Thermal Growth Research Articles

A Model for the Temperature Distribution in a Rolled Joint in a CANDU Reactor Exploiting the Decomposition of the β-Zr Phase

A competing-rates model is presented to account for operational changes in the metastable β-Zr phase of the Zr-2.5Nb alloy used to make CANDU reactor pressure tubes and is used to predict temperature gradients at the outlet rolled joints using the decomposition of the β-Zr phase as a proxy for temperature. High temperatures decompose the β phase by enhancing the formation of small particles of ω and α phases. Fast neutron flux causes the ω and α phases to shrink. This process is assumed to depend on the total volume of the particles, because they are comparable to, or smaller than, the size of the neutron displacement cascades. The barrier energy for thermal growth was determined to be 2.43 eV, when an Arrhenius A factor of 1013/s was assumed. The cross section for (ω+α)-phase shrinkage is 24.5 barns for Zr-2.5Nb irradiated in CANDU reactors. Assuming that the shrinkage is dominated by the migration of self-interstitial point defects, a defect production efficiency of 1.4% was found.

Comparative Analysis of Broiler Housing Systems: Implications for Production and Wellbeing.

This study compares the effects of modern colony cage systems and traditional floor systems on the production and welfare of broiler chickens. Through two trials spanning 35 days each, we evaluated various physiological parameters, including growth performance, bone health, stress responses, and meat quality. Colony cages demonstrated superior thermal regulation and growth performance compared to traditional floor systems, but also exhibited higher frequencies of leg deformity and reduced standing ability. Conversely, the broilers in traditional floor systems experienced heat stress-related challenges, impacting the meat quality. Our findings underscore the need to balance productivity with animal welfare in broiler farming practices. By understanding the distinct impacts of different housing systems, we can work towards improving broiler rearing methods to ensure optimal welfare and production outcomes.

Nonvolatile bipolar resistive switching characteristics of aluminum oxide grown by thermal oxidation processes

This study proposes a bipolar resistive random-access memory (RRAM), which is fabricated using an aluminum oxide (AlO x ) resistive switching (RS) layer. The RRAM shows a large memory window of 106 at a low read voltage of 0.5 V. In addition, high switching speed, long retention time, and superior read-disturb immunity are observed. AlO x layers are prepared by a thermal oxidation growth process. Aluminum metal films deposited on n+-Si wafers are oxidized at O2/(O2 + N2) flow rate ratios of 50%–100%. Al/AlO x /n+-Si device shows no RS behavior when the AlO x is grown in a pure O2 environment. As the O2/(O2 + N2) flow rate ratio decreases to 50%, Al/AlO x :N/n+-Si device reveals stable bipolar RS characteristics. A filamentary mode based on oxygen interstitial and Al vacancy is proposed to explain the difference in electrical characteristics of AlO x devices prepared at different O2 flow rates.

Suppressing the oxygen-ionic conductivity and promoting the phase stability of the high-entropy rare earth niobates via Ta substitution

