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.

Dry Sol–Gel Condensation of p-X-C6H4SiH3 (X=H, CH3, CH3O, F, Cl) to Organosilica p-X-C6H4SiO3 Using Nickelocene

2006 ◽  
Vol 6 (11) ◽  
pp. 3388-3391
Author(s):  
Myong-Shik Cho ◽  
Bo-Hye Kim ◽  
Yun-Mi Hwang ◽  
Hee-Gweon Woo ◽  
Do-Heyoung Kim
Keyword(s):  
Molecular Weight ◽  
Smooth Surface ◽  
Sol Gel ◽  
Ambient Air ◽  
Amorphous Structure ◽  
Polydispersity Index ◽  
High Yield ◽  
Air Atmosphere ◽  
Plausible Mechanism

The dry sol–gel reaction at toluene in ambient air atmosphere of p-X-C6H4SiH3 (X = H, CH3, CH3O, F, Cl) to p-C6H4SiO3 in high yield, catalyzed by nickelocene, is reported. 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 because of steric reason. 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 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.

The impacts of PLGA/PEG triblock copolymers with variable molecular weights on sustained release of buprenorphine

2021 ◽  
Vol 18 ◽  
Author(s):  
Hossein Kamali ◽  
Elham Khodaverdi ◽  
Fatemeh Mohammadpour ◽  
Ali Kakavand ◽  
Seyedeh Nesa Rezaeian Shiadeh ◽  
...  
Keyword(s):  
Sustained Release ◽  
Sol Gel ◽  
In Vitro Release ◽  
Burst Release ◽  
Sustained Release Formulation ◽  
Melting Method ◽  
Initial Burst ◽  
Initial Burst Release ◽  
Molecular Weights

Introduction: Current in-situ injectable implants of buprenorphine (BP) such as Sublocade® consist of N-methyl-2-pyrrolidone (NMP)-dissolved PLGA. To control the initial burst release of Sublocade® during the first 24 hours after injection, we used a BP in-situ forming composite (ISFC) to employ different molecular weights of PLGA-PEG-PLGA triblock. Methods: The triblock was synthesized by ring-opening polymerization (ROP) using PEG molecules with weights of 1500, 3000, and 4000 Da via the melting method. The specifications of the triblock were evaluated by 1H-NMR, FTIR, GPC, and DSC. The sol-gel, gel-precipitate temperatures, in-vitro release, and composites’ morphology, degradation, and toxicity were assessed for determining the features of ISFC 1500, ISFC 3000, and ISFC 4000 formulations. ROP was performed successfully via the melting method. The yields of all polymerization reactions were greater than 83.4 %. Results: The PEG 1500 triblock showed both sol-gel and gel-precipitate temperatures, but PEG 3000 and 4000 only showed a sol-precipitate temperature. The values of initial burst release of BP from ISFC 1500, ISFC 3000, and ISFC 4000 were 6.52 ± 0.22 %, 12.39 ± 0.61 %, and 15.80 ± 0.98 %, respectively. BP release from the ISFCs was completed over three weeks for ISFC 1500 and 10 days for ISFC 3000 and ISFC 4000. The composites containing PEG 3000 and PEG 4000 were more spongy and porous than PEG 1500. The ISFC 1500 delivered a higher cell viability (95.17 ± 1.15 %) compared with ISFC 3000 (86.37 ± 2.25%) and ISFC 4000 (79.70 ± 3.77%). Conclusion: These results indicated that ISFC 1500 were biocompatible and delivered suitable early initial burst reactions compared with ISFC 3000 and 4000 and might be a good candidate for preparing sustained-release formulation of BP.

