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Diamond is considered the most promising next-generation semiconductor material due to its excellent physical characteristics. It has been more than three decades since the discovery of a special structure named n-diamond. However, despite extensive efforts, its crystallographic structure and properties are still unclear. Here, we show that subdisordered structures in diamond provide an explanation for the structural feature of n-diamond. Monocrystalline diamond with subdisordered structures is synthesized via the chemical vapor deposition method. Atomic-resolution scanning transmission electron microscopy characterizations combined with the picometer-precision peak finder technology and diffraction simulations reveal that picometer-scale shifts of atoms within cells of diamond govern the subdisordered structures. First-principles calculations indicate that the bandgap of diamond decreases rapidly with increasing shifting distance, in accordance with experimental results. These findings clarify the crystallographic structure and electronic properties of n-diamond and provide new insights into the bandgap adjustment in diamond.

With the advantages of high efficiency and compact structure, supercritical carbon dioxide (sCO2) Brayton cycles have bright prospects for development in energy conversion field. As one of the core components of the power cycle, the centrifugal compressor tends to operate near the critical point (304.13 K, 7.3773 MPa). Normally, the compressor efficiency increases as the inlet temperature decreases. When the inlet temperature is close to the critical point, the density increases sharply as the temperature decreases, which results in quickly decreasing of volume flow rate and efficiency reducing. The flow loss mechanism of the sCO2compressor operating at low flow rate is studied in this paper. Computational fluid dynamics (CFD) simulations for sCO2compressor were carried out at various inlet temperatures and various mass flow rates. When the sCO2compressor operates at low volume flow rate, the flow loss is generated mainly on the suction side near the trailing edge of the blade. The flow loss is related to the counterclockwise vortexes generated on the suction side of the main blade. The vortexes are caused by the flow separation in the downstream region of the impeller passage, which is different from air compressors operating at low flow rates. The reason for this flow separation is that the effect of Coriolis force is especially severe for the sCO2fluid, compared to the viscous force and inertial force. At lower flow rates, with the stronger effect of Coriolis force, the direction of relative flow velocity deviates from the direction of radius, resulting in its lower radial component. The lower radial relative flow velocity leads to severe flow separation on the suction side near the trailing edge of the main blade.

Supercritical carbon dioxide (SCO2) centrifugal compressor is a key component of a closed Brayton cycle system based on SCO2. A comprehensive understanding of the loss mechanism within the compressor is vital for its optimized design. However, the physical properties of SCO2are highly nonlinear near the critical point, and the internal flow of the compressor is closely related to its properties, which inevitably influences the generation of aerodynamic losses within the compressor. This paper presents a comprehensive investigation of the compressor’s loss mechanism with an experimentally validated numerical method. The real gas model of CO2embodied in the Reynolds-Averaged Navier-Stokes (RANS) model was used for the study. Firstly, the numerical simulation method was validated against the experimental results of Sandia SCO2compressor. Secondly, performance and loss distribution of the compressor were compared among three fluids including SCO2, ideal CO2(ICO2) and ideal air (IAir). The results showed that the performance of SCO2was comparable to IAir under low flow coefficient, however markedly inferior to the other two fluids at near choke condition. Loss distribution among the three fluids was distinctive. In the impeller, SCO2was the most inefficient, followed by ICO2and IAir. The discrepancies were magnified as the flow coefficient increased. This is due to a stronger Blade-to-Blade pressure gradient that intensifies boundary layer accumulation on walls of the shroud/hub. Furthermore, owing to the reduced sonic speed of SCO2, a shock wave appears earlier at the throat region and SCO2encounters more intense boundary layer separation.

Electronic paper (e‐paper) is a reflective display technology with unique advantages, such as bistability, low‐power consumption, and high ambient contrast ratio. These features make e‐paper a promising candidate for future Internet of Things applications. Among different technologies of e‐paper, electrophoretic display (EPD) is the most successful one for commercialization. However, the edge ghosting (also known as the fringing effect) still limits the performance of EPD. Herein, we established a model of particle dynamics of electrophoresis, simulated the edge ghosting of microcapsule EPD, analyzed the edge ghosting effect, and revealed the relationship between thicknesses, dielectric constants of the back binder layer, and the edge ghosting. Two EPD panels with different thicknesses of back binder layer were demonstrated, which verifies the accuracy of this simulation model. With the proposed model, many device mechanisms and product issues can be analyzed and illustrated, which is supposed to guide the researchers in optimizing the device structure design of EPD. We developed a particle dynamics model for electrophoresis, simulating microcapsule EPD's edge ghosting and its correlation with back binder layer thicknesses and dielectric constants. By demonstrating two EPD panels with different back binder layer thicknesses, our simulation confirmed the predicted trend.

