Nanocomposites — the Multifunctional Family of Materials

1989 ◽  
Vol 175 ◽  
Author(s):  
Rustum Roy
Keyword(s):  
Single Phase ◽  
Sol Gel ◽  
Multifunctional Materials ◽  
Gel Processing ◽  
Successes And Failures

AbstractThis paper starts by discussing the concept of multifunctional materials. Multifunctionality can be achieved in a single phase in a composite or a mixture. While a few exceptional single phase materials such as diamond, Al2O3, CaSrZr4P6O24 exhibit peak values of more than one function, it will be argued that the “invention” of the nanocomposite class of materials made by solution sol-gel processing has opened up the potential for designing several multifunctional materials.Examples will be drawn from our recent results—both successes and failures—in trying to design and synthesize nanocomposites of two or more ceramic phases for various chemical, thermal, and electrical functions.

Sol-gel processing of cordierite: Effect of seeding and optimization of heat treatment

1990 ◽  
Vol 5 (5) ◽  
pp. 1095-1103 ◽  
Author(s):  
Ann M. Kazakos ◽  
Sridhar Komarneni ◽  
Rustum Roy
Keyword(s):  
Heat Treatment ◽  
Single Phase ◽  
Excess Free Energy ◽  
Sol Gel ◽  
Nucleating Agents ◽  
Optimum Conditions ◽  
Nanosized Powders ◽  
Nanocomposite Gels ◽  
Powder Compacts ◽  
Gel Processing

Three series of cordierite powders were prepared by the sol-gel route: a single phase (monophasic) gel prepared from alkoxides, a nominally triphasic nanocomposite gel made with two nanosized powders and one solution phase, and a truly compositionally triphasic nanocomposite gel prepared from three nanosized powders. Crystalline α-cordierite seeds were also incorporated with the gels and their effectiveness as nucleating agents was investigated and found to lower the crystallization temperature of α-cordierite by 125–150°C. The densification behavior of powder compacts was examined and alterations made to the heat treatment until optimum conditions were found. The truly triphasic compact sintered at 1300°C for 2 h resulted in 100% of theoretical density whereas the nominally triphasic and monophasis pellets densified to 96% and 80%, respectively. The enhanced densification achieved with powder compacct prepared for triphasic nanocomposite gels is due to part to the excess free energy of the three components.

Epitaxial Growth of (110) KnbO3 Films on (100) MgO Substrates via Sol-Gel Processing

1994 ◽  
Vol 341 ◽  
Author(s):  
Garo J. Derderian ◽  
James D. Barrie ◽  
Kenneth A. Aitchison ◽  
Martha L. Mecartney
Keyword(s):  
Surface Layer ◽  
Epitaxial Growth ◽  
Interfacial Layer ◽  
Single Phase ◽  
Annealing Temperature ◽  
Sol Gel ◽  
Sol Gel Process ◽  
Defective Surface ◽  
Gel Processing

AbstractEpitaxial, single phase (110) KnbO3 films were grown on (100) MgO substrates using a sol-gel process employing ethoxide precursors in methanol. The degree of epitaxy was dependent on both the annealing temperature and the amount of potassium in the film. Excess potassium in the sol-gel solution (K/Nb = 1.2) was necessary to produce single phase films. An amorphous or polycrystalline MgO interfacial layer was observed in some films, postulated to have developed after nucleation of KnbO3 and due to a highly defective surface layer.

scholarly journals PDMS-urethanesil hybrid multifunctional materials: combining CO2 use and sol–gel processing

2020 ◽  
Vol 95 (3) ◽  
pp. 693-709
Author(s):  
Florian Günther ◽  
Elton F. S. Lima ◽  
Kelen M. F. Rossi de Aguiar ◽  
Jefferson R. Bearzi ◽  
Mateus B. Simões ◽  
...  
Keyword(s):  
Sol Gel ◽  
Multifunctional Materials ◽  
Gel Processing

Luminescent Properties of Ce Doped LuAG Thin Films Prepared by Pechini Sol–Gel Method

