The interfacial reactions of Sn-Zn and Sn-Zn-Al solder balls with Au/Ni surface finish under aging at 150¢J were investigated. With microstructure evolution, quantitative analysis, elemental distribution by X-ray color mapping from an electron probe microanalyzer (EPMA), the reaction procedure of phase transformation was proposed. During the reflow, Au dissolved into the solder balls and reacted with Zn to form £^-Au3Zn7. As aging time increased, £^-Au3Zn7 transformed to £^3-AuZn4. Finally, Zn precipitated near the Au-Zn intermetallic compound. On the other hand, Zn reacted with the Ni layer and formed Ni5Zn21. But the Al-Au-Zn IMC formed at the interface of Sn-Zn-Al solder balls, the reaction of Ni with Zn was inhibited. Even though the aging time increased to 50 days, no Ni5Zn21 was observed. The Joule effect was more apparent than the electromigration in the biased solder balls. First of all, the new phase (Au, Ni)Zn4 was proposed in the biased condition and in 175¢Jaging. Secondly, the thickness of the Ni5Zn21 IMC were the same between the anode and the cathode. Finally, We directly measure the temperature of the biased solder balls which was up to 173¢J.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25302号 / 工博第5261号 / 新制||工||2001(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 阿部 竜, 教授 陰山 洋 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

As carbon dissolution rates have been determined for a few chars only, a systematic and comprehensive study was undertaken in this project on the dissolution behaviour of carbon from non-graphitic materials into liquid iron. In addition to measuring the kinetics of carbon dissolution from a number of coal chars into liquid iron as a function of parent coal and coal ash composition, the influence of chemical reactions between solute/solid carbon and ash oxides was also investigated. These studies were supplemented with investigations on one metallurgical coke for the sake of comparison. The wettability of coal chars and coke with liquid iron at 1550 degrees C was measured as a function of time. Being essentially non-wetting, only a marginal improvement in contact angles was observed with time. The accumulation of alumina at the interface was detected for all materials and was seen to increase with time in all cases. Calcium and sulphur also appeared to preferentially accumulate at the interface, concentrating at levels in excess of those expected from the ash composition alone. Despite the high levels of silica in the ash initially, very little silica was detected in the interfacial region, implying ongoing silica reduction reactions. A small amount of silicon was however detected in the iron droplets, indicating silica reduction with solute carbon. It was identified that the reduction reactions can also consume solute carbon in the liquid iron. As this is occurring simultaneously with carbon dissolution into liquid iron, the interdependency of silica reduction and carbon dissolution could potentially limit the observed carbon dissolution rate. A theoretical model was developed for estimating the interfacial contact area between chars and liquid iron. Wettability was found to have a very significant effect on the area of contact. A two-step behaviour was observed in the carbon dissolution of two chars and coke. Slow rates of carbon dissolution in stage II were attributed to very high levels of interfacial blockage by reaction products leading to much reduced areas of contact between carbonaceous material and liquid iron. The first order dissolution rate constants for four chars/coke and the observed trend in first order dissolution rate constants were calculated. These dissolution results compare well with the previously measured dissolution rate constants. The trends in dissolution can be adequately explained on the basis of carbon structure, silica reduction, sulphur concentration in the metal and ash impurities.

