Thermal Cycling Test Results Research Articles

Preparation of thermal energy storage microcapsule with double-layer ceramic shell possessing sponge effect to improve the thermal cycling performance

In present study, thermal energy storage microcapsules with double-layer ceramic shell were fabricated and thermal cycling test was conducted. Thermal cycling test results showed that when ceramic shell constituted of dense inner layer and loose outer layer, the microcapsule had excellent thermal stability. After 3000 thermal cycles, latent heat retention ratio of the microcapsule was more than 90 % and almost no leakage of molten core. This super durability and stability attributed to “sponge effect” of loose outer layer which offered volume buffer for microcapsule core and inhibited molten core overflow during phase change. According to the Mass Conservation Law, criterion Г for describing “sponge effect” was deduced. Г was defined as a quarter of the product of the specific surface area of the microcapsule and criterion Г was derived as Г≥1ρL−1ρS. The criterion shows that when the value of Г is larger than or equal to the difference between the specific volumes of liquid and solid phase change material, microcapsule core is not overflow during phase change. Criterion Г provides theoretical guidance for the preparation of thermal energy storage microcapsules with excellent thermal cycling performance.

Preparation of Pd membrane with high permeability and thermal stability on porous YSZ-Al2O3 tubes by two-step CeO2modification

Pd membranes were deposited on porous YSZ-Al2O3 tubes after different modification methods using an electroless plating technology. SEM, AFM, XRD and gas permeation tests were applied to investigating the effects of different modification methods on the surface quality of porous tubes and the permeation performance of the Pd composite membranes. The results showed that the surface of the porous tubes after the two-step CeO2 modification exhibited smaller pore distribution and roughness. Pd membranes on the porous tubes after the two-step CeO2 modification exhibited higher hydrogen permeation flux (0.549 mol·m−2·s−1) and H2/N2 selectivity (14241) at 500 °C and a pressure difference of 700 kPa. The results of different thermal cycling tests and the long-term permeation tests of 1000 h showed that Pd membranes on the porous tubes after the two-step CeO2 modification had higher permeation stability.

Estimation of radionuclides leaching characteristics in different sized geopolymer waste forms with simulated spent ion-exchange resin

This study presents a method to solidify spent ion-exchange resin (IER) in a metakaolin-based geopolymer and shows results of mechanical strength, immersion, leaching, irradiation, and thermal cycling tests for waste acceptance criteria (WAC) to repository. The geopolymer waste form with 20 wt% of simulated spent IER met the WAC in South Korea (ROK), and the leaching tests of various sized-waste forms up to 15.0 × 30.0 cm and waste loadings up to 20 wt% for 1–5 d and 1–90 d achieved a leachability index, Li > 6. In a leaching test for 5 d, the cumulative fraction leached (CFL) for Cs, which leached the most, was linearly correlated with the square root of leaching time for all waste forms, and Li increased as the size of the waste form increased. The CFL was also correlated with elapsed time in the 90 d leaching test. The correlations among CFL, time, and volume-to-surface area ratio of waste forms used to estimate the Li of Cs of a 200-L sized geopolymer with 15 wt% IER showed the Li values as 14.73 (5 d) and 17.71 (90 d), respectively, indicating that the large-sized geopolymer waste form met the WAC.

Configuration and characters of novel Li2TiO3 tritium breeder cubic units with tuned channel structure via lithography-based 3D printing

Li2TiO3 is regarded as a vital tritium breeder candidate due to its favorable properties in Helium-Cooled Pebble Bed. However, the point contact stress breakage for traditional pebble structure can cause the blocking of tritium recovery system, and seriously reduce the safety and tritium self-sufficiency ability of fusion reactor. For addressing above problems, in this paper, complex-shaped Li2TiO3 cubic units were manufactured firstly via lithography-based 3D printing. According to the principle of tritium transport, the cubic unit structures with ordered channels were built and evaluated by finite element analysis. The photocuring parameters were optimized to improve printing accuracy by establishing an overgrowth model. After optimizing the sintering schedule, the Li2TiO3 cubic units with excellent relative density (92.3%TD) and packing factor (80.99%) were yielded, and it also had an outstanding compressive strength (84.4 MPa). The results of thermal cycling test shown that the Li2TiO3 cubic units possessed a prominent thermal cyclic durability.

