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Cation-Exchange-Derived InGaP Alloy Quantum Dots toward Blue Emissivity
摘要： In contrast to a substantial progress of heavy metal-free green and red emitters exclusively from indium phosphide (InP) quantum dots (QDs), the development of non-Cd blue QDs remains nearly unexplored. Synthesis of blue InP QDs with a bright, deep-blue emissivity is not likely viable, which is primarily associated with their intrinsic size limitation. To surmount this challenge, herein, the first synthesis of blue-emissive ternary InGaP QDs through In3+-to-Ga3+ cation exchange strategy is implemented. Pre-grown InP QDs turn out to be efficiently Ga-alloyed at a relatively low temperature of 280oC in the presence of Ga iodide (GaI3) and degree of Ga alloying is also found to be systematically adjustable by varying GaI3 amount. Such cation-exchanged InGaP cores are surface-passivated sequentially with ZnSeS inner and ZnS outer shell. As the amount of GaI3 added for cation exchange increases, the resulting double-shelled InGaP/ZnSeS/ZnS QDs produce consistent blue-shifts in photoluminescence (PL) from 475 to 465 nm, while maintaining high PL quantum yield in the range of 80?82%. Among a series of QD samples above 465 nm-emitting InGaP/ZnSeS/ZnS QDs are further employed as an emitting layer of all-solution-processed electroluminescent device. This unprecedented InGaP QD-based blue device generates maximum values of 1038 cd/m2 in luminance and 2.5% in external quantum efficiency.
关键词： InGaP alloy quantum dots,electroluminescent device,blue emissivity,cation exchange
更新于2025-09-19 17:13:59
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Microstructure and properties of 24CrNiMoY alloy steel prepared by direct laser deposited under different preheating temperatures
摘要： The direct laser deposition (DLD) process, evolution mechanism between preheating temperature and structure are visually described in this graph. Fig. 1(a) displays the DLD process design for preheating the substrate, the main heat transfer method is heat conduction. Fig. 1(b) shows the formation mechanism of the pores in the DLD process, it can be seen that the pores in the sample mainly underwent three processes of formation, floating, and growth. Fig. 1(c) exhibits the evolution mechanism between the bainite structure and preheating temperature of 24CrNiMoY alloy steel, it can be deduced the microstructure of the sample changes from lath bainite (LB) to granular bainite (GB) with the rise of preheating temperature. The proper preheating temperature of 200℃ can effectively eliminate the crack, decrease the pores and significantly improve the structure and properties of the DLD 24CrNiMoY alloy steel.
关键词： Preheating,24CrNiMoY alloy steel,Bainite,Direct Laser Deposited,Mechanical properties
更新于2025-09-19 17:13:59
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Gold Nanobipyramid Enveloped in Alloyed Nanoshell for Stable Plasmonic Sensors
摘要： Compared to monometallic nanoparticles, alloyed and bimetallic nanostructures are of great interest for their high stability and improved physicochemical properties. In this work, an effective method has been developed to obtain core-shell nanorods, in which the core is uniform gold nanobipyramids (AuBPs) enveloped in AuxAg1-x alloyed nanoshell. The penta-twinned AuBP@AuxAg1-x nanorods with x ranging from 0 to 1 integrate the advantages of AuBPs core and AuAg alloy shell effectively. Specifically, they combine the superiority of Au and Ag, exhibiting excellent both thermal and chemical stability, high refractive index sensitivity, and stable surface-enhanced Raman scattering (SERS) effect in harsh environment. Furthermore, the surface plasmon resonance of AuBP@AuxAg1-xNRs could be finely tailored in a large wavelength region with a narrow full width at half maximum (FWHM) by simply varying the alloy shell thickness and the AuBPs core size. These improved properties offer the obtained core-shell nanostructures novel and viable perspectives in severe environments. The simple and feasible synthetic strategy is also versatile to fabricate other noble metallic nanostructures enveloped in alloyed nanoshell.
