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Determination of dopamine using the indium tin oxide electrode modified with direct electrodeposition of gold–platinum nanoparticles
摘要： Gold–platinum (Au–Pt) nanoparticles (NPs) with a ratio of 3:1 solution of chloride salts in the starting electrolyte were deposited on an indium tin oxide (ITO) surface, using a direct electrochemical method, by 40 successive cyclic voltammetry (CV) scans to obtain AuPtNPs/ITO electrode. The deposited nanoparticles were defined by energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) and electrochemical methods. The nanoparticles size of electrodeposited was ~ 30 nm based on SEM results. The efficacy of number of CV scans in the electrodeposition of nanoparticles on the size of electrodeposited nanoparticles was tested. The elemental composition of AuPtNPs/ITO electrode was determined by EDX. Electrochemical studies proved that the electrocatalytic activity of prepared electrode is excellent towards the oxidation of dopamine (DP). The concentration range of DP from 400 nM to 350 μM was linear and limit of detection DP was 20 nM. It was shown that the AuPtNPs/ITO electrode can be used as a sensor with high reproducibility, sensitivity, and long term stability. The selectivity of electrode for determination of DP was verified with investigating the effect of substances by potential interference on the response of electrode. AuPtNPs/ITO electrode was used for the determination of DP in injection and real samples, with acceptable results.
关键词： Dopamine,Gold–platinum alloy,Nanoparticles,Indium tin oxide electrode
更新于2025-09-19 17:15:36
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Influence of Heat Treatments on Microstructure and Mechanical Properties of Ti–26Nb Alloy Elaborated In Situ by Laser Additive Manufacturing with Ti and Nb Mixed Powder
摘要： In the present work, a Ti–26Nb alloy was elaborated in situ by laser additive manufacturing (LAM) with Ti and Nb mixed powders. The alloys were annealed at temperatures ranging from 650 °C to 925 °C, and the effects of the annealing temperature on the microstructure and mechanical properties were investigated. It has been found that the microstructure of the as-deposited alloy obtained in the present conditions is characterized by columnar prior β grains with a relatively strong <001> fiber texture in the build direction. The as-deposited alloy exhibits extremely high strength, and its ultimate tensile strength and yield strength are about 799 MPa and 768 MPa, respectively. The annealing temperature has significant effects on the microstructure and mechanical properties of the alloys. Annealing treatment can promote the dissolution of unmelted Nb particles and eliminate the micro-segregation of Nb at the elliptical-shaped grain boundaries, while increasing the grain size of the alloy. With an increase in annealing temperature, the strength of the alloy decreases but the ductility increases. The alloy annealed at 850 °C exhibits a balance of strength and ductility.
关键词： microstructure,Ti–Nb alloy,mechanical properties,in situ alloying,laser additive manufacturing,heat treatment
更新于2025-09-19 17:15:36
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PVP-Mediated Galvanic Replacement Synthesis of Smart Elliptic Cu-Ag Nanoflakes for Electrically Conductive Pastes
摘要： Elliptic Cu-Ag nanoflakes were syntheszied via a facile in-situ galvanic replacement between prepared Cu particles and Ag ions. The alloy nanoflakes with high purity and uniformity present a size of 700 × 500 nm, with a thinness of 30 nm. Nontoxic and low-cost polyvinyl pyrrolidone was used as dispersant and structure-directing agent, promoting the formation of the remarkable structure. The synthesized nanoflakes were utilized as a filler for conductive paste in an epoxy resin matrix. Conductive patterns on flexible substrates with a resistivity of 3.75 × 10-5 Ω·cm could be achieved after curing at 150°C for 2 h. Compared with traditional silver microflakes, the smart alloy nanoflakes provide much improved conductive interconnection, whose advantage could be attributed to their nanoscale thicknesses. It is also noteworthy that the conductive patterns are able to tolerate multiple bending at different angles, having good conductivity even after 200 repeated bendings. Therefore, the alloy nanoflakes could be a promising candidate conductive filler for flexible printing electronics, electronic packaging and other conductive applications.
