Luminescence Properties of SnO2 Nanoparticles Dispersed in Eu3+ Doped SiO2 Matrix

2008 ◽  
Vol 8 (3) ◽  
pp. 1489-1493 ◽  
Author(s):  
R. S. Ningthoujam ◽  
V. Sudarsan ◽  
A. Vinu ◽  
P. Srinivasu ◽  
K. Ariga ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Sno2 Nanoparticles ◽  
Phase Segregation ◽  
The Other ◽  
Significant Extent ◽  
Sio2 Matrix ◽  
Transmission Electron ◽  
Heat Treated ◽  
The Matrix ◽  
Different Temperatures

SnO2 nanoparticles dispersed in Eu3+ doped silica (SnO2-SiO2:Eu3+) were prepared at a low temperature (185 °C) in ethylene glycol medium. Transmission electron microscopy studies on as-prepared samples have established that SnO2 nanoparticles having size of 4.6 nm are uniformly covered by the SiO2 matrix. Significant extent of exciton mediated energy transfer between SnO2 and Eu3+ ions in heat treated SnO2-SiO2:Eu3+ samples has been attributed to the diffusion of Eu3+ ions from the SiO2 matrix to the near vicinity of SnO2 nanoparticles and its incorporation in the SnO2 matrix. On the other hand, very weak energy transfer exists for SnO2:Eu3+ nanoparticles heated at different temperatures due to the phase segregation of Eu3+ ions from the matrix.

Liquid-Liquid Phase Separation and Phase Diagrams of Simulated Fernald Waste Glasses

1993 ◽  
Vol 333 ◽  
Author(s):  
E. Wang ◽  
F. Perez-Cardenas ◽  
H. Kuang ◽  
A.C. Buechele
Keyword(s):  
Electron Microscope ◽  
Phase Separation ◽  
Heat Treating ◽  
Liquidus Curve ◽  
Miscibility Gap ◽  
Transmission Electron ◽  
Heat Treated ◽  
The Matrix ◽  
Different Temperatures ◽  
Liquid Liquid Phase Separation

ABSTRACTPrevious study of crystallization behavior in heat-treated Fernald waste glasses has produced an extensive data base of crystal phases likely to appear in various composition ranges and their corresponding liquidus temperatures. In addition, we have frequently observed amorphous phase separation in these glasses and, occasionally, evidence of crystallization originating from such phase separation. These glasses contain more than 10 components. The composition ranges for the major components are: MgF2 10–26 wt%; CaO 4–27 wt%; Al2O3 3–15 wt%; SiO2 25–40 wt%. The morphology of the phase separation as observed in the Scanning Electron Microscope (SEM) is dark, spherical globules dispersed in a continuous matrix. Globules are depleted in Mg, Ca and F, and enriched in Al and Si compared to the matrix. Phase separation occurs more frequently in melts relatively higher in Si and F. A more systematic study on a simplified and simulated seven component system (Al2O3, B2O3, CaO, Fe2O3, SiO2, Na2O and MgF2) has been undertaken to determine the subliquidus miscibility gap and liquidus curve data. Glasses were formulated by varying the concentrations of MgF2, CaO, Al2O3 and SiO2 within the ranges specified above at fixed levels of Fe2O3, B2O3 and Na2O. The miscibility gap and liquidus curve were obtained by heat-treating the glass samples at different temperatures and observing any phase separation and crystallization in the SEM and the Transmission Electron Microscope (TEM). We report here the results of this study to enhance the understanding of the thermodynamic properties of multi-component silicate systems which are usually the basis of nuclear waste glasses.

The effect of ageing duration on the mechanical properties of Al alloy 6061-garnet composites

2001 ◽  
Vol 215 (2) ◽  
pp. 113-119
Author(s):  
S C Sharma
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Al Alloy ◽  
Destructive Testing ◽  
Transmission Electron ◽  
Heat Treated ◽  
The Matrix ◽  
Reinforcing Particle ◽  
Alloy 6061

A well-consolidated composite of Al alloy 6061 reinforced with 4, 8 and 12 wt% garnet was prepared by a liquid metallurgy technique, the composite was heat treated for different ageing durations (T6 treatment), and its mechanical properties were determined by destructive testing. The results of the study indicated that, as the garnet particle content in the composites increased, there were marked increases in the ultimate tensile strength, compressive strength and hardness but there was a decrease in the ductility. There was an improvement in the tensile strength, compressive strength, and hardness with ageing due to precipitation. Precipitation in Al alloy 6061, with and without garnet particulate reinforcement, was studied using transmission electron microscopy. The fracture behaviour of the composites was altered significantly by the presence of garnet particles and the crack propagation through the matrix, and the reinforcing particle clusters resulted in final fracture.

