Thermal Shock Cycles Research Articles

Thermal shock resistance of carbon-based composites reinforced by HfC nanowires under extreme conditions

Lightweight composites with excellent thermal shock performance exhibit significant potential for thermal structural components. Herein, HfC nanowires modified carbon/carbon (HfCNWs-C/C) composites are fabricated, establishing a three-dimensional network within the matrix. The microstructure of the composites before and after thermal shock cycles were characterized by SEM, XRD and TEM. Additionally, the flexural strength with varied thermal shock were analyzed, which were initially increasing before subsequently decreasing with the number of thermal shock cycles under Ar atmosphere, exhibiting thermal shock strengthening phenomena. While within oxy-acetylene system, the strength of HfCNWs-C/C exhibit an increasement of 75 % compared with C/C after ablation for 6 cycles, which can be attributed to the sintering and the generation of molten film of partial HfO2 phases that can mitigates oxidation of the matrix, but still lead to a declining trend in the strength following ablative thermal cycles.

Structure and properties of the hot pressing molded anodized aluminum alloy/polyformaldehyde hybrids

The metal-plastic hybrid is one of the important solutions for lightweight and high-strength composite. The anodized aluminum alloy（AAA）/polyformaldehyde（POM） hybrids with excellent mechanical properties were processed by the hot pressing technology. The surface of the aluminum alloy plate was firstly pretreated with phosphoric acid and oxalic acid anodizing, resulting in a large number of micro-nano scale pores on the surface. These pores were well embedded with plastic melt during hot pressing to form micro-nano mechanical interlocking structures and the Al–O–C chemical bond at the interface is generated, thus ensuring good bonding strength at the metal and plastic interface. The maximum tensile-shear strength of the metal-plastic hybrid was 30.65 MPa, meanwhile, the metal-plastic interface failure presented mainly a mixed failure mode, including resin removal from the metal surface and plastic tearing from the plastic surface. At the same time, the salt spray test, thermal shock test, and variable temperature test were adopted to investigate the application performance of the metal-plastic hybrid. The Al/POM hybrids were able to maintain their mechanical strength above 20 MPa for 28 days in a salt spray environment, 14 times in a thermal shock cycle, and at high temperatures. The high mechanical strength of hybrid has good potential for automotive applications.

A novel approach for brazing MgF2 ceramic to TA15 alloy using AgCu/GH4169/Bi2O3[sbnd]B2O3[sbnd]ZnO composite braze fillers

A two-step brazing process was successfully employed to join MgF2 ceramic and TA15 alloy using eutectic Ag28% (in mass fraction) Cu alloy and Bi2O3B2O3ZnO (BBZ) glass as fillers, by introducing a 100 μm thick GH4169 interlayer. Multiscale characterization revealed that interdiffusion and reaction occurred at the joint interfaces. As a result, a reliable joint system consisting of TA15/TiCu/TiCu2Al/Ag(s,s) + Cu(s,s)/TiCu2Al/TiCu Ni + Ag-rich layer/GH4169/nano-oxide layer/glass/Mg3(BO3)F3+MgO + MgF2 reaction layer/MgF2 was formed. The GH4169-interlayer exhibited adaptive compatibility though its interaction with AgCu and BBZ glass fillers, effectively accommodating strong interface bonding and thermal mismatch stress between TA15 and MgF2 substrates. It shows an excellent shear strength (32 MPa, at room temperature) as well as thermal cycling stability without any cracking or spallation observed after the 20 thermal shock cycles between room temperature and 300 °C. It provides valuable insights into designing highly reliable ceramic/metal joints that demonstrate superior stability and adaptability in specific applications.

