Composite Interlayer Research Articles

Evaluation of oxidation resistant SiC-ZrB2 composite interlayer for plasma sprayed Y2O3 coating over graphite

The SiC-ZrB2 composite interlayer coating is developed by pack cementation over high density graphite (HDG) for the deposition of plasma sprayed yttria (Y2O3) topcoat for U-Zr (Uranium-Zirconium) melting application. The performance of Y2O3 coating with interlayer for enhancing its durability are investigated by performing thermal cycling experiments at 1450 and 1550 °C. The interlayer morphology with infiltrated and diffused coating of SiC with entrapped ZrB2 particles reduces the differential thermal mismatch stresses and offers passive oxidation protection for HDG. The role of composite SiC-ZrB2 interlayer enhancing threefold increase in the life of Y2O3 coating and its mechanisms at high temperature are provided.

Microstructure and mechanical properties of laser welded titanium alloy and stainless steel joint with composite interlayer

Abstract In this work, TA2/T2 was used as a composite interlayer to prevent the formation of brittle Ti-Fe intermetallics when joining TC4 Ti alloy to 304 stainless steel. The TA2/T2 (commercially pure Ti and Cu) composite interlayer was prepared by explosive welding. The laser was focused on the TC4-TA2 interface, which joined the TC4 and TA2 by fusion welding. At the TC4-TA2 interface, a weld zone was formed due to the mixing of molten TC4 and TA2. The laser was also focused on the T2-304 stainless steel interface, a weld zone was formed due to the mixing of molten T2 and 304 stainless steel. Composite interlayer TA/T2 was used not only to prevent the formation of Ti-Fe intermetallics during welding but also to improve microstructure and properties of the stainless steel–Ti alloy joint. The joint fractured at the TA2/T2 explosive welding interface with a maximum tensile strength of 428 MPa.

Characterization of NH4-montmorillonite under conditions relevant to Ceres

Research interest in NH4-smectites in planetology is increasing after the discovery of their high abundance on the surface of Ceres. This dwarf planet is considered a relic ocean world, showing evidence of extended aqueous alteration and cryovolcanic activity that occurred during the course of its history (De Sanctis et al., 2020). Despite the position of Ceres in the asteroid belt, a variety of ammonium-rich minerals, including phyllosilicates, carbonates, and chlorides, have been reported on its surface (Raponi et al., 2019). Ammonium-rich phases are expected to be found at greater distances from the Sun. Consequently, the study of the stability of ammonium-bearing phases such as smectites under environmental conditions relevant to the interior of Ceres and its regolith can help elucidate certain ambiguities concerning the provenance of its precursor materials. In this study, smectites were characterized by Raman and infrared spectroscopy, X-ray diffraction, and scanning electron microscopy under conditions mimicking the surface environment of Ceres, that is, at low temperatures (110–145 K) and near-vacuum conditions (1–0.001 Pa). When NH4-montmorillonite was freeze-dried, different structural stabilities were observed depending on the aggregation texture of the sample. In case the clay minerals on the surface of Ceres have an endogenic origin, its chemical composition and predominant interlayer cation are expected to provide insights into the type of fluids and chemical reactions that occur at deeper layers of the icy crust. The results of this characterization study are relevant for the future selection of payloads for space missions. The strength of combining different analytical methods in characterizing and interpreting mineralogical composition has been demonstrated in this study.

Friction stir spot welding of AA5052 with additional carbon fiber-reinforced polymer composite interlayer

AbstractIn this study, similar aluminum alloys AA5052 with additional carbon fiber-reinforced polymer composite (CFRP) interlayer were selected to investigate the effect of welding parameters (rotational speed and dwell time) on the mechanical properties, joint efficiency, and microstructure of friction stir spot weld joint. The maximum tensile shear load was 1779.6 N with joint efficiency of 14.6% obtained at rotational speed of 2,000 rpm and 2 s dwell time, which is 39.5% higher than the value at low rotational speed 850 rpm and 2 s dwell time. Meanwhile, the maximum microhardness 58 HV was attained in the keyhole region at rotational speed of 2,000 rpm and dwell time of 5 s, which is 22.4% higher compared to low rotational speed. The SEM-EDS results reveal the presence of intermetallic compounds (Al–Mg–C), which enhance the intermetallic bonding between elements.

