Elemental analysis of wood materials by external millibeam thick target PIXE

PIXE (Particle Induce X-ray Emission spectrometry) was used for analysing stem bark and stem wood of Scots pine, Norway spruce and Silver birch. Thick samples were irradiated, in laboratory atmosphere, with 3 MeV protons and the beam current was measured indirectly using a photo multiplicator (PM) tube. Both point scans and bulk analyses were performed with the 1 mm diameter proton beam. In bulk analyses, whole bark and sectors of discs of the stem wood were dry ashed at 550 ˚C. The ashes were homogenised by shaking and prepared to target pellets for PIXE analyses. This procedure generated representative samples to be analysed, but the enrichment also enabled quantification of some additional trace elements. The ash contents obtained as a product of the sample preparation procedure also showed to be of great importance in the evaluation of results in environmental studies. Spot scans from the pith of pine wood outwards, showed clearly highest concentrations of manganese, calcium and zinc in the first spot irradiated, or 2-3 times higher than in the surrounding wood. For stem wood from the crown part of a pine this higher concentration level was found in the first four spots/mms, including the pith and the two following growth rings. Zinc showed increasing concentrations outwards in sapwood of the pine stem, with the over-all lowest concentrations in the inner half of the sapwood. This could indicate emigration of this element from sapwood being under transformation to heartwood. Point scans across sapwood of pine and spruce showed more distinct variations in concentrations relative to hearth wood. Higher concentrations of e.g. zinc, calcium and manganese were found in earlywood than in denser latewood. Very high concentrations of iron and copper were also seen for some earlywood increments. The ash content of stem bark is up to and order higher than for the stem wood. However, when the elemental concentration in ashes of bark and wood of the same disc were compared, these are very similar – this when trees are growing at spots with no anthropogenic contamination from the atmosphere. The largest difference was obtained for calcium which appeared at two times high concentrations in ashes of bark than in ashes of the wood (ratio of 2). Pine bark is often used in monitoring of atmospheric pollution, where concentrations in bark samples are compared. Here an alternative approach is suggested: Bark and the underlying stem wood of a pine trees are dry ashed and analysed. The elemental concentration in the bark ash is then compared to the concentration of the same element in the wood ash. Comparing bark to wood includes a normalisation for the varying availability of an element from the soil at different sites. When this comparison is done for the ashes of the materials, a normalisation is also obtained for the general and locally different enrichment of inorganic elements from wood to bark. Already a ratio >2 between the concentration in the bark ash and the concentration in the wood ash could indicate atmospheric pollution. For monitoring where bark is used, this way of “inwards” comparison is suggested - instead of comparing to results from analyses of bark from other trees (read reference areas), growing at sites with different soil and, locally, different climate conditions. This approach also enables evaluation of atmospheric pollution from sampling of only relative few individual trees –preferable during forest felling.

Histochemical aspects of reserves mobilization of Caesalpinia peltophoroides (Leguminosae) seeds during germination and seedlings early growth

The objective of this study was to investigate reserve mobilization in Caesalpinia peltophoroides seeds during germination and initial seedling growth. The variation in these compounds was analyzed from the pre-germination period (0 to 5 days after sowing - DAS) to the total cotyledon senescence and abscission at 35 DAS. For this histochemical tests were made on cotyledons fixed in FAA50 or included in glycol-metacrylate. To follow the mobilization of the main reserve compounds, sudan III was used to detect total lipids, xylidine Ponceau to detect total proteins, lugol to detect starch and polarized light to visualize the crystals. The lipids, present in a great quantity in the cotyledon, gradually decreased in the period studied. A greater quantity of starch was observed on the 10th DAS than in the previous periods and it was totally consumed by 30 DAS. The distribution pattern and the morphology of the protein material were very modified by 10 DAS, a period during which it was intensely consumed, remaining only parietally fragments distributed, that practically disappeared at 25 DAS. The calcium oxalate druses were not consumed during the period studied, there was only crystal agglutination.

