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Nowadays the main challenge for the energy system is the capability of storing the energy forlater use. To deal with this problem, molten salt storage technology is being used in some solarfacilities. By its implementation, the energy can be stored in the form of heat. However, thefeasibility of this technology is in a testing stage. Its implementation could be done in differentenergy fields. In this thesis, a novel implementation is suggested nearby a CHP, with the aim ofutilizing the excess electricity provided by the grid in high energy production days. Differentimplementation methods and a real scenario are presented. A study analysis of the tank’s sizeand the amount of molten salt needed as well as an economic analysis are provided. Numericalapproximations are given and results shown according to the theoretical analysis developed.

Les accidents graves de centrales nucléaires ont une probabilité d’occurrence très faible, mais compte tenu des risques encourus, il est nécessaire de savoir prédire l’évolution de l’accident. Dans le scénario le plus critique, le dégagement de chaleur induit par la désintégration des produits de fission entraînerait la fusion du cœur et la formation d’un magma (« corium ») qui tomberait sur le radier en béton du bâtiment réacteur, provoquant sa fusion. L’objectif des études est d’évaluer la vitesse de fusion du béton. Dans ce contexte, le travail effectué dans cette thèse se situe dans la continuité du modèle de ségrégation de phases développé par Seiler et Froment, et s’appuie sur les résultats expérimentaux des essais ARTEMIS. D’une part, nous avons développé un nouveau modèle de transferts à travers le milieu interfacial. Ce modèle fait intervenir trois mécanismes de transfert : la conduction, la convection et un dégagement de chaleur latente. D’autre part, nous avons revu la modélisation couplée du bain et du milieu interfacial, ce qui a conduit au développement de deux nouveaux modèles : « le modèle liquidus », pour lequel on suppose qu’il n’y a pas de résistance au transfert de soluté, et le « modèle à épaisseur de milieu interfacial constante », pour lequel on suppose qu’il n’y a pas de dissolution du milieu interfacial. Le modèle à épaisseur de milieu interfacial constante permet de prédire correctement les valeurs expérimentales de la vitesse de fusion du béton et de la température du bain, dans les essais 3 et 4 tandis que le modèle liquidus, appliqué aux essais 2 et 6, prédit correctement l’évolution de la vitesse de fusion et de la température du bain / Severe accidents of nuclear power plants are very unlikely to occur, yet it is necessary to be able to predict the evolution of the accident. In some situations, heat generation due to the disintegration of fission products could lead to the melting of the core. If the molten core falls on the floor of the building, it would provoke the melting of the concrete floor. The objective of the studies is to calculate the melting rate of the concrete floor. The work presented in this report is in the continuity of the segregation phase model of Seiler and Froment. It is based on the results of the ARTEMIS experiments. Firstly, we have developed a new model to simulate the transfers within the interfacial area. The new model explains how heat is transmitted to concrete: by conduction, convection and latent heat generation. Secondly, we have modified the coupled modelling of the pool and the interfacial area. We have developed two new models: the first one is the “liquidus model”, whose main hypothesis is that there is no resistance to solute transfer between the pool and the interfacial area. The second one is “the thermal resistance model”, whose main hypothesis is that there is no solute transfer and no dissolution of the interfacial area. The second model is able to predict the evolution of the pool temperature and the melting rate in the tests 3 and 4, with the condition that the obstruction time of the interfacial area is about 105 s. The model is not able to explain precisely the origin of this value. The liquidus model is able to predict correctly the evolution of the pool temperature and the melting rate in the tests 2 and 6

