scholarly journals Formation and Thermal Behaviors of Ternary Silicon Oxycarbides derived from Silsesquioxane Derivatives

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1721
Author(s):  
Yoshiaki Iwase ◽  
Teruaki Fuchigami ◽  
Yoji Horie ◽  
Yusuke Daiko ◽  
Sawao Honda ◽  
...  
Keyword(s):  
Mechanical Stability ◽  
Sol Gel ◽  
Silicon Oxycarbide ◽  
High Yield ◽  
Amorphous Sio2 ◽  
Gaseous Hydrocarbon ◽  
Spectroscopic Analyses ◽  
Sio2 Nanocomposites ◽  
Derivatives Of

Silsesquioxane (SQ) derivatives possessing intramolecular H2C = CH- groups and Si-H groups were designed as precursors for ternary silicon oxycarbide (SiOC). By using R-Si(OMe)3, H-Si(OEt)3 and (H-Si(Me)2)2O as starting compounds, SQ derivatives of VH-SQ (R = vinyl) and St-H-SQ (R = stylyl) were successfully synthesized through the conventional sol-gel route. Simultaneous thermogravimetric and mass spectroscopic analyses up to 1000 °C revealed that in situ cross-linking via hydrosilylation and demethanation of VH-SQ suppressed the evolution of gaseous hydrocarbon species to afford amorphous SiOC having a composition close to the desired stoichiometric SiO2(1−x)Cx (x = ca. 0.3) with a high yield. The effect of carbon content on the phase separation and crystallization of the SQ-derived amorphous SiOC was studied by several spectroscopic analyses and TEM observation. The results were discussed aiming to develop a novel polymer-derived ceramics (PDCs) route for in situ formation of binary β-SiC-amorphous SiO2 nanocomposites with enhanced thermal and mechanical stability.

scholarly journals APPLICATION OF SELF–CLEANING TREATMENT ON COTTON AND PES/CO FABRIC USING TiO2 AND SiO2 COATING SYNTHESIZED BY SOL–GEL METHOD

2018 ◽  
Vol 55 (1B) ◽  
pp. 77
Author(s):  
Bui Mai Huong
Keyword(s):  
Red Wine ◽  
Sol Gel ◽  
Amorphous Sio2 ◽  
Sol Gel Process ◽  
Ft Ir ◽  
Sio2 Nanocomposites ◽  
Self Cleaning ◽  
Coated Cotton ◽  
Cleaning Treatment ◽  
Scanning Electron

The photocatalytic activity of TiO2–SiO2 coated and TiO2 coated on 100% cotton and PES/Co fabrics was investigated through the self–cleaning of red wine stains and coffee stains. It was shown that a TiO2 species could be produced at temperatures of 25 °C, 40 °C and 60 °C with acceptable photo–activity and TiO2–SiO2 nanocomposites were prepared by a sol–gel process at a low temperature. The discoloration of red wine and coffee led to CO2 evolution that was more efficient for TiO2–SiO2 coated cotton for samples than of TiO2 coated ones. The textile surface did not show any change after several consecutive light–induced discoloration cycles of a red wine stain and coffee stain. The structural properties of these nanocomposites were characterized with scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT–IR). The scanning electron microscope (SEM) photo showed that the TiO2–SiO2 layer is thicker than TiO2 layer on the cotton fabric and PES/Co fabric and the Ti–particles were always surrounded by amorphous SiO2 and never alone by themselves. The TiO2–SiO2 nanocomposites were coated onto cotton and PES/Co fabrics by a simple dip–pad–dry–cure process.

