Showing papers by "Zhong Chen published in 2014"
TL;DR: This article provides a review of the visible light (λ > 400 nm) active perovskite-based photocatalyst systems, summarizing the current state of the work and offering useful insights for their future development.
Abstract: Perovskite-based photocatalysts are of significant interest in the field of photocatalysis. To date, several perovskite material systems have been developed and their applications in visible light photocatalysis studied. This article provides a review of the visible light (λ > 400 nm) active perovskite-based photocatalyst systems. The materials systems are classified by the B site cations and their crystal structure, optical properties, electronic structure, and photocatalytic performance are reviewed in detail. Titanates, tantalates, niobates, vanadates, and ferrites form important photocatalysts which show promise in visible light-driven photoreactions. Along with simple perovskite (ABO3) structures, development of double/complex perovskites that are active under visible light is also reviewed. Various strategies employed for enhancing the photocatalytic performance have been discussed, emphasizing the specific advantages and challenges offered by perovskite-based photocatalysts. This review provides a broad overview of the perovskite photocatalysts, summarizing the current state of the work and offering useful insights for their future development.
440 citations
TL;DR: A stirring hydrothermal process that enables the formation of elongated bending TiO2 -based nanotubes is presented, which can cycle over 10 000 times in half cells while retaining a relatively high capacity.
Abstract: A stirring hydrothermal process that enables the formation of elongated bending TiO2 -based nanotubes is presented. By making use of its bending nature, the elongated TiO2 (B) nanotubular crosslinked-network anode electrode can cycle over 10 000 times in half cells while retaining a relatively high capacity (114 mA h g(-1)) at an ultra-high rate of 25 C (8.4 A g(-1)).
390 citations
TL;DR: This paper designs a patch-based nonlocal operator (PANO) to sparsify magnetic resonance images by making use of the similarity of image patches to achieve lower reconstruction error and higher visual quality than conventional CS-MRI methods.
329 citations
TL;DR: The stirring hydrothermal method was used to control the aspect ratio of viscous titanate nanotubes, which were used to fabricate additive-free TiO2 -based electrode materials, and it was found that the battery performance at high charging/discharging rates is dramatically boosted when the aspects ratio is increased.
Abstract: The fundamental understanding of the relationship between the nanostructure of an electrode and its electrochemical performance is crucial for achieving high-performance lithium-ion batteries (LIBs). In this work, the relationship between the nanotubular aspect ratio and electrochemical performance of LIBs is elucidated for the first time. The stirring hydrothermal method was used to control the aspect ratio of viscous titanate nanotubes, which were used to fabricate additive-free TiO2-based electrode materials. We found that the battery performance at high charging/discharging rates is dramatically boosted when the aspect ratio is increased, due to the optimization of electronic/ionic transport properties within the electrode materials. The proof-of-concept LIBs comprising nanotubes with an aspect ratio of 265 can retain more than 86 % of their initial capacity over 6000 cycles at a high rate of 30 C. Such devices with supercapacitor-like rate performance and battery-like capacity herald a new paradigm for energy storage systems.
173 citations
TL;DR: It is demonstrated that the main contribution of the T1 contrast of magnetic nanoplates is the chemical exchange on the iron-rich Fe3O4(111) surfaces, whereas the T2 relaxation is dominated by the intrinsic superparamagnetism of the nanoplate with an enhanced perturbation effect.
Abstract: Iron oxide has been developed as either T1 or T2 magnetic resonance imaging (MRI) contrast agents by controlling the size and composition; however, the underlying mechanism of T1 and T2 contrasts in one iron oxide entity is still not well understood. Herein, we report that freestanding superparamagnetic magnetite nanoplates with (111) exposed facets have significant but interactional T1 and T2 contrast effects. We demonstrate that the main contribution of the T1 contrast of magnetic nanoplates is the chemical exchange on the iron-rich Fe3O4(111) surfaces, whereas the T2 relaxation is dominated by the intrinsic superparamagnetism of the nanoplates with an enhanced perturbation effect. We are able to regulate the balance of T1 and T2 contrasts by controlling structure and surface features, including morphology, exposed facets, and surface coating. This study provides an insightful understanding on the T1 and T2 contrast mechanisms, which is urgently needed to allow more sophisticated design of high-performa...
