The Pleistocene cinder cones surrounding Volcán Colima, Mexico re-visited: eruption ages and volumes, oxidation states, and sulfur content

Free-cutting steel gains specific working properties thanks to the high content of sulfur and phosphorus. These elements, especially sulfur, have a rather high tendency to segregation. Therefore, segregation defects in free-cutting steel continuously cast billets can be significantly developed. The aim of the work was to study the influence of the chemical composition of freecutting steel and casting technological parameters on the quality of the macrostructure of continuously cast billets. A metallographic assessment of the internal structure of cast metal made of free-cutting steel and data processing by application of correlation and regression analysis were the research methods. The array of production data of 43 heats of free-cutting steel of grade A12 was studied. Steel casting on a five-strand radial type continuous casting machine was carried out by various methods of metal pouring from tundish into the molds. Metal of 19 heats was poured with an open stream, and 24 heats – by a closed stream through submerged nozzles with a vertical hole. High-quality billets had a cross-sectional size of 150×150 mm. The macrostructure of high-quality square billets made of free-cutting steel of A12 grade is characterized by the presence of central porosity, axial segregation and peripheral point contamination, the degree of development of which was in the range from 1.5 to 2.0 points, segregation cracks and strips – about 1.0 points. In the course of casting with an open stream, almost all of these defects are more developed comparing with the casting by a closed stream. As a result of correlation and regression analysis, linear dependences of the development degree of segregation cracks and strips both axial and angular on the sulfur content in steel and on the ratio of manganese content to sulfur content were established. The degree of these defects development increases with growing of sulfur content in steel of A12 grade. These defects had especially strong development when sulfur content in steel was of more than 0.10%. To improve the quality of cast metal, it is necessary to have the ratio of the manganese content to the sulfur content in the metal more than eight.

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Acceptorless amine dehydrogenation and transamination using Pd-doped layered double hydroxides

10.26434/chemrxiv.6998204.v2 ◽

2018 ◽

Author(s):

Diana Ainembabazi ◽

Nan An ◽

Jinesh Manayil ◽

Kare Wilson ◽

Adam Lee ◽

...

Keyword(s):

Layered Double Hydroxides ◽

Oxidation States ◽

Secondary Amines ◽

Primary Amines ◽

Acid Dissolution ◽

Oxidative Amination ◽

Strong Function ◽

Excellent Activity ◽

High Yields ◽

Double Hydroxides

<div> <p>The synthesis, characterization, and activity of Pd-doped layered double hydroxides (Pd-LDHs) for for acceptorless amine dehydrogenation is reported. These multifunctional catalysts comprise Brønsted basic and Lewis acidic surface sites that stabilize Pd species in 0, 2+, and 4+ oxidation states. Pd speciation and corresponding cataytic performance is a strong function of metal loading. Excellent activity is observed for the oxidative transamination of primary amines and acceptorless dehydrogenation of secondary amines to secondary imines using a low Pd loading (0.5 mol%), without the need for oxidants. N-heterocycles, such as indoline, 1,2,3,4-tetrahydroquinoline, and piperidine, are dehydrogenated to the corresponding aromatics with high yields. The relative yields of secondary imines are proportional to the calculated free energy of reaction, while yields for oxidative amination correlate with the electrophilicity of primary imine intermediates. Reversible amine dehydrogenation and imine hydrogenation determine the relative imine:amine selectivity. Poisoning tests evidence that Pd-LDHs operate heterogeneously, with negligible metal leaching; catalysts can be regenerated by acid dissolution and re-precipitation.</p> </div> <br>

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Catalytic Fluorination of Boron Compounds at a Bismuth Redox Platform

10.26434/chemrxiv.9729143 ◽

2019 ◽

Author(s):

Oriol Planas ◽

Feng Wang ◽

Markus Leutzsch ◽

Josep Cornella

Keyword(s):

