scholarly journals SILICA-BASED CERAMIC MATERIALS FOR INVESTMENT CASTING: THE EFFECT OF ALUMINA NANOPARTICLES

2019 ◽  
pp. 1-9
Author(s):  
Xiao Chen
Keyword(s):  
Investment Casting ◽  
Ceramic Materials ◽  
Alumina Nanoparticles

scholarly journals Synthesis Based on a Preceramic Polymer and Alumina Nanoparticles via UV Lithography for High Temperature Applications

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1140
Author(s):  
Mohammed S. Almeataq ◽  
Eid M. Alosime
Keyword(s):  
Ceramic Materials ◽  
Primary Objective ◽  
Alumina Nanoparticles ◽  
High Tech ◽  
Al2o3 Nanoparticles ◽  
Preceramic Polymers ◽  
Uv Lithography ◽  
Low Thermal Expansion ◽  
Temperature Ranges ◽  
Silicon Based

Because of the increased demand for preceramic polymers in high-tech applications, there has been growing interest in the synthesis of preceramic polymers, including polysiloxanes and alumina. These polymers are preferred because of their low thermal expansion, conformability to surfaces over large areas, and flexibility. The primary objective was to evaluate the aspects of polymer-derived ceramic routs, focusing on the UV lithography process of preceramic polymers and the pyrolyzing properties of the final ceramics. We found that the p(DMS-co-AMS) copolymer was effective in scattering the hydrophilic Al2O3 nanoparticles into the exceedingly hydrophobic solvent. The physico-chemical behavior of characterized copolymers was explored during their pyrolytic transformation into amorphous silicon-based ceramics. The results indicate that an increase of the pyrolysis temperature degraded the Si–O network through the carbothermic reaction of silicon. We also found a rapid elimination of copolymer pores and densification when the temperature increased (1100 to 1200 °C). At different but specific temperature ranges, there are different distinct rearrangement reactions in the conversion of polymer to ceramic; reductions of the melting point (Tm) of the total heat of melting (ΔHm) of the pyrolysis process resulted in the crystallization of ceramic materials; hence, lithography based on pyrolysis properties of preceramic polymers is a critical method in the conversation of polymers.

Functionalisation of Textiles with Nanotechnology

2006 ◽  
Vol 920 ◽  
Author(s):  
Torsten Textor ◽  
Frank Schröter ◽  
Eckhard Schollmeyer
Keyword(s):  
Sol Gel ◽  
Ceramic Materials ◽  
Nano Particles ◽  
Alumina Nanoparticles ◽  
Medical Systems ◽  
Hybrid Polymers ◽  
Organic Hybrid ◽  
Technical Textiles ◽  
Stab Resistance ◽  
Technical Effort

AbstractThe present development of textile market is connected with an ever increasing demand for new functionalities for highly specific applications. At the same time, the industrial supply has been restricted to only a few types of synthetic fibers. Given that background, surface modification became one of the most important topics to create new textiles. Beside other techniques, the functionalisation of fibers by making use of concepts of the nanotechnology is part of our work for several years. Coatings based on nanosols and inorganic-organic hybrid polymers, derived from sol-gel process, have an immense potential for creative modifications of surface properties and can be applied with a comparatively low technical effort and at moderate temperatures. The coatings often combine properties of organic polymers with those of ceramic materials [1-11]. Therefore those hybrid polymers are of an enormous interest for technical textiles. The basic materials offer the opportunity to produce very hard but flexible coatings, especially by filling or modifying the networks with nano-particles. Approaches to modify these systems by various inorganic or organic substances can lead to a huge number of additional functionalities which are increasingly demanded from the textile industries [12-18]. Coatings of a thickness of less then one micron can act as effective barriers against chemical attacks, super-repellent surfaces can be created, or the wear-resistance of textile materials can be improved. Coatings incorporating nanoparticles as employed in sun creams protect sensitive polymers against decomposition due to ultraviolet radiation. Ballistic body wear based on fabrics protects against gun attacks but generally not against knives. For these products, thin coatings based on inorganic-organic hybrid polymers filled with alumina nanoparticles were found to give good stab-resistance. Further approaches deal e.g. with reversible photochromic coatings – coatings that change its color if irradiated with sun light -, (superpara-)magnetic hybrid polymers or medical systems based on porous sol-gel-coatings with immobilized drugs that are released in contact with skin. This paper will focus on approaches to improve ballistic body wear with respect to stab-resistance, UV-protection and water and oil repellence.