关键词： Cu-Ag,Elliptic,Conductive paste,Structure-directing,Alloy nanoflakes
更新于2025-09-19 17:15:36
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Microstructural characterization and tensile behavior of Nd:YAG laser beam welded thin high strength low alloy steel sheets
摘要： Laser beam welding (LBW) has many advantages to join high strength low alloy (HSLA) steels compared with conventional fusion welding processes. The present work is focused on joining HSLA plates of 2 mm thickness efficiently through the application of Nd:YAG laser source. Only one process variable i.e. the welding speed was operated between 70 mm/s to 120 mm/s while the rest of the variables were maintained constant. The microstructure evolution of the fusion zone was recorded through optical, scanning and transmission electron microscopy. The fusion zone was observed to be wider but no major defects were present. Fusion zone experienced a change in morphology of ferrite and pearlite depending upon the rate of cooling and exposure time. Fusion zone showcased various ferrites such as acicular ferrite, widmanstatten ferrite, and grain boundary ferrite. Advancement in the welding speed helped in the formation of acicular ferrite. EBSD results presented a descending tendency of prior austenite grain size against increasing welding speed. TEM micrographs affirmed the ferrite transformation and showed the presence of dense dislocations. The changes in hardness and tensile behavior under the experimental conditions were further reported.
关键词： High strength low alloy steel,Microstructure,Tensile strength,Laser beam welding
更新于2025-09-19 17:13:59
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Pore space characteristics and corresponding effect on tensile properties of Inconel 625 fabricated via laser powder bed fusion
摘要： In this work, the tensile behavior of Inconel 625 parts fabricated via laser powder bed fusion (LPBF) at different laser power levels is examined, and correlated to bulk porosity as well as pore characteristics such as pore size, aspect ratio morphology, and polar orientation extracted from X-ray computed tomography (CT). Scanning electron microscopy (SEM) is employed to identify the fracture mode and origin of failure in the pulled samples. Microstructural examination on the as-built samples showed that increasing the laser power resulted in the transition of melting mode, from lack of fusion to keyhole, with an increase in part bulk density from 98.86% to 99.29%, respectively. It was found that the general bulk porosity level does not correlate directly with the Ultimate Tensile Strength (ranging between 780–820 MPa) and strain to fracture (ranging between 0.2–0.39) behavior of the parts. Detailed pore space characteristics obtained from CT datasets before and after the tensile test contributed to establishing a relationship between defects size, morphology, orientation and tensile properties of the samples. In general, it was found that strain to failure is directly influenced by pore space characteristics, while tensile strength is influenced by a combination of pore space and microstructural characteristics. This study also identified that there are systematic bias effects in the LPBF process, likely introduced by the combination of nuisance variables such as powder layer spreading and gas flow.
关键词： Inconel 625 alloy,Pore space characteristics,Laser powder bed fusion,Tensile behavior,X-ray computed tomography
更新于2025-09-19 17:13:59
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Synergistic Effect of Plasma and Laser Processes in Liquid for Alloyed-Nanoparticle Synthesis
摘要： Cu-Ag-alloy nanoparticles (NPs) are synthesized from micropowders of pure Cu and Ag by two consecutive nonequilibrium processes based on plasma and lasers in liquids. The plasma process reduces the size of the particles forming the initial powders from micrometer size to nanometer size, at which the laser fluence is sufficient to melt them, making alloying possible. Measurements at macroscopic (solution absorption), microscopic (scattering of individual NPs), and nanoscopic (electron microscopy) scales confirm alloying of NPs and homogenization of size and composition. This has a noticeable effect on the final colloidal solution, which absorbs yellow-orange light (550–600 nm) after laser treatment. With a synthesis rate of 360 mg/h, this process opens up possibilities for nonequilibrium nanometallurgy of functional NPs.
关键词： plasma process,Cu-Ag-alloy nanoparticles,laser process,nonequilibrium nanometallurgy,functional NPs
更新于2025-09-19 17:13:59
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Microstructure and microhardness of a novel TiZrAlV alloy by laser gas nitriding at different laser powers
摘要： The Ti–20Zr–6.5Al–4V (T20Z, wt%) alloy surface was treated by the process of laser surface nitriding. The evolution of microstructures and microhardness has been investigated by changing the laser power parameter from 120 to 240 W. All laser-treated T20Z samples show two regions with distinctly different microstructural features, as compared with the untreated substrate: dense TiN dendrites and (a ? b) - Ti (remelting zone, RMZ), nanoscale a laths doped with part of b phase (heat-affected zone, HAZ). The formation of TiN dendrites can be analyzed by a series of complex reactions during the process of melting and solidi?cation. The increase in laser power results in the increase in content of TiN dendrite which is mainly due to the increase in energy input. In HAZ, the self-quenching effect leads to the formation of nanoscale a laths and the residue of b phase. Microhardness pro?le of different regions was measured from the surface to the interior, and the highest microhardness was obtained (* HV 916.8) in the RMZ, as the laser power was set to 240 W. In the present study, we explained various microstructural characteristics induced by laser surface nitriding treatment.
