High Temperature Durability Research Articles

High temperature durability of fiber reinforced high alumina cement composites

The effect of high temperature exposure on the durability of fiber-reinforced composite materials based on high alumina cement is studied. A combination of X-ray diffraction- and thermal analyses of hydrated phases shows a simultaneous presence of all principal hydrates (CAH10, C2AH8, C3AH6, AH3) in significant amounts during the whole 2–28 days hydration period. The application of basalt aggregates and basalt fibers is found to improve significantly the high-temperature durability, in a comparison with the cement paste. The residual values of compressive and bending strength of the most successful mix with the combination of longer and shorter basalt fibers in a 90:10 ratio are 50% and 34%, respectively, after 1000 °C exposure. The fiber reinforced composite material with the most favorable mechanical properties exhibits also the highest resistance to water and water vapor transport and the lowest water vapor adsorption after 1000 °C pre-heating, which correlates well with its lowest amount of pores bigger than 100 nm. The thermal conductivity and specific heat capacity of all analyzed composites show a significant increase with the increasing moisture content; the differences between the values in dry and water saturated state are up to 100% and 65%, respectively. The thermal strain of all studied materials is almost linear within the whole 20–1000 °C range, with the basalt fibers being able to decrease it by up to 7% at 1000 °C.

High temperature durability of a bond-coatless plasma-sprayed thermal barrier coating system with laser textured Ni-based single crystal substrate

Thermal barrier coating systems are usually build-up with bond coats to ensure a good adhesion of the ceramic top coat and to protect the substrate against oxidation and corrosion. Such system is often subjected to complex thermo-mechanical loading. Because of the very different damage processes encountered during service operations, a simplified system was investigated by removing the bond-coat. Recently adhesion bond strength was enhanced using laser surface texturing of the substrate in thermal spraying processes. Atmospheric plasma spray yttria-stabilized-zirconia thermal barrier coating system was deposited on the Ni-based AM1 single crystalline superalloy without bond coat. Adhesion bond strength was already increased compared to conventional processing method. Top coat durability was evaluated at high temperature and damage mechanisms were studied. Isothermal and cyclic oxidation tests showed durability of 1000h and 400cycles at 1100°C. The oxidation mechanisms at the substrate/top coat interface changed due to fast solidification during the laser texturing process. Then, TBC system was studied under high temperature mechanical solicitation in tension creep. The textured interfaces were not damaged after 1% creep strain while top-coat/substrate interfacial cracking was observed for grit-blasted specimens. Moreover, no preferential crack development in the substrate was observed. Patterns provided an enhanced adhesion by changing the stress distribution near the interface.

Mn-Doped CaBi4Ti4O15/Pb(Zr,Ti)O3 Ultrasonic Transducers for Continuous Monitoring at Elevated Temperatures

Continuous ultrasonic in-situ monitoring for industrial applications is difficult owing to the high operating temperatures in industrial fields. It is expected that ultrasonic transducers consisting of a CaBi4Ti4O15(CBT)/Pb(Zr,Ti)O3(PZT) sol-gel composite could be one solution for ultrasonic nondestructive testing (NDT) above 500 °C because no couplant is required and CBT has a high Curie temperature. To verify the high temperature durability, CBT/PZT sol-gel composite films were fabricated on titanium substrates by spray coating, and the CBT/PZT samples were tested in a furnace at various temperatures. Reflected echoes with a high signal-to-noise ratio were observed up to 600 °C. A thermal cycle test was conducted from room temperature to 600 °C, and no significant deterioration was found after the second thermal cycle. To investigate the long-term high-temperature durability, a CBT/PZT ultrasonic transducer was tested in the furnace at 600 °C for 36 h. Ultrasonic responses were recorded every 3 h, and the sensitivity and signal-to-noise ratio were stable throughout the experiment.

Self-propagating high-temperature synthesis, phase composition and aqueous durability of Nd–Al bearing zirconolite-rich composites as nuclear waste form

ABSTRACTIn this study, the zirconolite-rich composite was rapidly synthesised from self-propagating high-temperature synthesis plus quick pressing using MoO3 as the oxidant and Ti as the reductant. As a surrogate of trivalent actinides, Nd was introduced to substitute the Ca site of zirconolite and Al was employed as the charge compensator to replace the Ti site (nominally Ca1−xNdxZrTi2−xAlxO7). The phase composition and Nd occupancy were analysed after Nd2O3 addition. Nd-bearing zirconolite was produced as the major ceramic phase. Nd mostly substitutes the Ca sites of zirconolite, which results in waste loading higher than 8.6 wt-% Nd. The aqueous durability of Nd–Al codoped sample (with 15 at.-% Nd substitutes the Ca site of zirconolite) was evaluated at 90°C as well. The 42 days normalised leaching rates of Mo, Ca and Nd were measured to be 3.70, 1.90 × 10−2 and 3.46 × 10−4 g m−2 d−1.

