Metal Components Research Articles

Ambient exposure to fine particulate matter with oxidative potential affects oxidative stress biomarkers in pregnancy.

Prenatal exposures to ambient particulate matter (PM2.5) from traffic may generate oxidative stress, and thus contribute to adverse birth outcomes. We investigated whether PM2.5 constituents from brake and tire wear affect levels of oxidative stress biomarkers (malondialdehyde (MDA), 8-hydroxy-2'-deoxyguanosine (8-OHdG)) using urine samples collected up to three times during pregnancy in 156 women recruited from antenatal clinics at the University of California Los Angeles. Land use regression models with co-kriging were employed to estimate average residential outdoor concentrations of black carbon (BC), PM2.5 mass, PM2.5 metal components, and three PM2.5 oxidative potential metrics during the 4-weeks prior to urine sample collection. 8-OHdG concentrations in mid-pregnancy increased by 24.8% (95% CI: 9.0, 42.8) and 14.3% (95% CI: 0.4%, 30.0%) per interquartile range (IQR) increase in PM2.5 mass and BC, respectively. The brake wear marker (barium) and the oxidative potential metrics were associated with increased MDA concentration in the 1st sample collected (10-17 gestational week), but 95% CIs included the null. Traffic-related air pollution contributed in early to mid-pregnancy to oxidative stress generation previously linked to adverse birth outcomes.

Effect of Electric Pulse Treatment on Microstructure and Mechanical Property of Laser Powder Bed Fused IN718

This study investigated the impact of electric pulse treatment (EPT) on the microstructure and mechanical properties of laser powder bed fused Inconel 718 (IN718). Through a comprehensive experimental characterization, we found that EPT induced significant improvements in the microstructure of IN718. In the YOZ plane of EPT-700, the molten pool diminished and replaced by a grain boundary with granular Ni3Nb precipitates, and the dislocations increased while the irregular porosity decreased. Concurrently, enhanced mechanical properties of EPT-700 were obtained, including a hardness of 354.7 HV, an ultimate tensile strength of 930.21 MPa, and an elongation of 34.35%. Fractographic analysis revealed a transition in fracture mechanisms, highlighting the intricate relationship between microstructural modifications induced by EPT and mechanical response under load. These findings underscore the potential of EPT as a promising post-processing technique for optimizing the microstructure and mechanical properties of IN718 components fabricated via laser powder bed fusion additive manufacturing. This study contributes to the advancement of knowledge in the field of additive manufacturing and provides valuable insights for the development of high-performance metallic components.

Enhancing surface quality and tool life in SLM-machined components with Dual-MQL approach

Selective laser melting (SLM) can produce complex metal components with high densities, thereby surpassing the limitations of traditional machining methods. However, achieving accurate dimensions, geometries, and acceptable surface states in parts fabricated through SLM remains a concern as they often fall short compared to traditionally machined components. As a solution, a hybrid additive-subtractive manufacturing (HASM) method was developed to effectively utilize the advantages of both techniques. In this study, SLM-made 316 L stainless steel was machined under distinct cooling conditions to investigate the effects of roughness and tool wear. After a thorough investigation, the dual-MQL strategy was evaluated and compared with dry and MQL cutting strategies. The findings showed that the dual-MQL condition led to a significant reduction in flank wear by 54–56% and 29–34%, respectively, associated with dry and MQL cutting techniques, making it a highly promising key for machining SLM-made steel components. Machine learning techniques are potential tools for prediction and classification capabilities in machining processes. For milling SLM-made 316 L SS, multilayer perceptron (MLP) proved to be the most effective prediction model and for classification MLP and Random forest performed better.