144 citations
TL;DR: It was found that lower surface energy leads to lower ice adhesion regardless of theroughness, while the roughness plays a more complicated role, and the anti-icing performance is closely related to the antiwetting property of the surfaces at subzero temperatures.
Abstract: Sol–gel coatings with different roughness and surface energy were prepared on glass substrates. Methyl triethoxysilane (MTEOS), 3-Glycidyloxypropyl trimethoxysilane (GLYMO) and fluoroalkylsilane (FAS) were used to obtain a mechanically robust icephobic coating. Different amount of hydrophobic silica nano particles was added as fillers to introduce different roughness and surface energy to the coatings. The microstructure, roughness, and surface energy, together with elemental information and surface chemical state, were investigated at room temperature. The contact angle and sliding angle were measured at different temperatures to correlate the wetting behavior at low temperature with the anti-icing performance. The ice adhesion shear strength was measured inside an ice chamber using a self-designed tester. The factors influencing the ice adhesion were discussed, and the optimum anti-icing performance found in the series of coatings. It was found that lower surface energy leads to lower ice adhesion regar...
143 citations
TL;DR: The tunable T1 and T2 contrast abilities of engineered iron oxide nanoparticles with high performance for liver contrast-enhanced magnetic resonance imaging (MRI) in mice are demonstrated and revealed that the MRI contrast effects of MnIO nanoparticles are highly size-dependent.
Abstract: In this paper, we demonstrate the tunable T1 and T2 contrast abilities of engineered iron oxide nanoparticles with high performance for liver contrast-enhanced magnetic resonance imaging (MRI) in mice. To enhance the diagnostic accuracy of MRI, large numbers of contrast agents with T1 or T2 contrast ability have been widely explored. The comprehensive investigation of high-performance MRI contrast agents with controllable T1 and T2 contrast abilities is of high importance in the field of molecular imaging. In this study, we synthesized uniform manganese-doped iron oxide (MnIO) nanoparticles with controllable size from 5 to 12 nm and comprehensively investigated their MRI contrast abilities. We revealed that the MRI contrast effects of MnIO nanoparticles are highly size-dependent. By controlling the size of MnIO nanoparticles, we can achieve T1-dominated, T2-dominated, and T1-T2 dual-mode MRI contrast agents with much higher contrast enhancement than the corresponding conventional iron oxide nanoparticles.
128 citations
TL;DR: The results indicate that surfactant-thermal synthesis could be a promising method for growing novel crystalline oxochalcogenides with interesting structures and properties.
Abstract: A new two-dimensional (2D) oxosulfide, (N2H4)2Mn3Sb4S8(μ3-OH)2 (1), has been successfully synthesized under surfactant-thermal conditions with hexadecyltributylphosphonium bromide as the surfactant. Compound 1 has a layered structure and contains a novel [Mn3(μ3-OH)2]n chain along the b-axis. The photocatalytic activity for compound 1 has been demonstrated under visible-light irradiation and continuous H2 evolution was observed. Our results indicate that surfactant-thermal synthesis could be a promising method for growing novel crystalline oxochalcogenides with interesting structures and properties.
75 citations
TL;DR: In this paper, a lead-free Ag-based soldering technique through transient-liquid-phase (TLP) bonding is proposed for high-temperature microelectronic packaging applications.
71 citations
TL;DR: It is suggested that polysilane may be a promising anode material for Na-ion and Li-ion batteries with high charge-discharge rates because of the large surface area and available free volume for the large Na cation.