Variable geometry twin-entry turbine has advantages in fuel economy, low-end torque, emission and turbo-engine matching of internal combustion engine. The reliability of performance prediction method for nozzled twin-entry turbine is heavily dependent on the understanding of flow mechanism of the turbine which is always confronted by time-dependent unequal admissions. This paper establishes a new meanline model of a nozzled twin-entry turbine based on the internal flow features. Firstly, flow mechanism of the twin-entry turbine with a vaned nozzle under different admissions is investigated via an experimentally validated CFD method. Results clearly demonstrate that the flow distortion in spanwise direction caused by unequal admissions notably influences the turbine efficiency discrepancy between symmetric unequal admissions, especially the two partial admissions. The evolution of flow distortion in the nozzle passage is the key to the performance discrepancy, which is impossible to be considered by a conventional performance model of a nozzled twin-entry turbine. Inspired by this, a newly-designed meanline model, named ‘parallel nozzle’ is proposed. Specifically, a nozzle passage is divided into two parallel sub-passages in spanwise direction to consider the flow distortion in nozzle passage. The model is validated against the detailed CFD results in terms of both overall performance and detailed flow parameters over different admissions. Results prove that turbine performance and flow parameters are well predicted by the model. Specifically, the influence of admissions on nozzled twin-entry turbine performance and flow parameters can be predicted by the method in satisfying accuracy.

The chelating ligands of boric acid and amino trimethyl phosphonate prepared a novel flame retardant (BAP) for the cotton fabric. A stable chemical and coordination bond was formed on the surface of the cotton fibers by a simple three‐curing finishing process to make the fabric exhibits excellent durable flame retardancy. Cotton fabrics' tensile strength and whiteness got substantially retained after BAP treatment. 90 g/L BAP‐treated samples (3 curing times, 50 laundry cycles) showed good flame retardancy and durability, holding the largest limit oxygen index, 29.7%, and the shortest damage length, 61 mm. A condensed phase and gas phase synergistic flame retardant mechanism was concluded by thermogravimetric, cone calorimeter tests, and thermogravimetric infrared analysis. BAP was synthesized by urea, boric acid, pentaerythrotol and ATMP with a one pot synthesis method. BAP solution finished cotton fiber was shown the best flame retardancy and durability, the LOI data up to 25%, and the damaged length was 61 mm, after 50 launderings.

With the advancement of geo-systems and the increased availability of satellite data, a plethora of land-use and land-cover (LULC) products have been developed. The existing LULC products primarily relied on time-series imagery to classify land by pixel-based classifiers, allowing for local analysis and accurate boundary detection. However, the advent of deep learning has shifted toward the use of patch-based CNN models for generating land cover maps. In this article: 1) we create a training dataset for China using a voting strategy based on three off-the-shelf available LULC products, avoiding the labor-intensive manual annotation. 2) We design a novel CNN-based model for the LULC task, called multimodal fine-grained dual network (dubbed as Dual-Net), which takes dual-date images to generate final maps and reduces the need for gap-free temporal sequences or separate cloud detection. To leverage the correlation between location, date, and category, we embed modal information (dates and geo-locations) into the model. Furthermore, by incorporating low-level constraints and using pseudolabel refinement, we continually improve the performance and achieve more refined segmentation. 3) Due to the lack of a suitable validation dataset for China, we create a new validation dataset called the China Sentinel2 Validation Dataset (CSVD) by manually annotating 733 finely labeled images of $1024 \times 1024$ pixels of China-specific Sentinel2 data. 4) Extensive experiments demonstrate that our model outperforms existing LULC products and produces more fine-grained segmentation results comparable to other patch-based products. Finally, we release annual LULC maps for China in 2020–2022 and also make our model accessible online for real-time results export.

