Due to coming emission legislations, the temperature is expected to increase in heavy-duty diesel engines, specifically in the hot-end of the exhaust system affecting components, such as exhaust- and turbo manifolds. Since the current material in the turbo manifold, a ductile cast iron named SiMo51, is operating close to its limits there is a need for material development in order to maintain a high durability of these components. When designing for increased life, many material properties need to be considered, for example, creep-, corrosion- and fatigue resistance. Among these, the present work focuses on the latter two up to 800°C improving the current material by additions of Cr, for corrosion resistance, and Ni, for mechanical properties. The results show improved high-temperature corrosion resistance in air from 0.5 and 1wt% Cr additions resulting in improved barrier layer at the oxide/metal interface. However, during oxidation in exhaust-gases, which is a much more demanding environment compared to air, such improvement could not be observed. Addition of 1wt% Ni was found to increase the fatigue life up to 250°C, resulting from solution strengthening of the ferritic matrix. However, Ni was also found to increase the oxidation rates, as no continuous SiO2-barrier layers were formed in the presence of Ni. Since none of the tested alloys showed improved material properties in exhaust gases at high temperature, it is suggested that the way of improving performance of exhaust manifolds is to move towards austenitic ductile cast irons or cast stainless steels. One alloy showing good high-temperature oxidation properties in exhaust atmospheres is an austenitic cast stainless steel named HK30. This alloy formed adherent oxide scales during oxidation at 900°C in gas mixtures of 5%O2-10%H2O-85%N2 and 5%CO2-10%H2O-85%N2 and in air. In the two latter atmospheres, compact scales of (Cr, Mn)-spinel and Cr2O3 were formed whereas in the atmosphere containing 5%O2 and 10%H2O, the scales were more porous due to increased Fe-oxide formation. Despite the formation of a protective, i.e. compact and adherent, oxide scale on HK30, exposure to exhaust-gas condensate showed a detrimental effect in form of oxide spallation and metal release. Thus, proving the importance of taking exhaust-gas condensation, which may occur during cold-start or upon cooling of the engine, into account when selecting a new material for exhaust manifolds. / <p>QC 20130508</p>

Additive manufacturing (AM) techniques are being studied for their application in the aerospace industry. Numerous benefits come from the already in shape final piece, which needs reduced amount of prime material for its production and can have its shape numerically optimized for weight reduction. Austenitic stainless steels (AuSS) are widely used in aerospace and their manufacturing through AM is a popular research topic in order to accelerate their effective incorporation in air-crafts and spaceships. The special microstructures of AM has been observed with characterization techniques. The present work studies the high temperature stability of three AuSS (316L, MOD-316 and 21-6-9) considering two approaches; surface corrosion and microstructure evolution. First, for high temperature corrosion, thermogravimetric analysis has been performed from 850°C to 1150°C. From the results, kinetic analysis were performed and the activation energy was extracted from Arrhenius fits. Two mechanism were found for alloy 316L (first 435.41 kJ/mol and second 593.24 kJ/mol) and MOD-316 (first 740.01 kJ/mol and second 495.58 kJ/mol). Further SEM observations on the scales have shown Ni diffusion through the chromia scale in MOD-316 alloy, which could explain the higher oxidation rates at 1150°C. Alloy 21-6-9 has the best passivation behaviour with an activation energy of 190.47 kJ/mol. Secondly, long heat treatment (HT) at 725°C in air atmosphere has been performed, for 24 and 240h. Samples were initially as-built or annealed (900°C for 1h), to compare the effect of the HT on the microstructure evolution and precipitates formation. LOM observation showed preferable nucleation in grain boundaries (GB), an increment of the number of precipitates and a growth towards elongated shapes following GB with increased time. It was also observed a reduction in precipitates number with the annealing HT for all the alloys. XRD, SEM and EDS analysis has been carried out to identify the structure and composition of the precipitates. Various chromium, tungsten, copper, molybdenum and niobium carbides and oxides have been found in MOD-316. Higher porosity is observed in 21-6-9, that presented mainly chromium oxides, carbides and nitrides in GB and surrounding the AM defects. / SeSSA

A nickel alloy with high chrome and molybdenum content was found to form a highly resistive and passive oxide layer. The donor density and mobility of ions in the oxide layer has been determined as a function of the electrical potential when alkaline water layers are on the alloy surface in order to account for the relative inertness of the nickel alloy in corrosive environments.

