Showing papers on "Thermogravimetry published in 2013"

Highly active and durable nanostructured molybdenum carbide electrocatalysts for hydrogen production

Abstract: In an attempt to tailor low-cost, precious-metal-free electrocatalysts for water electrolysis in acid, molybdenum carbide (β-Mo2C) nanoparticles are prepared by in situ carburization of ammonium molybdate on carbon nanotubes and XC-72R carbon black without using any gaseous carbon source. The formation of Mo2C is investigated by thermogravimetry and in situ X-ray diffraction. X-ray absorption analysis reveals that Mo2C nanoparticles are inlaid or anchored into the carbon supports, and the electronic modification makes the surface exhibit a relatively moderate Mo–H bond strength. It is found that carbon nanotube-supported Mo2C showed superior electrocatalytic activity and stability in the hydrogen evolution reaction (HER) compared to the bulk Mo2C. An overpotential of 63 mV for driving 1 mA cm−2 of current density was measured for the nanotube-supported Mo2C catalysts; this exceeds the activity of analogous Mo2C catalysts. The enhanced electrochemical activity is facilitated by unique effects of the anchored structure coupled with the electronic modification.

Synthesis and Thermophysical Properties of Biocompatible Cholinium-Based Amino Acid Ionic Liquids

Abstract: Nowadays the knowledge of thermodynamic properties for amino acid ionic liquids (AAILs) has been paramount for the design of many chemical processes. In this present work, a series of cholinium-based AAILs ([Ch][AA]) were synthesized by neutralization of choline hydroxide solution with five amino acids and then were characterized by 1H NMR, Fourier transform infrared (FT-IR), elemental analysis, thermogravimetry, and differential scanning calorimetry (DSC) analysis. Physico-chemical properties such as density, viscosity, refractive index, and conductivity were measured and correlated with the empirical equations in a wide temperature range. The thermal expansion coefficient values were also calculated from the acquired experimental density values. From the experimental data, it was found that the density, viscosity, and refractive index decreased while conductivity increased with the increase of temperature. The correlation results were proposed to be in good agreement with the experimental data, and opti...

Nuclear Magnetic Resonance Studies of Interfacial Phenomena

Abstract: Unmodified and Modified Silicas Interfacial Phenomena at a Surface of Nanosilica Silica gels, Aerogels, Silochrome, and Poly(methylsiloxane): Structural, Interfacial and Adsorption Characteristics, and Structure-Property Relationships Interfacial Phenomena at Surfaces of Structurally Ordered Silicas Thin Films and Other Moieties on Silica Supports Interfacial Phenomena at Surfaces of Mixed Oxides Mixed Nanooxides Porous Oxides as a Function of Morphology Structurally Ordered Oxides Nanocrystalline and Microcrystalline Materials Clays, Zeolites, and Other Natural Minerals Interfacial Phenomena at Surfaces of Carbon Materials Texture of Carbonaceous Materials and Chemical Shift of Adsorbed Molecules Activated Carbons Graphitized Carbons and Graphite Carbon Nanotubes Interfacial Phenomena at Carbon-Mineral Composites Carbon Blacks Carbonized Silicas and Mixed Oxides Interfacial Phenomena at Polymer Surfaces Natural Polymers: Cellulose, Starch, Chitosan, Hyaluronic Acid, and Others Synthetic Polymers Hydrogels and Cryogels Polymer-Nanooxide Systems Polymers in Confined Space of Pores Interactions of Biomacromolecules with Water, Organic Compounds, and Oxides, Polymers, and Carbon Adsorbents Proteins Proteins in Adsorbed State DNA Lipids Water Associated with Bio-Objects: Cells and Tissues Yeast Saccharomyces cerevisiae Cells Intracellular Water in Partially Dehydrated Bone Marrow Cells Freeze-Dried Bovine Gametes with Organic Additives Red Blood Cells Bone Tissue Muscular Tissues Intracellular Water and Cryopreservation Interaction of Seeds, Herbs, and Related Materials with Water and Nanooxides Recurring Trends in Adsorption, Spectroscopy, and Other Interfacial Experiments Methods Low-Temperature 1H NMR Spectroscopy Low-Temperature Nitrogen Adsorption Adsorption of Water and Organics Polymer and Protein Adsorption Infrared Spectroscopy Thermogravimetry Differential Scanning Calorimetry Auger Electron Spectroscopy Temperature-Programmed Desorption with Mass-Spectrometry Control Thermally Stimulated Depolarization Current Dielectric Relaxation Spectroscopy Ultraviolet-Visible Spectroscopy Rheometry Potentiometric Titration Photon Correlation Spectroscopy Adsorption of Metal Ions X-Ray Diffraction Raman Spectroscopy AFM, SEM, and TEM Quantum Chemistry Conclusions

Synthesis, characterization, and investigation of optical and magnetic properties of cobalt oxide (Co3O4) nanoparticles