AbstractDiamond is an ultrawide bandgap semiconductor with excellent electronic and photonic properties, which has great potential applications in microelectronic and optoelectronic devices. As an allotrope of diamond, graphene also has many fantastic properties like diamond, which caught much attention in combing them together. In this work, a direct sp3-to-sp2conversion method was proposed to fabricate graphene layers on single crystal diamond by thermal treatment with Ni film catalyst. By optimizing the conversing conditions, a thin graphene layer with low sheet resistance was obtained on diamond. Based on this, an all-carbon sandwich structural graphene-diamond-graphene (GDG) detector was fabricated, which shows low dark current of 0.45 nA at 0.5 V μm−1applied electric field. The maximum sensitivity of this detector is obtained when the incident X-ray is 12 keV, with the value of 2.88 × 10−8C Gy−1. Moreover, the rise time and delay time of the GDG detector is about 1.2 and 22.8 ns, respectively, which are very close to that of diamond detector with Ti/Au electrode. The realization of the direct in-situsp3-to-sp2conversion on diamond shows a promising approach for fabricating diamond-based all-carbon electronic devices.

A model of particles dynamics of electrophoretic display was established to simulate the distribution of charged particles, edge ghosting effect with different thicknesses, dielectric constants of back binder layer. Reflectivities corresponding to particles distributions were simulated, which evaluated the extent of edge ghosting. The model can suggest the best values of the above parameters.

A model of particles dynamics of electrophoretic display was established to simulate the distribution of charged particles, edge ghosting effect with different thicknesses, dielectric constants of back binder layer. Reflectivities corresponding to particles distributions were simulated, which evaluated the extent of edge ghosting. The model can suggest the best values of the above parameters.

A new two-dimensional material B2S2has been successfully synthesized for the first time and validated using first-principles calculations, with fundamental properties analyzed in detail. B2S2has a similar structure as transition-metal dichalcogenides (TMDs) such as MoS2, and the experimentally prepared free-standing B2S2nanosheets show a uniform height profile lower than 1 nm. A thickness-modulated and unique oxidation-level dependent band gap of B2S2is revealed by theoretical calculations, and vibration signatures are determined to offer a practical scheme for the characterization of B2S2. It is shown that the functionalized B2S2is able to provide favorable sites for lithium adsorption with low diffusion barriers, and the prepared B2S2shows a wide band photoluminescence response. These findings offer a feasible new and lighter member for the TMD-like 2D material family with potential for various aspects of applications, such as an anode material for Li-ion batteries and electronic and optoelectronic devices.

Cyclic steam stimulation with horizontal well (CSSHW) has emerged as an efficient commercial recovery technique for heavy oil reservoirs. Accurately calculating the evolution of the heated zone and the production performance closely linked to it is crucial for addressing the economic and environmental issues that arise in the CSSHW process. Most previous analytical or semi-analytical models have relied on the assumption of uniform temperature distribution and have focused on thin-layer heavy oil reservoirs. In this study, through analyzing the evolution of the heated zone in the CSSHW experiment, the study observes that the temperature distribution within the heated region is non-uniform and exhibits a centrally symmetric distribution with the wellbore as the axis. Then, a semi-analytical model was developed to predict the heated zone evolution and production performance of CSSHW for thick-layer heavy oil reservoirs. Next, the model was validated using field data and numerical simulation. Finally, this study analyzed the evolution of the heated zone under a multi-cycle mode and examined the effects of various factors on oil production. The results reveal that the heat, the area, and the average temperature within the heated zone all increase with the number of cycles attributed to the influence of residual heat. Single-variable analysis indicates that increasing BHP reduces the pressure differential, lowering oil production, and that permeability significantly affects oil production. Multivariate analysis shows that lowering BHP with constant steam amount improves COSR or thermal efficiency. Lower steam amount achieves higher efficiency in high vertical or horizontal permeability reservoirs, while higher BHP maintains high efficiency in such reservoirs due to better fluid mobility. The temperature-dependent threshold pressure gradient (TTPG) analysis reveals that although TTPG reduces oil production, the reduction lessens with more cycles. TTPG's impact varies with steam amount, BHP, and permeability; increasing steam enhances TTPG's effect in low vertical or horizontal permeability reservoirs, while higher vertical or horizontal permeability reduces TTPG's effectiveness. This article provides a tool for rapid optimization and performance forecasting in thick-layer heavy oil field applications.

