Mechanical properties and thermal stability of SiBCN films prepared by ion beam assisted sputter deposition

The high hardness, exceptional high temperature stability, and oxidation resistance of bulk Si–B–C–N ceramics have led to the expectation that these materials will be good candidates for superior coating materials in high-temperature applications. In this study, SiBCN films were prepared using ion beam assisted sputter (IBAS) deposition, and the mechanical properties and thermal stabilities of the films at 600, 700, and 800 °C in air were investigated. In particular, the effects of the ion beam assist on the properties of the SiBCN films were examined. The SiBCN films were deposited on Si plates by sputtering a target composed of Si + BN + C using a 2-keV Ar⁺ ion beam. A low-energy N₂⁺ and Ar⁺ mixed ion beam irradiated the samples during the sputter deposition. The Si content in the SiBCN films was controlled by changing the Si/(BN + C) ratio of the target. BCN films were also deposited for comparison. The composition and chemical bonding structure of the prepared films were investigated by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. We found that c-BN bonds were formed in the ion-assisted BCN film. The oxide layer thickness on the SiBCN films after thermal annealing decreased due to the IBAS deposition and an increase in the Si content. Ion-assisted SiBCN films annealed at 800 °C showed the highest hardness of 20 GPa.     

Adjustable iron-containing SiBCN ceramics with high-temperature microwave absorption and anti-oxidation properties

Quaternary siliconboron carbonitride (SiBCN) ceramics show excellent high-temperature stability and oxidation resistance, indicating great potential as high-temperature electromagnetic (EM) wave absorbing materials. In this contribution, an efficient and facile method was developed to prepare bulk iron-containing SiBCN (Fe–SiBCN) ceramics with remarkable EM wave absorption at high temperature by pyrolyzing boron and iron containing precursors (PSZV-B–Fe). The introduction of boron and iron not only improves the high-temperature stability but also influences the complex permittivity and EM wave absorption. The minimum reflection coefficient (RC_min) is −61.05 dB, and the effective bandwidth absorption (EAB) is 3.35 GHz (9.05–12.4 GHz). The RC_min will be decreased to −52.3 dB at 600°C as well as the EAB covers more than 67% of the X band (2.8 GHz). The high-temperature stable Fe–SiBCN ceramics with adjustable dielectric properties can be utilized as high-performance EM wave-absorbing materials in high-temperature and harsh environments.     

Synthesis of NiMn2O4 thin films via a simple solid-state reaction route

Herein, NiMn₂O₄ (MNO) spinel oxide thermistor films were synthesized on a SiO₂/Si substrate via annealing the electron beam evaporated Mn–Ni–Mn metal trilayers in air at different temperatures. The X-ray diffraction (XRD) results indicate that polycrystalline spinel-structured MNO thermistor films were formed. The surface particle size of the series MNO films quickly reduced from ~300 to ~120 nm with a temperature increase from 650 to 750 °C, and then, slowly reduced to 80 nm or even smaller with a temperature increase from 750 to 950 °C. Specifically, 750 °C anneal formed the spinel MNO film with largest B value of 5067 and Ea value of 0.4366. The proposed synthesis route for MNO spinel oxide film has been proven to be feasible.     

Polymer-derived ceramic thin-film thermocouples for high temperature measurements

Thin-film thermocouples are used as temperature detection components in aircraft engines. However, the preparation of traditional thin-film thermocouples is complex, and their high-temperature stability performance attributes are poor. In this study, polymer-derived ceramic (PDC) technology is introduced to prepare polymer-derived ceramic thin-film thermocouples. Due to the superior high-temperature and adhesion performance characteristics of polymer-derived ceramics and the protective effects of the products of polymer precursors on the thin films, the performance attributes of thin-film thermocouples are greatly improved. After simplifying the preparation process and outputting a large thermoelectric potential, the polymer-derived ceramic thin-film thermocouple exhibits good repeatability, stability, and thermoelectric potential output consistency. At 1200 °C, the peak output is 203 mV, and the average Seebeck coefficient is approximately 182 μV/°C. The temperature measurement error is 0.316%. In the 8-h drift test, the coefficient first increases at 1.26 °C/h and then steadily decreases at −0.63 °C/h. This polymer-derived ceramic thin-film thermocouple has excellent performance and can be applied to the in situ monitoring of thermal components in high-temperature and harsh environments, such as engines.     

