Etude d'oxydes monocristallins et de céramiques transparentes dopés Pr3+ ou Nd3+ pour la réalisation de lasers visibles

This thesis is aimed to find efficient oxide based solid-state materials for the development of lasers, particularly in visible spectral regions. We focused on Pr3+ and Nd3+ luminescent ions, doped in oxide-based hosts. Pr3+ ions are suitable for direct visible emissions in various regions, whereas the emission of Nd3+ ions in near infrared around 0.9 μm can be converted into blue laser by Second Harmonic Generation. A large-covered visible region could be expected in the range of 450 nm – 750 nm. First, we selected appropriate oxide hosts by using optical spectroscopy tools. All selected materials with congruent melting behavior were grown as single crystal. On the other hand, cubic materials with very high melting point, Nd:Y2O3 and Nd:Y3Al5O12, were prepared as standard and micro-core composite transparent ceramics, respectively. Next, all samples were thoroughly investigated in terms of physical, optical and spectroscopic properties. In the meantime, Judd-Ofelt analysis were computationally performed by using ground state absorption data to calculate radiative properties of studied solid-state materials, including radiative lifetime and branching ratio. Finally, laser operations were carried out within a plane-concave or V-type resonant cavity under blue and near infrared pumping for Pr3+ and Nd3+ solid-state materials, respectively. We achieved visible lasers in the relevant range with satisfying efficiencies with Pr:Sr1-xLaxAl12-xO19 single crystal and Nd:Y3Al5O12 micro-core transparent ceramic. Both present a real potential for the development of laser emissions in visible spectral regions.L’objectif de cette thèse est l’étude de matériaux oxydes pour le développement de lasers solides, émettant en particulier dans le domaine visible. Nous nous sommes intéressés à des matériaux monocristallins et à des céramiques transparentes. Des ions Pr3+ ont été envisagés comme dopants en raison de leurs niveaux d’énergie adaptés pour des émissions directes (bleu, vert, orange, rouge et rouge foncé). En outre, des ions Nd3+ émettant dans le proche infrarouge, autour de 0.9 μm, ont été utilisés comme dopants afin de générer un laser bleu par un processus de conversion de fréquence. Nous avons ainsi préparé des matrices oxydes sous forme polycristalline pour des mesures de spectroscopie optique permettant de sélectionner les meilleurs matériaux. Des matrices d’oxyde à fusion congruente étudiées correspondent aux différentes familles comme suit : hexa-aluminate, mélilite, germanate, tungstate et sesquioxide. Les cristaux ont été élaborés par la méthode de Czochralski. En plus, certains matériaux cubiques a haut point de fusion comme Nd:Y2O3 et Nd:Y3Al5O12 ont été étudiés sous forme de céramiques transparentes de type classique ou composite. Nous avons ensuite caractérisé les propriétés physiques, optiques et spectroscopiques. Finalement, des émissions lasers dans le visible ont été démontrées en régime continu dans une cavité résonante de type plan-concave ou déplié (V). Pour les matériaux dopés Nd3+ et dopés Pr3+, nous avons obtenu l’effet lasers dans le visible avec les efficacités satisfaisantes. Les matériaux monocristallins: Pr:Sr1-xLaxAl12-xO19 et céramique composite Nd:Y3Al5O12 présentent un potentiel important pour le développement de lasers dans le domaine visible

Study of Pr3+ or Nd3+ doped single crystals or transparent ceramics for visible laser emissions