The Use of Flexible Ultrasound Transducers for the Detection of Laser-Induced Guided Waves on Curved Surfaces at Elevated Temperatures.

In this study, a flexible ultrasonic transducer (FUT) was applied in a laser ultrasonic technique (LUT) for non-destructive characterization of metallic pipes at high temperatures of up to 176 °C. Compared with normal ultrasound transducers, a FUT is a piezoelectric film made of a PZT/PZT sol-gel composite which has advantages due to its high sensitivity, curved surface adaptability and high temperature durability. By operating a pulsed laser in B-scan mode along with the integration of FUT and LUT, a multi-mode dispersion spectrum of a stainless steel pipe at high temperature can be measured. In addition, dynamic wave propagation behaviors are experimentally visualized with two dimensional scanning. The images directly interpret the reflections from the interior defects and also can locate their positions. This hybrid technique shows great potential for non-destructive evaluation of structures with complex geometry, especially in high temperature environments.

Flexible Paper Photodetectors Based on 2D BN Nanosheets

The market for printed and flexible electronics, key attributes for internet of things, is estimated to reach $45 billion by 2016 and paper-based electronics shows great potential to meet this increasing demand due to its popularity, flexibility, low cost, mass productivity, disposability, and ease of processing. However, conventional flexible devices made of paper and plastic substrates are expected to have thermal issues due to their poor thermal conductivity. In this work, we demonstrated flexible solar-blind deep-ultraviolet (DUV) sensors based on 2D boron nitride nanosheets (BNNSs) composited paper with good detectivity (up to 8.05 × 1010 cm Hz1/2/W), fast recovery time (down to 0.393 s), great thermal stability (146 W/m K, 3-order-of-magnitude larger than conventional flexible substrates), high working temperature (up to 200 oC), excellent flexibility and bending durability (showing repeatable ON/OFF switching during 200-time bending cycles). This shows great potential to be a key component to solve thermal problems and fully activate flexible electronics for meeting the demand of internet of things.

A simple and efficient method for the synthesis of SiBNC ceramics with different Si/B atomic ratios

The high-temperature durability of SiBNC ceramics is significantly influenced by Si/B ratios and the synthetic procedures. Single-source synthetic routes can yield homogeneous ceramics at the atomic level, but the Si/B ratio cannot be efficiently adjusted. In this paper, a simple and efficient method for the synthesis of SiBNC precursor polyborosilazanes (PBSZs) with different Si/B ratios has been established via a one-pot reaction involving boron trichloride, dichloromethylsilane and hexamethyldisilazane in different molar ratios. The Si/B ratios of the derived SiBNC ceramics were consistent with that of the precursor PBSZs. When pyrolysed at 1000°C, PBSZs with 0.52, 0.94 and 2.12 Si/B ratios transformed into SiB2.6N5C2.2, SiB0.9N2.7C1.3 and Si2BN3C1.4 ceramics respectively. The polymer-to-ceramic process was also studied and featured ceramic yields of 43.2wt%, 50.1wt% and 62.2wt%, respectively. The derived ceramic SiB0.9N2.7C1.3 resisted crystallization up until 1700°C, whereas the SiB2.6N5C2.2 and Si2BN3C1.4 could remain amorphous up to 1600°C only. Using the precursor with 0.94 Si/B ratio, the SiBNC ceramic fibres were also obtained.

