Rate of decay of specific surface area of snow during isothermal experiments and morphological changes studied by scanning electron microscopy

2003 ◽  
Vol 81 (1-2) ◽  
pp. 459-468 ◽  
Author(s):  
L Legagneux ◽  
T Lauzier ◽  
F Domin ◽  
W F Kuhs ◽  
T Heinrichs ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Specific Surface ◽  
Decay Rate ◽  
Surface Area ◽  
Specific Surface Area ◽  
Morphological Changes ◽  
Main Process ◽  
Snow Crystals ◽  
Scanning Electron

The quantification of the specific surface area (SSA) of snow crystals and of its variation during metamorphism are essential to understand and model the exchange of reactive gases between the snowpack and the atmosphere. Therefore, the decay rate of SSA of five fresh snow samples was studied in the laboratory at –4, –10, and –15°C under isothermal conditions in closed systems. The time-evolution of the snow SSA can in all cases be very well described by an empirical law of the form, SSA = – A log(t + Δt) + B, where A, B, and Δt are adjustable parameters. B seems to be closely related to the initial SSA of the snow, and A describes the SSA decay rate. Our preliminary findings at –15°C suggest that a linear relationship exists between A and B, so that it may be possible to predict the decay rate of snow SSA from its initial value. For the first time, images obtained from scanning electron microscopy show that crystal rounding of snow is the main process taking place during isothermal metamorphism. New grain boundaries also form. More surprising, however, was the formation of new basal, prismatic, and pyramidal crystal faces, sometimes with very sharp angles, especially at –15°C. The growth of facets with sharp angles is not fully explained by current theories of snow metamorphism and has not been observed before. PACS Nos.: 68.35Md, 68.37Hk, 81.20Ev, 81.05Rm

scholarly journals Selective Crystallization of Silicoalumophosphate Sapo-11 With A Micromesoporous Structure

2021 ◽  
Vol 9 (2) ◽  
pp. 109-111
Author(s):  
Zulfiya Khayrullina ◽  
Kanaan R. Ahmed ◽  
Samara Kambarova ◽  
Marat Agliullin
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Molecular Sieve ◽  
Mesoporous Structure ◽  
Selective Crystallization ◽  
Scanning Electron

ABSTRACT:The authors have proposed a method for the selective crystallization of a SAPO-11 silicoaluminophosphate molecular sieve with a micro-mesoporous structure. It has been shown that crystallization of a silicoaluminophosphate gel, in the preparation of which its isopropoxide is used as a source of aluminum, makes it possible to obtain a SAPO-11 molecular sieve with a specific surface area of ​​~ 207 m2 / g, a volume of micro- and mesopores of ~ 0.08 and 0.09 cm3 / g. , respectively. Using scanning electron microscopy, it was demonstrated that the crystals of the material are pseudospherical particles ~ 8-10 microns in size, consisting of aggregates of nanocrystals ~ 100-200 nm in size.

scholarly journals Nanomaterial identification of powders: comparing volume specific surface area, X-ray diffraction and scanning electron microscopy methods

2019 ◽  
Vol 6 (1) ◽  
pp. 152-162 ◽  
Author(s):  
Claire Dazon ◽  
Olivier Witschger ◽  
Sébastien Bau ◽  
Vanessa Fierro ◽  
Philip L. Llewellyn
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
X Ray Diffraction ◽  
Reliable Criterion ◽  
X Ray ◽  
Area X ◽  
Scanning Electron

This work shows that the volume specific surface area could be a reliable criterion for nanomaterial identification.

Structural and morphological features of MgO powders. The key role of the preparative starting compound

1998 ◽  
Vol 13 (8) ◽  
pp. 2218-2223 ◽  
Author(s):  
S. Ardizzone ◽  
C. L. Bianchi ◽  
B. Vercelli
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Specific Surface ◽  
Surface Area ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Starting Compound ◽  
Scanning Electron

The present paper reports data concerning magnesia samples obtained by calcination of different precursor salts at different increasing temperatures (873–1253 K). The oxides are characterized by x- ray diffraction, scanning electron microscopy, and N2 adsorption at subcritical temperatures. The samples appear to be composed, at any temperature, of pure periclase with a degree of crystallinity which increases with the temperature of calcination. Morphologically, the products have the shape either of lamellas or of cubes of variable dimensions, depending on the nature and route of preparation of the precursor salts. The variation of the specific surface area and the degree of porosity with the nature of the precursors and the temperature is discussed.

Effects of dry grinding on pyrophyllite

Clay Minerals ◽  
1988 ◽  
Vol 23 (4) ◽  
pp. 399-410 ◽  
Author(s):  
J. L. Pérez-Rodríguez ◽  
L. Madrid Sánchez del Villar ◽  
P.J. Sánchez-Soto
Keyword(s):  
Electron Microscopy ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Grinding Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dry Grinding ◽  
Scanning Electron ◽  
Area Data

AbstractDry grinding of pyrophyllite (Hillsboro, USA) has been studied by X-ray diffraction (XRD), specific surface area measurements (BET) and scanning electron microscopy (SEM). At the beginning of the grinding process, some effects such as delamination, gliding and folding of the layers, and decrease in particle size were detected by SEM and XRD, resulting in a large increase in specific surface area, up to a maximum of ∼60 m2·g−1. Marked changes in the structure take place between 30 and 32 mins grinding. Longer grinding times increase the degree of disorder and SEM and specific surface area data suggest that aggregation occurs. XRD results indicate that some residual order persists in the degraded structure.

scholarly journals Influence of mechanical activation on synthesis of zinc metatitanate

