Diss. (sammanfattning) Uppsala : Uppsala universitet, 2009. / Härtill 8 uppsatser.

This thesis work brings fresh insights and improved understanding of nanoscale materials through introducing new hybrid composites, 2D hexagonal in MCM-41 and 3D random interconnected structures of different materials, and application relevance for developing fields of science, such as fuel cells and solar cells.New types of porous materials and organometallic crystals have been prepared and characterized in detail. The porous materials have been used in several studies: as hosts to encapsulate metal-organic complexes; as catalyst supports and electrode materials in devices for alternative energy production. The utility of the new porous materials arises from their unique structural and surface chemical characteristics as demonstrated here using various experimental and theoretical approaches.New single crystal structures and arene-ligand exchange properties of f-block elements coordinated to ligand arene and halogallates are described in Paper I. These compounds have been incorporated into ordered 2D-hexagonal MCM-41 and polyhedral silica nanofoam (PNF-SiO2) matrices without significant change to the original porous architectures as described in Paper II and III. The resulting inorganic/organic hybrids exhibited enhanced luminescence activity relative to the pure crystalline complexes.A series of novel polyhedral carbon nanofoams (PNF-C´s) and inverse foams were prepared by nanocasting from PNF-SiO2’s. These are discussed in Paper IV. The synthesis conditions of PNF-C’s were systematically varied as a function of the filling ratio of carbon precursor and their structures compared using various characterization methods. The carbonaceous porous materials were further tested in Paper V and VI as possible catalysts and catalyst supports in counter- and working electrodes for solar- and fuel cell applications. / QC 20101207

During the last 30 years a new research and technology field of organic electronic materials has grown thanks to a groundbreaking discovery made during the late 70’s. This new field is today a worldwide research effort focusing on exploring a new class of materials that also enable many new areas of electronics applications. The reason behind the success of organic electronics is the flexibility to develop materials with new functionalities via clever chemical design and the possibility to use low‐cost production techniques to manufacture devices. This thesis reports different aspects of electrochemical applications of organic electronics. We have shown that the color contrast in reflective and transmissive electrochromic displays can be almost doubled by adding an extra electrochromic polymer. The choice of electrochromic material was found to be limited by its electrochemical over‐oxidation (ECO) properties, which is one of the main degradation mechanisms found in displays. The irreversible and non‐conducting nature of over‐oxidized films encouraged us to use it in a novel patterning process in which polythiophene films can be patterned through local and controlled deactivation of the conductivity. ECO can be combined with various patterning tools such as screen printing for low‐cost roll‐to‐roll manufacturing or photolithography, which enables patterning of small features. Studies have shown that electronic conductivity contrasts beyond 107 can be achieved, which is enough for various simple electronic systems. To generate better understanding of the ECO phenomenon, the effect of pH on the over‐oxidation characteristics was studied. The results suggest that a part of the mechanism for over‐oxidation depends on the OH– concentration of the electrolyte used. Over‐oxidation has also been used in electrochemical loggers, where the temperature and time dependence of the propagation of an over‐oxidation front is used to monitor and record the temperature of a package. / Dagligen kommer vi i kontakt med olika plastmaterial. Dessa har vanligtvis mycket dålig elektrisk ledningsförmåga och används oftast som isolerande material. Det finns dock en klass av plaster som är halvledande eller ledande. Sedan upptäckten av dessa material för mer än 30 år sedan har nya material och användningsområden utvecklats och nu börjar de första produkterna baserad på organisk elektronik komma ut på marknaden. En stor fördel med de ledande plasterna är att egenskaperna kan anpassas genom att ändra den kemiska strukturen. Man kan dessutom lösa upp dem och skapa ledande bläck, som sedan kan användas i vanliga tryckmaskiner. Detta gör det möjligt att på ett enkelt och billigt sätt tillverka elektronik på liknande sätt som till exempel tidningar trycks idag. Den här avhandlingen behandlar en del av det nya området som berör elektrokemiska komponenter och några av dess tillämpningar. Fokus ligger främst på billig, tryckt elektronik. Bland annat presenteras ett sätt att fördubbla kontrasten för tryckta pappersdisplayer, ett nytt sätt att mönstra ledande plaster och elektrokemisk temperaturloggningsetikett som kan övervaka temperaturen för förpackningar under transport. Den mekanism som förstör ledningsförmågan vid höga spänningar har varit ett återkommande inslag i de studier som har genomförts här. Denna mekanism förstör komponenterna under drift men kan också användas för att ta bort ledningsförmågan som mönstringsmetod eller för att lagra information, permanent, i temperaturloggningsetiketten.

