Magnetic, electrical, and microstructural properties of YBa2Cu3O7: A comparison of sol-gel, co-precipitated, and solid state processing routes

1989 ◽  
Vol 4 (5) ◽  
pp. 1099-1102 ◽  
Author(s):  
E. A. Hayri ◽  
M. Greenblatt ◽  
K. V. Ramanujachary ◽  
M. Nagano ◽  
J. Oliver ◽  
...  
Keyword(s):  
Solid State ◽  
Sol Gel ◽  
Meissner Effect ◽  
Uniform Size ◽  
High Temperature Reaction ◽  
Sol Gel Process ◽  
Solution Methods ◽  
Yttrium Barium ◽  
Co Precipitation ◽  
State Processing

Samples of YBa2Cu3O7 were prepared by sol-gel, co-precipitation, and solid state processes. Sol-gel samples were prepared from a solution of yttrium, barium, and copper nitrates dissolved in ethylene glycol, co-precipitated samples were made by the amorphous citrate method, and solid state samples were prepared by conventional high temperature reaction of the appropriate metal oxides and carbonates. The sol-gel process was shown to yield superconducting samples of superior Meissner effect, critical current, and critical field. The co-precipitated samples contain impurities that affect the critical properties. The sol-gel and co-precipitated processes yield materials with well-formed, plate-like particles with a fairly uniform size of about 10 μm. The grains in the solid state sample are smaller but have a much wider distribution of sizes than the samples prepared by solution methods.

Preparation and Microwave-Absorption Property of SiO2-SiC-Based Composites

2010 ◽  
Vol 434-435 ◽  
pp. 231-234
Author(s):  
Li Guan ◽  
Bing Bing Fan ◽  
Ming Liang Li ◽  
He Jing Wen ◽  
Kai Li ◽  
...  
Keyword(s):  
Solid State ◽  
Microwave Absorption ◽  
Solid State Reaction ◽  
Sol Gel ◽  
Composite Particles ◽  
Network Analyzer ◽  
Epoxide Resin ◽  
Maximum Reflectivity ◽  
Sol Gel Process ◽  
Sic Composites

SiO2-SiC composite particles were prepared using a sol-gel process. BaTiO3 powders were synthesize through solid-state reaction. They were mixed as microwave absorbents with Fe3O4 powders to obtain the complex absorption. Epoxide resin (EP) was used as matrix and solidified with the mixtures. The techniques of DSC-TG, XRD were used to characterize the composite particles and the obtained compacts. A vector network analyzer was used to measure the reflectivity of the SiO2-SiC-based composites. The effects of the aborbents’ contents on the reflection of the microwave absorption materials were disscussed. It was found that SiO2-SiC composites could be prepared using sol-gel process and BaTiO3 powders could be synthesize through solid-state reaction. The results indicated that SiO2-SiC composite is contribute to absorb microwave, where SiO2-SiC: BaTiO3: Fe3O4 = 6:2:2 (vol %), the frequency region in which the maximum reflectivity is more than -10 dB is 5.4-7.6 GHz.

scholarly journals Immobilization of Bacillus licheniformis using Fe3O4@SiO2 nanoparticles for the development of bacterial bioreactor

2019 ◽  
Vol 35 (2) ◽  
pp. 854-862
Author(s):  
Ayoub Nadi ◽  
Marouane Melloul ◽  
Aicha Boukhriss ◽  
Elmostafa El-Fahime ◽  
Damien Boyer ◽  
...  
Keyword(s):  
Bacillus Licheniformis ◽  
Fe3o4 Nanoparticles ◽  
Sol Gel ◽  
Sio2 Nanoparticles ◽  
Industrial Applications ◽  
Basic Medium ◽  
Magnetite Fe3o4 ◽  
Sol Gel Process ◽  
Co Precipitation

In the biotechnology field, nanoparticles with a strong magnetic moment can bring attractive and novel potentialities. They are detectable, manipulable, stimulable by a magnetic field and they could be applied as nano-tracers for medical imaging and nano-vectors for transporting therapeutic agents to a target. For our part, we applied Fe3O4 nanoparticles to immobilize bacteria of Moroccan strains in order to develop bacterial bioreactor. For this aim, we got through the synthesis and characterization of magnetite Fe3O4 nanoparticles by co-precipitation in basic medium. The obtained nanoparticles were encapsulated in silica by sol-gel process. The results of this step allowed us to use Fe3O4@SiO2 nanoparticles to immobilize Bacillus licheniformis by adsorption and separate it magnetically. The principle of this system gives us the opportunity to develop a bacterial bioreactor for industrial applications.

