Since the last five decades, polymer-derived ceramics (PDCs) are in use and envisaged for a variety of applications. The transition of a precursor to an inorganic ceramic by pyrolysis and heat-treatment results in either amorphous or nanocrystalline composites with the evolution of phases strongly controlled by the processing conditions. Understanding the deformation behaviour under ambient conditions and at elevated temperatures is key to designing these materials for long-term use. However, quantitative reliable estimation of mechanical properties is quite challenging due to its unique structure which in turn is strongly governed by the precursor chemistry. The mechanical behaviour of PDCs in the form of fibres, bulk and foams are different and they are discussed separately. Both experimental and simulation-based studies are considered in this review. Recently, additive manufacturing processes have been used for the fabrication of PDCs, the mechanical properties of which are also included in this review.

Core−rim structures are found as a general microstructural feature in SiC ceramics gas–pressure sintered with AlN−Y2O3 additives in different ratio, combined with a range of α/β‐SiC seeding to control the phase transformation. Using analytical electron microscopy, the authors investigate the re‐distribution of additives to detect uniform level of AlN solution into SiC rims, independent to the seeding ratio, and also not proportional to additives. The behavior of AlN solution reveals the presence of sintering melt based on nitro‐carbide to start the reprecipitation of SiC rims, while the cores are remnants from starting powders to control the phase transformation as well as the grain growth behavior. Among various intergranular phases, Y10Al2‐zSi3+zO18+zN4‐z is observed as common hence the secondary phase, while its Al level changes in an opposite trend to AlN solution in SiC rims. This oxynitride phase precipitates from the Y‐rich oxynitride melt, which extends and regulates the solution−reprecipitation process and develops into the Y−Si−O−(C) melt to create a series of residual intergranular oxides. Post‐annealing can fully devitrify the viscous intergranular glass to reach complete crystallization of ceramic body, which leads to improved creep resistance at high temperature for this SiC ceramic system.

The article contains sections titled: 1. Introduction 2. Physical Properties 3. Mechanical Properties 4. Chemical Properties 5. Resources, Raw Material 6. Production 6.1. Beryl Processing 6.1.1. Beryl Processing: Sulfate Process 6.1.2. Beryl Processing: Fluoride Process 6.1.3. Beryl Processing: Chloride Process 6.2. Processing of Bertrandite: SX-Carbonate Process 6.3. Beryllium Hydroxide Separation Processes 6.4. Beryllium Metal Production from Beryllium Hydroxide 6.5. Beryllium Metal Production from Reduction of Metals and Fusion Electrolysis 6.5.1. Reduction with Metals 6.5.2. Fusion Electrolysis 6.6. Beryllium Refining and Further Processing 6.6.1. Vacuum Refining 6.6.2. Melting and Casting 6.6.3. Powder Manufacture 6.6.4. Powder Consolidation 6.6.5. Production of Single Crystals 7. Beryllium Specifications 8. Commercial Uses of Beryllium 8.1. Alloys Containing Less than 2% Beryllium 8.2. Pure Beryllium Metal and Alloys Containing Over 60% Beryllium 8.3. Beryllia (BeO) Ceramics 9. Beryllium Compounds 10. Chemical Analysis 11. Storage, Transportation, and Regulatory Aspects 12. Beryllium in the Environment 12.1. Major Sources of Beryllium in Water 12.2. Air 12.3. Estimated Total Exposure of the General Population to Beryllium 12.4. Beryllium Release by Plant Degradation 13. Economic Aspects 14. Occupational Health and Toxicology 14.1. Occupational Exposure 14.2. Toxicokinetics and Metabolism 14.3. Mechanism of Action 14.4. Effects in Humans 14.5. Occupational Health Regulations 15. Acknowledgement

The condensation of organometallic compounds into merely inorganic materials by a proper thermal treatment (referred to as thermolysis or pyrolysis) under controlled atmosphere is a unique and fairly simple process of producing new types of ceramics, which are—due to their origin—referred to as precursor- or polymer-derived ceramics (PDCs).

