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We have built and tested a prototype miniaturized thermoelectric power source that generates 450μW of electrical power in a system volume of 4.3cm3. The measured power density of 104μWcm−3 exceeds that of any previously reported thermoelectric power system of equivalent size. This improvement was achieved by implementing a novel thermopile design in which wagon wheel-shaped thermoelectric elements contact the entire circumference of the heat source whereas traditional approaches utilize only one heat source surface. The thermopile consists of 22 wagon wheel-shaped elements (11 P–N thermocouples) fabricated from 215-μm thick bismuth–telluride wafers having ZT=0.97 at 30°C. The power source operates on a 150mW thermal input provided by an electrical resistance heater that simulates a capsule containing 0.4g of 238PuO2 located at the center of the device. Our primary research objective was to develop and demonstrate a prototype thermopile and radioisotopic thermoelectric generator (RTG) architecture with improved power density at small scales. Output power from this device, while optimized for efficiency, was not optimized for output voltage, and the maximum power was delivered at 41mV. We also discuss modifications to our prototype design that result in significantly improved voltage and power. Numerical predictions show that a power output of 1.4mW, power density of 329μWcm−3, and voltage of 362mV, is possible in the same package size.
In this paper, we propose a new strategy to develop high performance sulfur electrode by impregnating sulfur into the micropores of a Li+-insertable carbon matrix with the simultaneous use of a carbonate electrolyte, which does not dissolve polysulfides, to restrain the solution of the reaction intermediates of sulfur. To proof this concept, we prepared a Li+-insertable microporous carbon–sulfur composite by vaporizing sulfur into the micropores of the nanofiber-wired carbon microspheres. The experimental results demonstrate that, in the carbonate electrolyte of 1M LiPF6/PC-EC-DEC, such S/C composite electrode exhibits not only stable cycling performance with a reversible capacity of 720mAhg−1 after 100 cycles, but also superior high coulombic efficiency of ∼100% upon extended cycling (except the first three cycles). The structural and electrochemical analysis indicates that the improved electrochemical behaviors of the S/C composite arise from a new reaction mechanism, in which Li+ ions and electrons transport through the carbon matrix into the interior of the cathode and then react with the embedded sulfur in the S/C solid–solid interfaces, avoiding the solution of the intermediates into the bulk electrolyte. More significantly, the structural design and working mechanism of such a sulfur cathode could be extended to a variety of poorly conductive and easily soluble redox-active materials for battery applications.
Finding a non-noble metal (NNM) electrocatalyst with comparative hydrogen evolution reaction (HER) activity in a broad pH range is essential but challenging. Here, we report a unique shrunken hollow spherical shell with Mo2N and Mo2C dual active phases encapsulated by nitrogen-doped carbon (Mo-N/C@N-C). As NNM electrocatalyst, it shows high HER activity and stability in a broad pH range. This material can be synthesized by pyrolysis of sulfonated polystyrene@polyaniline-MoOx sphere-like precursors using sulfonated polystyrene as template and polyaniline as carbon and nitrogen source. In an alkaline solution, the as-prepared Mo-N/C@N-C only needs an overpotential of 135 mV to reach the current density of 10 mA cm−2, and exhibits high electrochemical and structural durability. The catalyst also possesses similar performance in acidic and neutral media, making it a suitable candidate for hydrogen production in all pH media. Such excellent catalytic performance is mainly driven by the synergy of abundant Mo2N and Mo2C dual active centers, and shrunken hollow sphere structures with high packing density, as well as the N-C active site and protection of N-doped carbon frameworks.
CuS thin films were obtained using the SILAR method on an amorphous glass substrate. All experiments were performed at room temperature. CuS thin films were deposited at 30, 40, 50 and 60 cycles, respectively. Structural, morphological and optical properties of the structures that increase the thickness of nanostructured CuS thin films were investigated. X-ray diffraction, scanning electron microscopy, atomic force microscopy, RAMAN and optical absorption measurements were carried out in order to examine the physical properties of CuS thin films. As a result of the analysis, we can say that the thickness increase positively affects the crystal structure of CuS thin films. In addition, the energy bandgap range of CuS thin films ranged from 2.22 to 1.78 eV. Analysis results of CuS thin films using SILAR method show that thickness is an important factor for thin film studies.
