Dendritic Particles Research Articles

Optimizing methane plasma pyrolysis for instant hydrogen and high-quality carbon production

The European Green Deal has set a target for Europe to achieve net-zero greenhouse gas emissions by 2050, necessitating a transition to more sustainable energy sources. Hydrogen gas (H2) has emerged as a promising solution, with methane pyrolysis presenting a viable method for its production. This study explores the optimization of methane plasma pyrolysis for hydrogen and high-quality carbon production. Employing a statistical approach by a design of experiment software, critical process parameters are systematically analyzed to predict their impact within a defined range. Additionally, the paper conducts comprehensive characterization of the solid carbon produced during pyrolysis using imaging, spectroscopic and elemental analysis, and gas sorption analysis methods. The experimental investigation was conducted using a thermal plasma reactor with several settings of influential parameters including methane gas (CH4) content in the plasma gas, electric current, and arc length. The DC-transferred plasma arc is formed using a variable gas mixture of argon gas (Ar) and CH4, with a constant flow rate of 5 Nl/min. Thirteen tests were designed, evaluating responses such as power input, process stability, and H2 yield. The H2 yield indicates the hydrogen produced from CH4, with 100% representing total conversion. While the process exhibited inconstancy, attributed to reactor design constraints, a high H2 yield of 67%–100% was achieved. The results indicate that a higher CH4 content in the plasma gas and extended arc lengths disturb the plasma arc, hence reducing the H2 yield. Increased power input, achieved through higher amperage levels, and a wider reaction zone eased by extending the arc length both led to an improved H2 yield. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) revealed microstructural differences, with carbon samples from the filter exhibiting finer textures and carbon samples from the reactor larger sizes and dendritic particles. Raman spectroscopy confirmed crystalline graphitic-like structures with low defect concentrations, a finding supported by X-ray diffraction (XRD) analysis. Inductively coupled plasma mass spectroscopy (ICP-MS) analysis confirmed high-purity carbon with slight impurities from initial filter contamination. Brunauer-Emmett-Teller (BET) specific surface area calculations based on gas sorption analysis showed significant variations, with filter-collected samples exhibiting 40–170 m2/g and reactor-collected ones showing 7–30 m2/g.

The first microwave and submillimetre closure study using particle models of oriented ice hydrometeors to simulate polarimetric measurements of ice clouds

Abstract. The first closure study involving passive microwave and submillimetre measurements of ice clouds with the consideration of oriented particles is presented, using a unique combination of polarised observations from the ISMAR spectral-like radiometer, two radars with frequencies of 35 and 95 GHz, and a variety of in situ instruments. Of particular interest to this study are the large V–H polarised brightness temperature differences measured from ISMAR above a thick frontal ice cloud. Previous studies combining radar and passive submillimetre measurements have not considered polarisation differences. Moreover, they have assumed particle habits a priori. We aim to test whether the large V–H measurements can be simulated successfully by using an atmospheric model consistent with in situ microphysics. An atmospheric model is constructed using information from the in situ measurements, such as the ice water content, the particle size distribution, and the mass and shape of particles, as well as background information obtained from dropsonde profiles. Columnar and dendritic aggregate particle models are generated specifically for this case, and their scattering properties are calculated using the independent monomer approximation under the assumption of horizontal orientation. The scattering properties are used to perform polarised radiative transfer simulations using ARTS to test whether we can successfully simulate the measured large V–H differences. Radar measurements are used to extrapolate the 1-D microphysical profile to derive a time series of particle size distributions which are used to simulate ISMAR brightness temperatures. These simulations are compared to the observations. It is found that particle models that are consistent with in situ microphysics observations are capable of reproducing the brightness temperature depression and polarisation signature measured from ISMAR at the dual-polarised channel of 243 GHz. However, it was required that a proportion of the particles were changed in order to increase the V–H polarised brightness temperature differences. Thus, we incorporated millimetre-sized dendritic crystals, as these particles were observed in the probe imagery. At the second dual-polarised channel of 664 GHz, the brightness temperature depressions were generally simulated at the correct locations; however, the simulated V–H was too large. This work shows that multi-frequency polarisation information could be used to infer realistic particle shapes, orientations, and representations of the split between single crystals and aggregates within the cloud.

