scholarly journals Alumina-Doped Zirconia Submicro-Particles: Synthesis, Thermal Stability, and Microstructural Characterization

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2856 ◽  
Author(s):  
Gregor Thomas Dahl ◽  
Sebastian Döring ◽  
Tobias Krekeler ◽  
Rolf Janssen ◽  
Martin Ritter ◽  
...  
Keyword(s):  
Grain Growth ◽  
Sol Gel ◽  
Microstructural Characterization ◽  
Alumina Content ◽  
Stabilizing Agents ◽  
Precise Control ◽  
Size And Shape ◽  
Elemental Analyses ◽  
Sol Gel Synthesis ◽  
And Control

Zirconia nanoceramics are interesting materials for numerous high-temperature applications. Because their beneficial properties are mainly governed by the crystal and microstructure, it is essential to understand and control these features. The use of co-stabilizing agents in the sol-gel synthesis of zirconia submicro-particles should provide an effective tool for adjusting the particles’ size and shape. Furthermore, alumina-doping is expected to enhance the particles’ size and shape persistence at high temperatures, similar to what is observed in corresponding bulk ceramics. Dispersed alumina should inhibit grain growth by forming diffusion barriers, additionally impeding the martensitic phase transformation in zirconia grains. Here, alumina-doped zirconia particles with sphere-like shape and average diameters of ∼ 300 n m were synthesized using a modified sol-gel route employing icosanoic acid and hydroxypropyl cellulose as stabilizing agents. The particles were annealed at temperatures between 800 and 1200 ∘ C and characterized by electron microscopy, elemental analysis, and X-ray diffraction. Complementary elemental analyses confirmed the precise control over the alumina content (0–50 mol%) in the final product. Annealed alumina-doped particles showed more pronounced shape persistence after annealing at 1000 ∘ C than undoped particles. Quantitative phase analyses revealed an increased stabilization of the tetragonal/cubic zirconia phase and a reduced grain growth with increasing alumina content. Elemental mapping indicated pronounced alumina segregation near the grain boundaries during annealing.

Formation of Nanostructured Energetic Materials via Modified Sol-Gel Synthesis

2003 ◽  
Vol 800 ◽  
Author(s):  
Jeremy Walker ◽  
Rina Tannenbaum
Keyword(s):  
Succinic Acid ◽  
Propylene Oxide ◽  
Energetic Materials ◽  
Sol Gel ◽  
Interfacial Area ◽  
X Ray Diffraction ◽  
Ph Profile ◽  
Carboxylate Groups ◽  
Sol Gel Synthesis ◽  
And Control

ABSTRACTThis study is concerned with the development of a modified sol-gel synthesis of Fe2O3 xerogels that would allow the design and control of the interfacial area between the oxidant iron oxide matrix and the metal reducing agent, thus optimizing the energetic yield of these highly energetic reactions. The modification consisted in the addition of a new class of di-functional template molecules, such as diamines or di-acids, as gelation agents. pH profile measurements indicated that the mechanism of reaction of propylene oxide and of succinic acid as the gelation agents was fundamentally different. Propylene oxide acts as a proton scavenger, reducing the hydrated iron species to Fe2O3, thus reducing the concentration of protons in the reaction mixture leading to an increase in pH. When succinic acid is used as the gelation agent, a decrease in pH versus time during the reaction indicates the formation of carboxylate ions, thus creating reactive molecules that are capable of stabilizing the Fe2O3 clusters during the growth process. Infrared spectra of the products in both reactions support presence of carboxylate groups in the Fe2O3 xerogels. X-ray diffraction analyses revealed low levels of crystallinity in both products, and the presence of different phases of Fe2O3.

scholarly journals Sol-gel synthesis of α-Al2O3 with enhanced porosity via dicarboxylic acid templating

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Simon Carstens ◽  
Christian Splith ◽  
Dirk Enke
Keyword(s):  
Citric Acid ◽  
Thermal Analyses ◽  
Sol Gel ◽  
Dicarboxylic Acids ◽  
Precise Control ◽  
Sol Gel Process ◽  
Successful Establishment ◽  
The One ◽  
Α Al2o3 ◽  
Sol Gel Synthesis

AbstractOne of the major routes to synthesize macroporous α-Al2O3 is the sol-gel process in presence of templates. Templates include polymers as well as carboxylic acids, such as citric acid. By careful choice of the template, pore diameters can be adjusted between 110 nm and several µm. We report the successful establishment of plain short-chain dicarboxylic acids (DCA) as porogenes in the sol-gel synthesis of macroporous α-Al2O3. By this extension of the recently developed synthesis route, a very precise control of pore diameters is achieved, in addition to enhanced macropore volumes in α-Al2O3. The formation mechanism thereof is closely related to the one postulated for citric acid, as thermal analyses show. However, since branching in the DCA-linked alumina nuclei is not possible, close monomodal pore width distributions are attained, which are accompanied by enhanced pore volumes. This is a significant improvement in terms of controlled enhanced porosity in the synthesis of macroporous α-Al2O3.

scholarly journals Influence of the Microwaves on the Sol-Gel Syntheses and on the Properties of the Resulting Oxide Nanostructures