Growth, magnetic and transport properties of InSb and II-IV-As2 semiconductors doped with manganese

This thesis is devoted to growth and investigations of Mn-doped InSb and II-IV-As2 semiconductors, including Cd1-xZnxGeAs2:Mn, ZnSiAs2:Mn bulk crystals, ZnSiAs2:Mn/Si heterostructures. Bulk crystals were grown by direct melting of starting components followed by fast cooling. Mn-doped ZnSiAs2/Si heterostructures were grown by vacuum-thermal deposition of ZnAs2 and Mn layers on Si substrates followed by annealing. The compositional and structural properties of samples were investigated by different methods. The samples consist of micro- and nano- sizes clusters of an additional ferromagnetic Mn-X phases (X = Sb or As). Influence of magnetic precipitations on magnetic and electrical properties of the investigated materials was examined. With relatively high Mn concentration the main contribution to magnetization of samples is by MnSb or MnAs clusters. These clusters are responsible for high temperature behavior of magnetization and relatively high Curie temperature: up to 350 K for Mn-doped II-IV-As2 and about 600 K for InMnSb. The low-field magnetic properties of Mn-doped II-IV-As2 semiconductors and ZnSiAs2:Mn/Si heterostructures are connected to the nanosize MnAs particles. Also influence of nanosized MnSb clusters on low-field magnetic properties of InMnSb have been observed. The contribution of paramagnetic phase to magnetization rises at low temperatures or in samples with low Mn concentration. Source of this contribution is not only isolated Mn ions, but also small complexes, mainly dimmers and trimmers formed by Mn ions, substituting cation positions in crystal lattice. Resistivity, magnetoresistance and Hall resistivity properties in bulk Mn-doped II-IV-As2 and InSb crystals was analyzed. The interaction between delocalized holes and 3d shells of the Mn ions together with giant Zeeman splitting near the cluster interface are respond for negative magnetoresistance. Additionally to high temperature critical pointthe low-temperature ferromagnetic transition was observed Anomalous Hall effect was observed in Mn doped samples and analyzed for InMnSb. It was found that MnX clusters influence significantly on magnetic scattering of carriers.

Corrosion behaviour of boiler tube materials during combustion of fuels containing Zn and Pb

Många förbränningsanläggningar som bränner utmanande bränslen såsom restfraktioner och avfall råkar ut för problem med ökad korrosion på överhettare och/eller vattenväggar pga. komponenter i bränslena som är korrosiva. För att minimera problemen i avfallseldade pannor hålls ångparametrarna på en relativt låg nivå, vilket drastiskt minskar energiproduktionen. Beläggningarna i avfallseldade pannor består till största delen av element som är förknippade med högtemperaturkorrosion: Cl, S, alkalimetaller, främst K och Na, och tungmetaller som Pb och Zn, och det finns också indikationer av Br-förekomst. Det låga ångtrycket i avfallseldade pannor påverkar också stålrörens temperatur i pannväggarna i eldstaden. I dagens läge hålls temperaturen normalt vid 300-400 °C. Alkalikloridorsakad (KCl, NaCl) högtemperaturkorrosion har inte rapporterats vara relevant vid såpass låga temperaturer, men närvaro av Zn- och Pb-komponenter i beläggningarna har påvisats förorsaka ökad korrosion redan vid 300-400 °C. Vid förbränning kan Zn och Pb reagera med S och Cl och bilda klorider och sulfater i rökgaserna. Dessa tungmetallföreningar är speciellt problematiska pga. de bildar lågsmältande saltblandningar. Dessa lågsmältande gasformiga eller fasta föreningar följer rökgasen och kan sedan fastna eller kondensera på kallare ytor på pannväggar eller överhettare för att sedan bilda aggressiva beläggningar. Tungmetallrika (Pb, Zn) klorider och sulfater ökar risken för korrosion, och effekten förstärks ytterligare vid närvaro av smälta. Motivet med den här studien var att få en bättre insikt i högtemperaturkorrosion förorsakad av Zn och Pb, samt att undersöka och prediktera beteendet och motståndskraften hos några stålkvaliteter som används i överhettare och pannväggar i tungmetallrika förhållanden och höga materialtemperaturer. Omfattande laboratorie-, småskale- och fullskaletest utfördes. Resultaten kan direkt utnyttjas i praktiska applikationer, t.ex. vid materialval, eller vid utveckling av korrosionsmotverkande verktyg för att hitta initierande faktorer och förstå deras effekt på högtemperaturkorrosion.

