Role of liquid sintering aids in the synthesis of SiAlON materials

2021 ◽  
Vol 25 (7) ◽  
pp. 93-97
Author(s):  
B. Mandal ◽  
T. Das
Keyword(s):  
Coming Out ◽  
Chemical Properties ◽  
Ceramic Materials ◽  
Lower Amount ◽  
Oxide Ceramic ◽  
Potential Candidate ◽  
Sintering Aid ◽  
Liquid Sintering ◽  
And Chemical Properties

The synthesis of dense sintered sialon with external additives selected from the system Y2O3-AlN-SiO2 is described. The highest density (3.21g/cc) was achieved at 1750ºC at 90 min of sintering with 5 wt% additive. Non-oxide ceramic materials are increasingly coming out as a potential candidate in engineering applications and among them, sialon is one of the most important materials. β-Sialon was first to be discovered in this class of compounds. It has an excellent combination of thermal, mechanical and chemical properties. The degree of sialon substitution increased with the amount of liquids, the YSiO2N crystalline phase formed concurrently. Strength degradation occurred above 1000ºC.The fracture toughness of the material sintered with a lower amount of sintering aid remained relatively unchanged to 1200ºC.

The Nature of S-N Bonding in Sulfonamides and Related Compounds: Insights into π-Bonding Contributions from Sulfur K-Edge XAS

2020 ◽  
Author(s):  
Tulin Okbinoglu ◽  
Pierre Kennepohl
Keyword(s):  
Density Functional ◽  
Chemical Properties ◽  
Functional Theory ◽  
Rotational Barriers ◽  
Td Dft ◽  
Nitrogen Bonds ◽  
X Ray Absorption ◽  
Related Compounds ◽  
And Chemical Properties

Molecules containing sulfur-nitrogen bonds, like sulfonamides, have long been of interest due to their many uses and chemical properties. Understanding the factors that cause sulfonamide reactivity is important, yet their continues to be controversy regarding the relevance of S-N π bonding in describing these species. In this paper, we use sulfur K-edge x-ray absorption spectroscopy (XAS) in conjunction with density functional theory (DFT) to explore the role of S<sub>3p</sub> contributions to π-bonding in sulfonamides, sulfinamides and sulfenamides. We explore the nature of electron distribution of the sulfur atom and its nearest neighbors and extend the scope to explore the effects on rotational barriers along the sulfur-nitrogen axis. The experimental XAS data together with TD-DFT calculations confirm that sulfonamides, and the other sulfinated amides in this series, have essentially no S-N π bonding involving S<sub>3p</sub> contributions and that electron repulsion and is the dominant force that affect rotational barriers.

Transportation pathways of pesticides in two major watersheds of Istanbul, Turkey

2004 ◽  
Vol 49 (3) ◽  
pp. 165-172 ◽  
Author(s):  
M. Yazgan ◽  
A. Tanik
Keyword(s):  
Chemical Properties ◽  
Surface Flow ◽  
Priority List ◽  
Pesticide Pollution ◽  
Consumption Values ◽  
Annual Consumption ◽  
Agricultural Areas ◽  
Physical And Chemical ◽  
And Chemical Properties

The study covers the investigation of pesticides in terms of consumption, toxicological classification and various intrinsic physical and chemical properties like DT50, KOC, GUS, solubility that describe the important mechanisms prevailing in soil, namely persistence and mobility. These mechanisms help to estimate the transportation pathways of pesticides on soil till they reach the receiving water after being applied on land. Classification is done in three groups, those likely to appear in surface flow, those that appear in groundwater and those that present transient conditions. Such an approach that also takes into account toxicological levels and annual consumption values of pesticides will act as a tool to prepare the priority list of pesticides that need special care during their transportation. The fate of pesticides is a difficult task to solve, however, such a methodology, puts forth a rough estimate on their behavior in spite of uncertainties in many of the parameters describing mechanisms like persistence and mobility. The agricultural areas of two watersheds of Istanbul are selected as target areas to describe the approach, which is also checked with another approach estimating pesticide pollution potential that considers various other properties of pesticides. Almost similar findings are depicted with 85% proximity. The methodology presented in the paper illustrates and emphasizes the significant role of pesticide properties in determining their fate in soil after being applied.