The product of interaction between Al and TiO2 at elevated temperature has a wide range of applications in refractory, structural and electronics industries (refractory tiles, tank armor, fuel cells, and microelectronic devices). This research attempts to understand the extent of interaction between Al and TiO2 when the reactant surfaces are in contact at elevated temperature and normal atmospheric pressure. The interfacial region between the reactant compounds is examined using analytical techniques; and the formation of TiAl as the interfacial compound is described. The thermodynamics of the Al – Ti – O system is explained as it relates to the particular conditions for the Al – TiO2 reaction research. Thermodynamic principles have been used to demonstrate that the formation of TiAl is favored instead of other TixAly compounds for the set of conditions outlined in this thesis. A study of the mechanism of interactions in the interfacial region can help towards being able to determine the reaction kinetics that lead to the control of microstructure and thus an improvement in the material performance. An appropriate model that describes the formation of TiAl at the interface is described in this study. The formation of TiAl at the interface is a result of the reduction reaction between TiO2 and Al. The O released during the reduction of TiO2 has been investigated and demonstrated to partly remain dissolved in TiAl at the interfacial region. Some O reacts with Al as well to form crystalline Al2O3 in the interfacial layer. / Ph. D.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23515号 / 工博第4927号 / 新制||工||1769(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 陰山 洋, 教授 作花 哲夫 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

<p>  The interfacial reactions of the electrolytes at the electrode-electrolyte interface determine critical properties of the battery chemistries including the reaction reversibility, kinetic, and thermal stability etc. Rationally designing the solvation structure of the liquid electrolytes is paramount in altering their interfacial behaviors and achieving desirable battery performance. This thesis aims to provide fundamental understandings to the electrolyte solvation structure design in its correlations to the battery interphase stability and formation mechanism, interfacial desolvation kinetic, and thermal stability, providing strategies to build next-generation secondary batteries with improved energy density, wide-temperature capability, and thermal safety. </p> <p>Developing high-voltage lithium metal battery (LMB) with metallic Li anode and nickel-rich metal oxide cathode is a feasible approach to enhance the battery energy density. However, inferior interfacial stabilities of conventional electrolytes towards highly reductive anode and oxidative cathode cause severe parasitic reactions. This thesis investigates the solvation structures of ether-based electrolytes and their interfacial decomposition pathways to selectively control the solid electrolyte interphase (SEI) composition. Combined theoretical and experimental studies demonstrate that lessening the coordination strength of the solvent molecules can improve the ion aggregating degrees in the solvation shell and preferentially promote the anion decomposition. Detailed surficial characterizations identify that weakly-solvating electrolytes generate robust SEIs with enriched inorganic components on anode and cathode surface, which kinetically prohibits parasitic reactions. The strategy successfully facilitates the long-term cycling of high energy LMBs. Weakening the solvent coordination ability is also identified effective to promote the desolvation kinetic and realize high battery energy retention at low temperatures.</p> <p>The approach of tailoring ion-pairing behavior to achieve stabilized electrode-electrolyte interface is further validated in multivalent battery systems such as Magnesium-ion batteries (MIBs). Multivalent cations like Mg2+ and Zn2+ possess high electron density which results in strong coordination to solvent molecules and hindered desolvation process. They usually induce large reaction overpotential and low efficiency. The methoxy-amine-based electrolytes for MIBs are selected in terms of elucidating their interfacial failure mechanism and the solvation structure-dependent reaction stabilities with Mg metal anode. The study reveals an unknown amine solvent dehydrogenation mechanism that compromises the Mg anode stability. The tight coordination between solvent amine group (-NH2) and cation causes its direct reduction with H2 release. The dehydrogenation products tend to diffuse into the liquid electrolyte phase, which promotes the interfacial electrolyte decay. This work also demonstrates the approach to strengthen the solvent molecule stabilities via restructuring the Mg2+ solvation shell. Introducing anion coordination to Mg2+ can effectively relief the amine-cation interaction and suppress its reduction. As the result, hundreds of stable cycling from Mg metal anode with more than 99.6 % efficiency is achieved.</p> <p>Finally, the thermal stability of electrolytes featuring various solvation structures are studied in LMBs via quantitative thermal analysis and surficial characterization techniques. The thermal runaway of batteries which is known to be initiated via SEI decomposition and propagated by exothermic electrode-electrolyte reactions exhibit great dependence on the solvation structures of the liquid electrolytes. The results suggest that strong solvent-coordinating electrolytes with solvent-separated ion pair structures are prone to exothermic reduction decompositions. While the organic-rich SEI tends to decompose at low temperatures and initiate thermal runaway easily. Therefore, designing electrolytes with anion involved solvation shells that generate inorganic SEI can effectively mitigate the thermal runaway behavior. Supplementary research focusing on the thermal safety of Potassium-ion battery also indicates the critical role of SEI stability on the overall battery safety aspect, which is governed by the electrolyte composition.</p>