A study of the oxidation behavior of CrN and CrZrN ceramic thin films prepared in a magnetron sputtering system

CrN and CrZrN ceramic thin films were produced by a planar type reactive sputtering system on glass and stainless steel substrates. We investigated oxidation resistance of CrN and CrZrN ceramic thin films with different Zr contents. The structure of the films at different thermal-annealing temperatures was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The mechanical properties of the films at different thermal-annealing temperatures were measured by nano-indentation. The results of this study showed that the addition of few amount of Zr (0.4 at%), can improve thermal stability of CrZrN ceramic thin film and increase the oxidation temperature of the film from 600 °C to 800 °C. The relatively good oxidation resistance (800 °C) and high hardness of the film with the lowest Zr content, indicates that this film is a good candidate for high temperature applications.     

Effect of silver content on the microstructure,thermal stability and mechanical properties of CrNx/Ag nanocomposite films

CrN_x/Ag nanocomposite films with varying Ag content were prepared by reactive magnetron sputtering under a constant Ar/N₂ stream. The films were annealed between 500 – 800 °C in the air. The microstructure and elemental composition of films were studied by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The mechanical properties were characterized with respect to nano-hardness and high-temperature tribology. The results reveal that the incorporation and concentration of Ag influence the morphology and microstructure of films. The microstructure of films evolves by annealing, and the films with higher Ag concentration exhibit more severe structure evolution. Annealing at 650 °C results in the sublimation of Ag, and the oxide emerges on the film surface. Annealing at 800 °C reveals that the film with 6.2 at.% Ag exhibits superior structural stability, while the one with 20.2 at.% Ag deteriorates. The hardness of films decreases with the increasing Ag concentration and heating temperature. Films with 12.6 at.% Ag and above possess solid lubrication during the sliding at 350–650 °C. Both the friction coefficient and wear resistance are found dependent on the Ag concentration and sliding temperature.     

Microstructure and electromagnetic wave absorption property of reduced graphene oxide-SiCnw/SiBCN composite ceramics

In this account, RGO-SiC_nw/SiBCN composite ceramics were fabricated using polymer derived ceramic (PDC) combined with chemical vapor infiltration (CVI) technology. Dielectric property of as-obtained RGO-SiC_nw/SiBCN composite ceramics was significantly enhanced thanks to established conductive pathway through overlapped nanoscale SiC_nw and micro-sized RGO. The minimum RC of composite ceramics with 0.5 wt% GO and 2.29 wt% SiC_nw at thickness of 3.6 mm reached -42.02 dB with corresponding effective absorption bandwidth (EAB) of 4.2 GHz. As temperature rose from 25 to 400 °C, permittivity increased with enhanced charge carrier density and then it decreased due to oxidation process of RGO from 400 to 600 °C. The minimum reflection coefficient (RC) was recorded as -39.13 dB and EAB covered the entire X-band at 600 °C. EMW absorption ability was evaluated after high-temperature oxidation experiment under protective effect of wave-transparent Si₃N₄ coating. RGO-SiC_nw/SiBCN composite ceramics maintained outstanding EMW absorption ability with minimum RC of -10.41 dB after oxidation at 900 °C, indicating RGO-SiC_nw/SiBCN composite ceramics with excellent EMW absorption characteristic even at high temperatures and harsh environments.     

Optical and electrical properties of ITO film on flexible fluorphlogopite substrate

Indium Tin Oxide (ITO) films were prepared, at room temperature, on a fluorphlogopite substrate using magnetron sputtering technology. At various temperatures of 500 °C, 600 °C, 700 °C, 800 °C, and 900 °C, the samples were (had) annealed for 2 h (a 2-h duration). The results showed improvement in the crystalline performance of ITO film at selected annealing temperatures, with a significant reduction in resistivity at 800 °C. The lowest resistivity is 4.08 × 10^?4 Ω-cm, which is nearly an order of magnitude lower than the unannealed sample. All samples have an average light transmittance above 85% in the visible light range (400–800 nm), and with increasing annealing temperature, the average light transmittance tends to decrease. Besides, at the sensitive wavelength of 550 nm, the light transmittance is as high as 93.74%. The sheet resistance testing of the sample was through the number of bending times, which revealed that with the increase of the number of bending, the sheet resistance increases. However, after 1200 bending times, the change rate of the sheet resistance remains below 5%. Thus, the ITO film prepared on the flexible fluorphlogopite substrate revealed excellent optical and electrical properties, good flexibility, and improved stability after high-temperature annealing, which guarantees successful application in flexible electronic devices.     