This thesis presents a study on several series of unconventional Fe-based superconductors; namely, derivatives of NaFeAs and LiFeAs, as well as molecular-intercalated FeSe. Primarily using muon spin rotation (SR), but also x-ray diffraction (XRD) and magnetic susceptibility measurements, the nature of both magnetic and superconducting phases within these systems is studied. Particular attention is focussed on how these states compete or coexist with one another. The aforementioned experimental techniques are first used to explore the phase diagram of NaFe1xCoxAs. This phase diagram includes regions of long-range antiferromagnetism and short-range order, that both coexist with superconductivity. Magnetism is gradually destroyed, primarily through a diminishment of the size of the ordered moment, as superconductivity is enhanced by Co substitution. This interplay is explored in detail. By contrast, superconductivity in LiFeAs cannot be enhanced by transition metal substitution, suggesting that it is intrinsically optimally-doped. I investigate this conclusion by studying the evolution of the penetration depth in superconducting compositions of LiFe1xCoxAs and LiFe1xNixAs, and comparing these data to those from other electron-doped systems. I also study an unusual and emergent magnetic phase in Li1yFe1+yAs. This work suggests that LiFeAs supports a superconducting phase that resembles those in other Fe-pnictides, but is uniquely close to an additional magnetic instability. I then move on to the study of a recently discovered series, based on FeSe intercalated with ammonia and various metals. I study both the penetration depth and the intrinsic magnetic phases in these systems using SR and compare them with other compounds based on FeSe. I find that these intercalated systems support spacially separated regions of dynamic magnetism and superconductivity and I discuss how much these phases depend on the precise chemical details of the intercalated layer. Finally, I return to the experimental study of NaFe1xCoxAs, extending the range of techniques employed by using high-field magnetometry and high-pressure SR. These studies reveal new features of this system that were not accessible using low-field and ambient-pressure methods. In particular, I show that the magnetic moment size in NaFeAs unexpectedly increases with pressure, suggesting that the electronic structure of this compound may be unique amongst known Fe-based superconductors.

The development of molybdenum - silicon - boron (Mo-Si-B) composites having a combination of high temperature strength, creep, and oxidation residence has the potential to substantially increase the efficiency of gas turbines. The refractory nature of the αMo, Mo3Si (A15), and Mo5SiB2 (T2) phases results in good strength and creep resistance up to 1300°C. At this temperature, the formation of a borosilicate surface scale from the two intermetallic phases is able to provide oxidation resistance. However, realization of these advantages has been prevented by both a high brittle to ductile transition temperature and difficulty in forming the initial surface borosilicate to provide bulk oxidation resistance. This dissertation addresses two factors pertaining to this material system: 1) improvements to powder processing techniques, and 2) development of compositions for oxidation resistance at 1300°C. The processing of Mo-Si-B composites is strongly tied to their mechanical properties by establishing the αMo matrix, limiting impurity content, and reducing silicon supersaturation. These microstructural aspects control the brittle to ductile transition temperature which has traditionally been too high for implementation of Mo-Si-B composites. The processing here built upon the previously developed powder processing with silicon and boron nitrides which allowed for a low oxygen content and sintering of fine starting powders. Adjustments were made to the firing cycle based upon dew point measurements made during the hydrogen de-oxidation stage. Under a relatively high gas flow rate, 90% of the total water generated occurred during a ramp of 2°C /min between 450 and 800°C followed by a hold of 30 minutes. The oxidation resistance of Mo-Si-B composites was studied for a wide range of compositions. Silicon to boron atomic ratios were varied from 1 to 5 and iron, nickel, cobalt, yttria, and manganese were included as minor additions. In all these compositions, the αMo volume fraction was kept over 50% to ensure the potential toughness of the composite. For the oxidized surface glass, a silica fraction of 80 to 85% was found to be necessary for the borosilicate to have a sufficiently high viscosity and low oxygen permeability for oxidation resistance at 1300°C. For the Mo-Si-B bulk composition this corresponds to a Si/B atomic ration of 2 to 2.5. Higher viscosity compositions failed due to spallation of poorly attached, high silica scales. Lower viscosity compositions failed from continuous oxidation, either through open channels or repetitive MoO3 bubble growth and popping. Additionally, around 1% manganese was necessary for initial spreading of the borosilicate at 1300°C. In conjunction with flowing air to prevent MoO3 accumulation, oxidation weight loss rates below 0.05 mg/cm2-hr were measured. Finally, a theory is proposed here to describe the mechanisms responsible for the development of oxidation resistance. This theory involves three stages associated with: 1) generation of an initial surface borosilicate, 2) thickening of the borosilicate layer, and 3) slow parabolic oxidation controlled by the high silica surface scale.

