High Cycle Efficiency Research Articles

Highly Stable Germanium Microparticle Anodes with a Hybrid Conductive Shell for High Volumetric and Fast Lithium Storage.

The ability to realize a highly capacitive/conductive electrode is an essential factor in large-scale devices, requiring a high-power/energy density system. Germanium is a feasible candidate as an anode material of lithium-ion batteries to meet the demands. However, the application is constrained due to low charge conductivity and large volume change on cycles. Here, we design a hybrid conductive shell of multi-component titanium oxide on a germanium microstructure. The shell enables facile hybrid ionic/electronic conductivity for swift charge mobility in the germanium anode, revealed through computational calculation and consecutive measurement of electrochemical impedance spectroscopy. Furthermore, a well-constructed electrode features a high initial Coulombic efficiency (90.6%) and stable cycle life for 800 cycles (capacity retention of 90.4%) for a fast-charging system. The stress-resilient properties of dense microparticle facilitate to alleviate structural failure toward high volumetric (up to 1737 W h L-1) and power density (767 W h L-1 at 7280 W L-1) of full cells, paired with highly loaded NCM811 in practical application.

A polymeric cathode-electrolyte interface enhances the performance of MoS2-graphite potassium dual-ion intercalation battery

Anion intercalation in the graphite cathode of a dual-ion battery (DIB) occurs at unusually high voltage (>4.5 V K + /K). This exacerbates electrolyte degradation and corrosion of Al current collectors, leading to poor coulombic efficiency (CE), typically <90%, and short cell life as a result. These limitations can be mitigated if a stable cathode-electrolyte interface layer (CEI) can form on the graphite electrode. In this study, we demonstrate that the performance of a potassium-based DIB can be improved with a triallyl phosphate (TAP) monomer added in 6 m KN(SO 2 CF 3 ) 2 (KTFSI)-dimethyl carbonate (DMC) electrolyte. The TAP additive forms a stable polymeric CEI on the graphite particles and thus increases the CE of the cell to 97%–99%. Together with MoS 2 -negative electrodes with a pre-formed solid electrolyte interphase (SEI) layer, the DIB concept has been shown to offer specific capacities from ∼40 to 80 mAh g −1 with an average discharge voltage of 3.7 V. • Design principle for high-performance MoS 2 -graphite dual-ion battery is proposed • Impact of electrolyte additives on the negative and positive electrodes is investigated • Triallyl phosphate is used to generate a polymeric CEI on graphite cathode • MoS 2 with pre-formed SEI layer ensures stable cycling and high coulombic efficiency A dual-ion battery operates at unusually high voltage, which is needed to intercalate anions in a graphite cathode. Asfaw et al. explore strategies to create more stable electrode-electrolyte interfaces in an effort to design potassium-based MoS 2 -natural-graphite dual-ion battery with high coulombic efficiency and long cycle life.

Breathable Artificial Interphase for Dendrite-Free and Chemo-Resistive Lithium Metal Anode.

A dendrite-free and chemically stabilized lithium metal anode is required for extending battery life and for the application of high energy density coupled with various cathode systems. However, uneven Li metal growth and the active surface in nature accelerate electrolyte dissipation and surface corrosion, resulting in poor cycle efficiency and various safety issues. Here, the authors suggest a thin artificial interphase using a multifunctional poly(styrene-b-butadiene-b-styrene) (SBS) copolymer to inhibit the electrochemical/chemical side reaction during cycling. Based on the physical features, hardness, adhesion, and flexibility, the optimized chemical structure of SBS facilitates durable mechanical strength and interphase integrity against repeated Li electrodeposition/dissolution. The effectiveness of the thin polymer film enables high cycle efficiency through the realization of a dendrite-free structure and a chemo-resistive surface of Li metal. The versatile anode demonstrates an improvement in the electrochemical properties, paired with diverse cathodes of high-capacity lithium cobalt oxide (3.5mAh cm-2 ) and oxygen for advanced Li metal batteries with high energy density.

Ultrastable Zinc Anode by Simultaneously Manipulating Solvation Sheath and Inducing Oriented Deposition with PEG Stability Promoter.