Mechanical and Thermal Properties of Particleboard Manufactured from Waste Peachnut Shell with Glass Powder

In this study, polymeric composite particleboards were produced by using peachnut shell, an agricultural waste, as filling material and phenol–formaldehyde resin as polymeric binder. Effects of molding pressure and temperature, particle size of filling material have been investigated. Waste glass powder and Turkish tea fiber were used for improving fire resistance and tensile strength properties. The swelling properties of the particleboard which has 900 \(\upmu \)m particle size were also investigated. The tensile strength of particleboard decreased with increasing molding pressure between 2.72 and 9.8 MPa. Additionally, it decreased with increasing particle size of filling material which changes between 150 and 900 \(\upmu \)m. The best tensile strength and limiting oxygen index values of the particleboards were obtained as 34 MPa and 44.5, respectively, at 2.72 MPa and 120 \(^{\circ }\)C with 150 \(\upmu \)m particle size of filling material. This particleboard was also produced by adding 5% glass powder and 3% tea fiber as flame retardant and reinforcement material. The water absorption capacity of particleboard increased with the increase of molding pressure. It changed from 0.15 g water/g material to 0.32 g water/g material varying the pressure between 2.72 and 9.8 MPa. Particleboards which have been produced from peachnut shell and phenol–formaldehyde resin have very high temperature durability. It is seen that the water resistance of the produced polymeric composite particleboards are better than commercial boards.

Mechanical Design and Analysis of Ceramic Stator Blades for Gas Turbine Stage

The demand for higher power, better thermal efficiencies and lower weight gas turbines engines, calls for the research in the area of high temperature resistant materials to increase the TET (Turbine entry Temperatures). Research programs conducted so far by GARETT/DARPA indicated that replacing certain metal hot section parts with ceramics in gas turbine could improve engine output power, thermal efficiency with reduced SFC. Ceramic materials are better viable candidates for modern day gas turbine engine needs, because of their high temperature durability, lower specific weight, and high resistance to hot corrosion. Ceramics, especially silicon based carbides and nitrides (SiC& Si3N4) can withstand temperatures up to 1300°C. This paper presents a mechanical design and non-linear axi-symmetric steady state thermo-mechanical finite element analysis of stator (nozzle guide vane) blades of HP turbine with Si3N4 (Silicon Nitride).Mechanical design of stator blade is carried out using Si3N4 to replace existing metal stator blade of HP turbine. Designed stator blade has been subjected to steady state thermo-mechanical finite element analysis to validate the design. The stress distributions, concentration are evaluated for failure and factor of safety criteria. The life limiting stress concentrations in the critical zones of stator are evaluated aiming at a probability of success based on “Weakest Link Theory” and Mohr's-Coulomb Theory. The designed ceramic stator blade eliminates cooling requirements and weight of the blade has been reduced by 63%.

Research for Brazing Materials of High-Temperature Thermoelectric Modules with CoSb3 Thermoelectric Materials

Metallic glass (MG) can be a candidate for an alternative brazing material of high-temperature thermoelectric modules, since we can expect both a lower brazing temperature and a high operating temperature for the junction from the MG brazers. Another advantage of MG powders is their outstanding oxidation resistance, namely, high-temperature durability in atmosphere. We fabricated three compositions of Al-based MGs—Al-Y-Ni, Al-Y-Ni-Co, and Al-Y-Ni-Co-La—by using the melt spinning process, and their Tgs were 273°C, 264°C, and 249°C, respectively. The electrical resistivity of the Al-Y-Ni MG ribbon dropped significantly after annealing at 300°C. The electrical resistivity of crystallized Al-Y-Ni reduced down to 0.03 mΩ cm, which is an order of magnitude lower than that of the amorphous one. After the MG ribbons were pulverized to sub-100 μm, the average particle size was about 400 μm.

ChemInform Abstract: High Temperature Electrical Energy Storage: Advances, Challenges, and Frontiers

AbstractReview: 247 refs.

Optical properties and thermal stability of La1−xSrxCoO3−δ (0.2 ⩽ x ⩽ 0.8) ceramics

Perovskite-type La1−xSrxCoO3−δ (0.2⩽x⩽0.8) ceramics were prepared by tape casting and solid state reaction method. The room temperature optical properties of these samples were studied in detail. The temperature dependent emittance measurements and high-temperature durability tests were carried out. Results showed that these materials exhibited low reflectance at the solar spectrum wavelengths and high reflectance in the infrared region, with an optimal spectral selectivity of 3.2. The investigated samples showed low thermal emittance at high temperatures. More importantly, the sample was highly stable in air at 800°C, as the performance criterion value was lower than 0.05 after 10 cycles (90h) heat treatment. Our results demonstrate that the La1−xSrxCoO3−δ ceramics have the potential to emerge as high temperature (∼800°C) solar absorbers for the future solar power systems.

