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Electrochemical water splitting is a promising technology to enable a sustainable energy supply; however, it remains a formidable challenge to find efficient and stable electrocatalysts. Particularly, oxygen evolution, the half-reaction at the anode, imposes serious overpotential penalties due to its sluggish kinetics. The continued rational design and optimization of OER catalysts via different strategies such as chemical substitution provide an understanding of the way that catalytic properties can be finely tuned. Here, we show a facile synthetic approach involving a Ce(NO3)3 precursor to yield a nitrogen and cerium co-doped CoS2 electrocatalyst. Remarkably, it requires an overpotential of only 190 mV to reach a current density of 10 mA cm−2 and exhibits long-term stability for 120 h. More importantly, a suite of advanced characterization techniques and theoretical calculations reveal complementary roles of the dual dopants which stabilize the intermediates as a result of the formation of two higher oxidation state metal active centers and maintain the surface structure. This work correlates the electronic structure and heteroatom doping, providing insights into electrochemical activity and stability and guiding the rational design of efficient electrocatalysts.

Infiltrated molten Al matrix by mechanical-pressure infiltration method into the ceramic scaffold prepared by freeze-drying technology could prepare dense lamellar Al matrix composites without damage of the biomimetic microstructure of the scaffold. However, the investigation of lamellar Al matrix composites prepared by freeze-drying and mechanical-pressure infiltration method has not been fully understood yet. In the present work, the Al2O3 scaffold with pearl layer structure was prepared by freezing-dry method, and eventually the lamellar Al2O3p/Al composite was fabricated by mechanical-pressure infiltration method. The Al matrix was infiltrated well into the large pores of the Al2O3 scaffold, and the lamellar structure of the Al2O3 was well preserved. The hardness of the lamellar Al2O3p/Al composite was isotropic in transvers and perpendicular directions. However, the compressive strengths of the lamellar Al2O3p/Al composite were significant anisotropic while the compressive strength in transvers direction was 127.7% higher than that in the perpendicular direction, indicating the integrality of the lamellae microstructure (especially the bridging layers). Due to the mismatched deformability, weak debonding was observed between Al and Al2O3p/Al layers in the fracture surface of the lamellar Al2O3p/Al composite. It indicates that the interfacial bonding between Al and Al2O3p/Al layers is rather strong, which is beneficial for higher strength in transvers direction but lead to lower strength in perpendicular direction.

Photocatalytic water splitting is a promising approach to convert solar energy into storable hydrogen fuel. In theory, the optimization of light-harvesting and catalytic molecular conversion ability is necessary for high-efficiency hydrogen evolution; however, the establishment of a photocatalytic system composed of a light-harvesting center and an active center is limited by poor light absorption capacity, high overpotential for catalytic conversion, as well as the low efficiency of charge transfer between the two components. In this work, we demonstrate that a high-efficiency photocatalytic system consisting of two-dimensional carbon nitride (2D-C3N4) as the light-harvester and nickel sulfide (NiSx) as the active component can serve as an efficient catalyst for hydrogen evolution, wherein the tight interface formed using two-step solvothermal treatment bridges the charge transfer. The 2D structure of 2D-C3N4 can shorten the charge migration distance from the bulk to the contact interface with NiSx and minimize the charge recombination in the light-harvesting center. NiSx with a highly active surface can capture the photo-generated electrons through a tight contact interface, completing the conversion from H+ to H2. As a result, the hydrogen evolution rate of the optimal NiSx/2D-C3N4 catalyst achieves a high value of ∼4640 μmol g−1 h−1 under visible light irradiation, which is more active than most of the Pt-free 2D-C3N4 supported photocatalysts under the same reaction conditions.

Graphene has extremely high theoretical strength and electrothermal properties, and its application to Cu-based composites is expected to achieve a breakthrough in the performance of existing composites. As a nano-reinforced body, graphene often needs a long time of ball milling to make it uniformly dispersed, but the ball milling process inevitably brings damage to the graphene, causing the performance of the composite to deviate from expectations. Therefore, this paper uses CH4 as a carbon source to repair graphene through a CVD process to prepare low-damage graphene/Cu composites. The process of graphene defect generation was studied through the ball milling process. The effects of defect content and temperature on the graphene repair process were studied separately. The study found that the graphene defect repair process, the decomposition process of oxygen-containing functional groups, and the deposition process of active C atoms existed simultaneously in the CVD process. When the repair temperature was low, the C atom deposition process and the oxygen-containing functional group decomposition process dominated. In addition, when the repair temperature is high, the graphene defect repair process dominated. 3 wt% graphene/Cu composites were prepared by pressure infiltration, and it was found that the bending strength was increased by 48%, the plasticity was also slightly increased, and the thermal conductivity was increased by 10–40%. This research will help reduce graphene defects, improve the intrinsic properties of graphene, and provide theoretical guidance for the regulation of C defects in composites.

Coral concrete has low cost and convenient materials, making it an excellent raw material for processing. However, its lower strength limits the application of coral concrete. Surface modification is expected to increase the properties of porous coral concrete. In this study, single and compound modification treatments were applied to the surface of a coral aggregate to improve its properties for promoting the mechanical performance of coral concrete. The results showed that the micro-aggregate effect and pozzolanic activity of granulated blast furnace slag (GBFS) and the permeability and polycondensation of sodium silicate (SS) could be mutually promoted. The GBFS and SS could effectively fill the pores of the coral aggregate, enhancing the properties of the aggregate, such as density and load-bearing capacity, and reducing the water absorption and crushing index by more than 50%. GBFS and SS could intensify and accelerate the hydration of cement, and generate a large number of hard hydration products at the interfacial transition zone (ITZ), which could strengthen the bonding between the aggregate and mortar, improving the strength of the ITZ. The compressive strength of the coral concrete was significantly increased.

