Microwave hydrothermal synthesis of nano Co3O4 with various morphologies

The precursors with various morphologies including nanowires, nanosheets, and hexagonal nanoplatelets were synthesized under different conditions by the microwave hydrothermal method. The precursors are transformed into Co(3)O(4) with various nanostructures through thermal decomposition. It is very important to synthesize the precursors controlling the microwave hydrothermal conditions, such as the mineralizer, the reaction temperature, and the reaction time. The microwave assisted hydrothermal approach presented here opens a potential avenue to explore the synthesis of various other metal oxides with different nanomorphologies

Microwave synthesis of homogeneous YAG nanopowder leading to a transparent ceramic

A homogeneous and extremely fine yttrium aluminum garnet (YAG) precursor powder was synthesized from solutions with a low [urea]/[metal ions] ratio under microwave irradiation, and pure phase YAG was directly crystallized from it at 1173 K. In the presence of sulfate ions, a fibrillar precursor that takes on a dendritic skeleton was generated, and easily dispersible YAG nanopowder with a particle size of 20–30 nm was obtained at 1373 K. A transparent YAG ceramic with fine grains was sintered from this YAG nanopowder at 1973 K for 10 min in a graphite furnace. At the wavelength of 1060 nm, the in-line light transmittance of the YAG ceramic is up to 67%. The mechanism behind the influence of the microwave irradiation and sulfate ions on the characteristics of YAG is thoroughly discussed

Ultrathin porous NiO nanoflake arrays on nickel foam as binder-free electrodes for supercapacitors

NiO nanopowders and NiO/nickel foam (NF) hybrid were synthesized by microwave hydrothermal method and the following heating process. NiO nanopowders show the morphology of microspheres (diameter is about 3μm), which are composed of porous nanoflakes. NiO/NF hybrid shows a porous nanoflakes array structure, the thickness of nanoflakes is 10nm. Electrochemical measurements indicate that the maximum specific capacitance of NiO nanopowders is about 85.4 F/g at a scan rate of 5 mV/s, while this value is up to 234.8 F/g for NiO/NF hybrid. Electrochemical impedance spectrum (EIS) data show that the Rs and Rct values of NiO/NF hybrid (1.9Ù and 0.25Ù) are smaller than that of the NiO nanopowders which are coated on nickel foam (3.6Ù and 0.3Ù). In conclusion, the ultrathin porous NiO/NF is directly used as a binderfree supercapacitor electrode, which exhibited significantly improved supercapacitor performance compared to NiO nanopowders

Layered δ-MnO2 as positive electrode for lithium intercalation

Layer structured δ-MnO2 was synthesized by a microwave-assisted hydrothermal method. The morphology of the product consists of flower-like spheres that range from about 200 nm to 3 μm in diameter and are composed of sheets about 5–10 nm in thickness. When tested in the voltage range of 2 to 4.5 V vs. Li+/Li in coin cells, the separator is blocked, handicapping Li+ conductivity and leading to cell failure. When tested in the voltage range of 2 to 4 V in ethylene carbonate/dimethyl carbonate (EC/DMC), the δ-MnO2 delivers an initial reversible capacity of 143.7 mAh g−1 and can maintain 120 mAh g−1 at the 60th cycle. The δ-MnO2 electrode shows good cycling stability at different current densities and delivers a discharge capacity of about 90 mAh g−1 at 1 C, indicating that it is a promising cathode material for lithium ion batteries

Synergistic combination of a Co-doped σ-MnO2 cathode with an electrolyte additive for a high-performance aqueous zinc-ion battery