2012 ◽  
Vol 512-515 ◽  
pp. 1516-1519
Author(s):  
Qing Ma ◽  
Si Qing Shen ◽  
Jian Jun Xie ◽  
Fei Zhong Ma ◽  
Ying Shi ◽  
...  
Keyword(s):  
Single Phase ◽  
Sol Gel ◽  
Luminescent Properties ◽  
X Ray Diffraction ◽  
Low Loss ◽  
X Ray ◽  
Display Devices ◽  
Pl Spectra ◽  
Xrd Patterns ◽  
Gel Processing

Compared to phosphors, scintillating films are shown as a better feature for high–resolution display devices with low loss diffusion. Ce 3+ doped lutetium aluminum garnet (Lu3Al5O12, LuAG) scintillating films with different Ce 3+ concentration have been fabricated by Pechini sol–gel processing combined with the spin–coating technique and characterized by X–ray diffraction (XRD) and photoluminescence (PL) under excitation of UV–VIS light. The results of XRD patterns indicated that the specimen under study is a well–crystallized single–phase of cubic structure. Under an excitation of 442nm , it was found that the PL spectra was the typical Ce 3+ emissions located in the 460–650 nm consisting of two emission bands due to the transitions from the lowest 5d excited state (2D) to the 4f ground state of Ce 3+ , which matches well with the sensitivity curve of the Si–photodiode . The luminescent intensity of LuAG: Ce 3+ films varies with the Ce 3+ contents and reaches the maximum at 1.0 mol% doped. With the increase of calcining temperature, the luminescence intensity in the PL spectra of LuAG:Ce 3+ films was found to increased accordingly due to the improved crystallization.

Synthesis of silicon carbide powders from fumed silica powder and phenolic resin

2006 ◽  
Vol 21 (5) ◽  
pp. 1167-1174 ◽  
Author(s):  
Satoru Ishihara ◽  
Hidehiko Tanaka ◽  
Toshiyuki Nishimura
Keyword(s):  
Silicon Carbide ◽  
Fumed Silica ◽  
Single Phase ◽  
Phenolic Resin ◽  
Sol Gel ◽  
Molar Ratio ◽  
Homogeneous Distribution ◽  
Mixing Ratio ◽  
Silica Powder ◽  
Gel Processing

Silicon carbide powders were synthesized by application of sol-gel processing. Fumed silica powder was used as the starting material for the silicon source, and phenolic resin was used for the carbon source. The effects of mixing ratio and difference between hydrophilic and hydrophobic types of fumed silica powders were investigated. The stirred mixtures of fumed silica powders and phenolic resin became apparent sol states owing to homogeneous distribution. SiC powders were formed derived from both the types of fumed silica powders after the gelation and pyrolysis up to 1800 °C. The hydrophilic silica powder was effective to synthesize more homogeneous SiC powders than the hydrophobic type. Single-phase SiC was obtained in the C/Si (molar ratio after pyrolysis at 1000 °C) range between 1.0 and 2.5, while free carbon was contained in the obtained powders of C/Si > 2.5. In contrast, formation of SiC was insufficient, and SiO2 was retained at ratios of C/Si < 1.0.

Sintering and Microstructural Modification of Seeded and Neodymium Doped Lanthanum Hexaaluminate

2016 ◽  
Vol 835 ◽  
pp. 237-250 ◽  
Author(s):  
P. Jana ◽  
P.S. Jayan ◽  
S. Mandal ◽  
Koushik Biswas
Keyword(s):  
Rare Earth ◽  
Heterogeneous Nucleation ◽  
Single Phase ◽  
Sol Gel ◽  
Phase Evolution ◽  
Neodymium Oxide ◽  
Lower Temperature ◽  
House Structure ◽  
Gel Processing ◽  
Lanthanum Hexaaluminate

