Thermal Test Research Articles

Grooved TiO2/ZrO2 ceramic fibers with thermal insulation and mechanical properties prepared by coaxial electrospinning

In this study, grooved TiO2/ZrO2 ceramic fibers were prepared via coaxial electrospinning, which exhibit enhanced thermal insulation and superior mechanical properties. The fibers were architected with a distinctive core-shell structure, comprising a TiO2 shell that serves as an effective radiation shield and a ZrO2 core that maintains mechanical robustness. The interdiffusion of Zr and Ti atoms at the interface facilitated a seamless transition between TiO2 and ZrO2, effectively inhibiting TiO2 grain coarsening and substantially enhancing the tensile strength of the fibers, exemplified by the 1.47 ± 0.08 MPa achieved in the TZ-5 sample. Through control of the injection rate during electrospinning, we optimized the fibrous morphology to attain a synergistic balance of strength, flexibility and thermal insulation. The fibers showcased exceptional thermal insulation properties with thermal conductivity values ranging from 0.0294 to 0.0278 W m−1 K−1 and an average infrared reflectance exceeding 87 %. Practical thermal insulation tests confirmed the superior insulation performance of the TiO2/ZrO2 fibrous membranes.

Research on hot workability and deformation mechanism of as-extruded Ti-6554 alloy over a broad temperature range

The favorable mechanical characteristics of Ti-6554 offer potential uses in the aerospace industry. To broaden the potential uses of as-extruded Ti-6554 alloy, it is essential to conduct additional assessments on its hot workability and deformation mechanisms. This study, through a series of hot compression tests conducted over a broad temperature range using a thermal simulation testing machine, established the activation energy map and the hot processing map, while examining the evolution of microstructures and deformation mechanisms. The findings indicate that the activation energy of the Ti-6554 alloy reduces as strain rises. The ideal conditions for hot processing are 850-900 °C and 10-3-10-2s-1. The precipitation of the α phase occurs when deforming in the two-phase region, some maintain burgers orientation relationship (BOR) with the matrix, and some maintain random orientation with the matrix. In addition, the α phase precipitation significantly promotes dynamic recrystallization (DRX), resulting in obvious flow softening. The examination of misorientation angles reveals that DRX mechanisms of the β phase. At a slow strain rate, DDRX gradually dominates as the temperature rises. At constant temperatures, CDRX increasingly takes precedence with the increase of strain rate.

Synthesis of a perovskite surface-coated polymer brush by photo-induced atom transfer radical polymerization

Lead halide perovskite nanocrystals (PNCs) are expected to be applied in the field of optoelectronics due to their color tunability, high color purity, and near-unity photoluminescence quantum yields. Moreover, the construction of nanocomposite structures with functional polymers has been reported to improve the material stability as well as the ordered structure with high orientation and periodicity. In this study, we demonstrated the synthesis of polymethyl methacrylate (PMMA) on the PNCs by surface-initiated polymerization. We synthesized PMMA polymer brushes by photo-induced atom transfer radical polymerization (p-ATRP) after coordinating the initiator on the PNC surface. We succeeded in obtaining PMMA-PNCs with a degree of polymerization of 21. Moreover, thermal stability tests showed that PMMA-PNCs achieved improved thermal stability compared to pristine-PNCs. This work can provide guidance for developing polymer brush-PNCs via surface-initiated polymerization.

A new method for direct welding of alumina and zirconia ceramics by ultrashort pulse laser for high temperature application

The direct welding of alumina and zirconia ceramics by ultrashort pulse laser is presented for the first time. Compared to traditional dissimilar ceramic joining techniques such as brazing and diffusion welding, this method shows various advantages, including operation at room-temperature, higher welding efficiency, and negligible impact on base materials. The joint microstructure consists of a combination of Al2O3 and ZrO2 phases, without new phases detected. By adjusting the laser focal point position, the phase content within joint is effectively regulated, successfully preventing crack formation in alumina substrate. The influence of laser power and welding speed on joint morphology and mechanical property is fully investigated. The highest four-point bending strength of 365.5MPa and shear strength of 33.4MPa are achieved. After experiencing thermal cycling test at 1000°C, the joint strength and microstructure does not exhibit significant changes, demonstrating the excellent high-temperature durability of the sample.

