Synthesis of Nanocrystalline Powders for Oxide Ceramics by Microwave Plasma Pyrolysis

1992 ◽  
Vol 269 ◽  
Author(s):  
Dieter Vollath ◽  
Ravi Varma ◽  
Kurt E. Sickafus
Keyword(s):  
Microwave Plasma ◽  
Nanocrystalline Powders ◽  
Oxide Ceramics ◽  
Ceramic Powders ◽  
Proper Selection ◽  
Experimental Conditions ◽  
Grain Sizes ◽  
Plasma Pyrolysis ◽  
Cubic Structure ◽  
Selection Of

ABSTRACTPyrolytically prepared ceramic powders usually exhibit excellent homogeneity and small grain sizes. The energy efficiency of those methods for synthesis is, particularly in systems heated electrically, very poor. The situation can be improved drastically using a microwave plasma as a source of energy. This has been confirmed by the synthesis of alumina- and zirconia-based ceramic powders for which an efficiency of more than 80% was found. Aqueous solutions of nitrates of zirconium, yttrium, and aluminum were used as starting materials. Electron microscopy revealed that, through proper selection of the experimental conditions, it is possible to obtain nanocrystalline powders with cubic structure. Because of the extreme conditions during synthesis, it is possible to prepare solid solutions in systems without solubility.

The Use of Colour Codes in Ceramics Build-up for Achievement Esthetic Anterior Restorations

2017 ◽  
Vol 68 (5) ◽  
pp. 953-956
Author(s):  
Radu Rica ◽  
Ionela Teodora Dascalu ◽  
Mihaela Jana Tuculina ◽  
Ana Maria Rica ◽  
Oana Andreea Diaconu ◽  
...  
Keyword(s):  
Chemical Durability ◽  
Base Layer ◽  
Dental Ceramics ◽  
Ceramic Powders ◽  
Successful Result ◽  
Proper Selection ◽  
Dental Ceramic ◽  
Dental Technician ◽  
Ceramic Restorations ◽  
Selection Of

The ability to mimic the optical characteristics of enamel and dentin, the excellent biocompatibility and the chemical durability of dental ceramics are the reason reasons why this topic is considered of great importance in dentistry. The aim of this study was to highlight the differences during the process of manufacturing anterior esthetic restorations, i.e. the proper selection of color shades of dental ceramics and their correct deposition.Techniques for performing aesthetic ceramic restorations are influenced by the experience of the dental technician and their skills in realizing the restoration, which should be as little complicated, even if the dental ceramic powders has coded shades of color. Some dental technicians prefer their own color labels in order to facilitate their work and to modify or to highlight some effects of the powders, during the dental ceramics build-up. Naturalness of eight anterior restorations was obtained by alternating the opalescent base layer of the dental ceramic and the fluorescence of crystalline layers subsequently applied over opaque. Different translucent type of ceramic layers was used in order to create the true aspect of the incisal area, with a natural halo appearance. The increasing expectations of the patients in aesthetic restoration of anterior area of dental arches demand a complex build-up of the porcelain layers and this technique requires that the dental technician to possess special skills for obtaining a successful result.

Electron Microscopy Study on Zirconia and Alumina Ceramic Powders Synthesized by Microwave Plasma Pyrolysis

1992 ◽  
Vol 269 ◽  
Author(s):  
Kurt E. Sickafus ◽  
Dieter Vollath ◽  
Ravi Varma
Keyword(s):  
Electron Microscopy ◽  
Microwave Plasma ◽  
Hollow Spheres ◽  
Microscopy Study ◽  
Dark Field ◽  
Ternary Oxide ◽  
Ceramic Powders ◽  
Pure Alumina ◽  
Pure Zirconia ◽  
Plasma Pyrolysis

ABSTRACTMorphology, chemistry and microstructure of zirconia and alumina based ceramic powders synthesized by microwave plasma pyrolysis were studied by transmission electron microscopy. Electron diffraction was used to determine the phases present, while conventional bright field and dark field imaging were used to characterize grain size and density variations. Materials analyzed in this study were either pure zirconia, pure alumina, or a ternary zirconia-yttria-alumina oxide. Solid spheres, hollow spheres, and fragments of hollow spheres were observed. All three modifications of zirconia were observed in the pure zirconia powder. In alumina, the predominant phase was cubic, gamma alumina. In the ternary oxide, most structures exhibited cubic zirconia diffraction patterns. Energy dispersive x-ray spectroscopy revealed chemical inhomogeneities in the ternary oxide powder.

