High Thermal Expansion Research Articles

Temperature sensing by hybrid interferometer based on Vernier like effect

A temperature sensitive hybrid interferometer is developed and tested experimentally. The hybrid interferometer consists of a Michelson interferometer (MI) cascaded with a Fabry-Perot interferometer (FPI). It is fabricated by successively fusion splicing a single-mode fiber (SMF), a small section of multi-mode fiber (MMF), double side hole fiber (DSHF) and hollow Core fiber (HCF) together. The end of the HCF is filled with a thermosensitive polymer to form a reflecting surface of the FPI. The free spectral range of the MI and the FPI are designed to similar so that the Vernier-like effect can be generated. The Vernier Effect and the high thermal expansion coefficient of the polymer filled into the HCF enhance the temperature sensitivity of the hybrid interferometer. The maximum temperature sensitivity of 710.9 pm/°C has been achieved through experiments, which is much higher than silica-based temperature sensors.

Investigation of thermophysical properties of ZrO2-Sm3TaO7 ceramics

ABSTRACT This study investigates rare earth RE3TaO7 ceramics and shows that these materials may be optimal for thermal barrier coatings. ZrO2-Sm3TaO7 ceramics were prepared through a solid-state reaction. X-ray diffusion and structural refinement revealed a phase structure with an ordered orthorhombic phase for the Ccmm space group. The degree of structural disorder increased with increasing ZrO2 content. Gaussian function fitting of the oxygen 1s X-ray photoelectron spectra showed that the Sm3+ and Ta5+ ions were replaced by Zr4+ ions. At high temperatures, 8 mol% ZrO2-Sm3TaO7 has a high thermal expansion coefficient (10.9 × 10−6 K−1). The thermal conductivities of ZrO2-Sm3TaO7 (1.17 − 1.75 W·m−1 K−1) are lower than those of 7–8 wt.% yttria-stabilized zirconia, while those of 2% ZrO2-Sm3TaO7 are the lowest. The oxygen vacancies maintain the charge in equilibrium and enhance phonon scattering while decreasing the thermal conductivity. These results indicate that Sm3TaO7 can be used as a TBC.

Оценка параметров сварки промышленных соединений из толстых листов из алюминия 6082-T6 по европейским стандартам

Tungsten inert gas (TIG) welding had been applied to produce four double-V butt welded joints performed on thick plates made from 6082-T6 aluminum alloy. The thicknesses of the plates are 18, 45, 60, and 80mm.This type of aluminum alloy is very sensitive to heat due to its high conductivity and high thermal expansion coefficient. Heat from TIG welding reduces the strength of the cited welded plates in the welding zone and in the heat affected zone (HAZ) and favorites the formation of porosities and solidification cracks in the welded joints. Porosities and solidification cracks are the most frequent imperfection that appear in this type of welded joints and they are often the reason which prevent them to comply with the requirements of the BS EN ISO 10675-2: 2017 Non destructive testing of welds: Acceptance levels for radiography testing-Aluminium and its alloys, and of the BS EN ISO 23277: 2015 penetrant testing of welds –Acceptance levels. This article represents the type of the filler metal that used and the welding parameters that applied to perform TIG welding of the cited thick plates in order to get welded joints that are free from porosities and solidification cracks as confirmed by X-ray radiography and by red dye penetrant testing of these welded joints.

Effect of MnO on the crystallization, microstructure, and properties of MgO-Al2O3-SiO2 glass-ceramics

