Understanding of the interrelationship between structure, thermodynamic properties and phase diagrams is very useful for rationalizing the behavior of materials and development of predictive models, which can be used to optimize the composition of materials and their fabrication processes. The properties of materials are governed by its electronic and crystallographic structure. Chemical bonding determines the electronic structure of materials. Furthermore, the electronic structure plays a predominant role in determining the physical, electrical, magnetic, thermal and optical properties of materials. Crystal structure also influences most properties of materials. Since changes in thermodynamic variables such as temperature, pressure, and composition dramatically alter the physical properties of materials and its structure, it is desirable to study the thermodynamic stability of materials in conjunction with phase relations. Phase diagrams can indicate the ranges of pressure, temperature and chemical composition where specific phases and mixtures of phases are stable. If the Gibbs energies of all the phases involved are known, phase diagram can be computed using Gibbs energy minimization algorithms. In recent times, one of the important uses of thermodynamics in materials science has been in the computation of phase diagrams. To materials scientists phase diagrams are like maps to travelers. They guide the path through the composition space to find phases, fulfilling specific materials performance requirements. As phase diagrams are the graphic representations of minimizations of Gibbs energy under given constraints, computational thermodynamics significantly expands our capability to walk in the multi-component space of engineering materials. High-temperature phase-equilibrium studies, thermodynamics and materials processing have had a close relationship over a number of decades. Successful utilization of ceramic materials under different environmental conditions at high temperatures requires accurate thermodynamic data. Focus of the present investigation is to obtain correct phase relations and accurate thermodynamic data in selected technologically important ceramic oxide systems in which the data are either not available or are inconsistent. Based on the experimental data, different types of phase diagrams are computed for the systems of contemporary relevance. After a brief introduction, Chapter 1 discusses the brief overview of the experimental techniques available for determining the phase relations and thermodynamic properties at high temperatures and the methods used in this study. The chapter reviews the possible sources of errors in experimental techniques and tests for correct functioning. In Chapter 2, systematic studies on high-temperature phase equilibria and thermodynamic properties of compounds in the ternary systems Ln-Pd-O (Ln = La, Pr, Eu, Gd, Tb, Dy, Ho and Er) are presented. Some of the ternary oxides on the Ln-Pd-O systems have potential application in catalysis and electrochemistry. To optimize the parameters for the synthesis and to understand the behavior of the catalysts, it is useful to have information on the thermodynamic stability domain of each compound. Quantitative information on the stability of the ternary oxides is also useful for assessing the interaction of metal Pd with ceramic compounds containing rare-earth elements under different environments. Furthermore, the thermodynamic data are beneficial for the design of processes for the recovery of rare earth and precious metals from scrap. There is very little thermodynamic and phase diagram information on the Ln-Pd-O systems. Isothermal sections of phase diagram for the ternary system La-Pd-O at 1200 K and for the systems Ln-Pd-O (Ln = Pr, Eu, Gd, Tb, Dy, Ho and Er) at 1223 K, were established by the isothermal equilibration technique at high temperatures. Phases were identified after quenching by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy (EDS). Based on the phase relations, the thermodynamic properties of ternary interoxide compounds were determined by the solid-state galvanic cell technique over a range of temperature between 925 - 1400 K. An advanced version of the solid-state cell incorporating a buffer electrode was used for high temperature thermodynamic measurements. The function of the buffer electrode, placed between reference and working electrodes, was to absorb the electrochemical flux of the mobile species through the solid electrolyte caused by trace electronic conductivity. The buffer electrode prevented polarization of the measuring electrode and ensured accurate data. Yttria-stabilized zirconia was used as the solid electrolyte and pure oxygen gas at a pressure of 0.1 MPa as the reference electrode. These novel features enhanced the accuracy of thermodynamic data. From electrochemical measurements, the standard enthalpies of formation of these oxides from elements and their standard entropies at 298.15 K were also evaluated. The variation of the lattice parameters and unit cell volume as a function of rare earth atomic number for the three ternary compounds Ln4PdO7, Ln2PdO4 (Ln = La, Pr, Nd, Sm, Eu, Gd) and Ln2Pd2O5 (Ln = La to Er) are discussed. The systematic variations of thermodynamic properties of all the ternary compounds as a function of rare earth atomic number are presented and correlated with structural features. Thermodynamic and structural parameters of uninvestigated Ln-Pd-O systems (Ln = Ce, Pm) can be obtained by interpolation. Based on the thermodynamic information obtained in this study and auxiliary data on binary compounds available in the literature, different types of phase diagrams, isothermal oxygen potential diagrams, isobaric phase diagrams, isothermal two dimensional and three-dimensional chemical potential diagrams for the systems Ln-Pd-O (Ln = La, Pr, Eu, Gd, Tb, Dy, Ho and Er) are constructed. Chapter 3 contains the studies on partial phase diagrams of the systems M-Ru-O (M = Ca and Sr) at 1300 K and determination of Gibbs energies of formation of calcium and stronsium ruthenates in the temperature range from 925 to 1350 K using solid-state cells with yttria-stabilized zirconia as the electrolyte and Ru + RuO2 as the reference electrode. Gibbs energies, enthalpies and entropies of formation of calcium and strontium ruthenates from their component binary oxides were deduced. The standard enthalpies of formation of these oxides from elements and their standard entropies at 298.15 K were also evaluated. Based on the thermodynamic data obtained in this study and auxiliary information from the literature, the three dimensional representation of oxygen potential diagram for the M-Ru-O systems (M = Ca and Sr) as a function of composition and temperature are computed. The purpose of this chapter is to determine the thermodynamic stability of alkaline earth metal ruthenates in the perovskite related layered system Mn+1RunO3n+1 (n = 1, 2, and ¥ for Ca-Ru-O system and n = 1, 2, 3 and µ for