Multidimensional poly (vinyl alcohol) particles for the construction of thermal conductive filler networks

Loading filler onto the polymer particle with specific morphology is an effective way to construct filler networks. Here, non-solvent-induced phase separation and vacuum-assisted filtration are used to prepare polymer particles and Al2O3@Polymer composite films. The content and variation of Al2O3 loading are obtained by thermogravimetric analysis after ultrasonication treatment to films, showing that dendritic particles can be stably loaded with considerable filler compared to lamellae and tiny particles owing to the large specific surface area and “wrapped” structure. On the other hand, adding a good solvent during the blending process enhances the filler loading and network constructing capabilities by softening and changing the particle morphology. However, the excessive good solvent decreases filler loading due to the vanishment of microstructure, meaning a balance between dissolution and softening. Finally, Al2O3@PVA/epoxy composites based on dendritic particles are prepared whose thermal conductivity can reach 0.37 W/(m·K) (37.76 wt% Al2O3), 1.7 times higher than pure epoxy.

High-Speed Thermo-Compression Sinter-Bonding Properties in Air of a Paste Containing Dendritic Cu Particles Having Oxalate Skins

To enhance the sinter-bonding speed of Cu dendrite particle-based paste, the particles were surface-treated with oxalic acid solution. This treatment transitioned the particle surface from an oxide layer to a CuC 2 O 4 phase, which suppressed the oxidation of Cu until thermal decomposition between 284-315 °C generating Cu nanoparticles. Using the surface-treated Cu dendrite particle-based paste, sinter bonding at 320 °C under 5 MPa pressure in air provided a sufficient shear strength of 23.4 MPa in just 60 s, reaching the maximum of 28.7 MPa after 180 s. The in situ generated Cu nanoparticles from the thermal decomposition of CuC<sub>2</sub>O<sub>4</sub> directly contributed to the very rapid sintering-bonding behavior at 320 °C. However, the bondings at 300 °C and 350 °C showed poorer bonding characteristics than that of before treatment, indicating that the surface treatment strategy for forming CuC<sub>2</sub>O4 skins is effectively implemented by appropriately setting the following sinter-bonding temperature.

Effect of Ti/Nb content on microstructure evolution and wear properties of in-situ (Ti,Nb)C reinforced composite coatings by plasma spray welding

Due to their superior wear resistance, multi-particle reinforced composite coatings have caught the interest of numerous researchers. In this research, a method of preparing composite coatings containing in-situ (Ti,Nb)C particles was proposed using plasma spray welding with a mixture of Fe-based alloy, pure Ti, and pure Nb powders. The research involved a detailed analysis of the nucleation mechanism, particle shape and strengthening behavior of (Ti,Nb)C particles in the composite coatings with different atomic ratio of Ti/Nb. The microstructure and phase were examined, and the wear resistance was tested and examined. The phase analysis results manifested that the composite coatings had primarily (Ti,Nb)C reinforcing phase and α-Fe matrix. The (Ti,Nb)C particles were not added in the raw powders, but in-situ generated via the reactions between the powders. The microstructure analysis results indicated that the reinforced particles transformed from irregular dendritic particles into lumpy and spherical particles, and then into an interspersed distribution of laths and spheres as the atomic ratio of Ti/Nb decreased. The microhardness value of these composite coatings when the Ti/Nb ratios were different were 550 HV–650 HV, while the microhardness value of the steel was 174 HV. However, with the increase of Ti/Nb atomic ratio, the change of wear resistance showed the trend: increase → decrease → increase. In-situ (Ti,Nb)C particles were uniformly distributed in the coatings and beneficial to improving the wear resistance. When Ti/Nb ratio is 1:1, the mass loss of the composite coating was only 0.6 mg, which was a quarter of the steel substrate (2.4 mg).