Thesis (MSc (Physics))--Stellenbosch University, 2010. / ENGLISH ABSTRACT: This dissertation reports on the impact of a set of selected nuclear fuel management parameters on reactor operations of the PBMR core. This is achieved by performing an assessment of the impact of nuclear fuel management parameter variations on the most important safety and economics issues for the PBMR core. These include the maximum fuel temperature at steady state and during Depressurized Loss of Forced Cooling (DLOFC) accident conditions. The reactivity worth of the Reactor Control System (RCS which determines the shutdown capability of the reactor core and the average discharge burn-up of fuel are also established. The fuel management parameters considered in this study include different enrichment levels, heavy metal loadings and fuel sphere circulation regimes. The impact and importance of these parameters on plant safety and economics is assessed. The dissertation will report the effects on the standard core physics parameters such as power peaking, multiplication factor, burn-up (safety and economics) and derive the benefits and drawbacks from the results. Based upon the findings from this study, and also experimental data, an optimum fuel management scheme is proposed for the PBMR core. / AFRIKAANSE OPSOMMING: Hierdie verhandeling beskryf die uitwerking van ‘n gekose stel kernbrandstofparameters op die bedryf van die PBMR reaktor. Die impak wat variasies in kernbrandstofparameters op belangrike veiligheids- en ekonomiese oorwegings het, is tydens hierdie studie ondersoek. Van die belangrikste oorwegings is die maksimum brandstoftemperatuur tydens normale, konstante bedryf, asook gedurende ‘n “Depressurized Loss of Forced Cooling (DLOFC)” insident waar alle verkoeling gestaak word. Ander belangrike fasette wat ondersoek is, is die reaktiwiteitwaarde van die beheerstelsel (RCS), wat die aanleg se vermoë om veilig af te sluit bepaal, asook die totale kernverbruik van die brandstof. Die kernbrandstofparameters wat in ag geneem is, sluit die brandstofverryking, swaarmetaalinhoud en die aantal brandstofsirkulasies deur die reaktorhart in. Die belangrikheid en impak van elk van hierdie parameters is ondersoek en word in die verhandeling beskryf . Daar word verslag gelewer oor die voor- en nadele, asook die uitwerking van hierdie variasies op standaard reaktorfisika-parameters soos drywingspieke in die brandstof, neutronvermenigvuldigingsfaktore en kernverbuik van die brandstof, vanaf ‘n veiligheids- en ekonomiese oogpunt. Gebaseer op die gevolgtrekkings van hierdie studie, tesame met eksperimentele data, word ‘n optimale kernbrandstofbestuurprogram voorgestel.

Thesis (MIng) --Stellenbosch University, 1999. / ENGLISH ABSTRACT: A method was developed at the Atomic Energy Corporation of South Africa (AEC) for the plasma based production of tetrafluoroethylene (TFE). The process involves the feeding of carbon particles into a direct-current CF4 plasma. The resultant plasma gas is quenched rapidly to obtain TFE and other fluorocarbons. The mixing of the particles with the plasma gas is very important in order to achieve a high C:F-ratio in the gas phase, which promotes the desired reactions. The gas enthalpy in the reactor is a governing factor in the TFE yields that are obtained. In this study research was done on particle mixing and the enthalpy distribution in the laboratory scale reactor. An enthalpy probe was used as the main diagnostic tool. Results indicated that particle mixing is quite uniform throughout the reactor. A basic one-dimensional mechanistic model of the reactor was also expanded to assist in· the scale-up of the process. In its present form the model is adequate for predicting trends in the reactor. The model could still be expanded further to include reaction kinetics and internal heat transfer in the particles. Considering the restrictions of the model, satisfactory agreement was obtained between the model and experimental results. / AFRIKAANSE OPSOMMING: 'n Proses vir die plasmagebaseerde produksie van tetrafluoroetileen (TFE) is deur die Atoomenergiekorporasie van Suid-Afrika (AEK) ontwikkel. Koolstofpartikels word in 'n gelykstroomCF4- plasma gevoer en die resulterende plasmagas word vinnig geblus ten einde TFE en ander fluoor-koolstofverbindings as produkte te verkry. Goeie vermenging van die koolstofpartikels met die plasmagas is van uiterste belang ten einde 'n hoe C:F-verhouding, wat die gewenste reaksies bevorder, in die gasfase te verkry. Die entalpie van die plasmagas in die reaktor is 'n bepalende faktor in die opbrengs TFE wat verkry word. Vir die doel van hierdie werkstuk is navorsing op laboratoriumskaal gedoen oor partikelvermenging en die entalpie-verspreiding in die reaktor. Die hoof diagnostiese apparaat wat vir die doel aangewend is, is die entalpiesonde. Resultate toon dat partikelvermenging naastenby uniform deur die reaktor voorkom. Verder is 'n basiese een-dimensionele meganistiese model van die reaktor uitgebrei ten einde van nut te wees in die opskaling van die proses. In sy huidige vorm is die model voldoende om algemene neigings in die reaktor te voorspel. Die model kan nog verder uitgebrei word om reaksie-kinetika en interne hitte-oordrag in die partikels in te sluit. Die beperkings van die model in ag genome, is ooreenstemming tussen die model en eksperimentele resultate egter bevredigend.

