scholarly journals Synthesis and Study of Properties of Organic and Carbon Xerogels from Abies Bark Tannins

2020 ◽  
pp. 175-188
Author(s):  
Nadezhda M. Mikova ◽  
Ivan P. Ivanov ◽  
Vladimir A. Levdanskiy ◽  
Boris N. Kuznetsov
Keyword(s):  
Room Temperature ◽  
Sol Gel ◽  
Fire Retardant ◽  
Argon Atmosphere ◽  
Polymer Chains ◽  
Alkyl Ether ◽  
Significant Development ◽  
Carbon Xerogels ◽  
Carbon Gels ◽  
Crosslinking Reactions

Methods of organic and carbon xerogels synthesis based on the use of condensed tannins isolated from abies bark were developed. Organic gels were synthesized by sol-gel condensation of tannins with formaldehyde in a solution of ethanol in the presence of catalysts (NaOH or HCl). The final gelation products were dried by alternating low (-18 – -40 °C) and room temperature to obtain tanninformaldehyde (TF) xerogels. FTIR study indicates that the formation of xerogels was accompanied by crosslinking reactions mainly due to the formation of carbon-carbon and alkyl ether bonds. Using the method of thermogravimetry, it was found that organic TF xerogels are thermally stable up to a temperature of 295 °C and they are resistant to ignition in air at temperatures up to 600 °C and can be used as thermo- and fire-retardant materials. Carbon tannin-formaldehyde xerogels were obtained by carbonization of organic xerogels at 800 °C in an argon atmosphere. The porous structure and surface morphology of organic and carbon xerogels was studied by BET- and SEM–methods. A significant development of the specific surface area (to 483–524 m2/g)as a result of the organic xerogels carbonization was established. Using SEM, it was shown that in carbon gels a spatially cross-linked structure of polymer chains consisting of 5-10 nmsized globule particles forming nanometer-sized pores is retained

Synthesis, characterization, and properties of new polystyrene-SiO2 hybrid sol-gel materials

1993 ◽  
Vol 8 (5) ◽  
pp. 1143-1152 ◽  
Author(s):  
Yen Wei ◽  
Dachuan Yang ◽  
Liguang Tang ◽  
MaryGail K. Hutchins
Keyword(s):  
Hybrid Materials ◽  
Room Temperature ◽  
Sol Gel ◽  
Glass Network ◽  
Radical Copolymerization ◽  
Polymer Chains ◽  
Free Radical Copolymerization ◽  
New Family ◽  
Polymer Precursors ◽  
Covalently Bonded

A new family of organic-inorganic hybrid materials has been prepared by incorporating polystyrene structure units covalently into the SiO2 glass network via the sol-gel approach. The polymer precursors were synthesized by free-radical copolymerization of styrene with 3-(trimethoxysilyl)propyl methacrylate (MSMA) at various feeds. These copolymers were then hydrolyzed and co-condensed with tetraethyl orthosilicate in tetrahydrofuran at room temperature to afford monolithic polystyrene-SiO2 hybrid sol-gel materials having SiO2 contents of 15 to 84% by weight. The hybrid materials derived from the copolymers with MSMA contents greater than 22 mol% have excellent optical transparency. In these transparent hybrid materials, the polymer chains should be uniformly distributed in and covalently bonded to the amorphous SiO2 matrices. The bulk properties of these materials including density, refractive index, and hardness were found to be related to their molecular compositions and can be tailored by varying the polymer contents.

Improved Sol-Gel Materials for Efficient Solid State Dye Lasers

1993 ◽  
Vol 329 ◽  
Author(s):  
Michael Canva ◽  
Patrick Georges ◽  
Jean-Fran^ois Perelgritz ◽  
Alain Brun ◽  
Fréddric Chaput ◽  
...  
Keyword(s):  
Solid State ◽  
Physical Properties ◽  
Room Temperature ◽  
Sol Gel ◽  
Tunable Lasers ◽  
Optical Quality ◽  
Dye Lasers ◽  
Laser Dyes ◽  
Host Matrix ◽  
Host Matrices

AbstractPhotoresistant laser dyes were trapped in silica based xerogel host matrices to obtain solid state tunable lasers. For this purpose very dense xerogel samples with improved chemical and physical properties were prepared at room temperature by the sol-gel technology. The as-prepared materials were polished to obtain optical quality surfaces and were used as new lasing media.Lasing action of such different dyes as rhodamine, perylene and pyrromethene doping dense sol-gel matrices was demonstrated. Efficiencies of 30 % or lifetimes of more than 100,000 shots were achieved with different new ≤dye dopant/host matrix≥ couples. Their different performances are reviewed and discussed.

Nickel (II) and oxovanadium (IV) complexes supported on MCM-41 mesoporous and their application in catalytic selective sulfide and thiol oxidation

2020 ◽  
Vol 23 ◽  
Author(s):  
Mohsen Nikoorazm ◽  
Maryam Khanmoradi ◽  
Masoumeh Sayadian
Keyword(s):  
Catalytic Activity ◽  
Room Temperature ◽  
Sol Gel ◽  
Reaction Times ◽  
Significant Loss ◽  
Spectral Studies ◽  
High Catalytic Activity ◽  
Catalytic Systems ◽  
Solvent Free Conditions ◽  
Mcm 41

Introduction:: MCM-41 was synthesized using the sol-gel method. Then two new transition metal complexes of Nickel (II) and Vanadium (IV), were synthesized by immobilization of adenine (6-aminopurine) into MCM-41 mesoporous. The compounds have been characterized by XRD, TGA, SEM, AAS and FT-IR spectral studies. Using these catalysts provided an efficient and enantioselective procedure for oxidation of sulfides to sulfoxides and oxidative coupling of thiols to their corresponding disulfides using hydrogen peroxide at room temperature. Materials and Methods:: To a solution of sulfide or thiol (1 mmol) and H2O2 (5 mmol), a determined amount of the catalyst was added. The reaction mixture was stirred at room temperature for the specific time under solvent free conditions. The progress of the reaction was monitored by TLC using n-hexane: acetone (8:2). Afterwards, the catalyst was removed from the reaction mixture by centrifugation and, then, washed with dichloromethane in order to give the pure products. Results:: All the products were obtained in excellent yields and short reaction times indicating the high activity of the synthesized catalysts. Besides, the catalysts can be recovered and reused for several runs without significant loss in their catalytic activity. Conclusion:: These catalytic systems furnish the products very quickly with excellent yields and VO-6AP-MCM-41 shows high catalytic activity compared to Ni-6AP-MCM-41.

