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Direct ink writing (DIW) offers significant advantages for efficient manufacturing of complex ceramic composite components. However, the mechanical properties of short carbon fiber-reinforced ceramic composites fabricated by DIW technology were not ideal, mainly be ascribed to the absence of a suitable coating on the fiber as an interface. In this work, C sf /ZrB 2 green bodies were printed by an optimized extrusion process using pyrolytic carbon-coated short carbon fibers (C sf). High-performance C sf /ZrB 2 –SiC composites were obtained through the infiltration and pyrolysis of SiC precursor six times. With increasing C sf content, the dimensional deviations decreased and the mechanical properties increased. When the C sf content was 30 vol%, the dimensional deviation of the C sf /ZrB 2 –SiC composite was less than −0.5 % in the X and Y directions and about −2 % in the Z direction. A marked increase in the flexural strength and fracture toughness of the composite was also obtained, reaching 275.0 MPa and 5.26 MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]

The mechanical properties of anisotropic carbons such as the pyrocarbon (pyC) matrices in C/C composites remain poorly documented, especially at elevated temperatures where these materials find most of their applications. We provide here a comprehensive molecular dynamics investigation of the high temperature – up to 4000 K – elastic behavior of six nanoscale pyC models in the context of fast temperature increases, not allowing for major structural modifications such as graphitization. We show that the structure of the most anisotropic and less disordered carbons, like the rough laminar (RL) pyC, is mostly not affected by annealing at the nanosecond timescale, aside from healing unstable defects like two-coordinated atoms at graphene edges. Conversely, highly disordered and less anisotropic carbons like the smooth laminar (SL) pyC show some significant rearrangements at grain boundaries and the development of some limited microporosity. The elastic constants of all highly anisotropic models moderately decrease with increasing temperature, somehow similarly to what is observed for graphite. Elastic constants of the SL pyC show a stronger decrease at high temperature, due to the decrease in density even though all models retain an important degree of stiffness up to 4000 K.

3D printing has emerged as a highly efficient process for fabricating electrodes in hydrogen evolution through water splitting, whereas metals are the most popular choice of materials in hydrogen evolution reactions (HER) due to their catalytic activity. However, current 3D printing solutions face challenges, including high cost, low surface area, and sub-optimal performance. In this work, we introduce metal-deposited 3D printed pyrolytic carbon (PyC) as a facile and cost-effective HER electrode. We adopt an integrated approach of resin 3D printing, pyrolysis, and electrochemical metal deposition. 3D printing of a resin and its subsequent pyrolysis led to 3D complex architectures of the conductive substrate, facilitating the electrochemical metal deposition and leading to layered 3D metal architecture. Both monolayers of metals (such as copper and nickel) and bi-metallic 3D PyC structures are demonstrated. Each metal layer thickness ranges from 6 to10 µm. The metal coatings, particularly the bi-metallic configurations, result in achieving significantly higher mechanical properties under compressive loading and improved electrical properties due to the synergistic contributions from each metal counterpart. The metalized PyC structures are further demonstrated for HER catalysts, contributing to the development of highly efficient and durable catalyst systems for hydrogen production. Among the materials studied here, Ni@Cu bimetallic 3D PyC electrodes are particularly well-suited, demonstrating a low HER overpotential value of 264 mV (100 mA/cm2, KOH (1 M)) with corresponding Tafel slopes of 107 mV/dec, with exceptional stability during a 10 h operation at a high applied current of −50 mA/cm2.

In this work, chopped carbon fibre reinforced silicon carbide (CCF/SiC) composites were fabricated by selective laser sintering (SLS) combined with reaction melt infiltration (RMI), using the SiC interface and pyrolytic carbon layer as a dual protection to protect the CCF from the erosion of molten silicon. The pyrolytic carbon layer encapsulates the CCF@SiC and the outer carbon preferentially reacts with silicon to form a β-SiC layer, which hinders the reaction of liquid silicon to CCF. Moreover, the fine-crystal β-SiC generated by the Si–C reaction optimizes the microstructure and enhances the mechanical performance of CCF/SiC composites. The CCF under the dual protection maintains its original high strength and high modulus, and the toughness of the CCF/SiC composites is significantly improved through the fibre debonding and fibre pull-out mechanism. The bending strength and toughness of CCF/SiC composites are 265.2 MPa and 3.5 MPa m1/2, respectively. The insights gained from this study contribute to a better understanding of microstructural engineering in SLS&RMI-fabricated CCF/SiC composites. This paves the way for future breakthroughs in composite material design and low-cost manufacturing for extreme environments. [ABSTRACT FROM AUTHOR]

Maskless UV photolithography is increasingly used, especially in research environments where low turn-around time for new designs improves productivity. Here, we fabricate pyrolytic carbon interdigitated microelectrodes with small interelectrode gaps, good adhesion to the carrier substrate, high surface area and excellent electrochemical properties using maskless UV photolithography with two negative epoxy-based photoresists, namely the commonly used SU-8 and the recently developed mr-DWL. The minimum realizable trench width in 15 μm thick photoresist films is 2.4 ± 0.15 μm for mr-DWL 5 and 3.1 ± 0.10 μm for SU-8 2035. After pyrolysis, the two resulting pyrolytic carbon materials show similar electrochemical properties. However, shrinkage during pyrolysis is significantly lower for mr-DWL compared to SU-8, which is beneficial for the fabrication of interdigitated microelectrodes. Furthermore, delamination of the electrodes during processing and operation is prevented due to the introduction of poly silicon adhesion structures. This work provides valuable insights into maskless UV lithography as well as into the pyrolytic carbon process to increase the yield, performance and productivity for fabrication of microelectrodes.

