Thermal Decomposition and Crystallization of Aqueous Sol-gel Derived Zirconium Acetate Gels Occurring During the Preparation of Ceramic Coatings PDF Download

Author: Araldina Corina Geiculescu
Publisher:
ISBN:
Category :
Languages : en
Pages : 442

View

Book Description

Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 856

View

Book Description

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 28

View

Book Description
We have investigated the effects of precursor nature and heat treatment schedule on the densification and crystallization behavior of sol-gel derived zirconia thin films. Precursor solutions were prepared from n-propanol, zirconium (IV) n-propoxide, and either acetic acid, or 2,4-pentanedione (acac) and water additions. By controlling the ligand type and ligand-to-metal ratio, we were able to prepare films which displayed significant differences in densification behavior. We attribute the dissimilarity in densification to variations in the nature of the as-deposited films, as influenced by ligand type and concentration. While the acac- derived film was a physical gel, (i.e., a physical aggregation of the oligomeric species), the acetic acid-derived film, which exhibited less consolidation, was a chemical gel that could not be redissolved in the parent solvent. Films prepared with large acac/metal ratios and small water additions exhibited minimal crosslinking at 25°C, displayed the greatest consolidation ((approximately)86% shrinkage) and the highest refractive index (n = 2.071) when heat treated. These results indicate the importance that M-O-M bonds (crosslinks) formed at low temperature can have on densification behavior. We also report on the effects of heat-treatment schedules and ramp rates on densification behavior. All of the films of the present study crystallized into the cubic phase, at temperatures ranging from (approximately)400°C to greater than 700°C, depending on the heating rate.

Author: American Ceramic Society
Publisher:
ISBN:
Category : Ceramics
Languages : en
Pages : 1252

View

Book Description

Author:
Publisher:
ISBN:
Category : Ceramic materials
Languages : en
Pages : 658

View

Book Description

Author: Charles David Edward Lakeman
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
Research is reported for the relationships that exist between processing, composition and structure development, and properties, for sol-gel derived $rm Pb(Zrsb{0.53}Tisb{0.47})Osb3$ (PZT) thin layers. Emphasis was placed on the effect of thermal processing conditions on the gel-to-ceramic conversion. In addition, the effects of interfacial reactions, and residual stresses on the measured properties were also considered. The purpose of the work was to contribute to the fundamental understanding of processes which occur during the high temperature treatment of sol-gel derived thin layers. The gel-to-ceramic conversion was monitored by transmission electron microscopy, diffuse reflectance infrared spectroscopy, and X-ray diffraction. As-deposited coatings were found to be amorphous with compositional heterogeneity at the nanoscale. This is the first report which identifies the nature of the compositional heterogeneity. Structural rearrangement occurred during thermal processing and, for slow heating (50$spcirc$C/min), the coatings approached compositional uniformity on crystallization into the perovskite phase. However, for faster heating rates, the degree of structural rearrangement was limited, thereby decreasing the shrinkage normal to the coating, and crystallization was shifted to a higher temperature. Also, for very rapid thermal processing (5000$spcirc$C/min), compositional heterogeneity was retained in the coatings after crystallization. An apparent dependence on thickness for the properties for ferroelectric PZT thin layers was observed. It was confirmed that a cover coat of a PbO-precursor deposited onto the gel-derived layers prior to firing compensated for the volatilization of PbO which occurred during heating, resulting in coatings which displayed improved properties over those prepared without a cover coat. A simple series capacitor model was investigated to interpret the data. SIMS and TEM analyses indicated that diffusion of some of the species resulted in the formation of a sub-electrode nano-crystalline phase, however, no second phases were observed between the electrode and the coating. Measurements of the residual stress state in PZT coatings deposited onto platinized silicon substrates, and fired at 700$spcirc$C, indicated a tensile stress of approximately +200MPa in the plans of the coating. Thermal expansion mismatch stresses were calculated to be of the order of $-$300MPa in compression, indicating that large tensile stresses were generated during constrained shrinkage.

