Fluorine Doping of Pyrogenic Silica

1986 ◽  
Vol 88 ◽  
Author(s):  
T. J. Miller ◽  
D. A. Nicol ◽  
K. D. Pohl ◽  
H. R. Clark
Keyword(s):  
Low Temperature ◽  
Elevated Temperatures ◽  
Fluorine Doping ◽  
Soot Deposition ◽  
Atomic Fluorine ◽  
Pyrogenic Silica ◽  
Doped Glass ◽  
Deposition Step ◽  
Low Temperature Process

ABSTRACTThe incorporation of atomic fluorine into flame synthesized silica boules has been investigated. Soot boules were doped with fluorine using three different methods: (A) in a low temperature process, using XeF2 as the fluorinating agent prior to consolidation, (B) utilizing SiF4 or SF6 in the reagent gas mix during the combustion synthesis and soot deposition step and (C) in situ treatment with SF6 during the dehydration/ consolidation step at elevated temperatures. All three methods produced uniformly down-doped glass after consolidation, although the maximum fluorine incorporation and level of down-doping for each method followed A <B <C. Fluorine incorporation mechanisms are proposed for each method.

A Low Temperature CVD Process for TiN Coatings

1989 ◽  
Vol 168 ◽  
Author(s):  
A. Aguero ◽  
D. Little ◽  
P. Lowden
Keyword(s):  
Wear Resistance ◽  
Low Temperature ◽  
Titanium Nitride ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
Reduced Pressure ◽  
Tin Coatings ◽  
Excellent Adhesion ◽  
Low Temperature Process

AbstractA novel low temperature process for the chemical vapour deposition of titanium nitride films has been developed. Titanium sub-halides generated “in situ” by chlorination of titanium pellets are subsequently reacted with ammonia at reduced pressure and temperatures of 450–600° C. The coatings have excellent adhesion and wear resistance. A description of the process and the properties of the coatings produced by it will be presented.

Study on Low-Temperature Oxidation Process of Low Rank Coal by In Situ FTIR

2013 ◽  
Vol 652-654 ◽  
pp. 871-876 ◽  
Author(s):  
Xiao Xing Zhong ◽  
Guo Lan Dou ◽  
Hai Hui Xin ◽  
De Ming Wang
Keyword(s):  
Low Temperature ◽  
Functional Groups ◽  
Oxidation Process ◽  
Low Rank ◽  
In Situ Ftir ◽  
Low Rank Coal ◽  
Low Temperature Oxidation ◽  
Temperature Oxidation ◽  
Low Temperature Process

Low temperature oxidation of two different low rank coals was measured by in-situ FTIR. Curve-fitting analysis was employed to identify functional groups types of raw coals, and series technology was carried out on in-situ infrared spectrum of sample coals at low-temperature oxidation process to analyze the changes of main active functional groups with temperature. The results indicate that -CH3, -CH2, -OH, C=O, COOH are the main active functional groups in low rank coal. In the oxidation process, with temperature increasing, the methyl and methylene show the tendency of increase after decrease and then decrease, and all of hydroxyl, carboxyl and carbonyl group present the tendency of increase after decrease, there exists some differences among the main functional groups in the coal low-temperature process.

Properties of Hot-Pressed Cr-Cr3Si

1994 ◽  
Vol 364 ◽  
Author(s):  
Joseph W. Newkirk ◽  
Joseph E. Price
Keyword(s):  
Mechanical Properties ◽  
Powder Metallurgy ◽  
Low Temperature ◽  
High Temperatures ◽  
Hot Pressing ◽  
Elevated Temperatures ◽  
Arc Melting ◽  
Cast Alloys ◽  
Strength And Toughness

