Die neuen TRIP-Matrix-Composite-Werkstoffe - verstärkt durch mit MgO teilstabilisiertem ZrO2 - gestatten es, durch die Besonderheiten der beteiligten Phasen eine gute Eigenschaftskombination hinsichtlich hoher Festigkeits- und Dehnungswerte zu erzielen. Aus diesem Grund ist die vorliegende Arbeit der Erforschung wissenschaftlicher Grundlagen zur Herstellung von TRIP-Matrix-Compositen sowie zur Analyse deren Eigenschaften in Abhängigkeit von den unterschiedlichen pulvermetallurgischen Herstellungsverfahren, wie konventionelles und konduktives Sintern sowie Heißpressen gewidmet worden. Als Ergebnis ist ein tieferes Verständnis der Kinetik von Sinterprozessen mit dem Aufbau eines physikalisch-mathematischen Modells festzuhalten. Ferner wurden mit weiterführenden Untersuchungen erste Ansätze zur Auslegung von Warmumformprozessen von gesinterten Halbzeugen aus dem Verbundwerkstoff durch quantitative Beschreibung der Entfestigungskinetik geleistet.

In recent decades, the necessity to find a completely environmentally friendly substitute for synthetic fibres in composite applications has intensified, driven by the objective of reducing emissions in both the production and disposal of composite components. Natural fibres present a potential solution, yet they have some issues such as the inhomogeneous quality of their cross-section and mechanical properties, depending on different aspects, for example, growing conditions and the amount of intake water. Another potential solution is organic man-made fibres, such as fibre made from Cellulose NanoFibrils, which do not present the previously cited drawbacks.This thesis investigates and compares the potentials of organic fibres, either man-made or natural, in composite reinforcement applications. To accomplish this, organic fibres are integrated into composite plates using two distinct thermoset matrices, epoxy and vinyl ester, respectively via methods of hot pressing and vacuum infusion. Subsequently, the produced composite plates undergo tensile testing, with the results being compared with the theoretical values. Furthermore, microscopy is employed to examine the adhesion at the interface between reinforcement and matrix.The findings indicate that man-made fibres from Cellulose NanoFibrils bind more efficiently with thermoset matrices compared to flax fibres, making them more adept as reinforcement materials for thermoset composites. / Under de senaste decennierna har behovet av att hitta en helt miljövänlig ersättning för syntetiska fibrer i kompositapplikationer intensifierats, drivet av målet att minska utsläppen både vid produktion och avfallshantering av kompositkomponenter. Naturliga fibrer presenterar en potentiell lösning, men de har vissa problem som den ojämna kvaliteten på deras tvärsnitt och mekaniska egenskaper, beroende på olika aspekter, till exempel växtförhållanden och mängden intaget vatten. En annan potentiell lösning är organiska konstgjorda fibrer, som fibrer tillverkade av cellulosa nanofibriller, som inte har de tidigare nämnda nackdelarna.Denna avhandling undersöker och jämför potentialen hos organiska fibrer, antingen konstgjorda eller naturliga, i kompositförstärkningsapplikationer. För att uppnå detta integreras organiska fibrer i kompositplattor med hjälp av två olika termohärdande matriser, epoxi och vinyl-ester, via metoder för varmpressning och vakuuminfusion. Därefter genomgår de producerade kompositplattorna dragprovning, med resultaten jämförda med de teoretiska värdena. Dessutom används mikroskopi för att undersöka vidhäftningen vid gränssnittet mellan förstärkning och matris.Resultaten indikerar att konstgjorda fibrer från cellulosa nanofibriller binder effektivare med termohärdande matriser jämfört med linfibrer, vilket gör dem mer lämpliga som förstärkningsmaterial för termohärdande kompositer.

Thermoelectric (TE) ZrNiSn samples with a half-Heusler atomic structure were synthesized by mechanical alloying (MA) and consolidation by either Spark Plasma Sintering (SPS) or hot pressing (HP). X-Ray diffraction patterns of as milled powders and consolidated samples were compared and analyzed for phase purity. Thermal conductivity, electrical conductivity and Seebeck coefficient are measured as a function of temperature in the range 300 K to 800 K and compared with measurements reported for high temperature solid state reaction synthesis of this compound. HP samples, compared to SPS samples, demonstrate increased grain growth due to longer heating times. Reduced grain size achieved by MA and SPS causes increased phonon scattering due to the increased number of grain boundaries, which lowers the thermal conductivity without doping the base system with addition phonon scattering centers. Mechanical characterization of the samples by microindentation and depth sensing indentation for hardness and elastic modulus will be discussed.