Behaviour of RC Beam Using Concrete Mixed With Magnetically Treated Water

The most important challenge for concrete construction is to improve the performance of concrete. In the last two decades, in Russia and China, a new technology, called magnetic water technology, has been used in making concrete. As per this technology, by passing water through a magnetic field, some of its physical properties tend to change and, as a result of such changes, the number of molecules in the water cluster decreases from 13 to 5 or 6, which cause a decrease in the surface tension of water, with an improvement in the workability and strength of concrete. Magnetic treatment of water increases the ion solubility and pH. The influence of magnetic flux changes the mode of calcium carbonate precipitation such that circular disc-shaped particles are formed rather than the dendritic (branching or tree like) particles observed in non-treated water. This technique is mostly used for the softening of water and, for the first time in this research, it has been adopted by the scientists for the production of concrete with improved strength. Some researchers hypothesize that magnetic treatment affects the nature of hydrogen bonds between water molecules which increases the pH and softens the water.

Tribological property of dendritic fibrous nano silica composite particle as lubricant additive

In this study, a novel Dendritic Fibrous Nano Silica (DFNS) solid-liquid composite lubricant additive (DFNS@ILs) was prepared by the simple of bi-continuous microemulsion polymerization and vacuum impregnation adsorption ionic liquids (ILs) method. The microstructure and chemical composition were characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The oil lubrication properties of the DFNS@ILs were investigated and the results showed that the DFNS@ILs additive had the most excellent tribological properties when compared to the pure PAO6 oil, commercially available ZDDP and nano-silica. Moreover, DFNS@ILs have long-term stability as lubricant additives. Based on the analysis of the wear surfaces, it is concluded that the excellent performance of DFNS@ILs additive are owing to the synergistic lubrication effect of DFNS and ILs as well as the formation of transfer film, which makes it a promising lubricant material.

Oxygen exchange kinetics of mixed conducting oxide ceramics covered by dendritic surface particles

The oxygen exchange process between the gas phase and a mixed conducting solid oxide was simulated by application of finite element modeling (FEM). The solid oxide was covered by inert surface particles of different shape and size. The effect of spherical, ellipsoidal, rectangular, and dendritic surface particles on the oxygen exchange kinetics was elaborated in detail. Relaxation curves for the total amount of exchanged oxygen upon an instantaneous change of the oxygen activity (partial pressure) of the surrounding atmosphere were calculated. One-dimensional analytical solutions of the diffusion equations were fitted to the numerically calculated relaxation curves, yielding apparent chemical diffusivities and surface exchange coefficients. The FEM simulations of the oxygen exchange process were carried out as a function of surface coverage for the various particle types. The apparent surface exchange coefficient decreased with increasing surface coverage. In case of small spherical and ellipsoidal particles with a fairly small extension of the shorter axis (large aspect ratio) the surface exchange coefficient decreased almost linearly with increasing surface coverage caused by the reduction of the active (uncovered) surface area. An additional decrease of the surface exchange coefficient (non-linear variation with surface coverage) was observed with respect to dendritic particles. This peculiar behavior could be interpreted in terms of flux constriction effects, i.e. lateral diffusion processes underneath the inert surface particles. The surface area blocked for the exchange reaction seems to be significantly larger than the cross-section of the dendritic surface particles.

