High Temperature Adhesion Research Articles

Development of eco-friendly and high-content rubberized asphalt modified by waste cooking oil desulfurized crumb rubber and waste crumb rubber

To conserve non-renewable petroleum-based asphalt resources and address the limitations of incorporating high-content waste crumb rubber (CR) in conventional crumb rubber modified asphalt (CRMA), this study examines the feasibility of utilizing waste cooking oil desulfurized crumb rubber (ODR) in conjunction with CR to prepare high-content rubberized asphalt (HCRA). The basic, chemical, rheological, and asphalt-aggregate adhesion properties of HCRA, both with and without a small quantity of styrene-butadiene-styrene (SBS) copolymer modifier, were evaluated using infrared spectroscopy (FTIR), dynamic shear rheometer (DSR), bending beam rheometer (BBR), asphalt-aggregate pull-off test, contact angle test, and atomic force microscopy (AFM). The results showed that the modification involving ODR and CR primarily constitutes a physical process, rather than a chemical reaction, as evidenced by the lack of new functional groups. Similarly, the addition of an SBS modifier predominantly results in physical modifications accompanied by minor chemical interactions. The improved desulfurization degree of ODR diminishes the elastic stiffening effect of CR on the matrix asphalt at the high-temperature (low-frequency) domain and reduces adhesion properties between HCRA and aggregates, while enhancing the flexibility of HCRA at the low-temperature (high-frequency) domain. The inclusion of a small quantity of SBS modifier allows HCRA to demonstrate high-temperature performance and adhesion properties on par with CRMA, alongside superior low-temperature stress relaxation, phase stability, storage stability, and water damage resistance. These attributes indicate that the HCRA with a small quantity of SBS modifier has a broader service temperature range compared to CRMA. This study achieves approximately 33.3 % replacement of asphalt materials while preserving the performance of rubberized asphalt.

Preparation and Properties of Waterborne Polyurethane and SBS Composite-Modified Emulsified Asphalt

To address the issue of insufficient durability of traditional modified emulsified asphalt in the application of cold mix and cold paving anti-skid wear layers, this study utilizes cationic waterborne polyurethane (PU+) for composite modification to enhance adhesion and performance across a range of temperatures. Initially, composite-modified emulsified asphalt samples were prepared with varying dosages of PU+ according to a gradient method. Routine performance tests were conducted on the evaporated residues for analysis. Advanced rheological tests, including temperature sweep (TS), frequency sweep (FS), linear amplitude sweep (LAS), and multi-stress creep recovery (MSCR) tests, were performed using a dynamic shear rheometer (DSR). Surface free energy (SFE) tests were conducted with a fully automated surface tension meter (STM). A comprehensive evaluation of the high-temperature rheological properties, fatigue properties, adhesion properties, and water damage resistance of the modified emulsified asphalt residues was carried out. Chemical changes before and after modification were characterized using Fourier transform infrared spectroscopy (FTIR), and the distribution of polymers in the evaporated residue was observed using fluorescence microscopy (FM). The results demonstrated that cationic waterborne polyurethane significantly enhanced the fatigue and adhesion properties of SBS-modified emulsified asphalt, but it also weakened the water damage resistance of asphalt. MSCR tests revealed that the addition of cationic waterborne polyurethane might reduce the elastic recovery performance of modified asphalt, thereby weakening its resistance to rutting. Among the samples, the modified asphalt with a PU+ content of 6% exhibited good high-temperature shear resistance and elastic recovery performance, demonstrating the best anti-rutting performance.

Investigation of Phenolic Resin-Modified Asphalt and Its Mixtures.