Le mélange de polymères est une méthode répandue pour élaborer des matériaux polymères. Cependant, la plupart des polymères sont thermodynamiquement immiscibles entre eux, engendrant une séparation de phase des mélanges et une détérioration de leurs propriétés. Afin de palier ces problèmes, la méthode dite compatibilisation réactive est souvent employée. Elle est basée sur la formation in-situ de copolymères à bloc ou greffés par l’intermédiaire de réactions interfaciales entre polymères réactifs. Cette thèse a pour objet de développer un concept dit agent compatibilisant-traceur réactif qui permettra d’utiliser de faibles quantités d’agents compatibilisants réactifs pour évaluer leurs efficacités de compatibilisation directement sur des extrudeuses bi-vis industrielles, d’une part ; et de caractériser la performance du mélange d’une extrudeuse bi-vis en fonction des conditions opératoires et/ou du profil de vis employé. Ses principales contributions se résument ci-après. L’anthracène de 9-méthylaminométhyle (MAMA), une molécule fluorescente, est incorporée dans un copolymère statistique de styrène (St) et d’isocyanate de 3-isopropenyle-?, ?’-diméthylebenzène (TMI), noté PS-TMI, pour former un agent compatibilisant-traceur réactif, noté PS-TMI-MAMA. Ce dernier sert à la fois comme agent compatibilisant réactif grâce aux groupements isocyanate et traceur grâce aux groupements fluorescents. Il est utilisé pour les mélanges à base de polystyrène (PS) et de polyamide 6 (PA6) afin d’évaluer son efficacité de compatibilisation. Les mélanges PS/PA6 sont élaborés dans un mélangeur discontinu et une extrudeuse bi-vis, respectivement. Dans le cas du mélangeur discontinu, la quantité du copolymère greffé formé in-situ, noté PS-g-PA6-MAMA, augmente alors que le diamètre des domaines de la phase dispersée (DDD) diminue considérablement au début du mélange. Lorsque le mélange se poursuit, le nombre de greffons en PA6 du PS-g-PA6-MAMA augmente, engendrant une composition très asymétrique du PS-g-PA6-MAMA qui est thermodynamiquement instable aux interfaces. De ce fait, il peut être arraché des interfaces vers la phase PA6 et peut y former des micelles. Lorsqu’il est arraché des interfaces, il perdra son efficacité de compatibilisation et le DDD augmentera. L’action du mélange a un double effet sur le procédé de compatibilisation réactive. Il promeut la réaction interfaciale entre le PS-TMI-MAMA et le PA6, d’une part ; et aggrave l’arrachage du PS-g-PA6-MAMA de l’interface, d’autre part. L’utilisation de faibles quantités de l’agent compatibilisant-traceur réactif permet de mesurer les évolutions de la teneur en agent compatibilisant-traceur réactif, du DDD et de la teneur en agent compatibilisant-traceur réactif ayant réagi en fonction du temps de séjour dans une extrudeuse bi-vis. Pour une masse molaire donnée, l’efficacité de compatibilisation d’un agent compatibilisant-traceur réactif augmente avec l’augmentation de la teneur en TMI dans une certaine limite. Pour une teneur en TMI donnée, la réaction interfaciale est plus rapide avec la diminution de la masse molaire dans une certaine limite et le DDD devient plus petit en un temps plus court. L’influence du taux de remplissage de la vis est plus significative que celle du temps de séjour. Lorsque le taux de remplissage de la vis augmente, le taux de la réaction interfaciale augmente et le DDD diminue. Lorsque l’angle d’un élément de mélange augmente, les efficacités du mélange distributif et du mélange dispersif augmentent, ce qui se traduit par une augmentation de la quantité du PS-g-PA6-MAMA formée et une diminution du DDD par rapport à la même quantité de PS-g-PA6-MAMA produite. Lorsque la largeur d’un élément de mélange augmente, l’efficacité du mélange distributive augmente alors que celle du mélange dispersif demeure inchangée. La substitution d’éléments de mélange par des éléments inverses améliore l’efficacité du mélange distributif et celle du mélange dispersif / Polymer blending is a common method to prepare high-performance polymer materials. However, most polymer pairs are thermodynamically immiscible, leading to phase separation and deterioration in material properties. To overcome such problems, the most common method is reactive compatibilization which is based on the in-situ formation of a graft or block copolymer by interfacial reaction between reactive polymers. This thesis aims at developing a concept of reactive compatibilizer-tracer which will allow using small amounts of reactive compatibilizers to evaluate their compatibilizing efficiency in industrial scale twin screw extruders, on the one hand; and to characterize the mixing performance of a twin screw extruder as a function of process conditions and/or screw profile. Its main contributions are summarized below. 9-(methylaminomethyl) anthracene (MAMA), a fluorescent molecule, is incorporated into a random copolymer of styrene (St) and 3-isopropenyl-?, ?’