[pt] Neste trabalho é realizada a determinação dos parâmetros cinéticos críticos da redução eletroquímica do dissulfeto de ferro numa mistura de haletos clorados fundidos. Este catodo é empregado como material alternativo em sistemas de elevado grau tecnológico, por exemplo, componente em coletores de energia solar, anodo despolarizador para a produção de hidrogênio e material catódico em baterias e pilhas de alta densidade de energia. Cabe ressaltar que o par eletroquímico Li / FeS2 vem sendo testado em novas configurações com diversos eletrólitos, especialmente com sais fundidos em pilhas térmicas e polímeros orgânicos em veículos elétricos / híbridos. Os ensaios desta pesquisa foram realizados em uma célula de teste num forno vertical com leitura digital em tempo real da temperatura e dos dados eletroquímicos. A estabilidade de diversos eletrodos de referência de primeira espécie foi avaliada em testes em branco de longa duração, sendo analisados os seguintes materiais: prata, platina, níquel, molibdênio. A célula eletroquímica teve a configuração de três eletrodos: prata como referência; dissulfeto de ferro, na forma de pó compactado, de trabalho e grafite sendo o contra-eletrodo. A metodologia empregada foi a voltametria linear cíclica com taxa de varredura lenta (0,002 Vs-1), garantindo quasi equilíbrio. O cálculo dos potenciais padrão em circuito aberto, de equilíbrio termodinâmico, indicou 0,3306 ± 0,014 V (773 K) em relação ao eletrodo de referência de Ag / AgCl. O coeficiente de transferência catódico ficou determinado como valendo 0,48, comprovando a reversibilidade do processo e apontando para a possibilidade de utilização deste sistema eletroquímico em baterias. Foi estudado o comportamento eletrocatalítico do eletrodo de FeS2 pelo levantamento das curvas de Tafel a partir dos voltamogramas. O parâmetro indicador desta espontaneidade reacional foi as correntes de transferência, que para o sistema foram determinadas como 14,75 ± 2,73 kA m-2. A avaliação dos produtos reacionais e intermediários foi realizada aliando dados eletroquímicos e técnicas de caracterização. O mecanismo de reação proposto é iniciado pela redução do FeS2 a Fe metálico, como etapa controladora da reação, envolvendo a troca de um elétron, seguida de duas reações envolvendo íons enxofre e uma etapa final puramente química com a formação de Li2S. Uma série de reações químicas e eletroquímicas são propostas para explicar a formação de polissulfetos intermediários, sendo o mais importante o Li2FeS2 ( fase X ), caracterizado neste estudo através de micrografias com a formação de cristais de hábito acicular. / [en] In this work the measurement of the critical kinetics parameters of iron disulphide electrochemical reduction in molten chloride halides mixture was made. This cathode is applied as alternative material in high technology systems, such as, solar energy collector`s components, anode depolariser for hydrogen production and cathodic materials for high energy density primary and secondary batteries. It should be notice that the Li / FeS2 electrochemical pair is being tested in new configurations together with several electrolytes, specially molten salts in thermal batteries and organic polymers in hybrid / electrical vehicles. The experiments in this research were carried in a test cell placed inside a vertical furnace having a real time data acquisition system for temperature and electrochemical data. The stability of many first kind reference electrodes was evaluated in long duration blank tests, being selected the following materials: silver, platinum, nickel and molybdenum. The chosen three- electrode cell configuration was: silver as reference, iron disulphide compacted powder as working electrode and graphite as counter-electrode. The applied methodology was the cyclic linear voltammetry at slow sweep rate (0,002 Vs-1), ensuring quasi equilibrium conditions. For the thermodynamical equilibrium the standard potential determinations for open circuit resulted 0,3306 +- 0,014 V (773 K) with respect to the Ag / AgCl reference. The cathodic transfer coefficient measured to be 0,48 indicates the reversibility of the electrode process and points at its possible application as secondary battery. The FeS2 electrocatalytical behaviour was evaluated though the Tafel curves extracted from the voltammograms. The indicating parameter for this reaction spontaneity, the transfer currents, for this systems were measured to be 14,75 +- 2,73 kA m-2. The evaluation of the reaction intermediaries and products were made allying electrochemical data and characterization techniques. The proposed reaction mechanism is initiated by the reduction of FeS2 to metallic iron as the controlling step, followed by two reactions involving sulphur ions and terminated by the chemical formation of Li2S. A series of chemical and electrochemical processes are proposed to explain formation of intermediary polisulphides, being the most important Li2FeS2 (phase X) spotted here though micrographies displaying it`s characteristic crystals of needle-like morphology.