Carbon nanotube (CNT) cathodes have attracted much attention in recent years due to the advantages of large field enhancement factor and low emission threshold. However, the severe ablation under intense emission makes the lifetime short and therefore limits the application in the field such as high power microwave generation. To resolve this problem, this paper proposes to mix CNTs with metals, and a novel CNT/Cu composite cathode is manufactured. The lifetime experiments under voltage of 940 kV and repetition frequency of 20 Hz demonstrate that the lifetime of the CNT/Cu composite cathode is over 3 × 105 pulses, which is much longer than that of the normal copper cathode by at least one order of magnitude. The microscopic morphology analysis reveals that the CNT micro-protrusions and whiskers should be vital for the good emission property of the new cathode.

Silane coupling agent (SCA), a kind of organic solvent, was introduced to improve the performance of coral coarse aggregates and enhance the interfacial adhesion between the inorganic coral aggregate and the cement paste of coral concrete. The crushing indicator and water absorption of the coral aggregates over various dipping times were measured, and the slump, interface microhardness, and compressive strength of coral concrete tested. The microscopic appearances of the coral concrete before and after modification were analyzed based on SEM images. The experimental results indicate that SCA can effectively reduce the crushing indicator and water absorption of coral coarse aggregates, and the modification performance becomes better over time. SCA facilitates the generation of chemical forces between the coral aggregates and cement mortars, improves adhesion between the aggregates and mortars, augments the microhardness of the interface, and increases the compressive strength. According to the microscopic appearance of the treated and untreated coral aggregate interfaces, the aggregates and the mortars are in closer combination after modification.

In this paper, six-layer AlN/Al gradient composites were prepared by a spark plasma sintering process to study the influences of sintering temperature and holding time on the microstructure and mechanical properties. The well-bonded interface enables the composite to exhibit excellent thermal and mechanical properties. The hardness and thermal expansion properties of the composite exhibit a gradient property. The hardness increased with the volume fraction of AlN while the CTE decreased as the volume fraction of AlN. The thermal expansion reaches the lowest value of 13–14 ppm/K, and the hardness reaches the maximum value of 1.25 GPa, when the target volume fraction of AlN is 45%. The simulation results show that this gradient material can effectively reduce the thermal stress caused by the mismatch of the thermal expansion coefficient as a transmitter and receiver (T/R) module. This paper attempts to provide experimental support for the preparation of gradient Al matrix composites.

High-performance extruded aluminum alloys with complex textures suffer significant dimension variation under environmental temperature fluctuations, dramatically decreasing the precision of navigation systems. This research mainly focuses on the effect of the texture of extruded pure aluminum on its dimensional stability after various annealing processes. The result reveals that a significant increment in the area fraction of recrystallized grains with &lt, 100&gt, orientation and a decrement in the area fraction of grains with &lt, 111&gt, orientation were found with increasing annealing temperature. Moreover, with the annealing temperature increasing from 150 °C to 400 °C, the residual plastic strain after twelve thermal cycles with a temperature range of 120 °C was changed from −1.6 × 10−5 to −4.5 × 10−5. The large amount of equiaxed grains with &lt, orientation was formed in the microstructure of the extruded pure aluminum and the average grain size was decreased during thermal cycling. The area fraction of grain with &lt, crystallographic orientation of the sample annealed at 400 °C after thermal cycling was 30.9% higher than annealed at 350 °C (23.7%) or at 150 °C (18.7%). It is attributed to the increase in the proportion of recrystallization grains with &lt, direction as the annealing temperature increases, provided more nucleation sites for the formation of fine equiaxed grains with &lt, orientation. The main orientation of the texture was rotated from parallel to &lt, to parallel to &lt, after thermal cycling. The change in the orientation of grains contributed to a change in interplanar spacing, which explains the change in the dimension along the extrusion direction during thermal cycling.

The fundamental understanding of the surface reconstruction induced by the applied potential is of great significance for enhancing the oxygen evolution reaction (OER). Here, we show that a previously overlooked discharge current in the low applied potential region also leads to in situ electrochemical activation of a nitrogen-doped nickel oxyhydroxide surface. We exploit the fact that doping of heteroatoms weakens the surface structure, and hence, a weak discharge current originating from the capacitive nature of nickel oxyhydroxide has a strong structure-reforming ability to promote the formation of nitrogen and oxygen vacancies. The current density at 1.4 V (vs. Hg/HgO) can dramatically increase by as much as 31.3 % after discharge in the low applied potential region. This work provides insight into in situ enhancement of the OER and suggests that the low applied potential region must be a primary consideration in evaluating the origin of the activity of electrocatalysts.

Enhancement of integrity and stability of crystal lattice are highly challenging for polycrystalline perovskite films. In this work, a strategy of incorporation of nickel (Ni) ions is presented to modulate the crystal structure of the CH3NH3PbI3 perovskite film. A broad range of experimental characterizations reveal that the incorporation of Ni ions can substantially eliminate the intrinsic halide vacancy defects, since Ni ions have a strong preference for octahedral coordination with halide ions, resulting in significantly improved integrity and short-range order of crystal lattice. Moreover, it is also demonstrated that the stronger chemical bonding interaction between Ni ions and halide ions as well as organic group can improve the stability of the perovskite material. Simultaneously, the surface morphology of the perovskite thin film is also improved by the incorporation of nickel ions. As a result, a planar heterojunction perovskite solar cell incorporated with 1.5% Ni exhibits a power conversion efficiency of 18.82%, which is improved by 25% compared with 14.92% for the pristine device. Simultaneously, the device formed incorpration of 1.5% Ni shows remarkable stability with 90% of the initial efficiency after storage in an air environment for 800 h. The studies provide a new insight into metal-incorporated perovskite materials for various optoelectronic applications.

