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Raw materials, such as metals and minerals, that are not only part of our daily lives butalso of decisive economic importance, while having a high supply risk, are called criticalraw materials. The criticality of the raw materials implies that they are vital to thefunctioning and integrity of a wide range of industrial ecosystems. For example, galliumand indium are part of light-emitting diode (LED) technology in lamps1. Vanadium is notonly a vital part of performance enhancement of certain ferrous alloys but also ofemerging scientific interest as V-redox batteries can be an alternative for lithium-ionbatteries for storage of renewable energy2,3. Vanadium, like other critical raw materialshas an immense economic value to the EU, combined with a high risk associated with itssupply4. During the reduction of V2O5 with aluminum, fluxed with lime5, a residue of theferrovanadium production process is generated containing large amount of calciumaluminates and magnesia alumina spinel (MgAl2O4) together with smaller amount ofmagnesia. Different paths of vanadium recovery from industrial residues have beenestablished6–8, with some of those9 leaving the matrix intact after extraction. However,in the current research a direct valorisation approach was adopted for the V-bearingresidues. Alumina-spinel castables are the state of the art for some parts of the steelladle lining10. The V-bearing residues that were studied contain significant amounts ofalumina (mainly bound to calcium aluminate phases) and spinel. Thus, they can be partof alumina-spinel self-flow castables’ matrix substituting totally or, in large proportionsthe traditionally used calcium aluminate cement (CAC). (PDF) Valorisation potential of V-bearing residues. Available from: https://www.researchgate.net/publication/351153984_Valorisation_potential_of_V-bearing_residues#fullTextFileContent [accessed Jun 30 2023].

The anticoagulation treatment of cardiovascular patients, which is mandatory after implantation of heart valves or stents, has significantly adverse effects on life quality. This treatment can be reduced or even circumvented by developing novel antithrombogenic surfaces of blood-contacting implants. Thus, we aim to discover materials exhibiting outstanding hemocompatibility compared to other available synthetic materials. We present promising surficial characteristics of single crystalline alumina in terms of platelet activation inhibition. In order to elucidate the relation between its crystallographic properties including the plane orientation and blood cell behavior, we examined endothelialization, cytocompatibility, and platelet activation at the blood-alumina interfaces in a controlled experimental setup. We observed that the cell response is highly sensitive to the plane orientation and differs significantly for (0001) and (11-20) planes of Al2O3. Our results reveal for the first time the dependence of platelet activation on crystallographic orientation, which is assumed to be a critical condition controlling the thrombogenicity. Additionally, we used an endothelial cell monolayer as an internal control since endothelial cells have an impact on vessel integrity and implant acceptance. We successfully demonstrate that Al2O3(11-20) exhibits enhanced hemocompatibility in contrast to Al2O3(0001) and is comparable to the physiological endothelial monolayer in vitro.

The quasi-ternary TiB2-CrB2-WB2 system has been studied up to 2300 °C by means of hot-pressing, SPS and pressureless dilatometry. Liquid phase is generated by two binary eutectics at the TiB2-WB2 edge at 2230 ± 30 °C (e1) and at the CrB2-WB2 edge at 1965 °C (e2). A large homogeneity range of a (Ti,W,Cr)B2 solid solution has been noticed. A new ternary γ-phase emerges from a critical tie line between (W,Cr,Ti)2B4 and α-(Ti,W,Cr)B2 solid solution at 1950 °C, spreads slightly into both the WB2 and CrB2 direction and decomposes by the peritectic reaction P: γ ⇆ α-(Ti,Cr,W)B2 + (W,Cr,Ti)2B4 + Liquid at 2170 ± 30 °C. γ reacts with the CrB2-WB2-rich liquid according to the transition equilibrium T: δ-(Ti,Cr,W)B2 + (W,Cr,Ti)2B4 ⇆ γ + Liquid at 2050 °C. The γ-phase is characterized by broad 00 l x-ray reflections which implies a layerwise accumulation and differentiation of Cr and W atoms in the basal plane of the AlB2-type structure.