Abstract: By means of density functional theory, we systematically investigate the insertion and diffusion of Na and Li in layered Si materials (polysilane and H-passivated silicene), in comparison with bulk Si. It is found that Na binding and mobility can be significantly facilitated in layered Si structures. In contrast to the Si bulk, where Na insertion is energetically unfavorable, Na storage can be achieved in polysilane and silicene. The energy barrier for Na diffusion is reduced from 1.06 eV in the Si bulk to 0.41 eV in polysilane. The improvements in binding energetics and in the activation energy for Na diffusion are attributed to the large surface area and available free volume for the large Na cation. Based on these results, we suggest that polysilane may be a promising anode material for Na-ion and Li-ion batteries with high charge–discharge rates.
71 citations
TL;DR: It is shown that the stability of the triple-layered WO3 photoanodes can be considerably enhanced by adding an ultrathin (10 nm) TiO2 protective overlayer.
Abstract: Unique nanorods/nanoparticles/nanoflakes (NRs/NPs/NFs) WO3 triple-layers are grown on a metallic W foil by a simple one-step anodization method. The triple-layered structure is formed through a self-organization process, the film thickness (up to 3 μm) being controlled by the anodization time. A first layer made of an array of WO3 densely-packed vertically-aligned NRs (1.2–1.4 μm in height) grow atop the tungsten foil, followed by a second layer of small NPs (50–80 nm) and finally a third layer made of rectangular NFs (200–300 nm). When irradiated by white light in a photoelectrochemical cell these WO3 triple-layers generate a photocurrent as high as 0.9 mA cm−2 at 1.2 V/RHE. Moreover, we show that the stability of the triple-layered WO3 photoanodes can be considerably enhanced by adding an ultrathin (10 nm) TiO2 protective overlayer.
TL;DR: In this article, a square wave voltammetry deposition method was used for in situ deposition of Cu2O nanoparticles onto the inner surfaces and interfaces of n-type TiO2 nanotubes arrays.
Abstract: Heterojunction composites based on n-type TiO2 nanotubes arrays (TNAs) coupled with p-type Cu2O nanoparticles were synthesized using a square wave voltammetry deposition method for in situ deposition of Cu2O nanoparticles onto the inner surfaces and interfaces of TNAs. The prepared samples were characterized by field-emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and UV-vis spectroscopy. When compared with pure TNAs, the Cu2O–TNAs heterojunction composites exhibit considerably higher photocurrent density under visible-light irradiation and enhanced photocatalytic activity for the visible-light-driven photodegradation of methyl orange. Moreover, the photocurrent densities and photocatalytic activity of the Cu2O–TNAs heterostructures largely depend on the deposition potential which determines the content of the Cu2O nanoparticles. The Cu2O–TNAs prepared by the deposition potential of −1.0 V showed the highest photocurrent density (0.91 mA cm−2) and the largest photodegradation rate of methyl orange (88.8%) at the applied potential of 0.5 V under visible light irradiation. The enhanced photoelectrocatalytic activity can be attributed to reducing the recombination rate of the photoexcited electron–hole pairs in TNAs when coupled with Cu2O nanoparticles.
TL;DR: In this paper, the authors deal with the computation of effective elastic properties of braided textile composites assisted by finite element analysis, where dynamic representative unit cells are used to calculate the elastic properties.
Abstract: This article deals with the computation of effective elastic properties of braided textile composites assisted by finite element analysis In this approach, dynamic representative unit cells are fi
TL;DR: In this paper, an electrolessly plated Ni-Co-P alloy was developed as the solder metallization in order to address the reliability challenges brought about by the accelerated reaction with the implementation of lead-free solders.
TL;DR: In this paper, the authors investigated the thermodynamic stability of doped NaTaO3 and co-doped NTAO3 systems using DFT-PBE as well as hybrid (PBE0) functional calculations.