Improving and optimizing the target properties of ceramics via the high entropy strategy has attracted significant attention. Rare earth niobate is a potential thermal barrier coating (TBCs) material, but its poor high-temperature phase stability limits its further application. In this work, four sets of TBCs high-entropy ceramics, (Sm1/5Dy1/5Ho1/5Er1/5Yb1/5)(Nb1/2Ta1/2)O4 (5NbTa), (Sm1/6Dy1/6Ho1/6Er1/6Yb1/6Lu1/6)(Nb1/2Ta1/2)O4 (6NbTa), (Sm1/7Gd1/7Dy1/7Ho1/7Er1/7Yb1/7Lu1/7)(Nb1/2Ta1/2)O4 (7NbTa), (Sm1/8Gd1/8Dy1/8Ho1/8Er1/8Tm1/8Yb1/8Lu1/8) (Nb1/2Ta1/2)O4 (8NbTa) are synthesized using a solid-state reaction method at 1650 °C for 6 h. Firstly, the X-ray diffractometer (XRD) patterns display that the samples are all single-phase solid solution structures (space group C2/c). Differential scanning calorimetry (DSC) and the high-temperature XRD of 8NbTa cross-check that the addition of Ta element in 8HERN increases the phase transition temperature above 1400 °C, which can be attributed to that the Ta/Nb co-doping at B site introduces the fluctuation of the bond strength of Ta-O and Nb-O. Secondly, compared to high-entropy rare-earth niobates, the introduction of Ta atoms at B site substantially reduce thermal conductivity (reduced by 44 %, 800 °C) with the seven components high entropy ceramic as an example. The low thermal conductivity means strong phonon scattering, which may originate from the softening acoustic mode and flattened phonon dispersion in 5–8 principal element high entropy rare earth niobium tantalates (5–8NbTa) revealed by the first-principles calculations. Thirdly, the Ta/Nb co-doping in 5–8NbTa systems can further optimize the insulation performance of oxygen ions. The oxygen-ion conductivity of 8NbTa (3.31 × 10−6 S cm−1, 900 °C) is about 5 times lower than that of 8HERN (15.8 × 10−6 S cm−1, 900 °C) because of the sluggish diffusion effect, providing better oxygen barrier capacity in 5–8NbTa systems to inhibit the overgrowth of the thermal growth oxide (TGO) of TBCs. In addition, influenced by lattice distortion and solid solution strengthening, the samples possess higher hardness (7.51–8.15 GPa) and TECs (9.78 × 10−6 K−1–10.78 × 10−6 K−1, 1500 °C) than the single rare-earth niobates and tantalates. Based on their excellent overall properties, it is considered that 5–8NbTa can be used as auspicious TBCs.

Interfacial delamination mechanism of thermal barrier coatings with real microstructure considering gradient thermal and growth strains based on the fracture phase field

The interface of atmospheric plasma spray (APS) thermal barrier coatings (TBCs) is highly irregular and rough, while their microstructure is porous and extremely uneven. This complexity leads to intricate patterns during the growth of thermally grown oxide (TGO), the distribution and evolution of the generated stress, as well as the initiation and expansion of cracks. Along these lines, in this work, a phase-field theory considering both the thermal gradient strain and TGO growth was established to thoroughly investigate the interface oxidation cracking in TBCs. More specifically, a two-dimensional geometric model of APS TBCs was established, incorporating real interface morphology and microstructure. Numerical simulations and experiments were also conducted to study the temperature and stress distribution, as well as the underlying mechanism of interface cracking during the service of TBCs. The results indicated that at high temperatures, the bottom temperature of the top coating (TC) layer with a porosity of 3.1% and a thickness of 200 μm was approximately 5 °C lower than that of the TC layer without porosity. Compared to the ideal model without pores, the model considering the real microstructure, with the presence of microcracks in the TC, makes it easier for the normal stress in the TGO at the peak region to be released. The inter-lamella cracks (Type A) in the TC near the peaks initiated earliest, followed by the creation of inter-lamella cracks at other locations, accompanied by the appearance of lamella-fracture cracks (Type B), inter-lamella to interfacial cracks (Type C), inter-lamella to TGO cracks (Type D), and internal TGO cracks (Type E). The coalescence of all these types of cracks will ultimately lead to coating failure.

Energy induced carbon nanotube rapidly assemble variable interweaving networks at the carbon fiber interface

Regulating carbon fiber with carbon nanotubes (CNTs) is important to improve the interface mechanical properties of composite materials. Therefore, a “thermotropic flash assembly (TFA)” process for the synthesis of CNTs in liquid phase is proposed. This work achieves the continuous and controllable formation of a micro-nano interweaving network of CNTs, with predictions made from a thermal perspective through enhancements to the process. Firstly, 12 working conditions and a large number of sample data are established by microcontrolling carbon fiber energy, and the growth thickness of CNTs is predicted by self-learning algorithm. Secondly, the “liquid-solid-solid” thermotropic growth of CNTs is proposed for the first time, which is different from the existing “gas-liquid-solid” and “gas-solid-solid” growth mechanisms of CNTs. Theoretical deductions and calculations are made for the interfacial temperature, exothermic, and endothermic energies during the growth process, which leads to the determination of a thermal growth space radius of 2.4 μm at the interface. Finally, it is found that the shear strength is increased by at least 27.7 %, although some tensile strength is sacrificed. This work not only points out the direction for low-cost, large-scale and customized control of interface properties, but also lays a theoretical foundation for exploring the growth mechanism of CNTs in an open environment at low temperature.