Lithium-ion batteries require higher energy densities to meet with a broad acceptance in the fields of electric vehicles and grid storage solutions. LiNi0.5Mn1.5O4 (LNMO) can fulfill this goal due to its high operating voltage. Cycling of LNMO is known to be stable vs. lithium metal anode. Cycling in an LNMO/graphite configuration leads to severe capacity fade. Ti-doped LNMO (LNMTO)/graphite cells experience a lower, but still strong loss of capacity. In order to understand capacity fade, cycling tests of LNMTO vs. graphite and vs. lithium metal were carried out and additionally, three electrode tests were performed. Both cell configurations showed similar Coulombic efficiencies correlating with the applied C-rate. Experimental data and mathematical modeling indicated that loss of active lithium with a constant reaction rate of (3.76 ± 0.46) · 10−8 mol Li h−1 is responsible for capacity fade in LNMTO/graphite cells and that no degradation of the active material occurs. It was concluded that lithium loss also occurs when lithium metal anodes are used. Here, the lithium metal anode can compensate for lithium consumption, as a result of which the capacity is not influenced. Further support for lithium consumption is given by a three-electrode cell with a lithiated graphite anode. The lithium in the graphite anode can compensate the lithium loss for 120 cycles. During this time, the cell experienced hardly any capacity fade and the voltage profile was similar to that of a cell with LNMTO/Li configuration.
Nanoparticles having four different ratios of crystalline silicon (Si) cores and amorphous SiOx shells were synthesized by using a microwave-generated plasma. Their microstructures were analyzed to find quantitative relationships with electrochemical properties. By measuring XRD, SEM, HR-TEM, and Raman spectra of four samples with different core-shell microstructures, the quantitative fractions of crystalline Si core and amorphous SiOx shell in the nanoparticles were calculated. Also, electrochemical properties of the nanoparticles were measured and compared with the calculated fractions. The electrochemical properties such as the initial reversible capacity, the initial coulombic efficiency, and the capacity retention exhibited tendencies remarkably similar to those implied by the calculated fractions. Analysis of each sample's dQ/dV profile also gave us good evidence of understandable relationships between the fractions and electrochemical properties. Details of calculating the fractions from microstructural data are given, with suitable consideration having been given to the fact that several assumptions could lead to errors during the analysis. The approach introduced in this research offers a good means of analysis with which to further the optimal design of nanoparticle microstructure for Li-ion battery anodes.
The objectives of this pilot study were to assess the feasibility of recruitment and adherence to an eight-session mindfulness meditation program for community-dwelling older adults with chronic low back pain (CLBP) and to develop initial estimates of treatment effects. It was designed as a randomized, controlled clinical trial. Participants were 37 community-dwelling older adults aged 65 years and older with CLBP of moderate intensity occurring daily or almost every day. Participants were randomized to an 8-week mindfulness-based meditation program or to a wait-list control group. Baseline, 8-week and 3-month follow-up measures of pain, physical function, and quality of life were assessed. Eighty-nine older adults were screened and 37 found to be eligible and randomized within a 6-month period. The mean age of the sample was 74.9 years, 21/37 (57%) of participants were female and 33/37 (89%) were white. At the end of the intervention 30/37 (81%) participants completed 8-week assessments. Average class attendance of the intervention arm was 6.7 out of 8. They meditated an average of 4.3 days a week and the average minutes per day was 31.6. Compared to the control group, the intervention group displayed significant improvement in the Chronic Pain Acceptance Questionnaire Total Score and Activities Engagement subscale (P =.008, P =.004) and SF-36 Physical Function (P =.03). An 8-week mindfulness-based meditation program is feasible for older adults with CLBP. The program may lead to improvement in pain acceptance and physical function.
