scholarly journals Ageing of Al-Mn-Cu-Be Alloys for Stimulating Precipitation of Icosahedral Quasicrystals

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 937
Author(s):  
Tonica Bončina ◽  
Mihaela Albu ◽  
Franc Zupanič
Keyword(s):  
Ageing Temperature ◽  
Number Density ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Range ◽  
Transmission Electron ◽  
Icosahedral Quasicrystals ◽  
Increasing Temperature ◽  
20 Nm ◽  
Icosahedral Quasicrystalline

In this work, the ageing of some Al-Mn-Cu-Be alloys was investigated in the temperature range in which predominantly icosahedral quasicrystalline (IQC) precipitates can form. The alloys were cast into a copper mould, directly aged (T5 heat treatment) between 300 and 440 °C for different times. Afterwards, they were examined using scanning and transmission electron microscopy, X-ray diffraction and hardness testing. The main aim of the work was to determine the conditions at which a high number density of spherical icosahedral quasicrystalline precipitates can form. The highest number density of IQC precipitates was obtained at 300 °C after prolonged ageing. The spheroidal precipitates had a diameter less than 20 nm. The size of IQC precipitates increased with the increasing temperature, and in addition, decagonal quasicrystalline precipitates appeared. The time to maximum hardness decreased strongly with increasing ageing temperature. The IQC precipitates can form in a fairly broad temperature range in Al-Mn-Cu-Be alloys and that by varying ageing temperature and duration, rather different distributions of precipitates can be obtained. The presence of precipitates caused rather strong aluminium alloys and fast work hardening during initial plastic deformation.

On the Mechanical Milling of the AlCuFe Icosahedral Phase with Water

2014 ◽  
Vol 793 ◽  
pp. 23-27
Author(s):  
C. Patiño-Carachure ◽  
J. Luis López-Miranda ◽  
F. de la Rosa ◽  
M. Abatal ◽  
R. Pérez ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Milling Time ◽  
Induction Furnace ◽  
Icosahedral Phase ◽  
Quasicrystalline Phase ◽  
X Ray Diffraction ◽  
Cast Sample ◽  
X Ray ◽  
Transmission Electron ◽  
Icosahedral Quasicrystalline

In this investigation the Al64Cu24Fe12 alloy was melted in an induction furnace and solidified under normal casting conditions. The as-cast sample was subject to a heat treatment at 700 oC under argon atmosphere in order to obtain the icosahedral quasicrystalline phase in a monophase region. Subsequently, the icosahedral phase was milled for different times and water added conditions. The pre-alloyed and milled powders were characterized using scanning electron microscopy, X-Ray diffraction, and transmission electron microscopy. The experimental results showed that the icosahedral phase is sensitive to the reaction between water and aluminum of the quasicrystalline alloy to generate hydrogen. As the milling time and the amount of water are increased, the embrittlement reaction of the alloy is accentuated releasing more hydrogen.

scholarly journals Chemical Stability of Ti3C2 MXene with Al in the Temperature Range 500–700 °C

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1979 ◽  
Author(s):  
Jing Zhang ◽  
Shibo Li ◽  
Shujun Hu ◽  
Yang Zhou
Keyword(s):  
Electron Microscopy ◽  
Chemical Stability ◽  
Metal Matrix ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Range ◽  
Transmission Electron ◽  
Work First ◽  
Scanning Electron

Ti3C2Tx MXene, a new 2D nanosheet material, is expected to be an attractive reinforcement of metal matrix composites because its surfaces are terminated with Ti and/or functional groups of –OH, –O, and –F which improve its wettability with metals. Thus, new Ti3C2Tx/Al composites with strong interfaces and novel properties are desired. To prepare such composites, the chemical stability of Ti3C2Tx with Al at high temperatures should be investigated. This work first reports on the chemical stability of Ti3C2Tx MXene with Al in the temperature range 500–700 °C. Ti3C2Tx is thermally stable with Al at temperatures below 700 °C, but it reacts with Al to form Al3Ti and TiC at temperatures above 700 °C. The chemical stability and microstructure of the Ti3C2Tx/Al samples were investigated by differential scanning calorimeter, X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy.