L’objectif de cette thèse est l’étude de matériaux oxydes pour le développement de lasers solides, émettant en particulier dans le domaine visible. Nous nous sommes intéressés à des matériaux monocristallins et à des céramiques transparentes. Des ions Pr3+ ont été envisagés comme dopants en raison de leurs niveaux d’énergie adaptés pour des émissions directes (bleu, vert, orange, rouge et rouge foncé). En outre, des ions Nd3+ émettant dans le proche infrarouge, autour de 0.9 μm, ont été utilisés comme dopants afin de générer un laser bleu par un processus de conversion de fréquence. Nous avons ainsi préparé des matrices oxydes sous forme polycristalline pour des mesures de spectroscopie optique permettant de sélectionner les meilleurs matériaux. Des matrices d’oxyde à fusion congruente étudiées correspondent aux différentes familles comme suit : hexa-aluminate, mélilite, germanate, tungstate et sesquioxide. Les cristaux ont été élaborés par la méthode de Czochralski. En plus, certains matériaux cubiques a haut point de fusion comme Nd:Y2O3 et Nd:Y3Al5O12 ont été étudiés sous forme de céramiques transparentes de type classique ou composite. Nous avons ensuite caractérisé les propriétés physiques, optiques et spectroscopiques. Finalement, des émissions lasers dans le visible ont été démontrées en régime continu dans une cavité résonante de type plan-concave ou déplié (V). Pour les matériaux dopés Nd3+ et dopés Pr3+, nous avons obtenu l’effet lasers dans le visible avec les efficacités satisfaisantes. Les matériaux monocristallins: Pr:Sr1-xLaxAl12-xO19 et céramique composite Nd:Y3Al5O12 présentent un potentiel important pour le développement de lasers dans le domaine visible.This thesis is aimed to find efficient oxide based solid-state materials for the development of lasers, particularly in visible spectral regions. We focused on Pr3+ and Nd3+ luminescent ions, doped in oxide-based hosts. Pr3+ ions are suitable for direct visible emissions in various regions, whereas the emission of Nd3+ ions in near infrared around 0.9 μm can be converted into blue laser by Second Harmonic Generation. A large-covered visible region could be expected in the range of 450 nm – 750 nm. First, we selected appropriate oxide hosts by using optical spectroscopy tools. All selected materials with congruent melting behavior were grown as single crystal. On the other hand, cubic materials with very high melting point, Nd:Y2O3 and Nd:Y3Al5O12, were prepared as standard and micro-core composite transparent ceramics, respectively. Next, all samples were thoroughly investigated in terms of physical, optical and spectroscopic properties. In the meantime, Judd-Ofelt analysis were computationally performed by using ground state absorption data to calculate radiative properties of studied solid-state materials, including radiative lifetime and branching ratio. Finally, laser operations were carried out within a plane-concave or V-type resonant cavity under blue and near infrared pumping for Pr3+ and Nd3+ solid-state materials, respectively. We achieved visible lasers in the relevant range with satisfying efficiencies with Pr:Sr1-xLaxAl12-xO19 single crystal and Nd:Y3Al5O12 micro-core transparent ceramic. Both present a real potential for the development of laser emissions in visible spectral regions

Structural Rearrangement in LSM Perovskites for Enhanced Syngas Production via Solar Thermochemical Redox Cycles

Oxygen carriers undergo many physiochemical changes such as particle growth and phase transformation during thermochemical redox reactions aimed at synthesizing solar fuels. In suitable materials, these changes favor the cyclic production of synthesis gas. Advanced study of these properties is of prime importance when strengthening the material selection criteria for thermochemical applications. Considering this, we investigate the redox behavior of LaxSr1-xMnO3 (LSM) perovskite oxide systems during dry and steam chemical looping reforming of methane. The durability and structural stability are studied for cyclic regeneration to the parent perovskite structure. It is observed that lanthanum addition suppresses the LSM structural disintegration during the reduction reaction and promotes its regeneration upon reoxidation. High syngas yields of up to 2.7 mmol g-1 are produced with 25% lanthanum content during 30 consecutive cycles of dry reforming of methane. H2 purity is also increased by up to 18% in lanthanum-rich LSM structures when compared to pure SrMnO3 with ∼74% H2 purity. It is found that despite structural disintegration, manganese plays an active role in redox activities and its oxidation state is greatly influenced by lanthanum concentration and oxidation medium. We think that this study will supplement the in-depth investigation of the material's physiochemical properties before and after the redox reactions prior to selection of a suitable oxygen carrier/catalyst