International journal of ceramic engineering & science 4(1), 16-22 (2022). doi:10.1002/ces2.10111 special issue: "Refractories and UNITECR 2022", Published by Wiley, Hoboken, NJ

Journal of CO2 utilization 58, 101928 (2022). doi:10.1016/j.jcou.2022.101928, Published by Elsevier, Amsterdam [u.a.]

International journal of ceramic engineering & science 3(6), (2021). doi:10.1002/ces2.10110, Published by Wiley, Hoboken, NJ

International journal of ceramic engineering & science (2022). doi:10.1002/ces2.10129, Published by Wiley, Hoboken, NJ

The quasi-ternary TiB2-CrB2-WB2 and the related quasi-binary subsystems were investigated by means of hot pressing and pressureless dilatometry in the temperature range between 1650 and 1900 °C. Long-term annealing up to 14 h was necessary for equilibration. Thus, samples were obtained first by densification and then by subsequent cooling to the respective temperature with continuous annealing for up to 16 h in some cases. In all binary subsystems the low-temperature range of the solidus and the liquidus lines could be determined. The CrB2-WB2 and the TiB2-WB2 systems are of eutectic type while the CrB2-TiB2 shows a continuous solid solubility. Furthermore, the miscibility gap proposed earlier for the CrB2-TiB2 could not be proven. The borders of the large homogeneity range of the AlB2-type (Ti,W,Cr)B2 solid solution were described. The presence of less than 5 mol% of CrB2 aids accommodating W into the AlB2-structure which agrees with previous sintering studies very well. Within the ternary composition range no indication for a ternary eutectic was found up to 1900 °C. Implications of impurities to the obtained phase diagrams are discussed.

This study investigates thermal expansion and thermal vibration behavior of borides using HT-XRD. In the previous research, it has been known that the vibrational behavior directly expresses the behavior of materials at high temperatures. In this work, the high temperature X-ray diffraction (HT-XRD) measurements of TiB2, W2B4, and CrB2 were conducted at the high temperature ranges; up to 1500 K. From the generated results, the study calculates thermal expansion coefficients, which coincides the previous research. Rather, the study calculates the mean square displacements of borides for evaluating the thermal vibration behaviors at elevated temperatures, demonstrating that: (1) the application of a formula into HT-XRD data could determine Debye-Waller factors of these borides; (2) a term of “agglomeration” could contribute to defining the mean square displacement u2; (3) both the Debye-Waller factor and the thermal expansion may function to design new boride-based materials at the high temperature; and (4) CrB2 has a quick increase in mean square displacement and is remarkably large value at elevated temperatures.

Cytocompatibility and hemocompatibility are essential features for tissue- and blood-contacting implants such as artificial heart valves, vascular grafts and stents. Platelet activation as the main...

The mechanisms during pressureless sintering of TiB2 with 0–50 wt.% Ni were analysed by differential dilatometry after mechanical alloying with hard metal beads. Three main stages of sintering could be identified by means of the changing dilatation rate. The first interval (200–600 °C) comprises reactions with oxygen and moisture (H3BO3, B2O3 formation, melting, evaporation). The second stage (600–700 °C) is governed by solid state sintering and reactions of Ni and/or Co with TiB2 yielding Ni3B, Ni2B, the corresponding Co-compounds and the ternary ω-phase of W2NiB2-type. The third main shrinkage interval is due to liquid phase sintering (987–1640 °C) and is accompanied by a significant weight-loss. Both precipitation of ω-phase as well as a (Ti,W)B2 solid solution in form of a core-shell structure are responsible for a grain growth retardation and the homogeneous microstructure. The results explain well all features reported in the corresponding literature while encountering the role of WC, too.