Strong and flexible MXene-based nanocomposite films for atomic oxygen resistance and electromagnetic interference shielding

MXene has garnered considerable attention as a promising candidate for multifunctional artificial materials, owing to its exceptional mechanical performance and superior electric conductivity. However, macroscopically layered films assembled by MXene nanosheets are usually accompanied by serious degradation of mechanical properties. Moreover, there is a notable paucity of investigations on MXene in low Earth orbit (LEO) environment. Inspired by the layered structure of nacre, we applied polyurethane (PU) as an interfacial crosslinking agent to improve the mechanical properties of MXene films. The optimized MXene/PU (MP) nanocomposite film exhibited a tensile strength of 298.02 MPa and a toughness of 13.81 MJ m−3, surpassing those of the pure MXene film by 260 % and 1300 %, respectively. The atomic oxygen (AO) erosion yield of MP was approximately one order of magnitude lower than that of commercial Kapton films, which was attributed to the shielding effect of MXene against AO attacks. Remarkably, the MP nanocomposite film demonstrated exceptional retention of tensile strength under various extreme conditions including AO irradiation, cryogenic-high temperature, cyclic thermal shock and hot water. Contributed by multi-layer structural design and high conductivity, the MP exhibited a high electromagnetic interference shielding effectiveness (EMI SE) of 48 dB and a specific SE divided by thickness (SSE/t) of 13,479 dB cm2 g−1 at the thickness of 20 μm. Consequently, the nacre-like MP nanocomposite film with exceptional mechanical properties and high-level functional performance holds substantial promise as a multifunctional space material for LEO environments.

Enhancing thermal-mechanical performance of micron Ag/ZrW2O8 nanorod die-attach paste with low thermal expansion

Negative thermal expansion not only challenges the traditional lattice concept, but also provides new opportunities for regulating the thermal expansion coefficient and addressing the increasing reliability demands in power device packaging. In this study, ZrW2O8 nanorods were firstly introduced into the micron Ag paste via a facile low-temperature (≤300 ℃) low-pressure (<10 MPa) sintering. The pinning and negative thermal expansion mechanisms contributed by the homogeneously dispersed ZrW2O8 nanorods significantly mitigate the thermal expansion mismatch and suppress the microstructure deterioration in SiC power module, which was also verified by finite element (FE) simulation. The Ag@2%ZrW2O8 (2% of the total weight of Ag) specimen possessed outstanding long-term reliability with a die-shear strength of 29.63 MPa after 1000 thermal shock cycles from −50–250 ℃. The novel findings can be inspiring on interconnected material optimization and selection in electric packaging application as well as reliability evaluation in the service condition.

The Influence of Cyclic Thermal Shocks at High Temperatures on the Microstructure, Hardness and Thermal Diffusivity of the Rene 41 Alloy.

The precipitation-hardenable nickel-based superalloy Rene 41 exhibits remarkable mechanical characteristics and high corrosion resistance at high temperatures, properties that allow it to be used in high-end applications. This research paper presents findings on the influence of thermal shocks on its microstructure, hardness, and thermal diffusivity at temperatures between 700 and 1000 °C. Solar energy was used for cyclic thermal shock tests. The samples were characterized using microhardness measurements, optical microscopic analysis, scanning electron microscopy coupled with EDS elemental chemical analysis, X-ray diffraction, and flash thermal diffusivity measurements. Structural transformations and the variation of properties were observed with an increase in the number of shocks applied at the same temperature and with temperature variation for the same number of thermal shocks.

A rapid-sintering Cu-Cu joints with ultrahigh shear strength and super reliability for power electronics package

Sintered Cu interconnection technology for power electronics has been widely investigated owing to its unique low temperature sintering high temperature service characteristics and price superiority. However, the currently research usually requires long sintering time (>30 min) and high pressure (>5 MPa). Here, we synthesized copper formate coated Cu nanoparticles (Cu-FA) by a solvothermal reaction, which can achieve rapid sintering at 260 °C with pressure of 5 MPa in 5 min to obtain robust joints of 67.41 MPa for fabricating SiC MOSFET devices. After 1000 h thermal aging and 1000 cycles thermal shock, the strength of joints can still maintained above 50 MPa. Moreover, SiC MOSFET modules were demonstrated using Cu-FA die attachment, which exhibit a 43.6 % lower thermal resistance compared to commercial Sn–Pb solder. Furthermore, copper paste performs better in long-term reliability. This paper provides an effective way to obtain high quality sintered Cu joints rapidly, which is suitable for the packaging of next generation power devices.