Aqueous zinc-ion batteries are a low-cost and safe energy storage system, but suffer from detrimental side reactions and Zn dendrites due to the strong interactions between Zn2+ and water molecules in the electrolytes, and random Zn2+ deposition on the anode surface. Here, an electrolyte involving a dual-functional additive of polyethylene glycol (PEG) to bypass these issues is reported. The electrolyte can not only tailor the solvation sheath of Zn2+ but also enable favorably oriented deposition of Zn2+ on the anode surface. The dendrite-free Zn anode in Zn//Zn cells is obtained with high Columbic efficiency (98.8%) and long cycling lifespan (1500 h), six times longer than that of electrolyte without PEG at 0.25mA cm-2 . What is more, the excellent cycling stability of the prepared batteries (Zn//V2 O5 ·1.6 H2 O) suggests that the developed tailoring strategy may propel a promising pathway for stabilizing Zn metal anodes.

Vortex Tracking of Purge-Mainstream Interactions in a Rotating Turbine Stage

Abstract The use of purge flow in gas turbines allows for high turbine entry temperatures, which are essential to produce high cycle efficiency. Purge air is bled from the compressor and reintroduced in the turbine to cool vulnerable components. Wheel-spaces are formed between adjacent rotating and stationary discs, with purge air supplied at low radius before exiting into the mainstream gas-path through a rim-seal at the disc periphery. An aerodynamic penalty is incurred as the purge flow egress interacts with the mainstream. This study presents unparalleled three-dimensional velocity data from a single-stage turbine test rig, specifically designed to investigate egress–mainstream interaction using optical measurement techniques. Volumetric velocimetry is applied to the rotating environment with phase-locked measurements used to identify and track the vortical secondary flow features through the blade passage. A baseline case without purge flow is compared to experiments with a 1.7% purge mass fraction; the latter was chosen to ensure a fully sealed wheel-space. A non-localized vortex tracking function is applied to the data to identify the position of the core centroids. The strength of the secondary flow vortices was determined using a circulation criterion on rotated planes aligned to the vortex filaments. The pressure-side leg of the horseshoe vortex and a second vortex associated with the egress flow were identified by the experimental campaign. In the absence of purge flow, the two vortices merged, forming the passage vortex (PV). With the addition of purge flow, the two cores remained independent to 40% of the blade axial chord, while also demonstrating an increased radial migration and intensification of the PV. The egress core was shown to remain closer to the suction-surface with purge flow. Importantly, where the vortex filaments demonstrated strong radial or tangential components of velocity, the circulation level calculated from axial planes underpredicted the true circulation by up to 50%.

Cationic Cyclopropenium-Based Hyper-Crosslinked Polymer Enhanced Polyethylene Oxide Composite Electrolyte for All-Solid-State Li-S Battery.

The development of solid-state polymer electrolytes is an effective way to overcome the notorious shuttle effect of polysulfides in traditional liquid lithium sulfur batteries. In this paper, cationic cyclopropenium based cross-linked polymer was firstly prepared with the one pot method, and then the counter ion was replaced by TFSI− anion using simple ion replacement. Cationic cyclopropenium hyper-crosslinked polymer (HP) was introduced into a polyethylene oxide (PEO) matrix with the solution casting method to prepare a composite polymer electrolyte membrane. By adding HP@TFSI to the PEO-based electrolyte, the mechanical and electrochemical properties of the solid-state lithium-sulfur batteries were significantly improved. The PEO-20%HP@TFSI electrolyte shows the highest Li+ ionic conductivity at 60 °C (4.0 × 10−4 S·cm−1) and the highest mechanical strength. In the PEO matrix, uniform distribution of HP@TFSI inhibits crystallization and weakens the interaction between each PEO chain. Compared with pure PEO/LiTFSI electrolyte, the PEO-20%HP@TFSI electrolyte shows lower interface resistance and higher interface stability with lithium anode. The lithium sulfur battery based on the PEO-20%HP@TFSI electrolyte shows excellent electrochemical performance, high Coulombic efficiency and high cycle stability. After 500 cycles, the capacity of the lithium-sulfur battery based on PEO-20%HP@TFSI electrolytes keeps approximately 410 mAh·g−1 at 1 C, the Coulomb efficiency is close to 100%, and the cycle capacity decay rate is 0.082%.