The accumulation of waste tires has resulted in very urgent environmental problems. Pyrolysis has been regarded as a green eco-friendly technology to deal with waste tires, and it is vital to make use of the pyrolysis carbon. Herein, we propose a new way to utilize pyrolysis carbon, to prepare carbon nanotubes with the help of ferrocene. The optimal preparation processes were determined by optimizing the parameters including the solvent, temperature, time, etc. The results of scanning electron microscopy and transmission electron microscopy evidenced the successful formation of carbon nanotubes. Meanwhile, the Brunauer–Emmett–Teller (BET) method and N2-adsorption showed that the yielded carbon nanotubes featured a large surface area and abundant pore structure in comparison with the pyrolytic carbon. Finally, the as-prepared carbon nanotubes were applied as the supports for Pt-based catalysts for the dehydrogenation of methylcyclohexane to produce hydrogen. The results showed that the Pt/carbon-nanotubes catalyst exhibited the highest conversion of methylcyclohexane (28.6%), stability, and hydrogen evolution rate (336.9 mmol/gPt/min) compared to the resulting Pt/commercial-activated-carbon (13.6% and 160.2 mmol/gPt/min) and Pt/pyrolytic-carbon catalysts (0.19% and 2.23 mmol/gPt/min). [ABSTRACT FROM AUTHOR]

To reduce the lattice oxygen content of Si3N4 green bodies, samples were prepared using an N,N-dimethylacrylamide (DMAA) system. The endothermic and exothermic peaks are related to the decomposition of organic matter and the reaction between pyrolytic carbon and impurity oxides in the sintering process. Multi-step heat preservation during the thermal degreasing process reduced the carbon content and defects. The α→β phase transformation and aspect ratio of grains changed from 89.2% to 4.84:1 at 1640 °C to 96.3% and 7.80:1 at 1700 °C, respectively. The relative density, hardness, fracture toughness, and thermal conductivity of the Si3N4 samples reached 98.5%, 1353 HV, 8.51 MPa·m1/2, and 97.1 W·m−1·K−1, respectively. Pyrolytic carbon can react with SiO2, which reduces the content of the glass phase in the green body and affects the dissolution and precipitation process and lattice oxygen content. In the structure of the Si3N4 sample, carbon particles with sizes of 100–500 nm and near-spherical shapes were observed. Intergranular-phase YMgSi2O5N was formed during the sintering process, which was conducive to improving the thermal conductivity. This article uses lower temperature and no pressure conditions to prepare Si3N4 ceramics, which can provide reference for batch and low-cost production.

The main purpose of these studies was to obtain carbon–carbon composites with a core built of carbon fibers and a matrix in the form of pyrolytic carbon (PyC), obtained by using the chemical vapor deposition (CVD) method with direct electrical heating of a bundle of carbon fibers as a potential electrode material for nerve tissue stimulation. The methods used for the synthesis of PyC proposed in this paper allow us, with the appropriate selection of parameters, to obtain reproducible composites in the form of rods with diameters of about 300 µm in 120 s (CF_PyC_120). To evaluate the materials, various methods such as scanning electron microscopy (SEM), scanning transmission electron microscope (STEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and tensiometer techniques were used to study their microstructural, structural, chemical composition, surface morphology, and surface wettability. Assessing their applicability for contact with nervous tissue cells, the evaluation of cytotoxicity and biocompatibility using the SH-SY5Y human neuroblastoma cell line was performed. Viability and cytotoxicity tests (WST-1 and LDH release) along with cell morphology examination demonstrated that the CF_PyC_120 composites showed high biocompatibility compared to the reference sample (Pt wire), and the best adhesion of cells to the surface among all tested materials. [ABSTRACT FROM AUTHOR]

While shoulder hemiarthroplasty is still used to treat young patients with shoulder pathology, the use of this procedure has substantially declined in recent years due to its significant complication profile. Glenoid wear with arthrosis is one of the major postoperative complications following shoulder hemiarthroplasty, and efforts to prevent this complication led many scientists to explore alternative weight-bearing surfaces on arthroplasty implants to decrease joint wear and improve patient outcomes. Pyrolytic carbon, or pyrocarbon, is a material that has better biocompatibility, survivorship, strength, and wear resistance compared to the materials used in traditional shoulder hemiarthroplasty. Pyrocarbon implants have been used in orthopedics for over 50 years; recently, their utility in shoulder hemiarthroplasty has garnered much interest. The purpose behind the use of pyrocarbon in shoulder hemiarthroplasty is to decrease the risk of progressive glenoid wear, especially in young active patients in whom joint preservation is important. Promising survivorship and outcomes have been demonstrated by recent studies, including limited glenoid wear following pyrocarbon hemiarthroplasty. Nevertheless, these clinical studies have been limited to relatively small case series with limited long-term follow-up. Accordingly, additional research and comparative studies need to be conducted in order to properly assess the therapeutic efficacy and value of pyrocarbon hemiarthroplasty.

Hydrogen production via methane pyrolysis is projected to have a key role in achieving net zero GHG emission by 2050. Carbon makes up to 75% by mass of the products of methane pyrolysis, indicating the importance of a thorough characterization to find its potential applications. A new approach is methane pyrolysis utilizing microwaves, where the carbon product serves as receptors for the microwave energy. In this method, methane decomposes and forms solid carbon. In this study, we evaluated the morphological and structural features of the produced carbon using SEM, XRD, XPS, Raman spectroscopy, and thermogravimetric analysis. The analysis indicates that the pyrolytic carbon produced through this process is highly pure and exhibits a semi-graphitic structure with localized defects. Additionally, the surface morphology of the carbon material was observed to possess a rough cauliflower-like texture. A thorough characterization of carbon revealed several potential applications, including the utilization of granular carbon in electric arc furnace for steelmaking, the feedstock for graphene production, and serving as an anode material in Na-ion batteries with further optimization of the production process. Safe sequestration of the carbon due to limited demand is feasible as the carbon is pure and oxygen-free, indicating its potential to remain unreacted over a long period after sequestration.