Sr-Ru-O system) since these calcium and stronsium ruthenates have interesting magnetic and electronic device applications. Moreover, there is no literature available for thermodynamic properties on first and second members of the Ruddelsdon-Popper (R-P) series in Ca-Ru-O system, Ca2RuO4, Ca3Ru2O7 and third member of R-P series in Sr-Ru-O system, Sr4Ru3O10. Some of the available literature information on thermodynamic properties for other compounds of R-P series in Mn+1RunO3n+1 (M = Ca, Sr) are found to be based on incorrect assumptions and erroneous calculation. Thus, this chapter provides the complete thermodynamic information for all the electronically and magnetically applicable alkaline earth metal ruthenates for optimizing the deposition condition in device fabrications. Chapter 4 gives the structure-properties correlations of 2-3 spinel compounds and spinel-corundum equilibria for the system NiO-Al2O3-Cr2O3 at 1373 K. Nickel, aluminum and chromium are important base-constituent elements of high-temperature oxidation-resistant alloys. A spinel phase is usually found in the protective scale formed on the surface of the alloys. There is no thermodynamic data on spinel solid solution NiAl2O4-NiCr2O4. Thus, the phase relations and mixing properties of the spinel solid solution have been determined in this chapter. The inter-crystalline ion-exchange equilibrium between NiAl2+2xO4+3x-NiCr2O4 spinel solid solution and Al2O3-Cr2O3 solid solution with corundum structure in pseudo-ternary system NiO-Al2O3-Cr2O3 have been determined by the conventional tie-line rotation method at 1373 K. The nonstoichiometry of NiAl2+2xO4+3x has been taken into consideration. Lattice parameters were used to obtain the compositions of the corundum and spinel solid solutions at equilibrium. Formation of homogeneous solid solutions and attainment of equilibrium were confirmed by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). From the experimental tie-line information and thermodynamic data on Al2O3-Cr2O3 solid solution available in the literature, the activities in the spinel solid solution were derived by using a modified Gibbs-Duhem integration technique. Gibbs energy of mixing of the spinel solid solution has been calculated from the derived activity data. Since high temperature data generation is expensive and time consuming, it is useful to develop models, which relate thermodynamic properties to electronic and crystallographic structure, leading to predictive modeling of mixing properties. By comparing the results from models with experimental information, one can evolve methodologies for the prediction of the properties of uninvestigated system. A model can be used to discriminate among conflicting experimental data and extrapolate the data into regions where direct measurements are lacking or difficult to perform. In this chapter, a model approach has also been considered to analyze the activity-composition relationship in the NiAl2O4-NiCr2O4 spinel solid solution in terms of the intra-crystalline exchange of cations between the tetrahedral and octahedral sites of the spinel structure governed by site preference energies of the cations. Since Ni2+ and Cr3+ ion in tetrahedral coordination exhibits Jahn-Teller distortion, an entropy corresponding to randomization of the distortion in the cubic phase has been incorporated in the cation distribution model. The thermodynamic mixing properties of stoichiometric spinel solid solution NiAl2O4-NiCr2O4 in terms of one mole of mixing species were computed at 1373 K. The strain energy caused by size mismatch was added as a separate term to the Gibbs energy of mixing using empirical relationship between enthalpy of mixing for a pair of ions and the difference in their ionic volumes. Madelung constant and electrostatic contribution of energy of mixing of the spinel solid solution have also been computed. Comparison of Gibbs energy of mixing calculated using the cation mixing model for the stoichiometric spinel solid solution NiAl2O4-NiCr2O4 with that of the experimental tie-line data for nonstoichiometric spinel solid solution NiAl2+2xO4+3x-NiCr2O4 were included in this chapter. The thermodynamic mixing properties obtained in this study would be helpful in understanding the formation of complex spinel protective layers on alloys containing nickel, aluminium and chromium in high-temperature applications. The summary of the important finding and the conclusions arrived at on the basis of results obtained from the present investigations are presented in Chapter 5.

In this thesis research on synthesis, microstructure and properties of carbide-based coatings is reported. These coatings are electrically conducting, and can be tailored for high hardness, low friction and wear, along with load-adaptive behaviour. Tailoring these properties is achieved by controlling the relative phase content of the material. Coatings have been synthesised by dc magnetron sputtering, and their structures have been characterised, mainly by X-ray photoelectron spectroscopy and X-ray diffraction. It has been shown that nanocomposites comprising of a nanocrystalline transition metal carbide (nc-MeCx, Me = Ti, Nb or V) and an amorphous carbon (a-C) matrix can result in low contact resistance in electrical contacts. Such materials also exhibit low friction and high resistance to wear, making them especially suitable for application in sliding contacts. The lowest contact resistance is attained for small amounts of the amorphous carbon phase. It has been shown that specific bonding structures are present in the interface between nc-TiCx and the a-C phases in the nanocomposite.  It was found in particular that Ti3d and C2p states are involved, and that considerable charge transfer occurs across the interface, thereby influencing the structure of the carbide. Further design possibilities were demonstrated for TiCx-based nanocomposites by alloying them with weakly carbide-forming metals, i.e., Me = Ni, Cu or Pt.  Metastable supersaturated solid solution carbides, (T1-xMex)Cy, were identified to result from this alloying process. The destabilisation of the TiCx-phase leads to changes in the phase distribution in the deposited nanocomposites, thus providing further control over the amount of carbon phase formed. Additional design possibilities became available through the decomposition of the metastable (Ti1-xMex)Cy phase through an appropriate choice of annealing conditions, yielding either more carbon phase or a new metallic phase involving Me. This alloying concept was also studied theoretically for all 3d transition metals using DFT techniques. It has also been demonstrated that Ar-ion etching (commonly used in the analysis of carbide based nanocomposites) can seriously influence the result of the analysis, especially for materials containing metastable phases. This implies that more sophisticated methods, or considerable care are needed in making these analyses, and that many of the earlier published results could well be in error.

