scholarly journals Microstructure and Nanohardness of Ti-48Al-2Cr Alloy Solidified under High Pressure

2020 ◽  
Vol 10 (15) ◽  
pp. 5394
Author(s):  
Duo Dong ◽  
Li Liu ◽  
Dongdong Zhu ◽  
Yang Liu ◽  
Ye Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Lamellar Structure ◽  
Ambient Pressure ◽  
Testing Machine ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microstructure Observation ◽  
Transmission Electron ◽  
Holding Temperature

In this work, the Ti-48Al-2Cr alloy, solidified under different pressures and temperatures, was investigated in detail. The effect of high pressure on the microstructure and nanohardness of the Ti-48Al-2Cr alloy was investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and a nanoindenter XP testing machine. The results showed that the B2 phase disappeared after high-pressure solidification. Compared with ambient pressure solidification, high pressure led to the increase of (α2 + γ) lamellar structure and the decrease of γ phase. The nanohardness of the lamellar structure was discussed based on the microstructure observation. When solidified at 5 GPa/1873 K, the hardness rose to 5.54 GPa, an increase of 60.5% compared with that solidified at ambient pressure. However, the increased holding temperature of 1973 K made the dislocation density in the lamellar structures greatly decrease, and reduced the structure’s hardness to 4.48 GPa.

Microstructural analysis of high-pressure compressed C60

2001 ◽  
Vol 16 (7) ◽  
pp. 1960-1966 ◽  
Author(s):  
K. Miyazawa ◽  
H. Satsuki ◽  
M. Kuwabara ◽  
M. Akaishi
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Pressure ◽  
High Resolution ◽  
Microstructural Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Hardness Tests ◽  
Lattice Planes

The structure and hardness of C60 bulk specimens compressed under 5.5 GPa at room temperature to 600 °C are investigated by high-resolution transmission electron microscopy, x-ray diffraction, and micro-Vickers hardness tests. A strong accumulation of the [1 1 0]tr orientation of high-pressure-treated C60 specimens was developed along the compression axis, and stacking faults and nano-sized deformation twins were introduced into the C60 specimens compressed at 450–600 °C. Curved lattice planes indicating a polymerization of C60 were observed by high resolution transmission electron microscopy (HRTEM). The polymerization of the high-pressure-compressed C60 is also supported by the computer simulation of HRTEM images.

Structures and phase transitions of B-Ta2O5 and Z-Ta2O5: two high-pressure forms of Ta2O5

2000 ◽  
Vol 56 (4) ◽  
pp. 659-665 ◽  
Author(s):  
I. P. Zibrov ◽  
V. P. Filonenko ◽  
M. Sundberg ◽  
P.-E. Werner
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Pressure ◽  
Rietveld Method ◽  
High Pressure Chamber ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Transmission Electron ◽  
Heat Treated

A sample of Ta2O5, ditantalum pentaoxide, heat-treated in a `toroid'-type high-pressure chamber at P = 8 GPa and T = 1470 K, was studied by X-ray powder diffraction and high-resolution transmission electron microscopy (HRTEM). Two high-pressure modifications of Ta2O5, isostructural with B-Nb2O5 and Z-Nb2O5, were identified from the X-ray powder pattern. Both structures were refined by the Rietveld method from the X-ray diffraction data: B-Ta2O5, a = 12.7853 (4), b = 4.8537 (1), c = 5.5276 (2) Å, β = 104.264 (2)°, V = 332.45 Å3, Z = 4, space group C2/c; Z-Ta2O5, a = 5.2252 (1), b = 4.6991 (1), c = 5.8534 (1) Å, β = 108.200 (2)°, V = 136.53 Å3, Z = 2, space group C2. The Z-Ta2O5 modification is new. The Ta atoms are six-coordinated in B-Ta2O5 and seven-coordinated in Z-Ta2O5. The two structures are closely related, which makes an intergrowth and a transformation between them possible. An idealized model of the intergrowth structure has been given. The HRTEM study showed defect-rich B-Ta2O5 crystals, which could be interpreted as an intergrowth between the B-Ta2O5 and Z-Ta2O5 phases.