L’étude a pour objectif l’amélioration de la fiabilité des assemblages électroniques à travers la mise en œuvre de drains composites aluminium/fibres de carbone. Le travail a consisté à 1) modéliser, par la méthode des éléments finis, l’influence des propriétés thermiques et mécaniques du matériau de semelle sur l’assemblage életronique ; 2) élaborer (par frittage sous charge uniaxiale, frittage flash et extrusion à chaud) des matériaux composites aluminium/fibres de carbone ; et 3) lier les microstructures observées aux paramètres des procédés d’élaboration ainsi qu’aux propriétés thermiques et mécaniques mesurées. / This study has been done in order to improve power electronic devices reliability using aluminium/carbon fibres composites. This work has consisted in 1) determining, using finite elements method, the thermal and mechanical influence of the electronic base plate material; 2) elaborating (using hot pressing, spark plasma sintering and hot extrusion) aluminium/carbon fibres composites; and 3) linking the microstructures observed to the elaboration parameters and to the thermomechanical properties measured.

Si l'emploi des matériaux composites dans l'aéronautique est déjà effectif sur des éléments de structures principales et de grande taille, leur généralisation aux structures secondaires bute sur leur positionnement en termes de coûts et performances face aux métaux. Il s'agit dans ce travail de contribuer à la mise en place d'une filière française de pièces composites hautes performances à bas coûts en s'appuyant sur un procédé de moulage en grande série, à savoir le thermoformage à haute pression. Ainsi, il a été question dans un premier temps d'optimiser ce procédé vis-à-vis des principales matières rencontrées dans les structures aéronautiques. Ensuite, les stratifiés moulés ont été caractérisés et les effets des conditions environnementales sévères (humidité, température, impact) sur leur comportement mécanique étudiés. Par ailleurs, réduire les coûts des pièces signifie également réduire les coefficients de sécurité qui restent très élevés pour les pièces composites. Cela passe par une meilleure prédictibilité de la rupture des matériaux et du comportement mécanique au-delà du linéaire. Sur le carbone/PEEK satin de 5 pris comme matériau d'illustration, les phénomènes non linéaires (viscoplasticité) ainsi que les mécanismes d'endommagement et de rupture ont été étudiés. Un accent particulier a été mis sur le délaminage et un critère permettant de prédire son amorçage a été proposé. La possibilité de faire des modèles éléments finis des pièces directement à l'échelle mésoscopique (du pli) a été également explorée et laisse entrevoir des pistes prometteuses pour des dimensionnements plus sûrs et donc moins conservatifs. / If the use of composite materials is already effective on elements of main structures and large size parts, their generalization to secondary parts is not effective due to their cost and their performances compared to metals. The framework of this thesis is to contribute to the establishment of a French chain of high performance composite parts at low cost. Thus, it was initially question of optimizing the process vis-à-vis the main composite materials used in the aerospace structures. Then, the molded laminates were characterized and the effects of severe conditions (humidity, temperature, impact) on their mechanical behavior were studied. Also, reduce the cost of parts also means reducing the safety factors which remain very high. This requires a better prediction of the failure and the mechanical behavior beyond the linear. Taking the five harness satin weave carbon/PEEK material as example, non-linear phenomena (viscoplasticity), damage mechanisms and failure criteria were studied, with particular emphasis on the delamination. The possibility to perform finite element analysis of the parts directly at the mesoscopic scale (ply-scale) was also explored and suggests promising expectations for a less conservative sizing of composite structures.

