Thermal Expansion Values Research Articles

Preparation and Properties of Fluorine‐Free and Organo‐Soluble Polyesterimides and the Films With Good Optical Transparency and Thermal Stability

ABSTRACTFluorine‐free, fully aromatic polyimide (PI) films, characterized by the excellent optical transparency and high‐temperature endurance, have been successfully synthesized through either homopolymerization or copolymerization of an ester‐containing diamine, 2‐(4‐aminobenzoate)‐5‐aminobiphenyl (ABABP) and two distinct dianhydrides: 2,2‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) and 9,9‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]fluorene dianhydride (BPFPA). Owing to the good solubility of the developed PI‐I to PI‐V resins in polar aprotic solvents, particularly in N,N‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP) and N,N‐dimethylformamide (DMF), the synthesis process was performed through a two‐stage chemical imidization technique. The polymer solutions of PI‐I to PI‐V in DMAc were fabricated into films that showed exceptional optical clarity, featured with the ultraviolet cutoff wavelength (λ) below 375 nm, the light transmission at 450 nm (T450) surpassed 80%, the b* values (CIE indices) below 4.5, and the turbidity percentage (haze values) under 0.5%. Despite the fact that a higher molar concentration of BPFPA components in the dianhydride segments led to a decline in the optical characteristics of the films, the thermal resistance was concurrently enhanced. The resulting copolymerized PI films exhibited a glass transition temperature (Tg) over 264.9°C, along with the coefficients of linear thermal expansion (CTE) values of 56.7 ~ 65.9 ppm/K in temperature range of 50 ~ 200°C.

Thermal and electrical characteristics of praseodymium-based perovskites as a function of iron and cobalt substitution

Praseodymium-based perovskite samples (PSFCO) were made using the sol–gel process, consisting of Pr[Formula: see text]Sr[Formula: see text]Fe[Formula: see text]Co[Formula: see text][Formula: see text]O3 (where [Formula: see text] = 0.2, 0.4, 0.6, and 0.8). Images obtained through TEM confirmed the magnitude and clustering of particles according to their shape. In order to build solid-oxide fuel cells, it is essential to assess electrical characteristics and thermal behavior of produced samples using a dilatometer and an LCR impedance meter. Researchers looked examined how each sample’s dielectric constant and dielectric loss changed with respect to frequency, temperature, and thermal expansion. A significant change in the dielectric performance and also thermal expansion coefficient is observed when iron and cobalt contents are substituted. This change explains the compound compatibility of the cathode materials when used with electrolytes which leads to greater ionic conductivity and less thermal expansion values, together of which are important in SOFC applications.

Experimental Investigations on the Comparison of Multi-Objective Design for High Thermal Energy Applications: An Insight into Response Surface Methodology

ABSTRACT This paper focuses on optimizing the thermal properties of aluminum, copper, and iron. Response Surface Methodology was employed to determine the optimal values for thermal conductivity and thermal expansion, minimizing experimental repetitions, and reducing costs by using pre-determined input parameters. These parameters include the volume percentages of aluminum, copper, and iron. The optimized output values for thermal conductivity and thermal expansion are measured using the two-probe method and buoyancy method, respectively, and inferred from ANOVA. The Response Surface Methodology is utilized for optimization, and various approaches analyzed include Central-Composite-Design, Box-Behnken-Design, Full-Factorial-Design, and Optimal-I method. For Central-Composite-Design, deviations are 1.07 for thermal conductivity and 0.98 for thermal expansion, with R2 values of 0.9898 and 0.9355 and F values of 96.910 and 29. For Full-Factorial-Design, deviations are 39.42 for thermal conductivity and 26.83 for thermal expansion, with R2 values of 0.86 and 0.89 and F values of 20.2936 and 17.3521. For BBD, deviations are 13.49 for thermal conductivity and 22.47 for thermal expansion, with R2 values of 0.9756 and 0.9768, and F values of 66.5 and 70.1. For Optimal-I, deviations are 12.67 for thermal conductivity and 22.56 for thermal expansion, with R2 values of 0.9937 and 0.9793, and F values of 87.38 and 63.02.