BCl3 modified tris(dichloromethylsilylethyl)borane as a precursor for SiBCN ceramics applied in lithium-ion battery anodes

Tris(dichloromethylsilylethyl)borane is a compound containing a B–C bond and Cl and H elements. Herein, we propose a novel method to synthesize polyborosilazanes using tris(dichloromethylsilylethyl)borane and boron trichlorosilane as boron sources and hexamethyldisilazane as a nitrogen source. The microstructure and chemical composition of the as-synthesized polyborosilazanes and as-annealed SiBCN ceramics were investigated using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, Raman spectroscopy, scanning electron microscope, and transmission electron microscope methods. The organic precursors were converted entirely into inorganic ceramics at 800 °C, and the ceramic yield of the polyborosilazanes was 88% at 1000 °C. SiBCN ceramics with irregular shapes contained chemical bonds of B–N, Si–N, and Si–C at 1500 °C and retained an amorphous structure below 1600 °C. After the first cycle, the fabricated SiBCN ceramic anodes exhibited a reversible capacity of 261.3 mA h/g, which was 2.6 times that reported in the literature (101 mA h/g). The discharge capacity decreased to 157.6 mA h/g after 30 cycles. The satisfactory electrochemical performance of the resulting SiBCN ceramic anodes can be attributed to the formation of conductive carbon species favoring the transport properties of lithium ion.     

Densification behavior and microstructure evolution of hot-pressed SiC–SiBCN ceramics

Densification behavior and microstructure evolution of hot-pressed SiC–SiBCN ceramics were studied between 1660 °C and 1830 °C. Polyborosilazane was chosen as the SiBCN precursor and pyrolyzed at 1000 °C in inert atmosphere before use. Samples with SiBCN contents of 10% and 20% in weight were prepared. During the sintering, at temperatures <1660 °C, the density of all the samples showed a minor increase because of solid state particles rearrangement. Above 1660 °C, the density increased rapidly because of the grain boundary sliding with a non-Newtonian viscous boundary phase. After grain boundary sliding, grain-boundary diffusion enhanced by B and C elements from the SiBCN material was responsible for the further densification. The microstructure of the samples hot pressed at 1660 °C appeared particle packing state. The two samples can achieve almost full density when they were hot pressed at 1830 °C/40 MPa for 90 min.     

Temperature influence on the interlayer and surface morphology of diamond coating on 3D porous titanium substrates

Nanocrystalline (NCD) and/or microcrystalline (MCD) diamond films grown on three-dimensional porous titanium (Ti) substrate were obtained by hot filament chemical vapor deposition (HFCVD) technique. The morphology variation of diamond films grown on porous three-dimensional titanium substrate was studied at four different deposition temperatures to investigate their influence on nucleation density. Scanning electron microscopy images depicted the continuous change from microcrystalline diamond grains with a random crystallographic orientation, at 500 °C and 600 °C, to a cauliflower-like structure for deposits at 700 °C and 800 °C. Visible Raman spectroscopy confirmed the good quality of diamond films and revealed that the amount of amorphous carbon increased associated to the film morphology changes from MCD to NCD. X-ray diffraction analyses, performed both through θ–2θ scans and at grazing incidence angle, allowed the investigation of the crystallographic properties and structural evolution of the different film/substrate interface phases, such as TiC(111), TiC(200) and TiH₂. The results revealed that the temperature enhanced the nucleation sites for diamond growth.     

Reaction of palladium thin films with an Si-rich 6H-SiC(0001)(3×3) surface

The reaction of Pd thin films evaporated in ultrahigh vacuum on a clean and Si-rich 6H-SiC(0001)(3×3) surface has been investigated in situ by low-energy electron diffraction (LEED) and photoelectron spectroscopy (UPS and XPS), and ex situ by atomic force microscopy (AFM) and glancing-incidence X-ray diffraction (GIXRD). For studying the interface formation, submonolayer amounts of Pd were sequentially deposited up to ∼20 Å on the substrate maintained at room temperature. This deposit was subsequently annealed to 600–800 °C. At room temperature, Pd starts to react with SiC when the thickness attains ∼2.5 Å, giving an interface Pd₂Si silicide. Under annealing the film is transformed into Pd₂Si islands standing on the SiC (1×1) surface. No extra-structure of C 1s is observed in the two cases; only an energy shift of about 0.25 eV is detected during the metal deposition, which is attributed to a change in the band bending. Further deposition of ∼100 Å of Pd on this annealed surface gives an epitaxial Pd(111) film, despite a lattice mismatch of more than 10% between the metal and the semiconductor. The film is disrupted after annealing at 600–800 °C. The combination of XPS, AFM and GIXRD analyses indicates that the film annealed at 800 °C is discontinuous and formed of sharp epitaxial Pd₂Si islands and graphite which probably surrounds the islands.     

