Impact of surface roughness on diffusion of confined fluids

Using event-driven molecular dynamics simulations, we quantify how the self diffusivity of confined hard-sphere fluids depends on the nature of the confining boundaries. We explore systems with featureless confining boundaries that treat particle-boundary collisions in different ways and also various types of physically (i.e., geometrically) rough boundaries. We show that, for moderately dense fluids, the ratio of the self diffusivity of a rough wall system to that of an appropriate smooth-wall reference system is a linear function of the reciprocal wall separation, with the slope depending on the nature of the roughness. We also discuss some simple practical ways to use this information to predict confined hard-sphere fluid behavior in different rough-wall systems

Certification of the Specific Micropore Volume and the Median Micropore Width of Two Microporous Reference Materials According to Draft-DIN 66135-4, BCR-704, BCR-705.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Maximizing the Educational Investment with a Required Personal and Professional Development Program for Business Majors

Higher-education institutions have been asked to go beyond the classroom and provide a better return on investment for students. With no line item in the budget, the Pamplin School of Business of the University of Portland linked both formation of the person and professional development by creating a mechanism of a credit-based program designed to marry theoretical, self-assessment, and experiential learning. Students engage in a series of holistic processes and professional development coursework challenging them to find and fulfill their potential while effectively exploring the core question of the university, “Who am I?” Between 2012 and 2016, 93 percent of business students acquired a vocational career position within six months of graduation, maximizing their education investment. This article is dedicated to the student workers who were instrumental in assisting in the development and implementation of the program. This program could not have been developed without them. These workers include Dani Remy Baker, Jasmine Dudley, Larissa Woods, Brooke Murphy, Cole Preece, and Amanda Stowe. The graphics in the paper are by Cole Preec

Strukturelle Umordnungen in Aluminiumlegierungen : ein komplementärer Ansatz aus der Perspektive von Leerstellen und Fremdatomen

Aluminiumlegierungen zeichnen sich vor allem durch die Kombination von guten Festigkeitseigenschaften mit einem geringen spezifischen Gewicht aus. Aus diesem Grund finden sie breite Verwendung in jenen Bereichen, die zwingend eine Leichtbauweise erfordern. Eine besondere Rolle, zum Beispiel im Flugzeugbau, spielen dabei aushärtbare Aluminiumlegierungen, deren Eigenschaften durch eine thermomechanische Behandlung eingestellt werden können. Obwohl diese Legierungssysteme, zu denen u.a. Al-Cu-Mg und Al-Mg-Si zählen, bereits seit fast hundert Jahren intensiv untersucht worden sind, besteht insbesondere hinsichtlich der Ausscheidungsfrühstadien noch erheblicher Klärungsbedarf. Für viele experimentelle Methoden der Festkörperphysik ist der in diesen Stadien verfügbare Kontrast aufgrund der geringen Größe der sich bildenden Strukturen zu gering. Um dieses Kontrastproblem zumindest teilweise zu umgehen, wurden in dieser Arbeit die Positronenannihilations- sowie Röntgenabsorptionsspektroskopie kombiniert zur Strukturaufklärung der Entmischungsfrühstadien in Aluminiumlegierungen eingesetzt. Wesentlich dafür ist die Sensitivität der beiden oben genannten Methoden für die atomare Umgebung jeweils eines essentiellen Bestandteils aller aushärtbaren Al-Legierungen, nämlich von Leerstellen bzw. von Fremdatomen. Am Beispiel von Al-Cu-Au wird dabei das Zusammenspiel beider experimenteller Methoden verdeutlicht. Die negativen Auswirkungen einer Au-Mikrolegierung auf das aushärtbare System Al-Cu können in diesem Zuge mikroskopisch durch eine Leerstellenbindung an homogen verteilte Goldatome erklärt werden. Für die technologisch hochrelevanten Systeme Al-Cu-Mg sowie Al-Mg-Si ergeben sich hinsichtlich ihrer jeweiligen Frühstadien ferner die folgenden wesentlichen Ergebnisse: Die Kaltaushärtung von Al-Cu-Mg verläuft aus Leerstellenperspektive in zwei klar trennbaren Stufen. Während die erste Stufe hauptsächlich durch Clusterwachstum gekennzeichnet ist, kommt es anschließend zur Einbettung von Leerstellen und evtl. zur Bildung von Guinier-Preston-Bagaryatski-Zonen. Aus Kupferperspektive agglomerieren Legierungsatome bereits vor Eintritt einer makroskopisch beobachtbaren Aushärtung. Die beobachtete Koordinationszahl von Cu legt es dabei nahe, dass eine flächen- bzw. zonenhafte Agglomeration ausgeschlossen werden kann. Für Al-Mg-Si Legierungen zeigt die Temperaturabhängigkeit der mittleren Positronenlebensdauer die Existenz von Positronenfallen mit relativ geringer Bindungsenergie, sogenannten flachen Fallen, an. Der Einfluss einer Kaltauslagerung auf das Warmauslagerungsverhalten dieses Systems wird deshalb auf das unterschiedliche Koordinationsverhalten von Clustern und Leerstellen in Abhängigkeit von der konkreten Legierungszusammensetzung zurückgeführt

