High-performance grinding of ceramic matrix composites

Ceramic matrix composites(CMCs)are highly promising materials for the next generation of aero-engines.However,machining of CMCs suffers from low efficiency and poor surfacefinish,which presents an obstacle to their wider application.To overcome these problems,this study investigates high-efficiency deep grinding of CMCs,focusing on the effects of grinding depth.The results show that both the sur-face roughness and the depth of subsurface damage(SSD)are insensitive to grinding depth.The material removal rate can be increased sixfold by increasing the grinding depth,while the surface roughness and SSD depth increase by only about 10%.Moreover,it is found that the behavior of material removal is strongly dependent on grinding depth.As the grinding depth is increased,fibers are removed in smaller sizes,with thefiber length in chips being reduced by about 34%.However,too large a grinding depth will result in blockage by chip powder,which leads to a dramatic increase in the ratio of tangential to normal grinding forces.This study demonstrates that increasing the depth of cut is an effective approach to improve the machining efficiency of CMCs,while maintaining a good surfacefin-ish.It provides the basis for the further development of high-performance grinding methods for CMCs,which should facilitate their wider application.

Laser‑Induced and MOF‑Derived Metal Oxide/Carbon Composite for Synergistically Improved Ethanol Sensing at Room temperature

Advancements in sensor technology have significantly enhanced atmospheric monitoring.Notably,metal oxide and carbon(MO_(x)/C)hybrids have gained attention for their exceptional sensitivity and room-temperature sensing performance.However,previous methods of synthesizing MO_(x)/C composites suffer from problems,including inhomogeneity,aggregation,and challenges in micropatterning.Herein,we introduce a refined method that employs a metal–organic framework(MOF)as a precursor combined with direct laser writing.The inherent structure of MOFs ensures a uniform distribution of metal ions and organic linkers,yielding homogeneous MO_(x)/C structures.The laser processing facilitates precise micropatterning(<2μm,comparable to typical photolithography)of the MO_(x)/C crystals.The optimized MOF-derived MO_(x)/C sensor rapidly detected ethanol gas even at room temperature(105 and 18 s for response and recovery,respectively),with a broad range of sensing performance from 170 to 3,400 ppm and a high response value of up to 3,500%.Additionally,this sensor exhibited enhanced stability and thermal resilience compared to previous MOF-based counterparts.This research opens up promising avenues for practical applications in MOF-derived sensing devices.

Ti_(3)C_(2)T_(x) MXene/carbon composites for advanced supercapacitors:Synthesis,progress,and perspectives

MXenes are a family of two-dimensional(2D)layered transition metal carbides/nitrides that show promising potential for energy storage applications due to their high-specific surface areas,excellent electron conductivity,good hydrophilicity,and tunable terminations.Among various types of MXenes,Ti_(3)C_(2)T_(x) is the most widely studied for use in capacitive energy storage applications,especially in supercapacitors(SCs).However,the stacking and oxidation of MXene sheets inevitably lead to a significant loss of electrochemically active sites.To overcome such challenges,carbon materials are frequently incorporated into MXenes to enhance their electrochemical properties.This review introduces the common strategies used for synthesizing Ti_(3)C_(2)T_(x),followed by a comprehensive overview of recent developments in Ti_(3)C_(2)T_(x)/carbon composites as electrode materials for SCs.Ti_(3)C_(2)T_(x)/carbon composites are categorized based on the dimensions of carbons,including 0D carbon dots,1D carbon nanotubes and fibers,2D graphene,and 3D carbon materials(activated carbon,polymer-derived carbon,etc.).Finally,this review also provides a perspective on developing novel MXenes/carbon composites as electrodes for application in SCs.

Electrostatic Interaction-directed Construction of Hierarchical Nanostructured Carbon Composite with Dual Electrical Conductive Networks for Zinc-ion Hybrid Capacitors with Ultrastability

Metal-organic framework(MOF)-derived carbon composites have been considered as the promising materials for energy storage.However,the construction of MOF-based composites with highly controllable mode via the liquid-liquid synthesis method has a great challenge because of the simultaneous heterogeneous nucleation on substrates and the self-nucleation of individual MOF nanocrystals in the liquid phase.Herein,we report a bidirectional electrostatic generated self-assembly strategy to achieve the precisely controlled coatings of single-layer nanoscale MOFs on a range of substrates,including carbon nanotubes(CNTs),graphene oxide(GO),MXene,layered double hydroxides(LDHs),MOFs,and SiO_(2).The obtained MOF-based nanostructured carbon composite exhibits the hierarchical porosity(V_(meso)/V_(micro)∶2.4),ultrahigh N content of 12.4 at.%and"dual electrical conductive networks."The assembled aqueous zinc-ion hybrid capacitor(ZIC)with the prepared nanocarbon composite as a cathode shows a high specific capacitance of 236 F g^(-1)at 0.5 A g^(-1),great rate performance of 98 F g^(-1)at 100 A g^(-1),and especially,an ultralong cycling stability up to 230000 cycles with the capacitance retention of 90.1%.This work develops a repeatable and general method for the controlled construction of MOF coatings on various functional substrates and further fabricates carbon composites for ZICs with ultrastability.

