthesized through a ball milling process. The Zn metal powder, milled for durations ranging from 0 to 150 h, underwent analysis using X-ray diffraction (XRD). The study focused on determining PS (particle size) and assessing the influence of LS (lattice strain) on the DWFs (Debye–Waller factors), employing XRD principles. LSs were induced in zinc through varying milling durations, and X-ray diffractograms were captured at different stages of the milling process. The results revealed a reduction in PS and an increase in LS with prolonged milling, reaching a predominantly amorphous state at 150 h. By establishing the correlation between strain and effective DWF, the study estimated DWFs for zero strain in zinc.

Influence of zinc (Zn) powder on the microhardness characteristic and microstructure properties of stainless steel SS304 hybrid joint using low power microwave heating

AbstractMicrowave hybrid heating (MHH) process is a unique and novel approach of joint materials. Several lightweight materials (medium and high melting point) such as nickel, copper and aluminum have been successfully joined in the past research. However, small dimensions and low melting point of light weight materials such as zinc (Zn) metal or zinc (Zn) powder were always being a challenging mere for creating bond via any joining techniques. The sheets of stainless steel SS304 (17 mm×7.9 mm×0.2 mm) have been fabricated and joined at lap joint by using novel Microwave hybrid heating technique with mini heat chamber of 2.45 GHz of frequency and 200 W–360 W of microwave power, using pure zinc powder (99.9 %) as an interface material. Epoxy rate and exposure time have been varied from 10 % to 20 % and 2 min to 4 min, respectively. A developed heat chamber has been set in domestic microwave oven properly as proposed. To evaluate the microstructure correlation and microhardness at joint interface, the field emission scanning electron microscopy (FESEM – EDS), x‐ray diffraction (XRD) and Vickers hardness were used. For the experimental studies, it had found an excellent bonding was produced at interface layer between the upper and lower sections with good penetration rate of 360 W of microwave power, 4 min of exposure time and 20 % of epoxy rate as the 183.1 HV 0.05 of excellent microhardness and the intermetallic phase of iron‐zinc (FeZn11), nickel‐zinc (NiZn) and nickel‐zinc (NiZn3) were observed at interface layer.

Grain boundary diffusion efficiency of sintered Nd-Fe-B magnets by Al, Sn and Zn addition

The composition and structure of sintered Nd-Fe-B magnets influence the depth and efficiency of grain boundary diffusion. In this paper, the submicron Al, Sn, Zn metal powders are introduced in the precursor powder to improve the infiltration effect. The transformation temperature of the Nd-rich phase decreases from 471 °C for the standard alloy to 436 °C, 442 °C and 443 °C for Al, Sn and Zn elements addition, respectively. The addition of Al, Sn and Zn improves the microstructure and promotes the diffusion of Tb into the 2:14:1 phase. The addition of these low melting point elements effectively promotes the diffusion depth and the total amount of Tb element at the early stage of the diffusion. The intrinsic coercivity of Al-, Sn- and Zn-added magnets increased by 8.86 kOe, 9.70 kOe and 8.98 kOe, respectively. These results provide a basis for the preparation of high coercivity Nd-Fe-B magnets using less heavy rare earth elements.

Selective precipitation of ammonium hexachloropalladate from leaching solutions of cemented palladium with zinc

Palladium (Pd) present in spent electroplating solutions is concentrated by cementation with zinc (Zn) metal powder. Therefore, it is necessary to recover Pd from the cemented Pd. In this work, recovery of pure Pd(IV) compounds from the leaching solutions of the cemented Pd was investigated by using selective precipitation method. It was found that the existence of Pd(IV) in the aqueous solutions is critical for the precipitation with NH4Cl. Precipitation experiments of Pd(IV) from the synthetic aqua regia solution containing Pd(IV) and Zn(II) was tested. Afterwards, the optimum precipitation conditions were applied to recover Pd(IV) precipitates from the real H2SO4 and HCl leaching solutions containing NaClO as an oxidizing agent. The selective precipitation resulted in the recovery of extra pure (NH4)2PdCl6 from real leaching solutions under the conditions of 1:30 molar ratio of Pd(IV) to NH4Cl at 60oC within 30 min. The precipitation percentage of Pd(IV) from the H2SO4 and HCl solutions was over 99.9 and 98.2%, respectively. A simple hydrometallurgical process consisting of cementation, leaching, and precipitation was proposed for the recovery of pure Pd(IV) compounds from spent electroplating solution.