The  supply  of  energy  and  the  protection  of  the  environment  have  been  two  of  the most  important problems  to have affected mankind  in  recent decades.The waste management  is become a very  crucial environmental problem in the world, due to the ever increasing amount of waste material, domiciliary and industrial, generated. The main strategies for the waste management are the protection of the environment and used to produce energy.  Lignin, the second most abundant component besides cellulose in biomass. In this study,  lignosulfonate, is used as fuel in the solid oxide fuel cell to produce a power and heat, which is a byproducts from the wood pulp using sulfite pulping. To enhance the performance and conductivity of the biomass based fuel cell, the lignin was treated with hydroxides (Li/K) and chlorides (Fe2Cl3) at different temperature 200 -500 °C.  The maximum obtained power density was about 20 mW/cm2. And the calculated electrical efficiency of the cell was about 30%.   Also,  this kind of biomass fuel was used  in single component fuel cell and  results were compared with three components fuel cell.  The phase analysis, microstructure and conductivity of lignin was analysed by XRD, SEM and AC impedance technique.  It has been concluded that a sulfonated  lignin from waste of the paper industry can be used  as a energy sources with fuel cell operation.

Denna licentiatavhandling behandlar effekten av två inneboende egenskaper (fissions produkter och egenbestrålning) hos utbränt kärnbränsle på hastigheten för strålningsinducerad upplösning av bränslematris (UO2). I ett framtida djupförvar kommer det utbrända kärnbränslet att deponeras 500 meter ner i berggrunden i en reducerande miljö. Under dessa förhållanden är UO2-matrisen själv en av de skyddande barriärerna mot frigörande av radionuklider, på grund av dess låga löslighet. När bränslet kommer i kontakt med vatten kommer U(IV) att oxideras till U(VI) av radiolysprodukter från vattnet och lösligheten för bränslematrisen kommer därmed att öka betydligt. De flesta tidigare studier har utförts på obestrålad UO2 som skiljer sig signifikant från utbränt kärnbränsle. I utbränt kärnbränsle är de flesta fissionsprodukterna och neutronaktivieringsprodukterna radioaktiva och bränslet kommer därför bli bestrålat av sig självt. Effekten av joniserande strålning på reaktiviteten för UO2(s) har undersökts här. UO2 (pulver och fragment av en kuts) bestrålades i en 60Co γ-källa eller framför en elektronaccelerator varpå reaktiviteten för UO2 studerades genom oxidation av UO2 med MnO4 -. Det visade sig att reaktiviteten för UO2 ökar när det blir bestrålat för första gången (<20 kGy). Effekten ökar med ökande dos tills den når ett maxvärde ~1.3 gånger reaktiviteten för obestrålad UO2 vid torrbestrålning. Vid våtbestrålning ökar en dos på 140 kGy reaktiviteten 2.5 gånger. Effekten verkar vara permanent. Tidigare studier har visat att H2O2 är den viktigaste oxidanten för upplösning av utbränt kärnbränsle under djupförvarsförhållanden. I vätgasatmosfär, som förväntas i ett djupförvar, har det visat sig att upplösningshastigheten är långsammare. Det har delvis förklarats med reaktionen mellan H2O2 och H2, som är väldigt långsam utan katalysator. Den katalytiska effekten av UO2 på den reaktionen har undersökts och det visades att den inte katalyseras av UO2. En annan möjlig katalysator för reaktionen är ε-partiklar (ädelmetallpartiklar bestående av Mo, Ru, Tc, Pd och Rh) som bildats av fissionsprodukterna. Pd är en välkänd katalysator för reduktion med H2. Den eventuella katalytiska effekten av Pd har undersökts här. Även en eventuell katalytisk effekt av Pd på reduktionen av U(VI) med H2 undersöktes, både i vattenfas och i UO2-kutsar