The growth of mica polytypes as studied by conventional and high-resolution TEM

1983 ◽  
Vol 41 ◽  
pp. 174-177
Author(s):  
A. Baronnet ◽  
M. Amouric
Keyword(s):  
Water Pressure ◽  
Point Of View ◽  
Temperature Fields ◽  
Natural Occurrence ◽  
Growth Mechanisms ◽  
Long Period ◽  
High Resolution Tem ◽  
Layer Stacking ◽  
Experimental Works ◽  
Potential Use

The origin of mica polytypes has long been a challenging problem for crystal- lographers, mineralogists and petrologists. From the petrological point of view, interest in this field arose from the potential use of layer stacking data to furnish further informations about equilibrium and/or kinetic conditions prevailing during the crystallization of the widespread mica-bearing rocks. From the compilation of previous experimental works dealing with the occurrence domains of the various mica "polymorphs" (1Mr, 1M, 2M1, 2M2 and 3T) within water-pressure vs temperature fields, it became clear that most of these modifications should be considered as metastable for a fixed mica species. Furthermore, the natural occurrence of long-period (or complex) polytypes could not be accounted for by phase considerations. This highlighted the need of a more detailed kinetic approach of the problem and, in particular, of the role growth mechanisms of basal faces could play in this crystallographic phenomenon.

TEM Analysis of Long-Period Polytypes in SiC—S

1976 ◽  
Vol 34 ◽  
pp. 630-631
Author(s):  
S. Shinozaki ◽  
J. W. Sprys
Keyword(s):  
Electron Diffraction ◽  
Isothermal Annealing ◽  
Tem Analysis ◽  
Long Period ◽  
Transmission Electron ◽  
Average Grain Size ◽  
High Resolution Tem ◽  
Structural Lattice ◽  
The Stability ◽  
Continuous Curves

In reaction sintered SiC (∽ 5um average grain size), about 15% of the grains were found to have long-period structures, which were identifiable by transmission electron microscopy (TEM). In order to investigate the stability of the long-period polytypes at high temperature, crystal structures as well as microstructural changes in the long-period polytypes were analyzed as a function of time in isothermal annealing.Each polytype was analyzed by two methods: (1) Electron diffraction, and (2) Electron micrograph analysis. Fig. 1 shows microdensitometer traces of ED patterns (continuous curves) and calculated intensities (vertical lines) along 10.l row for 6H and 84R (Ramsdell notation). Intensity distributions were calculated based on the Zhdanov notation of (33) for 6H and [ (33)3 (32)2 ]3 for 84R. Because of the dynamical effect in electron diffraction, the observed intensities do not exactly coincide with those intensities obtained by structure factor calculations. Fig. 2 shows the high resolution TEM micrographs, where the striped patterns correspond to direct resolution of the structural lattice periodicities of 6H and 84R structures and the spacings shown in the figures are as expected for those structures.

scholarly journals Emerging Technology for a Green, Sustainable Energy Promising Materials for Hydrogen Storage, from Nanotubes to Graphene—A Review

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2499
Author(s):  
Krzysztof Jastrzębski ◽  
Piotr Kula
Keyword(s):  
Energy Source ◽  
Hydrogen Storage ◽  
Mobile Applications ◽  
Emerging Technology ◽  
Green Energy ◽  
Point Of View ◽  
Energy Industry ◽  
Volumetric Density ◽  
Potential Use ◽  
Carbon Based

The energetic and climate crises should pose a challenge for scientists in finding solutions in the field of renewable, green energy sources. Throughout more than two decades, the search for new opportunities in the energy industry made it possible to observe the potential use of hydrogen as an energy source. One of the greatest challenges faced by scientists for the sake of its use as an energy source is designing safe, usable, reliable, and effective forms of hydrogen storage. Moreover, the manner in which hydrogen is to be stored is closely dependent on the potential use of this source of green energy. In stationary use, the aim is to achieve high volumetric density of the container. However, from the point of view of mobile applications, an extremely important aspect is the storage of hydrogen, using lightweight tanks of relatively high density. That is why, a focus of scientists has been put on the use of carbon-based materials and graphene as a perspective solution in the field of H2 storage. This review focuses on the comparison of different methods for hydrogen storage, mainly based on the carbon-based materials and focuses on efficiently using graphene and its different forms to serve a purpose in the future H2-based economy.