Meriel Talbot and the Society for the Overseas Settlement of British Women, 1919–1937

2017 ◽  
Vol 10 (1) ◽  
pp. 32-52
Author(s):  
Bonnie White
Keyword(s):  
Domestic Service ◽  
Agricultural Workers ◽  
British Government ◽  
Early Failure ◽  
Proper Selection ◽  
Domestic Servants ◽  
Female Workers ◽  
Female Migrants ◽  
Post War ◽  
Selection Of

In 1917 the British government began making plans for post-war adjustments to the economy, which included the migration of surplus women to the dominions. The Society for the Overseas Settlement of British Women was established in 1920 to facilitate the migration of female workers to the dominions. Earlier studies have argued that overseas emigration efforts purposefully directed women into domestic service as surplus commodities, thus alleviating the female ‘surplus’ and easing economic hardships of the post-war period. This article argues that as Publicity Officer for the SOSBW, Meriel Talbot targeted women she believed would be ideal candidates for emigration, including former members of the Women's Land Army and affiliated groups. With the proper selection of female migrants, Talbot sought to expand work opportunities for women in the dominions beyond domestic service, while reducing the female surplus at home and servicing the connection between state and empire. Dominion authorities, whose demands for migrant labour vacillated between agricultural workers during the war years and domestic servants after 1920, disapproved of Talbot's efforts to migrate women for work in agriculture. Divergent policies led to the early failure of the SOSBW in 1923.

scholarly journals Design Concepts for NiTiNOL Wires to Function as a Sensor

2021 ◽  
Author(s):  
D. Josephine Selvarani Ruth
Keyword(s):  
Shape Memory Alloy ◽  
Electrical Resistance ◽  
Nickel Titanium ◽  
The Other ◽  
Sensing Element ◽  
Proper Selection ◽  
Design Concepts ◽  
Mechanical Element ◽  
Selection Of ◽  
Inverse Hysteresis

AbstractNickel Titanium Naval Ordinance Laboratory (NiTiNOL) is widely called as a shape memory alloy (SMA), a class of nonlinear smart material inherited with the functionally programmed property of varying electrical resistance during the transformation enabling to be positioned as a sensing element. The major challenge to instrument the SMA wires is to suppress the wires’ nonlinearity by proper selection of two important factors. The first factor is influenced by the mechanical biasing element and the other is to identify the sensing current for the sensing device (SMA wires + biasing). This paper focuses on developing SMA wires for sensing in different orientation types and configurations by removing the non-linearity in the system’s output by introducing inverse hysteresis to the wires through the passive mechanical element.

A Non-Normality Measure of the Condition Number for Monitoring and Control

1997 ◽  
Vol 119 (2) ◽  
pp. 217-222 ◽  
Author(s):  
Kunsoo Huh ◽  
Jeffrey L. Stein
Keyword(s):  
Optimal Control ◽  
Condition Number ◽  
Minimization Problem ◽  
Monitoring And Control ◽  
Proper Selection ◽  
Modal Structure ◽  
L2 Norm ◽  
And Control ◽  
Normality Measure ◽  
Selection Of

Because the behavior of the condition number can have highly steep and multi-modal structure, optimal control and monitoring problems based on the condition number cannot be easily solved. In this paper, a minimization problem is formulated for κ2(P), the condition number of an eigensystem (P) of a matrix in terms of the L2 norm. A new non-normality measure is shown to exist that guarantees small values for the condition number. In addition, this measure can be minimized by proper selection of controller and observer gains. Application to the design of well-conditioned controller and observer-based monitors is illustrated.

scholarly journals Influence of the Chemical Composition on Electrical Conductivity and Mechanical Properties of the Hypoeutectic Al-Si-Mg Alloys

2016 ◽  
Vol 61 (1) ◽  
pp. 353-360 ◽  
Author(s):  
B. Dybowski ◽  
J. Szymszal ◽  
Ł. Poloczek ◽  
A. Kiełbus
Keyword(s):  
Mechanical Properties ◽  
Electrical Conductivity ◽  
Chemical Composition ◽  
Aluminium Alloys ◽  
Mg Alloys ◽  
High Electrical Conductivity ◽  
Transportation Industry ◽  
Proper Selection ◽  
Ti Addition ◽  
Selection Of

Due to low density and good mechanical properties, aluminium alloys are widely applied in transportation industry. Moreover, they are characterized by the specific physical properties, such as high electrical conductivity. This led to application of the hypoeutectic Al-Si-Mg alloys in the power generation industry. Proper selection of the alloys chemical composition is an important stage in achievement of the demanded properties. The following paper presents results of the research on the influence of alloys chemical composition on their properties. It has been revealed that Si and Ti addition decreases electrical conductivity of the Al-Si-Mg alloys, while Na addition increases it. The mechanical properties of the investigated alloys are decreased by both silicon and iron presence. Sodium addition increases ductility of the Al-Si-Mg alloys.

