bluuebunny/crossref_metadata_2025_split huggingface dataset:
Corrosion and passivity of Hastelloy C4 in a high salinity brine
Authors: Thies A. , Schultze J. W. 
Published: May 2005

AbstractCorrosion and passivity of Hastelloy C4 in Q‐brine, a magnesium chloride rich brine of pH 4.5 at room temperature, was studied by potentiodynamic (i(U) and C(U)) or potentiostatic polarisation. While the alloy rests passive at room temperature, no coherent, protecting passive layer is formed at temperatures above 60°C and potentials exceeding 0.2 V SHE. XPS analysis shows that at the rest potential and temperatures below 110°C, the oxide layer is about 1 nm thick and composed of chromium and molybdenum oxides without incorporation of Mg2+or Cl−from the electrolyte. At 200°C, its thickness increases 20 nm after 4 days and Mg+inclusions are found. Across the weld, Scanning Reference Electrode measurements in dilute NaCl showed a homogeneous potential distribution indicating that bulk material, heat affected zone and weld have the same electrochemical properties.
PH‐Abhängigkeit der korrosionsinhibierenden bzw. ‐stimulierenden Wirkung von Polyacrylsäuren auf Aluminiumpigmente
Authors: Müller B. , Dawidowski U. 
Published: May 2005

AbstractDer isoelektrische Punkt (IEP: pH ≈ 9) von Aluminiumoxid ist von entscheidender Bedeutung für die korrosionsinhibierende Wirkung von Polyacrylsäuren in Bezug auf Aluminiumpigmente im alkalisch wäßrigen Medium:
Oberhalb des IEP (pH 10):
Hoch‐ und niedrigmolekulare Polyacrylsäuren inhibieren die Korrosion, wobei deren Wirkung mit zunehmender Molmasse abnimmt.

Unterhalb des IEP (pH 8):
Niedrigmolekulare Polyacrylsäuren inhibieren die Korrosion, aber weniger effektiv als bei pH 10; die korrosionsinhibierende Wirkung nimmt mit zunehmender Molmasse ab.
Hochmolekulare Polyacrylsäuren stimulieren die Korrosion; d. h. am IEP findet eine Wirkungsumkehr statt.
In Situ Polymerization of Hybrid Polyethylene‐Alumina Nanocomposites
Authors: Zhang Xi , Simon Leonardo C. 
Published: May 2005

AbstractSummary: Polyethylene‐alumina nanocomposites were prepared using in situ polymerization. Alumina nanomers were prepared by treating alumina nanoparticles with an alkylaluminium compound and a vinyl alcohol. This approach led to (a) grafting double bonds onto the alumina surface, and (b) dispersion of alumina nanoparticles in toluene minimizing aggregation. The level of dispersion of nanomers was a function of the molar ratio between the alkylaluminium compound and the vinyl alcohol. Copolymerization of ethylene and nanomers catalyzed by the coordination catalyst (diimine)NiCl2/MAO produced hybrid nanocomposites with polyethylene chains covalently bonded to the surface of alumina nanoparticles. Using excess of vinyl alcohol produced crosslinked material. Appropriate preparation of nanomers has produced a good dispersion of alumina nanoparticles in the polyethylene matrix. At certain compositions the final material had better mechanical properties, such as yield strength and toughness, than the homopolyethylene.
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Pressure, the Critical Factor Governing Final Microstructures of Cured Rubber/Clay Nanocomposites
Authors: Liang Yu‐Rong , Lu Yong‐Lai , Wu You‐Ping , Ma Yong , Zhang Li‐Qun 
Published: May 2005

AbstractSummary: The changes in both local intercalated structures and spatial distribution states of organoclays (OC) in rubber/clay nanocomposites (RCNs) caused by vulcanization were monitored by using WAXD and TEM, and the corresponding mechanism was studied. It was first discovered that the pressure was the critical factor determining the final microstructures of cured RCNs. The cured RCNs with fine dispersion could be obtained through vulcanization under atmospheric pressure.TEM images of SBR/clay nanocomposites cured at 15 MPa pressure (left) and atmospheric pressure (right).magnified imageTEM images of SBR/clay nanocomposites cured at 15 MPa pressure (left) and atmospheric pressure (right).
Glasfasern—Herstellung—Erzeugnisse
Authors: Hansmann Joseph 
Published: May 2005

