Mechanical Property Characterisation of Crystalline, Ion Implantation Amorphised and Annealed Relaxed Silicon with Spherical Indenters

1993 ◽  
Vol 308 ◽  
Author(s):  
J.S. Williams ◽  
J.S. Field ◽  
M.V. Swain
Keyword(s):  
Amorphous Material ◽  
Crystalline Material ◽  
Substantial Evidence ◽  
Depth Of Penetration ◽  
Annealed Material ◽  
Mean Pressure ◽  
The Difference ◽  
Force Displacement ◽  
Similar Force ◽  
Continuous Loading

ABSTRACTSilicon single crystals have been ion implanted with Si ions at various energies and doses sufficient to achieve amorphisation to a depth of more than 1μm. This surface was subsequently annealed at 450°C for 30 minutes in vacuum to relax the implanted amorphous silicon. Mechanical properties of the different materials (crystalline, amorphous and annealed) were measured using a nominally 10 μm radius diamond tipped indenter and two indenting procedures; continuous loading and load partial-unloading. The crystalline material exhibited similar force-displacement behaviour to that observed by Weppelmann et al. [1] including a critical pressure to induce deformation on loading and a "pop-out" event during unloading. The amorphous and annealed materials showed a greater degree of plastic deformation but did not exhibit "pop-out" behaviour at lower loads (200 mN). The results are analysed to determine the difference of mean pressure with depth of penetration for all the materials. The onset of ductility was 5.5 to 6 GPa for the amorphous material and 10.9 GPa for the crystalline material. The depth dependence of hardness for the amorphous and annealed material showed substantial evidence of work hardening whereas the crystalline material did not.

scholarly journals Impact of Thermal Oxidation on Morphological, Structural and Magnetic Properties of Fe-Ni Wire-Like Nanochains

2021 ◽  
Author(s):  
Marcin Krajewski ◽  
Mateusz Tokarczyk ◽  
Sabina Lewińska ◽  
Kamil Bochenek ◽  
Anna Ślawska-Waniewska
Keyword(s):  
Magnetic Properties ◽  
Thermal Oxidation ◽  
Amorphous Material ◽  
Crystalline Material ◽  
Future Application ◽  
Energy Storage Devices ◽  
Storage Devices ◽  
Structural And Magnetic Properties ◽  
Source Of Information ◽  
The Magnetic Field

AbstractThis work presents the evolution of morphological, structural and magnetic properties of amorphous Fe-Ni wire-like nanochains caused by thermal oxidation. The initial Fe1−xNix samples (x = 0.75; 0.50; 0.25) were prepared through the magnetic-field-induced synthesis, and then they were heated in dry air at 400 °C and 500 °C. These treatments led to two competing simultaneous processes occurring in the investigated samples, i.e., (i) a conversion of amorphous material into crystalline material, and (ii) their oxidation. Both of them strictly affected the morphological and structural properties of the Fe-Ni nanochains which, in turn, were associated with the amount of iron in material. It was found that the Fe0.75Ni0.25 and Fe0.50Ni0.50 nanochains were covered during thermal treatment by the nanoparticle oxides. This coverage did not constitute a good barrier against oxidation, and these samples became more oxidized than the Fe0.25Ni0.75 sample which was covered by oxide nanosheets and contained additional Ni3B phase. The specific morphological evolutions of the Fe-Ni nanochains also influenced their saturation magnetizations, whereas their coercivities did not vary significantly. The obtained results constitute an important source of information for future application of the thermally treated Fe-Ni nanochains which could be applied in the energy storage devices or catalysis.

