Synthesis of magnesium-based binary powders with high reactivity using a coprecipitation method

2021 ◽  
Vol 23 (4) ◽  
Author(s):  
Bong-Gu Kim ◽  
Hyun-Hee Choi ◽  
Jung-Hun Son ◽  
SeungCheol Yang ◽  
Yun-Ki Byeun ◽  
...  
Keyword(s):  
High Reactivity ◽  
Coprecipitation Method

PREPARATION OF 3 MOL.% YTTRIA-FULLY-STABILIZED ZIRCONIA NANOPOWDERS BY MOLTEN SALTS/COPRECIPITATION METHOD AT LOW TEMPERATURE

NANO ◽  
2013 ◽  
Vol 08 (02) ◽  
pp. 1350015
Author(s):  
YIQUN DENG ◽  
BIN YANG
Keyword(s):  
Low Temperature ◽  
Molten Salts ◽  
Synthesis Temperature ◽  
High Reactivity ◽  
Coprecipitation Method ◽  
Stabilized Zirconia ◽  
Mechanical Mixing ◽  
Zirconia Nanopowders ◽  
Synthesis Procedure ◽  
Precursor Powders

In this paper, we present a facile process for preparing 3 mol.% yttria-fully-stabilized zirconia (3Y-FSZ) nanopowders by molten salts/coprecipitation method at low temperature. By this method, precursor powders in molten salts have a high reactivity and diffusivity, and react easily and completely, which can greatly reduce the synthesis temperature. Furthermore, the synthesis procedure involves neither mechanical mixing nor repeated grinding and thus ultrapure nanopowders with a better uniformity and fewer agglomerates can be obtained. The results illustrated that 3Y-FSZ nanopowders particle diameters ranging from 7 nm to 10 nm were successfully synthesized at 500°C.

Role of Aluminium on the Microstructure and Corrosion Behaviour of Magnesium Prepared by Powder Metallurgy Method

2020 ◽  
Vol 17 (3) ◽  
pp. 8206-8213
Author(s):  
J. Alias
Keyword(s):  
Corrosion Resistance ◽  
Powder Metallurgy ◽  
Corrosion Behaviour ◽  
Corrosion Current ◽  
Optical Microscope ◽  
High Reactivity ◽  
Aluminium Content ◽  
Powder Metallurgy Method ◽  
X Ray Diffraction ◽  
Promising Development

Much research on magnesium (Mg) emphasises creating good corrosion resistance of magnesium, due to its high reactivity in most environments. In this study, powder metallurgy (PM) technique is used to produce Mg samples with a variation of aluminium (Al) composition. The effect of aluminium composition on the microstructure development, including the phase analysis was characterised by optical microscope (OM), scanning electron microscopy (SEM) and x-ray diffraction (XRD). The mechanical property of Mg sample was performed through Vickers microhardness. The results showed that the addition of aluminium in the synthesised Mg sample formed distribution of Al-rich phases of Mg17Al12, with 50 wt.% of aluminium content in the Mg sample exhibited larger fraction and distribution of Al-rich phases as compared to the 20 wt.% and 10 wt.% of aluminium content. The microhardness values were also increased at 20 wt.% and 50 wt.% of aluminium content, comparable to the standard microhardness value of the annealed Mg. A similar trend in corrosion resistance of the Mg immersed in 3.5 wt.% NaCl solution was observed. The corrosion behaviour was evaluated based on potentiodynamic polarisation behaviour. The corrosion current density, icorr, is observed to decrease with the increase of Al composition in the Mg sample, corresponding to the increase in corrosion resistance due to the formation of aluminium oxide layer on the Al-rich surface that acted as the corrosion barrier. Overall, the inclusion of aluminium in this study demonstrates the promising development of high corrosion resistant Mg alloys.

Bimetallic Radical Redox-Relay Catalysis for the Isomerization of Epoxides to Allylic Alcohols

2019 ◽  
Author(s):  
Ke-Yin Ye ◽  
Terry McCallum ◽  
Song Lin
Keyword(s):  
Ring Opening ◽  
High Reactivity ◽  
Hydrogen Atom Transfer ◽  
Organic Radicals ◽  
Epoxide Ring ◽  
Allylic Alcohols ◽  
Epoxide Ring Opening ◽  
Bond Forming ◽  
Co Catalysts ◽  
The Rich

Organic radicals are generally short-lived intermediates with exceptionally high reactivity. Strategically, achieving synthetically useful transformations mediated by organic radicals requires both efficient initiation and selective termination events. Here, we report a new catalytic strategy, namely bimetallic radical redox-relay, in the regio- and stereoselective rearrangement of epoxides to allylic alcohols. This approach exploits the rich redox chemistry of Ti and Co complexes and merges reductive epoxide ring opening (initiation) with hydrogen atom transfer (termination). Critically, upon effecting key bond-forming and -breaking events, Ti and Co catalysts undergo proton-transfer/electron-transfer with one another to achieve turnover, thus constituting a truly synergistic dual catalytic system.<br>