An investigation into the temperature phase transitions of synthesized lithium titanate materials doped with Al, Co, Ni and Mg by in situ powder X-ray diffraction

2020 ◽  
Vol 35 (4) ◽  
pp. 233-246
Author(s):  
X. van Niekerk ◽  
E. E. Ferg ◽  
C. Gelant ◽  
D. G. Billing
Keyword(s):  
Phase Transitions ◽  
Crystalline Phase ◽  
Room Temperature ◽  
Spinel Phase ◽  
Sol Gel ◽  
Amorphous State ◽  
Amorphous Structure ◽  
Temperature Phase ◽  
Prolonged Heating

Li4Ti5O12 (LTO) and its doped analogues Li4Ti4.95M0.05O12 (M = Al3+, Co3+, Ni2+, and Mg2+) were synthesized and characterized using in situ PXRD to monitor the phase transitions during the sol–gel synthesis of the spinel material. These results are complimented by thermogravimetric analysis, which illustrates the decomposition of the materials synthesized, where the final LTO products are seen to form at approximately 550 °C. The material has an amorphous structure from room temperature, coupled with a crystalline phase which is speculated to be H2Ti2O5·H2O. This crystalline phase disappears at 250 °C, with the material still in the amorphous state. The crystalline LTO phase starts at approximately 550 °C, with anatase co-crystallizing with the spinel phase. Rutile appears at 600 °C and co-crystallizes with the final product at 850 °C, where anatase is no longer seen. The rutile impurity remains present after cooling the material to room temperature, and results indicate that prolonged heating at 850 °C is required to reduce the rutile content. Rietveld refinement of diffraction patterns show that the unit-cell parameter increases with increasing temperature, coupled with a decrease when cooling the sample. The crystallite sizes follow the same trend, with a significant increase above temperatures of 750 °C.

scholarly journals Preparation of Orthorhombic WO3 Thin Films and Their Crystal Quality-Dependent Dye Photodegradation Ability

Coatings ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 90 ◽  
Author(s):  
Yuan-Chang Liang ◽  
Che-Wei Chang
Keyword(s):  
Thin Films ◽  
Annealing Temperature ◽  
Ambient Air ◽  
Amorphous Structure ◽  
Orthorhombic Structure ◽  
Dc Magnetron Sputtering ◽  
Dc Sputtering ◽  
Coarsening Behavior ◽  
Wo3 Thin Films

Direct current (DC) magnetron sputtering deposited WO3 films with different crystalline qualities were synthesized by postannealing at various temperatures. The in-situ DC sputtering deposited WO3 thin film at 375 °C exhibited an amorphous structure. The as-grown WO3 films were crystallized after annealing at temperatures of 400–600 °C in ambient air. Structural analyses revealed that the crystalline WO3 films have an orthorhombic structure. Moreover, the crystallite size of the WO3 film exhibited an explosive coarsening behavior at an annealing temperature above 600 °C. The density of oxygen vacancy of the WO3 films was substantially lowered through a high temperature annealing procedure. The optical bandgap values of the WO3 films are highly associated with the degree of crystalline quality. The annealing-induced variation of microstructures, crystallinity, and bandgap of the amorphous WO3 thin films explained the various photoactivated properties of the films in this study.

Catalytic Si–Si/Si–O Dehydrocoupling of 1,1-Dihydrotetraphenylsilole to Optoelectronic Polysiloles with Colloidal Silver Nanoparticles

2007 ◽  
Vol 7 (11) ◽  
pp. 3926-3931
Author(s):  
Bo-Hye Kim ◽  
Myong-Shik Cho ◽  
So-Yeun Kim ◽  
You-Jeong Kim ◽  
Hee-Gweon Woo ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Green Light ◽  
Ambient Air ◽  
Nitrogen Atmosphere ◽  
High Yield ◽  
Colloidal Silver ◽  
Polymer Backbone ◽  
Air Atmosphere ◽  
Colloidal Silver Nanoparticles ◽  
Oxidation Of No

The combinative Si–Si/Si–O dehydrocoupling at ambient air atmosphere of 1,1-dihydrotetraphenylsilole 1 with 2 mol% of AgNO3 and Ag2 SO4 in toluene at 90 °C produces optoelectronic polysiloles 2 in high yield. The complexes such as Cp2Co, Cp2Ni, Cp2ZrCl2/Red-Al, and AgCl were found to be ineffective for the dehydrocoupling of 1. The polysiloles mainly have Si—Si bonds along with the small portion of Si—O bonds in the polymer backbone chain. Interestingly, the Si–O linkage increased with increasing the concentration of catalyst AgNO3, implying that while Ag(0) species catalyze the Si–Si dehydrocoupling, Ag(I) species catalyze the Si–O dehydrocoupling along with the simultaneous oxidation of NO3− ion to NO2. The silver complexes transformed to colloidal silver nanoparticles during the catalytic reaction. The Si–Si/Si–O dehydrocoupling of 1 with AgNO3 even at dry nitrogen atmosphere is occurred, supporting that the oxidation of NO3− ion to NO2 is only the possible oxygen source, but not from the adventitious moisture in air. α-, β-, and γ-Cyclodextrins considerably deteriorated the dehydrocoupling of 1 probably due to both the formation of insoluble inclusion complexes in toluene and the encapsulation of SiH2 moiety. The resulting silole polymer 2 emits green light at 520 nm and is electroluminescent at 520 nm.