Instantaneous thermal fracture behaviors of a bimaterial with a penny-shaped interface crack via generalized fractional heat transfer

In the high-temperature environment, a larger thermal expansion mismatch of a bimaterial leads to pronounced thermal stresses and interface crack growth. In this paper, a generalized fractional heat conduction model is used to determine the instantaneous thermal fracture behaviors of a bimaterial interface crack. An axisymmetric thermoelastic problem is solved with the aid of Goodier's thermoelastic displacement potential and Love's potential functions. A mixed initial-boundary value problem is then converted to a singular integral equation of second kind by using the Hankel and Laplace integral transforms. Numerical results of the intensity factors of heat flux and thermal stresses are evaluated using Stehfest's Laplace inversion scheme. The influence of fractional kernel functions with power and exponential law are analyzed, respectively, for aluminum-steel and steel-epoxy, respectively. The thermal stress intensity factors exhibit more wave-like behaviors based on Riemann-Liouville and Atangana-Baleanu models which is different from Caputo-Fabrizio and the complete diffusion model.

Synthesis, crystallization behavior and mechanical property of biodegradable Poly(butylene succinate-co-2-methyl succinate) copolyesters

In this research, a series of biodegradable poly(butylene succinate-co-2-methyl succinate) (PBSMS) random copolyesters with butylene 2-methyl succinate (BMS) unit content from about 10 to 90 mol% were successfully synthesized. Both the homopolymers poly(butylene succinate) (PBS), poly(butylene 2-methyl succinate) (PBMS), and PBSMS copolyesters showed relatively high intrinsic viscosity values of over 0.8 dL/g. The basic thermal parameters, crystallization behavior, crystal structure, spherulitic morphology and growth rate, and mechanical properties of PBSMS copolyesters were extensively studied and compared with those of PBS. The incorporation of methyl group not only effectively increased the toughness of PBSMS copolyesters but also significantly restrained the crystallizability of these copolyesters, showing that PBSMS copolyesters with the BMS unit content higher than 50 mol% were amorphous. Among these copolyesters, PBSMS30 (BMS unit content = 30 mol%) exhibited the most outstanding mechanical properties, with a Young's modulus of 188.0 ± 19.1 MPa, a tensile strength of 19.1 ± 1.8 MPa, and an elongation at break of 714.5 ± 23.2 %. By randomly introducing methyl as a side group into the PBS main chain, the mechanical properties of PBSMS copolyesters have been significantly improved. From the perspective of structure and properties, this study should be interesting and crucial for the development and research of biodegradable polymers.

Nanostructured Yb2SiO5/mullite-SiC/Si environmental barrier coating with long-term stability at 1250 °C

In this work, nanostructured Yb2SiO5/mullite-SiC/Si environmental barrier coatings (EBCs) were prepared to investigate the effect of heat treatment on the microstructure and phase transition of nanostructured Yb2SiO5/mullite-SiC/Si coatings. The Yb2SiO5 content and microstructure evolution in the coatings were thoroughly analyzed before and after heat treatment. The results demonstrate a slight decrease in the porosities of nanostructured Yb2SiO5 and mullite-SiC coatings, accompanied by a gradual growth in grain sizes with increasing heat treatment time, indicating the nanostructured EBCs show good resistance to sintering. Moreover, the thickness of thermal growth oxidation layer is only 200 nm at 1250 °C for 500 h of heat treatment. In particular, the presence of the Yb2O3 phase has been observed to exert a favorable influence on the thermal stability of nanostructured EBCs. This work provides an innovative strategy for designing advanced EBCs with excellent high-temperature thermal stability.