In this paper a short review of our results on the synthesis of nanosized CeO2, CaMnO3 and BaCeO3 solid solutions are presented. The nanopowders were prepared by two innovative methods: self propagating room temperature synthesis (SPRT) and modified glycine/nitrate procedure (MGNP). Different types of solid solutions with rare earth dopants in concentrations ranging from 0-0.25 mol% were synthesized. The reactions forming solid solutions were studied. In addition, the characteristics of prepared nanopowders, phenomena during sintering and the properties of sintered samples are discussed.

In order to clarify inconsistencies in the literature and to verify assumed ternary solubilities, the phase equilibria in the Y 2 O 3 –Al 2 O 3 –SiO 2 system at 1600, 1400, and 1300 °C were experimentally determined using x-ray diffraction (XRD), scanning electron microscope with attached energy-dispersive detector system (SEM-EDX), and electron probe microanalyzer (EPMA). Six quasibinary phases were observed: Y 4 Al 2 O 9 (YAM), YAlO 3 (YAP), Y 3 Al 5 O 12 (YAG), Y 2 SiO 5 , Y 2 Si 2 O 7 (C and D modifications), and ˜ 3 Al 2 O 3 · 2SiO 2 (mullite). Y 4 Al 2 O 9 forms an extended ternary solid solution with the formula Y 4 Al 2(1- x ) Si 2 x O 9+ x ( x = 0 2 ˜0.31). The lowest ternary eutectic temperature was determined at 1371 ± 5 °C by high-temperature differential scanning calorimetry (DSC). The results were compared with previous data available for the Y 2 O 3 –Al 2 O 3 –SiO 2 system and with data for other RE 2 O 3 –Al 2 O 3 –SiO 2 (RE = rare earth element) systems.

It is shown that, on employing a practically relevant type of a potentiometric solid state CO2 sensor comprising Na-beta-alumina as solid electrolyte and Na2CO3 as gas sensitive electrode, the voltage response may be remarkably affected by electronic transference. This is in contradiction to what is commonly stated in the literature about the measuring properties of such a type of a sensor. On the other hand, the observation of a non-negligible amount of electronic conduction confirms previous findings on the behaviour of Na-beta-alumina under the conditions of a CO2sensor.

Enthalpies of formation were determined for β-sialon phases (Si 6– z Al z O z N 8– z , z = 0.46 to 3.6) by high-temperature oxidative drop solution calorimetry using an alkali-metal borate (52 wt% LiBo 2 ; 48 wt% NaBO 2 ) solvent. Oxygen gas was bubbled through the melt to accelerate oxidation of the oxynitride samples during dissolution. Sialons near z = 2 appear less stable energetically than ones with higher or lower nitrogen content. A large configurational entropy contribution for sialons with z > 2 may further stabilize these materials. This larger free energy driving form may be the reason for success in pulse-activated processing of these materials. The enthalpies of formation further suggest that a greater driving form for oxynitride formation exists in batch synthesis using SiO 2 rather than Al 2 O 3 .

Thin films of ZrO2 were deposited from aqueous solution on Si(100) substrates precovered by functionalized alkyltrichlorosilane self-assembled monolayers (SAMs). The interface structure, thermal stability, and densification of these films in the temperature range from room temperature to 750 °C in vacuum were measured using in situ x-ray reflectivity. The growth rate is a nonlinear function of time in solution, with a pronounced nonuniformity during the first 30 min. The as-deposited films exhibit about 3-nm roughness and a density below that of bulk ZrO2. Measurements in vacuum reveal decreasing film thickness, increasing film density, and decreasing roughness upon annealing up to 750 °C. The densification saturates at the highest measured temperatures, presumably following evaporation of residual contaminants from the aqueous synthesis procedure. Above 200 °C the SAM/ZrO2 interface began to deteriorate, possibly due to interdiffusion. The ZrO2 film structure obtained at the highest annealing temperatures persisted upon cooling to room temperature, and there was no visible evidence of stress-induced microstructural changes, such as peeling or cracking.