As a cocatalyst, NiO has shown a great potential in facilitating photocatalytic water splitting for hydrogen evolution. In this work, a new photocatalyst thin film (Ni/NiO/NaTaO3: La) is successfully prepared to optimize the performance of the photocatalytic water splitting. The NiO cocatalyst is prepared by a simple heat treatment method. An efficient heterojunction can be formed between NiO and NaTaO3, which is beneficial to the transmission and separation of photogenic carriers. The photocatalytic activity of Ni/NiO/NaTaO3: La is 10.83 µmol/h cm2 under high-pressure mercury lamp irradiation, which is two times higher than that of Ni/NaTaO3: La. In addition, the Ni/NiO/NaTaO3: La thin film is treated under different temperatures. It can be observed that annealing temperature has a great influence on the photocatalytic activity of Ni/NiO/NaTaO3: La thin film. When the sample annealed in 700 °C, the photocatalytic activity for water splitting is the highest, indicating the temperatures have an effect on the formation of NiO and photocatalytic efficiency. Our photocatalyst thin film (Ni/NiO/NaTaO3: La) provides sustainable photocatalysts by taking both photocatalyst stability and repeated utilization into consideration. More importantly, this work also provides a new insight into the synthesis of Ni/NiO/NaTaO3: La thin film, which has a great application prospects in the field of photocatalytic water splitting. NiO cocatalyst is prepared by a simple heat treatment method and this novel photocatalyst thin film (Ni/NiO/NaTaO3: La) is successfully prepared to optimize the performance of the photocatalyst.

Evolution of graphene nanosheets (GNSs) during mechanical milling process was investigated to fabricate GNSs/Al nanocomposite by routes combined of pressure infiltration and hot extrusion. The structural integrity and dispersion homogeneity of GNSs together with the degree of interfacial reaction were systematically discussed. It was revealed that a moderate milling time existed for well dispersion and small quantities of Al4C3 (partial reaction bonding) via mechanical milling technique. A highest tensile strength of 276 MPa was obtained only with 0.3 wt% GNSs, which was 22.5% enhancement over the unreinforced Al matrix with the same preparation process and no decrease in elongation. Meanwhile, compared with reference Al, a great enhancement of electrical conductivity was achieved about 17.4%, which had not been reported previously. This study could provide new insights into the control factors of mechanical milling process for GNSs/Al composite and improve the interfacial bonding condition in situ during ball milling and subsequent densification processes to take full advantage of the extraordinary performance of graphene in metal matrix composites.

The lack of high active and stable electrocatalysts has impeded the development of electrochemical water splitting device, which is promising technique for renewable energy conversion system. Here, we report a one-step protocol to synthesize P doped NiSe2 (P-NiSe2) by selenylation process derived from nickel foam with assistant of NaH2PO2 and Se powder. The P-NiSe2 could be directly used as working electrode and shows the superior electrochemical activity, offering current density of 10 mA cm−2 with overpotential of 270 mV for OER and 71 mV for HER. The enhanced electrochemical activity can be ascribed to the P atom doping. The P atom doping leads to the high valence state of Ni active sites, which have high catalytic ability towards OER. Moreover, the P doping makes the d-band center of Ni atoms in P-NiSe2 move close to Fermi level, facilitating the HER kinetics with respect to proton adsorption and hydrogen desorption. When employed P-NiSe2 as both anodic and cathodic electrode in alkaline water electrolyzer, a current density of 10 mA cm−2 can be achieved at 1.58 V. Our work highlights the importance of P doping in determining the surface electron configuration for full device water splitting and the facile synthesis protocol would be promising for realistic applications.

Herein, a novel actinomorphic flower-like ZnO/Au/CdS nanorods ternary composite photocatalyst is prepared to extend the light-responsive range, reduce the photogenerated charge carriers recombination, and ultimately improve the water splitting performance. Flower-like ZnO nanorods are synthesized by a chemical bath method and the CdS nanoparticles are sensitized by successive ionic layer adsorption and reaction method. Then the Au nanoparticles as co-catalysts are introduced by the photodeposition method to modify the interface of ZnO/CdS for reducing the photogenerated electron recombination rate and further improving the performance of water splitting. Detailed characterizations and measurements are employed to analyse the crystallinity, morphology, composition, and optical properties of the flower-like ZnO/Au/CdS nanorods samples. As a result, the flower-like ZnO/Au/CdS nanorod samples present significantly enhanced water splitting performance with a high gas evolution rate of 502.2 &mu, mol/g/h, which is about 22.5 and 1.5 times higher than that of the pure ZnO sample and ZnO/CdS sample. The results demonstrate that the flower-like ZnO/Au/CdS nanorods ternary composite materials have great application potential in photocatalytic water splitting for the hydrogen evolution field.

Designing and fabricating economically viable, high active and stable electrocatalysts play an important role for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Crystal phase is the crucial factor that governs the electrochemical property and electrocatalytic reaction pathways. Here, a one-step nickel foam derived sulfidation method was presented to synthesize self-supported NiS2 and Ni3S2. The crystal phase-dependent chemical properties related to electrocatalytic behavior were evaluated by a series of advanced characterization and density functional theory calculations. Overall, the self-supported Ni3S2 shows high electrochemical activity towards both HER and OER in alkaline conditions, which afford the current density of 10 mA cm−2 with overpotentials of 245 mV for OER and 123 mV for HER, respectively. When employed the self-supported Ni3S2 as the bifunctional electrocatalysts for overall water splitting, the entire device provides the current density of 10 mA cm−2 at 1.61 V. These results indicate that the electrocatalytic properties can be exert greater improved by controlling the crystal phase, offering the prospect for advanced materials design and development.