scholarly journals Enhanced Photocatalytic Activity of Vanadium-Doped SnO2 Nanoparticles in Rhodamine B Degradation

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
H. Letifi ◽  
Y. Litaiem ◽  
D. Dridi ◽  
S. Ammar ◽  
R. Chtourou
Keyword(s):  
Photocatalytic Activity ◽  
Rhodamine B ◽  
Crystal Size ◽  
Sno2 Nanoparticles ◽  
X Ray Diffraction ◽  
Optical Studies ◽  
Vanadium Concentration ◽  
X Ray ◽  
Transmission Electron ◽  
20 Nm

In this paper, we have reported a novel photocatalytic study of vanadium-doped SnO2 nanoparticles (SnO2: V NPs) in rhodamine B degradation. These NPs have been prepared with vanadium concentrations varying from 0% to 4% via the coprecipitation method. Structural, morphological, and optical properties of the prepared nanoparticles have been investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscope (TEM), and UV-Vis and photoluminescence (PL) spectroscopy. Structural properties showed that both undoped and SnO2: V NPs exhibited the tetragonal structure, and the average crystal size has been decreased from 20 nm to 10 nm with the increasing doping level of vanadium. Optical studies showed that the absorption edge of SnO2: V NPs showed a redshift with the increasing vanadium concentration. This redshift leads to the decrease in the optical band gap from 3.25 eV to 2.55 eV. A quenching in luminescence intensity has been observed in SnO2: V NPs, as compared to the undoped sample. Rhodamine B dye (RhB) has been used to study the photocatalytic degradation of all synthesized NPs. As compared to undoped SnO2 NPs, the photocatalytic activity of SnO2: V NPs has been improved. RhB dye was considerably degraded by 95% within 150 min over on the SnO2: V NPs.

scholarly journals Synthesis, Structure, and Luminescent Properties of Europium-Doped Hydroxyapatite Nanocrystalline Powders

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Carmen Steluta Ciobanu ◽  
Simona Liliana Iconaru ◽  
Florian Massuyeau ◽  
Liliana Violeta Constantin ◽  
Adrian Costescu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Textural Properties ◽  
Average Crystallite Size ◽  
Luminescent Properties ◽  
Nanocrystalline Powders ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Vibrational Studies ◽  
20 Nm

The luminescent europium-doped hydroxyapatite (Eu:HAp, Ca10−xEux(PO4)6(OH)2) with0≤x≤0.2nanocrystalline powders was synthesized by coprecipitation. The structural, morphological, and textural properties were well characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The vibrational studies were performed by Fourier transform infrared, Raman, and photoluminescence spectroscopies. The X-ray diffraction analysis revealed that hydroxyapatite is the unique crystalline constituent of all the samples, indicating that Eu has been successfully inserted into the HAp lattice. Eu doping inhibits HAp crystallization, leading to a decrease of the average crystallite size from around 20 nm in the undoped sample to around 7 nm in the sample with the highest Eu concentration. Furthermore, the samples show the characteristic5D0→7F0transition observed at 578 nm related to Eu3+ions distributed on Ca2+sites of the apatitic structure.

Structural, morphological, and magnetic study of nanocrystalline cobalt-copper powders synthesized by the polyol process

1995 ◽  
Vol 10 (6) ◽  
pp. 1546-1554 ◽  
Author(s):  
G.M. Chow ◽  
L.K. Kurihara ◽  
K.M. Kemner ◽  
P.E. Schoen ◽  
W.T. Elam ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Copper Powders ◽  
Face Centered ◽  
Increasing Temperature ◽  
X Ray Absorption