Made available in DSpace on 2014-10-09T12:54:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:42Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:54:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:42Z (GMT). No. of bitstreams: 0 / Este trabalho tem como objetivo principal investigar o comportamento frente à corrosão de aços inoxidáveis avançados em meios fisiológicos. Foram selecionados para o estudo quatro aços inoxidáveis visando avaliar o potencial destes para aplicações em implantes cirúrgicos: um aço superferrítico (DIN W. Nr. 1.4575), a Incoloy MA 956, contendo alumínio e óxido de ítrio, um aço austenítico DIN W. Nr. 1.4970 e um aço superaustenítico obtido por meio da adição de 0,87% de nitrogênio ao aço dúplex DIN W. Nr. 1.4460. Os três primeiros aços contêm baixo teor de níquel e suas películas protetoras são ricas em cromo, enquanto a Incoloy MA 956 é isenta de níquel, e rica em alumínio, o que influencia o seu filme passivo. Os materiais foram analisados usando técnicas de espectroscopia de impedância eletroquímica (EIE), polarização potenciodinâmica, técnica do eletrodo vibrante, microscopia eletroquímica de varredura, microscopia eletrônica de varredura de emissão de campo, microscopia ótica e microscopia eletrônica de varredura. Os meios escolhidos para avaliação da resistência à corrosão foram a solução de Hanks, um meio de cultura e uma solução tamponada com fosfato. Os resultados de EIE foram interpretados usando circuitos elétricos equivalentes que simularam uma camada passiva dúplex em todos os materiais analisados. Todos os materiais analisados apresentaram resistência à corrosão superior à do aço inoxidável AISI 316L, correspondente ao ASTM F-138, que é o mais utilizado na fabricação de implantes metálicos. Também foi destacada a importância do tratamento de solubilização nos aços com alto teor de nitrogênio. O DIN W. Nr. 1.4970 foi considerado citotóxico e sua potencialidade para uso como biomaterial, rejeitada. O DIN W. Nr. 1.4575 e Incoloy MA 956 podem ser usados como biomateriais, mas somente em próteses odontológicas ou de fácil remoção, devido ao seu comportamento ferromagnético. O DIN W. Nr. 1.4460 com 0,87% de nitrogênio foi o que apresentou as condições mais apropriadas para uso como biomaterial, inclusive para próteses ortopédicas. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP

Climate change is no longer imminent but eminent. To combat climate change, effective, efficient and smart energy use is imperative. Thermal energy storage (TES) with phase change materials (PCMs) is one attractive choice to realize this. Besides suitable phase change temperatures and enthalpies, the PCMs should also be robust, non-toxic, environmental-friendly and cost-effective. Cost-effective PCMs can be realized in bulk blends. Blends however do not have robust phase change unless chosen articulately. This thesis links bulk blends and robust, cost-effective PCMs via the systematic design of blends as PCMs involving phase equilibrium evaluations. The key fundamental phase equilibrium knowledge vital to accurately select robust PCMs within blends is established here. A congruent melting composition is the most PCM-ideal among blends. Eutectics are nearly ideal if supercooling is absent. Any incongruent melting composition, including peritectics, are unsuitable as PCMs. A comprehensive state-of-the-art evaluation of the phase equilibrium-based PCM design exposed the underinvestigated categories: congruent melting compositions, metal alloys, polyols and fats. Here the methods and conditions essential for a comprehensive and transparent phase equilibrium assessment for designing PCMs in blends are specified. The phase diagrams of the systems erythritol-xylitol and dodecane-tridecane with PCM potential are comprehensively evaluated. The erythritol-xylitol system contains a eutectic in a partially isomorphous system unlike in a non-isomorphous system as previous literature proposed. The dodecane-tridecane system forms a probable congruent minimum-melting solid solution, but not a maximum-melting liquidus or a eutectic as was previously proposed. The sustainability aspects of a PCM-based TES system are also investigated. Erythritol becomes cost-effective if produced using glycerol from bio-diesel production. Olive oil is cost-effective and has potential PCM compositions for cold storage. A critical need exists in the standardization of methods and transparent results reporting of the phase equilibrium investigations in the PCM-context. This can be achieved e.g. through international TES collaboration platforms. / Energi är en integrerad del av samhället men energiprocesser leder till miljöbelastning, och klimatförändringar. Därför är effektiv energianvändning, ökad energieffektivitet och smart energihantering nödvändigt. Värmeenergilagring (TES) är ett attraktivt val för att bemöta detta behov, där ett lagringsalternativ med hög densitet är s.k. fasomvandlingsmaterial (PCM). Ett exempel på ett billigt, vanligt förekommande PCM är systemet vatten-is, vilket har använts av människor i tusentals år. För att tillgodose de många värme- och kylbehov som idag uppstår inom ett brett temperaturintervall, är det viktigt med innovativ design av PCM. Förutom lämplig fasförändringstemperaturer, entalpi och andra termofysikaliska egenskaper, bör PCM också ha robust fasändring, vara miljövänlig och kostnadseffektiv. För att förverkliga storskaliga TES system med PCM, är måste kostnadseffektivitet och robust funktion under många cykler bland de viktigaste utmaningarna. Kostnadseffektiva PCM kan bäst erhållas från naturliga eller industriella material i bulkskala, vilket i huvudsak leder till materialblandningar, snarare än rena ämnen. Blandningar uppvisar dock komplexa fasförändringsförlopp, underkylning och/eller inkongruent smältprocess som leder till fasseparation. Denna doktorsavhandling ger ny kunskap som möjliggör att bulkblandningar kan bli kostnadseffektiva och robusta PCM-material, med hjälp av den systematiskutvärdering av fasjämvikt och fasdiagram. Arbetet visar att detta