Синтез слоев графена из рисовой шелухи и их характеристики

In this work, a method of obtaining graphene layers from natural source specifically from rice husk was developed. A rice husk (RH) was used as a raw material, and potassium hydroxide was used as activation agent. The graphene layers were obtained after four successive stages: pre-carbonization, desilication in 1M NaOH solution, chemical activation and exfoliation of the carbonized rice husk (CRH). The obtained samples were studied using Raman spectroscopy, TEM and SEM; the Raman peaks evidenced the presence of graphene multilayers in the sample. A detailed observation of Raman spectroscopy showed that the obtained samples with ratio of 1/4 and 1/5 (RH/KOH) consisted of graphene layers with a high content of amorphous component. The yield of the product was ~ 3% by weight. This study can provide a new way to the large-scale synthesis of low-cost single and multi-layered graphene using rice husk or other renewable resources

RECENT ADVANCES AND CHALLENGES OF CURRENT COLLECTORS FOR SUPERCAPACITORS

Global energy and environmental issues are driving the development of modern advances in efficient and environmentally friendly energy storage systems. Such systems must meet a range of requirements, which include high energy and power density, long service life, flexibility, industrial scalability, security and reliability. Progressive achievements in the field of energy storage are associated with the development of various kinds of batteries and supercapacitors. Supercapacitors are state-of-the-art energy storage devices with high power density, long lifespan, and the ability to bridge the power/energy gap between conventional capacitors and batteries/fuel cells. However, supercapacitors have limitations associated with low energy density, which can be solved by using various types of current collectors, since current collectors are one of the main massive components of supercapacitors. This review gives a complete understanding of the effect of current collectors on the actual performance and properties of supercapacitors. We reviewed current collectors based on carbon and metal-containing materials, and supercapacitor configurations to identify possible improvements in electrochemical performance in terms of specific capacitance, energy density, power density, service life and variability in their application

EFFECTIVENESS OF BIO-WASTE-DERIVED CARBON DOPING ON DE-ICING PERFORMANCE OF AN ELECTRICALLY RESISTANT CONCRETE

This paper proposes a modified carbon-based concrete filler composition, which can potentially be used as a self-de-icing pavement. Carbon fibers (CNFs), graphene-like porous carbon (GLC), and a CNF/GLC composite were developed to reinforce concrete with the aim to improve its electrical conductivity and mechanical properties. The effect of the CNF and GLC loadings on the electrical conductivity of the filled concrete was evaluated in a climatic chamber at temperatures simulating water-freezing conditions on a concrete road. The results show that even a negligible loading (0.2 wt.%) of concrete with CNF/GLC results in a dramatic decrease in its resistance when compared to the same loadings for CNF and GLC added separately. Depending on the number of fillers, the temperature of the modified concrete samples reached up to +19.8 °C at low voltage (10 V) at −10 °C, demonstrating the perspective of their heat output for anti-icing applications. Additionally, this study shows that adding 2.0 wt.% of the CNF/GLC composite to the concrete improves its compressive strength by 33.93% compared to the unmodified concrete

Amorphous silicon dioxide as an anode material for li-ion batteries

In recent decades, progress in Li-ion batteries (LIBs) has grown dramatically. In 2016, about 6.4 billion cells were sold of LIBs and this is equivalent to 90 GWh [1]. even the Nobel Prize in Chemistry in 2019 was awarded to John Goodenough (USA), Stanley Whittingham (Great Britain) and Akira Yoshino (Japan) for the development of lithium-ion batteries. But work on improving the Li-ion batteries is still ongoing. SiO2 is one of the most widely used materials on earth. SiO2 is one of the most widely used materials on earth and is uses in the fields of medicine, cosmetics, agroindustry, electronics [2,3], and has also begun research on the use of SiO2 as an anode material in lithium-ion batteries [4]. It has a high theoretical capacity (1965 mAh•g-1) [5]. SiO2 obtained by us is amorphous and the source is rice husk (RH) from Kazakhstan (Kyzylorda region). Material synthesis is divided into two stages. Stage 1 includes washing pre-treatment by HCl and calcination at 600°C (SiO2-1). Stage 2 includes purification by dissolving in NaOH and extraction pure (SiO2-2) by adding HCl and washing by distilled water. The use of 1 stage material as an anode material in lithium-ion batteries has shown good stability. Microstructure of SiO2-1 and SiO2-2 differs from each other. SiO2-2 at the beginning showed good stability, but from the 10th cycle, it began to lose capacity

Modification of Biomass-Derived Nanoporous Carbon with Nickel Oxide Nanoparticles for Supercapacitor Application