Iridium-Catalyzed Silylation of C-H bonds in Unactivated Arenes: A Sterically-Encumbered Phenanthroline Ligand Accelerates Catalysis Enabling New Reactivity

2019 ◽  
Author(s):  
Caleb Karmel ◽  
Zhewei Chen ◽  
John Hartwig
Keyword(s):  
High Activity ◽  
Functional Group ◽  
Activity Analysis ◽  
High Reactivity ◽  
High Yield ◽  
Phen Ligand ◽  
Mechanistic Studies ◽  
Phenanthroline Ligand ◽  
First Time ◽  
New System

We report a new system for the silylation of aryl C-H bonds. The combination of [Ir(cod)(OMe)]<sub>2</sub> and 2,9-Me<sub>2</sub>-phenanthroline (2,9-Me<sub>2</sub>phen) catalyzes the silylation of arenes at lower temperatures and with faster rates than those reported previously, when the hydrogen byproduct is removed, and with high functional group tolerance and regioselectivity. Inhibition of reactions by the H<sub>2</sub> byproduct is shown to limit the silylation of aryl C-H bonds in the presence of the most active catalysts, thereby masking their high activity. Analysis of initial rates uncovered the high reactivity of the catalyst containing the sterically hindered 2,9-Me<sub>2</sub>phen ligand but accompanying rapid inhibition by hydrogen. With this catalyst, under a flow of nitrogen to remove hydrogen, electron-rich arenes, including those containing sensitive functional groups, undergo silylation in high yield for the first time, and arenes that underwent silylation with prior catalysts react over much shorter times with lower catalyst loadings. The synthetic value of this methodology is demonstrated by the preparation of key intermediates in the synthesis of medicinally important compounds in concise sequences comprising silylation and functionalization. Mechanistic studies demonstrate that the cleavage of the aryl C-H bond is reversible and that the higher rates observed with the 2,9-Me<sub>2</sub>phen ligand is due to a more thermodynamically favorable oxidative addition of aryl C-H bonds.

Isotopically Labeled Desthiobiotin Azide (isoDTB) Tags Enable Global Profiling of the Bacterial Cysteinome

2019 ◽  
Author(s):  
Patrick R. A. Zanon ◽  
Lisa Lewald ◽  
Stephan M. Hacker
Keyword(s):  
Binding Sites ◽  
Bacterial Resistance ◽  
Mevalonate Pathway ◽  
Rapid Development ◽  
High Reactivity ◽  
Functional Importance ◽  
Essential Proteins ◽  
Covalent Inhibitors ◽  
Druggable Targets ◽  
Covalent Ligands

Rapid development of bacterial resistance has led to an urgent need to find new druggable targets for antibiotics. In this context, residue-specific chemoproteomic approaches enable proteome-wide identification of binding sites for covalent inhibitors. Here, we describe isotopically labeled desthiobiotin azide (isoDTB) tags that are easily synthesized, shorten the chemoproteomic workflow and allow an increased coverage of cysteines in bacterial systems. We quantify 59% of all cysteines in essential proteins in <i>Staphylococcus aureus</i> and discover 88 cysteines with high reactivity, which correlates with functional importance. Furthermore, we identify 268 cysteines that are engaged by covalent ligands. We verify inhibition of HMG-CoA synthase, which will allow addressing the bacterial mevalonate pathway through a new target. Overall, a comprehensive map of the bacterial cysteinome is obtained, which will facilitate the development of antibiotics with novel modes-of-action.

Synthesis of 2-amino-5,7-dimethyl-4-oxopyrido[3,4-e]-1,3-thiazines

1983 ◽  
Vol 48 (12) ◽  
pp. 3426-3432 ◽  
Author(s):  
Dušan Koščík ◽  
Pavol Kristian ◽  
Ondrej Forgáč
Keyword(s):  
Spectral Data ◽  
Chlorine Atom ◽  
Mass Spectra ◽  
High Reactivity ◽  
Secondary Amines ◽  
Dimroth Rearrangement ◽  
H Nmr ◽  
New Synthesis ◽  
C Nmr

New synthesis of pyrido[3,4-e]-1,3-thiazines consisting in reaction of 2,6-dimethyl-4-chloronicotinoyl isothiocyanate with primary or secondary amines, or with benzaldehyde phenylhydrazone, is described. High reactivity of the chlorine atom does not allow isolation of the corresponding thioureas, arising as intermediates, except in the case of the benzylamino derivative. Structure of the products was unequivocally confirmed by their spectral data (IR, UV, 1H NMR, 13C NMR and mass spectra). The synthesized derivatives do not undergo the Dimroth rearrangement.