Protective Graphite Coating for Two-Dimensional Carbon/Carbon Composites

Two-dimensional carbon/carbon(2D C/C)composites are a special class of carbon/carbon composites,generally obtained by combining resin-impregnated carbon fiber clothes,which are then cured and carbonized.This study deals with the preparation of a protective coating for these materials.This coating,based on graphite,was prepared by the slurry method.The effect of graphite and phenolic resin powders with different weight ratios was examined.The results have shown that the coating slurry can fill the pores and cracks of the composite surface,thereby densifying the surface layer of the material.With the increase of the graphite powder/phenolic resin weight ratio,the coating density is enhanced while the coating surface flatness decreases;moreover,the protective ability of coating against erosion first increases(from 1:3 to 2:2)and then decreases(from 2:2 to 3:1).When the weight ratio is about 1:1,the coating for 2D C/C composites exhibits the best erosion resistance,which greatly aids these materials during gas quenching.In this case,the erosion rate is decreased by approximately 41.5%at the impact angle of 30°and 52.3%at normal impact,respectively.This can be attributed to the ability of the coating slurry to infiltrate into the substrate,thereby bonding the fibers together and increasing the compactness of the 2D C/C composites.

Flexible piezoresistive pressure sensor based on a graphene-carbon nanotube-polydimethylsiloxane composite

Flexible sensors are used widely in wearable devices, specifically flexible piezoresistive sensors, which are common and easy to manipulate.However, fabricating such sensors is expensive and complex, so proposed here is a simple fabrication approach involving a sensor containing microstructures replicated from a sandpaper template onto which polydimethylsiloxane containing a mixture of graphene and carbon nanotubes is spin coated. The surface morphologies of three versions of the sensor made using different grades of sandpaper are observed, and the corresponding pressure sensitivities and linearity and hysteresis characteristics are assessed and analyzed. The results show that the sensor made using 80-mesh sandpaper has the best sensing performance. Its sensitivity is 0.341 kPa-1in the loading range of 0–1.6 kPa, it responds to small external loading of 100 Pa with a resistance change of 10%, its loading and unloading response times are 0.126 and 0.2 s, respectively,and its hysteresis characteristic is ~7%, indicating that the sensor has high sensitivity, fast response, and good stability. Thus, the presented piezoresistive sensor is promising for practical applications in flexible wearable electronics.

Multi-scale design of silicon/carbon composite anode materials for lithium-ion batteries:A review

Silicon/carbon composites,which integrate the high lithium storage performance of silicon with the exceptional mechanical strength and conductivity of carbon,will replace the traditional graphite electrodes for high-energy lithium-ion batteries.Various strategies have been designed to synthesize silicon/carbon composites for tackling the issues of anode pulverization and poor stability in the anodes,thereby improving the lithium storage ability.The effect of the regulation method at each scale on the final negative electrode performance remains unclear.However,it has not been fully clarified how the regulation methods at each scale influence the final anode performance.This review will categorize the materials structure into three scales:molecular scale,nanoscale,and microscale.First,the review will examine modification methods at the molecular scale,focusing on the interfacial bonding force between silicon and carbon.Next,it will summarize various nanostructures and special shapes in the nanoscale to explore the construction of silicon/carbon composites.Lastly,the review will provide an analysis of microscale control approaches,focusing on the formation of composite particle with micron size and the utilization of micro-Si.This review provides a comprehensive overview of the multi-scale design of silicon/carbon composite anode materials and their optimization strategies to enhance the performance of lithium-ion batteries.