Study on magnesia alumina spinel heat storage ceramics for solar thermal power generation

AbstractSolar thermal storage ceramic materials use photothermal power generation technology to store heat energy, which is an important way to use clean energy and reduce carbon emissions. In this paper, MgAl2O4 ceramics were prepared by pressureless sintering with fused magnesia and α‐Al2O3 as the primary raw materials and TiO2 as the additive. The phase composition, microstructure, physical properties, thermal shock resistance, and thermal physical properties of MgAl2O4 thermal storage ceramics were studied. The results show that the main crystalline phase of B4 is MgAl2O4 and the secondary crystalline phase is MgTi2O5. Ti4+ is dissolved into MgAl2O4 lattice, which distorts the lattice, reduces activation energy, and promotes sintering. The sample B4 (69.73 wt% α‐Al2O3, 30.27 wt% fused magnesia, and 7 wt% TiO2) sintered at 1510°C had the best comprehensive physical properties, and its bending strength and bulk density were 89.41 MPa and 3.27 g/cm3, respectively. After 30 thermal shock cycles, the bending strength of the sample B4 is slightly lost. The thermal stress generated during the expansion and contraction of the grain volume led to the decrease of the bending strength. From room temperature to 1000°C, the specific heat capacity of sample B4 is .44–1.25 J/(g·K). The heat capacity increases with the increase of temperature, and the heat storage density increases. The heat storage density is 1218.75 kJ/kg (1000°C). Heat capacity increases with temperature due to intensified lattice vibration at high temperatures. Therefore, magnesia alumina spinel ceramics show great potential in solar thermal energy storage.

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.

Deuterium retention in cyclic transient heat loaded tungsten with increasing cycle numbers

Surface damage and microscopic defect evolution of tungsten (W) armor under transient heat loads are key factors for fuel retention in fusion reactors. In this work, experiments were conducted to investigate the effects of cyclic thermal shocks on deuterium (D) retention and surface blistering in W. Thermal shock experiments were conducted on recrystallized W using an electron beam with a power density of 0.15 GW m−2 across 100–1500 cycles, followed by D plasma exposure with high-fluence (∼1 × 1026 D m−2). The results demonstrate that samples subjected to 500 and 1500 cycles exhibit a significant presence of sub-grains within 90 μm. Notably, the inhibition of blistering induced by thermal shock leads to a substantial reduction in D retention (5.45 × 1019 D m−2) at lower cycle numbers (100 cycles) compared to the reference sample (2.35 × 1020 D m−2) which was only exposed to D plasma. When cycle numbers increase to 500 and 1500, D retention reaches 1.98 × 1020 D m−2 and 4.56 × 1020 D m−2, respectively. Based on the tritium migration analysis program, we propose that total D retention is a consequence of the competition between defects reduced by thermal shock-induced suppression of blistering and defects generated by plastic deformation induced by thermal stress. D retention initially decreases with the increase in cycle numbers, followed by a subsequent rise, with the inflection point slightly higher than 500 cycles. Additionally, due to the extensive scope of thermal stress, an escalated exposure period will result in substantial D captured by heat-induced defects, consequently intensifying the D retention. Whether there exists an upper limit to D retention induced by the increasing thermal shock cycles necessitates further experimental analysis. Nonetheless, it is evident that thermal shock significantly contributes to D retention within a profoundly deep bulk region under high cycles.