Real-Time Object Classification on an Enamel Paint Coating Conveyor Line Using Mask R-CNN

The rising demand to efficiently acquire live production data has added more significance to automated monitoring and reporting within the industrial manufacturing sector. Real-time parts screening requiring repetitive human intervention for data input may not be a feasible solution to meet the demands of modern industrial automation. The objective of this study is to automatically classify and report on manufactured metal sheet parts. The metal components are mechanically suspended on an enamel paint-coating conveyor line in a household appliance manufacturing plant. At any given instant, the parts may not be in the exact coordinates within the desired area of interest and the classes of objects vary based on changing production requirements. To mitigate these challenges, this study proposes the use of a trained Mask R-CNN model to detect the objects and their associated class. Images are acquired in real-time using a video camera located next to the enamel coating line which are subsequently processed using the object detection algorithm for automated entry into the plant management information system. The highest achieved average precision obtained from the model was 98.27% with an overall accuracy of 98.24% using the proposed framework. The results surpassed the acceptable standard for the average precision of 97.5% as set by the plant production quality engineers.

Electropolishing of complex-shaped bulk metallic glasses in NaCl-ethylene glycol electrolyte

Electropolishing (EP) has been widely used to obtain good surface roughness of metallic structures; however, precisely-shaped cathodes are still necessary for the EP of bulk metallic glass (BMG) devices and components. In this work, the EP behavior of a Zr-based BMG was investigated using a plain steel cathode in NaCl-ethylene glycol electrolyte. The recast layer of wire electrical discharge machined (WEDMed) BMG surfaces with crystallization was effectively removed through the EP process, restoring the surface properties of BMGs. The effects of processing parameters, such as voltage, temperature, time, and electrolyte concentration, on the EP performance were explored, and the optimal EP parameters were determined. The EP mechanisms were discussed, where pitting formation was found to consist of three stages. Finally, the EP of a curved BMG part was successfully achieved based on the optimized processing parameters, further validating the feasibility to electropolish complex-shaped BMG structures using direct current (DC) power and NaCl-ethylene glycol electrolyte.

Tracheomalacia and tracheomegaly in infants and children with congenital diaphragmatic hernia managed with and without fetoscopic endoluminal tracheal occlusion (FETO): a multicentre, retrospective cohort study

Temporary fetoscopic endoluminal tracheal occlusion (FETO) promotes lung growth and increases survival in selected fetuses with congenital diaphragmatic hernia (CDH). FETO is performed percutaneously by inserting into the trachea a balloon designed for vascular occlusion. However, reports on the potential postnatal side-effects of the balloon are scarce. This study aimed to evaluate the prevalence of tracheomalacia in infants with CDH managed with and without FETO and other consequences related to the use of the balloon. In this multicentre, retrospective cohort study, we included infants who were live born with CDH, either with FETO or without, who were managed postnatally at four centres (UZ Leuven, Leuven, Belgium; Antoine Béclère, Clamart, France; BCNatal, Barcelona, Spain; and HCor-Heart Hospital, São Paulo, Brazil) between April 5, 2002, and June 2, 2021. We primarily assessed the prevalence of all (symptomatic and asymptomatic) tracheomalacia as reported in medical records among infants with and without FETO. Secondarily we assessed the prevalence of symptomatic tracheomalacia and its resolution as reported in medical records, and compared tracheal diameters as measured on postnatal x-rays. Crude and adjusted risk ratios (aRRs) and 95% CIs were calculated via modified Poisson regression models with robust error variances for potential association between FETO and tracheomalacia. Variables included in the adjusted model were the side of the hernia, observed-to-expected lung-to-head ratio, and gestational age at birth. Crude and adjusted mean differences and 95% CIs were calculated via linear regression models to assess the presence and magnitude of association between FETO and tracheal diameters. In infants who had undergone FETO we also assessed the localisation of balloon remnants on x-rays, and the methods used for reversal of occlusion and potential complications associated with balloon remnants as documented in clinical records. Finally we investigated whether the presence of balloon remnants was influenced by the interval between balloon removal and delivery. 505 neonates were included in the study, of whom 287 had undergone FETO and 218 had not. Tracheomalacia was reported in 18 (6%) infants who had undergone FETO and in three (1%) who had not (aRR 6·17 [95% CI 1·83-20·75]; p=0·0030). Tracheomalacia was first reported in the FETO group at a median of 5·0 months (IQR 0·8-13·0). Symptomatic tracheomalacia was reported in 13 (5%) infants who had undergone FETO, which resolved in ten (77%) children by 55·0 months (IQR 14·0-83·0). On average, infants who had undergone FETO had a 31·3% wider trachea (with FETO tracheal diameter 7·43 mm [SD 1·24], without FETO tracheal diameter 5·10 mm [SD 0·84]; crude mean difference 2·32 [95% CI 2·11-2·54]; p<0·0001; adjusted mean difference 2·62 [95% CI 2·35-2·89]; p<0·0001). At birth, the metallic component was visible within the body in 75 (37%) of 205 infants with available thoraco-abdominal x-rays: it was located in the gastrointestinal tract in 60 (80%) and in the lung in 15 (20%). No side-effects were reported for any of the infants during follow-up. The metallic component was more likely to be in the lung than either outside the body or the gastrointestinal tract when the interval between occlusion reversal and birth was less than 24 h. Although FETO was associated with an increased tracheal diameter and an increased probability of tracheomalacia, symptomatic tracheomalacia typically resolved over time. There is a higher risk of retention of metallic balloon components if reversal of the occlusion occurs less than 24 h before delivery. Finally, there were no reported side-effects of the metallic component of the balloon persisting in the body during follow-up. Longer-term follow-up is needed to ensure that no tracheal problems arise later in life. None.