This work continues on from previous studies showing that mineral sequestration by carbonation of magnesium or calcium silicates under high pressure and high temperature can be successfully carried out by processing in an autoclave. The paper is focused on the influence of experimental parameters on avoiding scale formation during pre-treatment in an autoclave and a subsequent leaching. Amorphous silica and magnesite, respectively, were the main reaction products in a carbonation of olivine under high pressure conditions in an autoclave. In addition, the examined peridotites may be accompanied by small to medium amounts of nickel or other metals, the recovery of which will be investigated in the present study: Extraction of metals such as nickel, iron, and magnesium from olivine bearing ore using hydrochloric acid under atmospheric pressure was studied between 50 and 90 &deg, C in 1 h. The obtained results have shown maximal leaching efficiency of about 35% for Ni, Fe, and Mg under atmospheric pressure, in comparison to more than 60% obtained under the same conditions after a carbonation pre-treatment in an autoclave. Silica gel was formed during leaching without a pre-treatment of peridotite blocking the leaching process, which is not the case for the pre-treated material. The influence of temperature, reaction time, particle size and pre-treatment of peridotite in an autoclave during carbonation at 175 &deg, C and 71.5 bar was studied. A new mechanism model for metal extraction from olivine-bearing ore by avoiding silica gel formation during leaching with hydrochloric acid including a carbonation pre-treatment is proposed. This study explains additionally a behavior of metals such as nickel, magnesium, and iron during a carbonation of olivine bearing ore and leaching of a carbonated solid product.

Ceramics : art and perception 3(1), 101-113 (2020). doi:10.3390/ceramics3010011 special issue: "Special Issue "Design, Properties, Damage and Lifetime of Refractory Ceramics" / Special Issue Editor: Prof. Jacques Poirier, Guest Editor", Published by Informit, Melbourne

Bioinert ceramic, such as zirconia, provides the mechanical strength required in implants, but its limited bioactivity renders it incapable of osseointegration. Thus, its biomedical application is limited. Graphene and its derivatives possess excellent bioactivity and can enhance osseointegration, hemocompatibility and antibacterial properties. Here, we introduce an innovative technique for functionalizing bioinert ceramic by immobilizing reduced graphene oxide (rGO) onto the surface by tailored self-assembled monolayer (SAM). Three routes have been applied for immobilization: i) spontaneous reaction between OH groups of zirconia and organic functional groups of rGO, ii) spontaneous reaction between NH2 functionalized ZrO2 attained by silanization and COOH groups of rGO and iii) reaction between NH2 functionalized zirconia and activated COOH groups of rGO attained by using the catalysts EDC and NHS. The most efficient immobilization was obtained between activated COOH groups of rGO and NH2 functionalized zirconia. Thereby, for the first time rGO was successfully coupled to ZrO2 using SAM technique. Through this technique, the properties of rGO and zirconia could be merged to create a versatile biomaterial.

Zirconia has been commonly used in the dental industry because of its excellent biological, mechanical and aesthetic properties. This material, however, is classified as nearly inert. To bioactivate the ceramic surface, biomimetic depositions of calcium phosphate coatings have been developed. We demonstrate an accelerated biomimetic coating method on zirconia using a specific pre-treatment with biological agents. We have chosen bovine serum albumin as a standard protein. Through the pre-treatment of the zirconia using a hydroxylation or additionally immobilizing the bovine serum albumin on the surface, we could influence the CaP deposition rate. Immunohistochemical analyses verified the presence of BSA on the zirconia surfaces. After immersion in simulated body fluid at 40 °C, the samples were analyzed by scanning electron microscopy and X-ray diffraction to visualize the CaP formation. Here we could show as proof-of-principle that it is possible to accelerate biomimetic coating processes on zirconia implants containing BSA on their surface.

This study aimed to join the proven osteogenic properties of graphene oxide (GO) with bioinert zirconia implants. The dip-coating technique allows achieving this goal by forming a thin, homogenous, hydrolytically, and mechanically stable GO film onto silanized ceramic-substrates. SEM, AFM, XPS, and contact angle measurements confirmed the presence, transparency, integrity, and homogenous covering character of the GO film. The GO film is hydrolytically stable since it remained intact after a soaking period of 24 days in double-distilled water (ddH2O) and phosphate buffered saline and resisted a ten-minute sonication treatment for in ddH2O. This strong hydrolytic stability is due to the silanization with 3-amino-propyl-diisopropylethoxy-silane (APDS) enhancing the anchoring of GO flakes onto zirconia surfaces. Besides, the GO film disinfectable in 70% ethanol. Subsequently, we assessed our immobilized GO film as cytocompatible for L929 mouse fibroblast and human mesenchymal stem cells and propitious for the osteogenic differentiation demonstrated by a two times upregulation of the osteogenic transcription factor RunX2. The active hydroxyl and carboxyl groups of the GO film open new perspectives for the functionalization of ceramic implants by immobilization of biological agents, such as growth factors or antibiotics, and thus enhance the osseointegration.