Objectives Older adults experience higher risks of getting severely ill from coronavirus disease 2019 (COVID-19), resulting in widespread narratives of frailty and vulnerability. We test: (a) whether global aging narratives have become more negative from before to during the pandemic (October 2019 to May 2020) across 20 countries; (b) model pandemic (incidence and mortality), and cultural factors associated with the trajectory of aging narratives. Methods We leveraged a 10-billion-word online-media corpus, consisting of 28 million newspaper and magazine articles across 20 countries, to identify nine common synonyms of “older adults” and compiled their most frequently used descriptors (collocates) from October 2019 to May 2020—culminating in 11,504 collocates that were rated to create a Cumulative Aging Narrative Score per month. Widely used cultural dimension scores were taken from Hofstede, and pandemic variables, from the Oxford COVID-19 Government Response Tracker. Results Aging narratives became more negative as the pandemic worsened across 20 countries. Globally, scores were trending neutral from October 2019 to February 2020, and plummeted in March 2020, reflecting COVID-19’s severity. Prepandemic (October 2019), the United Kingdom evidenced the most negative aging narratives; peak pandemic (May 2020), South Africa took on the dubious honor. Across the 8-month period, the Philippines experienced the steepest trend toward negativity in aging narratives. Ageism, during the pandemic, was, ironically, not predicted by COVID-19’s incidence and mortality rates, but by cultural variables: Individualism, Masculinity, Uncertainty Avoidance, and Long-term Orientation. Discussion The strategy to reverse this trajectory lay in the same phenomenon that promoted it: a sustained global campaign—though, it should be culturally nuanced and customized to a country’s context.

Photocatalysis technology has potential application in the field of energy and environment. How to expand visible light utilization and promote the separation efficiency of the carriers are the key issues for the high active photocatalysts preparation and future practical applications. In this work, a ternary metal sulfide Nb0.9Ta0.1S2 was prepared and used as an electron collector in the photocatalytic application. As a result, the generated electrons are quickly transferred to the surface of the composite to participate in the reaction. It was demonstrated that the photocatalytic activity of 2D-C3N4 was enhanced after the modification of Nb0.9Ta0.1S2. The Nb0.9Ta0.1S2/2D-C3N4 composite material was synthesized by solvothermal method. The composition of 5% Nb0.9Ta0.1S2/2D-C3N4 showed the highest H2 evolution rate of 1961.6 μmolg−1h−1, which was 6.6 times that of 2D-C3N4. The 15% Nb0.9Ta0.1S2/2D-C3N4 exhibited the best activity in Rhodamine B degradation rate of 97% in 2 h, which is 50% higher than that of 2D-C3N4. Nb0.9Ta0.1S2/2D-C3N4 can be used as electron trap to promote the effective separation of electron–hole pairs. This work provides benchmarks in exploring low-cost and efficient cocatalyst.

In this study, titania/silica nanocomposite and mesoporous TiO

In order to correctly understand the mechanical behavior, damage mode and damage mechanism of AlSi10Mg optimized structure under compressive load, a series of experimental and simulation studies were carried out. The stress-strain response, bearing capacity, energy absorption characteristics, damage mode and mechanism of the structure are analyzed and discussed. The results show that AlSi10Mg porous structure has obvious strain hardening effect, but no obvious strain rate effect. The volume fraction of AlSi10Mg porous structure increased from 9.43% to 22.15%, and its bearing strength increased from 22.34 MPa to 50.98 MPa. The optimized design structure is complex in this paper, which eliminates undesirable failure modes, and the benefit of high specific energy absorption is retained. The experimental and simulation results show that shear failure is the main cause of structural damage, and the normal of the failure section and the load action direction are roughly inclined at an angle of 45° ∼ 55°. The research results can provide an important reference for the optimal design of porous metal structure.

In the present work, the effect of the W coatings prepared by the magnetron sputtering method on the stability of the thermal and mechanical properties of the Diamond/Al composites has been investigated. Due to the decomposition of the interfacial Al4C3 phase, the thermal conductivity and bending strength of the Diamond/Al composites without W coating were decreased 23% and 33%, respectively. However, the variation of the normalized thermal conductivity (NTC) of the Diamond/Al composites has been changed from polynomial to linear relationships after the W-coating treatment, indicating the enhancement of the thermal conductivity and the bending strength stability. Diamond/Al composite with 45 nm W coating demonstrated the best thermal and mechanical stability with slight decrement of 3% after 720 h heat-moisture treatment (HMT). Due to the decomposition of the Al4C3 phase and the corresponding weakened interfacial bonding, more “clean {111} planes” of the diamond particles were observed in the fracture surface of Diamond/Al composites without W coating after HMT. However, no significant difference was found in the fracture surface of the Diamond/Al composites with 45 nm and thicker W coatings before and after HMT. It is suggested that the continuous, stable and well bonded interfacial structure without the formation of the Al4C3 phase is the key for the improvement of the stability of the Diamond/Al composites.

In the present work, 5083Al matrix composites reinforced with graphene oxide (GO) and graphene nanoplates (GNPs) have been prepared by the pressure infiltration method. Regardless of the graphene types, no peaks of Al4C3 phase have been detected by the XRD analysis. However, needle-like Al4C3 phase has been observed in the GO/5083Al and the GNPs/5083Al composites, while the content of the Al4C3 phase in the GNPs/5083Al composite was much lower. Furthermore, the segregation of Mg element at the surface of the GNPs has been found in the GNPs/5083Al composite, implying the inhibition effect of Mg element on the formation of the Al4C3 phase. It has been found that the yield strength of the composites was slightly improved by the addition of the GO and GNPs, and the GNPs/5083Al composite demonstrated 14% increment in the tensile strength. Meanwhile, the pulling-out of the GO and GNPs have been observed.