The surface morphology of TiO 2 - and ZrO 2 -based thin films, deposited from aqueous solution at 70–80 °C onto functionalized organic self-assembled monolayers (SAMs) on silicon has been examined using atomic force microscopy (AFM). The films have been previously shown to consist, respectively, of nanocrystalline TiO 2 (anatase) and of nanocrystalline tetragonal ZrO 2 with amorphous basic zirconium sulfate. The films exhibit characteristic surface roughnesses on two length scales. Roughness on the nanometer scale appears to be dictated by the size of the crystallites in the film. Roughness on the micron scale is postulated to be related to several factors, including the topography of the SAM and the effects of larger, physisorbed particles or agglomerates. The topographies of the oxide thin films, on both the nanometer and micron scales, are consistent with a particle-attachment mechanism of film growth.

The densification of Si3N4 with nano-sized sintering aids that were in situ incorporated by a combustion process was studied in comparison with that of sintering aids mixed by ball milling. The combustion process directly produces amorphous and nano-sized Y–Al oxides within the Si3N4 powder. X-ray diffraction results indicate that amorphous Y–Al oxides begin to crystallize into Y3Al5O12 at about 600 °C. Additionally the nano-sized sintering aids are more homogeneously distributed and thereby promote the formation of eutectic melts at lower temperatures during liquid-phase sintering. Therefore, the densification process of Si3N4 during liquid-phase sintering is strongly accelerated. The microstructure of as-sintered parts from combusted powder seems more dense and homogeneous.

We report on an alternative route to quaternary ceramics which can be prepared by polycocondensation of commercially available polysilazanes with the appropriate alkyl amides (M(NRR’)X with M = B or P and subsequent pyrolysis in argon atmosphere at 1000°C. Ceramic monoliths are obtained if the modified polysilazane is crosslinked at 400°C for 3 h. After ball-milling, sieving and cold isostatic pressing the green body is directly pyrolysed to the appropriate monolith. The obtained material is amorphous to X-ray-diffraction. Investigations by electron spectroscopie imaging (ESI) in TEM indicate a homogeneous distribution of the elements M, Si, C and N (M = B, P) within a resolution of 2 nm. Upon annealing at elevated tempertures in a nitrogen atmosphere crystallization of the appropriate thermodynamically stable phases occurs around 1400°C yielding a micro/nano-, nano/nano- or micro/microcrystalline microstructure with design-tailored properties depending on the element M.

A polyvinylmethylsilane precursor has been used for the epitaxial growth of SiC thin films on 6H–SiC single crystal substrates. The films were prepared by dipping the single crystal 6H–SiC substrates into the precursor polymer solution with subsequent thermal treatments at different temperatures. Transmission electron microscopy (TEM) was used to characterize the microstructure and chemistry of the different SiC films. At 1100 °C, the film was amorphous and contained substantial oxygen. At 1600 °C, an epitaxial, single crystalline β–SiC film was observed.

The quasi binary systems LaMnO 3 –SrMnO 3 and LaMnO 3 –CaMnO 3 were studied. Both systems show a miscibility gap at intermediate La:Sr and La:Ca ratios below about 1400 °C in air. This phenomenon causes the decomposition of single-phase (La,Sr)MnO 3− x and (La,Ca)MnO 3− x solid solution into La-rich SrMnO 3− x + Sr-rich LaMnO 3− x and La-rich CaMnO 3− x + Ca-rich LaMnO 3− x at lower temperatures, respectively. At 1400 °C in the system LaMnO 3 –SrMnO 3 , a structure transformation of (La,Sr)MnO 3 from orthorhombic to rhombohedral with increasing Sr content was not observed, and the structure of La 0.7 Sr 0.3 MnO 3 was determined to be orthorhombic with a = 0.54927 ± 0.0009 nm, b = 0.54582 ± 0.0009 nm, and c 4 0.76772 ± 0.0034 nm.