scholarly journals Modelling of pollutants concentrations from the biomass combustion process

2011 ◽  
Vol 32 (4) ◽  
pp. 423-433 ◽  
Author(s):  
Aneta Magdziarz ◽  
Małgorzata Wilk ◽  
Monika Zajemska
Keyword(s):  
Computer Simulation ◽  
Coming Out ◽  
Combustion Process ◽  
Chemical Properties ◽  
Biomass Combustion ◽  
Physical And Chemical Properties ◽  
Influence Of Temperature ◽  
Complex Phenomena ◽  
Physical And Chemical ◽  
And Chemical Properties

Modelling of pollutants concentrations from the biomass combustion process This paper presents possibilities for of numerical modelling of biomass combustion in a commercially available boiler. A sample of biomass was tested with respect to its physical and chemical properties. Thermogravimetry studies of biomass were carried out. Computer simulation makes it possible to analyse complex phenomena which are otherwise difficult to observe. The aim of this work was to model biomass combustion to predict the amount of pollutants generated (NOx, CO, SO2) in the exhaust gases coming out from boilers The calculations were made using the CHEMKIN program. Results of calculations were performed taking into account the influence of temperature, pressure and residence time.

Exploring the role of dosing procedure and chemical properties in in vitro assays using a fish gill cell line

2009 ◽  
Vol 153 (2) ◽  
pp. S89
Author(s):  
Kristin Schirmer ◽  
Katrin Tanneberger ◽  
Nynke I. Kramer ◽  
Frans J.M. Busser ◽  
Joop L.M. Hermens ◽  
...  
Keyword(s):  
Cell Line ◽  
Chemical Properties ◽  
In Vitro Assays ◽  
Fish Gill ◽  
Gill Cell ◽  
And Chemical Properties

Basic Performance Research of Polymer Intercalation Clay

2012 ◽  
Vol 578 ◽  
pp. 183-186
Author(s):  
Xiao Chun Cao ◽  
Yi Qin ◽  
Yan Na Zhao ◽  
Kun Ke
Keyword(s):  
Drilling Fluid ◽  
Chemical Properties ◽  
Drilling Fluids ◽  
Technical Problems ◽  
Clay Particles ◽  
Polymer Properties ◽  
Physical And Chemical ◽  
Performance Research ◽  
And Chemical Properties

Using the preliminary research of the polymer properties, the different between the physical and chemical properties of new polymer-clays nanometer composites and clay have been studied. Different polymers are used to evaluate experiment. Based on a large number of lab experiments, the changes of rheological property and API filtration property of polymer-clay drilling fluids nanometer composites are studied. The results show that clay particles could become smaller and the composites drilling fluid have the role of controlling loss and enhancing cake quality. The prepared composites could be used to solve the technical problems in drilling fluid.

Role of lattice defects in catalytic activities of graphene clusters for fuel cells

2015 ◽  
Vol 17 (26) ◽  
pp. 16733-16743 ◽  
Author(s):  
Lipeng Zhang ◽  
Quan Xu ◽  
Jianbing Niu ◽  
Zhenhai Xia
Keyword(s):  
Fuel Cells ◽  
Electronic Structures ◽  
Chemical Properties ◽  
Lattice Defects ◽  
Physical And Chemical Properties ◽  
Catalytic Activities ◽  
Physical And Chemical ◽  
And Chemical Properties

Defects are common but important in graphene, which could significantly tailor the electronic structures and physical and chemical properties.

