Microstructural development of rapidly solidified, phase-separated SiO2-Al2O3 glass

1986 ◽  
Vol 44 ◽  
pp. 442-443
Author(s):  
A. P. Taglialavore ◽  
W. M. Kriven ◽  
S. H. Risbud
Keyword(s):  
Liquid Immiscibility ◽  
Miscibility Gap ◽  
Microstructural Development ◽  
Indirect Methods ◽  
Immiscibility Region ◽  
Wide Range ◽  
Quenched Glass ◽  
Rapidly Solidified ◽  
Ice Water ◽  
Sharp Interfaces

A metastable miscibility gap has been shown to exist oyer much of the SiO2(s) -mullite(s) phase field by various indirect methods. The various proposed boundaries of this liquid-liquid immiscibility region, however, significantly disagree in their widths and critical point positions. The overall aim of our research is to directly determine the miscibility gap boundaries by using TEM/EDS on suitably equilibrated phases of rapidly solidified SiO2-Al2O3 glass. Rapid solidification by roller quenching (∼106°C/sec) and by ice- water quenching (~1035°C/sec) was used so that a wide range of compositions could be studied. SiO2-Al2O3 melts with more than ∼30 wt% Al2O3 readily crystallize when slowly cooled. A suitable microstructure for EDS requires homogeneous phases that are separated by sharp interfaces, and are large enough to withstand beam damage. In an attempt to meet these requirements, the as-quenched glass microstructures were developed by annealing for various times at suitable temperatures.

Calculation of metastable immiscibility region in the Al2O3–SiO2 system

1996 ◽  
Vol 11 (6) ◽  
pp. 1421-1427 ◽  
Author(s):  
Takayuki Ban ◽  
Shigeo Hayashi ◽  
Atsuo Yasumori ◽  
Kiyoshi Okada
Keyword(s):  
Phase Separation ◽  
Phase Diagrams ◽  
Regular Solution ◽  
Regular Solution Model ◽  
Liquid Immiscibility ◽  
Miscibility Gap ◽  
Stable Phase ◽  
Liquidus Data ◽  
Metastable Liquid ◽  
Immiscibility Region

Metastable liquid-liquid immiscibility region in the Al2O3–SiO2 system was calculated by a regular solution model using three sets of liquidus data from the stable phase diagrams reported. These calculations indicated that the immiscibility region was richer in Al2O3 composition than those reported before. A miscibility gap calculated using the liquidus data reported by Klug et al. [F. J. Klug, S. Prochazka, and R. H. Doremus, J. Am. Ceram. Soc. 70, 750 (1987)] (model A) ranged from 2.6 to 71 mol % Al2O3 at around 1000 °C, which was the most compatible result with the idea that metastable pseudotetragonal mullite crystallized at around 1000 °C became Al2O3-rich composition due to the immiscibility phase separation before mullitization among three sets of liquidus data.

scholarly journals Use of simulation model for measurement of MilkRun system performance

2019 ◽  
Vol 9 (1) ◽  
pp. 600-605 ◽  
Author(s):  
Gabriel Fedorko ◽  
Martin Vasil ◽  
Michaela Bartosova
Keyword(s):  
Simulation Model ◽  
Production Systems ◽  
Operational Performance ◽  
Transport Systems ◽  
Indirect Methods ◽  
Operational Characteristics ◽  
Wide Range ◽  
Effective Operation ◽  
And Performance ◽  
Plant Simulation

AbstractIntra-plant transport systems within their operation directly impact on the performance of production systems. For their effective operation, it is, therefore, necessary to realize evaluation of operational performance and effectivity. For the realization of this type of evaluation, in addition to a wide range of sensors that can be difficult for installation and operation, we can also use indirect methods that are equally able to provide reliable operational characteristics. Indirect analytical methods are presented above all by the approach which is based on the use of simulation methods. The method of computer simulation provides a wide range of options for the evaluation of efficiency and performance. The paper describes the use of a simulation model created in the program Tecnomatix Plant Simulation for analyzing the supply of production workplaces within the MilkRun system.

