Observation and formation mechanism of stable face-centered-cubic Fe nanorods in carbon nanotubes

2003 ◽  
Vol 18 (5) ◽  
pp. 1104-1108 ◽  
Author(s):  
Hansoo Kim ◽  
Michael J. Kaufman ◽  
Wolfgang M Sigmund ◽  
David Jacques ◽  
Rodney Andrews
Keyword(s):  
Carbon Nanotubes ◽  
Growth Temperature ◽  
Room Temperature ◽  
Iron Nanoparticles ◽  
Cubic Phase ◽  
Crystallographic Structure ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Iron Particles ◽  
Face Centered

The crystallographic structure and orientation of iron nanoparticles present in carbon nanotubes (CNTs) was studied when iron was used as a catalyst. It was found that while most of the nanoparticles encapsulated inside the CNTs had the expected α–Fe (body-centered-cubic) phase, a significant number of them formed and retained the γ–Fe (face-centered-cubic) phase that is not the normal bulk phase at room temperature (nor even expected to form at the growth temperature used). It was also found iron particles at the tips of the nanotubes were either α–Fe or cementite (Fe3C). On the basis of these observations and thermodynamics, a mechanism for the formation of these particles and insights into CNT growth is proposed.

Critical factors that determine face-centered cubic to body-centered cubic phase transformation in sputter-deposited austenitic stainless steel films

2004 ◽  
Vol 19 (6) ◽  
pp. 1696-1702 ◽  
Author(s):  
X. Zhang ◽  
A. Misra ◽  
R.K. Schulze ◽  
C.J. Wetteland ◽  
H. Wang ◽  
...  
Keyword(s):  
Thin Films ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Phase Stability ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Bcc Structure ◽  
Face Centered ◽  
Sputter Deposited

Bulk austenitic stainless steels (SS) have a face-centered cubic (fcc) structure. However, sputter deposited films synthesized using austenitic stainless steel targets usually exhibit body-centered cubic (bcc) structure or a mixture of fcc and bcc phases. This paper presents studies on the effect of processing parameters on the phase stability of 304 and 330 SS thin films. The 304 SS thin films with in-plane, biaxial residual stresses in the range of approximately 1 GPa (tensile) to approximately 300 MPa (compressive) exhibited only bcc structure. The retention of bcc 304 SS after high-temperature annealing followed by slow furnace cooling indicates depletion of Ni in as-sputtered 304 SS films. The 330 SS films sputtered at room temperature possess pure fcc phase. The Ni content and the substrate temperature during deposition are crucial factors in determining the phase stability in sputter deposited austenitic SS films.

On the new structural phases in Al65Cu20Cr15 quasicrystalline alloy

1995 ◽  
Vol 10 (8) ◽  
pp. 1905-1912 ◽  
Author(s):  
Varsha Khare ◽  
N.P. Lalla ◽  
R.S. Tiwari ◽  
O.N. Srivastava
Keyword(s):  
Metastable Phase ◽  
Structural Characteristics ◽  
Icosahedral Phase ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Structural Variants ◽  
Simple Cubic ◽  
Face Centered ◽  
Specific Orientation

The quasicrystalline (qc) alloy Al65Cu20Cr15, unlike its Ru- and Fe-bearing counterparts like Al65Cu20Ru15 and Al65Cu20Fe15, is a metastable phase. This qc alloy has been shown to possess several structural variants and curious structural characteristics. We have investigated the qc alloy Al65Cu20Cr15 with special reference to the possible occurrence of new structural variants. TEM exploration of the as-quenched qc alloy has indeed revealed the existence of several new phases. These are (i) body-centered cubic (bcc) (a = 12.60 Å, disordered) and simple cubic (s.c.) (a = 12.60 Å, ordered), which are the 1/1 approximants of the primitive icosahedral phase (i phase); (ii) a twice order-induced modulated cubic phase (bcc, a = 25.20 Å) which has been shown to correspond to 1/1 approximant of the ordered i phase [i.e., face-centered icosahedral (FCI)]; and (iii) real crystalline bcc (a = 8.90 Å) and face-centered cubic (fcc) (a = 17.98 Å) phases possessing a specific orientation relationship with the icosahedral matrix phase. Tentative structural models showing the interrelationships between the bcc/fcc phases have been outlined.

The role of vacancies in the pressure amorphisation phenomenon observed in Ge-Sb-Te phase change alloys

2010 ◽  
Vol 1251 ◽  
Author(s):  
Milos Krbal ◽  
Alex Kolobov ◽  
Paul Fons ◽  
Junji Tominaga ◽  
Julien Haines ◽  
...  
Keyword(s):  
Amorphous Phase ◽  
Cubic Phase ◽  
Initial Structure ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Atomic Displacements ◽  
Face Centered ◽  
Fcc Phase ◽  
Trigonal Phase