scholarly journals New Condensation Polymer Precursors Containing Consecutive Silicon Atoms—Decaisopropoxycyclopentasilane and Dodecaethoxyneopentasilane—And Their Sol–Gel Polymerization

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 841
Author(s):  
Sung Jin Park ◽  
Myong Euy Lee ◽  
Hyeon Mo Cho ◽  
Sangdeok Shim
Keyword(s):  
Solid State ◽  
Sol Gel ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Cross Polarization ◽  
Reaction Conditions ◽  
Polymer Precursors ◽  
Sol Gel Process ◽  
Angle Spinning ◽  
Magnetic Resonances

The sol–gel polymerization of alkoxysilanes is a convenient and widely used method for the synthesis of silicon polymers and silicon–organic composites. The development of new sol–gel precursors is very important for obtaining new types of sol–gel products. New condensation polymer precursors containing consecutive silicon atoms—decaisopropoxycyclopentasilane (CPS) and dodecaethoxyneopentasilane (NPS)—were synthesized for the preparation of polysilane–polysiloxane material. The CPS and NPS xerogels were prepared by the sol–gel polymerization of CPS and NPS under three reaction conditions (acidic, basic and neutral). The CPS and NPS xerogels were characterized using N2 physisorption measurements (Brunauer–Emmett–Teller; BET and Brunauer-Joyner-Halenda; BJH), solid-state CP/MAS (cross-polarization/magic angle spinning) NMRs (nuclear magnetic resonances), TEM, and SEM. Their porosity and morphology were strongly affected by the structure of the precursors, and partial oxidative cleavage of Si-Si bonds occurred during the sol–gel process. The new condensation polymer precursors are expected to expand the choice of approaches for new polysilane–polysiloxane.

Preparation and properties of polyimide-polysiloxane hybrid materials by the sol-gel process

1994 ◽  
Vol 6 (2) ◽  
pp. 95-107 ◽  
Author(s):  
Yoshitake Iyoku ◽  
Masa-aki Kakimoto ◽  
Yoshio Imai
Keyword(s):  
Solution Method ◽  
Sol Gel ◽  
Mechanical Analysis ◽  
Methanol Solution ◽  
Heating Process ◽  
Hybrid Films ◽  
Polyamic Acid ◽  
Sol Gel Process ◽  
Solution Methods ◽  
Polyimide Matrix

Polyimide-poly(methylsiloxane) hybrid films were successfully prepared by the sol-gel process with methyltriethoxysilane (MTES) and/or dimethyldiethoxysilane (DMDES) in the polymer solution. Two methods were used for making hybrid films. First, MTES and/or DMDES were dissolved in the N,N-dimethylacetamide (DMAc) solution of the polyamic acid (polyimide precursor) prepared from 4,4'-diaminodiphenyl ether (ODA) and pyromellitic dianhydride (PMDA). During the heating process at 300°C the polyamic acid was converted to polyimide and the sol-gel reaction, which consists of hydrolysis and condensation of MTES and/or DMDES, proceeded simultaneously. Second, methanol was used as the solvent to make the hybrid films by using the triethylamine salt of polyamic acid. The IR spectra proved that the sol-gel reactions started from MTES and DMDES readily proceeded in the polymer matrix. The hybrid films prepared in methanol were more transparent than those prepared in DMAc. Measurement by dynamic mechanical analysis indicated that the polystloxane was dispersed homogeneously in the polyimide matrix even after the heat treatment at 300°C, in the case of both DMAc and methanol solution methods. With respect to the tensile properties, the tensile strength and the elongation at break of the hybrid films prepared by the methanol solution method were higher than those by the DMAc solution method. The modulus of the obtained hybrid films decreasing with increasing DMDES ratio in the silicone unit in both cases.

COMPARATIVE STUDY OF Bi-2223/Ag SUPERCONDUCTORS DERIVED FROM PARTICLES SIZE OF STARTING MATERIALS

2007 ◽  
Vol 21 (18n19) ◽  
pp. 3246-3249 ◽  
Author(s):  
D. SÝKOROVÁ ◽  
O. SMRČKOVÁ ◽  
K. RUBEŠOVÁ ◽  
P. VAŠEK
Keyword(s):  
Solid State ◽  
Comparative Study ◽  
Temperature Dependence ◽  
Solid State Reaction ◽  
Sintering Temperature ◽  
Sol Gel ◽  
Sol Gel Process ◽  
Current Densities ◽  
Size Of Particles ◽  
Micrometer Size

