Crystal Growth of Energetic Materials During High Acceleration

1995 ◽  
Vol 418 ◽  
Author(s):  
M. Y. D. Lanzerotti ◽  
J. Autera ◽  
L. Borne ◽  
J. Sharma
Keyword(s):  
Crystal Growth ◽  
Pressure Gradient ◽  
Temperature Variation ◽  
Energetic Materials ◽  
Outer Edge ◽  
Crystal Defects ◽  
Saturated Solution ◽  
High Acceleration ◽  
Simultaneous Movement ◽  
Solvent Molecules

AbstractStudies of the growth of crystals of energetic materials under conditions of high acceleration in an ultracentrifuge are reported. When a saturated solution is accelerated in an ultracentrifuge, the solute molecules move individually through the solvent molecules to form a crystal at the outer edge of the tube if the solute is more dense than the solvent. Since there is no evaporation or temperature variation, convection currents caused by simultaneous movement of solvent and solute are minimized and crystal defects are potentially minimized. Crystal growth is controlled by the g-level of the acceleration. In addition, solution inclusions and bubbles migrate out of the saturated solution as a result of the pressure gradient induced by the g-force. We present results of TNT, RDX, and TNAZ grown at high g from various solutions.

Density of RDX Crystals Grown During High Acceleration in an Ultracentrifuge

2005 ◽  
Vol 896 ◽  
Author(s):  
Mary Y. D. Lanzerotti ◽  
Richard Z. Squillace ◽  
Alexander Gandzelko ◽  
Jagadish Sharma
Keyword(s):  
Crystal Growth ◽  
Maximum Density ◽  
Crystal Defects ◽  
Commercial Grade ◽  
Theoretical Maximum ◽  
High Acceleration ◽  
Cyclotrimethylene Trinitramine ◽  
Crystal Density ◽  
Defect Content ◽  
Solvent Molecules

AbstractRDX (cyclotrimethylene-trinitramine) crystals were grown during high acceleration (high g) in an ultracentrifuge. These crystals are found to have a density ∼0.6% greater than 1 g crystals and to have a greatly reduced defect content. The high g crystals should therefore have significantly reduced shock sensitivity as compared to commercial grade RDX. When a RDX saturated acetone solution is accelerated at 200,000 g, the RDX solute molecules move individually through the acetone solvent molecules to form a RDX crystal because the density of the RDX (Theoretical Maximum Density 1.806 g/cc) solute is more dense than the acetone (0.79 g/cc)solvent. Crystal growth is controlled by the g-force. Crystal defects including voids and solution inclusions caused by temperature variation or evaporation at 1 g are minimized and the RDX crystal density increases. A nitrogen pycnometer was used to measure the density of the RDX crystals grown at 1 g and at 200,000 g. The density of the RDX crystals grown at 200,000 g (1.7980±0.0003 g/cc) is found to be greater than the density of RDX crystals grown at 1 g (1.7881±0.0003 g/cc) by 0.0099 g/cc. The density of the high g crystal is 99.6% of the Theoretical Maximum Density of RDX.

Crystal Growth of Energetic Materials during High Acceleration using an Ultracentrifuge

1994 ◽  
pp. 181-184
Author(s):  
M. Y. D. Lanzerotti ◽  
J. Autera ◽  
J. Pinto ◽  
J. Sharma
Keyword(s):  
Crystal Growth ◽  
Energetic Materials ◽  
High Acceleration

Mechanical Behavior of Energetic Materials During High Acceleration in An Ultracentrifuge

1994 ◽  
Vol 362 ◽  
Author(s):  
M. Yvonne D. Lanzerotti ◽  
J. Sharma
Keyword(s):  
Mechanical Behavior ◽  
Surface Area ◽  
Energetic Materials ◽  
Area Ratio ◽  
Crystal Defects ◽  
Surface Area Ratio ◽  
High Acceleration ◽  
New Information ◽  
Binding Surface ◽  
Effective Additive

AbstractThe mechanical behavior of explosives subjected to high acceleration (high g) has been studied in an ultracentrifuge. The experiments reported here reveal new information on the mechanical behavior of such materials and the influence of grain size on the fracture process. Through measurement and analysis of fracture surfaces, we have found that predominately intergranular failure occurs when the shear or tensile strength of the explosive is exceeded. We have found that the mechanical strength of melt-cast polycrystalline TNT varies inversely with crystal size. That is, if the sample consists of large, homogeneous crystals, these are found to separate from the sample at lower g-levels due to the larger mass-to-binding surface area ratio of the crystals. Conversely, smaller original crystallites are found to separate at higher g-levets due to the smaller mass-to-binding surface area ratio. Our results show that single crystals of TNT fracture under a higher g-level at crystal defects. We have also found that the fracture acceleration of Octol decreases with increasing percent TNT and decreasing percent HMX. Hexanitrostilbene (HNS) has been shown by other investigators to be an effective additive to prevent growth of large TNT grains. We have found that the fracture acceleration increases when HNS is added to Octol.