AbstractWe demonstrate, both experimentally and by computer simulation, that while the metastable face-centered cubic (fcc) phase of Ge-Sb-Te becomes amorphous under hydrostatic compression at about 15 GPa, the stable trigonal phase remains crystalline. We present evidences that the pressure-induced amorphisation phenomenon strongly depends on the concentration of vacancies included in the Ge/Sb sublattice, but is thermally insensitive. Upon higher compression, a body-centered cubic phase is obtained in both cases at around 30 GPa. Upon decompression, the amorphous phase is retained when starting with the fcc phase while the initial structure is recovered when starting with the trigonal phase. We argue that the presence of vacancies and the associated subsequent large atomic displacements lead to nanoscale phase separation and the loss of the initial structure memory in the fcc staring phase of Ge-Sb-Te. We futher compare the amorphous phase obtained via the pressure route with the melt quenched amorphous phase.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

scholarly journals Irradiation Behaviors in BCC Multi-Component Alloys with Different Lattice Distortions

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 706
Author(s):  
Yue Su ◽  
Songqin Xia ◽  
Jia Huang ◽  
Qingyuan Liu ◽  
Haocheng Liu ◽  
...  
Keyword(s):  
Single Phase ◽  
Vacuum Arc ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Chemical Complexity ◽  
Arc Melting ◽  
Vacuum Arc Melting ◽  
Lattice Distortions ◽  
Face Centered ◽  
Displacement Per Atom

Recently, the irradiation behaviors of multi-component alloys have stimulated an increasing interest due to their ability to suppress the growth of irradiation defects, though the mostly studied alloys are limited to face centered cubic (fcc) structured multi-component alloys. In this work, two single-phase body centered cubic (bcc) structured multi-component alloys (CrFeV, AlCrFeV) with different lattice distortions were prepared by vacuum arc melting, and the reference of α-Fe was also prepared. After 6 MeV Au ions irradiation to over 100 dpa (displacement per atom) at 500 °C, the bcc structured CrFeV and AlCrFeV exhibited significantly improved irradiation swelling resistance compared to α-Fe, especially AlCrFeV. The AlCrFeV alloy possesses superior swelling resistance, showing no voids compared to α-Fe and CrFeV alloy, and scarce irradiation softening appears in AlCrFeV. Owing to their chemical complexity, it is believed that the multi-component alloys under irradiation have more defect recombination and less damage accumulation. Accordingly, we discuss the origin of irradiation resistance and the Al effect in the studied bcc structured multi-component alloys.

scholarly journals Green Synthesis and Characterization of Pullulan Mediated Silver Nanoparticles through Ultraviolet Irradiation

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2382 ◽  
Author(s):  
Muhammad Jamshed Khan ◽  
Suriya Kumari ◽  
Kamyar Shameli ◽  
Jinap Selamat ◽  
Awis Qurni Sazili
Keyword(s):  
Silver Nanoparticles ◽  
Uv Irradiation ◽  
Irradiation Time ◽  
Edible Films ◽  
Crystallographic Structure ◽  
Face Centered Cubic ◽  
Selected Area Electron Diffraction ◽  
Vis Spectroscopy ◽  
Face Centered ◽  
Average Lattice

Nanoparticles (NPs) are, frequently, being utilized in multi-dimensional enterprises. Silver nanoparticles (AgNPs) have attracted researchers in the last decade due to their exceptional efficacy at very low volume and stability at higher temperatures. Due to certain limitations of the chemical method of synthesis, AgNPs can be obtained by physical methods including sun rays, microwaves and ultraviolet (UV) radiation. In the current study, the synthesis of pullulan mediated silver nanoparticles (P-AgNPs) was achieved through ultraviolet (UV) irradiation, with a wavelength of 365 nm, for 96 h. P-AgNPs were formed after 24 h of UV-irradiation time and expressed spectra maxima as 415 nm, after 96 h, in UV-vis spectroscopy. The crystallographic structure was “face centered cubic (fcc)” as confirmed by powder X-ray diffraction (PXRD). Furthermore, high resolution transmission electron microscopy (HRTEM) proved that P-AgNPs were covered with a thin layer of pullulan, with a mean crystalline size of 6.02 ± 2.37. The average lattice fringe spacing of nanoparticles was confirmed as 0.235 nm with quasi-spherical characteristics, by selected area electron diffraction (SAED) analysis. These green synthesized P-AgNPs can be utilized efficiently, as an active food and meat preservative, when incorporated into the edible films.

Stacking Faults in a High Nitrogen Face-Centered-Cubic Phase Formed on Nitrogen-Modified Austenitic Stainless Steel

2008 ◽  
Vol 373-374 ◽  
pp. 318-321
Author(s):  
J. Liang ◽  
M.K. Lei
Keyword(s):  
Stainless Steel ◽  
Plasma Source ◽  
Peak Shift ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
High Nitrogen ◽  
X Ray ◽  
Peak Asymmetry ◽  
Face Centered

Effects of stacking faults in a high nitrogen face-centered-cubic phase (γΝ) formed on plasma source ion nitrided 1Cr18Ni9Ti (18-8 type) austenitic stainless steel on peak shift and peak asymmetry of x-ray diffraction were investigated based on Warren’s theory and Wagner’s method, respectively. The peak shift from peak position of the γΝ phase is ascribed to the deformation faults density α, while the peak asymmetry of the γΝ phase is characterized by deviation of the center of gravity of a peak from the peak maximum (Δ C.G.) due to the twin faults density β. The calculated peak positions of x-ray diffraction patterns are consistent with that measured for plasma source ion nitrided 1Cr18Ni9Ti stainless steel.

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