The Ceramist as Chemist - Opportunities for New Materials

1984 ◽  
Vol 32 ◽  
Author(s):  
D. R. Uhlmann ◽  
B.J.J. Zelinski ◽  
G.E. Wnek
Keyword(s):  
Wide Spectrum ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Glass Ceramics ◽  
Chemical Properties ◽  
Ceramic Materials ◽  
Process Technology ◽  
Chemical Homogeneity ◽  
And Chemical Properties

ABSTRACTThe use of sol-gel techniques to prepare glasses and crystalline ceramics offers outstanding opportunity for breakthroughs in technology. The areas of particular promise include novel glasses; crystallineceramics with exceptional microstructures; coatings for modification of electrical, optical, mechanical and chemical properties; porous media with high surface area and tailored chemistry; ceramic powders with high chemical homogeneity and narrow distributions of particle size; matrix materials in ceramicceramic composites; and a wide spectrum of specialty ceramic materials, ranging from abrasives and fibers to glass ceramics and films. Opportunities in each of these areas will be discussed and related to the advances in understanding and process technology required for their achievement. The theses will be advanced that creative chemistry provides the key to many of these advances, that ceramists simply MUST learn more chemistry, but that we dare not rest from our labors when the chemistry is done.

scholarly journals Zeolites application in terrestrial and space industry – a review

2020 ◽  
Vol 32 ◽  
pp. 209-223
Author(s):  
Adelina Miteva ◽  
Valeria Stoyanova
Keyword(s):  
Chemical Properties ◽  
Waste Materials ◽  
Ion Exchangers ◽  
Science And Engineering ◽  
Space Industry ◽  
Synthetic Zeolites ◽  
The Impact ◽  
And Chemical Properties

This brief overview presents an attempt to systematize some of the available historical and recent data on the impact of zeolite science and engineering on the progress of various areas of Earth and Space development. The basic structural and chemical properties of natural and synthetic zeolites are presented. Valuable applications of the zeolites, such as catalysts, gas adsorbers and ion exchangers are also included. The most commonly used methods for the synthesis of zeolites from different materials are presented, as well as some Bulgarian developments for the reuse of waste materials to zeolites. The important role of zeolites as an indispensable material for improving the quality of soil, fuels, water, air, etc., required for the needs of orbiting space stations and spacecrafts has been confirmed by typical examples.

scholarly journals Partial synthetic models of FeMoco with sulfide and carbyne ligands: Effect of interstitial atom in nitrogenase active site

2021 ◽  
Vol 118 (49) ◽  
pp. e2109241118
Author(s):  
Linh N. V. Le ◽  
Gwendolyn A. Bailey ◽  
Anna G. Scott ◽  
Theodor Agapie
Keyword(s):  
Active Sites ◽  
Chemical Properties ◽  
Metal Centers ◽  
Bridging Ligand ◽  
Reduction Potentials ◽  
Protein Active Sites ◽  
Physical And Chemical ◽  
Synthetic Models ◽  
And Chemical Properties

Nitrogen-fixing organisms perform dinitrogen reduction to ammonia at an Fe-M (M = Mo, Fe, or V) cofactor (FeMco) of nitrogenase. FeMco displays eight metal centers bridged by sulfides and a carbide having the MFe7S8C cluster composition. The role of the carbide ligand, a unique motif in protein active sites, remains poorly understood. Toward addressing how the carbon bridge affects the physical and chemical properties of the cluster, we isolated synthetic models of subsite MFe3S3C displaying sulfides and a chelating carbyne ligand. We developed synthetic protocols for structurally related clusters, [Tp*M’Fe3S3X]n−, where M’ = Mo or W, the bridging ligand X = CR, N, NR, S, and Tp* = Tris(3,5-dimethyl-1-pyrazolyl)hydroborate, to study the effects of the identity of the heterometal and the bridging X group on structure and electrochemistry. While the nature of M’ results in minor changes, the chelating, μ3-bridging carbyne has a large impact on reduction potentials, being up to 1 V more reducing compared to nonchelating N and S analogs.

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