This article has been retracted at the request of the Editor-in-Chief, with agreement of the authors: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). Substantial parts of this review paper are similar to the texts of existing papers in the literature. The co-authors state that the corresponding author submitted the manuscript without their approval. The following works are affected: IEEE Transactions on Power Electronics, 26 (2011) 3472-3480, http://dx.doi.org/10.1109/TPEL.2011.2161096. The Journal of Physical Chemistry Letters, 4 (2013) 1260-1267, http://dx.doi.org/10.1021/jz4002967. The Journal of Physical Chemistry Letters, 4 (2013), 3367-3376, http://dx.doi.org/10.1021/jz4014163. Physical Chemistry Chemical Physics, 16 (2014), 6519-6538, http://dx.doi.org/10.1039/c3cp55186e. The Authors unreservedly apologise for this violation of the publishing policies, and offer sincere apologies to the parties affected. The journal apologises to its readers and the authors that the overlap was not detected during the submission and review process.
In recent decades most countries have experienced substantial increases in recycling. During the same period, international trade of recyclable materials between developed countries and developing countries has also grown. Increasingly, waste materials recovered in developed countries are exported for utilization in developing countries. We investigate the causes of this trend,focusing on two materials: paper and lead. Trade patterns of these materials are analyzed for the developed and developing world. We find that countries that have actively participated in trade of recyclables have higher recycling rates than those with closed recycling systems. Other factors that contribute to the intensity of recycline are geographic and economic conditions.
To form BaLi2Ti6O14/Ag, highly dispersed Ag nanoparticles are successfully deposited on the surface of BaLi2Ti6O14 by a simple chemical deposition method. The morphology, quantity and size of Ag nanoparticles in BaLi2Ti6O14/Ag composites are significantly influenced by the Ag coating contents. Electrochemical results show that Ag nanoparticles play a positive role in reducing redox polarization and improving electrical conductivity of BaLi2Ti6O14 during lithiation/delithiation processes. Among all the as-obtained products, 6wt.% Ag coated BaLi2Ti6O14 shows the highest initial charge specific capacity of 160mAhg−1 at the current density of 100mAg−1 (1C), which is much higher than the 149.1mAhg−1 for bare BaLi2Ti6O14. After 100 charge/discharge cycles, the reversible capacity can be maintained at 117.0mAhg−1. Moreover, this sample also shows excellent rate performance with high reversible charge capacities of 147.5, 139.7, 132.6, and 126.7mAhg−1 at the rates of 2C, 3C, 4C and 5C, respectively. Compared with bare BaLi2Ti6O14, the superior electrochemical performance indicates that BaLi2Ti6O14/Ag can be a good anode material in lithium ion batteries.
In Mutale Local Authority of South Africa, a photovoltaic pilot project was commissioned to provide off-grid electricity to 582 households residing in Folovhodwe village. The aim was to try a renewable source of energy supply in a rural settlement area. The Beneficiaries Assessment method was used to assess the problems of the implementation and operation of the solar energy project in Folovhodwe. The project initiators did not realize that there would be the problem of the sustainable implementation of the project. The problem of sustainability was related to the inadequate definition of the role of each stakeholder. For example the end users were not taught how to properly operate and repair faulty equipment because it was not built into the planning and implementation stages of the project. Skill acquisition through capacity building for the end users can promote the sustainability of the project on a long-term basis. In Folovhodwe, improper planning and implementation of the project was responsible for the failure of the project. The project initiators did not foresee the problem of theft of materials, problems related to the procurement of spare parts and who would bear the cost of maintenance of the facilities. The failure of the project was also related to the inability of the policy makers to tackle the question of the role that each stakeholder should play to ensure the success of the project in a rural setting. The suggestion to policy and decision-makers is that pilot projects with relatively new technology input in a rural area should reconsider the importance of culture, capacity development and the level of income of the end users at the initial planning stage and implementation.