innehållande olika mängder Pd (som en modell för ε-partiklar). Vi fann att Pd har en katalytisk effekt på reaktionen mellan H2O2 och H2 och andra ordningens hastighetskonstant är bestämd till (2.1±0.1)x10-5 m s-1. Pd har också en katalytisk effekt på reduktionen av U(VI) med H2 både i vattenlösning, hastighetskonstant (1.5±0.1)x10-5 m s-1, och i den fasta fasen. Hastighetskonstanten för processen i fast fas är 4x10-7 m s-1 och 7x10-6 m s-1 för kutsar med 1 respektive 3 % Pd. Dessa värden är väldigt nära diffusionsgränsen för den här typen av system. Den katalytiska effekten i den fasta fasen visar att upplösningen för 100 år gammalt bränsle kan stoppas helt. Vid 40 bar H2 krävs 10-20 ppm ädelmetallpartiklar och med 1 % ädelmetallpartiklar räcker det med 0.1 bar H2 för att stoppa upplösningen. / This licentiate thesis deals with the influence of two inherent properties (fission products and self irradiation) of spent nuclear fuel on the rate of radiation induced fuel matrix (UO2) dissolution. In a future deep repository the spent nuclear fuel will be deposited 500 meters down in the bedrock in a reducing environment. Under these conditions the UO2-matrix itself is one of the protective barriers against release of radionuclides due to its very low solubility. When the fuel comes in contact with water, U(IV) will be oxidized to U(VI) by products from radiolysis of water and the solubility of the fuel matrix will increase significantly. Most previous studies have been performed on unirradiated UO2 which differ significantly from spent nuclear fuel. In spent nuclear fuel most of the fission products and neutron activation products are radioactive and therefore the fuel will be irradiated by itself. The effect of ionizing radiation on the reactivity of UO2 has been investigated here. UO2 (powder and fragment of a pellet) has been exposed to irradiation in a 60Co γ-source or in an electron accelerator and then the redox reactivity was studied. The kinetics for oxidation of UO2 by MnO4 - was used as a monitoring reaction. It was shown that the reactivity of UO2 increases when being irradiated for the first time (<20kGy). The effect increases with increasing dose until reaching a maximum value ~1.3 times the reactivity of unirradiated UO2 for dry irradiation. For wet irradiation a dose of 140 kGy increases the reactivity ~2.5 times. This effect appears to be permanent. Previous studies have shown that H2O2 is the most important oxidant for spent nuclear fuel dissolution under deep repository conditions. Under H2 atmosphere, as expected in a deep repository, it has been shown that the dissolution rate is slower. This has partly been attributed to the reaction between H2O2 and H2 which is very slow without a catalyst. The catalytic effect of UO2 on this reaction was examined showing that UO2 does not catalyze this reaction. Another possible catalyst for this reaction is the ε-particles (noble metal particles containing Mo, Ru, Tc, Pd and Rh) formed by the fission products. Pd is a well known catalyst for reduction by H2. The possible catalytic effect of Pd on the reaction between H2O2 and H2 is examined here. The possible catalytic effect of Pd on the reduction of U(VI) by H2 is also examined, both in aqueous phase and in UO2 pellets containing different amounts of Pd (as a model for spent fuel containing ε-particles). It was found that Pd has a catalytic effect on the reaction between H2O2 and H2, the second order rate constant is determined to (2.1±0.1)x10-5 m s-1. Pd also has a catalytic effect on the reduction of U(VI) by H2 both in aqueous solution, rate constant (1.5±0.1)x10-5 m s-1, and in the solid phase, rate constants 4x10-7 m s-1 and 7x10-6 m s-1 for pellets with 1 and 3 % Pd respectively. These values are very close to the diffusion limit for these systems. The catalytic effect in the solid phase shows that the dissolution for 100 year old fuel can be completely inhibited, at 40 bar H2 a noble metal particle content of 10-20 ppm is needed and with 1 % noble metal particle content 0.1 bar H2 is enough to stop the dissolution. / QC 20101119