Phase transition heat storage and self-healing mechanism of spinel-calcium aluminate composite aggregate in corundum castable

Corundum-spinel castable is a vital refractory material used in steel ladle linings. Conventional approaches for assessing the thermal shock resistance of corundum-spinel refractory are not entirely representative of the actual application scenarios. This study investigates the influence of spinel-calcium aluminate composite aggregate on the thermal shock resistance of corundum castable using supersonic frequency induction heating technology. The research uncovers how CMA aggregate enhances the thermal shock resistance of corundum castable by cyclic thermal shock tests under varying operational conditions. Results reveal that the incorporation of CMA aggregate led to significant improvements in cold crushing strength and strength retention ratio following thermal shocks. The observed enhancement predominantly stems from the presence of CA/CA2 phase within the CMA aggregate, which undergoes a solid-liquid phase transition at high temperatures, enabling the absorption and retention of substantial heat and aiding in the repair of microcracks within the materials and at the interfacial regions.

Crack behaviour and failure mechanisms of air plasma sprayed (Gd, Yb) doped YSZ thermal barrier coatings under oxy-acetylene flame thermal shock

This paper examines the performance and failure mechanisms of atmospheric plasma sprayed (Gd, Yb)-doped YSZ (RYSZ) thermal barrier coatings (TBCs) under oxy-acetylene flame thermal shock conditions. The study involved cyclic thermal shock testing at temperatures of 1400 °C, 1500 °C, and 1600 °C for 10-min intervals until failure occurred, with failure counts recorded as 6, 2, and 2, respectively. During the thermal shock tests, tensile stress in the top coat (TC) caused vertical cracks. The growth of the thermally grown oxide (TGO) layer concentrated stress at the top coat/bond coat interface, leading to transverse interfacial cracks. As the shock temperature increased, the density of vertical cracks and the length of transverse interfacial cracks also increased. Additionally, transverse cracks developed in the TC due to sintering of the surface region at higher shock temperatures. The interaction between vertical and transverse cracks was critical to the spalling of the TC. Variations in crack densities and lengths resulted in different failure modes of the TBCs, depending on the thermal shock temperatures (1400 °C, 1500 °C, and 1600 °C).

Novel high-entropy (La0.35Gd0.35Y0.35Sm0.35Yb0.6)Zr2O7 thermal barrier coatings: Thermal cycling performance and failure behavior

The high-entropy ceramic (HEC) (La0.35Gd0.35Y0.35Sm0.35Yb0.6)Zr2O7 has emerged as a strong candidate for thermal barrier coatings (TBCs) due to its exceptional thermal properties. We investigated the thermal shock resistance of HEC–lanthanum zirconate (LZ)/yttria partially stabilized zirconia (YSZ) (i.e., the HEC coating) and LZ/YSZ (i.e., the LZ coating) double-ceramic-layer TBCs fabricated via plasma spraying. During thermal shock testing at 1100°C, the LZ coating failed after 60 ± 3 cycles, while the HEC coating had a considerably longer thermal cycling lifetime of 135 ± 5 cycles. The HEC coating’s superior performance is attributable to its enhanced oxygen barrier properties and inherent lattice disorder; the former reduced the growth rate of the thermally grown oxide, and the latter increased lattice defects and distortion. These factors helped improve the thermal expansion coefficient and reduced interlayer thermal stress accumulation. Furthermore, the higher fracture toughness of the HEC layer impeded crack propagation, collectively enhancing the TBCs’ thermomechanical shock resistance. These findings underscore the potential of (La0.35Gd0.35Y0.35Sm0.35Yb0.6)Zr2O7 as a robust material for extending the service life of TBCs in high-temperature environments.