Effect of Annealing Time on the Cyclic Characteristics of Ceramic Oxide Thin Film Thermocouples.

Oxide thin film thermocouples (TFTCs) are widely used in high-temperature environment measurements and have the advantages of good stability and high thermoelectric voltage. However, different annealing processes affect the performance of TFTCs. This paper studied the impact of different annealing times on the cyclic characteristics of ceramic oxide thin film thermocouples. ITO/In2O3 TFTCs were prepared on alumina ceramics by a screen printing method, and the samples were annealed at different times. The microstructure of the ITO film was studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results show that when the annealing temperature is fixed, the stability of the thermocouple is worst when it is annealed for 2 h. Extending the annealing time can improve the properties of the film, increase the density, slow down oxidation, and enhance the thermal stability of the thermocouple. The thermal cycle test results show that the sample can reach five temperature rise and fall cycles, more than 50 h, and can meet the needs of stable measurement in high temperature and harsh environments.

Effect of porous carbon on thermal and physical properties of composite pure alkane/expanded vermiculite phase change energy storage materials

Nine kinds of mixed N-alkanes with different proportions were prepared by mixed eutectic method. A set of ratios with enthalpy values up to 289.8 J/g were selected for encapsulated PCM. Using potato starch solution with a concentration of 30 % as porous carbon source, the heat transfer capacity of expanded vermiculite was enhanced by modification between expanded vermiculite channels, and matrix coated phase change material was prepared. SEM images show that the PCM are successfully adsorbed in the pores. The latent heat and temperature of phase change in the melting and solidification process are 208.1 J/g and 21.2 °C, 203.11 J/g and −3.4 °C, respectively. FT-IR, XRD, TGA and thermal cycling test results show that phase change energy storage particles have good thermal performance. Therefore, the prepared materials have excellent properties.

Properties of Scots pine wood impregnated with capric acid for potential energy saving building material

Abstract Scots pine sapwood (Pinus sylvestris L.) was impregnated with different concentrations of capric acid (CA) (20, 40, 60 and 80%) as phase change material (PCM). The hygroscopic, mechanical properties and thermal energy storage (TES) characteristics of the CA-impregnated wood were studied. The morphology, crystalline properties, phase change properties and thermo-regulative performance of CA-impregnated wood were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetry (TGA), differential scanning calorimetry (DSC) and thermal performance analysis. CA-impregnated wood demonstrated an excellent performance of storing and releasing heat during phase change process, confirmed by DSC and FTIR analysis after an accelerated thermal cycling test. In addition, the accelerated thermal cycling test results indicated that CA-impregnated wood showed good thermal reliability and CA did not leach from the wood after the thermal cycling. Wood impregnated with CA solution of 80% concentration reduced the maximum temperature by 4.04 °C at the end of the heating period while it increased the minimum temperature by 2.83 °C at the end of the cooling period. The performance of storing and releasing heat during phase change process of CA impregnated Scots pine proves that it can be used as a thermal regulating building material to reduce energy consumption and cost caused by day and night temperature fluctuations.

Photo-to-thermal conversion and energy storage of polyethylene glycol/copper sulfide composite PCMs

In order to improve the energy storage performance of polyethylene glycol (PEG), copper sulfide (CuS) was introduced into PEG to endow the function of photo-to-thermal conversion. A series of novel PEG/CuS composite phase change materials (PCMs) were prepared by melt blending method with polyethylene pyrrolidone (PVP) employed as a stabilizer. Results of the dispersion stability experiment and 100 thermal cycles test showed that 2 wt% PVP can effectively improve the stability of PEG/PVP/CuS composite PCMs. And the CuS nanoparticles were uniformly dispersed in the PEG through physical action with the help of PVP. DSC results showed that the melting enthalpy of PEG/PVP/CuS composite PCM is as high as 171.8 J/g, 164.0 J/g, and 156.2 J/g when the content of CuS is 2 wt%, 6 wt%, and 10 wt%, respectively. Thermal cycling test and TGA results demonstrated that PEG/PVP/CuS composite PCMs have excellent reliability and stability. The photo-absorption property of PEG/PVP/CuS composite PCM increases to the range of 0.44–0.852, 0.938–1.533, 1.335–2.462 respectively within the addition of 2 wt%, 6 wt%, 10 wt% CuS in the radiation range of 300–900 nm. And the photo-to-thermal conversion efficiency of PEG/PVP/CuS composite PCMs was tested up to 87.36%. Therefore, the prepared PEG/PVP/CuS composite PCMs show remarkable potential in solar thermal utilization applications.

