Clogging of the nozzle and tundish during the continuous casting of Al-killed steel is a common issue in the industry due to clogging caused by alumina and other non-metallic inclusions. To investigate this effect, four samples from the production of Al-killed steel (0.95-1 wt% C and undergoing vacuum degassing) were analysed. The first sample was taken before vacuum degassing, the second sample was taken after vacuum degassing, the third sample at the start of continuous casting and the fourth sample during continuous casting. These samples were examined using a scanning electron microscope combined with electrolytic extraction. A total of 16 alumina inclusions, which can directly lead to clogging, were found. Most of these alumina inclusions were present in the first and fourth samples, indicating that the inclusions before vacuum degassing and during continuous casting contribute most significantly to clogging. Additionally, the alumina inclusions in the fourth sample were larger than those in the first sample, suggesting that these initial inclusions pose a greater risk of clogging. The alumina inclusions had a globular/regular morphology, which is consistent with the literature review. Furthermore, inclusions containing magnesium oxide, calcium oxide and calcium sulphide were found, however, it is difficult to conclude how these inclusions affect clogging. / Igensättning av skänkröret och skänken under stränggjutning av Al-deoxiderat stål är ett vanligt problem inom industrin på grund av aluminumoxid och andra icke-metalliska inneslutningar. För att undersöka igensättningseffekten av aluminiumoxid och andrainneslutningar undersöks fyra prover från tillverkningen av ett Al-deoxiderat stål (0.95-1 wt% C som också genomgick vakuumbehandling).Första provbiten togs före vakuumbehandling, andra provbiten efter vakuumbehandling, tredje provbiten i början av stränggjutningen och fjärde provbiten togs understränggjutningen. Provbitarna undersöktes med svepelektronmikroskop kombinerat medelektrolytisk extraktion. Totalt hittades 16 aluminiumoxidinneslutningar (Al2O3-inneslutningar) som direkt kan leda tilligensättning. De flesta Al2O3-inneslutningarna hittades i den första och den fjärde provbiten, vilket innebär att inneslutningarna före vakuumbehandling och under stränggjutning leder tilligensättning i störst utsträckning. Dessutom var storleken på Al2O3-inneslutningarna understränggjutning större än innan vakuumbehandling, vilket tyder på att Al2O3-inneslutningarna iden första provbiten utgör en större risk för igensättning. Al2O3-inneslutningarna hade dessutom en globulär/reguljär morfologi som överensstämmer med litteratur. Dessutom hittades inneslutningar som innehåller magnesiumoxid, kalciumoxid och kalciumsulfid, men det är svårt att dra slutsatser om hur dessa inneslutningar påverkarigensättningen

Bulk metallic glasses (BMGs) have received significant research interest due to their completely amorphous structure which results in unique structural and functional properties. Absence of grain boundaries and secondary phases in BMGs results in high corrosion resistance in many different environments. Understanding and tailoring the corrosion behavior can be significant for various structural applications in bulk form as well as coatings. In this study, the corrosion behavior of several Zr-based and Fe-Co based BMGs was evaluated to understand the effect of chemistry as well as quenched in free volume on corrosion behavior and mechanisms. Presence of Nb in Zr-based alloys was found to significantly improve corrosion resistance due to the formation of a stable passive oxide. Relaxed glasses showed lower rates compared to the as-cast alloys. This was attributed to lowering of chemical potential from the reduced fraction of free volume. Potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) techniques helped in quantifying the corrosion rate and polarization resistance. The effect of alloy composition was quantified by extensive surface analysis using Raman spectroscopy, energy dispersive x-ray spectroscopy and auger spectroscopy. Pitting intensity was higher in the as-cast glasses than the relaxed glasses. The electrochemical behavior of a Zr-Ti-Cu-Ni-Be bulk metallic glass subjected to high strain processing was studied. High strain processing caused shear band formation and an increase in the free volume. Potentiodynamic polarization and EIS showed a strong correlation between the enthalpy of structural relaxation and corrosion rate and polarization resistance. Pitting was observed to preferentially occur on shear bands in the processed samples, while it was stochastic in unprocessed glass. The corrosion analysis of Co-Fe glasses showed an increase in corrosion current density when Fe content was increased from 0 to 7 at%. The corrosion resistance improved when Fe content was further increased to 15 at%. Similar trend was seen in EIS studies. The improved corrosion resistance at 15 at% Fe can be attributed to the large supercooled region that facilitates the formation of completely amorphous alloy, in contrast to lower Fe containing alloys, where short range ordering may deteriorate the corrosion resistance. Porous metallic glass structure was developed by electrochemical dealloying via cyclic voltammetry. Mechanical properties and changes in electrical conductivity were measured as a function of depth from surface by nano-indentation and nano electrical contact resistance technique. The nanoporous layer was found have hardness of 0.41 GPa and elastic modulus of nearly 22 GPa. The resistivity of the nanoporous layer continuously decreased when moving towards the substrate as the indentation depth increased which is attributed to the gradient in pore size.