Surface modification for improving interfacial, mechanical and thermal performance characteristics in epoxy composites: Electroless nickel enhancement of dendritic copper particle-reinforced epoxy

While studies on the incorporation of metal particles into the epoxy matrix are quite common, this research introduces a novel approach by incorporating electroless Ni-coated Cu particles with functional features into the epoxy matrix. Thus, it presents an innovative investigation of epoxy composites with enhanced both thermal and mechanical properties. Therefore, three samples of pure epoxy, dendritic Cu particle reinforced (20 wt%), and electroless Ni-coated dendritic Cu particle reinforced (20 wt%) epoxy composites were fabricated by mixing followed by casting into the mold. The epoxy and composite specimens underwent phase analysis through XRD, and morphological examinations were conducted using SEM equipped with an EDS analyzer, respectively. The hardness, tensile, and bending tests were conducted for mechanical characterization. To evaluate the thermal properties, DSC and TGA tests were employed to assess the impact of the Cu and the electroless Ni-coated Cu particles on the thermal stability of the composites. The mechanical analysis results showed that the pure epoxy sample had tensile and flexural strengths of 23.2 MPa and 43 MPa, respectively. These values increased significantly by 90 % and 311 % in the presence of Ni-coated dendritic Cu particles, reaching 54 MPa and 177 MPa, respectively. Thermal analysis results indicated that the Tg increased with the incorporation of dendritic Cu particles and Ni-coated dendritic Cu particles. Furthermore, the highest thermal conductivity was observed in the Cu-reinforced composites.

A novel strategy to prepare high performance multifunctional composite films by combining electrostatic assembly, crosslinking, topology enhancement and sintering.

Currently, polymer-fiber composite films face the challenge of striking a balance between good mechanical properties and multi-functionalities. Here, aramid fibers (ANFs), chitosan (CS) dendritic particles, and silver nanowires (AgNWs) were used to create high-performance multifunctional composite films. AgNWs and polymer dendritic particles form an interpenetrating segregated network that ensures both a continuous conductive filler and a polymer network. Electrostatic assembly eliminates repulsion between negatively charged ANFs, cross-linked CS particles generate a stable three-dimensional network, and a "brick-mortar" structure composed of multiple materials contributes to topological enhancement. Sintering encourages local overlap and fusing of the AgNWs while reducing their internal flaws. Based on the above strategy, these films achieve a strength of 306.5 MPa, a toughness of 26.5 MJ m-3, and a conductivity of 392 S cm-1. Density functional theory (DFT) and Comsol simulations demonstrate that the introduction of CS thin layers leads to strong hydrogen bonds and three-dimensional continuous conductive networks. With its outstanding mechanical and electrical properties, the AgNW@ANF/CS-CH film demonstrates excellent electromagnetic shielding (22 879.1 dB cm2 g-1) and Joule heating (70 °C within 10 s) capabilities. This work presents a novel approach to fabricate high-performance conductive films and expand their potential applications in lightweight wearable electronics and electrothermal therapy.

Origin of surface-bonded oxygen on dendritic Ag particles towards 3D-nanocrystalline carbon formation during CO2 electrochemical reduction reaction

Formation of nanocrystalline carbon allotropes under the electrocatalytic reduction reaction of CO2 (CO2RR) on the dendritic Ag electrocatalysts was investigated at the applied potential −1.6 V vs. Ag/AgCl under the electrolyte system containing [BMIM]+[BF4]-, propylene carbonate, and water. The surface Ag − O bonds play an important role in developing the N+ stabilized highly energetic negatively charged Ag nanoclusters on which the nanocrystalline solid carbon was formed. Herein, the surface-bonded oxygen on dendritic Ag particles was originated from (i) the ultrathin natural silver oxide layers (unmodified Ag), (ii) anodization treatment (AD), and (iii) cyclic voltammetry treatments at a scan rate 1 (CV1) or 200 mV/s (CV200) for 5 cycles. Their capability to catalyze CO2RR towards solid carbon products depends on the stabilization of the active state of negatively charged nascent Ag nanoclusters under [BMIM]+[BF4]-. Even though each catalytic system yielded a major crystalline solid carbon product, a slight shift towards gaseous CO formation was noted in the case of AD compared to the unmodified Ag, CV200, and CV1, respectively. The increased intricacy in the three-dimensional structure of dendritic Ag particles following CV1 post-treatment, coupled with a stronger Ag − O bond could hinder agglomeration of anion Ag clusters. The crystalline solid carbon films containing sp2 − sp3 hybridization were grown on the facets of Ag nanocrystals as the building blocks and were matched with graphite and Diamond-C structures. The discoveries have significance in propelling the progress of electrocatalysts containing oxides, aiming to attain enhanced yields of higher value nanocrystalline carbon products through CO2RR.