Evaluation of the Thermal and Light Stability of β-Carotene Extracted from Mauritia flexuosa Using Ionic Liquid

The growing concern over the adverse effects of synthetic dyes has generated interest in the use of natural pigments by the food industry. β-carotene, a carotenoid found in various plant sources, is recognized for its antioxidant properties and provitamin A activity. The fruit of the buriti palm (Mauritia flexuosa), which is particularly rich in β-carotene, serves as a significant natural source of this pigment. This study aimed to extract β-carotene from buriti fruit using ionic liquids as an alternative to conventional organic solvents like acetone. β-carotene content was determined by HPLC and showed that extraction with [C4mim] [BF4] not only improved β-carotene extraction efficiency compared to acetone (19.21 and 13.13 mg/100 g, respectively) but also provided greater pigment stability during light, thermal and color stability tests. Moreover, ionic liquids are aligned with the principles of green chemistry and offer a sustainable and safe alternative for the food industry. Its favorable characteristics not only reduce environmental impacts associated with conventional solvents, but also ensure an increase in the shelf life of natural dyes, thus promoting the safety and quality of food products.

Thermal conductivity of insulating materials using a peltier cell based cooling system

Abstract In this work we have built and evaluated a system that allows us to determine the thermal conductivity of insulating materials. We use this system to study the thermal properties of suitable for building materials, typical of high altitude Andean regions. The equipment’s setup is of a Guarded Hot Plate Apparatus (GHPA), the equipment’s central part has a circular hot plate and a concentric crown shaped disc (guard), which are not in contact each other. Two circular samples are placed on both sides of the hot plate and then the square cold plates are mounted at the lower and upper sides of the samples. The cold plates are refrigerated by mean of liquid which flows through an spiral coil embedded in it. The liquid is cooled by Peltier cells whose hot sides are in contact with air radiators. The temperature’s gradient is measured between the hot plate and the guard with a Type E thermocouple and to measure the temperature of the cold plates Type K thermocouples are used. To show the equipment’s performance, some thermal conductivity tests were carried out on the following materials: sugar cane bagasse, adobe with Stipa ichu, ashlar and glass.

Crimp Height influence over Resistivity in Wiring Crimping Process

Abstract The main purpose of this paper is to present the influence between the crimp height and the resistivity for a crimp joint between a copper contact and a wire copper stranded cable using statistical relevant analysis. The experiment followed the analysis of 45 crimped assemblies grouped in 3 main categories to simulate a potential validation procedure according to the international validation process requirements from: DIN (“Deutsches Institut fu r Normung”) with the corresponding Romanian standard SR EN 60352-2:2006 and SAE/USCAR-21 REVISION 3. The baseline used was the behaviour of the resistivity versus the pre-set crimp height of the crimped joints before and after thermal shock test to enable us to conclude if we have a significant relation between the crimp height of the assembly joint and the resistivity.

Failure behavior of RE2M2O7/YSZ TBCs prepared by EB-PVD in gas thermal shock-CMAS corrosion environment

Three types of thermal barrier coatings (TBCs), YSZ, LZC/YSZ and GZO/YSZ, were deposited by EB-PVD. These coating systems were then subjected to thermal shock-CMAS corrosion testing using a high-temperature gas spray gun. The results demonstrate that the double-layer thermal barrier coatings exhibit excellent resistance to thermal shock-CMAS corrosion. Microstructural analysis revealed that the LZC/YSZ coating mitigated thermal damage owing to the formation of a sealing layer at the CMAS/LZC interface through high-temperature chemical interactions with CMAS. Compared to LZC/YSZ, the GZO/YSZ coatings showed greater resistance to CMAS-induced damage, which was associated with lower theoretical optical basicity values. This research provides valuable insights into the coupled thermal shock-CMAS corrosion failure mechanisms of TBCs on turbine blades and paves the way for new system-safe applications of TBCs.