Ceramics 2(2), 260 - 270 (2019). doi:10.3390/ceramics2020021, Published by MDPI, Basel

Magnesium carbonate powders are essential in the manufacture of basic refractories capable of withstanding extremely high temperatures and for special types of cement and powders used in the paper, rubber, and pharmaceutical industries. A novel synthesis route is based on CO2 absorption/sequestration by minerals. This combines the global challenge of climate change with materials development. Carbon dioxide has the fourth highest composition in earth&rsquo, s atmosphere next to nitrogen, oxygen and argon and plays a big role in global warming due to the greenhouse effect. Because of the significant increase of CO2 emissions, mineral carbonation is a promising process in which carbon oxide reacts with materials with high metal oxide composition to form chemically stable and insoluble metal carbonate. The formed carbonate has long-term stability and does not influence the earth&rsquo, s atmosphere. Therefore, it is a feasible and safe method to bind carbon dioxide in carbonate compounds such as magnesite. The subject of this work is the carbonation of an olivine (Mg2SiO4) and synthetic magnesia sample (&gt, 97 wt% MgO) under high pressure and temperature in an autoclave. Early experiments have studied the influence of some additives such as sodium bicarbonate, oxalic acid and ascorbic acid, solid/liquid ratio, and particle size on the carbonation efficiency. The obtained results for carbonation of olivine have confirmed the formation of magnesium carbonate in the presence of additives and complete carbonation of the MgO sample in the absence of additives.

Open ceramics 4, 100037 (2020). doi:10.1016/j.oceram.2020.100037 special issue: "SI: Advances in Additive Manufacturing of Ceramics / Edited by Giorgia Franchin, Andrea Zocca, David Karl, Hui-suk Yun, Xiaoyong Tian", Published by Elsevier, Amsterdam

Bioinert high performance ceramics exhibit detrimental features for implant components with direct bone contact because of their low osseointegrating capability. We hypothesized that periodical microstructures made of inert alumina ceramics can influence the osteogenic differentiation of human mesenchymal stromal cells (hMSC). In this study, we manufactured pillared arrays made of alumina ceramics with periodicities as low as 100 μm and pillar heights of 40 μm employing direct inkjet printing (DIP) technique. The response of hMSC to the microstructured surfaces was monitored by measuring cell morphology, viability and formation of focal adhesion complexes. Osteogenic differentiation of hMSCs was investigated by alkaline phosphatase activity, mineralization assays and expression analysis of respective markers. We demonstrated that MSCs react to the pillars with contact guidance. Subsequently, cells grow onto and form connections between the microstructures, and at the same time are directly attached to the pillars as shown by focal adhesion stainings. Cells build up tissue-like constructs with heights up to the micropillars resulting in increased cell viability and osteogenic differentiating properties. We conclude that periodical micropatterns on the micrometer scale made of inert alumina ceramics can mediate focal adhesion dependent cell adhesion and stimulate osteogenic differentiation of hMSCs.

This work evaluates the impact of added zirconia on the thermomechanical and thermoelastic fatigue properties of high-alumina refractory castables. Three testing scenarios are presented in the study: 1) Resonant Frequency Damping Analysis (RFDA) after cyclic temperature changes with and without mechanical load, 2) Refractoriness under Load (RuL) tests, and 3) results of abrupt temperature shifts between two high temperatures in a special thermal shock furnace. The tested refractory formulations were a reference castable based on tabular alumina and two castables each containing 13.75 mass-% of zirconia. The formulations of the zirconia castables had an addition of either fully-stabilized zirconia doped with 8 mol-% yttria (Y-FSZ) or partially-stabilized zirconia doped with 3 mol-% calcia (Ca-PSZ). The Y-FSZ castable displayed elastic and mechanical behaviour by means of RFDA and RuL similar to the reference sample and had good recovery after thermal shock testing. The Ca-PSZ formulation showed some beneficial toughening through energy dissipation of progressing cracks, but after cooling exhibited the matrix fracturing influence of the martensitic zirconia phase transformation which would negatively impact service life of the refractory.

