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Laser welding characteristics of Ti-Pb dissimilar couples and element diffusion in the molten pool
摘要： Laser welding lead metal to titanium or titanium alloy, which is a typical dissimilar welding process, have a great challenge. Couples of Ti-Pb, Ti6Al4V-Pb were welded by a 3kW continuous wave Nd:YAG laser. The influences of process parameters such as laser power and laser beam offset on welding depth were investigated. Microstructure, element distribution and micro-hardness of the welds were tested. The element diffusion characteristics during laser welding of Ti-Pb couple and Ti6Al4V-Pb couple were studied based on the experiments data. Experimental results show laser beam offset is a primary factor for welding titanium alloy and lead metal, and laser power plays a critical role for welding pure titanium and lead metal. A chemical potential calculation model of Ti-Pb-Al ternary alloy was established. The calculation results show that chemical potential of Ti element increases with enhancing Pb content in Ti-Pb-Al ternary system, however, the chemical potential of Ti element decreases with increasing Pb content in Ti-Pb binary system. According to the calculation results, for Ti-Pb-Al ternary system, because of the Al element in the molten pool, the Ti element tends to diffuse into the Al element, and the diffusion driving force of Ti element to the Pb element is weak. Compared with the Ti-Pb binary system and the Ti-Pb-Al ternary system, it is more likely to form a mixed fusion weld for the binary system, and the mass transfer interface phenomenon is more serious for the ternary system, which is consistent with EDS line scan and microhardness testing results.
关键词： Chemical potential,Interface,Microstructure,Lead metal,Titanium alloy,Laser dissimilar welding
更新于2025-11-21 11:18:25
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Origin of anisotropy and compositional dependence of phonon and electron transport in ZnO based natural superlattices and role of atomic layer interfaces
摘要： Reaction of ZnO with trivalent ions can form natural superlattice (SL) compounds, which possess unusual structural characteristics and strong anisotropic physical transport properties. In this work, by synthesizing strongly textured bulk polycrystals of pure SL phases and performing characterization and measurements for both in-plane and cross-sectional directions, we revealed the strongly crystal orientation dependent transport properties. The observed compositional or SL interface spacing dependent electrical conductivity is largely attributed to the overall doping of ZnO wurtzite regions. The atomic layer SL interfaces are phonon barriers, and the interfacial thermal (Kapitza) resistance depends on SL interface spacing. The transport direction perpendicular to these SL interfaces are electron-conductive paths with remarkably higher electron mobility. There are electron potential barriers associated with these atomic layer SL interfaces. The effective and absolute potential barrier heights are determined, which are proportional to the natural conduction band discontinuities. The current study provides new findings and knowledge about the role of SL interfaces in phonon and electron transport process in these ZnO based natural SLs. The present work can be useful and inspiring to design and modify complex layer-structured compounds, including synthetic superlattice systems, for a variety of applications where energy carriers transport is involved.
关键词： Interfaces,Superlattices,Electron potential barrier,Interfacial thermal (Kapitza) resistance,Thermal conductivity,ZnO
更新于2025-11-21 11:03:13
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Effect of concentration of DH6T on the performance of photoconductor fabricated using blends of P3HT and DH6T
摘要： The influence of small molecule (SM) α, ω-di-hexyl-sexithiophene (DH6T) concentration, in the blends of conjugated polymer (CP) poly (3-hexylthiophene) (P3HT) and DH6T, was investigated in terms of barrier potential reduction and improved photoresponse of the fabricated photoconductor using these blends. Barrier potential in Au/P3HT:DH6T/Au device structure, occurring at the interface of Au (top)/P3HT:DH6Twas estimated by Fowler Nordheim (FN) tunneling model-based analysis of I-V characteristics. The barrier potential of the fabricated device was observed to decrease upon addition of a small quantity of DH6T in comparison to the pristine polymer-based device. This reduction in barrier was attributed to the improved ordering and morphology of the polymer chains upon blending it with an SM. The variation in the ordering of the polymer chains was further confirmed with Photoluminescence spectroscopy, Absorption spectroscopy, and XRD data. Subsequently, it was also observed that only up to a definite SM concentration (25% in this study) ordering of polymer chains improved causing a reduction in barrier potential and subsequent improvement in the photoresponse of the fabricated devices. Finally, it was observed that the optimized blending of CP and SM could to be useful in reducing the effect of penetration of Au inside the CP matrix in the top contact configuration thereby resulting in the reduction of a barrier for carrier injection which is generally lower in the bottom contact configurations. These studies are critical from the point of view of the development of photoconductors and photosensitive top contact organic field effect transistors (OFETs).