What controls the onset of winter stratification in a deep, dimictic lake?

AbstractThe transition from summer stratification to winter stratification is considered for deep, dimictic Lake Superior. The fall transition is dynamically distinct from the better‐studied spring transition; it is characterized by a wind‐driven collapse of weakening summer stratification, a surface‐cooling–driven period during which the water column is essentially isothermal, and eventual onset of inverse (cold upper layer) stratification, after which sub‐thermocline water temperatures are largely fixed for the rest of the season. Due to the small value of thermal expansivity near the temperature of maximum density, temperature gradients do not impart much stability to the water column, and it is difficult for winter stratification to form immediately upon dropping below the temperature of maximum density. Instead, the water column continues to cool until the thermal expansivity is sufficiently large in magnitude to allow temperature gradients to impart stability. This observation implies that the temperature locked into the deep water for the winter season will be a consequence of the specific meteorological forcing experienced in a given year; there may be long‐term climate change driven trends in the timing of the onset of stratification but not trends in winter deep‐water temperature. To address this hypothesis, 15 yr of moored temperature data collected in Lake Superior are examined, and a scaling argument and climatological data are applied to better understand interannual variability in the onset of winter stratification.

Synergetic effect of diamond particle size on thermal expansion of Cu-B/diamond composite

Diamond particles reinforced Cu matrix (Cu/diamond) composites have promising applications for heat dissipation of high-power electronic devices because of their high thermal conductivity and suitable coefficient of thermal expansion. The effect of diamond particle size on thermal conductivity has been addressed; however, the effect of diamond particle size on thermal expansion still needs to be clarified. In this study, Cu-B/diamond composites with various diamond particle sizes ranging from 66 μm to 701 μm were fabricated to assess the impact of diamond particle size on the thermal expansion behavior. The composites exhibit low and adjustable coefficient of thermal expansion (CTE) values of 4.58–6.63 × 10−6 K−1, which align with 4–8 × 10−6 K−1 of widely employed semiconductors. The CTE of the Cu-B/diamond composites first decreases and then increases with increasing diamond particle size, which arises from a synergetic effect of interfacial bonding strength and matrix strengthening effect. As the diamond particle size is smaller than 272 μm, the interfacial bonding strength rises with increasing particle size, enabling the diamond particles to restrain the expansion of the Cu matrix more effectively and to reduce the CTE. As the diamond particle size exceeds 272 μm, the dislocation density in the Cu matrix continually decreases with increasing particle size, reducing the strength increment in the Cu matrix and increasing the CTE. The effect of thermal cycling on the thermal expansion of the Cu-B/diamond composites was also investigated, and all the composites show an increase in the CTE after 100 thermal cycles. Notably, the composite with 272 μm diamond particle size exhibits the lowest CTE increment. It shows a CTE value of 5.29 × 10−6 K−1 after thermal cycling, still compatible with the semiconductors for electronic packaging applications.

Modelling and optimisation of thermal expansion and thermal conductivity using face-centred central composite design-based response surface methodology: An experimental approach

Due to the shortage in availability of potable water the risk of water scarcity has reached its heights. Researchers have developed methods to increase the availability of potable water in various ways. Solar desalination technique using solar still would assure to have efficient water yield. Thermal energy plays an essential role in the output efficiency of PV panel and the production of solar still. The purpose of our paper is focused on optimisation of thermal properties of Aluminium, Copper and Iron. To obtain the optimised value of thermal properties namely thermal conductivity and thermal expansion an approach called response surface methodology is used. It would reduce the count in which the experiment is repeated as it has a pre-determined set of input parameters and further helps in cost reduction. The optimised input parameters are the volume percentage of Aluminium-0.17 percentage, Copper-2.42 percentage and Iron-2.64 percentage. The optimized output values obtained are of thermal conductivity and thermal expansion. A method called the two-probe method is used for determining the thermal conductivity and the Buoyancy method helps in determining the thermal expansion of the considered samples. The obtained optimised values are inferred from ANOVA. For thermal conductivity, the Adjusted R2 is 0.9796 and for thermal expansion the Adjusted R2 is 0.9032. The Standard Deviation is observed to be 0.202 whereas the Mean value is observed to be 0.4666. The resulting optimised values of thermal conductivity and thermal expansion are 0.467 W/(m*K) and 1.534*10−5(1/K). This ensured the reduced repetition of the experimental run to identify the optimal output value of the system using response surface methodology through central composite design.