On the Thermal Shock Resistance and Failure Mechanism of the Pt-Modified Aluminide Bond Coating

The failure mechanism of the Pt-modified aluminide (Pt-Al) bond coating (β-(Ni, Pt)Al coating) in a simulated service environment has seldom been investigated. Based on a self-developed thermal barrier coating service environment simulator, a thermal shock experiment of single-phase Pt-Al bond coating on DD419 substrate at a temperature of 1170 °C was conducted combined with a real-time monitoring infrared thermal imager. The lifespan and failure mechanism of the coating are analyzed in detail. The results reveal that specimens of the Pt-Al bond coating, subjected to three repeated tests, exhibit failure after 650, 528, and 793 thermal shock cycles at 1170 °C, respectively. After failure, the contents of Pt and Al elements in the peeled region are lower than those in the unpeeled area, and a diffusion zone emerges in the bond coating. The failure mechanism of the Pt-Al bond coating during the thermal shock test can be attributed to three main aspects: (1) the diffusion and consumption of the Pt element reduced the oxidation resistance of the Pt-Al bond coating; (2) the diffusion and depletion of elemental Al causes a phase change in the coating, leading to the failure of the coating; (3) thermal stresses are generated in the Pt-Al bonded coating during the thermal shock test, which ultimately leads to wrinkling.

Pressure induced thermal conduction paths in liquid metal-boron nitride fillered thermal interface materials with high thermal conductivity

With the continuous evolution of wearable and mobile devices, flexible electronics, and intelligent thermal management, there is a growing interest in thermal interface materials (TIMs) that combine high thermal conductivity with low modulus for stretchability. However, materials with high thermal conductivity often come with elevated Young's modulus. Here, we have developed a TIMs by combining liquid metal and BN with polydimethylsiloxane (PDMS), achieving a blend of low modulus and high thermal conductivity. To enhance thermal conductivity, we introduced boron nitride sheets as “scalpel”, puncturing the oxide layer of the liquid metal under pressure to establish a continuous thermal path. After pressure induction, the LM-BN/PDMS composite exhibits a thermal conductivity of 4.3 W/(m K), with a Young's modulus of only 193 kPa and a fracture strain of 483%. Furthermore, it demonstrates outstanding thermal stability under multiple thermal shock cycles, indicating significant potential for applications in future thermal management for flexible electronic devices, wearable devices, and beyond.

Enhanced Reliability for Power Modules via a New Ag/Si Sinter Joining Strategy

In this work, with an appropriate adding amount of 20 vol% Si, the novel Ag-Si sintering demonstrated enhanced reliability during thermal shock cycling, specifically including the improved bonding strength stability as well as good microstructure maintenance. The high reliability can be attributed to the reduced CTE value of composited Ag-Si sintering inhibition of thermomechanical stress generation, allowing for the ultra-stable joining structure without coarsening, delamination and deformation. Additionally, the well-adhered interface between sintered Ag and Si additive was also verified by examining the microstructure, ensuring the reliable bonding characteristics of the Ag/Si sintered joint.

Reliability of Copper Sintered Interconnects under Extreme Thermal Shock Conditions

Copper flakes-based sinter paste showed high reliability under thermal shock conditions. A dense and homogeneous interconnect was realized while sintering for 5 min at 275°C under 15 MPa bonding pressure, with the flakes showing the unique behavior of stacking over each other to realize a dense and homogeneous interconnect. Porosity under 10% could be achieved. The paste could be sintered under a constant nitrogen flow and did not need a fully inert atmosphere during sintering. Under high stress thermal shock cycling of +175/-65°C, the sintered interconnects showed a drop of 25% in the shear strength values after 1000 TST, consistent with observations made with Ag sintering. Thermal conductivity more than 200 W/mK and electrical conductivity of 20 Ms/m is achieved using the Cu sinter paste.

