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NiFe2O4 is a kind of bimetallic oxide possessing excellent theoretical capacity and application prospect in the field of supercapacitors. Whereas, due to the inherent poor conductivity of metal oxides, the performance of NiFe2O4 is not ideal in practice. Oxygen vacancies can not only enhance the conductivities of NiFe2O4 but also provide better adsorption of OH, which is beneficial to the electrochemical performances. Hence, oxygen vacancies engineered NiFe2O4 NiFe2O4−δ) is obtained through a two-step method, including a hydrothermal reaction and a further heat treatment in activated carbon bed. Results of electron paramagnetic resonance spectra indicate that more oxygen vacancies exist in the treated NiFe2O4−δ than the original one. UV-Vis diffuse reflectance spectra prove that the treated NiFe2O4−δ owns better conductivity than the original NiFe2O4. As for the electrochemical performances, the treated NiFe2O4−δ performs a high specific capacitance of 808.02 F·g−1 at 1 A·g−1. Moreover, the asymmetric supercapacitor of NiFe2O4−δ//active carbon displays a high energy density of 17.7 Wh·kg−1 at the power density of 375 W·kg−1. This work gives an effective way to improve the conductivity of metal oxides, which is beneficial to the application of metal oxides in supercapacitors. [ABSTRACT FROM AUTHOR]

Few-layers WS2 was obtained through unique chemical liquid exfoliation of commercial WS2. Results showed that after the exfoliation process, the thickness of WS2 reduced significantly. Moreover, the NiFe2O4 nanosheets/WS2 composite was successfully synthesized through a facile hydrothermal method at 180 °C, and then proven by the analyses of field emission scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The composite showed a high specific surface area of 86.89 m2·g−1 with an average pore size of 3.13 nm. Besides, in the three-electrode electrochemical test, this composite exhibited a high specific capacitance of 878.04 F·g−1 at a current density of 1 A·g−1, while in the two-electrode system, the energy density of the composite could reach 25.47 Wh·kg−1 at the power density of 70 W·kg−1 and maintained 13.42 Wh·kg−1 at the higher power density of 7000 W·kg−1. All the excellent electrochemical performances demonstrate that the NiFe2O4 nanosheets/WS2 composite is an excellent candidate for supercapacitor applications. [ABSTRACT FROM AUTHOR]

The new inorganic material known as "high-entropy oxides" (HEOs) has a single-phase structure and is made up of several different main metal elements. It has many useful properties, including a high specific capacity, excellent cycling performance, high structural stability, and super-electronic conductivity. For lithium-ion batteries, it is viewed as a promising electrode material (LIBs). It is significant to develop high entropy oxides with different components and study their properties. Herein, Mg, Ni and Li are added to the quaternary medium entropy (CrFeMnCo)3O4. Four new spinel high entropy oxides were synthesized by glycine-nitrate SCS method at 750 °C and their material characterization and electrochemical properties were investigated respectively. The experimental results show that the four obtained samples have uniform particle size distribution. As for the electrochemical test, the capacities of the (CrFeMnCoMg)3O4 and (CrFeMnCoNi)3O4 do not decrease significantly after 800 cycles at 2000 mA·g−1. They have better cycle stability than the (CrFeMnCoMgLi)3O4 and (CrFeMnCoNiLi)3O4. As the anode of LIBs, all HEOs show excellent cycle stability and rate capability. This work provides a new strategy for designing high-entropy energy storage materials. [ABSTRACT FROM AUTHOR]

With the advancement of multimedia technology and coming of big data era, the size of image data is significantly increased. However, the traditional image encryption methods cannot solve the emerging problems of efficient compression. To settle with this challenge, an effective content-adaptive image compression and encryption method based on compressive sensing and double random phase encoding (DRPE) is proposed in this paper. The original image is converted to one low-frequency part and three high-frequency parts by DWT and then permutated by sorting-based chaotic sequences. Afterward, a novel measurement matrix optimization algorithm based on adaptive step size is presented to measure the high-frequency components. To enhance the security of the scheme, the DRPE, quantization, and diffusion are successively performed on the complex matrix composed of the shuffled low-frequency component and three measurement value matrices to obtain the cipher image. Logistic-Sine chaotic system is utilized to produce the chaotic keystreams for the encryption process, and its system parameter and initial value are determined by the information entropy of the plain image and external key parameters, so that the proposed cipher can withstand known-plaintext and chosen-plaintext attacks effectively. Numerical experiments demonstrate the effectiveness of the proposed image compression and encryption algorithm. [ABSTRACT FROM AUTHOR]

Compared to 1D compressed sensing (CS), 2D CS is more efficient for compressing the plaintext image from two directions, but security level of current 2D CS-based ciphers is unsatisfactory. To solve this problem, this paper presents a novel color image compression and encryption algorithm by combining 2D CS, information entropy and chaos. Firstly, the color image is decomposed into red, green and blue components, then they are sparsely transformed by the discrete wavelet transform (DWT) to get three sparse matrices. Next, the obtained matrices are observed by two asymptotical deterministic random measurement matrices based on information entropy and counter (ADMMIC), which not only encrypts the plaintext image, but also compresses it in proportion to reduce the transmission bandwidth and storage space. Subsequently, the corresponding measurement value matrices are shuffled by a double random scrambling based on Arnold map and index vector (DRSAIV) to eliminate the correlation between adjacent pixels. Furthermore, the obtained permutated matrices are diffused by a simultaneous multiple random diffusion of inter–intra components (SMRDIC) to obtain the final cipher image, the plaintext pixel to be diffused, the key matrix involved in diffusion and the position of the obtained ciphertext pixel are all unpredictable, which makes statistical attack invalid. In addition, information entropy values of plaintext image are obtained to generate the initial values of the used chaotic systems, which greatly improve the ability to resist the known-plaintext and chosen-plaintext attacks. Simulation results and security analyses verify that this algorithm has good compression and high security. [ABSTRACT FROM AUTHOR]