The direction of core solidification in asteroids: Implications for dynamo generation

Paleomagnetic studies of meteorites over the past two decades have revealed that the cores of multiple meteorite parent bodies, including those of certain chondritic groups, generated dynamo fields as they crystallised. However, uncertainties in the direction and mode of core solidification in asteroid-sized bodies have meant using the timings and durations of these fields to constrain parent body properties, such as size, is challenging. Here, we use updated equations of state and liquidus relationships for Fe-FeS liquids at low pressures to calculate the locations at which solids form in these cores. We perform these calculations for core-mantle boundary (CMB) pressures from 0–2 GPa, and Fe-FeS liquid concentrations on the iron-rich side of the eutectic, as well as two values of iron thermal expansivity that cover the measured uncertainties in this parameter, and adiabatic and conductive cooling of these cores. We predict inward core crystallisation from the CMB in asteroids due to their low < 0.5 GPa pressures regardless of the uncertainties in other key core parameters. However, due to low internal pressures in these cores, remelting of any iron snow, as proposed to generate Ganymede’s present-day field, may be unlikely as the cores are approximately isothermal. Therefore a different mode of inward core solidification is possibly required to explain compositionally-driven dynamo action in asteroids. Additionally, we identify possible regimes at higher > 0.6 − 2 GPa pressures in which crystallisation can occur concurrently at the CMB and the centre.

Poly(ether ketone ketone)/hollow silica filler substrates and application for sixth generation communication

AbstractThe influence of density and shape of hollow silicas (silica hollow tubes (SHT) or hollow glass microspheres (HGM)) on dielectric and heat‐resisting characteristics of poly(ether ketone ketone) (PEKK)/SHT and PEKK/HGM films was systematically investigated. The dielectric characteristics of PEKK/SHT or PEKK/HGM films decrease to a minimum, as their SHT or HGM contents approach 8 or 20 wt%, respectively, and the minimum dielectric constant (εr) and dielectric loss (tan δ) of PEKK/SHT or PEKK/HGM films decrease visibly with decreasing SHT densities. By filling with 0.46 g cm−3 mean density of SHT or HGM fillers, the minimum εr and tan δ of PEKK/SHT films are somewhat smaller than those of PEKK/HGM films. The linear coefficient of thermal expansion (LCTE) values of PEKK/SHT or PEKK/HGM films reduce and their onset degradation temperature values increase gradually with increasing SHT and HGM contents. Low εr/tan δ (2.11/0.0022 and 2.2/0.0027 at 1 MHz), LCTE (35.5 × 10−6 and 31.2 × 10−6 °C−1) and excellent heat‐resisting properties favorable for sixth generation (6G) ultrarapid communication are realized for appropriately prepared PEKK/SHT and PEKK/HGM substrate films. The free‐volume‐hole characteristics of PEKK/HGM or PEKK/SHT films approach a maximum as SHT or HGM contents reach an optimum value of 8 or 20 wt%, respectively. © 2024 Society of Chemical Industry.