Supercapacitors are one of the promising devices for the accumulation and storage of electrical energy. The purpose of this study is to develop a synthesis and modification method of carbon material to improve the electrochemical characteristics of a supercapacitor. In the proposed study, by varying the sequence and parameters of the processes of carbonization, mechanoactivation and thermochemical activation, the conditions for obtaining nanoporous carbon with a specific surface area of 2200 (±50) m2/g from walnut shells (WSs) are optimized. In addition, to increase the electrochemical efficiency of the electrode material, the resulting nanoporous carbon was modified with nickel oxide (NiO) nanoparticles by the thermochemical method. It is shown that the modification with nickel oxide nanoparticles makes it possible to increase the specific capacitance of the supercapacitor electrode by 16% compared to the original unmodified nanoporous carbon material

Investigations of Activated Carbon from Different Natural Sources for Preparation of Binder-Free Few-Walled CNTs/Activated Carbon Electrodes

In this study, we present another approach to fabricating high-performance supercapacitor electrodes by combining activated carbon particles with carbon nanotubes (AC/CNT). We synthesized activated carbon from diverse biomass sources using a carbonization process and chemical activation with KOH. By incorporating carbon nanotubes, we significantly augmented the electrode’s surface area, resulting in exceptional ion transport and a substantial increase in specific capacitance. Our investigation reveals that the optimized composition, 85:10:5 of AC, CNT, and conductive additive, achieved outstanding specific capacitance values, notably 125.6 F g−1 at 1 mV s−1 and 118 F g−1 at 1 A g−1, along with a maximum energy density of 4 Wh kg−1. Electrochemical impedance spectroscopy (EIS) further demonstrated the superior charge transfer capabilities of these electrodes, notably at a frequency range from 100 kHz to 10 mHz. Additionally, our research highlights the influence of different biomass precursors, such as apricot kernels, walnut shells, and rice husks, on the electrochemical behavior of these electrodes. Overall, this study provides valuable insights into the development of high-performance supercapacitors, emphasizing the potential of diverse biomass sources in optimizing electrode materials

Modified Activated Graphene-Based Carbon Electrodes from Rice Husk for Supercapacitor Applications

The renewable biomass material obtained from rice husk, a low-cost agricultural waste, was used as a precursor to synthesize a highly porous graphene-based carbon as electrode material for supercapacitors. Activated graphene-based carbon (AGC) was obtained by a two-step chemical procedure and exhibited a very high specific surface area (SSA) of 3292 m2 g−1. The surface morphology of the synthesized materials was studied using scanning and transmission electron microscopy (SEM, TEM). Furthermore, the AGC was modified with nickel hydroxide Ni(OH)2 through a simple chemical precipitation method. It was found that the most significant increase in capacitance could be reached with Ni(OH)2 loadings of around 9 wt.%. The measured specific capacitance of the pure AGC supercapacitor electrodes was 236 F g−1, whereas electrodes from the material modified with 9 wt.% Ni(OH)2 showed a specific capacitance of up to 300 F g−1 at a current density of 50 mA g−1. The increase in specific capacitance achieved due to chemical modification was, therefore 27%

EFFECT OF GRAPHENE OXIDE/HYDROXYAPATITE NANOCOMPOSITE ON OSTEOGENIC DIFFERENTIATION AND ANTIMICROBIAL ACTIVITY

This paper presents the fabrication and characterization of electrospun graphene oxide/calcium hydroxyapatite/polycaprolactone composite. Polycaprolactone is well-known for its excellent medical property and chemo-resistance. On the other hand graphene oxide (GO) and calcium hydroxyapatite (HAp) are both known for their superior biocompatibility, high mechanical properties, considerable electrical and thermal conductivity. Under current research GO and HAp were synthesized from an abundant bio-wastes material. As-prepared GO/HAp composite was dispersed in biodegradable polymer – polycaprolactone (PCL) in order to device a composite scaffold with the purpose to enhance osteogenic differentiation of osteoblasts for potential medical application. Synthesised composite was characterised using various chemo-physical methods. Biocompatibility was tested in the cell proliferation assay with preosteoblasts MC3T3-E1 cell line in order to identify any cytotoxic effect caused by its compounds. The bacteriostatic effect of GO was assessed using Staphylococcus aureus and Escherichia coli bacterial strains. Obtained GO/HAp/PCL composite scaffold can serve as a biologically compatible matrix for potential bone tissue regeneration with antimicrobial effect; provides an excellent biological compatibility for prospective application in medicine and clinical dentistry