Superplastic Deformation and Viscous Flow in an Zr-Based Metallic Glass at 410°C

1998 ◽  
Vol 554 ◽  
Author(s):  
T. G. Nieh ◽  
J. G. Wang ◽  
J. Wadsworth ◽  
T. Mukai ◽  
C. T. Liu
Keyword(s):  
Strain Rate ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Single Strain ◽  
Transmission Electron ◽  
Heat Treated ◽  
Different Temperatures

AbstractThe thermal properties of an amorphous alloy (composition in at.%: Zr-10Al-5Ti-17.9Cu-14.6Ni), and particularly the glass transition and crystallization temperature as a function of heating rate, were characterized using Differential Scanning Calorimetry (DSC). X-ray diffraction analyses and Transmission Electron Microscopy were also conducted on samples heat-treated at different temperatures for comparison with the DSC results. Superplasticity in the alloy was studied at 410°C, a temperature within the supercooled liquid region. Both single strain rate and strain rate cycling tests in tension were carried out to investigate the deformation behavior of the alloy in the supercooled liquid region. The experimental results indicated that the alloy did not behave like a Newtonian fluid.

Solute Partitioning and Interfacial Segregation in TiAl-Based Alloys

1998 ◽  
Vol 552 ◽  
Author(s):  
D. J. Larson ◽  
M. K. Miller
Keyword(s):  
Phase Segregation ◽  
Atom Probe ◽  
Heat Treatments ◽  
The Other ◽  
Alloying Additions ◽  
Segregation Behavior ◽  
Annealed State ◽  
The Matrix ◽  
Interfacial Segregation ◽  
Lamellar Interfaces

ABSTRACTAtom probe microscopy has been used to investigate elemental partitioning and segregation behavior in a TiAl-based alloy with a variety of alloying additions including Cr, Nb, W and B. These results indicate that in a stress-relieved state (2 h at 900°C) and a reheated state (2 h at 900°C, 2184 h at 800°C and 2 h at 1210°C) chromium, and to a lesser extent tungsten, is partitioned to the α2 phase. However, in an annealed state (2 h at 900°C and 720 h at 800°C), these elements are partitioned to the, γ phase. Segregation of chromium and tungsten to lamellar interfaces is observed in the stress-relieved material, but significant segregation was not observed in material subjected to the other heat treatments. A W- and B-enriched precipitate was observed in the reheated material and provides a possible explanation for the low tungsten concentrations measured in the matrix phases.

Characterization and Optimized Ageing Parameters of Aluminium Alloy AA6110

2014 ◽  
Vol 931-932 ◽  
pp. 312-316 ◽  
Author(s):  
Adisorn Kodwichian ◽  
Patiphan Juijerm
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Aluminium Alloy ◽  
Ageing Time ◽  
Precipitation Sequence ◽  
Automotive Manufacturing ◽  
Treatment Processes ◽  
Transmission Electron ◽  
Heat Treated ◽  
Different Temperatures

Copper containing aluminium alloy AA6110 is introduced to automotive industries for the last few decades. An understanding of its precipitation sequence and mechanical properties during ageing treatment is valuable to optimize some heat treatment processes in the automotive manufacturing. Therefore, in this study, the precipitation sequence, microstructures and mechanical properties of copper containing aluminium alloy AA611 were investigated. A differential scanning calorimeter (DSC) with regular heating rate of 10 °C/min was performed on the solid solution heat treated aluminium alloy AA6110 for the precipitation sequence investigation. Solid solution heat treated samples were aged at different temperatures and times. Hardness values of differently aged aluminium alloy AA6110 were measured to determine optimized parameters of the ageing process. It was found that the maximum hardness value of 141 HV was detected at an ageing temperature of 160 °C for about 12 hr. Tensile properties and microstructures using transmission electron microscope (TEM) of specimens aged at a temperature of 160 °C with different ageing time will be investigated and shown.