Cooperative composites anchored with single atom Pb and carbon confined PbO nanoparticles for superior lead-carbon batteries

The mitigation of sulphation and parasitic hydrogen evolution is considered as prominent research emphasis for the development of lead-carbon batteries(LCBs)in large-scale energy storage applications.Here,cooperative Pb-C composites consisting of single atom Pb and carbon-encapsulated PbO nanoparticles were prepared by freeze-drying technique and pyrolytic reduction to address above obstacles.The innovative use of Pb^(2+)to cross-link sodium alginate enabled a uniform distribution of Pb in the composites,generating Pb-C-PbO three-phase heterostructure.Experimental analysis and theoretical calculations revealed the synergistic interactions between single-atom Pb and PbO nanoparticles in suppressing parasitic hydrogen evolution and promoting the adsorption of Pb atoms.The presence of monatomic Pb and PbO enhanced the affinity of the composites for the negative active materials and facilitated the transformation of the active materials from bulk into spherical shapes to enhance the specific surface area,thereby counteracting sulphation.Through the coordinated integration of various functionalities offered by Pb@C-x,the cycle life of the battery at HRPSoC reaches 7025 cycles,which is two times for LCB with pure carbon materials.Additionally,the discharge capacity increased from 3.52 to 3.79 Ah.This study provides substantial insights into the construction of Pb-C composites for LCBs to inhibit negative sulphation and hydrogen evolution.

Simultaneously enhanced thermal conductivity and mechanical performance of carbon nanotube reinforced ZK61 matrix composite

Alloying seriously deteriorates the thermal conductivity of magnesium(Mg)alloys,thus,restricts their applications in the fields of computer,communication,and consumer products.In order to improve the thermal conductivity of Mg alloys,adding carbon nanotube(CNT)combined with aging treatment is proposed in this work,i.e.fabricating the D-CNT(a kind of dispersed CNT)reinforced ZK61 matrix composite via powder metallurgy,and conducting aging treatment to the composite.Results indicate the as-aged ZK61/0.6 wt.%D-CNT composite achieved an excellent thermal conductivity of 166 W/(mK),exhibiting 52.3%enhancement in comparison with matrix,as well as tensile yield strength of 321 MPa,ultimate tensile strength of 354 of MPa,and elongation of 14%.The simultaneously enhanced thermal conductivity and mechanical performance are mainly attributed to:(1)the embedded interface of the D-CNT with matrix and(2)the coherent interface of precipitates with matrix.It is expected the current work can provide a clue for devising Mg matrix composites with integrated structural and functional performances,and enlarge the current restricted applications of Mg alloys.

Indispensable gutter layers in thin-film composite membranes for carbon capture

Industrial thin-film composite(TFC)membranes achieve superior gas separation properties from high-performance selective layer materials,while the success of membrane technology relies on high-performance gutter layers to achieve production scalability and low-cost manufacturing.However,the current literature predominantly focuses on the design of polymer architectures to obtain high permeability and selectivity,while the art of fabricating gutter layers is usually safeguarded by industrial manufacturers and appears lackluster to academic researchers.This is the first report aiming to provide a comprehensive and critical review of state-of-the-art gutter layer materials and their design and modification to enable TFC membranes with superior separation performance.We first elucidate the importance of the gutter layer on membrane performance through modeling and experimental results.Then various gutter layer materials used to obtain high-performance composite membranes are critically reviewed,and the strategies to improve their compatibility with the selective layer are highlighted,such as oxygen plasma treatment,polydopamine deposition,and surface grafting.Finally,we present the opportunities of the gutter layer design for practical applications.

Numerical study of directional heat transfer in composite materials via controllable carbon fiber distribution

Carbon fiber reinforced polyamide 12(CF/PA12),a new material renowned for its excellent mechanical and thermal properties,has drawn significant industry attention.Using the steady-state research to heat transfer,a series of simulations to investigate the heat transfer properties of CF/PA12 were conducted in this study.Firstly,by building two-and three-dimensional models,the effects of the porosity,carbon fiber content,and arrangement on the heat transfer of CF/PA12 were examined.A validation of the simulation model was carried out and the findings were consistent with those of the experiment.Then,the simulation results using the above models showed that within the volume fraction from 0% to 28%,the thermal conductivity of CF/PA12 increased greatly from 0.0242 W/(m·K)to 10.8848 W/(m·K).The increasing porosity had little influence on heat transfer characteristic of CF/PA12.The direction of the carbon fiber arrangement affects the heat transfer impact,and optimal outcomes were achieved when the heat flow direction was parallel to the carbon fiber.This research contributes to improving the production methods and broadening the application scenarios of composite materials.

