The release of toxic and harmful gases seriously endangers human health and social and environmental safety. Sensitive determination of these gases is urgently needed to meet the demands of people ...and society. ZnO-based gas sensors have been widely used due to fast response, low detection limit, high selectivity, reliable performance and low manufacturing cost. In this review, we highlight the possible sensing mechanism of n-type ZnO materials, and discuss various strategies for enhancing sensitivity and selectivity of ZnO-based gas sensing materials, including regulation of the material morphology, composite of materials, photoexcitation, etc. Then, the current challenges of ZnO-based gas sensing materials are outlined, followed with the future research interests and directions of these materials.
•This paper details the different gas sensing mechanisms of ZnO-based nanomaterials.•The relationship between the four different dimensional structures of ZnO and the gas-sensitive performance is explained.•The composite action of ZnO with other materials is described in detail.•We analyze the effects of visible light and ultraviolet light on the gas-sensitive properties of materials.
There is a growing interest in the development of natural fiber-reinforced composites, most likely due to their wide availability, low cost, environment friendliness, and sustainability. The market ...size for natural fiber-reinforced composites is projected to reach $5.83 billion by 2019, with a compound annual growth rate of 12.3%. The composite materials reinforced with wood, cotton, jute, flax or other natural fibers fall under this category. Meanwhile, some major factors limiting the large scale production of natural fiber composites include the tendency of natural fiber to absorb water, degradation by microorganisms and sunlight and ultimately low strength and service life. This paper has focused to review the different natural fiber treatments used to reduce the moisture absorption and fiber degradation. The effect of these treatments on the mechanical properties of these composites has also been summarized.
Metal-organic frameworks (MOFs) have lately obtained great attention of scientists as potential materials applied for supercapacitor electrodes. Due to their crystalline structure, MOFs show proper ...electrochemical double-layer capacitance at the enlarged specific surface area of the material and the mechanical supports for the composite materials. In this study, Zn-MOF was synthesized and composited with reduced graphene oxide (rGO) to be applied as a supercapacitor electrode material. To improve the electrodes working performance, polyaniline (PANI) was synthesized by different methods and added to the composite. The electrochemical properties of these materials were studied to identify the effect of PANI and Zn-MOF on the electrode materials. Among the composites obtained, the best specific capacitance of about 372 F/g was obtained at 0.1 A/g charge-discharge analysis of rGO/Zn-MOF@PANI sample due to its large surface with high pores sizes. The capacitance retentions of electrodes were also tested to decipher the effect caused by varied composites fabrication.
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Hydrogen evolution reaction (HER) has been identified as a sustainable and environment friendly technology for a wide range of energy conversion and storage applications. The big barrier in realizing ...this green technology requires a highly efficient, earth-abundant, and low-cost electrocatalyst for HER. Various HER catalysts have been designed and reported, still, their performance is not up to the mark of Pt. Among them, cobalt-based, especially cobalt disulfide (CoS2) has shown significant HER activity and found suitable candidature for HER due to its low cost, simple to prepare, and exhibits good stability. Herein, we synthesized various nanostructured materials including pure CoS2, Co3O4 and their composites by wet chemical methods and found them active for HER. The scanning electron microscopy (SEM) has revealed a morphology of composite as a mixture of nanowires and round shape spherical nanoparticles with several microns in dimension. The X-ray diffraction (XRD) confirmed the cubic phase of CoS2 and cubic phase of Co3O4 in the composite materials. The chemical deposition of CoS2 onto Co3O4 has tailored the HER activity of CoS2@Co3O4 composite material. Two CoS2@Co3O4 composite materials were produced with varying amounts of Co3O4 and labeled as samples 1 and 2. The Co3O4 reduced the adsorption energy for hydrogen, decreased the aggregation of CoS2 and uplifted the stability of CoS2@Co3O4 a composite material in alkaline media. Sample 1 requires an overpotential of 320 mV to reach a current density of 10 mA/cm2 and it exhibits a Tafel slope of 42 mVdec−1which is the key indicator for the fast HER kinetics on sample 1. The sample 1 is highly durable for 50 h and also it has excellent stability. The electrochemical impedance spectroscopy (EIS) revealed a small charge transfer resistance of 28.81 Ohms for the sample 1 with high capacitance double-layer value of 0.81 mF. EIS has supported polarization and Tafel slope results. Based on the partial physical characterization and the electrochemical results, the as-obtained sample 1 (CoS2@Co3O4 composite material) will find potential applications in an extended range of energy conversion and storage devices owing to its low cost, high abundance, and excellent efficiency.