Interactions between Superalloys and Mould Materials for Investment Casting of Turbine Blades

2010 ◽  
Vol 70 ◽  
pp. 130-135 ◽  
Author(s):  
Fabrizio Valenza ◽  
Rafal Nowak ◽  
Natalia Sobczak ◽  
Alberto Passerone ◽  
Michele Di Foggia ◽  
...  
Keyword(s):  
Investment Casting ◽  
Gas Turbines ◽  
Sessile Drop ◽  
Turbine Blades ◽  
Casting Process ◽  
Ceramic Materials ◽  
Processing Parameters ◽  
Industrial Gas Turbines ◽  
Materials Used ◽  
Manufacturing Technologies

The need of increased efficiency of industrial gas turbines comes also through the improvement of the composition of superalloys (addition of new solutes) and of the manufacturing technologies involved in the investment casting process of the turbine blades. Thus, the knowledge of the interactions between the ceramic materials used for casting and the molten superalloys must be deepened in order to minimize the formation of internal defects, to improve the casting surface and to optimize finishing and casting operations. In this work, a study of the wetting behaviour of some Ni- or Co -based superalloys, used for the fabrication of turbine blades, has been performed with reference to the interactions of these alloys in the molten state with the silica-aluminate based ceramic materials forming the shell or the core in the casting process. Wettability tests have been performed by means of the sessile drop method at 1500°C; the characterization of the interfaces between the molten drop and the substrates has been made on solidified sessile drop samples by SEM/EDS analysis to check the final characteristics of the interfaces. The results are discussed in terms of chemical interactions in relation to the processing parameters and as a function of the surface and interfacial energetic properties of the systems.

scholarly journals Investment Casting vs Replicast CS Considered in Terms of the Ceramic Mould Making and Dimensional Accuracy of Castings

2014 ◽  
Vol 14 (1) ◽  
pp. 45-48 ◽  
Author(s):  
A. Karwiński ◽  
R. Haratym ◽  
R. Biernacki ◽  
A. Soroczyński
Keyword(s):  
Investment Casting ◽  
Dimensional Accuracy ◽  
Casting Process ◽  
Ceramic Materials ◽  
Fused Silica ◽  
Crystalline Quartz ◽  
Linear Dimensions ◽  
Zirconium Silicate ◽  
Wide Range ◽  
Investment Casting Process

Abstract The article presents an analysis of the applicability of the Replicast CS process as an alternative to the investment casting process, considered in terms of the dimensional accuracy of castings. Ceramic shell moulds were based on the Ekosil binder and a wide range of ceramic materials, such as crystalline quartz, fused silica, aluminosilicates and zirconium silicate. The linear dimensions were measured with a Zeiss UMC 550 machine that allowed reducing to minimum the measurement uncertainty

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

Stress-Induced Ordering in Y203-Stabilized Tetragonal Zr02

1985 ◽  
Vol 43 ◽  
pp. 222-223
Author(s):  
J. Y. Koo ◽  
M. P. Anderson
Keyword(s):  
Electron Diffraction ◽  
Ionic Conduction ◽  
Electron Diffraction Study ◽  
Ceramic Materials ◽  
Bright Field Image ◽  
Transformation Toughening ◽  
Ion Milling ◽  
Thin Foils ◽  
Carbon Coated ◽  
Convergent Beam

Tetragonal Zr02 has been used as a toughening phase in a large number of ceramic materials. In this system, complex diffraction phenomena have been observed and an understanding of the origin of the diffraction effects provides important information on the nature of transformation toughening, ionic conduction, and phase destabilization. This paper describes the results of an electron diffraction study of Y203-stabilized, tetragonal Zr02 polycrystals (Y-TZP).Thin foils from the bulk Y-TZP sample were prepared by careful grinding and cryo ion-milling. They were carbon coated and examined in a Philips 400T/FEG microscope. Fig. 1 shows a typical bright field image of the 100% tetragonal(t) Zr02. The tetragonal structure was identified by both bulk x-ray diffraction and convergent beam electron diffraction (Fig. 2. A local region within a t-Zr02 grain was subjected to an intense electron beam irradiation which caused partial martensitic transformation of the t-Zr02 to monoclinic(m) symmetry, Fig. 3 A.