This study comprehensively examines the influence of phenol-formaldehyde resin (PF) on the performance of base asphalt and its mixtures for road applications, emphasizing its innovative use in enhancing pavement quality. Optimal PF content was determined through the evaluation of standard indicators and rotational viscosity. In-depth analyses of PF-modified asphalt's high- and low-temperature rheological properties and viscoelastic behavior were conducted using dynamic shear rheometers and bending beam rheometers. Aging resistance was assessed through short-term aging and performance grade (PG) grading. Moreover, Marshall and water stability tests were performed on PF-modified asphalt mixtures. Findings indicate that the uniform dispersion of PF particles effectively inhibits asphalt flow at high temperatures, impedes oxygen penetration, and delays the transition from elasticity to viscosity. These unique properties enhance the high-temperature stability, rutting resistance, and aging resistance of PF-modified asphalt. However, under extremely low temperatures, PF's brittleness may impact asphalt flexibility. Nonetheless, the structural advantages of PF-modified asphalt, such as improved mixture density and stability, contribute to enhanced high-temperature performance, water stability, adhesion, and freeze-thaw cycle stability. This research demonstrates the feasibility and effectiveness of using PF to enhance the overall performance of base asphalt and asphalt mixtures for road construction.

Preparation and properties of high molecular weight high temperature resistant carborane polyurethane adhesive

The long-term use temperature of the traditional high-temperature adhesive can only reach about 280 °C, and it cannot be used in extreme environments such as acid and alkali for a long time, which greatly limits its application in aerospace and other fields. Because of its unique three-dimensional structure, carborane has excellent thermal stability and chemical stability. Based on this, first, this article introduced carborane monomer into polyurethane structure, using indirect copolymerization method, Hydroxyl carborane derivative (m8) and conventional polyether diols were used as soft segments. By adjusting the introduction ratio of m8, a series of copolymerized carborane polyurethane (Co-CBR-PU) with controllable thermal and mechanical properties were successfully prepared. Its structure and molecular weight were characterized by FTIR and gel permeation chromatography (GPC), its surface morphology were observed by SEM. The thermal stability and mechanical properties were studied by thermogravimetric test, tensile test and rheological dynamic mechanical analysis test., and its activity, solvent resistance and hydrophobic properties were studied by finger contact method, solvent resistance test and contact Angle test. Second, the high temperature resistant carborane polyurethane adhesive (PUAS) was prepared using Co-CBR-PU as matrix and its adhesion was studied. The results show that a series of Co-CBR-PU has good high temperature resistance, mechanical properties and solvent resistance after adding carborane monomer, and its various properties were optimal when the addition amount of m8 was 15 wt%. The carborane PUAS prepared by using it as the substrate has excellent high temperature adhesion to different adhesive parts. The aim of this study is to reduce the cost of synthesis of carborane polyurethane by regulating the proportion of carborane, and then realize the industrial trial production of high temperature resistant carborane adhesive.

Enhanced Thermal Shock Resistance of High-Temperature Organic Adhesive by CF-SiCNWs Binary Phase Structure.

The development of high-temperature organic adhesive for bonding ultra-high-temperature ceramics with excellent thermal shock resistance has important significance to thermal protection systems for high-temperature environment application. In this study, high-temperature organic adhesive (HTOA) with carbon-fiber-SiC nanowires (CF-SiCNWs) binary phase enhancement structure was prepared. The method is that the SiCNWs grow on the chopped carbon-fiber surface and in the matrix of modified HTOA during high-temperature heat treatment with the help of a catalyst by a tip-growth way and with a vapor-liquid-solid (V-L-S) growth pattern. The results showed that the CF-SiCNWs binary phase enhancement structure plays a significant role in improving thermal shock resistance of high-temperature organic adhesive. The retention rate of the joint bond strength for the bonding samples after 20 cycles of thermal shock testing reaches 39.19%, which is higher than for the ones without CF, whose retain rate is only 6.78%. The shear strength of the samples with the CF-SiCNWs binary phase enhancement structure was about 10% higher than for those without the enhancement structure after 20 cycles of thermal shock.