X-ray diffraction and transmission-electron microscopy of natural polycrystalline graphite recovered from high pressure

1994 ◽  
Vol 49 (1) ◽  
pp. 22-27 ◽  
Author(s):  
Shoichi Endo ◽  
Naoki Idani ◽  
Ryuichiro Oshima ◽  
Kaoru J. Takano ◽  
Masao Wakatsuki
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Polycrystalline Graphite ◽  
Transmission Electron

Novel Tribological Behavior of Hybrid MWCNTs/MLNGPs as an Additive on Lithium Grease

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
M. E. Ashour ◽  
T. A. Osman ◽  
A. Khattab ◽  
A. B. Elshalakny
Keyword(s):  
Electron Microscopy ◽  
Testing Machine ◽  
X Ray Diffraction ◽  
Optimum Ratio ◽  
Wear Scar Diameter ◽  
Multiwalled Carbon ◽  
Lithium Grease ◽  
X Ray ◽  
Transmission Electron ◽  
Worn Surface

The goal of this paper is to investigate tribological characteristics of nanographene platelets and hybridized nanocomposite of multiwalled carbon nanotubes (MWCNTs)/multilayer nanographene platelets (MLNGPs)/lithium based-grease. Characterization is done through high resolution transmission electron microscopy (TEM) and X-ray diffraction. While grease properties were tested using Falex four-ball testing machine. Scanning electron microscopy (SEM) and energy dispersive X-ray diffraction (EDX) were utilized to characterize the lubrication mechanism and the worn surface. The results showed that 1% of MLNGPs is the optimum concentration. Wear scar diameter (WSD) was reduced by 66%, friction coefficient was reduced by 91%, while maximum nonseizer load was increased by 90 kg over ordinary lithium grease. Hybrid MWCNTs\MLNGPs were studied, and the optimum ratio of MLNGPs to MWCNTs was found to be 4:1.

scholarly journals Study of ZnO-CNT Nanocomposites in High-Pressure Conditions

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5330
Author(s):  
Laura-Madalina Cursaru ◽  
Sorina Nicoleta Valsan ◽  
Maria-Eliza Puscasu ◽  
Ioan Albert Tudor ◽  
Nicoleta Zarnescu-Ivan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron ◽  
Specific Morphology ◽  
Ft Ir ◽  
Nanocomposite Powders

Recently, carbon nanotubes (CNTs) have been used extensively to develop new materials and devices due to their specific morphology and properties. The reinforcement of different metal oxides such as zinc oxide (ZnO) with CNT develops advanced multifunctional materials with improved properties. Our aim is to obtain ZnO-CNT nanocomposites by in situ hydrothermal method in high-pressure conditions. Various compositions were tested. The structure and morphology of ZnO-CNT nanocomposites were analyzed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry—thermogravimetry (DSC-TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). These analyses showed the formation of complex ZnO-CNT structures. FT-IR spectra suggest possible interactions between CNT and ZnO. DSC-TG analysis also reveals the formation of some physical bonds between ZnO and CNT, through the appearance of endothermic peaks which could be assigned to the decomposition of functional groups of the CNT chain and breaking of the ZnO-CNT bonds. XRD characterization demonstrated the existence of ZnO nanocrystallites with size around 60 nm. The best ZnO:CNT composition was further selected for preliminary investigations of the potential of these nanocomposite powders to be processed as pastes for extrusion-based 3D printing.

