bluuebunny/crossref_metadata_2025 huggingface dataset:
Leichte Turbolader‐Verdichterräder aus Aluminium‐ und Magnesium‐Feinguß
Authors: Sonsino C. M. , Kaufmann H. , Keiper R.
Published: May 2005

Im Rahmen einer Zusammenarbeit zwischen der Kühnle, Kopp & Kausch AG, Volkswagen AG, Sterling International Technologies Ltd. und dem Fraunhofer‐Institut für Betriebsfestigkeit LBF wurden Verdichterräder aus Aluminium‐ und Magnesiurn‐Feingußlegierungen entwickelt und untersucht. Festigkeits‐ und Schwingfe‐stigkeitsuntersuchungen, Schleuder‐ und Feldversuche sowie metallographische Untersuchungen wurden von Finite‐Element‐Berechnungen begleitet, mit denen Spannungsverteilungen am Bauteil optimiert wurden. Anhand der ermittelten Ergebnisse soll geklärt werden, inwieweit Magnesium‐Feingußlegierungen die gegenwärtig für Turbolader‐Verdichterräder eingesetzten Aluminium‐Feingußlegierungen ersetzen können.
Berechnungs‐ und experimentelle Verfahren zur Charakterisierung thermischer Mikroeigenspannungen in Stückverbunden
Authors: Pyzalla A. , Berns H.
Published: May 2005

Stückverbunde sind Teilchenverbundwerkstoffe, die aus einer metallischen Matrix (MM) mit eingelagerten quasikeramischen Hartphasen (HP) bestehen. Sie werden industriell zum Verschleißschutz eingesetzt. In Stückverbunden entstehen während der Abkühlung Mikroeigenspannungen aufgrund der unterschiedlichen physikalischen und mechanischen Eigenschaften der Hartphasen und der Metallmatrix. Weitere Einflußfaktoren auf die Höhe und Verteilung der Mikroeigenspannungen sind die Größe, Form und die Verteilung der Hartphasen.

Zur Charakterisierung des Mikroeigenspannungszustandes werden Berechnungsverfahren (analytische Berechnungen, FEM) und experimentelle Verfahren (Dilatometrie, Mikro‐Moiré‐Verfahren, Röntgenbeugung, winkeldispersive Neutronenbeugung, Neutronenflugzeitspektrometrie, Torsionspendelversuche, Differentialkalorimetrie und Ultraschallabsorptionsmessungen) angewendet und bewertet.
Naturally Occurring Organic Substances as Corrosion Inhibitors for mild Steel in Acid Medium: Concentration and temperature effects
Authors: Rahim M. A. Abdel , Hassan Hanaa B. , Khalil M. W.
Published: May 2005

Potentiodynamic cathodic and anodic polarization technique was used to study the effect of some common amino acids concentration on the corrosion inhibition of mild steel in H2SO4. A value of 1.0 × 10−4 M represents a critical concentration, for the aliphatic amino acids, above which the corrosion rate increases. The increase of the sulphur‐containing amino acids concentration largely decreases the corrosion rate. A mono‐layer adsorption of the amino acid molecules on the metal surface was proposed with the adsorption behaviour following the Temkin isotherm at 30°C.

The effect of temperature on the corrosion inhibition of amino acids was also studied over the temperature range 25 to 60°C. Values of the apparent activation energy in the range of 42 ‐ 49 kJ mol−1 were estimated for the steel corrosion in the inhibited acid solutions.
Corrosion inhibition of iron by 1‐benzylidene‐4‐ Phenylthiosemicarbazone derivatives in acid solution
Authors: Abd El‐Maksoud S. A. , El‐Shafei A. A. , Fouda A. S.
Published: May 2005

The inhibition action of 1‐benzylidene‐4‐phenylthiosemicarbazone derivatives on the corrosion behaviour of iron in 1M H2SO4 was investigated using potentiostatic and potentiodynamic techniques. Results showed that these derivatives act as mixed‐type inhibitors, but the cathode is more preferentially polarized. All the inhibitors follow the Frumkin adsorption. The results of the potentiodynamic indicate that the adsorption process depends on both adsorption potential (Eads) and adsorption time (tads). THe results obtained were analysed and discussed on the basis of competitive adsorption.
Evaluation of Novalak Resins as a precursor for fabrication of carbon – carbon composites. Part I. Optimization of curing stages
Authors: Sedghi A. , Fard F. Golestani
Published: May 2005

Curing of novalak resin has been investigated by applying different thermal analysis methods and solvent extraction technique. Results revealed that cure can be optimized by finding the critical steps in cure and hold resin in these steps for appropriate time. Best results were also achieved by using resins which contained lower free phenol and hexamine amount. Application of pressure is necessary in initial stages of cure but found to be harmful in the final stages. It was also found that due to the defects produced in the final stages of curing, this process cannot be completed and long time post cure should be applied on these resins. By applying a special curing regime, it was proved that defects during pyrolysis stage could be decreased profoundly and a carbon residue of more than 67 percent expected. The results are explained by emphasis on carbon – carbon applications.
Finite Element Stress and strain analysis of a double shear creep specimen
Authors: Peter G. , Probst‐Hein M. , Kolbe M. , Neuking K. , Eggeler G.
Published: May 2005

This paper reports on creep stress and strain results obtained by the finite element method (FEM) for a double shear specimen which was recently developed [1]. It considers stress redistribution during creep, small changes in specimen geometry during testing and high local stress states at the positions where the specimen is loaded. The results of the present study show that the unconstrained double shear test technique proposed in [1] yields viable results for shear strains of at least up to 0.10. ([1]: C. Mayr et al., Materials Science and Engineering, A 199 (1995) p. 121)
Mikrofraktographie an CFK mit thermoplastischer Matrix (APC‐2)
Authors: Franz Horst E.
Published: May 2005

