On the mechanism of formation of the granular structure and interfaces in self-reinforced aluminum nitride

2021 ◽  
Vol 2021 (2) ◽  
pp. 63-71
Author(s):  
G. S. Oleynik ◽  
◽  
A. V. Kotko ◽  
Keyword(s):  
Solid Solution ◽  
Aluminum Nitride ◽  
Sintering Temperature ◽  
High Mobility ◽  
Nitrogen Atmosphere ◽  
Width Ratio ◽  
Mechanism Of Formation ◽  
Common Boundary ◽  
Temperature Range ◽  
The Common

Results of an investigation by scanning electron microscopy methods of the microstructure of self-reinforced aluminum nitride obtained on the basis of aluminum nitride powder and containing 3 mass.% oxygen by plasma-chemical synthesis in the temperature range 1700-2000 °C are presented. Initial aluminum nitride was represented by the wurtzite (2H) phase. Samples were obtained by free sintering in a nitrogen atmosphere. It was established that, during sintering of AlN in the indicated temperature range, three microstructural types of the material and six types of interfaces (three types of intergranular and three types of intragranular ones) formed. The features of the microstructure of the materials are fully determined by the development of intergranular crystal-oriented polytype transitions of 2H AlNmultilayer polytypes (MP) in sintering. The sequence of successive structural transformations that determine the development of polytype transitions was established. 1. Formation of initial 2H AlN grains of the solid solution 2H AlN-O. The substitution of nitrogen by oxygen takes place. 2. The development of isomorphous delamination of the solid solution in every grain with the precipitation of an interlayer enriched in oxygen. 3. In interlayers, polytypes consisting of a series of polytypes with different number of layers (MP) form. Such an interlayer has developed base surfaces and propagates from one boundary to another in the grain, which determines the formation of a special structural state of fragments of boundaries, that border interlayers in the direction <hk0>. 4. The high mobility of the indicated fragments of boundaries determines their break-off from the common boundary and formation of a grain nucleus of anisometric (plate-like) shape. This process begins already at a sintering temperature Tsint. = 1800 °C, and, at Tsint. = 2000 °C, polycrystals practically entirely consist of grains of plate-like shape. In this case, with increase in the sintering temperature, the aspect ratio (the length-to-width ratio) of such grains rises. Keywords: aluminum nitride, polytype transformations, grains, microstructure, boundaries, self-reinforcement.

Ethanol conversion over Ga2O3-ZrO2 solid solution: empirical evidences of the reaction pathway, the surface acid–base property, and role of isolated gallium ion

2021 ◽  
Author(s):  
Takashi Yamamoto ◽  
Akihito Kurimoto ◽  
Riona Sato ◽  
Shoki Katada ◽  
Hirotaka Mine ◽  
...  
Keyword(s):  
Solid Solution ◽  
Reaction Pathway ◽  
Ethanol Conversion ◽  
Acid Base ◽  
Base Property ◽  
Temperature Range ◽  
Acid Base Property

Ethanol conversion by Ga2O3-ZrO2 solid solution was examined in the temperature range 573–773 K, and acetone/isobutene formation was confirmed under cofeeding of H2O vapor. The reaction pathway was empirically investigated...

Amorphous Polymeric Dithiazine apDTZ Solid Fouling: Critical Review, Analysis and Solution of an Ongoing Challenge in Triazine-Based Hydrogen Sulphide Mitigation

2021 ◽  
Author(s):  
Grahame Taylor ◽  
Jonathan Wylde ◽  
Walter Samaniego ◽  
Ken Sorbie
Keyword(s):  
Hydrogen Sulphide ◽  
Reaction Pathway ◽  
Theoretical Calculations ◽  
Mechanism Of Formation ◽  
Review Analysis ◽  
Operational Problem ◽  
Depth Study ◽  
The Common ◽  
By Products ◽  
A Current

Abstract Despite attempts to inhibit or avoid the formation of fouling deposits (polymeric amorphous dithiazine or apDTZ for short) from the use of MEA triazine, this remains a major operational problem and limits the use of this most popular and ubiquitous hydrogen sulphide (H2S) scavenger. This paper (a) reviews and summarizes previous work, (b) provides fresh insights into the reaction product and mechanism of formation, (c) proposes an effective method of removal, and (d) proposes some mechanisms of apDTZ digestion. The mechanism of apDTZ formation is discussed and reasoning is provided from a variety of perspectives as to the mechanism of MEA-triazine reaction with H2S. These include basicity and nucleophilic substitution considerations, steric properties and theoretical calculations for electron density. Novel procedures to chemically react with and destroy this solid fouling are presented with an in-depth study and experimental verification of the underlying chemistry of this digestion process. A review of agents to chemically destroy apDTZ is undertaken and a very effective solution has been found in peroxyacetic acid, which is much more powerful and effective than previously suggested peroxides. The structure of amorphous polymeric dithiazine is emphasized and the reason why this fouling cannot be 1,3,5-trithiane is stressed. This work therefore overcomes a current industry misconception by providing insight on two major paradoxes in the reaction pathway; namely i) why the thiadiazine reaction product from tris hydroxyethyl triazine (MEA triazine) is never observed and ii) why does the dithiazine in all cases never progress to the trithiane (3rd sulphur molecule substitution)? The latter issue is probably the biggest misconception in the industry and literature regarding triazine and H2S reactions. Many reasons for this are put forward and the common misconception of "overspent" triazine is refuted. A very effective chemical reaction that results in soluble by-products, counteracting the problems produced by this intractable polymer is found and their composition is proposed and experimentally verified.