Biodegradable packaging materials in 2013 and their feasibility in chocolate industry

The development of biopolymers has been rapid in recent years and the range of available bioplastics is increasing continuously, driven by a growing demand for sustainable solutions. There are several key drivers behind this growth. The oil reservoirs are decreasing which is causing a price increase for the traditional plastic materials and therefore the gap to bioplastics’ price is getting smaller. In addition, other environmental topics, such as waste disposal and green production, have become more and more important factors for institutes, companies and consumers. Legislation and directives have to be taken into account as well in decision making concerning different packaging materials. The new environmental law with waste disposal responsibility will also have an effect on the packaging business. Therefore a need has risen to study closer the current offering closer of bio-based materials that could be used in chocolate packaging. In this Master’s Thesis the bioplastics’, and especially biodegradable materials’ technical properties and their development, availability, possible existing products in the markets, waste disposal possibilities and consumers attitude towards environmental friendly packaging is studied. This is a case study where the offering of biodegradable materials was investigated during March 2013 for Fazer Confectionary.

Modified nano- and microcellulose based adsorption materials in water treatment

In recent decades, industrial activity growth and increasing water usage worldwide have led to the release of various pollutants, such as toxic heavy metals and nutrients, into the aquatic environment. Modified nanocellulose and microcellulose-based adsorption materials have the potential to remove these contaminants from aqueous solutions. The present research consisted of the preparation of five different nano/microcellulose-based adsorbents, their characterization, the study of adsorption kinetics and isotherms, the determination of adsorption mechanisms, and an evaluation of adsorbents’ regeneration properties. The same well known reactions and modification methods that were used for modifying conventional cellulose also worked for microfibrillated cellulose (MFC). The use of succinic anhydride modified mercerized nanocellulose, and aminosilane and hydroxyapatite modified nanostructured MFC for the removal of heavy metals from aqueous solutions exhibited promising results. Aminosilane, epoxy and hydroxyapatite modified MFC could be used as a promising alternative for H2S removal from aqueous solutions. In addition, new knowledge about the adsorption properties of carbonated hydroxyapatite modified MFC as multifunctional adsorbent for the removal of both cations and anions ions from water was obtained. The maghemite nanoparticles (Fe3O4) modified MFC was found to be a highly promising adsorbent for the removal of As(V) from aqueous solutions due to its magnetic properties, high surface area, and high adsorption capacity . The maximum removal efficiencies of each adsorbent were studied in batch mode. The results of adsorption kinetics indicated very fast removal rates for all the studied pollutants. Modeling of adsorption isotherms and adsorption kinetics using various theoretical models provided information about the adsorbent’s surface properties and the adsorption mechanisms. This knowledge is important for instance, in designing water treatment units/plants. Furthermore, the correspondence between the theory behind the model and properties of the adsorbent as well as adsorption mechanisms were also discussed. On the whole, both the experimental results and theoretical considerations supported the potential applicability of the studied nano/microcellulose-based adsorbents in water treatment applications.

Effect of different covering materials used during the pre-harvest stage on the quality and storage life of 'Sultana Seedless' grapes

Covering the grapevine rows to delay the maturity and harvest date became widely practiced in 'Sultana Seedless' vineyards. The research work was conducted to test different cover materials (polypropylene cross-stitch, life pack, mogul and transparent polyethylene) in respect to their effects on grape quality and storability. Harvest was delayed for one month in covered plots. Harvested grapes were packed and transferred to storage rooms after pre-cooling. During packing, the grape clusters were sealed in PE bags with sulphur dioxide pads. The grapes were stored for 90 days in the first year and 120 days in the second year, at -0.5ºC and 90% RH. All the grape clusters were healthy and of marketable quality after 90 days of storage period. In the first year, at the end of the storage, only those grapes harvested from the rows covered with polypropylene cross-stitch showed fungal growth. The sensory quality scores revealed a lower level of preference after 120 days of storage. The effects of the covering materials tested were similar regarding grape quality and storage performance except the transparent polyethylene that damaged the grapevine leaves.