Recovery of Pure Pd(II) from Spent Electroplating Solutions by Solvent Extraction with Ionic Liquids from Sulfuric Acid Leaching Solution of Cemented Pd

Palladium (Pd) electroplating is widely practiced in the manufacture of advanced electronic devices. The Pd(II) present in spent electroplating solutions is treated by cementation with zinc (Zn) metal powder. In order to recover pure Pd from the cemented Pd, a process that consisted of leaching followed by solvent extraction was investigated. For this purpose, solvent extraction experiments using synthesized ionic liquids (ILs) with organic and inorganic anions were performed to find separation conditions at which selective extraction of Pd(II) over Zn(II) from synthetic H2SO4 leaching solutions is possible. The concentration of sulfuric acid was varied from 0.5 to 9 M. The complete separation of Pd(II) over Zn(II) by ILs such as ALi–CY301 (N-methyl-N,N,N-trioctylammonium bis(2,4,4-trimethylpentyl) dithiophosphinic), ALi–SCN (N-methyl-N,N,N-trioctylammonium thiocyanate), ALi–I (N-methyl-N,N,N-trioctylammonium iodide) and ALi–Br (N-methyl-N,N,N-trioctylammonium bromide) depends on H2SO4 concentration, while ALi–LIX63 (N-methyl-N,N,N-trioctylammonium 5,8-diethyl-7-hydroxydodecane-6-oxime) and ALi–LIX84 (N-methyl-N,N,N-trioctylammonium 2-hydroxy-5-nonylacetophenone oxime) can completely separate Pd(II) irrespective of H2SO4 concentration. Additionally, the mixture of HCl and thiourea, aqua regia solution, NH3 solution and the mixture of NH4Cl and NH3 are powerful stripping agents for Pd(II) from the loaded ALi–LIX63/ALi–LIX84, ALi–CY301, ALi–Br/ALi–I and ALi–SCN, respectively. However, application of the separation conditions to the real 5 M sulfuric acid leaching solutions of cemented Pd indicated that it was difficult to separate the two ions by extraction with ALi–LIX63 and ALi–LIX84. Use of NaClO as an oxidizing agent during the sulfuric acid leaching of real cemented Pd resulted in an enhancement of Zn(II) extraction by ALi–LIX63 and ALi–LIX84. Therefore, removal of chloride ions from the sulfuric acid leaching solutions is necessary to apply the separation conditions obtained from synthetic sulfuric acid leaching solutions.

Comparison of Thermoelectric Properties of ZnO and ZnSnO Thin Films Grown on Si Substrate by Thermal Evaporation

In this manuscript, we compared the thermoelectric properties of ZnO and ZnSnO thin films grown on silicon (100) substrate. We have evaporated Zn and Sn+Zn metal powders were evaporated in vacuum tube furnace alternatively, under same experimental conditions for the growth of ZnO and ZTO respectively. After the deposition, these grown films were cut into pieces and post growth annealed at different annealing temperatures from 600oC to 800oC in the air using programmable muffle furnace. Seebeck and Hall data suggested that ZTO sample shows highest value of Seebeck coefficient, electrical conductivity and power factor as compared to the ZnO samples. It is also observed that the value of Seebeck coefficient showing an increasing trend for both of the samples as we increase the post growth annealing temperature. The higher thermoelectric properties for ZTO are due the presence of Sn atoms in ZnO structure. Tin dopants may generate secondary phases and/or enhanced the carrier mobility which might be the reason that ZTO has improved thermo-electric properties as compared to ZnO. XRD and Raman measurements were used to confirm the formation of ZTO. XRD data verified the hexagonal structure of ZnO but a slight red shift is observed for the case of ZTO samples. To further justify our argument, we have also performed Raman spectroscopy measurements which confirmed the presence of Sn elements in ZTO.

The effect of ball milling on crystallite size

Homogeneous mixing of Al, varying amounts of Cu, Mg and Zn metal powders and SiC ceramic powders and mechanical alloys of metal powders by using high energy ball milling were carried out in the Retsch MM400 model mixer device, which performs movement in a spex manner. After this process, X-ray diffraction (XRD) was applied to the powdered mixtures. With the data obtained from XRD graphics; The crystallite size was calculated using the Scherrer equation, and the lattice stresses were calculated using the Williamson-Hall equation and comparisons between these two data were made. It was observed that the amount of Cu by weight, both the crystallite size, did not make a notable change for this property. Then, powder mixtures were sintered in hot isostatic press in argon atmosphere, which is a shielding gas, and turned into samples. These samples were polished and scanning electron microscopy (SEM) images were taken.