Ziel der vorliegenden Arbeit war es belastungsspezifische mikrofraktographische Charakteristika am CFK Material ACP‐2 (PEEK/IM6)zu erarbeiten. Bei statischer Modus, I II und Mixed Modus Beanspruchung wurden definierte interlaminare Brüche, bei gleichzeitiger Ermittlung der Energiefreisetzungsrate, erzeugt. Des weiteren wurde der Einfluß der Bruchgeschwindigkeit und der Temperatur auf die Bruchmorphologie ermittelt. Die drei unterschiedlichen Belastungsmodi führen jeweils zu Bruchflächen, die örtlich wechselnde belastungsmodusspezifische duktile und spröde mikrofraktographische Morphologien aufweisen. Die duktilen Bruchmorphologien entsprechen örtlich geringerer, die Spröden örtlich höherer Bruchfortschrittsgeschwindigkeiten. Die Flächenantiele der duktilen Bruchmorphologie nehmen mit abnehmender Bruchgeschwindigkeit und zunehmender Temperatur zu, gleichzeitig nimmt die interlaminare Energiefreisetzungsrate (Bruchzähigkeit) zu. Letzteres stellt eine anschauliche Korrelation dar.

Bei Belastungsmodi mit einer Zugspannungskomponente (Modus I, Mixed Modus) konnten innerhalb der Bruchflächenbereiche mit spröder Bruchmorphologie Rastlinien (Orte an denen sich die örtliche Bruchgeschwindigkeit ändert) detektiert werden, mit deren Hilfe man die Bruchfortschrittsrichtung ermitteln kann. Bei Modus II Belastung kann lediglich die Richtung der Scherspannung anhand der örtlichen mikrofraktographischen Verformungsrichtung bestimmt werden.

Interlaminare Schwingbrüche (an gekerbten Biegeproben) weisen spezifische, auf den sphärolithischen Gefügeaufbau der semikristallinen Matrix zurückzuführende, Bruchmorphologien auf. Es ist eine, an den Fasern beginnende, „Auflösung”︁ der PEEK‐Matrix in Einzelfäden, die wahrscheinlich durch eine Delamination in amorphe Fibrillen und eine Auflösung der kristallinen Lamellen zustande kommt, festzustellen. Grundsätzlich weisen CFK Materialien mit thermoplastischer Matrix völlig andere Bruchmorphologien auf als solche mit duromeren Epoxidharzmatrices. Dies ist verständlich, wenn man bedenkt, daß die Bruchdehnung von PEEK eine Größenordung größer ist als jene von EP‐Harz.
Scratch‐Tests zur Untersuchung der Abrasionsbeständigkeit
Authors: Patzelt B. , Hemmann U.
Published: May 2005

An Chromgußeisen, mit 4 unterschiedlichen Temperaturregimen wärmebehandelt, zwei Manganhartstählen, einem C 45 und einem C 15, wurden Scratch‐Tests unter furchender Beanspruchung durchgeführt. Dabei erfolgte ein Ritzen mit einem kegelförmigen Probekörper bei Variation der Normalkraft. Die erzeugten Ritze wurden nach dem Versuch mit Hilfe eines Laserabtastgerätes ausgemessen, die deformierten Flächen sowie die Ritzenergiedichten bestimmt. Aus den Ergebnissen der Ritzversuche können Möglichkeiten zur abrasiven Verschleißbeständigkeit und zum Einsatzgebiet von Bauteilen aus den geprüften Werkstoffen abgeleitet werden.
Lasergaslegieren – ein Verfahren zur Erzeugung verschleißfester Randschichten auf Titanwerkstoffen
Authors: Bonß S. , Brenner B. , Scheibe H.‐J. , Ziegele H.
Published: May 2005

Titanlegierungen besitzen hohe spezifische Festigkeiten, sind korrosionsbeständig und haben eine gute Biokompatibilität. Daraus resultiert ihr Einsatz im Bereich Luft‐ und Raumfahrt, der chemischen Industrie, der Medizin und zunehmend auch im Straßenfahrzeugbau. Ein Nachteil der Titanlegierungen ist ihr geringer Widerstand gegen Abrasiv‐ und Gleitverschleiß. Durch Erhöhung der Verschleißfestigkeit können den Titanlegierungen neue Anwendungsfelder erschlossen werden. Mit der im Fraunhofer IWS Dresden entwickelten Methode des Lasergaslegierens gelingt es, sehr tragfähige und verschleißfeste Randschichten auf Titanlegierungen in einem technologisch sicheren Prozeß zu erzeugen. Durch eine zusätzlich mit dem Laser‐Arc‐Verfahren aufgebrachte harte amorphe Kohlenstoffschicht lassen sich die Gleitverschleißeigenschaften noch einmal erheblich verbessern. Nach einer kurzen Vorstellungen der neuen Methoden des Lasergaslegierens werden die enormen Verbesserungen des Verschleßverhaltens anhand von Ergebnissen verschiedener Verschleißversuche nachgewiesen.
Hochproduktive PVD‐Großflächenbeschichtung von Aluminiumbändern zum Zwecke der Reflexionserhöhung
Authors: Reinhold E. , Melde C. , Strümpfel J. , Gänz K.
Published: May 2005

Das wachsende Umwelt‐ und Energiebewußtsein unserer Gesell‐schaft stellt bestimmte Industriezweige vor besondere Aufgaben. So steht die Beleuchtungsindustrie in der Pflicht, über die Verbesserung des Beleuchtungswirkungsgrades durch Einsatz von Reflektormaterialien höchster Reflektivität Wege der Energieersparnis zu eröffnen.

Mit Hilfe ökologisch vorteilhafter PVD‐Verfahren können reflexionserhöhende Schichtsysteme großflächig auf Aluminiumbänder für die Beleuchtungsindustrie aufgetragen werden. Auf diese Weise werden bis zu 15 % höhere Beleuchtungswirkungsgrade erzielt.

Die von Ardenne Anlagentechnik GmbH entwickelte eine hochproduktive Großflächenbeschichtungstechnologie und baute hierfür im Auftrag der Alanod Aluminiumveredlung GmbH eine kontinuierlich produzierende Beschichtungsanlage, die Metallbänder bis zu einer Breite von 1250 mm mit einem Schichtsystem versieht, das den Reflexionsgrad auf 96 % erhöht.