The Mn-doped MgO-Al2O3-SiO2 (MAS) glass-ceramics were prepared by the melt quenching technique. The effect of MnO on the crystallization, microstructure, and properties of MAS was discussed. XRD results showed that MnO promotes the phase transformation from indialite to Mg0.6Al1.2Si1.8O6 and enstatite. Crystallization kinetics suggested that MnO inhibits the precipitation of indialite. Both the crystallization index and SEM photographs proved that the bulk crystallization plays an important role in the Mn-doped MAS system. EDS analyses indicated that the large grain corresponds to Mg0.6Al1.2Si1.8O6 and the small grain corresponds to the magnesium-rich phase. Due to the addition of 0.5 wt% MnO, the flexural strength was enhanced from 146 to 247 MPa, and the coefficient of thermal expansion was increased from 3.52 × 10−6/°C to 5.41 × 10−6/°C. • Mn-modified MAS glass-ceramic with high flexural strength and low thermal expansion was developed. • Small addition of MnO markedly improved the flexural strength and Young’s modulus. • The relation between CTE values and crystal phases was revealed. • Crystallization kinetics suggested that MnO inhibited the precipitation of indialite.

Inherently Distinctive Potentialities and Uses of Nanocellulose Based on its Nanoarchitecture

Native cellulose is mainly found in phytomass, such as trees and other plants. It has a regular hierarchical nanoarchitecture, in which the extended macromolecular chains are aligned and closely packed in parallel to form the crystalline nanofibrils of cell walls. In the context of material utilization, nanocellulose is a collective term for nano-ordered assemblies of cellulose chains. In recent times, it has been produced in large quantities from woody bioresources. In addition, nanocellulose has some fascinating physicochemical properties, such as high strength, light weight, transparency, birefringence, and low thermal expansion. These properties have enabled broad functional design of nanocellulose-based materials; but most of them are facing serious competition from various products that already exist. However, nanocellulose is not just a green alternative to existing materials. Rather, it is expected to make a profound difference in terms of pioneering novel functions. The present review focuses on the unexpected features of nanocellulose materials, triggered by details of the inherent nanoarchitecture of native cellulose.

Effects of Er stabilization on thermal property and failure behavior of Gd2Zr2O7 thermal barrier coatings

This work focuses on the effects of Er stabilization on thermal property and failure behavior. The GdErZrO/YSZ TBCs exhibit a defect fluorite structure with high thermal expansion coefficient and low thermal conductivity. The as-deposited TBCs show a high thermal life and a good microstructure stability at 1100 °C due to the Er stabilization and the feathery microstructure. After thermal cycling test, the broken of thermally grown oxide is generally attributed to the Al2O3 growth and cracks evolution. Furthermore, the element diffusion might be critical factor for cracks extension leading to the spallation and delamination failure.

Defects, diffusion, dopants and encapsulation of Na in NaZr2(PO4)3

NaZr2(PO4)3 is an attractive ceramic material in the application of Na-ion batteries due to its high ionic conductivity and low thermal expansion. Here we employ classical simulation techniques to examine the defect processes, Na-ion migration and solution of various dopants in NaZr2(PO4)3. We find that the Na Frenkel (0.70 eV) is the most favourable defect process ensuring the formation of Na vacancies required for the vacancy assisted Na-ion migration. Long-range sodium vacancy migration was considered and it is calculated that Na-ions diffuse fast with a low activation energy of migration of 0.26 eV. The most favourable isovalent dopants on the Na and Zr sites are the K and Ge, respectively. The formation of Na interstitials and oxygen vacancies can be favoured by doping of Yb, Y, Ga and In on the Zr site. Encapsulation of Na was considered using density functional theory simulations and it is found that the incorporation is exoergic. Furthermore, the formation of Na+ ions and electrons simultaneously constitutes this material metallic together with high concentration of Na+ ions. The final encapsulated composite can be suitable for the preparation of electrodes in rechargeable Na-ion batteries.