scholarly journals The contemporary cartographic presentation of geographical names of objects lying on the border between Poland and the Czech Republic

2015 ◽  
Vol 47 (3) ◽  
pp. 159-174
Author(s):  
Maciej Zych
Keyword(s):  
Czech Republic ◽  
Topographic Maps ◽  
National Register ◽  
The Czech Republic ◽  
Common Boundary ◽  
Mountain Ranges ◽  
Single Region ◽  
The Common ◽  
Mountain Basins ◽  
Own Name

Abstract The aim of this paper is the analysis of the names used on cartographic publications in Poland and the Czech Republic for transboundary geographical objects lying on the common boundary. After the analysis of the Czech and Polish topographic maps that are available on the national geoportals, maps of the divisions into natural regions, and toponymic databases (Polish the National Register of Geographical Names, and Czech Geonames – the Database of geographic names of the Czech Republic) it was established that 360 named geographic objects lie on this boundary. This number includes: 123 hydronyms (names of rivers and other streams), 224 oronyms (139 names of summits, 22 names of mountain passes, 35 names of mountain ranges and ridges, 15 names of highlands, plateaus and uplands, 7 names of mountain basins, valleys and depressions, 3 names of lowlands, and 3 names of rocks), 9 names of forests, 1 name of mountain meadow (alp), and 3 names of tracks. 212 of these objects (59%) have names in both languages – Polish and Czech, however, in 99 cases (47% of objects that have name in both Polish and Czech languages) the Polish and Czech toponyms entirely do not correspond to each other. From the remaining objects 67 (18%) have only the Czech name, and 81 (23%) only the Polish name. In some natural regions, the limits of their ranges set by the Czech and Polish geographers vary widely, for example a single region on one side of the boundary corresponds to two or more regions on other side of the boundary. In other cases illustrations of incorrectness are more sophisticated, like the river that has different course according to the Czech or Polish maps (stream regarded as a main watercourse in one country, which has its own name, in another country is considered as a tributary one with a different name). In the summary, it should be stated that in the large part of the Polish and Czech names of the geographical objects lying on the common boundary were drawn regardless of the names used in the neighboring country.

scholarly journals Flaming Oxidation of Reduced CeO2-ZrO2 Solid Solution in the Near-Room-Temperature Range.

2002 ◽  
Vol 110 (1286) ◽  
pp. 899-903 ◽  
Author(s):  
Tsuyoshi SASAKI ◽  
Yoshio UKYO ◽  
Akihiko SUDA ◽  
Masahiro SUGIURA ◽  
Kotaro KURODA ◽  
...  
Keyword(s):  
Solid Solution ◽  
Room Temperature ◽  
Temperature Range

scholarly journals Formation of porous ceramics using cullet and biological waste of water purification

2011 ◽  
Vol 43 (1) ◽  
pp. 81-94 ◽  
Author(s):  
M. Vlasova ◽  
I. Rosales ◽  
M. Kakazey ◽  
Parra Parra ◽  
R. Guardian
Keyword(s):  
Mechanical Properties ◽  
Water Absorption ◽  
Water Purification ◽  
Sintering Temperature ◽  
Porous Ceramics ◽  
Absorption Capacity ◽  
Water Absorption Capacity ◽  
Red Clay ◽  
Temperature Range

Porous ceramics (bricks) was obtained using red clay, milled fusible cullet, and biowaste in the temperature range 950-1000?C. The high content of water in biowaste eliminates the necessity of introducing water in soft mud forming of bricks. The porosity, water absorption capacity, and mechanical properties of the prepared ceramics depend on content of milled cullet and sintering temperature.

scholarly journals Подавление температурной зависимости длины волны излучения в светодиодных структурах со ступенчатым гетеропереходом II типа InAsSb/InAsSbP

2021 ◽  
Vol 55 (3) ◽  
pp. 277
Author(s):  
А.А. Семакова ◽  
В.В. Романов ◽  
Н.Л. Баженов ◽  
К.Д. Мынбаев ◽  
К.Д. Моисеев
Keyword(s):  
Experimental Data ◽  
Solid Solution ◽  
Active Region ◽  
Molar Fraction ◽  
Type Ii ◽  
Ternary Solid Solution ◽  
Dominant Contribution ◽  
Temperature Range ◽  
Radiative Transitions ◽  
Operating Wavelength