Die nachgewiesene Produktionsreife der Großflächen‐PVD‐Beschichtungstechnologie für optische Beschichtungsaufgaben fordert zur Eröffnung weiterer industrieller Anwendungsfelder heraus.
Aktivierungsenergie der wiederholten Karbidausscheidung in Stählen
Authors: Hildebrand H. , Heinzel G. , Heger D.
Published: May 2005

Dispersionsgefüge in Stählen werden aus dem martensitischen Zustand durch wiederholte Ausscheidung und Vergröberung von M3C‐Partikeln (oder M6C) gebildet. Das Ausscheidungsstadium umfaßt gemäß r ∝ t1/2 (r – Partikelradius, t – Zeit) die Keimbildung und das Wachstum einer Partikelgeneration und geht schon nach wenigen Minuten in die dominierende Vergröberung gemäß der OSTWALD‐Reifung r ∝ t1/3 über. Die Vergröberung zuerst ausgeschiedener Partikelgenerationen überlagert sich mit der nachfolgenden Ausscheidung und Vergröberung weiterer Partikelgenerationen. Sie können mit Hilfe der Koerzitivfeldstärke, der unteren Streckgrenze, mit Gefügemittelwertsdaten rasterelektronenmikroskopischer Abbildungen des Dispersionsgefüges und durch Kleinlasthärteprüfungen nachgewiesen werden. Die auftretenden Ausscheidungsmaxima gestatten die Abschätzung der Aktivierungsenergie für die effektive Volumendiffusion in der α – Fe – Phase. Durch Einbeziehung der Elektronegativitätswerte (hier nach L. PAULING) wird die vorliegende kovalente Bindung der M3C‐Partikel berücksichtigt. Durch sie ergibt sich eine Zuordnung der abgeschätzten Aktivierungsenergie zu dem Hauptlegierungselement und darüber hinaus zur Gesamtzusammensetzung eines Stahles.
Entwicklung der Mikrostruktur in Alloy 800HT unter Hochtemperaturkriechbeanspruchung
Authors: Nicolini G. , Martin U. , El‐Magd E. , Oettel H.
Published: May 2005

In der vorliegenden Arbeit wird die Entwicklung der Mikrostruktur, gekennzeichnet durch die Merkmale Versetzungsdichte, Partikelvolumenanteil und ‐abstand bei Hochtemperaturkriechbeanspruchung, der Eisenbasislegierung Incoloy Alloy 800HT (X10 NiCrAlTi 32 20 HT) untersucht. Zur Beschreibung der Evolution der Mikrostruktur in Abhängigkeit von Temperatur und Kriechverformung werden isotherme Wärmebehandlungen und Kriechexperimente bei 800° / 800° und 70MPa sowie 900° / 900° und 45MPa durchgeführt. Die Untersuchung der sich durch die Beanspruchungen einstellenden Gefügeänderugen erfolgt mit Methoden der Elektronenmikroskopie, vornehmlich im Transmissionselektronenmikroskop. Eine detaillierte Auswertung der sich ergebenden Versetzungsdichten und Größen der ausgeschiedenen Karbide wird mit den Zeitstandkenngrößen in Beziehung gesetzt, analysiert und diskutiert.
Electrochemical evaluation of thin films and coatings deposited with ion beam assisted deposition (IBAD) using scanning electrochemical microelectrode
Authors: Vera E. , Stippich F. , Meinert K. , Wolf G. K.
Published: May 2005

In this contribution the application of a modern technique‐scanning electrochemical microelectrode – for the evaluation of thin films which were deposited (IBAD) is illustrated. New tendencies in the development of thin films with anticorrosive purpose lead to the development of multi‐layer systems acting similar to those commonly, applied in the industry, however, being much thinner. Imperfections and defects are commonly introduced in the coating during the deposition process, and these affect the anticorrosive properties of the film. In order to make a local electrochemical study of these multi‐layer systems we have developed equipment in order to perform electrochemical surface‐scans (potential and current density) on the basis of a microelectrode with a good lateral resolution (approximately 20 μm). Al‐Al2O3 multilayers on steel substrates with differently designed interfaces were investigated to show the variation of uniform and local electrochemical information obtained in dependence on the coating deposition parameters.
Ventilwerkstoffe für Verbrennungsmotoren
Authors: Müller R. , Weintz R.
Published: May 2005

Nach einem Überblick über Produktionszahlen, allgemeine Anforderungen und Eigenschaften von Ventilen für Verbrennungsmotoren, wird in einem Rückblick die Werkstoffentwicklung für die Ventilstähle von den ersten Anfängen bis zum heutigen Stand aufgezeigt. Schwerpunktmäßig wird die Gruppe der Chrom‐Mangan‐Stickstoff‐Stähle behandelt. Daneben werden die Ventilwerkstoffe geordnet nach schweren und leichten und innerhalb dieser Gruppen nach Legierungsmerkmalen beschrieben. Es wird über die vielfältigen Werkstoffanstrengungen am Ventil informiert, die mit wenigen genormten Werkstoffgüten und speziellen Fertigungsverfahren problemlos mit niedrigsten Fehlerraten beherrscht werden. Der Weg des Werkstoffes vom Halbzeug bis zum fertigen Ventil wird in allen Schritten verfolgt. Die in den letzten Dekaden forcierte Motorenentwicklung führte zu verschärften Betriebsbedingungen auch für die Ventile, die mit einer kontinuierlichen Weiterentwicklung bestehender Werkstoffgüten und Verbesserungen der Gestaltsfestigkeit der Ventile aufgefangen wurden. In diesem Zusammenhang werden spezielle Lösungen zur Festigkeitssteigerung aller Ventilwerkstoffe bis in den Bereich von über 1100 MPa erläutert, die nach bekannten metallkundlichen Gesetzen ermöglicht wurden. Als wesentliches Prinzip werden ortsabhängig, besonders an der Oberfläche, erhöhte Festigkeits‐ und Verschleißeigenschaften zur Optimierung der Gestalts‐ und Betriebsfestigkeit eingesetzt. Über Entwicklungen zur Technologie der Hohlventile und von erweiterten Lösungen beim Auftragschweißen von Ventilsitzen im Zusammenhang mit Eigenspannungen wird ausführlich berichtet. Einer kurzen allgemeinen Betrachtung zum Legierungsaufwand der wichtigsten Ventilwerkstoffe folgt ein Kapitel über Titan, Intermetallische Verbindungen und Keramik, die möglicherweise als zukünftige leichte Ventilwerkstoffe Verwendung finden können.
Hard coatings on light‐metal components under mechanical surface loading
Authors: Fuchs O. , Friedrich C. , Berg G. , Broszeit E. , Leyland A. , Matthews A.
Published: May 2005

