Sarah Nistler, Christoph Hofstetter, Stefan Baudis
et al.
In this study, we successfully created an implant to mimic natural bone by combining a load-bearing shell made of zirconia (cortical bone) with an osteoconductive filling made of hydroxyapatite (cancellous bone). Using additive manufacturing, both parts were produced separately followed by a sinter-joining process to form one hybrid final part. We first tested the sinter-joining process on a simple ring-in-ring design, creating a defined press-fit between the outer and inner ring. We also introduced sinter supports to ensure excellent alignment and manufactured biaxial bending plates to test the mechanical resistance. We found a significant increase in the maximal measured force from (72±53) N to (366±88) N for a 5 % and 10 % press-fit, respectively. Furthermore, we successfully manufactured a more complex bone implant with this sinter-joining method.
ABSTRACTThis study prepared ultralow electron-loss perovskites with spinel-like structures via a solid-state reaction. The (Mg0.95Co0.05)2(Ti0.95Sn0.05)O4 (MCTS) ceramic exhibited approximate values for ultrahigh quality factor, permittivity, and negative temperature coefficient (τf) of 310,000 GHz, 14.25, and −48.1 ppm/oC, respectively. To bring the τf closer to zero, a trace amount of (Ca0.95Sr0.05)(Ti0.97Sn0.03)O3 (CSTS) perovskite was added to MCTS during ceramic manufacturing. CSTS exhibited a permittivity of 92 and a large positive τf value of 810 ppm/°C. A 0.92MCTS–0.08CSTS hybrid ceramic sintered at 1325°C achieved remarkable microwave dielectric properties of εr ~18.42, Q×f ~ 237,000 GHz and τf ~3.72 ppm/°C. This mixed ceramic has significant potential for applications in manufacturing microwave devices.
Hussain Shendy, G.A. Khater, Mohamed G. Shahien
et al.
The preparation of affordable glass-ceramic materials by induced crystallization of glass-based mica schists and other natural raw materials (dolomite & limestone), as well as magnesite as a mine waste, was investigated for the first time. Five glass batches were designed based on the eutectic composition of the diopside-anorthite ratio with increasing the enstatite content from 0–40 wt.% within the quaternary CaO–MgO–Al2O3–SiO2 system. After melting at 1400 to 1500 °C, casting into discs & rod shapes, and annealing process, the prepared glasses were subjected to careful heat treatment schedules. Several techniques were used to characterize the applied raw materials, glass, and glass-ceramic materials such as X-ray Fluorescence (XRF), Differential Thermal Analysis (DTA), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Polarizing-light Microscopy. The produced glass-ceramic from the glass batch with 30 wt% enstatite that was nucleated at 750 °C /2h followed by crystallization at 950 °C /h, displayed the well-developed product on the level of volume crystallization and pore formation.
Thiemo Fildhuth, Matthias Oppe, Clea Kummert
et al.
After several years of renovation, the Renaissance castle of Villers-Cotterêts, hosting the “Cité internationale de la langue française” desired by the French president and developed by Olivier Weets Architecte, has been opened to the public in October 2023. Centerpiece and emblematic symbol of the castle is the fully glazed, double curved grid shell covering the interior courtyard, which has been developed and engineered by the authors throughout all construction stages. The cushion-shaped, 16m x 36m roof consists of a rhombic grid structure of slender, custom-welded steel profiles glazed with 2m x 2m, diagonally curved insulating glass units. The shell geometry and tesselation have been form-found to be clad with single curved glass. The shallow rise of 1.3m combined with a low glass curvature of 25m, the structural node geometry, the irregular courtyard shape, the incapacity of the masonry to absorb horizontal forces, rainwater drainage and the building regulations were key challenges to be met. In the present contribution, the solution to these topics is discussed within the context of other quadrangulated glazed grid shells, such as the Academy Museum of Motion Pictures in Los Angeles or the roof of lightrailstation in The Hague. The comparison shows the necessity to develop individual glazing and construction solutions depending on the boundary conditions and complexity of each project.