In the technically important ZrO 2 –SiO 2 phase system we studied liquid phase formation and solidification by means of the containerless aero acoustic levitation preventing contamination by contact to crucible material. The behaviour of the melt was recorded by a high-speed camera allowing for direct observation of convection, formation and solidification of emulsified reams. For the first time since 1956, we re-treated the liquidus miscibility gap between 59.5 mol-% and 78 mol-% SiO 2 at 2250 °C with the critical point at 2430 °C and 70 mol% SiO 2 . Quenching preserved primary microstructures of the monotectic equilibrium with ZrO 2 -dendrites in a matrix of silica glass and secondary ZrO 2 but also frozen-in Benard-Marangoni cell patterns of metastably undercooled of emulsified droplets. These microstructures remind to the partitioning and coagulation behaviour of alkali-borosilicate glasses.

Active fillers play a major role in the dry grinding of stainless steel. However, the mechanism altering the process is still unknown. In this work, the efficiency of cryolite as filler was studied with a pin-on-disk tribometer. Simplified coated abrasives with and without active filler were used to reduce possible non-cryolite related interactions to a minimum. Diffusion experiments with stainless steel pins and cryolite were performed and the change in efficiency during abrasion investigated. The analysis of the pins revealed a FexCr1-xF2 phase. Tensile tests were performed of heat-treated specimens to investigate changes in brittleness. Finally, dissolution experiments were conducted, which proved a decrease in built-up edge volume in presence of cryolite, leading to a higher cutting efficiency.

The quasi-ternary TiB2-CrB2-WB2 was studied by means of hot pressing and pressureless dilatometry in the temperature range between 1650 and 2300 °C. Long-term annealing up to 14 h was necessary for equilibration. Thus, samples were obtained first by densification and then by subsequent cooling to the respective temperature with continuous annealing for up to 16 h in some cases. A large homogeneity range of a (Ti,W,Cr)B2 solid solution has been noticed. A new ternary γ-phase emerges from a critical tie line between (W,Cr,Ti)2B4 and α-(Ti,W,Cr)B2 solid solution at 1950 °C, spreads slightly into both the WB2 and CrB2 direction and decomposes by the peritectic reaction P: γ ⇆ α-(Ti,Cr,W)B2 + (W,Cr,Ti)2B4 + Liquid at 2170 ± 30 °C. At 2050 °C γ reacts with the CrB2-WB2-rich liquid according to the transition equilibrium T: δ-(Ti,Cr,W)B2 + (W,Cr,Ti)2B4 ⇆ γ + Liquid. The γ-phase possesses the composition of (Ti0.31W0.63Cr0.06)B2 expanding slightly towards the TiB2 and WB2-corner depending on temperature. It is clearly characterized by broad 00l x-ray reflections and a small c/a-ratio of 1.005–1.010 which implies a layerwise accumulation and differentiation of Cr and W atoms in the basal plane of the AlB2-type structure. FESEM and TEM studies reveal spinodal decomposition products at nanometer scale as well as coherent platelet-shaped W2B4 and β-WB precipitates of nanometer thickness.

Das technisch wichtige pseudobinare System ZrO2-SiO2 wurde im Liquidus-Bereich mittels tiegelfreier aeroakustischer Levitation und Hochgeschwindigkeitskamera hinsichtlich der Mischungslucke untersucht. Das Monotektikum L1 = ZrO2 + L2 bei 2250 °C mit der Entmischung L1 + L2 zwischen 59,5 Mol-% und 78 Mol-% SiO2 konnte erstmals seit 1956 experimentell bestatigt werden. Schmelzezusammensetzungen innerhalb der Mischungslucke zeigen eine turbulente Marangoni-Konvektion, die beim Abschrecken zum Einfrieren von Benard-Marangoni-Zellen fuhrt. Der erste Teil der Veroffentlichung befasst sich mit der wechselreichen Geschichte des Phasendiagramms sowie mit der Primarkristallisation von ZrO2 im stabilen Liquidus-Solidus-Bereich. Der zweite Teil behandelt die weitere Reifung und Differentiation der entmischten Schmelzen wahrend der Unterkuhlung. Die metastabile Fortsetzung der Mischungslucke bis 1000 °C wird detailliert untersucht.