Abstract: Electronic structures of doped NaTaO3 compounds are of significant interest to visible light photocatalysis. This work involves the study of the band gap, band edge potentials, and thermodynamic stability of certain mono-doped and co-doped NaTaO3 systems, using DFT-PBE as well as hybrid (PBE0) functional calculations. Doping of certain non-magnetic cations (Ti, V, Cu, Zn, W, In, Sn, Sb, Ce, and La), certain anions (N, C, and I), and certain co-dopant pairs (W-Ti, W-Ce, N-I, N-W, La-C, Pb-I, and Cu-Sn) is investigated. Our calculations suggest that substitutional doping of Cu at the Ta site, Cu at the Na site, and C at the O site narrows the band gap of NaTaO3 to 2.3, 2.8, and 2.1 eV, respectively, inducing visible light absorption. Additionally, passivated co-doping of Pb-I and N-W narrows the band gap of NaTaO3 to the visible region, while maintaining the band potentials at favorable positions. Hybrid density of states (DOS) accurately describe the effective band potentials and the location of mid-gap states, which shed light on the possible mechanism of photoexcitation in relation to the photocatalysis reactions. Furthermore, the thermodynamic stability of the doped systems and defect pair binding energies of co-doped systems are discussed in detail. The present results provide useful insights into designing new photocatalysts based on NaTaO3.
TL;DR: The feasibility of HR 1H NMR spectroscopy based on intermolecular multiple-quantum coherence (iMQC) technique is explored and it provides an alternative for the investigation in cases with field distortions and with samples unsuitable for spinning.
Abstract: National Natural Science Foundation of China [11074209, 11174239, 21203155]; Fundamental Research Fund for the Central Universities [2010121008]
TL;DR: An NMR approach based on intermolecular double-quantum coherences to recover high-resolution two-dimensional (2D) J-resolved spectra from inhomogeneous magnetic fields, such as those created by susceptibility variations in intact biological tissues are proposed.
TL;DR: In this paper, a spatially resolved electroluminescence (SREL) as a function of injection current was investigated for the external quantum efficiency (EQE) droop in InGaN quantum well blue light emitting diodes.
Abstract: We perform both spatially resolved electroluminescence (SREL) as a function of injection current and spatially resolved photoluminescence (SRPL) as a function of excitation power on InGaN quantum well blue light-emitting diodes to investigate the underlying physics for the phenomenon of the external quantum efficiency (EQE) droop. SREL allows us to study two most commonly observed but distinctly different droop behaviors on a single device, minimizing the ambiguity trying to compare independently fabricated devices. Two representative devices are studied: one with macroscopic scale material non-uniformity, the other being macroscopically uniform, but both with microscopic scale fluctuations. We suggest that the EQE–current curve reflects the interplay of three effects: nonradiative recombination through point defects, carrier localization due to either In composition or well width fluctuation, and nonradiative recombination of the extended defects, which is common to various optoelectronic devices. By comparing SREL and SRPL, two very different excitation/detection modes, we show that individual singular sites exhibiting either particularly strong or weak emission in SRPL do not usually play any significant and direct role in the EQE droop. We introduce a two-level model that can capture the basic physical processes that dictate the EQE–current dependence and describe the whole operating range of the device from 0.01 to 100 A/cm2.
10 Apr 2014-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, an electroless Ni-P-TiO 2 (17.5% at% of P) composite coating was used as a pad finish for advanced electronic packaging, where the majority of the added TiO 2 nanoparticles were proved to be uniformly distributed in UBM by scanning electronic microscopy and X-ray diffraction (XRD).