Nitrogen and oxygen annealing effects on properties of aluminum-gallium oxide films grown by pulsed laser deposition

Aluminum-gallium oxide (AGO) films on c-plane sapphire substrates by pulsed laser deposition are described. Both nitrogen and oxygen annealing effects on the structural and optical properties of AGO films are investigated. The AGO film shows an amorphous structure when deposited at low temperatures (≤400 °C) while a crystalline structure at 800 °C. After post annealing at 900 °C, an amorphous-to-crystalline phase transformation for the 400°C-deposited film occurs and shows the preferred β phase. The corresponding optical bandgap also increases from 5.14 eV to 5.41–5.46 eV depending on the annealing ambience. From Raman measurements, the 800°C-deposited AGO sample possesses a more stable O–Ga–O bonding compared to that of the 400°C-deposited one after annealing. Unusually, an evident increase in the nitrogen content is observed for the samples after post annealing at 900 °C in nitrogen atmosphere. The rapid dissociation of oxygen atoms may accelerate the disintegration of crystals and rearrangement, which makes the AGO film adsorb nitrogen atoms and cause the grain size to be significantly reduced. However, the extent of the nitrogen incorporation seems to have no apparent effect on the optical properties. All the AGO films show the optical transmittance over 80% in the ultraviolet–visible region with the calculated bandgaps more than 5.4 eV. Details of the mechanism about the nitrogen incorporation into the annealed AGO films via the oxygen vacancies or micro-pores will be discussed.     

Improvement of ageing issue in Zn0.4Fe2.1Co2Mn1.5O8 thermistor films

The Zn-Fe-Mn-Co-O spinel-structured thermistor films were synthesized by chemical solution deposition methods. The ageing performance of these films was investigated by co-doping Fe and Zn into the films and annealing at different temperatures. The surface morphology and microstructure of these films were improved with the increasing temperature. The contents of Mn³⁺ and Mn⁴⁺ were stable with the annealing temperature due to iron and zinc co-doping. Annealing at 700 °C was necessary for the iron cation to be fully activated in the spinel lattice. The optimal electrical properties and ageing performance of the films were obtained at 800 °C, with an optimal B value of ˜4472 K and the lowest rate of change for the film resistance.     

Influence of substrate temperature on the microstructure of YSZ films and their application as the insulating layer of thin film sensors for harsh temperature environments

Thin film sensors are employed to monitor the health of hot-section components of aeroengine intelligence (for instance, blades), and electrical insulating layers are needed between the metal components and thin film sensors. For this purpose, the electrical insulation characteristics of an yttria-stabilized zirconia (YSZ)/Al₂O₃ multilayer insulating structure were investigated. First, YSZ thin films were deposited by DC reactive sputtering at various substrate temperatures, and the microstructural features were investigated by scanning electron microscopy and X-ray diffraction. The results indicate that the micromorphology of the YSZ thin film gradually became denser with increasing substrate temperature, and no new phases appeared. The compact and uniform topography of the YSZ thin film improved the insulation properties of the multilayer insulating structure and enhanced the adhesion of the thin film sensors. In addition, the electrical insulation properties of the YSZ/Al₂O₃ multilayer insulating structure were evaluated via insulation resistance tests from 25 to 800 °C, in which the YSZ thin film was deposited at 550 °C. The results show that the insulation resistance of the multilayer structure increased by an order of magnitude compared with that of the conventional Al₂O₃ insulating layer, reaching 135 kΩ (5.1 × 10^?6 S/m) at 800 °C. Notably, the insulation resistance was still greater than 75 kΩ after annealing at 800 °C for 5 h. Finally, the shunt effect of the YSZ/Al₂O₃ multilayer insulating structure was estimated using a PdCr thin film strain gauge. The relative resistance error was 0.24%, which demonstrates that the YSZ/Al₂O₃ multilayer insulating structure is suitable for thin film sensors.     

MXene-derived TiC/SiBCN ceramics with excellent electromagnetic absorption and high-temperature resistance

Demand for high-performance electromagnetic (EM) wave absorbing materials with high-temperature resistance is always urgent for application in a harsh environment. In this contribution, two-dimensional material, Ti₃C₂T_x MXene, was introduced into a hyperbranched polyborosilazane. After pyrolyzation, the as-prepared TiC/SiBCN ceramics present excellent EM wave absorption in X-band. The TiC nanograins appearing after annealing provide multilevel reflection and interface polarization. Dipole polarization formed at interface defects, in company with interfacial polarization, also makes a great contribution to enhanced EM wave absorption. The TiC/SiBCN nanocomplex prepared with 5 wt% Ti₃C₂T_x MXene possesses a minimum reflection coefficient of −45.44 dB at 10.93 GHz and abroad bandwidth 8.4 and 12.4 GHz, almost covering the entire X-band. Tuning the thickness in the range of 2.35-2.54 mm, the effective absorption band can achieve the entire X-band. And the EM wave absorbing performance has been maintained to a large extent at 600°C with the minimum reflection coefficient of −26.12 dB at 12.13 GHz and the effective absorption bandwidth of 2 GHz. Last but not the least, TiC/SiBCN ceramics offer a good thermal stability in argon as well as in air atmosphere, making it possible to serve in high-temperature detrimental environments. This study is expected to provide a new perspective for the design of high-performance absorbing materials that are able to be used in harsh environments, especially in high temperatures.     

