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  • 1
    Electronic Resource
    Electronic Resource
    Microcalorimetric studies of zeolite acidity (1992)
    Springer
    Catalysis letters 12 (1992), S. 201-211 
    Details
    ISSN: 1572-879X
    Keywords: Acidity ; gravimetry ; heat of adsorption ; H-Mordenite ; H-Y ; H-ZSM-5 ; microcalorimetry ; pyridine ; zeolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The acidity characteristics of H-ZSM-5, H-Mordenite and H-Y zeolite have been studied by microcalorimetric and gravimetric measurements of pyridine adsorption. H-ZSM-5 and H-Mordenite have Brønsted acid sites of primarily homogenous strength, with H-Mordenite having the stronger sites, whereas H-Y zeolite had Brønsted sites of varying strength. The effects of Na exchange level in H-Y zeolite and high temperature calcination for H-Mordenite have also been examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00767202
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Thermogravimetric and microcalorimetric studies of ZSM-5 acidity (1993)
    Springer
    Catalysis letters 18 (1993), S. 183-192 
    Details
    ISSN: 1572-879X
    Keywords: Acidity ; zeolites ; microcalorimetry ; thermogravimetry ; pyridine adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The combination of thermogravimetry, microcalorimetry and infrared spectroscopy studies of pyridine adsorption has been used to characterize the acidity of a ZSM-5 catalyst. The majority of the acid sites are Brønsted acid centers associated with framework Al species, with heats of pyridine adsorption equal to 140 kJ/mol. Non-framework Al species in the zeolite sample of this study eliminate an approximately equal number of Brønsted acid sites. These nonframework Al species also produce strong Lewis acid sites with pyridine adsorption heats greater than 140 kJ/mol, as well as weak adsorption sites (e.g., weak Bransted acid sites or hydrogen bonding sites) with heats equal to 90–140 kJ/mol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769437
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of liming and carbofuran on groundnut yield in sandy soils in Niger (1992)
    Springer
    Nutrient cycling in agroecosystems 33 (1992), S. 203-208 
    Details
    ISSN: 1573-0867
    Keywords: Al ; Arachis hypogaea ; carbofuran ; lime ; nematodes ; pH ; yields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract One of the constraints to groundnut production in sandy soils of Niger is crop growth variability. In early 1989, a trial on the effect of lime and carbofuran on soil pH, Al toxicity, nematode population and groundnut yield was initiated to study crop growth variability. Groundnut was sown in the 1989 rainy season, followed by pearl millet (Pennisatum glaucum) in the 1989–90 dry season and again groundnut in the 1990–91 rainy, and dry seasons. In 1989 the carbofuran treatment increased the pod yield. Lime application did not change the pH and exchangeable Al+++ contents in the soil and did not increase groundnut yield. In the 1990–91 rainy and dry season, however, the application of 10 t ha−1 of lime increased pH, decreased exchangeable Al+++, improved crop growth and increased the yield of groundnut to the same level as was achieved by the carbofuran treatment. Application of lime did not affect the nematode population, which were reduced by the carbofuran.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01050875
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  • 4
    Electronic Resource
    Electronic Resource
    Role of Scutellonema clathricaudatum in etiology of groundnut growth variability in Niger (1992)
    Springer
    Plant and soil 143 (1992), S. 133-139 
    Details
    ISSN: 1573-5036
    Keywords: aluminium toxicity ; Arachis hypogaea ; crop growth variability ; groundnut ; peanut ; pesticide ; plant-parasitic nematodes ; Niger ; Sahel ; Scutellonema clathricaudatum ; soil pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Variation in crop growth is an important limiting factor for groundnut production in Niger. Populations of Aphelenchoides sp., Ditylenchus sp., Helicotylenchus sp., Hoplolaimus pararobustus, Macroposthonia curvata, Paralongidorus bullatus, Scutellonema clathricaudatum, Telotylenchus indicus and Xiphinema parasetariae have been associated with groundnut crop growth variability. S. clathricaudatum, X. parasetariae and T. indicus were widespread and S. clathricaudatum was most abundant nematode. Population densities of S. clathricaudatum was always higher in the roots of poorly growing, chlorotic and stunted plants than in the roots of apparently healthy plants. A preplant population density of 1.3 S. clathricaudatum cm-3 soil caused (p=0.05) reduction in plant growth of groundnut cv. 55–437. S. clathricaudatum was mainly confined to 0–15 cm soil depth at the time of planting in June and was not found below 45 cm depth at any time during the crop growth period. Soil application of carbofuran (10 kg a.i ha-1) reduced the nematode population densities and resulted in vigorous and uniform crop growth. Higher Al and H-ion concentrations (0.50 meq 100 g-1 soil) also was associated with poorly growing chlorotic seedlings. Symptoms of nematode-caused variable growth were evident 3 to 4 weeks after seedling emergence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009138