High interface compatibility and phase change enthalpy of heat storage wood plastic composites as bio-based building materials for energy saving

Phase change materials (PCMs) is one of the most efficient and reliable methods to store latent heat and reduce energy consumption. This work focused on heat-storage bio-based building materials for energy-saving using encapsulate poly (ethylene glycol) (PEG)/organic diatomite (O-Dt) as the latent heat storage agents, and wood fiber (WF)/high-density polyethylene (HDPE) as the matrix. PEG was encapsulated into the porous structure of Dt, and the obtained form-stable PCM has desired great interface action, high latent heat (105.35 J/g), good packaging capability, and excellent thermal stability. The heat-storage WPCs incorporated with form-stable PCM possessed considerable thermal storage capacity (60.42 J/g) and temperature-regulating ability (12 °C–15 °C). The thermal conductivity of WPC-20% was increased by 26.7% than WPC-0%. The mechanical strength and hydrophobicity of WPCs were increased when the loading percentage of PCM was 5%. Thermal cycling test results demonstrated that the heat storage WPCs had considerable heat storage reliability and chemical stability. The satisfying latent heat capacity and acceptable mechanical strength indicated the heat-storage WPCs could be potentially utilized as building materials for low carbon and energy conservation.

Mechanical and thermal performance assessment of paraffin/expanded vermiculite-diatomite composite phase change materials integrated mortar: Experimental and numerical approach

In this paper, the influence of paraffin/expanded vermiculite-diatomite form stable composite phase change materials (paraffin/EVC-D FSCPCM) on the strength and thermal properties of the mortar was studied through experiments and numerical simulations. The mechanical properties, thermal conductivity and thermoregulation performance of the paraffin/EVC-D FSCPCM integrated mortar were studied in detail. Meanwhile, the energy-saving effect of the paraffin/EVC-D FSCPCM integrated mortar in building was studied by numerical simulation. Thermal-cycling test results indicated a 10.9% leakage reduction of form stable composite phase change material with a diatomite coating. Strength test results showed the addition of diatomite increased the compressive strength of paraffin/EVC-D FSCPCM integrated mortar. The thermoregulation performance test showed the paraffin/EVC-D FSCPCM integrated mortar displayed good thermoregulation performance regardless of the testing conditions (lab-scale or actual environment). During laboratory-scale thermal regulation performance testing, when the volume replacement rate of paraffin/EVC-D FSCPCM to sand reaches 70%, the paraffin/EVC-D FSCPCM integrated mortar reduced the maximum temperature of the testing room by 3.1 °C; in an actual environment, it reduced the maximum temperature of the wall board by 2.68 °C. The simulation results showed that in summer, compared with cement mortar, the use of paraffin/EVC-D FSCPCM integrated mortar in the building could save 17.03% of energy consumption.

Thermal Cycling Test and Simulation of Six-Side Molded Panel-Level Chip-Scale Packages (PLCSPs)

Abstract In this study, the reliability of the solder joints of a six-side molded panel-level chip-scale package (PLCSP) is investigated. Emphasis is placed on the thermal cycling test (−55°C Δ 125°C, 50-min cycle) of the six-side molded PLCSP on a printed circuit board. For comparison purpose, the one without six-side molded (ordinary) PLCSP is also subjected to the same test. The thermal cycling test results are plotted into a Weibull distribution, and the true Weibull slope and true characteristic life at 90% confidence are presented. The solder joint mean life ratio of these two cases and its confidence level are also determined. Furthermore, their solder joint failure location and failure mode are provided. Finally, a nonlinear, time- and temperature-dependent 3-D finite element simulation is performed for these two cases and correlated with the thermal cycling test results.

