Measurement Of Thermal Expansion Coefficient Research Articles

Comparative investigation of composition, microstructure and property influences on electrocatalysis of two representative cathodes: BaCo0.4Fe0.4Zr0.1Y0.1O3-δ versus Ba0.5Sr0.5Co0.8Fe0.2O3-δ

BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) and Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) perovskites are two representative high-performance cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Here, symmetric cell tests demonstrate that polarization resistance values of BCFZY cathode are only 0.21–0.29 times those of BSCF cathode at 740–660 °C, and 0.21–0.26 times those of BSCF cathode at the oxygen partial pressures of 1.00–0.10 atm. Distribution of relaxation times (DRT) is applied to detect individual electrode processes overlapped in impedance spectra, which finds that the dominant processes of oxygen dissociation, subsequent species transfer and reduction on BCFZY cathode are superior to those of BSCF cathode. By temperature-programmed desorption of oxygen (O2-TPD), thermal expansion coefficient (TEC) measurements, scanning electron micrograph (SEM) and energy dispersive spectra measurements, the strong oxygen combination ability with higher activation energy of oxygen desorption (Ed = 84 kJ/mol), peculiar surface state with evident nano-particle structure, more matchable TEC (19.0 × 10-6 K−1) and excellent interfacial connection with the electrolyte are observed on BCFZY cathode to account for its distinctive catalysis, as compared to BSCF cathode (Ed = 68 kJ/mol, TEC = 24.2 × 10-6 K−1).

Adhesion Characterization and Enhancement between Polyimide-Silica Composite and Nodulated Copper for Applications in Next-Generation Microelectronics.

As the need for high-speed electronics continues to rise rapidly, printed wiring board (PWB) requirements become ever-more demanding. A typical PWB is fabricated by bonding dielectric films such as polyimide to electrically conductive copper foil such as rolled annealed (RA) copper and is expected to become thinner, flexible, durable, and compatible with high-frequency 5G performance. Polyimide films inherently feature a higher coefficient of thermal expansion (CTE) than copper foils; this mismatch causes residual thermal stresses. To attenuate the mismatch, silica nanoparticles may be used to reduce the CTE of PI. A nodulated copper surface can be used to enhance the Cu/PI adhesion by additional bonding mechanisms that could include a type of mechanical bonding, which is a focus of this study. In this investigation, a 90° peel test was used to measure the peel strength in copper/polyimide/copper laminates containing nodulated copper and polyimide reinforced with 0, 20, and 40 wt % silica nanoparticles. The influence of silica nanoparticles on the peel strength was quantitatively evaluated. Laminates incorporating polyimide films lacking silica nanoparticles had a ∼3.75× higher peel strength compared with laminates reinforced with 40% silica. Their failure surfaces were analyzed by using scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy to identify the mode of failure and to understand bonding mechanisms. The key bonding mechanism, mechanical interlocking, was achieved when the polyimide surrounded or engulfed the copper nodules when the laminate was created. Post-testing failure surface analysis revealed the presence of copper on the polyimide side and polyimide on the copper side, indicating mixed mode failure. An analytical model was developed to determine the impact of applied pressure, temperature, and time on the polyimide penetration and mechanical interlocking around the copper nodules. The model was validated by measuring the peel strength on another set of specimens fabricated using increased temperature and pressure that showed a 3× increase in peel strength compared to lower temperature/pressure processing conditions. This enhanced adhesion resulted from the lower polymer material viscosity at higher temperatures, which fosters deeper and more complete penetration around the copper nodules during processing at higher pressures for longer durations. The methodology of combining peel testing, viscosity and CTE measurement, SEM/EDX, surface chemical analysis, and penetration depth calculation developed herein enables the calculation of the desired processing parameters to enhance functionality and improve adhesion.

