Core-shell Composite Material Research Articles

Preparation and study on combustion performance of AP@ZrH2 core-shell composite energetic materials with high volume energy density

The development of composite energetic material with high volume energy density could increase the range and loading capacity of solid propellants. In this study, a series of core-shell composite energetic materials AP@ZrH2 were fabricated by decorating ZrH2 on the ammonium perchlorate (AP) through a solvent-nonsolvent method. A substantial increase in combustion heat (13373.67 J/g) and maximum burning temperature (1415.33 °C) are detected in composites in contrast to physically mixed sample (10660.46 J/g and 837.22 °C). This is due to the enhancement of the decomposition performance of AP, which provides sufficient oxidation gas atmosphere for combustion of ZrH2. In addition, the delay time (524 ms) and burning time (114 ms) of composites are significantly decreased compared to the physical mixed sample (2145 and 256 ms). The remarkable combustion performance and burning rate could be attributed to reduced mass and heat transfer distances. Finally, the improvement of combustion efficiency in the composites makes the size of the residual particles smaller.

Preparation and soldering performance of SAC305@Sn-bi Core-shell solder balls based on eutectic co-deposition

SnBi eutectic thin film alloys are widely used in microelectronic devices, sensors, biomedical devices due to their high resistance, low temperature coefficient, chemical stability, and biocompatibility. However, the large standard electrode potential difference (454 mV) between Sn (−0.136 V) and Bi (+0.3118 V) makes them difficult to be co-deposited, especially with eutectic composition. In this study, cathodic polarization curves were used to analyze the negative shift of the cathodic reduction potentials of Sn and Bi induced by gelatin and EDTA-2Na, respectively, which reduced the potential difference between the two to 184 mv (Sn:-0.958 v; Bi:-0.774 v) and enabled the co-deposition of Sn and Bi; cathodic overpotentials were analysed to show that catechol not only improves the degree of cathodic polarization, but also raises the overpotentials, resulting in flatter surface coatings; By adjusting the temperature, current density, and pulse current, a SnBi eutectic thin film coating with good weldability, controllable thickness, flat surface, density, and uniformity was obtained on copper foil using a platinum as the anode in a methanesulfonic acid solution. The results indicate that it is feasible to deposit SnBi solder alloy at eutectic points (Sn41.53Bi58.47, At.%). Under the synergistic effect of gelatin and unidirectional square wave pulse, a typical eutectic network morphology can be obtained, which is the same as the microstructure of industrial SnBi eutectic solder. Based on these, a core-shell composite soldering material for low-temperature soldering was obtained by using SAC305 solder balls as cores and a SnBi low-temperature soldering material coating was roll-plated on their surfaces. This study provides a reliable technical way and theoretical guidance for low-temperature soldering, preparation of low-temperature solderable core-shell composite soldering material, and application of sensors and optoelectronic devices.

Core–shell engineered g-C3N4 @ NaNbO3 for enhancing photocatalytic reduction of CO2

Photocatalytic reduction of carbon dioxide is a technology that effectively utilizes CO2 and solar energy. Sodium niobate (NaNbO3) has received much attention in the field of photocatalysis due to its excellent photocatalytic properties. However, the application of NaNbO3 in the field of photocatalysis is still limited by poor reaction to visible light and easy recombination of photo-generated carriers. Heterojunction with g-C3N4 to construct core–shell structure can effectively improve the above problems. Combining the two can design a core–shell composite material that is beneficial for photocatalytic reduction of CO2. Herein, we prepared a core–shell heterojunction g-C3N4/NaNbO3 by uniformly impregnating urea on the surface of NaNbO3 chromium nanofibers with NaNbO3 nanofibers prepared by electrospinning as a catalyst carrier, and urea as a precursor of g-C3N4. The core–shell structure of g-C3N4/NaNbO3 was verified by a series of characterization methods such as XPS, XRD, and TEM. It was found that under the same conditions, the methanol yield of core–shell g-C3N4/NaNbO3 was 12.86 μmol·g−1·h−1, which is twice that of pure NaNbO3 (6.67 μmol·g−1·h−1). This article highlights an impregnation method to build core–shell structures for improved photocatalytic reduction of CO2.