This thesis is about the design of the gating system and selection of proper alloy for defects free (grate bar) casting. The gating system plays an important role in casting manufacturing process. The gating system has different elements like pouring cup, sprue, well, runner, riser, and ingates. The function of the gating system is to provide molten metal to the mould cavity through different gating system elements.  Casting is a metal shaping process which is used to produce a cast component. The casting process depends upon the material, type of pattern, mould and various techniques like sand casting, investment casting, die casting, squeeze casting and lost foam casting. The sand mould casting process is used in this report. The casting process is used for making small to large cast parts, complicated shapes, and precision parts, etc. Making a casting without defects is an important requirement for its strength. The effective and efficient design of the gating system is necessary for making defects free castings. There are various defects like shrinkage cavity, porosity, pinholes, blowholes and incomplete filling that may occur in sand casting. The simulation software like Magma Soft and Nova Flow Solid are used to predict the possible defects in the casting. The uses of the simulation improve product quality and increase productivity. It also helps to reduce the rejection rate by identifying and controlling defects. This work is done at AB Bruzaholms Bruk as part of master thesis work at Jönköping University, Sweden. The company provides all the necessary data for simulation purposes. The design of the gating system is finalized as per company requirements and needs. The research questions that have been answered in this report based on the following points. 1) What does zero-defect mean? 2) Which is the best design among the ones that are prepared and simulated? 3) Which is the best alloy combination for casting parts that give defects free casting and better fluidity and filling?

Le développement des moteurs aéronautiques du futur a permis d’accentuer les recherches concernant les matériaux composites thermostructuraux SiC/SiC. La voie classique d’élaboration de ces matériaux consiste en l’infiltration de la matrice via un procédé par voie gazeuse. Due à leur porosité résiduelle importante, ces matériaux possèdent une faible conductivité thermique. Cette dernière peut générer de forts gradients thermiques pouvant entrainer une rupture prématurée de la pièce. Afin de réduire cette porosité, un procédé alternatif peut être utilisé : l’infiltration par du silicium liquide (procédé MI : Melt Infiltration). L’objectif de ce travail est de comprendre l’ensemble des mécanismes intervenant au cours de l’infiltration du silicium au sein d’une préforme fibreuse composée de fibres SiC Hi-Nicalon S. Ce procédé nécessite une étape en amont de l’imprégnation du silicium consistant en l’introduction de particules de SiC au sein de la préforme.La première partie de ce travail a consisté d’une part, en la définition de l’architecture poreuse des matériaux et, d’autre part, en la réalisation de tests de montée capillaire en utilisant des fluides organiques modèles. A l’aide de l’équation de Washburn, il est ainsi possible d’identifier des tailles de pores caractéristiques au sein de la préforme fibreuse et de la matrice granulaire et de prévoir le courbes d’ascension capillaire du silicium liquide au sein des matériaux. La seconde partie de ce travail décrit la mise en place d’un four permettant de réaliser le suivi in-situ de la prise de masse en silicium au cours du procédé MI. Une comparaison entre les résultats expérimentaux et les courbes prévisionnelles obtenues à l’aide de l’équation de Washburn a ainsi pu être effectuée. La dernière partie de ce travail a consisté en la réalisation d’essai d’imprégnation partielle afin d’identifier les mécanismes de montée capillaire du silicium liquide durant le procédé MI. / The development of aeronautic engines increased the need in high temperature SiC/SiC composite researches. A standard way to proceed is to infiltrate the matrix by chemical vapor infiltration. Due to their high porosity, their thermal conductivity is generally low. This could lead to strong thermal gradients and an early failure in a harsh environment. To reduce porosity, an alternative process can be used: the infiltration of molten silicon (MI: Melt Infiltration). The aim of this work is to understand all mechanisms occurring during the infiltration of silicon in a fibrous preform composed of SiC Hi-Nicalon S fibers. This process needs a first step which consists in the introduction of SiC particles into the preform before the MI process.First, this work focused on the definition of the porous structure of studied materials and capillarity tests using wetting organic solvent. With the use of Washburn’s law, it was possible to identify pore sizes within the fibrous preform and the granular matrix, and so to predict the capillarity ascent graphs of molten silicon into our material. A second part was devoted to the conception of an infiltration furnace which allows in situ following of the samples weight gain. The correlation between graphs obtained with the Washburn model and the experimental process could be established. Finally, the last part of this work presents partial infiltrations of molten silicon into studied materials which permit to identify capillary mechanisms occurring during the MI process.

