Silicon Tetrachloride Synthesis from Rice Hulls: Transmission and Scanning Electron Microscope Study

1972 ◽  
Vol 30 ◽  
pp. 236-237 ◽  
Author(s):  
Richard S. Thomas ◽  
Prabir K. Basu ◽  
Francis T. Jones
Keyword(s):  
Silicon Tetrachloride ◽  
Silica Sand ◽  
Mineral Matter ◽  
Chemical Heterogeneity ◽  
Scanning Electron Microscope Study ◽  
Rice Hulls ◽  
Hull Structure ◽  
Lower Temperature ◽  
Image Position ◽  
Disposal Problem

Silicon tetrachloride, used in industry for the production of highest purity silicon and silica, is customarily manufactured from silica-sand and charcoal.SiCl4 can also be made from rice hulls, which contain up to 20 percent silica and only traces of other mineral matter. Hulls, after carbonization, actually prove superior as a starting material since they react at lower temperature. This use of rice hulls may offer a new, profitable solution for a rice mill byproduct disposal problem.In studies of the reaction kinetics with carbonized hulls, conversion of SiO2 to SiCl4 was found to proceed within a few minutes to a constant, limited yield which depended reproducibly on the ambient temperature of the reactor. See Fig. 1. This suggested that physical or chemical heterogeneity of the silica in the hull structure might be involved.

Excursus on the Carnot-Kelvin aspect of Thermodynamics

1937 ◽  
Vol 32 (5) ◽  
pp. 748-750
Keyword(s):  
Specific Heat ◽  
Work Function ◽  
Physical System ◽  
Thermal Capacity ◽  
General Function ◽  
Available Energy ◽  
Universal Space ◽  
Different Temperatures ◽  
Lower Temperature ◽  
Image Position

According to Carnot's postulate heat can give rise to work only by falling to lower temperature. This negation ensures that at each temperature a definite physical system possesses a work-function A, named by W. Thomson its available, energy at that temperature. This aspect of Carnot's postulate was enforced especially in Thomson and Tait's Nat. Phil. (1867). These available energies at different temperatures combine into one more general function, the isothermal available energy, which is a function of temperature θ as well as configuration. (Cf. the Minkowski condensation of personal spaces and times into a single universal space-time.) Thus we are entitled to assert the equationwhere Ψ1r is the force exerted by the coordinate ψr of configuration. The final term in δA though regular has not to do with ostensible work: and −η, as yet arbitrary, here equal to A/θ, may be described as the thermal capacity or specific heat of available energy.

scholarly journals 11.8. High collimation of electron-positron pair jets proceeding to radio jets

1998 ◽  
Vol 184 ◽  
pp. 471-472
Author(s):  
M. Kondo
Keyword(s):  
Black Hole ◽  
Radiation Pressure ◽  
Massive Black Hole ◽  
Radio Jets ◽  
Electron Positron ◽  
The Creation ◽  
Lower Temperature ◽  
The One ◽  
Image Position ◽  
Electron Positron Pair

The one of the possibilities concerning the cause of AGN jets is the super-Eddington luminocity around the Massive Black Hole. If the case of optically thick state is assumed, we can define the super-Eddington temperature in the optically thick case, from the following condition that where r∗ = 2c2r/GM. The creation of electron- positron pairs and the pahse change are expected to occur in the such temperature rage around 109K, where the radiation pressure is dominant in the lower temperature and the pair pressure be in the higher one.