Aerodynamic interaction of rotor with stator is the primary cause of high cycle fatigue of radial turbine blade. However, few studies have been carried out on aerodynamic interaction in nozzleless radial turbines. This paper studies aerodynamic interaction in a nozzleless radial turbine via the experimentally validated numerical method. The results suggest that several flow phenomena are related to blade excitation. Firstly, when the blade sweeps by the volute tongue, the tongue wake induces a strong separation vortex at blade leading edge and interacts with it. As the tongue wake migrates downstream, it deforms into a triangular shape across the rotor passage. Secondly, the potential field of the volute leads to drastic fluctuations of blade load as well as tip leakage flow. Importantly, the tongue wake interacts with the tip leakage vortex in the vicinity of blade trailing edge. This phenomenon results in strong disturbance to pressure fluctuations on suction surface at low pressure ratio and the frequency of disturbance is roughly one order higher than that of potential field. However, its influence can be neglected at high pressure ratio. Furthermore, the details of vortex evolution in the rotor passage are discussed via the time-space contour plots of pressure difference. Various behaviors including propagation speed, direction and strength can be well manifested by this method. Finally, the strong influence of unsteady interaction on blade excitation in the nozzleless turbine is confirmed by a direct comparison of blade loads in unsteady condition with that in quasi-steady condition.

One-dimensional (1D) modelling is critical for turbomachinery unsteady performance prediction and system response assessment of internal combustion engines. This paper uses a novel 1D modelling (TURBODYNA) and proposes two additional features for the application to a twin-entry turbocharger turbine. Compared to single-entry turbines, twin-entry turbines enhance turbocharger transient response and reduce engine exhaust valve overlap periods. However, out-of-phase high frequency pulsating pressure waves lead to an unsteady mixing process from the two flows and pose great challenges to traditional 1D modelling. The present work resolves the mixing problem by directly solving mass, momentum and energy conservation equations during the mixing process instead of applying constant pressure assumption at the limb-rotor joint. Comparisons of TURBODYNA and an experimentally validated CFD suggest that TURBODYNA can not only provide a very good agreement on turbine performance, but also accurately capture unsteady features due to flow field inertial and pressure wave propagation. Levels of accuracy achieved by TURBODYNA have proved superior to traditional 1D modelling on turbine performance and the generality of the current 1D modelling has been explored by extending the application to another turbine featuring distinct characteristics.

Flexible liquid crystal displays (LCDs) are regarded as one of the most promising candidates to achieve flexible displays. In this paper, we proposed a novel technique to fabricate flexible LCDs combining polymer walls (PWs) and self‐assembled‐monolayer(SAM). The PWs with fine morphology and line‐width (about 20 µm) were fabricated to keep uniform cell gap and provided a larger aperture opening ratio for flexible LCDs. Alignment by alkyl trichlorosilane(TS) SAM was achieved at room temperature. In this way, general flexible substrates could be used for flexible LCDs. This work is promising for the manufacture of flexible LCDs.

Centrifugal compressor is exposed to pulsating backpressure due to the movement of intake valves in internal combustion engine. The performance of compressor deviates from the steady performance map, which affects the matching between turbocharger and engine. The behavior of compressor system at pulsation conditions are investigated via an in-house developed 1D unsteady code validated by experimental results. The influence of pulse frequency, magnitude and compressor characteristic curve on the compressor transient responses, including filling-emptying effect and wave dynamics, are analyzed. Results show that the strength of wave dynamics grows stronger with the increasing of pulse frequency, while the strength of filling-emptying effect increases first then decreases. The rise of pulse magnitude results in an almost linearly increasing of filling-emptying effect, while it can hardly affect the wave dynamics. Furthermore, the influence of pulsation magnitude and frequency represents the influence of local pressure gradient, and a correlation as quadratic curve can be evaluated between the pressure gradient and compressor unsteadiness. On the other hand, the influence of operating point, including the average mass flow rate and the slope of characteristic curve, is confirmed to be evidently smaller, comparing to the influence of pulsation frequency and magnitude. This study is helpful to estimate the behavior of compressor and the discrepancy of performance when operating at unsteady environment or matched with engine.