This review focuses on techniques for modifying the surface of carbon that is produced from sustainable resources, such as pyrolytic carbon. Many of these materials display high specific surface area and fine particle distribution. Functionalization of a surface is a commonly used approach in designing desired surface properties of the treated material while retaining its bulk properties. Usually, oxidation is a primary step in carbon functionalization. It can be performed as wet oxidation, which is a type of chemical surface modification. Wet oxidation is usually performed using nitric acid and hydrogen peroxide, as well as using hydrothermal and solvothermal oxidation. On the other side, dry oxidation is representative of physical surface modification. This method is based on corona discharge and plasma oxidation which are promising methods that are in line with green chemistry approaches. Whilst the oxidation of the carbon surface is a well-known method, other chemical modification techniques, including cycloadditions and various radical reactions on graphene layers, are presented as an alternative approach. Regarding secondary functionalization, coupling organosilanes to activated carbon is a common technique. Organosilanes bearing reactive groups present a bridge between inorganic species and polymer systems, e.g., epoxy and polyurethane resins, and facilitate the use of carbonaceous materials as reinforcing components for polymers and thermosetting resins. Along with the presented functionalization methods, this review also provides an overview of new applications of modified (i.e., functionalized) carbon materials, e.g., for the building industry, wastewater treatment, semiconducting materials and many more. [ABSTRACT FROM AUTHOR]

Carbon/carbon-polyimide composites were prepared by chemical vapor infiltration and vacuum-pressure impregnation curing process. Firstly, the carbon felt was deposited with pyrolytic carbon by chemical vapor infiltration method to prepare porous carbon/carbon materials with pyrolytic carbon contents of 7.33%(mass fraction, the same below), 14.55% and 22.00%, respectively. Then, through a specific impregnation curing process, the carbon/carbon-polyimide composites P1, P2 and P3 and the control group P0 without pyrolytic carbon were obtained in turn. Through SEM, linear expansion coefficient test and mechanical properties test, the effects of different pyrolytic carbon contents on the microstructure, average linear expansion coefficient and mechanical properties of carbon/carbon-polyimide composites were investigated. The results show that in the temperature range of 20-300℃, the XY-direction average linear expansion coefficients of P0, P1, P2 and P3 are between (0.67-0.79)×10-6℃-1, and the XY-direction average linear expansion coefficients of four groups are basically the same. The Z-direction average linear expansion coefficients of P1, P2 and P3 decrease by 41.6%, 41.8% and 24.1%, respectively compared with P0. Pyrolytic carbon significantly reduces the Z-direction average linear expansion coefficient of materials. The XY-direction compressive strengths of P0, P1, P2 and P3 are 243.91, 244.73, 216.65 MPa and 210.79 MPa, respectively, and the Z-direction compressive strengths are 269.22, 258.80, 246.68 MPa and 219.20 MPa, respectively. The compressive strength of P1 is equivalent to that of P0. The Z-direction bending strengths of P0, P1, P2 and P3 are 92.77, 77.11, 80.71 MPa and 86.06 MPa, respectively. Different pyrolytic carbon contents have different effects on the mechanical properties of materials. The lower pyrolytic carbon content can basically maintain compressive strength of materials, while the higher pyrolytic carbon content can basically maintain bending strength of materials.

Background: In vitro data demonstrate the potential benefits of the pyrocarbon as a bearing material against cartilage or bone. And pyrocarbon-free interposition arthroplasty has been used with positive outcomes for over 10 years for hand and wrist joint replacements. This study reports the midterm results of a Pyrocarbon Interposition Shoulder Arthroplasty (PISA) in primary and secondary glenohumeral osteoarthritis and in avascular osteonecrosis. Methods: This prospective noncontrolled, multicenter study included 67 consecutive patients who underwent PISA in France and Sweden. Results: A cohort of 48 patients, aged 50 ± 12 years, was available for clinical assessment at a mean follow-up of 67.6 ± 9.3 months. A favorable change was reported with a mean absolute Constant score improvement of 32 ± 20 points. The highest Constant score improvement was observed in patients with avascular osteonecrosis (42 ± 18 points; P ≤ .0001). Between the earliest and the latest follow-up, radiographic analyses revealed only 2 major glenoid erosions and 4 tuberosity thinnings and thus that 86.4% of 44 shoulders remained stable with no or minor radiologic evolutions. The survival rate was 84 % at 65 months of follow-up considering all causes of revision. Conclusion: The radiographic findings seem to confirm the interest of pyrocarbon in preserving bony surfaces. But the risk of tuberosity thinning suggests considering the use of PISA with caution in most degenerative glenohumeral joint pathologies, although the midterm outcomes highlight PISA as a suitable solution for patients presenting with posttraumatic osteonecrosis without malunion of the tuberosities and with an intact rotator cuff.

The accumulation of waste tires has resulted in very urgent environmental problems. Pyrolysis has been regarded as a green eco-friendly technology to deal with waste tires, and it is vital to make use of the pyrolysis carbon. Herein, we propose a new way to utilize pyrolysis carbon, to prepare carbon nanotubes with the help of ferrocene. The optimal preparation processes were determined by optimizing the parameters including the solvent, temperature, time, etc. The results of scanning electron microscopy and transmission electron microscopy evidenced the successful formation of carbon nanotubes. Meanwhile, the Brunauer–Emmett–Teller (BET) method and N2-adsorption showed that the yielded carbon nanotubes featured a large surface area and abundant pore structure in comparison with the pyrolytic carbon. Finally, the as-prepared carbon nanotubes were applied as the supports for Pt-based catalysts for the dehydrogenation of methylcyclohexane to produce hydrogen. The results showed that the Pt/carbon-nanotubes catalyst exhibited the highest conversion of methylcyclohexane (28.6%), stability, and hydrogen evolution rate (336.9 mmol/gPt/min) compared to the resulting Pt/commercial-activated-carbon (13.6% and 160.2 mmol/gPt/min) and Pt/pyrolytic-carbon catalysts (0.19% and 2.23 mmol/gPt/min).