I det svenska djupförvaret för kärnbränsle ska kompakterad bentonit användas som barriär mellan kopparkapslar med utbränt kärnbränsle och berget. I kontakt med vattenförande sprickor kan bentonitbarriären under vissa omständigheter avge montmorillonitkolloider. Förutom att barriärens egenskaper urholkas pga förlusten av material kan kolloiderna, om de är stabila, underlätta transporten av sorberade radionuklider ut mot biosfären. Den här studien fokuserar på att undersöka vilka effekter grundvattenkemin har på montmorillonitkolloiders stabilitet. Grundvattnets sammansättning, pH och jonstyrka, kommer sannolikt att förändras under djupförvarets livslängd, delvis pga inträngandet av glactialt smältvatten. Initialt kommer omgivande berg att värmas upp pga värmealstring från det radioaktiva sönderfallet i det utbrända kärnbränslet. Effekterna av pH, jonstyrka och temperatur på montmorillonitkolloiders stabilitet har analyserats genom att följa hur kolloiderna aggregerar med tiden. Minskningen av partikelkoncentration med tiden mättes med Photon Correlation Spectroscopy (PCS). Aggregationsexperimenten visar att, vid ett givet pH och en given temperatur, ökar hastighetskonstanten för aggregation med ökande jonstyrka. Kritiska koaguleringskoncentrationen (CCC) för NaCl och CaCl2 för Na-montmorillonit och Ca-montmorillonit beräknas utifrån ett samband mellan hastighetskonstanterna och jonstyrkan. Hastighetskonstanten för aggregation minskar med ökande pH eftersom ytpotentialen ökar. Effekten blir tydligare vid högre jonstyrkor och högre temperaturer, men kan däremot inte observeras vid låga temperaturer. Temperatureffekten på bentonitkolloidernas stabilitet är pH-beroende. Vid pH≤4 ökar hastighetskonstanten för kolloidaggregation med ökande temperatur, oavsett jonstyrka.Vid pH≥10 minskar hastighetskonstanten med ökande temperatur. I mellanliggande pH-område minskar hastighetskonstanten för aggregation med ökande temperatur, förutom vid den högsta jonstyrkan, där den ökade. Beräkningar baserade på DLVO-teori matchar de experimentella resultaten. / In deep geological repositories in Sweden, encapsulated nuclear waste will be surrounded by compacted bentonite in the host rock. In future contact with water-bearing fractures, this bentonite barrier can release montmorillonite colloids under certain conditions. This process can lead to loss of buffer material. Furthermore, these colloids, if stable, may facilitate the transport of associated radionuclides towards the biosphere. Colloid stability is determined by groundwater chemistry. This study addresses the effects of groundwater chemistry on the stability of montmorillonite colloids. During the lifetime of the repository, the pH and ionic strength of the groundwater are expected to vary, partly due to intrusion of glacial melt water. Initially, the temperature will be higher in the surrounding host rock due to heat released from radioactive decay in the spent nuclear fuel. The effects of these parameters on the stability of montmorillonite suspensions were evaluated by studying the aggregation kinetics. The change in particle concentration with time was monitored by Photon Correlation Spectroscopy (PCS). Aggregation kinetics experiments showed that for a given pH and temperature, the rate constant for colloid aggregation increased with increasing ionic strength. The relationship between the rate constant