Six ã-Al2O3 supported metallic nitride and carbide catalysts were chosen for a scouting test for the production of a diesel fuel cetane enhancer from canola oil. The six catalysts chosen for study were ã-Al2O3 supported molybdenum (Mo) carbide and nitride, tungsten (W) carbide and nitride, and vanadium (V) nitride and carbide. All six catalysts were prepared by the impregnation method and characterized using various techniques. The six catalysts were screened for their affinity for oxygen removal, fatty acid conversion, alkane/olefin selectivity, hydrogen consumption, and gas-by product production from oleic acid. The scouting test was carried out at a reaction temperature of 390°C, a LHSV of 0.46 hr-1, and elevated hydrogen partial pressures of greater than 7000 kPa, in a laboratory microreactor in an upflow configuration. The scouting test revealed that the two molybdenum catalysts performed the best with oxygen removal near 100% and alkane/olefin content of greater than 30%. <p>Next, the supported molybdenum carbide and nitride catalysts were compared against one another over a wider range of operating conditions. A temperature range of 380 390°C, a LHSV range of 0.64 1.28 hr-1, and a hydrogen partial pressure of 7100 kPa were used. Both catalysts had the same metal loading of 7.4 wt% molybdenum. The two catalysts were compared on the basis of oxygen removal, alkane/olefin selectivity, diesel fuel selectivity, and hydrogen consumption, while using both triolein and canola oil as the feed. It was found that the supported molybdenum nitride was the superior choice for this process, specifically when using the more complex canola oil feed. The supported molybdenum nitride catalyst delivered oxygen removal of greater than 85%, alkane/olefin selectivity of greater than 20%, and diesel fuel selectivity of greater than 40%, for all conditions studied. <p>Finally, a preliminary catalyst and process optimization was carried out on the chosen ã-Al2O3 supported molybdenum nitride catalyst. The catalyst optimization consisted of varying the metal loading of the catalyst from 7.4 wt% to 22.7 wt%. The catalysts were examined over a temperature range of 390 410°C, a LHSV range of 0.9 1.2 hr-1, and a hydrogen partial pressure of 8300 kPa, with canola oil as the chosen feed. It was found that the increase in molybdenum loading on the catalyst delivered an average increase in the alkane/olefin selectivity of 43.2% and an average increase in the diesel fuel selectivity of 5.3 %. The process optimization studied a temperature range of 390 410°C, a LHSV range of 0.6 1.2 hr-1, and a hydrogen partial pressure range of 7800 - 8900 kPa, with canola oil as the chosen feed. Within the limits of the design, it was found that the optimum operating conditions were 395°C, 1.05 hr-1, and 8270 kPa. At these conditions the predicted yields of alkane/olefin products and diesel fuel are 47.3 and 50.5 g/100g liquid fed, respectively.