A uniform and compact CdTe thin film is successfully electrodeposited on Ni flexible sheets. The influence of the concentration of sodium citrate in the growth solution on the morphological, compositional and electrical conductive properties of CdTe films is investigated. The results show that sodium citrate plays a significant role in directing the morphological evolution of CdTe from three-dimensional rod-shaped array to two-dimensional thin film. The composition of the film is changed from Te-rich to Cd-rich, and the conversion from p-type conduction to n-type in CdTe films is also achieved with the increase of sodium citrate concentration. When the concentration of sodium citrate is 0.08 mol L−1, the composition of CdTe film is near stoichiometric and the amount of excess Te is small. Furthermore, the effect of sodium citrate on the photoelectric conversion properties of CdTe-based solar cells is also analyzed. The fabricated solar cell based on the CdTe film prepared using 0.08 mol L−1 sodium citrate shows a short-circuit current density of 10.46 mA cm−2 and an open-circuit voltage of 0.53 V, yielding a better energy conversion efficiency of 2.73% with a fill factor of 49.28%. The better energy conversion efficiency is 2.1 and 1.6 times higher than that of the devices based on CdTe films prepared using 0.07 and 0.09 mol L−1 sodium citrate, respectively. This study indicates that the as-prepared CdTe thin film has a great potential for application in thin film solar cells, and the sodium citrate-assisted synthesis of CdTe film suggests a promising technique for large-scale fabrication of flexible solar cells.

In the present work, the effect of W coatings prepared by the magnetron sputtering method on the mechanical performance of the Al matrix composites reinforced with diamond particles (Diamond/Al) has been explored. Since no debonding was observed between the diamond and the Al matrix in the composites with 45 nm and thicker W coatings while serious debonding was found in the composite without W coating, the interfacial bonding between the diamond particles (all the {100} and {111} facets) and the Al matrix has been improved. Further TEM observation indicated that the W coating has been well bonded with the diamond particle and the Al matrix, and no interfacial reaction product has been found. Furthermore, the fracture behaviors of the Diamond/Al composites were also affected by the W coatings. Compared to that of the Diamond/Al composite without W coating, the bending strength and the displacement of the bending failure of the Diamond/Al composites with 45 nm W coating have been improved 24% (from 245 to 304 MPa) and 120% (from 0.28 to 0.62 mm), respectively. Moreover, the summative results from the literatures and the present work indicate that the Diamond/Al composites have higher strength usually demonstrates higher thermal conductivity, which might be related to the interfacial performance of the composites.

In the present work, microstructure and mechanical behavior of the graphene nanoplates (GNPs) reinforced pure Al (GNPs/Al) composites prepared by the pressure infiltration method was investigated. No Al4C3 phase was detected in the composites, while GNPs have been well bonded with the Al matrix. It is suggested that the reaction between pure Al matrix and graphene could also be inhibited by using graphene with fewer defects. It has been found that the mechanical properties of the composites could be significantly improved by the addition of graphene. After addition of 0.54 wt% GNPs, the improvement of the yield and tensile strength before the extrusion was 116% and 45%, respectively. However, after the extrusion treatment, the corresponding increment of the yield and tensile strength was increased to 228% and 93%, respectively. Moreover, the fracture surface of the GNPs/Al composites before and after the extrusion treatment was mainly characterized by the lamellar structure with bridging of GNPs and the fine equiaxed structure with the pulling-out of the GNPs, respectively. Based on the modified shear-lag model, the strengthening mechanism of the GNPs/Al composites has been discussed, and the effect of GNPs and the extrusion treatment on the yield strength of the composites have been analyzed.

Oxytetracycline (OTC) is a common antibacterial agent used for the control of animal diseases. OTC abuse can seriously affect human health. Herein, based on the Fe(III)-3,3’,5,5’-tetramethylbenzidine (Fe(III)-TMB) system, a facile and rapid colorimetricassay for oxytetracycline (OTC) was successfully developed. The addition of OTC could remarkably enhance the Fe(III)-oxidized TMB reaction and the absorbance increase of Fe(III)-TMB solution is proportional to the added OTC. The linear range of proposed sensor for OTC was from 20 nM to 1000 nM with the detection limit of 7.97 nM. The high sensitivity for OTC detection was successfully achieved under optimal conditions. For real sample analysis, recoveries of 89.93% to 100.02% was obtained. This is the first report for detecting OTC based on the nonenzymatic colorimetric reaction using the intrinsic oxidized activity of OTC/Fe3+ complex. The present simple, low-cost and visualized sensor has great potential for OTC detection in food.

In this paper, an ultrahigh-strength marine concrete containing coral aggregates is developed. Concrete fabricated from marine sources is considered an effective and economical alternative for marine engineering and the construction of remote islands. To protect sea coral ecosystems, the coral aggregates used for construction are only efflorescent coral debris. To achieve the expected mechanical performance from the studied concrete, an optimal mixture design is conducted to determine the optimal proportions of components, in order to optimize the compressive strength. The mechanical properties and the autogenous shrinkage, as well as the heat flow of early hydration reactions, are measured. The hydration products fill up the pores of coral aggregates, endowing our concrete with flowability and self-compacting ability. The phases in the marine concrete are identified via X-ray diffraction analysis. The 28-day compressive and flexural strength of the developed marine concrete achieve 116.76 MPa and 18.24 MPa, respectively. On account of the lower cement content and the internal curing provided by coral aggregates, the volume change resulting from autogenous shrinkage is only 63.11% of that of ordinary reactive powder concrete.

