Real Structure and Internal Friction of Boron Doped with Zirconium

1987 ◽  
Vol 97 ◽  
Author(s):  
G. Sh. Darsavelidze ◽  
G. V. Tsagareishvili ◽  
M. E. Antadze ◽  
O. A. Tsagareishvili ◽  
A. G. Khvedelidze ◽  
...  
Keyword(s):  
Internal Friction ◽  
Twin Boundary ◽  
Boundary Motion ◽  
Continuous Change ◽  
Elastic Fields ◽  
Linear Defects ◽  
Boron Doped ◽  
Diffraction Patterns ◽  
High Level ◽  
Simulated Analysis

ABSTRACTThe nature of interaction of point and linear defects in semiconductor boron doped with zirconium (∼ 1.5% at.) has been studied using electron microscope and internal friction methods. It was shown that doping with zirconium promoted the multiplication of polysynthetic twins and stacking faults. A computer simulated analysis of diffraction patterns was performed in terms of trigonal presentation. At the frequency of free torsional vibrations of ∼ 1Hz a high level of internal friction with maxima at 250, 300–320 and 380–420°C was revealed. It is supposed that the maxima are respectively due to: the twin-boundary motion accompanied by breaking of intericosahedral bonds (a); the process of ordering-disordering of atoms in the impurity atmospheres under the continuous change of the temperature and elastic fields of moving twinning dislocations in the {100} system (b); the impurity controlled twin-boundary motion in the {511} system.

scholarly journals Demographic transformation in the agglomerations of Dnipropetrovsk region

2019 ◽  
Vol 28 (1) ◽  
pp. 3-10
Author(s):  
V. V. Bezugly ◽  
Z. V. Boyko ◽  
О. V. Tsvietaieva
Keyword(s):  
Reproductive Age ◽  
Low Fertility ◽  
The European Union ◽  
Negative Consequences ◽  
Continuous Change ◽  
Urban Agglomerations ◽  
Active Population ◽  
Labour Potential ◽  
Negative Balance ◽  
High Level

This article examines the demographic situation in Dnipropetrovsk region and identifies the main demographic problems of the region , among which the most important are low fertility, reduced family size, high divorce rates and unregistered marriages, contimuing aging of the population, increased gender disproportion among the population, intra-regional and especially modern external migrations of the population, etc. The Dnipropetrovsk settlement system includes four industrial agglomerations: Dniprovsky-Kamianske, Kryvyi Rih, Nikopol and Pavlohrad, where more than 83.5% of the region’s population lives , indicating a high level of urbanization of the territory. It was found that the dynamics of the population of the urban agglomerations of the Dnipropetrovsk region over the past 20 years has a tendency to progressive reduction: if in 1997 the size of the existing population amounted to 3,888.8 thousand people, in 2017it amounted to 3,227.5 thousand people. It is stated that the natural replenishment of the population provides a continuous change of generations, creating the quantitative boundaries of labour resources of urban agglomerations of Dnipropetrovsk region. The current state of migration processes in the agglomerations of Dnipropetrovsk region is caused by socio-economic and political problems. This has led to an increase in labour out-migration, which now has already become catastrophic, not only in the Dnipropetrovsk region, but throughout Ukraine. Negative consequences of this are the depopulation of cities and areas of agglomerations, the outflow of high quality labour potential (and in particular qualified labour), the collapse of families, rise in crime and corruption, etc. In general, it is established that the demographic aspect, due to natural and mechanical movements, has become a determining factor inthe formation of the labour resource situation and affects not only the process of replenishmnent itself, but also the structure of the economically active population. We present the general demographic features of the population's reproduction, in the urban agglomerations of Dnipropetrovsk region from 1997 to 2017; a decrease in the total population, a negative natural population growth (mortality rates will prevail over birth rates), aging of the population, which is reflected in an increase in the number of people aged 70, disproportion in the sexual structure of the population (prevalence of women), negative balance of migration and continuous outflow of inhabitants of reproductive age, especially to the countries of the European Union.

XIII. The Bakerian Lecture .—On the viscosity or internal friction of air and other gases

1866 ◽  
Vol 156 ◽  
pp. 249-268 ◽  
Keyword(s):  
Internal Friction ◽  
Continuous Change ◽  
Liquid Form ◽  
Gaseous State ◽  
Solid States ◽  
Gaseous Form

The gaseous form of matter is distinguished by the great simplification which occurs in the expression of the properties of matter when it passes into that state from the solid or liquid form. The simplicity of the relations between density, pressure, and temperature, and between the volume and the number of molecules, seems to indicate that the molecules of bodies, when in the gaseous state, are less impeded by any complicated mecha­nism than when they subside into the liquid or solid states. The investigation of other properties of matter is therefore likely to be more simple if we begin our research with matter in the form of a gas. The viscosity of a body is the resistance which it offers to a continuous change of form, depending on the rate at which that change is effected.

scholarly journals Dynamic Behaviour of Dislocations in HF-Doped Ice Ih

1980 ◽  
Vol 25 (91) ◽  
pp. 133-150 ◽  
Author(s):  
J. Perez ◽  
C. Maï ◽  
J. Tatibouët ◽  
R. Vassoille
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
High Temperature ◽  
Internal Friction ◽  
Dynamic Behaviour ◽  
Dislocation Glide ◽  
Linear Defects ◽  
Doping Effects ◽  
Crystalline Core ◽  
Accumulation Effect