The survival and entrainment of molecules and dust in galactic winds

ABSTRACT Recent years have seen excellent progress in modelling the entrainment of T ∼ 104 K atomic gas in galactic winds. However, the entrainment of cool, dusty T ∼ 10–100 K molecular gas, which is also observed outflowing at high velocity, is much less understood. Such gas, which can be 105 times denser than the hot wind, appears extremely difficult to entrain. We run 3D wind-tunnel simulations with photoionization self-shielding and evolve thermal dust sputtering and growth. Unlike almost all such simulations to date, we do not enforce any artificial temperature floor. We find efficient molecular gas formation and entrainment, as well as dust survival and growth through accretion. Key to this success is the formation of large amounts of 104 K atomic gas via mixing, which acts as a protective ‘bubble wrap’ and reduces the cloud overdensity to χ ∼ 100. This can be understood from the ratio of the mixing to cooling time. Before entrainment, when shear is large, tmix/tcool ≲ 1, and gas cannot cool below the ‘cooling bottleneck’ at 5000 K. Thus, the cloud survival criterion is identical to the well-studied purely atomic case. After entrainment, when shear falls, tmix/tcool > 1, and the cloud becomes multiphase, with comparable molecular and atomic masses. The broad temperature PDF, with abundant gas in the formally unstable $50 \, {\rm K} \lt T \lt 5000 \, {\rm K}$ range, agrees with previous ISM simulations with driven turbulence and radiative cooling. Our findings have implications for dusty molecular gas in stellar and active galactic nuclei outflows, cluster filaments, ‘jellyfish’ galaxies, and asymptomatic giant branch winds.

Structural evolution and enhanced thermal cycling life of HVAF-sprayed NiCrAlY bond coat modified by YSZ

Thermal barrier coatings with varied bond coat structures were deposited using high-velocity air fuel spraying. Highly hard YSZ particles are introduced into the NiCrAlY bond layer by accelerating to supersonic speeds at low temperatures to change the porous structure of the bond coat. We systematically increased the YSZ content in NiCrAlY bond coats and extensively investigated microstructure, oxidation behavior, thermal cycling life, and residual stress variation of the bond coats suing a combination of scanning electron microscopy, optical microscope, confocal Raman microprobe. Introduction of YSZ particles reduced the porosity of NiCrAlY bond coat from 2.69% to 0.45%, and altered the oxidation behavior of the bond layer. The NiCrAlY mixed YSZ composite structure induced the formation of a complex and thin thermal growth oxide layer on the bond coat during oxidation process, greatly alleviating and reducing the thermal stress generated of the coating and during the thermal cycling test. And the thermal cycling life of the NiCrAlY mixed YSZ composite structure coating is 2.8 times longer than that of the ordinary NiCrAlY coating. This finding highlights the significance of the bond coat structure in enhancing the service life of thermal barrier coatings.

Radiative loss and ion-neutral collisional effects in astrophysical plasmas.

In this paper, we study the role of radiative cooling (RC) in a two-fluid model consisting of coupled neutrals and charged particles. We first analyse the linearized two-fluid equations where we include radiative losses in the energy equation for the charged particles. In a one-dimensional geometry for parallel propagation and in the limiting cases of weak and strong coupling, it can be shown analytically that the instability conditions for the thermal mode and the sound waves, the isobaric and isentropic criteria, respectively, remain unchanged with respect to one-fluid radiative plasmas. For the parameters considered in this paper, representative for the solar corona, the RC produces growth of the thermal mode and damping of the sound waves. In the weak coupling limit, the growth of the thermal instability and the damping of the sound waves is as derived in Field (Field 1965 Astrophys. J. 142, 531(doi:10.1086/148317)) using the charged fluid properties. When neutrals are included and are sufficiently coupled to the charges, the thermal mode growth rate and the wave damping both reduce by the same factor, which depends on the ionization fraction only. For a heating function that is constant in time, we find that the growth of the thermal mode and the damping of the sound waves are slightly larger. The numerical calculation of the eigenvalues of the general system of equations in a three-dimensional geometry confirm the analytic results. We then run two-dimensional fully nonlinear simulations that give consistent results: a higher ionization fraction or lower coupling will increase the growth rate. The magnetic field contribution is negligible in the linear phase. Ionization-recombination effects might play an important role because the RC produces a large range of temperatures in the system. In the numerical simulation, after the first condensation phase, when the minimum temperature is reached, the fraction of neutrals increases four orders of magnitude because of the recombination. This article is part of the theme issue 'Partially ionized plasma of the solar atmosphere: recent advances and future pathways'.