Low-pressure performance of a Fabry–Pérot cavity based optical pressure standard working at the zero-thermal-expansion temperature

Fabry–Pérot cavity (FPC) refractometer based optical pressure standard (OPS) is very promising for a new realization of the pascal in the range 1 Pa–100 kPa. Although FPCs are made using ultra-low-expansion glass, cavity baseline (frequency) shifts due to temperature changes caused by gas pumping and filling are still a crucial factor limiting the accuracy of the OPS developed at the National Institute of Metrology (NIM) of China at the low-pressure end. In this study, the baseline shift in the NIM-OPS is eliminated by setting the working temperature at the zero-thermal-expansion (ZTE) point, which is determined by measuring the coefficient of thermal expansion (CTE) of the FPC in the temperature range 23–40 °C. CTE measurements are obtained under a background vacuum, and also under the condition of remaining gas in order to minimize the temperature gradient. The performance of the OPS for low-pressure measurements is investigated at two different working temperatures, i.e. 30.1 °C used previously and the determined ZTE temperature of 36.8 °C. An indirect comparison between the OPS and a static expansion system is performed at 1 Pa using a capacitance diaphragm gauge as the transfer standard. The disagreement of ∼ 254 mPa at 30.1 °C is reduced to within 10 mPa at the ZTE temperature.

Design and application testing of imaging probe for strain measurement

To address the challenge of obtaining key device strain parameters within narrow spaces, this paper presents the design of a small-sized optical imaging probe with an independent optical system based on the basic principle of digital image correlation (DIC). To validate the strain measurement accuracy of the probe, a high-temperature heating system was built under in a laboratory setting, and experimental tests involving room temperature strain measurement and high temperature thermal expansion coefficient measurement were conducted. The findings demonstrate the potential of the developed probe for strain measurement in critical components situated in restricted spaces.

Uncertainty Quantification of Thermophysical Property Measurement in Space and on Earth: A Study of Liquid Platinum Using Electrostatic Levitation

A study of uncertainty analysis was conducted on four key thermophysical properties of molten Platinum using a non-contacting levitation technique. More specifically, this work demonstrates a detailed reporting of the uncertainties associated with the density, volumetric thermal expansion coefficient, surface tension and viscosity measurements at higher temperatures for a widely used refractory metal, Platinum using electrostatic levitation (ESL). The microgravity experiments were conducted using JAXA’s Electrostatic Levitation Furnace (ELF) facility on the International Space Station and the terrestrial experiments were conducted using NASA’s Marshal Space Flight Center’s ESL facility. The performance of these two facilities were then quantified based on the measurement precision and accuracy using the metrological International Standards Organization’s Guide to the Expression of Uncertainty Measurement (GUM) principles.

High-Accuracy Thermal Expansion Coefficient Measurement Based on Fiber-Optic EFPIs With Automatic Temperature Compensation

High-Accuracy Thermal Expansion Coefficient Measurement Based on Fiber-Optic EFPIs With Automatic Temperature Compensation

Development of Pyros Alloy as a Certified Reference Material for Thermal Expansion Coefficient Measurements

The push-rod dilatometer is the most widely used and popular commercial apparatus for measuring the thermal expansion coefficient of metals, it should be metrological verified before testing. Certified reference materials are the most applicable and effective means of verifying such equipment. Here, a reference material [termed Pyros (Ni-based) alloy] was developed for measuring the thermal expansion coefficient. The Pyros alloy reference material exhibited a high thermal expansion coefficient: a range of 12.7–16.8 (× 10–6 °C−1). The maximum temperature of the certified value was 1000 °C. This range and value almost span the entire application needs of metals, especially steel alloy or superalloys. Thus, Pyros alloy is suitable as a reference material for validating the push-rod dilatometer based on comparative measurements.

Defect Chemistry Engineering Promotes the Dopability of Cu for an Extraordinary Thermoelectric Performance of Hole-Doped PbSe with Resonant States