Exploration of novel lanthanide fluoride framework materials in inorganic-organic hybrid systems under solvothermal conditions towards development of new luminescent materials is discussed. X-ray single crystal and powder diffraction methods have been used as crystallographic characterisation techniques. Determination and study of luminescence properties for selected hybrid materials has also been carried out. The first organically templated luminescent lanthanide fluoride framework, [C₂N₂H₁₀]₀.₅ [Ln₂F₇] (Ln= Nd, Tb, Dy, Ho, Er, Yb and Lu), has been synthesised and characterised. This structure type consists of a three-dimensional yttrium fluoride framework incorporating two similar, but crystallographically distinct, yttrium sites. Photoluminescence studies of [C₂N₂H₁₀]₀.₅ [Y₂F₇]: Ln³⁺ (Ln³⁺ = Gd³⁺, Eu³⁺ and Tb³⁺) have been explored and characteristic luminescence emissions are reported. An inorganic-organic hybrid indium fluoride and its scandium fluoride analogue, [C₄H₁₄N₂][MF₅](M=In and Sc) is reported. The structure consists of infinite trans vertex sharing (InF₅)[subscript(∞)] chains, which are linked via H-bonded organic moieties. The scandium and fluorine local environments of [C₄H₁₄N₂][ScF₅] are characterised by ¹⁹F, and ⁴⁵Sc solid-state MAS NMR spectroscopies. A single scandium site has been confirmed by ⁴⁵Sc MAS NMR. ¹⁹F MAS NMR clearly differentiates between bridging and terminal fluorine. The photoluminescence properties of these complexes, [C₄H₁₄N₂][In[subscript(1-x)] Ln[subscript(x)]F₅] (Ln=Tb and/or Eu), have been explored. The optimum composition for Eu³⁺ doped samples occurs at x = 0.05 Eu³⁺ and the “asymmetry ratio” of R = I₅₉₀/I₆₁₅ ( ⁵D₀ → ⁷F₂ and ⁵D₀ → ⁷F₁) gives a clear picture of the sensitivity for crystal field of the compound. For x = 0.08 Tb³⁺, a strong down-conversion fluorescence corresponding to ⁵D₄ → ⁷F₅ (green at 543.5 nm) occurs. In addition, a Tb³⁺/Eu³⁺ co-doped sample exhibits a combination of green (Tb³⁺) and orange (Eu³⁺) luminescence, with Tb³⁺ enhancing the emission of Eu³⁺ in this host. Exploration of novel indium, aluminium, and zirconium fluoride crystal structures with potential luminescent properties has also been undertaken. A chiolite-like phase K₅In₃F₁₄ (space group P4/mnc) has been synthesised. No phase transition occurs over the temperature range 113K< T< 293 K, as has been seen in other chiolite-like structures. An organically templated indium fluoride, [NH₄]₃[C₆H₂₁N₄]₂[In₄F₂₁] has been prepared; this features the trimeric unit [In₃F₁₅]³⁻ which appears to be the first of its type in a metal fluoride. A new hybrid fluoride, Sr[N₂C₂H₁₀]₂[Al₂F₁₂].H₂O has been synthesised. Because the ionic radius of Eu²⁺ is similar to that of Sr ²⁺ this may be a potential host for blue luminescent Eu²⁺. The new material KZrF₅.H₂O shows pentagonal-bipyramidal geometry of Zr⁴⁺ with a polar space group, Pb2₁m, which may potentially have ferroelectric properties.

