scholarly journals Using Multigrain Crystallography to Explore the Microstructural Evolution of the α-Olivine to γ-Ringwoodite Transformation and ε-Mg2SiO4 at High Pressure and Temperature

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 424
Author(s):  
Brian Chandler ◽  
Michelle Devoe ◽  
Martin Kunz ◽  
Hans-Rudolf Wenk
Keyword(s):  
Microstructural Evolution ◽  
Secondary Phase ◽  
Phase Identification ◽  
X Rays ◽  
Ambient Conditions ◽  
Single Experiment ◽  
Ambient Temperatures ◽  
Orientation Relations ◽  
San Carlos Olivine ◽  
Ε Phase

The introduction of multigrain crystallography (MGC) applied in a laser-heated diamond anvil cell (LH-DAC) using synchrotron X-rays has provided a new path to investigate the microstructural evolution of materials at extreme conditions, allowing for simultaneous investigations of phase identification, strain state determination, and orientation relations across phase transitions in a single experiment. Here, we applied this method to a sample of San Carlos olivine beginning at ambient conditions and through the α-olivine → γ-ringwoodite phase transition. At ambient temperatures, by measuring the evolution of individual Bragg reflections, olivine shows profuse angular streaking consistent with the onset of yielding at a measured stress of ~1.5 GPa, considerably lower than previously reported, which may have implications for mantle evolution. Furthermore, γ-ringwoodite phase was found to nucleate as micron to sub-micron grains imbedded with small amounts of a secondary phase at 15 GPa and 1000 °C. Using MGC, we were able to extract and refine individual crystallites of the secondary unknown phase where it was found to have a structure consistent with the ε-phase previously described in chondritic meteorites.

Microstructural Refinement in a Commercial Aluminum Alloy Processed by ECAP Using a Die Channel Angle of 110 Degrees

2015 ◽  
Vol 1114 ◽  
pp. 3-8
Author(s):  
Nicolae Şerban ◽  
Doina Răducanu ◽  
Nicolae Ghiban ◽  
Vasile Dănuţ Cojocaru
Keyword(s):  
Grain Refinement ◽  
Cross Section ◽  
High Strength ◽  
Secondary Phase ◽  
Coarse Grained ◽  
Metallographic Analysis ◽  
Second Phase ◽  
Channel Angle ◽  
Ambient Temperatures ◽  
Fine Grained

The properties of ultra-fine grained materials are superior to those of corresponding conventional coarse grained materials, being significantly improved as a result of grain refinement. Equal channel angular pressing (ECAP) is an efficient method for modifying the microstructure by refining grain size via severe plastic deformation (SPD) in producing ultra-fine grained materials (UFG) and nanomaterials (NM). The grain sizes produced by ECAP processing are typically in the submicrometer range and this leads to high strength at ambient temperatures. ECAP is performed by pressing test samples through a die containing two channels, equal in cross-section and intersecting at a certain angle. The billet experiences simple shear deformation at the intersection, without any precipitous change in the cross-section area because the die prevents lateral expansion and therefore the billet can be pressed more than once and it can be rotated around its pressing axis during subsequent passes. After ECAP significant grain refinement occurs together with dislocation strengthening, resulting in a considerable enhancement in the strength of the alloys. A commercial AlMgSi alloy (AA6063) was investigated in this study. The specimens were processed for a number of passes up to nine, using a die channel angle of 110°, applying the ECAP route BC. After ECAP, samples were cut from each specimen and prepared for metallographic analysis. The microstructure of the ECAP-ed and as-received material was investigated using optical (OLYMPUS – BX60M) and SEM microscopy (TESCAN VEGA II – XMU). It was determined that for the as-received material the microstructure shows a rough appearance, with large grains of dendritic or seaweed aspect and with a secondary phase at grain boundaries (continuous casting structure). For the ECAP processed samples, the microstructure shows a finished aspect, with refined, elongated grains, also with crumbled and uniformly distributed second phase particles after a typical ECAP texture.

scholarly journals Changing mass liner system for generation of soft X rays

1997 ◽  
Vol 15 (1) ◽  
pp. 133-138 ◽  
Author(s):  
A.M. Buyko ◽  
O.M. Burenkov ◽  
V.K. Chernyshev ◽  
S.F. Garanin ◽  
S.D. Kuznetsov ◽  
...  
Keyword(s):  
Current Pulse ◽  
High Precision ◽  
X Rays ◽  
Stored Energy ◽  
Single Experiment ◽  
X Ray ◽  
Liner System ◽  
The Cost