Effect of Temperature on Fe3O4 Magnetic Nanoparticles Prepared by Coprecipitation Method

2014 ◽  
Vol 900 ◽  
pp. 172-176 ◽  
Author(s):  
Ji Mei Niu ◽  
Zhi Gang Zheng
Keyword(s):  
Magnetic Nanoparticles ◽  
Coprecipitation Method ◽  
Effect Of Temperature ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Magnetic Carriers ◽  
Average Grain Size ◽  
Or Gene ◽  
Block Temperature

The Fe3O4 magnetic nanoparticles obtained by the aqueous coprecipitation method are characterized systematically using scanning electron microscope, X-ray diffraction and vibrating sample magnetometer. These magnetic nanoparticles are spheric, dispersive, and have average grain size of 50 nm. The size and magnetic properties of Fe3O4 nanoparticles can be tuned by the reaction temperature. All samples exhibit high saturation magnetization (Ms=53.4 emu·g-1) and superparamagnetic behavior with a block temperature (TB) of 215K. These properties make such Fe3O4 magnetic nanoparticles worthy candidates for the magnetic carriers of targeted-drug or gene therapy in future.

scholarly journals Oxidation of Citalopram with Sodium Hypochlorite and Chlorine Dioxide: Influencing Factors and NDMA Formation Kinetics

Molecules ◽  
2019 ◽  
Vol 24 (17) ◽  
pp. 3065
Author(s):  
Juan Lv ◽  
Yan Wang ◽  
Na Li
Keyword(s):  
Sodium Hypochlorite ◽  
Chlorine Dioxide ◽  
Wastewater Treatment Plants ◽  
Ph Value ◽  
High Reactivity ◽  
Secondary Effluent ◽  
Water Matrix ◽  
Formation Kinetics ◽  
Operational Variables ◽  
Two Stages

The highly prescribed antidepressant, citalopram, as one of newly emerging pollutants, has been frequently detected in the aquatic environment. Citalopram oxidation was examined during sodium hypochlorite (NaOCl) and chlorine dioxide (ClO2) chlorination processes since conventional wastewater treatment plants cannot remove citalopram effectively. Citalopram has been demonstrated to form N-nitrosodimethylamine (NDMA) during chlorination in our previous study. Further investigation on NDMA formation kinetics was conducted in the present study. Influences of operational variables (disinfectant dose, pH value) and water matrix on citalopram degradation, as well as NDMA generation, were evaluated. The results indicated high reactivity of citalopram with NaOCl and ClO2. NDMA formation included two stages during CIT oxidation, which were linear related with reaction time. NaOCl was more beneficial to remove CIT, but it caused more NDMA formation. Increasing disinfectant dosage promoted citalopram removal and NDMA formation. However, no consistent correlation was found between citalopram removal and pH. Contrary to the situation of citalopram removal, NDMA generation was enhanced when citalopram was present in actual water matrices, especially in secondary effluent. DMA, as an intermediate of citalopram chlorination, contributed to NDMA formation, but not the only way.

scholarly journals Azanone (HNO): generation, stabilization and detection

2021 ◽  
Author(s):  
Cecilia Mariel Gallego ◽  
Agostina Mazzeo ◽  
Paola Vargas ◽  
Sebastián Suárez ◽  
Juan Pellegrino ◽  
...  
Keyword(s):  
Reactive Nitrogen Species ◽  
High Reactivity ◽  
Reactive Nitrogen ◽  
Nitrogen Species ◽  
Biologically Relevant

HNO (nitroxyl, azanone), joined the ‘biologically relevant reactive nitrogen species’ family in the 2000s. Azanone is impossible to store due to its high reactivity and inherent low stability. Consequently, its...

scholarly journals Pressureless Sintering of YIG Ceramics from Coprecipitated Nanopowders

2021 ◽  
Vol 7 (5) ◽  
pp. 56
Author(s):  
Yimin Yang ◽  
Xiaoying Li ◽  
Ziyu Liu ◽  
Dianjun Hu ◽  
Xin Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Calcination Temperature ◽  
Sintering Temperature ◽  
Raw Materials ◽  
Secondary Phase ◽  
Coprecipitation Method ◽  
Pressureless Sintering ◽  
Densification Behavior ◽  
Sintering Process

Nanoparticles prepared by the coprecipitation method were used as raw materials to fabricate Y3Fe5O12 (YIG) ceramics by air pressureless sintering. The synthesized YIG precursor was calcinated at 900–1100 °C for 4 h in air. The influences of the calcination temperature on the phase and morphology of the nanopowders were investigated in detail. The powders calcined at 1000–1100 °C retained the pure YIG phase. YIG ceramics were fabricated by sintering at 1200–1400 °C for 10 h, and its densification behavior was studied. YIG ceramics prepared by air sintering at 1250 °C from powders calcinated at 1000 °C have the highest in-line transmittance in the range of 1000-3000 nm. When the sintering temperature exceeds 1300 °C, the secondary phase appears in the YIG ceramics, which may be due to the loss of oxygen during the high-temperature sintering process, resulting in the conversion of Fe3+ into Fe2+.

Sign in / Sign up

Export Citation Format

Share Document