kräver förståelse av relevanta grundläggande fasjämviktsteorier, omfattande termiska och fysikalisk-kemiska karakteriseringar, och allmänt tillämpliga teoretiska utvärderingar. Denna avhandling specificerar befintlig fasjämviktsteori för PCM-sammanhang, men sikte på att kunna välja robusta PCM blandningar med specifika egenskaper, beroende på tillämpning. Analysen visar att blandningar med en sammansättning som leder till kongruent smältande, där faser i jämvikt har samma sammansättning, är ideala bland PCM-blandningar. Kongruent smältande fasta faser som utgör föreningar eller fasta lösningar av ingående komponenter är därför ideala. Eutektiska blandningar är nästan lika bra som PCM, så länge underkylning inte förekommer. Därmed finns en stor potential för att finna och karakterisera PCM-ideala blandningar som bildar kongruent smältande föreningar eller fasta lösningar. Därigenom kan blandningar med en skarp, reversibel fasändring och utan fasseparation erhållas – egenskaper som liknar rena materialens fasändringsprocess. Vidare kan man, via fasdiagram, påvisa de blandningar som är inkongruent smältande, inklusive peritektiska blandningar, som är direkt olämpliga som PCM. Denna avhandling ger grundläggande kunskap som är en förutsättning för att designa PCM i blandningar. Genom en omfattande state-of-the-art utvärdering av fas-jämviktsbaserad PCM-design lyfter arbetet de PCM-idealiska blandningarna som hittills inte fått någon uppmärksamhet, såsom kongruenta smältande blandningar, och materialkategorierna metallegeringar, polyoler och fetter. Resultatet av arbetet visar dessutom att vissa PCM-material som ibland föreslås är direkt olämpliga då fasdiagram undersöks, bl a pga underkylning och även peritektiska system med fasseparation och degradering av kapaciteten (t ex Glauber-salt och natriumacetat-trihydrat). Denna avhandling specificerar och upprättar grundläggande teori samt tekniker, tillvägagångssätt och förhållanden som är nödvändiga för en omfattande och genomsynlig fasjämviktsbedömning, för utformning av PCM från blandningar för energilagering. Med detta som bas har följande fasdiagramtagits fram fullständigt: för erytritol-xylitol och för dodekan-tridekan, med PCM-potential för låg temperaturuppvärmning (60-120 °C) respektive frysning (-10 °C till -20 °C) utvärderas fullständigt. Erytritol-xylitol systemet har funnits vara eutektiskt i ett delvis isomorft system, snarare än ett icke-isomorft system vilket har föreslagits tidigare litteratur. Dodekan-tridekan systemet bildar ett system med kongruent smältande fast lösning (idealisk som en PCM) vid en minimumtemperatur, till skillnad från tidigare litteratur som föreslagt en maximumtemperatur, eller ett eutektiskt system. Teoretisk modellering av fasjämvikt har också genomförts för att komplettera det experimentella fasdiagrammet för systemet erytritol-xylitol. Efter granskning av de metoder som använts tidigare i PCM-litteraturen har här valts ett generiskt tillvägagångssätt (CALPHAD-metoden). Denna generiska metod kan bedöma vilken typ av material och fasändring som helst, till skillnad från en tidigare använda metoder som är specifika för materialtyper eller kemiska egenskaper. Denna teoretiska studie bekräftar termodynamiskt solvus, solidus, eutektisk punkt och erytritol-xylitol fasdiagrammet i sin helhet. Vad gäller hållbarhetsaspekter med PCM-baserad TES, lyfter denna avhandling fokus på förnybara och kostnadseffektiva material (t.ex. polyoler och fetter) som PCM. Som exempel har här undersökts erytritol och olivolja, med förnybart ursprung. Erytritol skulle kunna bli ett kostnadseffektivt PCM (163 USD/kWh), om det produceras av glycerol vilket är en biprodukt från biodiesel/bioetanolframställning. Olivolja är ännu ett kostnadseffektivt material (144 USD/kWh), och som här har påvisats innehålla potentiella PCM sammansättningar med lämpliga fasändringsegenskaper för kylatillämpningar. En övergripande slutsats från denna avhandling är att det finns ett behov av att standardisera tekniker, metoder och transparent resultatrapportering när det gäller undersökningar av fasjämvikt och fasdiagram i PCM-sammanhang. Internationella samarbetsplattformar för TES är en väg att koordinera arbetet. / <p>QC 20170830</p>

<p>Applications of Aluminum (Al) alloys in harsh environments involving high stress and high temperatures are often hindered because of their inherently low strength and poor performance at high temperatures. The strongest commercial Al alloys reported up to date have a maximum strength less than 700 MPa. Although ultrafine grained Al alloys prepared by severe plastic deformation have higher strength, they encounter grain growth at moderate temperatures. </p> <p>This thesis focuses on adopting transition metal solutes and non-equilibrium approach to fabricate high-strength, thermally stable nanotwinned Al alloys. To understand the underlying deformation mechanisms of nanotwinned Al alloys, <i>in-situ</i> micromechanical tests, high resolution and analytical transmission microscopy and atomistic simulations were used. Our studies show that nanotwinned supersaturated Al-Fe alloys have a maximum hardness and flow stress of ~ 5.5 GPa and 1.6 GPa, respectively. The apparent directionality of the vertical incoherent twin boundaries renders plastic anisotropy and compression-tension asymmetry in the nanotwinned Al-Fe alloys, revealed by systematic <i>in-situ</i> tensile and compressive micromechanical experiments conducted from both in-plane and out-of-plane directions. Moreover, the nanotwinned Al-Fe alloys experience no apparent softening when tested at 200 °C. When selectively incorporating with one additional solute as stabilizer, the ternary nanotwinned Al alloys can preserve an exceptionally high flow stress, exceeding 2 GPa, prior to precipitous softening at an annealing temperature of > 400 °C. The thesis offers a new perspective to the design of future strong, deformable and thermally stable nanostructured Al alloys. </p>