关键词： TiZrAlV alloy,TiN dendrites,Microstructure,Laser surface nitriding,Microhardness
更新于2025-09-19 17:13:59
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Research on Laser-TIG Hybrid Welding of 6061-T6 Aluminum Alloys Joint and Post Heat Treatment
摘要： The 6061-T6 aluminum (Al) alloys was joined by the laser induced tungsten inert gas (TIG) hybrid welding technique. It mainly studied the influences of welding parameters, solution, and aging (STA) treatment on the microstructure and tensile properties of Al alloy hybrid welding joints. Microstructures of the joints were also analyzed by optical microscopy and transmission electron microscopy. Results showed that the laser induced arc hybrid welding source changed the microstructure of the fusion zone and heat effect zone. STA treatment effectively improved the mechanical properties of the softening area in the hybrid welding joint, whose values of the tensile strength and elongation were on average 286 MPa and 20.5%. The distribution of the reinforcement phases and dislocations distributed were more uniform, which improved the property of STA treated joint.
关键词： Al alloy,laser induced arc hybrid welding,microstructure,heat treatment
更新于2025-09-19 17:13:59
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Influence of Magnesium on Spatter Behavior in Laser Deep Penetration Welding of Aluminum Alloys
摘要： The quality of welds, as well as the necessity of post-processing, is challenged by spatter generation during the laser keyhole welding process. In this study, the influence of the magnesium content on spatter behavior is studied for three aluminum alloys (Al99.5, AlMg3, and AlMg5). A synchronized dual high-speed camera system is used to observe the spatter behavior and to reconstruct 3D spatter trajectories as well as determine the characteristics of spatter velocity, flight path angle, and approximate spatter size. The mean spatter velocities and flight path angles of the welding experiments with the three alloys were in welding direction between 4.1 m/s and 4.6 m/s and 44.8°, respectively. Furthermore, the AlMg alloys show excessive spatter behavior with spray events of more than 50 spatters at a time, and less frequently spatter explosions. Spatter spray events show a character similar to spatter explosions. Volumetric evaporation is proposed as effecting these events. In contrast, and resulting from a different mechanism, pure aluminum (Al99.5) shows group ejection events with at least 10 spatters at a time. In this study, there are no correlations between spatter velocities and flight path angles, nor between velocities and approximate spatter sizes.
关键词： high-speed imaging,keyhole welding,aluminum alloy,welding,laser welding,spatter
更新于2025-09-19 17:13:59
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Influence of Post-Weld Processing Techniques on Laser Beam-Welded Ala??3Mga??0.25Sc Alloy Sheets
摘要： Fusion welding in aluminium alloys had always remained an issue for aero- and auto industries. An Al–3Mg–0.25Sc alloy is classi?ed as weldable aluminium alloys. In this study, two welding techniques, keyhole and conduction welding, have been used for joining Al–3Mg–0.25Sc sheets of thickness 1.6 mm. Experiments were carried out using different beam diameter (0.16–2 mm dia), beam power (2–4.5 kW) and laser head speed (ranging from 0.5 to 6 m/min). The results for all autogenous keyhole welding clearly demonstrated a drop in ductility (\ 0.8%) compared to base metal for all beam power and welding speed combinations although the yield strength was reasonably good (175–180 MPa, i.e. [ 50% of base metal). Residual stress-induced distortions affected the ?nal shape of the product, and for that, a suitable stress relief annealing was also required. Hereby, we chose two heat treatment schedules: (1) solution treatment and annealing and (2) retrogression and re-ageing. Retrogression and re-ageing is a precipitation-controlled phenomenon and comprises of an intermediate annealing step between tempering and solutionizing temperature to dissolve the nano-clusters present in the matrix (retrogression) and re-precipitating and growing them by ageing (re-ageing). These two steps were repeated cyclically, and as a result, the strength (190 MPa) and ductility (* 9%) of the material were improved substantially. The improvement of ductility and strength was explained in detail in the light of microstructural studies.
关键词： Strength,Post weld treatment,Weldment,Al-3Mg-0.25Sc alloy,Ductility,Laser welding
更新于2025-09-19 17:13:59