Growth and Characterisation of Radio Frequency Magnetron Sputttered Indium Tin Oxide Thin Films

The increasing interest in the interaction of light with electricity and electronically active materials made the materials and techniques for producing semitransparent electrically conducting films particularly attractive. Transparent conductors have found major applications in a number of electronic and optoelectronic devices including resistors, transparent heating elements, antistatic and electromagnetic shield coatings, transparent electrode for solar cells, antireflection coatings, heat reflecting mirrors in glass windows and many other. Tin doped indium oxide (indium tin oxide or ITO) is one of the most commonly used transparent conducting oxides. At present and likely well into the future this material offers best available performance in terms of conductivity and transmittivity combined with excellent environmental stability, reproducibility and good surface morphology. Although partial transparency, with a reduction in conductivity, can be obtained for very thin metallic films, high transparency and simultaneously high conductivity cannot be attained in intrinsic stoichiometric materials. The only way this can be achieved is by creating electron degeneracy in a wide bandgap (Eg > 3eV or more for visible radiation) material by controllably introducing non-stoichiometry and/or appropriate dopants. These conditions can be conveniently met for ITO as well as a number of other materials like Zinc oxide, Cadmium oxide etc. ITO shows interesting and technologically important combination of properties viz high luminous transmittance, high IR reflectance, good electrical conductivity, excellent substrate adherence and chemical inertness. ITO is a key part of solar cells, window coatings, energy efficient buildings, and flat panel displays. In solar cells, ITO can be the transparent, conducting top layer that lets light into the cell to shine the junction and lets electricity flow out. Improving the ITO layer can help improve the solar cell efficiency. A transparent ii conducting oxide is a material with high transparency in a derived part of the spectrum and high electrical conductivity. Beyond these key properties of transparent conducting oxides (TCOs), ITO has a number of other key characteristics. The structure of ITO can be amorphous, crystalline, or mixed, depending on the deposition temperature and atmosphere. The electro-optical properties are a function of the crystallinity of the material. In general, ITO deposited at room temperature is amorphous, and ITO deposited at higher temperatures is crystalline. Depositing at high temperatures is more expensive than at room temperature, and this method may not be compatible with the underlying devices. The main objective of this thesis work is to optimise the growth conditions of Indium tin oxide thin films at low processing temperatures. The films are prepared by radio frequency magnetron sputtering under various deposition conditions. The films are also deposited on to flexible substrates by employing bias sputtering technique. The films thus grown were characterised using different tools. A powder x-ray diffractometer was used to analyse the crystalline nature of the films. The energy dispersive x-ray analysis (EDX) and scanning electron microscopy (SEM) were used for evaluating the composition and morphology of the films. Optical properties were investigated using the UVVIS- NIR spectrophotometer by recording the transmission/absorption spectra. The electrical properties were studied using vander Pauw four probe technique. The plasma generated during the sputtering of the ITO target was analysed using Langmuir probe and optical emission spectral studies.

Growth and Characterization of ZnO based Heterojunction diodes and ZnO Nanostructuresby Pulsed Laser Ablation