AbstractDie eingeführten Werkstoffbezeichnungen und Definitionen sind der Beschreibung der Glasfasererzeugnisse und ihrer Herstellungs‐verfahren vorangestellt. Die verschiedenen ‐ den einzelnen Erzeugnisgruppen angepaßten ‐ Ausrüstungen sind nicht nur Verarbeitungshilfsmittel, sondern entscheiden über die Einsatzmöglichkeiten. Für die Vielfalt der Anwendungsgebiete spricht die steigende Weltproduktion von 470 000 t im Jahre 1970. Einige wirtschaftlich und technisch interessante Anwendungen werden beschrieben. Vom Straßenbau bis zum Raumanzug, von der Wärme‐und Schalldämmung bis zur Glasfaseroptik streuen die Möglichkeiten. Sind die Glasfaser‐Dämmung und ‐Isolierung noch weithin bekannt, so ist der Einsatz von über 100 Mill m2 Glasvlies im Dach‐und Dichtungsbahnsektor oder von 8 Mill. m2 Dekostoff in Westeuropa (1970) ebenso weithin unbekannt. Drainage, Heißmetallpressen, Luftfilter, Putzarmierung, Akkuscheider, Rohrleitungs‐und Bootsbau, Autoreifen und Fußbodenbelag demonstrieren die Vielfalt der Anwendungen.
Haftung und Grenzflächenreaktionen im Verbundsystem α‐Al2O3/Ni
Authors: Grünling H. W. , Hennicke H. W. 
Published: May 2005

AbstractAn Verbundwerkstoffmodellen aus zylindrischen Saphirstäben mit aufgesintertem Nickelring wird der Einfluß geringer Mengen von Titan oder Zirkon als Legierungsbestandteil im Nickel auf die Haftung und Verträglichkeit zwischen den Partnern unter‐sucht. Mit unlegiertem Nickel werden zeitlich und thermisch stabile Scherfestigkeitswerte zwischen 50 und 70 N/mm2 erzielt. Enthält das Nickel 0,05 At‐% Titan oder Zirkon, steigt bei günstigen Sinterbedingungen (z. B. 1300°C, 1 h) die Scherfestigkeit auf 250–280 N/mm2 an. Dieser Anstieg ist auf eine, Verbesserung der Haftung zwischen den Partnern zurückzuführen, die sich mit der Ausbildung chemischer Haftkräfte als Folge von Reaktionen zwischen der Saphiroberfläche und den im Nickel enthaltenen aktiven Legierungselementen Titan oder Zirkon erklären lassen. Bei längeren Haltezeiten, höheren Sintertemperaturen und/oder höheren Aktivmetallkonzentrationen führen diese Reaktionen zur Aufrauhung des Saphir und zur Ausscheidung von Oxidphasen der im Nickel enthaltenen aktiven Elemente in der Grenzfläche oder in einer grenzflächennahen Zone des Nickels. Diese reaktionsbedingten Grenzflächenveränderungen bewirken eine Änderung des Scherverhaltens, die sich in einer Verringerung der Scherfestigkeit äußern kann. Die an solchen Proben gemessenen Scherfestigkeitswerte lassen keine Rückschlüsse auf die tatsächliche Haftung zwischen den Partnern mehr zu.
Nichtmetallische Hochtemperaturwerkstoffe
Authors: Petzow Günter , Buresch Friedrich Erich 
Published: May 2005

AbstractEinige Sonderkeramiken kommen als Werkstoffe für Temperaturbeanspruchungen oberhalb von 1100°C in Betracht. Sie verfügen über ausreichende Warmfestigkeiten und gute Korrosionseigenschaften und mit einigen Einschränkungen auch über einen brauchbaren Thermoschock‐ und Schlagwiderstand. Im Vergleich zu den Metallen ist diese interessante Materialklasse noch sehr entwicklungsfähig.
Durch veränderliche Betriebslasten in Kerben erzeugte Eigenspannungen und ihre Bedeutung für die Anwendbarkeit der linearen Schadensakkumulations‐Hypothese
Authors: Schütz D. , Gassner E. 
Published: May 2005