Effect and mechanism of inorganic anions on the adsorption of Cd2+ on two-dimensional copper-based metal–organic framework

Metal-organic frameworks exhibit strong adsorption performance for Cd2+ in wastewater due to their multi-level pores and easily modified structure. In this paper, a copper based metal–organic framework: [Cu·(HL)·(DMF)]n (1) (H3L = 5-hydroxy isophthalic acid; DMF = N,N-dimethylformamide), was synthesized by hydrothermal synthesis method. The structural analysis shows that each Cu(II) in 1 is coordinated with four carboxylate O atoms from HL2− and one O atom from DMF. The two carboxylate groups in HL2− take μ2-η1:η1 to bridge two Cu(II) ions formed a two-dimensional structure. The scanning electron microscope (SEM) analysis shows that the nanomaterials prepared by the crushing method have dendritic structures and particle diameters of approximately 100 nm. The experimental results of the nano adsorbent adsorbing Cd2+ show that at an isoelectric point pH = 6, the optimal adsorbent concentration is 0.20 g/L. The maximum adsorption capacity at this time is 75.22 mg/g, which is superior to most MOFs adsorbents. At this optimal adsorbent concentration, as the solution pH increases, the adsorption capacity of the adsorbent for Cd2+ significantly increases. The thermodynamic analysis results of adsorption show that the △G < 0 and △H < 0 of the adsorbent in the range of 20–40 ℃, indicating that the adsorption of Cd2+ by the adsorbent is a spontaneous and exothermic process. The inorganic anions Cl−, HCO3−, NO3−, SO42− inhibit the adsorption of Cd2+ by nano adsorbent at a pH of 6. However, at low pH values (4, 5), it promotes the adsorption of Cd2+. This is mainly because the presence of inorganic anions changes the form of Cd2+ in solution, affecting the adsorption of it by the adsorbent.

Synergistic effect of silanols in mesopores leading to unexpected catalysis of dendritic mesoporous silica particles in the aqueous-phase synthesis of 5-hydroxymethylfurfural from fructose

Synthesis of 5-hydroxymethylfurfural (5-HMF) from fructose in water over acids catalysts usually produces unsatisfactorily low yield and selectivity due to inevitable side reactions, i.e., rehydration and condensation. Unprecedentedly, these complications in the aqueous phase synthesis of 5-HMF could be overcome by dendritic mesoporous silica particles (DMSNs). In the hydrothermal reactions of fructose, it was discovered that the synergy of silanols and mesopores transformed seemingly inert DMSNs into active catalysts, leading to a fructose conversion and 5-HMF yield of over 90%. The silanols on DMSNs offered weak Brønsted acid sites for catalyzing the dehydration of fructose to 5-HMF, while undesired reactions were substantially prohibited. The presence of glucose in the reaction suggests that fructose converts to 5-HMF via the acyclic route, and the competing reaction is indeed the isomerization. As revealed experimentally, mesopores full of silanols promoted the conversion of fructose to 5-HMF, but mesopores with a few silanols were relatively hydrophobic, offering a preferential partitioning of 5-HMF in mesopores of DMSNs. DFT analysis theoretically supported that in the presence of silanols, transforming fructose to 5-HMF is thermodynamically more favorable than the isomerization of fructose to glucose.

