Effect of Chemistry on the Performance of Calcium Disilicide Primers

2012 ◽  
Vol 1405 ◽  
Author(s):  
Paul Anderson ◽  
Chris Csernica ◽  
Mark C. Hash ◽  
Joseph Hartvigsen ◽  
Raymond A. Cutler
Keyword(s):  
Pressure Rise ◽  
Secondary Phase ◽  
Rietveld Analysis ◽  
Surface Areas ◽  
Order Of Magnitude ◽  
Calcium Disilicide ◽  
Peak Pressures ◽  
The Military ◽  
Synthesized Materials ◽  
Line Compound

ABSTRACTRotary atomization was used to synthesize spheres of CaSi2-based compositions in order to understand issues relative to primer performance for military applications. Elemental silicon and calcium were used to synthesize the line compound CaSi2or the eutectic composition between CaSi2and Si. Fe was added to form FeSi2as a secondary phase in selected compositions. Rietveld analysis showed that CaSi2polytypes in the synthesized materials consisted primarily of 6R, with less 3R and some hexagonal material. Synthesized materials had low surface areas (≈0.1 m2/g), but short milling times increased the surface area by an order of magnitude. Peak pressures, pressure rise time, and ignition voltage showed no significant differences between experimentally prepared samples and existing commercial samples. Stoichiometric CaSi2performed as well as CaSi2-Si or CaSi2-FeSi2-Si mixtures. The military specification for calcium disilicide should be changed to reflect the broad chemistry which can be used for primer performance.

Effect of Cu-Excess on the Microstructure and Microwave Dielectric Properties of CaCu3Ti4O12 Ceramics

2015 ◽  
Vol 1087 ◽  
pp. 50-54 ◽  
Author(s):  
Mohamad Johari Abu ◽  
Julie Juliewatty Mohamed ◽  
Mohd Fadzil Ain ◽  
Zainal Arifin Ahmad
Keyword(s):  
Dielectric Constant ◽  
Microwave Dielectric Properties ◽  
Secondary Phase ◽  
Solid State Reaction Method ◽  
Lattice Parameter ◽  
Tangent Loss ◽  
Conventional Solid State Reaction ◽  
Microwave Dielectric ◽  
Order Of Magnitude ◽  
Grain Growth Behavior

CaCu(3+x)Ti4O12 (CCTO) ceramics with different Cu-excess (x = 0 – 0.6) were prepared by conventional solid-state reaction method. Characterization of the prepared ceramics with XRD and FESEM showed that lattice parameter and grain size are slightly increased, indicating Cu-excess to have the big impact on the both phase structure and microstructure. The XRD profiles indicated that the secondary phase (CuO or Cu2O) existed at edge/corner of CCTO grain, which promoted inhibited grain growth behavior. The CCTO ceramics exhibited two trends of dielectric constant related to frequency, which showed a flatter curve about ~50 in 1 – 25 GHz regions, and it’s dropped rapidly to ~35 in 25 – 50 GHz region. With Cu-excess, the dielectric constant of the ceramics was increased for an average of a quarter-order of magnitude, while the tangent loss also increased up to triple times than x = 0, for the same frequency range. Despite enormous increase of dielectric constant related to varying Cu-excess, the tangent loss also increased.

Aqueous Dissolution and Surface Alteration Studies of Nd-bearing Zirconolite in 0.001M Citric Acid at 90°C

2003 ◽  
Vol 807 ◽  
Author(s):  
Peter J. McGlinn ◽  
Terry McLeod ◽  
Gilles Leturcq ◽  
Zaynab Aly ◽  
Mark G. Blackford ◽  
...  
Keyword(s):  
Citric Acid ◽  
Secondary Phase ◽  
Citric Acid Solution ◽  
Release Rates ◽  
Water Release ◽  
Phase Development ◽  
Surface Alteration ◽  
Order Of Magnitude ◽  
Parallel Tests ◽  
Influence Of Ph