Revealing Structural Evolution of Nickel Phosphide-Iron Oxide Core-Shell Nanocatalysts in Alkaline Medium for the Oxygen Evolution Reaction.

Metal phosphide-containing materials have emerged as a potential candidate of nonprecious metal-based catalysts for alkaline oxygen evolution reaction (OER). While it is known that metal phosphide undergoes structural evolution, considerable debate persists regarding the effects of dynamics on the surface activation and morphological stability of the catalysts. In this study, we synthesize NiP x -FeO x core-shell nanocatalysts with an amorphous NiP x core designed for enhanced OER activity. Using ex situ X-ray absorption spectroscopy, we elucidate the local structural changes as a function of the cyclic voltammetry cycles. Our studies suggest that the presence of corner-sharing octahedra in the FeO x shell improves structural rigidity through interlayer cross-linking, thereby inhibiting the diffusion of OH-/H2O. Thus, the FeO x shell preserves the amorphous NiP x core from rapid oxidation to Ni3(PO4)2 and Ni(OH)2. On the other hand, the incorporation of Ni from the core into the FeO x shell facilitates absorption of hydroxide ions for OER. As a result, Ni/Fe(OH) x at the surface oxidizes to the active γ-(oxy)hydroxide phase under the applied potentials, promoting OER. This intriguing synergistic behavior holds significance as such a synthetic route involving the FeO x shell can be extended to other systems, enabling manipulation of surface adsorption and diffusion of hydroxide ions. These findings also demonstrate that nanomaterials with core-shell morphologies can be tuned to leverage the strength of each metallic component for improved electrochemical activities.

Narażenie dermalne – ważny aspekt bezpieczeństwa pracy z nanomateriałami

Dermal exposure – an important aspect of safety in working with nanomaterials Taking into account dermal exposure is an important aspect in ensuring safe working conditions with nanomaterials. Quantum dots and nanomaterials with a larger particle size, metallic or with a metallic component, have the highest probability of absorption through the skin. A crucial factor in the process of absorption of nanomaterials through the skin is the disruption of its protective function, which may result in an increased risk of penetration and permeation of nanomaterials into the dermis and the human bloodstream. Keywords: nanoparticles, nanomaterials, skin absorption, skin exposure

Electron beam powder bed fusion of Ti-30Ta high-temperature shape memory alloy: microstructure and phase transformation behaviour

ABSTRACT The present study reports on additive manufacturing of a Ti-30Ta (at.%) high-temperature shape memory alloy (HT-SMA) using electron beam powder bed fusion (PBF-EB/M) technique. Detailed microstructure analysis was conducted to reveal the microstructural evolution along the entire process chain, i.e. from gas-atomised powder to post-processed material. PBF-EB/M processed structures with near full density and an isotropic, β-phase stabilised microstructure, i.e. equiaxed β-grains of around 20 µm in diameter with no preferred crystallographic orientation, are reported. As revealed by differential scanning calorimetry, post-process heat-treated Ti-Ta demonstrates a reversible martensitic phase transformation well above 100°C. Although partly unmolten Ta-particles after both gas atomisation and PBF-EB/M remain a challenge towards robust processing, PBF-EB/M appears to show significant potential for fabrication of Ti-Ta HT-SMAs, especially when functional metal parts and components with complex shapes are required, which are difficult to fabricate conventionally.