关键词： Barrier potential,Small molecule,Photoconductor,Conjugated polymer
更新于2025-11-19 16:56:35
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The characteristics of Cu(In, Ga)Se2 thin-film solar cells by bandgap grading
摘要： The performance of CIGSe-1 and CIGSe-2 absorber layers are compared with Eg grading such that a higher Ga content is incorporated into the back region. A wider depth range of the high-Ga region near the back of a CIGSe absorber layer can reduce its performance due to the increased formation of Ga-related defects and defect clusters. Therefore, for an Eg-graded CIGSe layer with a wider Eg on the back surface, appropriate Eg grading can improve its performance.
关键词： CIGSe,bandgap grading,defect,surface potential,solar cell
更新于2025-11-14 17:28:48
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Silver Nanoparticles - Fabrication, Characterization and Applications || Synthesis and Optical Properties of Highly Stabilized Peptide- Coated Silver Nanoparticles
摘要： The interaction between the silver nanoparticle and peptide surfaces has been of increased interest for the applications of bionanotechnology and tissue engineering. In order to completely understand such interactions, we have examined the optical properties of peptide-coated silver nanoparticles. However, the effect of peptide binding motif upon the silver nanoparticles surface characteristics and physicochemical properties of these nanoparticles remains incompletely understood. Here, we have fabricated sodium citrate stabilized silver nanoparticles and coated with peptide IVD (ID3). The optical properties of these peptide-capped nanomaterials were characterized by UV-visible, transmission electron microscopy (TEM), and z-potential measurement. The results indicate that the interface of silver nanoparticles (AgNP)-peptide is generated using ID3 peptide and sug-gested that the reactivity of peptide is governed by the conformation of the bound pep-tide on the silver nanoparticle surface. The interactions of peptide-nanoparticle would potentially be used to fabricate specific functionality into the various peptide-capped nanomaterials and antibacterial applications.
关键词： Z-potential,silver nanoparticles,peptide,physicochemical properties
更新于2025-11-14 17:04:02
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Preliminary analysis on thermodynamic and thermo-economic performance of a solar CPC-KCS hybrid system
摘要： Using solar collectors to actuate Kalina cycle system (KCS) for electricity generation has been an attractive way to take advantage of solar energy. Most of the existing research is about KCS integrated with flat plate collector, evacuated tube collector, or concentrating collectors; however, little research focuses on the KCS powered by compound parabolic concentrator (CPC). Considering the merits of CPC, a Kalina 11 cycle system which is directly powered by CPC, named as solar CPC–KCS hybrid system is studied as the research object. Energy, exergy and thermo-economic models are established to estimate the system performance by varying the solar radiation, evaporating temperature and concentration of working fluid. Results show that higher evaporating temperature improves thermal and exergy efficiency. There are optimal values of Te for maximum wnet, is, Te,opt = 422.15, 434.15, and 446.15 K, respectively, at Xr = 0.95, 0.93, and 0.91; while Te,opt = 443.15, 437.15, and 425.15 K at Xb = 0.8, 0.7, and 0.6. Higher Xr and lower Xb is generally favorable for system performance. But when Te ≥ 422.15 K, lower Xb is not beneficial to ηex improvement anymore. Additionally, once evaporating temperature exceeds 439.15 K, it is cost-effective to install a superheater to avoid erosion potential risk.
关键词： Kalina cycle,corrosion potential,thermo-economic analysis,compound parabolic concentrator
更新于2025-09-23 15:23:52
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Theoretical elaboration about the excited state dynamical behaviors for a novel fluorescent sensor
摘要： Using the density functional theory (DFT) and time‐dependent density functional theory (TDDFT) methods, we theoretically explore a novel fluorescent sensor molecule (abbreviated as “2”) (Sensors Actuat B‐Chem. 2018, 263, 585). Because of its symmetry, three stable structures can be located, ie, 2‐enol, 2‐SPT, and 2‐DPT forms in both S0 and S1 states. Via comparing the bond lengths and bond angles involved in the hydrogen bonding moieties, we find the dual intramolecular hydrogen bonds should be strengthened in the S1 state. And based on infrared (IR) vibrational simulations, we further confirm the strengthening dual hydrogen bonds. Upon the photo‐excitation process, the charge redistribution via frontier molecular orbitals (MOs) reveals the tendency of excited state intramolecular proton transfer (ESIPT) reaction. In addition, the constructed S0‐state and S1‐state potential energy curves demonstrate that the excited state single proton transfer (ESSPT) should be the most supported one from 2‐enol to 2‐SPT form. In view of the S1‐state stable 2‐SPT and 2‐DPT structures as well as the fluorescence peaks of them, we can further confirm the ESSPT mechanism for 2 chemosensor. This work not only clarifies the excited state behaviors of 2 system but also successfully explain the previous experimental phenomenon.