ABSTRACTNd-bearing zirconolite was leached at 90°C for 6 months in 0.001M citric acid, and also in deionised water, to determine the effect of organic-bearing solutions on durability. The pH of the citric acid solution was adjusted to 5 using KOH, approximating that of the water in the parallel tests, to avoid the influence of pH on chemical durability of the zirconolite.Releases were incongruent in the tests carried out in water. Release rates of Ti, Zr and Nd were comparatively very low (commonly too low to be measured) over the first 80 days of leaching. Rates for Ca and Al were 2 to 4 orders of magnitude higher than Ti, Zr and Nd over this same period. At about 80 days, there was an anomalous decrease in pH from 6 to 4 which enhanced release rates of Ti and Nd in particular. There was development of titania crystals, and the suggestion of hydrolysed titania, on the surface after 6 months. Thermodynamic equilibrium between the leachates and hydrolysed species on the surface of the zirconolite may be the key to apparent cessation of alteration, at least during thefirst 80 days of leaching.By contrast, zirconolite leached in 0.001M citric acid maintained release rates of Ti, Zr and Nd 2 to 4 orders of magnitude greater than those in water for the first 80 days, values sustained, within an order of magnitude, for the remainder of the leach tests. Releases were congruent. The surface of the zirconolite showed no signs of secondary phase development. This suggests complexation by citrate ions prevented control by hydrolysed species on zirconolite solubility.

scholarly journals Metals uptake behaviour in Miscanthus x giganteus plant during growth at the contaminated soil from the military site in Sliač, Slovakia

2018 ◽  
Vol 20 (2) ◽  
pp. 1-7 ◽  
Author(s):  
Valentina V. Pidlisnyuk ◽  
Larry E. Erickson ◽  
Josef Trögl ◽  
Pavlo Y. Shapoval ◽  
Jan Popelka ◽  
...  
Keyword(s):  
Plant Growth ◽  
Bioconcentration Factor ◽  
Plant Roots ◽  
Miscanthus X Giganteus ◽  
Biofuel Crop ◽  
Accumulation Of Metals ◽  
Order Of Magnitude ◽  
Stems And Leaves ◽  
Metals Accumulation ◽  
The Military

Abstract Peculiarities of metals uptake by the biofuel crop Miscanthus x giganteus were explored during plant growth at soil from the military site (Sliač, Slovakia). The experiment was carried out in greenhouse during two vegetation seasons. Research soil was predominantly elevated in Fe and Ti, while other metals (As, Cu, Mn, Sr, Zn and Zr) were presented at order of magnitude lower concentrations. No inhibition of plant growth was observed. The calculated Bioconcentration Factor showed that levels of metals’ accumulation by plant roots, stems and leaves were independent of metals’ concentrations in the soil. The accumulation of metals by stems and leaves was much lower than by roots. As, Zr, Ti were almost not accumulated by stems and leaves during both seasons; accumulation of Cu, Fe, Mn, Zn and Sr was not essential which confirmed that biomass of M. x giganteus might be processed for the energy purpose.

scholarly journals Nanocracks upon Fracture of Oligoclase

2021 ◽  
Vol 57 (6) ◽  
pp. 894-899
Author(s):  
V. I. Vettegren ◽  
A. V. Ponomarev ◽  
R. I. Mamalimov ◽  
I. P. Shcherbakov
Keyword(s):  
Free Radicals ◽  
Power Law ◽  
Time Interval ◽  
Electron Traps ◽  
Surface Areas ◽  
Electronically Excited ◽  
Order Of Magnitude ◽  
20 Nm

Abstract—The spectrum of fractoluminescence (FL) upon fracture of the surface of oligoclase is obtained. The analysis of the spectrum has shown that fracture of crystals leads to the formation of electronically excited free radicals ≡Si−O• and Fe3• ions as well as electron traps. FL consisted of a set of the signals with the intensities varying by an order of magnitude. The duration of the signals was ~50 ns and the time interval between them varied from ~0.1 to 1 μs. Each signal contained four maxima associated with the destruction of barriers preventing the motion of dislocations along the sliding planes. These breakthroughs cause the formation of the smallest (“primary”) cracks. All other, larger cracks are formed by the coalescence of the “primary” cracks. The sizes of “primary” cracks range from ~10 to 20 nm and the time of their formation is 16 ns. The distribution of cracks by size (surface areas of crack walls) is power law with the exponent –1.9.

scholarly journals Sea spray aerosol as a unique source of ice nucleating particles

2015 ◽  
Vol 113 (21) ◽  
pp. 5797-5803 ◽  
Author(s):  
Paul J. DeMott ◽  
Thomas C. J. Hill ◽  
Christina S. McCluskey ◽  
Kimberly A. Prather ◽  
Douglas B. Collins ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Radiative Forcing ◽  
Marine Boundary Layer ◽  
Strong Increase ◽  
Sea Spray ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Surface Areas ◽  
Order Of Magnitude ◽  
Sea Spray Aerosol