2005 ◽  
Vol 37 (2) ◽  
pp. 115-122 ◽  
Author(s):  
Nebojsa Labus ◽  
Nina Obradovic ◽  
Tatjana Sreckovic ◽  
V. Mitic ◽  
Momcilo Ristic
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Temperature ◽  
Specific Surface ◽  
Mechanical Activation ◽  
Surface Area ◽  
Perovskite Structure ◽  
Mechanical Treatment ◽  
X Ray ◽  
Scanning Electron

Investigations of a ZnO-TiO2 binary oxide mixture during mechanical treatment were mainly focused on obtaining orthotitanate Zn2TiO4 with a spinel structure. Due to the specific way of energy transfer during mechanical treatment using a high-energy ball mill, the system passes through low temperature ZnTiO3 metatitanate phase formation. Mechanical activation was performed on an equimolar ratio mixture of ZnO and TiO2. The anatase phase was previously submitted to heat treatment for achieving a starting mixture rich in a rutile phase. Milling conditions were preset for observing the formation of a low temperature ZnTiO3 phase with a perovskite structure. The powder microstructure was characterized using scanning electron microscopy. A nitrogen gas sorption analyzer with the BET method was used to determine the specific surface area and porosity, indicating changes of powder sample properties during mechanical activation. Also, X ray powder diffractometry was applied to obtain the phase composition. Powders were then pressed into pellets and their compressibility was observed through density changes. According to microstructures obtained by scanning electron microscopy analysis, the system underwent a primary and secondary agglomeration process. Specific surface area measurements supported that conclusion. Compressibility investigations established the difference between compressibility of the non-activated mixture and activated powders. X-ray diffraction analysis revealed that a perovskite structure forms simultaneously with a spinel phase during the process of mechanical activation.

scholarly journals Capture and scanning electron microscopy of individual snow crystals

1994 ◽  
Vol 40 (134) ◽  
pp. 195-197
Author(s):  
E. W. Wolff ◽  
A. P. Reid
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Liquid Nitrogen Temperature ◽  
Experimental Methods ◽  
Snow Crystal ◽  
Snow Crystals ◽  
First Time ◽  
Scanning Electron

AbstractA snow crystal has been successfully collected on to a scanning electron microscope (SEM) stub in central Greenland. It was preserved at liquid-nitrogen temperature for 5 months, prior to examination in the SEM. This is believed to be the first time a snow crystal has been observed directly in the SEM and offers some new experimental methods for understanding crystals and their chemistry.

Distribution of diaphragmatic lymphatic stomata

1991 ◽  
Vol 70 (4) ◽  
pp. 1544-1549 ◽  
Author(s):  
D. Negrini ◽  
S. Mukenge ◽  
M. Del Fabbro ◽  
C. Gonano ◽  
G. Miserocchi
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Surface Area ◽  
Frequency Distribution ◽  
Maximum Diameter ◽  
Minimum Diameter ◽  
Average Value ◽  
Scanning Electron

In seven anesthetized rabbits we measured the size, shape, and density of lymphatic stomata on the peritoneal and pleural sides of the diaphragm. The diaphragm was fixed in situ and processed for scanning electron microscopy. Results are from 2,902 peritoneal and 3,086 pleural fields (each 1,620 microns 2) randomly chosen from the various specimens. Stomata were seen in 9% of the fields examined, and in 30% of the cases they appeared grouped in clusters with 2-14 stomata/field. Stoma density was 250 +/- 242 and 72 +/- 57 (SD) stomata/mm2 on peritoneal and pleural sides, respectively, and it was similar over the muscular and tendinous portion of the two surfaces. The maximum diameter ranged from less than 1 to approximately 30 microns, with an average value of 1.2 +/- 3.1 micron. The ratio of the maximum to the minimum diameter and the surface area averaged 2 +/- 1.4 and 0.7 +/- 2.4 micron 2, respectively. The maximum and minimum diameter and surface area values followed a lognormal frequency distribution, suggesting that stomata geometry is affected by diaphragmatic tension.

Field-Emission Scanning Electron Microscopy and Energy-Dispersive X-Ray Analysis to Understand the Role of Tannin-Based Dyes in the Degradation of Historical Wool Textiles

2014 ◽  
Vol 20 (5) ◽  
pp. 1534-1543 ◽  
Author(s):  
Annalaura Restivo ◽  
Ilaria Degano ◽  
Erika Ribechini ◽  
Josefina Pérez-Arantegui ◽  
Maria Perla Colombini
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Elemental Composition ◽  
Field Emission ◽  
Cross Sections ◽  
Morphological Changes ◽  
Energy Dispersive ◽  
X Ray ◽  
Edx Analysis ◽  
Scanning Electron

Abstract:An innovative approach, combining field-emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDX) analysis, is presented to investigate the degradation mechanisms affecting tannin-dyed wool. In fact, tannin-dyed textiles are more sensitive to degradation then those dyed with other dyestuffs, even in the same conservation conditions.FESEM-EDX was first used to study a set of 48 wool specimens (artificially aged) dyed with several raw materials and mordants, and prepared according to historical dyeing recipes. EDX analysis was performed on the surface of wool threads and on their cross-sections. In addition, in order to validate the model formulated by the analysis of reference materials, several samples collected from historical and archaeological textiles were subjected to FESEM-EDX analysis.FESEM-EDX investigations enabled us to reveal the correlation between elemental composition and morphological changes. In addition, aging processes were clarified by studying changes in the elemental composition of wool from the protective cuticle to the fiber core in cross-sections. Morphological and elemental analysis of wool specimens and of archaeological and historical textiles showed that the presence of tannins increases wool damage, primarily by causing a sulfur decrease and fiber oxidation.

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