Abstract 15322: Trifecta vs. Mitroflow: Superior Hemodynamics Despite Similar Design

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Mahmoud Diab ◽  
Gloria Faerber ◽  
Ivliane Tsanava ◽  
Martin Breuer ◽  
Mario Walther ◽  
...  
Keyword(s):  
Aortic Annulus ◽  
Special Consideration ◽  
Pressure Gradients ◽  
Valve Design ◽  
Innovative Design ◽  
Mean Pressure ◽  
The Difference ◽  
Different Diameters

Purpose: Hemodynamic results of stented tissue valves are influenced by both valve design and sizing strategy. The Mitroflow and the Trifecta have an innovative design where the pericardium is wrapped around the stent. The goal of this study was to compare both valves giving special consideration to the suggested sizing strategies. Methods: We obtained pressure gradients from discharge echocardiograms from all patients having received an isolated Trifecta (n=104) or Mitroflow (n=246) between 01/2007 and 01/2014. We compared the results by size label and by the most likely selected size according to the suggested sizing strategy. This is important because the prostheses, despite having a similar design, have different diameters for the same size label and different sizing strategies. Results: The majority of implanted valves were size labels 21 and 23 (82.7% of the Trifecta and 74.8% of the Mitroflow). Mean pressure radients were lowest with Trifecta (Trifecta vs. Mitroflow, label-21: 11.4±4.65 vs 13.6±5.23 mmHg, label-23: 9.23±3.38 vs. 11.8±4.42 mmHg, p< 0.05, and label-25: 11.2±4.97 vs 12.0±4.46 mmHg, n.s.). The sizers for the Trifecta are metric, while those for the Mitroflow are 2-3 mm larger than the corresponding size label. It is therefore likely that for a patient with a 23 mm aortic annulus, a 23 Trifecta but often only a 21 Mitroflow is selected. Thus, comparing the Trifecta to the Mitroflow not by size label but by selected valve (e.g., 23 vs. 21) would therefore only increase the difference. Conclusion: The Trifecta shows a hemodynamic advantage over the Mitroflow which is not likely associated with the applied sizing strategy.

scholarly journals The Relationship Between Alcohol Beverage Types and Violence

2018 ◽  
Vol 49 (1) ◽  
pp. 183-200
Author(s):  
Aleksandra J. Snowden
Keyword(s):  
Regression Models ◽  
Neighborhood Characteristics ◽  
Substantial Evidence ◽  
Alcohol Outlets ◽  
Observation Instrument ◽  
Beverage Type ◽  
Social Observation ◽  
Ecological Association ◽  
The Difference ◽  
The Relationship

There is substantial evidence of an ecological association between off-premise alcohol outlets and violence. We know less, however, about how specific beverage types that are sold in the outlets might explain the difference in violence rates across different alcohol outlets. Data on alcohol beverage types were collected for all off-premise alcohol outlets in Milwaukee, Wisconsin, using a systematic social observation instrument. Spatially lagged regression models were estimated to determine whether the variation in alcohol beverage types is related to robbery density net of important neighborhood predictors of crime rates. Availability of all alcohol beverage types (beer, wine, spirits, premixed, single beer, single spirits, single premixed) was positively associated with the density of robberies, net of neighborhood characteristics. Reducing alcohol beverages, regardless of the beverage type, sold at off-premise alcohol outlets may reduce violence in communities.

Mechanism of the Crystallization of High Polymers

1954 ◽  
Vol 27 (2) ◽  
pp. 374-384 ◽  
Author(s):  
G. Schuur
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Amorphous Material ◽  
Crystalline Polymer ◽  
Longitudinal Direction ◽  
Crystalline Material ◽  
Current View ◽  
X Ray ◽  
Made In ◽  
High Polymers