Genome-wide association analyses reveal genotype-by-environment interactions of growth and organ weights in gilthead seabream (Sparus aurata)

Gilthead seabream is one of the most important fish species for Mediterranean aquaculture. More than 80% of the genetically improved fingerlings of this species originate from a single country, Greece. A previous study revealed moderate genotype-by-environment (G x E) interactions for growth traits and organ weights between commercial production sites in Greece and Spain. The main objectives of this study were to identify QTLs and genes associated with growth traits and organ weights in gilthead seabream and to identify the biological processes and pathways controlling these traits under different temperature environments. For growth traits, we found fourteen genome-wide suggestive SNP effects in Spain. A strong peak between 1.97 Mb to 4.69 Mb on chromosome (chr) 22 was shared among three growth traits (harvest weight, fillet weight and thermal growth coefficient). Fourteen genome-wide suggestive SNP effects were also identified in Greece. However, none overlap with those found in Spain. Two SNPs on chr5 (chr5:5729959, chr5:2336903) and two SNPs on chr6 (chr6:1957732, chr6:3659811) were associated with all three growth traits. For organ weights, a total of 15 SNPs were associated above the suggestive threshold in Spain. Four SNPs (chr22:1966940, chr22:6094383, chr22:67838, chr15:16798259) are shared between viscera weight and liver weight, while one SNP (chr22:67838) is shared among viscera, liver and heart weight. Interestingly, three of these four SNPs (chr22:1966940, chr22:67838, and chr15:16798259) also overlap with significant SNPs associated with growth traits. None of the SNPs associated with viscera weight, liver weight and heart weight are shared with Greece. GO and KEGG functional enrichment analyses showed that light absorption and ECM-receptor interaction are significantly enriched with growth traits QTLs in Spain but not in Greece. For organ weights, response to stimulus is the most prominent process in Spain, while cell adhesion, and regulation of phosphorylation are more prominent in Greece. Genomic architectures for growth traits and organ weights differ between environments. These findings not only explain part of the G x E interactions, but also give insight into how genetics determines differences in how environmental conditions affect growth and organ weights.

Combination of chemical vapor deposition and thermal growth methods for facile synthesis of tin oxide-doped multiwalled carbon nanotubes

Combination of chemical vapor deposition and thermal growth methods for facile synthesis of tin oxide-doped multiwalled carbon nanotubes

Study on thermal ignition and growth characteristics of CL-20 and HMX-based explosives

In order to understand the ignition and growth process of CL-20-based explosives, a comparative study of ignition and growth characteristics of CL-20 and HMX-based explosives was carried out. The ignition and ignition growth of CL-20, HMX, CL-20 and HMX-based explosives were studied respectively by means of ignition test and time-pressure test. The results showed that the reaction growth rate of CL-20 explosives was the fastest, indicating that the CL-20 explosives were easy to ignite, and it was easy to grow into more intense reaction form after ignition.

Thermal shock resistance of a novel (Gd1/6Tb1/6Dy1/6Tm1/6Yb1/6Lu1/6)2Si2O7 environmental barrier coating

AbstractMulticomponent rare earth (RE) disilicates have been recognized as promising candidates for environmental barrier coatings (EBCs). In this work, a novel EBC system with (Gd1/6Tb1/6Dy1/6Tm1/6Yb1/6Lu1/6)2Si2O7 as top coat and Si as bond coat was deposited on SiC‐based substrates by atmospheric plasma spraying technology and subjected to 200 thermal shock cycles at 1350°C. The composition and microstructure evolution in the coating during thermal cycling were investigated using x‐ray diffraction analysis and scanning electron microscopy. The results show that the as‐prepared EBC remains dense and integrated, and no obvious spalling or penetrating cracks could be observed in the coating after 200 thermal shock cycles. Furthermore, the average thickness of thermal growth oxide layer between (6RE1/6)2Si2O7 top coat and Si bond coat is 0.71 ± 0.17 µm and 0.98 ± 0.23 µm before and after the thermal cycling, respectively, indicating the excellent thermal shock resistance of (6RE1/6)2Si2O7 EBC. The present study presents a novel EBC with excellent thermal shock ability and is expected to contribute to the development of EBC for advanced SiCf/SiC ceramic matrix composites.