Analytical and High-Resolution EM Study of Crystalline Phases formed at Metal-Ceramic Interface

1990 ◽  
Vol 48 (2) ◽  
pp. 426-427
Author(s):  
N. Merk ◽  
A. P. Tomsia ◽  
G. Thomas
Keyword(s):  
Cross Section ◽  
Dissimilar Materials ◽  
Ceramic Materials ◽  
Electron Micrograph ◽  
Scanning Electron Micrograph ◽  
Structural Applications ◽  
Metal Ceramic ◽  
The Subject ◽  
Ceramic Compounds ◽  
Scanning Electron

A recent development of new ceramic materials for structural applications involves the joining of ceramic compounds to metals. Due to the wetting problem, an interlayer material (brazing alloy) is generally used to achieve the bonding. The nature of the interfaces between such dissimilar materials is the subject of intensive studies and is of utmost importance to obtain a controlled microstructure at the discontinuities to satisfy the demanding properties for engineering applications . The brazing alloy is generally ductile and hence, does not readily fracture. It must also wett the ceramic with similar thermal expansion coefficient to avoid large stresses at joints. In the present work we study mullite-molybdenum composites using a brazing alloy for the weldment.A scanning electron micrograph from the cross section of the joining sequence studied here is presented in Fig. 1.

Analytical Electron Microscopy of Surface-Modified Ceramics

1985 ◽  
Vol 43 ◽  
pp. 276-279
Author(s):  
P. S. Sklad
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Theoretical Models ◽  
Ceramic Materials ◽  
Solute Concentration ◽  
Second Phase ◽  
Analytical Electron ◽  
Implantation Techniques ◽  
Lattice Damage ◽  
Surface Modified

Over the past several years, it has become increasingly evident that materials for proposed advanced energy systems will be required to operate at high temperatures and in aggressive environments. These constraints make structural ceramics attractive materials for these systems. However it is well known that the condition of the specimen surface of ceramic materials is often critical in controlling properties such as fracture toughness, oxidation resistance, and wear resistance. Ion implantation techniques offer the potential of overcoming some of the surface related limitations.While the effects of implantation on surface sensitive properties may be measured indpendently, it is important to understand the microstructural evolution leading to these changes. Analytical electron microscopy provides a useful tool for characterizing the microstructures produced in terms of solute concentration profiles, second phase formation, lattice damage, crystallinity of the implanted layer, and annealing behavior. Such analyses allow correlations to be made with theoretical models, property measurements, and results of complimentary techniques.

Interface structures in polycrystalline ceramic materials

1986 ◽  
Vol 44 ◽  
pp. 468-471
Author(s):  
K. J. Morrissey
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Physical And Mechanical Properties ◽  
High Resolution Electron Microscopy ◽  
Ceramic Materials ◽  
Polycrystalline Materials ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Interface Structures

Grain boundaries and interfaces play an important role in determining both physical and mechanical properties of polycrystalline materials. To understand how the structure of interfaces can be controlled to optimize properties, it is necessary to understand and be able to predict their crystal chemistry. Transmission electron microscopy (TEM), analytical electron microscopy (AEM,), and high resolution electron microscopy (HREM) are essential tools for the characterization of the different types of interfaces which exist in ceramic systems. The purpose of this paper is to illustrate some specific areas in which understanding interface structure is important. Interfaces in sintered bodies, materials produced through phase transformation and electronic packaging are discussed.

Probing vacancies and structural distortions at individual defects in ceramics using EELS

1996 ◽  
Vol 54 ◽  
pp. 678-679
Author(s):  
D. J. Wallis ◽  
N. D. Browning
Keyword(s):  
Structural Information ◽  
Core Loss ◽  
Nearest Neighbors ◽  
Ceramic Materials ◽  
Scanning Transmission Electron Microscope ◽  
Real Space ◽  
Atomic Scale ◽  
Structure Property ◽  
Scanning Transmission ◽  
Key Issues

In electron energy loss spectroscopy (EELS), the near-edge region of a core-loss edge contains information on high-order atomic correlations. These correlations give details of the 3-D atomic structure which can be elucidated using multiple-scattering (MS) theory. MS calculations use real space clusters making them ideal for use in low-symmetry systems such as defects and interfaces. When coupled with the atomic spatial resolution capabilities of the scanning transmission electron microscope (STEM), there therefore exists the ability to obtain 3-D structural information from individual atomic scale structures. For ceramic materials where the structure-property relationships are dominated by defects and interfaces, this methodology can provide unique information on key issues such as like-ion repulsion and the presence of vacancies, impurities and structural distortion.An example of the use of MS-theory is shown in fig 1, where an experimental oxygen K-edge from SrTiO3 is compared to full MS-calculations for successive shells (a shell consists of neighboring atoms, so that 1 shell includes only nearest neighbors, 2 shells includes first and second-nearest neighbors, and so on).

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