Damage mechanisms in an EB-PVD thermal barrier coating system during TMF and TGMF testing conditions under combustion environment

Modern high pressure turbine blades and vanes of aero-engines are cooled and thermally protected using a thermal barrier coating (TBC) system. TBC systems are submitted to very complex service loadings, with a combination of mechanical and thermal fatigue under complex thermal gradients, in addition to the contribution of oxidation to the damage processes.The high temperature durability under combustion environment of the AM1/NiAlPt/EB-PVD TBC system used for high temperature blades and vanes has been investigated performing out of phase load-controlled thermo-mechanical fatigue (TMF) and thermal-gradient-mechanical fatigue (TGMF) tests in the 500–1100°C temperature range. This characterization has been performed using the MAATRE burner where massive or hollow samples can be mechanically loaded under hot gas flow conditions. This unique test rig allows for gas testing temperatures up to 1600°C and internal cooling of hollow samples.The damage mechanisms under different TMF conditions are presented and the impact of a through thickness thermal gradient (induced by means of internal cooling) is analyzed. Moreover, a prior thermal over-aging of the whole system is investigated to mimic service degradation. It is shown in this work that depending on the tensile stress applied at low temperature, a change in the main degradation mechanism of the TBC system is observed. Moreover, the thermal over-aging before TMF tests favors cycling ratcheting in compression during thermo-mechanical cycling due to the degradation of the substrate microstructure.

Processing and Performance of MOF (Metal Organic Framework)-Loaded PAN Nanofibrous Membrane for CO2 Adsorption

The objective of this experimental study is to produce a nanofibrous membrane functionalized with adsorbent particles called metal organic framework (MOF) in order to adsorb CO2 from a gas source. Therefore, Polyacrylonitrile (PAN) was chosen as the precursor for nanofibers and HKUST-1, a Cu-based MOF, was chosen as adsorbent. The experimental process consists of electrospinning PAN solution blended with HKUST-1 to produce a nanofibrous mat as working substrates. The fibers were collected in a cylindrical canister model. SEM image of this mat showed nanofibers with the presence of small adsorbent particles, impregnated into the as-spun fibers discretely. To increase the amount of MOF particles for effectual gas adsorption, a secondary solvothermal process of producing MOF particles on the fibers was required. This process consists of multiple growth cycles of HKUST-1 particles by using a sol-gel precursor. SEM images showed uniform distribution of porous MOF particles of 2-4 µm in size on the fiber surface. Energy dispersive spectroscopy report of the fiber confirmed the presence of MOF particles through the identification of characteristic Copper elemental peaks of HKUST-1. To determine the thermal stability of the fibrous membrane, Thermogravimetric analysis of HKUST-1 consisting of PAN fiber was performed where a total weight loss of 40% between 210 and 360 °C was observed, hence proving the high-temperature durability of the synthesized membrane. BET surface area of the fiber membrane was measured as 540.73 m2/g. The fiber membrane was then placed into an experimental test bench containing a mixed gas inflow of CO2 and N2. Using non-dispersive infrared CO2 sensors connected to the inlet and outlet port of the bench, significant reduction of CO2 in concentration was measured. Comparative IR spectroscopic analysis between the gas-treated and gas untreated fiber samples showed the presence of characteristic peak in the vicinity of 2300 and 2400 cm−1 which verifies the adsorption of CO2.

Fully CMOS-compatible titanium nitride nanoantennas

CMOS-compatible fabrication of plasmonic materials and devices will accelerate the development of integrated nanophotonics for information processing applications. Using low-temperature plasma-enhanced atomic layer deposition (PEALD), we develop a recipe for fully CMOS-compatible titanium nitride (TiN) that is plasmonic in the visible and near infrared. Films are grown on silicon, silicon dioxide, and epitaxially on magnesium oxide substrates. By optimizing the plasma exposure per growth cycle during PEALD, carbon and oxygen contamination are reduced, lowering undesirable loss. We use electron beam lithography to pattern TiN nanopillars with varying diameters on silicon in large-area arrays. In the first reported single-particle measurements on plasmonic TiN, we demonstrate size-tunable darkfield scattering spectroscopy in the visible and near infrared regimes. The optical properties of this CMOS-compatible material, combined with its high melting temperature and mechanical durability, comprise a step towards fully CMOS-integrated nanophotonic information processing.

Facile preparation of supramolecular ionogels exhibiting high temperature durability as solid electrolytes

Facilely prepared supramolecular ionogels can remain in the gel state at high temperature and exhibit high conductivity and relatively low activation energy.