AbstractDie lineare Schadensakkumulations‐Hypothese liefert häufig sehr ungenaue Schätzwerte der Lebensdauer. Um zu einer Klärung beizutragen, wurden an gelochten Stäben, Formzahlak= 2,5, aus den Leichtmetallegierungen AlCuMg 2 und AlZnMgCuAg im Kerbgrund während des ersten von Makrorissen freien Lebensdauerabschnittes die Eigenspannungen gemessen und darauf aufbauend eine bezüglich der Eigenspannungen korrigierte Hypothese angewendet.
Ermüdungsverhalten von SiSiC
Authors: Richter H. , Willmann G. , Heider W. 
Published: May 2005

AbstractAuf der Basis der Theorie der linear‐elastischen Bruchmechanik wird die für die Konstruktion benötigte, zeitabhängige mechanische Festigkeit (Ermüdung) von stranggepreßtem und schlickergegossenem Siliziumcarbid (SiSiC) bei Raumtemperatur bestimmt.Der Zusammenhang zwischen Belastungshöhe, Ausfallswahrscheinlichkeit und Zeit wird in Form von SPT‐Diagrammen dargestellt.
Quasistatisches Verformungsverhalten reiner Sintereisen im Temperaturbereich von –184 bis 600°C
Authors: Klumpp S. , Palma E. S. , Vöhringer O. , Macherauch E. 
Published: May 2005

AbstractReine Sintereisenwerkstoffe mit Dichten zwischen 6,88 und 7,57 g/cm3 wurden im Temperaturbereich von –184 bis 600°C quasistatisch zugverformt. Ergänzende Druckverformungen erfolgten bei 20°C. Anwachsende Dichte bewirkt ansteigende Werkstoffwiderstands‐ und Duktilitätskenngrößen aufgrund zunehmender tragender Probenquerschnitte, geringerer Porenzahl, runderer Poren mit geringerer Kerbwirkung sowie einer geringeren Zahl der von Poren ausgehenden Rissen. Bei Druckverformung entstehen nach gleichen Deformationen groößere Fließspannungen als bei Zugverformung, da Porenschließeffekte und die Behinderung von Rißbildungen die tragenden Probenquerschnitte vergrößern. Das Verformungsverhalten wird bei tiefen Temperaturen durch thermisch aktivierte Prozesse mit kurzreichenden Wechselwirkungen von Versetzungen mit Gleithindernissen, bei mittleren Temperaturen durch dynamische Reckalterungsvorgänge aufgrund von elastischen Wechselwirkungen bewegter Versetzungen mit diffundierenden Kohlenstoffatomen und bei hohen Temperaturen durch erholungskontrollierte Versetzungskriechprozesse bestimmt.
Fluid phase equilibria in supercritical fluid chromatography with CO2‐based mixed mobile phases: A review
Authors: Page Steven H. , Sumpter Sheldon R. , Lee Milton L. 
Published: May 2005

AbstractIn supercritical fluid chromatography (SFC), cosolvents (modifiers) have been added to CO2 in order to deactivate the analytical column and to improve the solvating power of CO2 for extending the utility of SFC to polar and high molecular weight solutes. However, the use of modifiers has proven to be difficult, and irreproducibility in retention and selectivity is often observed.This comprehensive review focuses on the phase behavior of analytically useful CO2‐based mixed mobile phases in SFC. All of the CO2‐based mixed mobile phases which have been used in packed or open tubular column SFC are reviewed. All of the available fluid phase equilibria data for such binary fluids are discussed, and the P‐T‐x region which is applicable to SFC is compiled in both graphs and tables. Single phase regions (pressure and temperature) are listed by mol% modifier. However, only mixtures of CO2 + benzene, + ethanol, + hexane, + methanol, or + toluene have enough P‐T‐x data points to enable extrapolation to any other conditions used in conventional SFC (0–20 mol% modifier, 40–400 atm, and 0–200°C). Problems associated with estimating the critical parameters of the pure components or the mixtures are reviewed. Phase transitions in the syringe pump, transfer lines, injector, column, and restrictor are delineated. Equilibration problems associated with the preparation of mixed mobile phases (premixed cylinders, liquid or gas phase saturation, and dual pumps with on‐column mixing) and phase transitions during the operation of SFC instrumentation are discussed. Finally, future research needs are outlined.
Evaluation of surface‐bonded polyethylene glycol and polyethylene imine in capillary electrophoresis
Authors: Huang Mingxian , Vorkink William P. , Lee Milton L. 
Published: May 2005