Precipitation behaviors and the related strengthening mechanism in 2219 Al alloy fabricated by wire arc additive manufacturing

Normally, a large number of dislocations could be introduced into the metallic component in the additive manufacturing process. The effects of these thermal stress-induced dislocations on the precipitation of 2219 Al alloy have thus far not been comprehensively studied. In the present study, the precipitation behaviors of 2219 Al alloys fabricated by wire arc additive manufacturing are investigated in detail by multi-scale experimental methods, including transmission electron microscopy, scanning electron microscopy, and X-ray diffraction analyses. Our study suggests that the stress-induced dislocations could act as the heterogenous nucleation sites, facilitating the precipitation of θ′ and θ′′ phases in the deposition process. During the subsequent artificial aging, θ′ and θ′′ phases are present in the 160°C peak-aged sample. Raising the aging temperature from 160°C to 180°C could facilitate the transformation of θ′′ to θ′ phases. Moreover, for the 200°C peak-aged sample, the number density of θ′ phases appears to decrease with accompanied coarsening. An evident improvement occurs in the comprehensive mechanical properties of the as-deposited sample by appropriate heat treatment (540℃/3 h-180℃/14 h). The ultimate tensile strength significantly increases from 238 MPa to 408 MPa, exhibiting an enhancement of approximately 70 %, while the elongation increases from 14 % to 15 %. Additionally, a quantitative correlation is established between the precipitate characteristics and mechanical properties.

Sustainable metal-infused polymer feedstock compatible with low-cost metal sinter-based 3D printing

Additive manufacturing has been employed to fabricate metallic parts; however, prevalent techniques are expensive and energy consuming. Therefore, fused deposition modeling (FDM) technique has grabbed the attention of researchers and industries. Despite the promising results, available materials for metal FDM 3D printing are very limited. The current study presents the development of a novel metal-infused polymeric feedstock for FDM 3D printing, consists of spiky-shaped recycled nickel powders and polylactic-acid (PLA) polymer matrix. A low-cost desktop 3D printer is employed to produce green parts; subsequently, debinding/sintering processes can be conducted to achieve a fully metallic part. The low-cost recycled nickel powder that has been used in this study is produced using the low-carbon footprint Mond process, with a significant application in production and recycling of nickel- and iron-based batteries. Furthermore, PLA is chosen because it is bio-based and biodegradable with a lower carbon footprint in the carbon cycle than fossil-fuel-derived polymers. Therefore, the whole process is an ecofriendly cycle, stepping toward the sustainable and affordable production of metallic components. Regarding development of a novel feedstock material compatible with 3D printing, it is important to understand its properties. So, the developed feedstock materials were rheologically and physico-mechanically analyzed to find the optimum filler concentration.

Optimized precipitation process for the treatment of radioactive effluents from Ni-alloy decontamination using a chemical oxidation reduction process