关键词： sensitivity,alloy nanoshell,gold nanobipyramids,stability,optical property
更新于2025-09-19 17:13:59
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Formation Mechanism of Dilute Region and Microstructure Evolution in Laser Solid Forming TA15/Ti2AlNb Dual Alloy
摘要： TA15/Ti2AlNb multiple-layer samples and a dual-alloy sample were fabricated by laser solid forming (LSF) in this study. The formation mechanism of the dilute region and microstructure evolution of the dual alloy were analyzed. The results con?rmed a “step” distribution of the composition among several initial layers in the multiple-layer samples, which can be explained by calculating the ratio of the remelted zone to the deposited Ti2AlNb zone in each deposited layer. However, the “step” compositional distribution disappears, and the compositional variation tends to be more continuous and smooth in the TA15/Ti2AlNb dual-alloy sample, which is attributed to alloy elements’ di?usion at the subsequent multiple re-melting and the longer thermal cycle. The macrostructure of the TA15/Ti2AlNb dual-alloy sample consists of epitaxially grown columnar prior β grains at the TA15 side and equiaxed grains at the Ti2AlNb side, while the microstructure shows a transition of α+β→α+α2 +B2+O with increasing amounts of Ti2AlNb, leading to the microhardness also changing signi?cantly.
关键词： dilute region,microstructure evolution,laser solid forming,TA15/Ti2AlNb dual alloy
更新于2025-09-19 17:13:59
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A Review on Energy Band‐Gap Engineering for Perovskite Photovoltaics
摘要： Metal halide perovskites are attractive for highly efficient solar cells. As most perovskites suffer large or indirect bandgap compared with the ideal bandgap range for single-junction solar cells, bandgap engineering has received tremendous attention in terms of tailoring perovskite band structure, which plays a key role in light harvesting and conversion. In this Review, various reported bandgap engineering strategies are summarized. The recently widely used two main strategies including impurity and pressure as well as their underlying mechanisms are reviewed comprehensively. In addition, intermediate band and external electric field for bandgap engineering are also investigated. Moreover, future research directions are outlined to guide the further investigation.
关键词： band-gap engineering,pressure,photovoltaics,impurity alloy,perovskites
更新于2025-09-19 17:13:59
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Fiber laser spot welding of molybdenum alloy in a hyperbaric environment
摘要： The e?ect of the growth of ambient pressures on the penetration of laser welded molybdenum (Mo) alloy was explored. It was found that when ambient pressure rose from 0.1 MPa to 1.8 MPa, the penetration of base metal (BM) was signi?cantly reduced, which was only 17% of that obtained under ambient pressure of 0.1 MPa. Moreover, the mechanism underlying the signi?cant reduction of the penetration of BM was analyzed. At ?rst, by using a high-resolution scanning electron microscope (SEM), the size and the number of nano-sized metallic particles generated during laser welding under di?erent ambient pressures were surveyed. Furthermore, the scattering and absorption of the nano-sized metallic particles for laser energy under di?erent ambient pressures were investigated; afterwards, by applying a high-speed camera and a spectrometer, the transient behaviors and spectral signals of plasmas during ?ber laser spot welding under di?erent ambient pressures were monitored. On this basis, the inverse bremsstrahlung absorption of plasmas for laser energy under di?erent ambient pressures was explored; ?nally, ?ber laser spot welding test was carried out on glass/metal composite samples under di?erent ambient pressures to survey the in?uence of the change of ambient pressure on dynamic behaviors of the molten pool during the welding.
关键词： penetration,nano-sized metallic particles,molybdenum alloy,spot welding,fiber laser,hyperbaric environment,plasmas,molten pool
更新于2025-09-19 17:13:59
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Characterization of laser beam offset welding of titanium to steel with 38Zn-61Cu alloy filler
摘要： Laser welding of TC4 Titanium (Ti) alloy to 304 austenitic stainless steel (SS) has been applied using 38Zn-61Cu alloy as filler metal. A new welding process for SS-Ti alloy joint was introduced on the basis of the controlling the formation of Ti-Fe intermetallics in the joint. One pass welding involving creation of a joint with one fusion weld and one diffusion weld separated by remaining unmelted Ti alloy. When laser beam on the Ti alloy side was 1.5 mm, Ti alloy would not be completely melted in joint. Through heat conduction of unmelted Ti alloy, the atomic diffusion occurred at the SS-Ti alloy interface. A diffusion weld was formed at the SS-Ti alloy interface with the main microstructure of β-CuZn + Fe3Zn7, β-CuZn and Ti2Zn3 + Ti3Cu4. The joint fractured at the diffusion weld with the maximum tensile strength of 128 MPa.
