scholarly journals Crystal growth and aggregation in suspensions of δ-MnO2 nanoparticles: implications for surface reactivity

2018 ◽  
Vol 5 (2) ◽  
pp. 497-508 ◽  
Author(s):  
Francesco Femi Marafatto ◽  
Bruno Lanson ◽  
Jasquelin Peña
Keyword(s):  
Crystal Growth ◽  
Crystallite Size ◽  
Ph Control ◽  
Sodium Content ◽  
Surface Reactivity ◽  
Mno2 Nanoparticles ◽  
Suspension Ph

Sodium content and suspension pH control crystallite size and aggregation in δ-MnO2 nanoparticles.

scholarly journals Comment on “Crystal growth and aggregation in suspensions of δ-MnO2 nanoparticles: implications for surface reactivity” by F. F. Marafatto, B. Lanson and J. Peña, Environ. Sci.: Nano, 2018, 5, 497

2018 ◽  
Vol 5 (9) ◽  
pp. 2198-2200 ◽  
Author(s):  
Alain Manceau
Keyword(s):  
Crystal Growth ◽  
Crystallite Size ◽  
Strain Gradient ◽  
Lognormal Distribution ◽  
Surface Reactivity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mno2 Nanoparticles

We show that X-ray diffraction of δ-MnO2 nanoparticles is sensitive to the lognormal distribution of the crystallite size and to the strain gradient across the nanosheet.

Reply to the ‘Comment on “Crystal growth and aggregation in suspensions of δ-MnO2 nanoparticles: implications for surface reactivity”’ by A. Manceau, Environ. Sci.: Nano, 2018, 5, DOI: 10.1039/C8EN00126J

2018 ◽  
Vol 5 (9) ◽  
pp. 2201-2203
Author(s):  
Bruno Lanson ◽  
Francesco F. Marafatto ◽  
Jasquelin Peña
Keyword(s):  
Crystal Growth ◽  
Surface Reactivity ◽  
Mno2 Nanoparticles

This reply clarifies the conservative assumptions underlying the XRD modeling performed in the initial article.

Precipitation of Carbonated Calcium Phosphate Powders from a Highly Supersaturated SBF Solution

2007 ◽  
Vol 330-332 ◽  
pp. 59-62 ◽  
Author(s):  
Ingo Hofmann ◽  
Lenka Müller ◽  
Peter Greil ◽  
Frank A. Müller
Keyword(s):  
Crystal Growth ◽  
Calcium Phosphate ◽  
Crystallite Size ◽  
High Specific Surface Area ◽  
Precipitation Method ◽  
Human Blood Plasma ◽  
Mineral Phase ◽  
Carbonated Apatite ◽  
Sbf Solution ◽  
20 Nm

Hydroxy carbonated apatite (HCA) powders were prepared by precipitation from a modified SBF solution (5x M-SBF). The ionic concentrations were 5 times higher than in human blood plasma with the exception of Mg2+ and HCO3 - concentrations that were reduced in order to accelerate crystal growth. Spheroaggregates of HCA platelets with molar (Ca+Mg)/P ratios ranging from 1.44 to 1.56 were obtained after precipitation at 50 °C. The crystallite size in c-direction was approximately 20 nm and depending on the precipitation time a CO3 2- content of 1.8 to 5.2 wt.-% was determined. Using this low temperature precipitation method, HCA powders with a high specific surface area of 83 m2/g and a composition and crystallite size close to those of the mineral phase of human bone were obtained.

Mechanochemical Synthesis of Zinc Ferrite, ZnFe2O4

2007 ◽  
Vol 534-536 ◽  
pp. 201-204
Author(s):  
Yutaka Sawada ◽  
Kiyokata Iizumi ◽  
Tomokazu Kuramochi ◽  
Mei Han Wang ◽  
Li Xian Sun ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Crystallite Size ◽  
Powder Mixture ◽  
Mechanochemical Synthesis ◽  
Zinc Ferrite ◽  
Diffraction Spectrum ◽  
X Ray Diffraction ◽  
X Ray ◽  
Milled Powders

Mechanochemical synthesis of zinc ferrite, ZnFe2O4, was attempted from a powder mixture of iron (III) oxide, alpha-Fe2O3 and zinc (II) oxide, ZnO. Nanocrystalline zinc ferrite, ZnFe2O4 powders were successfully synthesized only by milling for 30 hours. The X-ray diffraction spectrum of the as-milled powders (without heating) showed twelve ZnFe2O4 peaks and four weak peaks of coexisting unreacted Fe2O3. The crystallite size of the mechanochemicallysynthesized ZnFe2O4 was 26.3 nm. Evidence of the ZnFe2O4 formation was absent for the powders milled for 10 and 20 hours; milling lowered the crystallinity of the starting materials. Heating after milling enhanced the formation of ZnFe2O4, the crystal growth of ZnFe2O4 and the unreacted starting materials. The unreacted starting materials decreased their amounts by heating at higher temperatures.

