Oxidative Catalytic Decomposition of Toxic Gases Using Hydroxyapatite and Fluorhydroxyapatite

1994 ◽  
Vol 368 ◽  
Author(s):  
Timothy P. Palucka ◽  
Nicholas G. Eror ◽  
Thomas A. Mcnamara
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Catalytic Decomposition ◽  
Reaction Products ◽  
Fluorine Substitution ◽  
Dimethyl Methylphosphonate ◽  
Surface Areas ◽  
Percent Nitrogen ◽  
Protection Period

ABSTRACTAn oxidative catalytic route for the decomposition of nerve gases was investigated using hydroxyapatite (HA, chemical composition Ca10(PO4)6(OH)2) and its partially fluorinated analog fluorhydroxyapatite (FHA, Ca10(PO4)6Fx(OH)2−x). Samples were prepared with surface areas ranging from 34 to 238 m2/g to study surface area effects; 1.2 wt. % platinum was deposited on one substrate to investigate the effect of a transition metal on activity and selectivity. Reaction studies were performed using dimethyl methylphosphonate (DMMP), a nerve gas simulant, in a stream of 80 percent nitrogen and 20 percent oxygen at 573 K and atmospheric pressure. High surface area FHA samples showed an increase in the "protection period" (period of 100% conversion) with increasing fluorine substitution; such an increase was not seen for low surface area FHA samples. In the absence of platinum, the reaction products were methanol and dimethyl ether; with platinum, CO2 was also obtained.

Preparation of CuCrO2 Powders with High Surface Areas

2014 ◽  
Vol 617 ◽  
pp. 187-190 ◽  
Author(s):  
Te Wei Chiu ◽  
Yi Wei Feng
Keyword(s):  
Nitric Acid ◽  
Surface Area ◽  
Chemical Treatment ◽  
High Surface ◽  
High Surface Area ◽  
Phase Evolution ◽  
Surface Areas ◽  
Pure Phase ◽  
Cu Ions

In this study, the effects of glycine-nitrate ratios and postcombustion chemical treatment on the phase evolution and surface area of CuCrO2powders were investigated. The pure phase of CuCrO2powders was obtained at a glycine-nitrate ratio of 1.2–1.4. When the glycine-nitrate ratio was higher than 1.9, the Cu ions were reduced to Cu(0) and the phase of Cu metal and Cr2O3were observed. However, when the glycine-nitrate ratio was lower than 1.1, the Cu ions were partially maintained as Cu(2+), and a bluish residue was observed. As-combusted CuCrO2powder with a high surface area (50 m2/g) was obtained at a glycine-nitrate ratio of 1.2. Furthermore, a high surface area (> 60 m2/g) was obtained by leaching as-combusted CuCrO2powder with diluted nitric acid.

Pyrolysis of Organosilicon Gels to Silicon Carbide

1986 ◽  
Vol 73 ◽  
Author(s):  
Joseph R. Fox ◽  
Douglas A. White ◽  
Susan M. Oleff ◽  
Robert D. Boyer ◽  
Phyllis A. Budinger
Keyword(s):  
Silicon Carbide ◽  
Surface Area ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Carbon Chain ◽  
Carbon Chain Length ◽  
Pyrolysis Products ◽  
Surface Areas ◽  
Physical Measurements

AbstractSol-gel precursors to silicon carbide have been prepared using trifunctional chloro and alkoxysilanes which contain both the silicon and carbon necessary for SiC formation. Crosslinked gels having the ideal formula [RSiO1 5].]n have been synthesized by a hydrolysis/condensation scheme for a series of saturated and unsaturated R groups. The starting gels have been characterized by a variety of elemental analysis, spectroscopic and physical measurements including IR. XRD. TGA.. surface area and pore volume. A particularly powerful method for characterizing these gels is the combination of 13C and 29 Si solid state NMR which can provide information about the degree of crosslinking as well as residual hydroxy/alkoxy content.The controlled pyrolysis of these gels has been used to prepare silicon carbide-containing ceramic products with surface areas in excess of 600m2/gm. The pyrolysis products are best described as a partially crystalline, partially amorphous mixture of β-SiC, silica and carbon. The effect of carbon chain length and the degree of unsaturation in the R group on the composition and surface area of the product has been determined. The origin of the high surface area of the pyrolysis products has been identified and its implications on potential uses of these materials is discussed.