Thesis (PhD (Physics))--University of Stellenbosch, 2002. / Includes bibliography. / ENGLISH ABSTRACT: High temperature superconductivity is an important topic in contemporary solid state physics, and an area of very active research. Due to it’s potential for application in low temperature electronic devices, the material has attracted the attention of researchers in the electronic engineering and material science fields alike. Moreover, from a fundamental point of view, several questions remain unanswered, related to the origin of superconductivity of this class of materials and the nature of quantised magnetic flux present in magnetised samples. In this work, flux creep phenomena in a thin superconducting YBa₂Cu₃O₇ film deposited by pulsed laser deposition, is investigated near the critical temperature 0 ≤ Tc – T ≤ 10 K. Creep activation energy U0 and critical current density jc were determined as a function of temperature close to Tc, providing important data to a problem of high-Tc superconductivity which is still a matter of debate. In particular it is still an open question whether restoring the temperature in a creep freezing experiment in fact restores the film to it's original state before the freezing. The most important novel results concern the regime of critical fluctuations in the vicinity Tc - T < 1 K. We studied the isothermal relaxation of trapped magnetic flux, and determined that the long time decay follows a power law, where the exponent is inversely proportional to the creep activation energy. The temperature dependence of the critical current density jc(T) of the YBa₂Cu₃O₇ film close to Tc was obtained during warming runs. It was determined that jc(T) follows a square root dependence on T to high accuracy in the range 0.2 ≤ Tc – T ≤ 1.5 K. During flux creep experiments an interesting phenomenon called creep freezing related to the strong temperature dependence of the relaxation rate was observed. A pronounced slowing of relaxation with only a small drop in temperature from a starting temperature close to Tc was detected. Experiments were conducted by initiating an isothermal flux decay run. At a certain point the temperature was slightly lowered, and the flux decay stopped within experimental accuracy. When the temperature was restored to the initial value, the flux decay resumed at the previous rate before cooling. An argument based on vortex drift velocity was employed to explain the phenomenon qualitatively. During the course of this investigation, a pulsed laser deposition (PLD) system was designed and built from scratch. PLD involves the interaction of a focussed laser pulse with a multielemental solid target material. Material ablated from the target forms a fast moving plume consisting of atomic and molecular particles, directed away from the target, and towards a usually heated substrate on which the particles condense layer by layer to form a thin film. The substrate temperature and background gas are carefully controlled to be conductive to the growth of a desired phase of the multi-elemental compound. The PLD system proved to be quite versatile in the range of materials that could be deposited. It was used to deposit thin films of different materials, most notable were good quality superconducting YBa₂Cu₃O₇, thermochromic VO2, and magnetoresistive LaxCa1-xMnO3. Metallic Au and Ag layers were also successfully deposited on YBa2Cu3O7 thin films, to serve as protective coatings. The critical temperatures of the best superconducting films were 90 K as determined by resistivity measurement. The optimal deposition conditions to deposit high quality superconducting YBa₂Cu₃O₇ thin films was found to be: deposition temperature 780°C, laser energy density 2-3 J/cm2, oxygen partial pressure 0.2 mbar, and target-substrate distance 35 mm. This yields film with Tc ~ 90 K. It was found that deposition temperature plays the predominant role in determining the quality of YBa₂Cu₃O₇ thin films deposited by PLD. / AFRIKAANSE OPSOMMING: Hoë temperatuur supergeleiding is tans ’n aktuele onderwerp van vastetoestandfisika en dit is ’n gebied van baie aktiewe navorsing. Weens die potensiaal vir toepassings van hoë temperatuur supergeleiers in elektronika, het dié klas