Thermal Cycling Test and Simulation of Fan-Out Chip-Last Panel-Level Packaging for Heterogeneous Integration

Abstract In this study, the reliability of the solder joints of a heterogeneous integration of one large chip (10 × 10 mm) and two smaller chips (7 × 5 mm) by a fan-out method with a redistribution layer-first substrate fabricated on a 515 × 510-mm panel is investigated. Emphasis is placed on the thermal cycling test (−55°C Δ 125°C, 50-min cycle) of the heterogeneous integration package on a printed circuit board (PCB). The thermal cycling test results are plotted into a Weibull distribution. The Weibull slope and characteristic life at median rank are presented. At 90% confidence, the true Weibull slope and the true 10% life interval are also provided. A linear acceleration factor is adopted to map the solder joint reliability at the test condition to the solder joint reliability at an operating condition. The failure location and failure mode of the PCB assembly of the heterogeneous integration package are provided and discussed. A nonlinear, time- and temperature-dependent 3-D finite element simulation is performed for the heterogeneous integration PCB assembly and correlated with the thermal cycling test results.

Synthesis and characterization of phase change materials microcapsules with paraffin core/cross-linked hybrid polymer shell for thermal energy storage

Phase change materials microcapsules (PCMM) with cross-linked hybrid polymer shell were developed by in-situ polymerization and paraffin melting at 47 °C was used as PCM. The cross-linked hybrid polymer shell of microcapsules was prepared by copolymerizing methyl methacrylate (MMA), acrylic acid (AA), n‑butyl acrylate (BA), and trimethylpropane triacrylatec (TMPTA) which were employed as crosslinking agents. Microcapsules with core–shell structure were studied by polarizing optical microscope (POM), and their morphologies were obtained by scanning electronic microscope (SEM). Fourier transform infrared (FR-IR) was used to characterize the PCMM with paraffin core. The results of differential scanning calorimetry (DSC) showed that the measured enthalpy of PCMM was significantly higher than the theoretical value, and the increment percentage was as high as 58.7% and 63.9% during the heating/cooling process, respectively. In addition, PCMM's good thermal stability and long-term property were obtained by thermogravimetric analysis (TGA) and thermal cycle test results.

Production and characterization of Nd and Dy doped lanthanum zirconate-based thermal barrier coatings

In this study, thermal barrier coatings in (La0.7(Nd, Dy)0.3)2Zr2O7 compound were produced by the plasma spray method as a single and double layer with YSZ. Microstructure, X-ray diffraction analysis, thermal conductivity measurements in the temperature range of 25–805 °C, tensile adhesion strengths, and thermal cycle tests at 1250–1300 °C of the coatings were performed. It was observed that the thermal conductivity values of single-layer and double-layer coatings were lower than in the undoped lanthanum zirconate coating, and that thermal conductivity value increased with increasing temperature. According to thermal-cycle test results, the single-layer Dy, Nd doped lanthanum zirconate-based coating was damaged at 163 and 300 cycles respectively. There was no damage after 400 cycles in the double-layer coatings. The adhesion-strength values of single-layer coatings were lower than those of double-layer coatings. Such results imply that LDZ and LNZ ceramics can be top-layer materials on YSZ for a double-layer TBC system.

Solder Immersion Process of Ceramic Column Grid Array Package Assembly for Space Applications

Ceramic column grid array (CCGA) packages are progressively being utilized for logic and microprocessor functionalities requiring very high-density interconnections. These packages offer various advantages, such as high reliability, good thermal and electrical performance, and reduced size and weight, due to which the use of these packages in space applications is becoming more and more popular. Assembly of such packages is always challenging for assembly and quality assurance engineers due to its post assembly inspection and rework limitations. These packages are usually assembled using the standard surface-mount technology (SMT) assembly processes involving solder paste printing on printed circuit boards (PCBs), component placement, and reflow soldering. An innovative tweak to the SMT process named solder immersion process (SImP) for assembly of CCGA is invented, where the solder paste is applied on the columns of the CCGA packages replacing the conventional solder paste printing/dispensing. SImP is useful for prototyping and reworkability and results in substantial improvement of the solder joint quality. This article explains the SImP in detail, test vehicle preparation, quality evaluation and subsequent accelerated thermal cycling test results, its applications, and advantages in the field of prototyping and reworkability.