关键词： charge redistribution,ESIPT,potential energy curves,intramolecular hydrogen bond
更新于2025-09-23 15:23:52
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Energy/exergy based-evaluation of heating/cooling potential of PV/T and earth-air heat exchanger integration into a solar greenhouse
摘要： Through the present paper, a solar greenhouse integrated with an Earth-Air Heat Exchanger (EAHE) and Photovoltaic/Thermal collectors (PV/Ts) was theoretically studied in terms of energy and exergy and validated against an experimental study presented in literature i.e. a solar greenhouse with floor area, buried pipe length and PV area of 24m2, 39m and 9.68m2, respectively. The comparisons showed a fairly good agreement between the theoretical and experimental results with a relatively high coefficient of correlation around 95%. Afterwards, the given solar greenhouse was optimized in terms of energy and exergy efficiencies while the results indicated that only length of EAHE pipes showed an optimum value equal to 38m on average. Moreover, the results showed that PV/Ts did not have a significant heating potential for raising the greenhouse air and plant temperatures and only the electricity generation potential of PVs was favorable. However, the EAHE integration seemed promising in raising and lowering the temperatures of greenhouse air by 9°C and 8°C in summer and winter, respectively. Moreover, the Temperature Load Leveling (TLL) due to integration of only EAHE was achieved 46% and 58% in summer and winter, respectively.
关键词： Greenhouse,Heating potential,PV/T,Earth-air heat exchanger
更新于2025-09-23 15:23:52
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First principles study of electronic structures of Cd0.9375Co0.0625X (X?=?S, Se, Te) for magnetic, optical and thermoelectric device applications
摘要： The present article investigates the structural and electronic properties of Co doped (xCo = 6.25%) CdS/Se/Te diluted magnetic semiconductors to understand the optical and thermoelectric characteristics. The electronic properties, computed by applying generalized gradient approximation (GGA) and then modified Becke Johnson (mBJ) functional, are contrasted to identify the appropriate electronic parameters. The stable ferromagnetic states have been justified to arise due to the p-d hybridization that has been found responsible in inducing magnetic moments at the interstitial and at the non-magnetic sites. The computed direct band gap and the exchange constants (N0α and N0β) have suggested, respectively, the potential optical and spintronic device applications. The studied compounds operate within visible-ultraviolet energy range. The thermoelectric response improves with temperature, while deteriorated due to Co doping. The studied compounds exhibiting various significant physical properties evidence the potential consumption in various technologically important spintronic, optoelectronic and thermoelectric devices.
关键词： Optical properties,Ferromagnetism,Diluted magnetic semiconductors,Thermoelectric properties,mBJ potential
更新于2025-09-23 15:23:52
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Nanostars on Nanopipettes: A Raman Probe for Quantifying Oxygen Levels in Hypoxia in Single Cells and Tumors
摘要： Multiple sharp-edged gold nanostars were efficiently assembled on nanopipette tips by 3-aminopropyltrimethoxysilane (APTES) via an electrostatic interaction for a potent intracellular hypoxia-sensing Raman probe. Colloidal stability and surface immobilization was checked using scanning electron microscopy, light scattering and zeta potential measurements. Site-specific intracellular hypoxia levels can be estimated in vitro and in vivo using Raman lancets (RL). Distinct Raman spectral changes for the nitro-(NO2) functional group of the redox maker 4-nitrothiophenol (4NTP) can be quantified according to the intracellular oxygen (O2) contents, ranging from 1% to 10%. Facile removal of RL from cells can be achieved after a short measurement time. Redox potential changes in mitochondrial respiration could also be examined using serial injection of inhibitors. Three-dimensional (3D)-cultured cells and in vivo tests were used to validate our methods of measuring tumour hypoxia; potential applications were validated in terms of judging the aggressiveness of cancer cells by differentiating spectral changes between malignant and benign cells.
关键词： Cancer aggressiveness,Hypoxia,Surface enhanced resonance Raman,Intracellular redox potential,Nanopipette lancets
更新于2025-09-23 15:23:52