scholarly journals The chemistry of ZnWO4 nanoparticle formation

2016 ◽  
Vol 7 (10) ◽  
pp. 6394-6406 ◽  
Author(s):  
Espen D. Bøjesen ◽  
Kirsten M. Ø. Jensen ◽  
Christoffer Tyrsted ◽  
Aref Mamakhel ◽  
Henrik L. Andersen ◽  
...  
Keyword(s):  
Nucleation And Growth ◽  
Ex Situ ◽  
New Approach ◽  
Total Scattering ◽  
Nanoparticle Formation ◽  
Characterization Techniques ◽  
Classical Models

The need for a new approach to describing nanoparticle nucleation and growth different from the classical models is highlighted. In and ex situ total scattering experiments combined with additional characterization techniques are used to unravel the chemistry dictating ZnWO4 formation.

scholarly journals Investigating Processes of Nanocrystal Formation and Transformation via Liquid Cell TEM

2014 ◽  
Vol 20 (2) ◽  
pp. 425-436 ◽  
Author(s):  
Michael H. Nielsen ◽  
Dongsheng Li ◽  
Hengzhong Zhang ◽  
Shaul Aloni ◽  
T. Yong-Jin Han ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Nucleation And Growth ◽  
Ex Situ ◽  
Bulk Solution ◽  
Dynamic Information ◽  
Transmission Electron ◽  
Classical Models ◽  
Liquid Cell ◽  
Temporal And Spatial

AbstractRecent ex situ observations of crystallization in both natural and synthetic systems indicate that the classical models of nucleation and growth are inaccurate. However, in situ observations that can provide direct evidence for alternative models have been lacking due to the limited temporal and spatial resolution of experimental techniques that can observe dynamic processes in a bulk solution. Here we report results from liquid cell transmission electron microscopy studies of nucleation and growth of Au, CaCO3, and iron oxide nanoparticles. We show how these in situ data can be used to obtain direct evidence for the mechanisms underlying nanoparticle crystallization as well as dynamic information that provide constraints on important energetic parameters not available through ex situ methods.

Effects of Surface Wettability on Heterogeneous Boiling

2009 ◽  
Author(s):  
Hai Trieu Phan ◽  
Nadia Caney ◽  
Philippe Marty ◽  
Ste´phane Colasson ◽  
Je´roˆme Gavillet
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Contact Angles ◽  
Surface Wettability ◽  
Water Contact ◽  
New Approach ◽  
Major Subject ◽  
Nucleate Boiling Heat Transfer ◽  
Classical Models

Although boiling process has been a major subject of research for several decades, its physics still remain unclear and require further investigation. This study aims at highlighting the effects of the surface wettability on pool boiling heat transfer. Nanocoating techniques were used to vary the water contact angle from 20 to 110° by modifying nanoscale surface topography and chemistry. The experimental results obtained disagree with the predictions of the classical models. A new approach of nucleation mechanism is established to clarify the nexus between the surface wettability and the nucleate boiling heat transfer. In this approach, we introduce the concept of macro- and micro-contact angles to explain the observed phenomenon.

Development of an in situ synchrotron X-ray total scattering setup under pressurized hydrogen gas

2018 ◽  
Vol 51 (3) ◽  
pp. 796-801 ◽  
Author(s):  
Kouji Sakaki ◽  
Hyunjeong Kim ◽  
Akihiko Machida ◽  
Tetsu Watanuki ◽  
Yoshinori Katayama ◽  
...  
Keyword(s):  
Pair Distribution Function ◽  
Hydrogen Gas ◽  
Ex Situ ◽  
Sample Holder ◽  
Hydrogen Storage Materials ◽  
X Ray Diffraction ◽  
Total Scattering ◽  
X Ray ◽  
Diffraction Patterns

This article describes the development of an in situ gas-loading sample holder for synchrotron X-ray total scattering experiments, particularly for hydrogen storage materials, designed to collect diffraction and pair distribution function (PDF) data under pressurized hydrogen gas. A polyimide capillary with a diameter and thickness of 1.4 and 0.06 mm, respectively, connected with commercially available Swagelok fittings was used as an in situ sample holder. Leakage tests confirmed that this sample holder allows 3 MPa of hydrogen gas pressure and 393 K to be achieved without leakage. Using the developed in situ sample holder, significant background and Bragg peaks from the sample holder were not observed in the X-ray diffraction patterns and their signal-to-noise ratios were sufficiently good. The PDF patterns showed sharp peaks in the r range up to 100 Å. The results of Rietveld and PDF refinements of Ni are consistent with those obtained using a polyimide capillary (1.0 mm diameter and 0.04 mm thickness) that has been used for ex situ experiments. In addition, in situ synchrotron X-ray total scattering experiments under pressurized hydrogen gas up to 1 MPa were successfully demonstrated for LaNi4.6Cu.