2020 ◽  
Author(s):  
Luminita Predoana ◽  
Dániel Attila Karajz ◽  
Vincent Otieno Odhiambo ◽  
Irina Stanciu ◽  
Imre M. Szilágyi ◽  
...  
Keyword(s):  
Sol Gel ◽  
Oxide Nanoparticles ◽  
Processing Temperature ◽  
Microwave Assisted ◽  
Oxide Nanostructures ◽  
Gel Technique ◽  
Gel Preparation ◽  
Sol Gel Synthesis ◽  
And Control ◽  
Preparation Techniques

Among the chemical methods in the liquid phase, the sol–gel technique is a versatile and efficient method for pure or doped metal oxide films or powders preparation, showing some advantages over other preparation techniques (high homogeneity, the possibility to introducing dopants in large amount, low processing temperature and control over the stoichiometry). Combining the sol–gel (SG)method with the effect of ultrasounds(US) or microwaves (MW) leads to improving the sol–gel procedure. The microwave-assisted sol–gel method is most frequently used for obtaining nanocrystalline, monodispersed oxide nanoparticles, or to transform amorphous gels into well-crystallized nanopowders. Less studied is the influence of the microwaves on the sol–gel reactions in solutions. The benefit of using microwave-assisted sol–gel preparation highly depends on the reagents used and on the composition of the studied systems. In the present chapter, results on the influence of the microwaves on the chemical reactions that take place during the sol–gel synthesis and on the properties of the resulted samples are discussed.

Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

1988 ◽  
Vol 46 ◽  
pp. 550-551
Author(s):  
R. E. Franck ◽  
J. A. Hawk ◽  
G. J. Shiflet
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Grain Growth ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Second Phase ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

Inorganic-organic Hybrid Materials for Real 3-D Sub-νm Lithography

2003 ◽  
Vol 780 ◽  
Author(s):  
R. Houbertz ◽  
J. Schulz ◽  
L. Fröhlich ◽  
G. Domann ◽  
M. Popall ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Sol Gel ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Hybrid Polymer ◽  
Organic Hybrid ◽  
Two Photon ◽  
Applied Technology ◽  
Scale Structures ◽  
Sol Gel Synthesis

AbstractReal 3-D sub-νm lithography was performed with two-photon polymerization (2PP) using inorganic-organic hybrid polymer (ORMOCER®) resins. The hybrid polymers were synthesized by hydrolysis/polycondensation reactions (modified sol-gel synthesis) which allows one to tailor their material properties towards the respective applications, i.e., dielectrics, optics or passivation. Due to their photosensitive organic functionalities, ORMOCER®s can be patterned by conventional photo-lithography as well as by femtosecond laser pulses at 780 nm. This results in polymerized (solid) structures where the non-polymerized parts can be removed by conventional developers.ORMOCER® structures as small as 200 nm or even below were generated by 2PP of the resins using femtosecond laser pulses. It is demonstrated that ORMOCER®s have the potential to be used in components or devices built up by nm-scale structures such as, e.g., photonic crystals. Aspects of the materials in conjunction to the applied technology are discussed.

Sol-Gel Synthesis, Structure and Optical Properties of Nickel-Manganese Ferrites

2019 ◽  
Vol 11 (3) ◽  
pp. 03021-1-03021-5
Author(s):  
V. S. Bushkova ◽  
◽  
I. P. Yaremiy ◽  
B. K. Ostafiychuk ◽  
N. I. Riznychuk ◽  
...  
Keyword(s):  
Optical Properties ◽  
Sol Gel ◽  
Sol Gel Synthesis ◽  
Nickel Manganese

Sol-Gel Synthesis of Nano-Scale, End-Member Albite Feldspar (NaAlSi3O8)

2021 ◽  
Author(s):  
L.M. Anovitz ◽  
A. Affolter ◽  
M.C. Cheshire ◽  
A.J. Rondinone ◽  
Lawrence F. Allard
Keyword(s):  
Sol Gel ◽  
Nano Scale ◽  
Sol Gel Synthesis

scholarly journals Aqueous Sol-Gel Synthesis of Different Iron Ferrites: From 3D to 2D

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1554
Author(s):  
Justinas Januskevicius ◽  
Zivile Stankeviciute ◽  
Dalis Baltrunas ◽  
Kęstutis Mažeika ◽  
Aldona Beganskiene ◽  
...  
Keyword(s):  
Magnetic Measurements ◽  
Substrate Surface ◽  
Sol Gel ◽  
Synthesis Method ◽  
Xrd Analysis ◽  
Dip Coating ◽  
Yttrium Iron ◽  
Iron Garnet ◽  
Dip Coating Technique ◽  
Sol Gel Synthesis

In this study, an aqueous sol-gel synthesis method and subsequent dip-coating technique were applied for the preparation of yttrium iron garnet (YIG), yttrium iron perovskite (YIP), and terbium iron perovskite (TIP) bulk and thin films. The monophasic highly crystalline different iron ferrite powders have been synthesized using this simple aqueous sol-gel process displaying the suitability of the method. In the next step, the same sol-gel solution was used for the fabrication of coatings on monocrystalline silicon (100) using a dip-coating procedure. This resulted, likely due to substrate surface influence, in all coatings having mixed phases of both garnet and perovskite. Thermogravimetric (TG) analysis of the precursor gels was carried out. All the samples were investigated by X-ray powder diffraction (XRD) analysis. The coatings were also investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Mössbauer spectroscopy. Magnetic measurements were also carried out.

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