Transparent conducting oxides (TCO’s) have been known and used for technologically important applications for more than 50 years. The oxide materials such as In2O3, SnO2 and impurity doped SnO2: Sb, SnO2: F and In2O3: Sn (indium tin oxide) were primarily used as TCO’s. Indium based oxides had been widely used as TCO’s for the past few decades. But the current increase in the cost of indium and scarcity of this material created the difficulty in obtaining low cost TCO’s. Hence the search for alternative TCO material has been a topic of active research for the last few decades. This resulted in the development of various binary and ternary compounds. But the advantages of using binary oxides are the easiness to control the composition and deposition parameters. ZnO has been identified as the one of the promising candidate for transparent electronic applications owing to its exciting optoelectronic properties. Some optoelectronics applications of ZnO overlap with that of GaN, another wide band gap semiconductor which is widely used for the production of green, blue-violet and white light emitting devices. However ZnO has some advantages over GaN among which are the availability of fairly high quality ZnO bulk single crystals and large excitonic binding energy. ZnO also has much simpler crystal-growth technology, resulting in a potentially lower cost for ZnO based devices. Most of the TCO’s are n-type semiconductors and are utilized as transparent electrodes in variety of commercial applications such as photovoltaics, electrochromic windows, flat panel displays. TCO’s provide a great potential for realizing diverse range of active functions, novel functions can be integrated into the materials according to the requirement. However the application of TCO’s has been restricted to transparent electrodes, ii notwithstanding the fact that TCO’s are n-type semiconductors. The basic reason is the lack of p-type TCO, many of the active functions in semiconductor originate from the nature of pn-junction. In 1997, H. Kawazoe et al reported the CuAlO2 as the first p-type TCO along with the chemical design concept for the exploration of other p-type TCO’s. This has led to the fabrication of all transparent diode and transistors. Fabrication of nanostructures of TCO has been a focus of an ever-increasing number of researchers world wide, mainly due to their unique optical and electronic properties which makes them ideal for a wide spectrum of applications ranging from flexible displays, quantum well lasers to in vivo biological imaging and therapeutic agents. ZnO is a highly multifunctional material system with highly promising application potential for UV light emitting diodes, diode lasers, sensors, etc. ZnO nanocrystals and nanorods doped with transition metal impurities have also attracted great interest, recently, for their spin-electronic applications This thesis summarizes the results on the growth and characterization of ZnO based diodes and nanostructures by pulsed laser ablation. Various ZnO based heterojunction diodes have been fabricated using pulsed laser deposition (PLD) and their electrical characteristics were interpreted using existing models. Pulsed laser ablation has been employed to fabricate ZnO quantum dots, ZnO nanorods and ZnMgO/ZnO multiple quantum well structures with the aim of studying the luminescent properties.

Amorphous Oxide Transparent Thin Films: Growth, Characterisation and Application to Thin Film Transistors

This work mainly concentrate to understand the optical and electrical properties of amorphous zinc tin oxide and amorphous zinc indium tin oxide thin films for TFT applications. Amorphous materials are promising in achieving better device performance on temperature sensitive substrates compared to polycrystalline materials. Most of these amorphous oxides are multicomponent and as such there exists the need for an optimized chemical composition. For this we have to make individual targets with required chemical composition to use it in conventional thin film deposition techniques like PLD and sputtering. Instead, if we use separate targets for each of the cationic element and if separately control the power during the simultaneous sputtering process, then we can change the chemical composition by simply adjusting the sputtering power. This is what is done in co-sputtering technique. Eventhough there had some reports about thin film deposition using this technique, there was no reports about the use of this technique in TFT fabrication until very recent time. Hence in this work, co-sputtering has performed as a major technique for thin film deposition and TFT fabrication. PLD were also performed as it is a relatively new technique and allows the use high oxygen pressure during deposition. This helps to control the carrier density in the channel and also favours the smooth film surface. Both these properties are crucial in TFT.Zinc tin oxide material is interesting in the sense that it does not contain costly indium. Eventhough some works were already reported in ZTO based TFTs, there was no systematic study about ZTO thin film's various optoelectronic properties from a TFT manufacturing perspective. Attempts have made to analyse the ZTO films prepared by PLD and co-sputtering. As more type of cations present in the film, chances are high to form an amorphous phase. Zinc indium tin oxide is studied as a multicomponent oxide material suitable for TFT fabrication.

Optimization of Two Stage Process for the Growth of In2S3 , CuInSe2 and CuIn (Sel-xSx)2Thin Films for Solar Cell Application