materiale die aandag van fisici and elektronici getrek. Verskeie fundamentele vraagstukke bly steeds onbeantwoord, veral met betrekking tot die oorsprong van supergeleiding in hierdie materiale en die gedrag van gekwantiseerde magnetiese vloed (“vortekse”) in gemagnetiseerde monsters. In hierdie werk word diffusie van vortekse in dun supergeleidende YBa₂Cu₃O₇ films ondersoek naby die kritieke temperatuur (0 ≤ Tc - T ≤ 10 K). Die temperatuur afhanklikheid van die diffusie aktiveringsenergie U0 en die kritieke stroomdigtheid jc word bepaal naby Tc. Dit verskaf belangrike inligting tot probleme in hoë temperatuur supergeleiding wat tans nog onbeantwoord bly. In die besonder is dit steeds ’n ope vraag of die herstel van die aanvanklike temperatuur in ’n vloedstollings eksperiment waarlik die film tot die oorspronklike toestand herstel. Die belangrikste nuwe resultate hou verband met die gebied van kritieke fluktuasies van die orde parameter in die omgewing 0 < Tc - T < 1 K. Ons het die isotermiese ontspanning van vortekse verstrik in die kristalstruktuur bestudeer, en bepaal dat die lang tydsverval ’n magsverwantskap handhaaf, waar die eksponent omgekeerd eweredig is aan U0. Die temperatuur afhanklikheid van die kritieke stroomdigtheid jc(T) van die YBa₂Cu₃O₇ film naby Tc is bepaal tydens verhittingslopies. Daar is bevind dat naby Tc, jc ’n vierkantswortel verband met T volg, tot hoë noukeurigheid in die gebied 0.2 ≤ Tc – T ≤ 1.5 K. Gedurende vorteksdiffusie eksperimente is ’n interessante verskynsel naamlik vloedstolling (“flux freezing”) waargeneem. Dit hou verband met die sterk temperatuur afhanklikheid van die vervaltempo van die magnetiese moment van ’n gemagnetiseerde film. ’n Skerp daling van die vervaltempo, weens slegs ’n klein temperatuurdaling vanaf die begin temperatuur naby Tc, is waargeneem. Gedurende eksperimente is daar aanvanklik ’n isotermiese vloedontspanning teweeg gebring. Op ’n sekere tydstip is die temperatuur effens verlaag, waarby die vloedontspanning tot stilstand gekom het binne grense van waarneming. Wanneer die temperatuur weer herstel is na die oorspronklike, het die vloedontspanning voortgegaan teen die tempo voor die temperatuurverlaging. ’n Verklaring wat gebaseer is op vorteks dryfsnelheid was aan die hand gedoen om hierdie gedrag te verklaar. ’n Groot komponent van die projek was om die dun YBa₂Cu₃O₇ films self te vervaardig. Tydens hierdie ondersoek, is ’n gepulseerde laser deposisie (“PLD”) sisteem eiehandig ontwerp en gebou. PLD behels die interaksie van ’n gefokuseerde laser puls met ’n teiken bestaande uit ’n multi-element vastestofverbinding. Materiaal wat verdamp (“ablate”) word, vorm ’n snelbewegende pluim bestaande uit atomiese en molekulêre deeltjies. Dit beweeg vanaf die teiken na ’n verhitte substraat, waarop die deeltjies kondenseer om laag vir laag ’n dun film te vorm. Die substraat temperatuur en agtergrond gas word sorgvuldig beheer om die groei van die verlangde fase van die multi-element verbinding teweeg te bring. Die PLD sisteem is baie veeldoelig ten opsigte van die verskeidenheid materiale wat suksesvol neergeslaan kan word. Dit was aangewend om verskillende materiale neer te slaan, onder andere supergeleidende YBa₂Cu₃O₇, termochromiese VO2, en magnetoresistiewe LaxCa1-xMnO3. Geleidende Au en Ag lagies is ook suksesvol neergeslaan op YBa₂Cu₃O₇ dun films, om te dien as beskermingslagies. Die kritieke temperatuur van die beste supergeleidende films was 90 K soos bepaal deur weerstandsmetings. Die optimale neerslaan toestand vir hoë kwaliteit YBa₂Cu₃O₇ dun films was: substraat temperatuur 780°C, laser energiedigtheid 2 - 3 J/cm2, suurstofdruk 0.2 mbar, en teiken-substraat afstand 35 mm. Daar is bevind dat die substraat temperatuur die deurslaggewende rol speel tydens die neerslaan proses om die kwaliteit van die supergeleidende films te bepaal.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / This thesis is concerned with the fabrication of high temperature bi-epitaxial grain boundary Josephson junctions for use in superconducting microelectronic circuits. It aims to provide a proof-of-concept manufacturing process which can serve as a basis for future research at the University of Stellenbosch. The work in this thesis integrates ...