Recrystallization of Amorphized α-TCP

2011 ◽  
Vol 493-494 ◽  
pp. 219-224
Author(s):  
Nicola Döbelin ◽  
Laëtitia Galea ◽  
Urs Eggenberger ◽  
José M.F. Ferreira ◽  
Marc Bohner
Keyword(s):  
Calcination Temperature ◽  
Amorphous Material ◽  
Milled Powder ◽  
High Energy ◽  
Planetary Mill ◽  
Transformation Rate ◽  
Calcination Time ◽  
High Temperature Xrd ◽  
Time Required

Phase-pure α-TCP powder was milled using a high-energy planetary mill to obtain a partially X-ray amorphous material. Calcination at temperatures between 350 and 600 °C was employed to recrystallize the powder. The phase composition as a function of calcination time and temperature was determinedin-situusing high-temperature XRD equipment. It was found that the amorphous fraction recrystallized mainly to α-TCP, with only small amounts of β-TCP formed. At low temperatures (≤ 450 °C), a stable composition with approximately 85 wt-% α-TCP was found once 100% crystallinity was reached. The time required to reach full crystallinity depended on the calcination temperature. For temperatures > 450 °C a slow transformation to β-TCP was observed. The transformation rate depended on the calcination temperature and on the milling intensity. A moderately milled powder recrystallized to α-TCP, followed by a slow transformation to β-TCP at 600 °C, whereas an intensely milled powder also recrystallized to α-TCP, followed by a fast transformation to β-TCP at the same temperature.

Characterization of Tantalum Carbide Reinforced Copper Composite Developed Using Mechanical Alloying

2011 ◽  
Vol 471-472 ◽  
pp. 798-803 ◽  
Author(s):  
Emee Marina Salleh ◽  
Zuhailawati Hussain
Keyword(s):  
Milled Powder ◽  
Graphite Powder ◽  
Copper Matrix ◽  
High Energy ◽  
Planetary Mill ◽  
Tantalum Carbide ◽  
Mechanically Alloyed ◽  
Consolidation Pressure ◽  
Copper Composite

The effects of the consolidation pressure on the properties of novel Cu-15vol% TaC composite was investigated. The copper-based composite has been prepared using a high energy planetary mill via in-situ route. A mixture of copper, tantalum and graphite powder was mechanically alloyed for milling time of 8 hours at speed of 400 rpm. The as-milled powder was consolidated by cold pressing under various pressure (i.e. 100, 200, 300 and 400 MPa) at room temperature and sintered in argon atmosphere at 900 °C for an hour. TaC phase was formed in copper matrix after sintering process. An increase in consolidation pressure resulted in an increase in hardness, electrical conductivity and density of the composites. The changes of bulk properties of the in-situ Cu-TaC composite were correlated to the formation of TaC phase and a reduction of porosity which led to an increasing in densification.

Characterization of Binary Mg-Mn Alloy Synthesized through Mechanical Alloying: Effects of Milling Speed

2015 ◽  
Vol 1087 ◽  
pp. 479-483 ◽  
Author(s):  
Emee Marina Salleh ◽  
Sivakumar Ramakrishan ◽  
Zuhailawati Hussain
Keyword(s):  
Mechanical Alloying ◽  
Milled Powder ◽  
High Energy ◽  
Milling Process ◽  
Planetary Mill ◽  
Argon Atmosphere ◽  
Solid Solution Phase ◽  
Mechanically Alloyed ◽  
Bulk Properties ◽  
Solid State Route

In this work, the effect of the milling speed on the properties of biodegradable Mg-1Mn alloy prepared by mechanical alloying was investigated. The magnesium-based alloy was prepared in solid state route using a high energy planetary mill. A mixture of pure magnesium and manganese powder was mechanically alloyed for 5 hours in argon atmosphere. Milling process was performed at various rotational speeds in order to investigate milling speed effect (i.e., 100, 200, 300 and 400 rpm) on phase formation and bulk properties. The as-milled powder was uniaxially compacted by cold pressing under 400 MPa at room temperature and sintered in argon atmosphere at 500 °C for an hour. X-ray diffraction analysis indicated that a single α-Mg phase was formed in magnesium matrix after sintering process. An increase in milling speed up to 300 rpm resulted in an increase in density and hardness of the binary alloy. The changes of bulk properties of the Mg-Mn alloys were correlated to the formation of solid solution phase and a reduction of porosity which led to an increasing in densification.

scholarly journals A CASE STUDY OF DIFFERENT LIMESTONES DURING QUICK LIME AND SLAKED-LIME PRODUCTION

2017 ◽  
Vol 43 (5) ◽  
pp. 2485
Author(s):  
G. Leontakianakos ◽  
I. Baziotis ◽  
G. Ekonomou ◽  
G. Delagrammatikas ◽  
C.T. Galbenis ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Calcination Temperature ◽  
Calcination Time ◽  
Quick Lime ◽  
Lower Reactivity ◽  
Slaked Lime ◽  
Different Temperatures ◽  
Time Required ◽  
Lime Production

