Linear response function around a localized impurity in a superconductor

Imaging the effects of an impurity like Zn in high-Tc superconductors [Nature 61 (2000) 746] has rekindled interest in defect problems in the superconducting phase. This has prompted us here to re-examine the early work of March and Murray [Phys. Rev. 120 (1960) 830] on the linear response function in an initially translationally invariant Fermi gas. In particular, we present corresponding results for a superconductor at zero temperature, both in the s- and in the d-wave case, and mention their direct physical relevance in the case when the impurity potential is highly localized

Particle formation in a laser-heated aerosol reactor. Application to silicon and silicon nitride synthesis

Applied Science

Modellering van de oplosbaarheid van een zout in gemengde oplosmiddelen

Het doel van deze scriptie is een overzicht te geven van de methoden die een beschrijving geven van de oplosbaarheid van een zout in gemengde oplosmiddelen, of die daar eventueel voor gebruikt zouden kunnen worden. Het eerste deel behandelt de verschillende semi-empirische modellen voor de beschrijving van de oplosbaarheid van een zout in gemengde oplosmiddelen; het tweede deel beschrijft de verschillende modellen voor de activiteitscoefficienten van ionen in gemengde oplosmiddelen, waaruit op verschillende manieren de oplosbaarheid bepaald kan worden. Het literatuuronderzoek gebeurde aan de hand van enkele bron-artikelen en een search in Chemical Abstracts, vanaf 1968. Aan de hand van de gevonden artikelen werd verder teruggezocht. De conclusies zijn dat de semi-empirische modellen zich niet lenen voor nauwkeurige beschrijving van de oplosbaarheden, zelfs het beste model, het solventing out model van Alfassi, is slechts in een beperkt gebied toepasbaar en niet erg nauwkeurig. De modellen voor de activiteiten van de ionen lijken beter geschikt maar ook gelijk veel ingewikkelder; er moeten waarschijnlijk data regressie methoden op toegepast worden. Er moet dan wel een verband gelegd worden tussen activiteit en oplosbaarheid. Als er binaire (vloeistof-zout en vloeistof-vloeistof) vloeistof-damp gegevens beschikbaar zijn, is het Schuberth model het eenvoudigst. Voor het NRTL en UNIQUAC model is de dielectrische constante van het solvent nodig; verder moet voor het NRTL model nog een geschikte ion-ion interactie term gevonden worden.Applied Science

Het Actieve Kool proces van Bergbau Forschung voor het simultane verwijdering van SO2 en NOx uit rookgassen

Document(en) uit de collectie Chemische Procestechnologie.DelftChemTechApplied Science

High-speed imaging and statistics of puffing and micro-exploding droplets in spray-flame synthesis

Thermally-induced breakup of metal-precursor-laden droplets in spray-flame synthesis occurs via a rapid and disruptive disintegration, i.e., “puffing” and “micro-explosion”. To assess the temporal evolution and statistics of droplet disruption, LED-illuminated droplet shadowgraphs were imaged with a microscope onto a high-speed camera and morphological image analysis was applied. The atomized liquid was a mixture of 35 vol.-% ethanol and 65 vol.-% 2-ethylhexanoic acid mixed with iron(III) nitrate nonahydrate (INN) as a precursor. Droplet evaporation and disruption were also simulated with a population balance model. The model finds solid precipitates forming in the droplets because of the decomposition of the precursor intermediate iron(III) 2-ethylhexanoate. The precipitates form a particle shell, which favors the superheating of the droplets’ interior, and they facilitate heterogeneous bubble nucleation. Imaging experiments and modelling find that per 10 µs lifetime of a droplet, the probability for disruption increases from 5 to 13% and 5 to 19%, respectively, when increasing the INN concentration from 0.05 to 0.5 mole/l. The probability of disruption suggests that throughout their lifetime in the spray flame, nearly all droplets will undergo disruption and many of them multiple times. In the experiment, droplets before disruption are 15% smaller than regular, non-disrupting droplets. Once disrupted, the droplets have a 45% smaller mean diameter than regular droplets. Under all conditions, disrupting and disrupted droplets are slower than regular droplets while the disruption does not significantly accelerate disrupted droplets

The transition from spark to arc discharge and its implications with respect to nanoparticle production

The synthesis of nanoparticles by means of electrical discharges between two electrodes in an inert gas at atmospheric pressure, as driven by a constant current ranging from a few milliamps to tens of amps, is investigated in this work. An extensive series of experiments are conducted with copper as a consumable electrode and pure nitrogen as the inert gas. Three different DC power supplies are used to drive electrical discharges for the entire operating current range. Then, three electrical discharge regimes (spark, glow, and arc) with distinct voltage–current characteristics and plasma emission spectra are recognized. For the first time, nanoparticles are synthesized by evaporation of an electrode by atmospheric pressure inert gas DC glow discharge of a few millimeters in size. The discharge regimes are characterized in terms of the mass output rate and the particle size distribution of the copper aerosols by means of online (tapered element oscillating microbalance, TEOM; and scanning mobility particle sizer, SPMS) and offline (gravimetric analysis; small and wide angle X-ray scattering, SWAXS; and transmission electron microscopy, TEM) techniques. The electrical power delivered to the electrode gap and the gas flow rate are two major parameters determining the aerosol mass output rate and the aerosol particle size distribution. The mass output rate of copper aerosols raises from 2 mg h-1 to 2 g h-1 when increasing the electrical power from 9 to 900 W. The particle mean size (SMPS dg) varies between 20 and 100 nm depending upon the electrical power and the gas flow rate, whereas the particle size dispersion (SMPS sg) ranges from 1.4 to 1.7 and is only weakly dependent on the gas flow rate