Background Seldom in history does one get a ‘front row seat’—with large-scale dynamic data—on how online news media narratives shift with a global pandemic. News media narratives matter because they shape societal perceptions and influence the core tent poles of our society, from the economy to elections. Given its importance—and with the benefit of hindsight—we provide a systematic framework to analyze news narratives of Covid-19, laying the groundwork to evaluate policy and risk communications. Objectives We leverage a 10-billion-word-database of online news, taken from over 7,000 English newspapers and magazines across 20 countries, culminating in 28 million articles. First, we track the volume of Covid-19 conversations across 20 countries from before to during the pandemic (Oct’19 to May’20). Second, we distill the phases of global pandemic narratives, and elucidate regional differences. Methods To track the volume of Covid-19 narratives, we identified 10 target terms—Coronavirus, Covid-19, Covid, nCoV, SARS-CoV-2, Wuhan Virus, Virus, Disease, Epidemic, Pandemic—and tracked their combined monthly prevalence across eight months from October 2019 through May 2020. Globally, across 20 countries, we identified 18,042,855 descriptors of the target terms. Further, these descriptors were analysed with natural language processing models to generate the top five topics of Covid-19 that were labelled by two independent researchers. This process was repeated across six continents to distil regional topics. Results Our model found four phases of online news media narratives: Pre-pandemic, Early, Peak and Recovery. Pre-pandemic narratives (Oct’19–Dec’19) were divergent across regions with Africa focused on monkeypox, Asia on dengue fever, and North America on Lyme disease and AIDS. Early (Jan–Feb’20) and Peak Pandemic (Mar–May’20) evidenced a global convergence, reflecting the omnipresence of Covid-19. The brief transition from early to peak pandemic narratives underscored the pandemic’s rapid spread. Emerging from the embers of the pandemic’s peak were nascent recovery words that are regionally divergent—Oceania focused on hope and an uncertain future while North America centered on re-opening the economy and tackling discrimination. Conclusions Practically, we presented a media barometer of Covid-19, and provided a framework to analyse the pandemic’s impact on societal perceptions—laying the important groundwork for policy makers to evaluate policy communications, and design risk communication strategies.

Aerobic photocatalytic oxidative desulfurization (APODS) is a rapidly growing organosulfur compound conversion technique that operates at mild temperature and ambient pressure and, eliminating the requirement of expensive hydrogen gas as required in industrial hydrodesulfurization technology. In this study, mesoporous LaVO4 was synthesized hydrothermally using a KIT-6-based template etching for deep desulfurization. The as-synthesized photocatalyst was characterized by several techniques, including SEM, STEM, FTIR, UV–Vis DRS, Raman, PL, and N2 physisorption analyses. The synthesized material offered a large surface area and enlarged pore size with a narrow bandgap (2.05 eV) and reduced particle size with a dominant monoclinic phase of LaVO4, making it suitable for capturing more light photons, offering plentiful active sites, and reducing electron-hole recombination rate compared with standard techniques; this results in an enhanced visible-light-driven APODS performance. The optimum parameters such as reaction temperature, solution pH, oxygen flow rate, solvent/oil ratio, catalyst dosage, and agitation rate for APODS were determined to be 20 °C, pH 4, 100 mL/min, 1:5 (v/v), 3 g/L, and 750 rpm, respectively. Mesoporous LaVO4 was tested on commercial diesel fuel containing 410 ppm sulfur over a visible-light irradiation period of three hours, exhibiting excellent performance in desulfurizing diesel up to 88.17%, which was more than twice that of conventional LaVO4. The kinetic study demonstrated a good fit with the pseudo-first-order kinetic reaction model, and the reaction mechanism was suggested. The developed photocatalytic material also exhibited excellent regeneration and recyclability.

In this study, a uniform CdTe nanorods (NRs) arrays are grown on Ni substrates by a simple one-step electrochemical deposition method. The effects of deposition parameters such as the concentration of reactants and reaction time on the growth of CdTe NRs arrays are systematically investigated. Na2TeO3 and CdSO4 have a significantly different influence on the growth of CdTe NRs. With the increase of Na2TeO3 concentration, the diffraction intensity increases slightly at the peak (111) to promote axial growth. The diffraction intensity of (002) can increase with the concentration of CdSO4 increasing, which is conducive to lateral growth. The morphology of CdTe film varies from a thin layer to nanoparticles, and finally to NRs with the extension of time. Based on the characterization results, the possible growth mechanism of CdTe NRs arrays is proposed. The as-prepared CdTe NRs arrays are then embedded into CdS film, forming a novel three-dimensional (3D) heterojunction photovoltaic device. An extensive study of the effect of NRs length on device performance is presented. The results indicate that the device performance is highly dependent on the length of CdTe NRs, and a power conversion efficiency of 2.50% is obtained for optimal length of 1 μm. The better photovoltaic performance can be attributed to its efficient charge separation and direct pathways for carriers transport. What's more, this novel 3D nanostructured concept suggests great potential for other optoelectronic devices.

In the present work, tungsten (W) coatings with thickness range of 35–130 nm on the diamond particles were prepared by magnetron sputtering method, and then the Diamond/Al composites were prepared by the vacuum infiltration method. The prepared W coatings were smooth and dense on all the facets of the diamond particles. Moreover, the presence of W-coatings inhibited the interfacial debonding phenomenon and improved the interfacial bonding between diamond particles and Al matrix. The Diamond/Al composite with the 45 nm W-coating achieved the maximum thermal conductivity (622 W/(m·K)). To the best of our knowledge, it is the highest thermal conductivity obtained in the Al matrix composites reinforced with 100 μm diamond particles with coatings. Based on the Hasselman and Johnson (H-J) model, the thermal conductivity behavior of the Diamond/Al composites has been discussed. It indicates that the magnetron sputtering is a feasible and successful method to prepare thin and reliable tungsten coatings for the Diamond/Al composites.