Preparation and properties of CMAS resistant bixbyite structured high-entropy oxides RE2O3 (RE = Sm, Eu, Er, Lu, Y, and Yb): Promising environmental barrier coating materials for Al2O3f/Al2O3 composites

Y2O3 is regarded as one of the potential environmental barrier coating (EBC) materials for Al2O3f/Al2O3 ceramic matrix composites owing to its high melting point and close thermal expansion coefficient to Al2O3. However, the relatively high thermal conductivity and unsatisfactory calcium-magnesium-aluminosilicate (CMAS) resistance are the main obstacles for the practical application of Y2O3. In order to reduce the thermal conductivity and increase the CMAS resistance, four cubic bixbyite structured high-entropy oxides RE2O3, including (Eu0.2Er0.2Lu0.2Y0.2Yb0.2)2O3, (Sm0.2Er0.2Lu0.2Y0.2Yb0.2)2O3, (Sm0.2Eu0.2Er0.2Y0.2Yb0.2)2O3, and (Sm0.2Eu0.2Lu0.2Y0.2Yb0.2)2O3 were designed and synthesized, among which (Eu0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 and (Sm0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 bulks were prepared by spark plasma sintering (SPS) to investigate their mechanical and thermal properties as well as CMAS resistance. The mechanical properties of (Eu0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 and (Sm0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 are close to those of Y2O3 but become more brittle than Y2O3. The thermal conductivities of (Eu0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 and (Sm0.2Er0.2Lu0.2Y0.2Yb0.2)2O3 (5.1 and 4.6 W·m−1·K−1) are only 23.8% and 21.5% respectively of that of Y2O3 (21.4 W·m−1·K−1), while their thermal expansion coefficients are close to those of Y2O3 and Al2O3. Most importantly, HE RE2O3 ceramics exhibit good CMAS resistance. After being attacked by CMAS at 1350 °C for 4 h, the HE RE2O3 ceramics maintain their original morphologies without forming pores or cracks, making them promising as EBC materials for Al2O3f/Al2O3 composites.

3D printed polymer positive models for the investment casting of extremely thin-walled single crystals

Abstract The aim of this research work is the adjustment of the conventional investment casting process for the single crystal casting of thin-walled near net shape specimen with cast wall thickness down to 0.4 mm. Polymer models for manufacturing of shell molds for investment casting of Ni-based superalloys were produced by additive manufacturing from three different thermosets and one thermoplastic. Temperature dependent mass change, thermal expansion and burnout behavior of the polymers were investigated. All thermosets turned out to have inappropriate burnout behavior due to high thermal expansion. Smoothed polyvinyl butyral (PVB) could be burned out without cracking the shell mold. High quality thin-walled single crystal Ni-based superalloy M247LC was cast successfully in shell molds manufactured using polyvinyl butyral (PVB) models which were subsequently burned out and thereafter the shell molds were sintered.

Near-zero thermal expansion of ZrW2O8/Al–Si composites with three dimensional interpenetrating network structure

Negative thermal expansion (NTE) materials can compensate high thermal expansion of metal materials, showing great potential use in precision instruments and microelectronics field. We developed a near-zero thermal expansion ZrW2O8/Al–Si composites with three dimensional mutually interpenetrated structure. Pressure infiltration ensured dense structure and mild interface reaction. The resulting composite has ultra-low thermal expansion (1.09 × 10−6 K−1) in a broad temperature range of −50 to 120 °C (ΔT = 170 °C). The content of high pressure phase (γ-ZrW2O8) drops dramatically from 71.4% for the particle reinforced composite to 18.7% for the interpenetrating composite. Raman tests and numerical computational results indicated that the residual stress can be effectively released in the interpenetrating composites. This low dense and ultralow thermal expansion results in ideal materials for precision instruments and microelectronics component such as optical communication and gyroscope.