Effect of multi-arc current on the microstructure and properties of TiAlSiN coating on zircaloy-4 alloy

TiAlSiN coatings are deposited on zircaloy-4 by multi-arc ion plating at 50 A, 60 A and 70 A, respectively. The macro-morphology, micro-morphology, chemical composition and phases of the prepared coatings are observed and analyzed, and the high temperature oxidation behavior and adhesion strength of coatings are tested. The results demonstrate that the quantity of large particles on TiAlSiN coating increases gradually as the arc current increases, the coating becomes denser and denser with the porosity decreases gradually, and the content of Al elements in the coating increases gradually with the increase of multi-arc current. The phases of TiAlSiN coatings deposited at different multi-arc currents before oxidation mainly includes Ti3AlN, AlN, Ti2N. Meanwhile, the high temperature oxidation behavior of the coating is also improved gradually and the adhesion strength increases first and then decreases. When the arc current is 60 A, the adhesion strength is up to 23 N which is relatively large. The coatings deposited at 70 A shows the best high temperature oxidation resistance behavior, mainly due to the generation of a large amount of Al2O3 oxide in the coating after oxidation.

Regeneration mechanisms of aged SBS modified asphalt from RAP materials: Molecule structure, morphology, phase transition, and interface adhesion characteristics

In this study, the environmentally friendly rejuvenators with waste thermal conductive oil, polymer, and the interfacial reinforcing agent were prepared. And the influence of the different rejuvenators on the rejuvenation mechanisms of aged SBS modified asphalt was characterized by different scales including the molecule structure, morphology, phase transition and interface adhesion characteristic, and macro performance. The results show that the thermal-oxidative aging process increases the molecular weight of asphalt, promotes the SBS phase to agglomerate, and decreases the high and low temperature performance, thermal stability, and adhesion. When the rejuvenator was added, the molecular weight distribution of asphalt binders can be improved, while adding the regenerant-II can supplement the SBS modifier and reform the cross-linking structure. Furthermore, the regenerant-II has a better recovery effect on the morphology structure and resumes the thermal behavior. And then softening point and ductility can be recovered by 89.7% and 94.8% of the original SBS modified asphalt. Under the action of the interfacial reinforcing agent, the regenerant-III could increase the adhesion work to 95.49% of the original SBS modified asphalt.

Foamed crumb rubber asphalt binder: Preparation, rheological properties and adhesion characteristics

In this study, the rheological properties and adhesion characteristics of foamed CRA binder were studied. Firstly, the optimum foaming conditions of foamed CRA binder with different crumb rubber powder (CRP) content and foaming agent were studied. Secondly, stress creep recovery (MSCR) test, temperature scanning and frequency scanning tests were carried out by using dynamic shear rheometer (DSR), and the high temperature performance, temperature sensitivity and viscoelastic characteristics of each asphalt binder sample before and after aging were studied. Finally, the surface free energy theory was used to evaluate the adhesion characteristics of each sample. The results showed that the commonly used foaming agent cetyl trimethyl ammonium bromide has no effect on the foaming of CRA binder. With the increase of CRP content, the foaming temperature became higher, and it was difficult to foam successfully when the rubber powder content was higher than 15%. Increasing the content of CRP in a certain range can improve the high temperature performance and adhesion of foamed CRA binder and reduce its temperature sensitivity. With the aging process of the sample, the high temperature performance of foamed CRA binder increased, and the temperature sensitivity and adhesion characteristics decreased. The surface free energy of foamed CRA binder is mainly composed of dispersion component, and the polarity component is relatively small. The surface free energy of foamed CRA binder increased with the increase of CRP content. In addition, foaming agent B (water-in-oil emulsifier) would reduce the temperature sensitivity and high-temperature performance of foamed CRA binder, but it had no obvious effect on adhesion.

Preparation of double-layer film modified polyacrylonitrile fiber modifier for designing and performance evaluation of PAN/SBS composite asphalt