scholarly journals Hydrogen Gas Sensors Fabricated on Atomically Flat 4H-SiC Webbed Cantilevers

2008 ◽  
Vol 600-603 ◽  
pp. 1199-1202 ◽  
Author(s):  
Philip G. Neudeck ◽  
David J. Spry ◽  
Andrew J. Trunek ◽  
Laura J. Evans ◽  
Liang Yu Chen ◽  
...  
Keyword(s):  
Gas Sensors ◽  
Rapid Detection ◽  
Hydrogen Gas ◽  
Current Gain ◽  
Proper Selection ◽  
Hydrogen Gas Sensors ◽  
Sensor Current ◽  
Atomically Flat ◽  
Initial Results ◽  
Selection Of

This paper reports on initial results from the first device tested of a “second generation” Pt-SiC Schottky diode hydrogen gas sensor that: 1) resides on the top of atomically flat 4H-SiC webbed cantilevers, 2) has integrated heater resistor, and 3) is bonded and packaged. With proper selection of heater resistor and sensor diode biases, rapid detection of H2 down to concentrations of 20 ppm was achieved. A stable sensor current gain of 125 ± 11 standard deviation was demonstrated during 250 hours of cyclic test exposures to 0.5% H2 and N2/air.

Preparation and Characterization of ZrO2 Nanopowders for Solid Oxide Fuel Cells

2010 ◽  
Vol 105-106 ◽  
pp. 660-663 ◽  
Author(s):  
Yun Xia Chen ◽  
Xing Yong Gu ◽  
Chun’e Cao ◽  
Yang Huang
Keyword(s):  
Solid Oxide Fuel Cells ◽  
Lattice Distortion ◽  
Raw Materials ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Experimental Conditions ◽  
Hydrothermal Temperature ◽  
Grain Sizes ◽  
Xrd And Tem

ZrOCl2•6H2O and Y(NO3)3 were used as raw materials to fabricated Y2O3 stabilized ZrO2(YSZ) nanopowders by hydrothermal method. The addition of Y2O3, different precipitants, different hydrothermal temperatures and times were studied. XRD and TEM were employed to characterize phase compositions, grain sizes and lattice parameters of the as-prepared YSZ nanopowders. The results show that less than 10nm and well crystallized cubic YSZ were obtained under a certain experimental conditions. Different precipitants affect the formation of precursors and final products. The addition of NaOH is benefit to the growth of YSZ crystals with the max grain size and the minimum lattice distortion among the three kinds of precipitants. Amorphous YSZ powders are obtained at lower hydrothermal temperature of 150°Cfor longer treating time of 6h. However, when the hydrothermal temperature is elevated at 180°C, well crystallized YSZ powders are prepared only treated for 2h.

Available Energy: I. Gibbs Revisited; II. Gibbs Extended

1999 ◽  
Author(s):  
Richard A. Gaggioli ◽  
David H. Richardson ◽  
Anthony J. Bowman ◽  
David M. Paulus
Keyword(s):  
The Body ◽  
Nonequilibrium Condition ◽  
Balance Equations ◽  
Proper Selection ◽  
Additive Property ◽  
Property Relations ◽  
Available Energy ◽  
Dead State ◽  
Energy Equilibrium ◽  
Selection Of

Abstract The concept of available energy, as defined by Gibbs (1873b) is revisited. He gave representations of available energy for two circumstances. The first was the available energy of a “body,” for the case when a body, alone, is in a nonequilibrium condition and therefore has energy available. In turn, he presented the available energy of “the body and medium,” for the energy which is available because a body is not in equilibrium with some arbitrarily specified medium. Gibbs’ representations were graphical. Since Gibbs, representations with formulas have been developed and are common, for the “available energy of body and medium.” Gaggioli (1998a, b) has developed formulas which are more general, to represent “the available energy of the body (alone)” and to assign an exergy to subsystems of the body as a measure of each sub-system’s contribution to the available energy. In contrast to the available energy, exergy is an additive property, so that balance equations can be written. And the formulas are independent from any “medium,” which is important both theoretically and practically — because of its relevance to proper selection of “the dead state.” These issues are discussed and extended, after reviewing Gibbs development of available energy and additional concepts which he introduced, such as “available vacuum” and “capacity for entropy.” It is argued that these “availabililty” and “capacity” concepts are all equivalent to one another. In turn, because of interconvertability, it is seen that available energy is something more fundamental than “maximum useful work.” Furthermore, it is illustrated that available energy, equilibrium and stability, and thermostatic property relations are relative, to “constraints.”

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