Polypyrrole/Graphene Composite Interlayer: High Redox Kinetics of Polysulfides and Electrochemical Performance of Lithium–Sulfur Batteries Enabled by Unique Pyrrolic Nitrogen Sites

AbstractIt is still a grand challenge to achieve high performance lithium–sulfur (Li−S) batteries of high capacity, high‐rate performance and long cycling performance, especially at lean electrolyte condition. Herein, a multi‐functional composite interlayer is developed by in‐situ polymerizing pyrrole (PPy) on graphene nanosheet (PPy/G) and examined by Fourier Transformed infrared spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy. The graphene layers in PPy/G assure the high conductivity of the composite interlayer, while the high content of pyrrolic nitrogen sites of PPy in PPy/G composite interlayer can effectively trap the polysulfides (PSs) and promote the redox kinetics of PSs, which is valuable to suppress PSs dissolution and enhance utilization of sulfur content in Li−S batteries. Besides, the composite interlayer also facilitates the homogenous flux of Li+ and inhibits the growth of Li dendrite on Li metal anode. As a result, PPy/G interlayer delivers an impressive capacity of 535 mAh g−1 at 5 C and an area capacity of 5.18 mAh cm−2 at a sulfur load of 5.8 mg cm−2 after 100 cycles. A steady capacity of 664 mAh g−1 is also accomplished in lean‐electrolyte condition after 100 cycles.

Microstructure and corrosion behavior of Si3N4/316L joints brazed with Ag-Cu/Ag/Mo/Ag/Ag-Cu-Ti multilayer filler

In this work, a novel Mo/Ag composite interlayer was designed for joining of Si3N4 to 316 L stainless steel. The effect of Mo/Ag composite interlayer on the microstructure evolution and corrosion behavior of the joint was studied. It was verified that the addition of Ag layer in the 316 L/Ag-Cu/Ag/Mo/Ag/Ag-Cu-Ti/Si3N4 joint could eliminate Cu-rich phase and relieve residual stress of the joint. When inserting the thickness of 0.3 mm Ag into the joint, the bulk Cu-rich phase is almost divided into tiny particles and distributed in Ag-based solid solution. By the observation of scanning electron microscope after performing the potentiodynamic polarization test, the resistance corrosion of the seam in the joint was enhanced due to the formation of Ag-based solid solution, but had a slight unfavorable effect on that of the 316 L substrate and Mo. The corrosion current density of the joint was 1.97 μA/cm2. Large Cu-rich phase was eliminated by inserting Ag layer into the seam. The corrosion mechanism was changed from the pitting of Cu to the uniform corrosion of 316 L and Mo, which can improve the stability of joint. In addition, it was found that the 316 L substrate was subjected to residual tensile stress by FEM analysis. This residual tensile stress may have a negative effect on corrosion resistance of the 316 L substrate of the joint.

Plasma-enhanced Si-SiC low-temperature bonding based on graphene composite slurry interlayer

Recently, silicon carbide (SiC) has replaced silicon (Si) as a potential material for next-generation power devices. In this study, a Si-SiC low-temperature bonding method based on graphene composite slurry as an interlayer was developed. Ar plasma was used to treat the surfaces of Si and SiC to improve surface hydrophilicity for higher strength bonding. With the increase of discharge power, the root-mean -square (RMS) surface roughness of Si and SiC has obviously increased and the bonding quality was also greatly improved. For 70 W discharge power, the RMS surface roughness values of Si and SiC were 3.22 nm and 1.67 nm respectively, and the bonding strength reached approximately 10 MPa. Through SEM interface analysis, it can be found that a seamless bonding interface was obtained using this bonding process.

Additive manufacturing of W–Fe composites using laser metal deposition: Microstructure, phase transformation, and mechanical properties

A strong, ductile W–Fe functional composite interlayer is desirable for relieving the thermal stress between W and steel for applications in the nuclear industry. In this study, we fabricated high-density W–Fe composites using laser metal deposition (LMD). The influence of the composition and thermal history of the composites on their microstructural evolution and mechanical properties were investigated via single-bead and multi-layer LMD experiments. Unmelted W particles and micro-/nano-sized Fe2W particles were observed in the as-fabricated W–Fe composites. Unique core–shell structures of W/Fe7W6/Fe2W, W/Fe2W, and Fe7W6/Fe2W were also formed during the cyclic deposition process. Fine Fe2W nanoparticles were precipitated in-situ and dispersed owing to the high solidification rate and subsequent ageing treatment resulting from the multiple thermal cycles of the LMD process. The dispersed Fe2W nanoparticles resulted in a high compressive yield strength of over 1700 MPa with superior ductility in the as-printed W–Fe composite with 46 wt% W. This work demonstrated the feasibility of fabricating high-strength and ductile W-based composites via additive manufacturing without requiring energy-intensive and time-consuming treatments.