The subject of this thesis is preparation of CoCrFeMnNiNx high entropy mixtures via the methods of mechanical alloying and spark plasma sintering (SPS). Three series of specimens were fabricated in this thesis: samples milled in argon (benchmark materials), samples milled in nitrogen atmosphere (to observe their ability of nitrogen absorption) and samples microalloyed with CrN, FeN nitrides (to observe their dissociation into the solid solution potential). The fabricated powders and SPS compacts were subsequently observed by electron microscopy and their phase content by X-Ray diffraction (XRD) and elemental composition by EDS analysis were carried out. A method of reduction melting in inert atmosphere was used to determine the exact oxygen and nitrogen content in powders, while the respective particle size distribution measured by laser diffraction method. The influence of nitrogen content on the hardness of the samples was studied via the microhardness measured. After completing the process of mechanical alloying under the Nitrogen atmosphere was the maximal concentration of nitrogen in the structure 0,208% after 24 hours of milling (dependency on time was linear), which means, the method of milling under the Nitrogen atmosphere was successful. XRD of milled samples showed the existence of the only FCC single solid solution phase, while samples milled under the Nitrogen atmosphere showed the trend of the growth of the lattice parameter with the increasing nitrogen content. There was observed the presence of the chromium nitrides precipitates on the grain boundaries of the FCC phase in microalloyed samples. All specimen were contaminated by a mixture of metallic oxides and manganeese sulphides, which were present in the default manganeese powder. The greatest value of microhardness showed the duplex sample. The increase in values of microhardness (344 HV 0,3) in comparison with the standard sample (262,9 HV 0,3) was recorded on the samples milled under the nitrogen atmosphere, which conforms the positive influence of the nitrogen content on strength characteristics of this alloy.

The subject of this doctoral thesis was to elucidate the mechanism of reaction leading to the formation of dicalcium silicate (C2S), its solid solutions and other phosphatic calcium silicate phases using the sol-gel method of synthesis. SiO2 (Tosil A), CaO (calcium nitrate tetra-hydrate) and H3PO4 (as a source of P2O5) were used as starting materials. Series of samples with different content of P2O5 were synthesized. The characterization of Tosil A and samples was based on the following methods: DTA/TGA and EGA, XRD and SEM and EDS analy-ses. It is known, that phosphorous oxide can enter the structure of C2S and possibly form solid solutions and different phosphatic calcium silicate phases in C2SâC3P system. Depending on the P2O5 concentration in mixtures, three distinct phases are formed: larnite (2CaOâSiO2), Ca14,92(PO4)2,35(SiO4)5,65 and 5CaOâSiO2âP2O5, as detected by XRD. Local microanalysis de-monstrated the presence of calcium phosphate epicenters (C3P) containing SiO2, calcium sili-cate (C2S) zones with minimum content of P2O5 and intermediary areas of various phosphatic calcium silicates. The formation of two distinct islets of C2S and C3P is due the affinity of acid oxides (SiO2, P2O5) towards the basic one (CaO) during the sol-gel process. Then, the formation of various phosphatic calcium silicates results from the diffusion of P2O5 and SiO2 towards calcium silicate and calcium phosphate, respectively.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24231号 / 工博第5059号 / 新制||工||1790(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 乾 晴行, 教授 田中 功, 教授 安田 秀幸 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The present work investigates the synthesis and nanocrystal deposition of some selected solid solutions of transition metal trihalides with 2-dimensional crystal structure - specifically, the solutions of CrCl3 – CrBr3, CrBr3 – CrI3, RhCl3 – RhBr3, RhBr3 – RhI3, CrCl3 – RuCl3, and CrCl3 – MoCl3. Theoretical simulations of phase equilibria and partial pressures were applied to estimate suitable synthesis conditions for phase-pure solid solutions, before the syntheses were subsequently performed practically. It was found that for most of the systems investigated, special conditions, such as an appropriate excess of halogen or a specific temperature range, are crucial for successful synthesis. The purity of the corresponding products was confirmed by X-ray powder diffraction. These measurements were further used to investigate the course of the lattice parameters within the series of mixtures in order to be able to observe potential deviations from ideal mixing behavior of the parent compounds. These investigations revealed only small or no deviation from Vegard’s law for all investigated systems except CrCl3 – MoCl3. For CrCl3 – CrBr3, CrBr3 – CrI3, RhCl3 – RhBr3, RhBr3 – RhI3 and CrCl3 – RuCl3, the prepared powder material with different compositions was further used for the deposition of high-quality nanocrystals on a substrate. For this purpose, chemical vapor transport was applied. Suitable deposition conditions were also previously estimated by simulations before finally performing an experimental optimization of the transport conditions. The 2D nanocrystals thus obtained generally exhibit heights in the low 2-digit nm range, while monolayers were also observed in the case of RhCl3 – RhBr3. The compositions of the deposited structures were analyzed by energy dispersive X-ray spectroscopy to detect possible enrichment effects of the solid solutions during vapor transport. With the knowledge of these relationships, nanocrystals with controllable composition can be deposited by the developed method. The high quality of the deposited nanocrystals was ensured by transmission electron microscopy, selected area electron diffraction, and X-ray photoemission spectroscopy. Depending on the system, selected material properties were determined using powder samples, bulk or nanocrystals, such as the photoluminescence behavior of the CrCl3 – CrBr3 and CrBr3 – CrI3 series or the optical band gap characteristics