Effects of thermal shocks on integrity of existing and newly-designed sealants for CCS applications

Sealants that can guarantee long-term wellbore sealing integrity are of great significance to the safe and sustainable storage of CO2 in carbon capture and storage (CCS). In this study, we investigate how abrupt cyclic thermal shocks affect the integrity of four sealants of different compositions. These sealants include two reference OPC-based blends (S1 and S2), one newly-designed OPC-based blend that contains CO2-sequestering additives (S3), and one calcium aluminate cement (CAC)-based blend designed for CCS applications (S4). We have measured the thermal properties of these samples, followed by quenching and flow-through experiments to apply strong cyclic thermal shocks on samples of the four sealants, where we heated the samples to 120 °C, and quenched them in, or flowed through water of 20 °C. Using X-ray tomography (32 µm/voxel) before and after the experiment showed that both S1, S2 (reference OPC-based) and S4 (CAC-based) broke after thermal-shocking experiments. Cracks and new voids developed in the samples. Post-treatment strength testing shows that thermal shocks reduce the unconfined compressive strength of these three sealants. This implies that these compositions may not be optimal materials for long-term wellbore sealing during CO2 injection and storage afterward. For all these three sealant compositions, quenching resulted in a greater reduction in strength (by 53 % on average) than flow-through experiments (by 29 % on average). On the contrary, we have not observed any cracks after either quenching or flow-through experiments in S3 sealant (OPC with CO2-sequestering additives). We attribute the intactness of this sealant after thermal shocks to its higher thermal diffusivity than the other three sealants. Heat transfers more rapidly in this sealant and the associated thermal stresses are mild and insufficient to cause any damage to its integrity, which makes this sealant a good candidate for wellbore sealing material that can effectively withstand strong thermal shocks encountered during CCS, though further studies are required.

Microstructure, mechanical properties and thermal shock behavior of 2.5D oxide fiber preform reinforced oxide matrix composites

The 2.5D oxide/oxide composites become attractive for their excellent integrity and mechanical properties. The thermal shock resistance performance of the material is very important in the actual high temperature application. In this work, the evolution of microstructure and mechanical behavior of the 2.5D oxide/oxide composites from thermal shock at different temperatures and cycles was investigated experimentally mainly by optical microscope, X-ray computed tomography and macro-mechanical tests. The thermal shock resistance mechanism of oxide/oxide composites was qualitatively explored. The results showed that cracks propagation was the main manifestation of thermal shock damage in composites. Compared with 2D composites, 2.5D composites exhibited the finite domain effect on crack propagation due to its reinforcement had certain fibers in Z-direction. This directly caused the critical thermal shock temperature difference of the 2.5D composites (∼900 °C) was more than twice that of the 2D oxide/oxide composites (∼400 °C). In addition, the finite domain effect also significantly reduced the damage growth rate of the 2.5D composites from cyclic thermal shock, highlighting its excellent thermal shock damage resistance.

Thermal shock effects on the microstructure and mechanical properties of iron-based composites reinforced by in-situ Fe2B/FeB ceramic phases

Recently, high-temperature composites reinforced with in-situ phases have been developed as a new class of composites for harsh environments. The behaviour of these composites under sudden heating and cooling conditions is greatly influenced by the type and fraction of components. The aim of this study is to investigate the microstructural properties and mechanical response of iron based composites after thermal shock cycling. The fabrication process involved in-situ powder metallurgy (IPM) sintering of Fe–B4C starting powders. The samples were subjected to thermal shock with a constant temperature differences (ΔT: 600 °C) and varied cycles (N: 1–50). Comparison of microstructural changes and mechanical behaviour before and after thermal shock has been carried out. The boron atoms released from the initial B4C generated diffusion zones in the matrix dominated by iron boride phases (Fe2B/FeB). An effective matrix-reinforcement interface has been created by in-situ powder metallurgy, where boride phases are almost homogeneously distributed in the iron matrix. While the hardness of the composites was significantly developed by the Fe2B/FeB phases, the addition of B4C resulted in a reduction in the coefficient of thermal expansion (CTE). The in-situ phases contributed in the minimisation of the coefficient mismatch by balancing the thermal expansion coefficients between iron and the initial B4C. Under the influence of thermal shock, microcracks and then macrocracks formed on the sample surfaces, increasing in width and depth with thermal cycles. This resulted in accelerated fracture damage under post-thermal loading. Both the impact and flexural strengths of the samples were significantly reduced as the number of thermal cycles increased. Although the 20% B4C reinforced composite provided maximum hardness, it showed poor resistance to thermal loading. The best results for mechanical loads were achieved by the 5% B4C reinforced composite, which showed no cracks even after 50 thermal cycling.