Selectivity of Copper by Amine-Based Ion Recognition Polymer Adsorbent with Different Aliphatic Amines

This paper investigates the selectivity of GMA-based-non-woven fabrics adsorbent towards copper ion (Cu) functionalized with several aliphatic amines. The aliphatic amines used in this study were ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). The non-woven polyethylene/polypropylene fabrics (NWF) were grafted with glycidyl methacrylate (GMA) via pre-radiation grafting technique, followed by chemical functionalization with the aliphatic amine. To prepare the ion recognition polymer (IRP), the functionalized amine GMA-grafted-NWF sample was subjected to radiation crosslinking process along with the crosslinking agent, divinylbenzene (DVB), in the presence of Cu ion as a template in the matrix of the adsorbent. Functionalization with different aliphatic amine was carried out at different amine concentrations, grafting yield, reaction temperature, and reaction time to study the effect of different aliphatic amine onto amine density yield. At a concentration of 50% of amine and 50% of isopropanol, EDA, DETA, TETA, and TEPA had attained amine density around 5.12, 4.06, 3.04, and 2.56 mmol/g-ad, respectively. The amine density yield decreases further as the aliphatic amine chain grows longer. The experimental condition for amine functionalization process was fixed at 70% amine, 30% isopropanol, 60 °C for grafting temperature, and 2 h of grafting time for attaining 100% of grafting yield (Dg). The prepared adsorbents were characterized comprehensively in terms of structural and morphology with multiple analytical tools. An adsorptive removal and selectivity of Cu ion by the prepared adsorbent was investigated in a binary metal ion system. The IRP samples with a functional precursor of EDA, the smallest aliphatic amine had given the higher adsorption capacity and selectivity towards Cu ion. The selectivity of IRP samples reduces as the aliphatic amine chain grows longer, EDA to TEPA. However, IRP samples still exhibited remarkably higher selectivity in comparison to the amine immobilized GMA-g-NWF at similar adsorption experimental conditions. This observation indicates that IRP samples possess higher selectivity after incorporation of the ion recognition imprint technique via the radiation crosslinking process

Selectivity of Copper by Amine-Based Ion Recognition Polymer Adsorbent with Different Aliphatic Amines

This paper investigates the selectivity of GMA-based-non-woven fabrics adsorbent towards copper ion (Cu) functionalized with several aliphatic amines. The aliphatic amines used in this study were ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). The non-woven polyethylene/polypropylene fabrics (NWF) were grafted with glycidyl methacrylate (GMA) via pre-radiation grafting technique, followed by chemical functionalization with the aliphatic amine. To prepare the ion recognition polymer (IRP), the functionalized amine GMA-grafted-NWF sample was subjected to radiation crosslinking process along with the crosslinking agent, divinylbenzene (DVB), in the presence of Cu ion as a template in the matrix of the adsorbent. Functionalization with different aliphatic amine was carried out at different amine concentrations, grafting yield, reaction temperature, and reaction time to study the effect of different aliphatic amine onto amine density yield. At a concentration of 50% of amine and 50% of isopropanol, EDA, DETA, TETA, and TEPA had attained amine density around 5.12, 4.06, 3.04, and 2.56 mmol/g-ad, respectively. The amine density yield decreases further as the aliphatic amine chain grows longer. The experimental condition for amine functionalization process was fixed at 70% amine, 30% isopropanol, 60 °C for grafting temperature, and 2 h of grafting time for attaining 100% of grafting yield (Dg). The prepared adsorbents were characterized comprehensively in terms of structural and morphology with multiple analytical tools. An adsorptive removal and selectivity of Cu ion by the prepared adsorbent was investigated in a binary metal ion system. The IRP samples with a functional precursor of EDA, the smallest aliphatic amine had given the higher adsorption capacity and selectivity towards Cu ion. The selectivity of IRP samples reduces as the aliphatic amine chain grows longer, EDA to TEPA. However, IRP samples still exhibited remarkably higher selectivity in comparison to the amine immobilized GMA-g-NWF at similar adsorption experimental conditions. This observation indicates that IRP samples possess higher selectivity after incorporation of the ion recognition imprint technique via the radiation crosslinking process