Nanocrystalline CoxCu100−x (4 ⋚ x ⋚ 49 at. %) powders were prepared by the reduction of metal acetates in a polyol. The structure of powders was characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), extended x-ray absorption fine structure (EXAFS) spectroscopy, solid-state nuclear magnetic resonance (NMR) spectroscopy, and vibrating sample magnetometry (VSM). As-synthesized powders were composites consisting of nanoscale crystallites of face-centered cubic (fcc) Cu and metastable face-centered cubic (fcc) Co. Complementary results of XRD, HRTEM, EXAFS, NMR, and VSM confirmed that there was no metastable alloying between Co and Cu. The NMR data also revealed that there was some hexagonal-closed-packed (hcp) Co in the samples. The powders were agglomerated, and consisted of aggregates of nanoscale crystallites of Co and Cu. Upon annealing, the powders with low Co contents showed an increase in both saturation magnetization and coercivity with increasing temperature. The results suggested that during preparation the nucleation of Cu occurred first, and the Cu crystallites served as nuclei for the formation of Co.

Nanoporous Ni and Ni-Cu Fabricated by Dealloying

2009 ◽  
Vol 1228 ◽  
Author(s):  
Masataka Hakamada ◽  
Yasumasa Chino ◽  
Mamoru Mabuchi
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Noble Metals ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Difference ◽  
20 Nm ◽  
Good Workability ◽  
Scanning Electron

AbstractMetallic nanoporous architecture can be spontaneously attained by dealloying of a binary alloy. The nanoporous architecture can be often fabricated in noble metals such as Au and Pt. In this study, nanoporous Ni, Ni-Cu are fabricated by dealloying rolled Ni-Mn and Cu-Ni-Mn alloys, respectively. Unlike conventional Raney nickel composed of brittle Ni-Al or Cu-Al intermetallic compounds, the initial alloys had good workability probably because of their fcc crystal structures. After the electrolysis of the alloys in (NH4)2SO4 aqueous solution, nanoporous architectures of Ni and Ni-Cu with pore and ligament sizes of 10–20 nm were confirmed by scanning electron microscopy and transmission electron microscopy. X-ray diffraction analyses suggested that Ni and Cu atoms form a homogeneous solid solution in the Ni-Cu nanoporous architecture. The ligament sizes of nanoporous Ni and Ni-Cu were smaller than that of nanoporous Cu, reflecting the difference between diffusivities of Ni and Cu at solid/electrolyte interface. Ni can reduce the pore and ligament sizes of resulting nanoporous architecture when added to initial Cu-Mn alloys.

Tem Structure Investigations of Low-Temperature MBE Grown Inalas Layers on INP Substrate

1992 ◽  
Vol 263 ◽  
Author(s):  
P. Werner ◽  
Z. Liliental-Weber ◽  
K.M. Yu ◽  
E.R. Weber ◽  
Z. Rek ◽  
...  
Keyword(s):  
Electrical Resistance ◽  
Stacking Faults ◽  
X Ray Diffraction ◽  
Real Crystal ◽  
X Ray ◽  
Group Iii ◽  
Temperature Range ◽  
Density Of Dislocations ◽  
Transmission Electron ◽  
Structure Investigations

ABSTRACTThe real crystal structure of In0.52A10.48As layers grown on InP<001> substrate as a function of the growth temperature (between 150°C and 450°C) was investigated. The following structural / electrical analyses were applied to the samples: transmission electron microscopy (TEM), x-ray diffraction and particle induced x-ray emission (PIXE). In the temperature range between 200°C and 450°C good epitaxial growth of InAlAs layers can be achieved with a low density of dislocations and stacking faults. Ordering of group-III elements on {111} planes was observed for these layers. Structure models of such ordered domains are discussed. At growth temperatures below 300 °C additional As (≈2%) is incorporated in the lattice. Growth at temperatures below 200°C leads to the formation of pyramidal defects with As grains in their cores. As-grown as well as annealed InAlAs layers show a nearly constant, high electrical resistance (106-107Ωcm) in the whole temperature range.