The carryover effects of embryonic incubation temperature on subsequent growth and thermal tolerance in white sturgeon

Environmental variation experienced during early periods of development can lead to persistent phenotypic alteration, known as carryover effects. Such effects increase concern for threatened or endangered species such as the white sturgeon (Acipenser transmontanus), particularly considering expected thermal changes due to climate change. We evaluated how temperature during embryonic development affects physiological parameters such as larval and early juvenile growth and thermal tolerance. Nechako River white sturgeon embryos were incubated at different environmental temperatures (Te) of 12 °C (the natural spawning temperature of this population), 15 °C (the hatchery incubation temperature), and 18 °C (representing potential increases in river temperatures given global climate change). After hatch, fish were reared at a common 15 °C for 80 days post-hatch (dph). Individuals from each temperature treatment were tested for thermal tolerance using the critical thermal maximum method (CTmax), euthanized, and measured. Fish were examined at regular intervals from 13 to 80 dph, which bridged the time from the start of exogenous feeding through the transition into early juveniles. We found carryover effects of high embryonic Te in the short term for both thermal tolerance and growth. Fish that developed at 18 °C had the lowest thermal tolerance during the start of exogenous feeding. However, differences in thermal tolerance were small for early juveniles and were unlikely to be ecologically relevant in the longer term. Fish that developed at 18 °C were smallest over the observation period, indicating a possible cost for survival from increasing environmental temperatures during embryonic development. This research represents a window into a critical period of development during which fish are particularly vulnerable to climatic variation, and shows that cooler temperatures (12 °C) during incubation are optimal for this population. The results can inform environmental managers on the best strategies to help conserve current white sturgeon populations across their range.

Effect of Different Integrated Nutrient Management Approaches on Growth, Yield Attributes and Yield of Wheat (Triticum aestivum L.) Crop: A Review

The adequate and balanced supply of plant nutrients is of critical importance in improving the productivity of wheat crop. Due to prohibitive cost of chemical fertilizers, Indian farmers, mostly marginal and small, do not supply the recommended doses of nutrients to these energy rich crops, indigenously available organic sources of nutrients have been recorded to enhance the efficiency and reduce the requirement of chemical fertilizers. The nutrients (N, P, K and Zn) can be supplied through fertilizers, organic manures, biofertilizers, bio-stimulants and their combined applications under integrated nutrient management. Wheat varieties differ in their phenology, requirement of thermal and photoperiod units and growth habits which cumulatively determine the varietal adaptation at different locations and sowing times. Therefore, comparative evaluation of varieties suitable for early, normal and late sown conditions is warranted to identify the growth patterns, physiological traits and yield attributes that will favorably influence the grain yield and biomass in wheat under normal and late sown conditions. This review examines response of wheat varieties to integrated nutrient management practices in wheat crop sown under normal and late planting conditions.

A CFRP/steel hybrid rotating shaft for a high-speed motorized spindle

Most key industry machines have a rotating structure for power transmission, which plays a crucial role in diverse engineering practices. In machine tools, a spindle is the heart of machining centers, and the quality of the spindle has a critical influence on overall machining errors across different manufacturing processes. Especially, axial growth due to thermal displacement of the shaft directly adds depth accuracy error of the tool. While additional compensation control techniques have been developed to cover such errors of spindles in practice, fewer efforts have been made to improve the actual amount of error in the spindle. This study introduces a new carbon fiber-reinforced composite (CFRP) fabricated hybrid design in a rotating shaft for a high-speed motorized spindle. With superior material characteristics of CFRP, it aimed to improve thermal displacement as well as light-weighting of the shaft. The developed spindle with composite shaft was tested in comparison with an equivalent spindle with a conventional single material shaft, and it achieved 18 % shaft weight reduction and 22 % improvement in shaft thermal growth. Furthermore, it was successfully tested in vertical face grinding of silicon carbide (SiC), providing accuracies over 99 %. Machining precision achieved conspicuous difference with 45.4 % enhancement at 3000 rpm and 27.3 % at 5000 rpm grinding. The significance of this study lies in that it suggests the first generalized method of adopting carbon fiber composite in rotating systems, including high-speed motorized spindles, which also proves its feasibility in actual machining.

Low cycle fatigue behavior and life prediction of a directionally solidified alloy

Low cycle fatigue behavior and life prediction of a directionally solidified alloy