Ice nucleating particles (INPs) are vital for ice initiation in, and precipitation from, mixed-phase clouds. A source of INPs from oceans within sea spray aerosol (SSA) emissions has been suggested in previous studies but remained unconfirmed. Here, we show that INPs are emitted using real wave breaking in a laboratory flume to produce SSA. The number concentrations of INPs from laboratory-generated SSA, when normalized to typical total aerosol number concentrations in the marine boundary layer, agree well with measurements from diverse regions over the oceans. Data in the present study are also in accord with previously published INP measurements made over remote ocean regions. INP number concentrations active within liquid water droplets increase exponentially in number with a decrease in temperature below 0 °C, averaging an order of magnitude increase per 5 °C interval. The plausibility of a strong increase in SSA INP emissions in association with phytoplankton blooms is also shown in laboratory simulations. Nevertheless, INP number concentrations, or active site densities approximated using “dry” geometric SSA surface areas, are a few orders of magnitude lower than corresponding concentrations or site densities in the surface boundary layer over continental regions. These findings have important implications for cloud radiative forcing and precipitation within low-level and midlevel marine clouds unaffected by continental INP sources, such as may occur over the Southern Ocean.

scholarly journals Buoyancy-driven lacustrine calving, Glaciar Nef, Chilean Patagonia

2001 ◽  
Vol 47 (156) ◽  
pp. 135-146 ◽  
Author(s):  
Charles Warren ◽  
Doug Benn ◽  
Vanessa Winchester ◽  
Stephan Harrison
Keyword(s):  
Tidewater Glaciers ◽  
Glacier Tongue ◽  
Surface Areas ◽  
Chilean Patagonia ◽  
Flow Speeds ◽  
Order Of Magnitude ◽  
Calving Rate ◽  
Data Yield ◽  
Ubiquitous Presence ◽  
Term Data

AbstractGlaciar Nef, a 164 km2 eastern outlet of Hielo Patagónico Norte (the northern Patagonia icefield), terminates in a proglacial lake that has formed in conjunction with 20th-century glacier retreat. The terminus is inferred to be transiently afloat. A hinge-calving mechanism is proposed in which buoyant forces impose a torque on the glacier tongue, resulting in the release of coherent sections of the glacier tongue as “tabular” icebergs. A simple model shows how torque and tensile stress reach a maximum at the up-glacier limit of the buoyant zone, and that glacier thinning causes this point to migrate up-glacier. Empirical evidence supporting this model includes elevated thermo-erosional notches ≤6.5 m above lake level, and the ubiquitous presence since 1975 of “tabular” icebergs with surface areas ≤0.3 km2. Flow speeds of 1.2–1.3 m d−1 were measured near the terminus in February 1998. Extrapolations from these short-term data yield a calving rate of 785–835 m a−1 and a calving flux of 232 × 106 m3 a−1 or 0.2 km3 a−1. The calculated mean water depth at the terminus is 190 m. This calving rate is higher than at grounded temperate glaciers calving in fresh water, but is nevertheless almost an order of magnitude less than calving rates at both grounded and floating tidewater glaciers.

A COMPARISON OF THE X-RAY DIFFRACTION AND NITROGEN ADSORPTION SURFACE AREAS OF CARBON BLACKS AND CHARCOALS

1948 ◽  
Vol 26a (4) ◽  
pp. 236-242 ◽  
Author(s):  
J. C. Arnell ◽  
W. M. Barss
Keyword(s):  
Carbonaceous Material ◽  
Nitrogen Adsorption ◽  
Activation Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Carbon Blacks ◽  
Surface Areas ◽  
Crystallite Surface ◽  
Adsorption Surface ◽  
Order Of Magnitude

The surface areas, as determined from X-ray diffraction and low temperature nitrogen adsorption data, were compared for a number of carbon blacks and activated charcoals. Comparative data were also obtained on samples of charcoal at various stages of activation and after calcination. The X-ray diffraction data indicated that all the samples examined were composed of small graphitelike crystallites of the same order of magnitude, which had specific surfaces of about 2500 to 3000 sq. m. per cc. The nitrogen adsorption surface of a highly activated charcoal was found to be about equal to the X-ray surface. It is suggested that the crystallite surface represents the potential adsorption surface of a carbonaceous material and, providing that crystal growth does not occur during activation, the activation process makes these surfaces available to external adsorbate.