In high temperature gas-cooled reactors (HTGRs), Tri-isotropic (TRISO)-coated fuel particles are employed as fuel. In the high burnup coated fuel particle, stress due to fission gas pressure and irradiation-induced pyrolytic carbon (PyC) shrinkage is introduced into the coating layers and consequently the stress could cause failure of coating layers under high burnup irradiation condition. A failure model has developed to predict failure fraction of TRISO-coated particle under high burnup irradiation. In the model, failure probability is strongly dependent on the irradiation characteristics of PyC. This paper describes the outline of the failure model and evaluation result of high burnup fuel irradiation experiment by the model.

Pyrocarbon disc interposition arthroplasty is an effective treatment for thumb base osteoarthritis. However, as with all implant techniques, the disc can (sub)luxate over time. The relationship between disc position, the experienced pain, and the necessity for revision surgery is not known. This study evaluated the effect of radiographic pyrocarbon disc position on the Michigan Hand Questionnaire (MHQ) outcome measurement. In addition, the correlation between disc position and other factors, including pain intensity, thumb strength, and occupation, was assessed. In this retrospective study, we included 136 patients (161 thumbs) with a mean follow-up of 6.7 years (range 3.3–11). Radiographs were scored on disc position and classified as 'well aligned' (Grade 1) up to 'luxated' (Grade 4). A database used for outcome measures included MHQ scores, pain intensity, satisfaction, thumb strength, range of motion, occupation, and hand dominance. In bivariate analyses, we assessed any association between disc position and outcome measurements. Eighty of the 136 implants (59%) were well-positioned (not displaced), 41% were (slightly) displaced (grade 2–3). No relationship existed between the degree of disc displacement and MHQ scores. Manual labor occupation was the only factor that correlated with more severe disc displacement. We could not detect any association between disc position and other outcome variables including pain intensity, thumb strength, or hand dominance. In conclusion, our study suggests that radiographic disc displacement has little clinical consequences. Future studies must assess if there is a causality between heavy mechanical stress to the CMC1 joint and luxation of the pyrocarbon disc over time. Level of evidence: IV Therapeutic—Retrospective case series. [ABSTRACT FROM AUTHOR]

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\nIMPACT STATEMENT3D printing has emerged as a highly efficient process for fabricating electrodes in hydrogen evolution through water splitting, whereas metals are the most popular choice of materials in hydrogen evolution reactions (HER) due to their catalytic activity. However Current 3D printing solutions face challenges, including high cost, low surface area, and sub-optimal performance. In this work, we introduce metal-deposited 3D printed pyrolytic carbon (PyC) as a facile and cost-effective HER electrode. We adopt an integrated approach of resin 3D printing, pyrolysis, and electrochemical metal deposition. 3D printing of a resin and its subsequent pyrolysis led to 3D complex architectures of the conductive substrate, facilitating the electrochemical metal deposition and leading to layered 3D metal architecture. Both monolayers of metals (such as copper and nickel), and bi-metallic 3D PyC structures are demonstrated. Each metal layer thickness ranges from 6 to10 µm. The metal coatings, particularly the bi-metallic configurations, result in achieving significantly higher mechanical properties under compressive loading and improved electrical properties due to the synergistic contributions from each metal counterpart. The metalized PyC structures are further demonstrated for HER catalysts, contributing to developing highly efficient and durable catalyst systems for hydrogen production. Among the materials studied here, Ni@Cu bimetallic 3D PyC electrodes are particularly well-suited, demonstrating low HER overpotential value 264 mV (100 mA/cm2, KOH (1 M)) with corresponding Tafel slopes of 107 mV/dec, with exceptional stability during a 10 h operation at a high applied current of -50 mA/cm2.This study introduces electrodeposited bilayer copper-nickel coated 3D printed pyrolytic carbon structures as cost-effective electrodes and demonstrates their performance as effective electrocatalysts in hydrogen evolution reaction applications. [ABSTRACT FROM AUTHOR]

Carbon's electrochemistry depends on its type and microstructure, and how these affect the electrode's electronic density of states. We demonstrate how pyrolysis of electro-mechanically stressed Polyacrylonitrile (PAN) nanofibers, infused with carbon nanotubes, will result in a unique graphitic electrode, which possesses enhanced and multifaceted electrochemical behavior. As corroborated by materials characterization, the microstructure of the stress-activated pyrolytic carbon (SAPC) characteristically contains a high proportion of disorders in the forms of edge planes and embedded heterogeneous nitrogen atoms. These disorders introduce a range of energy states near the Fermi level, yielding enhanced kinetics in the as-synthesized SAPC electrodes. A comprehensive electrochemical study of the SAPC electrode in surface sensitive ([Fe(CN)6]3-/4-), surface insensitive ([IrCl6]2-/3-), and adsorption sensitive (dopamine) redox probes demonstrates 5–14-fold increases in its heterogeneous electron transfer rate compared to regular PAN-based carbon electrodes. The fast kinetics of SAPC electrodes in adsorption sensitive analytes translates into its capability for simultaneous detection of dopamine, uric acid, and ascorbic acid. The results point to a new class of pyrolytic carbon electrodes with an attractive electrocatalytic capacity, geared toward electrochemical sensing platforms.