Carbides are typical electromagnetic microwave (EM) absorbing materials, due to their excellent dielectric properties. Large-scale synthesis of carbides through simple and low-cost methods is a necessary demand for EM pollution treatment. In this work, molybdenum carbide (MoC) was synthesized by a facile solid-state reaction method using carbon nanotubes and carbon black as carbon sources. The as-prepared MoC powders possessed irregular shape and rough surface. The EM absorption property as well as the EM parameters in the range of 2–18 GHz were investigated. It is found that the MoC powders, either carbon nanotubes or carbon black as carbon sources, showed satisfactory EM absorption performance. The powders using carbon nanotubes and carbon black as carbon source displayed the minimum reflection loss of –42.2 dB with a 1.5 mm thickness and –34.3 dB with a 3.0 mm thickness, respectively. The experimental results show that MoC is a promising EM microwave absorbing candidate, and the low-cost synthesis of MoC will be helpful for its large-scale development in EM protection field. [ABSTRACT FROM AUTHOR]

In this work, we synthesized K2Ti6O13 nanowires coated with sulfur-doped carbon for the first time, with fulvic acid and cystine as the carbon source, which exhibit higher capacity and rate performance compared with pure potassium titanate. Via analyzing the cyclic voltammetry curves obtained at different scan rates, it is revealed that the capacity increase is due to the improved ion diffusivity induced by the carbon coating. Moreover, cystine is demonstrated to be a better carbon source than fulvic acid. [ABSTRACT FROM AUTHOR]

In this research, a novel layered O3-type NaNi0.48Mn0.3Ti0.2Ru0.02O2 is fabricated by using solid-state method for sodium-ion batteries. Sodium-ion battery (SIB) can be a promising alternative to the current lithium-ion battery (LIB) technology due to the shortage of lithium in nature and higher cost. As a promising cathode material, NaNi0.48Mn0.3Ti0.2Ru0.02O2 electrode shows a high reversible capacity of 155.3 mA h g−1 at 0.05 C (12 mA g−1) in the range of 1.5-4.5 V and exhibits a favorable coulombic efficiency. DFT calculation and X-ray diffraction, Raman, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy analysis are introduced to reveal the effects of substitution of Ru4+ for Ni2+ including the decreasing electronic localization, more stable material structure, wider sodium-ion diffusion channels and good diffusion coefficient of Na. The doping of Ru has paved a new way to enhance the electrochemical performances of O3-type cathode materials for SIBs. [ABSTRACT FROM AUTHOR]

Porous SiO-SiN composite ceramics with high porosity and excellent mechanical properties were fabricated by pressureless-sintering at relatively low temperature of 1 500 °C using diatomite as pore forming agent. The effects of diatomite on flexural strength, fracture toughness, shrinkage, porosity and phase transformation of the porous ceramics were investigated in detail. Compared with that of the ceramic without adding diatomite, the porosity of the ceramic with 10% diatomite is increased by about 27.4%, the flexural strength and fracture toughness reaches 78.04 MPa and 1.25 MPa·m, respectively. As the porosity increases, the dielectric constant of porous SiO-SiN ceramic decreases obviously from 3.65 to 2.95. [ABSTRACT FROM AUTHOR]

The concentrations of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) and organic carbon in surface sediments, collected from the southern Bohai Bay, were determined to assess the potential contamination and determine the environmental risks associated with heavy metals. Results showed that heavy metal concentrations in the sediments generally met the China Marine Sediment Quality criteria. Both the ecotoxicological index and the potential ecological risk index suggest that the combined ecological risk of the six studied metals may be low, with the highest ecotoxicological potential zones located in the offshore area. The methods of enrichment factor and geoaccumulation index suggested that elevated concentrations of Cd, Cr, and Ni are presented in the region. Multivariate analysis also indicated that the lithogenic factor dominates the distribution of most part of the considered metals in the study area, whereas Cd and Cr are clearly influenced by anthropogenic inputs. The results of this study are likely to be a useful tool to authorities in charge of sustainable marine management. [ABSTRACT FROM AUTHOR]

2A12 Al alloy was suffered from equal-channel angular pressing(ECAP) in this experiment. The influence of ECAP pass number on ultimate strength(UTS), hardness and elongation was studied. The results show that during ECAP the number of sample passing through the channels is very important for mechanical properties and microstructure refinement. ECAP not only increases their plasticity and hardness but also leads to refined grain. But the elongation reduces from 17.5% to11.8 % after 1 pass ECAP, then almost tends to be unchanged with the increasing of pass number. The value of ultimate strength of 2A12 Al alloy increases by 135%, hardness by 51%, and ultra fine grains of about 200 nm can be observed after 8 passes. [ABSTRACT FROM AUTHOR]

In this work, the setting process of reduced graphene (RGO)/carbon nanotubes (CNTs) reinforced calcium phosphate cement (CPC) were conducted in a microwave environment. The introduction of microwave can increase the reaction temperature, speed up the vibration of water molecules and eliminate bubbles from the interface between RGO, CNTs and the substrate. Comparing with CPC without microwave treatment, the final setting time of composites after microwave treatment are almost a half, the flexural strength and the compressive strength are increased by 19.86% and 21.68% respectively, which are 17.38 MPa and 104.52 MPa. Meanwhile, the CPC composites remain the excellent bioactivity. [ABSTRACT FROM AUTHOR]