MXene Hollow Spheres Supported by a C-Co Exoskeleton Grow MWCNTs for Efficient Microwave Absorption.

High-performance microwave absorption (MA) materials must be studied immediately since electromagnetic pollution has become a problem that cannot be disregarded. A straightforward composite material, comprising hollow MXene spheres loaded with C-Co frameworks, was prepared to develop multiwalled carbon nanotubes (MWCNTs). A high impedance and suitable morphology were guaranteed by the C-Co exoskeleton, the attenuation ability was provided by the MWCNTs endoskeleton, and the material performance was greatly enhanced by the layered core-shell structure. When the thickness was only 2.04mm, the effective absorption bandwidth was 5.67GHz, and the minimum reflection loss (RLmin) was - 70.70dB. At a thickness of 1.861mm, the sample calcined at 700°C had a RLmin of - 63.25dB. All samples performed well with a reduced filler ratio of 15wt%. This paper provides a method for making lightweight core-shell composite MA materials with magnetoelectric synergy.

Mesoscopic Simulation of Core-Shell Composite Powder Materials by Selective Laser Melting.

Mechanical ball milling is used to produce multi-materials for selective laser melting (SLM). However, since different powders have different particle size distributions and densities there is particle segregation in the powder bed, which affects the mechanical properties of the printed part. Core-shell composite powder materials are created and used in the SLM process to solve this issue. Core-shell composite powder materials selective laser melting (CS-SLM) has advanced recently, expanding the range of additive manufacturing applications. Heat storage effects and heat transfer hysteresis in the SLM process are made by the different thermophysical characteristics of the core and the shell material. Meanwhile, the presence of melt flow and migration of unmelted particles in the interaction between unmelted particles and melt complicates the CS-SLM molding process. It is still challenging to investigate the physical mechanisms of CS-SLM through direct experimental observation of the process. In this study, a mesoscopic melt-pool dynamics model for simulating the single-track CS-SLM process is developed. The melting characteristics of nickel-coated tungsten carbide composite powder (WC@Ni) were investigated. It is shown that the powder with a smaller particle size is more likely to form a melt pool, which increases the temperature in the area around it. The impact of process parameters on the size of the melt pool and the distribution of the reinforced particles in the melt pool was investigated. The size of the melt pool is significantly affected more by changes in laser power than by changes in scanning speed. The appropriate control of the laser power or scanning speed can prevent enhanced particle aggregation. This model is capable of simulating CS-SLM with any number of layers and enables a better understanding of the CS-SLM process.

Preparation of core-shell composite materials capable of slowly releasing phosphate and their remediation performance of uranium-contaminated groundwater

Acid in-situ leach uranium mining significantly alters the geochemistry of the ore zone, and leaves uranium, residual acid, as well as other potential contaminants in groundwater, which bring harm to human health and ecological environment. Many investigators have been trying to propose remediation strategies for the uranium-contaminated groundwater. Phosphate is an effective immobilization reagent of uranium in the groundwater. However, direct injection of phosphate tends to quickly form precipitates, resulting in fast blockage of the seepage passages in the ore zone around the injection holes and hindering its diffusion. In this paper, HAP@SiO2-600, HAP@SiO2-600@25SA, and HAP@SiO2-600@75SA with core-shell structures were prepared. Their slow-release of phosphate, the effects of pH, contact time, initial uranium concentration, and coexisting ions on their removal rate and efficiency of uranium, and their function of remediating uranium-contaminated groundwater were investigated. It was found that the increase of SA content in the outer layer of HAP@SiO2-600@25SA and HAP@SiO2-600@75SA resulted in the slow release rate of phosphate, decreasing the removal rate of uranium. The adsorption capacities of HAP@SiO2-600, HAP@SiO2-600@25SA, and HAP@SiO2-600@75SA from the aqueous solution at pH = 3.0 and 303 K were up to 582.6, 558.5, and 507.3 mg g−1, respectively. In addition, the materials showed excellent uranium removal performance in experiments where multiple ions coexisted. For actual acidic uranium-contaminated groundwater, HAP@SiO2-600, HAP@SiO2-600@25SA, and HAP@SiO2-600@75SA effectively increased the pH from 2.75 to 4.40, 3.87, and 3.72, respectively, and decreased the uranium concentration from 5.12 to 0.0062, 0.0065, and 0.0058 mg L−1, respectively. The FT-IR, XRD, TEM and XPS characterizations were performed to further clarify the uranium removal mechanism, and it was found that the elimination of U(VI) was ascribed to dissolution-precipitation, adsorption and ion exchange. The results show that the core-shell composite material capable of slowly releasing phosphate is effective in remediating uranium-contaminated groundwater.