Powerful pulse installations are usually used to produce large yields of X-ray radiation. With an increase of the stored energy up to 100 MJ, the costof a single experiment on these installations becomes comparable to the cost of a shot with explosive magnetic generators (EMG), according to expert estimates. The physical scheme of a device with a changeable mass liner forlarge soft X-ray (in the range of 0.3 to 0.5 keV) yields eneration is investigated. The scheme investigated is substantially free from difficulties connected with high precision liners and fast switches for current pulse sharpening.

Diffraction

2012 ◽  
Vol 20 (2) ◽  
pp. 7-7
Author(s):  
Charles Lyman
Keyword(s):  
Electron Diffraction ◽  
100Th Anniversary ◽  
Primary Phase ◽  
Phase Identification ◽  
X Rays ◽  
X Ray Diffraction ◽  
Identification Methods ◽  
X Ray ◽  
Structure Of Matter

This year marks the 100th anniversary of the discovery of X-ray diffraction and the 85th anniversary of electron diffraction (see Microscopy Pioneers). For most of the time since their introduction, microscopists have known these two techniques as the primary phase identification methods used in conjunction with various microscopies. However, these two diffraction methods also have played enormous roles in understanding the structure of matter, as well as the nature of both X rays and electrons.

Using Thermoelectric Cooling With Tourniquets for Nerve Preservation

2016 ◽  
Author(s):  
M. Trupiano ◽  
S. Aarabi ◽  
A. F. Emery
Keyword(s):  
Thermal Conditions ◽  
Ambient Conditions ◽  
Transfer Coefficients ◽  
Thermoelectric Coolers ◽  
Ambient Temperatures ◽  
Nerve Preservation ◽  
Heat Transfer Coefficients ◽  
Surface Temperatures ◽  
Element Simulation ◽  
Free And Forced Convection

The use of a tourniquet leads to nerve damage, even if applied for short periods of time. This damage can be minimized if the limb is cooled. Because of the low conductivities of human tissue, core limb cooling is slow unless the surface temperature is very cool. Subzero surface temperatures can lead to skin injury (i.e., frostbite). Ideally one would adjust the limb surface temperatures as a function of time to maximize the cooling rate while avoiding permanent tissue damage. One possible approach is to use a thermoelectric cooler (TEC) in conjunction with a programmable power supply. TEC performance varies strongly with heat absorption rate, a function of limb thermal properties, and hot side temperatures that are strongly affected by the surface conditions on the hot side, i.e., overall heat transfer coefficients and ambient conditions. The paper describes the use of finite element simulation to predict the usefulness of using thermoelectric coolers applied to the surface of a limb when compared to the standard approach of using ice packs. Since the TEC performance is strongly influenced by its warm side thermal conditions, experimental results are presented for different ambient temperatures, free and forced convection, and evaporation of water from a wickable covering.

NOVEL AND COST-EFFECTIVE SYNTHESIS OF SILVER NANOCRYSTALS: A GREEN SYNTHESIS

NANO ◽  
2011 ◽  
Vol 06 (04) ◽  
pp. 295-300 ◽  
Author(s):  
NISHAT ARSHI ◽  
FAHEEM AHMED ◽  
M. S. ANWAR ◽  
SHALENDRA KUMAR ◽  
BON HEUN KOO ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Secondary Phase ◽  
Cost Effective ◽  
Silver Foil ◽  
Face Centered Cubic ◽  
X Rays ◽  
Xrd Pattern ◽  
Average Grain Size ◽  
Vis Spectroscopy ◽  
Face Centered

This paper reports the study on the synthesis and characterization of silver nanocrystals by a two-step synthesis procedure. The first step is the solution-free hand grinding of silver foil and sugar at room temperature for few minutes. The second step is the thermal decomposition of silver/sugar composite to form silver nanocrystals. The as-synthesized silver nanocrystals were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet visible (UV/Vis) spectroscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM) studies. The XRD pattern showed a face-centered cubic structure (single phase) with high crystallinity. The lattice parameters calculated from XRD pattern were found to be a = 4.12 Å for silver nanocrystals with average grain size of ~ 19 nm. The energy dispersive analysis of X-rays (EDAX) of silver nanocrystals confirmed the presence of silver and no peak of any secondary phase was detected. FESEM and AFM studies showed that the crystals have cube-like morphology. TEM results showed that the size of silver nanocrystals was found to be ~ 22 nm. This novel synthesis route, not reported earlier, would be a promising candidate for a variety of future applications of silver nanocrystals.