クレイ強化ナイロン6の熱曝露が及ぼす劣化解析

The thermal exposure tests are conducted to evaluate high temperature durability of nylon 6 clay hybrid nanocomposite (NCH). The degree of crystallinity is reduced by the thermal exposure at 120 °C and 150 °C, based on Differential Scanning Calorimetry (DSC) analysis. The tensile strength, elongation and fatigue strength are also decreased by the thermal exposure. The fracture origin is changed from the surface in as-received specimens to interior in the exposed specimens.

Silicon carbide-based membranes with high soot particle filtration efficiency, durability and catalytic activity for CO/HC oxidation and soot combustion

We report here the solution coatings of Diesel Particulate Filter (DPF) with allylhydridopolycarbosilane (AHPCS)-based polymers leading to supported silicon carbide (SiC)-based membranes with high temperature soot particle filtration efficiency, durability and catalytic activity. In a first part of the present study, our objective was to reduce the pore size of DPF to filtrate finer particles without altering filtration efficiency by coating DPF with an additional fine porous AHPCS-derived SiC membrane. The latter is produced by dip-coating AHPCS on DPF following by a pyrolysis of the AHPCS membrane-modified DPF at 1000°C under argon. We investigated the influence of dip-coating parameters and viscosity of different AHPCS solutions on the SiC membrane-coated DPF by SEM, mercury porosimetry, XRD and high-temperature thermogravimetric analysis. The evolution of the filtration capacity has been determined with a synthetic gas bench. An additional fine SiC membrane (∼150nm in thickness) prepared from a 10vol% of AHPCS in THF deposited on DPF allowed maintaining filtration efficiency as high as the virgin DPF while the pore size of the SiC membrane coated-DPF decreased to filter finer particles. Results are confirmed using a commercially-available polysiloxane (Si–C–O precursor). Furthermore, the SiC membrane acted as a thermal barrier coating and provided a better durability to the DPF by preventing apparition of cracks after heat-treatment to 1500°C under argon. The use of mixed oxide and metallic phases formed in-situ in SiC constitutes one of the solutions to generate new and effective catalytic performances to membranes. Within this context, in a second part of the study, we applied a reverse AHPCS-based microemulsion to combine SiC and oxide phases in the same additional porous membrane. As a proof of concept, we have prepared catalytically active Ce–O–Fe–Pt/SiC membrane coated DPF after dip-coating and pyrolysis under argon. These materials have been characterized and tested with regard to CO/HC oxidation and soot combustion. Ce–O–Fe–Pt/SiC membrane coated DPF showed an activity for CO conversion reaching a light-off temperature T50=270°C and the presence of the catalytic phase allowed burning soot at 486°C.

High-temperature-immersion ultrasonic probe without delay line using PbTiO3/Pb(Zr,Ti)O3 ultrasonic transducer

The behavior of a high-temperature-immersion ultrasonic probe without a delay line using a PbTiO3/Pb(Zr,Ti)O3 (PT/PZT) ultrasonic transducer was investigated empirically. A ∼100-µm-thick PT/PZT film was fabricated on a 200-µm-thick stainless steel substrate. After PT/PZT film fabrication, the substrate was bonded to a stainless steel pipe using a high-temperature waterproof adhesive material. The probe was tested in a water bath from room temperature to 100 °C for system verification. During three thermal cycles, the ultrasonic echoes had a high signal-to-noise ratio (SNR) and reasonable repeatability. After that, the same probe was verified by testing it in the silicone oil from room temperature to 200 °C. The test was also repeated three times and the probe successfully demonstrated high-temperature durability, a high SNR, and repeatability throughout the experiments.

Effects of thermomechanical properties of polarizer components on light leakage in thin-film transistor liquid-crystal displays

In this paper, we present static thermal analysis of stress and strain on a thin-film transistor liquid-crystal display (TFT-LCD) panel and their correlation with light leakage phenomena under high-temperature durability test. Three-dimensional (3D) finite element analysis (FEA) is coupled with experimental parameters of key components of the TFT-LCD panel for the analysis. A strong correlation exists between light leakage and retardation difference induced by stress on triacetyl cellulose (TAC) films. Moreover, shrinkage in stretched poly(vinyl alcohol) (PVA) film and modulus of the adhesive layer are key factors affecting stress distribution and displacement of polarizer stack. An increase in Young’s modulus (E) of the adhesive layer effectively reduces polarizer shrinkage and light leakage at the center of the panel. A TAC film with lower Young’s modulus and/or coefficient of thermal expansion (CTE) is also an effective solution.