Carbon's electrochemistry depends on its type and microstructure, and how these affect the electrode's electronic density of states. We demonstrate how pyrolysis of electro-mechanically stressed Polyacrylonitrile (PAN) nanofibers, infused with carbon nanotubes, will result in a unique graphitic electrode, which possesses enhanced and multifaceted electrochemical behavior. As corroborated by materials characterization, the microstructure of the stress-activated pyrolytic carbon (SAPC) characteristically contains a high proportion of disorders in the forms of edge planes and embedded heterogeneous nitrogen atoms. These disorders introduce a range of energy states near the Fermi level, yielding enhanced kinetics in the as-synthesized SAPC electrodes. A comprehensive electrochemical study of the SAPC electrode in surface sensitive ([Fe(CN)6]3-/4-), surface insensitive ([IrCl6]2-/3-), and adsorption sensitive (dopamine) redox probes demonstrates 5–14-fold increases in its heterogeneous electron transfer rate compared to regular PAN-based carbon electrodes. The fast kinetics of SAPC electrodes in adsorption sensitive analytes translates into its capability for simultaneous detection of dopamine, uric acid, and ascorbic acid. The results point to a new class of pyrolytic carbon electrodes with an attractive electrocatalytic capacity, geared toward electrochemical sensing platforms.

The main purpose of these studies was to obtain carbon–carbon composites with a core built of carbon fibers and a matrix in the form of pyrolytic carbon (PyC), obtained by using the chemical vapor deposition (CVD) method with direct electrical heating of a bundle of carbon fibers as a potential electrode material for nerve tissue stimulation. The methods used for the synthesis of PyC proposed in this paper allow us, with the appropriate selection of parameters, to obtain reproducible composites in the form of rods with diameters of about 300 µm in 120 s (CF_PyC_120). To evaluate the materials, various methods such as scanning electron microscopy (SEM), scanning transmission electron microscope (STEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and tensiometer techniques were used to study their microstructural, structural, chemical composition, surface morphology, and surface wettability. Assessing their applicability for contact with nervous tissue cells, the evaluation of cytotoxicity and biocompatibility using the SH-SY5Y human neuroblastoma cell line was performed. Viability and cytotoxicity tests (WST-1 and LDH release) along with cell morphology examination demonstrated that the CF_PyC_120 composites showed high biocompatibility compared to the reference sample (Pt wire), and the best adhesion of cells to the surface among all tested materials.

A binary C/C brake disc (i.e., the test brake disc) was prepared with a C/C (pyrolytic carbon/resin carbon) matrix using modified natural gas as the carbon source through the isothermal chemical vapor infiltration (ICVI) process with a directed flow and the pressure impregnation carbonization (PIC) process with liquid-phase furfural acetone resin. The microstructural, mechanical, thermal, friction and wear properties of the test brake disc were comprehensively analyzed and compared with commercial ones. The results showed that the production efficiency of the test brake disc was 36% higher than that of the commercial ones, which were manufactured through a thermal-gradient chemical vapor infiltration (TCVI) process. The favorable mechanical and thermal properties of the test brake disc were comparable to the commercial ones. While the test brake disc had a more consistently rough laminar microstructure on the worn surface of the brake disc than the commercial ones, this avoided the annular grinding grooves on the worn surface after the braking tests. In addition, the test brake disc had a stable friction coefficient with a low dispersion coefficient of 3.90%, which would improve the friction stability of C/C brake discs used in aircrafts. [ABSTRACT FROM AUTHOR]

The solid-state persistent free radicals (PFRs) on pyrolytic carbons are attracting increasing attentions as they can directly degrade pollutants in water, while the redox behaviors and pathways over the PFRs during remediating coexisting aqueous pollutants have never been clarified. Herein, we discovered that the PFRs-induced remediation was an integrated process, where the original PFRs on the model pyrolytic carbon (TLRB) would first deliver electrons to the exterior heavy metals (HMs) forming derivative solid radicals (DSRs). The DSRs then acted as an electroactive bridge to further attract, stabilize, and degrade the surface-bound organic pollutants (OCs), eventually achieving a highly efficient removal of coexisting HMs and OCs. It is appealing to find that the HMs can trigger the in-situ upgrading of original PFRs to the DSRs by acting as an oxidant, rather than a pollutant. Such a peroxide-free regime alleviated the direct self-corrosion by radicals, thus promising a better effectiveness and recyclability of catalytic system. [Display omitted] • • Persistent free radicals (PFRs) coordinating with exterior heavy metals can form strong redox-active sites (DSRs). • The DSRs can directly degrade antibiotics into smaller molecular products without additional oxidant input. • The DSRs facilitated system durability through peroxide-free oxidation. [ABSTRACT FROM AUTHOR]

Surface modification is believed to be one of the most effective solutions to prevent thrombus formation associated with mechanical heart valves. Herein, we report, for the first time, the fabrication of a gradient cobblestone pattern on the pyrolytic carbon (PyC) surface aiming to improve its anti-thrombotic properties. A unique cobblestone pattern with gradient changing interspacing was generated on the PyC surface through laser etching. After coating with fluorosilane, the surface exhibited a water contact angle gradient ranging from 110 to 173°. The morphological and physicochemical properties, mechanical durability, drag reduction, in vitro anti-thrombotic properties, and in vivo biocompatibility of the surface were investigated to evaluate its potential as a heart valve replacement. It was found that the hydrophobic gradient wettability surface exhibited an excellent self-driving effect and mechanical durability, significantly reduced hemolysis rate and platelet adhesion, and prolonged coagulation time compared to the counterpart without gradient wettability. Furthermore, the gradient wettability surface demonstrated excellent in vivo biocompatibility. These findings are important for the design of artificial heart valves with improved anti-thrombotic performance. [Display omitted] [ABSTRACT FROM AUTHOR]

