Identification of T1 phase in Al-Li-Cu alloy (2090)

1992 ◽  
Vol 50 (1) ◽  
pp. 188-189
Author(s):  
J.S. Kim ◽  
S. S. Baek ◽  
G. H. Kim ◽  
C. H. Chun
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Zone Axis ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cu Alloy ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
Optical Laser

In Al-Li-Cu alloy(2090) the extra spots in the Selected Area Diffraction Pattern (SADP) of [112]α zone axis have been argued. Huang and Ardell described that the extra spots were originated from T1 variants tilted to electron beam. Rioja and Ludwiczak, however, presented that die precursor of T1 termed T1' was present in alloy(2090) and generated the extra spots. Rioja and Ludwiczak explained die existence of extra spots as making the simulated SADP diagrams and analyzing x ray diffraction lines of T1'. The existence of T1' has been inconsistent with the other papers. Huang and Ardell's model has been well recognized in present. The investigations on the extra spots had mainly been restricted in [112]α SADP. In the present paper, the extra spots from [110]αand [100]α zone axes were investigated using High Resolution Electron Microscope (HREM) and optical laser diffractometer.

Crystal Structures Of L-Nb205 AND L-Ta205

1977 ◽  
Vol 35 ◽  
pp. 188-189
Author(s):  
Sumio Iijima
Keyword(s):  
Electron Microscope ◽  
Complex Nature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resolution Electron ◽  
Unit Cells ◽  
System 2 ◽  
High Resolution Electron Microscope ◽  
Diffraction Patterns ◽  
Phase Relationships

Although structures of tantalum pentoxides have been extensively studied, they have not been fully understood because of the complex nature of their X-ray diffraction patterns. In this study we made some observations on crystals of L-Ta2O5 and L-Nb2O5 using a high resolution electron microscope. The latter structure has been believed to be isostructural with L-Ta2O5. The samples were prepared by Dr. Roth at NBS and were parts of the products used for determining phase relationships in niobium pentoxides (1) and the Ta2O5-Ta2WO8 system (2).According to the X-ray data both structures have orthorhombic unit cells with a = 6.2, b = 29.3, c = 3.9Å. The structures are based on the U03-type and the b spacings are nearly 8 times those of the subcell. Electron diffraction (E.D.) patterns of L-Nb2O5 and L-Ta3O5 crystals showing a*-b* reciprocal sections confirmed generally the results of X-ray works (Figs, la and lc).

scholarly journals The Preparation and Characterization ofβ-SiAlON Nanostructure Whiskers

2008 ◽  
Vol 2008 ◽  
pp. 1-6 ◽  
Author(s):  
Pengli Dong ◽  
Xidong Wang ◽  
Mei Zhang ◽  
Min Guo ◽  
Seshadri Seetharaman
Keyword(s):  
Electron Microscope ◽  
Diameter Distribution ◽  
Growth Mechanisms ◽  
X Ray Diffraction ◽  
Vapor Liquid Solid ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
Sintering Method

Two kinds ofβ-SiAlON nanostructure whiskers, rod-like and wool-like whiskers, were synthesized by pressure-less sintering method at 1773 K for 5 hours. The whiskers synthesized were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and high-resolution electron microscope (HREM) techniques. It was found that diameter distribution of rod-like whiskers was about 80–250 nm, while it was about 45–55 nm in diameter for the wool-like whiskers. The growth mechanisms ofβ-SiAlON nanostructure whiskers are discussed by the vapor-solid (VS) and vapor-liquid-solid (VLS) mechanisms, respectively.

Computer-Controlled Hrem Alignment Using Automated Diffractogram Analysis

1990 ◽  
Vol 48 (1) ◽  
pp. 532-533
Author(s):  
G.Y. Fan ◽  
O.L. Krivanek
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
The Other ◽  
Full Information ◽  
Resolution Electron ◽  
Skilled Operator ◽  
Automatic Alignment ◽  
High Resolution Electron Microscope ◽  
Computer Controlled ◽  
Recorded Image