Construction of multiple heterogeneous interface and its effect on microwave absorption of SiBCN ceramics

Iron-containing siliconboron carbonitride (SiBCN) ceramics with multiple heterogeneous interfaces were fabricated using the microstructural design and polymer-derived ceramics (PDC) approach. The characterization results revealed the in-situ generation of nanocrystals, including graphite, belt-like silicon nitride (Si₃N₄), and silicon carbide (SiC) whiskers, in amorphous SiBCN matrix after annealing. At the same time, these dielectric lossy phases successfully constructed multiple heterogeneous interfaces and three-dimensional network structures. Consequently, the conductivity of the ceramics increased from 4.49 × 10⁻⁹ (annealed at 800 °C) to 0.67 × 10⁻⁴ S cm⁻¹ (annealed at 1600 °C). The real part of permittivity improved from 4.57–3.36 (annealed at 800 °C) to 10.90–8.38 (annealed at 1600 °C) in the frequency range of 2–18 GHz. The formation of multiple heterogeneous interfaces caused interfacial polarization and increased the multiple relaxations, which ultimately led to a superior microwave absorption property with a minimum reflection loss (RL_min) of −34.28 dB and an effective absorption bandwidth (EAB) of 3.76 GHz (8.64–12.4 GHz).     

Ageing resistance of SiBCN ceramics

Amorphous SiBCN alloys are known – depending on the elemental composition – for their thermal stability and high-temperature (up to 1500 °C) oxidation resistance, hardness, optical transparency or electrical and/or thermal conductivity. The paper reports ageing of SiBCN ceramics prepared in the form of thin films in a wide range of elemental compositions and preparation conditions. I focus on the room-temperature oxidation resistance, expressed in terms of the thickness and properties of the surface oxide layer 12 years since the deposition. I identify which compositions exhibit perfect long-time room-temperature oxidation resistance (this includes those, but not only those, which exhibit short-time high-temperature oxidation resistance) and which do not. For the latter I discuss the complex relationships between the characteristics of the surface oxide layer, the elemental composition of the films and the ion bombardment during the film growth. The results are important for tailoring long-lifetime ceramics combining the aforementioned functional properties.     

Low‐Temperature Sintered NTC Thermistor Ceramics for Thick‐Film Temperature Sensors

Negative temperature coefficient (NTC) thermistor thick films were fabricated by screen printing on alumina substrates and firing at 900°C. Spinel‐type NiMn₂O₄ exhibits limited stability in air between 730 and 970°C only and interacts with the Bi₂O₃ additive. The Zn–Co‐substituted spinel Zn_0.75Ni_0.5Co_0.5Mn_1.25O₄ with 3 wt% additive shows complete densification at 900°C; no interaction between spinel and additive was observed. Alternatively, a Cu–Zn–Co‐substituted Cu_0.37Zn_0.52Ni_0.44Co_0.44Mn_1.23O₄ spinel with excellent sintering characteristics even without sintering additive was investigated. The thermistor films display a sheet resistance of about 300 kΩ/□ and B = 3300 K. The firing behavior, microstructure formation, and electrical properties of NTC thick films are reported.     

Corrosion resistant polymer derived ceramic composite environmental barrier coatings

Corrosion resistant coatings are a promising solution to protect structural metals in harsh environments. Ceramic composite coatings made from polymer-derived ceramics are highly attractive due to the ease of their processing and the ability to work in various environments. This paper is focused on the performance of a TiSi₂-filled SiOC ceramic composite coating system on 316 stainless steel (SS) substrates as a corrosion resistant coating. The best-performing quadruple-dip coatings were shown to be able to reduce the weight loss due to hot sulfuric acid (95+%, 104–107 °C) corrosion by 85% over a 30-day period. Coatings from the same system were also examined under 800 °C static (100 h) and cyclic (10 cycles) oxidation. Our results indicate that the coatings perform well under both conditions of prolonged high temperature oxidation and thermal cycling, suggesting the strong potential of this system as an environmental barrier coating (EBC).