Transition Metal ◽

Main Group ◽

Group Element ◽

Oxidation States ◽

Boron Compounds ◽

Main Text ◽

Main Group Element ◽

Rational Ligand Design ◽

Supplementary Material

The ability of bismuth to maneuver between different oxidation states in a catalytic redox cycle, mimicking the canonical organometallic steps associated to a transition metal, is an elusive and unprecedented approach in the field of homogeneous catalysis. Herein we present a catalytic protocol based on bismuth, a benign and sustainable main-group element, capable of performing every organometallic step in the context of oxidative fluorination of boron compounds; a territory reserved to transition metals. A rational ligand design featuring hypervalent coordination together with a mechanistic understanding of the fundamental steps, permitted a catalytic fluorination protocol based on a Bi(III)/Bi(V) redox couple, which represents a unique example where a main-group element is capable of outperforming its transition metal counterparts.<br>A main text and supplementary material have been attached as pdf files containing all the methodology, techniques and characterization of the compounds reported.<br>

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Engine Performance with Diesel-Biodiesel Blends Fuel and Emission Characteristics

Engineering and Technology Journal ◽

10.30684/etj.v38i5a.419 ◽

2020 ◽

Vol 38 (5A) ◽

pp. 779-788

Author(s):

Marwa N. Kareem ◽

Adel M. Salih

Keyword(s):

Sulfur Content ◽

Diesel Fuel ◽

Engine Performance ◽

Esterification Reaction ◽

Biodiesel Fuel ◽

Exhaust Gas ◽

Gas Temperature ◽

Biodiesel Blends ◽

Fuel Blends ◽

Hc Emissions

In this study, the sunflowers oil was utilized as for producing biodiesel via a chemical operation, which is called trans-esterification reaction. Iraqi diesel fuel suffers from high sulfur content, which makes it one of the worst fuels in the world. This study is an attempt to improve the fuel specifications by reducing the sulfur content of the addition of biodiesel fuel to diesel where this fuel is free of sulfur and has a thermal energy that approaches to diesel.20%, 30% and 50% of Biodiesel fuel were added to the conventional diesel. Performance tests and pollutants of a four-stroke single-cylinder diesel engine were performed. The results indicated that the brake thermal efficiency a decreased by (4%, 16%, and 22%) for the B20, B30 and B50, respectively. The increase in specific fuel consumption was (60%, 33%, and 11%) for the B50, B30, and B20 fuels, respectively for the used fuel blends compared to neat diesel fuel. The engine exhaust gas emissions measures manifested a decreased of CO and HC were CO decreased by (13%), (39%) and (52%), and the HC emissions were lower by (6.3%), (32%), and (46%) for B20, B30 and B50 respectively, compared to diesel fuel. The reduction of exhaust gas temperature was (7%), (14%), and (32%) for B20, B30 and B50 respectively. The NOx emission increased with the increase in biodiesel blends ratio. For B50, the raise was (29.5%) in comparison with diesel fuel while for B30 and B20, the raise in the emissions of NOx was (18%) and...

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Lower oxidation states in gallium halides

10.31274/rtd-180813-15014 ◽

1956 ◽

Author(s):

Richard K. McMullan

Keyword(s):

Oxidation States ◽

Lower Oxidation

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MOTUNG 652

Alloy Digest ◽

10.31399/asm.ad.ts0061 ◽

1957 ◽

Vol 6 (8) ◽

Keyword(s):

Fracture Toughness ◽

Physical Properties ◽

Tensile Properties ◽

Sulfur Content ◽

High Speed ◽

High Speed Steel ◽

Heat Treating ◽

Bend Strength ◽

Machining Properties

Abstract MOTUNG 652 is an intermediate molybdenum-tungsten type of high-speed steel conforming to the M-2 analysis. It is available with normal sulfur content or with high sulfur for free machining properties. This datasheet provides information on composition, physical properties, hardness, tensile properties, and compressive and bend strength as well as fracture toughness. It also includes information on forming, heat treating, and machining. Filing Code: TS-61. Producer or source: Cyclops Corporation.

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