AbstractA model of dislocation glide in ice Ih was recently proposed. This model was developed on certain assumptions, namely that transitions occur through cooperative movements of H2O molecules in the non-crystalline core of dislocations. A relation between the velocityvdof linear defects and shear stressτor temperatureTis obtained. This relation shows thatvdvaries linearly withτat low values ofτand (or)Tbut varies more rapidly at higher stresses; this non-linearity is more pronounced the higher the temperature. Such an analysis is extended in order to take into account doping effects. The case of HF-doped ice is considered: it is shown that there is a strong accumulation effect of HF molecules in the dislocation cores, which induces an increase of the rate of transitions. The results are in agreement with experimental data concerning both the velocity of dislocations and high-temperature internal friction in HF-doped ice.

Effect of H-Doping on Damping Capacity of Various NiTi-Based Alloys at kHz Frequencies

2006 ◽  
Vol 128 (3) ◽  
pp. 254-259 ◽  
Author(s):  
B. Coluzzi ◽  
A. Biscarini ◽  
G. Mazzolai ◽  
F. M. Mazzolai ◽  
A. Tuissi
Keyword(s):  
Internal Friction ◽  
Twin Boundary ◽  
Room Temperature ◽  
Mechanical Energy ◽  
Noise Pollution ◽  
Metal Alloy ◽  
Maximum Efficiency ◽  
Damping Capacity ◽  
Good Opportunity ◽  
Hydrogen Doping

The internal friction Q−1 and the Young’s modulus E of NiTi based alloys have been measured as a function of temperature after various thermomechanical and hydrogen-doping treatments given to the materials. Hydrogen is found to play a major role introducing tall damping peaks associated with Snoek-type and H-twin boundary relaxations. Levels of Q−1 as high as 0.08 have been detected, which are among the highest to date measured in metal alloy systems. For appropriate alloy compositions, these peaks occur at around room temperature (for acoustical frequencies), thus providing a good opportunity to reduce machinery vibrations and noise pollution. In the paper, the conditions are highlighted under which maximum efficiency can be reached in the conversion of mechanical energy into heat.

scholarly journals Effect of Twin Boundary Motion and Dislocation-Twin Interaction on Mechanical Behavior in Fcc Metals

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2238
Author(s):  
Jaber Rezaei Mianroodi ◽  
Bob Svendsen
Keyword(s):  
Twin Boundary ◽  
Partial Dislocation ◽  
Shear Loading ◽  
Dislocation Nucleation ◽  
The Other ◽  
Boundary Motion ◽  
Normal Loading ◽  
Fcc Metals ◽  
Boundary Orientation ◽  
Normal Twin

The interplay of interface and bulk dislocation nucleation and glide in determining the motion of twin boundaries, slip-twin interaction, and the mechanical (i.e., stress-strain) behavior of fcc metals is investigated in the current work with the help of molecular dynamics simulations. To this end, simulation cells containing twin boundaries are subject to loading in different directions relative to the twin boundary orientation. In particular, shear loading of the twin boundary results in significantly different behavior than in the other loading cases, and in particular to jerky stress flow. For example, twin boundary shear loading along ⟨ 112 ⟩ results in translational normal twin boundary motion, twinning or detwinning, and net hardening. On the other hand, such loading along ⟨ 110 ⟩ results in oscillatory normal twin boundary motion and no hardening. As shown here, this difference results from the different effect each type of loading has on lattice stacking order perpendicular to the twin boundary, and so on interface partial dislocation nucleation. In both cases, however, the observed stress fluctuation and “jerky flow” is due to fast partial dislocation nucleation and glide on the twin boundary. This is supported by the determination of the velocity and energy barriers to glide for twin boundary partials. In particular, twin boundary partial edge dislocations are significantly faster than corresponding screws as well as their bulk counterparts. In the last part of the work, the effect of variable twin boundary orientation in relation to the loading direction is investigated. In particular, a change away from pure normal loading to the twin plane toward mixed shear-normal loading results in a transition of dominant deformation mechanism from bulk dislocation nucleation/slip, to twin boundary motion.

Real-time observation of twin boundary motion in organic crystal (TMTSF)2X

2001 ◽  
Vol 251 (1) ◽  
pp. 199-205 ◽  
Author(s):  
Kazushige Kawabata ◽  
Yasuyoshi Hosokawa ◽  
Takashi Kawauchi ◽  
Takashi Sambongi
Keyword(s):  
Real Time ◽  
Twin Boundary ◽  
Organic Crystal ◽  
Boundary Motion ◽  
Time Observation ◽  
Real Time Observation

Nonuniform twin-boundary motion in Ni–Mn–Ga single crystals

2004 ◽  
Vol 84 (20) ◽  
pp. 4071-4073 ◽  
Author(s):  
Miguel A. Marioni ◽  
Samuel M. Allen ◽  
Robert C. O’Handley
Keyword(s):  
Single Crystals ◽  
Twin Boundary ◽  
Boundary Motion
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