AbstractA procedure for bonding polyethylene glycol (PEG) and polyethylene imine (PEI) onto the capillary surface through a highly crosslinked polysiloxane layer containing epoxy groups has been developed. Systematic variation of the coatings can be used to (a) allow separations over a pH range of 3 to 9, (b) provide for adjustment of electro‐osmotic flow, and (c) reduce the adsorption of peptides and proteins. The variation of electroosmotic flow on these coated columns at different operational conditions can be explained using electrical double layer theory. Separations of substituted aromatic compounds and peptides on these coated columns were much improved over similar separations on untreated columns. The results indicate that PEI coated columns are suitable for the separation of basic proteins and PEG coated columns are suitable for acidic proteins. Separations of simple oligonucleotides which differ by only one base were also achieved.
Configurational and conformational analysis of norbornane‐and norbornene‐fused 4,1‐oxazepinones
Authors: Sohár P. , Stájer G. , Bernáth G. 
Published: May 2005

AbstractThe preferred conformations and, for the 3‐methyl‐substituted analogues also the configurations of the C‐3 atom, for 3‐unsubstituted and 3‐methyl‐substituted di‐exo‐ and di‐endo‐annellated oxazepinone derivatives fused with a norbornane or norbornene skeleton were determined by 1H and 13C NMR spectroscopy, including the use of DNOE measurements.
Application of the conformational transmission effect for the assignment of diastereotopic proton resonances
Authors: van Genderen Marcel H. P. , Buck Henk M. 
Published: May 2005

AbstractA new method is presented for the assignment of the NMR resonances of the diastereotopic protons in tetrahydrofur‐furyl and pyrrolidinylmethyl groups, based on the conformational transmission effect This effect describes the conformational changes produced by an increase of coordination from four to five of a phosphorus, silicon or germanium atom attached to the tetrahydrofurfuryl or pyrrolidinylmethyl moieties. The 1H NMR conformational analysis of these cyclic four‐ and five‐coordinated compounds yields two possible results, based on two assignments of the diastereotopic proton resonances. Comparison with the conformations of the analogous four‐ and five‐coordinated systems with acyclic 2‐methoxyethyl and dimethylaminoethyl groups (which lack diastereotopic protons) directly shows which assignment is correct, since a similar conformational transmission occurs in both the cyclic and the acyclic compounds.
Long‐range tin‐tin coupling constants. III‐Four‐ and five‐bond coupling via carbon
Authors: Mitchell T. N. , Nettelbeck C. 
Published: May 2005

AbstractMultinuclear NMR data (1 H, 13 C, 119 Sn) have been obtained for almost all possible isomers of the composition Me3Sn(C3Hm)SnMe3 (m = 2, 4, 6) and Me3Sn(C4Hn)SnMe3 (n = 0, 2, 4, 6, 8). The coupling constants xJ(Sn, Sn) (x = 4, 5) are not linearly related to the corresponding coupling constants xJ(H, H), but are particularly large when tin‐carbon bonds can interact hyperconjugatively with carbon‐carbon double or triple bonds.
Monitoring electrochemical reactions by 13C NMR spectroscopy
Authors: Albert Klaus , Dreher Eberhard‐Ludwig , Straub Hermann , Rieker Anton 
Published: May 2005

AbstractThe anodic conversion of 2,4,6‐tri‐tert‐butylphenol in methanol, leading to 2,4,6‐tris(1,1‐dimethylethyl)‐4‐methoxy‐2,5‐cyclohexadien‐1‐one, has been followed by two types of 13C NMR experiments: (a) a static procedure, inserting the electrodes directly into a rotating NMR tube and (b) a continuous flow procedure, combining electrochemical and NMR flow cells. During electrolysis the resolution of the 13C NMR spectra decreased in the static procedure owing to magnetic field gradients. In the flow procedure the resolution was comparable with that of routine spectra.
1H and 13C NMR spectra of the opioid analgesics metazocine, pentazocine and cyclazocine
Authors: Grassi Antonio , Pappalardo Giuseppe C. , Perly Bruno 
Published: May 2005