Abstract: Spinel-type cobalt oxide (Co3O4) nanoparticles have been easily prepared through a simple thermal decomposition route at low temperature (175°C) using carbonatotetra(ammine)cobalt(III) nitrate complex, [Co(NH3)4CO3]NO3·H2O, as a new precursor. The structure and morphology of as-prepared Co3O4 nanoparticles were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), UV–vis spectroscopy, Brunauer-Emmett-Teller specific surface area measurement and magnetic measurements, and thermogravimetry/differential thermal analysis. The FT-IR, XRD, and EDS results indicated that the product was highly pure well-crystallized cubic phase of Co3O4. The TEM images showed that the product powder consisted of dispersive quasi-spherical particles with a narrow size distribution ranged from 6 to 16 nm and an average size around 11 nm. The magnetic measurements confirmed that the Co3O4 nanoparticles show a little ferromagnetic behavior which could be attributed to the uncompensated surface spins and/or finite size effects. The ferromagnetic order of the Co3O4 nanoparticles is raised with increasing the decomposition temperature. Using the present method, Co3O4 nanoparticles can be produced without the need of expensive organic solvents and complicated equipments.

Synthesis, Characterization, and Thermochemical Redox Performance of Hf4+, Zr4+, and Sc3+ Doped Ceria for Splitting CO2

Abstract: We present results on the thermochemical redox performance and analytical characterization of Hf4+, Zr4+, and Sc3+ doped ceria solutions synthesized via a sol–gel technique, all of which have recently been shown to be promising for splitting CO2. Dopant concentrations ranging from 5 to 15 mol % have been investigated and thermally cycled at reduction temperatures of 1773 K and oxidation temperatures ranging from 873 to 1073 K by thermogravimetry. The degree of reduction of Hf and Zr doped materials is substantially higher than those of pure ceria and Sc doped ceria and increases with dopant concentration. Overall, 10 mol % Hf doped ceria results in the largest CO yields per mole of oxide (∼0.5 mass % versus 0.35 mass % for pure ceria) based on measured mass changes during oxidation. However, these yields were largely influenced by their rate of reoxidation, not necessarily thermodynamic limitations, as equilibrium was not achieved for either Hf or Zr doped samples after 45 min exposure to CO2 at all oxida...

Eco-friendly synthesis, characterization and properties of a sodium carboxymethyl cellulose/graphene oxide nanocomposite film

Abstract: A previously unreported nanocomposite (CMC/GO) high-performance film was prepared by a simple solution mixing-evaporation method. The structure, thermal stability, and mechanical properties of the composite films were investigated by wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, thermogravimetry analysis, and mechanical testing. The results obtained from these different studies revealed that CMC and graphene oxide were able to form a homogeneous mixture. Compared with pure CMC, the tensile strength and Young’s modulus of the graphene-based materials were improved significantly upon incorporation of 1 wt% graphene oxide by 67 ± 6 % and 148 ± 5 %, respectively. In addition, the DMA composite films also showed a high storage modulus up to 250 °C.

Adsorption of Cationic Dyes on a Cellulose-Based Multicarboxyl Adsorbent

Abstract: A novel adsorbent based on cellulose (CGD) was prepared via modifying with glycidyl methacrylate (GMA) and diethylenetriamine pentaacetic acid (DTPA), characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential thermogravimetry (DTA/TGA). Malachite green (MG) and basic fuchsine (BF) were used to resemble cationic dyes in wastewaters. The influences of several parameters (contact time, pH, temperature, initial concentration) were evaluated to determine the best adsorption conditions. Langmuir adsorption isotherm items explained MG adsorption well, while BF was fitted well with the Freundlich model. The maximum adsorption capacities were greater than some other reports, 1155.76 mg·g–1 for a BF internal concentration of 2000 mg·L–1 and 458.72 mg·g–1 for MG in theory. Kinetics and thermodynamics were adopted to explain in-depth information associated with the adsorption process. The adsorption processes of dyes were both feasib...

Microemulsion-assisted synthesis of hierarchical porous Ni(OH)(2)/SiO2 composites toward efficient removal of formaldehyde in air

Abstract: Ni(OH)2/SiO2 composites with hierarchical flake-like nanostructures were synthesized using water-in-oil microemulsion and characterized by X-ray diffraction, thermogravimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption, and X-ray photoelectron spectroscopy. The as-prepared hierarchical porous Ni(OH)2/SiO2 composites show an excellent performance for formaldehyde (HCHO) removal in air at an ambient temperature. It was found that the aging time had a significant impact on the pore structure, surface area and HCHO adsorption. The Ni(OH)2/SiO2 composite aged for 4 h in the presence of tetraethyl orthosilicate (TEOS) exhibited a relatively high HCHO adsorption capacity as well as good recyclability compared with Ni(OH)2, attributed to a relatively large BET surface area, an optimal pore size, a suitable proportion between Ni(OH)2 and SiO2, and a synergistic effect between Ni(OH)2 and SiO2. The results from this work not only demonstrate that hierarchical porous Ni(OH)2/SiO2 composites can act as an efficient adsorbent toward HCHO in air, but suggest a new route for the rational design of cost-effective, high-performance and environmentally benign adsorbents for indoor air cleanup.