• Innovative application of APTES, co-deposition of PEI and PDA in the modification of polyacrylonitrile fibers. • Double-layer membrane structure modified polyacrylonitrile fibers. • P-P/A-P/PAN and A-P/PAN with higher surface free energy, roughness and adhesion. • P-P/A-P/PAN/SBS@MA and A-P/PAN/SBS@MA had better viscoelastic properties. • P-P/A-P/PAN/SBS@MA and A-P/PAN/SBS@MA had better low temperature crack resistance and high temperature adhesion properties. To further enhance the properties of polyacrylonitrile (PAN) fiber incorporated modified asphalt, a new method of PAN fiber modification with a double membrane was developed. The influence of interface characteristics of modified fiber on the properties of fiber-reinforced asphalt was revealed from the free energy of the fiber surface and the adhesion between the modified fiber and matrix asphalt. Two types of PAN modified fibers with single-layer membrane structure (A-P/PAN) and double-layer membrane structure (P-P/A-P/PAN) were prepared, which were applied to synthesize three types of modified asphalts (Mas), i.e., PAN/SBS@MA, A-P/PAN/SBS@MA, and P-P/A-P/PAN/SBS@MA. Dynamic shear rheometer (DSR) experiment showed that at 46℃, the G*, G', and G' of P-P/A-P/PAN/SBS@MA were 24%, 19%, and 37% higher than those of PAN/SBS@MA. Similarly, at 175 ℃, the maximum yield strength of P-P/A-P/PAN/SBS@MA was 16.38% and 32.7% higher than those of A-P/PAN/SBS@MA and PAN/SBS@MA, respectively, which was attributed to the better surface free energy and adhesion work of the modified fibers. The surface contact angle test results showed that free energy of the surface and adhesion work of P-P/A-P/PAN fibers are 62% and 26.5% higher than those of PAN fibers, respectively. Scanning electron microscopy, atomic force microscopy, and UV-Vis tests indicated that the fiber's surface has successfully constructed a double-layer membrane structure. The fluorescent microscopy and cryo-SEM tests of the modified asphalt further confirmed that the modified PAN fiber had better interfacial interaction with the base asphalt. This study shows that the double-layer film modified PAN fiber composite SBS asphalt has good viscoelastic properties, high temperature adhesion, and low temperature fracture resistance, and hence carries critical practical engineering applications for highways, low temperature area pavements, airport pavements, and construction pavement.

Factors affecting the characteristics of high-temperature spraying and adhesion strength of the coating to the base

The main characteristics of the plasma jet, which affect the spraying of wire or powder during coating, are considered. The factors that improve the adhesion of the coating to the surface of the composite material are established. It is also determined that wear resistance is an important operational indicator of material quality. Keywords: methods and means of diagnostics, elements of the power supply system, troubleshooting of electrical equipment. boss2569@yandex.ru

Effect of PAN fiber with bionic layered surface structure generated in situ by Fenton reaction on performance of SBS/RP asphalt binder

• Innovative application of Fenton reaction in the modification of polyacrylonitrile fibers. • Biomimetic multi-layered structure modified polyacrylonitrile fibers. • KF-PAN/SBS/RP modified asphalt had better viscoelastic performance. • KF-PAN/SBS/RP modified asphalt had better low temperature anti-cracking performance, high temperature stability and fatigue damage resistance. • KF-PAN/SBS/RP modified asphalt had better rutting resistance and high temperature adhesion performance. In this study, a surface modified polyacrylonitrile fiber (KF-PAN) with a fish-scale whisker-like biomimetic hierarchical structure was successfully prepared via in situ competition effect of Fenton reaction. The modified fibers were used as secondary modifiers to prepare fiber-reinforced styrene–butadienestyrene (SBS) block copolymers and rubber powder (RP) modified asphalt binders (KF-PAN/SBS/RP). Energy dispersive spectroscopy, scanning electron microscopy, and atomic force microscopy analyses revealed the successful construction of bionic hierarchy on the fiber surface, and confirmed rough surface of the KF-PAN fibers. The hierarchical structure of the fiber surface acted as a buffer in the asphalt and strengthened the mutual interaction of the fiber and asphalt. Dynamic rheometer shear and strip-tensile tests showed that the KF-PAN/SBS/RP modified asphalt exhibited better viscoelasticity, rutting resistance, and tensile properties than the PAN/SBS/RP modified asphalt. The linear amplitude sweep test showed that KF-PAN/SBS/RP modified asphalt had better fatigue resistance. Thermogravimetric analysis tests indicated that the surface bionic structure of KF-PAN fibers boosted thermal stability of the fibers, which in turn enhanced the thermal stability of KF-PAN/SBS/RP modified asphalt. Fluorescence microscopy analysis showed that incorporating KF-PAN fibers improved the SBS and RP microstructure inside the asphalt, forming a good mesh structure, and alleviating the stress concentration phenomenon in SBS/RP asphalt under external traffic load.