Microstructure and Thermal Stability of Ultra Fine Grained Mg and Mg-Gd Alloys Prepared by High-Pressure Torsion

2005 ◽  
Vol 482 ◽  
pp. 183-186 ◽  
Author(s):  
Jakub Čížek ◽  
Ivan Procházka ◽  
Bohumil Smola ◽  
Ivana Stulíková ◽  
Radomír Kužel ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
High Pressure ◽  
Positron Lifetime ◽  
High Pressure Torsion ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fine Grained ◽  
Transmission Electron ◽  
Thermal Stability Of

Bulk samples of pure Mg and Mg-Gd alloys were prepared by high-pressure torsion (HPT). The HPT made samples exhibit ultra fine grained (UFG) structure with grain size around 100 nm. Results of microstructure investigations of the UFG samples obtained by positron lifetime (PL) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) are presented. In particular, lattice defects introduced by HPT were characterized. The data obtained at atomistic level are compared with macroscopic properties given by microhardness measurements.

Behavior of carbon nanotubes under high pressure and high temperature

2000 ◽  
Vol 15 (2) ◽  
pp. 560-563 ◽  
Author(s):  
D. S. Tang ◽  
L. C. Chen ◽  
L. J. Wang ◽  
L. F. Sun ◽  
Z. Q. Liu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
High Pressure ◽  
High Temperature ◽  
Structural Changes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Diamond Crystallization ◽  
Graphite Sheets

The structural changes of carbon nanotubes induced by high pressure and high temperature were investigated by means of x-ray diffraction, Raman scattering, scanning electron microscopy, and transmission electron microscopy. It is shown that, with increasing pressure and temperature, the lattice constant d002 of tubes shortens, and then tubes collapse into tapelike ones; at the same time the C–C bonds at high curvature break, which lead the tapelike tubes to break into graphite sheets as diamond crystallization centers. Compared with graphite, the diamond particles from carbon nanotubes have many defects as the trace of tubes.

Influence of High-Pressure Torsion on the Microstructure and the Hardness of a Ti-Rich High-Entropy Alloy

2016 ◽  
Vol 879 ◽  
pp. 732-737 ◽  
Author(s):  
Anita Heczel ◽  
Lola Lilensten ◽  
Julie Bourgon ◽  
Loic Perrière ◽  
Jean Philippe Couzine ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
High Pressure ◽  
High Pressure Torsion ◽  
High Entropy Alloy ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Entropy ◽  
Transmission Electron ◽  
Bcc Structure

High-Pressure Torsion (HPT) is one of the most effective severe plastic deformation techniques in grain refinement. The goal of this study was to investigate the influence of HPT on the microstructure and hardness of a Ti-rich High-Entropy Alloy (HEA). The evolution of the grain size due to 1 turn of HPT was studied by transmission electron microscopy. Besides the refinement of the microstructure, a phase transition also occurred during HPT, as revealed by X-ray diffraction. The initial bcc structure transformed into a martensitic phase throughout the material. The features of this phase transformation were studied on a sample compressed to low strain values. The hardness as a function of the distance from the center in the HPT-processed disk was measured and correlated to the microstructure.

Preparation, Characterization of N-Ti-MCM-22 Molecular Sieve and its Photocatalytic Properties

2012 ◽  
Vol 602-604 ◽  
pp. 205-208
Author(s):  
Yue Cheng ◽  
Xiao Yuan Su
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Methylene Blue ◽  
High Pressure ◽  
Liquid Phase ◽  
Molecular Sieve ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

Nanocrystalline N-doped and Ti-containing MCM-22 catalyst was synthesized by the static hydrothermal method, using sodium azide as nitrogen source for doping, and tetra-n-butyl titanate [Ti(OC4H9)4] as precursors of TiO2. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, and energy-dispersive spectroscopy.During liquid phase photocatalytic degradation of methylene blue (MB) under high-pressure Hg arc lamp irradiation, the asprepared N-doped Ti-MCM-22 exhibited much higher activity than the undoped Ti-MCM-22, attributed to the effect of nitrogen dopant.

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

1982 ◽  
Vol 40 ◽  
pp. 722-723 ◽  
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulations ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

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