Cu substitution for Pb (CuPb) has been theoretically predicted to introduce resonant states near the valence band edge of PbSe. However, experimentally, it has not been verified yet due to the extremely low solubility (∼0.3 atom %) of CuPb. In this study, we demonstrate that the solubility limit of CuPb is extended to at least 1.5 atom % in PbSe by pairing with an identical amount of Cu interstitials (Cui), while excess Cu precipitates out as a Cu2Se phase at grain boundaries. As a result of the increased dopability of CuPb, a significant enhancement of the Seebeck coefficient is realized in hole-doped PbSe because of CuPb-induced resonant states. This is also testified by first-principles calculations. Moreover, the rich point defects (CuPb, Cui), line defects (dislocations), and Cu2Se precipitates remarkably frustrate the phonon propagation of PbSe, leading to ∼45% reduction of lattice thermal conductivity (κlat) at room temperature. At elevated temperatures (>623 K), there is a dynamic migration of Cu atoms from Cu2Se precipitates to tetrahedral interstices of the PbSe matrix as evidenced by the temperature-variant Hall study and thermal expansion coefficient measurement. This diffusion-like process of Cu further drops the κlat to ∼0.27 W m–1 K–1 at 823 K. Consequently, a peak ZT of ∼1.8 at 873 K is achieved in the (Cui)0.01Pb0.97(CuPb)0.01Na0.02Se sample. This work highlights the potential of the defect structure design in innovating new functional materials, particularly high-performance thermoelectrics.

Determination of the coefficient of thermal expansion of ultra-low-expansion glass using anultrasonic immersion testing method.

The coefficient of thermal expansion (CTE) of ultra-low-expansion (ULE) glass is critical to the development of precision optical systems. Herein, an ultrasonic immersion pulse-reflection method is proposed to characterize the CTE of ULE glass. The ultrasonic longitudinal wave velocity of ULE-glass samples with significantly different CTE values was measured using a correlation algorithm combined with moving-average filtering, which can achieve 0.2m/s precision with a contribution to the ultrasonic CTE measurement uncertainty of 0.47ppb/°C. Furthermore, the established ultrasonic CTE measurement model predicted the 5°C-35°C mean CTE with a root-mean-square error of 0.9ppb/°C. Notably, a complete uncertainty analysis methodology was established in this paper, which can provide directional guidance for the subsequent development of higher-performance measurement devices and the improvement of relevant signal processing procedures.

Reducing the Cobalt Content in SrCo0.95Ti0.05O3-δ-Based Perovskites to Produce Cleaner Cathodes for IT-SOFCs

Recent studies have demonstrated the possibility of stabilizing the cubic or tetragonal perovskite phases in the SrCoO3-δ system at room temperature by partially replacing Co atoms with small amounts of highly charged cations like Ti4+ in SrCo0.95Ti0.05O3-δ. This material gives extraordinary performances as a cathode for solid oxide fuel cells (SOFCs) at intermediate temperatures (800–850 °C). In this work, we have tried to still improve this cathode in a cleaner and low-priced material by reducing its Co content, since Co is a high-cost and toxic element, additionally reducing its thermal expansion coefficient (TEC), to make it more mechanically compatible with the rest of the components of a SOFC. SrCo0.50Fe0.45Ti0.05O3-δ perovskite has been obtained by the citrate method, introducing 45% of Fe in the Co and Ti positions. Its crystalline structure has been studied by X-ray diffraction (XRD) and neutron powder diffraction (NPD) and has been correlated with mechanical and electrical properties. A chemical compatibility study between SrCo0.50Fe0.45Ti0.05O3-δ and the electrolyte La0.8Sr0.2Ga0.83Mg0.17O3-δ (LSGM) revealed that both materials do not interact at high temperatures. TEC measurements show a linear expansion over the entire temperature range. Finally, the perovskite showed good electrical conductivity and an encouraging power density value of 667 mW/cm2 at 850 °C, which indicate that this material is a promising cathode for SOFCs at intermediate temperatures.

A Dual-Cavity Fiber Fabry-Pérot Interferometer for Simultaneous Measurement of Thermo-Optic and Thermal Expansion Coefficients of a Polymer.