In this work the behaviour of hard coated light‐metal components was investigated when they are mechanically loaded. Three lightmetal alloys, Ti‐6Al‐4V, AlSi7Mg and AlMgSi0.5 and 100Cr6 steel (as a reference material) were coated by two different physical vapour deposition processes: radio frequency magnetron sputtering and electron beam evaporation. The coating materials utilised were CrN and TiN. Standard test methods with different loading conditions were used to evaluate the substrate/coating‐combinations: the hardness test (applying a static normal load), the scratch test (applying a combination of a static normal and a static tangential force) and the impact test (applying a dynamic normal load).

It was observed that the load support of coated materials depends on the loading conditions. The coated aluminium alloys showed poor load support under all loading test conditions but produced a higher surface hardness than uncoated steel. Coated Ti‐6Al‐4V showed very good load support properties, similar to coated steel. All coated light‐metal substrates demonstrated significant improvement in load support behaviour with an increase in coating thickness.

The results of the scratch test, which is commonly used to asses adhesion properties of thin coatings, showed an immediate indenter‐breakthrough on the aluminium alloy substrates, but causing no coating delamination. Due to this behaviour, the scratch test is not suitable to evaluate adhesion properties on coated soft light‐metals. Yet the impact test allowed assessment of coating delamination on the aluminium alloys, proving its usefulness for adhesion measurement even on soft substrates.

The study indicates that substitution of steel with coated lightmetal alloys is a viable proposition for certain applications.
Vermessung von 3dimensionalen Eigenspannungszuständen an festgewalzten hochfesten Stäben
Authors: Müller E.
Published: May 2005

Bei der Bestimmung der 3dimensionalen Eigenspannungszustände zeigt sich, daß die einzelnen Eigenspannungsverläufe miteinander korrespondieren. Die Druckeigenspannungsbereich reicht beim Festwalzen bis in eine Tiefe von 2 mm, wobei sich ein Druckeigenspannungsplateau im Bereich ab 0,5 mm Tiefe für mehre Zehntel Millimeter ausbildet. Bei F=27 kN sind die Effekte entsprechend ausgeprägter. Im Vergleich zum Festwalzen ist beim Kugelstrahlen die Druckeigenspannung im Bereich bis 0.5 mm Tiefe zu finden.
Polyether/polyhydroxy gel network – a new Thermotropic Material
Authors: Seeboth A. , Holzbauer H.‐R. , Lange R.
Published: May 2005

The aim of this study has been to examine the possibility of preparing thermotropic aqueous gel networks that exhibit multiphase transitions in connection with changing the transparency of the system depending on temperature variation. As polymers polyvinyl alcohol (PVA) and ethoxylated polydimethylsiloxane (ePS) were chosen. Thermotropic materials can be used as intelligent shadegivers.
The mechanical and physical properties of Compacted Graphite Iron
Authors: Shao S. , Dawson Steve , Lampic M.
Published: May 2005

The mechanical and physical properties of compacted graphite iron (CGI) have been studied. While it is known that CGI provides at least 70% higher tensile strength, 35% higher elastic modulus and 80% higher fatigue limits than conventional grey cast iron, the objective of this paper was to determine how the properties change with varying nodularity (graphite shape) and pearlite content. Tensile properties, hardness, damping capacity and thermal conductivity were determined over the range 0–90% nodularity and 25–100% pearlite. Compressive properties, wear resistance and fatigue behaviour of CGI are also reported upon. Of greatest importance is the influence of patches of flake graphite in predominantly CGI microstructures. As soon as flake patches appear, which can occur with a loss of as little as 0.001% active magnesium, the mechanical properties of CGI abruptly decrease by 25–40%. Proper foundry control technology and quality procedures are therefore required to ensure the reliable production of this improved material.
Lokale Schichterzeugung beim HF‐Magnetronsputtern
Authors: Berg G. , Friedrich Chr. , Senf J. , Broszeit E. , Kloos K.‐H.
Published: May 2005

Der folgende Artikel zeigt den Stand der Beschichtungstechnologie „HF‐Magnetronsputtern”︁ für tribologische Anwendungen auf. Dabei wird zunächst dargestellt welche Parameter das Beschichtungsergebnis bestimmen und wie eine systematische Schichtentwicklung für tribologische Anwendungen aussehen kann. Im Einzelnen werden exemplarisch Einblicke in verschiedene Einflußparameter gegeben. Die makrogeometrischen Randbedingungen der Beschichtungsanlagen und Beschichtungsobjekte spielen dabei eine ebenso wichtige Rolle wie die Kinematik der Objekte mit dreidimensionalen, zu beschichtenden Funktionsflächen. Zusätzlich ist der Substratwerkstoff (Beschichtungsobjekt) wie auch letztlich das Beanspruchungsverhalten des zu beschichteten körpers im tribologischen Einsatz von zentraler Bedeutung. Die vorliegenden Meßergebnisse sind der angegebenen Publikation entnommen.
Untersuchung von IBBD‐Aluminium‐Schichten mittels elektrochemischer Rauschanalyse
Authors: Burkert A. , Heyn A. , Göllner J. , Garz I. , Vera E. , Wolf G. K.
Published: May 2005