Low-temperature synthesis of doped MnO2–carbon dots nanocomposite: an analysis of nanostructure and electrical properties

The synthesis of δ-MnO2, δ-MnO2 carbon dots nanocomposite, and Fe/Cu-doped δ-MnO2 carbon dots nanocomposite has been successfully carried out through a stirring process at room temperature and 80 °C. The synthesized powder shows a low crystallization determined through XRD and TEM analysis. Furthermore, the carbon dots are well attached to MnO2 performing a core–shell composite material, while the doping ions Fe and Cu were incorporated into the matrix substitute Mn in the MnO6 octahedron, although potassium ions were also detected. The manganese possess an oxidation state of + 3 and + 4, which promotes the oxygen vacancy creation {V}_{mathrm{O}}^{cdotcdot} denoting the conductivity decrease.

Core-Shell Composite MIL-101(Cr)@TiO2 for Organic Dye Pollutants and Vehicle Exhaust.

MIL-101(Cr)@TiO2 core-shell composite material was synthesized via the hydrothermal method, where MIL-101(Cr) served as the core and TiO2 acted as the shell. SEM results revealed that the metal-organic framework core effectively prevented the aggregation of TiO2 nanoparticles and facilitated their dispersion. Characterization techniques such as XRD, XPS, and TGA were utilized to confirm the successful loading of TiO2 onto MIL-101(Cr) and its excellent thermal stability. MIL-101(Cr)@TiO2 was employed in photocatalytic degradation of dye pollutants and vehicle exhaust, and the potential degradation mechanisms were investigated in detail. The results showed that MIL-101(Cr)@TiO2 exhibited excellent photocatalytic degradation performance towards dye pollutants, with degradation efficiencies of 91.7% and 67.8% achieved for MB and RhB, respectively, under visible light irradiation for 90 min. Furthermore, the photocatalytic degradation of automobile exhaust revealed that the MIL-101(Cr)@TiO2 composite material also exhibited degradation effects on NOx, CO, and HC. The degradation efficiency for NO reached 24.2%, indicating its broader applicability.

Study on Bonded Dispersant for Ultrafine CL-20

To improve the problem that ultrafine hexanitrohexaazaisowurtzite (CL-20) is prepared by the solvent nonsolvent method, which tends to coalesce and automatically affects its thermal properties, the bonding agent @CL-20 core-shell composite energetic materials (ammonium dodecylbenzene sulfonate@CL-20, trimethylsilyl monooleate@CL-20 and boron nitride@CL-20) were prepared by water suspension method. The coated ultrafine CL-20 was characterized by an optical microscope, scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC), and its sensitivity was tested according to GJB 772-1997. The results showed that the three bonded dispersants completely coated CL-20, and the crystal form of CL-20 was still ε-. Compared with the raw material CL-20, the characteristic drop increased by 27.5cm at most and the thermal decomposition temperature increased by 4 °C.

Core-Shell Structured Carbon Nanofiber-Based Electrodes for High-Performance Supercapacitors.