Sulfurized polyacrylonitrile (SPAN) is a prospective cathode candidate for Li-S batteries due to capable of solving polysulfides dissolution and shuttle effect and presenting stable electrochemical performance. Despite the extensive research conducted on the synthetic conditions and pathways for SPAN modification, details of the molecular structure of SPAN and electrochemical reaction mechanism of SPAN electrode remain controversial. Herein, the formation of conjugate aromatic radical and new C-S bond during discharge process is proposed for the first time. During charge process, the S atom prioritize to combine with C radical on the aromatic ring, resulting in avoiding the generation of polysulfides over long cycles, which potentially account for the remarkable cycling stability observed in the SPAN cathode. This study offers novel insights into the underlying reaction mechanisms, thereby providing valuable guidance for further development of sulfurized cathode materials applied in advanced Li-S battery.

Electrophoretic displays (EPDs) utilize the electrophoretic particles in electronic ink (e-ink) to display different color states with bistability. Bistability of EPDs is achieved by placing colloidal particles in a highly viscous solvent to keep the distribution of colloidal particles stable without sustaining the external field, so it only consumes power when updating the image. The feature of low power consumption makes it suitable for applications such as advertising boards, price tags, etc. Apart from these applications, recent research on lateral-driving EPDs extends its applications to smart windows, privacy control, and so on. However, achieving bistability by simply increasing the viscosity of solvent is inefficient in the case of lateral driving operation. Therefore, it is deserving to have intensive study on the mechanism of bistability from other aspects. Herein, we propose a mechanism to investigate the charge adsorption behavior on the electrode to affect the bistability of particles, which is based on the “Stern layer adsorption/desorption” model. Based on the above mechanism, we further fabricated a hexadecyl trimethylammonium bromide (CTAB)/poly(vinyl alcohol) (PVA) composite film on the electrode to improve the bistability of lateral-driving EPD by reducing the diffusion current caused by unabsorbed charges. This developed lateral-driving EPD can significantly improve the bistability, which is enhanced from 40 s to 7 min, an increase by a factor of approximately 10. This work gives a way to consider the bistability of colloidal particles in nonpolar solvent.

Carbon dots (CDs) have various attractive properties and potential applications, but there is much less attention paid to their phosphorescent phenomenon and mechanism. Herein, we prepared a kind of highly efficient CD-based phosphorescent material by a subtle design method that incorporated N-doped CDs (NCDs) into composite matrices (the melting recrystallization urea and biuret from the heating urea) by a one-pot heating treatment for the mixture of urea and NCDs. Through systematic investigation, CN bonds on the surface of the NCDs can create new energy level structures, and for the first time, evidence that shows they are the origin of phosphorescence is presented. Composite matrices play a dual role to suppress the vibrational dissipation of long-lived triplets by combining the rigidity of the melting recrystallization urea and hydrogen bonding between biuret and NCDs, which have obvious advantages over a single-component matrix. The results show the obtained materials have an ultralong phosphorescent lifetime of 1.06 s under 280 nm excitation and a high phosphorescent quantum yield of 7% under 360 nm excitation in air, which are the highest values recorded for the CD-based materials. These CD-based room-temperature phosphorescent materials have also shown potential in white light-emitting diodes and data security.

Li dendrite and the shuttle effect are the two primary hindrances to the commercial application of lithium–sulfur batteries (LSBs). Here, a multifunctional separator has been fabricated via successively coating carbon nanotubes (CNTs) and lithium phytate (LP) onto a commercial polypropylene (PP) separator to improve the performance of LSBs. The LP coating layer with abundant electronegative phosphate group as permselective ion sieve not only reduces the polysulfide shuttle but also facilitates uniform Li+flux through the PP separator. And the highly conductive CNTs on the second layer act as a second collector to accelerate the reversible conversion of sulfide species. The synergistic effect of LP and CNTs further increases the electrolyte wettability and reaction kinetics of cells with a modified separator and suppresses the shuttle effect and growth of Li dendrite. Consequently, the LSBs present much enhanced rate performance and cyclic performance. It is expected that this study may generate an executable tactic for interface engineering of separator to accelerate the industrial application process of LSBs.