Nuclear power plays a major role in the generation of electricity with low carbon emissions. However, it generates significant amounts of radioactive waste, mainly from contaminated metallic components such as steam generators. Decontamination is essential for the safe handling and eventual recycling or disposal of these materials. Various decontamination techniques can be utilized but chemical processes are recommended for complex geometries such as the tubular parts of steam generators. COREMIX (Chemical Oxidation REduction using nitric permanganate and oxalic acid MIXture) is a process that is similar to the CORD (Chemical Oxidation Reduction Decontamination) process currently utilized in the industry which involves dissolving the contaminated oxide layers from metallic surfaces. This process generates a large quantity of radioactive effluent that requires appropriate treatment. The objective is to reduce metallic concentration and the radioactivity by precipitating metals in solution as hydroxides M(m-n)(OH)n (with m the oxidation number of the metal M). The optimization of a two-step precipitation protocol is presented here, with a study of the contact time (1–24 h) and the reagents used (NaOH and KOH). The resulting precipitates from this process are characterized using several techniques (FTIR, TGA and XRD). Tests were conducted on surrogate samples to demonstrate the viability of the process on more complex samples. Finally, the optimized protocols were implemented on radioactive Ni-alloy samples. Decontamination factors were calculated portraying the efficiency of both the COREMIX and the subsequent two-stage precipitation process. Characterization of the sludge produced during the process shows that the precipitate obtained at pH 8.5 consists mainly of iron (III) oxide-hydroxides, whereas the precipitate obtained at pH 12 is mainly composed of manganese (II,III) oxide. The optimization steps show that the contact time during the first precipitation and the choice of precipitants does not influence the efficiency of the protocol while the destruction of oxalic acid proves to be critical to quantitatively precipitate chromium. Ultimately, the COREMIX process can effectively decontaminate contaminated Ni-alloy samples, removing between 12% and 14% of the contamination in each cycle. Decontamination of effluent using the precipitation protocol results in a very high decontamination factor of between 3000 and 6000.

Spectral Behavior of Fiber Bragg Gratings during Embedding in 3D-Printed Metal Tensile Coupons and Cyclic Loading.

Additive manufacturing (AM) enables the spatially configurable 3D integration of sensors in metal components to realize smart materials and structures. Outstanding sensing capabilities and size compatibility have made fiber optic sensors excellent candidates for integration in AM components. In this study, fiber Bragg grating (FBG) sensors were embedded in Inconel 718 tensile coupons printed using laser powder bed fusion AM. On-axis (fiber runs through the coupon's center of axis) and off-axis (fiber is at 5° and 10° to the coupon's center of axis) sensors were buried in epoxy resin inside narrow channels that run through the coupons. FBGs' spectral evolutions during embedment in the coupons were examined and cyclic loading experiments were conducted to analyze and evaluate the sensor integration process, complex strain loading, process flaws, and sensing performance. This study also demonstrates that the AM process-born deficiencies such as poor surface finish and staircase effects can be detrimental to the embedded sensors and their sensing performance.

Microstructural and mechanical characterization of direct energy deposited 316L stainless steel developed using an evolutionary computational approach

Wire arc additive manufacturing (WAAM) is a technology that has revolutionized the fabrication of large metallic components in various industries. However, previous studies have predominantly relied on trial and error or statistical techniques to determine process parameters, neglecting the potential of evolutionary algorithms for optimizing. In the present work, detailed investigations were performed on the WAAM-based gas tungsten arc welding to predict and optimize the process parameters of the 316L austenitic stainless steel. The input process parameters viz., current, wire feed speed, travel speed, and wire feed direction play a significant role in determining the single bead geometry. The study investigated the influence of these parameters on bead characteristics (such as height to width ratio and percentage dilution) and surface roughness. Multiobjective optimization was carried out using both the response surface methodology-desirability approach (RSM-DA) and the non-dominated sorting genetic algorithm-II (NSGA-II). In the case of NSGA-II, the optimal parameters were determined through a fuzzy decision method and it was validated experimentally. The NSGA-II approach showed superior performance over the traditional RSM-DA model in predicting the responses. In addition, the thin-walled structure printed for the parameters suggested using RSM-DA and NSGA-II approach. In a comprehensive property-based comparative analysis, the NSGA-II optimized parameters demonstrated improved mechanical properties attributed to increased low-angle grain boundaries and kernel average misorientation values. This study highlights the effectiveness of evolutionary computation methods in achieving superior performance and mechanical characteristics in the fabrication of SS316L components.

Investigating the Feasibility and Performance of Hybrid Overmolded UHMWPE 3D-Printed PEEK Structural Composites for Orthopedic Implant Applications: A Pilot Study.