Kalman filter-driven state observer for thermal error compensation in machine tool digital twins

Sustainable reduction of thermal errors during production is the key challenge in modern high-precision manufacturing. Numerical compensation models provide an energy-efficient solution, but in the case of data-driven models, high-quality experimental data must be time-consuming and expensive to produce, negatively impacting overall productivity. Furthermore, robustness concerns arise in the case of new operating conditions, which were not contained in the training data. This paper presents a novel use of a Kalman filter together with model order reduced finite element models to observe the entire thermal state, which allows the subsequent solution of the mechanical model and computation of the thermal errors in real-time without requiring any training data but instead purely based on the physical system model. The effectiveness of this approach is evaluated using experiments on a thermal test bench with 16 out of 40 temperature sensors employed for observation and demonstrated on a 5-axis machine tool (MT) with 13 out of 25 temperature sensors used. Due to the combination of the reduced order model and Kalman filter these 13 temperature sensors are sufficient to represent a MT mesh of more than 350’000 elements. The entire temperature profile of the thermal test bench is reconstructed to achieve a root mean square error (RMSE) of the unobserved temperature sensors of only 2.7 °C, which accounts for more than 83% of all temperature variations and 1.3 °C for the 5-axis MT. For the thermal error of the thermal test bench, the RMSE could be reduced from 67.4μm to 33.3μm, corresponding to a reduction of 52.7 %. This could be achieved without the need for experimental data for model calibration, in a real-time capable physics-based model.

Design and Verification of Thermal Control System of Communication Satellite

The multiple working modes, complex working conditions, frequent changes in external heat flux, and high power consumption of communication satellites all pose great difficulties to their thermal design. This paper mainly describes the design of a thermal control system for high-power communication satellites. Firstly, new efficient heat transfer technologies and thermal control materials for spacecraft are introduced. Secondly, the structure and internal heat source of the satellite are introduced. Thirdly, the external heat fluxes are analyzed, and the position of the heat dissipation surface and extreme conditions are confirmed. Then, a thermal control system is designed around the difficulties of thermal control. With heat pipes, the temperature uniformity of +Y deck, −Y deck, and +Z deck increased by 8 °C, 9.9 °C, and 34.2 °C, respectively. Furthermore, the maximum temperature of the power controller, secondary power supply, bidirectional frequency converter, and solid discharge decreased by 32.5 °C, 22.0 °C, 14.0 °C, and 164 °C, respectively. Finally, a thermal balance test is performed. The test results show that the temperatures of the solid-state power amplifier, on-board computer, power controller, secondary power supply, and bidirectional frequency converter meet the requirements of the thermal control indices. In addition, the temperature of thermal-sensitive components such as batteries and the storage tank also meets the requirements. The thermal design scheme is reasonable and feasible, and the thermal balance test verifies the correctness of the thermal design.

Impact of partial substitution of sand by compost on the mechanical and thermal parameters of concrete

The study investigates recycling organic waste in Algeria due to the rising use of natural resources and energy in concrete production and the large amount of organic waste discarded. The aim is to use compost as a partial replacement for sand, reducing the use of natural aggregates in the concrete industry while also reusing previously discarded waste as part of a circular economy. An experimental study was carried out on concrete’s thermal and mechanical properties to determine the effect of partial compost replacement on these properties. Five mixtures were created by replacing sand with compost in different proportions: 0, 5, 10, 15, and 20%. Slump and density were assessed in the formulations’ original state. Mechanical tests were performed on the hardened concrete to determine porosity, compressive strength, and flexural strength. Thermal tests were also conducted on various types of concrete to determine thermal conductivity. The findings show that the texture of the compost reduced the slump, highlighting the importance of incorporating an admixture to achieve the desired workability. While meeting normal-weight concrete standards, concrete density was reduced. The mechanical properties of concrete with small amounts of compost were similar to regular concrete; instead, waste porosity improved insulation.

Delamination of Perovskite Solar Cells in Thermal Cycling and Outdoor Tests

For the commercialization of perovskite solar cells (PSCs), detection of associated degradation mechanisms and mitigation of their effect is of paramount importance. The former requires outdoor and indoor stability tests to detect these mechanisms under real operation conditions and to accelerate them under controlled environments. Herein, the thermomechanical stability of encapsulated PSCs in outdoor tests at three locations coupled with indoor thermal cycling tests is investigated. Results show that encapsulant‐induced partial delamination can occur in outdoor and indoor tests, leading to disruption in device integrity and substantial loss in the cell active area and short‐circuit current. The findings suggest that delamination involves C60 and SnO2 layers as the mechanically weakest point in the device stack. To the best of our knowledge, this work is the first demonstration of delamination in encapsulated PSCs under real operation conditions. While partial delamination emerged on some of the cells exposed in Israel and Cyprus in just a few weeks, it did not occur in Germany over 2.5 years of outdoor exposure. This highlights the importance of multiclimate outdoor testing to validate the significance of failure modes observed through accelerated indoor testing.