Study on Heating Profile of Liquid-mixing-synthesized ZnTiO3

The synthesis of monophasic ZnTiO3 powder has been reported as one of the challenges in material chemistry because under normal condition and as prepared by various synthesis methods, ZnTiO3 phase readily decomposes to Zn2TiO4 and TiO2 rutile phases. This is due to the temperature range of ZnTiO3 phase formation was very narrow, i.e. 600 - 800 °C; above that temperature, the decomposition of ZnTiO3 phase took place. This paper is intended to introduce a facile route, named liquid mixing method, to prepare ZnTiO3 powder from Zn and Ti metal powders as the raw materials and HCl as the solvent. Via this route, ZnTiO3 phase was formed at a temperature as low as 550 °C with particle size distributed homogeneously. The heating profile of ZnTiO3 phase from 440 to 900 °C was studied based on TG/DTA, XRD and FTIR data. However, when a ‘normal’ stoichiometric ratio of Zn: Ti = 1: 1 was applied, TiO2 rutile phase becomes dominant, while ZnTiO3 phase is only a secondary phase. This affects to the crystallinity of the ZnTiO3 phase. An effort to overcome the dominance of TiO2 phase was also demonstrated in this paper.

Microstructure and Mechanical Properties of Nanocrystalline Al-Zn-Mg-Cu Alloy Prepared by Mechanical Alloying and Spark Plasma Sintering.

In this study, Al, Zn, Mg and Cu elemental metal powders were chosen as the raw powders. The nanocrystalline Al-7Zn-2.5Mg-2.5Cu bulk alloy was prepared by mechanical alloying and spark plasma sintering. The effect of milling time on the morphology and crystal structure was investigated, as well as the microstructure and mechanical properties of the sintered samples. The results show that Zn, Mg and Cu alloy elements gradually dissolved in α-Al with the extension of ball milling time. The morphology of the ball-milled Al powder exhibited flaking, crushing and welding. When the ball milling time was 30 h, the powder particle size was 2–5 μm. The α-Al grain size was 23.2 nm. The lattice distortion was 0.156% causing by the solid solution of the metal atoms. The grain size of ball-milled powder grew during the spark plasma sintering process. The grain size of α-Al increased from 23.2 nm in the powder to 53.5 nm in the sintered sample during the sintering process after 30 h of ball milling. At the same time, the bulk alloy precipitated micron-sized Al2Cu and nano-sized MgZn2 in the α-Al crystal. With the extension of ball milling time, the compression strength, yield strength and Vickers hardness of spark plasma sintering (SPS) samples increased, while the engineering strain decreased. The compression strength, engineering strain and Vickers hardness of sintered samples prepared by 30 h milled powder were ~908 MPa, ~8.1% and ~235 HV, respectively. The high strength of the nanocrystalline Al-7Zn-2.5Mg-2.5Cu bulk alloy was attributed to fine-grained strengthening, dislocation strengthening and Orowan strengthening due to the precipitated second phase particles.

Synthesis of ZnO Nanocrystal–Graphene Composite by Mechanical Milling and Sonication-Assisted Exfoliation

A ZnO nanocrystal–graphene composite was synthesized by a two-step method involving mechanical milling and sonication-assisted exfoliation. Zn metal powder was first ball-milled with graphite powder for 30 h in water medium. This ball-milled mixture was then subjected to exfoliation by sonication in the presence of sodium lauryl sulfate surfactant to produce graphene decorated with spherical agglomerates of ultrafine nanocrystalline ZnO. The presence of a few layers of graphene was confirmed by Raman spectroscopy and atomic force microscopy measurements. The size, phase identity and composition of the ZnO nanocrystals was determined by transmission electron microscopy measurements.