In this work, different quantities of TiO2 incorporated into TiO2-KIT6 nanostructured catalysts were considered to improve the photocatalytic abatement of volatile organic compounds (VOCs; ethylene, propylene) at ambient temperature. The best optimized activity and stability of the catalysts toward(s) ethylene and propylene degradation has been shown for 30 wt% TiO2, while the worst conversion has been observed for a 90 wt% TiO2 loading. This was likely due to the dispersion and stabilization of the anatase TiO2 with 30 wt% on KIT-6, which in turn allowed more VOCs adsorption and better light penetration than 90% TiO2/KIT-6 in which it showed a bulk phase and large agglomerates with light penetration limitations. VOC abatement has been found to be not only influenced directly by the dispersed TiO2 contents but also by the calcination temperatures, and 500 °C has been found to be the best calcination condition to achieve the highest propylene conversion. The optimized nanostructured photocatalyst developed for ethylene and propylene, could also be promising candidate for other VOCs and different applications.

It has not been reported in the existed literatures that whether it is possible to prepare GNFs/Al composites by pressure infiltration method due to the poor wettability and severe reaction behavior between carbon and molten Al. In the present study, microstructure and mechanical behavior of graphene nanoflakes (GNFs) reinforced Al-20Si (GNFs/Al-20Si) composites prepared by the pressure infiltration method have been thoroughly investigated. The Al-20Si matrix was chosen to inhibit the formation of Al 4 C 3 . It has found that the GNFs and Al alloy matrix has been well bonded without formation of Al 4 C 3 , which authenticated the effectiveness of the alloying treatment. Moreover, the hardness and the elastic modulus of the composites were increased linearly with the increase in the GNFs content. After addition of 1.5 wt% GNFs, the ultimate tensile strength and bending strength attained the peak values, which increased 130% and 230% to that of Al matrix, respectively. To the best of our knowledge, it is the highest strengthening ratio in Al matrix composites reinforced with graphene reinforcements. Furthermore, based on the modified shear-lag model and combined with the literatures’ data, the strengthening behavior of GNFs/Al composites has been extensively discussed. It is concluded that the pressure infiltration method is the most feasible and successful way to prepare GNFs/Al composites without formation of Al 4 C 3 and with high strengthening ratio.

A thorough understanding of the effect of N doping on the oxygen evolution reaction (OER) is greatly significant for constructing next-generation electrocatalysts with an optimal configuration and high efficiency for the fuel cell. Herein, we reported the synthesis of N-doped CoS2 through a facile method using ammonium hydroxide as the N source, the subjection of N-doped CoS2 as efficient electrocatalysts for OER, and the identification of intrinsic activities by exploring the composition and electronic configurations and their correlations with the electrochemical performance. The DFT studies evidenced that N doping could alter the electronic density of the adjacent Co atoms and thus form well-defined electronic configurations for adsorption of intermediates. Specifically, the N-enriched CoS2 afford a small overpotential of 240 mV at the current density of 10 mA cm–2 and long-term durability, endowing these N-doped materials to be ideal (but not limited to) OER electrocatalysts.

The precipitation sequence of 6061Al has changed after introducing high amount SiC nanowires due to the serious segregation of Mg element. In the present work, 0.8 wt% Mg element was added into 6061Al matrix to compensate the segregation effect, and the 15 vol% SiCnw/6061Al+0.8Mg composite was prepared by pressure infiltration method. Regardless of aging time, the hardness of SiCnw/6061Al composite could be improved by the addition of Mg. MgAl 2 O 4 phase at SiC nanowire-Al matrix interface was found in SiCnw/6061Al+0.8Mg composite after solid solution treatment. The ultimate precipitate of Al matrix in SiCnw/6061Al+0.8Mg composite has been restored from B′ (MgSi >1 ) to β (Mg 2 Si). Moreover, the hardness of composites was improved 10% after addition of Mg in the over-aging status, implying that the strengthening effect of B′ phase might be inferior to that of β' and β phases. Due to early failure behavior, the tensile strength of the peak-aged composites was slightly decreased by the addition of Mg element. However, the yield strength of the composites was improved, which could be well explained by the modified shear-lag model. It is suggested that addition of extra alloying elements to compensate the segregation effect might be an effect method to improve the yield strength. However, for the application favor high tensile strength, design of performance matching in elastic-plastic behavior between matrix and reinforcement and the ability of Al matrix to relax the stress concentration might be the advisable choice.

Recently, it has been found that SiC nanowires have significant strengthening effect on Al matrix. The shear-lag model was used to explain the strengthening behavior after considering the aspect ratio of reinforcement in the previous work. However, the effect of alloying elements has not been considered yet. Moreover, the significant strengthening effect of SiC nano-particles over micron-scale particles could not been explained by the modified shear-lag model due to their same aspect ratio. Therefore, pure Al matrix composites reinforced with SiC nanowires, which could minimize the strengthening effect of the alloying elements, were selected to explore in this work. SiCnw/pure Al composites with different fractions (15, 20 and 25 vol%) have been prepared by pressure infiltration method. The yield strength was improved with the increased content of SiC nanowires. Based on the previous work, the modified shear-lag model has been further developed after considering the surface-to-volume ratio of the reinforcement. It has been taken into account that initially the effective atoms participated into the interfacial load transferring, and eventually the strengthening behavior of Al composites reinforced with SiC-type reinforcements was explored. Based on the developed model, the key research fields have also been discussed in order to exploit the strengthening effect of SiC nanowires.