The combination of multiple electrode materials and their reasonable structural design are conducive to the preparation of composite electrodes with excellent performance. In this study, based on carbon nanofibers grown with Ni(OH)2 and NiO (CHO) prepared by electrospinning, hydrothermal growth, and low-temperature carbonization, five transition metal sulfides (MnS, CoS, FeS, CuS, and NiS) were hydrothermally grown on their surfaces, exhibiting that CHO/NiS had the optimal electrochemical properties. Subsequently, the effect of hydrothermal growth time on CHO/NiS revealed that the electrochemical performance of CHO/NiS-3h was optimal, with a specific capacitance of up to 1717 F g-1 (1 A g-1), due to its multistage core-shell structure. Moreover, the diffusion-controlled process of CHO/NiS-3h dominated its charge energy storage mechanism. Finally, the asymmetric supercapacitor assembled with CHO/NiS-3h as the positive electrode demonstrated an energy density of 27.76 Wh kg-1 at a maximum power density of 4000 W kg-1, and it still maintained a power density of 800 W kg-1 at a maximum energy density of 37.97 Wh kg-1, exhibiting the potential application of multistage core-shell composite materials in high-performance supercapacitors.

Subppb level monitoring and UV degradation of triclosan pollutants using ZnO multipod and Ag nanocomposites

A unique nanomaterial platform was developed for trace detection and efficient degradation of triclosan (TCS). A facile spectroscopic technique for surface-enhanced Raman scattering (SERS)-supported identification and ultraviolet (UV) degradation of TCS using a SERS template based on silver spherical nanoparticle (AgNP)-modified ZnO multipods (ZnO@Ag) is reported. Core-shell composite materials of ZnO multipods with a dimension of around 3 μm and AgNPs with an average diameter of ∼27 nm was designed not only as a substrate for TCS degradation up to ∼92% upon UV irradiation (λ = 365 mm, 300 μW/cm2) but also as a monitoring platform sensitive to TCS at a detection limit as low as 10−9 M (≈0.3 ppb). Herein, the first investigation into ZnO@Ag bimetallic composites is established for both the SERS-based detection and UV-assisted degradation of environmental TCS pollutants. The calibration curve was estimated to be linear at R2 > 0.97. The validated technology was successfully used to determine the antibacterial agent and TCS in distilled or river water. The advantages of the ZnO@Ag template are highlighted over conventional detection and excellent degradation.

Microstructure and Mechanical Properties of Core-Shell B4C-Reinforced Ti Matrix Composites.

Composite material uses ceramic reinforcement to add to the metal matrix to obtain higher material properties. Structural design is an important direction of composite research. The reinforcement distribution of the core-shell structure has the unique advantages of strong continuity and uniform stress distribution. In this paper, a method of preparing boron carbide (B4C)-coated titanium (Ti) powder particles by ball milling and preparing core-shell B4C-reinforced Ti matrix composites by Spark Plasma Sintering was proposed. It can be seen that B4C coated on the surface of the spherical Ti powder to form a shell structure, and B4C had a certain continuity. Through X-ray diffraction characterization, it was found that B4C reacted with Ti to form layered phases of titanium boride (TiB) and titanium carbide (TiC). The compressive strength of the composite reached 1529.1 MPa, while maintaining a compressive strain rate of 5%. At the same time, conductivity and thermal conductivity were also characterized. The preparation process of the core-shell structure composites proposed in this paper has high feasibility and universality, and it is expected to be applied to other ceramic reinforcements. This result provides a reference for the design, preparation and performance research of core-shell composite materials.

Carbon tungsten oxide composite cathode materials for aluminum-ion batteries

Aluminum-ion batteries use more abundant materials and suffer from fewer safety risks than lithium-ion batteries. In this work, new cathode materials for Al-ion batteries were synthesized and tested. WO3, carbon materials, and WO3-carbon composite were prepared by sol-gel and chemical vapor deposition methods. These materials differ in microstructure and other physicochemical properties and the possibility of using them as cathode materials was tested. The correlation between the phase composition, structure, microstructure, electrical properties, and electrochemical performance was described based on X-ray diffraction, scanning electron microscopy, electrochemical impedance spectroscopy, and galvanostatic discharge results. WO3, Norit, and WO3/carbon core-shell composite materials exhibit the smallest average grain size in the range of tens of nanometers while materials based on potato starch carbons contain grains in the range of tens of micrometres. The highest values of the open cell voltage and capacitance of Al-ion cells were found for single-phase WO3 and Norit materials, whereas in the case of single-phase Carbon PS these parameters acquire much lower values.