Series of the samples with nominal compositions Bi 3.2 Pb 0.8 Sr 4 Ca 5 Cu 7 O x and Bi 3.2 Pb 0.8 Sr 4 Ca 5 Cu 7 O x / Ag (10 wt%) were prepared by the standard solid state reaction at the same calcination and sintering temperature and time. Three starting mixtures were used, carbonates, oxides and silver i) with nanoparticles, ii) with micrometer size of particles and iii) powder obtained by modified sol-gel process. The main phase in all samples was Bi -2223 and silver formed the separate phase. The sol-gel process was found to be effective way in term of porosity, bulk density and connectivity of the grains. The effect of the microstructure on the transport properties were described by the temperature dependence of resistivity and critical current densities.

Synthesis and characterization of sol-gel derived hexa-aluminate phosphors

1997 ◽  
Vol 12 (3) ◽  
pp. 819-824 ◽  
Author(s):  
D. Ravichandran ◽  
R. Roy ◽  
W. B. White ◽  
S. Erdei
Keyword(s):  
Sol Gel ◽  
Broad Band ◽  
Blue Emission ◽  
Emission Spectra ◽  
Steam Treatment ◽  
Optical Pyrometer ◽  
Processing Route ◽  
Sol Gel Process ◽  
State Processing

Two refractory phosphors, BaMg2Al16O27: Eu2+ (BAM) and MgAl11O17.5: Ce3+, Tb3+ (MAO), have been synthesized both by the conventional solid-state processing route (using oxides as the starting materials) and by reacting precursors made by the sol-gel process using organic precursors. The phases formed were reacted at 1000 °C in (a) steam and (b) steam + AlF3. The phosphors were well crystallized with particle sizes in the range of 1–10 μm. The emission spectra showed the characteristic broad band blue emission of Eu2+ for BAM and a narrow band green luminescence of Tb3+ for MAO. The melting points of BAM and MAO were measured to be 1920 ± 20 °C and 1950 ± 20 °C, respectively, using an Ir-strip furnace and optical pyrometer. BAM and MAO phosphor materials are congruently and incongruently melting, respectively. Excellent crystallization via the sol-gel route was found even at 1220 °C. Enhancement of the luminescent output by the steam treatment by some 25% was determined.

A Solid State Multinuclear Magnetic Resonance Study of the Sol-Gel Process using Polysilicate Precursors

1986 ◽  
Vol 73 ◽  
Author(s):  
W. G. Klemperer ◽  
V. V. Mainz ◽  
D. M. Millar
Keyword(s):  
Solid State ◽  
Magnetic Resonance ◽  
Sol Gel ◽  
Building Blocks ◽  
Magnetic Resonance Study ◽  
Solvent Content ◽  
Molecular Building Blocks ◽  
Nmr Study ◽  
Sol Gel Process ◽  
Nmr Techniques

ABSTRACTA solid state multinuclear NMR study of the sol-gel process was performed using the molecular building blocks tetramethoxysilane, hexamethoxydisiloxane, octamethoxytrisiloxane and octamethoxyoctasilsesquioxane as precursor monomers. Water content, solvent content, and hydrolysis/condensation processes were monitored using 17O, 13C, and 29Si FT, FTMAS and CPMAS NMR techniques.

The use of multinuclear solid state NMR for the characterization of siloxane-oxide hybrid nanocomposites

2004 ◽  
Vol 847 ◽  
Author(s):  
Christel Gervais ◽  
Beatriz Julián ◽  
Eloisa Cordoncillo ◽  
Purificación Escribano ◽  
Mark E. Smith ◽  
...  
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Sol Gel ◽  
Hybrid Nanocomposites ◽  
Sol Gel Process ◽  
Hydrolysis And Condensation ◽  
Silicon Alkoxides ◽  
Different Types ◽  
Nmr Techniques

ABSTRACTThe objective of this paper is to review various solid state NMR techniques that have been, or can be used for the structural characterization of siloxane—oxide hybrid systems prepared by sol-gel process, and to discuss the type of information they provide, as well as their limitations. More precisely, this paper focuses on NMR techniques to probe and quantify the different types of oxo-bridges (M–O–M of oxide network, Si–O–Si of siloxane chains and Si–O–M siloxane–MxOy interface) in siloxane-oxide nanocomposites prepared through hydrolysis and condensation of organosilanes and M(OR)n alkoxides. In addition the influence of the functionality of the silicon alkoxides and the nature of the MxOy oxides on the extent of the Si-O-M interface will be examined.

Sign in / Sign up

Export Citation Format

Share Document