We presented the fabrication of N doped NiS2 nanoarrays using NH3·H2O as the dopant precursor for the electrocatalytic OER. N doping primarily affects the configuration of electrons and the density of d-states near the Fermi level, together with the adsorption of the OER intermediate, thus overcoming the intrinsic limits of reaction kinetics.

In the present work, microstructure and mechanical performance of extruded SiCnw/Al composites have been investigated. The extrusion treatment leads to the alignment of SiC nanowires and the densification of the composites. The average length of SiC nanowires has been shortened after extrusion. High density dislocation tangles have been observed in Al matrix after extrusion. As the “non-deformable” phases, SiC nanowires inhabited the movement and deformation of surrounding Al matrix, leading to the formation of the grain boundaries. Therefore, SiC nanowires were mainly found at the boundary of Al grains in the extruded composites. Regardless of content of SiC nanowires, the yield strength, tensile strength and elongation of SiCnw/6061Al composites have been improved after extrusion treatment. Based on generalized mixture rule considering the effect of porosity, the increase of elastic modulus of SiCnw/6061Al composites is mainly due to the densification effect. The strengthening factor and efficiency of SiC nanowires are highest among all SiC reinforcements, and the strengthening behavior of SiC reinforced Al matrix composites could be well explain by the modified shear-lag model. The ratio of strengthening efficiency of SiCnw/Al composites before and after extrusion was about 0.6, indicating that orientation optimization of SiC nanowires is an effective method to improve the mechanical properties of SiCnw/Al composites.

In the present research work, the effect of extrusion temperature from 480 to 560 &deg, C on the microstructure and mechanical behavior of the SiCnw/2024Al composite (15 vol.%) has been explored. It has been found that extrusion at higher temperature (above 520 &deg, C) was beneficial for the densification of the composite, while the residual average length and alignment of the SiC nanowires were also increased with the extrusion temperature. Moreover, higher extrusion temperature was helpful for the mechanical strength of the SiCnw/2024Al composite, and the peak-aged SiCnw/2024Al composite extruded at 560 &deg, C revealed the highest strength (709.4 MPa) and elastic modulus (109.8 GPa).

Transition metal sulfides with their own capability of ultrafast electron extraction have aroused wide concerns in the field of photocatalysis research. In this work, CoS nanoflower as cocatalyst is in-situ mounted on two-dimension carbon nitride (2D CN) to realize the enhanced photocatalytic performance for the degradation of rhodamine B (RhB). As demonstrated by the photoluminescence (PL) spectra and photocurrent measurement, the CoS nanoflower can work as co-catalyst to extract photogenerated electrons rapidly from 2D CN to promote efficient charge separation. As expected, the maximum degradation activity of CoS/2D CN displays a distinct improvement compared with that of 2D CN. Meanwhile, the CoS/2D CN displays a superior photostability after four cycles. Moreover, the CoS/2D CN can also be used for photocatalytic H2 evolution reaction.

Developing photocatalysts with high efficient photoinduced carriers separation is a key challenge in the photocatalytic field. Herein, one kind metallic 3R NbS2 modified 2D graphitic carbon nitride (g-C3N4) photocatalyst was synthetized by a solvent thermal synthesis process. The morphology, structure, photoelectric property and the structure–activity relationship between the components of the composite were investigated and analyzed systematically. It is proven that the good conductivity of metallic 3R NbS2 facilitates the migration and transfer of electrons through the constructed NbS2/2D g-C3N4 interface, and controls the recombination of photoinduced carriers. The 5% NbS2/2D g-C3N4 possesses the optimal photocatalytic degradation activity of rhodamine B (RhB) (the degradation rate of 87% in 75 min). The introduction of NbS2 can effectively enhance the photocatalytic degradation activity.

In the present work, the wire electrical discharge machining (WEDM) process of the 65 vol% SiCp/2024Al composite prepared by pressure infiltration methods has been investigated. The microstructure of the machined composite was characterized by scanning electron microscope, the average surface roughness (Ra), X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy (TEM) techniques. Three zones from the surface to the interior (melting zone, heat affected zone and un-affected zone) were found in the machined composites, while the face of SiC particles on the surface toward the outside was “cut” to be flat. Increase in Al and Si but decrease in C and O were observed in the core areas of the removed particles. Si phase, which was generated due to the decomposition of SiC, was detected after the WEDM process. The irregular and spherical particles were further observed by TEM. Based on the microstructure observation, it is suggested that the machining mechanism of 65 vol% SiCp/2024Al composite was the combination of the melting of Al matrix and the decomposition of SiC particles.

The detection of glyphosate (Glyp) in water is of increasing importance because of its potential danger to environmental and health. In this study, a simple and label free colorimetric method for Glyp detection is proposed based on the inhibition of peroxidase-like activity of Cu2+. Cu2+ possesses the peroxidase-like activity that could catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to oxidized TMB (oxTMB) in the presence of H2O2, resulting in a color change of the solution. However, the peroxidase-like activity of Cu2+ could be strongly hindered by Glyp due to the formation of Glyp–Cu2+ complexes. The color change of the solution or the absorbance change of oxTMB is utilized to monitor the concentration of Glyp. The linear range of the proposed method is 2–200 μM and the detection limit is 1 μM. Furthermore, as low as 10 μM Glyp can be clearly distinguished by naked eyes. Also, this proposed method is successfully applied for screening Glyp in real samples and shows great promise for environmental monitoring owing to its simplicity, rapidness and high selectivity.