We report a novel hybrid method for fabricating high aspect ratio 3D pyrolytic carbon electrodes combining UV photolithography and additive manufacturing with commercially available SLA 3D printers and materials. By using a 3D printed chip holder, aligned 3D printing on a patterned silicon chip was possible. This allowed for the fabrication of cylindrical polymer micropillars with a height of 2173 ± 26 μm and a width of 316 ± 11 μm on SU-8 precursor structures defining the leads, contact pads and underlying 2D electrode prepared using UV lithography. Microfabrication of 3D structures with these dimensions is impossible to achieve with SU-8 photolithography alone. The hybrid polymer structures were converted into 3D carbon electrodes with high structural integrity using a 3-step pyrolysis process optimized for the specific 3D print resin. During this process, the micropillars shrunk to 30 ± 3% in height and 35 ± 1% in width of the polymer precursor structures, while maintaining the macroscopic shape and microscopic surface roughness. Electrochemical experiments confirmed that the pyrolytic carbon formed a monolithic conductive 3D electrode. The surface roughness contributed to a 17 ± 5% increase in electroactive surface area compared to the geometrical surface area of the micropillars.

The study investigated the morphology, microstructure, structure, texture, and mechanical properties of heat-treated at 1600 °C and 2000 °C pyrolytic carbon (PyC) deposited from methane using various methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy, and ultrasonic dynamic measurements of Young's modulus. The PyC was synthesised at 1100 °C using a chemical vapour deposition (CVD) method with direct electrical heating of the two types of carbon fibres (CFs). The results showed that the PyC had a low- and medium-texture (LT and MT PyC). Analysis of the graphitization trajectory allowed the determination of structural changes in the material as a function of temperature, including the growth of crystallites and an increase in the crystallinity proportion without the significant rearrangement within PyC. The crystallite size and the number of interstitial defects has increased with temperature that controlled mechanical properties. Therefore, based on the results obtained, the most suitable composites for further research in the context of electrodes for stimulation of nervous tissue were obtained at the temperature of their synthesis, i.e. at 1100 °C. [Display omitted] • The matrix area distinguished low-textural (LT) and medium-textural (MT) PyC. • The surface can be significant during the deposition only of initial PyC layers. • Amorphous forms may evolve towards turbostratic ones. • Thermodynamically, the organising process may occur but is kinetically limited. • The mechanism of the graphitization trajectory was the formed domains growth. [ABSTRACT FROM AUTHOR]

This review focuses on techniques for modifying the surface of carbon that is produced from sustainable resources, such as pyrolytic carbon. Many of these materials display high specific surface area and fine particle distribution. Functionalization of a surface is a commonly used approach in designing desired surface properties of the treated material while retaining its bulk properties. Usually, oxidation is a primary step in carbon functionalization. It can be performed as wet oxidation, which is a type of chemical surface modification. Wet oxidation is usually performed using nitric acid and hydrogen peroxide, as well as using hydrothermal and solvothermal oxidation. On the other side, dry oxidation is representative of physical surface modification. This method is based on corona discharge and plasma oxidation which are promising methods that are in line with green chemistry approaches. Whilst the oxidation of the carbon surface is a well-known method, other chemical modification techniques, including cycloadditions and various radical reactions on graphene layers, are presented as an alternative approach. Regarding secondary functionalization, coupling organosilanes to activated carbon is a common technique. Organosilanes bearing reactive groups present a bridge between inorganic species and polymer systems, e.g., epoxy and polyurethane resins, and facilitate the use of carbonaceous materials as reinforcing components for polymers and thermosetting resins. Along with the presented functionalization methods, this review also provides an overview of new applications of modified (i.e., functionalized) carbon materials, e.g., for the building industry, wastewater treatment, semiconducting materials and many more.

The rational design and construction of transition metal catalysts with high performance and low cost are imperative for liquid hydrogen storage materials. In this study, carbon-stabilised ultrathin Co-doped Co x O y nanofilms (C–Co/Co x O y NFs) are prepared by an ionic liquid/water interface strategy for sodium borohydride (NaBH 4) hydrolysis. Owing to its two-dimensional (2D) NFs structure and the protective effect of the composite carbon, C–Co/Co x O y NFs catalyst exhibits remarkable activity and durability in hydrogen generation from NaBH 4 hydrolysis. The hydrogen generation rate achieves 8055 mL·min−1·g Co −1 and the catalyst can be recycled more than 20 times, surpassing most of the reported metal-based catalysts under comparable conditions. This excellent 2D Co-based NFs structure with numerous active sites assists in the activation of NaBH 4 and water molecules to promote hydrogen production. These results provide an in-depth understanding of hydrogen generation from NaBH 4 hydrolysis, as well as an effective strategy for rationally designing 2D NFs catalysts with high activity and durability. [Display omitted] • Stabilized cobalt-based nanofilm exhibit outstanding activity for NaBH 4 hydrolysis • Cobalt-based nanofilm assists the activation of NaBH 4 and water molecules. • Carbon prevent the formation of Co(OH) 2 and avoid the loss of active Co The design and construction of transition metal catalysts with high performance and low-cost characteristics are imperative for liquid hydrogen storage materials. In this study, we prepared ultrathin carbon-stabilized Co-doped Co x O y nanofilms (C–Co/Co x O y NFs) using an ionic liquid/water interface strategy for sodium borohydride (NaBH 4) hydrolysis. Owing to its two-dimensional (2D) NF structure and the protective effects of the composite carbon, the C–Co/Co x O y NF catalyst exhibited remarkable activity and durability for hydrogen generation from NaBH 4 hydrolysis. The hydrogen generation rate reached 8055 mL·min−1·g Co −1 (5106 mL·min−1·g Cat −1) and the catalyst could be recycled more than 20 times, surpassing most reported metal-based catalysts under comparable conditions. In addition, the exceptional 2D Co-based NF structures, with numerous active sites, assisted in the activation of NaBH 4 and water molecules, promoting hydrogen production. Thus, these results provided an in-depth understanding of hydrogen generation from NaBH 4 hydrolysis, and an effective strategy for rationally designing highly active and durable 2D NF catalysts. [ABSTRACT FROM AUTHOR]