Nanocrystallization of gas atomized Cu47Ti33Zr11Ni8Si1 metallic glass

2006 ◽  
Vol 21 (3) ◽  
pp. 597-607 ◽  
Author(s):  
S. Venkataraman ◽  
S. Scudino ◽  
J. Eckert ◽  
T. Gemming ◽  
C. Mickel ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Primary Crystallization ◽  
Nanocrystalline Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
20 Nm ◽  
Annealing Experiments

Cu47Ti33Zr11Ni8Si1 metallic glass powder was prepared by gas atomization. Decomposition in the amorphous alloy and primary crystallization has been studied by differential scanning calorimetry (DSC), x-ray diffraction (XRD), and transmission electron microscopy (TEM). The glassy powder exhibits a broad DSC exotherm prior to bulk crystallization. Controlled annealing experiments reveal that this exotherm corresponds to a combination of structural relaxation and nanocrystallization. A uniform featureless amorphous contrast is observed in the TEM prior to the detection of nanocrystals of 4–6 nm in size. High-resolution TEM studies indicate that this nanocrystalline phase has a close crystallographic relationship with the γ–CuTi phase having a tetragonal structure. The product of the main crystallization event is also nanocrystalline, hexagonal Cu51Zr14, having dimensions of 20 nm. However, there is no evidence for possible amorphous phase separation prior to the nanocrystallization events.

scholarly journals Investigation of the γ′ Precipitates Dissolution in a Ni-Based Superalloy During Stress-Free Short-Term Annealing at High Homologous Temperatures

2021 ◽  
Author(s):  
Łukasz Rakoczy ◽  
Małgorzata Grudzień-Rakoczy ◽  
Fabian Hanning ◽  
Grzegorz Cempura ◽  
Rafał Cygan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Lattice Parameters ◽  
X Ray Diffraction ◽  
Short Term ◽  
X Ray ◽  
Transmission Electron ◽  
Thermodynamic Simulations ◽  
The Matrix ◽  
Increasing Temperature

AbstractThe equiaxed Ni-based superalloy René 108 was subjected to short-term annealing at five temperatures between 900 °C and 1100 °C. The phase composition, phase lattice parameters, microstructure, stereological parameters, and chemical composition of γ′ precipitates were investigated by thermodynamic simulations, X-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Analysis of the γ and γ′ lattice parameters using the Nelson-Riley extrapolation function showed that the misfit parameter for temperatures 900 °C to 1050 °C is positive (decreasing from 0.32 to 0.11 pct). At 1100 °C, the parameter becomes negative, δ = − 0.18 pct. During the short-term annealing, γ′ precipitates dissolution occurred progressing more rapidly with increasing temperatures. The surface fraction of γ′ precipitates decreased with increasing temperature from 0.52 to 0.34. The dissolution of γ′ precipitates did not only proceed through uninterrupted thinning of each individual precipitate, but also included more complex mechanisms, including splitting. Based on transmission electron microscopy, it was shown that after γ′ precipitates dissolution, the matrix close to the γ/γ′ interface is strongly enriched in Co and Cr and depleted in Al.

scholarly journals Facile Synthesis of High {001} Facets Dominated BiOCl Nanosheets and Their Selective Dye-Sensitized Photocatalytic Activity Induced by Visible Light

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Da Zhang ◽  
Liang Chen ◽  
Chengjing Xiao ◽  
Jing Feng ◽  
Lingmin Liao ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Atmospheric Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dye Sensitized ◽  
Selective Area ◽  
Transmission Electron ◽  
Organic Surfactant ◽  
20 Nm

Single-crystal BiOCl nanosheets, with high{001}facets exposed, were synthesized through a facile hydrolysis reaction under general atmospheric pressure, without adding any organic surfactant or agent. The thickness of the BiOCl nanosheets is about 20 nm, and the diameter is arranged from 200 to 400 nm. The structure of the BiOCl nanosheets was characterized by X-ray diffraction, energy disperse X-ray spectrum, transmission electron microscopy, and selective area electron diffraction. Moreover, three different dyes were used as model molecules to test the photocatalytic activity of BiOCl nanosheets under visible light. It was found that the BiOCl nanosheets possess selective photocatalytic behavior as their activity over RhB is much higher than that over MO or MB. Based on the analysis of the experimental results, the potential mechanism was discussed.

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