Al-containing MAX phase ceramic has demonstrated great potential in the field of high-performance low-voltage electrical contact material. Elucidating the anti-arc erosion mechanism of the MAX phase is crucial for further improving performance, but it is not well-understood. In this study, Ag/Ti3AlC2 electrical contact material was synthesized by powder metallurgy and examined by nanoindentation techniques such as constant loading rate indentation, creep testing, and continuous stiffness measurements. Our results indicated a gradual degradation in the nano-mechanical properties of the Ti3AlC2 reinforcing phase with increasing arc erosion times, although the rate of this degradation appeared to decelerate over arc erosion times. Specifically, continuous stiffness measurements highlighted the uneven mechanical properties within Ti3AlC2, attributing this heterogeneity to the phase’s decomposition. During the early (1–100 times) and intermediate (100–1000 times) stages of arc erosion, the decline in the nano-mechanical properties of Ti3AlC2 was primarily ascribed to the decomposition of Ti3AlC2 and limited surface oxidation. During the later stage of arc erosion (1000–6200 times), the inner region of Ti3AlC2 also sustained arc damage, but a thick oxide layer formed on its surface, enhancing the mechanical properties and overall arc erosion resistance of the Ag/Ti3AlC2.
Abstract Owing to economic reasons and the morphology of the surface of particles, carbothermal reduction is a suitable method for the synthesis of the desired materials. In this research, ZrC nanopowder was synthesized using phenolic resin as the carbon source and ZrO2 powder as the source of zinc by the carbothermal method. ZrO2 powder was milled for 1, 2, 3, 4, 6, and 7 h followed by combining with phenolic resin and ethanol with stoichiometric and nonstoichiometric ratios, and then the samples were pyrolyzed for 60 min at 800°C. Then, the samples were heat treated in an argon atmosphere in two stages at 1,600°C for 60 and 90 min. XRD and FE‐SEM were used to investigate the microstructure of the samples. By increasing the molar ratio and increasing the heat treatment time, the ZrC phase content in the samples increased so that the highest amount of ZrC phase was observed in the samples with the carbon to zirconium ratios of 1:6 and 1:9 and the holding time of 90 min. By increasing the heat treatment time, the average size of ZrC particles increased from 130 to 180 nm and the size of crystallites increased from 36 to 46 nm.
Maria Celeste Legarto, Damian Benito, Alberto Scian
et al.
A monolithic porous composite was synthesized by sol–gel process, containing the maximum and significant amount of bentonite that allows its use as a filter bed in aqueous effluents treatment. This process is able to apply on an industrial scale.The bentonite used was an efficient adsorbent for various contaminant molecules in aqueous media when is operated in a batch stirred tank, but presents difficulty in the separation stage of suspended particles. In this laboratory-scale work, cylindrical monoliths of 9 cm length by 2 cm diameter were made that can be used as a filter bed. The primary composite, silica-resin, was prepared by the sol–gel precursor mixture of the partially hydrolyzed tetraethylorthosilicate and a phenol-formaldehyde resin. Bentonite was added to the pre-gelling, obtaining the silica-resin-bentonite composite, made up the gel which is then dried and cured at 270 °C. The different composites mineralogical and structurally were evaluated. The preliminary performance of the developed bentonite filter bed showed almost 90% adsorption of diphenylamine, a commercial agrochemical widely used as anti-antiscaldant in postharvest treatment of fruit, and showed that the bentonite conserves its adsorption capacity and controls the swelling of the interlayer space which encourages further research studies applied to water treatment. Resumen: Se sintetizó vía sol-gel un compuesto híbrido monolítico poroso, con la máxima cantidad significativa de bentonita que permite su uso como lecho filtrante, lo que podría aplicarse en el tratamiento de efluentes acuosos a escala industrial.La bentonita utilizada es un eficiente adsorbente de varias moléculas de contaminantes presentes en medios acuosos cuando se opera por lotes en tanque agitado, pero presenta la dificultad de separar las partículas suspendidas. Para este trabajo a escala de laboratorio se realizaron monolitos cilíndricos de 9 cm de largo por 2 cm de diámetro que pueden ser usados como lecho filtrante. El compuesto primario, sílice-resina, se preparó mediante la mezcla precursora sol-gel de tetraetilortosilicato parcialmente hidrolizado y resina fenol-formaldehído. Se añadió bentonita a la mezcla precursora durante la gelificación, para obtener el compuesto sílice-resina-bentonita. Luego del proceso de envejecimiento del gel se cura a 270 °C. Los diferentes compuestos fueron evaluados mineralógica y estructuralmente. El rendimiento preliminar mostró casi el 90% de adsorción de difenilamina, un agroquímico comercial altamente utilizado como antiescaldante en las industrias poscosecha de frutas, y mostró que la bentonita conserva su capacidad de adsorción y controla el hinchamiento del espacio interlaminar, lo que motiva a futuras investigaciones aplicadas al tratamiento de aguas.