AbstractThe high‐frequency 1 and 13C NMR spectra (at 500 and 75.47 MHz, respectively) of metazocine (MTZ) fumarate, pentazocine (PTZ) and cyclazocine (CLZ) hydrochlorides in 2H2O solution were recorded and analysed with the aid of both homonuclear 1H1H and heteronuclear 13C1H chemical shift correlation experiments. At neutral pH all compounds were found to be configurationally heterogeneous, with the N‐equatorial isomer more populated than the N‐axial isomer (ratio ca 80:20). The low‐intensity peaks of the superimposed spectral pattern of the less populated isomer were also assigned on correlative grounds in both the 1H and 13C NMR spectra of MTZ, PTZ and CLZ. The occurrence of distinct spectra for the two configurational isomers was diagnostic of a ‘slow’ exchange process on the NMR time‐scale at the field frequencies employed for the experiments, thus suggesting a high‐energy barrier to interconversion. The experimental proton–proton coupling constants measured for the N‐equatorial form of MTZ, PTZ and CLZ were consistent with a chair conformation of the piperdinic ring in all compounds. The distinct relative agonist–antagonist potencies of the drugs investigated could therefore not be correlated with the above‐described configurational and conformational features.
Carbon‐13 NMR spectra of cyclohexaneaminonitriles
Authors: Manoharan Muthiah , Eliel Ernest L. 
Published: May 2005

AbstractThe 13C NMR spectra of nine 1‐(N‐piperidino) cyclohexanenitriles and of 1‐dimethylaminocyclohexanenitrile have been recorded and assigned.
195Pt and1H NMR studies of platinum(II) complexes with ethylenediamine derivatives
Authors: Rochon F. D. , Morneau André 
Published: May 2005

AbstractComplexes of the types Pt(L)Cl2, [Pt(L)(D2O)2](NO3)2, [Pt(L)(D2O)(NO3)](NO3), Pt(L)(OD)2, [Pt(L)(D2O)Cl]+and Pt(L)(OD)Cl, where L = ethylenediamine,N,N‐dimethylethylenediamine,N,N′‐dimethylethylenediamine andN,N,N′,N′‐tetramethylethylenediamine, were characterized mainly by195Pt and1H (high‐ and low‐field) nuclear magnetic resonance. The NMR spectra were measured in D2O. The dichloro complexes showed a195Pt resonance between −2355 and −2433 ppm (relative to Na2PtCl6) whereas the diaqua compounds absorbed at lower field from −1821 to −1977 ppm. The signals of the monoaqua‐monochloro species were observed at intermediate field between −2030 and −2173 ppm. The dihydroxo complexes showed a resonance at lower field (about 100 ppm) than the diaqua compounds, whereas the monochloro‐monohydroxo species absorbed at about 50 ppm from the monoaqua‐monochloro species. The monoaqua‐mononitrato compounds with only two ligands absorbed at about −20 ppm from the diaqua species. The high‐field proton NMR spectra of the complexes were also measured. The195Pt–1H coupling constants were obtained from the low‐field proton NMR spectra.
Investigations utilizing the 18O isotope shift in 13C nuclear magnetic resonance spectroscopy. 1. Correlation with 17O NMR chemical shifts
Authors: Risley John M. 
Published: May 2005

AbstractA survey of the one‐bond upfield 18O isotope effects on 13C NMR chemical shifts shows that a linear relationship exists between the magnitude of the isotope shift and the 17O NMR chemical shift for the corresponding oxygen atom in the molecule. The relationship holds over the entire range of functional groups to a significance level of >99.999% for 66 pairs of data points. This relationship permits an estimation with confidence of the general magnitude of an 18O isotope shift in 13C NMR, simply from a knowledge of the 17O NMR chemical shift for an oxygen atom of interest. Extrapolation of this relationship anticipates observation of downfield isotope shifts and may assist in an explanation of this rare and unusual phenomenon in NMR spectroscopy.
Conjugation of spirocyclopropane with the carbonyl group. Conformational analysis of spiro [cyclopropane‐1,2′‐steroids]
Authors: Desai Umesh R. , Trivedi Girish K. 
Published: May 2005