This paper presents a novel method based on a dual-cavity fiber Fabry-Pérot interferometer (DCFFPI) for simultaneously measuring the thermo-optic coefficient (TOC) and thermal expansion coefficient (TEC) of a polymer. The polymer is, by nature, highly responsive to temperature (T) in that its size (length, L) and refractive index (RI, n) are highly dependent on the thermal effect. When the optical length of the polymer cavity changes with T, it is difficult to distinguish whether there is a change in L or n, or both. The variation rates of L and n with a change in T were the TOC and TEC, respectively. Therefore, there was a cross-sensitivity between TOC and TEC in the polymer-based interferometer. The proposed DCFFPI, which cascades a polymer and an air cavity, can solve the above problem. The expansion of the polymer cavity is equal to the compression of the air cavity with the increase in T. By analyzing the individual optical spectra of the polymer and air cavities, the parameters of TOC and TEC can be determined at the same time. The simultaneous measurement of TOC and TEC with small measured deviations of 6 × 10-6 (°C-1) and 3.67 × 10-5 (°C-1) for the polymer NOA61 and 7 × 10-6 (°C-1) and 1.46 × 10-4 (°C-1) for the NOA65 can be achieved. Experimental results regarding the measured accuracy for the class of adhesive-based polymer are presented to demonstrate the feasibility and verify the usefulness of the proposed DCFFPI.

Preparation and Properties of Ce0.8Sm0.16Y0.03Gd0.01O1.9-BaIn0.3Ti0.7O2.85 Composite Electrolyte

Samarium, gadolinium, and yttrium co-doped ceria (Ce0.8Sm0.16Y0.03Gd0.01O1.9, CSYG) and BaIn0.3Ti0.7O2.85 (BIT07) powders were prepared by sol-gel and solid-state reaction methods, respectively. CSYG-BIT07 composite materials were obtained by mechanically mixing the two powders in different ratios and calcining at 1300 °C for 5 h. Samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), as well as electrical properties and thermal expansion coefficient (TEC) measurements. A series of CSYG-BIT07 composite materials with relative densities higher than 95% were fabricated by sintering at 1300 °C for 5 h. The performance of the CSYG-BIT07 composite electrolyte was found to be related to the content of BIT07. The CSYG-15% BIT07 composite exhibited high oxide ion conductivity (σ800°C = 0.0126 S·cm−1 at 800 °C), moderate thermal expansion (TEC = 9.13 × 10−6/K between room temperature and 800 °C), and low electrical activation energy (Ea = 0.89 eV). These preliminary results indicate that the CSYG-BIT07 material is a promising electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs).

Thin film combinatorial sputtering of Al-Ce alloys: Investigating the phase separation of as-deposited solid solutions and determining the coefficient of thermal expansion

AlxCe100−x thin films with a composition range of ~75.0 < x < 99.5 at% (36.5 < x < 97.5 wt%) were synthesized via combinatorial co-sputtering from an Al and an Al50Ce50 target. The crystal structure, phase fraction, film morphology, electrical resistivity, and temperature-dependent coefficients of thermal expansion (CTE) are all correlated to the AlxCe100−x composition. The as-deposited films form a metastable solid-solution, and annealing leads to the formation of the thermodynamically stable two-phase system of Al and the α-Al11Ce3 intermetallic. Temperature dependent x-ray diffraction (XRD) reveals that the two phases expand independently of one another, and the thin film Al temperature-dependent CTE is similar to bulk Al. The thin film Al11Ce3 intermetallic phase has a nearly constant CTE of ~1.5 × 10−5/°C within the temperature range studied (25–550 °C). To confirm the thin film Al11Ce3 results, bulk stoichiometric Al11Ce3 and +/- 1 wt% Ce samples were prepared and the CTE of each was measured with the same conditions. A Rietveld analysis of the bulk data enabled an estimation of the CTE in each of the 3 orthorhombic lattice parameters, which displayed anisotropic behavior. The thin film and bulk CTE measurements were in very good agreement. Estimations of the temperature dependent CTE of the two-phase alloys are made via the Reuss and Voigt models. By demonstrating the efficacy of the approach, more complex multi-component rapid materials discovery of low CTE Al-alloys can be pursued via the combinatorial thin film synthesis and XRD measurement.