1. Beim feldaktivierten Sintern im Temperaturbereich von 500 bis 1000 °C fließen elektrische Ströme mit einer Dichte von 1 bis 3 A/mm². 2. Daraus folgt für die größten verwendeten Pulverteilchen mit einem Radius von 50 µm ein Strom je Teilchenkontakt von 10 bis 50 mA. 3. Die durch das Aufbringen des prozesstechnisch notwendigen Pressdruckes gebildeten relativen Kontaktradien (Kontaktradius geteilt durch Teilchenradius) haben eine Größe von 0,05 bis 0,3. 4. Die Einengung der Strompfade im Kontakt der Pulverteilchen erhöht, zusammen mit dem elektrischen Widerstand der Oxidschicht auf den Pulverteilchen, den elektrischen Widerstand des Pulverpresslings. 5. Der Stromfluss durch die Teilchenkontakte führt mit dem zusätzlichen elektrischen Widerstand dieser Teilchenkontakte zu einer lokalen Temperaturerhöhung (Übertemperatur) von 10-4 bis 1 Kelvin für Kupfer- respektive Stahlpulver. 6. Der zusätzliche elektrische Widerstand der Oxidschicht kann die Übertemperatur beim Kupferpulver auf bis zu 1 mK erhöhen. 7. Mit abnehmendem Teilchenradius sinkt die Übertemperatur quadratisch. 8. Das Wachstum der Teilchenkontakte im Verlauf der Verdichtung führt zu einer kontinuierlichen Verringerung der Übertemperatur. 9. Das Auftreten von schmelzflüssiger Phase, von Metalldampf oder von Plasma wird in den untersuchten metallischen Systemen ausgeschlossen. 10. Auch Elektromigration, Thermomigration oder andere Wirkungen des elektrischen Stromes spielen keine Rolle für die Verdichtung beim feldaktivierten Sintern. 11. Die Verwendung von gepulstem anstelle von kontinuierlichem Gleichstrom beeinflusst die Verdichtung der untersuchten Werkstoffe nicht. 12. Die Verdichtung vom Pulver zum kompakten Werkstoff findet für Pulverteilchen mit einem Radius größer als R = 10 µm über plastische Verformung durch verschiedene Formen des Kriechens statt. 13. Die Verformung ist im Anfangsstadium auf den Kontaktbereich begrenzt. 14. Bei Pulverteilen mit Teilchenradien unter R = 10 µm findet die Verdichtung zunächst als Folge von Leerstellenströmen in die Kontaktkorngrenze statt (Sintern). 15. Durch die schnelle Verdichtung bei niedriger homologer Temperatur werden Kornwachstum und Rekristallisation verringert.

In this thesis, novel bulk Al-based alloys with high content of Al have been produced by powder metallurgy methods from amorphous and partially amorphous materials. Different processing routes, i.e. mechanical alloying of elemental powder mixtures, controlled pulverization of melt-spun glassy ribbons and gas atomization, have been employed for the production of the Al-based powders. Among the different processing routes, gas atomization is the best choice for the production of Al-based amorphous and partially amorphous powders as precursors for the subsequent consolidation step because it allows the production of large quantities of powders with homogeneous properties (e.g. structure and thermal stability) along with a uniform size distribution of particles. Amorphous and nanocrystalline powders have to be consolidated to achieve dense bulk specimens. However, consolidation of these phases is not an easy task and special care has to be taken with respect to accurate control of the consolidation parameters in order to achieve dense bulk specimens without inducing undesirable microstructural transformations (e.g. crystallization and grain coarsening) or insufficient particle bonding. Consequently, the effect of temperature on viscosity as well as on phase formation has been studied in detail in order to select the proper consolidation parameters. Following their characterization, the Al-based powders have been consolidated into bulk specimens by hot pressing (HP), hot extrusion and spark plasma sintering (SPS) and their microstructure and mechanical properties have been extensively investigated. Consolidation into highly-dense bulk samples cannot be achieved without extended crystallization of the glassy precursors. Nevertheless, partial or full crystallization during consolidation leads to remarkable mechanical properties. For example, HP Al84Gd6Ni7Co3 samples display a remarkably high strength of about 1500 MPa, which is three times larger than the conventional high-strength Al-based alloys, along with a limited but distinct plastic deformability (3.5 – 4%). Lower strength (930 MPa) but remarkably larger plastic strain exceeding 25 % has been achieved for the Al87Ni8La5 gas-atomized powders consolidated by SPS above their crystallization temperature. Similarly, HP Al90.4Y4.4Ni4.3Co0.9 bulk samples display high compression strength ranging between 820 and 925 MPa combined with plastic strain in the range 14 – 30%. Finally, preliminary tensile tests for the Al90.4Y4.3Ni4.4Co0.9 alloy reveal promising tensile properties comparable to commercial high-strength Al-based alloys. The mechanical behavior of the consolidated specimens is strictly linked with their microstructure. High strength and reduced plasticity are observed when a residual amorphous phase is present. On the other hand, reduced strength but enhanced plastic deformation is a result of the complete crystallization of the glass and of the formation of a partially or fully interconnected network of deformable fcc Al. These results indicate that the combined devitrification and consolidation of glassy precursors is a particularly suitable method for the production of Al-based materials characterized by high strength combined with considerable plastic strain. Through this method, the mechanical properties of the consolidated samples can be varied within a wide range of strength and ductility depending on the microstructure and the consolidation techniques used. This might open a new route for the development of innovative high-performance Al-based materials for transport applications.