Die Qualität von extrem dünnen Oberflächenbeschichtungen für den Korrosions‐ und Verschleißschutz wird stark durch das Vorhandensein von Poren und Schichtdefekten (Hohlräume, Mikrorisse, Flimmer etc.)beeinflußt, die infolge des Herstellungsprozesses auftreten können. Diese Stellen sind maßgeblich verantwortlich für eine mechanische oder chemische Degradation der Beschichtung bei Kontakt mit der jeweiligen Umgebung. Um den erforderlichen Schutz durch die Beschichtung zu gewährleisten wird der Beschichtungsvorgang durch eine Minimierung von Poren und Fehlstellen optimiert. dazu ist eine Untersuchungsmethode erforderlich, die die Auflösung des Substrates an diesen Fehlstellen im frühesten Stadium anzeigt, um auch große Probenserien zur statistischen Absicherung mit vertretbarem Zeitaufwand zu untersuchen. An IBAD‐Aluminium‐schichten (ion beam assisted deposition) auf unlegiertem Stahl (Ck45) wurden mit Hilfe der elektrochemischen Rauschanalyse erfolgreich Untersuchungen zur Optimierung von Beschichtungsparametern duchgeführt.
Mikrotribologie von PVD‐Schichten
Authors: Sander H. , Petersohn D.
Published: May 2005

Transparenz des Tribovorgangs durch sensorische und audio‐visuelle Prozeßerfassung. Durch multimediale Erfassung des Reibungsvorgangs werden die elementaren Kontaktprozesse transparent, so daß Schädigungsursachen erkannt werden können. Dabei werden neben den üblichen tribologischen Meßdaten audiovisuelle Informationen zeitsynchron erfaßt. Durch Einsatz integrierter Dünnschichtsensoren unmittelbar im tribologischen Kontaktsystem werden Temperatur oder Druck während des Reibungsprozesses mit hoher Ortsauflösung kontinuierlich ermittelt. Die Schädigungsmechanismen werden systematisch analysiert und ermöglichen Einflußmaßnahmen zur Schichtoptimierung, um ein vorzeitiges Versagen eines tribologischen Systems auszuschließen.
Microbore high performance liquid chromatography–ion spray mass spectrometry for the determination of peptides
Authors: Lee Edgar D. , Henion Jack D. , Covey Thomas R.
Published: May 2005

Microbore high performance liquid chromatography‐ion spray mass spectrometry is demonstrated for the determination of peptides. The ion spray mass spectra of peptides contained primarily only (M + nH)n+ ions (n is the degree of protonation). The linearity for a dilution series of leucine enkephalin was determined to be 4.9 orders of magnitude (r = 0.990), from 29 fmol to 90 pmol injected, and the smallest discernible signal (S/N of 3/1) was 65 amol. The tandem mass spectrometry daughter‐ion mass spectrum of the multiply‐charged molecular ion of dynorphin 1–9 exhibited daughter ions consistent with the sequence of the peptide. The micro‐LC gradient elution separation for a tryptic digest of recombinant bovine somatotropin was acquired. The mass spectra obtained from the components in the tryptic digest were consistent with previously identified peptides. The mass spectrum of the tryptic fragment ISLLLIQSWLGPLQFLSR (MW 2083) contained multiply‐charged ions that made it possible to detect this fragment even though its molecular weight is beyond the mass range of the mass spectrometer.
Retention of catechols in capillary electrophoresis with micellar and mixed micellar solutions
Authors: Wallingford Ross A. , Curry Paul D. , Ewing Andrew G.
Published: May 2005

Zone electrophoresis in capillaries filled with micellar and mixed micellar solutions was examined for the separation of borate‐complexed catechols. The mechanism for solute velocity was shown to involve both retention by hydrophobic interaction with the micelles and electrophoretic mobility. Mixed micellar systems involving SDS and SOS surfactants were shown to allow greater selectivity and increased separation efficiency.
Multidimensional open‐tubular column supercritical fluid chromatography using a flow‐switching interface
Authors: Davies Ilona L. , Xu Bingjiu , Markides Karin E. , Bartle Keith D. , Lee Milton L.
Published: May 2005

A multidimensional system based on capillary supercritical fluid chromatography (SFC) was constructed that utilizes a simple flow‐switching interface between two open‐tubular 50‐μm i.d. columns. A novel solvent‐venting injection technique was incorporated in the system that enables single or multiple 0.5‐μL volumes to be injected into an uncoated, yet deactivated, length of capillary precolumn without flooding of the analytical column. The effectiveness of multidimensional capillary SFC (SFC‐SFC) for complex mixtures is demonstrated by the analysis of polycyclic aromatic hydrocarbons (PAH) in a coal tar extract, the trace determination of a methylcarbamate pesticide and its metabolites in a bird extract, and a group‐type separation of hydrocarbons in a high‐boiling petroleum distillate. These examples show for the first time that capillary SFC‐SFC is a complementary alternative to other multidimensional chromatographic methods involving liquid or gaseous mobile phases.
Analysis for polychlorinated biphenyls by dual capillary column gas chromatography
Authors: Scott B. F. , Onuska F. I.
Published: May 2005

A dual‐column, gas chromatographic, congener‐specific methodology was developed that allows determination of polychlorinated biphenyl (PCB) concentrations in water and sediment samples. The linearity of the detector responses was checked over a range of 1000 at the sub‐ppb range of total PCB in the dual‐column mode, with less than 10−12 g of each congener impinging on the detector. The chromatographic method was checked to ensure that there was minimal interference by the organochlorines with the PCB analysis and vice versa. PCB standards were analyzed, and they yielded values within 10% of the expected amounts. Extracts from sediments were analyzed, and the organochlorine pesticide (OC) values agreed with values obtained using standard methods. The PCB values obtained from the standard and presented methods agreed within a factor of two. Use of the method provides results that are comparable to current methodology, and it requires less time.
Separation of steroid isomers using a liquid crystalline polysiloxane stationary phase in capillary supercritical fluid chromatography
Authors: Chang Huey‐Ching , Markides Karin E. , Bradshaw Jerald S. , Lee Milton L.
Published: May 2005