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  • 5
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    Detection of Chamber Conditioning by CF4 in the GEC Cell (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: During oxide etch processes, buildup of fluorocarbon residues on reactor sidewalks can cause to drift and will necessitate time for conditioning and cleaning of the reactor. Various measurements in CF4 and Ar plasmas are made in an attempt to identify a metric able to indicate the chamber condition. Mass spectrometry and a Langmuir probe shows that the buildup of fluorocarbon films on the reactor surface causes a decrease in plasma floating potential, plasma potential, and ion energy in argon plasmas. This change in floating potential is also observed in CF4 plasma operation, and occurs primarily during the first hour and a half of plasma operation. A slight rise in electron density is also observed in the argon plasmas. Because the change is seen in an argon plasma, it is indicative of altered physical, not chemical, plasma-surface interactions. Specifically, the insulating films deposited on metal surfaces alter the electromagnetic fields seen by the plasma, affecting various parameters including the floating potential and electron density. An impedance probe placed on the inductive coil shows a slight reduction in plasma impedance due to this rising electron density. The optical emission of several species, including CF, C2, atomic Si and atomic C, is also monitored for changes in density resulting from the buildup of film on the chamber wall. Changes in the optical emission spectrum are comparable to the noise levels in their measurement.
    Keywords: Inorganic, Organic and Physical Chemistry
    Format: text
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  • 6
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    A Survey of Electron Impact Cross-Sections for Halogens and Halogen Compounds of Interest to Plasma Processing (1998)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Published electron impact cross section data on halogens Cl2, F2, and halogen containing compounds such as Cx Fy, HCl, Cx Cly Fz are reviewed and critically evaluated based on the information provided by various researchers. The present work reports data on electron impact excitation, ionization, dissociation, electron attachment, electron detachment, and photo detachment. Elastic scattering cross sections and data on bulk properties such as diffusion coefficients in various background gases are also evaluated. Since some of the cross sectional data is derived from indirect measurements such as drift velocity, care has been taken to reconcile the differences among the reported data with due attention to the measurement technique. In conclusion, the processes with no or very limited amount of data and questionable set of data are identified and recommendation for further research direction is made.
    Keywords: Inorganic, Organic and Physical Chemistry
    Type: Gaseous Electronics Conference; Oct 19, 1998 - Oct 23, 1998; HI; United States
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  • 7
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    CF2 Detection in Radio-Frequency Ar/CHF3 Plasmas by Fourier Transform Infrared Spectroscopy (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: CFx radicals, in particular CF2, are instrumental in anisotropic etching of SiO2. In order to optimize the CFx radical population in a given process environment, it is imperative that we understand their production mechanism. Towards this goal, we have conducted a series of quantitative measurements of CF2 radicals in low pressure RF plasmas similar to those used in SiO2 etching. In this study, we present preliminary results for Ar/CHF3 plasmas operating at pressures ranging from 10-50 mTorr and powers ranging from 100-500 W in the GEC reference cell, modified for inductive (transformer) coupling. Fourier transform infrared (FTIR) spectroscop) is used to observe the absorption features of the CF2 radical in the 1114 cm-1 and 1096 cm-1 spectral regions. The FTIR spectrometer is equipped with a high-sensitivity mercury cadmium telluride (MCT) detector and has afixed resolution of 0.125 cm- 1. The CF2 concentrations are measured for a range of operating pressures and discharge power levels, and are compared to measurements of the relative CF2 concentrations made by mass spectrometry using the method of appearance potential for radical selectivity.
    Keywords: Inorganic, Organic and Physical Chemistry
    Type: 52nd Annual Gaseous Electronics Conference; Oct 05, 1999 - Oct 08, 1999; Norfolk, VA; United States
    Format: text
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