Pulsating turbocharging system with a dual-entry turbine is always applied for the utilization of pulsating energy and improvement of low-speed torque for the internal combustion engine. With the enhancement of pulsating energy via the pulsating turbocharging system and dual-entry turbine, the interaction between exhaust manifolds and dual-entry turbine cannot be disregarded by either side when confronted by pulsating inflows. This paper proposes a gasdynamic model of double-entry turbine coupling with exhaust manifolds to examine the interaction effect between turbine and exhaust manifolds. This gasdynamic model can predict the propagation of pressure and mass flow rate from exhaust manifolds to the double-entry turbine as well as transient turbine performance. Predictions of this gasdynamic model are validated against detailed 3-D simulation and show good consistency with 3-D results. The performance and energy distribution of the double-entry turbine coupled to exhaust manifolds under various pulsating conditions are thoroughly discussed via this reduced-order model. Results show that with increasing frequency or amplitude of pulsating inflows imposed on inlets of the exhaust manifolds, the performance of the entire system deviates from the quasi-steady hypothesis, particularly the swallowing capacity. This phenomenon indicates that the matched operating point between the turbine and engine deviates from the quasi-steady conditions. In addition, exhaust manifolds geometries have a notable impact on turbine performance and energy distributions in exhaust systems. It is found that with an increase in the volume or length of the exhaust manifolds, the pulse at the turbine inlet is amplified, and available energy at the turbine inlet is increased, even though the inlet conditions of exhaust manifolds remain unchanged. This study may provide a guiding effect for the optimization of the turbo-engine matching process and the development of high-performance turbocharged engines.

Pt nanodendrites were electrodeposited at activated carbon as a catalyst for electrochemical hydrogen production. The fabricated Pt nanodendrites exposed numerous highly active atoms at (111) facet, which contribute to a low Tafel slope of 22.2 mV/dec and improvement of hydrogen production efficiency.

Once two-dimensional boron-based materials were forecasted, their excellent physical and chemical properties have realized attractive application value in the field of materials science. However, borophene could not exist independently and stably in nature. Molecular beam epitaxy is the only way being used currently for the preparation of borophene, which has low yield and harsh experimental installation conditions. Here, we propose the theory that few-layer borophene supported by silver nanoparticles can exist stably and large-scale preparation of few-layer borophene can be performed by mechanical resonance first. We have revealed that the structure of the prepared borophene is α-sheet and its thickness is less than 4 nm. The oxidation rate of borophene from the experiment is about 0.19, which indicates that the few-layer borophene possesses good structure stability. We have also studied the structure stability of borophene on silver nanoparticles by first principles calculation. The calculation proves that few-layer borophene can exist stably supported with silver nanoparticles. Furthermore, the terahertz shielding and stealth performance of the few-layer borophene have been explored. The maximum terahertz shielding effectiveness value of the prepared material could reach up to 50 and 21.5 dB for the reflection loss value in the broadband range of 0.1–2.7 THz. The large-scale preparation of few-layer borophene through the mechanical method makes it possible to study the properties of borophene and achieve low-cost large-scale applications, such as the study of terahertz shielding and stealth performance in the article, which facilitates the lightweight material design for terahertz shielding and stealth.

Unsaturated polyester resin (UPR) wastewater is highly acidic with poor biodegradability, which is difficult to treat. In this paper, the UPR wastewater was treated by distillation and cooling to solve these problems. And the effects of distillation and cooling on the parameters, such as conductivity, total dissolved solids, chemical oxygen demand (COD)Cr, biochemical oxygen demand (BOD)5and organic acid content of the UPR wastewater were studied. Through experiments, it was found that there is no obvious effect on the treatment of UPR wastewater by distillation or cooling. But through combination of distillation and cooling, the CODCr, conductivity and the BOD5of the wastewater decreased by 22.4%, 24.6% and 30.9%, respectively, and the pH was increased from 2.23 to 4.03. A mass number of white flocs were precipitated while the irritating odor is significantly reduced, and the biodegradability of the UPR wastewater was improved. The experiment results showed that the distillation or cooling could not affect the parameters above of the UPR wastewater, but the method designed in this paper can easily and effectively treat UPR wastewater, which can be used in industry.