A liquid crystalline biphenylcarboxylate ester polysiloxane stationary phase was used to study the effect of solute structure on retention for the separation of isomeric steroids in capillary supercritical fluid chromatography. It was determined that theretention mechanism is related to solute molecular shape rather than to properties such as volatility or polarity. The elution order of isomeric androstanes and estrogens could be correlated with the planarity of molecules: more‐planar molecules were retained longer on the column. The resolution of steroid isomers was improved significantly using the liquid crystalline stationary phase when compared with results obtained using other stationary phases.
New cyanophenyl‐containing polysiloxane stationary phases for capillary column gas chromatography
Authors: Juvancz Zoltan , Pulsipher Michael A. , Tarbet Bryon J. , Schirmer Michelle M. , Johnson R. Scott , Markides Karin E. , Bradshaw Jerald S. , Lee Milton L.
Published: May 2005

New p‐cyanophenylethylpolysiloxane and p‐cyanophenylpolysiloxane stationary phases exhibiting high efficiency, cross‐Iinkability, and thermal stability up to 300°C are reported in this paper. These stationary phases possess a unique blend of polar and polarizable character that has resulted in excellent selectivities for compounds having delocalized nelectrons. Another advantage of the p‐cyanophenyl phases is their demonstrated relatively low elution temperatures for polar materials compared with the typical cyanopropyl polysiloxane phases.
Capillary zone electrophoresis–mass spectrometry with electrospray ionization of peptides and proteins
Authors: Loo Joseph A. , Jones Harlan K. , Udseth Harold R. , Smith Richard D.
Published: May 2005

Capillary zone electrophoresis (CZE) coupled with an on‐line mass spectrometric (MS) detection system by an atmospheric pressure electrospray ionization (ESI) interface has been used successfully for Separations of peptide and protein mixtures. For CZE‐MS, ESI produces multiply charged molecular ions and thus allows mas spectrometers with a limited mass‐to‐charge range to analyze proteins having molecular weights greater than 100,000. Various pH buffer systems have been investigated, including buffer systems in which pH > pI (isoelectric point of analytes) and pH « pI are designed to reduce protein adsorption onto silica capillary surfaces and thus improve separation efficiencies. More than 125,000 theoretical plates have been obtained from a CZE‐MS separation of less than 1 pmol per component of leucine enkephalin and horse heart myoglobin. CZE‐MS of other large peptides and proteins are demonstrated.
Sample loss and its control with internal‐loop injection valves in supercritical fluid chromatography
Authors: Chester T. L. , Innis D. P.
Published: May 2005

Large losses of solute can occur with internal‐loop injection valves, especially if the assignments of the injection and waste ports are reversed and a highly volatile diluent is used. However, good performance can be obtained even with the port assignments reversed and with a volatile diluent if a flow restrictor is attached to the waste port.
Multidimensional chromatography using on–line coupled microcolumn size exclusion chromatography–capillary gas chromatography–mass spectrometry for determination of polymer additives
Authors: Cortes Hernan J. , Bell Bruce M. , Pfeiffer Curt D. , Graham Jeffrey D.
Published: May 2005

A multidimensional system consisting of microcolumn size exclusion chromatography coupled online with capillary gas chromatography and utilizing mass spectrometry for the rapid identification of polymer additives is described. Applicability of the system was demonstrated for a broad spectrum of commercial polymer products and a wide variety of additives including antioxidants, plasticizers, lubricants, flame retardants, waxes, and UV stabilizers. Advantages of this system include reduced sample preparation time, potential for automation, and minimization of the extraction losses inherent in conventional sample preparation techniques.
Supercritical fluid extraction of chlorpyrifos methyl from wheat at part per billion levels
Authors: Campbell Robert M. , Meunier David M. , Cortes Heman J.
Published: May 2005

The use of supercritical fluid extraction (SFE) to recover pesticides from environmental matrices was investigated using chlorpyrifos methyl spiked on a wheat kernel substrate. Volume‐based extraction recovery profiles were generated to determine the pressure, temperature, and fluid composition that yielded the maximum analyte recovery and minimum extraction time. On‐line coupled microcolumn liquid chromatography‐gas chromatography (LC‐GC) with electron capture detection was used to effect cleanup of the extracts and to determine the recoveries of chlorpyrifos methyl.

With unmodified CO2 as the extraction solvent, we obtained only 65% recovery of chlorpyrifos methyl spiked at the 50 parts per billion (ppb) level on the wheat. The use of CO2 mixed with 2% methanol, however, yielded recoveries averaging 97.8%, with a relative standard deviation of 4.0%. Extraction times were 10 min or less for a 1‐g sample size. The use of PEEK seqling material in the extraction vessels and in the ferrules of the finger‐tight fittings in the SFE system permitted rapid cycling between multiple samples and reliable, leak‐free operation. This approach could significantly shorten the sample preparation time associated with pesticide residue analysis.
Group separation of crude oil by supercritical fluid chromatography using packed narrow bore columns, column switching, and backflushing
Authors: Skaar H. , Norli H. R. , Lundanes E. , Greibrokk T.
Published: May 2005