The effect of (i) heterogeneous nucleation by seeding or (ii) doping with neodymium on the formation of lanthanum hexaaluminate was studied during sol to gel conversion. The resultant dried gels were calcined at various temperatures starting from 1100°C to 1600°C for 2 h to study the phase evolution and microstructure.The combined effects of advanced sol gel processing and heterogeneous nucleation promoted the formation of lanthanum hexaaluminate phase at lower temperature (1200°C) than the conventional routes (1300°C). Lanthanum hexaaluminate phase was detected at 1200°C and 1300°C in seeded gel (SG) and unseeded gel (UG), respectively. Heterogeneous nucleation of SG decreases the temperature of formation of lanthanum hexaaluminate by 100°C. Single phase lanthanum hexaaluminate was formed at 1600°C in seeded gel whereas trace of lanthanum monoaluminate phase was still present in UG even at 1600°C.On the doped ones, randomly grown platelets of lanthanum magnesium hexaaluminate form a porous interlocking structure. Presence of various percentages of neodymium oxide significantly modifies the porous interlocking microstructure into self-reinforced, card-house like microstructure. Platelets of rare earth rich magnesium hexaaluminate were grown preferentially more than the stoichiometric rare earth magnesium hexaaluminate at elevated temperature greater than 1450°C. Rare earth rich magnesium hexaaluminate platelets formed the skeleton of a card house structure and the tiny platelets of stoichiometric rare earth magnesium hexaaluminate fill the rest. Lattice parameters of the hexagonal unit cell (c and a) decrease, relative density increases and pore size distribution remained almost unaltered with the increment of doping concentration.

Synthesis of SrRuO3 by Sol-Gel Processing

1998 ◽  
Vol 548 ◽  
Author(s):  
Y. Wu ◽  
S. Zamani ◽  
G. Z. Cao
Keyword(s):  
Low Temperatures ◽  
Single Phase ◽  
Sol Gel ◽  
Partial Hydrolysis ◽  
Ceramic Powders ◽  
Processing Methods ◽  
Conductive Oxide ◽  
Petri Dishes ◽  
Gel Processing ◽  
Hydrolysis Of

ABSTRACTElectronic conductive oxide SrRuO3has been synthesized by sol-gel processing. Various precursors were tested and four different processing methods were developed. Stable SrRuO3sols were obtained using these four processing methods with various precursors. It was found that partial hydrolysis of strontium precursors was required to achieve a cross-condensation of ruthenium and strontium, so as to obtain a single phase SrRuO3perovskite at relatively low temperatures. The stable sols were either poured into petri-dishes to form xerogels or dip-coated on substrates to form thin films. Single phase SrRuO3perovskite was obtained after heat-treatment at 800 °C or higher temperatures. TGA/DTA, XRD and SEM were applied to characterize sol-gel derived SrRuO3ceramic powders and films.

Effect of MCl (M = Na, K) addition on microstructure and electrical conductivity of forsterite

2020 ◽  
Vol 92 (1) ◽  
pp. 10901
Author(s):  
Saloua El Asri ◽  
Hamid Ahamdane ◽  
Lahoucine Hajji ◽  
Mohamed El Hadri ◽  
Moulay Ahmed El Idrissi Raghni ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Electrical Conductivity ◽  
Single Phase ◽  
Sol Gel ◽  
Complex Impedance ◽  
Transmission Spectra ◽  
Electrical Measurements ◽  
Cation Type ◽  
Edx Analyses ◽  
The Fourier Transform

Forsterite single phase powder Mg2SiO4 was synthesized by sol–gel method alongside with heat treatment, using two different cation alkaline salts MCl as mineralizers (M = Na, K) with various mass percentages (2.5, 5, 7.5, and 10 wt.%). In this work, we report on the effect of the cation type and the added amount of used mineralizer on microstructure and electrical conductivity of Mg2SiO4. The formation of forsterite started at 680–740  °C and at 630–700  °C with KCl and NaCl respectively, as shown by TG-DTA and confirmed by XRD. Furthermore, the Fourier transform infrared (FTIR) transmission spectra indicated bands corresponding to vibrations of forsterite structure. The morphology and elemental composition of sintered ceramics were examined by SEM-EDX analyses, while their densities, which were measured by Archimedes method, increased with addition of both alkaline salts. The electrical measurements were performed by Complex Impedance Spectroscopy. The results showed that electrical conductivity increased with the addition of both mineralizers, which was higher for samples prepared with NaCl than those prepared with KCl.

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