Refinements to Ice Particle Mass Dimensional and Terminal Velocity Relationships for Ice Clouds. Part II: Evaluation and Parameterizations of Ensemble Ice Particle Sedimentation Velocities

2007 ◽  
Vol 64 (4) ◽  
pp. 1068-1088 ◽  
Author(s):  
Andrew J. Heymsfield ◽  
Gerd-Jan van Zadelhoff ◽  
David P. Donovan ◽  
Frederic Fabry ◽  
Robin J. Hogan ◽  
...  
Keyword(s):  
Climate Models ◽  
Doppler Radar ◽  
Terminal Velocity ◽  
Fall Velocity ◽  
Particle Sedimentation ◽  
Cloud Properties ◽  
Wide Range ◽  
Single Moment ◽  
Ice Water Content ◽  
Ice Water

Abstract This two-part study addresses the development of reliable estimates of the mass and fall speed of single ice particles and ensembles. Part I of the study reports temperature-dependent coefficients for the mass-dimensional relationship, m = aDb, where D is particle maximum dimension. The fall velocity relationship, Vt = ADB, is developed from observations in synoptic and low-latitude, convectively generated, ice cloud layers, sampled over a wide range of temperatures using an assumed range for the exponent b. Values for a, A, and B were found that were consistent with the measured particle size distributions (PSD) and the ice water content (IWC). To refine the estimates of coefficients a and b to fit both lower and higher moments of the PSD and the associated values for A and B, Part II uses the PSD from Part I plus coincident, vertically pointing Doppler radar returns. The observations and derived coefficients are used to evaluate earlier, single-moment, bulk ice microphysical parameterization schemes as well as to develop improved, statistically based, microphysical relationships. They may be used in cloud and climate models, and to retrieve cloud properties from ground-based Doppler radar and spaceborne, conventional radar returns.

Formation of Quasicrystals In Rapidly Solidified Al Alloys

1985 ◽  
Vol 58 ◽  
Author(s):  
Robert J. Schaefer ◽  
Leonid A Bendersky
Keyword(s):  
Electron Beam ◽  
Electron Beam Melting ◽  
Icosahedral Phase ◽  
Intermetallic Phases ◽  
Moderate Growth ◽  
Wide Range ◽  
Beam Surface ◽  
Equilibrium Phases ◽  
Rapidly Solidified ◽  
T Phase

ABSTRACTElectron beam surface melting has been used to study Al-Mn and Al-Mn-Si alloys subjected to a wide range of solidification conditions. Several of the reported equilibrium intermetallic phases are not found even at moderate growth rates. Beyond a composition-dependent critical velocity the equilibrium phases are all replaced by the quasicrystalline icosahedral and decagonal (T) phases. The icosahedral phase is favored over the T phase by higher solidification velocities. The addition of Si to Al-Mn alloys eliminates the T phase, but does not significantly facilitate the formation of the icosahedral phase by electron beam melting because the ternary α and β phases of Al-Mn-Si are able to grow rapidly into the electron beam melts.

scholarly journals Study on the nonexistence of liquid miscibility gap in the Ce-Mn system

2007 ◽  
Vol 43 (1) ◽  
pp. 21-28 ◽  
Author(s):  
C. Tang ◽  
Y. Du ◽  
H. Xu ◽  
S. Hao ◽  
L. Zhang
Keyword(s):  
Xrd Analysis ◽  
Miscibility Gap ◽  
Composition Analysis ◽  
Phase Identification ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microstructure Observation ◽  
Arc Melting ◽  
Ice Water ◽  
Liquid Miscibility Gap

To ascertain whether the liquid miscibility gap exists in the Ce-Mn system, 3 key alloys are prepared by arc melting the pure elements, annealed at specified temperature for 20 minutes, quenched in ice water and then subjected to X-ray diffraction (XRD) analysis for phase identification and to scanning electron microscopy (SEM) with energy dispersive X-ray analysis for microstructure observation and composition analysis. The XRD examination indicated that terminal solutions based on Ce and Mn exist in the water-quenched alloys. No compound was detected. Microstructure observation and composition analysis indicate the nonexistence of the liquid miscibility gap. The newly assessed Ce-Mn phase diagram was presented. .

scholarly journals A statistical analysis of the influence of deep convection on water vapor variability in the tropical upper troposphere

2009 ◽  
Vol 9 (15) ◽  
pp. 5847-5864 ◽  
Author(s):  
J. S. Wright ◽  
R. Fu ◽  
A. J. Heymsfield
Keyword(s):  
Water Vapor ◽  
Deep Convection ◽  
Tropical Rainfall Measuring Mission ◽  
Upper Troposphere ◽  
Ambient Relative Humidity ◽  
Wide Range ◽  
Ice Water Content ◽  
The Tropics ◽  
Ice Water ◽  
Tropical Upper Troposphere