A high-performance solid electrolyte assisted with hybrid biomaterials for lithium metal batteries

The demand for high safety lithium batteries has led to the rapid development of solid electrolytes. However, some inherent limitations of solid polymer electrolytes (SPEs) impede them achieving commercial value. In this work, a novel polyethylene oxide (PEO)-based solid electrolyte is reported. For the first time, biomaterial-based chitosan-silica (CS) hybrid particles serve as fillers, which can interact with polymer matrix to significantly improve the electrochemical performance. The optimized polymer electrolyte exhibits a maximum ion conductivity of 1.91 × 10−4 S·cm−1 at 30 °C when the mass ratio of PEO and CS is 4:1 (PCS4). All-solid-state LiFePO4|PCS4|Li cells deliver a high coulombic efficiency and stable cycling performance, remaining an excellent capacity of more than 96.2 % after 150 cycles. Furthermore, the wide electrochemical window (5.4 V) and steady interfacial stability provide the possibility for high-voltage batteries applications. NCM811|| Li cells are assembled and display reliable charge and discharge cycle properties.

Transformation of Al-CDC from 3D crystals to 2D nanosheets in macroporous polyacrylates with enhanced CH4/N2 separation efficiency and stability

Development of materials with high efficiency and long-life cycles for CH4/N2 separation is of importance for coal-bed methane purification. Herein, a composite was prepared by in-situ growing the specific aluminum-based metal–organic framework (MOF) with trans-1,4-cyclohexanedicarboxylicacid as ligand (Al-CDC) on the internal macroporous surface of polyacrylates (PA). Due to the surface-induced low-energy-barrier orientation crystallization, the morphology of Al-CDC was transformed from three-dimensional (3D) crystals to two-dimensional (2D) nanosheets, forming ultrathin films with higher adsorption efficiency and lower diffusion barrier. As a result, the adsorption efficiency can be increased by 1.73 times compared with bulk Al-CDC and the selectivity of CH4/N2 (50/50, v/v) mixed gas is 13.75, which is the highest value reported so far. Furthermore, the hydrophobic feature of PA enhanced the water and recycling stability of composite, providing promising adsorbent for coal-bed methane purification using pressure swing adsorption process.

High energy density in poly(vinylidene fluoride-trifluoroethylene) composite incorporated with modified halloysite nanotubular architecture

Dielectric polymer capacitors with high power density as well as efficient charge-discharge rate are widely investigated in past decades. The development of polymer film with large electric capability has become the research topic for the energy storage of advanced power equipment. Here the tubular architecture in poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) composite film has been constructed with modified halloysite nanotubes (HNTs) to accomplish an effective diffusion of matter and energy units under high electric field. The nanotube surface was functionalized with poly(dopamine) (PDA) in tris-buffer solution to improve the compatibility with fluoropolymer. The energy capability of P(VDF-TrFE) composite film is enhanced owing to the large content of electroactive phase and interfacial polarization. The dielectric constant in 4 wt% PDA-HNTs/P(VDF-TrFE) film is 34.1 at 100 Hz, and the energy density in 2 wt% composite achieves 5.6 J/cm3 with charge-discharge efficiency of 74% at 250 MV/m based on the efficient transportation of ions within hollow nanotubular structure. This work delivers a simple method to construct the efficient diffusion route in polymer dielectrics for film capacitor with high energy density and cycle efficiency.