Zirconium- and titanium- based compounds (borides, carbides and nitrides) are of importance because of their attractive properties including: high melting temperature, high-temperature strength, high hardness, high elastic modulus and good wear-erosion-corrosion resistance. The ultra high temperature ceramics (UHTCs) - zirconium diboride (ZrB2) and zirconium carbide (ZrC) in combination with SiC are potential candidates for ultra-high temperature applications such as nose cones for re-entry vehicles and thermal protection systems, where temperature exceeds 2000°C. Titanium nitride (TiN) and titanium diboride (TiB2) composites have been considered for cutting tools, wear resistant parts etc. There are problems in the processing of these materials, as very high temperatures are required to produce dense composites. This problem can be overcome by the development of composites through reactive hot processing (RHP). In RHP, the composites are simultaneously synthesized and densified by application of pressure and temperatures that are relatively low compared to the melting points of individual components. There have been earlier studies on the fabrication of dense ZrB2-ZrC, ZrB2-SiC and TiN-TiB2 composites by the following methods: Pressureless sintering of preformed powders at high temperatures (1800-2300°C) with MoSi2, Ni, Cr, Fe additions Hot pressing of preformed powders at high temperatures (1700-2000°C) with additives like Ni, Si3N4, TiSi2, TaSi2, TaC Melt infiltration of Zr/Ti into B4C preform at 1800-1900°C to produce ZrB2-ZrC-Zr and TiB2-TiC composites RHP of Zr-B4C, Zr-Si-B4C and Ti-BN powder mixtures to produce ZrB2-ZrC, ZrB2-SiC and TiN-TiB2 powder mixtures at 1650-1900°C Spark plasma sintering of powder mixtures at 1800-2100°C There has been a lack of attention paid to the conditions under which ceramic composites can be produced by simple hot pressing (~50 MPa) with minimum amount of additives, which will not affect the mechanical properties of the composites. There has been no systematic study of microstructural evolution to be able to highlight the change in relative density (RD) with temperature during RHP by formation of sub-stoichiometric compounds, and liquid phase when a small amount of additive is used. The present study has been undertaken to establish the experimental conditions and densification mechanisms during RHP of Zr-B4C, Zr-B4C-Si and Ti-BN powder mixtures to yield (a) ZrB2-ZrC, (b) ZrB2-SiC, (c) ZrB2-ZrC-SiC and (d) TiN-TiB2 composites. The following reactions were used to produce the composites: (1) 3 Zr + B4C → 2 ZrB2 + ZrC (2) 3.5 Zr + B4C → 2 ZrB2 + 1.52rCx- 0.67 (3) (1+y) Zr + C → (1+y) ZrCx- 1/ (1+y) (y=0 to 1) (4) 2 Zr + B4C + Si → 2 ZrB2 + SiC (5) 2.5 Zr + B4C + 0.65 Si → 2 ZrB2 + 0.5 ZrCx + 0.65 SiC (6) 3.5 Zr + B4C + SiC → 2 ZrB2 + 1.5 ZrCx + SiC (5 to 15 vol%) (7) (3+y) Ti + 2 BN → (2+y) TiN1/(1+y) + TiB2 (y=0 to 0.5) (a) ZrB2-ZrC Composites: The effect of different particle sizes of B4C (60-240 μm, <74 μm and 10-20 μm) with Zr on the reaction and densification of composites has been studied. The role of Ni addition on reaction and densification of the composites has been attempted. The effect of excess Zr addition on the reaction and densification has also been studied. The RHP experiments were conducted under vacuum in the temperature range 1000-1600°C for 30 min without and with 1 wt% Ni at 40 MPa pressure. The RHP composites have been characterized by density measurements, x-ray diffraction for phase analysis and lattice parameter measurements, microstructural observation using optical and scanning electron microscopy. Selected samples have been analyzed by transmission electron microscopy. The hardness of the composites has also been measured. The results of the study on the effect of different particle sizes B4C and Ni addition on reaction and densification in the stoichiometric reaction mixture as follows. With the coarse B4C (60-240 μm and <74 μm) particles the temperature required are higher for completion of the reaction (1600°C and above). The microstructural observation showed that the material is densified even in the presence of unreacted B4C particles. The composite made with 10-20 μm B4C and 1 wt% Ni showed completion of the reaction at 1200°C, whereas composite made without Ni showed unreacted B4C (∼3 vol%) and the final densities of both the composites are similar (5.44 g/cm3). Increase in