Dry Sol–Gel Polycondensation of Hydrosilanes to Organosilicas Catalyzed by Colloidal Nickel Nanoparticles

2007 ◽  
Vol 7 (11) ◽  
pp. 3964-3968 ◽  
Author(s):  
Bo-Hye Kim ◽  
Myong-Shik Cho ◽  
So-Yeun Kim ◽  
You-Jeong Kim ◽  
Hee-Gweon Woo ◽  
...  
Keyword(s):  
Nickel Nanoparticles ◽  
Sol Gel ◽  
Ambient Air ◽  
Amorphous Structure ◽  
High Yield ◽  
Catalytic Activities ◽  
Molecular Weights ◽  
Air Atmosphere ◽  
Plausible Mechanism

The dry sol–gel polycondensation at toluene in ambient air atmosphere of p-X-C6H4SiH3 (X = H, CH3, CH3O, F, Cl) to silica p-X-C6H4SiO1.5 in high yield, catalyzed by colloidal nickel nanoparticles in-situ generated from nickelocene(II), nickel(II) acetate, and bis(1,5-cyclooctadiene)nickel(0), is described. Similar catalytic activities were observed for the catalysts. Similarly, the dry sol–gel polyco-condensation p-X-C6H4SiH3 (X = CH3, CH3O, F, Cl):C6H4SiH3 (9:1 mole ratio) at toluene in ambient air atmosphere of was performed to yield co-silicas (p-X-C6H4SiO1.5)9(p-X-C6H4SiO1.5)1 in high yield using nickelocene. The co-gels with higher molecular weights and TGA residue yield were obtained when compared to the homogels. The highest yield, molecular weight, polydispersity index, and TGA residue yield were obtained for p-Cl-C6H4SiH3. Some degree of unreacted Si—H bonds still remained in the gel matrix because of steric bulkiness. All the insoluble gels adopt an amorphous structure with a smooth surface. A plausible mechanism for the dry sol–gel reaction was suggested.

scholarly journals Synthesis of monolithic shape-stabilized phase change materials with high mechanical stability via a porogen-assisted in situ sol–gel process

RSC Advances ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 3072-3083 ◽  
Author(s):  
Felix Marske ◽  
Juliana Martins de Souza e Silva ◽  
Ralf B. Wehrspohn ◽  
Thomas Hahn ◽  
Dirk Enke
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Mechanical Stability ◽  
Sol Gel ◽  
High Loading ◽  
Core Shell ◽  
Loading Capacity ◽  
Sol Gel Process ◽  
High Mechanical Stability

Nanoconfinement of PCMs in core-shell-like silica structures via an inexpensive porogen-assisted sol–gel process to produce shape-stabilized PCMs as monoliths with high mechanical stability and high loading capacity.

In-Situ Study of NiO Growth on Textured Nickel Tape Using Environmental Scanning Electron Microscope (ESEM) and Hot Stage

2001 ◽  
Vol 7 (S2) ◽  
pp. 1276-1277
Author(s):  
Y. Akin ◽  
R.E. Goddard ◽  
W. Sigmund ◽  
Y.S. Hascicek
Keyword(s):  
Buffer Layer ◽  
Lattice Mismatch ◽  
Sol Gel ◽  
Surface Oxidation ◽  
Dip Coating ◽  
Buffer Layers ◽  
Superconducting Film ◽  
Environmental Scanning ◽  
Cold Rolling And Annealing

Deposition of highly textured ReBa2Cu3O7−δ (RBCO) films on metallic substrates requires a buffer layer to prevent chemical reactions, reduce lattice mismatch between metallic substrate and superconducting film layer, and to prevent diffusion of metal atoms into the superconductor film. Nickel tapes are bi-axially textured by cold rolling and annealing at appropriate temperature (RABiTS) for epitaxial growth of YBa2Cu3O7−δ (YBCO) films. As buffer layers, several oxide thin films and then YBCO were coated on bi-axially textured nickel tapes by dip coating sol-gel process. Biaxially oriented NiO on the cube-textured nickel tape by a process named Surface-Oxidation- Epitaxy (SEO) has been introduced as an alternative buffer layer. in this work we have studied in situ growth of nickel oxide by ESEM and hot stage.Representative cold rolled nickel tape (99.999%) was annealed in an electric furnace under 4% hydrogen-96% argon gas mixture at 1050°C to get bi-axially textured nickel tape.