Evaluation of tribo-mechanical measurements and thermal expansion of Cu-based nanocomposites reinforced by high strength hybrid ceramics

It is known that Copper’s (Cu) electrical conductivity makes it a desirable material for use in industry. Due to poor properties such as hardness, thermal expansion, and corrosion resistance, its applications are limited. This manuscript solves these problems while maintaining no breakdown in electrical conductivity. In this study, high-strength ceramics (SiC nanoparticles and graphene nanosheets) were used as reinforcements in the manufacture of Cu-based hybrid nanocomposites using powder metallurgy technique. X-ray diffraction analysis (XRD) was used to investigate phase composition and crystal size of the milled powders. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM), respectively examined the microstructure of the prepared powder powders and sintered nanocomposites. Then, various properties of the sintered samples are measured, including physical, electrical and thermal properties and wear resistance. The obtained XRD technique and TEM images showed decreases in the crystal and particle size of milled samples reaching up to 14.08 and 28.30 nm, respectively for the sample contained 8 vol. % SiC + 0.8 vol. % graphene (SG8). A surprising improvement in the mechanical properties of up to 809.15, 341.84 MPa and 336.56 GPa for microhardness, strength and longitudinal modulus for the sample containing the highest reinforcements, achieving an improvement of up to 122, 61.37 and 41 percent compared to the Cu matrix. Moreover, there was a noticeable improvement in the coefficient of thermal expansion (CTE) and wear rate values of the samples by increasing the percentages of hybrid reinforcements in the examined sintered nanocomposite samples. The Sample SG8 recorded the lowest value, decreasing by about 50.2 and 76.5% compared to the SG1 sample. Finally, adding reinforcements to the Cu matrix had a negative effect on the relative density and electrical conductivity, and the lowest values was 92.94% and8.59 × 106 S/m, respectively for the SG sample.

Evaluating the impact of ZnO doping on electrical and thermal properties of calcium-aluminosilicate oxynitride glass-ceramics

This study aimed to investigate the impact of ZnO content on the structure, thermal, and electrical properties of oxynitride glass-ceramic(s) within the Ca–Al–Si–O–N (CASON) system. The base glass had the composition of Ca7Al14Si17O52N7, with ZnO additions ranging from 3 to 15 % by weight. A pristine Ca7Al14Si17O52N7 glass was successfully prepared by melt-quenching technique followed by converted into glass-ceramic by incorporating various amounts of ZnO using the field-assisted sintering technique. XRD and FESEM analysis confirmed that increasing the amount of Zn increases the crystallinity in the glass matrix. The observed crystalline phases were formed mostly from ZnO and showed higher conductivity than the remaining dielectric matrix. IR spectra confirmed the presence of bands correlated with the presence of Zn and suggested the progressive depolymerization of the silicate-aluminate network as a consequence of increasing Zn content. Density values varied between 2.75 and 2.94 gcm−3 and increased with increasing the Zn content in the glass-ceramic. The thermal expansion and thermal conductivity values increased and decreased, respectively, with the increase of Zn content in the matrix. The electrical properties of the samples were investigated using impedance spectroscopy over a wide range of frequencies (10 mHz to 1 MHz) and temperatures (153 K–623 K). The results showed that in the glass without ZnO and glass-ceramic(s) with a small addition of ZnO, the conductivity is mainly dominated by the transfer of oxygen ions and, to a small extent, by the presence of electronic conductivity. As the ZnO content increases, continuous conduction paths are formed between the ZnO crystallites, and the electrical conductivity increases rapidly and becomes dominated by electron transfer.

Characterization of microstructure, texture, grain structure, and thermal properties of Al/Ni/Al multilayered composites fabricated through cross-accumulative roll bonding

This research investigates microstructure, texture, and thermal properties of Al/Ni/Al composites fabricated by cross-accumulative roll bonding (CARB) process. According to the microstructural results, ultra-fine grain structure was observed in severely deformed layers. More grain refinement occurred when the content of Ni increased. In addition, shear texture components became stronger by increasing the CARB passes and Ni content even though the Copper-based texture components of {112}<111> existed in all deformed samples. Also, despite an improvement in thermal features of deformed aluminum and nickel layers versus temperature rise, the TD, and TC decreased as the number of passes increased. However, by increasing the rolling passes, the measured thermal capacity values modestly increased while the thermal expansion values first decreased and then increased. Regarding composites, all thermal features decreased with an increase in Ni volume fraction. Due to the restricting effect of harder reinforcement layers, the measured thermal expansion declined from 17.01 × 10−6 1/k in Al/0.2 Vf Ni to 15.4 × 10−6 1/k in Al/0.8 Vf Ni.