History: changing the forms or forming the changes?

2005 ◽  
Vol 13 (1) ◽  
pp. 47-66 ◽  
Author(s):  
SVEND ERIK LARSEN
Keyword(s):  
Cultural History ◽  
18Th Century ◽  
Point Of View ◽  
Future Planning ◽  
Long Period ◽  
Close Analysis ◽  
Vitruvian Man ◽  
Human Responsibility ◽  
The Individual ◽  
Individual Human

Change in European cultural history has, for a long period, been discussed through two interrelated notions, that of science and that of history. This paper traces the various stages of this discussion from Antiquity to the present day from the point of view of history. Two reoccurring and paradigmatic characters of mythological descent, Odysseus and Prometheus, illustrate how history as a realm for human responsibility and future planning has established itself as a specific European construct, with the 18th century as its final breakthrough in practical and ideological terms. A close analysis of Leonardo da Vinci's drawing the Vitruvian Man, in statu nascendi, shows how the individual human being carrying the obligations and the promises of this history, is envisioned. The final remarks underline the importance of scientific knowledge in the concrete shaping of this responsibility and a plea for an increased cooperation across the disciplines.

scholarly journals To the casuistry of tetany

2021 ◽  
Vol 30 (9) ◽  
pp. 904-906
Author(s):  
E. M. Auslender
Keyword(s):  
Point Of View ◽  
Parathyroid Glands ◽  
Symptom Complex ◽  
Experimental Works

If the case of tetany is given in the present work, it is done not because this disease is rare, but because our case is interesting from the point of view of the etiological moment, which gave such pronounced symptom complex of tetany. The fact that tetany is an expression of hypofunction of parathyroid glands is considered incontestable after the work of Erdheim, the experimental works of Gleil and others.

Use of Scrap Tire Chips in Asphaltic Membrane

1996 ◽  
Vol 1530 (1) ◽  
pp. 59-63
Author(s):  
Kamyar C. Mahboub ◽  
Phillip R. Massie
Keyword(s):  
Cost Effective ◽  
Waste Materials ◽  
Scrap Tire ◽  
Research Project ◽  
Moisture Barrier ◽  
Waste Tires ◽  
Long Period ◽  
Tire Chips ◽  
Potential Use

Findings of a study involving the use of scrap tire chips in an asphaltic membrane are reported. The research project was designed with two objectives in mind: investigate the effectiveness of an asphaltic membrane on top of a subgrade for maintaining moisture equilibrium in subgrade and study the potential use of scrap tire chips in asphaltic membranes. The effectiveness of the membrane as a moisture barrier needs to be evaluated over a long period of time. However, the method proved to be a cost-effective way of recycling waste tires in pavements. It is hoped that this study will contribute to various efforts in the area of cost-effective and sound use of waste materials in construction.

scholarly journals General Theory of Subglacial Cavitation and Sliding of Temperate Glaciers

1968 ◽  
Vol 7 (49) ◽  
pp. 21-58 ◽  
Author(s):  
L. Lliboutry
Keyword(s):  
Frictional Force ◽  
Atmospheric Pressure ◽  
Hydraulic System ◽  
Water Pressure ◽  
Realistic Model ◽  
Point Of View ◽  
Small Scale ◽  
Sliding Velocity ◽  
Surface Slope ◽  
Geometrical Progression

AbstractEarlier theories of Weertman and the present author are reviewed and compared; both are insufficient to account for the facts observed at the tongue of the Allalingletscher.A calculation of the stresses and heat flow at the bed of a glacier with a sinusoidal profile is given which takes account of any degree of subglacial cavitation. The sliding due to plasticity and that due to pressure melting are related to this degree of cavitation and it is shown that these two terms are additive. There results an expression for the frictionfωin terms of the total sliding velocityuand the height of the bumpsa. For a given and large enough value ofu,fω(a) exhibits two maxima which are equal and independent ofu.The paper then considers a more realistic model of the bed consisting of a superposition of sine waves all having the same roughnessr, andadecreasing in a geometrical progression. The biggestamay be inferred from the overall profile of the bedrock; the resulting frictional force can be regarded either as part of the total frictional forcefin an overall view for whichf=ρghsinαholds, or else as a correction to such a value on the small scale (the best point of view for crevasse studies). To a first approximation Coulomb’s law of friction holds provided one takes account of the interstitial water pressure at the ice-rock interface.This interstitial pressurepis next related to the thickness of the glacierh. If the subglacial hydraulic system is at atmospheric pressure,pis proportional toh. Next, if the sliding velocity is not too large, the surface slope approaches 1.6r≈ 0.12 and kinematic waves (which move four times as fast as the ice) disappear rapidly. If the hydraulic system is not at atmospheric pressure the surface slope is smaller and flow instabilities can occur.