Morphology and electrochromic properties of nanostructured polyterthiophene films formed by different deposition modes

Nanostructured electrochromic polymer (ECP) materials are commonly explored in electrochromic devices (ECDs) because of their fast switching speed, high coloration efficiency and long cycle life. However, the preparation of nanostructured ECP films with a single component is still a great challenge. Herein, we present a facile, efficient, low-cost strategy to construct three-dimensional reticular macroporous (3DRM) ECP films without using templates. Polyterthiophene (PTTh) is selected as the model polymer due to its good EC behaviour. The 3DRM PTTh films on indium tin oxide (ITO) glass are fabricated by potentiostatic deposition (PSD) and pulsed electrodeposition (PED) of terthiophene (TTh), and further assembled into the ECDs. We investigate the morphology, structure and electrochemical properties of PTTh films, and EC performance of corresponding ECDs. The results indicate that the PTTh film with a PED time of 240 s (PTTh-PED-240) possesses loose 3DRM morphology and large surface area. The EC properties of corresponding ECD is significantly enhanced, exhibiting a large optical contrast, high coloration efficiency, short switching time, and improved cycling. Compared with the ECD based on PTTh film with a PSD time of 120 s on ITO glass (PTTh-PSD-120/ITO), the optical contrast of ECD based on PTTh-PED-240/ITO (ECD-240) increases by 45% (31 → 45%), and its coloration efficiency increases by 107% (258 → 534 cm 2 /C). This study suggests that PED might be a facile strategy for fabricating high-performance nanostructured ECP films, and its preparation process is low-cost, easily conducted under ambient conditions, showing great potential applications in nanostructured polymer-based ECDs. • A facile, efficient and low-cost strategy was proposed to construct nanostructured ECP films without using templates. • The as-prepared PTTh-PED films possessed loose 3DRM morphology and large surface area. • The ECD based on PTTh-PED-240/ITO exhibited a superior electrochromic performance. • The relationship of microstructure, surface morphology and thickness of 3DRM PTTh films to EC properties was revealed.

High-conversion reduction synthesis of porous silicon for advanced lithium battery anodes

For practical implementation of high-capacity silicon anodes, porous silicon (pSi) structures have demonstrated outstanding cycling stability against the large volume changes typical of solid silicon particles. The conventional magnesiothermic reduction (MR) of silica under static conditions limits the yield of pSi and sometimes produces low-purity of pSi owing to limited mass transfer and many side reactions. Hence, we devise a rotational MR (R-MR) system with rapid magnesium transport in which a uniform Mg/SiO2 molar ratio is readily achievable, and a short reaction time can be applied. Compared to conventional MR, the R-MR process has an extremely high yield (∼90 wt%) of pSi at almost complete conversion of precursor, whereas side reactions are substantially suppressed. Mg 2p X-ray photoelectron spectroscopy analysis of the reduction product reveals that pSi yield is well correlated with the conversion of Mg to MgO. The carbon-coated pSi/C samples and their hybrids with graphite (pSi/C@Gr) composites demonstrate stable cycling performance for 300−600 cycles at high capacity with high cycling efficiency (∼99.9%). Therefore, high-conversion R-MR can be a very efficient and scalable process for obtaining pSi for use in carbon composites (such as pSi/C and pSi/C@Gr) that offer outstanding cycling performance in high-capacity anodes for high-energy LIBs.

Implanted cobalt ions in two zinc-based frameworks: Improved electrocatalyst for hydrogen evolution reaction

Hydrogen energy has been considering as an ideal renewable energy source and playing a very important role in daily life. Noble metal catalysts have shown excellent catalytic performance in electrolysis of water for hydrogen evolution, but their scarcity and high cost limit their large-scale use. Therefore, the design of non-noble metal catalysts with high catalytic activity and stability and low cost is an urgent problem to be solved. Two zinc-based coordination polymers have been synthesized by one-pot method. We developed an effective method through simple Co2+ doping, which improved and optimized the electrocatalytic performance to obtain two high-quality electrocatalysts for electrolysis of water to produce hydrogen with low starting potential (−210 mV and −240 mV), high Tafel efficiency (117.7 mV dec-1 and 127.8 mV dec-1) and excellent cycle stability (>95% LSV retention after at least 2000 cycles). We also synthesized two isomorphic Co-based or Ni-based coordination polymers, and found that their electrocatalytic performances were improved to some extent after the introduction of Co ions, but the effects were not as good as that of zinc-based coordination polymers. This work not only provides two examples of good electrocatalyst, but also provides an idea to improve and optimize the electrocatalytic performance.