We have examined 5 different limestones in order to study their behavior i) during calcination at different temperatures (900, 1050 and 1200°C for 30 min) and ii) after hydration of quick limes derived to slaked lime. Quick limes calcined at 900°C show the lower reactivity values. This could be related to the low calcination temperature or to the short calcination time of 30 min which was unable to produce enough lime. The samples calcined at temperatures of 1200°C are less reactive compared to the hydrated limes which were prepared by hydration of quick lime calcined at 1050°C, indicating by parameters such as the (CaO+MgO)Lime, the time required to become the temperature maximum and the reactivity rate. These, probably could be due to crystal growth at relative high temperatures.

In Situ Synthesis of TiC-TiB2 Composites via High Energy Ball Milling and Pressureless Sintering

2013 ◽  
Vol 401-403 ◽  
pp. 635-638
Author(s):  
Ping Luo ◽  
Shi Jie Dong ◽  
Zhi Xiong Xie ◽  
Wei Yang ◽  
An Zhuo Yangli
Keyword(s):  
Ball Milling ◽  
Milled Powder ◽  
High Energy ◽  
High Energy Ball Milling ◽  
Sintering Process ◽  
Composite Ceramics ◽  
X Ray Diffraction ◽  
Powder Mixtures ◽  
Energy Ball

TiC-TiB2 composite ceramics were successfully fabricated via planetary ball milling of 72 mass% Ti and 28 mass % B4C powders, followed by low temperature sintering process at 1200°C. The microstructure of the ball-milled powder mixtures and composite ceramics were characterized by Differential thermal analysis equipment (DTA), field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results showed that the ball-milled powder mixtures (Ti and B4C powders) were completely transformed to TiC-TiB2 composite ceramics as the powders were milled for 60 h and sintered at 1200°C for 1 h. The formation mechanism of the TiC-TiB2 composite was discussed. The high energy ball milling and necessary sintering for the powder mixtures plays an important role in the formation of the composites.

scholarly journals In situ Freezing of the Brain for Metabolic Studies: Evaluation of the “Box” Method for Large Experimental Animals

1988 ◽  
Vol 8 (5) ◽  
pp. 742-749 ◽  
Author(s):  
T. P. Obrenovitch ◽  
L. Bordi ◽  
O. Garofalo ◽  
M. Ono ◽  
F. Momma ◽  
...  
Keyword(s):  
Lactate Concentration ◽  
Lateral Geniculate Body ◽  
High Energy ◽  
Brain Regions ◽  
Metabolic Studies ◽  
Brain Surface ◽  
Box Method ◽  
Time Required ◽  
The Brain

The box method of freezing the brain in situ was assessed in baboons. The cooling rate of the tissue was monitored in several regions located at various depths from the skull surface. These measurements allowed us to examine the time required for the tissue to reach 0°C, in relation to its depth measured from the top of the skull. To define brain regions with proven ischaemia, frozen tissue sections were surveyed for areas of decreased pH. In addition, concentrations of ATP, phosphocreatine, and lactate were determined in gray matter located at various depths from the top of the brain surface. Normal tissue pH and low lactate concentration, without any significant decrease in high-energy phosphate levels, were found in regions at a depth < ∼10 mm from the brain surface. Deep structures including the inferiomedial aspect of the temporal lobe, the lateral geniculate body, and the limbic system (hippocampus) consistently showed mild tissue acidosis, indicating that these regions were subjected to some degree of ischaemia before they were reached by the freezing front. In some cases, acidosis was also detectable in the thalamus, basal ganglia, and in the deeper part of some sulci. We conclude that, with baboons, in situ freezing using the box method is valid for metabolic studies of the cerebral cortex and structures located at a depth <∼10 mm from the top of the brain surface.

scholarly journals Solid-State Dewetting Dynamics of Amorphous Ge Thin Films on Silicon Dioxide Substrates

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2542
Author(s):  
Dimosthenis Toliopoulos ◽  
Alexey Fedorov ◽  
Sergio Bietti ◽  
Monica Bollani ◽  
Emiliano Bonera ◽  
...  
Keyword(s):  
Thin Films ◽  
Amorphous Material ◽  
High Vacuum ◽  
High Energy ◽  
Ex Situ ◽  
Material Transport ◽  
Dewetting Process ◽  
Very High ◽  
High Vacuum Environment

We report on the dewetting process, in a high vacuum environment, of amorphous Ge thin films on SiO2/Si (001). A detailed insight of the dewetting is obtained by in situ reflection high-energy electron diffraction and ex situ scanning electron microscopy. These characterizations show that the amorphous Ge films dewet into Ge crystalline nano-islands with dynamics dominated by crystallization of the amorphous material into crystalline nano-seeds and material transport at Ge islands. Surface energy minimization determines the dewetting process of crystalline Ge and controls the final stages of the process. At very high temperatures, coarsening of the island size distribution is observed.