Tailored Sr-Co-free perovskite oxide as an air electrode for high-performance reversible solid oxide cells

Sr-Co containing perovskite oxides are prospective air electrode candidates for reversible solid oxide cells (RSOCs). However, their efficiencies are limited by Sr segregation and the high thermal expansion coefficient (TEC) of Co-based perovskites. Herein, La0.6Ca0.4Fe08Ni0.2O3−δ (LCaFN) is tailored as an Sr-Co-free perovskite air electrode for highperformance RSOCs. Compared with La0.6Sr0.4Fe0.8Ni0.2O3−δ (LSFN) and La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCoF), LCaFN has a high electrical conductivity (297 S cm−1), TEC compatibility (11.2 × 10−6 K−1) and improved chemical stability. Moreover, LCaFN has high oxygen reduction reaction (ORR) activity with a low polarization resistance (0.06 Ω cm2) at 800°C. A single-cell Ni-YSZ/YSZ/gadolinium-doped ceria (GDC)/LCaFN-GDC operated at 800°C yields a maximum power density of 1.08 W cm−2 using H2 as fuel. In the solid oxide electrolysis cell (SOEC) mode, the cell can achieve a current density of approximately 1.2 A cm−2 at 1.3 V with 70% humidity at 800°C. The cell exhibits good reversibility and remains stable in continuous SOEC and solid oxide fuel cell (SOFC) modes. These findings indicate the potential application of LCaFN as an air electrode material for RSOCs.

Preparation and characterization of high chemical durability and low thermal expansion borosilicate glass-ceramics by recycling of borosilicate glass

Borosilicate glass recycling is a challenge because it has high melting point and different chemical structure which makes it non-recyclable in the glass industry. This work focuses on borosilicate recycling through the preparation of a low thermal expansion and chemically durable borosilicate glass-ceramic (BsGC). Low thermal expansion and high chemical durability ceramics are advantageous in many applications such as lab supplies, corning ware, automobile components, and other low expansion products that are resistant to thermal shock. Kaolin and borosilicate were chosen for the preparation of glass-ceramic, because they have low thermal expansion and good chemical durability. BsGC was prepared by sintering borosilicate glass waste (e.g., Pyrex laboratory glassware, household glass) and kaolin at different temperatures (750-900 ° C). Water absorption method was used to measure the apparent porosity of the prepared composites. Surface morphology of the prepared BCGs was investigated using scanning electron microscopy (SEM). Phase composition of the prepared BGC samples was characterized sing X-ray diffraction technique (XRD). The XRD results showed that at sintering of 750 °C a monocrystalline quartz was only existing. By increasing sintering temperature up to 800°C the quartz phase decreased, while at 850 oC the quartz phase completely disappeared. The sintered BCG composites obtained exhibited low coefficients of thermal expansion in the range of 48 x 10-7 oC-1 and exhibited high chemical durability.

Cryopreservation of a cell-based biosensor chip modified with elastic polymer fibers enabling ready-to-use on-site applications

An efficient preservation of a cell-based biosensor chip to achieve a ready-to-use on-site system is still very challenging as the chip contains a living component such as adherent mammalian cells. Herein, we propose a strategy called on-sensor cryopreservation (OSC), which enables the adherent cells to be preserved by freezing (−80 °C) on a biosensor surface, such as the light-addressable potentiometric sensor (LAPS). Adherent cells on rigid surfaces are prone to cryo-injury; thus, the surface was modified to enhance the cell recovery for OSC. It relies on i) the integration of elastic electrospun fibers composed of polyethylene vinyl acetate (PEVA), which has a high thermal expansion coefficient and low glass-transition temperature, and ii) the treatment with O2 plasma. The modified sensor is integrated into a microfluidic chip system not only to decrease the thermal mass, which is critical for fast thawing, but also to provide a precisely controlled micro-environment. This novel cryo-chip system is effective for keeping cells viable during OSC. As a proof-of-concept for the applicability of a ready-to-use format, the extracellular acidification of cancer cells (CHO-K1) was evaluated by differential LAPS measurements after thawing. Results show, for the first time, that the OSC strategy using the cryo-chip allows label-free and quantitative measurements directly after thawing, which eliminates additional post-thaw culturing steps. The freezing of the chips containing cells at the manufacturing stage and sending them via a cold-chain transport could open up a new possibility for a ready-to-use on-site system.