Research on a New Loading Method for Nano TiO2 Photocatalytic Asphalt Pavement

The main goal of our work was to study a new loading method for photocatalytic asphalt pavement that could effectively solve the problems of photocatalytic degradation efficiency and durability. We adhered nano TiO2 particles to the microscopically textured structure on the surface of glass microbeads by cold alkaline corrosion and high-temperature adhesion technology. We observed good adhesion of nano TiO2 on glass microbeads by a microscopic performance characterization of the composites. The improvement in the light transmittance of the composite material improved the catalytic efficiency of nano TiO2 to a certain extent. Three different groups were established to verify the durability of the nano TiO2 loading method. The result shows that the exhaust gas degradation rate of the spray embedding group did not decrease significantly with the increase in road friction time. Our research provides a new idea for the design of exhaust degradation pavement.

Super-Flexibility and High-Temperature Adhesion of Epoxy Structural Adhesives Endowed by Homogeneous Rigid–Flexible Crosslinking Networks

Epoxy adhesives that combine flexibility, high-temperature adhesion property, and medium–low-temperature curing ability are an urgent need in the microelectronic device era. Unfortunately, it is still a challenge so far. In this context, two kinds of curing agents are combined to construct homogeneous rigid–flexible crosslinking networks via the stepwise curing method for preparing an epoxy adhesive with prominent deformation ability and high-temperature adhesive strength. Detailed analysis showed that the crosslinking network constructed by the stepwise curing method was higher and more homogenous than that of the one-step curing method. Benefitting from the homogeneous rigid–flexible crosslinking network, the elongation at break and high-temperature adhesion strength (200 °C) of the epoxy adhesive prepared by the stepwise method were up to about 100% and 1.60 MPa, respectively, which were about 1677.7 and 112.5% higher than those of the epoxy adhesive cured by the one-step curing method. The epoxy adhesive with medium–low-temperature curing ability, excellent flexibility, and high-temperature adhesion was first reported. It is expected that this work could provide some inspiration to design the special epoxy adhesives.

Component Design of Environmentally Friendly High-Temperature Resistance Coating for Oriented Silicon Steel and Effects on Anti-Corrosion Property

Oriented silicon steel is vital for power transformer cores, while the high-temperature annealing process limits the industrialization of environmentally friendly coatings on the surface. In this paper, the high-temperature binders Al(H2PO4)3 solution and silica sol were introduced innovatively. They condensed into macromolecular polymer chains, network structures and SiO2 particles at high temperatures, providing high-temperature stability and adhesion. The influence of types of silica sol, additives and functional fillers on the corrosion resistance of the coating was studied. The prepared environmentally friendly inorganic insulating coating for oriented silicon steel has excellent corrosion resistance after curing at 475 °C and annealing at 800 °C, which was matched with the currently rolling process of oriented silicon steel. The salt-spray resistance can last for more than 24 h and up to 72 h.

Improving the high-temperature adhesion strength between an Al/polysiloxane coating and a polyimide/carbon fiber substrate by a thermal pre-treatment step and structural design

In this study, the adhesion strength between a low-emissivity Al/polysiloxane coating and the polyimide/carbon fiber substrate at high-temperatures was successfully enhanced. The surface microstructure, adhesion, thermal properties, and optical performance of the samples were measured by scanning electron microscopy, tensile testing, simultaneous thermal analysis, infrared spectroscopy, and infrared thermal imaging. The coating structural analysis results showed that the emissivity of the top of the coating was lower than that of the bottom owing to the high enrichment ratio of Al powder with good infrared reflectance on the top. The thermal stability of the polyimide/carbon fiber substrate was studied to explore the effects of high temperature on the substrate surface structure and composition. Moreover, the failure mechanism of the adhesion strength between the coatings and substrate was explained, and the adhesion strength after being heated at 500 °C for 30 min was successfully enhanced using a resin intermediate layer and thermal pre-treatment step. Substrate pre-treatment at 500 °C for 6 min increased the adhesion strength by 3.5 ± 0.4 MPa because of the polysiloxane resin intermediate layer. The adhesion strength increased from 0.5 ± 0.4 to 5.0 ± 0.4 MPa when the pre-treatment time of polyimide/carbon fiber increased from 0 to 6 min. The potential applications of carbon fiber on the infrared stealth and energy saving fields at high temperatures might be improved by adding high-temperature resistant low-emissivity organic coatings to reduce infrared absorption and radiation.