Fabrication of highly dissimilar TC4/steel joint with V/Cu composite transition layer by laser melting deposition

The high production flexibility of laser additive manufacturing is a significant advantage in the fabrication of functionally graded materials such as TC4 alloy and 30CrNi2MoVA steel, which have applications in the nuclear and aerospace industries. A laser melting deposition (LMD) process was employed to bond TC4 alloy with a high-strength 30CrNi2MoVA steel by the insertion of different intermediate materials, the intermediate materials consisted of either a pure-V layer or a V/Cu composite layer. The microstructure, elements distribution, phase composition, and mechanical properties of the joints were characterized. The appropriate transition interlayer composition was determined using ThermoCalc software. The experimental results indicated that using a pure V interlayer to bond TC4 with steel via LMD was extremely difficult, due to the generation of Fe-Ti intermetallic compounds. Consequently, the maximum tensile strength was only 58 ± 14 MPa. However, the V/Cu composition transition interlayer successfully suppressed the diffusion and mixing of Ti and Fe during LMD, forming joints between TC4 alloy and 30CrNi2MoVA steel with a tensile strength of 191 ± 20 MPa. In summary, this paper reports a new route to prepare a relatively strong TC4/30CrNi2MoVA dissimilar joint by the insertion of a V/Cu composite transition interlayer that does not require additional supplementary processes and does not limit the component geometry.

A review on filler materials for brazing of carbon-carbon composites

Abstract It is needed to join C/C composite to other materials since its individual use is limited. Brazing is a method to join C/C composite that has been studied most, maturest and most widely used in recent decades. The quality of a brazed joint is largely determined by the intermediate layer material. It is significant to choose filler materials reasonably. C/C composite is difficult to be wetted by common brazing filler materials. Moreover, there is a large difference in the coefficient of thermal expansion between C/C composite and metals. At present, there is no brazing filler alloy exclusively recommended for commercial C/C composites and metal brazing. Usually, active elements are added into filler metals to improve the wettability of them on C/C composite surface. The existing research includes Al-based, Ag-based, Cu-based, Ti-based, Ni-based brazing filler metals, and so on. In addition, various particle reinforced composite filler materials and stress buffer metal interlayer added composite filler materials have been studied for brazing C/C composite. The summarization of the overview on the application of intermediate filler metals is made in this paper. The basic reference basis is provided for the subsequent brazing filler metals development and joint performance improvement for C/C composite brazing.

The effect of cutting parameter changeover position on interface borehole quality in drilling of aerospace CFRP/Al stacks

Drilling multi-material aerospace stacks (e.g. CFRP/Aluminum) at the interface region represents the most challenging phase of the drilling cycle due to bi-material engagement of the cutting edges. This research investigates the impact of several drilling strategies on interface borehole quality, to allow for a fundamental understanding of the machining process taking place at the stack interface. In the experiments, cutting parameters were changed over from one workpiece material layer to the next at different positions relative to the interface, and the resultant impact on interface borehole quality was assessed based on borehole diameter, composite surface damage and interlayer burr height.

In situsynthesis of graphitic C3N4–poly(1,3-dioxolane) composite interlayers for stable lithium metal anodes

A g-C3N4–poly(1,3-dioxolane) (CN–PDOL) composite interlayer wasin situsynthesized by polymerization upon a lithium metal anode. The synergistic effect could increase the electrochemical performance of the lithium metal anode.

Hybrid TiO-TiO2 nanoparticle/B-N co-doped CNFs interlayer for advanced Li S batteries

Herein, a novel composite nanofiber, which consists of TiO-TiO2 heterostructure nanoparticles and boron, nitrogen co-doped carbon nanofibers (BNCNF), has been successfully prepared through a facile electrospinning method. Remarkably, as interlayer for LiS batteries, the TiO-TiO2 heterostructure not only enhances the adsorbability of the interlayer to lithium polysulfides (LiPSs) via the Lewis acid-base interactions, but also accelerates the redox reaction kinetics of the LiS batteries dramatically. Moreover, the BNCNF as a flexible framework can remit the volumetric change of the sulfur cathode, physically retard the migration of LiPSs and chemically adsorb to the LiPSs. Attributing to the synergistic effect of TiO-TiO2 nanoparticle and BNCNF membrane, the LiS batteries with the novel composite interlayer (named as TiO-TiO2/BNCNF) exhibit outstanding cycling stability and high discharge capacity, especially at high current density. With the sulfur loading of 2.5 mg cm−2, the cell with the TiO-TiO2/BNCNF interlayer delivers a high initial discharge capacity of 1014.7 mA h g−1 with a decay rate of 0.092% over 400 cycles at 0.5C, and also possesses excellent initial discharge capacity of 650.0 mA h g−1 with a decay rate of 0.068% over 120 cycles even at 2.0C.

