Homogeneous grain growth and fast-firing of chemically modified nanocrystalline MnZn ferrites

1999 ◽  
Vol 34 (14-15) ◽  
pp. 2361-2368 ◽  
Author(s):  
Yong S. Cho ◽  
Deborah Schaffer ◽  
Vernon L. Burdick ◽  
Vasantha R.W. Amarakoon
Keyword(s):  
Grain Growth ◽  
Chemically Modified ◽  
Mnzn Ferrites ◽  
Fast Firing

Calcium Behaviors in MnZn Ferrite at Different Temperatures

2012 ◽  
Vol 512-515 ◽  
pp. 1412-1415 ◽  
Author(s):  
Ya Qiu Cai ◽  
Yang Yi Lin ◽  
X. Li ◽  
Jin Tao Huang ◽  
Takuya Aoki
Keyword(s):  
Critical Temperature ◽  
Grain Growth ◽  
Sintering Temperature ◽  
Magnetic Core ◽  
Homogeneous Microstructure ◽  
Grain Boundary Mobility ◽  
Liquid Phases ◽  
Different Temperatures ◽  
Temperature Ranges ◽  
Mnzn Ferrites

MnZn ferrites have been widely used as magnetic core materials. It is well known that Ca addition is effective to obtain homogeneous microstructure of fine grains and highly resistive grain boundaries. However, the behaviors of calcium as one of the main additives at different temperature ranges during sintering process are not completely understood yet. In this study, the influence of CaCO3 content and sintering temperature on the microstructure was investigated in 1473-1623 K. It was found that there existed a critical temperature around 1550 K. The grain size decreased with the increase of Ca content when the sintering temperature was lower than the critical temperature, but completely opposite result was observed at higher temperatures range. Possible mechanisms were discussed. When the sintering temperature was lower than the critical temperature, Ca content greatly affected the grain boundary mobility and dominated the grain growth. At higher temperatures, however, formation of liquid phases might be the main cause for the grain growth.

The Fast Firing of the Ferroelectric Relaxor Pb(Mn1/3Nb2/3).02 (Mg1/2 W1/2 ).48 Zr.23 Ti.27O3

1989 ◽  
Vol 167 ◽  
Author(s):  
Sean F. Mansfield ◽  
Jenifer A.T. Taylor ◽  
Aristianto M. Barus ◽  
Steven M. Landin
Keyword(s):  
Dielectric Constant ◽  
Grain Growth ◽  
Secondary Phases ◽  
Ferroelectric Relaxor ◽  
Sintering Time ◽  
The Cost ◽  
Fast Firing

AbstractThe possibility of fast firing a relaxor dielectric to suppress grain growth, mitigate the lead loss and reduce the cost of sintering has been investigated. The relaxor Pb(Mn1/3 Nb2/3).02 (Mg1/2 W1/2 ).48 Zr.23 Ti.27 O3 [1] exhibits a highly desirable broad phase transistion range when the prbcessing procedures are carefully controlled and fired conventionally. When fast fired, this material's density, percentage of secondary phases, and dielectric constant were highly dependent on the sintering time. A sample fired for 6 minutes possessed a dielectric constant nearly equal to the same material conventionally fired for 16 hours.

Grain Refinement in Titanium-Erbium Alloys

1974 ◽  
Vol 32 ◽  
pp. 522-523
Author(s):  
B. B. Rath ◽  
J. E. O'Neal ◽  
R. J. Lederich
Keyword(s):  
Electron Microscopy ◽  
Size Distribution ◽  
Grain Refinement ◽  
Grain Growth ◽  
Volume Fraction ◽  
Pure Titanium ◽  
Systematic Investigation ◽  
Second Phase ◽  
Titanium Matrix ◽  
Average Size

Addition of small amounts of erbium has a profound effect on recrystallization and grain growth in titanium. Erbium, because of its negligible solubility in titanium, precipitates in the titanium matrix as a finely dispersed second phase. The presence of this phase, depending on its average size, distribution, and volume fraction in titanium, strongly inhibits the migration of grain boundaries during recrystallization and grain growth, and thus produces ultimate grains of sub-micrometer dimensions. A systematic investigation has been conducted to study the isothermal grain growth in electrolytically pure titanium and titanium-erbium alloys (Er concentration ranging from 0-0.3 at.%) over the temperature range of 450 to 850°C by electron microscopy.

Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

1988 ◽  
Vol 46 ◽  
pp. 550-551
Author(s):  
R. E. Franck ◽  
J. A. Hawk ◽  
G. J. Shiflet
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Grain Growth ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Second Phase ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

Binding of Tissue Plasminogen Activator to Vascular Grafts

1989 ◽  
Vol 61 (01) ◽  
pp. 131-136 ◽  
Author(s):  
Richard A Harvey ◽  
Hugh C Kim ◽  
Jonathan Pincus ◽  
Stanley Z Trooskin ◽  
Josiah N Wilcox ◽  
...  
Keyword(s):  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Fibrinolytic Activity ◽  
Polymer Surface ◽  
Enzymic Activity ◽  
Vascular Prostheses ◽  
Chemically Modified ◽  
Insoluble Surfactant ◽  
Tissue Plasminogen

SummaryTissue plasminogen activator labeled with radioactive iodine (125I-tPA) was immobilized on vascular prostheses chemically modified with a thin coating of water-insoluble surfactant, tridodecylmethylammonium chloride (TDM AC). Surfactant- treated Dacron, polytetrafluoroethylene (PTFE), silastic, polyethylene and polyurethane bound appreciable amounts of 125I- tPA (5-30 μg 125I-tPA/cm2). Upon exposure to human plasma, the amount of 125I-tPA bound to the surface shows an initial drop during the first hour of incubation, followed by a slower, roughly exponential release with a t½ of appoximately 75 hours. Prostheses containing bound tPA show fibrinolytic activity as measured both by lysis of clots formed in vitro, and by hydrolysis of a synthetic polypeptide substrate. Prior to incubation in plasma, tPA bound to a polymer surface has an enzymic activity similar, if not identical to that of the native enzyme in buffered solution. However, exposure to plasma causes a decrease in the fibrinolytic activity of both bound tPA and enzyme released from the surface of the polymer. These data demonstrate that surfactant-treated prostheses can bind tPA, and that these chemically modified devices can act as a slow-release drug delivery system with the potential for reducing prosthesis-induced thromboembolism.

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