A comprehensive analysis of cermet design and thermal cyclic stability via elasto-viscoplastic crystal plasticity modeling

Ceramic-metal composites, or cermets, exhibit beneficial properties resulting in their use in many industrial applications. One challenge with cermets is mismatches in the coefficient of thermal expansion (CTE) values between the ceramic and metal phases that lead to residual stresses after processing, plasticity in the metal phase, internal stresses, and instability after thermal cycling. In order to make predictions of these properties to inform the design of cermets, we employ an incremental elasto-viscoplastic, self-consistent formulation to calculate the thermal, elastic, and plastic strains in two-phase polycrystalline cermet materials. This framework is extended to include temperature dependent properties, which are called implicitly within the temperature-dependent, incremental elasto-viscoplastic, self-consistent (TE-VPSC) model. Temperature-induced cooling and thermal cycling simulations are conducted using the TE-VPSC framework to study the residual stresses and plastic strains in the metal phases. Two materials are discussed in detail exhibiting stark differences based on the CTE between their ceramic and metal phases, WC/57-vol% Cu (exhibiting a pronounced CTE mismatch) and Y2O3/27-vol% Nb (exhibiting a negligible CTE mismatch). The model demonstrates high residual stresses in the Cu phase during processing and reverse plasticity leading to recovery of plastic strain during thermal cycling of the WC/Cu cermet. Moreover, the model demonstrates relatively low residual stresses and plasticity in Y2O3/Nb and a thermal stability point of 1251 °C, below which no plasticity develops in the cermet. We employ the TE-VPSC model as a design tool for cermets to systematically investigate the effects of process-induced microstructure variations (volume fraction, grain aspect ratio, and crystallographic texture are investigated) and compositional differences (19 compositions are explored) on the residual stress, degree of plasticity in the metal phase, and thermal stability point. The computational efficiency of the TE-VPSC framework makes it a desktop design tool that can be used to quantify the impact of changing composition, processing, and thermo-mechanical loading on the performance of the cermet, which can help reduce the number of time intensive and costly high temperature experiments.

Calculated purpose of the distance between the expansion joints of cement concrete pavements of roads

Problem. The article discusses current issues of increasing the efficiency and quality of construction of cement concrete pavements for highways. It is shown that the regulatory documents in force in Ukraine recommend reducing the distances between compression joints and expansion joints during the construction of roads made of cement concrete. However, such a reduction leads to a slowdown in the pace of road construction and a significant increase in construction costs. The increase in cost occurs due to frequent stoppages of a set of concrete-laying machines and the formation of a large amount of concrete waste. The cost of this waste can reach UAH 200 thousand per 1 kilometer of road. In addition, frequent stops of a set of machines when laying cement concrete pavements of highways slow down the time it takes to put roads into operation. Purpose of the work. The aim is to calculate the expansion of cement concrete pavement when heated under operating conditions. Methodology. The work used formulas for thermophysical calculations during thermal expansion of concrete. The paper presents the results of thermophysical calculations of the expansion of cement concrete pavements of highways during their operation at elevated temperatures. It has been shown that when there are a large number of compression joints, they can partially compensate for the space required for concrete expansion. At the same time, they can act as compression joints during low temperatures. A design of double expansion seams has been proposed, which allows increasing the distance between them. The joint work of compression and expansion seams makes it possible to increase the distance between expansion seams. Due to this, it is possible to reduce their number, while simultaneously increasing the speed of construction and maintaining the quality indicators of the coating concrete. Originality: The article presents the results of a production test of thermophysical calculations. It is shown that two experimental sections of road surfaces were built. The concept of the maximum value of thermal expansion of concrete was further developed. Practical value: On one of them, the distance between expansion joints was 101 m, and on the other – about 300 meters. In this case, the distance between the expansion joints in the double seam was 1.5 meters. These parameters were sufficient for efficient and high-quality operation of double expansion joints.