Effect of Particle Morphology on Thermal Properties of TiB<sub>2</sub> Particle Dispersed Pure Aluminum Composites

Particle size and distribution affect the thermal properties such as thermal conductivity, thermal expansion, and mechanical properties. In this study, TiB2 particles were used for the dispersant of pure aluminum composites because of high thermal conductivity and low thermal expansion of TiB2. Composites with different dispersibility and volume fraction of particles were prepared by spark plasma sintering. The effect of particle dispersibility in composites on thermal conductivity was estimated quantitatively by the simulation and experiments. As increasing dispersibility, the thermal conductivity was decreased and Vickers's hardness increased, but alternation for thermal conductivity was very small. With increasing volume fraction of particles, the effect of the particle dispersion on the change of the thermal conductivity increased. In addition, the empirical equation of the thermal conductivity considering dispersibility was estimated. The coefficient of thermal expansion decreased with increasing the particle volume fraction, and the experimental value quite accorded with a result provided by the rule of mixture.

OPTIMISATION OF A RESIN-COATED CHROMITE SAND FOR RAPID SAND CASTING APPLICATIONS

Applications of three-dimensional printing (3DP) to sand casting have been well-established in the last two decades. The preferred raw material is silica (quartz) sand, as it is the most readily available and cost effective sand. However, silica sand as a refractory material has some technical limitations, including high thermal linear expansion, low refractoriness, and thermal conductivity. Therefore, it is not suitable for all castings. Other refractory sand types are available, including chromite sand, which is abundantly available in South Africa. Analysis of the physical and chemical properties of in-laboratory coating of a locally available chromite sand was conducted through known metal foundry tests that provide an understanding of the quality and suitability of the use of chromite sand as a potential substitute for silica material for rapid sand-casting applications. The results of this study will inform the industry about the optimisation of parameters for the manufacturing of a resin-coated chromite sand and its use in additive manufacturing using a Voxeljet VX 1000 printer.

Development of High Heat Dissipation and Low Thermal Expansion Printed Circuit Boards using Copper-Molybdenum Composites

Development of High Heat Dissipation and Low Thermal Expansion Printed Circuit Boards using Copper-Molybdenum Composites

Behaviour of flange joints in Steam Generator under thermal loads

Pressure vessels such as steam generators are subjected to high temperature, in addition to high pressure during the operating condition. Flanges and bolts are made up of different materials whose coefficient of thermal expansion varies. Usually, thermal expansion in bolts is greater than that of flanges. At elevated temperatures bolts expand more than that of flanges, resulting in decrease of compression in connected members achieved during assembly stage, which in turn decreases the contact stress in gasket. This can lead to leakage of internal fluid. The loss in gasket contact stress due to differential thermal expansion can be nullified by using sleeves of higher thermal expansion between the flange-nut and flange-bolt head interfaces. At higher temperatures sleeves expand more than bolts and flanges, pushing the flanges closer towards each other, thus decreasing gap created due to differential thermal expansion. The behaviour of gasketed blind flange joint with and without sleeves is analysed and the performances are compared under thermal loads. The non-linear behaviour of gaskets is included by specifying the loading and unloading characteristics with hysteresis.

Phase composition, microstructure and thermophysical properties of the Srx(Zr0.9Y0.05Yb0.05)O1.95+x ceramics

