Microstructural Development in Nano-Crystalline Zinc Sulfide Powders

1992 ◽  
Vol 286 ◽  
Author(s):  
Y. Han ◽  
E.T. Voiles ◽  
L.S. Chumbley ◽  
M. Akinc
Keyword(s):  
Zinc Sulfide ◽  
Elevated Temperatures ◽  
Ambient Pressure ◽  
Microstructural Development ◽  
Vapor Pressures ◽  
Electron Microscopic ◽  
Nano Crystalline ◽  
High Vapor ◽  
The Individual ◽  
Individual Particles

ABSTRACTMonodispersed, spherical, submicron size zinc sulfide powders were previously prepared in our laboratory utilizing homogeneous precipitation by thermal decomposition of thioacetamide in acidic aqueous solutions. Electron microscopic investigations of these powders indicated that the individual particles were agglomerates of 8∼14 nm size crystallites. It has been known that zinc sulfide does not sinter under ambient pressure due to the covalent nature of its bonding, high melting point, and relatively high vapor pressures at elevated temperatures. The heat treatment of these nano-crystalline zinc sulfide powders, however, showed some degree of sintering at temperatures as low as 600°C under vacuum.

Some Effects of Oxidant Air Pollutants (Ozone and Peroxyacetyl Nitrate) on the Ultrastructure of Leaf Tissues

1972 ◽  
Vol 30 ◽  
pp. 360-361
Author(s):  
William W. Thomson ◽  
Elizabeth S. Swanson
Keyword(s):  
Air Pollutants ◽  
Electron Microscopic Examination ◽  
Peroxyacetyl Nitrate ◽  
Electron Microscopic ◽  
Growth Physiology ◽  
Physiology And Biochemistry ◽  
Entire Plant ◽  
Leaf Tissues ◽  
Gaseous Hydrocarbons ◽  
The Individual

The oxidant air pollutants, ozone and peroxyacetyl nitrate, are produced in the atmosphere through the interaction of light with nitrogen oxides and gaseous hydrocarbons. These oxidants are phytotoxicants and are known to deleteriously affect plant growth, physiology, and biochemistry. In many instances they induce changes which lead to the death of cells, tissues, organs, and frequently the entire plant. The most obvious damage and biochemical changes are generally observed with leaves.Electron microscopic examination of leaves from bean (Phaseolus vulgaris L.) tobacco (Nicotiana tabacum L.) and cotton (Gossipyum hirsutum L.) fumigated for .5 to 2 hours with 0.3 -1 ppm of the individual oxidants revealed that changes in the ultrastructure of the cells occurred in a sequential fashion with time following the fumigation period. Although occasional cells showed severe damage immediately after fumigation, the most obvious change was an enhanced clarity of the cell membranes.

Pyroxene-type compounds NaM3+Ge2O6, withM= Ga, Mn, Sc and In

2014 ◽  
Vol 70 (9) ◽  
pp. 852-857 ◽  
Author(s):  
Günther J. Redhammer ◽  
Gerold Tippelt
Keyword(s):  
Ambient Pressure ◽  
Tetrahedral Site ◽  
Exceptional Case ◽  
Temperature Structure ◽  
Present Sample ◽  
Teller Distortion ◽  
Octahedral Sites ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
The Individual

The four title compounds, namely sodium gallium germanate, NaGaGe2O6, sodium manganese vanadate germanate, NaMnV0.1Ge1.9O6, sodium scandium germanate, NaScGe2O6, and sodium indium germanate, NaInGe2O6, adopt the high-temperature structure of the pyroxene-type chain germanates, with monoclinic symmetry and space groupC2/c. The lattice parameters, the individual and average bond lengths involvingM1, and the distortion parameters scale well with the ionic radius of theM1 cation. NaGaGe2O6has more distortedM1 sites and more extended tetrahedral chains than NaInGe2O6, in which a high degree of kinking is required to maintain the connection between the octahedral and tetrahedral building units of the pyroxene structure. An exceptional case is NaMnGe2O6, in which the strong Jahn–Teller effect of Mn3+results in more distorted octahedral sites than expected according to linear extrapolation from the other NaM3+Ge2O6pyroxenes. In contrast with the literature, minor incorporations of V5+in the tetrahedral site and a corresponding reduction of Mn3+to Mn2+in the octahedral sites in the present sample lower the Jahn–Teller distortion and stabilize the Mn-bearing pyroxene, even allowing its synthesis at ambient pressure.