Noble metal-free core-shell CdS/iron phthalocyanine Z-scheme photocatalyst for enhancing photocatalytic hydrogen evolution

Improving the separation efficiency of photogenerated carriers and broadening the light absorption range of the photocatalyst are two important factors for improving the performance of the photocatalyst. In this paper, a new and efficient Z-scheme CdS/iron phthalocyanine (CdS/FePc) core-shell nanostructure composite material is prepared by a simple solid-phase reaction method. There are two key points in the preparation of composite materials: one is that hydrogen bonding energy is closely connected with FePc, another is that FePc can be uniformly assembled on CdS nanoparticles. The photocatalytic hydrogen evolution (PHE) of the CdS/FePc nanocomposite (73.01 μmol/h) is 2.6 times higher than that of pure CdS (26.67 μmol/h). In addition, after 4 photocatalytic cycles, the PHE of the CdS/FePc composite is still 92.3% of the first cycle. There are three reasons for this situation: (1) The Z-scheme heterojunction is formed to improve the separation efficiency of photogenerated carriers; (2) FePc expands the visible light absorption range of CdS; (3) The large core-shell contact area is favorable for the separation of photo-induced carriers at the interfaces. This research is conducive to the further development of new photocatalytic materials with high efficiency, low cost and simple preparation.

Synthesis of ZnO@ZIF-8 Nanorods with Enhanced Response to VOCs

It is an effective way to produce core–shell composite materials by coating nano-metal oxides with metal-organic framework. A self-sacrificial method was reported. ZnO was transformed into ZIF-8 and attached to ZnO. Through the in situ transformation of zinc oxide particles in the matrix, a great many pores are formed to ensure that all parts of ZnO can contact the gas. ZnO has three main functions, providing Zn2+ for ZIF-8 and serving as a template for ZIF-8’s growth, and as an active material to detect gases. ZIF-8 has two functions. Firstly, it has hydrophobicity to avoid the impact of steam on the gas detection of ZnO; secondly, it can provide a large amount of pores, increase the specific surface area. A great many defects created at the interface of the two materials increases the active sites. The gas-sensing performance of ZnO to volatile organic compounds can be improved using the advantages of both materials. The composite sensor has an optimal operating temperature of 350 °C and has more than tripled its response to 50 ppm gases relative to the ZnO sensor. In addition, a gas-sensing mechanism is proposed. An effective strategy for developing high-response VOC sensors is presented in this work.

Lightweight, Low-Cost Co2SiO4@diatomite Core-Shell Composite Material for High-Efficiency Microwave Absorption.

The porous and biomimetic cobalt silicate@diatomite (Co2SiO4@diatomite) was successfully synthesized by a two-step method, including the hydrothermal method and calcination to improve the electromagnetic wave absorption property. Different hydrothermal times were well-tuned for Co2SiO4@diatomite composites with different loadings of Co2SiO4. Interestingly, the Co2SiO4@diatomite composites (6 h, 25 wt%) had a smaller minimum reflection loss. Moreover, the minimum reflection loss (RLmin) could reach −12.03 dB at 16.64 GHz and the matched absorber thickness was 10 mm, while the effective absorption bandwidth (EAB, RL ≤ −10 dB) could be 1.92 GHz. In principle, such findings indicate that Co2SiO4@diatomite nanocomposites could be a promising candidate for high-efficiency microwave absorption capability.