The key challenges in aqueous zinc-manganese dioxide batteries (MnO2//Zn) are their poor electrochemical kinetics and stability, which are mainly due to low conductivity and the inevitable dissolution of MnO2. A synergistic combination of a Co-doped σ-MnO2 electrode (Co-MnO2) and a Co(CH3COO)2•4H2O (CoAc) electrolyte additive is here developed to design a high-performance aqueous MnO2//Zn battery (denoted as a Co-MnO2//Zn battery with CoAc). The introduction of Co ions (Co3+/Co2+) into the σ-MnO2 electrode is achieved via a facile one-step electrodeposition method. Benefitting from the synergistic coupling effect of the Co-MnO2 electrode and the CoAc electrolyte additive, the fabricated Co-MnO2//Zn battery with CoAc shows a commendable discharge capacity of 313.8 mAh g−1 at 0.5 A g−1, excellent rate performance, excellent durability over 1000 cycles (∼ 92% capacity retention at 1.0 A g−1) and admirable energy density (439.3 Wh kg−1), which is a significant improvement compared with an un-doped σ-MnO2//Zn battery

WGCNA Analysis Identifies the Hub Genes Related to Heat Stress in Seedling of Rice (Oryza sativa L.)

Frequent high temperature weather affects the growth and development of rice, resulting in the decline of seed–setting rate, deterioration of rice quality and reduction of yield. Although some high temperature tolerance genes have been cloned, there is still little success in solving the effects of high temperature stress in rice (Oryza sativa L.). Based on the transcriptional data of seven time points, the weighted correlation network analysis (WGCNA) method was used to construct a co–expression network of differentially expressed genes (DEGs) between the rice genotypes IR64 (tolerant to heat stress) and Koshihikari (susceptible to heat stress). There were four modules in both genotypes that were highly correlated with the time points after heat stress in the seedling. We further identified candidate hub genes through clustering and analysis of protein interaction network with known–core genes. The results showed that the ribosome and protein processing in the endoplasmic reticulum were the common pathways in response to heat stress between the two genotypes. The changes of starch and sucrose metabolism and the biosynthesis of secondary metabolites pathways are possible reasons for the sensitivity to heat stress for Koshihikari. Our findings provide an important reference for the understanding of high temperature response mechanisms and the cultivation of high temperature resistant materials

Microwave homogeneous synthesis of porous nanowire Co3O4 arrays with high capacity and rate capability for lithium ion batteries

In this paper, an efficient microwave-assisted homogeneous synthesis approach by urea hydrolysis is used to synthesize cobalt-basic-carbonate compounds. The dimensions and morphology of the synthesized precursor compounds are tailored by changes in the incorporated anions (CO32− and OH−) under different conditions of temperature and time under microwave irradiation. The wire-like cobalt-basic-carbonate compound self-assembles into one-dimensional porous arrays of Co3O4 nanowires constructed of interconnected Co3O4 nanocrystals along the [1 1 0] axis after thermal decomposition at 350 °C. The textural characteristics of the Co3O4 products have strong positive effects on their electrochemical properties as electrode materials in lithium-ion batteries. The obtained porous nanowire Co3O4 arrays exhibit excellent capacity retention and rate capability at higher current rates, and their reversible capacity of 600 mAh g−1 can be maintained after 100 cycles at the high current rate of 400 mA g−1

Porous Co3O4 nanoplatelets by self-supported formation as electrode Material for lithium-ion batteries

In this paper, we have reported a simple and rapid approach for the large-scale synthesis of β-Co(OH)2nanoplatelets via the microwave hydrothermal process using potassium hydroxide as mineralizer at 140 °C for 3 h. Calcining the β-Co(OH)2 nanoplatelets at 350 °C for 2 h, porous Co3O4 nanoplatelets with a 3D quasi-single-crystal framework were obtained. The process of converting the β-Co(OH)2 nanoplatelets into the Co3O4 nanoplatelets is a self-supported topotactic transformation, which is easily controlled by varying the calcining temperature. The textural characteristics of Co3O4 products have strong positive effects on their electrochemical properties as electrode materials in lithium-ion batteries. The obtained porous Co3O4nanoplatelets exhibit a low initial irreversible loss (18.1%), ultrahigh capacity, and excellent cyclability. For example, a reversible capacity of 900 mAh g−1 can be maintained after 100 cycles