Insights into the improved electrochemical performance of lithium–sulfur battery with free-standing SiO2/C composite nanofiber mat interlayer

A free-standing SiO2/C composite nanofiber mat (FS-SiO2/C-CNFM), prepared by electrospinning with heat treatments, is used as a multifunctional interlayer on the cathode side to suppress the polysulfide shuttle effect in lithium–sulfur batteries. The polysulfide adsorption and conversion capabilities of the interlayer are evaluated by a static polysulfide adsorption test and an electrochemical conversion test in an FS-SiO2/C-CNFM symmetric cell. The effects of the FS-SiO2/C-CNFM on the electrochemical properties of the lithium–sulfur batteries are studied by cyclic voltammetry, galvanostatic charge–discharge cycle tests, and electrochemical impedance spectroscopy. The FS-SiO2/C-CNFM interlayer significantly improves the specific capacity, long-cycling stability, and self-discharge behavior of the lithium–sulfur batteries. The cell with the FS-SiO2/C-CNFM interlayer has an initial discharge capacity of 1304 mA h g−1 and retains 934 mA h g−1 over 50 cycles at 0.1 C, corresponding to a capacity retention of 72% with 100% Coulombic efficiency. The improved properties are attributed to the suppression of the shuttle effect and the high reutilization of the trapped polysulfides. The adsorption/conversion mechanisms of the polysulfides of the FS-SiO2/C-CNFM interlayer are further elucidated from the results of ex situ X-ray photoelectron spectroscopy (XPS) and field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy (EDS) analysis.

Improved tribological properties and corrosion protection of CrN coating by ultrathin composite oxide interlayer

The intrinsic columnar structure and pinholes existing in the hard coatings via physical vapor deposition (PVD) could deteriorate their tribological and electrochemical properties. In order to improve the tribological and corrosion protection properties of CrN, TiO2 and HfO2 composite oxides deposited by atomic layer deposition (ALD) were inserted into the sputtered CrN. The influence of TiO2 and HfO2 composite oxides on the micro-structure, mechanical, tribological and electrochemical corrosion properties of coatings was investigated. By contrast with the pure CrN, the ALD-oxide inserted CrN coatings particularly the one added with TiO2-HfO2 nanolaminate significantly decrease the grain size, surface roughness and enhance the mechanical property of CrN. Additionally, the TiO2-HfO2 nanolaminate inserted CrN delivers excellent tribological and anti-corrosion properties. It is attributed to the synergistic effect of TiO2 and HfO2, which not only blocks the defect proliferation and dislocation motion during sliding, but also prevents the diffusion of corrosive media from migrating through the intrinsic pinholes in coatings and delivers outstanding barrier properties.

The state of individual layers and interfaces in multilayer nanostructures [(Co40Fe40B20)34(SiO2)66/ZnO/C]46

The multilayer nanostructures have drawn attention in fields from spintronics to microwave electronics. The purpose of this work was to determine the composition of individual layers and to control interfaces in three‐layer superstructures [(Co40Fe40B20)34(SiO2)66/ZnO/C]46 by means of X‐ray diffraction and X‐ray reflectivity. The samples with different thicknesses of metal‐containing composite layers together with zinc oxide and carbon interlayers were deposited on the glass substrate by ion‐beam sputtering of three targets, one of which was a composite (Co40Fe40B20)34(SiO2)66. X‐ray diffraction results showed the X‐ray amorphous state of the ferromagnetic metal clusters CoFeB, the dielectric matrix of silicon oxide SiO2, and carbon interlayers. However, the intermediate layers of the zinc oxide ZnO were found to have a nanocrystalline structure. The X‐ray reflectivity measurements indicate a good agreement between the experimental and nominal values of both the periods of three‐layer superstructures and the thicknesses of metal‐containing composite layers and interlayers.