The results of a study of the electroluminescence of the asymmetric InAs/InAs1−ySby/InAsSbP LED heterostructures with a molar fraction of InSb in the ternary solid solution in the active region y=0.15 and y=0.16 in the temperature range 4.2−300 K are presented. Based on the experimental data, the formation of a staggered type II heterojunction at the InAs1−ySby/InAsSbP heterointerface was determined. The dominant contribution of the interface radiative transitions at the type II heterointerface in the temperature range 4.2−180 K was shown, which makes it possible to minimize the temperature dependence of the operating wavelength of the LEDs.

Synthesis of Aluminum Nitride Whiskers Via a Vapor-Liquid-Solid Process

1998 ◽  
Vol 547 ◽  
Author(s):  
Ying Dai ◽  
Ce-Wen Nan
Keyword(s):  
Carbon Black ◽  
Aluminum Nitride ◽  
Aluminum Powder ◽  
Nitrogen Atmosphere ◽  
Processing Conditions ◽  
Vapor Liquid Solid ◽  
Aluminum Powders ◽  
Sem And Tem ◽  
Vapor Liquid Solid Mechanism ◽  
Vapor Liquid

AbstractAluminum nitride whiskers were synthesized by nitridation of commercial aluminum powder at 1623K in a nitrogen atmosphere. The starting materials consisted of aluminum and carbon black. The carbon acted as a barrier between aluminum powders during nitridation and was removed by heating in air at 923K. The whiskers were about 0.5-1μm in diameter and 10-20μm in length. The droplets at the whisker tips showed that the whiskers grew via a vapor-liquid-solid mechanism. The morphologies of the whiskers were studied by means of SEM and TEM. The formation of the whiskers depended on the processing conditions.

Preparation and Microwave Permittivity of SiC-AlN Solid Solution Powders

2007 ◽  
Vol 336-338 ◽  
pp. 310-312
Author(s):  
Xiao Kui Liu ◽  
Wan Cheng Zhou ◽  
Fa Luo ◽  
Dong Mei Zhu
Keyword(s):  
Solid Solution ◽  
High Temperature ◽  
Carbon Black ◽  
Atomic Ratio ◽  
Nitrogen Atmosphere ◽  
Argon Atmosphere ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Microwave Permittivity ◽  
Shs Method

SiC-AlN solid solution powders were prepared from the mixtures of aluminum, silicon and carbon black in a nitrogen atmosphere with preheating self-propagating high temperature synthesis (SHS) method. The powders synthesized with different ratios of Al/Si were mixed with paraffin wax and the microwave permittivity of the mixtures was measured at the frequency of 8.2~12.4GHz. The results were contrasted with that of SiC powders synthesized by preheating SHS in argon and nitrogen atmosphere respectively. The ε′, ε″, and the tgδ (ε″/ε′) of the mixture of SiC prepared in a nitrogen atmosphere are highest, followed with those of the SiC-AlN solid solution powders and the SiC powders prepared in an argon atmosphere. Along with the increase of atomic ratio of Al/Si, the ε′, ε″, and tgδ of SiC-AlN solid solution decrease. We believe that, with the increase of AlN dissolved, the concentration of carriers and the effect of dielectric relaxation will decrease because of the two contrary dopants.

A Simple Practical Criterion to Guarantee Second Order Smoothness of Blend Surfaces

1989 ◽  
Author(s):  
J. Pegna ◽  
F.-E. Wolter
Keyword(s):  
Second Order ◽  
Geometric Design ◽  
Computer Aided Geometric Design ◽  
Common Boundary ◽  
First Order ◽  
Computer Aided ◽  
The Common ◽  
Blend Surfaces ◽  
Continuous Curves ◽  
Order Smoothness

Abstract Computer Aided Geometric Design of surfaces sometimes presents problems that were not envisioned by mathematicians in differential geometry. This paper presents mathematical results that pertain to the design of second order smooth blending surfaces. Second order smoothness normally requires that normal curvatures agree along all tangent directions at all points of the common boundary of two patches, called the linkage curve. The Linkage Curve Theorem proved here shows that, for the blend to be second order smooth when it is already first order smooth, it is sufficient that normal curvatures agree in one direction other than the tangent to a first order continuous linkage curve. This result is significant for it substantiates earlier works in computer aided geometric design. It also offers simple practical means of generating second order blends for it reduces the dimensionality of the problem to that of curve fairing, and is well adapted to a formulation of the blend surface using sweeps. From a theoretical viewpoint, it is remarkable that one can generate second order smooth blends with the assumption that the linkage curve is only first order smooth. This property may be helpful to the designer since linkage curves can be constructed from low order piecewise continuous curves.

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