•Mixed CoS2@Co3O4 composite material is prepared by hydrothermal method.•The composite achieves a current density of 10 mA/cm2 at overpotential of 320 mV.•The electrocatalyst exhibits favorable HER with a Tafel slope of 42 mVdec−1.•The chronopotentiometry shows that catalyst is highly durable for 50 h.
This paper presents an exploration of hierarchically bimetallic/trimetallic nanoporous metal oxide-based composite materials such as Co3O4/Ag and Co3O4/Ag/CuO via the sol-gel route and characterized ...by several spectroscopic techniques. Electrochemical tests are carried out to assess the supercapacitor performance viz. cyclic voltammetry (CV), galvanostatic discharge/charge (GCD), and electrochemical impedance spectroscopy (EIS). Because of the Faradaic type of capacitance, involving the redox process, Co3O4/Ag and Co3O4/Ag/CuO modified glassy carbon electrode (GCE) displayed pseudo-capacitance behavior. Moreover, the presence of a nanoporous CuO network enhanced the specific capacitance Csp of the Co3O4/Ag/CuO electrode. Herein, two different electrolytes, Potassium Chloride (KCl) and Sodium Hydroxide (NaOH) are employed to investigate the effect of electrolytes on the electrochemical performance of these materials. Electrochemical measurements revealed the maximum Csp of 189.29.00 Fg−1 for Co3O4/Ag-GCE and 1697.67 Fg−1 for Co3O4/Ag/CuO-GCE using GCD studies at a current density (CD) of 0.8 Ag−1. The Co3O4/Ag/CuO-GCE showed an admirable energy density (ED) of 99.62 WhKg−1 and power density (PD) of 14.34 kWkg−1. Furthermore, the Co3O4/Ag/CuO-GCE displayed excellent cycling stability (over 10,000 cycles) and robust rate capability.
•The Sol-Gel technique was employed to explore the bimetallic Co3O4/Ag and trimetallic Co3O4/Ag/CuO hybrid nanomaterials.•Co3O4/Ag/CuO material exhibited remarkable specific capacitance of 1697.67 Fg-1 at current density (CD) of 0.8 A g–1•The Co3O4/Ag/CuO-GCE demonstrates a notable specific energy density of 99.62 WhKg-1•The Co3O4/Ag/CuO-GCE exhibits a significant power density of 14.34 kWkg-1•Co3O4/Ag/CuO-GCE displays exceptional cycling stability, enduring over 10000 cycles, coupled with robust rate capability.
•Three machine learning methods are used to predict the ETC.•Machine learning methods have better predictive performance than EMT.•CNN can be a fast and accurate method of predicting the ETC.
...Composite materials have a wide range of engineering applications, and their effective thermal conductivities are important thermo-physical properties for real applications. The traditional methods to study effective thermal conductivities of composite materials, such as the effective medium theory, the direct solution of heat diffusion equation, or the Boltzmann transport equation, are all based on developing good physical understanding of heat transfer mechanisms in those composite materials. In this work, we take a completely different approach to predict the effective thermal conductivities of composite materials using machine learning methods. With a set of trustable data, the support vector regression (SVR), Gaussian process regression (GPR) and convolution neural network (CNN) are employed to train models that can predict the effective thermal conductivities of composite materials. We find that the models obtained from SVR, GPR, and CNN all have a better performance than the Maxwell-Eucken model and the Bruggeman model in terms of predicting accuracy. Our work demonstrates that machine learning methods are useful tools to fast predict the effective thermal conductivities of composite materials and porous media if the training data set is available. The machine learning approach also has the potential to be generalized and applied to study other physical properties of composite materials.