Determination of saturates, aromatics, and resins and asphaltenes in crude oil has been made using supercritical fluid chromatography (SFC) with a carbon dioxide mobile phase and flame ionization detection. The separation system consists of three columns. The first column separates resins and asphaltenes from saturates plus aromatics, and the other two columns separate the saturates from the aromatics. The saturates are eluted directly through the three columns, the aromatics are backflushed from the last two columns in the sequence, and the resins and asphaltenes are backflushed from the first column. The properties of three different systems — which respectively employ packed 0.25‐mm‐i.d. fused silica, 0.7‐mm‐i.d. glass‐lined steel, and 1‐mm‐i.d. steel columns — have been investigated. Column diameters of 0.5–0.7 mm are recommended to obtain the best flow rate compatibility with the detector. Good class separations were obtained on all three systems, but, due to practical considerations, the more rugged all‐steel columns were found to be more convenient. In order to improve column reproducibility and stability and increase column lifetime as compared to earlier SFC group separations, changes were made to the column packings. The current system consists of two cyano columns and one silver‐loaded cation exchanger. With standard mixtures and crude oils, close to 100% recoveries were obtained. The analysis time was approximately 15 min. Weight percents of aliphatics and aromatics were determined with response factors of 1.0 and those of the asphaltenes and resins with response factors of 0.7–0.8.
Development of a model for predicting retention times in solvent‐gradient micellar electrokinetic capillary chromatography
Authors: Powell A. Craig , Sepaniak Michael J.
Published: May 2005

Instrumentation and a computational method are described that are capable of predicting retention times of solutes separated by solvent‐gradient micellar electrokinetic capillary chromatography (MECC). Theoretical predictions are based on capacity factor, electroosmotic flow rate, and micellar flow rate data obtained by the separation (under isocratic conditions) of a test mixture of fluorescently labeled alkylamines with the use of differing concentrations of organic modifier in the mobile phase. Separations are performed using continuous concave, linear, and convex gradients, and the resultant solute retention times are shown to correlate reasonably well with values obtained from the theoretical model. Thus, a computational method for optimization of solvent‐gradient MECC is made possible.
A comparison of tryptic digests of bovine and equine cytochrome C by comprehensive reversed‐phase HPLC–CE
Authors: Bushey Michelle M. , Jorgenson James W.
Published: May 2005

Comprehensive two‐dimensional reversed‐phase HPLC–capillary electrophoresis (RP HPLC–CE) was used to compare the tryptic digest fingerprints of horse heart cytochrome C and bovine heart cytochrome C. The peptide fragments were labeled with fluorescamine and detected with a fluorescence detector. The two‐dimensional separation system proved to be reproducible enough to identify some species differences in the tryptic digest fingerprints. Improvements in instrumentation and daily procedures yielding faster analysis times and better reproducibility compared to a previous system are described. Improvements in software yielding gray‐scale images of the two‐dimensional data are described. Identification of selected tryptic fragments was achieved.
Rapid separation of proteins and peptides by reversed‐phase microcolumn liquid chromatography
Authors: Nagae Norikazu , Itoh Hiroko , Nimura Noriyuki , Kinoshita Toshio , Takeuchi Toyohide
Published: May 2005

Proteins and peptides were separated in the reversed‐phase mode on microcolumns packed with nonporous octadecyl‐group bonded silica gel with an average particle diameter of 4.5 or 20 μm. Separation columns were prepared from glass‐lined stainless steel tubing of 39 or 56‐mm × 0.5‐mm i.d. An artificial mixture of several proteins could be separated within 1 min by split‐flow gradient elution. The system was applied to the separation of a triptic digest of mouse amyloid A. On‐column sample enrichment allowed direct injection of 2‐5 μL of sample solution, leading to improved detectability. The limits of detection were ≤ 1 μg mL−1.
On‐line supercritical fluid extraction/chromatography system for trace analysis of pesticides in soybean oil and rendered fats
Authors: Murugaverl Balasingam , Voorhees Kent J.
Published: May 2005

A method for trace analysis incorporating solid phase extraction (extraction and clean‐up) with supercritical fluid chromatography (SFC) for analytes in fats and oils has been developed. Direct coupling (on‐line) of supercritical fluid solid phase extraction with supercritical fluid chromatography (SESPE/SFC) allows analysis of solutes in fats and oils for which on‐line SFE/SFC is unsuitable. The main feature of SFSPE/SFC is that extraction and clean‐up are accomplished in one step using unmodified supercritical carbon dioxide. Extraction/clean‐up is monitored by a photodiode array detector which allows fractionation. The operational set‐up and potential usefulness of the SFSPE/SFC system and applications for pesticide analysis of lipid sample matrices are described.
Capillary supercritical fluid chromatography and microwave‐induced plasma detection of cyclic boronate esters of hydroxy compounds
Authors: Luffer Debra R. , Novotny Milos V.
Published: May 2005

A Surfatron microwave‐induced plasma was used for selective detection after capillary supercritical fluid chromatography of various biologically important compounds. Cyclic boronates were formed by esterifying catechols, monosaccharides, and cortisone, with an alkyl‐ or aryl‐substituted boronic acid. An available spectroscopic system was modified so that the third‐order boron emission line at 749.4 nm was utilized. Sensitivity for boron in catechol boronate was 25 pg s−1, and the molar selectivity was >5,000 for both carbon dioxide and nitrous oxide mobile phase. Some comparisons were made with flame ionization detection.
Formic acid modified carbon dioxide as a mobile phase in capillary supercritical fluid chromatography
Authors: Crow Jeffrey A. , Foley Joe P.
Published: May 2005

A small percentage (0.3% w/w) of formic acid was added to supercritical carbon dioxide to increase mobile phase polarity and improve separation of polar solutes on three different commercially available capillary columns. Formic acid reduced retention and altered selectivity for several polar compounds. Thermodynamic studies revealed that the enthalpy of solvation was as much as 27 kcal mol−1 more negative when formic acid was added due to increased solute‐solvent interactions. Entropy measurements show that formic acid modified mobile phase is more ordered than a pure carbon dioxide mobile phase, apparently as a result of modifier clustering around polar solutes. Van't Hoff plots for some very polar solutes showed a region of retrograde behavior at low temperatures and pressures, indicating an increase in modifier clustering. Comparisons between pure and modified mobile phases were also made by examining practical separations obtained with each, revealing differences in retention, selectivity and peak shape.
Crown ether substituted polysiloxanes as stationary phases for open tubular column gas chromatography
Authors: Ge Jilong , Fu Ruonong , Zhang Aiqin , Zhu Rongping , Deng Jinghui , Gu Junling , Zhu Jiya , Huang Zaifu , Zhang Bin
Published: May 2005