and the ionic strength allowed the NaCl and CaCl2 critical coagulation concentration (CCC) for Na- and Ca-montmorillonite to be determined. The aggregation rate constant decreased with increasing pH as the surface potential increased. This effect became more pronounced at higher ionic strengths and higher temperatures but could not be observed at low temperature. The effect of temperature on the stability of the suspensions is pH-dependent. At pH≤4, the rate constant for colloid aggregation increased with increasing temperature, regardless of ionic strength. At pH≥10, the aggregation rate constant decreased with increasing temperature. In the intermediate pH interval, the aggregation rate constant decreased with increasing temperature except at the highest ionic strength, where it increased. The experimental results were in agreement with DLVO calculations. / QC 20101105

High entropy ceramics have rapidly developed as a class of materials based on high entropy alloys; the latter being materials that contain five or more elements in near-equal proportions. Their unconventional compositions and chemical structures hold promise for achieving unprecedented combinations of mechanical, electrical and chemical properties. In this thesis, high entropy ceramic films, (TiNbZrTa)Nx were deposited using reactive magnetron sputtering with segmented targets. The stoichiometry x was tuned with two deposition parameters, i.e., substrate temperature and nitrogen flow ratio fN, their effect on microstructure and mechanical, electric, and electrochemical properties were investigated. Understoichiometric MeNx (Me = TiNbZrTa, 0.25 ≤ x ≤ 0.59) films were synthesized at a constant fN when substrate temperature was varied from room temperature (RT) to 700 °C. For low-temperature deposition, the coatings exhibited fcc solid-solution polycrystalline structures. A NaCl-type structure with (001) preferred orientation was observed in MeN0.46 coating deposited at 400 ºC, while an hcp structure was found for the coatings deposited above 500 ºC. The maximum hardness value of 26 GPa as well as the highest <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Ctiny%7BH/E_r%7D" />  and <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Ctiny%7BH%5E3%7D%0A%0A" /><img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Ctiny%7B/E_r%5E2%7D%20" />  values (0.12 and 0.34 GPa) were obtained for the MeN0.46 coating. These films exhibited low RT electrical resistivities. In 0.1 M H2SO4 aqueous solution, the most corrosion resistant film was MeN0.46 featured dense structure and low roughness. The MeNx films (x=0, 0.57 &lt; x ≤ 0.83) were deposited with different fN. The maximum hardness was achieved at 22.1 GPa for MeN0.83 film. Their resistivities increased from 95 to 424 μΩcm with increasing nitrogen content. The corrosion resistance is related to the amount of nitrogen in the films. The corrosion current density was around 10-8 A/cm2, while the films with lower nitrogen contents (x &lt; 0.60) exhibited a nearly stable current plateau up to 4.0 V, similar to the metallic films, while the films with a higher nitrogen content only featured a plateau up to 2.0 V, above which a higher nitrogen content resulted in higher currents. The reason was that the oxidation of these films at potentials above about 2.0 V vs. Ag/AgCl resulted in the formation of porous oxide layers as significant fraction of the generated N2 was lost to the electrolyte. Hence, these observed effects of deposition temperature and nitrogen content on the overall properties of nonstoichiometric MeNx films provide insights regarding protective multicomponent nitride films, e.g. as corrosion resistant coatings on metallic bipolar plates in fuel cells or batteries.