To investigate and compare the chemical and optical stability of four restorative composite materials: two injectable resins, one flowable resin and one compomer.
Two injectable nano-filled composite ...resins: G-aenial Universal (GU) and Beautifil Injectable XSL (BI), a flowable composite resin: Filtek Supreme Flowable (FS) and a compomer: Dyract Flow (DF), in A2 shade were tested and compared. Water sorption and solubility were conducted according to ISO4049:2019 standard; ICP-OES and F-ion selective electrode were used to test the elemental release; Degree of conversion (DC) was obtained by using FTIR; water contact angle was obtained by static sessile drop method, and a spectrophotometer was used for optical properties (ΔE⁎, ΔL⁎ and TP). SPSS 28.0 was used for statistical analysis and the significant level was pre-set as α = 0.05.
GU performed the best in water sorption and solubility, FS had the lowest elemental release, the best colour stability, and the highest DCIM and DC24-h. DF, the compomer had the lowest, and GU and BI, the injectable composites had the largest water contact angle, respectively. Correlations were found between water sorption and water solubility.
The four composite restorative materials showed different chemical and optical behaviours. Overall, composite resins performed better than compomer, while additional laboratory and in vivo tests are necessary to obtain a more comprehensive comparison between injectable and flowable composite resins. Wsp and Wsl are influenced by many common factors, and the values are highly positively related.
A comprehensive understanding of materials is crucial before selecting materials for clinical practice. Composite resins rather than compomers are recommended because of their exceptional properties, which make them eligible for a wide range of clinical applications and an elongated lifespan.
In the realm of photocatalysis, the creation of clean and pollution-free composite material catalysts is critical. Electrostatic self-assembly techniques were used in this study to construct ZnIn2S4 ...nanosheets onto the surface of Cu-MOF, culminating in the development of a unique Cu-MOF/ZnIn2S4 composite catalyst. Cu-MOF was shown to have a strong interface impact with ZnIn2S4, which resulted in a large increase in the number of active sites and, consequently, the efficiency of hydrogen generation. This was demonstrated by a number of parameters. The Cu-MOF/ZnIn2S4-10 composite material's optimum hydrogen evolution rate was 0.3 mmol h−1g−1, which was 2.14 times larger than that of pure ZnIn2S4 nanosheets (0.14 mmol h−1g−1). Furthermore, the development of Cu-MOF/ZnIn2S4 heterojunctions considerably improved ZnIn2S4's deficiencies in photocatalytic hydrogen production, increasing charge separation rates and providing a viable approach to improve ZnIn2S4's hydrogen production efficiency.
This study describes the synthesis of Chitosan - corn protein (CSZ-TG) composites using TG enzyme (TG) as a cross-linking agent and the preparation of chitosan-based composite membrane material ...(CSZEO-TG) by blending citrus essential oil (EO) with the synthesized CSZ-TG. The prepared composite membrane material was used for fresh strawberry preservation and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-spectral diffraction, tensile properties, and water vapor and CO2 permeability. Scanning electron microscopy results showed a smooth surface of the composite membrane material after the addition of TG enzyme, while Fourier transforms infrared spectroscopy results showed a structural change of the composite membrane material after the addition of corn protein (Z). The tensile results showed an increase in the tensile strength of the composite membrane material after the addition of TG enzyme, while the flexibility of the composite membrane material was enhanced after the addition of EO. Compared with the pure chitosan membrane (CS), the water vapor and CO2 barrier properties of the composite membrane material after the addition of Z, TG, and EO did not change much, and they all showed better water vapor barrier properties. The results of the antioxidant analysis of the solution of the CSZEO-TG composite membrane material showed that the composite membrane material had efficient antioxidant properties. The effects of the composite film material on the storage period and quality of strawberries were evaluated by the indicators of weight loss, hardness, decay rate, soluble solids, titratable acid content, MDA content, and the content of four enzymes, SOD, POD, PPO and CAT. Comprehensive freshness data analysis showed that CSZEO-TG had the best freshness preservation performance and effectively extended the shelf life of strawberries.