O espinélio MgAl2O4 é utilizado prioritariamente na indústria de refratários. Atualmente há várias técnicas de síntese, visto que não é encontrado na natureza. A técnica de sais fundidos apresenta grande potencial para otimização e redução do custo energético na produção deste óxido. Este trabalho teve como objetivo o desenvolvimento da técnica de síntese via sais fundidos para obtenção do espinélio MgAl2O4, e a caracterização do pó produzido via diferentes técnicas. A dissertação explora as variáveis da produção do espinélio a partir de Al2O3 e MgO em KCl, e também alternando o sal para MgCl2 e o eutético KCl-MgCl2. As seguintes alterações foram testadas para verificar o resultado no pó produzido: redução da temperatura para 1150°C, aumento do MgO nos precursores em 10% e 30%, redução da granulometria da Al2O3 precursores para 0,60 μm, variação da razão sal/precursor (S/P) para 1:1 e 9:1. Foi testado o sal MgCl2 nas proporções de precursores estequiométrica, -50% de MgO e -100% de MgO. Por fim, o sal KCl-MgCl2 na razão eutética foi testado. Para caracterização do pó foram utilizadas as técnica de análise cristalográfica por difração de raios X (DRX) e pela técnica de RAMAN, granulometria por dispersão a laser (GDL), microestrutura por microscopia eletrônica por varredura (MEV) e análise de cristalitos por mircroscopia eletrônica de transmissão (MET). Os pós produzidos apresentaram as fases MgAl2O4, Al2O3 e MgO. A redução de temperatura reduziu a quantidade de espinélio em pequena proporção, a alteração de estequiometria dos precursores no sal KCl reduziu a quantidade de Al2O3 em um primeiro momento e também sobrou MgO na reação para um aumento maior de MgO. A redução de granulometria da Al2O3 propiciou aumento da proporção de espinélio na reação. A proporção S/P 1:1 não mostrou alteração, contudo para 9:1 houve sedimentação e um efeito de diluição/precipitação. Para o sal MgCl2, houve precipitação de MgO a partir do sal, alterando o perfil granulométrico dos pós e as fases obtidas: MgO e MgAl2O4. A redução de MgO aumentou a conversão para MgAl2O4, reduzindo também a granulometria. O sal na proporção eutética apresentou boa conversão de espinélio e pouco aumento de granulometria. / The MgAl2O4 spinel is mainly applied at the refractory industry. There are many techniques to produce that oxide, since it is not found in the nature. The molten salts technique shows potencial energy savings and cost reduction to produce spinel. This work aimed at the development of the molten salts synthesis technique to obtain the MgAl2O4 spinel, and characterization of the powder produced via different techniques. The dissertation explores the variables of production of spinel from Al2O3 and MgO in KCl, and also alternating salt to MgCl2 and KCl-MgCl2 eutectic. The following changes were tested to verify the result of the powder produced: reducing the temperature to 1150 ° C, an increase in the MgO precursor at 10% and 30% reduction in particle size of the Al2O3 precursor to 0.60 micrometres variation ratio of salt / precursor (S / P) to 1: 1 and 9: 1. MgCl2 salt was tested in the stoichiometric proportion of precursors, -50% of MgO and -100% MgO. Finally, the KCl-MgCl2 salt eutectic ratio was tested. For characterization of the powder was used the crystallographic analysis technique of X-ray diffraction (XRD) and RAMAN technique, laser scattering for particle size analisys, scanning electron microscopy (SEM) and crystallite analysis by transmission electron mircroscopy (TEM). The powders produced presented the MgAl2O4 phase, Al2O3 and MgO. The reduction in temperature reduced the amount of spinel in small proportion, the stoichiometry change of the precursors in the KCl salt reduced the amount of Al2O3 at first and also left MgO in reaction to a greater increase of MgO. The reduction of the Al2O3 particle size resulted in an increase in the proportion of the spinel reaction. The ratio S/P 1: 1 showed no change, however to 9: 1 was sedimentation and dilution / precipitation effect. To MgCl2 salt, there was precipitation of MgO from the salt, changing the physical profile of the powder and the obtained phases: MgO and MgAl2O4. The reduction of MgO increased the conversion MgAl2O4, by reducing the grain size. The salt in the proportion eutectic showed good conversion spinel and little increase in particle size.