scholarly journals Study Regarding the Potential Use of a Spent Microbial Biomass in Fertilizer Manufacturing

Agronomy ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 299
Author(s):  
Nicoleta Radu ◽  
Ana Aurelia Chirvase ◽  
Narcisa Babeanu ◽  
Ovidiu Popa ◽  
Petruta Cornea ◽  
...  
Keyword(s):  
Solanum Lycopersicum ◽  
Biomass Concentration ◽  
Positive Influence ◽  
Point Of View ◽  
Waste Dumps ◽  
Different Types ◽  
Germination Experiments ◽  
Positive Effect ◽  
Potential Use ◽  
Spent Biomass

A spent biomass, which results from the biopharma industry, is stabilized and functionalized by biosorption with microelements. The efficiency of this new biomaterial was tested in two experiments: 1) In a mixture with soil to determine its effects of the germination capacity of cereals and vegetables, and 2) in a formulation of mixed fertilizers to determine its influence on the development and production of the two types of vegetables. The results obtained during germination experiments performed in pots showed that at a biomass concentration less than 20%, the germination output was greater than 95% and the germination index was almost 1. The experiments performed in land on vegetables (including Solanum lycopersicum and Capsicum annuum) featured six types of fertilizers formulated with new biomaterials. The obtained results indicated that two types of fertilizers (N 10:0:0 and NP 5:5:0), which were formulated with functionalized biomass and featured the microelements Co, Cu, Fe, Mn, and Zn, exhibited significant effects when compared with vegetables cultivated on unfertilized soil surfaces (the untreated variant). The studies regarding the effect of the new fertilizers obtained based on spent biomass from biopharma industry indicate the following: a) This material, even if it is stabilized and functionalized, cannot be used as such as a germination substrate for vegetables; in addition, it cannot be introduced into soil together with cereals seeds (during the autumn work), because the germination can be affected negatively; b) the functionalized biomass can be used in the formulation of different types of fertilizers; if these fertilizers are introduced into soil with the autumn plowing, then they may have a positive influence on the yield of some species of vegetable, such as Solanum lycopersicum and Capsicum annum. The new fertilizers have a major environmental impact due to: 1) Removal of waste, which results from pharmaceutical biosyntheses, with significant impact on soil pollution, due to its storage in the form of waste dumps, on the soil; 2) recovery and reinsertion into the natural circuit of nutrients like C, N, P, K, Mg, and Ca contained in spent biomass, by their reuse in agriculture; and 3) high content of compounds with C from spent biomass can improve in time the content of fulvic and humic acids in soil, with a positive effect on soil characteristics from an agronomic point of view.

scholarly journals Thermal Conductivity of High Performance Concrete in Wide Temperature and Moisture Ranges

10.14311/174 ◽  
2001 ◽  
Vol 41 (1) ◽  
Author(s):  
J. Toman ◽  
R. Černý
Keyword(s):  
Thermal Conductivity ◽  
High Performance ◽  
Room Temperature ◽  
High Performance Concrete ◽  
Measuring Method ◽  
Point Of View ◽  
Temperature Measurements ◽  
Temperature Fields ◽  
Measured Temperature ◽  
Hot Wire

The thermal conductivity of two types of high performance concrete was measured in the temperature range from 100 °C to 800 °C and in the moisture range from dry material to saturation water content. A transient measuring method based on analysis of the measured temperature fields was chosen for the high temperature measurements, and a commercial hot wire device was employed in room temperature measurements of the effect of moisture on thermal conductivity. The measured results reveal that both temperature and moisture exhibit significant effects on the values of thermal conductivity, and these effects are quite comparable from the point of view of the magnitude of the observed variations.

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