AbstractPreviously, Cr-Cr3Si in-situ composites produced by arc-melting were shown to have good strengths at high temperatures1. For example, samples of a 25% Cr and 75% Cr3Si composite achieved bend strengths of 135 MPa at 1200°C. However, there is potential for even higher strengths at high temperatures and a need for improvement in the low temperature strength and toughness. In order to improve the properties, two approaches were taken. The first used powder metallurgy to develop a better microstructure than in the cast alloys, to try to improve both strength and toughness. The second approach was to incorporate erbia into the composites, to improve the strength and stability of the microstructure at elevated temperatures.High density samples of hot pressed Cr-15.5Si and Cr-18.6Si have been produced by mixing Cr and Gr3Si powders and hot pressing in a graphite die. Erbia powders have been incorporated into some compacts for comparison.Micros true tures have been characterized and mechanical properties determined. Both the hot pressing and the erbia affected the properties. In addition the erbia had a significant effect on consolidation of the samples.

One-pot low-temperature synthesis of a MnFe2O4–graphene composite for lithium ion battery applications

RSC Advances ◽  
2014 ◽  
Vol 4 (54) ◽  
pp. 28421-28425 ◽  
Author(s):  
Huang Tang ◽  
Peibo Gao ◽  
An Xing ◽  
Shuang Tian ◽  
Zhihao Bao
Keyword(s):  
Graphene Oxide ◽  
Low Temperature ◽  
Lithium Ion ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
One Pot ◽  
Graphene Composite ◽  
Reduced Graphene ◽  
Low Temperature Process

A MnFe2O4–reduced graphene oxide (rGO) nanocomposite was successfully synthesized by a one-pot low-temperature process by coprecipitation of Mn ions produced in the modified Hummer's method and in situ reduction of GO at 90 °C.

Dislocation Analysis of 4H-SiC Using KOH Low Temperature Etching

2014 ◽  
Vol 778-780 ◽  
pp. 358-361 ◽  
Author(s):  
Takahiro Sato ◽  
Yuya Suzuki ◽  
Hiroyuki Ito ◽  
Toshiyuki Isshiki ◽  
Munetoshi Fukui
Keyword(s):  
Electron Microscope ◽  
Low Temperature ◽  
Elevated Temperatures ◽  
Sampling Technique ◽  
Scanning Transmission Electron Microscope ◽  
Etch Pits ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Koh Etching

The conventional KOH etching method at elevated temperatures is an easy way to study SiC dislocations, but presents problems due to an increased etch rate. Here, we examine the application of low temperature KOH treatment for the analysis of dislocation cores and etch pits in SiC. A low energy scanning electron microscope (SEM) is effective to classify dislocation kinds. The scanning transmission electron microscope (STEM) observation of thick samples prepared by the in situ micro-sampling technique enables evaluation of detailed dislocation properties.

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

Role of boundaries in the crystallization of amorphous films

1988 ◽  
Vol 46 ◽  
pp. 626-627
Author(s):  
D. A. Smith
Keyword(s):  
Low Temperature ◽  
Amorphous State ◽  
Nucleation And Growth ◽  
Amorphous Films ◽  
Island Nucleation ◽  
Surface Steps ◽  
Transmission Electron ◽  
Component Systems ◽  
Temperature Deposition

The nucleation and growth processes which lead to the formation of a thin film are particularly amenable to investigation by transmission electron microscopy either in situ or subsequent to deposition. In situ studies have enabled the observation of island nucleation and growth, together with addition of atoms to surface steps. This paper is concerned with post-deposition crystallization of amorphous alloys. It will be argued that the processes occurring during low temperature deposition of one component systems are related but the evidence is mainly indirect. Amorphous films result when the deposition conditions such as low temperature or the presence of impurities (intentional or unintentional) preclude the atomic mobility necessary for crystallization. Representative examples of this behavior are CVD silicon grown below about 670°C, metalloids, such as antimony deposited at room temperature, binary alloys or compounds such as Cu-Ag or Cr O2, respectively. Elemental metals are not stable in the amorphous state.