Optimization of CVD parameters for long ZnO NWs grown on ITO/glass substrate

The optimization of chemical vapour deposition (CVD) parameters for long and vertically aligned (VA) ZnO nanowires (NWs) were investigated. Typical ZnO NWs as a single crystal grown on indium tin oxide (ITO)-coated glass substrate were successfully synthesized. First, the conducted side of ITO–glass substrate was coated with zinc acetate dihydrate to form seed layer of ZnO nanocrystals. Double zone tube furnace connected to vacuum pump was used for ZnO growth process. Zn metal powder was positioned at the first zone at temperature 900 ∘C. The ITO–glass substrate with pre-coated seed layer was then located in the second zone of tube furnace at growth temperature of 550 ∘C. The growth of ZnO NWs was controlled under constant concentration of seed layer, while other parameters such as argon and oxygen flow rates, substrate position, time and oxygen flow rate were varied. The VA ZnO NWs were finally characterized by scanning electron microscopy, X-ray diffractometer and high-resolution transmission electron microscope equipped with energy-dispersive X-ray spectroscopy. The results show that long and VA ZnO NWs were single crystalline with hexagonal wurtzite structure. The ultimate length and average diameter of ZnO NWs were 10 μm and 50–100 nm, respectively. These were achieved under optimized CVD growth parameters. The mechanism of vertical growth model of ZnO NWs is also discussed.

Fischer–Tropsch synthesis on cobalt-based catalysts with different thermally conductive additives

The effect of thermally conductive additive (Al, Cu or Zn metal powder) introduction to cobalt-based catalyst was investigated by testing in Fischer–Tropsch synthesis (FTS). Aluminum is the most promising metal for heat transfer intensification in catalytic bed since it forms an effective thermally conductive lattice, which improves the catalyst performance significantly. The introduction of copper or zinc to the catalyst composition does not result in heat transfer lattice formation; moreover, these metals demonstrate their own catalytic activity under FTS conditions. It is shown that catalyst pore volume is important: a substantial decrease in pore volume leads to formation of heat and mass transfer limitations in the catalyst pellet, which results in productivity and selectivity drop. The FTS product (C5+ hydrocarbons) composition depends on a metal used as a thermally conductive component and its catalytic activity.

ChemInform Abstract: Nickel‐Catalyzed Reductive Heck Type Coupling of Saturated Alkyl Halides with Acrylates and Oxabenzonorbornadiene.

The Heck reaction is a well-established transition-metal catalyzed reaction for coupling alkenes with sp2 alkyl halides to give novel unsaturated compounds. Herein we report an analogous Heck-inspired, simple efficient coupling of sp3 alkyl halides with electron-withdrawing alkenes to form reductive coupling products where saturated esters are obtained. A range of acrylates were coupled with sp3 alkyl halides in the presence of Ni(PPh3)2Cl2 catalyst, Zn metal powder, CH3CN solvent, and water, at 80 °C to form the reductive Heck type saturated ester products in good yields. This strategy was further extended to couple oxabenzonorbornadiene with the alkyl halides resulting in ring opening to give rise to bicyclic alcohol products. The mechanism for both the reactions appears to be the usual oxidative-addition driven alkene insertion reaction where the water appears to act as the protonating agent.

Highly selective and sensitive xylene sensors using Ni-doped branched ZnO nanowire networks

Branched ZnO nanowires (NWs) doped with Ni were grown by a three-step vapor phase method for the sensitive and selective detection of p-xylene. ZnO NWs were directly grown on sensor substrates with Au electrodes, which were transformed into NiO NWs by the thermal evaporation of NiCl2 powder at 700°C. ZnO branches doped with Ni were grown from NiO NWs by the thermal evaporation of Zn metal powder at 500°C. The stem NiO NWs played the role of catalyst for the growth of ZnO branches through vapor–liquid–solid mechanism. The Ni-doped branched ZnO NWs showed enhanced gas response (S=resistance ratio) to methyl benzenes, especially to 5ppm p-xylene (S=42.44) at 400°C. This value is 1.7 and 2.5 times higher than the responses to 5ppm toluene (S=25.73) and C2H5OH (S=16.72), respectively, and significantly higher than the cross-responses to other interfering gases such as benzene, HCHO, trimethylamine, H2, and CO. The selective detection of xylene was attributed to the catalytic role of the Ni component. This novel method to form catalyst-doped hierarchical ZnO NWs provides a promising approach to accomplish superior gas sensing characteristics by the synergetic combination of enhanced chemiresistive variation due to the increased number of branch-to-branch Schottky barrier contacts and the catalytic function of the Ni dopant.