Six ã-Al2O3 supported metallic nitride and carbide catalysts were chosen for a scouting test for the production of a diesel fuel cetane enhancer from canola oil. The six catalysts chosen for study were ã-Al2O3 supported molybdenum (Mo) carbide and nitride, tungsten (W) carbide and nitride, and vanadium (V) nitride and carbide. All six catalysts were prepared by the impregnation method and characterized using various techniques. The six catalysts were screened for their affinity for oxygen removal, fatty acid conversion, alkane/olefin selectivity, hydrogen consumption, and gas-by product production from oleic acid. The scouting test was carried out at a reaction temperature of 390°C, a LHSV of 0.46 hr-1, and elevated hydrogen partial pressures of greater than 7000 kPa, in a laboratory microreactor in an upflow configuration. The scouting test revealed that the two molybdenum catalysts performed the best with oxygen removal near 100% and alkane/olefin content of greater than 30%. <p>Next, the supported molybdenum carbide and nitride catalysts were compared against one another over a wider range of operating conditions. A temperature range of 380 390°C, a LHSV range of 0.64 1.28 hr-1, and a hydrogen partial pressure of 7100 kPa were used. Both catalysts had the same metal loading of 7.4 wt% molybdenum. The two catalysts were compared on the basis of oxygen removal, alkane/olefin selectivity, diesel fuel selectivity, and hydrogen consumption, while using both triolein and canola oil as the feed. It was found that the supported molybdenum nitride was the superior choice for this process, specifically when using the more complex canola oil feed. The supported molybdenum nitride catalyst delivered oxygen removal of greater than 85%, alkane/olefin selectivity of greater than 20%, and diesel fuel selectivity of greater than 40%, for all conditions studied. <p>Finally, a preliminary catalyst and process optimization was carried out on the chosen ã-Al2O3 supported molybdenum nitride catalyst. The catalyst optimization consisted of varying the metal loading of the catalyst from 7.4 wt% to 22.7 wt%. The catalysts were examined over a temperature range of 390 410°C, a LHSV range of 0.9 1.2 hr-1, and a hydrogen partial pressure of 8300 kPa, with canola oil as the chosen feed. It was found that the increase in molybdenum loading on the catalyst delivered an average increase in the alkane/olefin selectivity of 43.2% and an average increase in the diesel fuel selectivity of 5.3 %. The process optimization studied a temperature range of 390 410°C, a LHSV range of 0.6 1.2 hr-1, and a hydrogen partial pressure range of 7800 - 8900 kPa, with canola oil as the chosen feed. Within the limits of the design, it was found that the optimum operating conditions were 395°C, 1.05 hr-1, and 8270 kPa. At these conditions the predicted yields of alkane/olefin products and diesel fuel are 47.3 and 50.5 g/100g liquid fed, respectively.

Utilization of amorphous metallic alloy has received much attention for use in numerous microelectronic and electrochemical devices since they provide unique electrical, thermal conductivity, and magnetic properties. To develop these functional properties, it is essential to understand the amorphous structure and the property relationships. First principles calculations provide insight into the structure, thermodynamic stability, electronic and magnetic properties of amorphous alloys. For Ru- and Co-based alloys, the thermodynamic stability was examined by calculating the mixing energy along with those of crystalline counterparts. The amorphous RuP, CoP, RuB, and CoB alloys, become energetically more favorable than their crystalline counterparts at moderate P(B) content. The atomistic structures have well-defined local structures depending on the atomic size ratio and electronic interactions between constituent elements. Their local ordering is attributed to strong p-d hybridization, which contributes to stabilizing the Ru(Co)-P(B) alloys. Surface segregation of P(B) and interfacial adhesion with copper were also studied. Li-X (X: Si, Ge, and Sn) were examined when 1 or 2 Li atoms are inserted into the interstitial sites. Li insertion in the tetrahedral site, which is the most preferable site in the diamond matrix, causes outward displacement and charge localization around the X neighbors, thereby weakening of the covalent bonds leading to destabilization of the host matrix. We present the energetics, structure, electronic and mechanical properties of crystalline and amorphous Li-X (X: Si, Ge, Sn, and Si+Sn) alloys. Our calculations show that the incorporation of Li leads to disintegration of the tetrahedrally-bonded X network into small clusters of various shapes. Electronic structure analysis highlights that the charge transfer leads to weakening or breaking of X bonds with the growing splitting between s and p states, and consequently the Li-X alloys softens with increasing Li content. / text