Abstract The crystallization of higher polymers is a phenomenon which is not yet fully understood, one of the main difficulties being to explain how the spherulites arise. An attempt will be made in this paper to draw a clearer picture of the mechanism of crystallization and thus to account for the origin of spherulites. It will then be seen how several other phenomena involved in the crystallization of natural rubber can be shown to be logically interrelated. The current view is that a crystalline polymer consists of a continuous amorphous phase containing small crystalline regions, the crystallites. The evidence as to the size of these crystallites, however, is at present inconclusive, because only the lower limit of their size can be measured by means of x-ray examination. The reason is that, owing to the absence of reflections of a higher order, the effect of irregularities in the crystallites and of the heat motion of the molecules cannot be measured separately. Another doubtful question is whether the small angle interference maxima are to be interpreted as a measure of mean distances between the crystallites. To do this, Wallner has to resort to the assumption that the crystallites are unstable, whereas it is presumed, on the evidence of the mechanical properties of the high polymers, that a crystallite is stable and permanent. Hoffmann found 82 ± 7 per cent of crystalline material in polychlorotrifluoroethylene and Buckley, Cross, and Ray found as much as 95 per cent in polymethylene. Such high percentages make it doubtful whether the crystalline phase can be discontinuous at all. In this article any volume of material in which the molecules lie parallel is called a crystallite. The direction in which the molecules are oriented is termed the longitudinal direction of the crystallite. It is immaterial to the argument whether a crystallite consists of several crystallites, aligned in parallel separated by a small amount of amorphous material, or of a single crystallite containing large irregularities.

scholarly journals The sensitivity of atomic analysis by X-rays

1932 ◽  
Vol 135 (828) ◽  
pp. 637-656 ◽  
Keyword(s):  
Atomic Number ◽  
Target Material ◽  
High Sensitivity ◽  
Major Constituent ◽  
X Rays ◽  
Depth Of Penetration ◽  
X Ray ◽  
Constituent Element ◽  
The Difference ◽  
Atomic Analysis

In a previous paper it was shown that 0·0007 per cent, of 29 Cu and 0·0003 per cent, of 26 Fe could be detected in 30 Zn by atomic analysis by X-ray spectroscopy. This sensitivity is greater than that which was claimed by Noddack, Tacke, and Berg, who set the limit at about 0·1 per cent, for non-metals, and by Hevesy, who stated it to be about 0·01 per cent, for an element present in an alloy. It was later suggested by Hevesy that the high value of the sensitivity which we found might result from the fact that some of the alloys we had used were composed of elements of almost equal atomic number, and that the sensitivity would be smaller for a constituent of low atomic number mixed with a major constituent of high atomic number. To elucidate these disagreements we have made further observations of the sensitivity with elements of different atomic number and have investigated the conditions which can influence the sensitivity. The Factors Determining Sensitivity . The detection of one element in a mixture of elements depends upon the identification of its K or L lines in the general spectrum emitted by the mixture under examination. The intensity with which these lines are excited in the target (“excited intensity”) is proportional to the number of atoms of the constituent element excited, i. e ., to its concentration and to the volume of the target in which the cathode ray energy is absorbed. The depth of penetration of the cathode rays is determined by the density of the target material and by their velocity ( i. e ., by the voltage applied to the X-ray tube). Schonland has shown that the range of homogeneous cathode rays in different elements, expressed as a mass per unit area, is approximately constant and is independent of the atomic number of the absorbing element. When their velocity is increased, the cathode rays will penetrate to a greater depth, and therefore a greater number of atoms of all constituents will be ionised. This will increase the “excited intensity” of the lines due to the particular constituent sought equally with those lines of the other elements present. The intensity of a line further depends upon the difference between the voltage applied to the X-ray tube and that necessary to excite the series. For these reasons, a high applied voltage is required for a high sensitivity.

Heterogeneity of mean alveolar pressure during high-frequency oscillations

1987 ◽  
Vol 62 (1) ◽  
pp. 223-228 ◽  
Author(s):  
J. L. Allen ◽  
I. D. Frantz ◽  
J. J. Fredberg
Keyword(s):  
High Frequency ◽  
Flow Distribution ◽  
Transpulmonary Pressure ◽  
Alveolar Pressure ◽  
Regional Heterogeneity ◽  
Regional Flow ◽  
High Frequency Oscillations ◽  
Dynamic Head ◽  
Mean Pressure ◽  
The Difference