NiCo2O4 is synthesized by the hydrothermal route in the presence of urea. Material is characterized by a complementary combination of X-ray diffraction, nitrogen sorption, and Scanning electron microscopy. The electrochemical oxidation of methanol is investigated at NiCo2O4 modified electrode in the alkaline medium using cyclic voltammetry and chronoamperometry methods. Electrocatalytic activity of NiCo2O4 is compared with the NiO and Co3O4 modified electrodes. A detailed investigation is made for the electrocatalytic oxidation of methanol by varying several reaction parameters such as potential scan rate, methanol concentration, etc. Mechanism of methanol oxidation is proposed based on the cyclic voltammetry study. Double steps chronoamperometry study shows that the methanol electro-oxidation is an irreversible reaction. Electrocatalytic activity of the methanol oxidation at NiCo2O4 modified electrode is found to be significantly higher than that of NiO and Co3O4 modified electrodes.
With the development of digital TV, especially 3D technologies, some applications in the digital home industry have been reported to meet and even exceed customer expectation in the market place for enterprise. In order to evaluate the clothing comfort performance in the digital e-commerce service, the clothing comfort model is very important. Considered the physical, physiological and psychological factors, a theoretical clothing comfort evaluation model is presented based on the adaptive fuzzy neural network in this paper. According to the characters of clothing comfort, Fuzzy Neural Networks (FNN) can provide a very human machine knowledge representation scheme friendly for acquiring, representing and using the knowledge of the domain expert. This is a significant advantage for clothing comfort evaluation where the exact system transfer functions cannot be well modeled and adequate training data sets are not available. The experiment results shown that there has the same prediction trend about the experiment result and simulation result. This clothing comfort evaluation model is used as a component in the smart clothing function user experience system.
The fabrication of single crystalline Li0.44MnO2 nanowires for the positive electrode of lithium ion battery is reported. The single crystalline Li0.44MnO2 nanowires are obtained by lithium exchange reaction of Na0.44MnO2 nanowires with high aspect ratio. The Li0.44MnO2 nanowires indicate both the large specific capacity of around 250mAhg−1 (1.5–4.5V vs. Li/Li+) and the good high current density property for the positive electrode of lithium ion battery.
Carbon materials can be readily prepared from wood derivatives, monosaccharaides such as pentose/hexose and/or polysaccharides in addition to many starting materials by treatment of thermal, chemical and hydrothermal methods. Here, the porous carbon (PC) particles were prepared by removal of silica particles from previously prepared carbon-silica composites by hydrothermal and carbonization process from sucrose. Then, PC particles were modified with polyethyleneimine (PEI) to prepared amine functionalized PC-PEI particles and protonated with hydrochloric acid, PC-PEI+. Finally, these prepared carbon-based particles were used as catalyst for H2 release from NaBH4 methanolysis and PC-PEI+ was found as the most effective catalyst at 25 °C with 4040 ± 126 mL H2. min−1.g−1 HGR value. The Ea value of 23.9 kJ/mol in H2 release reaction from NaBH4 methanolysis catalyzed by PC-PEI+ that is comparable and/or better than most of studies reported in literature. The activity% of PC-PEI+ catalyst was 72% after fifth consequential runs. Additionally, the regeneration ability of PC-PEI+ catalyst was also shown that after fifth regeneration process, there is only 5% decrease in activity%.
The principal challenges facing the development of lithium ion batteries (LIBs) for hybrid electric/plug-in-hybrid (HEV/PHEV) vehicles and for off-peak energy storage are cost, safety, cell energy density (voltage × capacity), rate of charge/discharge, and service life. There are exciting developments in new positive electrode (cathode) materials to replace the LiCoO2 for use in the LIBs over the past decade. Monoclinic Li3V2(PO4)3 (LVP) with promising electrochemical properties including excellent cycling stability, high theoretical capacity (197 mAh g−1), low synthetic cost, improved safety characteristic, and low environmental impact emerges as highly suitable candidate. In this review, we focus on research work related to the LVP and discuss its host structure, mechanism of lithium insertion/extraction, transport properties (i.e., electronic conductivity, and lithium diffusion), synthesis and electrochemical properties. We highlight some recent development of LVP, which shows superior cycling stability and high rate capability and give some vision for the future research of LVP based electrodes.