The Effects of Dopants and Crystal Perfection on the Chemical Vapor Deposition of Tungsten on Silicon by Silicon Reduction of Tungsten Hexafluoride

1985 ◽  
Vol 54 ◽  
Author(s):  
M. L. Green ◽  
Y. S. Ali ◽  
B. A. Davidson ◽  
L. C. Feldman ◽  
S. Nakahara
Keyword(s):  
Thick Film ◽  
Film Growth ◽  
Chemical Vapor ◽  
Strong Temperature Dependence ◽  
Enhanced Diffusion ◽  
Tungsten Hexafluoride ◽  
Nucleation Barrier ◽  
Initial Stage ◽  
Lower Temperature ◽  
Image Position

ABSTRACTThe use of CVD W as a diffusion barrier between Al and Si is becoming widespread. The initial stage of the deposition involves the Si reduction of WF6 according to the following reaction:The reaction is thought to be self-limiting, since once a sufficiently thick W film forms, WF6 and Si are no longer able to be in contact. We have studied the effects of implanted dopant and damage on the rate of this reaction and the thickness of the self-limiting W film. To study the mechanism of W film growth, Si wafers were implanted with As, P or Sb. These wafers were either left in the as-implanted state (amorphized surface layer) or were annealed to drive-in the implant and recrystallize the Si. The reactivity with WF6 of these wafers, as well as unimplanted Si wafers, was then studied as a function of temperature between 210° C and 700° C. Si-WF6 reactivity is shown to have a strong temperature dependence, with maximum reactivity occuring at 340 °C, at which temperature a 960A thick film of W can form. Enhanced diffusion of Si through the growing W film is thought to be the mechanism responsible for thick film growth. At higher temperatures, thinner films form, due to the cessation of enhanced diffusion. Lower temperature films are also thinner, probably due to a nucleation barrier, not a kinetic barrier, to growth. Implantation lowers the temperature of the onset of enhanced reactivity between Si and WF6, when the wafers are reacted in the as-implanted state.

Manufacture of silicon tetrachloride from rice hulls

AIChE Journal ◽  
1973 ◽  
Vol 19 (3) ◽  
pp. 439-445 ◽  
Author(s):  
Prabir K. Basu ◽  
C. Judson King ◽  
Scott Lynn
Keyword(s):  
Silicon Tetrachloride ◽  
Rice Hulls

Simple Identification of Electron Diffraction Ring Patterns

1969 ◽  
Vol 27 ◽  
pp. 160-161
Author(s):  
Carolyn Nohr ◽  
Ann Ayres
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Diffraction Ring ◽  
Image Position

Texts on electron diffraction recommend that the camera constant of the electron microscope be determine d by calibration with a standard crystalline specimen, using the equation

Atomic orientation effects in proton stopping at low velocity

1983 ◽  
Vol 41 ◽  
pp. 708-709
Author(s):  
Kin Lam
Keyword(s):  
Polycrystalline Material ◽  
Charged Particles ◽  
Target Material ◽  
Stopping Power ◽  
Low Velocity ◽  
Electronic Density ◽  
Interatomic Distances ◽  
Frame Work ◽  
Image Position ◽  
Atomic Orientation

The energy of moving ions in solid is dependent on the electronic density as well as the atomic structural properties of the target material. These factors contribute to the observable effects in polycrystalline material using the scanning ion microscope. Here we outline a method to investigate the dependence of low velocity proton stopping on interatomic distances and orientations.The interaction of charged particles with atoms in the frame work of the Fermi gas model was proposed by Lindhard. For a system of atoms, the electronic Lindhard stopping power can be generalized to the formwhere the stopping power function is defined as

A Scanning Electron Microscope Study of Isolated Guard Cells

1973 ◽  
Vol 31 ◽  
pp. 454-455 ◽  
Author(s):  
P. Dayanandan ◽  
P. B. Kaufman
Keyword(s):  
Electron Microscope ◽  
Electron Microscope Study ◽  
Three Dimensional ◽  
Guard Cells ◽  
Scanning Electron Microscope Study ◽  
Psilotum Nudum ◽  
Subsidiary Cells ◽  
Welwitschia Mirabilis ◽  
Cycas Revoluta ◽  
Scanning Electron

A three dimensional appreciation of the guard cell morphology coupled with ultrastjuctural studies should lead to a better understanding of their still obscure dynamics of movement. We have found the SEM of great value not only in studies of the surface details of stomata but also in resolving the structures and relationships that exist between the guard and subsidiary cells. We now report the isolation and SEM studies of guard cells from nine genera of plants.Guard cells were isolated from the following plants: Psilotum nudum, four species of Equisetum, Cycas revoluta, Ceratozamia sp., Pinus sylvestris, Ephedra cochuma, Welwitschia mirabilis, Euphorbia tirucalli and Allium cepa.