of the RhCl3 – RhBr3 and RhBr3 – RhI3 systems. Unlike for the previously mentioned systems, in the case of CrCl3 – MoCl3, strong deviations from an ideal linear course of the lattice parameters were observed, where several phase regions can be distinguished within the series. To explain these anomalies, structural models were developed that explain the anomalies with the formation of differently arranged Mo-Mo dimers within the crystal structure. These hypotheses were investigated by different characterization methods such as IR spectroscopy or SQUID measurements and confirmed the hypotheses within the limits of the validity of the applied methods. The simulative and experimental methods developed in this work can be applied to numerous similar systems of transition metal trihalides, but should also work for other classes of compounds. The nanocrystals thus made available are suitable for follow-up studies with respect to property changes upon downscaling.:1. Introduction 1 2. Theoretical Background 3 2.1. Properties of Selected Transition Metal Trihalides and Their Solid Solutions . . . 3 2.1.1. Crystal Structures of 2D Transition Metal Trihalides . . . . . . . . . . . . . 4 2.1.2. CrX3 (X = Cl, Br, I) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1.3. RhX3 (X = Cl, Br, I) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.4. RuCl3 and CrCl3-RuCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.5. MoCl3 and CrCl3-MoCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2. Solid Solution Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.1. Structural Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.2. Chemical Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2.3. Thermodynamic Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3. Chemical Vapor Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.3.1. Bulk and Nanocrystal Growth by CVT . . . . . . . . . . . . . . . . . . . . . . 11 2.3.2. CVT of Solid Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.3.3. Simulation of CVT Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.4. Vapor Phase Chemistry of Selected Transition Metal Trihalides . . . . . . . . . . . 15 2.4.1. CrCl3, CrBr3 and CrI3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.4.2. RhCl3, RhBr3 and RhI3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4.3. RuCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.4.4. MoCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3. Material and Methods 19 3.1. Chemicals and Substrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.2. Synthesis, Purification and CVT of Materials . . . . . . . . . . . . . . . . . . . . . . 20 3.2.1. General Aspects of Preparation . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.2.2. CrX3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.2.3. CrCl3-CrBr3 and CrBr3-CrI3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.2.4. RhX3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 X Table of Contents 3.2.5. RhCl3-RhBr3 and RhBr3-RhI3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.2.6. Purification of commercial RuCl3 . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2.7. CrCl3-RuCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2.8. MoCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2.9. CrCl3-MoCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2.10. Delamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.3. Thermodynamic Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.3.1. Estimation of Unknown Thermodynamic Data . . . . . . . . . . . . . . . . 26 3.3.2. Simulations with Tragmin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.4. Instrumental Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.4.1. Optical Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.4.2. Powder X-ray Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.4.3. Single-Crystal X-ray Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.4.4. Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy 27 3.4.5. Transmission Electron Microscopy and Selected Area Electron Diffraction 28 3.4.6. Atomic Force Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.4.7. Raman Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.4.8. Infrared Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.4.9. Diffuse Reflection Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.4.10. Photoluminescence Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . 30 3.4.11. X-ray Photoelectron Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . 30 3.4.12. Inductively Coupled Plasma Optical Emission Spectroscopy . . . . . . . . 30 3.4.13. Simultaneous Thermal Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.4.14. Electron Energy-Loss Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . 31 3.4.15. Superconducting Quantum Interference Device Measurements . . . . . . 31 4. Results and Discussion 32 4.1. CrCl3 – CrBr3 and CrBr3 – CrI3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 4.1.1. Thermodynamic and CVT Simulations . . . . . . . . . . . . . . . . . . . . . 32 4.1.2. Solid Solution Synthesis and Basic Properties . . . . . . . . . . . . . . . . . 37 4.1.3. Structural Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.1.4. Nanocrystal Growth, Enrichment Effects and Delamination . . . . . . . . . 45 4.1.5. Further Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 4.2. RhCl3-RhBr3 and RhBr3-RhI3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4.2.1. Thermodynamic and CVT Simulations . . . . . . . . . . . . . . . . . . . . . 55 4.2.2. Solid Solution Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 4.2.3. Thermochemical Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.2.4. Structural Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.2.5. Crystal Growth and Delamination . . . . . . . . . . . . . . . . . . . . . . . . 65 4.2.6. Further Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 4.3. CrCl3-RuCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 4.3.1. Thermodynamic and CVT Simulations . . . . . . . . . . . . . . . . . . . . . 