Achieving fully reversible conversion in Si anode for lithium-ion batteries by design of pomegranate-like Si@C structure

Si/C materials are considered as the most promising anodes for the next generation lithium ion batteries. However, the Si/C anodes with high Coulombic efficiency are still a challenge. Here, pomegranate-like Si@C microspheres are successfully prepared with inexpensive AlSi alloy by surface modification, coating with resin, carbonization and acid etching processes. As high as 84.98% initial Coulombic efficiency (ICE) and 100% Coulombic efficiency are obtained for the sample (Si40@C3), and the specific capacity still maintained over 620 mAh g−1 with capacity retention of 70.4% over 250 cycles. The excellent electrochemical performance could be attributed to the distinctive pomegranate-like Si@C structure, which either stabilizes the porous structure of Si particle by inhibiting the volume expansion and pulverization or improves the electrochemical property by the appropriate carbon coating layer. This would provide a helpful guide to synthesize the Si/C anode with high ICE and Coulombic efficiency and stable cycling.

Investigation into ethanol effects on combustion and particle number emissions in a spark-ignition to compression-ignition (SICI) engine

Spark assistance along with oxygenated components addition is a promising method to achieve stable compression ignition, high thermal efficiency and low particle emission. To this end, ethanol blended with non-oxygenated gasoline was fueled to an engine working with spark-ignition to compression-ignition (SICI) mode under air dilution and exhaust-diluted conditions. The effects of ethanol addition on engine performance including combustion characteristics, fuel economy, particle number (PN) emissions, were studied in two categories: changing research octane number (RON) by varying ethanol content and maintaining RON by changing fuel type. The results showed that ethanol addition by splash blending suppressed knock tendency, and the knock intensity could be lowered by up to 65–75% with increasing ethanol content. However, when maintaining the same RON, the ethanol-gasoline blend exhibited higher knock intensity than pure gasoline due to synergistic effects between ethanol and aromatics on auto-ignition. Compared to pure spark ignition with high-RON gasolines, using ethanol-gasoline blends under SICI could reduce the minimum fuel consumption rate by up to 25 g/(kW·h). To characterize the high-efficiency cycles under SICI, two dimensionless parameters were proposed by considering the ratios of heat release amount and duration between the flame propagation stage and auto-ignition stage. The two parameters showed good exponential correlation. As for emissions, blending ethanol could basically reduce PN emissions under SICI mode except for the cases with significant increase in nucleation particles, such as those with high knock intensity under stoichiometric condition and poor combustion quality under heavily exhaust-diluted conditions. The total PN reduction by blending ethanol is mainly due to the decrease of accumulation mode particles, during the stage of flame propagation rather than auto-ignition. Blending ethanol into non-oxygenated gasoline will directly increase unburned hydrocarbons and nitrogen oxides due to the low auto-ignition propensity of ethanol under stoichiometric or moderately lean conditions according to the temperature-pressure trajectory. Therefore, a dedicated combustion system with higher compression ratio and lean-boosted mixture is required to enhance ethanol's reactivity and achieve better fuel economy along with low PN emission for diluted SICI combustion.

Energy, economy, and ecological (3E)‐based performance evaluation of a steam cycle power plant through optimization investigation

AbstractEnergy, economy, and ecological (3E)‐based analysis of steam cycle power plant evaluated through multiobjective investigation. The Montazer Ghaem steam‐based power plant situated in Iran is considered for investigation. Cycle efficiency, total cost, and ecological function of steam power cycle are treated as the 3E objective in the analysis. Simultaneous optimization of this performance parameter is executed through a heat transfer search algorithm. Fifteen operating variables of the steam power cycle, which includes different pressure, temperature, and isentropic efficiency are considered during the 3E‐based optimization investigation. The dryness fraction of the exhaust stream and condensing temperature are operating constraints considered in the present investigation. The results are presented in the form of Pareto solutions. The results of the Pareto solution indicate that a 6.73% variation in cycle efficiency, 44.67% variation in total cost rate, and 15.63% variation in ecological function (ECF) are observed between extreme values of 3E objectives. The obtained optimum condition is compared with the present actual operating condition of the steam power cycle. Comparative results reveal 5.27% higher cycle efficiency with 15.53% higher ECF as compared to the actual running case. For identical total cost rate of the system, 4.65% higher cycle efficiency with 1.21% rise in ECF was observed as compared to actual running case. Further, the uncertainty propagation of the Pareto points is obtained with different uncertainty levels to identify the robustness of the solutions. Finally, the important operating variables are identified and their effects on the 3E objectives are also investigated.