Novel core/void/shell composite phase change materials for high temperature thermal energy storage

• A novel core (=Al-Si/Bi)/void/shell (=Al 2 O 3 ) composite PCM was successfully prepared. • The Al-Si alloy and Al 2 O 3 shell were in-situ prepared by the displacement reaction. • The void layer was formed by the evaporation of most of the outer Bi in Al/Bi alloy. • The thermal stability of Al-Si/Bi/Al 2 O 3 was obviously improved due to the void layer. • The Al-Si/Bi/Al 2 O 3 possessed an adjustable thermal energy storage performance. Metallic solid-liquid phase change materials (SLPCMs) are crucial for the thermal energy storage technology of various industrial systems. However, the encapsulation of metallic SLPCMs is still technically difficult. In this pursuit, the present research envisaged the development of a novel technology to successfully prepare the core(=Al-Si/Bi)/void/shell(=Al 2 O 3 ) composite SLPCMs by using Al/Bi immiscible alloy powders as starting material and tetraethoxysilane as SiO 2 source. The Al-Si alloy and Al 2 O 3 shell were in-situ synthesized by the displacement reaction between SiO 2 and molten Al. Interestingly, most of the Bi distributed in the shell of Al/Bi immiscible alloy powders could not only improve the activity of alloy powders and promote the formation of precursor shell, but also be recycled by evaporation to form the void layer during the calcination process of composite SLPCMs. The produced void layer provided a space buffer to alleviate the volume expansion of the core SLPCM, and thereby improving the thermal cycling stability of the prepared composite SLPCMs. The thermal cycling test results showed that after 300 thermal cycles, the melting latent heat reduction of the core(=Al-Si/Bi)/void/shell(=Al 2 O 3 ) composite SLPCMs (24.3–31.7 J/g) was much less than that of the core(=Al-Si)/shell(=Al 2 O 3 ) composite SLPCM (58.1 J/g). Moreover, the prepared Al-Si/Bi/Al 2 O 3 exhibited an adjustable melting temperature (571.9 °C to 631.9 °C) and average particle diameter (39.3 μm to 112.6 μm), relatively high thermal conductivity [2.068 W(mK) −1 to 2.966 W(mK) −1 ], and excellent thermal energy storage capacity (209.5 J/g to 278.2 J/g). Thus, the prepared Al-Si/Bi/Al 2 O 3 composite SLPCMs are potential thermal energy storage materials, which can be used to improve the energy efficiency of various industrial systems.

Effect of Thermal Cycling on Operational Characteristics and Lifetime Prediction of Space Pulse Tube Refrigerator

This paper presents the operation status and results of ground thermal cycling test of pulse tube refrigerators (PTRs) for space application. Firstly, a thermal cycling degradation model was proposed by considering two physical mechanisms: contamination and fatigue damage. Then, a thermal cycling test scheme of two types of PTRs was designed and performed to demonstrate their long lifetime and high thermal stability. Two type A PTRs with cooling capacity of 1W@60 K and two type B PTRs with cooling capacity of 5W@80 K were continuously operated for about two years in a simulated vacuum thermal cycling environment. Effects of heat rejection temperature variation on thermal stability and dynamic performance of the PTRs were investigated. Furthermore, the thermal cycling degradation model was validated with the actual thermal cycling test data. Finally, the predicted pseudo-failure lifetime was acquired via experimental data and degradation model. Moreover, the estimated reliability of PTRs was obtained through using the Weibull distribution. The proposed thermal cycling test scheme and innovative lifetime prediction and reliability estimation method provide a quick and accurate approach for the cooler manufacturer to assess the lifetime and reliability of the space PTRs.