Revealing thermal shock behaviors and damage mechanism of 3D needled C/C–SiC composites based on multi-scale analysis

Understanding thermal shock behaviors and related damage mechanism of needled C/C–SiC composites is of much significance to their engineering application. In this study, a multi-scale framework is developed to characterize the degeneration of mechanical properties and damage accumulation in the needled composites comprehensively across different scales under cyclic thermal shock. Thermal shock temperature and thermal shock cycles are involved in the simulation, and the outcomes are verified with experiments performed in an inert atmosphere. The results show that the strength of C/C–SiC composites decreases continuously as the test temperature and thermal shock cycles increase. Meanwhile, the fracture of the material mainly occurs in the short-fiber felt. The damage initiates in the short-fiber felt near the contact area of the non-woven (NW) fiber tow and the needle-punched (NP) fiber tow when the test temperature is low (about 900 °C), and gets severe as temperature increases. With the increase of thermal shock cycles at 1700 °C, the fracture of the composites is more significant, and spreads from inside to the outer surface. Based on the multi-scale simulation and the microstructure of the composites after TSR tests, the primary damage mechanisms in the short-fiber felt are identified as ceramic-matrix damage and interface debonding.

Evaluating the versatility of stainless steel flakes and magnetite powder as polyvalent additives for wood paints

The objective of this study is to evaluate how various fillers, specifically stainless steel flakes and magnetite powder, affect the visual attributes, durability and versatility of a water-based wood paint. To examine the influence of these two specific pigments on the overall look of the coatings, colorimetric measurements were carried out. The impact of these distinct fillers on the durability of the layers was assessed by subjecting the samples to xenon arc light exposure and cyclic thermal shocks, followed by colorimetric inspections and adhesion tests. Furthermore, the fillers' impact on the coating's ability to act as a barrier was assessed through liquid resistance and water uptake tests. Additionally, the Buchholz hardness indentation test and the Taber test were conducted to quantify how these functional additives affect the mechanical properties of the coatings, such as hardness and resistance to abrasion. Lastly, two specific tests revealed the fillers' role in introducing unique electrical conductivity and magnetic attractive properties to the paint. In conclusion, this study underscores the intriguing influence of stainless steel flakes and magnetite powder, which not only impart vibrant colors and distinct visual characteristics to the paint but also maintain the coating's protective barrier properties, enhance the mechanical properties of the composite layer, and introduce specific multifunctional features to the coating.

The impact of stainless steel flakes as a novel multifunctional pigment for wood coatings

The purpose of this research was to determine the influence of three different amounts of stainless steel flakes on the aesthetic features and durability of a waterborne wood paint. Colorimetric measurements and optical microscope observations were employed to assess the impact of this novel pigment on the overall appearance of the coatings. The effect of the different amounts of metallic flakes on the durability of the layers was evaluated by subjecting the samples to UV-B radiation and cyclic thermal shocks, performing infrared spectroscopy analysis, colorimetric inspections, and adhesion test. In addition, the influence of the filler concentration on the coating barrier efficiency was assessed through the liquid resistance and water uptake tests. Moreover, Buchholz hardness indentation test and the scrub test were conducted to quantify the impact of the flakes on the mechanical characteristics of the coatings, such as hardness and abrasion resistance. Finally, the thermal test evidenced a specific role of the flake amount in altering the thermal behavior of the coatings. Ultimately, this work highlights the attractive effect of stainless steel flakes, which are capable of providing an intense coloring and specific aesthetic features to the paint, preserving the surface's barrier-protective properties, increasing the abrasion resistance of the composite layer, and influencing the thermal behavior of the coating.