AbstractIn recent years, diamond has shown great potential in solar-blind ultraviolet (UV) photodetection due to its ultrawide bandgap (∼ 5.5 eV) and other superior semiconductor properties. However, the response region of diamond photodetector is usually smaller than 230 nm, which cannot cover the whole solar-blind region from 200 to 280 nm. In this work, an ε-Ga2O3/diamond photodetector with wide spectra responsivity from 210 (or even lower) to 260 nm was fabricated. High-quality ε-Ga2O3film with columnar crystal was epitaxially grown on single crystalline CVD diamond substrate by pulse laser deposition (PLD). TEM characterization revealed that the ε-Ga2O3film grew along the <001> orientation on diamond (100) substrate. The deep ultraviolet (DUV) photodetector based on the ε-Ga2O3/diamond structure showed a high light-to-dark ratio over 5.7 × 104and good linear response to the incident light power density from 10 to 400 mW/cm2. Moreover, compared to other photodetectors, the fabricated ε-Ga2O3/diamond photodetector achieved high responsivity and wide spectra response region from 210 to 260 nm, with high solar-blind rejection ratio of 104 (R240/R280) and 165 (R210/R280), respectively. The extension of spectra region with high responsivity of the ε-Ga2O3/diamond photodetector can be attributed to the thin thickness of ε-Ga2O3film (around 200 nm) and parts of the DUV light were absorbed by diamond. The high responsivity and wide spectra response region indicate the fabricated ε-Ga2O3/diamond photodetector can be used for the detection of ultraviolet in the most of the DUV region.

A three-tiered thermal interface materials was proposed with the through-plane thermal conductivity up to176 W m−1K−1and contact thermal resistance as low as 4–6 K mm2W−1(double sides).The liquid metal acts as a buffer layer to connect vertically aligned graphene with the rough heater/heat sink, improving effective contact thermal conductance by more than an order of magnitude.

The pursuit of photodegrading environmental pollutants while efficiently utilizing solar energy remains a pivotal endeavor. Herein, Ag2S quantum dots (QDs)/reduced graphene oxide (rGO) composites with Ag2S QDs dispersed on porous stereoscopic rGO-based network were synthesized through a facile hydrothermal process without the addition of any other reducing agent or cross-linker. The as-obtained composites exhibited enhanced adsorption and photocatalysis performance under visible light because of the individual and synergistic effects. The hierarchically stereoscopic structure led to outstanding adsorption ability due to large specific surface area and spongy nature, which facilitated connection between the contaminants and the photocatalytic sites. The incorporation of rGO also suppressed the recombination of electron–hole pairs in the semiconductor and favored the separation from wastewater. Ag2S QDs, whose properties were influenced by quantum size effect, displayed a widened bandgap of 1.82 eV rather than initial 0.92 eV, attributing to stronger redox potential to degrade organic pollutants while efficiently absorbing the visible portion of solar light. With methyl orange as the model pollutant, the comprehensively optimized sample obtained at 150 °C exhibited adsorption capacity of 260 mg g−1at 25 °C and photodegradation rate 7.8 times that of commercial TiO2nanoparticles under visible light. Phenol was also analyzed to remove the influence of photosensitization of dyes. Our investigation gives a new insight into the design and fabrication of narrow band semiconductor/rGO composites with enhanced adsorption and photocatalysis.

Development of cheap, abundant and noble-metal-free materials as high efficient oxygen reduction electrocatalysts is crucial for future energy storage system. Here, one-dimensional (1D) MnO N-doped carbon nanofibers (MnO-NCNFs) were successfully developed by electrospinning combined with high temperature pyrolysis. The MnO-NCNFs exhibit promising electrochemical performance, methanol tolerance, and durability in alkaline medium. The outstanding electrocatalytic activity is mainly attributed to several issues. First of all, the uniform 1D fiber structure and the conductive network could facilitate the electron transport. Besides, the introduction of Mn into the precursor can catalyze the transformation of amorphous carbon to graphite carbon, while the improved graphitization means better conductivity, beneficial for the enhancement of catalytic activity for oxygen reduction reaction (ORR). Furthermore, the porous structure and high surface area can effectively decrease the mass transport resistance and increase the exposed ORR active sites, thus improve utilization efficiency and raise the quantity of exposed ORR active sites. The synergistic effect of MnO and NCNFs matrix, which enhances charge transfer, adsorbent transport, and delivers efficiency in the electrolyte solution, ensures the high ORR performance of MnO-NCNFs. 廉价、 储量丰富的非贵金属材料作为高效氧还原电催化剂是未来能量存储系统实际应用的关键. 基于此, 我们通过静电纺丝法并结合相应热处理制备了一维氮掺杂碳纳米纤维包覆一氧化锰(MnO-NCNFs). 该材料在碱性体系中表现出良好的电化学性能, 耐甲醇腐蚀性和稳定性. 其优异的电催化活性主要归结于以下几点: (1) 均一的一维纤维结构和导电网络能够促进反应过程中快速的电子转移; (2) 过渡金属锰的引入能够促进无定型碳向石墨碳的转变, 同时石墨化程度的提高意味着更好的导电性, 有利于氧还原活性的提高; (3) 多孔结构和高比表面积能够有效降低传质阻力并提高暴露的氧还原活性位点数量, 进而提高物质利用效率.