Abstract: One primary purpose of this study is to introduce an electroless Ni–P–TiO 2 (17.5 at% of P) composite coating as a pad finish for advanced electronic packaging. In this study, TiO 2 nanoparticles were incorporated into the Ni–P layer by electroless deposition and its function as novel under bump metallization (UBM) was intensively investigated. The majority of the added TiO 2 nanoparticles were proved to be uniformly distributed in UBM by scanning electronic microscopy (SEM) and X-ray diffraction (XRD). The interfacial reaction between electrolessly deposited Ni–P–TiO 2 layer and Sn–3.5Ag solder alloy was systematically analyzed. The prime Ni–P UBM was used for comparison to evaluate the effect of TiO 2 nanoparticle on the interfacial microstructure and mechanical property. Both solder/Ni–P and solder/Ni–P–TiO 2 joints were aged at temperature from 150 °C to 190 °C for different aging periods in order to study the intermetallic compounds (IMCs) growth and calculate the activation energy. It was found the growth of Ni 3 Sn 4 IMC layer and the void formation at the reaction interface were successfully suppressed with the help of the TiO 2 nanoparticle. The activation energies for the growth of Ni 3 Sn 4 on Ni–P and Ni–P–TiO 2 layers were calculated to be 50.9 kJ/mol and 55.7 kJ/mol, respectively. The extensive growth of Ni 3 P and Ni–Sn–P phases as well as the consumption rate of the amorphous UBM was controlled in joints with TiO 2 nanoparticles. Thus Ni–P–TiO 2 UBM blocked the Cu diffusion from substrate to interface. A detailed reaction induced diffusion mechanism was proposed. The solder/Ni–P–TiO 2 solder joint consistently demonstrated higher shear strength than solder/Ni–P joint as a function of aging time. TiO 2 nanoparticle contributed to slow down the declining rate of shear strength from 0.021 Mpa/h to 0.013 Mpa/h with the aging time. Moreover, after the shear strength test, fracture mainly occurred at solder matrix of the solder/Ni–P–TiO 2 joint; the morphology showed a ductile fracture pattern with a large distribution of dimples on the rough surface.
TL;DR: By modifying traditional remote phosphor-diffuser-packaged light-emitting diode systems, the authors in this article have managed to increase the luminous efficacy from 1457 to 1623 lm/W by randomizing the directions of light beams transmitting through an interior diffuser, whose position is optimized based on an overall merit.
Abstract: By modifying traditional remote phosphor-diffuser-packaged light-emitting diode systems, we have managed to increase the luminous efficacy from 1457 to 1623 lm/W One mechanism responsible for this achievement is associated with randomizing the directions of light beams transmitting through an interior diffuser, whose position is optimized based on an overall merit The other mechanism is identified as the gradual attenuation of the undesirable blue-ring image along the distance from the diffuser toward the phosphor base The identification of these two mechanisms is verified by luminous efficacy measurements, 3-D image plots, and combined Monte Carlo algorithm ray tracing simulation results In addition, merits related to correlated color temperatures and issues pertaining to costs are briefly discussed
TL;DR: In this paper, the authors reported that composites based on hydrogen titanate cores bearing shells of melon and graphitic carbon nitride (g-C3N4) as sensitizers are far superior in simulated solar (visible) light-driven photodegradation of methyl orange (MO) dye and ethanol photo-oxidation as compared to the individual components.
Abstract: Photocatalysis has become increasingly popular for applications in the energy and environmental fields. However, in its conventional form as a pristine (white) semiconductor oxide, e.g., titania (TiO2), the photocatalyst has a wide band gap and does not respond to a large fraction of the solar power available across the visible region. Recently, some success has been reported in the in situ synthesis and deposition of melon [poly (tri-s-triazine) with an empirical formulation of H3C6N9] onto TiO2 to act as a visible sensitizer. In the present contribution, we report the interesting finding that composites based on hydrogen titanate cores bearing shells of melon and the related graphitic carbon nitride (g-C3N4) as sensitizers are far superior in simulated solar (visible) light-driven photodegradation of methyl orange (MO) dye and ethanol photo-oxidation as compared to the individual components. These layered titanate nanotubes/nanobelts also offer a practical advantage by promoting the build-up of melon fr...
TL;DR: The results of the mechanical and microstructural characterizations demonstrate that Bi-based two phase glass frit bonding is an effective ceramic bonding method for harsh-environment electronic packaging.
TL;DR: The results indicate that the conductivity limit is approached by Ni doping in BFO, and the methodology presented here may be extended to search for the doping conductivity limits of other semiconductors of interest.