Nitrogen and Water Sorption Properties of Ethyl-Substituted Silica Aerogels and Xerogels

1994 ◽  
Vol 371 ◽  
Author(s):  
Chunling Liu ◽  
Sridhar Komarneni
Keyword(s):  
Pore Structure ◽  
Surface Area ◽  
Water Sorption ◽  
Ph Value ◽  
High Surface ◽  
High Surface Area ◽  
Silica Aerogels ◽  
Modified Silica ◽  
Surface Areas ◽  
Water Sorption Properties

AbstractHigh surface area ethyltrimethoxysilane (ETMS) modified silica aerogels and xerogels were synthesized by cohydrolyzing the mixtures of ETMS and tetramethylorthosilicate (TMOS). The effects of ETMS content, pH value and solvent addition were investigated. The surface area, pore structure and hydrophobicity were studied using nitrogen and water sorption measurements. By ETMS modification of TMOS gels, high surface area, density and hydrophobicity were achieved. The 25 mole% ETMS-75 mole% TMOS was found to be the best composition for both aerogel and xerogel, which are hydrophobic and have surface areas of 1221 and 832 m2/g, respectively.

New ultrasonic assisted co-precipitation for high surface area oxide based nanostructured materials

2018 ◽  
Vol 3 (3) ◽  
pp. 244-250 ◽  
Author(s):  
Dereck N. F. Muche ◽  
Flavio L. Souza ◽  
Ricardo H. R. Castro
Keyword(s):  
Metal Oxide ◽  
Surface Area ◽  
Metal Oxide Nanoparticles ◽  
High Surface ◽  
High Surface Area ◽  
Oxide Nanoparticles ◽  
Specific Method ◽  
Surface Areas ◽  
Ultrasonic Assisted ◽  
Co Precipitation

A non-system specific method for the synthesis of metal oxide nanoparticles with high homogeneity, spherical morphology and high surface areas is proposed based on an aqueous precipitation.

scholarly journals High Surface Area Nanoporous Graphitic Carbon Materials Derived from Lapsi Seed with Enhanced Supercapacitance

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 728 ◽  
Author(s):  
Lok Kumar Shrestha ◽  
Rekha Goswami Shrestha ◽  
Subrata Maji ◽  
Bhadra P. Pokharel ◽  
Rinita Rajbhandari ◽  
...  
Keyword(s):  
Surface Area ◽  
Current Density ◽  
Electrode Materials ◽  
Carbon Materials ◽  
High Surface ◽  
High Surface Area ◽  
Graphitic Carbon ◽  
High Rate ◽  
Surface Areas ◽  
Nanoporous Carbon Materials

Nanoporous activated carbon materials derived from agro-wastes could be suitable low-cost electrode materials for high-rate performance electrochemical supercapacitors. Here we report high surface area nanoporous carbon materials derived from Lapsi seed agro-waste prepared by zinc chloride (ZnCl2) activation at 700 °C. Powder X-ray diffraction (pXRD) and Raman scattering confirmed the amorphous structure of the resulting carboniferous materials, which also incorporate oxygen-containing functional groups as confirmed by Fourier transform infrared (FTIR) spectroscopy. Scanning and transmission electron microscopy (SEM and TEM) analyses revealed the granular, nanoporous structures of the materials. High-resolution TEM (HR-TEM) confirmed a graphitic carbon structure containing interconnected mesopores. Surface areas and pore volumes of the materials were found, respectively, in the ranges from 931 to 2272 m2 g−1 and 0.998 to 2.845 cm3 g−1, and are thus superior to commercially available activated carbons. High surface areas, large pore volumes and interconnected mesopore structures of these Lapsi seed-derived nanoporous carbon materials lead to their excellent electrochemical supercapacitance performance in aqueous electrolyte (1 M H2SO4) with a maximum specific capacitance of 284 F g−1 at a current density of 1 A g−1. Furthermore, the electrodes showed high-rate capability sustaining 67.7% capacity retention even at high current density of 20 A g−1 with excellent cycle stability achieving 99% capacitance retention even after 10,000 charge–discharge cycles demonstrating the potential of Lapsi seed derived nanoporous carbons as suitable electrode materials in high-performance supercapacitor devices.