Two new crown ether substituted polysiloxanes, 4‐propylbenzo‐15‐crown‐5polysiloxane(PSO‐B‐15C5) and propyloxydibenzo‐14‐crown‐4polysiloxane (PSO‐DB‐14C4), were prepared and used as stationary phases coated on fused‐silica open tubular columns. The chromatographic characteristics, including column efficiency, polarity, phase transition temperature, allowable operating temperature range and selectivity, were studied. A unique selectivity of these columns was found for the separation of all six dimethylphenol isomers. The separation mechanism is discussed.
Copper wire amperometric detector for capillary electrophoresis
Authors: Engstrom‐Silverman Charlotte E. , Ewing Andrew G.
Published: May 2005

The use of a copper wire amperometric detector for capillary electrophoresis is reported. Detection is accomplished by use of a porous glass joint, which allows amperometric detection at a copper wire electrode inserted in the end of the capillary. An anodic current is produced by a change in the copper oxide film solubility, resulting from complexation of copper ions with certain analytes at the electrode surface. This copper/copper oxide electrode has been used to detect nonelectroactive native amino acids and dipeptides. Subfemtomole detection limits in picoliter injection volumes have been obtained without solute derivatization. In addition, simultaneous analysis of nonelectroactive amino acids and electroactive catecholamines has been demonstrated.
Optimization of internal valve injection in open tubular column supercritical fluid chromatography
Authors: Tuominen Jari P. , Markides Karin E. , Lee Milton L.
Published: May 2005

As in the case of all chromatographic methods, the ideal sample introduction method for supercritical fluid chromatography (SFC) would provide a narrow and sharp solvent peak (or no solvent peak), quantitative transfer of the sample into the column, and high reproducibility. Elimination of the solvent before the solutes enter the column would be preferred; however, this practice is always associated with the risk of partial solute elimination. In open tubular column SFC, samples are normally introduced using a smallvolume internal loop valve. These valves can be operated such that none, some, or all of the solvent is eliminated. Several approaches were quantitatively evaluted, and optimized conditions were determined. Particular attention was given to trace analysis. The minimum detectable levels (S/N >4) achievable using a flame ionization detector were determined to be approximately 30 ng (150 ppm) for split injection, 4 ng (20 ppm) for delayed split injection, and 1 ng (5 ppm) for direct injection.
Free solution capillary electrophoresis of basic proteins in uncoated fused silica capillary tubing
Authors: Bullock John A. , Yuan Lung‐Chi
Published: May 2005

A series of buffer systems encompassing the pH range from 3.5 to 9.0 have been developed for free solution capillary electrophoretic (CE) analysis of basic proteins in uncoated fused silica capillaries. Separations of model proteins possessing isolectric points between 9.1–11.0 have been achieved with efficiencies in the range of 95,000–690,000 theoretical plates. In each case the modifier 1,3‐diaminopropane is incorporated in the operating buffers at concentrations of 30–60 mM along with moderate levels of alkali metal salts to suppress protein‐capillary wall interactions normally encountered with basic proteins. The combination of these buffer additives allows the analyses to be conducted at pHs below the protein isoelectric points. No special capillary pretreatment is required. The advantages of this approach to analyzing basic proteins include its simplicity, the ability to perform the analyses in the pH range where proteins are stable and the greater flexibility available in the choice of pH as a means of affecting selectivity changes.
High pressure microbore packed column gas chromatography using common liquid chromatography stationary phases
Authors: Liu Yan , Yang Frank J.
Published: May 2005

High pressure gas chromatography (GC) using microbore packed columns was investigated. The microbore columns were packed with common microparticulate liquid chromatography (LC) stationary phases such as 5‐μm alky‐modified silicas and a 5‐μm macroporous polymer beads. The effects of the stationary and mobile phases, the mobile phase linear velocity and the column temperature were studied. The LC stationary phases were found to retain the expected selectivity and efficiency under high pressure GC conditions using either helium or CO2 gas as the mobile phase. The results indicate that microbore columns packed with common LC microparticulate stationary phases can be used in high pressure GC to provide rapid and efficient separation of volatile polar and nonpolar compounds. The results also suggest that the same instrument components such as the pump, injector, column, restrictor, and detector can be used for both high pressure GC and supercritical fluid chromatography (SFC) separations.
High temperature stable OH‐terminated poly(3,3,3‐trifluoropropylmethylsiloxane/silphenylene) copolymer stationary phases for capillary gas chromatography
Authors: Blum Wolfgang , Aichholz Reiner
Published: May 2005

The unexpectedly good thermal stability of OH‐terminated 3, 3, 3‐trifluoropropylmethylsiloxane/silarylene copolymers can be attributed to both the inclusion of bulky aromatic units in the polysiloxane backbone and to an autocrosslinking process taking place at temperatures above 370°C, being specific for trifluoropropyl substituted polysiloxanes. The crosslinking mechanism is discussed. Both new OH‐terminated phases, sildiphenylene/trifluoropropylmethyl and sildiphenylene ether/trifluoropropylmethyl‐polysiloxane (SA‐TF and SDPE‐TF) were characterized, and their performance at high temperatures (>400°C) is demonstrated.
Xenon as a mobile phase in supercritical fluid chromatography
Authors: Raynor Mark W. , Shilstone Gavin F. , Clifford Anthony A. , Bartle Keith D. , Cleary Michael , Cook Bernard W.
Published: May 2005

Supercritical xenon and CO2 are compared as solvents by means of solubilities (calculated by means of the Peng‐Robinson equation of state) and chromatographic behavior for some polynuclear aromatic hydrocarbons; reasons for the apparent superiority of xenon are discussed. The advantages of the use of xenon as a mobile phase in coupled supercritical fluid chromatography‐Fourier transform infrared spectrometry are evaluated from analyses of monomer and oligomer mixtures.