Ultra-high-molecular-weight polyethylene (UHMWPE) components for orthopedic implants have historically been integrated into metal backings by direct-compression molding (DCM). However, metal backings are costly, stiffer than cortical bone, and may be associated with medical imaging distortion and metal release. Hybrid-manufactured DCM UHMWPE overmolded additively manufactured polyetheretherketone (PEEK) structural components could offer an alternative solution, but are yet to be explored. In this study, five different porous topologies (grid, triangular, honeycomb, octahedral, and gyroid) and three surface feature sizes (low, medium, and high) were implemented into the top surface of digital cylindrical specimens prior to being 3D printed in PEEK and then overmolded with UHMWPE. Separation forces were recorded as 1.97-3.86 kN, therefore matching and bettering the historical industry values (2-3 kN) recorded for DCM UHMWPE metal components. Infill topology affected failure mechanism (Type 1 or 2) and obtained separation forces, with shapes having greater sidewall numbers (honeycomb-60%) and interconnectivity (gyroid-30%) through their builds, tolerating higher transmitted forces. Surface feature size also had an impact on applied load, whereby those with low infill-%s generally recorded lower levels of performance vs. medium and high infill strategies. These preliminary findings suggest that hybrid-manufactured structural composites could replace metal backings and produce orthopedic implants with high-performing polymer-polymer interfaces.

Powder bed fusion factory productivity increases using discrete event simulation and genetic algorithm

AbstractPowder bed fusion is importance is growing with uses across industries in both polymer and metallic components, particularly in mass individualization. However, due to the relatively slow mass deposition speed compared to conventional methods, scheduling and production planning play a crucial role in scaling up additive manufacturing productivity to higher volumes. This paper introduces a framework combining discrete event simulation and a genetic algorithm showing makespan improvement opportunities for multiple powder bed fusion factories varying workers, jobs and available equipment. The results show that bottlenecks move among workstations based on worker and capital equipment availability, which depend on the size of the facility indicating a resource-driven constraint for makespan. A makespan reduction of 78% is achieved in the simulation. This shows the trade-off of worker and capital equipment to achieve makespan improvements. The addition of personnel or equipment increases production with further gains achieved by scheduling optimization. Two levels of job demands are analyzed showing productivity gains of 45% makespan improvement when adding the first worker and additional savings with scheduling optimization using a genetic algorithm up to 11%. Most research on additive manufacturing production has focused on the quality of produced parts and printing technology rather than factory level management. This is the first application of this methodology to varying sizes of these potential factories. The method developed here will help decision-makers to determine the appropriate number of resources to meet their customer demand on time, additionally, finding the optimal route for jobs before starting the production process.

Metallurgical Defects and Roughness Investigation in the Laser Powder Bed Fusion Multi-Scanning Strategy of AlSi10Mg Parts

Laser Powder Bed Fusion is the most attractive additive manufacturing technology for its capability to produce metal components with complex geometry. One of the main drawbacks is the poor surface roughness. In this work, different scan strategies and process parameters were studied and their effect on surface roughness, alloy microstructure, and metallurgical defects were discussed. The results highlighted that only tailored process conditions could combine acceptable roughness and absence of metallurgical defects. For the upskin, it has been seen that, although by increasing the Volumetric Energy Density value the Ra decreases, Volumetric Energy Density values higher than 69 J/mm3 determine meltpool instability with consequent formation of gas defects in the subsurface area. Similarly, by increasing the Linear Energy Density value, the Ra of the lateral surfaces decreases, but above 0.37 J/mm, metallurgical defects form in the subsurface area. This study also highlighted that the proposed process involves only a contained increase of the production times. In fact, the evaluation of the increased production times, related to the adoption of this multi-scanning strategy, is of fundamental importance to consider if the proposed process can be advantageously applied on an industrial scale.

Removal of Multi-heavy Metals from Simulated Wastewater using Hybrid Modified Carbonized Palm Shell and Rice Husk Adsorbents