73 4.3.2. Solid Solution Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 XI Table of Contents 4.3.3. Structural Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.3.4. Nanocrystal Growth, Enrichment Effects and Delamination . . . . . . . . . 78 4.3.5. Further Characterization of As-Grown Nanocrystals . . . . . . . . . . . . . 81 4.4. CrCl3-MoCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4.4.1. Thermodynamic and CVT Simulations . . . . . . . . . . . . . . . . . . . . . 84 4.4.2. Solid Solution Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 4.4.3. Structural Investigation by pXRD . . . . . . . . . . . . . . . . . . . . . . . . . 88 4.4.4. Further Structural Characterization . . . . . . . . . . . . . . . . . . . . . . . 93 4.4.5. Magnetic Investigations of Powder Samples by SQUID . . . . . . . . . . . . 98 4.4.6. Summary of Characterization Results . . . . . . . . . . . . . . . . . . . . . . 101 4.4.7. CVT Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 5. Summary and Outlook 104 References 107 List of Figures 120 List of Tables 121 Abbreviations 122 Used Symbols 124 A. Appendix 126 A.1. Atom Positions and Space Group Transformations of 2D TMTH . . . . . . . . . . 126 A.2. Raw pXRD Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 A.3. Refined Lattice Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 A.4. Additional Data of Characterizations . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 A.5. EDX-Mappings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 A.6. Thermodynamic Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 / Die vorliegende Arbeit beschäftigt sich mit der Synthese und Nanokristallabscheidung von einigen ausgewählten Festkörperlösungen von Übergangsmetalltriahlogeniden mit 2-dimensionaler Kristallstruktur - konkret die Lösungen von CrCl3 – CrBr3, CrBr3 – CrI3, RhCl3 – RhBr3, RhBr3 – RhI3, CrCl3 – RuCl3 und CrCl3 – MoCl3. Dabei wurden theoretische Simulationen der Phasengleichgewichte und Partialdrücke angewandt um geeignete Synthesebedingungen für phasenreine Festkörperlösungen abzuschätzen und diese Synthesen im Anschluss entsprechend zu realisieren. Dabei zeigte sich, dass für die meisten der untersuchten Mischphasen spezielle Bedingungen, wie z.B. ein entsprechender Halogenüberschuss oder ein enges Temperaturfenster entscheidend für die erfolgreiche Synthese sind. Die Phasenreinheit der entsprechenden Produkte wurde mittels Röntgenpulverdiffraktometrie bestätigt. Diese Messungen wurden weiterhin zur Untersuchung des Verlaufs der Gitterparameter innerhalb der Mischungsreihen verwendet um potenzielle Abweichungen von idealem Mischungsverhalten der Randverbindungen beobachten zu können. Dabei zeigte sich für alle Mischungen außer CrCl3 – MoCl3 nur geringe oder keine Abweichungen von der Vegard’schen Regel. Für CrCl3 – CrBr3, CrBr3 – CrI3, RhCl3 – RhBr3, RhBr3 – RhI3 und CrCl3 – RuCl3 wurde das hergestellte Pulvermaterial mit verschiedenen Zusammensetzungen für die Abscheidung von hochqualitativen Nanokristallen auf einem Substrat verwendet. Dafür wurde die Methode des chemischen Gasphasentransports angewandt, wobei ebenfalls geeignete Abscheidungsbedingungen zuvor mittels Simulationen ermittelt wurden, bevor schlussendlich eine experimentelle Optimierung der Transportbedingungen durchgeführt wurde. Die damit erhaltenen 2D Nanokristalle weisen in der Regel Höhen im niedrigen 2-stelligen nm-Bereich auf, wobei im Fall von RhCl3 – RhBr3 auch direkt abgeschiedene Monolagen beobachtet wurden. Die Zusammensetzungen der abgeschiedenen Strukturen wurden intensiv mittels energiedispersiver Röntgenspektroskopie analysiert um mögliche Anreicherungseffekte der Festkörperlösungen während des Gasphasentransports zu detektieren. Dabei zeigte sich, dass eine Anreicherung insbesondere im Fall der kationischen Festkörperlösungen auftritt, während bei anionischen Lösungen ein kongruenter Transport vorherrscht. Mithilfe der Kenntnisse dieses Zusammenhangs lassen sich Nanokristalle mit kontrollierbarer Zusammensetzung über die entwickelte Methode abscheiden. Die hohe Qualität der abgeschiedenen Nanostrukturen wurde mittels Transmissionselektronmikroskopie, Feinbereichselektronenbeugung und Röntgenphotoelektronenspektroskopie sichergestellt. Je nach System wurden weitere ausgewählte Materialeigenschaften anhand von Pulver-Proben, bulk- oder Nanokristallen ermittelt, wie beispielsweise das Photolumineszenzverhalten der CrCl3 – CrBr3 und CrBr3 – CrI3 Reihen oder den Verlauf der optischen Bandlücke der RhCl3 – RhBr3 und RhBr3 – RhI3 Systeme. Anders als für die zuvor beschriebenen Systeme wurden im Fall von CrCl3 – MoCl3 starke Abweichungen von idealem Verlauf der Gitterparameter beobachtet, wobei innerhalb der Mischungsreihe mehrere Phasengebiete unterschieden werden können. Zur Erklärung dieser Anomalien wurden verschiedene Strukturmodelle erdacht, welche die Bildung von unterschiedlich angeordneten Mo-Mo-Dimeren innerhalb der Kristallstruktur beschreiben. Diese Hypothesen wurden mittels verschiedener Charakterisierungsmethoden wie z.B. IR-Spektroskopie oder SQUID-Messungen untersucht und im Rahmen der Aussagekraft der Messmethoden bestätigt. Die in dieser Arbeit entwickelten simulativen und experimentellen Methoden lassen sich auf zahlreiche ähnliche Systeme von Übergangsmetalltrihalogeniden übertragen, sind aber auch auf andere Verbindungsklassen anwendbar. Die damit verfügbar gemachten Nanokristalle sind für Folgeuntersuchungen im Hinblick auf die Eigenschaftsveränderungen bei der Nanoskalierung geeignet.:1. Introduction 1 2. Theoretical Background 3 2.1. Properties of Selected Transition Metal Trihalides and Their Solid Solutions . . . 3 2.1.1. Crystal Structures of 2D Transition Metal Trihalides . . . . . . . . . . . . . 4 2.1.2. CrX3 (X = Cl, Br, I) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1.3. RhX3 (X = Cl, Br, I) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.4. RuCl3 and CrCl3-RuCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.5. MoCl3 and CrCl3-MoCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2. Solid Solution Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.1. Structural Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.2. Chemical Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2.3. Thermodynamic Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3. Chemical Vapor Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.3.1. Bulk and Nanocrystal Growth by CVT . . . . . . . . . . . . . . . . . . . . . . 