This paper presents the casting of volumetric glass components from glass waste as an alternative glass-recycling approach. The approach is characterized by its flexibility to accommodate a variety of compositions and ability to yield volumetric (solid or thick-walled) glass products that can tolerate higher contamination rates without a significant compromise to their properties. The novelty of the proposed glass-to-glass recycling method lies in the “as-received” recycling of glass waste, using relatively low forming temperatures (750o- 1200oC). This reduces both the need for expensive, labour-intensive and logistically complex purifying, segregation and treatment (e.g. removal of coatings) techniques, and the required energy and CO2 emissions for product forming. Aim of this paper is to provide an overview of the potential but also of the technical and supply-chain challenges and limitations that still need to be tackled, in order to introduce this recycling approach to the market. Addressing the supply-chain barriers of glass recycling, the principal challenges linked to the collection and separation of glass waste and the established quality standards for the prevailing glass production technologies are identified, in order to argue upon the potential of this new recycling approach. In continuation, addressing the technical challenges that are mainly linked to contamination, an overview is provided of the main experimental findings on the influence of cullet contaminants and casting parameters on the generation of defects, and how these affect the mechanical properties. The experiments study a broad variety of glass compositions, including soda-lime, borosilicate, aluminosilicate and lead/barium glasses, and different levels of cullet contamination, of embedded (e.g. frit, wire) or external (e.g. stones, glass ceramics) character. Based on the cullet characteristics and imposed firing schedules, different glass quality grades arise and critical defects are highlighted. Thereafter, the most promising glass waste sources that can be recycled via this novel recycling approach are distinguished and directions for future research are highlighted.
Genesis de O. Lima, Thaylan P. Araújo, José Renato de O. Lima
et al.
Using a microwave-assisted hydrothermal method, we synthesized BiOBr powders, with and without, glycine or phenylalanine as templates. The samples were characterized by X-ray Diffraction, UV–Vis Diffuse Reflectance Spectroscopy, and Field Emission Gun Scanning Electron Microscopy. The XRD patterns were indexed to the tetragonal structure and presented very different intensities from each other, which is consistent with changes in the structural organization. The FEG-SEM images showed morphology alterations, from nanoplates for unmodified BiOBr to nanolamellae for BiOBr with phenylalanine (BOB-phe). The catalytic activity of BOB-phe degraded 98% of Rhodamine B dye in approximately 20 min, while the other BiOBr compounds presented slower degradation kinetics, which could be explained by a higher amount of active sites on BOB-phe surface. Resumen: Utilizando un método hidrotermal asistido por microondas, sintetizamos los polvos de BiOBr, con y sin, glicina o fenilalanina como plantillas. Las muestras se caracterizaron por difracción de rayos X, espectroscopía de reflectancia difusa UV-Vis y microscopía electrónica de barrido con pistola de emisión de campo. Los patrones XRD se indexaron a la estructura tetragonal y presentaron intensidades muy diferentes entre sí, lo que es consistente con los cambios en la organización estructural. Las imágenes de FEG-SEM mostraron alteraciones de la morfología, desde nanoplacas para BiOBr no modificado hasta nanolamelas para BiOBr con fenilalanina (BOB-phe). La actividad catalítica de BOB-phe degradó el 98% del colorante de rodamina B en aproximadamente 20 minutos, mientras que los otros compuestos de BiOBr presentaron una cinética de degradación más lenta, lo que podría explicarse por una mayor cantidad de sitios activos en la superficie de BOB-phe.
In order to develop chrome-free refractory materials applicable in coal slurry gasification, SiC-CaAl12O19 (SiC-CA6) composite refractories were developed and prepared by using SiC aggregates and CA6 powders as main raw materials. The sintering behaviour of the composites was investigated. After firing at different temperatures under CO atmosphere, the effects of oxidation of SiC aggregates on the sintering behaviour and microstructures of SiC-CA6 composite refractorieswere investigated. SiC-CA6 composites could not be sintered when firing temperature was lower than 1500°C. SiC had a passive oxidation and the oxidation components were able to react with CA6 to form CaAl2Si2O8. The CaAl2Si2O8 melted into liquid when sintering temperature was in the range of 1500-1600°C, which promoted the sintering process of the SiC-CA6 composites. At temperatures above 1600 °C, an active oxidation of SiC occurred. Simultaneously, SiC could also reacted with the SiO2(s,l) to form SiO, leading to the precipitation of Al2O3 and CaO in the liquid to generate plate-like CA6. Above this temperature, the sintering of the SiC-CA6 composite refractories was affected by the growth of CA6 and oxidation of SiC. This work demonstrates that the optimal sintering temperature for the SiC-CA6 composite refractories was 1600°C.