The use of transmission and analytical electron microscopy in studying reactions and phase transformations in thin film

1993 ◽  
Vol 51 ◽  
pp. 842-843
Author(s):  
K. Barmak
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Phase Transformations ◽  
Analytical Electron Microscopy ◽  
Ex Situ ◽  
Multilayer Thin Films ◽  
Absolute Concentration ◽  
Analytical Electron ◽  
Deposition Step

Generally, processing of thin films involves several annealing steps in addition to the deposition step. During the annealing steps, diffusion, transformations and reactions take place. In this paper, examples of the use of TEM and AEM for ex situ and in situ studies of reactions and phase transformations in thin films will be presented.The ex situ studies were carried out on Nb/Al multilayer thin films annealed to different stages of reaction. Figure 1 shows a multilayer with dNb = 383 and dAl = 117 nm annealed at 750°C for 4 hours. As can be seen in the micrograph, there are four phases, Nb/Nb3-xAl/Nb2-xAl/NbAl3, present in the film at this stage of the reaction. The composition of each of the four regions marked 1-4 was obtained by EDX analysis. The absolute concentration in each region could not be determined due to the lack of thickness and geometry parameters that were required to make the necessary absorption and fluorescence corrections.

Electron and ion irradiation-induced dissolution of mechanical twins in the intermetalic U3Si: An in situ HVEM study

1989 ◽  
Vol 47 ◽  
pp. 652-653
Author(s):  
Charles W. Allen ◽  
Robert C. Birtcher
Keyword(s):  
Elevated Temperatures ◽  
Ion Irradiation ◽  
Ion Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Heavy Ion ◽  
High Energy ◽  
Mechanical Twinning ◽  
In Situ Experiments

The uranium silicides, including U3Si, are under study as candidate low enrichment nuclear fuels. Ion beam simulations of the in-reactor behavior of such materials are performed because a similar damage structure can be produced in hours by energetic heavy ions which requires years in actual reactor tests. This contribution treats one aspect of the microstructural behavior of U3Si under high energy electron irradiation and low dose energetic heavy ion irradiation and is based on in situ experiments, performed at the HVEM-Tandem User Facility at Argonne National Laboratory. This Facility interfaces a 2 MV Tandem ion accelerator and a 0.6 MV ion implanter to a 1.2 MeV AEI high voltage electron microscope, which allows a wide variety of in situ ion beam experiments to be performed with simultaneous irradiation and electron microscopy or diffraction.At elevated temperatures, U3Si exhibits the ordered AuCu3 structure. On cooling below 1058 K, the intermetallic transforms, evidently martensitically, to a body-centered tetragonal structure (alternatively, the structure may be described as face-centered tetragonal, which would be fcc except for a 1 pet tetragonal distortion). Mechanical twinning accompanies the transformation; however, diferences between electron diffraction patterns from twinned and non-twinned martensite plates could not be distinguished.

The threshold energy for atom displacement in fcc metals

1990 ◽  
Vol 48 (4) ◽  
pp. 530-531
Author(s):  
Wilfried Sigle ◽  
Matthias Hohenstein ◽  
Alfred Seeger
Keyword(s):  
Growth Rate ◽  
Elevated Temperatures ◽  
Threshold Energy ◽  
Dislocation Loops ◽  
Absolute Minimum ◽  
Voltage Electron ◽  
Atom Displacement ◽  
Electron Microscopes ◽  
Fcc Metal

Prolonged electron irradiation of metals at elevated temperatures usually leads to the formation of large interstitial-type dislocation loops. The growth rate of the loops is proportional to the total cross-section for atom displacement,which is implicitly connected with the threshold energy for atom displacement, Ed . Thus, by measuring the growth rate as a function of the electron energy and the orientation of the specimen with respect to the electron beam, the anisotropy of Ed can be determined rather precisely. We have performed such experiments in situ in high-voltage electron microscopes on Ag and Au at 473K as a function of the orientation and on Au as a function of temperature at several fixed orientations.Whereas in Ag minima of Ed are found close to <100>,<110>, and <210> (13-18eV), (Fig.1) atom displacement in Au requires least energy along <100>(15-19eV) (Fig.2). Au is thus the first fcc metal in which the absolute minimum of the threshold energy has been established not to lie in or close to the <110> direction.

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