<p>Thermodynamic, viscous and structural properties of melts and glasses in the AlCl₃-ZnCl₂ system have been investigated. The two pure components are fundamentally different in the molten state. Both metal atoms are four coordinated, however, ZnCl₂ forms a corner sharing tetrahedral network whereas AlCl₃ is a dimer, Al₂Cl₆. ZnCl₂ is one of two known single component halide glass formers and additions of AlCl₃ have shown to form stable glasses. The glass forming ability remains far into the binary AlCl₃-ZnCl₂ system.</p><p>The phase diagram of the AlCl₃-ZnCl₂ system has been investigated by differential thermal analysis. The system is a simple eutectic system, and the eutectic point was observed at 116±2°C and 0.52±0.05 mole fraction ZnCl₂. The system is highly glass forming in the range from pure ZnCl₂ up to about 0.46 mole fraction ZnCl₂. Glass transition temperatures measured by differential scanning calorimetry (heating rate 10 K/min) were recorded from 115°C for pure ZnCl₂ to -5.5°C for 0.46 mole fraction ZnCl₂. The reduced width of the glass transition ( T_g'-T_g )/T_g showed a maximum at 0.80 mole fraction ZnCl₂ giving a minimum in fragility at this composition.</p><p>The density of AlCl₃-ZnCl₂ melts has been determined using volume measurements in sealed quartz tubes. The molar volumes showed a negative deviation from ideality with a minimum at ~0.33 mole fraction ZnCl2 (ZnAl₂Cl₈). The volume expansion coefficient is strongly reduced from pure AlCl₃ to ZnCl₂, and the excess volume of mixing is strongly increasing with temperature. A simple model using molecular Al₂Cl₆, ZnCl₂ and ZnAl₂Cl₈ units was used to calculate equilibrium constants for the reaction of pure components ZnCl₂ and Al₂Cl₆ to ZnAl₂Cl₈. The density data showed that molecular ZnAl₂Cl₈ became more stable with increasing temperature. The viscosity of molten AlCl₃-ZnCl₂ in the range from pure ZnCl₂ to 0.40 mole fraction ZnCl₂ has been measured as a function of temperature by an oscillation cup method. The melts with ZnCl₂ content higher than 0.60 mole fraction ZnCl₂exhibited non-Arrhenius behavior. The viscosity clearly decreases with increasing AlCl₃ content. However, the viscosity of ZnCl₂is affected less by addition of AlCl₃ compared to addition of ionic chlorides which form terminal chloride bonds. The fragility of the melts obtained from a reduced Arrhenius plot, were observed to decrease with addition of AlCl₃ up to 0.80 mole fraction ZnCl₂. At higher AlCl₃ content the fragility increases in line with the more molecular nature of the melt. The present study has also demonstrated that the oscillation cup viscometer can be applied to record viscosities as high as 3 Pa·s.</p><p>IR spectroscopy has been performed on melts in the whole compositional range of the AlCl₃-ZnCl₂ system. The spectra were recorded using an IR reflection method of thin films (>10 µm). Compensation for any splitting of strong bands was performed by defining a specular reflectance, r*, where a thick melt (2-3 mm)\ was used as reference. For all the mixtures a splitting of the anti-symmetric stretching frequency ν3(F2) for the AlCl₄ tetrahedron into three bands was observed. This indicated a C2v perturbation of the T_d symmetry. From this observation it was proposed that the AlCl₄ units were always terminal consisting of two bridging and two terminal chlorines. The melts with compositions from 0.33 mole fraction ZnCl2 to pure Al2Cl6 are proposed to consist of a mixture of Al₂Cl₆ and ZnAl₂Cl₈. The temperature dependence of the 0.20 mole fraction ZnCl₂ spectra showed that the amount of ZnAl₂Cl₈ increased relative to the amount of Al₂Cl₆with increasing temperature. At 0.40 - 0.60 mole fraction ZnCl₂, the melts were proposed to remain molecular in nature, where the ZnCl₄ tetrahedra were enclosed by edge sharing AlCl₄ terminal units. At higher ZnCl₂ content or higher temperatures the connectivity of the molten structure is shifted from edge sharing AlCl₄ units to corner sharing AlCl₄ units bonded to two ZnCl₄ tetrahedra.</p>