Effects of composition on the structure, thermal and some physical characteristics of Bi2O3-B2O3-ZnO-SiO2 glasses

The influence of composition on the structure, thermal, and some physical characteristics of bismuth borate glasses, formulated as 55Bi2O3–(35-x-y)B2O3–(5+x)ZnO–(5+y)SiO2 (where 0 ≤ x, y ≤ 15 mol%), was investigated. Comprehensive analyses were conducted using techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), Differential Thermal Analysis (DTA), and Dilatometry. XRD confirmed the amorphous nature of the glass samples, while FTIR spectroscopy revealed that the glasses are primarily composed of BO4, BO3, BiO6, BiO3, ZnO4, and SiO4 structural units. DTA provided further evidence of the samples' glassy state and insights into key temperatures like glass transition (Tg), crystallization (Tc), and melting (Tm). The study finds that substituting B2O3 with SiO2 increases all characteristic temperatures, whereas replacing it with ZnO decreases Tg and Tc but increases Tm. The maximum thermal stability, indicated by a ΔT of 99°C, was observed in the glass with a 55Bi2O3–20B2O3–20ZnO–5SiO2 composition. Dilatometric measurements showed that the investigated glasses have a high coefficient of thermal expansion (10.0–10.7 ppm/°C) values, a low glass transition temperature (345–376°C), and a low dilatometric softening temperature (364–392°C). Additionally, the density and molar volume of the samples were accurately determined.

Oxoborates of the ludwigite group: Natural and mineral-like compounds as prospective materials

Research subject. Natural oxoborates of the ludwigite group, including azoproite, ludwigite, and vonsenite. Their empirical formulas based on five oxygen atoms have the following form: azoproite (Mg1.81Fe2+0.19)∑2.00(Fe3+0.36Ti0.26Mg0.26Al0.12)∑1.00 O2(BO3), ludwigite (Mg1.69Fe2+0.30Mn2+0.01)Σ2.00(Fe3+0.90Al0.07Mg0.02Sn0.01)Σ1.00O2(BO3) and vonsenite (Fe2+1.86Mg0.13)∑1.99 (Fe3+0.92Mn2+0.05Sn4+0.02Al0.02)∑1.01O2(BO3). Aim. To establish the relationship between the composition, crystal structure, and thermal behavior (293–1373 K) of the minerals. Materials and methods. Ludwigite was collected at the Iten’yurginskoe tin skarn deposit; vonsenite was collected at the Titovskoe magnesium-skarn boron deposit; azoproite was collected at magnesian skarns of the Tazheran alkaline massif. The methods of single crystal X-ray diffraction, energy dispersive X-ray spectroscopy, high-temperature X-ray diffraction, Mössbauer spectroscopy, and thermal analysis were used. Results. Low-charge cations (Fe2+, Fe2.5+, Mg2+) tend to occupy the M(1)–M(3) sites, and high-charge cations (Fe3+, Al3+, Ti4+, Sn4+) generally occupy the M(4) site. Azoproite is characterized by the highest melting temperature Tm &gt; 1650 K. Due to the low Fe2+ content, azoproite does not undergo solid-phase decomposition across the investigated temperature range. The melting point of ludwigite exceeds 1582 K, which is due to the high Mg content; as a result of the Fe2+ → Fe3+ oxidation, it gradually decomposes with the formation of hematite, warwickite, and magnetite. The temperatures of oxidation and solid-phase decomposition in the Fe2+-rich vonsenite are approximately 100 K lower than those in ludwigite. The melting point of vonsenite is 1571 K. All the minerals are characterized by a weak degree of thermal expansion anisotropy. The main contribution to the thermal expansion anisotropy is due to the preferred orientation of the [BO3]3– triangles. Conclusions. The thermal properties of the oxoborates depend on their chemical composition. It was established that Tm increases with an increase in the Mg and Ti4+ content, and decreases with an increase in the Fe2+ content. The Fe2+ → Fe3+ oxidation is observed when the FeO component in the minerals exceeds 10 wt %, which leads to the solid-phase decomposition starting at temperatures of about 500–600 K. The values of the 293KαV volume thermal expansion of ludwigite and azoproite are comparable, while the largest values were observed for vonsenite. This is associated with the largest average bond lengths, primarily those of &lt;Fe2+–O&gt;6.