AbstractThe conjugative ability of a spirocyclopropane on 4‐en‐3‐one steroids was studied with the help of 13C NMR and two‐dimensional experiments such as COSY and NOESY. The conformational analysis of the A ring of these compounds indicates a ‘normal’ (1α,2β)‐ half‐chair conformation rather than the expected ‘inverted’ (1β,2α)‐ half‐chair conformation. Application of the modified McConnell equation for the shielding influence of the cyclopropane aids the analyses.
13C NMR of some trans‐alkoxy‐β‐methyl‐β‐nitrostyrenes
Authors: Dawson Brian A. , By Arnold W. , Avdovich Hajro W. 
Published: May 2005

Abstract13C NMR chemical shift assignments for 30 trans‐alkoxy‐β‐methyl‐β‐nitrostyrenes and the parent compound were measured and interpreted. Chemical shift assignments for 20 of these compounds have not been reported previously. Data are based on a number of 1D and 2D experiments performed at 9.4 T.
Molecular complexes of explosives with cyclodextrins I. Characterization of complexes with the nitramines RDX, HMX and TNAZ in solution by 1H NMR spin‐lattice relaxation time measurements
Authors: Cahill S. , Bulusu S. 
Published: May 2005

AbstractInclusion complex formation between the explosive molecules of the nitramine type, RDX, HMX and TNAZ, and cyclodextrins (α, β and γ) was studied in aqueous solution by means of 1H spin–lattice relaxation time (T1) measurements. The results show that nitramines bind to cyclodextrins in solution; RDX and HMX bind most strongly to γ‐cyclodextrin whereas TNAZ binds most strongly to β‐cyclodextrin. The dynamic coupling coefficient and dissociation constant were determined for the complex of TNAZ with β‐cyclodextrin. The values obtained suggest that TNAZ forms a relatively weak complex with β‐cyclodextrin (Kd = 1.8 × 10−2 M) that displays considerable motion in the complex with respect to cyclodextrin (coupling coefficient = 0.23). This method of using 1H T1 measurements for characterizing complex formation in solution, while limited to guest molecules containing a pair of protons having a fixed internuclear distance, is shown to be useful when complexation‐induced chemical shifts are too small to be significant.
Interaction of phosphorylated molecules with protic solvents and cations. Discussion of the electronic perturbation at the phosphoryl bond of triphenylphosphine oxide
Authors: Hargé Jean‐Claude , Abdallaoui Habib El Alaoui El , Rubini Patrice 
Published: May 2005

AbstractLongitudinal relaxation times T1 of the 31P nucleus of triphenylphosphine oxide (TPPO) in the complexes Mg(TPPO)4(CF3SO3)2 and Cd(TPPO)4(BF4)2 were measured in nitromethane solutions at three different frequencies, leading to the determination of the chemical shift anisotropy (CSA) contribution to the total relaxation rate. The 31P shielding tensor anisotropy Δσ was measured from NMR static spectra recorded on solid samples, allowing the deduction of correlation times τr corresponding to the reorientation of the species in solution. From the line width of the 17O NMR signal, the 17O quadrupolar coupling constant χ was calculated, the value changing significantly from the free ligand (χ = 4.7 MHz) to bound molecules in complexes (χ = 6.7–7.2 MHz). This was explained by a modification of the electronic distribution around the oxygen atom, mainly due to less π back‐donation from O to P; π‐electron transfer was quantified from χ values using the Townes‐Dailey model. The nature of the interaction with these divalent cations is also discussed. The interaction of TPPO with protic solvents such as water, methanol, trifluoroacetic acid and sulphuric acid was studied using a‐procedure similar to that used for complexes, except for the determination of τr, which was reached from 13C relaxation time measurements on the para‐carbons of the phenyl groups. Variations of Δσ and χ are discussed in terms of hydrogen bonding and interaction with hydrogen ions.