Polymer Templating Method for the Formation of Hierarchically Porous Nitrogen-Rich Tin-Carbon Composite Anodes

This study aims to provide a new platform for the fabrication of metal-carbon composites. Herein we show that the high density crosslinking of a polymer can be used to homogenously trap metal nanoparticles and other components. In this setting, we utilized the cross-linking of poly(maleic anhydride-at 1-octadecene) [PMAO] with ethylene glycol to trap metal nanoparticles and carbon nitride (C3N4) within the polymeric structure. During inert, high-temperature pyrolysis, the polymer acts as a soft-template and prevents agglomeration of metallic tin during the synthesis. Inspired by the work of Tang et al. the carbon nitride is employed to act as a nitrogen dopant source and textural template for the final product. Through an analysis variable experimental parameter, we have shown that this method provides an avenue for the tunable fabrication of nitrogen-rich porous composites. To demonstrate the practicality of this synthetic method, composites with a variety of different nitrogen moieties and textural compositions were electrochemically analyzed. The resulting composites were then used as a platform to demonstrate not only the tunability of the synthetic method but also an example of how much these effects drastically dictate the electrochemistry of the system. Of the samples analyzed it was shown that a urea based composite demonstrated the best electrochemistry touting high rate capability, stable cycling, and high coulombic efficiency (CE).The results of long-term performance testing reveal the excellent electrochemical properties of the U-Sn-CN composite, supplying an initial capacity of ~ 600 mAh g–1 and 82.0 % capacity retention over 400 cycles at a high current density of 1 A g–1 (1C) with an average CE of 99.8 %. Lower current density studies [500 mA g-1 (C/2)] have shown the material to have an initial capacity of ~ 640 mAh g–1 with 86.0 % capacity retention over 400 cycles. Electrochemical and post-mortem analysis of this composite material suggest the performance properties can be attributed to the unique nitrogen-doped carbon framework, which is able to buffer the large volumetric expansion of the tin due to its disordered flexible nature whilst contributing to the overall capacity of the composite from its high degree of nitrogen doping (~11.9 at %). Figure 1

Natural Self-Confined Structure Effectively Suppressing Volume Expansion toward Advanced Lithium Storage.

Volume expansion hinders conversion-type transition-metal oxides (TMOs) as potential anode candidates for high-capacity lithium-ion batteries. While nanostructuring and nanosizing have been employed to improve the cycling stability of TMOs, we show here that both high initial Coulombic efficiency (ICE) and stable cycling reversibility are achieved in the layered compound Li0.9Nb0.9Mo1.1O6 (L0.9NMO) by inherent properties of the bulk crystal structure. In this model, MoO6 octahedra as active centers react with lithium ions and endow capacity, while a grid composed of NbO6 octahedra effectively suppresses the volume expansion, enhances the conductivity, and supports the structural skeleton from collapse. As a result, bulk L0.9NMO not only delivers a high discharge capacity of 1128 mA h g-1 at 100 mA g-1 with a considerable ICE of 87% but also exhibits long cycling stability and good rate performance (339 mA h g-1 after 500 cycles at 1 A g-1 with an average Coulombic efficiency approaching 100%). The self-confined structure provides a competitive strategy for stable conversion-type lithium storage.