Deformation Mechanisms in TiAl-Based Alloys Containing Low Oxygen

1990 ◽  
Vol 213 ◽  
Author(s):  
S. Sriram ◽  
Vijay K. Vasudevan ◽  
Dennis M. Dimiduk
Keyword(s):  
Analytical Electron Microscopy ◽  
Deformation Mechanisms ◽  
Low Oxygen ◽  
Weak Beam ◽  
Transmission Electron ◽  
Heat Treated ◽  
Analytical Electron ◽  
The Matrix ◽  
Recent Developments ◽  
High Purity Alloy

ABSTRACTThe effects of oxygen on the deformation behavior of Ti-(48-52)Al alloys is reported. Two types of studies were conducted. In the first, high purity alloy buttons containing low oxygen (~250 ppm) were prepared, whereas in the second, alloys with additions of 1 at.% Er to scavenge the oxygen from the matrix were prepared. The alloys were heat treated to produce large grains and the microstructures characterized by analytical electron microscopy. Samples prepared from the heat treated alloys were electropolished and deformed in compression to a plastic strain of 1.0-1.5% at temperatures between 25 and 800°C and the yield stress measured. The morphology of deformation, that is, slip lines and the presence of twinning, was studied by optical microscopy and the dislocation structures were characterized by weak-beam imaging in the transmission electron microscope. The results of these various studies are presented and discussed in terms of recent developments regarding the factors that appear to control the dislocation structure and the mobility of dislocations.

Magnetic Properties of Mg0.4Ca0.6Fe2O4 Nanoparticles Synthesized by Sol-Gel Method for Hyperthermia Treatment

2014 ◽  
Vol 631 ◽  
pp. 193-197
Author(s):  
A.M. Escamilla-Pérez ◽  
D.A. Cortés-Hernández ◽  
J.M. Almanza-Robles ◽  
D. Mantovani ◽  
P. Chevallier
Keyword(s):  
Magnetic Properties ◽  
Sol Gel ◽  
Average Diameter ◽  
X Ray Diffraction ◽  
Hyperthermia Treatment ◽  
X Ray ◽  
Transmission Electron ◽  
Heat Treated ◽  
Different Temperatures ◽  
Xrd Patterns

Powders of Mg0.4Ca0.6Fe2O4were prepared by sol-gel using ethylene glycol and Mg, Ca and Fe nitrates as starting materials. Those powders were heat treated at different temperatures (300, 400, 500 and 600 °C) for 30 min. The materials obtained were characterized by X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). The Ca-Mg ferrite with the most appropriate magnetic properties was further analyzed by transmission electron microscopy (TEM). The heating capability of the nanoferrites was also tested via magnetic induction. The XRD patterns of these Ca-Mg ferrites showed a cubic inverse spinel structure. Furthermore, neither traces of hematite nor orthorhombic Ca ferrite phases were detected. Moreover, all the Ca-Mg ferrites are superparamagnetic and the particle size distribution of these Ca-Mg magnetic nanoparticles exhibits an average diameter within the range of 10-14 nm. The needed temperature for hyperthermia treatment was achieved at around 12 min.

In Situ TEM Heating Study of the γ Lamellae Formation inside the α2 Matrix of a Ti-45Al-7.5Nb Alloy

2010 ◽  
Vol 146-147 ◽  
pp. 1365-1368 ◽  
Author(s):  
Li Mei Cha ◽  
Helmut Clemens ◽  
Gerhard Dehm ◽  
Zao Li Zhang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ex Situ ◽  
In Situ Tem ◽  
Transmission Electron ◽  
Initial Stage ◽  
Heat Treated ◽  
The Matrix ◽  
In Situ Heating

In-situ heating transmission electron microscopy (TEM) was employed to investigate the initial stage of lamellae formation in a high Nb containing γ-TiAl based alloy. A Ti-45Al-7.5Nb alloy (at %), which was heat treated and quenched in a non-equilibrium state such that the matrix consists of ordered a2 grains, was annealed inside a TEM up to 750 °C. The in-situ TEM study reveals that g laths precipitate in the a2 matrix at ~ 750 °C possessing the classical Blackburn orientation relationship, i.e. (0001)a2 // (111)g and [11-20]a2 // <110]g. The microstructure of the in-situ TEM experiment is compared to results from ex-situ heating and subsequent TEM studies.