关键词： Diffusion welding,Microstructure,TC4 Ti alloy,Filler metal,304 austenitic stainless steel,Laser welding
更新于2025-09-19 17:13:59
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[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Observation of keyhole and melt pool dynamics in laser welding of Al alloy by x-ray phase-contrast method
摘要： Aluminum alloy is a lightweight material frequently used for automotives parts, batteries, airplanes, etc. to reduce greenhouse gas emissions. A highly efficient and stable laser welding method has long been sought for Al alloy because of its poor weldability due to its high heat conductivity and high reflectivity of 1 μm wavelength laser light. Because welding phenomena and defect formation mechanism are still not properly understood due to their complexity, this research aims to investigate the laser welding phenomena of Al alloy. To understand the weld pool and keyhole dynamics during welding, the weld pool was observed with a high-speed camera and X-ray phase-contrast method. The keyhole behavior and solid-liquid interface during laser welding for A1050 can be observed more clearly than in X-ray absorption-contrast method. At a lower welding speed (0.5 m/min), frequent intensive keyhole expansion and high porosity could be observed. Although high porosity could be observed at a higher welding speed (1 m/min), keyhole expansion was barely observed. It is thought that at a low welding speed, intensive evaporation at keyhole bottom leads to unstable keyhole behavior due to high heat input, and as a result, high porosity is formed due to be intake of air into the keyhole. The effect of fan usage was evaluated. In the case without a fan, intensive keyhole expansion was observed frequently. It is supposed that the laser partly interacted with plume, which led to a sudden evaporation due to laser scattering. It was observed that a bubble from the keyhole bottom moved around the keyhole at a high speed, and the bubble was trapped at a solid-liquid interface. Then the bubble grew by absorbing other small bubbles in a melt pool. In all welding conditions, frequent small expansion at the keyhole bottom was observed. Therefore, the porosity formation mechanism is assumed to have a strong relationship with expansion of keyhole bottom, where major porosity was formed.
关键词： X-ray phase-contrast method,porosity formation,Aluminum alloy,laser welding,weld pool dynamics,keyhole dynamics
更新于2025-09-19 17:13:59
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Phosphorous Catalytic‐Doping of Silicon Alloys for the Use in Silicon Heterojunction Solar Cells
摘要： Herein, the effectiveness of post-deposition catalytic-doping (cat-doping) on various doped silicon alloys, i.e., microcrystalline silicon (μc-Si:H), nanocrystalline silicon oxide (nc-SiOx:H), and microcrystalline silicon carbide (μc-SiC:H), for the use in silicon heterojunction solar cells is investigated. Phosphorous (P) pro?les by secondary ion mass spectrometry (SIMS) reveal the P distribution and its difference in these three silicon alloy ?lms. Conductivity and effective charge carrier lifetime of different samples are found to increase to different extents after cat-doping process. Coexistence of thermal annealing, hydrogenation, and phosphorus doping is con?rmed by using different gases during the cat-doping process.
关键词： silicon alloy,post-depositions,silicon heterojunction solar cells,hot-wire chemical vapor depositions,catalytic chemical vapor deposition
更新于2025-09-19 17:13:59
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Low-temperature chemical vapor deposition growth of graphene films enabled by ultrathin alloy catalysts
摘要： This report introduces a method for fabricating graphene at low temperatures via chemical vapor deposition enabled by ultrathin (～1 nm) nickel-gold (Ni-Au) catalysts. The unique combination of high carbon (C) solubility Ni, low C solubility Au, and an ultrathin layer of a catalyst demonstrates the effectiveness to produce graphene at 450 °C with the layer number independent of growth duration. In contrast to grain-boundary defined catalyst morphology found in thicker (>20 nm) metal catalysts, the ultrathin catalyst morphology leads to the formation of nanoscale metal “islands” during the growth process, which results in curved graphene covering the catalyst. To test the effect of preactivation of the ultrathin catalyst for the formation of graphene, a preanneal process of the catalyst followed by the introduction of a carbon precursor was also investigated. The preanneal process resulted in the formation of carbon nanotubes (CNTs) in lieu of graphene, displaying the impact of the catalytic surface treatment in relation to the produced materials. The results and discussion presented here detail a low-temperature nanoscale manufacturing process that allows for the production of either graphene or CNTs on an ultrathin catalyst.
关键词： graphene,low-temperature growth,nickel-gold catalysts,chemical vapor deposition,ultrathin alloy catalysts
更新于2025-09-19 17:13:59