the temperature to 1400°C resulted in the completion of the reaction (without Ni) accompanied with a relative density (RD) of 95%. The composites produced with and without Ni at 1600°C had similar densities of 6.13 g/cm3 and 6.11 g/cm3 respectively (~97.3% RD). The Zr-Ni phase diagram suggests that the addition of Ni helps in formation of Zr-Ni liquid at ~960°C and leads to an increase in the reaction rate up to 1200°C. Once the reaction is completed, not enough Zr is available to maintain the liquid phase and further densification occurs through solid state sintering. The grain sizes of ZrB2 and ZrC phases after 1200°C are 0.4 μm and 0.3 μm, which are much lower than those reported in literature (2-10 μm), and may be the reason for reducing the densification temperature to 1600°C for stoichiometric ZrB2-ZrC composites. The effect of excess Zr (0.5 mol), over and above the stoichiometric Zr-B4C powder mixture, on reaction and densification of the composites is as follows. The formation of ZrB2 and ZrC phases with unreacted starting Zr and B4C is observed at 1000°C and with increase in temperature to 1200°C the reaction is completed. Since microstructural characterization reveals no indication of free Zr, it is concluded that the excess Zr is incorporated by the formation of non-stoichiometric ZrC (ZrCx-0.67). This observation is supported by lattice parameter measurements of ZrC in the stoichiometric and non-stoichiometric composites which are lower than those reported in the literature. X-ray microanalysis of ZrC grains in the stoichiometric and non-stoichiometric composites using transmission electron microscopy confirmed the presence of carbon deficiency. The composite produced at 1200°C showed the density of 6.1 g/cm3 (~97% RD), whereas addition of Ni produced 6.2 g/cm3 (~99% RD). The reduction in densification temperature for the non-stoichiometric composites is due to the presence of ZrCx even in the absence of Ni. The mechanism of densification of the composites at 1200°C is attributed to the lowering of critical resolved shear stress with increasing non-stoichimetry in the ZrC, which leads to plastic deformation during RHP. An additional mechanism may be enhanced diffusion through the structural point defects created in ZrC. The hardness of the composites are 20-22 GPa, which is higher than those of reported in literature due to the presence of a dense and fine grain microstructure in the present work. In order to verify the role of non-stoichiometric ZrC the study was extended to produce monolithic ZrC using various C/Zr ratios (0.5-1). Here again, stoichiometric ZrC does not densify even at 1600°C, whereas non-stoichiometric ZrC can be densified at 1200°C. (b) ZrB2-SiC Composites: Since ZrB2 and ZrC do not have good oxidation resistance unless they are reinforced with SiC, the present study has been extended to produce ZrB2-SiC (25 vol%) composites using Zr-Si-B4C powder mixtures. The samples produced at 1000°C showed the formation of ZrB2, ZrC and Zr-Si compounds with unreacted Zr and B4C and as the temperature is increased to 1200°C only ZrB2 and SiC remained. A fine grain (~0.5 μm) microstructure has been observed at 1200°C. During RHP, it was observed that the formations of ZrC, Si-rich phases and fine grain size at low temperatures was responsible for attaining the high relative density at a temperature of ~1600°C. The relative densities of the composites produced with 1 wt% Ni at 40 MPa, 1600°C for 30 min is 97% RD, where as composites without Ni showed a small amount of partially reacted B4C; extending the holding time to 60 min eliminated the B4C and produced 98% RD. The hardness of the composites is 18-20 GPa. (c) ZrB2-ZrC-SiC Composites: Since ZrC plays a crucial role in densification of ZrB2-ZrC and ZrB2-SiC composites, the study has been extended to reduce the processing temperature for ZrB2-ZrCx-SiC composites by two methods. In one of the methods, Si is added to the non-stoichiometric 2.5Zr-B4C powder mixture which is resulted in ZrB2-ZrCx-SiC (15 vol%) composites with ~98% RD at 1600°C. In another method, SiC particulates are added to the non-stoichiometric 3.5Zr-B4C powder mixture to yield ZrB2-ZrCx-SiCp (5-15 vol%) composites at 1400°C. The density of the 5 vol% SiC composite is 99.9%, whereas addition of 15 vol% SiC reduced the density to 95.5% RD. The mechanisms of densification of the composites are similar to those