A systematic variation in cationic distribution and its influence on the magnetization of mixed-metal (nickel and zinc) cobaltite spinels

Cobaltite oxide spinel (CoCo _2 O _4 ) is one promising material that has been extensively studied for decades due to its versatile applications. Revealing the correlation among chemical compositions, cationic distributions, and physical properties are crucial for exploring its novel application. Here, a series of nickel/zinc co-substituted cobaltite spinels, Zn _1−X Ni _X Co _2 O _4 (ZNCO-X; where X = 0.00, 0.25, …, 1.00), was synthesized by calcining the hydrothermal-derived precursors and their magnetic properties have been investigated. Multiple x-ray based characterization techniques (XRD, XRF, XPS, and XAS) were applied to determine the crystalline structure and appropriated compositions of cation species (Zn ^2+ , Ni ^2+ , Ni ^3+ , Co ^2+ , and Co ^3+ ). In conjunction with Neel’s theory of antiferromagnetism, the theoretical magnetization of the spinel series was calculated based on the assumption that Zn ^2+ ion was located in tetrahedral (A site) while nickel cations (Ni ^2+ and Ni ^3+ ) occupying the octahedral (B site). The theoretical magnetization profile exhibited a good correlation. Superparamagnetic effect and cationic site exchange can be used to explain the discrepancies between the measured and calculated magnetizations. This work reported a systematic controlling of materials structure and cationic distribution, which are crucial for fine-tuning the magnetic property of the Zn _1−X Ni _X Co _2 O _4 cobaltite system

Chelating ligands as electrolyte solvent for rechargeable zinc-ion batteries

Rechargeable zinc-ion batteries (RZIBs) are mostly powered by aqueous electrolytes. However, uncontrolled water interactions often confer a small voltage window and poor battery capacity retention. Here, we explore replacing water with ethylene glycol as the primary solvent in zinc electrolyte formulations. The assembled batteries reveal suppressed electrolyte-induced parasitic reactions, leading to (1) expanded voltage stability windows up to 2.2 V, (2) prolonged zinc stripping/plating stability up to 2.4 times longer compared to the water-based counterparts, and (3) doubled cathode capacity retentions as observed in full-cell Zn-FeVO4 RZIBs. Using a combination of synchrotron EXAFS and FTIR, we investigate the molecular level salt-solvent interactions and explain how the chelation ability of EG ligands reduces parasitic reactions to enable the enhanced electrochemical performances. The structural insights should provide guidelines on the selection of salt, concentration, and chelating solvents for robust multivalent-ion battery systems.National Research Foundation (NRF)Accepted versionThis work was funded by the National Research Foundation of Singapore Investigatorship Award Number NRFI2017-0

Multiscalar investigation of FeVO4 conversion cathode for a low concentration Zn(CF3SO3)2 rechargeable Zn-ion aqueous battery

Battery cathode materials operating on multivalent‐ion intercalation are prone to short operational lifetimes, traditionally explained to be due to poor solid‐state diffusion. Here, we overcome this problem by using a conversion‐type cathode material and demonstrate the benefits in a FeVO4 host structure. The rechargeable Zn‐ion battery exhibits stability for an unprecedented operational lifetime of 57 days with a high capacity of 272 mAh g−1 (60 mA g−1) over 140 cycles. We use a combination of synchrotron‐based XAS, SRXTM, Raman, XRD and HRTEM techniques to elucidate the cathode material evolution at multilength‐scale for understanding the Zn‐ion storage mechanism. We further highlight the benefits of using a low‐salt concentration electrolyte and pH‐consideration analysis in aqueous battery development, the optimization of which leads to a 4‐fold increase in battery performance as compared to conventional high‐salt concentration electrolyte formulations.National Research Foundation (NRF)Accepted versionThis work was financially supported by the National Research Foundation of Singapore (NRF) Investigatorship Award Number NRFI2017-08/NRF2016NRF-NRFI001-22