Abstract. The factors that control the influence of deep convective detrainment on water vapor in the tropical upper troposphere are examined using observations from multiple satellites in conjunction with a trajectory model. Deep convection is confirmed to act primarily as a moisture source to the upper troposphere, modulated by the ambient relative humidity (RH). Convective detrainment provides strong moistening at low RH and offsets drying due to subsidence across a wide range of RH. Strong day-to-day moistening and drying takes place most frequently in relatively dry transition zones, where between 0.01% and 0.1% of Tropical Rainfall Measuring Mission Precipitation Radar observations indicate active convection. Many of these strong moistening events in the tropics can be directly attributed to detrainment from recent tropical convection, while others in the subtropics appear to be related to stratosphere-troposphere exchange. The temporal and spatial limits of the convective source are estimated to be about 36–48 h and 600–1500 km, respectively, consistent with the lifetimes of detrainment cirrus clouds. Larger amounts of detrained ice are associated with enhanced upper tropospheric moistening in both absolute and relative terms. In particular, an increase in ice water content of approximately 400% corresponds to a 10–90% increase in the likelihood of moistening and a 30–50% increase in the magnitude of moistening.

scholarly journals Tailoring structural and magnetic properties of Mn3−x Fe x Ga alloys towards multifunctional applications

IUCrJ ◽  
2018 ◽  
Vol 5 (6) ◽  
pp. 794-800 ◽  
Author(s):  
Z.H. Liu ◽  
Z. J. Tang ◽  
J. G. Tan ◽  
Y. J. Zhang ◽  
Z. G. Wu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Magnetic Properties ◽  
Hexagonal Structure ◽  
Spin Transfer Torque ◽  
Tetragonal Structure ◽  
Practical Applications ◽  
Wide Range ◽  
Multiple Structures ◽  
Structural And Magnetic Properties ◽  
Ice Water

This study investigated the structural and magnetic properties of Mn3−x Fe x Ga alloys (x = 0, 0.2, 0.4, 0.6, 0.8, 1) under different heat-treatment conditions. A tetragonal structure was observed in samples that were heat treated at 623 K for three days followed by quenching in ice water. These tetragonal alloys present large coercive fields in the range 0.8–5 kOe and low saturation magnetization, and have great potential for application in spin-transfer torque-based devices. A hexagonal structure was observed in samples subjected to heat treatment at 883 K for three days following quenching in ice water. A moderate decrease in the coercive field has been observed for the hexagonal alloys compared with those with a tetragonal structure. However, the Mn3−x Fe x Ga alloys with a hexagonal structure exhibit other attractive magnetic properties, including collinear and non-collinear magnetic properties, holding high promise for technological applications. A face-centred-cubic (f.c.c.) structure was observed when subjected to annealing at 1073 K for three days followed by quenching in ice water. In contrast to the tetragonal and hexagonal structures, all f.c.c. alloys exhibit antiferromagnetic behaviour. This versatile material can display a wide range of multi-functionalities attributed to its tuneable crystal structure. This investigation will guide the design of multiple structures of these materials in order to utilise the wide functionalities for practical applications.

scholarly journals On the Use of Asymptotic Solutions to Plane Ice—Water Problems

1969 ◽  
Vol 8 (53) ◽  
pp. 285-300 ◽  
Author(s):  
G. S. H. Lock
Keyword(s):  
Boundary Conditions ◽  
Asymptotic Solutions ◽  
Variable Properties ◽  
Governing Equations ◽  
Freezing And Thawing ◽  
One Dimensional ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Water Problems ◽  
Ice Water

The paper considers one-dimensional freezing and thawing of ice–water systems for the conditions first examined by Stefan. An order-of-magnitude analysis applied to the governing equations and boundary conditions quantifies the error resulting from the neglect of various factors. Principal among these are density difference, initial superheat and variable properties.Asymptotic solutions for the temperature distribution and interface history are developed for a wide range of boundary conditions: prescribed temperature or heat flux, prescribed convection and prescribed radiation. Comparison with known results reveals the general adequacy of the asymptotic solutions and an estimate of the error incurred.

Sign in / Sign up

Export Citation Format

Share Document