Water vapour sorption and humidity - a survey on measuring methods and standards

Under environmental conditions water exists in all three classical states of matter: solid, liquid and gas. The water molecule is non-linear and therefore polar. In comparison with other liq-uids water has anomalous features; about 63 exceptional properties are recorded. This article starts with reviewing properties of water, typical occurrences and definitions such as relative and absolute humidity and moisture content. Water is present everywhere in nature and engineering; it may be helpful or harmful. The survey concerns both: atmospheric hygrometry and usual measuring methods of the mois-ture content of solids and liquids as well as water sorption. The determination of the atmos-pheric humidity is among the more difficult problems in metrology. In contrast, humidity de-termination of materials is simple; however the definition of the dry state is difficult. Because water is bound at and in solids and liquids in many different ways it turns out that the humidi-ty content of materials is difficult to define and to measure accurately. We provide a survey on the measuring methods, describe the most important ones and discuss advantages and ac-curacy. In the search for extraterrestrial water special remote measuring methods have been developed analysing the spectrum of electromagnetic radiation either of natural sources or produced by a probe and reflected. Spacious deposits have been detected photographically. In situ investigations are made using conventional methods. With regard to the problems of measurements, standardisation of measuring methods and procedures is required. There exist many institutions, which are engaged in investigating the use of water and standardising measuring methods. In tabular form, we give a survey on existing standards

The Li stance on precipitation in Al–Li-based alloys: an investigation by X-ray Raman spectroscopy

Decomposition and precipitation processes in a binary Al–Li alloy and a technical Al–Li–Cu–Mg alloy were investigated using differential scanning calorimetry and X-ray Raman spectroscopy (XRS). The formation of δ’ and T1 precipitates in the Al–Li and the T8 heat-treated Al–Li–Cu–Mg alloy, respectively, was confirmed using DSC. The XRS measurements complemented by simulated spectra allowed for probing specifically Li and its environment within the Al matrix. Based on linear combination fits of the XRS spectra, the relative contributions of δ′ and T1 precipitates were quantified. These results are in agreement with estimates of the relative amount of Li taking part in the precipitation process. Difficulties and limitations of the application of XRS to Al alloy systems are also discussed

An investigation on the evolution of granule formation by in-process sampling of a high shear granulator

Understanding the growth mechanisms in granulation process is an important topic, providing valuable insights and supports control strategies. Typically, observations in high shear granulators are made after stopping the process. In this work, an in-process sampling technique is described and applied to a high shear wet granulation process. Different samples can be collected over the cause of the high shear granulation process. This allowed observation of the evolution of granules during addition of water at a constant flowrate. For a typical pharmaceutical formulation, we observed that granules nucleate in the first 2 minutes after water addition starts and then grows in size and strength to an average size of 200–1200 μm at 12.5 minutes, corresponding to a sharp increase in torque. Longer water addition times lead to oversized granules and eventually a paste and highly fluctuating torque. Sampling was continued after stopping water addition which showed with time larger formed granules smoothen, whilst the smaller weaker ones disintegrate. The work shows the in-process sampling can facilitate the identification of the required binder quantity in high shear granulation

Elasticity and magnetocaloric effect in MnFe4_{4}Si3_{3}

The room temperature magnetocaloric material MnFe4Si3 was investigated with nuclear inelastic scattering (NIS) and resonant ultrasound spectroscopy (RUS) at different temperatures and applied magnetic fields in order to assess the influence of the magnetic transition and the magnetocaloric effect on lattice dynamics. The NIS data give access to phonons with energies above 3 meV, whereas RUS probes the elasticity of the material in the MHz frequency range and thus low-energy, ∼ neV, phonon modes. A significant influence of the magnetic transition on the lattice dynamics is observed only in the low-energy, long-wavelength limit. MnFe4Si3 and other compounds in the Mn5−xFexSi3 series were also investigated with vibrating sample magnetometry, resistivity measurements, and Mössbauer spectroscopy in order to study the magnetic transitions and to complement the results obtained on the lattice dynamic