scholarly journals Hydrolytic Modification of SiO2 Microspheres with Na2SiO3 and the Performance of Supported Nano-TiO2 Composite Photocatalyst

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2553
Author(s):  
Yu Tu ◽  
Weihua Ao ◽  
Chunhong Wang ◽  
Tianyu Ren ◽  
Lijuan Zhang ◽  
...  
Keyword(s):  
Sol Gel ◽  
Active Surface ◽  
Hydroxyl Groups ◽  
Nano Tio2 ◽  
Amorphous Sio2 ◽  
Composite Photocatalyst ◽  
Sio2 Shell ◽  
Functional Efficiency ◽  
Sio2 Microspheres ◽  
Better Than

Modified microspheres (SiO2-M) were obtained by the hydrolytic modification of silicon dioxide (SiO2) microspheres with Na2SiO3, and then, SiO2-M was used as a carrier to prepare a composite photocatalyst (SiO2-M/TiO2) using the sol-gel method; i.e., nano-TiO2 was loaded on the surface of SiO2-M. The structure, morphology, and photocatalytic properties of SiO2-M/TiO2 were investigated. Besides, the mechanism of the effect of SiO2-M was also explored. The results show that the hydrolytic modification of Na2SiO3 coated the surface of SiO2 microspheres with an amorphous SiO2 shell layer and increased the quantity of hydroxyl groups. The photocatalytic performance of the composite photocatalyst was slightly better than that of pure nano-TiO2 and significantly better than that of the composite photocatalyst supported by unmodified SiO2. Thus, increasing the loading capacity of nano-TiO2, improving the dispersion of TiO2, and increasing the active surface sites are essential factors for improving the functional efficiency of nano-TiO2. This work provides a new concept for the design of composite photocatalysts by optimizing the performance of the carrier.

scholarly journals Integrated Optical Phased Arrays for Beam Forming and Steering

2021 ◽  
Vol 11 (9) ◽  
pp. 4017
Author(s):  
Yongjun Guo ◽  
Yuhao Guo ◽  
Chunshu Li ◽  
Hao Zhang ◽  
Xiaoyan Zhou ◽  
...  
Keyword(s):  
Near Infrared ◽  
Phased Arrays ◽  
Mechanical Stability ◽  
Building Blocks ◽  
High Yield ◽  
Beam Forming ◽  
Integrated Optical ◽  
Optical Phased Arrays ◽  
Infrared Spectral ◽  
Spectral Ranges

Integrated optical phased arrays can be used for beam shaping and steering with a small footprint, lightweight, high mechanical stability, low price, and high-yield, benefiting from the mature CMOS-compatible fabrication. This paper reviews the development of integrated optical phased arrays in recent years. The principles, building blocks, and configurations of integrated optical phased arrays for beam forming and steering are presented. Various material platforms can be used to build integrated optical phased arrays, e.g., silicon photonics platforms, III/V platforms, and III–V/silicon hybrid platforms. Integrated optical phased arrays can be implemented in the visible, near-infrared, and mid-infrared spectral ranges. The main performance parameters, such as field of view, beamwidth, sidelobe suppression, modulation speed, power consumption, scalability, and so on, are discussed in detail. Some of the typical applications of integrated optical phased arrays, such as free-space communication, light detection and ranging, imaging, and biological sensing, are shown, with future perspectives provided at the end.

scholarly journals Carbon Nitride Quantum Dots Modified TiO2 Inverse Opal Photonic Crystal for Solving Indoor VOCs Pollution

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 464
Author(s):  
Jie Yu ◽  
Angel Caravaca ◽  
Chantal Guillard ◽  
Philippe Vernoux ◽  
Liang Zhou ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Carbon Nitride ◽  
Sol Gel ◽  
Green Energy ◽  
Inverse Opal ◽  
Oxidation Reactions ◽  
Composite Photocatalyst ◽  
Colloidal Photonic Crystals ◽  
Inverse Opal Structure