Thermodynamic, viscous and structural properties of melts and glasses in the AlCl3-ZnCl2 system have been investigated. The two pure components are fundamentally different in the molten state. Both metal atoms are four coordinated, however, ZnCl2 forms a corner sharing tetrahedral network whereas AlCl3 is a dimer, Al2Cl6. ZnCl2 is one of two known single component halide glass formers and additions of AlCl3 have shown to form stable glasses. The glass forming ability remains far into the binary AlCl3-ZnCl2 system. The phase diagram of the AlCl3-ZnCl2 system has been investigated by differential thermal analysis. The system is a simple eutectic system, and the eutectic point was observed at 116±2°C and 0.52±0.05 mole fraction ZnCl2. The system is highly glass forming in the range from pure ZnCl2 up to about 0.46 mole fraction ZnCl2. Glass transition temperatures measured by differential scanning calorimetry (heating rate 10 K/min) were recorded from 115°C for pure ZnCl2 to -5.5°C for 0.46 mole fraction ZnCl2. The reduced width of the glass transition ( Tg'-Tg )/Tg showed a maximum at 0.80 mole fraction ZnCl2 giving a minimum in fragility at this composition. The density of AlCl3-ZnCl2 melts has been determined using volume measurements in sealed quartz tubes. The molar volumes showed a negative deviation from ideality with a minimum at ~0.33 mole fraction ZnCl2 (ZnAl2Cl8). The volume expansion coefficient is strongly reduced from pure AlCl3 to ZnCl2, and the excess volume of mixing is strongly increasing with temperature. A simple model using molecular Al2Cl6, ZnCl2 and ZnAl2Cl8 units was used to calculate equilibrium constants for the reaction of pure components ZnCl2 and Al2Cl6 to ZnAl2Cl8. The density data showed that molecular ZnAl2Cl8 became more stable with increasing temperature. The viscosity of molten AlCl3-ZnCl2 in the range from pure ZnCl2 to 0.40 mole fraction ZnCl2 has been measured as a function of temperature by an oscillation cup method. The melts with ZnCl2 content higher than 0.60 mole fraction ZnCl2 exhibited non-Arrhenius behavior. The viscosity clearly decreases with increasing AlCl3 content. However, the viscosity of ZnCl2 is affected less by addition of AlCl3 compared to addition of ionic chlorides which form terminal chloride bonds. The fragility of the melts obtained from a reduced Arrhenius plot, were observed to decrease with addition of AlCl3 up to 0.80 mole fraction ZnCl2. At higher AlCl3 content the fragility increases in line with the more molecular nature of the melt. The present study has also demonstrated that the oscillation cup viscometer can be applied to record viscosities as high as 3 Pa·s. IR spectroscopy has been performed on melts in the whole compositional range of the AlCl3-ZnCl2 system. The spectra were recorded using an IR reflection method of thin films (&gt;10 µm). Compensation for any splitting of strong bands was performed by defining a specular reflectance, r*, where a thick melt (2-3 mm)\ was used as reference. For all the mixtures a splitting of the anti-symmetric stretching frequency ν3(F2) for the AlCl4 tetrahedron into three bands was observed. This indicated a C2v perturbation of the Td symmetry. From this observation it was proposed that the AlCl4 units were always terminal consisting of two bridging and two terminal chlorines. The melts with compositions from 0.33 mole fraction ZnCl2 to pure Al2Cl6 are proposed to consist of a mixture of Al2Cl6 and ZnAl2Cl8. The temperature dependence of the 0.20 mole fraction ZnCl2 spectra showed that the amount of ZnAl2Cl8 increased relative to the amount of Al2Cl6 with increasing temperature. At 0.40 - 0.60 mole fraction ZnCl2, the melts were proposed to remain molecular in nature, where the ZnCl4 tetrahedra were enclosed by edge sharing AlCl4 terminal units. At higher ZnCl2 content or higher temperatures the connectivity of the molten structure is shifted from edge sharing AlCl4 units to corner sharing AlCl4 units bonded to two ZnCl4 tetrahedra.

