The effect of undercooling and Nd422 phase content on the nucleation of large Nd–Ba–Cu–O grains fabricated by top-seeded melt processing

1999 ◽  
Vol 14 (10) ◽  
pp. 3859-3863 ◽  
Author(s):  
N. Hari Babu ◽  
W. Lo ◽  
D. A. Cardwell ◽  
Y. Shi
Keyword(s):  
Melt Processing ◽  
Phase Content ◽  
Slow Cooling ◽  
Solidification Temperature ◽  
Growth Technique ◽  
Temperature Range ◽  
Limited Temperature ◽  
Peritectic Solidification ◽  
Limited Temperature Range ◽  
Single Grain

The nucleation and growth of NdBa2Cu3O7–δ (Nd123)–Nd4Ba2Cu2O10 (Nd422) single-grain composites in a controlled 1% O2 in N2 atmosphere were investigated in detail as a function of solidification temperature and Nd422 phase content using a top-seeded melt growth technique. A schematic process phase diagram in the peritectic solidification region of Nd–Ba–Cu–O (NdBCO) was constructed primarily from constant isothermal growth experiments at various temperatures for several compositions and used to fabricate large single-grain material by both isothermal and continuous slow cooling over a limited temperature range. The nucleation at the seed surface and subsequent growth of uniform grains was observed to depend critically on the controlled rate of grain growth and the temperature range over which solidification occurred.

Reduction of binary sulfate mixtures containing CuSO4 by H2

1976 ◽  
Vol 54 (23) ◽  
pp. 3651-3657 ◽  
Author(s):  
Fathi Habashi ◽  
Shaheer A. Mikhail
Keyword(s):  
Intermediate Product ◽  
The Other ◽  
Temperature Range ◽  
Other Hand ◽  
First Case ◽  
Limited Temperature ◽  
Limited Temperature Range ◽  
The Individual

The reduction of a binary sulfate mixture cannot be predicted from the behavior of the individual components. Thus, while CuSO4 is reduced to Cu at 400 °C and NiSO4 is reduced to Ni3S2, the sulfate mixture yields Cu, Ni3S2, and Cu2S. Also while FeSO4 is completely stable in H2 at 400 °C, (Cu,Fe) SO4 yields Cu and Cu5FeS4. The formation of Cu2S in the first case and Cu5FeS4 in the second was unexpected. On the other hand, (Cu,Mn)SO4 is stable in H2 up to 550 °C although pure CuSO4 is completely reduced at 400 °C. CoSO4 also interferes when reduced in presence of CuSO4, while Na2SO4, MgSO4, Al2(SO4)3, ZnSO4, CdSO4 do not interfere within limited temperature range. Of these only Na2SO4 forms a complex sulfate with CuSO4. No Cu2SO4 was identified when CuSO4 was reduced in presence of other sulfates although it is an intermediate product during the reduction of pure CuSO4.

scholarly journals Phase Transitions and Local Polarity above TC in a PbZr0.87Ti0.13O3 Single Crystal

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 286
Author(s):  
Iwona Lazar ◽  
Andrzej Majchrowski ◽  
Andrzej Soszyński ◽  
Krystian Roleder
Keyword(s):  
Phase Transitions ◽  
Solid Solutions ◽  
Piezoelectric Materials ◽  
Temperature Range ◽  
Limited Temperature ◽  
Similar Chemical ◽  
Limited Temperature Range ◽  
Optical Dielectric ◽  
Top Seeded Solution Growth ◽  
First Time

Solid solutions of PbZr1−xTixO3 (PZT) are one of the most widely used piezoelectric materials with perovskite structure. Despite the decades of research, the phase diagram of PZT reported in 1971 has not been resolved yet. Recently, it turned out that single crystals of good quality of these solid solutions can be grown. By means of top-seeded solution growth (TSSG) technique, we succeeded to grow a single PbZr0.87Ti0.13O3 crystal. Hence, a partial verification of the diagram could be performed through investigations of the optical, dielectric, pyroelectric and elastic properties of this crystal, in a wide temperature range. The obtained results confirmed that the PbZr0.87Ti0.13O3 crystal undergoes a sequence of phase transitions, such as those observed in ceramics of similar chemical composition. However, additional anomalies of investigated physical properties were observed and discussed. Moreover, the influence of electric field on optical properties has been investigated for the first time and has proven the existence of local polar character of the phase above TC in a limited temperature range.