Recent Progress of TGV Technology for High Performance Semiconductor Packaging

In recent semiconductor packaging, the adoption of through silicon via (TSV) technology has become crucial for the integration of 2.5 and 3D Si chips, and interposers. The TSV offers significant advantages including high interconnect density, shortened signal pathways, and improved electrical performance. However, challenges such as electrical loss, substrate warpage, and high manufacturing costs are associated with TSV implementation. In contrast, glass-based through-glass vias (TGVs) exhibit promising characteristics such as excellent insulation properties, cost-effectiveness, and variable coefficient of thermal expansion (CTE) values that mitigate warpage in stacked devices. Moreover, they facilitate miniaturization and support high-frequency applications. This paper provides an overview of recent advancements in glass substrate, TGV drilling techniques, functional layer depositions, and Cu-filling processes in semiconductor packaging evolution.

Multi-response optimization of reinforcement parameters of aluminum alloy composites by Taguchi method and grey relational analysis

The present work describes the optimization of reinforcement parameters for hardness, thermal conductivity, and coefficient of thermal expansion while developing LM6 alloy/soda-lime glass particulate composite through Taguchi-based Grey Relational Analysis (GRA). Soda-lime glass particle weight % (1.5, 3.0 and 4.5 %), particle size (100, 150 and 300 μm) and pre-heat temperature (260, 380 and 500oC) are varied accordingly to explore the effect of reinforcement parameters on LM6 alloy/soda-lime glass composite properties. Composites are developed through stir casting based on the L9 Taguchi orthogonal array approach. The properties such as hardness, thermal conductivity and coefficient of thermal expansion of developed composites are assessed. Signal to Noise Ratios (S/N ratios) are calculated and used for the optimization of parameters. GRA is employed for multi-response optimization to find the levels of parameters that affect the desirable properties of the composite. Thus, the reinforcement parameters are optimized for attaining the combined objectives of higher hardness, higher thermal conductivity and lower coefficient of thermal expansion values considered in this investigation. The analysis shows that 4.5 wt %, particle size of 200 μm and pre-heat temperature of 380oC are optimal parameter levels. A confirmation test is carried out with the optimal parameter levels and the GRG value of 0.7778 is obtained. The GRG with the initial parameter settings is 0.4711, and the improvement of GRG is found to be 65.1 %. ANOVA is performed on GRG to find out significant parameters and the contribution of each parameter is identified. The wt.% of soda-lime glass is the most significant parameter and its contribution is 92.6 %.

Simulation, Structural, Thermal and Mechanical Properties of the FeTiTaVW High Entropy Alloy

Developing new materials to be applied in extreme environments is an opportunity and a challenge for the future. High entropy alloys are new materials that seem promising approaches to work in nuclear fusion reactors. In this work, FeTaTiVW high entropy alloys were developed and characterized with Molecular Dynamic and Hybrid Molecular Dynamic Monte Carlo simulations. The simulation results show that phase separation originates a lower potential energy per atom and a high level of segregation compared to those of a uniform solid solution. Moreover, the experimental diffractogram of the milled powder shows the formation of a body-centred cubic-type structure and the presence of TiO2. In addition, the microstructure of the consolidated material evidenced three phases: W-rich, Ti-rich, and a phase with all the elements. This phase separation observed in the microstructure agrees with the Hybrid Molecular Dynamic Monte Carlo simulation. Moreover, the consolidated material’s thermal conductivity and specific heat are almost constant from 25 °C to 1000 °C, and linear expansion increases with increasing temperature. On the other hand, specific heat and thermal expansion values are in between CuCrZr and W values (materials chosen for the reactor walls). The FeTaTiVW high entropy alloy evidences a ductile behaviour at 1000 °C. Therefore, the promising thermal properties of this system can be attributed to the multiple phases and systems with different compositions of the same elements, which is exciting for future developments.