Crystal Growth of Energetic Materials during High Acceleration

1997 ◽  
pp. 213-219
Author(s):  
M. Y. D. Lanzerotti ◽  
J. Autera ◽  
L. Borne ◽  
J. Sharma
Keyword(s):  
Crystal Growth ◽  
Energetic Materials ◽  
High Acceleration

Crystal growth of energetic materials during high acceleration using an ultracentrifuge

1994 ◽  
Author(s):  
M. Y. D. Lanzerotti ◽  
J. Autera ◽  
J. Pinto ◽  
J. Sharma
Keyword(s):  
Crystal Growth ◽  
Energetic Materials ◽  
High Acceleration

Optical characterization of silicon carbide polytypes

1996 ◽  
Vol 74 (S1) ◽  
pp. 225-232
Author(s):  
J. W. Bowron ◽  
S. Damaskinos ◽  
A. E. Dixon
Keyword(s):  
Collection Efficiency ◽  
Outer Edge ◽  
Crystal Defects ◽  
Grain Structure ◽  
Impurity Level ◽  
Deep Impurity ◽  
Spatially Resolved ◽  
Reflected Light ◽  
Grain Orientations ◽  
Spectrally Resolved

A modified experimental scanning laser photoluminescence microscope was used to perform spatially and spectrally resolved measurements on a SiC sample. A scanning grating monochromator integrated into the detection arm of the microscope yielded a high photon collection efficiency at the detector. A cold-finger stage mounted directly onto the X-Y translation stages of the microscope allowed low-temperature PL measurements to be made. One object of the experiment was to test the hypothesis that spectrally and spatially resolved PL could be used to identify different polytypes associated with the grain structure observed in reflected light. Four different regions of the SiC sample were identified and three of these were correlated with low spatial resolution X-ray measurements and found to be polytypes 4H, 6H, and 33R–(α)SiC. Room-temperature photoluminescence was used to map the distribution of a deep impurity level and to map crystal defects. Reflected-light measurements were used to map different grain orientations of SiC. The sample was observed to be polycrystalline with most of the grains at the outer edge of the sample.

Diffusion Cells for Integrating Temperature and Humidity Over Long Periods of Time

1988 ◽  
Vol 125 ◽  
Author(s):  
Fred Trembour ◽  
Franklin L. Smith ◽  
Irving Friedman
Keyword(s):  
Vapor Pressure ◽  
Pressure Gradient ◽  
Pure Water ◽  
Volcanic Glass ◽  
Saturated Solution ◽  
Rubber Stopper ◽  
Centrifuge Tube ◽  
Final Design ◽  
One Year ◽  
Vapor Pressure Gradient

ABSTRACTThe rate of many processes, including the diffusion of water into rhyolitic volcanic glass (obsidian), as well as the racemization of amino acids is temperature dependent, and a knowledge of temperatures integrated over time periods of at least a year is necessary to quantify these processes. The construction and properties of simple devices consisting of small plastic containers that change weight at a rate that is a function of temperature and the activity of water will be described. The cells function because water diffuses through the plastic across a constant vapor-pressure gradient. This vapor-pressure gradient is maintained constant between the substances within the cell and the materials outside the cell. The plastic cells are usually filled with water and surrounded by a dehydrating agent, such as silica gel. A better arrangement is to fill the cell with a mixture of solid sodium chloride (NaCl) and a saturated solution of NaCl, and to surround the cell with pure water. A number of plastics have been investigated, including polycarbonate, polystyrene, tefzel, polyallomer, and methacrylate. The cells have been sealed by various methods including screw caps, room-temperature vulcanizing silicone rubber sealant, and rubber stoppers. The final design consists of a small cell made of a polycarbonate plastic centrifuge tube containing solid NaCl plus NaCl-saturated solution sealed with a rubber stopper and placed in a polypropylene tube containing pure water. Our aim has been to develop cells that are sufficiently sensitive to yield a precision of ±0.2°C when exposed for one year at temperatures that range from 0° to 40°, and that will fit into metal fittings that can be screwed into standard 3/4-inch plastic water pipe (approximately 1 inch outside diameter).

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