Based on experiments aiming at depositing pyrolytic carbon onto carbon nanotubes by means of a chemical vapor deposition (CVD) process at 1400 °C, the work we report here demonstrates that the deposition involves the transient formation of a liquid phase (here organic), and that wetting physics is still able to apply in spite of the high temperature and the nanoscale, i.e., far beyond the condition range usually investigated. This was unexpected, because the high temperature makes all the physical and chemical processes involved transitory, including the fact that the liquid turns itself into solid carbon because of the ongoing carbonization process. The observations provide an estimate of the time scales of the involved processes, as they have to be short enough to complete in spite of the high temperature conditions. From a practical point of view, as the resulting material is a solid, all-graphenic carbon, the work demonstrates that using wetting physics in high temperature CVD can be a way to dramatically modify the surface energetics and the nano/microscale morphology of carbon nanofilaments. The statement is assumed to also apply to other chemical systems.

After implanting pyrocarbon into human body, patients will have symptoms such as inflammation and thromboembolism, so they must take anticoagulant drugs for life. To improve the blood compatibility of the pyrolytic carbon, a nanosecond laser was used to prepare microstructures on the surface of the pyrolytic carbon. The effects of laser power, scanning times and scanning spacing on the wettability of pyrolytic carbon are discussed. At the same time, dynamic coagulation, hemolysis rate and platelet adhesion test were performed on smooth samples and samples prepared at different scanning spacing. The results show that the contact angle of the modified parallel grating pyrocarbon surface is larger than that of the smooth sample. As the scanning spacing increases, the contact angle increases and then decreases, and the higher the contact angle, the better the blood compatibility of the sample. When the laser power is 27.5 W, the scanning times is 6, and the scanning distance is 90 µm, the contact angle of the sample reaches the best, which is 153.21°; the number of platelets adhering to the surface was the least, about 2, and mostly in an unactivated state; the anticoagulant effect is also the best, and the surface hemolysis is the lowest, which is only 0.88%. [ABSTRACT FROM AUTHOR]

Carbon fiber-SiC nanowire-hydroxyapatite-pyrolytic carbon composites (CHS) composed of carbon fiber, hydroxyapatite (HA), SiC nanowires (SiCnws) and pyrolytic carbon (PyC) were prepared by sol-gel, heat treating, electrochemical deposition (ECD) and isothermal chemical vapor infiltration (ICVI) for bone implant application. The morphology, microstructure and the composition of CHS were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The mechanical properties of CHS were tested and compared with the traditional bone implant materials. The in-vitro bioactivity was evaluated by testing the cell morphology, cell proliferation and cell differentiation. The results show that SiCnws and HA are distributed uniformly inside the CHS. SiCnws are attached on the carbon fibers. The diameter of the SiCnws is around 250 nm and the length is more than 100 μm. HA could grow on the surface of both SiCnws and carbon fibers, forming a brush shape. The flexural strength, shear strength, out-of-plane and in-of-plane compressive strength of CHS are 127 MPa, 90 MPa, 169 MPa and 213 MPa, respectively. The elastic modulus of CHS is 7.2 GPa. The mechanical properties of CHS are similar to those of cortical bone. In-vitro cell test shows that CHS has excellent cell proliferation and cell differentiation. CHS possessing good mechanical and biological performances may have potential to be applied for bone implant materials. [ABSTRACT FROM AUTHOR]

To improve electrical conductivity of the carbon-based pantograph strip, a sliding contact material of pyrolytic carbon (PyC) coated-copper foam/carbon composite was fabricated by chemical vapor deposition technology, followed by densifying processes of furan resin impregnation and carbonization. Morphology, electrical conductivity, wear and friction behavior of the composites are investigated to clarify the effect of PyC thickness (from 0 μm to 280 μm) on tribological behaviors and current transfer characteristic. The results show that there is a good interface combination between copper foam and resin carbon matrix in the composites after the improvement of interface wettability by inserting PyC layer. The composite has great advantages in electrical conductivity and density due to the copper foam and PyC layer with three-dimensional structure. With increasing the PyC thickness, both electrical conductivity and wear resistance of the composite have steadily increasing tendency, but friction coefficient has no obvious change. In addition, an analytical model is developed to explore current transfer mechanisms of the PyC-copper foam/carbon composite, and the theoretical predictions are in agreement with the experimental observations, in term of electrical conductivity and porosity of composite preform. [ABSTRACT FROM AUTHOR]

While shoulder hemiarthroplasty is still used to treat young patients with shoulder pathology, the use of this procedure has substantially declined in recent years due to its significant complication profile. Glenoid wear with arthrosis is one of the major postoperative complications following shoulder hemiarthroplasty, and efforts to prevent this complication led many scientists to explore alternative weight-bearing surfaces on arthroplasty implants to decrease joint wear and improve patient outcomes. Pyrolytic carbon, or pyrocarbon, is a material that has better biocompatibility, survivorship, strength, and wear resistance compared to the materials used in traditional shoulder hemiarthroplasty. Pyrocarbon implants have been used in orthopedics for over 50 years; recently, their utility in shoulder hemiarthroplasty has garnered much interest. The purpose behind the use of pyrocarbon in shoulder hemiarthroplasty is to decrease the risk of progressive glenoid wear, especially in young active patients in whom joint preservation is important. Promising survivorship and outcomes have been demonstrated by recent studies, including limited glenoid wear following pyrocarbon hemiarthroplasty. Nevertheless, these clinical studies have been limited to relatively small case series with limited long-term follow-up. Accordingly, additional research and comparative studies need to be conducted in order to properly assess the therapeutic efficacy and value of pyrocarbon hemiarthroplasty.