A Magnetic Spectrometer for a Scanning Transmission Electron Microscope

1974 ◽  
Vol 32 ◽  
pp. 436-437
Author(s):  
A. Kosiara ◽  
J. W. Wiggins ◽  
M. Beer
Keyword(s):  
Scanning Transmission Electron Microscope ◽  
Magnetic Spectrometer ◽  
Fringe Field ◽  
Curvature Radius ◽  
Magnetic Pole ◽  
Quadrupole Field ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Under Construction ◽  
Image Position

A magnetic spectrometer to be attached to the Johns Hopkins S. T. E. M. is under construction. Its main purpose will be to investigate electron interactions with biological molecules in the energy range of 40 KeV to 100 KeV. The spectrometer is of the type described by Kerwin and by Crewe Its magnetic pole boundary is given by the equationwhere R is the electron curvature radius. In our case, R = 15 cm. The electron beam will be deflected by an angle of 90°. The distance between the electron source and the pole boundary will be 30 cm. A linear fringe field will be generated by a quadrupole field arrangement. This is accomplished by a grounded mirror plate and a 45° taper of the magnetic pole.

Optimizing conditions for x-ray microchemical analysis in analytical electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 548-549 ◽  
Author(s):  
N. J. Zaluzec
Keyword(s):  
Solid Angle ◽  
Analytical Electron Microscopy ◽  
Incident Beam ◽  
Thin Foil ◽  
Experimental Conditions ◽  
X Ray ◽  
Microchemical Analysis ◽  
Analytical Electron ◽  
Image Position ◽  
Incident Beam Energy

The ultimate sensitivity of microchemical analysis using x-ray emission rests in selecting those experimental conditions which will maximize the measured peak-to-background (P/B) ratio. This paper presents the results of calculations aimed at determining the influence of incident beam energy, detector/specimen geometry and specimen composition on the P/B ratio for ideally thin samples (i.e., the effects of scattering and absorption are considered negligible). As such it is assumed that the complications resulting from system peaks, bremsstrahlung fluorescence, electron tails and specimen contamination have been eliminated and that one needs only to consider the physics of the generation/emission process.The number of characteristic x-ray photons (Ip) emitted from a thin foil of thickness dt into the solid angle dΩ is given by the well-known equation

X-ray microanalysis of thin specimens in the transmission electron microscope at voltages up to 1000 Kv.

1978 ◽  
Vol 36 (1) ◽  
pp. 540-541
Author(s):  
G. Cliff ◽  
M.J. Nasir ◽  
G.W. Lorimer ◽  
N. Ridley
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Weight Fraction ◽  
Present Series ◽  
Constant Independent ◽  
X Ray ◽  
Transmission Electron ◽  
Series Of Experiments ◽  
Image Position ◽  
X Ray Absorption

In a specimen which is transmission thin to 100 kV electrons - a sample in which X-ray absorption is so insignificant that it can be neglected and where fluorescence effects can generally be ignored (1,2) - a ratio of characteristic X-ray intensities, I1/I2 can be converted into a weight fraction ratio, C1/C2, using the equationwhere k12 is, at a given voltage, a constant independent of composition or thickness, k12 values can be determined experimentally from thin standards (3) or calculated (4,6). Both experimental and calculated k12 values have been obtained for K(11<Z>19),kα(Z>19) and some Lα radiation (3,6) at 100 kV. The object of the present series of experiments was to experimentally determine k12 values at voltages between 200 and 1000 kV and to compare these with calculated values.The experiments were carried out on an AEI-EM7 HVEM fitted with an energy dispersive X-ray detector.

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