Abstract: We investigate the limiting electrical conductivity of BiFeO3 (BFO) nanofibers via first-principles modelling and experiments. Based on a semi-empirical approach, all transition metals are first screened for their suitability to form an acceptor in BFO. The resultant candidates (e.g., Ni, Cu and Ag) are further studied by more sophisticated electronic structure theory and experiments. Accordingly, a systematic approach in forecasting the electrical conduction in BFO nanofibers is established. The calculated results show that Ag+ cations prefer substitutions of Bi3+ while Ni2+ and Cu2+ prefer substitution of Fe3+ sites to form acceptors. All three metals contribute to an increased overall hole concentration which may lead to a conductivity limit in BFO. These predictions were confirmed consistently through the synthesis and electrical testing of Ni-, Cu- and Ag-doped BFO nanofibers. Finally, our results indicate that the conductivity limit is approached by Ni doping in BFO. The methodology presented here may be extended to search for the doping conductivity limits of other semiconductors of interest.
TL;DR: In this paper, the authors used scanning electronic microscopy (SEM) to observe the morphology and the CNTs were proved to be uniformly distributed in Ni-P-CNT composite coatings by SEM and atomic force microscopy.
Abstract: Electroless Ni–P under bump metallization (UBM) has advantages of even surface, low cost and simplicity to deposit, but their mechanical strength, corrosion resistance and stability still face challenges under high soldering temperature. Incorporating carbon nanotubes (CNTs) into electroless Ni–P UBM might be expected to provide Ni–P–CNT composites with high mechanical strength and stability. Ni–P–CNT composite coatings as well as Ni–P coatings were fabricated by electroless plating process. In order to homogeneously disperse CNTs in composite coatings, acid pre-treatment and surfactant dispersant were introduced. During composite electroless plating, the ultrasonic agitation was also employed. In this study, scanning electronic microscopy (SEM) was used to observe the morphology and the CNTs were proved to be uniformly distributed in Ni–P–CNT coatings by SEM and atomic force microscopy. It was verified that the surface of the composite was quite smooth and continuous; CNTs are equably embedded in the matrix, which is advantageous for conductivity, mechanical strength and corrosion resistance. Shear tests were conducted to evaluate the effect of CNT reinforcement on the mechanical properties of joints, and the joints with CNT additions exhibited higher shear strength at different reflow cycles. Moreover, deposition mechanism of CNTs with Ni was analyzed and confirmed by transmission electron microscopy. Factors that affecting plating process was also discussed, and the optimum plating condition was suggested in this study.
TL;DR: It was observed that Electronic Flame Off (EFO) current and the cover gas type have a significant effect on palladium distribution in the FAB, and the impact of palladium on wire bondability and wire bond intermetallic using a high temperature storage test was studied.
TL;DR: The metabonomic analysis of body fluids and tissues indicated that MnIO-NPs induced metabolic perturbation in rats including energy, nucleotides, amino acids and phospholipid metabolisms, which would provide identifiable ground for the candidate selection and optimization.
Abstract: MnO-embedded iron oxide nanoparticles (MnIO-NPs) can be treated as potential dual-modal contrast agents. However, their overall bio-effects and potential toxicity remain unknown. In this study, the metabolic effects of MnIO-NPs (dosed at 1 and 5 mg Fe/kg) on Sprague–Dawley rats were investigated using metabonomic analysis, histopathological examination, and conventional biochemical analysis. The histological changes included a focal inflammation in the liver at high-dose and a slightly enlarged area of splenic white pulp after 48 h post-dose. Blood biochemical analysis showed that albumin, globulins, aspartate aminotransferase, lactate dehydrogenase, blood urea nitrogen, and glucose changed distinctly compared to the control. The metabonomic analysis of body fluids (serum and urine) and tissues (liver, kidney, and spleen) indicated that MnIO-NPs induced metabolic perturbation in rats including energy, nucleotides, amino acids and phospholipid metabolisms. Besides, the variations of supportive nutrients: valine, leucine, isoleucine, nicotinamide adenine dinucleotide (phosphate), and nicotinamide, and the conjugation substrates: glycine, taurine, glutamine, glutathione, and methyl donors (formate, sarcosine, dimethylglycine, choline, and betaine) were involved in detoxification reaction of MnIO-NPs. The obtained information would provide identifiable ground for the candidate selection and optimization.