Qualitative somatosensory evaluation of recipient and donor sites of subepithelial connective tissue grafts: a preliminary study.

The subepithelial connective tissue graft (SCTG) plus coronal advanced flap is commonly evaluated by clinical parameters, but potential sensory changes (patients' perception of painful or painless sensations) need to be further explored. This preliminary study aimed to qualitatively evaluate the somatosensory profile of recipient and palatal donor sites of SCTG. Sensory tests were applied at SCTG recipient and donor sites at baseline, after 3 and 6 months. A single calibrated examiner applied Douleur Neuropathique 4 questionnaire (DN4), qualitative sensory test (QualST), discriminating the areas as hypersensitive, hyposensitive or normosensitive, and two-point acuity test. Descriptive statistics, non-parametric Kruskal Wallis test for QualST evaluation and ANOVA for Two-point test (p < 0.05) were used. QualST revealed that recipient areas presented no significant differences in tactile, pressure and thermal tests. Brush test revealed hyposensitivity after 3 months (p = 0.03). In donor areas, only thermal evaluation showed a significant difference (p = 0.01), being hypersensitive after 3 months and hyposensitive after 6 months. At baseline, all evaluations in recipient and donor areas were normosensitive. According to DN4, no patient reported pain in recipient and donor sites. Non-painful sensory perception was reported as numbness in recipient (3.14% of patients) and donor (18.4%) areas. No significant differences were found for two-point acuity test values. Somatosensory variations were observed in donor and recipient areas using qualitative tests, with no detection of painful sensations, only non-painful sensations of numbness and electric shock. This preliminary study demonstrated that alterations of hypo- and hypersensitivity may occur in donor and recipient areas of gingival grafts. However, when present, these alterations were non-painful and did not impact oral functions. ReBEC #RBR-7zz3b6p.

Energy-Efficient Geopolymer Composites Containing Phase-Change Materials-Comparison of Different Contents and Types.

The purpose of this study was to analyze the effects of phase-change components on the properties of geopolymer foams. Geopolymer foams are lightweight foamed geopolymers that are characterized by a high degree of porosity. Phase change materials, on the other hand, are compounds that, when added to a material, allow it to absorb, store, and then release large amounts of energy. Three types of PCMs, i.e., MikroCaps, GR42, and PX25, were introduced at 15% by weight. Geopolymer materials were produced based on silica fly ash, and hydrogen peroxide H2O2 was used to foam the geopolymer structure. The PCM geopolymer composites were cured at 60 °C. The produced materials were tested for physical, chemical, and thermal properties. The tests included oxide and mineral composition analysis of the base material, PCM particle size analysis, apparent density and porosity tests on the foams, water leachability tests, thermal tests (λ, Cv, Cp, α), and structural and textural analysis. The most relevant tests to confirm the performance of the phase-change materials were thermal tests. With the introduction of PCMs, volumetric heat capacity increased by as much as 41% and specific heat by 45%, and thermal diffusivity decreased by 23%. The results confirm the great potential of geopolymer composites as modern insulation materials for buildings and structures.