A novel pure and N-doped waved-graphene electro-catalyst with various wavelengths for oxygen reduction reaction (ORR) is explored in acid medium based on the first-principles calculations. The associative and dissociative mechanism are both explored from the O2adsorption to the H2O formation step by step, from which the dissociative mechanism is likely the only way with an effective 4e−process. Furthermore, a very favorable and effective mechanism is proposed for the ORR process, which may provide a guideline on the design of new non-metal electro-catalysts. 本文基于第一性原理, 针对一种本征或氮掺杂的石墨烯在不同晶胞参数压缩比和在酸性条件下的氧气还原反应机理进行了探索. 文章假设了两种不同的反应机理, 并逐步分析了从氧气吸附到水分子形成的整个过程, 结果表明基于氧气分子解离机理的四电子过程是唯一有效的路径. 文章进一步提出了一种有效的氧气还原反应机理, 这为设计新的非金属电催化剂提供了新的思路.

Catalysts of oxygen reduction reaction (ORR) play key roles in renewable energy technologies such as metal-air batteries and fuel cells. Despite tremendous efforts, highly active catalysts with low cost remain elusive. This work used metal-organic frameworks to synthesize non-precious bimetallic carbon nanocomposites as efficient ORR catalysts. Although carbon-based Cu and Ni are good candidates, the hybrid nanocomposites take advantage of both metals to improve catalytic activity. The resulting molar ratio of Cu/Ni in the nanocomposites can be finely controlled by tuning the recipe of the precursors. Nanocomposites with a series of molar ratios were produced, and they exhibited much better ORR catalytic performance than their monometallic counterparts in terms of limited current density, onset potential and half-wave potential. In addition, their extraordinary stability in alkaline is superior to that of commercially-available Pt-based materials, which adds to the appeal of the bimetallic carbon nanocomposites as ORR catalysts. Their improved performance can be attributed to the synergetic effects of Cu and Ni, and the enhancement of the carbon matrix. 氧还原催化剂在金属空气电池和燃料电池的可再生能源技术中起至关重要的作用. 尽管该方面研究已有很多, 高活性低成本的催化剂的开发仍然十分困难. 本文以金属有机骨架为前驱体, 成功合成出非贵金属铜镍双金属碳基纳米复合物并作为高效的氧还原催化剂. 单金属复合物Cu/C和Ni/C皆具有较好的氧还原催化作用, 铜镍双金属复合物进一步综合了二者优点从而提升了催化性能. 本文所合成的铜镍双金属复合物中的金属比例可通过调整前驱体中的原料配比来准确控制, 所得的一系列金属比例的铜镍双金属碳基纳米复合物在极限电流密度、起始电位和半波电位三个方面都超过了单金属复合物. 此外, 铜镍双金属碳基纳米复合物在碱性环境中具有良好的稳定性且超过了目前最好的氧还原催化材料铂, 大大加强了其作为氧还原催化剂的优势. 铜镍双金属碳基纳米复合物优越的电化学催化性能归功于金属铜和镍以及碳材料基底的协同作用.

Si-based nanostructure composites have been intensively investigated as anode materials for next-generation lithium-ion batteries because of their ultra-high-energy storage capacity. However, it is still a great challenge to fabricate a perfect structure satisfying all the requirements of good electrical conductivity, robust matrix for buffering large volume expansion, and intact linkage of Si particles upon long-term cycling. Here, we report a novel design of Si-based multicomponent three-dimensional (3D) networks in which the Si core is capped with phytic acid shell layers through a facile high-energy ball-milling method. By mixing the functional Si with graphene oxide and functionalized carbon nanotube, we successfully obtained a homogeneous and conductive rigid silicon-based gel through complexation. Interestingly, this Si-based gel with a fancy 3D cross-linking structure could be writable and printable. In particular, this Si-based gel composite delivers a moderate specific capacity of 2711 mA h g–1at a current density of 420 mA g–1and retained a competitive discharge capacity of more than 800.00 mA h g–1at the current density of 420 mA g–1after 700 cycles. We provide a new method to fabricate durable Si-based anode material for next-generation high-performance lithium-ion batteries.