Effect of filler on adhesion characteristics of precursor ceramic coating against high-temperature molten ash

Abstract In view of the widespread high-temperature molten ash adhesion problem of heat exchanger surface in the chemical, power, metallurgy and other industries, precursor ceramic coating is proposed to reduce ash adhesion strength. Three ceramic coatings were obtained by adding hexagonal boron nitride (h-BN), zirconia (ZrO2) and aluminium oxide (Al2O3) inert fillers on TP347 steel sheets through the Czochralski method and high-temperature sintering. Results of the static contact angle test show that at 860°C, the contact angles of the molten ash on the coating surfaces of h-BN, ZrO2 and Al2O3 are 58°, 54° and 53°, respectively, which are greater than that (39°) of the steel sheet sample. The spreading radiuses of the three coatings are significantly less than that of the bare sample, indicating a strong anti-adhesion performance, in which the h-BN coating is the best. Spreading dynamic analysis of the bare and h-BN coating samples reveals that the spreading dynamics of both sample surfaces is driven by a combination of reaction, dissolution and diffusion. The inert filler in the coating makes the reaction and dissolution of molten ash on the coating surface weaker than those of the steel sheet. The micromorphology of the melt ash-sample sheet cross-section shows that the melt ash binds closely to the steel sheet sample oxide layer, whereas the boundary with the coating is clear and obvious. This result indicates that the coating can effectively weaken the wetting and permeability of the molten ash. The research results provide new ideas for precursor ceramic coating to solve the high-temperature melting ash adhesion problem of the heat exchanger surface.

Rheological properties of asphalt mortar with silane coupling agent modified oil sludge pyrolysis residue

The treatment of oil sludge pyrolysis residue is a difficult problem and results in low resource utilization rate. This paper investigated the performance of oil sludge pyrolysis residue modified by silane coupling agent used to replace mineral powder in asphalt mortar. Different dosages of silane coupling agent and filler-asphalt ratios were considered, and the modification effects and mechanisms of silane coupling agent on the rheological properties of asphalt mortar with oil sludge pyrolysis residue were analyzed. Firstly, the physical and chemical properties of oil sludge pyrolysis residue were explored by electron microscopy scanning and infrared spectroscopy. Then, the rheological properties of asphalt mortar were examined by three major indexes (asphalt mortar, rheological properties of asphalt mortar, and water boiling test) to investigate the effect of different dosages of silane coupling agent on the rheological properties of asphalt mortar of oil sludge pyrolysis residue. Finally, the microscopic interfacial properties and modification mechanism of oil sludge pyrolysis residue asphalt mortar modified by silane coupling agent were analyzed by electron microscopy and infrared spectroscopy tests. The results demonstrated that, the oil sludge pyrolysis residue presented a well-developed pore structure and can form strong adsorption with asphalt; After the modification by silane coupling agent, the high-temperature performance and adhesion performance of the oil sludge pyrolysis residue asphalt mortar were significantly improved, and the low-temperature performance was significantly optimized. The asphalt mortar modified by 1.5% silane coupling agent shows the best performance. Compared with mineral powder asphalt mortar, the creep properties of the modified asphalt mortar at −6℃, −12℃ and −18℃ is reduced by 9.6%, 7.5% and 2.5%, the rutting resistance factor at 64℃, 70℃, 76℃ and 82℃ isimproved by −8.4%, 2.9%, 3.8%, and 8.0%, and the mass-loss rate after boiling is reduced by 27.3%. The silane coupling agent makes the filler surface become rough, and have an activation effect to increase its porosity, improve the adsorption properties of oil sludge pyrolysis residue on the light components in asphalt. Therefore, a strong physical and chemical adsorption forms between the filler and asphalt, and thus improve the pavement performance of the modified asphalt mortar.