Sustainability of Asphalt Mixtures Containing 50% RAP and Recycling Agents

The substitution of virgin asphalt binder with reclaimed asphalt pavement (RAP) has environmental and economic merits, however, cracking susceptibility arises due to the aged asphalt binder within RAP. The objectives of this study are to (1) enhance the cracking resistance of asphalt mixtures containing 50% RAP utilizing recycling agents (RAs) derived from six petroleum-based and bio-based materials, (2) conduct an environmental impact assessment (represented by global warming potential “GWP”) for high-RAP mixtures including RAs, and (3) estimate the cost effectiveness of including high-RAP content in asphalt mixtures. Based on the RAP asphalt binder performance grade (PG), base asphalt binder PG, and RAP content, the RA contents were determined to achieve a target asphalt binder of PG 76-22. A control mixture was benchmarked for comparison, specified for high-traffic volume roads, and contained PG 76-22 polymer-modified asphalt binder. The engineering performance of studied asphalt mixtures was evaluated using the Hamburg wheel-tracking (HWT), semi-circular bend, Illinois flexibility index, Ideal cracking tolerance, and thermal stress-restrained specimen tensile strength tests. It was found that petroleum-derived aromatic oil, soy-based oil, and tall oil fatty acid-based RAs demonstrated a successful restoration of aged RAP asphalt binder without compromising the permanent deformation resistance. The 50% RAP mixtures emitted less GWP by 41% and 42.9% using petroleum- and bio-oil RAs, respectively, and achieved a 31% cost reduction compared to the control mixtures.

Synthesis of low-cost refractory cordierite for solar thermal storage: Characterization of mechanical, thermal and physical stability during thermal shock cycles

To guarantee the efficiency of solar thermal energy production, the thermal storage material must have exceptional resistance to thermal shock to withstand prolonged thermal cycles. In addition, it must have specific properties tailored to the requirements of this field. In this study, we developed a refractory cordierite for solar thermal storage, characterized by very high thermophysical properties, from an initial formulation containing 20 % of abundant clays. The properties of materials sintered at 900 °C, 1000 °C, 1100 °C, 1200 °C and 1250 °C were assessed by a series of analyses including X-ray diffraction (XRD), mass loss, volumetric shrinkage, bulk density, and porosity, scanning electron microscopy (SEM), thermal conductivity, thermal diffusivity, thermal storage capacity, chemical resistance, and mechanical testing. The incorporation of natural clays, rich in sintering aid elements, facilitated the formation of 74 % α-cordierite at 1200 °C and 92 % at 1250 °C, significantly enhancing the material's densification. Materials sintered at 1250 °C and containing 92 % refractory cordierite were subjected to 50 thermal shock cycles from 500 °C to 0 °C. The obtained materials showed excellent mechanical properties, including compressive strength of 398 MPa, low porosity of 0.21 %, density of 2.52 g/cm3, zero mass loss in acidic and basic environments for 30 days, and very high values of heat capacity (3429.80 J/(kg·K)), thermal conductivity (2.08 W/(m·K)) and thermal diffusivity (0.84 mm2/s) at room temperature.

Enhancement of strength and thermal shock resistance of MgO‐MgAl2O4 ceramic filters with microporous MgO powder: Effect of α‐Al2O3 micro‐powder content

AbstractIn this work, MgO‐MgAl2O4 ceramic filters were fabricated from microporous MgO powder and α‐Al2O3 micro‐powder, in which microporous MgO powder was prepared using Mg(OH)2 as initial raw material. With the α‐Al2O3 micro‐powder content increased from 0 to 15 wt%, the tight packing and reaction sintering between MgO microparticles and Al2O3 microparticles promoted the formation and growth of magnesium aluminate spinel necks, reduced the apparent porosity of ceramic filter skeletons, decreased the pore size, and improved the strength of the filters. When the α‐Al2O3 micro‐powder content further raised to 20 wt%, the thermal mismatch between MgO microparticles and spinel microparticles caused a small amount of crack generation, which lowered the strength of the filter. Besides, after introducing the α‐Al2O3 micro‐powder, more spinel necks were produced due to a small amount of MgO solid dissolved in the spinel lattice during the thermal shock test, which enhanced the thermal shock resistance of the filters. When the α‐Al2O3 micro‐powder content was 15 wt%, the filter had excellent comprehensive performance, the bulk density and apparent porosity of the filter skeleton were 3.09 g/cm3 and 10.7%, and the compressive strength before and after thermal shock test was 3.48 and 3.70 MPa, respectively.