Influences of size, shape and strain rate on mechanical properties of single coral particle

To understand the roles of particle size, shape, and strain rate on their mechanical properties, the crushing behavior of 800 coral particles with different shape factors and size groups (i.e., 2.36–4.75 mm, 4.75–9.5 mm and 9.5–16 mm) at various loading rates (i.e., 0.06 mm/min, 0.6 mm/min, 3 mm/min and 10 mm/min) are studied. The results show that the particle crushing strength and Young's modulus perfectly conform to the Weibull statistic law. Particle crushing strength decreases with an exponent of (−0.816) of particle size and increases with an exponent of 0.062 of strain rate, and a mathematical model incorporating particle size, shape, and strain rate is proposed to explain the change of characteristic crushing strength. Additionally, irregularity, elongation, and flatness strongly relate to the crushing strength and Young's modulus, and establish a functional relationship with the geometric similarity parameter of the Weibull model. The fragmentation behavior is classified into three typical modes, and the change of fragmentation modes is affected by particle size, strain rate, and irregularity. Young's modulus calculated by Hertz theory is 0.7–0.9 GPa. The characteristic Young's modulus is in descending order of rodlike, flaky, blocky, and dendritic particles, hardly influenced by particle size and strain rate. The results can provide a reference for the microscopic numerical analysis of coral concrete.

Synergistic effects of Mo and in-situ TiC on the microstructure and wear resistance of AlCoCrFeNi high entropy alloy fabricated by laser cladding

The AlCoCrFeNi high entropy alloy coatings reinforced by the high melting point element Mo and in-situ TiC were fabricated by using laser cladding. The BCC phase existed in all the coatings. When Mo and in-situ TiC were doped individually, the existence of the σ phase and dendritic TiC particles were detected, respectively. However, on simultaneous doping of Mo and in-situ TiC, no σ phase was observed, and flower-like TiC particles were detected. In addition, the simultaneous doping of Mo and in-situ TiC resulted in a wear resistance of 3.14 and 2.6 times greater than that in case of individual doping of Mo and in-situ TiC, respectively, indicating the manifestation of a synergistic effect in improving wear resistance.

EFFECT OF PARTICLE SHAPE AND SIZE OF COPPER POWDERS ON THE PROPERTIES OF SINTERED PARTS

The particle shape and size of the starting powders represent the most important physical properties, on which the quality of the compacts and final sintered products depends. Two types of powder were analyzed in the paper - electrolytic copper powder with a dendritic particle shape and water-atomized copper powder with an irregular particle shape. The starting powders were sieved through a sieve system with openings of 45 μm, 80 μm, and 120 μm. The characterization of the obtained fractions of both powders was performed by determining the shape and dimensions of the particles using SEM microscopy in combination with ImageJ software, and the apparent density and flow rate were determined using the Hall flowmeter funnel. Pressing of each powder fraction was done using a pressure of 600 MPa. The compacts were further sintered at 1000°C for 2 hours to obtain the final sintered parts. After sintering, their density, hardness, and electrical conductivity were determined and their microstructure was analyzed. The results indicate a great influence of the characteristics of the starting powders on the properties of the final parts obtained by the powder metallurgy route. The particle shape of the powders had a more pronounced influence compared to the particle size.

In situ characterization of particle structures generated at different flow velocities on a single fiber in the gas phase

For the design of a gas-cleaning filter, the morphology of particle deposits on filter fibers is of significant interest. In this study, particle structures were generated with polydisperse particulate material and mainly deposited by diffusion or by interception and inertia. The structures were characterized in situ with structures generated by monodisperse material known from literature. A quantitative comparison showed that the particle structures of polydisperse material are comparable to those of monodisperse material. It was demonstrated that only an in situ investigation provided artifact-free results for very dendritic particle structures of Carbon Black. At a Péclet number of Pe = 1.67⋅104, the dendrites are arranged uniformly around the fiber at an angle of 90° and folded down in the direction of the gravity field after the inflow was turned off. The particle structures of Carbon Black at higher Péclet numbers (2.6·105-1·106) are less dendritic and showed no visual change when the flow was switched off. However, they were not stable enough to be removed and further examined by laser scanning microscopy in addition to in situ observation. Only the particle structures made of glass spheres are stable enough and could be removed for further investigation.