-dimethylbenzene isocyanate (TMI), denoted as PS-TMI, to form a reactive compatibilizer-tracer, denoted as PS- TMI-MAMA. The latter serves both as a reactive compatibilizer due to its isocyanate moieties and a tracer due to its fluorescent moieites. It is used for polystyrene (PS)/polyamide 6 (PA6) blends to evaluate its compatibilizing efficiency. Compatibilized PS/PA6 blends are processed in a batch mixer and in a twin screw extruder, respectively. In the case of the batch mixer, the amount of the in-situ formed graft copolymer denoted as PS-g-PA6-MAMA increases and the dispersed phase domain diameter (DDD) decreases drastically in the initial period of mixing. As the mixing further proceeds, the number of PA6 grafts of the PS-g-PA6-MAMA increases, resulting in a highly asymmetrical composition of the PS-g-PA6-MAMA which causes thermodynamic instablility at the interface. As a result, it could be pulled out of the interface to the PA6 phase and form micelles. Once it is pulled out of the interface, it will lose its compatibilizing efficiency and the dispersed phase domain diameter increases sharply. Mixing has a dual effect on the reactive compatibilization process. On the one hand, it promotes the interfacial reaction between the PS-TMI-MAMA and PA6. On the other hand, it aggravates the pull out of the resulting PS-g-PA6-MAMA from the interface. The use of small amounts of the reactive compatibilizer-tracer together with transient experiments for RTD allows assessing the evolutions of the reactive compatibilizer-tracer content (CC), the dispersed phase domain diameter (DDD), and the reacted reactive compatibilizer-tracer content (RCC) as a function of residence time in a twin-screw extruder. Based on the above results, the emulsification curve (DDD vs. CC), the RCC vs. CC curve and effective emulsification curve (DDD vs. RCC) are obtained. When the molar mass of the reactive compatibilizer-tracer is fixed, its compatibilizing efficiency increases with increasing TMI content within an appropriate range. When its TMI content is fixed, the interfacial reaction goes faster as the molar mass of the reactive compatibilizer-tracer decreases within a certain range, and the DDD becomes smaller in a shorter time. The effect of degree of fill fixed by the throughput Q/screw speed N ratio is more dominant than that of residence time. As the degree of fill increases, the interfacial reaction increases and the DDD decreases. As the angle of adjacent the kneading block increases, its distributive and dispersive mixing efficiencies increase, resulting in an increase in interfacial area generation and a decrease in DDD on the basis of the same amount of PS-g-PA6-MAMA. On the other hand, as the width of the kneading block increases, the distributive mixing efficiency increases and the dispersive mixing efficiency remains unchanged. Substitution of kneading blocks by reverse ones increase both the distributive and dispersive mixing efficiencies

This thesis presents a research into the solder interconnects made through the reactive bonding process based on the self-propagating reaction. A numerical study of soldering conditions in the heat affected zone (HAZ) during bonding was initially carried out in order to understand the self-propagating reactive bonding and the related influencing factors. This was subsequently followed by an extensive experimental work to evaluate the feasibility and reliability of the reactive bonding process to enable the optimisation of processing parameters, which had provided a detailed understanding in terms of interfacial characteristics and bonding strengths. In addition, by focusing on the microstructure of the bonds resulted from the self-propagating reactions, the interfacial reactions and microstructural evolution of the bonded structures and effects of high-temperature aging were studied in details and discussed accordingly. To study the soldering conditions, a 3D time-dependent model is established to describe the temperature and stress field induced during self-propagating reactions. The transient temperature and stress distribution at the critical locations are identified. This thus allows the prediction of the melting status of solder alloys and the stress concentration points (weak points) in the bond under certain soldering conditions, e.g. ambient temperature, pressure, dimension and type of solder materials. Experimentally, the characterisation of interconnects bonded using various materials under different technical conditions is carried out. This ultimately assists the understanding of the feasibility, reliability and failure modes of reactive bonding technique, as well as the criteria and optimisation to form robust joints. The formation of phases such as intermetallic compounds (IMCs) and mechanism of interfacial reactions during reactive bonding and subsequent aging are elaborated. The composition, dimension, distribution of phases have been examined through cross-sectional observations. The underlying temperature and stress profile determining the diffusion, crystallization and growth of phases are defined by numerical predictions. XXI Through the comparative analysis of the experimental and numerical results, the unique phases developed in the self-propagating joints are attributed to the solid-liquid-convective diffusion, directional solidification and non-equilibrium crystallization. The recrystallization and growth of phases during aging are revealed to be resulted from the solid-state diffusion and equilibration induced by the high-temperature heating. In conclusion, the interfacial reactions and microstructural evolution of interconnect developed through self-propagating reactive bonding are studied and correlated with the related influencing factors that has been obtained from these predictions and experiments. The results and findings enable the extensive uses of self-propagating reactive bonding technology for new design and assembly capable of various applications in electronic packaging. It also greatly contributes to the fundamentals of the crystallization and soldering mechanism of materials under the non-equilibrium conditions.