Coefficient of Thermal Expansion of Concrete Produced with Recycled Concrete Aggregates

This study presents a comparison between the coefficient of thermal expansion (CTE) of concrete produced with natural aggregate and that of concrete produced with recycled concrete aggregate. In order to achieve this, natural aggregate concrete (NAC) specimens were produced, tested, then crushed and sieved in the laboratory to obtain recycled concrete aggregates, which was then used in the production of recycled aggregate concrete (RAC) specimens. The RAC samples were then tested and compared to the NAC samples. The CTE testing was carried out using a AFTC2 CTE measurement system produced by Pine Instrument Company. In addition to CTE testing, the water absorption, specific gravity, and unit weight of the aggregates was determined. A vacuum impregnation procedure was used for the water absorption test. The recycled aggregate properties showed a significantly higher absorption capacity than that of the natural aggregates, while the unit weight and specific gravity of the recycled aggregate were lower than that of the natural aggregates. The average CTE results showed that both the NAC and the RAC samples expanded similarly. The results show that the CTE of RAC depends on the natural aggregate used in the NAC, which was recycled to produce the RAC. Also, there was no significant difference between the average CTE values of the RAC and that of NAC that could discredit the use of recycled aggregate in concrete.

The development of the real-time Michelson interferometer for the measurement of thermal expansion coefficients of dental composites nanofiller

This study aims to design a thermal time-based expansion coefficient sensor system using a nickel interferometer that uses a 6 Watts heater to produce a similar oral cavity temperature of 30°C to 60°C. The light source used was the He-Ne Laser, with a wavelength of 632.8 nm. Hollow cylindrical samples with an outer diameter of 1.1 cm, an inner diameter of 1 cm, and a height of 1.5 cm were placed in the sample box behind one of the Michelson Interferometer mirrors. The interference pattern (fringes) formed was recorded using a webcam and counted using the principle of motion detection in the Delphi program. The temperature sensor used was LM 35 with LM 358 amplifier. The resulting voltage output was converted to a temperature value with Arduino. The data were then displayed on a PC with the Delphi interface. The purposely written Delphi program has four functions: recording and counting fringes, displaying temperature, and calculating the thermal expansion coefficient of acrylic resin and nanofiller composite. The generated data in the study included the heating time for 25,421 seconds to produce a temperature of 60°C, delay of (0,802 ± 0,006) second with the sensor performance of 99,76%, and software performance of 98,18%. In three data collections, the average thermal expansion coefficient of resin acrylic was (111.37 ± 10.93). 10-6 / ° C with an error percentage of 23.74% from the literature, while for the composite nanofiller samples, we obtained (49.6 ± 0.95). 10-6 / ° C with an error percentage of 6.9% from previous studies.

Measurement of the in-plane coefficient of thermal expansion of ceramic protective coatings from room temperature to 1400 °C

A technique for measuring the coefficient of thermal expansion (CTE) of ceramic protective coatings from 25 °C to 1400 °C is proposed. The surface of a self-standing mullite coating heated in a furnace was observed by a scanning laser microscope which detects only the blue laser light reflected from the sample surface as an image source and thereby eliminates the effect of thermal radiation. Images with constant contrast independent of temperature without halation by thermal radiation were obtained. The series of images from 25 °C to 1400 °C was used for the digital image correlation and the thermal strain was measured for each temperature; the CTE was calculated from the data as a function of temperature. The reliability of the measurement was confirmed through the CTE measurement of a c-plane sapphire plate and practically applied to the measurement of a mullite coating. For cases in which a self-standing coating cannot be obtained, we also proposed a method of CTE measurement for a coating adhered to a substrate, with consideration for the effect of substrate constraint.