Indoor toxic volatile organic compounds (VOCs) pollution is a serious threat to people’s health and toluene is a typical representative. In this study, we developed a composite photocatalyst of carbon nitride quantum dots (CNQDs) in situ-doped TiO2 inverse opal TiO2 IO for efficient degradation of toluene. The catalyst was fabricated using a sol-gel method with colloidal photonic crystals as the template. The as-prepared catalyst exhibited excellent photocatalytic performance for degradation of toluene. After 6 h of simulated sunlight irradiation, 93% of toluene can be converted into non-toxic products CO2 and H2O, while only 37% of toluene is degraded over commercial P25 in the same condition. This greatly enhanced photocatalytic activity results from two aspects: (i) the inverse opal structure enhances the light harvesting while providing adequate surface area for effective oxidation reactions; (ii) the incorporation of CNQDs in the framework of TiO2 increases visible light absorption and promotes the separation of photo-generated charges. Collectively, highly efficient photocatalytic degradation of toluene has been achieved. In addition, it can be expanded to efficient degradation of organic pollutants in liquid phase such as phenol and Rhodamine B. This study provides a green, energy saving solution for indoor toxic VOCs removal as well as for the treatment of organic wastewater.

scholarly journals Influence of partitioning parameters on the mechanical stability of austenite in a Q&P steel: A comparative in-situ study

Materialia ◽  
2021 ◽  
Vol 15 ◽  
pp. 101033
Author(s):  
Sandra Ebner ◽  
Ronald Schnitzer ◽  
Emad Maawad ◽  
Clemens Suppan ◽  
Christina Hofer
Keyword(s):  
Mechanical Stability ◽  
In Situ Study

scholarly journals The Fluoride Anion-Catalyzed Sulfurization of Thioketones with Elemental Sulfur Leading to Sulfur-Rich Heterocycles: First Sulfurization of Thiochalcones

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 822
Author(s):  
Grzegorz Mlostoń ◽  
Jakub Wręczycki ◽  
Katarzyna Urbaniak ◽  
Dariusz M. Bieliński ◽  
Heinz Heimgartner
Keyword(s):  
Elemental Sulfur ◽  
Fluoride Anion ◽  
Ring Size ◽  
Mild Conditions ◽  
Tetrabutylammonium Fluoride ◽  
Cesium Fluoride ◽  
Secondary Reactions ◽  
Derivatives Of

Fluoride anion was demonstrated as a superior activator of elemental sulfur (S8) to perform sulfurization of thioketones leading to diverse sulfur-rich heterocycles. Due to solubility problems, reactions must be carried out either in THF using tetrabutylammonium fluoride (TBAF) or in DMF using cesium fluoride (CsF), respectively. The reactive sulfurizing reagents are in situ generated, nucleophilic fluoropolysulfide anions FS(8−x)−, which react with the C=S bond according to the carbophilic addition mode. Dithiiranes formed thereby, existing in an equilibrium with the ring-opened form (diradicals/zwitterions) are key-intermediates, which undergo either a step-wise dimerization to afford 1,2,4,5-tetrathianes or an intramolecular insertion, leading in the case of thioxo derivatives of 2,2,4,4-tetramethylcyclobutane-1,3-dione to ring enlarged products. In reactions catalyzed by TBAF, water bounded to fluoride anion via H-bridges and forming thereby its stable hydrates is involved in secondary reactions leading, e.g., in the case of 2,2,4,4-tetramethyl-3-thioxocyclobutanone to the formation of some unexpected products such as the ring enlarged dithiolactone and ring-opened dithiocarboxylate. In contrast to thioketones, the fluoride anion catalyzed sulfurization of their α,β-unsaturated analogues, i.e., thiochalcones is slow and inefficient. However, an alternative protocol with triphenylphosphine (PPh3) applied as a catalyst, offers an attractive approach to the synthesis of 3H-1,2-dithioles via 1,5-dipolar electrocyclization of the in situ-generated α,β-unsaturated thiocabonyl S-sulfides. All reactions occur under mild conditions and can be considered as attractive methods for the preparation of sulfur rich heterocycles with diverse ring-size.

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