observed in ZrB2-ZrC composites. The hardness of the composites is 18-20GPa (d) TiN-TiB2 Composites: ZrB2, ZrC, TiB2, and TiN are members of the same class of transition metal borides, carbides and nitrides; however, their densification mechanisms appear to be different. In earlier work, the RHP of stoichiometric 3Ti-2BN powder mixtures yielded dense composite at 1400-1600°C with 1 wt% Ni addition, whereas composites without Ni required at least 1850°C. The major contributor to better densification at 1600°C (with Ni) appeared to be the formation of local Ni-Ti liquid phase at ~942°C (Ti-Ni phase diagram). The present work explores the additional role of non-stoichiometry in this system. It is shown that Ti excess can lead to a further lowering of the RHP temperature, but with a different mechanism compared to the Zr-B4C system. Excess Ti allows the transient alloy phase to remain above the liquidus for a longer time, thereby permitting the attainment of a higher relative density. However, eventually, the excess Ti is converted into a non-stoichiometric nitride. Thus, the volume fraction of a potentially low melting phase is not increased in the final composite by this addition. The contrast between these two systems suggests the existence of two classes of refractory materials for which densification may be greatly accelerated in the presence of non-stoichiometry, either through the ability to absorb a liquid-phase producing metal into a refractory and hard ceramic structure or greater deformability. Conclusions: The study on RHP of ZrB2-ZrC, ZrB2-SiC, ZrB2-ZrC-SiC and TiN-TiB2 composites led to the following conclusions: • It has been possible to densify the ZrB2-ZrC composites to ~97 % RD by RHP of stoichiometric Zr-B4C powder mixture with or without Ni addition. The role of B4C particle size is important to complete both reaction as well as densification. • Excess Zr (0.5 mol) to stoichiometric 3Zr-B4C powder mixtures produces dense ZrB2-ZrCx composite with 99% RD at 1200°C. The densification mechanisms in these non-stoichiometric composites are enhanced diffusion due to fine microstructural scale / stoichiometric vacancies and plastic deformation. • In the case of ZrB2-SiC composites, the formation of a fine microstructure, and intermediate ZrC and Zr-Si compounds at the early stages plays a major role in densification. • Starting with non-stoichiometric Zr-B4C powder mixture, the dense ZrB2-ZrCx-SiC composites can be produced with SiC particulates addition at 1400°C. • Non-stoichiometry in TiN and ZrC is route to the increased densification of composites through enhanced liquid phase sintering in TiN based composites that contain Ni and through plasticity of a carbon-deficient carbide in ZrC based composites.

The purpose of this thesis was to develop an economical, sustainable, and environmentally friendly straw Medium Density Fibreboard (MDF) process, capable of full-scale manufacturing and to produce MDF of requested quality. The investigated straw was based on wheat (Triticum aestivum L.) and rice (Oryzae sativa L.). In this thesis three different methods were taken for manufacture of straw MDF; (A) wheat-straw fibre was blowline blended with melamine-modified urea-formaldehyde (MUF), (B) rice-straw fibre was mixed with methylene diphenyl diisocyanate (MDI) in a resin drum-blender, and (C) wheat-straw fibre was activated in the blowline by the addition of Fenton’s reagent (H2O2/Fe2+) for production of non-resin MDF panels.  The MUF/wheat straw MDF panels were approved according to the requirements of the EN standard for MDF (EN 622-5, 2006). The MDI/rice-straw MDF panels were approved according to requirements of the standard for MDF of the American National Standard Institute (ANSI A208.2-2002). The non-resin wheat-straw panels showed mediocre MDF panel properties and were not approved according to the requirements in the MDF standard. The dry process for wood-based MDF was modified for production of straw MDF. The straw MDF process was divided into seven main process steps. 1.       Size-reduction (hammer-milling) and screening of straw 2.       Wetting and heating of straw 3.       Defibration 4.       Resination of straw fibre 5.       Mat forming 6.       Pre-pressing 7.       