It necessary to remove heavy metals from wastewater in order to comply with environmental regulations and for sake of human health and safety. The purposes of the present study was to prepare hybrid modified adsorbent from the carbonized palm shell and rice husk by physical treatment for the removal of 13 multi heavy metal component from simulated wastewater by single bed adsorption column. The Metals being studied are Cadmium, Chromium, Copper, Iron, Magnesium, Manganese, Lead, Lithium, Molybdenum, Nickel, Antimony, Vanadium and zinc. Six types of adsorbents were used for metal removal which are (100% BRH) adsorbent; (100% CPS) adsorbent , and four hybrids adsorbent prepared by mixing the blended rice husk and carbonized palm kernel shell with mixing ratios 20% , 40% , 60% , 80% wt Blended Rice Husk . The obtained results of the individual area under the graph analysis showed that cadmium, copper, lithium; vanadium elements were strongly adsorbed by hybrid adsorbents with achieved removal efficiency of 99.95%, 99.97%, 31.23%, and 89.58% with least area under the graph values of 3294.65, 2015.52, 118.231, and 115.18 respectively. As a conclusion, the mixing of blended rice husk and carbonized palm shell as hybrid adsorbent contributed to enhance the adsorption performance of cadmium, copper, lithium, vanadium, elements which demonstrated by less area under the graph values compared with pure carbonized palm shell and pure rice husk adsorbents.

Fracture mechanical and ablation behaviors of C/SiC–Cu3Si–Cu interpenetrating composites and their dependence on metal addition and interface thickness

The C/SiC–Cu3Si–Cu interpenetrating composites were prepared by the ceramization and metallization of carbon fiber reinforced carbon aerogel (C/CA) preforms. Fracture mechanical and ablation behaviors as well as their dependence on metal addition and PyC interface thickness were investigated. With the presence of metallic components, the C/SiC–Cu3Si–Cu composites show pseudo-plastic fracture, typical brittle-plastic mixed fracture, and then ladder-like fracture with the PyC interface thickness increasing due to the co-existence of ductile and brittle components, obviously different from the fracture of conventional ceramic matrix composites. The composite with 3.0 μm-thick interface has the highest flexural strength of 292.8 MPa due to the proper interfacial bond strength and residual compressive stress. The composite with 1.9 μm-thick interface has the highest work of fracture but relatively low fracture toughness due to the abundant modes of crack propagation. The anti-ablation property is deteriorated with increased PyC thickness due to the weakened transpiration cooling effect and reduced oxide scale quality. The composite with 0.9 μm-thick interface exhibits lower mass and linear ablation rates of 0.054 mg cm−2 s−1 and 0.018 μm s−1 after ablation at 2200 °C for 600 s, respectively. This work provides vital insights into the control of the overall performance of carbon fiber reinforced ceramic-metal matrix composites.

METAL DEBRIS RELEASE MAY BE UNDER-RECOGNIZED IN TOTAL ANKLE ARTHROPLASTY

Despite advancements, revision rates following total ankle replacement (TAR) are high in comparison to other total joint replacements. This explant analysis study aimed to investigate whether there was appreciable metal particulate debris release from various contemporary TARs by describing patterns of material loss. Twenty-eight explanted TARs (9 designs: 3 fixed and 6 mobile bearing), revised for any reason, were studied. The articulating surfaces of the metal tibial and talar components as well as the polyethylene insert were assessed for damage features using light microscopy. Based on the results of the microscopic analysis, scanning electron microscopy with energy dispersive X-ray spectroscopy was performed to determine the composition of embedded debris identified, as well as non-contacting 3D profilometry. Pitting, indicative of material loss, was identified on the articulating surfaces of 54% of tibial components and 96% of talar components. Bearing constraint was not found to be a factor, with similar proportions of fixed and mobile bearing metal components showing pitting. More cobalt-chromium than titanium alloy tibial components exhibited pitting (63% versus 20%). Significantly higher average surface roughness (Sa) values were measured for pitted areas in comparison to unpitted areas of these metal components (p&lt;0.05). Additionally, metallic embedded debris (cobalt-chromium likely due to pitting of the tibial and talar components or titanium likely from loss of their porous coatings) was identified in 18% of polyethylene inserts. The presence of hard 3rd body particles was also indicated by macroscopically visible sliding plane scratching, identified on 79% of talar components. This explant analysis study demonstrates that metal debris is released from the articulating surfaces and the coatings of various contemporary TARs, both fixed and mobile bearing. These findings suggest that metal debris release in TARs may be an under-recognised issue that should be considered in the study of painful or failed TAR moving forwards.