Mean alveolar pressure may exceed mean airway pressure during high-frequency oscillations (HFO). To assess the magnitude of this effect and its regional heterogeneity, we studied six excised dog lungs during HFO [frequency (f) 2–32 Hz; tidal volume (VT) 5–80 ml] at transpulmonary pressures (PL) of 6, 10, and 25 cmH2O. We measured mean pressure at the airway opening (Pao), trachea (Ptr), and four alveolar locations (PA) using alveolar capsules. Pao was measured at the oscillator pump, wherein the peak dynamic head was less than 0.2 cmH2O. Since the dynamic head was negligible here, and since these were excised lungs, Pao thus represented true applied transpulmonary pressure. Ptr increasingly underestimated Pao as f and VT increased, with Pao - Ptr approaching 8 cmH2O. PA (averaged over all locations) and Pao were nearly equal at all PL's, f's, and VT's, except at PL of 6, f 32 Hz, and VT 80 ml, where (PA - Pao) was 3 cmH2O. Remarkably, mean pressure in the base exceeded that in the apex increasingly as f and VT increased, the difference approaching 3 cmH2O at high f and VT. We conclude that, although global alveolar overdistension assessed by PA - Pao is small during HFO under these conditions, larger regional heterogeneity in PA's exists that may be a consequence of airway branching angle asymmetry and/or regional flow distribution.

Frictional anisotropy in nonmetallic crystals

1966 ◽  
Vol 295 (1442) ◽  
pp. 244-258 ◽  
Keyword(s):  
Magnesium Oxide ◽  
Plastic Flow ◽  
Lithium Fluoride ◽  
Crystal Surface ◽  
Shear Stresses ◽  
Depth Of Penetration ◽  
Diamond Crystals ◽  
Deformation And Fracture ◽  
Fluoride Crystals ◽  
The Difference

A study is made of the effect of the crystallographic direction of sliding on the friction of the (001) surfaces of diamond, magnesium oxide and lithium fluoride crystals. The friction shows marked anisotropy and with all the crystals it is greatest in the <100> directions and least in the <110> directions. The degree and magnitude of the anisotropy is dependent upon the shape of the slider and the ease with which it penetrates the crystal surface. Sharp sliders increase the degree of brittle failure and this leads to deeper penetration and to the removal of more material during sliding. With these crystals the depth of penetration is greater in the <100> directions then in the <110> and it is this which is primarily responsible for the frictional anisotropy. An explanation of frictional anisotropy is proposed which is based on the difference in the magnitude and distribution of resolved shear stresses during sliding in various crystallographic directions. This analysis is used to predict the effect of crystallographic orientation on the frictional behaviour when a (110) surface of magnesium oxide replaces the cube (001) surface used in the other experiments. Mechanisms of deformation and fracture associated with the friction are described. Brittle behaviour predominates in diamond crystals and only cleavage cracks are observed. Appreciable plastic flow occurs in both magnesium oxide and lithium fluoride crystals. With these crystals the initial plastic deformation leads to dislocation interactions which result in cracking and fracture along the {110} planes. These interact with cleavage cracks on {100} planes which are produced by tensile stress and cause surface fragmentation and wear of the crystal. Plastic flow is the only mode of deformation observed on (001) lithium fluoride surfaces when a very smooth blunt slider is used. This causes ‘pile-up’ of material along <110> directions (as previously observed in copper crystals) but it does not produce any appreciable anisotropy in the friction.

scholarly journals The Interpretation of HRTEM Images of Partially Amorphized Pyrochlore Structure Types.

1990 ◽  
Vol 183 ◽  
Author(s):  
Mark L. Miller ◽  
R. C. Ewing
Keyword(s):  
Limit Of Detection ◽  
Amorphous Material ◽  
Pyrochlore Structure ◽  
Image Contrast ◽  
Crystalline Material ◽  
Total Thickness ◽  
Volume Percent ◽  
Crystalline Materials ◽  
Image Simulations ◽  
Crystalline Matrix

