Absorption effects in photopolymerized ceramic suspensions

The effects of concentration of photoinitiator and concentration of an ultraviolet-absorbing dye on the cure depth and cure width of photopolymerized ceramic suspensions were investigated. Both the cure depth and cure width have a semilogarithmic dependence on the energy dose, with the suspension characterized by the following parameters: the depth critical energy dose and depth sensitivity and width critical energy dose and width sensitivity. The values of these four parameters are highly dependent on the concentration of absorbers in the suspension. The depth sensitivities and width sensitivities are given by the absorption model, while the depth critical energy doses and width critical energy doses are given by the inhibitor exhaustion model. Furthermore, the relationship between concentration of absorbers and the broadening depth was determined. The concentration of photoinitiator did not significantly change the broadening depth, while the concentration of dye decreased the broadening depth.     

Reciprocating wear response of Ti(C,N)–Ni3Al cermets

Abstract

Ti(C,N) based cermets have received significant attention due to their enhanced mechanical properties at elevated temperatures, low mass and increased chemical stability, when compared to WC–Co hardmetals. These properties have been found to be superior in many cases to traditional hardmetal replacements, such as TiC–Ni. The current study focuses on Ti(C,N)–Ni₃Al cermets formed through melt infiltration (with binder contents ranging from 20 to 40 vol.-%Ni₃Al). Comparison is made with TiC–Ni₃Al cermets using an identical binder alloy. The reciprocating ball on flat wear properties of the cermets were evaluated as a function of applied load (using a WC–Co counterface), together with the composite hardness and indentation fracture resistance. It is shown that nitrogen content negatively affects infiltration, resulting in non-infiltrated areas within low binder content cermets, which decreases the indentation fracture resistance and hardness. This problem can be largely mitigated by increasing binder content. When comparing fully infiltrated cermets, increasing nitrogen content decreases hardness and increases toughness, while all Ti(C,N) cermets outperform TiC (at 40 vol.-% binder). Reciprocating wear increased with increasing load, and typically was the most severe for the lowest binder contents. A combination of wear mechanisms were apparent, including both abrasive and adhesive wear, with the formation of an oxide tribolayer containing components from both the tested cermets and the WC–Co counterface material.

Les cermets à base de Ti(C,N) ont reçu une attention importante grâce à leurs propriétés mécaniques améliorées aux températures élevées, à leur faible masse et à leur stabilité chimique augmentée, lorsque comparés aux carbures métalliques de WC–Co. Dans plusieurs cas, on a trouvé que ces propriétés étaient supérieures à celles des remplacements traditionnels de carbures métalliques, comme le TiC–Ni. La présente étude se concentre sur les cermets de Ti(C,N) –Ni₃Al formés par infiltration du bain (la teneur du liant variant de 20 à 40% en volume de Ni₃Al). On les compare aux cermets de TiC–Ni₃Al en utilisant un alliage de liaison identique. On a évalué les propriétés d’usure par déplacement alternatif de bille sur disque des cermets en fonction de la charge appliquée (utilisant un antagoniste en WC–Co), ainsi que de la dureté du composite et de la résistance à la fracture d’indentation. On montre que la teneur en azote affecte négativement l’infiltration, ayant pour résultat des régions non infiltrées à l’intérieur des cermets à faible teneur en liant, ce qui diminue la résistance à la fracture d’indentation et la dureté. On peut largement atténuer ce problème en augmentant la teneur en liant. Lorsque l’on compare des cermets entièrement infiltrés, l’augmentation de la teneur en azote diminue la dureté et augmente la ténacité, alors que tous les cermets de Ti(C,N) surpassent le TiC (à 40% en volume de liant). L’usure par déplacement alternatif augmentait avec une augmentation de la charge, et était typiquement plus sévère pour les plus faibles teneurs en liant. Une combinaison de mécanismes d’usure était apparente, incluant tant l’usure par abrasion que l’usure d’adhérence, avec formation d’une couche tribologique oxyde contenant des composantes tant des cermets évalués que du matériau antagoniste en WC–Co.     

State-of-the-art review of interface bond testing devices for pavement layers: toward the standardization procedure

During the past thirty years, interface bonding between pavement layers has been a topical subject worldwide to research. In this context, many researchers have developed and utilized their own devices to investigate the properties of pavement interfaces. In the absence of an international standard procedure for interface bonding, it is inevitable that testing results are not comparable in all cases. In addition, various conducted studies reveal that parameters such as temperature, loading conditions, materials and so on exert an influence on interface properties. This paper aims to deal with the matter effectively via a thorough and comprehensive review of interface bond testing to lay the groundwork for standardization procedure. For this purpose, first, a general overview of interface bond function and its impact on pavement performance is presented. Then, different types of interface bond test methods according to loading conditions are explained; furthermore, the configuration of various setups is discussed and their function is compared together. Finally, given the prior experiences, a framework for a methodical approach to a standard evaluation of pavement interfaces is presented.     

Fabrication and characterization of iron oxide ceramic membranes for arsenic removal

Nanoscale iron oxide particles were synthesized and deposited on porous alumina tubes to develop tubular ceramic adsorbers for the removal of arsenic, which is an extremely toxic contaminant even in very low concentrations. Its natural presence affects rural and low-income populations in developing countries in Latin America and around the world, which makes it essential to develop a user-friendly, low energy demanding and low cost treatment technology. The fabricated ceramic membranes can be operated with minimal trans-membrane pressure difference and do not require pumping. The support tubes and final membrane have been characterized by surface area and porosity measurements, permeability tests and scanning electron microscopy (SEM) imaging. Arsenic concentrations were determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES). Due to its low cost and simple operation, the system can be applied as a point of use device for the treatment of arsenic contaminated groundwaters in developing countries.     