Srx(Zr0.9Y0.05Yb0.05)O1.95+x (x=1.0, 0.9, 0.8, 0.7) ceramics were prepared by solid state reaction sintering. The sintered Sr1.0(Zr0.9Y0.05Yb0.05)O2.95 is a single-phase solid solution while the sintered Srx(Zr0.9Y0.05Yb0.05)O1.95+x (x=0.9−0.7) are composites, and a significant grain growth inhibition is observed in the sintered Srx(Zr0.9Y0.05Yb0.05)O1.95+x (x=1.0, 0.9). Rare-earth elements distribution in the bulk materials indicates that Yb and Y preferentially substitute Zr-sites in SrZrO3, and the highest solubility of RE2O3 in pure SrZrO3 is ∼0.8 mol%. The sintered Srx(Zr0.9Y0.05Yb0.05)O1.95+x have high thermal expansion coefficients up to ∼11.0×10−6 K-1 (1200°C). Sr0.8(Zr0.9Y0.05Yb0.05)O2.75 has the lowest thermal conductivity of 1.38 W·m-1·K-1 at 800°C. Srx(Zr0.9Y0.05Yb0.05)O1.95+x (x=1.0, 0.9, 0.8) show no phase transition from 600 to 1400°C, whereas Srx(Zr0.9Y0.05Yb0.05)O1.95+x (x=0.9, 0.8) have excellent high-temperature phase stability over the whole investigated temperature range. Therefore, Srx(Zr0.9Y0.05Yb0.05)O1.95+x (x=1.0, 0.9, 0.8) are considered as promising TBCs materials that might be operated at higher temperatures compared to YSZ.

High TEC Copper to Connect Copper Bond Pads for Low Temperature Wafer Bonding

Copper to copper wafer hybrid bonding is the most promising technology for three-dimensional (3D) integration. In the hybrid bonding process, two silicon wafers are aligned and contacted. At room temperature (RT), these aligned copper pads contain radial-shaped nanometer-sized hollows due to the dishing effect induced by chemical-mechanical polishing (CMP). These wafers are annealed for copper to expand and connect upper and lower pads. This copper expansion is key to eliminate the radial-shaped hollows and make copper pads contacted. Therefore, in this research, we investigated the new high thermal expansion coefficient (TEC) electrodeposited copper to eliminate the dishing hollows at lower temperature than that with conventional copper using the combination of new additive A and low TEC additives. The TEC of new electrodeposited copper is 25.2 × 10−6 °C−1, 46% higher than conventional copper and the calculated contact area of copper surface at 250 °C with 5 nm dishing depth is 100%.

High TEC Copper to Connect Cu-Cu Pads for Wafer Bonding

Introduction Cu/SiO2 hybrid bonding is a promising method for 3D stacking of integrated circuits in which the copper bonding of the interconnection pads and direct bonding of the silicon dioxide surface occur simultaneously.1 This bonding technology requires a damascene-like process on each sample to be bonded (wafers and/or chips), including copper deposition and chemical mechanical polishing (CMP), in order to create the copper bonding pads and lines.2 Due to the higher erosion rate of copper in comparison with silicon dioxide, a dishing effect on the surface of copper is generated. This effect can prevent bonding and thereby lead to electrical connection failure between top and bottom pads. In order to overcome this dishing effect and enhance the copper bonding at lower temperature, we developed a high thermal expansion coefficient (TEC) electrodeposited copper.Result and discussionFigure 1 shows the thermal expansions of conventional copper (black line) and electrodeposited copper with the high TEC additives (red curve). For the conventional copper, the expansion length at 300oC is 69 μm. Meanwhile, the expansion length of high TEC copper at 300oC is 90 μm, 30% higher than conventional copper.Figure 2 shows the variation of contact area with annealing temperature for 4 nm dishing depth of circular copper pad for conventional copper and high TEC copper. Contact area values are calculated by the model in numerical study of C. Sart et al.3. Copper pad width is 4 μm and thickness is 500 nm. It can be easily seen that the contact area with high TEC copper is significantly higher than conventional copper. At 200oC, the contact area of conventional copper is only 63.5 %. Meanwhile, the contact area of high TEC copper is 93.6 %. Furthermore, 100% contact area is possible from 250oC for circular copper pads with dishing depth 4 nm.Reference Rebhan et al., 17th Electronics Packaging and Technology Conference Proceedings, 1-4 (2015).Beilliard et al., International Journal of Solids and Structures (2016). DOI: 10.1016/j.ijsolstr.2016.02.041 Sart et al., 6th Electronic System-Integration Technology Conference (ESTC) (2016). DOI: 10.1109/ESTC.2016.7764484 Figure 1