AbstractThe results of image simulations on partially amorphous microlite (Ca2Ta2O7, pyrochlore structure) are presented. Results indicate that HRTEM images are not sensitive to the position of amorphous layers within a crystalline matrix. In addition, it is observed that the limit of detection of amorphous material within a crystalline matrix is dependent upon the total thickness of the sample. In thin crystals (<150 Å), up to 75 volume percent crystalline material can give rise to aperiodic images, yet the addition of a small amount of crystalline material (80 volume percent crystalline) produces a periodic image. Images calculated for isolated spheres of amorphous material distributed within crystalline microlite suggest that isolated domains of amorphization are observable at sample thicknesses less than three times the diameter of the feature. The image contrast of amorphized domains is enhanced by imaging at defocus settings significantly different than Scherzer focus. These results indicate that interpretation of HRTEM images of partially amorphized crystalline materials should be undertaken with caution, and estimates of the volume of damage considered only qualitative.

scholarly journals Pulmonary hypertension. Clarifying concepts

ANALES RANM ◽  
2021 ◽  
Vol 138 (138(02)) ◽  
pp. 137-142
Author(s):  
J.R. de Berrazueta Fernández
Keyword(s):  
Pulmonary Hypertension ◽  
Pulmonary Arterial Hypertension ◽  
Arterial Hypertension ◽  
Structural Changes ◽  
Systolic Pressure ◽  
Pulmonary Artery Systolic Pressure ◽  
Current Classification ◽  
Mean Pressure ◽  
Pulmonary Arterial ◽  
The Difference

Pulmonary Arterial Hypertension is a central syndrome produced by a large number of cardiological, pulmonary, and systemic diseases that affect the lung bed. It is defined by the existence of a pulmonary artery systolic pressure greater than 30 or a mean pressure greater than 25 mmHg. This definition criterion has been maintained for more than 60 years. However, the current classification includes two concepts: a Pulmonary Arterial Hypertension (PAH) with two groups of disorders in which only pulmonary arterial resistance increases and five groups that are classified as Pulmonary Hypertension (PH): PH Secondary to Pulmonary Veno-occlusive Disease , HP secondary to diseases of the left side of the heart; HP Obliterative diseases and pulmonary hypoxemia; HP Pulmonary thrombus occlusive diseases, and a group of multifactorial HP. The difference is found in how the different diseases affect the pulmonary vascular bed, and how they alter the physiology or behavior of pulmonary resistance, which are the concepts that must be handled when talking about this syndrome and whose structural changes and management we will discuss in a later article.

scholarly journals Penetration Evaluation of Explosively Formed Projectiles Through Air and Water Using Insensitive Munition: Simulative and Experimental Studies

2016 ◽  
Vol 6 (1) ◽  
pp. 913-916 ◽  
Author(s):  
M. Ahmed ◽  
A. Q. Malik ◽  
S. A. Rofi ◽  
Z. X. Huang
Keyword(s):  
Formation Flying ◽  
Experimental Studies ◽  
Experimental Results ◽  
Jet Formation ◽  
Depth Of Penetration ◽  
X Ray ◽  
Steel Target ◽  
Great Reliability ◽  
Polymer Bonded Explosives ◽  
The Difference

The process of formation, flying, penetration of explosively-formed projectiles (EFP) and the effect of water on performance of the charge for underwater applications is simulated by Ansysis Autodyn 2D-Hydro code. The main objective of an explosively formed projectile designed for underwater applications is to disintegrate the target at longer standoff distances. In this paper we have simulated the explosively formed projectile from OFHC-Copper liner for 1200 conical angle. The Affect of water on the penetration of EFP is determined by simulations from Ansysis Autodyn 2-D Hydrocode and by varying depth of water from 1CD-5CD. The depth of penetration against steel target is measured experimentally. Flash X-Ray Radiography (FXR) is used to capture EFP jet formation and its penetration against target is measured by depth of penetration experiments. Simulation results are compared with experimental results. The difference in simulated and experimental results for depth of penetration is about 7 mm, which lies within favorable range of error. The jet formation captured from FXR is quite clear and jet velocity determined from Flash X-ray radiography is the same as the ones obtained by using other high explosives. Therefore, it is indicated that Insensitive Munition (8701) can be utilized instead of Polymer Bonded Explosives (PBX) for air and underwater environments with great reliability and without any hazard.

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