CO 2 (10.6 μm) laser for high tech ceramic materials production

2006 ◽  
Author(s):  
A. Casas Bedoya ◽  
H. A. Garcia Mejia ◽  
C. Goyes ◽  
E. Solarte
Keyword(s):  
Ceramic Materials ◽  
High Tech

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.

Importance of chemistry in high-tech ceramics design

2002 ◽  
Vol 74 (11) ◽  
pp. 2137-2144 ◽  
Author(s):  
P. Šajgalík
Keyword(s):  
Fracture Toughness ◽  
Silicon Carbide ◽  
Silicon Nitride ◽  
Liquid Phase ◽  
Grain Boundary ◽  
Ceramic Materials ◽  
High Tech ◽  
Polycrystalline Ceramics ◽  
Sintered Silicon

This paper deals with the role of chemistry in the design of high-tech ceramic materials. Grain boundary composition of polycrystalline ceramics dictates the hardness fracture toughness and creep resistance of liquid-phase sintered silicon nitride and silicon carbide materials.

A Ceramic Flat Slide Valve for Hydraulic Applications

2019 ◽  
Author(s):  
Stefan Aengenheister ◽  
Chao Liu ◽  
Christoph Broeckmann ◽  
Katharina Schmitz
Keyword(s):  
Service Life ◽  
Ceramic Materials ◽  
Slide Valve ◽  
High Tech ◽  
Main Stage ◽  
Flow Channels ◽  
Linear Behavior ◽  
Current Design ◽  
Pressure Compensation ◽  
Spool Valves

Abstract With a flat slide valve concept, a reduction in leakage and an increase in service life could be achieved compared to conventional piston spool valves. In order to achieve a reduction in leakage flows and guarantee the adjustability of the valves at the same time, a correct design of the pressure compensation is essential. The level of force depends on the operating point of the valve and the position of the slider. Due to the design of the flat slide valve, it is possible to use ceramic semi-finished products for the main stage, which consists of control plates and a slide plate. The geometries are simple enough to be inexpensively manufactured with sufficient accuracy from a ceramic pre-product using laser cutting technology. High-tech ceramics are a promising material, which can contribute to an improvement of the performance of the valves. The higher resistance of ceramic materials to abrasive wear further increases the service life of the valves. Furthermore, ceramic materials show lower friction coefficients compared to metallic materials, which is of great importance for the concept of the flat slide valve due to the sliding of the plates on top of each other. However, at the same time the use of ceramics, which are rarely used in hydraulics at the moment, means that the design must be appropriate to the material and must be taken into account when designing the main valve stage. This article presents the concept of the flat slide valve for a proportional 4/3-way valve. Therefore, the design of the pressure compensation is shown and the current design of the main valve stage is presented. This includes the design of the flow channels, which has to be suitable for ceramic materials. The preliminary design of the flow channels were executed with CFD-simulations. With the shown design the function of a 4/3-way valve, known from piston spool valves, can be implemented with a linear behavior between slide plate deflection and opening cross section.

scholarly journals Ceramics and its Importance

2013 ◽  
Vol 4 ◽  
pp. 80-82 ◽  
Author(s):  
Mitra Mani Subedi
Keyword(s):  
Space Shuttle ◽  
Electronic Devices ◽  
Ceramic Materials ◽  
High Tech ◽  
New Materials ◽  
Ceramic Tiles ◽  
Daily Lives

The term "ceramic" once referred only to clay-based materials. However, new generations of ceramic materials have tremendously expanded the scope and number of possible applications. Many of these new materials have a major impact on our daily lives and on our society. Ceramics has advanced far beyond its beginnings in clay pottery. Ceramic tiles cover the space shuttle as well as our kitchen floors. Ceramic electronic devices make possible high-tech instruments for everything from medicine to entertainment. Clearly, ceramics are our window to the future.The Himalayan Physics Vol. 4, No. 4, 2013 Page: 80-82 Uploaded date: 12/23/2013 

The Use of Mechanical Property Measurements to Characterize Gels and Gelation Processes