scholarly journals Thortveitite-type Tm2Si2O7

2014 ◽  
Vol 70 (7) ◽  
pp. i34-i35 ◽  
Author(s):  
Volker Kahlenberg ◽  
Paul Aichholzer
Keyword(s):  
Ambient Pressure ◽  
Point Group ◽  
Structure Type ◽  
Group Symmetry ◽  
Site Symmetry ◽  
Cation Site ◽  
Bond Lengths ◽  
Flux Synthesis ◽  
Distorted Octahedral ◽  
The Individual

Single crystals of dithulium disilicate, Tm2Si2O7, were obtained in flux synthesis experiments in the system SiO2–Tm2O3–LiF at ambient pressure. The compound belongs to the group of sorosilicates,i.e.it is based on [Si2O7]-units and crystallizes in the thortveitite (Sc2Si2O7) structure type. The Tm3+cation (site symmetry .2.) occupies a distorted octahedral site, with Tm—O bond lengths in the range 2.217 (4)–2.289 (4) Å. Each of the octahedra shares three of its edges with adjacent [TmO6] groups, resulting in the formation of layers parallel to (001). The individual [SiO4] tetrahedra are more regular,i.e.the differences between the bond lengths between Si and the bridging and non-bridging O atoms are not very pronounced. The layers containing the octahedra and the sheets containing the [Si2O7] groups (point group symmetry 2/m) form an alternating sequence. Linkage is provided by sharing common oxygen vertices.

scholarly journals An Experimental Observation Related To The Pore Space Between Particles Of Cement In Pastes At Early Ages

1988 ◽  
Vol 137 ◽  
Author(s):  
Hamlin M. Jennings
Keyword(s):  
Surface Charge ◽  
Experimental Observation ◽  
Cement Paste ◽  
Pore Space ◽  
The Individual ◽  
Individual Particles

Cement paste of water:cement ratios less than about 0.3 usually are not workable, but workability can be maintained at these lower water:cement ratios by using superplasticizers. A typical explanation [1] of the mechanism behind the effectiveness of superplasticizers is that they adsorb on the surface of cement particles and adjust the surface charge so that the particles become deflocculated. The individual particles flow more easily than larger flocs.

scholarly journals Prospects for the expansion of standing wave ambient pressure photoemission spectroscopy to reactions at elevated temperatures

2022 ◽  
Vol 40 (1) ◽  
pp. 013207
Author(s):  
Osman Karslıoğlu ◽  
Lena Trotochaud ◽  
Farhad Salmassi ◽  
Eric M. Gullikson ◽  
Andrey Shavorskiy ◽  
...  
Keyword(s):  
Standing Wave ◽  
Elevated Temperatures ◽  
Ambient Pressure ◽  
Photoemission Spectroscopy

Proof of the no-interaction theorem without hamiltonian and lagrangian formalism

1994 ◽  
Vol 445 (1923) ◽  
pp. 221-229 ◽  
Keyword(s):  
Angular Momentum ◽  
Conservation Laws ◽  
Lagrangian Formalism ◽  
The Individual ◽  
Individual Particles

The proofs of the no-interaction theorem have been given by many authors in the framework of hamiltonian and lagrangian formalism. They are based on the assumption that there is hamiltonian or lagrangian describing the interaction between particles. This paper presents the proof without such an assumption for one, two, three and four particles. We assume the conservation laws for the linear and angular momentum that are the sums of the respective quantities of individual particles. Then there is no interaction, i. e. the worldlines of the individual particles are straight.

scholarly journals The straggling of β-particles

1929 ◽  
Vol 125 (798) ◽  
pp. 420-445 ◽  
Keyword(s):  
Classical Theory ◽  
Experimental Investigations ◽  
Theoretical Treatment ◽  
A Value ◽  
Thin Foils ◽  
New Ideas ◽  
The Subject ◽  
The Individual ◽  
Individual Particles ◽  
Α Particles