In general, the basic concept of an intelligent material is defined as the multifunctional material that has a sensor, a processor and an actuator function in the material that allows it to maintain optimum conditions in response to environmental changes. Despite the fact that these materials have demonstrated varying degrees of success in shape and position control, active and passive control of vibration and acoustic transmission of materials subjected to dynamic loads, impact damage and creep resistance in structures and have been applied in industries from aerospace to biomechanics to civil engineering structures, very little literature is available on the subject. Thus, the objective of this dissertation is to add to the fundamental understanding of the behaviour of these special materials by investigating the possibility of a magnetostrictive SMA hybrid metalmatrix composite beam with piezoelectric actuator, to enhance the materials load attenuation and energy absorption characteristics under low velocity impact loading. The methodology employed in this investigation is driven by two primary factors. The first is the unique approach that the author puts forward to attempt to simplify the characterisation of damage in not just metal matrix composites, but in materials in general. The second factor is the lack of available literature on smart material energy absorption as well as a lack of precise theory for short fibre composites. The methodology includes an extensive literature review, the development of an analytical model, based on the new damage modulus approach, verification of the model using experimental results presented by Agag et. aI., adjustment of the model to include smart material effects and finally numerical simulation using the MATLAB® software to predict the effect of smart materials on the energy absorption capacity of the material under impact. The results show that the damage modulus (ED) is a material characteristic and can be derived from the stress strain diagram. Further, it takes into account degradation of the material through the plastic region, up to the point just before ultimate failure. Thus, ED lends itself to the simplification of many damage models in terms of a reducing sustainable load and energy absorption capacity. Only the energy consumed through material rupture remains to be characterised. The results also show that smart fibres diminish the capacity of the beam to sustain a load, but increase the displacement to failure. Thus, for a compatible substrate material, this increased displacement translates to a significant enhancement of energy absorption characteristics. The effect of prestrain on energy absorption is also considered and there appears to be a definite turning point where the dissertation thus achieves its objective in investigating the ability of smart materials to enhance the energy absorption characteristics of regular fibre reinforced metal-matrix composite materials subject to low velocity impact loading. Of equal importance to the achievement of this objective is the introduction in the dissertation of the unique damage modulus that goes to the foundation of material characterisation for mechanical engineering design and has profound implications in damage theory and future design methodologies. Significant learning has taken place in the execution of this PhD endeavour and this dissertation will no doubt contribute to other investigations in the field of smart materials. / Thesis (Ph.D.)-University of Natal,Durban,2003.

In this study, the possibilities to produce metallic glass as binder phase in hard metal by means of powder metallurgical methods have been investigated. The aim of the study was to do an initial investigation about metallic glass as alternative binder phase to cobalt in hard metal. Production of samples with metallic glass forming alloys and an amorphous powder as binder phase in hard metal by means of quenching and hot pressing have been performed. Moreover, mechanical alloying of metallic glass forming powder to achieve amorphicity has been performed. The samples and powders were analyzed by means of XRD, LOM, STA, SEM and EDS. The results showed that no glass formation of the binder phase was achieved by quenching, hot pressing or mechanical alloying. However, interesting information about glass formation by means of metallurgical methods was obtained. The main conclusion was that production of metallic glass by means of metallurgical methods is complicated due to changes in the binder phase composition throughout the production process as well as requirements of high cooling rates when quenching and high pressures when hot pressing.

Thesis (M. App. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 99-114). Also available in electronic format on the Internet.

Progress in nanotechnology has promoted an increasing interest in the rational design of the emerging hierarchical aerogels, which represents a second stage of the NC-based aerogel research. By fine-tuning the surface properties of the backbones, metallic hierarchical aerogels are able to address the growing demands of advanced electrocatalysts. In this dissertation, three types of metallic hierarchical aerogels were designed by introducing different nanostructures (i.e. hollow, porous/dendritic and core-shell) and alloy effects (with noble or transition metals) into the aerogels. Thus, as a proof-of-concept for fuel cells, advanced electrocatalytic performances have been achieved on the resulting metallic hierarchical aerogels towards both anode (oxidation of ethanol) and cathode (reduction of oxygen) reactions. First, alloyed PdxNi hollow nanospheres with controlled composition and shell thickness were utilized as building blocks for the design of hierarchical aerogels. The combination of transition-metal doping, hollow interior, as well as the 3D aerogel structure make the resulting aerogels promising electrocatalysts for ethanol oxidation with a mass activity up to 5.6-fold higher than that of the Pd/C. Second, continuously shape-engineering of the building blocks (ranging from hollow shells to dendritic shapes) was achieved by the synthesis of a series of multimetallic Ni-PdxPty hierarchical aerogels. By optimization of the nanoscale morphology and the chemical composition, the Ni-Pd60Pt40 aerogel exhibits remarkable electrocatalytic activity for oxidation of ethanol. Moreover, the particle growth mechanism underlying the galvanic replacement was revealed in terms of nanowelding of the nanoparticulate reaction intermediates based on experimental and theoretical results. Third, a universal approach was demonstrated for core-shell structuring of metallic aerogels by coating of an ultrathin Pt shell on a composition-tunable Pd-based alloyed core. Their activities for oxygen reduction exhibit a volcano-type relationship as a function of the lattice parameter of the core substrate. Largely improved Pt utilization efficiency was accomplished based on the core-shell motifs, as the mass activity reaches 5.25 A mg-1Pt which are 18.7 times higher than those of Pt/C. Different from the conventional aerogels with nanowire-like backbones, those hierarchical aerogels are generally comprised of at least two levels of architectures, i.e. an interconnected porous structure on the macroscale and a specially designed configuration at local backbones at the nanoscale. This combination “locks in” the inherent properties of the NCs, so that the beneficial genes obtained by nano-engineering are retained in the resulting monolithic hierarchical aerogels. These results expand the exploitation approach of the electrocatalytic properties of aerogels into morphology control of their NBBs and are of great importance for the future development of aerogels for many other electrochemical reactions.