Three different dispersants, a low molecular weight compound (aminoalkanol), a polymer (polyelectrolyte) and a block-co-polymer (block polyethylenoxide-polyacrylic acid) were investigated with AFM and rheology in an aqueous system in order to elucidate the influence of the size and structure of the molecule on the dispersion stabilization. The AFM studies indicate that the aminoalkanol gives repulsive forces due to electrostatic repulsion only. The polyelectrolyte seems to stabilize the dispersion with both steric and electrostatic repulsive forces. A new compound that was designed for pure steric stabilization in aqueous media a block-co-polymer consisting of a polar anchor block and a stabilizing neutral chain was investigated for its behavior. The AFM measurements show that it is likely that this compound causes repulsion of silicon nitride surfaces due to steric repulsion only. Rheological measurements of aqueous powder slurries show that the adsorption of the organic additives is of great importance. Due to a more silicon dioxide like acidic surface of the investigated Si3N4-powder the carboxylate anions of the block-co-polymer adsorb badly. Therefore, no sterically repulsive forces can be built up. This then causes an increase in the slurry's viscosity.

Fully amorphous ceramics in the system silicon-carbon-nitrogen were produced with the polymer precursor route using the commercially available polysilazane CerasetTM. Besides their high temperature thermal stability, these ceramics show excellent high temperature creep resistance. Not many investigations have been dedicated to the fracture mechanics of these materials. This paper provides data on toughness measurements utilizing bulk and indentation techniques. The double cantilever beam method (DCB) was used to study crack propagation. To determine the intrinsic toughness, the crack opening displacements (COD) of indentation cracks were determined.

I. THE PRODUCTION OF CERAMICS Traditional Ceramics Powder-based Methods Powder-free Methods II. THE CONSTITUTION OF CERAMICS Chemical Bonds Crystallography Lattice Defects Microstructures III. CHEMISTRY Thermochemistry Colloid Chemistry Surface Chemistry IV. PHYSICS Mathematical Models V. RHEOLOGY Engineering Ceramics Design - Ideas for Visionaries VI. SUPERPLASTICITY Future Ideas for Visionaries VII. FIELD-STRUCTURED CERAMICS Structuring by Sonic Fields Structuring by Electromagnetic Fields VIII. GRAVITOLASER-ACTIVE CERAMICS How Can We Generate Artificial Gravitational Fields? How Can We Produce Gravitolaser-active Ceramics?

In order to investigate the role played by the solid electrolyte in the H2 oxidation reaction, patterned Ni electrodes on YSZ (yttria stabilized zirconia) single crystals with different crystallographic orientations, on polycrystalline YSZ and on polycrystalline LSGM ((La,Sr)(Ga,Mg)O3−x) were studied in H2+H2O gas as a function of partial pressure of H2O in the temperature range of 673–823K. Symmetrical cells using YSZ single crystals exhibit a single almost perfect electrode semicircle in the Nyquist plot. The corresponding polarisation resistance (Rp) depends on the surface orientation of the YSZ single crystals with a maximum of Rp for <110> and a minimum for <100>. The capacitance obtained from the impedance arc is almost temperature independent but different for the three surfaces. In the case of polycrystalline YSZ a depressed impedance arc results with the capacitance being between the extreme values measured for single crystals of different orientation. A modified situation is found for patterned Ni electrode on LSGM: the capacitance of the single arc depends on temperature and is much larger than in the case of YSZ cells. The polarisation resistance on polycrystalline LSGM is much smaller than on polycrystalline YSZ while activation energies of the polarization resistance are still similar. Capacitances and resistances are discussed in terms of possible mechanisms.