Enhancing vertical thermal conductivity of carbon fiber reinforced polymer composites using cauliflower-shaped copper particles

Carbon fiber reinforced polymer (CFRP) composites are lightweight and mechanically robust, and therefore have received considerable attention with a wide range of applications from the aerospace to automotive industries. However, their low vertical thermal conductivity seriously limits the potential applicability of high-performance CFRPs in metal replacement. Herein, we propose a simple and effective, scalable strategy to fabricate thermally conductive and mechanically robust CFRP composites on the basis of formation of vertical heat transfer pathways using pressure-assisted thermal migration of cauliflower-shaped dendritic copper particles. A new type of CFRP composite was achieved by facile layer-by-layer coating of prepregs with dendritic coppers and subsequent pressure-assisted thermal processing under elevated temperature. The cauliflower-shaped dendritic copper particles efficiently infiltrated into the CFRP matrix and thereby provided an effective heat transfer pathway, resulting in a CFRP composite with an excellent vertical thermal conductivity of 2.321 W m−1 K−1, which is 155% higher than that of pristine CFRP. Moreover, the proposed CFRP composite afforded a high thermal diffusivity of 1.125 × 10−6 m2 s−1 and a low specific heat capacity of 1.267 J g−1 K−1, as well as an excellent flexural strength of about 2.4 GPa.

Interfacial microstructure and strength of magnetic pulse welded A5052 aluminum alloy/SPCC steel lap joint

A5052 aluminum alloy and SPCC steel plates were welded using magnetic pulse welding, and interfacial microstructure and strength of the lap joint were examined. The A5052 aluminum alloy and the SPCC steel plates were used for a flyer plate and a parent plate, respectively. Charging energy stored in capacitor and gap between the A5052 aluminum alloy and the SPCC steel plates were changed. Microstructure was examined by using an optical microscope, a scanning electron microscope and a scanning transmission electron microscope. Tensile-shear test was used for evaluating the strength of the joint. The magnetic pulse welding of A5052 aluminum alloy and SPCC steel was achieved at the charging energy above 6.0 kJ and at the gap between the plates above 1.0 mm. The range of charging energy in which the strong welding is accomplished was different at each gap and the range increased with decreasing the gap. The lap joint was not fractured at the welding interface by the tensile-shear test whereas the fracture occurred at a part of the aluminum base metal. The welding interface exhibited characteristic wavy morphology. An intermediate layer was produced along the wavy interface. Scanning transmission electron microscope observation revealed that the intermediate layer is composed of fine Al-Mg grains and dispersed dendritic Al-Fe intermetallic compound particles.

Preparation of Spherical Ultrafine Silver Particles Using Y-Type Microjet Reactor.

Herein, micron-sized silver particles were prepared using the chemical reduction method by employing a Y-type microjet reactor, silver nitrate as the precursor, ascorbic acid as the reducing agent, and gelatin as the dispersion at room temperature (23 °C ± 2°C). Using a microjet reactor, the two reaction solutions collide and combine outside the reactor, thereby avoiding microchannel obstruction issues and facilitating a quicker and more convenient synthesis process. This study examined the effect of the jet flow rate and dispersion addition on the morphology and size of silver powder particles. Based on the results of this study, spherical and dendritic silver particles with a rough surface can be prepared by adjusting the flow rate of the reaction solution and gelatin concentration. The microjet flow rate of 75 mL/min and the injected gelatin amount of 1% of the silver nitrate mass produced spherical ultrafine silver particles with a size of 4.84 μm and a tap density of 5.22 g/cm3.