Advanced high-temperature (RT-1100°C) resistant adhesion technique for joining dissimilar ZrO2 ceramic and TC4 superalloys based on an inorganic/organic hybrid adhesive

To meet the high demand for ceramic/superalloy composite structural components in various fields, an advanced high-temperature adhesion technique was firstly developed by preparing a novel inorganic/organic hybrid adhesive suitable for ZrO 2 and TC4. Chemical bonding started to work at ∼600°C, and became the crucial bonding mechanism at elevated temperatures. The formation of ZrSiO 4 and Ti 5 Si 3 at the interfaces of two substrates not only increased the interfacial connection strength, but also formed two gradient layers with a size of ∼2 μm to effectively alleviate the difference of composition and performance between the adhesive and substrates. In the temperature range of 500–900°C, the matching degree of CTE among ZrO 2 , adhesive and TC4 is higher, and the maximum difference does not exceed 3×10 -6 K -1 . Meanwhile, the formation of a composite structure containing various ceramics (ZrO 2 , SiC and ZrB 2 ) and intermetallics (Ni–Si, Al–Ni), and the improvement of structural compactness of adhesive from 500 to 900°C greatly improved the bonding strength to the maximum value of 31.4 MPa at 900°C. Also, the adhesive pretreated at 900°C showed good thermal cycling resistance, and the strength was still higher than 15 MPa after 50 cycles. For cured adhesive, when used directly in an extreme environment, it can provide bonding strength not less than 5 MPa in the whole temperature range, indicating that the adhesive possessed potential emergency repair convenience. This work significantly broadened the application of high-temperature-resistant adhesion technology in the connection of dissimilar ceramics and alloys.

High temperature electrical insulation and adhesion of nanocrystalline YSZ/Al2O3 composite film for thin-film thermocouples on Ni-based superalloy substrates

Electrical insulation and adhesion are two vital aspects for the integrated thin film sensors with Ni-based superalloy substrates. In this paper, nanocrystalline yttria-stabilized zirconia/alumina (YSZ/Al2O3) composite film was fabricated on Ni-based superalloy substrate by reactive magnetron sputtering. The X-ray diffraction and scanning electron microscope results show that tetragonal zirconia (t-ZrO2) nanocrystalline is homogeneously dispersed in the amorphous Al2O3 matrix. The crystal size of the t-ZrO2 nanocrystalline is well maintained with the temperature up to 1000 °C. The resistivity of the film is about 108 Ω·cm at 1000 °C, which is three orders of magnitude higher than that of the pure Al2O3 film. Furthermore, this YSZ/Al2O3 film demonstrates superior toughness and adhesion with the Ni-based superalloy substrate even after undergoing high-temperature cycles. Finally, a S-type thin-film thermocouple was fabricated on the YSZ/Al2O3 film shows good stability, repeatability, and linearity in multiple thermal cycling tests up to 900 °C exceeded 48 h.

Joining zirconia with nickel-based superalloys for extreme applications by using a pressure-free high-temperature resistant adhesive

In order to meet the high demand for joining ceramic/superalloy composite structure in extreme environments, a novel high-temperature resistant adhesion technique was developed for joining ZrO2 and Inconel 625 by applying an aluminum phosphate emulsion/zirconium sol based adhesive. With increasing temperature, a series of reactions occurred in adhesive, and its high-temperature bonding was attributed to the formation of a composite structure containing various ceramics and intermetallics. The adhesive after RT curing could find direct applications in extreme environments, and provide bonding strength no less than 2.5 MPa in the temperature range of RT-1100 °C. The bonding strength was higher than 4 MPa in the temperature range of 800–1000 °C, which was further attributed to the formation of an effective CTE-gradient relationship among ZrO2, adhesive and Inconel 625, as well as the interfacial reactions between the two substrates. The work broadened the application of adhesion technique and brought new ideas for joining dissimilar engineering materials.