scholarly journals Performance Analysis of Heat Pump Dryer with Unit-Room in Cold Climate Regions

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3125 ◽  
Author(s):  
Yuan ◽  
Lin ◽  
Mao ◽  
Li ◽  
Yang ◽  
...  
Keyword(s):  
Heat Pump ◽  
Ambient Air ◽  
Open Loop ◽  
Cold Climate ◽  
Coefficient Of Performance ◽  
Ambient Conditions ◽  
Total Energy Consumption ◽  
Ambient Temperatures ◽  
Moisture Extraction ◽  
Modelling System

This study presents the development and evaluation of a novel partially open-loop heat pump dryer with a unit-room (HPDU). The unit-room was designed to enable the ambient air to be mixed with the return air, thereby reducing the influence of the ambient air on the system performance, while maintaining a high system thermal efficiency. A modelling system for the HPDU was developed and validated based on a real-scale experimental study. By using the modelling system, the system characteristics under different ambient conditions and bypass factors were analyzed. The energy benefit of the proposed HPDU was quantified through a comparative study with a closed-loop heat pump dryer (CHPD). It is evident that a maximal specific moisture extraction rate (SMER) and a minimal total energy consumption (TEC) existed when changing the bypass factor of the HPDU under certain ambient temperatures. Compared to the CHPD, the coefficient of performance (COP) of the HPDU increased by up to 39.56%, presenting a significant energy benefit for the application of HPDU.

scholarly journals The Influence of Thermal Protection on Winter Den Selection by Porcupines, Erethizon dorsatum, in Second-Growth Conifer Forests

2005 ◽  
Vol 119 (2) ◽  
pp. 159
Author(s):  
Todd N. Zimmerling
Keyword(s):  
Selection Criteria ◽  
Thermal Protection ◽  
Energetic Cost ◽  
Ambient Conditions ◽  
Erethizon Dorsatum ◽  
Ambient Temperatures ◽  
Type Selection ◽  
Second Growth ◽  
Lower Critical Temperature ◽  
Thermal Cover

I investigated den type selection by Porcupines (Erethizon dorsatum), in relation to the thermal cover provided by the den type, over a period of four winters. Porcupines used log dens, stump dens and rock dens in proportion to the thermal cover provided by each den type. Based on behavioural observations of Porcupines, I assumed that the lower critical temperature for porcupines in my study area was -4°C. Both stump and rock dens provided adequate thermal protection, under most ambient conditions, to allow Porcupines to maintain their body temperature, without increasing basal metabolic rate. In most cases rock and stump dens maintained den temperatures above -4°C until ambient temperatures reached -12°C or lower. In contrast log dens provided poor thermal protection, even in years of thick snowcover. When ambient temperatures dropped below -4°C, den temperatures within log dens were also recorded below -4°C. Log dens were used least often by Porcupines, whereas stump and rock dens were used most often. Despite the large number of potential dens available to Porcupines within the study area, den use was generally limited to three dens per porcupine per winter. The limited use of dens by an individual porcupine during winter may be related to the energetic cost of finding a new den or it may be related to specific selection criteria used by Porcupines.

scholarly journals Thermally induced torpor in fullterm lizard embryos synchronizes hatching with ambient conditions

2006 ◽  
Vol 2 (3) ◽  
pp. 415-416 ◽  
Author(s):  
Rajkumar Radder ◽  
Richard Shine
Keyword(s):  
Environmental Conditions ◽  
Low Temperatures ◽  
Access To Information ◽  
Ambient Conditions ◽  
Thermally Induced ◽  
Ambient Temperatures ◽  
Ground Conditions ◽  
Soil Temperatures ◽  
Bassiana Duperreyi ◽  
Do So

Eggs inside an underground nest have limited access to information about above-ground conditions that might affect the survival of emerging hatchlings. Our measurements of heart rates of embryos inside the intact eggs of montane lizards ( Bassiana duperreyi , Scincidae) show that low temperatures induce torpor in fullterm embryos, but do not do so during earlier embryogenesis or later, post-hatching. Because above-ground conditions affect soil temperatures, this stage-dependent torpor effectively restricts hatching to periods of high ambient temperatures above ground. Torpor thus can function not only to synchronize activity with suitable environmental conditions during post-hatching life (as reported for many species), but also can occur in embryos, to synchronize hatching with above-ground conditions that facilitate successful emergence from the nest.