Nickel-catalyzed reductive Heck type coupling of saturated alkyl halides with acrylates and oxabenzonorbornadiene

The Heck reaction is a well-established transition-metal catalyzed reaction for coupling alkenes with sp2 alkyl halides to give novel unsaturated compounds. Herein we report an analogous Heck-inspired, simple efficient coupling of sp3 alkyl halides with electron-withdrawing alkenes to form reductive coupling products where saturated esters are obtained. A range of acrylates were coupled with sp3 alkyl halides in the presence of Ni(PPh3)2Cl2 catalyst, Zn metal powder, CH3CN solvent, and water, at 80 °C to form the reductive Heck type saturated ester products in good yields. This strategy was further extended to couple oxabenzonorbornadiene with the alkyl halides resulting in ring opening to give rise to bicyclic alcohol products. The mechanism for both the reactions appears to be the usual oxidative-addition driven alkene insertion reaction where the water appears to act as the protonating agent.

Co-doped branched ZnO nanowires for ultraselective and sensitive detection of xylene.

Co-doped branched ZnO nanowires were prepared by multistep vapor-phase reactions for the ultraselective and sensitive detection of p-xylene. Highly crystalline ZnO NWs were transformed into CoO NWs by thermal evaporation of CoCl2 powder at 700 °C. The Co-doped ZnO branches were grown subsequently by thermal evaporation of Zn metal powder at 500 °C using CoO NWs as catalyst. The response (resistance ratio) of the Co-doped branched ZnO NW network sensor to 5 ppm p-xylene at 400 °C was 19.55, which was significantly higher than those to 5 ppm toluene, C2H5OH, and other interference gases. The sensitive and selective detection of p-xylene, particularly distinguishing among benzene, toluene, and xylene with lower cross-responses to C2H5OH, can be attributed to the tuned catalytic activity of Co components, which induces preferential dissociation of p-xylene into more active species, as well as the increase of chemiresistive variation due to the abundant formation of Schottky barriers between the branches.

Hydrothermal Synthesis of ZnO/Zn Composites with Enhanced Photocatalytic Performance

ZnO/Zn composites photocatalysts were prepared by hydrothermal method using Zn powder as raw material, and the morphology, structure, and photocatalytic performance of composites were investigated. The results showed that the ZnO nanoparticles were produced at the surface of Zn metal powder during hydrothermal process. The thickness of ZnO outer layer (internal metal-semiconductor interfaces) can be controlled by varying hydrothermal treatment time. The resulting ZnO/Zn composites exhibit significantly higher photocatalytic activity than that of pure ZnO for degradation of anthraquinone dye (reactive brilliant blue KN-R) aqueous solution under ultraviolet light irradiation. The enhancement of photocatalytic performance of ZnO/Zn composites can be attributed to the formation of internal metal-semiconductor interfaces. The designed fabrication procedure is simple, feasible, and universal for a series of oxide/metal with controlled microstructure and improved performances.

Processes observed in high-energy systems comprising nanodimensional metal powders

Results of experimental investigations of structural changes in nanodimensional Al, Ti, Zn, Fe, Cu, and Ni metal powder agglomerates in the process of manufacturing solid-fuel systems are presented. Regular processes of metal powder interaction with polymer solutions during mixing and oxidation in the regime of programmable linear heating are described.

Electrochemical denitrification of metal-finishing wastewater: Influence of operational parameters

Experimental results are presented for the electrolytic ChemDen (Chemical-Denitrification) process which was designed to investigate the effect of operational parameters on the nitrate (NO 3 − ) removal from metal-finishing wastewater. The parameters included electrode materials, electrode gap, reducing agent, hydraulic retention time (HRT) and recycle ratio in the single electrolytic ChemDen reactor for lab-scale tests. The removal efficiency of nitrate is based upon a non-biological process which consists of chemical and electrolytic treatment. Results showed that removal efficiency of nitrate was highest when the zinc (Zn) electrodes were used for both anode and cathode. In the case of insoluble electrode, combining Pt anode with Ti cathode provided great improvement of nitrate removal. For the Pt-Ti electrode combination, increasing electrode gap tended to increase removal efficiency of nitrate significantly. However, no further increase in the nitrate removal was observed when the electrode gap was longer than 10mm. Using sulfamic acid and Zn metal powder as reducing agents for the electrolytic ChemDen reaction, highest nitrate removal was achieved when the mole ratio of Zn: sulfamic acid: nitrate was 1.2: 1: 1. Remarkable improvement in the nitrate removal was also observed with increasing HRT from 10 to 30 min, while the effectiveness was limited when HRT was increased to 60 min. Recycling in electrolytic ChemDen reactor affected nitrate removal positively because it could improve both dispersion and reuse of Zn metal powder as reducing agent in the reactor. Recycling effects were thought to be associated with increasing surface reactivity of the Zn metal powder in the electrolytic ChemDen reactor.