Die Optimierung der Zusammensetzung von Feuerbetonen ist seit Jahren der Schlussel zur Verbesserung der Standzeiten von ungeformten Feuerfestprodukten im Einsatz in der Eisen- und Stahlindustrie. In dieser Studie wird der Zusatz von funktionalen Aggregaten in zementarmen, hochtonerdehaltigen Feuerbetonen mit dem Ziel untersucht, die elastischen und mechanischen Eigenschaften des Feuerbetons zu modifizieren. Dies kann zu einer Verbesserung der Thermoschockbestandigkeit fuhren. Es wurden verschieden zusammengesetzte Feuerbetone auf Basis von Tonerde betrachtet. Als Referenzmaterial diente ein reiner Hochtonerde-Feuerbeton. Fur die anderen Zusammensetzungen wurde jeweils die groste Kornfraktion (2,24–3,0 mm) der Referenzmischung durch eines der drei zu untersuchenden Aggregate ersetzt. Andalusit wurde mit dem Ziel eingesetzt, die Bildung von Mikrorissen durch in-situ-Mullitbildung zu begunstigen. Zudem entstehen beim Sintern des Andalusits Glasphasen. Beide Mechanismen erklaren die verringerten elastischen und mechanischen Eigenschaften und daruber hinaus die Verringerung der eingespeicherten elastischen Energie im Werkstoff. Der Einsatz von Al2O3-ZrO2-Aggregaten kann ebenfalls zu Rissbildung fuhren, da das zikonoxidhaltige Aggregat und die Kalziumaluminat-Matrix unterschiedliche thermische Ausdehnungskoeffizienten aufweisen. Des Weiteren kommt es bei hohen Temperaturen zu einer martensitischen Umwandlung des Zirkonoxids, die mit einer erheblichen Volumenanderung einhergeht. Dies konnte die erhohte mechanische Belastung an den Korngrenzen zwischen Aggregaten und Matrix erklaren. Das dritte eutektische Aggregat besteht aus Al2O3-ZrO2-SiO2 und wird eingesetzt, um den Einfluss von Zirkonoxid im Beisein einer Glasphase zu untersuchen. Diese Arbeit beschaftigt sich hauptsachlich mit der Modifikation der elastischen und thermomechanischen Eigenschaften durch Einsatz von Andalusitaggregaten im Feuerbeton und dem Einfluss dieser auf die Thermoschockbestandigkeit.

A new method for the experimental estimation of radiant heat emittance at high temperatures has been developed which involves aero-acoustic levitation of samples, laser heating and contactless temperature measurement. Radiant heat emittance values are determined from the time dependent development of the sample temperature which requires analysis of both the radiant and convective heat transfer towards the surroundings by means of fluid dynamics calculations. First results for the emittance of a corundum sample obtained with this method are presented in this article and found in good agreement with literature values.

The topic of the present experiments are transition metal diboride coatings of composition (Ti0.49W0.51)B2 and (Ti0.44W0.30Cr0.26)B2. The coatings were deposited on steel substrates using dc magnetron sputtering. We investigated how annealing in argon at elevated temperatures modifies microstructure. The as-deposited films are amorphous. Annealing between 700 and 1100 °C results in the formation of nano-crystalline precipitates with average grain diameters of about 10–50 nm. A TiC phase (Fm-3m, a ≈ 4.3 Å) is observed as the dominating precipitate phase. In addition, small amounts (10%–20%) of a Cr23C6 phase (Fm-3m, a ≈ 10.6 Å) are observed. In contrast to literature data on the same coatings deposited on silicon substrates, the formation of boride precipitate phases is strongly suppressed here. From investigations with X-ray diffractometry, electron microscopy and secondary ion mass spectrometry we conclude that the nanostructure of the coatings is formed by reactive phase formation of the boride coating with the carbon containing steel substrate.