Fe-based bulk metallic glasses (BMGs) have gained considerable interest due to their excellent soft magnetic properties with high saturation magnetization, high electrical resistivity, very good corrosion resistance, low materials cost, extremely high mechanical strength and hardness. In spite of having excellent strength, Fe-based BMGs are not used as structural materials in service, so far. The major obstacle is their inherent brittleness under mechanical loading, once a crack is developed the material fails catastrophically. Owing to the ever growing industrial demand for the materials with outstanding properties, aside from exploring new alloy compositions, it is pertinent to understand why or why-not the existing system work and how to improve their properties. Recent reports suggested that the plastic deformability can be enhanced by introducing different microstructural heterogeneities such as free volume enhanced regions, separated phases, nano-crystals, atomic clusters caused by for instance additions of small amount of soft elements. Understanding the effect of addition of soft elements to Fe-based BMGs on thermal stability, structural evolution, magnetic and mechanical properties are the main point which this work addresses. In this work, a study on two different soft ferromagnetic Fe-based glass forming alloys are presented, both of them known to have very high mechanical strength and excellent soft magnetic properties but so far have not been used in any industrial applications. The important issue is with the brittle behavior of this BMGs, particularly under mechanical loading. In each glass forming alloys, the aim was to find out the optimum quantity of the soft elements (Cu and Ga), which can be added to improve their room temperature plastic deformability without affecting the glass forming ability (GFA) and soft magnetic properties. The first glass forming alloy that is studied is Fe36Co36B19.2Si4.8Nb4. This glass forming alloy is highly sensitive to the impurities, only pure elements were used to form this alloy. The addition of only 0.5 at.% Cu completely changes the thermal stability and structural evolution but it also improves the mechanical properties. In case of Ga addition up to 1.5 at.% the crystallization behavior remains unaltered and the thermal stability improves marginally. The addition of Ga improves the plastic deformability of the glass by forming soft zones, whose melting point is much lower compared to rest of the alloy. These soft zones are responsible for the plastic deformation of this glass. Thus addition of Ga is very beneficial in improving the mechanical properties of this Fe-based BMG. In the second part, Fe74Mo4P10C7.5B2.5Si2 glass forming alloy is studied. Unlike the aforementioned alloy, this glass forming alloy is not very sensitive to the impurities, industrial grade alloy elements can also be used to form this alloy. In this alloy addition of Cu is beneficial only up to 0.5 at.%, beyond that Cu addition deteriorates GFA and magnetic properties. In case of Ga addition up to 2 at.% the crystallization behavior remains unaltered and the thermal stability improves marginally. Similar to the FeCoBSiNb glass, the addition of Ga in FeMoPCBSi glass also improves the plastic deformability of the glass by formation of soft zones. Addition of small at.% Ga proved be an viable solution to improve the plastic deformability in the ferromagnetic Fe-based metallic glasses without compromising on thermal and magnetic properties of the glass. In the final part we tried to cast the Fe74Mo4P10C7.5B2.5Si2 glass in a complex shape using an industrial high pressure die casting (HPDC) set up. The important issues were with the casting alloy temperature, casting speed and die material. The aim of our work was to optimize the die material suitable for casting the BMGs and then address the issues with casting temperature and casting speed. We have thus attempted to gain a basic knowledge in casting the Fe-based BMG in industrial scale. Our effort was tremendously successful, we were able to produce fully amorphous complex shaped samples with excellent surface finish. We have thus made a considerable advancement towards understanding the basics behind improving the room temperature plastic deformability in Fe36Co36B19.2Si4.8Nb4 and Fe74Mo4P10C7.5B2.5Si2 ferromagnetic BMGs. We have also made a considerable progress in industrialization of bulk ferromagnetic BMGs.