When a beam of electric particles is passed through a sheet of matter the energy of the individual particles is reduced. The loss of energy is not the same for all the particles so that particles incident on the foil with the same energy emerge with different energies. This dispersion of the energy caused by the foil is known as the "straggling" of the particles. The straggling of α-particles has been the subject of several experimental investigations, and the theory in this case was adequately developed by Bohr in 1915. In the case of β-particles, however, the straggling was not experimentally investigated until quite recently and no theoretical treatment of the phenomenon has been given, the calculations of Bohr being, as he showed, applicable only to α-particles. The purpose of the work described in this paper is to develop a theory of the straggling of β-particles by thin foils and by means of it to interpret the results of experiment. The paper is arranged as follows. In 2 an account is given of the state of the experimental work on the subject, and in particular the effect of the complications introduced by "scattering" are considered. The formula derived by Bohr for the straggling of electric particles is given in 3 and its inapplicability to β-particles demonstrated. The present calculations of the straggling of β-particles are given in 4. The theory of the straggling of electric particles resolves itself into two parts. The first deals with the dynamics of collisions between electric particles and atoms, and is the same whether we are concerned with the straggling or some other phenomena such as ionisation of "stopping power." This may be called the fundamental theory and its requirements may be summarised in the function ϕ (Q) which express the frequency of collisions in which the electric particle loses energy of amount Q. The second part of the theory is the process of calculating the straggling by means of probability theory from the function ϕ . This may be regarded as the straggling theory proper and it is the main subject of 4. When the present calculations were started it was intended to calculate the straggling on the basis of classical theory only, the value of the function ϕ on this theory being definitely known. However, after some practice with the type of calculation involved it was decided to calculate the straggling for other forms of ϕ . From the results obtained it is possible to deduce the straggling corresponding to any form which ϕ may reasonably have, and if a new theory leads to a value of ϕ different from the classical value, the straggling on the new theory may readily be determined. Alternatively this fuller treatment may be used for the reverse process of calculating from the observed straggling the value of ϕ to which it corresponds. This is considered to be the most convenient procedure and in 5 the form of ϕ which explains the experimental results is deduced. this is compared in 6 with the value of ϕ on classical theory. A brief outline is given in 7 of certain new ideas concerning the nature of collisions of electric particles with electrons and atoms.

scholarly journals Microstructural Dynamic Study of Grain Growth

1985 ◽  
Vol 63 ◽  
Author(s):  
M. P. Anderson ◽  
G. S. Grest ◽  
D. J. Srolovitz
Keyword(s):  
Monte Carlo ◽  
Grain Growth ◽  
Materials Science ◽  
Primary Recrystallization ◽  
Lattice Points ◽  
Microstructural Development ◽  
Continuous Systems ◽  
Monte Carlo Techniques ◽  
Topological Features ◽  
The Individual

The complete prediction of microstructural development in polycrystalline solids as a function of time and temperature is a major objective in materials science, but has not yet been possible primarily due to the complexity of the grain interactions. The evolution of the polycrystalline structure depends upon the precise specification of the coordinates of the grain boundary network, the crystallographic orientations of the grains, and the postulated microscopic mechanisms by which elements of the boundaries are assumed to move. Therefore, a general analytical solution to this multivariate problem has not yet been developed. Recently, we have been able to successfully incorporate these aspects of the grain interactions, and have developed a computer model which predicts the main features of the microstructure from first principles [1,2]., The polycrystal is mapped onto a discrete lattice by dividing the material into small area (2d) or volume (3d) elements, and placing the centers of these elements on lattice points. Interactions and dynamics are then defined for the individual elements which are analagous to those postulated in continuous systems. This discrete model preserves the topological features of real materials, and can be studied by computer simulation using Monte Carlo techniques. In this paper we report the application of the Monte Carlo method to the metallurgical phenomenon of grain growth with isothermal annealing. Extension of the model to treat primary recrystallization is presented elsewhere [3,4].

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