Water insensitive and solvent‐free synthesis of biodegradable solid–solid phase change materials based on poly (ethylene glycol) for thermal energy storage

AbstractUsually, polyethylene glycol (PEG)‐based biodegradable solid‐solid phase change materials (BSSPCMs) are synthesized with isocyanate and PEG, removing water is necessary due to the sensitivity to water of isocyanate groups. In this study, a water insensitive synthetic scheme based on carboxyl and aziridinyl was employed to prepare PEG‐based BSSPCMs via solvent‐free bulk polymerization: First, a carboxyl modified polyethylene glycol was synthesized through esterification reaction of citric acid and PEG with the molar ratio 2:1. Then, the BSSPCMs were prepared based on an self‐curing and organic solvent‐free process, using trimethylolpropane tris(1‐aziridine propionate) as the cross‐linking agent. The chemical structure, crystalline properties, phase change properties, thermal stability, and reliability were investigated by Fourier transform infrared spectroscopy, X‐ray diffraction, polarizing optical microscopy, differential scanning calorimetry, thermogravimetric analysis, and accelerated thermal cycling testing, respectively. Solid–solid phase change behavior was testified by the leakage test. The biodegradation experiment was conducted to prove the biodegradability of solid–solid PCMs. The results indicated that BSSPCMs had a similar crystalline structure to PEG, and the crystal size was smaller than PEG. The phase change temperature of BSSPCMs was in the range of 25–65°C, and the latent heat of phase change materials (PCMs) was about 103–108 J/g. Moreover, the extent of supercooling of BSSPCMs was reduced. Thermogravimetric analysis and accelerated thermal cycling test results confirmed the considerable thermal stability and reliability of BSSPCMs. The prepared PCMs also exhibited a good biodegradability in the natural environment.

Use of calcium silicate-coated paraffin/expanded perlite materials to improve the thermal performance of cement mortar

Here we demonstrate thermal energy storage cement mortar (TESC) developed by integrating cement mortar with a calcium silicate-coated paraffin/expanded perlite based form-stable phase change material (CPEP). The thermophysical properties, microstructure and spectroscopic characterization of the CPEP and the thermal and mechanical properties of the TESC were studied. MIP and SEM results show that paraffin mixture PCM is adsorbed uniformly into the pores of expanded perlite treated by hydrochloric acid. The thermal-cycling test results indicate the good thermal stability of CPEP by the cladding of three-layer calcium silicate. Differential scanning calorimetry (DSC) results reveal that the CPEP has phase change temperature and latent heat of 24.58 °C and 88.57 J/g, respectively, and the lower phase change temperature of CPEP compared to paraffin mixture is supported by FT-IR. Moreover, the CPEP was incorporated in cement mortar at 10%, 15%, 20% and 25%, by weight of sand. It is found that the compressive strength of TESC decreases with increasing CPEP content. However, they can still be regarded as building maintenance structure materials to use. Further, the ITZ structures between CPEP and cement substrate are focused on by SEM. In addition, the thermal energy storage performance of TESCs is revealed by the results of specific heat capacity test and heating test.

Development of calcium silicate-coated expanded clay based form-stable phase change materials for enhancing thermal and mechanical properties of cement-based composite

In this study, the thermal energy storage cement mortar (TESCM) was developed by incorporating calcium silicate-coated paraffin/expanded clay based form-stable PCMs (CS-ECPCM). The thermophysical properties, microstructure and spectroscopic characterization of CS-ECPCM and the thermal and mechanical properties of the TESCM were investigated. MIP and SEM results show that the paraffin mixture consisted of 52# paraffin and liquid paraffin can be well impregnated into expanded clay (EC) pores. The thermal-cycling test results indicate the good thermal stability of CS-ECPCM by the cladding of three-layer calcium silicate. And DSC results reveal that the CS-ECPCM has the phase change temperature and latent heat of 23.67 °C and 24.43 J/g, respectively, and the lower phase change temperature of CS-ECPCM compared with pure paraffin mixture can be supported by FT-IR and Raman spectra results. Furthermore, the CS-ECPCM was incorporated in cement mortar at 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%, by weight of sand. However, the interfacial zone structures between CS-ECPCM and cement has been enhanced by secondary encapsulation of calcium silicate, relieving the decrease in the compressive strength of TESCM. In addition, the thermal conductivities of the TESCMs decrease with the increase of mixing amount of CS-ECPCM, which are positive to their thermal insulation performance. And the excellent thermal energy storage performance of TESCMs is clearly suggested by the results of specific heat capacity test and heating test.