1991 ◽  
Vol 248 ◽  
Author(s):  
Y. Yang ◽  
N. Ichise ◽  
Z. Li ◽  
Q. Yuan ◽  
J. E. Mark ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Phenol Formaldehyde ◽  
Structural Characteristics ◽  
Sol Gel ◽  
Ceramic Materials ◽  
Organic Polymer ◽  
High Tech ◽  
Aging Effects ◽  
Cross Links ◽  
Induction Times

AbstractThere are a variety of gels (highly swollen solids) that are of considerable interest to polymer scientists, materials scientists, and ceramists. One type consists of typical organic polymers such as polyethylene or polystyrene, in networks which are formed by means of physical cross links, such as crystallites or physical aggregates. Such gels are thermoreversible in that liquefaction occurs upon heating. Another type consists of chain-like structures permanently bonded into covalent networks. These permanently branched and cross-linked chains can be either organic (phenol-formaldehyde resins, epoxies, etc.), or inorganic [silica (SiO2), titania (TiO2), zirconia (ZrO2), etc.] Both the organic and inorganic covalent types have been used to prepare aerogels, and the inorganic ones are now much used to prepare high-tech ceramics by the new sol-gel route.In the case of the thermoreversible, organic polymer gels, moduli can be measured as a function of concentration, temperature, and structural characteristics of the polymer (molecular weight, molecular weight distribution, and nature and degree of any chain branching). Such equilibrium results give information on the nature of the gels, including the influence of morphology, and the presence of dangling-chain irregularities. Measurements carried out as a function of time, for example, on polyethylene homopolymers and copolymers, can give information about their gelation kinetics.In the case of the ceramic materials, the evolution of the shear modulus with time is very useful in establishing induction times, rates of gelation, and aging effects. Correlation of such information with results of scattering studies can give much insight into the nature of the sol-gel process.

scholarly journals STRUCTURAL AND MECHANICAL PROPERTIES OF A COMPOSITE MATERIAL BASED ON PARTIALLY STABILIZED ZIRCONIUM DIOXIDE DOPED WITH MAGNESIUM ALUMINATE SPINEL

2021 ◽  
pp. 78-85
Author(s):  
A.V. Sokolov ◽  
◽  
G.I. Deynega ◽  
N.A. Kuzmina ◽  
I.G. Kuzmina ◽  
...  
Keyword(s):  
Thermal Shock ◽  
Zirconium Dioxide ◽  
Chemical Resistance ◽  
Raw Materials ◽  
Ceramic Materials ◽  
High Tech ◽  
Magnesium Aluminate Spinel ◽  
Temperature Changes ◽  
Wide Range ◽  
Stabilized Zirconium Dioxide

Ceramic materials based on zirconia (ZrO2) are high-tech raw materials for structural products used in various fields of technology. ZrO2 has a wide range of application due to its unique strength characteristics, chemical resistance and fire resistance. However, the disadvantage of zirconium ceramics is low resistance to thermal shock, which limits its use in products functioning in conditions of frequent temperature changes. In this paper, we consider the possibility of increasing the resistance to thermal shock of ceramics based on zirconium dioxide, due to the introduction of an aluminum-magnesium spinel additive (MgAl2O4).

Spiritual Healing, Sick Kids and the Law: Inequities in the American Healthcare System

2003 ◽  
Vol 29 (2-3) ◽  
pp. 269-299
Author(s):  
Janna C. Merrick
Keyword(s):  
Medical Science ◽  
Spiritual Healing ◽  
Best Interests ◽  
Legal Rights ◽  
High Tech ◽  
Divine Love ◽  
Religious Minority ◽  
Human Need ◽  
East End ◽  
The Church

Main Street in Sarasota, Florida. A high-tech medical arts building rises from the east end, the county's historic three-story courthouse is two blocks to the west and sandwiched in between is the First Church of Christ, Scientist. A verse inscribed on the wall behind the pulpit of the church reads: “Divine Love Always Has Met and Always Will Meet Every Human Need.” This is the church where William and Christine Hermanson worshipped. It is just a few steps away from the courthouse where they were convicted of child abuse and third-degree murder for failing to provide conventional medical care for their seven-year-old daughter.This Article is about the intersection of “divine love” and “the best interests of the child.” It is about a pluralistic society where the dominant culture reveres medical science, but where a religious minority shuns and perhaps fears that same medical science. It is also about the struggle among different religious interests to define the legal rights of the citizenry.

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.

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