Tem Study of Crystallization of a-SiC in Contact With Silver

1995 ◽  
Vol 382 ◽  
Author(s):  
Nanchang Zh ◽  
Robert Sinclair
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Silicon Carbide ◽  
Amorphous Phase ◽  
Eutectic Phase ◽  
Crystalline Compound ◽  
Transmission Electron ◽  
Nucleation Sites ◽  
Form Compound ◽  
Silver Grains

ABSTRACTMetal mediated crystallization of an amorphous phase has been found in many systems, in which eutectic phase diagrams are formed. It is interesting to know if an amorphous phase containing two elements, which can form compound, can react and form a crystalline compound at a low temperature in contact with metals. In this paper we studied the Ag/Sil−xCx system by transmission electron microscopy(TEM). It was foundthat amorphous silicon carbide was crystallized into cubic SiC at about 800°C in areas containing Ag. The silver diffused and segregated into the a-SiC phase upon annealing. The silver grains in the original deposited layer as well as those segregated act as nucleation sites for the crystallization of β-SiC. A nucleation temperature as low as 800°C was observed.

In situ silicification of an Icelandic hot spring microbial mat: implications for microfossil formation

1995 ◽  
Vol 32 (12) ◽  
pp. 2021-2026 ◽  
Author(s):  
S. Schultze-Lam ◽  
F. G. Ferris ◽  
K. O. Konhauser ◽  
R. G. Wiese
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Hot Spring ◽  
Microbial Mat ◽  
Chloroflexus Aurantiacus ◽  
X Ray ◽  
Exceptional Preservation ◽  
Transmission Electron ◽  
Nucleation Sites

Transmission electron microscopy and energy-dispersive x-ray analysis revealed that filamentous phototrophic bacteria resembling Chloroflexus aurantiacus underwent rapid silicification in an Icelandic hot spring microbial mat. The mineralization associated with the cells occurred both extracellularly, within and on the external sheaths of the bacteria, and intracellularly, within the cytoplasm. The exceptional preservation of the bacterial sheaths is due to the presence of distinct mineral nucleation sites. This results in the production of silica casts of the bacteria, which bear a striking resemblance to microbial remains in ancient microfossil assemblages.

A transmission electron microscopy investigation of inverse melting in Nb45Cr55

1997 ◽  
Vol 12 (7) ◽  
pp. 1872-1884 ◽  
Author(s):  
W. Sinkler ◽  
C. Michaelsen ◽  
R. Bormann
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Amorphous Phase ◽  
Amorphous State ◽  
Transmission Electron ◽  
Microscopy Investigation ◽  
Electron Microscopy Investigation ◽  
Medium Range ◽  
High Resolution Tem ◽  
And Calorimetry

In inverse melting, a supersaturated crystalline phase transforms polymorphously under heat treatment to the amorphous state. Inverse melting of body-centered cubic (bcc) Nb45Cr55 is studied using transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The crystalline to amorphous transformation is heterogeneous, initiating at the bcc grain boundaries. HRTEM reveals 2–3 nm domains with medium range order (MRO) in the amorphous phase. Preferred orientation of MRO domains is found on a scale corresponding to the precursor bcc grain size. Using HRTEM and calorimetry, MRO development in cosputtered Nb45Cr55 films is characterized and compared to that in the amorphous phase produced by inverse melting.

Unusual Rapidity of Electron Beam Transient Tempering

1986 ◽  
Vol 80 ◽  
Author(s):  
Anjum Tauqir ◽  
Peter R. Strutt
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
Thermal Treatment ◽  
Rapid Solidification ◽  
High Speed ◽  
Defect Cluster ◽  
High Concentration ◽  
Transmission Electron ◽  
Nucleation Sites

AbstractElectron beam rapid solidification of molybdenum-base high speed steels results in quenched-in metastable phases containing a high concentration of alloying elements. Thermal reprocessing of such material by momentary interaction with the electron beam results in decomposition of martensite at a rate ≈ 100 times faster than that occurring during conventional thermal treatment. It is postulated that this arises from a high concentration of 'defect cluster nucleation sites' during the rapid up-quenching. The product of short thermal treatment is a dispersion of 2–5 nm very fine precipitates identified using transmission electron microscopy as MC type carbides.

scholarly journals Pengaruh Variasi H2SO4 Pada Pembentukan Nanosilika Berbasis Batu Apung

2019 ◽  
Vol 7 (2) ◽  
pp. 125-132
Author(s):  
Riska Trisna Nuraini ◽  
◽  
Posman Manurung ◽  
Suprihatin Suprihatin ◽  
◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Particle Size ◽  
Amorphous Phase ◽  
X Ray ◽  
Transmission Electron ◽  
Nanosilica Particle

Nanosilica was extracted by using NaOH, H2SO4 and HCl. The amounth of NaOH and HCl are 3,0 M and 1,0 M respectively. The titration using H2SO4 was varied of 4,0 M; 4,5 M; 5,0 M; 5,5 M; 6,0 M. The pumice powder was calcined for 4 hours at 500 ºC and the nanosilica powder was calcined for 5,5 hours at 800 ºC. The results of X-Ray Flouresence (XRF) showed nanosilica with the highest purity in variation of H2SO4 5,0 M at 95,32%. The results of the X-Ray Diffractometer (XRD) showed that pumice consistent the anorthite and albite phase. The variation of H2SO4 5,0 M produced an amorphous phase. The results of Transmission Electron Microscopy (TEM) show nanosilica particle size with variations of H2SO4 5,0 M in the range 4,8-11,3 nm with an average (7,62 ± 2,15) nm.

scholarly journals Влияние термообработки на свойства композитных кремний-углеродных анодов для литий-ионных аккумуляторов

2020 ◽  
Vol 46 (3) ◽  
pp. 14
Author(s):  
Е.В. Астрова ◽  
А.В. Парфеньева ◽  
А.М. Румянцев ◽  
В.П. Улин ◽  
М.В. Байдакова ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Silicon Carbide ◽  
Diffraction Analysis ◽  
Annealing Temperature ◽  
Argon Atmosphere ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Lithium Alloys

The effect of annealing temperature in argon atmosphere on the ability of Si-C nanocomposites to reversibly insert lithium was investigated. It was found that the higher the annealing temperature during the formation of the composite, the lower is the capacitance of the electrode made from it. X-ray diffraction analysis and transmission electron microscopy reveal that the reason of the capacitance decrease is formation at T  1100°C of silicon carbide of cubic modification -SiC, inactive with respect to the formation of lithium alloys or intercalates.

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