TL;DR: In this article, a method based on partial homogeneity is proposed for retrieving high-resolution one-dimensional NMR spectra under inhomogeneous magnetic fields, where signals from series of small voxels, which characterize high resolution due to small sizes, are recorded simultaneously.
Abstract: In nuclear magnetic resonance (NMR) technique, it is of great necessity and importance to obtain high-resolution spectra, especially under inhomogeneous magnetic fields. In this study, a method based on partial homogeneity is proposed for retrieving high-resolution one-dimensional NMR spectra under inhomogeneous fields. Signals from series of small voxels, which characterize high resolution due to small sizes, are recorded simultaneously. Then, an inhomogeneity correction algorithm is developed based on pattern recognition to correct the influence brought by field inhomogeneity automatically, thus yielding high-resolution information. Experiments on chemical solutions and fish spawn were carried out to demonstrate the performance of the proposed method. The proposed method serves as a single radiofrequency pulse high-resolution NMR spectroscopy under inhomogeneous fields and may provide an alternative of obtaining high-resolution spectra of in vivo living systems or chemical-reaction systems, where performances of conventional techniques are usually degenerated by field inhomogeneity.
TL;DR: This work puts forth a new class of pulse sequences for obtaining high-resolution heteronuclear spectra in magnetic fields with unknown spatial variations based on distant dipolar field modulations and shows that by encoding and decoding NMR observables spatially, an extra dimension containing J-coupling information can be obtained without increasing the time necessary to acquire a heteron nuclear correlation spectrum.
TL;DR: In this paper, the authors investigated time-dependent photovoltaic-thermoelectric hybrid systems by following the trajectory of the sun between sunrise and sunset, and the results of thermal efficiencies were parametrized in heat transfer coefficients, the thermal conductivities of the thermiolectric module, and Seebeck coefficients.
Abstract: Photovoltaic-thermoelectric hybrid systems that operate in steady state have attracted considerable attention due to the possibility of supplying more power output than the photovoltaic cell alone. In real life, however, the solar energy continually changes during a day, thus rendering the assumption of steady state unrealistic. In this study, we have investigated such time-dependent systems by following the trajectory of the sun between sunrise and sunset. Computed results of thermal efficiencies are parametrized in heat transfer coefficients, the thermal conductivities of the thermoelectric module, and Seebeck coefficients. For values of the Seebeck coefficient greater than 2.13 × 10−3 V/K thermal efficiencies of the hybrid system appear higher than those of the photovoltaic cells alone. To tackle the strong nonlinear coupling between nodal temperatures, and power outputs, we have adopted two-stage iterative schemes.
TL;DR: In this article, an electrolessly plated Ni-Sn-P alloy (6.7 wt.% P and 19.21 wt% Sn) was developed to suppress formation of the Ni3P phase.
Abstract: The voids formed in the Ni3P layer during reaction between Sn-based solders and electroless Ni–P metallization is an important cause of rapid degradation of solder joint reliability. In this study, to suppress formation of the Ni3P phase, an electrolessly plated Ni–Sn–P alloy (6–7 wt.% P and 19–21 wt.% Sn) was developed to replace Ni–P. The interfacial microstructure of electroless Ni–Sn–P/Sn–3.5Ag solder joints was investigated after reflow and solid-state aging. For comparison, the interfacial reaction in electroless Ni–P/Sn–3.5Ag solder joints under the same reflow and aging conditions was studied. It was found that the Ni–Sn–P metallization is consumed much more slowly than the Ni–P metallization during soldering. After prolonged reaction, no Ni3P or voids are observed under SEM at the Ni–Sn–P/Sn–3.5Ag interface. Two main intermetallic compounds, Ni3Sn4 and Ni13Sn8P3, are formed during the soldering reaction. The reason for Ni3P phase suppression and the overall mechanisms of reaction at the Ni–Sn–P/Sn–3.5Ag interface are discussed.