scholarly journals The Effect of Molybdenum on Precipitation Behaviour in Austenite of Strip-Cast Steels Containing Niobium

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1330
Author(s):  
Lu Jiang ◽  
Ross K. W. Marceau ◽  
Thomas Dorin ◽  
Huaying Yin ◽  
Xinjun Sun ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Energy Barrier ◽  
Isothermal Holding ◽  
The Other ◽  
Transmission Electron ◽  
Cast Steels ◽  
Heat Treated ◽  
Precipitation Behaviour ◽  
Strip Cast ◽  
Electron Energy Loss

Two low-C steels microalloyed with niobium (Nb) were fabricated by simulated strip casting, one with molybdenum (Mo) and the other without Mo. Both steels were heat treated to simulate coiling at 900 °C to investigate the effect of Mo on the precipitation behaviour in austenite in low-C strip-cast Nb steels. The mechanical properties results show that during the isothermal holding at 900 °C the hardness of both steels increases and reaches a peak after 3000 s and then decreased after 10,000 s. Additionally, the hardness of the Mo-containing steel is higher than that of the Mo-free steel in all heat-treated conditions. Thermo-Calc predictions suggest that MC-type carbides exist in equilibrium at 900 °C, which are confirmed by transmission electron microscopy (TEM). TEM examination shows that precipitates are formed after 1000 s of isothermal holding in both steels and the size of the particles is refined by the addition of Mo. Energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) reveal that the carbides are enriched in Nb and N. The presence of Mo is also observed in the particles in the Nb-Mo steel during isothermal holding at 900 °C. The concentration of Mo in the precipitates decreases with increasing particle size and isothermal holding time. The precipitates in the Nb-Mo steel provide significant strengthening increments of up to 140 MPa, higher than that in the Nb steel, ~96 MPa. A thermodynamic rationale is given, which explains that the enrichment of Mo in the precipitates reduces the interfacial energy between precipitates and matrix. This is likely to lower the energy barrier for their nucleation and also reduce the coarsening rate, thus leading to finer precipitates during isothermal holding at 900 °C.

A microstructural study of rapidly solidified and heat-treated austenitic Fe–Mn−Al–Mo–W–Nb–C alloys

1995 ◽  
Vol 10 (6) ◽  
pp. 1371-1378 ◽  
Author(s):  
Kwan H. Han ◽  
Hyun E. Lee
Keyword(s):  
Solidification Process ◽  
Vacancy Defect ◽  
Treatment Schedule ◽  
Depletion Effect ◽  
Transmission Electron ◽  
Heat Treated ◽  
Melt Spun ◽  
The Matrix ◽  
Means Of Transmission ◽  
Rapidly Solidified

The microstructural characteristics of melt-spun and heat-treated austenitic Fe−28Mn−8.6Al−0.5Mo−0.7W−0.5Nb−1.1C (in wt. %) alloys have been investigated by means of transmission electron microscopy. The melt-spun alloy contained fine austenitic cells and some intercelluar Nb(C, N) precipitates. Detailed observations revealed fine {100} modulations in the matrix of the cells, as well as a concomitant L′I2 atomic ordering arising from it. These observations indicate that the onset of decomposition of the initial austenite phase occurred during the rapid solidification process. Aging of the melt-spun alloy at 823–1173 K produced various microstructures, including a general precipitation of Nb(C, N) in the matrix. On isochronal annealing for 1 h, this matrix Nb(C, N) precipitation commenced at 1073 K with the formation of metastable coherent K-carbide (K′) near cell boundaries. On annealing at temperatures above 1123 K, only the Nb(C, N) precipitates were formed, on a fine scale, being accompanied by the formation of precipitate-free regions in the vicinity of cell and grain boundaries. Both intercellular and matrix Nb(C, N) precipitates obeyed a cube-to-cube orientation relationship with austenite. The general matrix precipitation of Nb(C, N) and formation of precipitate-free regions are discussed in terms of a vacancy (defect)-depletion effect. Finally, it was demonstrated that, by employing a double heat-treatment schedule of annealing at 1173 K followed by aging at 823 K, a novel microstructure consisting of fine dispersoids of Nb(C, N) carbo-nitride, distributed over the matrix of {100} modulated structure, could be produced.

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