Influence of welding sequences on the microstructure and mechanical properties of dual-pass electron beam welded Ti60/V/Cu/GH3128 joints

Electron beam welding of Ti60 titanium alloy to GH3128 nickel-base superalloy was realized by using V/Cu composite interlayers, based on the element metallurgical compatibility. The effects of welding sequences on the microstructures and properties of the joints were analyzed. Microstructures and energy spectrum analysis shown that the reaction of Ti and Ni atoms to form brittle intermetallic compounds (IMC) can be effectively prevented by the interlayers. When the electron beam was first focused on the V foil, the copper foil was melted due to the high melting point of vanadium (1890 °C). Continuously distributed CuTi IMCs were produced near the Ti60 side. When the electron beam was first focused on the Cu foil, CuTi IMCs were replaced by the formation of (Ti,V) solid solutions at the interface of Ti60. A joint with a maximum tensile strength of 392 MPa, 49% of that of the GH3218 alloy was obtained. The fracture morphology proved that the fracture type belonged to brittle fracture.

The switching control method for the nonlinear response of seismic surface based on the local T-S model

Based on the local T-S model, the switching control method for the nonlinear response of the seismic surface is studied, and the stiffness matrix of the composite interlayer element of viscoelastic damper and herringbone support is derived. The high-order single step ß method is applied to the nonlinear seismic response analysis and the instantaneous optimal active switching control. The local T-S model and controller are designed, and the approach and control of global nonlinear responses are realized through the multi-model switching control. The results show that the proposed method can accurately reflect the reduction of seismic ground load and the switching control of the main structure when the viscoelastic damper is installed. The switching control effect of the maximum spatial displacement becomes more and more obvious with the change of time history, and the control effect of all layers applying the switching control force is the most significant. Whether the controller is disturbed or not, it is always good and stable performance.

Composite brazing of C/C composite and Ni-based superalloy using (Ag-10Ti)+TiC filler material

With the aim of alleviating the residual thermal stress in the C/C-GH3044 joints, a novel composite brazing, which combines Ag-Ti reactive composite brazing and TiC particle-reinforced composite brazing, was adopted for joining C/C composite to Ni-based superalloy GH3044 using (Ag-10Ti)+TiC composite filler material. The results showed that the composite interlayer was strengthened by four kinds of reinforcements, containing the introduced TiC, the in situ synthesized AgTi and Ti 2 Ni phases, and the residual Ti particles. With increasing TiC content from 0 to 32 %, the thermal expansion coefficient of the composite interlayer declined by 18.2 %, which is helpful in alleviating the residual thermal stress in the joints. In addition, the introduced TiC particles decreased the fluidity of the filler material and inhibited the inter-diffusion of atoms between GH3044 and filler material. As a result, the continuous brittle compound Ti 2 Ni in the composite interlayer was effectively reduced, so the composite interlayer had good plasticity. Meanwhile, the thickness of the composite interlayer gradually increased from 260 μm to 520 μm, and the finite element analysis showed that the corresponding peak value of von Mises stress decreasedby 20.1 %. The highest shear strength of the joints was 67.2 MPa obtained with (Ag-10Ti)+24 %TiC at 1020°C for 30 min,which is almost the same strength as the C/C composite matrix used in this study.

Design of Gr/2024Al composite and Ti6Al4V titanium alloy joint brazed using AgCuSnTi filler and Ni/Nb/Ni composite interlayers

The AgCuSnTi filler was designed to braze Gr/2024Al composite and Ti6Al4V titanium alloy through investigating the effect of Sn and Ti addition in AgCuSnTi filler on the microstructure and mechanical property of the joint. The results showed that Sn and Ti addition decided the distribution of compounds (Al 2 Cu and Al 5 CuTi 2 phases) in the brazing seam. The increasing of Sn content could enhance the flowability of brazing alloy, and promote the compounds to be dispersive in the brazing seam. Ti in the filler induced the formation of Al 5 CuTi 2 phase instead of Al 2 Cu phase. When the Gr/2024Al and Ti6Al4V were brazed using the AgCuSnTi filler with 3 wt.% Ti and 27 wt.%Sn at 680℃ for 10 min, the Al 2 Cu and Al 5 CuTi 2 phases were dispersed in the brazing seam. The maximum shear strength of the brazed joint was 17 MPa and cracks propagated in the Gr/2024Al substrate. In addition, Ni/Nb/Ni composite interlayers were designed to strengthen the Gr/2024Al composite and Ti6Al4V titanium alloy joint, and the joint strength increased to 24 MPa owing to the adoption of the interlayers.