Boron-carbon thin films enriched with 10B are potential neutron converting layers for 10B-based solid state neutron detectors given the good neutron absorption cross section of 10B atoms in thin films. The common neutron-transparent base material, Al (melting point 660 °C), limits the deposition temperature and the use of chlorinated precursors forming corrosive by-products such as HCl. Therefore, the organoborons triethylboron B(C2H5)3 (TEB) and trimethylboron B(CH3)3 (TMB) are evaluated as precursors for CVD of BxC films. In order to get a complete understanding of the CVD behaviour of these precursors for deposition of boron containing films, both thermal CVD and plasma CVD of BxC films have been demonstrated. A gas phase chemical mechanism at the corresponding thermal CVD conditions was proposed by quantum chemical calculations while chemical mechanism in the plasma was suggested based on plasma composition obtained from Optical emission spectroscopy (OES). The behaviours of TEB and TMB in thermal CVD are investigated by depositing BxC films in both H2 and Ar atmospheres, respectively. Films deposited using TEB within a temperature window of 600 – 1000 °C are X-ray amorphous with 2.5 ≤ x ≤ 4.5. The impurity level of H is less than 1 at. % above 600 °C. Calculations predict that the gas phase reactions are dominated by β-hydride eliminations of C2H4 to yield BH3. In addition, a complementary bimolecular reaction path based on H2 assisted C2H6 elimination to BH3 is also present at lower temperatures in the presence of hydrogen molecules. As for films deposited with TMB, dense, amorphous, boron rich (B/C = 1.5-3) films are obtained at 1000 °C in both H2 and Ar atmosphere.  The quantum chemical calculations suggest that the TMB molecule is mainly decomposed by unimolecular α- elimination of CH4 complemented by H2 assisted elimination of CH4. Plasma CVD of BxC thin films has been studied using both TMB and TEB as single-source precursors in an Ar plasma at temperatures lower than that allowed by thermal CVD. The effect of plasma power, TMB/TEB and Ar gas flow on film composition and morphology are investigated. The highest B/C ratio of 1.9 is found for films deposited at highest plasma power (2400 W) and high TMB flow (7 sccm). The H content in the films stays almost constant at 15±5 at. %. The B-C bonding is dominant in the films while small amounts of C-C and B-O exist, likely due to formation of amorphous carbon and surface oxidation. Film density is determined as 2.16±0.01 g/cm3 and the internal compressive stresses are measured to be less than 400 MPa. OES shows that TMB is decomposed to mainly atomic H, C2, BH, and CH. A plasma chemical model for decomposition of the TMB is constructed using a combination of film and plasma composition. It is suggested that the decomposition of TMB starts with dehydrogenation of the methyl groups followed by breakage of the B-C bonds to form the CH radicals. This bond breaking is at least partly assisted by hydrogen in forming the BH radicals. When films are deposited using TEB flow of 5 and 7 sccm, the B/C ratio is found to be plasma power dependent while the carbon content is almost not affected. The highest B/C ratio of 1.7 is obtained at the highest power applied (2400 W) and attributed to better dissociation of TEB at higher plasma power. The H content in the films is within 14-20 at. %. The density of films is increased to 2.20 g/cm3 with increasing plasma power and attributed to a higher energetic surface bombardment during deposition. The oxygen content in the film is reduced to less than 1 at. % with increasing plasma power due to the densification of  the films preventing surface oxidation upon air exposure. Plasma composition from OES shows that the TEB molecules are also dissociated mainly to BH, CH, C2 and H. A plasma chemical model where the first ethyl group is split off by β-hydrogen elimination to form C2H4, which is further dehydrogenated to C2H2 and  forms C2 and CH is suggested. The BH species is assumed to be formed by the dehydrogenation of remaining ethyl groups and breakage of the remaining B-C bonds to form BH.