Effect of Annealing temperature on the Structural and Magnetic Properties of TbxY3-xFe5O12(x = 0.0, 1.0, 2.0) Thin Films Prepared by Sol-Gel Process

2012 ◽  
Vol 501 ◽  
pp. 236-241 ◽  
Author(s):  
Ftema W. Aldbea ◽  
Noor Bahyah Ibrahim ◽  
Mustafa Hj. Abdullah ◽  
Ramadan E. Shaiboub
Keyword(s):  
Thin Films ◽  
Magnetic Properties ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Sol Gel ◽  
Vibrating Sample Magnetometer ◽  
X Ray ◽  
Garnet Phase ◽  
Sol Gel Process ◽  
Amorphous Structures

Thin films nanoparticles TbxY3-xFe5O12 (x=0.0, 1.0, 2.0) were prepared by the sol-gel process followed by annealing process at various annealing temperatures of 700° C, 800° C and 900° C in air for 2 h. The results obtained from X-ray diffractometer (XRD) show that the films annealed below 900°C exhibit peaks of garnet mixed with small amounts of YFeO3 and Fe2O3. Pure garnet phase has been detected in the films annealed at 900°C. Before annealing the films show amorphous structures. The particles sizes measurement using the field emission scanning electron microscope (FE-SEM) showed that the particles sizes increased as the annealing temperature increased. The magnetic properties were measured at room temperature using the vibrating sample magnetometer (VSM). The saturation magnetization (Ms) of the films also increased with the annealing temperature. However, different behavior of coercivity (Hc) has been observed as the annealing temperature was increased.

Vacuum Annealing Induced Room-Temperature Ferromagnetism in Co 0.1 Ti 0.9 O 2−δ Films Prepared by Sol-Gel Method

2008 ◽  
Vol 25 (7) ◽  
pp. 2638-2641
Author(s):  
Liu Li-Feng ◽  
Kang Jin-Feng ◽  
Wang Yi ◽  
Zhang Xing ◽  
Han Ru-Qi
Keyword(s):  
Room Temperature ◽  
Vacuum Annealing ◽  
Room Temperature Ferromagnetism ◽  
Sol Gel ◽  
Gel Method ◽  
Sol Gel Method

Impedance Spectroscopy Study of LiTaO3 Powder Synthesized via Sol-Gel Method

2012 ◽  
Vol 545 ◽  
pp. 275-278 ◽  
Author(s):  
Lili Widarti Zainuddin ◽  
Norlida Kamarulzaman
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Sol Gel ◽  
Rhombohedral Structure ◽  
Spectroscopy Study ◽  
X Ray Diffraction ◽  
Gel Method ◽  
X Ray ◽  
Sol Gel Method ◽  
Impedance Spectroscopy Study

A ceramics sample of LiTaO3 was prepared using a sol-gel method. The sample is annealed at 750 °C for 48 hours. X-ray diffraction analysis indicate the formation of single phase, rhombohedral structure. An ac impedance study was used to analyse the conductivity of LiTaO3 at room temperature and at various temperatures.

Indium oxide octahedrons based on sol–gel process enhance room temperature gas sensing performance

2015 ◽  
Vol 637 ◽  
pp. 55-61 ◽  
Author(s):  
Xiaohui Mu ◽  
Changlong Chen ◽  
Liuyuan Han ◽  
Baiqi Shao ◽  
Yuling Wei ◽  
...  
Keyword(s):  
Indium Oxide ◽  
Room Temperature ◽  
Gas Sensing ◽  
Sol Gel ◽  
Sol Gel Process ◽  
Sensing Performance

scholarly journals Synthesis and electrical characterization of Ca2Nd4Ti6O20 ceramics

2016 ◽  
Vol 34 (1) ◽  
pp. 164-168
Author(s):  
Raz Muhammad ◽  
Muhammad Uzair ◽  
M. Javid Iqbal ◽  
M. Jawad Khan ◽  
Yaseen Iqbal ◽  
...  
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Room Temperature ◽  
Sol Gel ◽  
Electrical Characterization ◽  
Sintered Sample ◽  
First Time ◽  
Alkoxide Precursors ◽  
Room Temperature Dielectric Constant

AbstractCa2Nd4Ti6O20, a layered perov skite structured material was synthesized via a chemical (citrate sol-gel) route for the first time using nitrates and alkoxide precursors. Phase analysis of a sample sintered at 1625 °C revealed the formation of an orthorhombic (Pbn21) symmetry. The microstructure of the sample after sintering comprised rod-shaped grains of a size of 1.5 to 6.5µm. The room temperature dielectric constant of the sintered sample was 38 at 100 kHz. The remnant polarization (Pr) and the coercive field (Ec) were about 400 μC/cm2 and 8.4 kV/cm, respectively. Impedance spectroscopy revealed that the capacitance (13.7 pF) and activation energy (1.39 eV) of the grain boundary was greater than the capacitance (5.7 pF) and activation energy (1.13 eV) of the grain.

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