Full alignment of a high resolution electron microscope (HREM) requires five parameters to be optimized: the illumination angle (beam tilt) x and y, defocus, and astigmatism magnitude and orientation. Because neither voltage nor current centering lead to the correct illumination angle, all the adjustments must be done on the basis of observing contrast changes in a recorded image. The full alignment can be carried out by a computer which is connected to a suitable image pick-up device and is able to control the microscope, sometimes with greater precision and speed than even a skilled operator can achieve. Two approaches to computer-controlled (automatic) alignment have been investigated. The first is based on measuring the dependence of the overall contrast in the image of a thin amorphous specimen on the relevant parameters, the other on measuring the image shift. Here we report on our progress in developing a new method, which makes use of the full information contained in a computed diffractogram.

scholarly journals Deformation induced martensite characterization in Fe-30%Ni-5%Cu alloy

2012 ◽  
Vol 48 (2) ◽  
pp. 259-264 ◽  
Author(s):  
E. Güler ◽  
M. Güler
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Dsc Measurements ◽  
Cu Alloy ◽  
The Face ◽  
Xrd Techniques ◽  
Scanning Electron

Deformation induced martensite properties were examined according to existing martensite morphology, crystallography and formation temperatures for different prior austenite homogenization conditions in Fe-30%Ni-5%Cu alloy. Scanning electron microscope (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques were employed to investigation. Scanning electron microscope observations showed elongated deformation induced martensite morphology in the austenite phase of alloy. As well, after deformation martensite start temperatures (Ms) were determined as -101?C and -105?C from DSC measurements for different homogenization conditions. In addition, X-ray diffraction analysis revealed the face centred cubic (fcc) of austenite phases and body centred cubic (bcc) deformation induced martensite phases for all studied samples.

Crystalline silica nanowires

2004 ◽  
Vol 19 (8) ◽  
pp. 2216-2220 ◽  
Author(s):  
F.L. Deepak ◽  
Gautam Gundiah ◽  
Md. Motin Seikh ◽  
A. Govindaraj ◽  
C.N.R. Rao
Keyword(s):  
Fumed Silica ◽  
X Ray Diffraction ◽  
X Ray ◽  
Starting Mixture ◽  
Resolution Electron ◽  
Silica Nanowires ◽  
Microscope Images ◽  
High Resolution Electron Microscope ◽  
Silica Ratio ◽  
First Time

α-Cristobalite nanowires of 50–100 nm diameter with lengths of several microns have been synthesized for the first time by the solid-state reaction of fumed silica and activated charcoal. The nanowires have been characterized by x-ray diffraction, electron microscopy, photoluminescence, and Raman scattering. The nanowires are single crystalline as revealed by high-resolution electron microscope images. The crystalline nanowires are clad by an amorphous silica sheath when the carbon to fumed silica ratio in the starting mixture is small. Use of hydrogen along with Ar helps to eliminate the amorphous sheath.

Electron Microscope Study of Cation-Deficient Chalcogenide Spinels

1982 ◽  
Vol 21 ◽  
Author(s):  
Y. Komura ◽  
S. Takeda
Keyword(s):  
Electron Microscope ◽  
X Ray ◽  
Disordered Structures ◽  
Spinel Compounds ◽  
Vacancy Ordering ◽  
Resolution Electron ◽  
The Matrix ◽  
Lattice Images ◽  
Image Characteristic ◽  
High Resolution Electron Microscope

ABSTRACTHigh-resolution electron microscope observations were carried out on the cation-deficient spinel compounds Ga2/3Cr2S4 and InCr5/3S4. X-ray analysis of both compounds indicates that there exist 1/3 vacancy per formula unit in 8a positions. It was also found that the vacancy ordering occurs in Ga2/3Cr2S4 below about 1100°C, as well as in InCr5/3S4. Lattice images of vacancy ordered and disordered structures were obtained. In some electron micrographs of ordered InCr5/3 S4, several domains of disordered region were observed in between the matrix of the ordered structure. In a [110] image, characteristic lattice defects were observed on the (110) plane.