Transport near a vertical ice surface melting in saline water: some numerical calculations

1982 ◽  
Vol 117 ◽  
pp. 379-402 ◽  
Author(s):  
Van P. Carey ◽  
Benjamin Gebhart
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Flow ◽  
Saline Water ◽  
Interface Temperature ◽  
Ambient Conditions ◽  
Interface Motion ◽  
Ambient Temperatures ◽  
Thermal Buoyancy ◽  
Ice Surface ◽  
Layer Flow

Computed numerical results are presented for the laminar buoyancy-induced flows driven by combined thermal and saline transport near a vertical melting ice surface in saline water. Results are presented which indicate that conventional boundary-layer flow occurs for some combinations of ambient salinity and temperature in the ranges 0 to 31‰ and −1 to 20°C, respectively. These conditions are very common in terrestrial waters. The analysis used herein is the first to model fully the many complicated aspects of these flows. The present analysis includes simultaneous transport of salt and thermal energy as well as the effect of interface motion. The formulation uses the most recently available transport properties and a very accurate equation of state for the density of pure and saline water. The interface temperature and salinity, which are not known a priori, are here determined jointly from the transport equations, and from species-conservation and phase-equilibrium relations at the ice surface. At low ambient temperatures, the flow is found to be dominated by the upward saline buoyancy, resulting in upward flow. However, at high temperatures and low salinities, the downward thermal buoyancy overcomes the upward saline buoyancy near the surface to cause downward flow. For choices of ambient conditions between these extremes, the opposing saline and thermal buoyancy are about equal in strength. The resulting tendency for bi-directional flow at these intermediate circumstances caused numerical stability problems which made it impossible to obtain convergent solutions for some cases. However, calculated solutions were obtained at ambient salinities below 5‰, for ambient temperatures between 8 and 20°C, and at temperatures below 4°C, for ambient salinities between 0 and 31‰. These solutions indicate the limits of the range of conditions for which laminar boundary layer flow occurs. They further suggest that outside these ranges, the flow may be laminar and bi-directional. The very strong buoyancy which characterizes some of these conditions suggests that they may become turbulent at short downstream distances. The computed results are seen to be in excellent agreement with the limited experimental data and observations of previous studies.

Investigation Of Pozzolanic Binders Using Sulpho-Calcic Fly Ashes

1988 ◽  
Vol 136 ◽  
Author(s):  
J. Pera ◽  
A. Sadr Momtazi ◽  
J. Dejean
Keyword(s):  
Blast Furnace Slag ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Fly Ashes ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Ambient Temperatures ◽  
Slaked Lime ◽  
Hydrated Product ◽  
Furnace Slag

ABSTRACTBecause of their high SO3 content (∼11%), sulfo-calcic fly ashes cannot be used as a cement admixture without pretreatment. The fly ashes contain mainly quicklime (CaO), anhydrite (CaSO4) and larnite (BC2S). At ambient temperatures and at normal consistency, their hydration leads to the formation of ettringite, slaked lime and gypsum. As a result, cracking and splitting of the hydrated product quickly occurs due to the crystallization of the ettringite.The ability of these fly ashes to produce Portlandite, Ca(OH)2, led the authors to investigate pozzolanic binders by the addition of artificial pozzolans — siliceous fly ashes, slag and clay minerals — which had been calcined at moderate temperatures.The sulfo-calcic fly ashes are ground, then slaked either in ambient or hydrothermal conditions (2 or 6 hours at 130°C). In the case of slaking under ambient conditions, ettringite is quickly produced with a definitive crystallographical structure. As a result, no volume change is observed after re-hydration of the material. By comparison, autoclave slaking does not lead to this phenomenon, and only slaked lime is produced.The rate of hydration is studied through the development of compressive strength and by analyses of the products by differential thermal analysis (DTA) and X-ray diffraction (XRD) at various hydration times. The best results are obtained using calcined laterite or blast furnace slag.

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