Author: Lisa C. Klein
Publisher: Springer Science & Business Media
ISBN: 1461527503
Category : Technology & Engineering
Languages : en
Pages : 589

View

Book Description
Sol--Gel--Optics encompasses numerous schemes for fabricating optical materials from gels -- materials such as bulk optics, optical waveguides, doped oxides for laser and nonlinear optics, gradient refractive index (GRIN) optics, chemical sensors, environmental sensors, and `smart' windows. Sol--Gel--Optics: Processing and Applications provides in-depth coverage of the synthesis and fabrication of these materials and discusses the optics related to microporous, amorphous, crystalline and composite materials. The reader will also find in this book detailed descriptions of new developments in silica optics, bulk optics, waveguides and thin films. Various applications to sensor and device technology are highlighted. For researchers and students looking for novel optical materials, processing methods or device ideas, Sol--Gel--Optics: Processing and Applications surveys a wide array of promising new avenues for further investigation and for innovative applications. (This book is the first in a new subseries entitled `Electronic Materials: Science and Technology).

Author: Rajat Banerjee
Publisher: Elsevier
ISBN: 0857093495
Category : Technology & Engineering
Languages : en
Pages : 617

View

Book Description
Ceramic nanocomposites have been found to have improved hardness, strength, toughness and creep resistance compared to conventional ceramic matrix composites. Ceramic nanocomposites reviews the structure and properties of these nanocomposites as well as manufacturing and applications.Part one looks at the properties of different ceramic nanocomposites, including thermal shock resistance, flame retardancy, magnetic and optical properties as well as failure mechanisms. Part two deals with the different types of ceramic nanocomposites, including the use of ceramic particles in metal matrix composites, carbon nanotube-reinforced glass-ceramic matrix composites, high temperature superconducting ceramic nanocomposites and ceramic particle nanofluids. Part three details the processing of nanocomposites, including the mechanochemical synthesis of metallic–ceramic composite powders, sintering of ultrafine and nanosized ceramic and metallic particles and the surface treatment of carbon nanotubes using plasma technology. Part four explores the applications of ceramic nanocomposites in such areas as energy production and the biomedical field.With its distinguished editors and international team of expert contributors, Ceramic nanocomposites is a technical guide for professionals requiring knowledge of ceramic nanocomposites, and will also offer a deeper understanding of the subject for researchers and engineers within any field dealing with these materials. - Reviews the structure and properties of ceramic nanocomposites as well as their manufacturing and applications - Examines properties of different ceramic nanocomposites, as well as failure mechanisms - Details the processing of nanocomposites and explores the applications of ceramic nanocomposites in areas such as energy production and the biomedical field

Author: Alain C. Pierre
Publisher: Springer Nature
ISBN: 3030381447
Category : Technology & Engineering
Languages : en
Pages : 716

View

Book Description
This book presents a broad, general introduction to the processing of Sol-Gel technologies. This updated volume serves as a general handbook for researchers and students entering the field. This new edition provides updates in fields that have undergone rapid developments, such as Ceramics, Catalysis, Chromatropgraphy, biomaterials, glass science, and optics. It provides a simple, compact resource that can also be used in graduate-level materials science courses.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 52

View

Book Description
The effect of water of hydrolysis on nucleation, crystallization, and microstructural development of sol-gel derived single phase LiNbO3 thin films has been studied using transmission electron microscopy (TEM), atomic force microscopy (AFM), x-ray diffraction (XRD), and differential lithium and niobium in ethanol was used for the preparation of sol. DSC results indicated that adding water to the solution for hydrolysis of the double ethoxides lowered the crystallization temperature from 500 deg C (no water) to 390 deg C (2 moles water per mole ethoxide). The amount of water has no effect on the short range order in amorphous LiNbO3 gels but rendered significant microstructural variations for the crystallized films. AFM studies indicated that surface roughness of dip coated films increased with increasing water of hydrolysis.