In situ TEM studies of irradiation effects for materials improvement

1991 ◽  
Vol 49 ◽  
pp. 452-453
Author(s):  
Charles W. Allen
Keyword(s):  
Nuclear Reactor ◽  
Austenitic Stainless Steels ◽  
High Energy ◽  
Point Of View ◽  
In Situ Tem ◽  
Irradiation Effects ◽  
Tem Analysis ◽  
Radiation Induced ◽  
Analytical Tools

Irradiation effects studies employing TEMs as analytical tools have been conducted for almost as many years as materials people have done TEM, motivated largely by materials needs for nuclear reactor development. Such studies have focussed on the behavior both of nuclear fuels and of materials for other reactor components which are subjected to radiation-induced degradation. Especially in the 1950s and 60s, post-irradiation TEM analysis may have been coupled to in situ (in reactor or in pile) experiments (e.g., irradiation-induced creep experiments of austenitic stainless steels). Although necessary from a technological point of view, such experiments are difficult to instrument (measure strain dynamically, e.g.) and control (temperature, e.g.) and require months or even years to perform in a nuclear reactor or in a spallation neutron source. Consequently, methods were sought for simulation of neutroninduced radiation damage of materials, the simulations employing other forms of radiation; in the case of metals and alloys, high energy electrons and high energy ions.

In situ irradiation effects studies in medium- and high-voltage TEM

1995 ◽  
Vol 53 ◽  
pp. 234-235
Author(s):  
Charles W. Allen
Keyword(s):  
Cross Section ◽  
Particle Flux ◽  
Threshold Value ◽  
High Energy ◽  
Irradiation Damage ◽  
Defect Complexes ◽  
Lattice Position ◽  
Electrons And Ions ◽  
The Masses

With respect to structural consequences within a material, energetic electrons, above a threshold value of energy characteristic of a particular material, produce vacancy-interstial pairs (Frenkel pairs) by displacement of individual atoms, as illustrated for several materials in Table 1. Ion projectiles produce cascades of Frenkel pairs. Such displacement cascades result from high energy primary knock-on atoms which produce many secondary defects. These defects rearrange to form a variety of defect complexes on the time scale of tens of picoseconds following the primary displacement. A convenient measure of the extent of irradiation damage, both for electrons and ions, is the number of displacements per atom (dpa). 1 dpa means, on average, each atom in the irradiated region of material has been displaced once from its original lattice position. Displacement rate (dpa/s) is proportional to particle flux (cm-2s-1), the proportionality factor being the “displacement cross-section” σD (cm2). The cross-section σD depends mainly on the masses of target and projectile and on the kinetic energy of the projectile particle.

In situ TEM Studies of agglomeration of sub-nanometer Ru layers in Ru/C multilayers

1992 ◽  
Vol 50 (1) ◽  
pp. 256-257
Author(s):  
Tai D. Nguyen ◽  
Ronald Gronsky ◽  
Jeffrey B. Kortright
Keyword(s):  
Layered Structure ◽  
Driving Force ◽  
High Energy ◽  
Superior Performance ◽  
In Situ Tem ◽  
Rayleigh Instability ◽  
Practical Applications ◽  
Transmission Electron ◽  
Diffraction Patterns

Nanometer period Ru/C multilayers are one of the prime candidates for normal incident reflecting mirrors at wavelengths < 10 nm. Superior performance, which requires uniform layers and smooth interfaces, and high stability of the layered structure under thermal loadings are some of the demands in practical applications. Previous studies however show that the Ru layers in the 2 nm period Ru/C multilayer agglomerate upon moderate annealing, and the layered structure is no longer retained. This agglomeration and crystallization of the Ru layers upon annealing to form almost spherical crystallites is a result of the reduction of surface or interfacial energy from die amorphous high energy non-equilibrium state of the as-prepared sample dirough diffusive arrangements of the atoms. Proposed models for mechanism of thin film agglomeration include one analogous to Rayleigh instability, and grain boundary grooving in polycrystalline films. These models however are not necessarily appropriate to explain for the agglomeration in the sub-nanometer amorphous Ru layers in Ru/C multilayers. The Ru-C phase diagram shows a wide miscible gap, which indicates the preference of phase separation between these two materials and provides an additional driving force for agglomeration. In this paper, we study the evolution of the microstructures and layered structure via in-situ Transmission Electron Microscopy (TEM), and attempt to determine the order of occurence of agglomeration and crystallization in the Ru layers by observing the diffraction patterns.

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