Two stage processes consisting of precursor preparation by thermal evaporation followed by chalcogenisation in the required atmosphere is found to be a feasible technique for the PV materials such as n-Beta In2S3, p-CulnSe2, p-CulnS2 and p-CuIn(Sel_xSx)2. The growth parameters such as chalcogenisation temperature and duration of chalcogenisation etc have been optimised in the present study.Single phase Beta-In2S3 thin films can be obtained by sulfurising the indium films above 300°C for 45 minutes. Low sulfurisation temperatures required prolonged annealing after the sulfurisation to obtain single phase Beta-1n2S3, which resulted in high material loss. The maximum band gap of 2.58 eV was obtained for the nearly stoichiometric Beta-In2S3 film which was sulfurised at 350°C. This wider band gap, n type Beta-In2S3 can be used as an alternative to toxic CdS as window layer in photovoltaics .The systematic study on the structural optical and electrical properties of CuInSe2 films by varying the process parameters such as the duration of selenization and the selenization temperature led to the conclusion that for the growth of single-phase CuInSe2, the optimum selenization temperature is 350°C and duration is 3 hours. The presence of some binary phases in films for shorter selenization period and lower selenization temperature may be due to the incomplete reaction and indium loss. Optical band gap energy of 1.05 eV obtained for the films under the optimum condition.In order to obtain a closer match to the solar spectrum it is desirable to increase the band gap of the CulnSe2 by a few meV . Further research works were carried out to produce graded band gap CuIn(Se,S)2 absorber films by incorporation of sulfur into CuInSe2. It was observed that when the CulnSe2 prepared by two stage process were post annealed in sulfur atmosphere, the sulfur may be occupying the interstitial positions or forming a CuInS2 phase along with CuInSe2 phase. The sulfur treatment during the selenization process OfCu11 ln9 precursors resulted in Culn (Se,S)2 thin films. A band gap of 1.38 eV was obtained for the CuIn(Se,S)2.The optimised thin films n-beta 1n2S3, p-CulnSe2 and p-Culn(Sel-xSx)2 can be used for fabrication of polycrystalline solar cells.

Growth and characterisation of p-type delafossite transparent conducting thin films for heterojunction applications

In the present studies, various copper delafossite materials viz; CuAlO2, CuGaO2, CuFeO2 , CuGa1-xFexO2, CuYO2 and CuCaxY1-xO2 were synthesised by solid state reaction technique. These copper delafossite materials were grown in thin film form by rf magnetron sputtering technique. In general copper delafossites exhibit good optical transparency. The conductivity of the CuYO2 could be improved by Ca doping or by oxygen intercalation by annealing the film in oxygen atmosphere. It has so far been impossible to improve the p-type conductivity of CuGaO2 significantly by doping Mg or Ca on the Ga site. The ptype conductivity is presumed to be due to oxygen doping or Cu Vacancies [6]. Reports in literature show, oxygen intercalation or divalent ion doping on Ga site is not possible for CuGaO2 thin films to improve the p-type conductivity. Sintered powder and crystals of CuFeO2 have been reported as the materials having the highest p-type conductivity [14, 15] among the copper and silver delafossites. However the CuFeO2 films are found to be less transparent in the visible region compared to CuGaO2. Hence in the present work, the solid solution between the CuGaO2 and CuFeO2 was effected by solid state reaction, varying the Fe content. The CuGa1-xFexO2 with Fe content, x=0.5 shows an increase in conductivity by two orders, compared to CuGaO2 but the transparency is only about 50% in the visible region which is less than that of CuGaO2 The synthesis of α−AgGaO2 was carried out by two step process which involves the synthesis of β-AgGaO2 by ion exchange reaction followed by the hydrothermal conversion of the β-AgGaO2 into α-AgGaO2. The trace amount of Ag has been reduced substantially in the two step synthesis compared to the direct hydrothermal synthesis. Thin films of α-AgGaO2 were prepared on silicon and Al2O3 substrates by pulsed laser deposition. These studies indicate the possibility of using this material as p-type material in thin film form for transparent electronics. The room temperature conductivity of α-AgGaO2 was measured as 3.17 x 10-4 Scm-1and the optical band gap was estimated as 4.12 eV. A transparent p-n junction thin film diode on glass substrate was fabricated using p-type α-AgGaO2 and n-ZnO.AgCoO2 thin films with 50% transparency in the visible region were deposited on single crystalline Al2O3 and amorphous silica substrates by RF magnetron sputtering and p type conductivity of AgCoO2 was demonstrated by fabricating transparent p-n junction diode with AgCoO2 as p-side and ZnO: Al as n-side using sputtering. The junction thus obtained was found to be rectifying with a forward to reverse current of about 10 at an applied voltage of 3 V.The present study shows that silver delafossite thin films with p-type conductivity can be used for the fabrication of active devices for transparent electronics applications.