Regulating surface energy and establishing covalent bonds to enhance interface interaction between m‐BN and polyphenylene oxide for 5G applications

AbstractIncorporation of boron nitride (BN) into polymers is a promising method to obtain composites with high thermal conductivity, low dielectric constant (Dk), and dielectric loss (Df), while the practical applications are limited by the poor interface between BN and polymer because of surface energy mismatch and absence of covalent bond connection between them. Herein, polydopamine (PDA) with good adhesion is deposited onto the BN. Then, a different amount of silane coupling agent containing vinyl reactive groups is grafted onto PDA‐coated BN. In this way, the surface energy of modified BN (m‐BN) can be adjusted to ensure BN contacts well with polymers. Moreover, reactive groups were introduced on BN for further reaction. Subsequently, covalent bonds between the m‐BN and the polyphenylene oxide (PPO) were established in situ during the curing process. The effects of the m‐BN surface energy on interface quality and thermal conductivity of composites are investigated. The m‐BN/PPO composite achieves a through‐plane thermal conductivity of 5.87 W/m·K and a low Df value of 1.53 × 10−3, as well as a low coefficient of thermal expansion (CTE) value (7.8 ppm/K) when the m‐BN loading is 32.6 vol%. This research provides a simple and efficient strategy for fabricating high‐performance composites for high‐frequency applications.Highlights Hexagonal boron nitride was modified successfully by combining non‐covalent and covalent modifications. Regulating surface energy and establishing covalent bonds enhances interface interaction between BN and polyphenylene oxide. Modified BN/polyphenylene oxide composites display improvements in thermal conductivity and dimensional stability as well as dielectric loss. Provides a feasible strategy for designing polymer composites with high thermal conductivity, dimensional stability, and low dielectric loss for 5G applications.

Injection Temperature Impacts on Reservoir Response during CO2 Storage

SummarySustained injection of industrial-scale volumes of cold CO2 into warmer subsurface rock will result in extensive cooling which can alter rock mass mechanical behavior and fluid migration characteristics. Advanced simulation tools are available to assess and characterize such phenomena; however, the effective use of these tools requires appropriate injection temperatures and rock thermophysical parameters (in addition to geomechanical and hydraulic properties). The primary objective of this study was to demonstrate the sensitivity of injection-induced tensile fracturing and fault reactivation to injection temperature and reservoir thermophysical properties during CO2 injection operations. This was achieved by (1) compiling and reviewing thermophysical parameter data available for formations in the province of Alberta, Canada, and CO2 injection temperature records for CO2 injection projects in western Canada and (2) using a 3D, physics-based, fully integrated hydraulic fracturing and reservoir simulation numerical model to examine the geomechanical response of several potential CO2 reservoirs in the Alberta Basin as a function of injection temperature, thermal conductivity (TC), and coefficient of linear thermal expansion (CLTE) values. The simulation results indicate that reducing the fluid injection temperature from 15°C (assumed in previous work) to 2°C (conservative value selected based on temperature data reviewed in this work) could trigger extensive vertical (20–130 m high, 100–600 m long) tensile fractures with rapid fracture initiation and full vertical growth within short periods (weeks to months) and continued horizontal length increase. When low values for thermophysical properties are used, the results show that thermally-induced tensile fracturing is unlikely, whereas the use of high values results in extensive tensile fracturing in all simulations. A similar conclusion was reached for the thermally-induced reactivation (unclamping) of proximal, critically-stressed faults. Notably, slip is predicted for all simulations where high thermophysical property values are used. This confirms that accurate determination of minimum fluid injection temperature and thermophysical parameters is important for containment risk assessment for commercial-scale CO2 storage projects. Another significant outcome of this work is the observation that most thermophysical parameters in the available data were measured using experimental conditions and/or temperature paths that are not representative of CO2 injection projects. As such, the development and validation of best practice approaches for accurate assessment of these parameters seem necessary.