Controlled Growth of Germanium Nanowires via a Solid–Liquid–Solid (SLS) Mechanism

2012 ◽  
Vol 557-559 ◽  
pp. 523-529 ◽  
Author(s):  
Shih Fong Lee ◽  
Li Ying Lee ◽  
Yung Ping Chang
Keyword(s):  
Surface Density ◽  
High Surface ◽  
Average Diameter ◽  
Germanium Nanowires ◽  
Temperature Range ◽  
Au Film ◽  
Limited Temperature ◽  
Limited Temperature Range ◽  
Solid Liquid ◽  
Nano Wires

In this study, germanium nanowires (GeNWs) were grown directly on gold-evaporated germanium substrates by a solid-liquid-solid (SLS) mechanism in the temperature range 550°C- 650°C. The growth of GeNWs is very sensitive to the growth temperature and only in a limited temperature range (575°C-625°C) can GeNWs having excellent morphology and high surface density be successfully grown. These long, thin, and straight GeNWs have a high aspect ratio and are surrounded by an oxide layer. The composition of corresponding oxide layers is GeOx (x<2). As the thickness of Au film is decreased from 9 nm to 1 nm, the average diameter of GeNWs decreases from 119.3 nm to 38.5 nm. Our experimental results demonstrate that the diameter of germanium nano¬wires can be controlled by the thickness of Au metal film.

The thermal field of an oil layer for phase transformations within a limited temperature range

2012 ◽  
Vol 50 (2) ◽  
pp. 265-272
Author(s):  
A. I. Filippov ◽  
K. K. Nandi ◽  
R. G. Fattakhov ◽  
T. A. Ishmuratov
Keyword(s):  
Phase Transformations ◽  
Thermal Field ◽  
Temperature Range ◽  
Limited Temperature ◽  
Limited Temperature Range

Numerical Analysis of Aerospace Nickel-Based Single-Crystal Superalloy Weldability Part II: Nonequilibrium Solidification Behavior

2021 ◽  
Vol 1018 ◽  
pp. 33-41
Author(s):  
Zhi Guo Gao
Keyword(s):  
Single Crystal ◽  
Weld Pool ◽  
Heat Input ◽  
Dendrite Growth ◽  
Solidification Cracking ◽  
Solidification Temperature ◽  
Temperature Range ◽  
Solidification Temperature Range ◽  
Solid Liquid Interface ◽  
Nonequilibrium Solidification

The thermal metallurgical modeling by coupling of heat transfer model, dendrite selection model, columnar/equiaxed transition (CET) model and nonequilibrium solidification model was further developed to numerically analyze stray grain formation and solidification temperature range on the basis of three criteria of constitutional undercooling, marginal stability of planar front and minimum growth velocity during multicomponent nickel-based single-crystal superalloy weld pool solidification. It is indicated that the primary γ gamma phase microstructure development and solidification cracking susceptibility along the solid/liquid interface are symmetrically distributed throughout the weld pool in (001) and [100] welding configuration. The microstructure development and solidification cracking susceptibility along the solid/liquid interface are asymmetrically distributed in (001) and [110] welding configuration. Appropriate low heat input (low laser power and high welding speed) simultaneously minimizes stray grain formation, grain boundary misorientation and solidification temperature range in the vulnerable [100] dendrite growth region and beneficially maintains single-crystal nature of the material in the [001] epitaxial dendrite growth region to improve the cracking resistance, while high heat input (high laser power and low welding speed) increases the solidification cracking susceptibility to deteriorate weldability and weld integrity. The solidification temperature range in (001) and [110] welding configuration is detrimentally wider than that of (001) and [100] welding configuration due to crystallographic orientation of dendrite growth regardless of heat input. The mechanism of asymmetrical crystallography-dependant solidification cracking because of nonequilibrium solidification behavior is proposed. The elliptical and shallow weld pool shape is less susceptible to solidification cracking for successful crack-free laser welding. Moreover, the promising theoretical predictions agree well with the experiment results. The useful modeling is also applicable to other single-crystal superalloys with similar metallurgical properties during laser welding or laser cladding.