A theoretical morphologic analysis of convergently evolved erect helical colony form in the Bryozoa

Paleobiology ◽  
2000 ◽  
Vol 26 (4) ◽  
pp. 556-577 ◽  
Author(s):  
George R. McGhee ◽  
Frank K. McKinney
Keyword(s):  
Surface Area ◽  
Dimensional Space ◽  
High Surface ◽  
High Surface Area ◽  
Three Dimensional ◽  
Filter Feeding ◽  
Colony Form ◽  
Surface Areas ◽  
Morphologic Analysis ◽  
Intermediate Surface

Exploration of the theoretical morphospace of erect helical colony form in Bryozoa, created by McKinney and Raup (1982), reveals that only a small volume of the three-dimensional space of hypothetical form is occupied by actual colonies of the Paleozoic fenestrates (Class Stenolaemata) Archimedes and Helicopora, helical species of the cheilostome (Class Gymnolaemata) Bugula, and the cyclostome (Class Stenolaemata) Crisidmonea archimediformis. Actual helical-colony bryozoans are not found in regions of the morphospace characterized by colony geometries that possess the largest surface areas of filtration sheet. Examination of computer-simulated colonies in the theoretical morphospace reveals that, although possessing high surface areas, colonies in the empty region of high-surface-area morphospace possess other aspects of geometry that are unrealistic as filter-feeding geometries: the filtration-sheet whorls are held at small acute angles to the central colony axis and are deeply nested within one another, both of which are disadvantageous conditions for the system of filter feeding used by the extant cheilostome Bugula, and presumably by extinct helical-colony bryozoans as well.Even though actual bryozoans are found only in the low to intermediate surface-area regions of the theoretical morphospace, surface area of filtration sheet is a major determinant of form in these helical colonies, as is evidenced by a negative correlation in values of the parameters BWANG and ELEV exhibited by the colony data. Minimum values of BWANG are even further constrained by the apparent need of the Archimedes colonies to maintain filtration-sheet branching densities within the range of 20 to 50.

scholarly journals Nanoporous Gold Electrodes and Their Applications in Analytical Chemistry

2013 ◽  
Vol 2013 ◽  
pp. 1-21 ◽  
Author(s):  
Maryanne M. Collinson
Keyword(s):  
Analytical Chemistry ◽  
Surface Area ◽  
Chemical Sensors ◽  
High Surface ◽  
High Surface Area ◽  
Pore Network ◽  
Nanoporous Gold ◽  
Dna Sensors ◽  
Porous Framework ◽  
Surface Areas

Nanoporous gold prepared by dealloying Au:Ag alloys has recently become an attractive material in the field of analytical chemistry. This conductive material has an open, 3D porous framework consisting of nanosized pores and ligaments with surface areas that are 10s to 100s of times larger than planar gold of an equivalent geometric area. The high surface area coupled with an open pore network makes nanoporous gold an ideal support for the development of chemical sensors. Important attributes include conductivity, high surface area, ease of preparation and modification, tunable pore size, and a bicontinuous open pore network. In this paper, the fabrication, characterization, and applications of nanoporous gold in chemical sensing are reviewed specifically as they relate to the development of immunosensors, enzyme-based biosensors, DNA sensors, Raman sensors, and small molecule sensors.

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