scholarly journals REMOVAL OF NORFLOXACIN BY TiO2-SBA-15 PHOTOCATALYST

2020 ◽  
Vol 58 (3A) ◽  
pp. 13
Author(s):  
Nguyễn Thị Thu Trang ◽  
Trần Quang Vinh ◽  
Nguyễn Thành Đồng ◽  
Phạm Tuấn Linh ◽  
Nguyễn Viết Hoàng ◽  
...  
Keyword(s):  
Uv Light ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Surface Areas ◽  
Pluronic P123 ◽  
Adsorption Capacities ◽  
Transmission Electron ◽  
Photocatalytic Activities ◽  
Adsorption Desorption ◽  
Synthesized Materials

Ordered SBA-15 mesoporous silica support was synthesized by a sol-gel method using triblock copolymer Pluronic P123 and immobilized with different amounts of photocatalyst TiO2. The synthesized composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N2 adsorption-desorption isotherms. The synthesized materials possessed specific surface areas SBET of 768 m2/g, 544 m2/g, 421 m2/g and 333 m2/g at the TiO2:SiO2 ratio of 0, 0.25, 1.0 and 5.0, respectively. The adsorption capacities and photocatalytic activities under UV light irradiation of these materials were evaluated for Norfloxacin degradation. Experimental results indicate that the highest activity was observed on the sample with TiO2:SiO2 ratio of 1.

Initial Pressure Influence on Explosion Pressures of Methane-Air Deflagrations in Linked Vessels

2014 ◽  
Vol 936 ◽  
pp. 2130-2134
Author(s):  
Yi Hu Cui ◽  
Jun Cheng Jiang ◽  
Yuan Yu ◽  
Qing Wu Zhang
Keyword(s):  
Experimental Study ◽  
Linear Relationship ◽  
Peak Pressure ◽  
Pressure Rise ◽  
Initial Pressure ◽  
Pressure Variation ◽  
Peak Pressures ◽  
Vented Explosion ◽  
Pressure Evolution

An experimental study on pressure evolution during closed explosion and venting progress of methane–air mixtures ([CH4=10%]) in linked vessels was performed, for systems at various initial pressures (P0=0-0.08MPa). The effects of initial pressure on regularity of pressure variation in vessels were discussed. For the closed explosion in isolated vessel, the higher level of the initial pressure in isolated big vessel is, the larger the peak pressure and rate of pressure rise is, and the peak pressure increases nonlinearly with initial pressure; For closed explosion in linked vessels, the higher initial pressure within the linked vessels system leads to the higher peak pressures in two vessels and there is an approximate linear relationship between them, which is similar to explosion in isolated vessel. For vented explosion in linked vessels at higher initial pressure, venting has poorer effect on protection of the linked vessels.

Rotational Temperature in Helium, Argon, and Oxygen Microwave-Induced Plasmas: Comparison with Translational and Solid Surface Temperatures

1989 ◽  
Vol 43 (4) ◽  
pp. 681-687 ◽  
Author(s):  
J. Alandari ◽  
A. M. Diamy ◽  
J. M. Guillerme ◽  
J. C. Legrand ◽  
R. I. Ben-Aim
Keyword(s):  
Solid Surface ◽  
Rotational Temperature ◽  
Pressure Rise ◽  
Direct Determination ◽  
Power Input ◽  
Line Broadening ◽  
Experimental Conditions ◽  
Flow Rates ◽  
Order Of Magnitude

Translational temperature ( Tg), rotational temperature of OH ( Tr), and surface temperature ( Ts are determined in helium, argon, and oxygen plasmas. Measurements are carried out at different pressures and different flow rates as a function of microwave power input by using various methods (line broadening, pressure rise, spectroscopy, thermocouple, pyrometry). The three temperatures depend on the nature of the gas (oxygen < helium > argon) and increase with power input and pressure. Results show that Tg is of the same order of magnitude as Ts. But in all experimental conditions, Tr is always higher than Tg. Therefore, Tr is inadequate for estimating Tg. When no direct determination of Tg is available, Ts seems to give a better estimation of this important parameter.

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