Devitrification products of rapidly solidified Ni-Nb amorphous alloys.

1990 ◽  
Vol 48 (4) ◽  
pp. 950-951
Author(s):  
G. A. Bertero ◽  
W.H. Hofmeister ◽  
N.D. Evans ◽  
J.E. Wittig ◽  
R.J. Bayuzick
Keyword(s):  
Electron Microscopy ◽  
Amorphous Structure ◽  
Sulphuric Acid Solution ◽  
X Ray Diffraction ◽  
High Fracture ◽  
Transmission Electron ◽  
Xrd Techniques ◽  
Rapidly Solidified ◽  
Electromagnetically Levitated

Rapid solidification of Ni-Nb alloys promotes the formation of amorphous structure. Preliminary results indicate promising elastic properties and high fracture strength for the metallic glass. Knowledge of the thermal stability of the amorphus alloy and the changes in properties with temperature is therefore of prime importance. In this work rapidly solidified Ni-Nb alloys were analyzed with transmission electron microscopy (TEM) during in-situ heating experiments and after isothermal annealing of bulk samples. Differential thermal analysis (DTA), scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques were also used to characterize both the solidification and devitrification sequences.Samples of Ni-44 at.% Nb were electromagnetically levitated, melted, and rapidly solidified by splatquenching between two copper chill plates. The resulting samples were 100 to 200 μm thick discs of 2 to 3 cm diameter. TEM specimens were either ion-milled or alternatively electropolished in a methanol-10% sulphuric acid solution at 20 V and −40°C.

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 The influence of chemical parameters on the in-situ metal carbonyl complex formation studied with the fast on-line reaction apparatus (FORA)

2021 ◽  
Vol 109 (4) ◽  
pp. 243-260 ◽  
Author(s):  
Yves Wittwer ◽  
Robert Eichler ◽  
Dominik Herrmann ◽  
Andreas Türler
Keyword(s):  
Metal Carbonyl ◽  
Ambient Air ◽  
Single Atom ◽  
Carbonyl Complex ◽  
Carbonyl Complexes ◽  
On Line ◽  
Carrier Gases ◽  
And Performance ◽  
Atom Chemistry

Abstract A new setup named Fast On-line Reaction Apparatus (FORA) is presented which allows for the efficient investigation and optimization of metal carbonyl complex (MCC) formation reactions under various reaction conditions. The setup contains a 252Cf-source producing short-lived Mo, Tc, Ru and Rh isotopes at a rate of a few atoms per second by its 3% spontaneous fission decay branch. Those atoms are transformed within FORA in-situ into volatile metal carbonyl complexes (MCCs) by using CO-containing carrier gases. Here, the design, operation and performance of FORA is discussed, revealing it as a suitable setup for performing single-atom chemistry studies. The influence of various gas-additives, such as CO2, CH4, H2, Ar, O2, H2O and ambient air, on the formation and transport of MCCs was investigated. O2, H2O and air were found to harm the formation and transport of MCCs in FORA, with H2O being the most severe. An exception is Tc, for which about 130 ppmv of H2O caused an increased production and transport of volatile compounds. The other gas-additives were not influencing the formation and transport efficiency of MCCs. Using an older setup called Miss Piggy based on a similar working principle as FORA, it was additionally investigated if gas-additives are mostly affecting the formation or only the transport stability of MCCs. It was found that mostly formation is impacted, as MCCs appear to be much less sensitive to reacting with gas-additives in comparison to the bare Mo, Tc, Ru and Rh atoms.

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