Graphene-based cones with nanosized apex can be obtained by means of a high temperature pyrolytic carbon deposition process using methane and hydrogen as gaseous feedstock and single carbon nanotubes as deposition substrates. Aside the cones, micrometer-sized carbon beads or fibre segments are deposited meanwhile which are a key morphological component for allowing handling and mounting the carbon cones and then using them for various applications. Based on both the literature dealing with pyrolytic carbon deposition processes and experimental observations, a peculiar deposition mechanism is proposed, involving the transient formation of pitch-like liquid phase droplets which deposit onto the individual carbon nanotubes. In this picture, it is believed that a key parameter is the diameter ratio for the droplets and the nanotubes, respectively. The cone concentric texture and perfect nanotexture are shown by high resolution transmission electron microscopy, which allows interesting mechanical and conducting properties to be predicted. Correspondingly, applications of the carbon nanocones as electron emitters for cold-field electron sources on the one hand, and as probes for various modes of near-field microscopy on the other hand, have been tested. [ABSTRACT FROM AUTHOR]

With common manufacturing approaches it is impossible to fabricate complex free-standing 3D carbon electrodes with well-defined geometrical structures. Here, a novel and straightforward approach to generate free-standing 3D carbon structures is developed based on stereolithography printing followed by pyrolysis. By controlling the design, printing and pyrolysis parameters, complex 3D pyrolytic carbon electrodes with minimal features of less than 100 μm and excellent structural uniformity were fabricated. The effects of carbonization condition (kinetics of thermal degradation) and final pyrolysis temperature on the physicochemical properties of the derived carbons were examined. The results show that the microstructural and electrochemical properties of the electrodes are more dependent on the carbonization condition than the pyrolysis temperature. Approximately 20% higher cyclic voltammetry peak currents (Ip) and 31% lower charge transfer resistance (Rct) were recorded for the kinetically-fast carbonized electrodes, compared to the gradually (kinetically-controlled) carbonized ones, which is ascribed to their relatively higher specific surface area measured by N2 adsorption/desorption technique. Moreover, great flexibility to construct electrodes with different architectures, excellent electrochemical stability and repeatability was observed. Overall, we believe that the proposed approach opens up new possibilities for the simple preparation of free-standing 3D carbon electrodes for a broad spectrum of applications.

The generation IV nuclear reactors Tri-structural isotropic (TRISO) fuel suffer failure due to internal pressure generation, corrosion by fission products and kernel migration under temperature gradient. An innovative fuel particle design was conceptualized and realized for the first time in literature by embedding multi-wall carbon nanotube (MWCNT) into porous buffer pyrolytic carbon layer (B.PyC) of TRISO particle to address above issues. MWCNT embedded in B.PyC was obtained by sequential coating using novel chemical vapor deposition reactor. Scanning electron microscopy shows ~15 μm uniformly dispersed MWCNT into B.PyC layer. Transmission electron microscopy and Raman Spectroscopy analysis of the deposited CNT revealed to be multi walled with good crystalline. Results of small angle scattering technique of the composite layer using X-ray and neutrons (SAXS/SANS) reveal better pore structure and could pave new vistas for TRISO fuel development. Intrinsic MWCNT features offer immense potential to mitigate various shortcoming of TRISO particle during actual Generation IV nuclear reactor operation. [ABSTRACT FROM AUTHOR]

One‐dimensional (1D) hafnium carbide nanowires (HfCnws) were grown in situ on carbon fibers (CFs) via a Ni‐assisted pyrolysis method of organometallic polymer precursor. Scanning electron microscopy (SEM), transmission electron microscope (TEM), polarized‐light optical microscopy (PLM), and Raman were used to analyze the effect of HfCnws on the microstructure of pyrolytic carbon (PyC). The specific heat capacity (HC), thermal diffusivity (TD), thermal conductivity (TC), and coefficient of thermal expansion (CTE) of HfCnws‐C/C composites were also investigated. Results show that HfCnws wrapped by carbon nanosheet were successfully synthesized. The diameter of HfCnws is about 30 nm and the thickness of carbon nanosheet is about 10 nm, which could induce the formation of isotropic (ISO) PyC. After introducing HfCnws, the TD and CTE of HfCnws‐C/C composites were increased. Ni2HfCnws‐C/C composites show a higher TC and TD, and the CTE increased with the increasing content of HfCnws. [ABSTRACT FROM AUTHOR]

Under tritium production method using a high-temperature gas-cooled reactor loaded Li compound, Li compound has to be coated by ceramic materials in order to suppress the spreading of tritium to the whole reactor. Pyrolytic carbon (PyC) is a candidate of the coating material because of its high resistance for gas permeation. In this study, hydrogen permeation experiments using a PyC-coated isotropic graphite tube were conducted and hydrogen diffusivity, solubility and permeability were evaluated. Tritium permeation behavior through PyC-coated Li compound particles was simulated by using obtained data. Hydrogen permeation flux through PyC in a steady state is proportional to the hydrogen pressure and is larger than that through Al2O3 which is also candidate coating material. However, total tritium leak within the supposed reactor operation period through the PyC-coated Li compound particles is lower than that through the Al2O3-coated ones because the hydrogen absorption capacity in PyC is considerably larger than that in Al2O3.