Tough ceramics can be made by introducing weak interfaces which deflect a growing crack. A simple discrete element model was employed to study crack growth in SiC-C laminate with graphite as weak interfaces. By modelling the three-point-bending test of the notched laminate, de-bonding, de-lamination and crack deflection were observed dynamically. The fracture features of the laminate as like “graceful failure” and R-curve behaviour were replicated both qualitatively and quantitatively. It has been revealed that the strength of the weak interface should be in a certain range to assure the appearance of the toughening effect. A minimum presence of the weak interface is required to increase the strength of the laminate. The employed model is explicit and simple, it can be used to reproduce the dynamic process of crack propagation in ceramic laminates and guide the design of the laminate's structure in the future.

Silicon dioxide nanoparticles, also known as silica nanoparticles or nanosilica, are the basis for a great deal of biomedical and catalytic research due to their stability, low toxicity and ability to be functionalized with a range of molecules and polymers. A novel synthesis route is based on CO2 absorption/sequestration in an autoclave by forsterite (Mg2SiO4), which is part of the mineral group of olivines. Therefore, it is a feasible and safe method to bind carbon dioxide in carbonate compounds such as magnesite forming at the same time as the spherical particles of silica. Indifference to traditional methods of synthesis of nanosilica such as sol gel, ultrasonic spray pyrolysis method and hydrothermal synthesis using some acids and alkaline solutions, this synthesis method takes place in water solution at 175 &deg, C and above 100 bar. Our first experiments have studied the influence of some additives such as sodium bicarbonate, oxalic acid and ascorbic acid, solid/liquid ratio and particle size on the carbonation efficiency, without any consideration of formed silica. This paper focuses on a carbonation mechanism for synthesis of nanosilica under high pressure and high temperature in an autoclave, its morphological characteristics and important parameters for silica precipitation such as pH-value and rotating speed.

The potentials of the direct inkjet printing (DIP) method for manufacturing 3Y-TZP dental restorations were investigated. Aqueous inks of 3Y-TZP and carbon were developed and characterised for the DIP method. A sample 3Y-TZP framework of a dental bridge was produced by DIP. The stress distribution on this framework under realistic clenching conditions was simulated using finite element analysis. Four-point bending specimens produced by DIP and a slip cast reference sample were tested to characterise the flexural strength of the DIP produced components.

Transition metal diboride coatings of composition (Ti 0.44 W 0.29 Cr 0.27 )B 1.90 were deposited on silicon substrates by dc magnetron sputtering of compound targets. The chemical composition of the targets is transferred to the sputtered films. The as-deposited films are amorphous as indicated by grazing incidence X-ray diffraction. Investigations with electron microscopy revealed that the films show a columnar nano-structure. Annealing at temperatures between 1000 °C and 1300 °C leads to the formation of nano-crystalline precipitations, which can be attributed to (Ti,W,Cr)B 2 , β-(W, Ti, Cr)B and W 2 B 4 phases. Annealing can be used to tailor the average grain size of the precipitates, making these films a good candidate for hard coatings re-enforced by nano-structuring.

Mechanical reinforcement of hard ultrahigh-temperature materials often requires complex processing techniques involving the mixing of platelet-shaped particles into the matrix – ultimately leading to inhomogeneities that compromise strength and fracture toughness. Thus, this paper investigates in situ reinforcement of a TiB 2 ceramic matrix by controlled precipitation of W 2 B 4 platelets and β-WB nanolaminates. The results showed successful precipitation of: (i) W 2 B 4 platelets according to the phase diagram, (ii) epitaxial β-WB lamellas, and (iii) spinodal, i.e. fully coherent W-rich lamellas which change to either W 2 B 4 platelets or β-WB during ageing. The study of phase amount and microstructure as a function of homogenization temperature and annealing temperature/time regimes allows one to control the volume fraction, size as well as aspect ratio of precipitates. This enables the control of fracture toughness affected by crack deflection, particle pull-out, crack bridging and crack branching. Composition and milling treatment most affect microstructure. Successful precipitation is possible at 1650 °C.