11 2.3.2. CVT of Solid Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.3.3. Simulation of CVT Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.4. Vapor Phase Chemistry of Selected Transition Metal Trihalides . . . . . . . . . . . 15 2.4.1. CrCl3, CrBr3 and CrI3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.4.2. RhCl3, RhBr3 and RhI3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4.3. RuCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.4.4. MoCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3. Material and Methods 19 3.1. Chemicals and Substrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.2. Synthesis, Purification and CVT of Materials . . . . . . . . . . . . . . . . . . . . . . 20 3.2.1. General Aspects of Preparation . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.2.2. CrX3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.2.3. CrCl3-CrBr3 and CrBr3-CrI3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.2.4. RhX3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 X Table of Contents 3.2.5. RhCl3-RhBr3 and RhBr3-RhI3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.2.6. Purification of commercial RuCl3 . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2.7. CrCl3-RuCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2.8. MoCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2.9. CrCl3-MoCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2.10. Delamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.3. Thermodynamic Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.3.1. Estimation of Unknown Thermodynamic Data . . . . . . . . . . . . . . . . 26 3.3.2. Simulations with Tragmin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.4. Instrumental Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.4.1. Optical Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.4.2. Powder X-ray Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.4.3. Single-Crystal X-ray Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.4.4. Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy 27 3.4.5. Transmission Electron Microscopy and Selected Area Electron Diffraction 28 3.4.6. Atomic Force Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.4.7. Raman Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.4.8. Infrared Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.4.9. Diffuse Reflection Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.4.10. Photoluminescence Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . 30 3.4.11. X-ray Photoelectron Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . 30 3.4.12. Inductively Coupled Plasma Optical Emission Spectroscopy . . . . . . . . 30 3.4.13. Simultaneous Thermal Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.4.14. Electron Energy-Loss Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . 31 3.4.15. Superconducting Quantum Interference Device Measurements . . . . . . 31 4. Results and Discussion 32 4.1. CrCl3 – CrBr3 and CrBr3 – CrI3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 4.1.1. Thermodynamic and CVT Simulations . . . . . . . . . . . . . . . . . . . . . 32 4.1.2. Solid Solution Synthesis and Basic Properties . . . . . . . . . . . . . . . . . 37 4.1.3. Structural Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.1.4. Nanocrystal Growth, Enrichment Effects and Delamination . . . . . . . . . 45 4.1.5. Further Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 4.2. RhCl3-RhBr3 and RhBr3-RhI3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4.2.1. Thermodynamic and CVT Simulations . . . . . . . . . . . . . . . . . . . . . 55 4.2.2. Solid Solution Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 4.2.3. Thermochemical Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.2.4. Structural Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.2.5. Crystal Growth and Delamination . . . . . . . . . . . . . . . . . . . . . . . . 65 4.2.6. Further Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 4.3. CrCl3-RuCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 4.3.1. Thermodynamic and CVT Simulations . . . . . . . . . . . . . . . . . . . . . 73 4.3.2. Solid Solution Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 XI Table of Contents 4.3.3. Structural Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.3.4. Nanocrystal Growth, Enrichment Effects and Delamination . . . . . . . . . 78 4.3.5. Further Characterization of As-Grown Nanocrystals . . . . . . . . . . . . . 81 4.4. CrCl3-MoCl3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4.4.1. Thermodynamic and CVT Simulations . . . . . . . . . . . . . . . . . . . . . 84 4.4.2. Solid Solution Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 4.4.3. Structural Investigation by pXRD . . . . . . . . . . . . . . . . . . . . . . . . . 88 4.4.4. Further Structural Characterization . . . . . . . . . . . . . . . . . . . . . . . 93 4.4.5. Magnetic Investigations of Powder Samples by SQUID . . . . . . . . . . . . 98 4.4.6. Summary of Characterization Results . . . . . . . . . . . . . . . . . . . . . . 101 4.4.7. CVT Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 5. Summary and Outlook 104 References 107 List of Figures 120 List of Tables 121 Abbreviations 122 Used Symbols 124 A. Appendix 126 A.1. Atom Positions and Space Group Transformations of 2D TMTH . . . . . . . . . . 126 A.2. Raw pXRD Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 A.3. Refined Lattice Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 A.4. Additional Data of Characterizations . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 A.5. EDX-Mappings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 A.6. Thermodynamic Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144