Multifunctional modified polylactic acid nanofibrous scaffold incorporating sodium alginate microspheres decorated with strontium and black phosphorus for bone tissue engineering

Polylactic acid (PLA) nanofibrous scaffolds have received extensive attention in the field of tissue engineering due to their excellent degradability, biocompatibility and the biomimetic extracellular matrix (ECM) topographies. However, the cell affinity and osteogenic activity of PLA scaffolds is not satisfactory because of their intrinsic hydrophobicity, the absence of cell recognition sites and the nucleation sites of the in vivo biomineralization. Furthermore, effective anti-inflammatory activity for the in vivo scaffold could not be ignored, so a strategy to develop a multifunctional PLLA (poly-L-lactic acid) nanofibrous scaffold with improved hydrophilicity, osteoinductivity, excellent near-infrared photothermal-responsive drug release capacity and anti-inflammatory activity via incorporating sodium alginate microspheres decorated with strontium and ibuprofen-loaded black phosphorus (BP + IBU@SA microspheres) into aminated modified PLLA nanofiber network is proposed in this study. Scanning electron microscopy (SEM) observation showed that the BP + IBU@SA microspheres were homogeneously dispersed into the modified PLLA matrix with uniform nanofiber structure and the chemical composition of the as-prepared scaffolds was confirmed by X-ray diffraction analysis (XRD) and elemental mapping. The photothermal property of the scaffolds was assessed under near-infrared (NIR) light irradiation, the results manifested that the entrapment of BP nanosheets endowed PLLA nanofibrous scaffold with significantly high photothermal conversion efficiency and optical cycle stability. Meanwhile, the scaffold also displayed an excellent photothermal-responsive intelligent drug release performance toward Sr2+ and ibuprofen. Moreover, the in vitro studies revealed that the as-developed scaffolds possessed a good biocompatibility for cell adhesion and proliferation and an improved bioactivity to induce apatite formation. All these results indicated the potential of the fabricated scaffolds in tissue engineering applications.

Development of a novel dual heated cascade supercritical carbon dioxide cycle and performance comparison with existing two configurations for waste heat recovery

As an efficient method for the waste heat recovery of gas turbine, supercritical carbon dioxide (S-CO2) power cycle has gained much attention, due to the high efficiency and compact structure. Thus, in this work, a novel S-CO2 power cycle is developed for the waste heat recovery via the modification of dual heated cascade cycle with an intercooler (intercooling cycle). Compared with the dual heated cascade cycle (original cycle) and the intercooling cycle, the novel cycle has independent pressures at different heaters and turbines. To analyze the system performance, thermodynamic models are established and a genetic algorithm (GA) is applied to optimize the decision variables with the maximization of net work. These variables include two turbine inlet temperatures, a middle pressure, a low pressure, and a split ratio. Thereafter, thermodynamic parameters of the considered three cycles are obtained under different waste gas temperatures. For the recovery of 600°C waste gas, the novel cycle has the highest net work 3957.87 kW, while the lowest net work 3735.32 kW is obtained by the original cycle. For the effects of decision variables, a higher high-temperature turbine inlet temperature means a lower net work, while the increase of low-temperature turbine inlet temperature results in small increases of cycle performances. On the other hand, under the constraints of the pinch point, with the increase of low and middle pressures, the net work of the novel cycle increases. A higher net work is usually obtained at a lower split ratio. Furthermore, at different waste gas inlet temperatures, the highest cycle efficiency is always derived by the proposed cycle. For the net work, the proposed cycle has the highest value in the temperature range 600°C–750°C.

Approximate Relations for Optimum Turbine Operating Parameters in Allam Cycle

Abstract This article explores the relations between the cycle performance and the main operating parameters of the Allam cycle with uncooled turbine through a simplified thermodynamic analysis. The cycle efficiency is maximized with respect to turbine parameters. Expressions are derived for the estimation of optimum turbine inlet temperature (TIT) and pressure as well as optimum turbine exhaust pressure. The cryogenic air separation process developed by Allam is employed, which produces supercritical oxygen at combustion pressure. Typical numerical results are presented using the new expressions for optimum turbine parameters. The highest cycle efficiency is found to be 66.4% at a TIT/inlet pressure/exhaust pressure of 1306 K/300 bar/39.4 bar and a CO2 compressor exit pressure of 60 bar. The newly derived relationships for the key process parameters allow a better understanding of the operation of the Allam cycle.