Two-Dimensional Displacement Sensor Based on a Dual-Cavity Fabry-Perot Interferometer

Simultaneously and independently measuring two-dimensional (2D) displacement, one-dimensional (1D) for out-of-plane measurement and 1D for in-plane measurement, is important for practical applications. Although extrinsic fiber Fabry-Perot interferometers (EFPIs) have been reported for highly precise out-of-plane displacement measurements for many years, simultaneous measurement of 2D displacement with sub-micrometer accuracy has not been realized by a monolithic EFPI as far as we know. In this paper, a monolithic dual-cavity EFPI to realize 2D displacement measurement of a target is reported. By quantitatively analyzing and experimentally calibrating the linear dependences of the in-plane displacement sensitivity and interception on the cavity length, the effect of out-of-plane displacement on the in-plane displacement measurement is removed, which is the basis of the 2D displacement detection. 2D random movement detection and the repeatability of the system are investigated experimentally. Within the range of ±7 μm for in-plane displacement, and 352 μm-358 μm for cavity length, demodulation errors better than 96 nm are achieved. The 2D displacement measurement system based on the dual-cavity EFPI with the advantages of noncontact, high accuracy and compact size is promising to be applied in the 2D acceleration measurement, 2D rotor vibration measurement, 2D precise positioning in semiconductor manufacture, thermal expansion coefficient measurement, and so on.

The Dependence of Ultrasonic Velocity in Ultra-Low Expansion Glass on Temperature

The coefficient of thermal expansion (CTE) is an important property of ultra-low expansion (ULE) glass, and the ultrasonic velocity method has shown excellent performance for the nondestructive measurement of CTE in large ULE glass. In this method, the accurate acquisition of the ultrasonic velocity in ULE glass is necessary. Herein, we present a correlation method to determine the ultrasonic TOF in ULE glass and to further obtain the ultrasonic longitudinal wave velocity (cL) indirectly. The performance of this method was verified by simulations. Considering the dependence of cL on temperature (T), we carried out the derivation of the analytical model between cL and T. Based on reasonable constant assumptions in the physical sense, a cL–T exponential model was produced, and some experimental results support this model. Additional experiments were carried out to validate the accuracy of the cL–T exponential model. The studies we conducted indicate that the cL–T exponential model can reliably predict the ultrasonic velocity in ULE glass at different temperatures, providing a means for the nondestructive CTE measurement of large ULE glass at a specified temperature.

Structure and Thermal Expansion of Cu−90 vol. % Graphite Composites

Copper–graphite composites are promising functional materials exhibiting application potential in electrical equipment and heat exchangers, due to their lower expansion coefficient and high electrical and thermal conductivities. Here, copper–graphite composites with 10–90 vol. % graphite were prepared by hot isostatic pressing, and their microstructure and coefficient of thermal expansion (CTE) were experimentally examined. The CTE decreased with increasing graphite volume fraction, from 17.8 × 10−6 K−1 for HIPed pure copper to 4.9 × 10−6 K−1 for 90 vol. % graphite. In the HIPed pure copper, the presence of cuprous oxide was detected by SEM-EDS. In contrast, Cu–graphite composites contained only a very small amount of oxygen (OHN analysis). There was only one exception, the composite with 90 vol. % graphite contained around 1.8 wt. % water absorbed inside the structure. The internal stresses in the composites were released during the first heating cycle of the CTE measurement. The permanent prolongation and shape of CTE curves were strongly affected by composition. After the release of internal stresses, the CTE curves of composites did not change any further. Finally, the modified Schapery model, including anisotropy and the clustering of graphite, was used to model the dependence of CTE on graphite volume fraction. Modeling suggested that the clustering of graphite via van der Waals bonds (out of hexagonal plane) is the most critical parameter and significantly affects the microstructure and CTE of the Cu–graphite composites when more than 30 vol. % graphite is present.

Measurement of thermal expansion coefficient of rock minerals using XRD and its implications to thermal damage mechanism

The measurement of thermal expansion coefficient (TEC) of rocks is of vital importance to various geotechnical engineering applications, such as high-level radioactive waste disposal, enhanced geothermal energy exploitation, ultra-deep borehole stability, liquid nitrogen storage, etc. However, previous researchers mainly focused on the thermal expansion coefficient of various rocks, instead of the constituent minerals. In this manuscript, we measured the both temperature-dependent volume and linear thermal expansion coefficients of two rock-forming minerals (quartz and albite) using both high-temperature X-ray diffraction (XRD) as well as low-temperature XRD. It is found that there exist strong anisotropic linear thermal expansion coefficients of the two minerals, which can provide strong reference for the relevant engineering applications and numerical simulations.