Effect of Accelerated Aging Temperature under Artificial Seawater on the Properties of Carbon Fiber/Epoxy Composites and the Erosion Mechanism

In order to explore the effect of artificial accelerated aging temperature on the performance of carbon fiber/epoxy resin composites,we used artificial seawater as the aging medium,designed the aging environment of seawater at different temperatures under normal pressure,and studied the aging behavior of carbon fiber/epoxy composites.The infrared spectroscopy results show that,with the increase of aging temperature,the degree of hydrolysis of the composite is greater.At the same time,after 250 days of aging of artificial seawater at regular temperature,40 and 60 ℃,the moisture absorption rates of composite materials were 0.45%,0.63%,and 1.05%,and the retention rates of interlaminar shear strength were 91%,78%,and 62%,respectively.It is shown that the temperature of the aging environment has a significant impact on the hygroscopic behavior and mechanical properties of the composite,that is,the higher the temperature,the faster the moisture absorption of the composite,and the faster the decay of the mechanical properties of the composite.

Carbon Fiber Breakage Mechanism in Aluminum(Al)/Carbon Fibers(CFs) Composite Sheet during Accumulative Roll Bonding(ARB) Process

We put forward a method of fabricating Aluminum(Al)/carbon fibers(CFs) composite sheets by the accumulative roll bonding(ARB) method. The finished Al/CFs composite sheet has CFs and pure Al sheets as sandwich and surface layers. After cross-section observation of the Al/CFs composite sheet, we found that the CFs discretely distributed within the sandwich layer. Besides, the tensile test showed that the contribution of the sandwich CFs layer to tensile strength was less than 11% compared with annealed pure Al sheet. With ex-situ observation of the CFs breakage evolution with-16%,-32%, and-45% rolling reduction during the ARB process, the plastic instability of the Al layer was found to bring shear damages to the CFs. At last, the bridging strengthening mechanism introduced by CFs was sacrificed. We provide new insight into and instruction on Al/CFs composite sheet preparation method and processing parameters.

Study of the Diffusion Behavior of Seawater Absorption in Multi-Walled Carbon Nanotubes/Halloysite Nanotubes Hybrid Nanofillers Modified Epoxy-Based Glass/Carbon Fiber Composites

In the maritime industry, cost-effective and lightweight Fiber Reinforced Polymer (FRP) composites offer excellent mechanical properties, design flexibility, and corrosion resistance. However, their reliability in harsh seawater conditions is a concern. Researchers address this by exploring three approaches: coating fiber surfaces, hybridizing fibers and matrices with or without nanofillers, and interply rearrangement. This study focuses on evaluating the synergistic effects of interply rearrangement of glass/carbon fibers and hybrid nanofillers, specifically Multi-walled carbon nanotubes (MWCNT) and Halloysite nanotubes (HNT). The aim is to enhance impact properties by minimizing moisture absorption. Hybrid nanocomposites with equal-weight proportions of two nanofillers: 0 wt.%, 1 wt.%, and 2 wt.% were exposed to seawater for 90 days. Experimental data was subjected to modelling through the application of Predictive Fick’s Law. The study found that the hybrid composite containing 2 wt.% hybrid nanofillers exhibited a 22.10% increase in impact performance compared to non-modified counterparts. After 90 days of seawater aging, the material exhibited enhanced resistance to moisture absorption (15.74%) and minimal reduction in impact strength (8.52%) compared to its dry strength, with lower diffusion coefficients.

Research Progress of Carbon-Silicone Composite Materials

Silicone is a kind of polymer material with high cross-linked structure,which is com-posed by Si-O-Si main chain.Due to the special molecular chain structure,silicone mate-rials are characterized by oxidation resistance,aging resistance,high and low temperature resistance and chemical corrosion resistance.Moreover,silicone materials have process-able properties,simple forming process,good mechanical property,non-toxic and pollution-free.Therefore,silicone has been widely concerned by researchers at home and abroad.In this paper,the main research progress and application directions of carbon-silicone composite at home and abroad in recent years are reviewed.

Influence of Carbon Content on Element Diffusion in Silicon Carbide-Based TRISO Composite Fuel

The coating layers of Tri-structural Isotropic Particles(TRISO)serve to protect the kernel and act as barriers to fission products.Sintering aids in the silicon carbide matrix variably react with TRISO coating layers,leading to the destruction of the coating layers.Investigating how carbon content affects element diffusion in silicon carbide-based TRISO composite fuel is of great significance for predicting reactor safety.In this study,silicon carbide-based TRISO composite fuels with different carbon contents were prepared by adding varying amounts of phenolic resin to the silicon carbide matrix.X-ray Diffraction(XRD)and Scanning Electron Microscopy(SEM)were employed to characterize the phase composition,morphology,and microstructure of the composite fuels.The elemental content in each coating layer of TRISO was quantified using Energy-Dispersive X-ray Spectroscopy(EDS).The results demonstrated that the addition of phenolic resin promoted the uniform distribution of sintering aids in the silicon carbide matrix.The atomic percentage(at.%)of aluminum(Al)in the pyrolytic carbon layer of the TRISO particles reached its lowest value of 0.55%when the phenolic resin addition was 1%.This is because the addition of phenolic resin caused the Al and silicon(Si)in the matrix to preferentially react with the carbon in the phenolic resin to form a metastable liquid phase,rather than preferentially consuming the pyrolytic carbon in the outer coating layer of the TRISO particles.The findings suggest that carbon addition through phenolic resin incorporation can effectively mitigate the deleterious reactions between the TRISO coating layers and sintering aids,thereby enhancing the durability and safety of silicon carbide-based TRISO composite fuels.