Hot-pressing       The primary results were that the straw MDF process was capable of providing satisfactory straw MDF panels based on different types of straw species and adhesives. Moreover, the straw MDF process was performed in pilot-plant scale and demonstrated as a suitable method for producing straw MDF from straw bales to finished straw MDF panels. In the environmental perspective the agricultural straw-waste is a suitable source for producing MDF to avoid open field burning and to capture carbon dioxide (CO2), the biological sink for extended time into MDF panels, instead of converting straw directly into bio energy or applying straw fibre a few times as recycled paper. Additionally, the straw MDF panels can be recycled or converted to energy after utilization. A relationship between water retention value (WRV) of resinated straw fibres, the thickness swelling of corresponding straw MDF panels, and the amount of applied adhesive was determined. WRV of the straw fibre increased and the TS of straw MDF declined as a function of the resin content. The empirical models developed were of acceptable significance and the R2 values were 0.69 (WRV) and 0.75 (TS), respectively. Reduced thickness swelling of MDF as the resin content is increased is well-known. The increase of WRV as a function of added polymers is not completely established within the science of fibre swelling. Fortunately, more fundamental research can be initiated and likely a simple method for prediction of thickness swelling of MDF by analysis of the dried and resinated MDF fibres is possible. / Syftet med denna avhandling var att lägga grunden för en ekonomisk, hållbar och miljövänlig MDF process för halmråvara, kapabel för fullskalig produktion av MDF och goda skivegenskaper. Framställningen av MDF skivor utgick från halm av vete (Triticum aestivum L.) och ris (Oryzae sativa L.). Tre olika metoder användes för att producera MDF av halm; (A) fibrer av vetehalm belimmades i blåsledning med ett melaminmodifierat urea-formaldehydlim (MUF), (B) fibrer av rishalm belimmades i en limblandare med metylen difenyl diisocyanate (MDI), (C) Limfria MDF skivor av vetehalm framställdes med aktivering av fibrer genom tillsats av Fenton´s reagens (H2O2/Fe2+) i blåsledning utan någon tillsats av syntetiskt lim. Sammanfattningsvis kan det understrykas att framställda MDF-skivor av MUF/vetehalm var godkända enligt standard för MDF (EN 622-5, 2006). Dessutom var framställda MDF skivor av MDI/rishalm också godkända enligt krav i standard för MDF ”American National Standard Institute” (ANSI A2008.2-2002). Limfria vetehalmskivor visade på måttliga skivegenskaper och klarade inte kraven i MDF standard.   Fiberframställningsprocessen för MDF modifierades till en produktion utgående från halm. MDF processen för halm delades upp i sju primära processoperationer.   (1)            Storleksreducering och sållning av halm (2)            Vätning och uppvärmning av halm (3)            Defibrering (4)            Belimning av halmfiber (5)            Mattformning (6)            Förpressning (7)            Pressning   De viktigaste resultaten från denna studie är att MDF av halm kunde produceras utgående från olika typer av halmsorter och lim. Dessutom utfördes MDF-processen i pilotskala och visade på en lämplig metod för framställning av MDF-skivor från halmbalar till färdiga halmfiberskivor. Det miljömässiga perspektivet på att använda jordbruksavfall till framställning av halmskivor är att undvika förbränning av halm ute på fältet, men det är även möjligt att binda koldioxid (CO2) i halmskivor under längre tid än att omsätta halmråvaran omedelbart som bioenergi eller använda halmfiber som returpapper några få gånger. Dessutom kan MDF återanvändas eller bli omsatt till energi efter användning.   Ett förhållande mellan ”water retention value” (WRV), av belimmade halmfiber, tjocklekssvällning för motsvarande MDF av halmskivor och mängden av tillsatt lim vid olika nivåer har undersökts. Med ökande limhalt tilltog WRV fibersvällning, vidare minskade tjocklekssvällning för motsvarande MDF skivor. De framtagna empiriska modellerna var godtagbara och beräknade R2 värden var 0.69 (WRV) och 0.75 (TS). Minskad tjocklekssvällning med ökad limhalt är dokumenterad sen tidigare. Ökad fibersvällning WRV vid tillsats av polymerer (limmer) är inte fullständigt etablerad inom vetenskapen för fibersvällning. Lyckligtvis kan grundläggande forskning initieras och sannolikt föreligger en enkel metod för att prediktera tjocklekssvällning av MDF genom analyser av torkade och belimmad MDF fiber.