The traditional aluminum production process (Hall-Héroult process) involves electrolyzing the alumina dissolved in the molten cryolite salt. This process is energy intensive and emits massive amounts of CO2 and other greenhouse gases. The market demand of aluminum and the environmental impact of the current aluminum production process justify research and development of alternative electrolytic processes for aluminum production that can both reduce the cost and eliminate adverse environment impacts. Solid oxide membrane (SOM) based electrolysis process is an innovative technology that has been demonstrated to successfully produce many energy-intensive metals directly from their oxides in an efficient, economical and environmentally sound way. During the SOM electrolysis process, an oxygen-ion-conducting SOM tube made of ytteria-stabilized zirconia (YSZ) separates the pre-selected molten flux with dissolved metal oxide from the inert anode assembly inside the YSZ tube. When the applied DC potential between the cathode and the anode exceeds the dissociation potential of desired metal oxide, the metal is reduced at the cathode while oxygen ions migrate through the YSZ membrane and are oxidized at the anode. Employing the inert anode allows the oxygen to be collected at the anode as a value added byproduct. In this work, a zero-direct-carbon-emission aluminum production process utilizing SOM electrolysis is presented. The molten flux used in the electrolysis process is optimized through careful measurements of its physio-chemical properties. The liquidus temperature, volatilization rate, alumina solubility, aluminum solubility, YSZ membrane degradation rate and electrical conductivity of various flux compositions were measured, and the flux chosen for SOM electrolysis was a eutectic MgF2-CaF2 system containing optimized amounts of YF3, CaO and Al2O3. Laboratory scale SOM electrolysis employing the inert anode were performed at 1100 ~ 1200oC to demonstrate the feasibility of producing and collecting aluminum while producing pure oxygen as a byproduct. The aluminum product was characterized by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). An equivalent circuit model for the electrolysis process was developed in order to identify the polarization losses in the SOM electrolysis cell. / 2016-12-21T00:00:00Z

Future nuclear fission reactors (GEN IV) are designed to include fast breeder reactor technologies, which can accept transuranics (elements heavier than uranium) as fuel. This has the potential of being more fuel efficient but requires the closing of the nuclear fuel cycle: full recycling of existing and newly generated nuclear waste to extract uranium and transuranic elements which can be reused as fuel. In the UK a system being investigated is electrochemical pyroprocessing which uses molten LiCl-KCl eutectic (LKE), which aims to recover uranium by electrodeposition on an inert (steel) electrode and the transuranics by electrodeposition as alloys with an active metal electrode (bismuth, cadmium or aluminium). Of the three active metal candidates, aluminium has the best separation efficiency of actinides and lanthanides, which is important as lanthanides are neutron poisons and so are not to be extracted. The development of pyroprocessing requires fundamental understandings of electrochemical alloy formation, as well as on-line monitoring tools to ensure the reprocessing occurs safely and efficiently. To that end, this thesis investigates cerium-aluminium alloying (a non-radioactive model system for plutonium-aluminium) on macro- and microelectrodes to understand the limiting factors during the alloying reaction at each electrode scale and also the circumstances under which the Ce3+ concentration can be reliably determined for on-line monitoring. On a bulk aluminium macroelectrode one cerium-aluminium alloying reaction was observed. This reaction was kinetically limited by the phase change from cerium insertion into the aluminium, and resulted in lattice expansion and progressive roughening of the electrode surface. These factors made it difficult to reliably calculate the Ce3+ concentration. Li+ from the solution was also able to reduce and form alloys with aluminium, approximately 0.3 V more negative than the first cerium-aluminium alloying peak. Since lithium atoms are smaller than cerium, and there is an abundance of Li+ in the salt, lithium-aluminium alloy was found to form preferentially to cerium-aluminium alloy at these more negative potentials. By co-depositing Al3+ and Ce3+ together on a tungsten electrode which is inert under these conditions (it does not alloy), the kinetic barrier to alloy formation by cerium insertion was decreased, which is beneficial to studying the thermodynamics of alloying. Studies of pure aluminium plating and pure cerium plating showed each individual reaction was diffusion limited, with an increased contribution of convection to the mass transport at slow scan rates. Co-deposition on macroelectrodes with a low ratio of [CeCl3]:[AlCl3] showed only one cerium-aluminium alloying peak. The co-deposition currents, and ratio of oxidation peaks charges, showed that co-deposition was occurring with both species under diffusion control, resulting in an amorphous alloy with a Ce:Al ratio that smoothly varied with the [CeCl3]:[AlCl3] ratio. This was in contrast to the alloying behaviour of