Direct Observation of Crystalline Ordering In Naturally Graphitized Carbon Produced by Low Grade Metamorphism

1977 ◽  
Vol 35 ◽  
pp. 162-163
Author(s):  
Thomas R. McKee ◽  
Peter R. Buseck
Keyword(s):  
Crystallite Size ◽  
Sedimentary Rocks ◽  
Carbonaceous Material ◽  
Low Grade ◽  
X Ray ◽  
Graphitized Carbon ◽  
Transmission Electron ◽  
Heat Treated ◽  
Commercial Carbon ◽  
Metamorphic Zone

Sediments commonly contain organic material which appears as refractory carbonaceous material in metamorphosed sedimentary rocks. Grew and others have shown that relative carbon content, crystallite size, X-ray crystallinity and development of well-ordered graphite crystal structure of the carbonaceous material increases with increasing metamorphic grade. The graphitization process is irreversible and appears to be continous from the amorphous to the completely graphitized stage. The most dramatic chemical and crystallographic changes take place within the chlorite metamorphic zone.The detailed X-ray investigation of crystallite size and crystalline ordering is complex and can best be investigated by other means such as high resolution transmission electron microscopy (HRTEM). The natural graphitization series is similar to that for heat-treated commercial carbon blacks, which have been successfully studied by HRTEM (Ban and others).

Montmorillonite Dendrites

1974 ◽  
Vol 32 ◽  
pp. 454-455
Author(s):  
Necip Güven ◽  
Rodney W. Pease
Keyword(s):  
Crystal Growth ◽  
Growth Mechanism ◽  
Growth Front ◽  
Morphological Features ◽  
Dendritic Crystal ◽  
Crystal Growth Mechanism

Morphological features of montmorillonite aggregates in a large number of samples suggest that they may be formed by a dendritic crystal growth mechanism (i.e., tree-like growth by branching of a growth front).

TEM and cathodoluminescence of precipitates in II-VI semiconductors

1988 ◽  
Vol 46 ◽  
pp. 488-489
Author(s):  
Joanna L. Batstone
Keyword(s):  
Crystal Growth ◽  
Band Gap ◽  
Local Strain ◽  
Wide Band ◽  
Optoelectronic Device ◽  
Wide Band Gap ◽  
Bulk Crystal Growth ◽  
Transmission Electron ◽  
Device Applications ◽  
Stoichiometry Control

Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and HgxCd1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x.Two major sources of precipitation can be identified in II-VI materials; (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.

STM studies of crystal growth

1991 ◽  
Vol 49 ◽  
pp. 374-375
Author(s):  
M. G. Lagally
Keyword(s):  
Crystal Growth ◽  
Molecular Beam ◽  
Chemical Vapor ◽  
Sputter Deposition ◽  
Field Of View ◽  
Scanning Tunneling ◽  
Wide Field ◽  
Tunneling Microscopy ◽  
Wide Field Of View ◽  
The One

It has been recognized since the earliest days of crystal growth that kinetic processes of all Kinds control the nature of the growth. As the technology of crystal growth has become ever more refined, with the advent of such atomistic processes as molecular beam epitaxy, chemical vapor deposition, sputter deposition, and plasma enhanced techniques for the creation of “crystals” as little as one or a few atomic layers thick, multilayer structures, and novel materials combinations, the need to understand the mechanisms controlling the growth process is becoming more critical. Unfortunately, available techniques have not lent themselves well to obtaining a truly microscopic picture of such processes. Because of its atomic resolution on the one hand, and the achievable wide field of view on the other (of the order of micrometers) scanning tunneling microscopy (STM) gives us this opportunity. In this talk, we briefly review the types of growth kinetics measurements that can be made using STM. The use of STM for studies of kinetics is one of the more recent applications of what is itself still a very young field.

Cristal-growth dynamics of n-doped gaAs

1992 ◽  
Vol 50 (2) ◽  
pp. 1544-1545
Author(s):  
Pham V. Huong ◽  
Stéphanie Bouchet ◽  
Jean-Claude Launay
Keyword(s):  
Crystal Growth ◽  
Spatial Resolution ◽  
Epitaxial Layer ◽  
Outer Surface ◽  
Gaas Substrate ◽  
Structural Modification ◽  
Growth Dynamics ◽  
Argon Laser ◽  
High Anisotropy ◽  
Crystal Gaas

Microstructure of epitaxial layers of doped GaAs and its crystal growth dynamics on single crystal GaAs substrate were studied by Raman microspectroscopy with a Dilor OMARS instrument equipped with a 1024 photodiode multichannel detector and a ion-argon laser Spectra-Physics emitting at 514.5 nm.The spatial resolution of this technique, less than 1 μm2, allows the recording of Raman spectra at several spots in function of thickness, from the substrate to the outer deposit, including areas around the interface (Fig.l).The high anisotropy of the LO and TO Raman bands is indicative of the orientation of the epitaxial layer as well as of the structural modification in the deposit and in the substrate at the interface.With Sn doped, the epitaxial layer also presents plasmon in Raman scattering. This fact is already very well known, but we additionally observed that its frequency increases with the thickness of the deposit. For a sample with electron density 1020 cm-3, the plasmon L+ appears at 930 and 790 cm-1 near the outer surface.

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