Strengthening method of wheelset tires

2021 ◽  
pp. 51-54
Author(s):  
D.V. Glazunov ◽  
V.N. Krotov ◽  
E.Yu. Cherkesov
Keyword(s):  
Wear Resistance ◽  
Physical Properties ◽  
Rolling Stock ◽  
Performance Tests ◽  
Limited Temperature ◽  
Main Disadvantage ◽  
Limited Temperature Range ◽  
Component Content ◽  
Selection Of ◽  
Strengthening Method

The main ways to strengthen and increase the resourse of wheelset bandage as result of which it is determined that the most economical and quick-to-implement method is the use of tribotechnical materials are considered. The main disadvantage in using of tribotechnical materials is the limited temperature range of rolling stock operation is determined. Qualitative selection of anti-wear and heat-resistant additives, as well as binder is perfomed based on the physical properties required for tribotechnical materials and the range of component content in the lubricant is determined. The wear resistance of wheelset bands is increased by 28 % as result of performance tests.

scholarly journals Two generations of exsolution lamellae in pyroxene from Asuka 09545: Clues to the thermal evolution of silicates in mesosiderite

2019 ◽  
Vol 104 (11) ◽  
pp. 1663-1672
Author(s):  
Lidia Pittarello ◽  
Seann McKibbin ◽  
Akira Yamaguchi ◽  
Gang Ji ◽  
Dominique Schryvers ◽  
...  
Keyword(s):  
Thermal Evolution ◽  
Parent Body ◽  
Cooling History ◽  
Equilibrium Conditions ◽  
Slow Cooling ◽  
Temperature Range ◽  
Fine Grained ◽  
Two Generations ◽  
Mantle Component ◽  
The Antarctic

Abstract Mesosiderite meteorites consist of a mixture of crustal basaltic or gabbroic material and metal. Their formation process is still debated due to their unexpected combination of crust and core materials, possibly derived from the same planetesimal parent body, and lacking an intervening mantle component. Mesosiderites have experienced an extremely slow cooling rate from ca. 550 °C, as recorded in the metal (0.25–0.5 °C/Ma). Here we present a detailed investigation of exsolution features in pyroxene from the Antarctic mesosiderite Asuka (A) 09545. Geothermobarometry calculations, lattice parameters, lamellae orientation, and the presence of clinoenstatite as the host were used in an attempt to constrain the evolution of pyroxene from 1150 to 570 °C and the formation of two generations of exsolution lamellae. After pigeonite crystallization at ca. 1150 °C, the first exsolution process generated the thick augite lamellae along (100) in the temperature interval 1000–900 °C. By further cooling, a second order of exsolution lamellae formed within augite along (001), consisting of monoclinic low-Ca pyroxene, equilibrated in the temperature range 900–800 °C. The last process, occurring in the 600–500 °C temperature range, was likely the inversion of high to low pigeonite in the host crystal, lacking evidence for nucleation of orthopyroxene. The formation of two generations of exsolution lamellae, as well as of likely metastable pigeonite, suggest non-equilibrium conditions. Cooling was sufficiently slow to allow the formation of the lamellae, their preservation, and the transition from high to low pigeonite. In addition, the preservation of such fine-grained lamellae limits long-lasting, impact reheating to a peak temperature lower than 570 °C. These features, including the presence of monoclinic low-Ca pyroxene as the host, are reported in only a few mesosiderites. This suggests a possibly different origin and thermal history from most mesosiderites and that the crystallography (i.e., space group) of low-Ca pyroxene could be used as parameter to distinguish mesosiderite populations based on their cooling history.

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