Oxidation behavior of Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2)C-M_(x)C(M=Ti,Zr,Hf,Nb,Ta) composite ceramic at high temperature

Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2)C-M_(t)C composite ceramic was prepared by hot press sintering,with the Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2)C high-entropy carbide as the main phase.Secondary phase M_(x)C(M=Ti,Zr,Hf,Nb,Ta) was found to be distributed relatively uniform in the composite ceramic.The oxidation behavior of the ceramic was examined after exposure to 923 K and 1173 K.Morphology of the surface and cross sections of all oxidation samples were observed.The characteristics of the oxidation behavior of the high-entropy carbide and the secondary phase M_(x)C were compared and analyzed.The secondary phases(such as Ti-rich carbide or Hf-rich carbide) in the material were seriously oxidized at 923 K and 1173 K,which reflects the superior oxidation performance of the high-entropy carbide.The nano high-entropy oxides with Ti,Zr,Hf,Nb,Ta,and O elements were discovered by oxidation of the composite ceramic.This research will help deepen the understanding of the oxidation mechanism of high-entropy carbide and composite ceramic.

Effects of Co_(2)O_(3)Addition on Microstructure and Properties of SiC Composite Ceramics for Solar Absorber and Storage

SiC composite ceramics for solar absorber and storage integration are new concentrating solar power materials.SiC composite ceramics for solar absorber and storage integration were fabricated using SiC,black corundum and kaolin as the raw materials,Co_(2)O_(3)as the additive via pressureless graphite-buried sintering method in this study.Influences of Co_(2)O_(3)on the microstructure and properties of SiC composite ceramics for solar absorber and storage integration were studied.The results indicate that sample D2(5wt%Co_(2)O_(3))sintered at 1480℃exhibits optimal performances for 119.91 MPa bending strength,93%solar absorption,981.5 kJ/kg(25-800℃)thermal storage density.The weight gain ratio is 12.58 mg/cm2after 100 h oxidation at 1000℃.The Co_(2)O_(3)can decrease the liquid phase formation temperature and reduce the viscosity of liquid phase during sintering.The liquid with low viscosity not only promotes the elimination of pores to achieve densification,but also increases bending strength,solar absorption,thermal storage density and oxidation resistance.A dense SiO_(2) layer was formed on the surface of SiC after 100 h oxidation at 1000℃,which protects the sample from further oxidation.However,excessive Co_(2)O_(3)will make the microstructure loose,which is disadvantageous to the performances of samples.

Ceramic Nanocomposites Reinforced with a High Volume Fraction of Carbon Nanotubes

Multi-walled carbon nanotubes（MWNTs） were incorporated into precursor-derived ceramics made from a polysilazane.A ceramic nanocomposite reinforced with about 35 vol%of carbon nanotubes（CNTs）was fabricated by infiltrating CNT-preform with liquid-phased polymeric precursor followed by pyrolysis.The nanocomposite has a dense structure without micro-cracks.The results reveal that the nanocomposite has lower indentation hardness but higher fracture energy than non-reinforced ceramic from the microindentation tests results.The effect of the CNTs on the mechanical properties of the nanocomposite should be discussed accordingly.

Ablation Property of Ceramics/Carbon Fibers/Resin Novel Super-hybrid Composite

A novel super-hybrid composite (NSHC) is prepared with three-dimension reticulated SiC ceramic (3DRC), high performance carbon fibers and modified phenolic resin (BPR) in this paper. Ablation performance of super-hybrid composite is studied. The results show that the NSHC has less linear ablation rate compared with pure BPR and CF/BPR composite, for example, its linear ablation rate is 50% of CF/BPR at the same fiber content. Mass ablation rate of the NSHC is slightly lower than that of pure BPR and CF/BPR composite because of their difference in the density. Scanning electron microscopic analysis indicates that 3DRC can increase anti-erosion capacity of materials because its special reticulated structure can control the deformation of materials and strengthen the stability of integral structure.