A supervised approach for automated surface defect detection in ceramic tile quality control

Surface defect detection is very important to guarantee the quality of ceramic tiles production. At present, this process is usually performed manually in the ceramic tile industry, which is low efficiency and time-consuming. For small surface defects detection of high-resolution ceramic tiles image, an intelligent detection method for surface defects of ceramic tiles based on an improved you only look once version 5 (YOLOv5) algorithm is presented. Firstly, the high-resolution ceramic tile images are cropped into slices, and the Bottleneck module in the YOLOv5s network is optimized by introducing depthwise convolution and replaced in the whole network. Then, feature extraction is performed using the improved Shufflenetv2 backbone, and an attention mechanism is added to the backbone network to improve the feature extraction ability. The path aggregation network (PAN) and Feature Pyramid Networks (FPN) neck are used to enhance the feature extraction, and finally, the YOLO head is used to identify and locate the ceramic tile defects. The multiple sliding windows detection method is proposed to detect the original ceramic tile image which is faster than the single sliding window detection method. The experimental results show that compared with the original YOLOv5s detection algorithm, the parameters of the model are reduced by 20.46 %, the floating point operations are reduced by 26.22 %, and the mean average precision (mAP) of the proposed method is 96.73 % in the ceramic tile image slice test set which has 1.93 % improvement in mAP than the original YOLOv5s. Compare with other object detection methods, the method proposed in this paper also has certain advantages. In the high-resolution ceramic tile images test set, the mAP of the proposed algorithm is 86.44 % by using the multiple sliding window detection method. The ceramic defect detection experiment has verified the feasibility of the method proposed in this paper.     

Low-temperature sintering of porous silicon carbide ceramic support with SDBS as sintering aid

The sintering temperature of porous silicon carbide ceramic support (PSCS) is typically higher than 1500 °C. In this paper, sodium dodecyl benzene sulfonate (SDBS) was used as a sintering additive to fabricate PSCS with high gas permeance and high bending strength at a sintering temperature less than 1200 °C. The PSCS was prepared by the dry pressing method followed by in-situ reaction. The effects of SDBS loading on the porosity, bending strength, gas permeation performance, and microstructure of the PSCS were investigated. The results showed that without SDBS, the required sintering temperature was as high as 1550 °C and resulted in a bending strength of 6.5 MPa but the sintering temperature decreased to 1150 °C with 8% SDBS and the bending strength increased to 16 MPa. The main reason was that SDBS decomposed into Na₂O which reacted with SiO₂ and ZrO₂ to form strong bonding connections. The prepared PSCS with SDBS also showed good gas permeance of 900 m³/(m² h kPa), higher than the 750 m³/(m²·h·kPa) without SDBS. This work describes the effective use of SDBS as a ceramic additive to reduce sintering temperature, while achieving high gas permeation and bending strength. The use of the low cost and commercially available SDBS produces an excellent ceramic filter with much lower energy consumption, and could also be implemented in other ceramic systems.     

In-situ tensile tests under SEM and X-ray computed micro-tomography aimed at studying a self-healing matrix composite submitted to different thermomechanical cycles

Ceramic matrix composite (CMC) based on SiC fibres and matrix is gradually introduced in aeronautical application, mostly in hottest parts of engines. Three dimensional (3D) structured materials are good candidates for complex parts such as turbine blades. Material is submitted to mechanical stresses at high temperatures in oxidizing and corrosive environments for long durations. During thermomechanical cycles, damage, oxidation and healing-phenomenon occur and develop in the material. X-ray computed micro-tomography (μCT) and tensile test under scanning electron microscopy (SEM) are experimental means to study these phenomenons. These techniques are implemented for the understanding of the behaviour of the oxide (solid or liquid) in the crack of the material. The influence of the oxide in the crack was analyzed during tensile test under SEM or μCT. The observation allows to determine the influence of the oxide on the reclosure of the crack during the unloading.     

3D printing of CaO-based ceramic core using nanozirconia suspension as a binder

The 3D printing of a ceramic core with nanoceramic suspension as a binder was performed to investigate a novel method for the fabrication of a complex-shaped ceramic core. Green bodies were printed using CaO powder as a precursor material and nanozirconia-absolute ethyl alcohol solution suspension as a binder. The green bodies were sintered at 1300–1500 °C for 2 h. The effects of binder saturation level on the properties of the sintered bodies were investigated. Increasing the binder saturation level caused decreases in the linear shrinkage of the sintered bodies, but increases in hydration resistance and bending strength. The nanozirconia particles were deposited on the surfaces of the CaO particles and filled the pores of green bodies, and then formed a high melting temperature CaZrO₃ layer with the CaO at the surfaces of the CaO grains, which improved the hydration resistance of the CaO-based ceramic core parts.     

Innovative carbon-bonded filters based on a new environmental-friendly binder system for steel melt filtration

New carbon-bonded alumina filters for steel melt filtration were developed. The carbonaceous matrix was based on a new, environmental friendly binder system based on lactose and tannin. The filter preparation was analogous to the production of conventional foam filters according to the Schwartzwalder process. The processing as well as the rheology of the slurries was investigated. An addition of n-Si increased the carbon yield and the cold crushing strength (CCS) of the samples. Higher values of CCS were obtained after coating of the filters with alumina. The material was characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The applicability of these new filters was assessed in impingement tests with a steel melt, in which three out of four recipes survived the thermal shock.