Electron beam-induced surface modification and nano-engineering of carbon nanotubes: Single-walled and multiwalled

2006 ◽  
Vol 21 (12) ◽  
pp. 3109-3123 ◽  
Author(s):  
S. Gupta ◽  
R.J. Patel ◽  
R.E. Giedd
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Raman Spectroscopy ◽  
Electron Beam ◽  
Electron Microscope ◽  
High Resolution ◽  
Band Intensity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

Influence of low and medium energy electron beam (E-beam) irradiation on the single-walled (SW) and multiwalled (MW) carbon nanotube films grown by microwave chemical vapor deposition are investigated. These films were subjected to electron beam energy of 50 keV from scanning electron microscope for 2.5, 5.5, 8.0, and 15 h and 100, 200, and 300 keV from transmission electron microscope electron gun for a few minutes to approximately 2 h continuously. To assess the surface modifications/structural degradation, the films were analyzed prior to and post-irradiation using x-ray diffraction and micro-Raman spectroscopy in addition to in situ monitoring by scanning and high-resolution transmission electron microscopy. A minimal increase in intertube or interplanar spacing (i.e., d002) for MW nanotubes ranging from 3.25–3.29 Å (∼3%) can be analogized to change in c-axis of graphite lattice due to thermal effects measured using x-ray diffraction. Resonance Raman spectroscopy revealed that irradiation generated defects in the lattice evaluated through variation of: the intensity of radial breathing mode (RBM), intensity ratio of D to G band (ID/IG), position of D and G bands and their harmonics (D* and G*). The increase in the defect-induced D band intensity, quenching of RBM intensity, and only a slight increase in G band intensity are some of the implications. The MW nanotubes tend to reach a state of saturation for prolonged exposures, while SW transforming semiconducting to quasi-metallic character. Softening of the q = 0 selection rule is suggested as a possible way to explain these results. It is also suggestive that knock-on collision may not be the primary cause of structural degradation, rather a local gradual reorganization, i.e., sp2+δ ⇔ sp2+δ, sp2 C seems quite possible. Experiments showed that with extended exposures, both kinds of nanotubes displayed various local structural instabilities including pinching, graphitization/amorphization, and forming intra-molecular junction (IMJ) within the area of electron beam focus possibly through amorphous carbon aggregates. They also displayed curling and closure forming nano-ring and helix-like structures while mending their dangling bonds. High-resolution transmission electron microscopy electrons corroborated these conclusions. Manufacturing of nanoscale structures “nano-engineering” of carbon-based systems is tentatively ascribed to irradiation-induced solid-state phase transformation, in contrast to conventional nanotube synthesis from the gas phase.

300kv high-performance analytical TEM (H-9000)

1987 ◽  
Vol 45 ◽  
pp. 108-109
Author(s):  
H. Kobayashi ◽  
H. Sato ◽  
K. Miyauchi ◽  
T. Onai ◽  
K. Shii ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
High Performance ◽  
Image Resolution ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Analytical Microscopy ◽  
High Resolution Electron Microscope

Higher voltage operation has many advantages for transmission electron microscopy.These advantages include better TEM image resolution and ease of specimen imaging. For analytical microscopy, the higher voltage operation has advantages such as higher source brightness, and better spatial resolution.We reported development of a 300kV ultra high resolution electron microscope. At this time, we would like to report an analytical type 300kV electron microscope.We have incorporated a side entry specimen stage which permits ±45° specimen tilt and is convenient for characteristic x-ray detection. We have also incorporated an analytical objective polepiece which has Cs of 2. 5mm, Cc of 2. 3mm and theoretical TEM image resolution of 0.23nm.

Hrem of metal/metal multilayer materials

1986 ◽  
Vol 44 ◽  
pp. 404-405
Author(s):  
A.K. Petford-Long ◽  
C.-H Chang ◽  
M.B. Stearns ◽  
M.A. Kadin
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Structural Information ◽  
Si Substrate ◽  
Multilayered Structures ◽  
Optical Elements ◽  
X Ray ◽  
Resolution Electron ◽  
Metal Metal ◽  
High Resolution Electron Microscope

Multilayered structures (MLS) containing thin (<10nm) metallic layers of W or Mo with C or Si are undergoing development for use as x-ray reflectors and other x-ray optical elements. The two metals used are sputtered or evaporated in alternate layers onto a crystalline Si substrate (eg. [2]). The x-ray reflectance properties of these materials have been extensively studied, but until recently only indirect structural evidence has been available to allow a correlation between reflectance and structure to be made. A JEM 4000EX ultra-high resolution electron microscope has been used in this study to image the MLS and provide direct structural information.

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