Preparation and electrochemical performance of the layered cobalt oxide (Co 3 O 4 ) as supercapacitor electrode material

Abstract: Layered Co3O4 composed of oriented self-assembled micrometer-length rectangular 2D flakes has been successfully synthesized by a hydrothermal method in combination with subsequent calcination process. Structural and morphological characterizations were performed using powder X-ray diffraction and field emission scanning electron microscopy. The component and thermal stability of the sample were measured by FT-IR and thermal analyses, including thermogravimetry and differential thermal analysis. The electrochemical performances of the as-prepared Co3O4 product were investigated by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and constant current charge/discharge techniques. The electrochemical results demonstrate that the layered Co3O4 product displays good capacitive behavior with a specific capacitance of 263 F g−1 within a potential range of −0.4–0.55 V at a current density of 1 A g−1 and a large capacity retention with 89.4 % of the initial capacitance over 1,000 consecutive cycles at 3 A g−1, indicating that the as-prepared Co3O4 product can be a promising electroactive material for supercapacitor.

Fe3O4–graphene hybrids: nanoscale characterization and their enhanced electromagnetic wave absorption in gigahertz range

Abstract: Fe3O4–graphene hybrid materials have been fabricated by a simple polyol method, and their morphology, chemistry and crystal structure have been characterized at the nanoscale. It is found that each Fe3O4 nanoparticles decorated on the graphene has a polycrystalline fcc spinel structure and a uniform chemical phase. Raman spectroscopy, Fourier transform infrared spectroscopy, thermogravimetry/differential thermal analysis, X-ray diffraction, and transmission electron microscopy suggest that Fe3O4 nanoparticles are chemically bonded to the graphene sheets. Electromagnetic wave absorption shows that the material has a reflection loss exceeding −10 dB in 7.5–18 GHz for an absorber thickness of 1.48–3 mm, accompanying a maximum reflection loss value of −30.1 dB at a 1.48-mm matching thickness and 17.2-GHz matching frequency. Theoretic analysis shows that the electromagnetic wave absorption behavior obeys quarter-wave principles. The results suggest that the magnetic Fe3O4–graphene hybrids are good candidates for the use as a light-weight electromagnetic wave-absorbing material in X- and Ku-bands.

Microemulsion-assisted preparation of a mesoporous ferrihydrite/SiO2 composite for the efficient removal of formaldehyde from air.

Abstract: Mesoporous ferrihydrite/SiO2 composites were synthesized according to a water-in-oil microemulsion method and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry, nitrogen-adsorption/desorption, and by X-ray photoelectron spectroscopy. The as-prepared porous ferrihydrite/SiO2 composites showed an excellent adsorption performance for formaldehyde (HCHO) removal from indoor air at ambient temperature. It was found that the aging time during the synthesis had a significant impact on the pore structure, surface area, and HCHO adsorption of these materials. The ferrihydrite/SiO2 composite that was aged for 3 h in the presence of tetraethyl orthosilicate (TEOS) exhibited a relatively high HCHO adsorption capacity, as well as good recyclability, which was attributed to a relatively large BET surface area, optimal pore size, a suitable Si/Fe atomic ratio, and a synergistic effect between ferrihydrite and SiO2. This work not only demonstrates that porous ferrihydrite/SiO2 composites can act as an efficient adsorbent toward HCHO, but suggests a new route for the rational design of cost-effective and environmentally benign adsorbents with high performance for indoor air purification.

A simple SDS-assisted self-assembly method for the synthesis of hollow carbon nanospheres to encapsulate sulfur for advanced lithium–sulfur batteries

Abstract: The hollow carbon nanospheres (HCNSs) were prepared using a simple SDS-assisted self-assembly method, and a sulfur–carbon composite based on HCNSs was synthesized for lithium–sulfur batteries by a vapor phase infusion method. The sulfur–HCNS composite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetry (TG) measurements. It is found that the elemental sulfur was dispersed inside the pores of carbon spheres. It is demonstrated from the galvanostatic discharge–charge process and cyclic voltammetry (CV) that the sulfur–HCNS composite has a large reversible capacity and an excellent cycling performance as cathode materials. The sulfur–HCNS composite with a sulfur content of 47.6 wt% displays an initial discharge capacity of 1031 mA h g−1 and a reversible discharge capacity of 477 mA h g−1 after 100 cycles at 0.5 C charge–discharge rate.