Novel carbon nanotubes (CNTs)–polyethylene oxide (PEO) composite electrolyte for dye-sensitized solar cell (DSSC) was prepared and characterized for the first time. The strong bonding and interaction between CNTs and PEO in CNTs–PEO composites was observed by the characterization of X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Raman spectra. The introduction of CNTs into PEO matrix significantly improved the electrolyte properties of DSSC such as roughness, amorphicity and ionic conductivity. The solid-state DSSC fabricated with the optimum composite electrolyte (added 1% CNTs in PEO matrix, 1%CNT–PEO) achieved maximum conversion efficiency of 3.5%, an open circuit voltage (V OC ) of 0.589V, short circuit current density (J SC ) of 10.64mA/cm2 and fill factor (FF) of 56%. The highest IPCE in the DSSC fabricated with 1%CNT–PEO electrolyte is ascribed to the improved ionic conductivity of composite electrolytes and enhanced interfacial contact between electrode and electrolyte.
Sn–NiTi composite thin films consisting of different amounts of Sn, prepared by directly co-sputtering pure Sn and NiTi alloy, have been characterized as anodes for lithium ion batteries. The composite films with relative low Sn content (20.2, 25.2 wt%) had a microstructure of microsized Sn particles uniformly dispersed in the porous a-NiTi matrix. In contrast, in the film with a higher Sn content (39.0 wt%), a part of the Sn reacted with NiTi to formed Ni3Sn4 intermetallic surrounding the Sn. The inactive NiTi covered and protected most of the surface of Sn in these composite films and resulted in quite low initial irreversible capacity losses and greatly enhanced cycle performances. The results showed that the Sn–NiTi film with 39.0 wt% Sn delivered higher reversible capacity and superior capacity retention, which was attributed to the interfacial reaction between Sn and NiTi phases, as well as the good electrochemical reversibility of nanocrystalline Ni3Sn4 formed in NiTi matrix.
All-solid-state batteries comprising sulfide solid electrolytes are promising for energy storage in electric vehicles because of their safety record. There is a high demand for batteries in the form of stackable compact sheets with high cell-based energy density that are mass fabricated in a scalable process. A slurry coating is advantageous for fabricating sheet-type batteries, improves productivity, and allows control of the layer thickness. Here we present a slurry-mixing method for fabricating homogeneously dispersed composite sheets containing micrometer-sized silicon particles. Subsequent removal of the volatile binder from the stacked-sheet cells is demonstrated to reduce their internal resistance. The silicon composite sheets exhibit high initial Coulombic efficiencies of 95%, with practical areal capacities of 2.0–4.4 mAh cm−2 at the 47th cycle under 0.30 mA cm−2, a reversible specific capacity of 2300 mAh g−1 after 100 cycles, and long-term cycling stability (specific capacity above 1700 mAh g−1 after 375 cycles). Cracks that are vertical to the silicon composite layer after cycling buffer the internal strain originating from silicon volume changes, providing excellent cycling stability. These results can assist the rational design of silicon anodes for high-cell-performance all-solid-state batteries.
A high-capacity iron- and nickel-substituted Li 2 MnO 3 cathode [i.e., Li 1.26 Fe 0.11 Ni 0.11 Mn 0.52 O 2 (LFNM)] treated by carbothermal reduction was analyzed, and the results clarified that it has both high capacity and high safety levels. X-ray analysis of a reduced LFNM (R-LFNM) cathode clarified the following. Migration of transition metals in the lattice as a result of the carbothermal reduction stabilizes the layered lattice structure, which prevents lattice shrinkage during charging and enhances charge compensation. As a result, more lithium ions can return to the cathode during discharging; namely, the irreversible capacity of the cathode decreases. Thermal stability of the R-LFNM cathode was evaluated by differential scanning calorimetry (DSC), and the results show that the total heat evolved from the R-LFNM cathode remains at a lower level compared with that of other cobalt- and nickel-containing Li 2 MnO 3 cathodes. An analysis of the lattice structure reveals that low exothermic heat from the charged R-LFNM cathode results from the distinctive property of its crystal lattice changing from layered to thermally stable spinel during charging.