Ultra-small MnCo2O4 nanocrystals decorated on nitrogen-enriched carbon nanofibers as oxygen cathode for Li-O2 batteries

2020 ◽  
Vol 13 (06) ◽  
pp. 2051035
Author(s):  
Xiaoping Jiang ◽  
Ronghua Wang ◽  
Ning Hu ◽  
Chaohe Xu
Keyword(s):  
Particle Size ◽  
Cathode Materials ◽  
Nitrogen Doping ◽  
Carbon Nanofiber ◽  
Nucleation And Growth ◽  
Ex Situ ◽  
Aprotic Electrolyte ◽  
High Level ◽  
Oxygen Cathode

Ultra-small MnCo2O4 nanocrystals/nitrogen enriched carbon nanofiber composites, with particle size as small as 2–4[Formula: see text]nm and nitrogen content as high as [Formula: see text][Formula: see text]at.%, were designed and used as oxygen cathode materials for Li-O2 batteries, with an aprotic electrolyte. Via an in-situ nucleation and growth, the morphology, size and distribution of MnCo2O4 nanocrystals were well controlled on surface of nanofibers, with strong interfacial interactions between the two components. Benefitting from the unique microstructure and high-level nitrogen doping, the MnCo2O4/NCF composite can deliver discharge and charge capacities of 4147.8 and 3842.8[Formula: see text]mAh/g as oxygen cathode materials, and columbic efficiencies are about 92.6%. More importantly, the discharge products can completely decompose in charging process as evidenced by an ex-situ FESEM investigation, while for pure NCF cathode, particle and plate-like Li2O2 were still observed on its surface, which confirmed that the MnCo2O4/NCF composite has a superior electrocatalytic activity that that of NCF.

scholarly journals In situ oxidation kinetics of magnetite nanoparticles by total scattering

2014 ◽  
Vol 70 (a1) ◽  
pp. C736-C736
Author(s):  
Antonio Cervellino ◽  
Ruggero Frison ◽  
Antonella Guagliardi ◽  
Giuseppe Cernuto ◽  
Norberto Masciocchi ◽  
...  
Keyword(s):  
Materials Science ◽  
Particle Diameter ◽  
Indirect Evidence ◽  
Lattice Parameter ◽  
Oxidation States ◽  
Ex Situ ◽  
Total Scattering ◽  
X Ray ◽  
Specific Subset

Iron oxide nanoparticles (NPs) show different structures as a function of oxidation state. In particular, magnetite (Fe3O4) NPs are easily oxidized in air at moderate temperatures, eventually yielding maghemite (Fe2O3). Oxidation proceeds via the creation of iron vacancies. While the vacancies may be created with a random distribution throughout the octahedral Fe sites, they eventually order over a specific subset of these sites, lowering the symmetry from F-centered (magnetite) to P-centered (cubic maghemite). By ex situ X-ray Total Scattering studies of magnetite-maghemite NPs in different oxidation states[1] we have recently studied, by the DFA method[2], the correlation between particle diameter, stoichiometry and lattice parameter in polydisperse NP samples unraveling also the size dependence of lattice parameter and composition. Moreover, we have shown indirect evidence of the formation of a polycrystalline surface layer of maghemite on a magnetite core in the intermediate oxidation states. Motivated by the excellent ex-situ results, we have also performed in-situ studies where magnetite NPs were oxidised in air at moderate temperatures (50-200 C). We present here an in-situ study performed at the X04SA-Materials Science beamline of the Swiss Light Source synchrotron[3]. Total Scattering X-ray diffraction patterns were collected every few minutes, while the oxidation was completed within several hours. The mechanism of NPs oxidation - whereas a surface oxidised layer is formed by outwards diffusion of Fe, then the vacancies so created order themselves giving rise to the maghemite-magnetite phase transition, will be examined in great detail. We will discuss, on robust statistical basis, the calculation of kinetic and diffusion constants, the temperature effect on the lattice constant and on the thickness of the surface oxidised layer; the different possible structural models for the cubic-maghemite NPs. We thank for support Fondazione Cariplo (2009-0289).

Probing the stability of Pt nanoparticles encapsulated in sol–gel Al 2 O 3 using in situ and ex situ characterization techniques

2014 ◽  
Vol 485 ◽  
pp. 108-117 ◽  
Author(s):  
R.U. Ribeiro ◽  
D.M. Meira ◽  
C.B. Rodella ◽  
D.C. Oliveira ◽  
J.M.C. Bueno ◽  
...  
Keyword(s):  
Sol Gel ◽  
Pt Nanoparticles ◽  
Ex Situ ◽  
Characterization Techniques ◽  
The Stability

scholarly journals The risk status of polish local breeds under conservation programmes - new approach

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Grażyna Polak ◽  
Jędrzej Krupiński ◽  
Elżbieta Martyniuk ◽  
Jolanta Calik ◽  
Aldona Kawęcka ◽  
...  
Keyword(s):  
Cultural Value ◽  
Ex Situ ◽  
Farm Animals ◽  
Anthropogenic Factors ◽  
Risk Status ◽  
Demographic Trend ◽  
New Approach ◽  
Geographical Concentration ◽  
Adverse Environmental Conditions ◽  
Parentage Control

AbstractNative breeds of farm animals, despite their unique characteristics and adaptability to diverse and often adverse environmental conditions, are at risk due to their lower profitability and corresponding declining use. According to FAO data, there are currently around 8800 livestock breeds in the world (http://www.fao.org/dad-is/en/ update: 09.11.2019), of which 17% have been assessed to be endangered. The objective of the study was to develop a model for estimating the risk status of Polish native breeds. The proposed new model is based on 3 factors: demographic, genetic, and socio-economic. The last factor is composed of 6 elements: geographical concentration, demographic trend over the last 5 years, cultural value of a breed, parentage control, ex situ conservation and anthropogenic factors. Using the factors and elements above, among the examined 30 breeds of cattle, horses, pigs, sheep and goats, 1 was assessed as being critically endangered; 24 were determined to be endangered and in need of conservation; 5 were less endangered, but in need of constant monitoring. Out of 35 populations of poultry 29 were assessed as endangered as they were being kept in only single public collections. Six flocks of ducks were given a critical risk status, due to a very low number of females.

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