cerium with liquid bismuth, in which co-deposition occurred at specific ratios determined by the crystal phases that could be formed at the applied potentials, with higher co-deposition ratios being achieved at more negative potentials. Co-deposition on macroelectrodes with a high ratio of [CeCl 3]:[AlCl3] could result in up to five cerium-aluminium alloy peaks, corresponding to all five CexAly crystalline phases predicted by the phase diagram. This phase change from amorphous to crystalline was promoted by the high Ce:Al ratio in the amorphous alloy resulting from the high [CeCl3]:[AlCl3] ratio and by plating pure cerium on the surface, which could then insert into the alloy. Charge analysis of these peaks confirmed the expected stoichiometries of the crystal phase from these in-situ measurements which is important for rapid analysis, whereas all previous literature has relied on ex-situ techniques which cooled the alloy, possibly changing its composition and structure. In all circumstances of alloy formation on macroelectrodes, the rate of reduction of Ce3+ was time dependent and sensitive to convection. This significantly complicated analysis of the electrochemical signal, making it very difficult to reliably calculate the concentration of Ce3+, which is required for on-line monitoring. Co-deposition on in-house microfabricated tungsten microelectrodes resulted in steady state currents for both pure aluminium deposition and cerium-aluminium co-deposition (up to the beginning of lithium-aluminium alloying). Thus, unlike on macroelectrodes, the deposition rate occurred at the flux ratio of each species from solution and only one oxidation peak was observed corresponding to the amorphous cerium-aluminium phase, even at high [CeCl3]:[AlCl3] ratios. The steady state alloying current meant that calculating the Ce3+ concentration was relatively simple from co-deposition on microelectrodes. Co-deposition was highly beneficial for studying alloying, however to avoid the addition of Al3+ to the molten salt, in-house microfabricated thin film aluminium microelectrodes were also used to study alloying. Alloying on microfabricated thin film aluminium microelectrodes was hampered by the formation of a native aluminium oxide layer, which prevented cerium insertion into the aluminium. The oxide layer could be disrupted by reduction of lithium, which showed steady state currents (albeit with significant capacitance) could be achieved for alloying by cerium insertion. However, the full surface area of the microelectrode could not be attained and all microelectrodes lost their aluminium layer after multiple lithiation/de-lithiation cycles. These devices need further development to overcome the oxide layer, or prevent its formation, in order to study alloying in greater detail with aluminium microelectrodes to fully realise their advantages for sensing and monitoring in pyroprocessing.

Ce travail de thèse a pour objet le développement d'une nouvelle voie de synthèse de nanomatériaux métalliques à base d'éléments légers : bore et phosphore. L'intérêt porté à ces composés s'explique par les propriétés variées qu'ils présentent, tels que la supraconductivité, la thermoélectricité ou le stockage d'énergie. Dans le cadre de ce travail, les domaines de la catalyse et de l'électrocatalyse sont explorés. Les borures de différents métaux de transition, en particulier le nickel, le palladium et un composite nickel-cobalt, ont tout d'abord été étudiés. Pour cela une synthèse a été mise au point, reposant sur la réactivité de nanoparticules métalliques avec un précurseur de bore en milieu sels fondus inorganiques. Elle a notamment permis d'obtenir des nanoparticules de borures de nickel avec un bon contrôle de composition, structure, morphologie et taille. Les propriétés de ces nanomatériaux ont par la suite été étudiées en catalyse dans la réaction d'hydrodésoxygénation, et en électrocatalyse dans les réactions de génération d'hydrogène ou d'oxygène à partir de l'eau. Enfin la réactivité du phosphore rouge en milieu sels fondus a été abordée, ouvrant ainsi une nouvelle voie vers l'élaboration de phosphures de métaux de transition. / This PhD work deals with a novel synthesis of metal boride and metal phosphide nanomaterials. Nanostructures of these solids are subject to an increasing interest due to their exciting properties for various applications fields such as superconductivity, high temperature thermoelectricity, energy conversion and storage. In this work, the catalytic and electrocatalytic properties of these nanomaterials are explored. First of all, borides of various transition metals, such as nickel, palladium or a nickel-cobalt composite are studied. To do so, a new liquid-phase synthesis was developed, based on the reactivity of already formed metal nanoparticles with a boron precursor in inorganic molten salts. This new synthesis allowed a precise control over the nanoparticle morphology, size, composition and crystalline structure. By accessing such nanoscale objects, we were able to investigate their properties and performances, especially in the fields of catalysis with the hydrodeoxygenation reaction and electrocatalysis for the hydrogen evolution reaction and oxygen evolution reaction. Finally, the reactivity of red phosphorus in molten salts was addressed, thus paving the way to the extension of this synthetic pathway to metal phosphides.