Le procédé de coextrusion permet de combiner à l’état fondu plusieurs couches de polymères dans une même structure. La compatibilisation des différentes couches est généralement réalisée à l’aide de liants qui réagissent in-situ. Bien que la compatibilisation puisse permettre de réduire ou même supprimer les instabilités macroscopiques d’écoulement, un nouveau défaut qualifié de « granité » peut apparaitre. Très peu de travaux de la littérature traitent les mécanismes gouvernant ce type de défaut. Les phénomènes mis en jeu sont particulièrement complexes puisqu’ils impliquent de façon couplée des phénomènes hydrodynamiques via l’écoulement, la rhéologie des différentes couches et des phénomènes physico-chimiques via la diffusion et la réaction chimique aux interfaces polymère/polymère. Ce mémoire s’articule autour d’une étude multi-échelle du rôle des copolymères aux interfaces sur la stabilité des écoulements stratifiés. L’étude a été réalisée à la fois sur des systèmes non-réactifs et réactifs constitués d’une couche barrière, le polyamide 6 (PA6) ou le poly(éthylène-co-alcool vinylique) (EVOH), avec un polypropylène (PP) ou un polypropylène greffé anhydride maléique (PP-g-AM). Le défaut de « granité » a été mis en évidence en coextrusion. Les paramètres procédé et matériaux influençant son apparition ont été identifiés. Il a pu être différencié des défauts et des instabilités interfaciales généralement rencontrées en coextrusion. Le phénomène de compatibilisation a également été étudié via les caractérisations morphologiques (MET, MEB, AFM) et physico-chimiques (XPS) aux interfaces. Le comportement rhéologique en cisaillement et élongation en viscoélasticité linéaire et non linéaire s’est révélé très sensible à l’effet la présence de copolymères aux interfaces et à leur architecture moléculaire. Cette étude a permis de déterminer les propriétés intrinsèques de l’interface/interphase en fonction du copolymère formé entre le liant et le PA6 ou l’EVOH. Elles ont pu être corrélées aux défauts macroscopiques observés dans les films multicouches coextrudés. La stabilité de ces écoulements stratifiés résulte d’un couplage de phénomènes qui se produisent à différentes échelles : nano (réaction de copolymérisation), micro (interphase) et macro (écoulement dans le procédé). / Several polymers can be combined in one multilayer structure by reactive coextrusion. Tie-layers are often used to compatibilize the adjacent layers and may reduce or suppress the interfacial instabilities and the defects in the multilayer coextrusion flow. However, an additional defect defined as the “grainy” defect can be observed. In the best of our knowledge, no study in literature has been devoted to understand its origin. The phenomena are quite complex due to the coupling of the effects of flow and the physico-chemical mechanisms at the interface. The aim of this work is to understand the relations between the instabilities and the defects encountered in multilayer coextruded films and the role of the copolymer formed in-situ between tie and barrier layers. Polyamide 6 (PA6) and ethylene-vinyl alcohol copolymer (EVOH) were used as the barrier layers sandwiched in a polypropylene (PP) with or without a polypropylene grafted maleic anhydride (PP-g-MA) as a tie-layer. The effect of the process parameters and the structure of the polymers on the generation of the “grainy” defect was assessed in correlation with the rheological and the physicochemical properties of the layers. These experiments have shown that this defect appeared mainly in the compatibilized EVOH system and could be distinguished from the usual coextrusion instabilities. The interfacial properties between tie and barrier layers were investigated. The characterization of the interfacial morphology by TEM and AFM highlighted an irregular and rough interface between PP-g-MA and EVOH while a flat interface was observed with PA6 and PP-g-MA. Step shear and startup elongation rheology was shown to be sensitive to the copolymer at the polymer/polymer interface. The study of the interfacial properties highlighted that the copolymer architecture significantly impacts the interfacial roughness and the rheology of the multilayer stuctures. Hence, relations between the relaxation process, the interfacial morphology and the copolymer architecture were established in correlation with the generation of the macroscopic grainy defect in coextrusion.