Hierarchical FeCo2O4@CoSe core–shell nanosheet arrays on nickel foam for high-performance supercapacitor

Self-growing FeCo2O4@CoSe/NF layered core–shell composite materials on Ni foam (NF) were prepared by hydrothermal method and electrodeposition method. CoSe shell effectively increased the conductivity of FeCo2O4 core, and the synergistic effects of the two contents effectively improved the overall electrochemical performance. At a current density of 1A/g, FeCo2O4@CoSe/NF achieved a specific capacity of 724.2C/g and capacity retention rate of 94.1% after 5000 cycles. The assembled asymmetric capacitor (ASC) also achieved a high energy density of 57.19Wh/kg when the power density is 750 W/kg.

Supported Cu/W/Mo/Ni—Liquid Metal Catalyst with Core-Shell Structure for Photocatalytic Degradation

Room-temperature liquid metal is a very ideal material for the design of catalytic materials. At low temperatures, the liquid metal enters the liquid state. It provides an opportunity to utilize the liquid phase in the catalysis, which is far superior to the traditional solid-phase catalyst. Aiming at the low performance and narrow application scope of the existing single-phase liquid metal catalyst, this paper proposed a type of liquid metal/metal oxide core-shell composite multi-metal catalyst. The Ga2O3 core-shell heterostructure was formed by chemical modification of liquid metals with different nano metals Cu/W/Mo/Ni, and it was applied to photocatalytic degrading organic contaminated raw liquor. The effects of different metal species on the rate of catalytic degradation were explored. The selectivity and stability of the LM/MO core-shell composite catalytic material were clarified, and it was found that the Ni-LM catalyst could degrade methylene blue and Congo red by 92% and 79%, respectively. The catalytic mechanism and charge transfer mechanism were revealed by combining the optical band gap value. Finally, we provided a theoretical basis for the further development of liquid metal photocatalytic materials in the field of new energy environments.

Shape-selective alkylation of benzene with ethylene over a core–shell ZSM-5@MCM-41 composite material

A series of ZSM-5@MCM-41 core–shell composite materials prepared via a multi-cycle-sol–gel coating strategy is investigated as the catalyst for benzene alkylation with ethylene, in which both ethylbenzene and para-diethylbenzene ( p- DEB) are aimed as the target products. With multi-cycle-sol–gel coating, the external acid sites on the samples are gradually passivated by the inert MCM-41 shell. As a result, the shape selectivity to p- DEB is greatly enhanced. Nevertheless, the coating of mesoporous MCM-41 shell on ZSM-5 accelerates deactivation of the catalyst only due to the dilution effect of ZSM-5 content in the catalyst at the same space velocity, which is a reason that core–shell ZSM-5@MCM-41 will potentially be a practical catalyst in shape selective alkylation of benzene. In order to enhance the yield of p- DEB on ZSM-5@MCM-41, the reaction conditions at the fixed bed reactor including temperature, the molar rate of benzene to ethylene and GHSV, are also optimized.

Preparation and Characterizations of Nanomaterial by Pulsed Laser Ablation in Liquid (PLAIL) as Friendly Environment Paint

In this research, silver oxide and nickel oxide were prepared as collide using Pulsed Laser Ablation in Liquid (PLAIL) method in the water. In all preparation case, the laser parameters were fixed at optimum conditions (laser energy 600 mJ with frequency 1 Hz at room temperature) and nanomaterial was added in several proportions (2%, 4%, 6%, 8%, 10%, 12%) to the local paint. Physical properties of the nano-collide were studied by Uv-visible spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force Microscope (AFM), contact angle (CA). A colloid as core-shell (composite materials) was obtained when the two slices were placed together in the water and ablated them by laser. It has shown the best results compared to using its individual Ni or Ag. The local paint was tested in two cases: the first by adding nickel and silver as micro-scale, and in the other in nanoscale to compare which one the best in the self-cleaning. The nanomaterial at a percentage 12% showed the best results when it added to the paint; it for their properties such as adhesion strength and hardness strength, exposure to weather conditions of temperature, and humidity. The adhesive strength increased when adding the nanomaterial from 112 to 139 before exposure to the weather and from 58 to 108 after exposure. The hardness also increased from 77.9 to 86.5 before exposure to the surrounding environment and from 94.2 to 96.8 after exposure.