Tunable Thermal Expansion Research Articles

Development of novel Gd-Fe/Ti composites with tunable thermal expansion property

Abstract Titanium alloys are considered one of the most promising materials. However, their poor thermal expansion property remains a major obstacle to their widespread application. In this study, we explored an innovative design strategy to tune the thermal expansion properties of titanium alloy. Specifically, we used rare earth iron intermetallic compounds (Gd-Fe IMCs) with low coefficient of thermal expansion (CTE) as expansion inhibitors to prepare composites with the required thermal expansion properties via in situ reaction. The morphology and size of Gd-Fe IMCs can be effectively controlled by electromagnetic and ultrasonic fields, resulting in a dense distribution of micro/nano-structured Gd-Fe IMCs and strong interfacial bonding of the composites. This alloy has an excellent CTE of 6.8 × 10−6/K and a high ultimate tensile strength of 921 MPa. The improvement in the physical properties (especially in thermal expansion properties) of titanium alloy can be attributed to the synergistic effect between Gd-Fe IMCs and Ti matrix. This design strategy can also be extended to other titanium alloys as a reference for designing low thermal expansion titanium alloys.

Tunable thermal expansion via the magnetic phase competition in kagome magnets

Negative thermal expansion materials can solve the challenge of mismatched coefficients of thermal expansion of components in precision instruments, thereby improving the thermal shock resistance of devices. The adjustment of negative thermal expansion performance can improve the universality of its application. In this work, tunable thermal expansion has been achieved in Hf1−xTaxFe2 kagome magnets via magnetic phase competition. The transition from ferromagnetism to antiferromagnetism results in a sharp volume shrinkage of Hf0.83Ta0.17Fe2 within a narrow temperature range of 190–230 K, which limits its practical application. As the Ta content decreases, the ferromagnetic ground state becomes more robust and eventually suppresses the antiferromagnetism completely, achieving a negative thermal expansion in Hf0.88Ta0.12Fe2 caused by the ferromagnetic to paramagnetic transition over a wide temperature region and containing room temperature (αV = −37.63 × 10−6 K−1, 250–350 K). This work realizes the regulation of negative thermal expansion through magnetic phase competition, which provides guidance for the regulation of thermal expansion of magnetic materials in the future.

Classifying and Predicting the Thermal Expansion Properties of Metal-Organic Frameworks: A Data-Driven Approach.

Metal-organic frameworks (MOFs) are versatile materials for a wide variety of potential applications. Tunable thermal expansion properties promote the application of MOFs in thermally sensitive composite materials; however, they are currently available only in a handful of structures. Herein, we report the first data set for thermal expansion properties of 33,131 diverse MOFs generated from molecular simulations and subsequently develop machine learning (ML) models to (1) classify different thermal expansion behaviors and (2) predict volumetric thermal expansion coefficients (αV). The random forest model trained on hybrid descriptors combining geometric, chemical, and topological features exhibits the best performance among different ML models. Based on feature importance analysis, linker chemistry and topological arrangement are revealed to have a dominant impact on thermal expansion. Furthermore, we identify common building blocks in MOFs with exceptional thermal expansion properties. This data-driven study is the first of its kind, not only constructing a useful data set to facilitate future studies on this important topic but also providing design guidelines for advancing new MOFs with desired thermal expansion properties.

Localized magnetic moments variation for strengthening and tuning thermal expansion behavior of Mg alloys

We proposed the localized magnetic moments (LMMs) variation-induced strengthening for Mg alloys. Due to the strong interplay of magnetic and elastic, the introduction of merely 7 wt.% Mn3Ga0.7Ge0.3N in WE43 Mg alloy could not only reduce the coefficient of thermal expansion (CTE) but also enable an enhancement of ∼70% on compressive yield strength and less decrease of ∼2.1% on the elongation. We observed localized uniform lattice deformations and magnetic phase transitions for stress response and verified that the strain involves LMMs variation in the frustrated antiperovskite system, realizing simultaneously reinforcing and toughening in the compressive deformation process. Meanwhile, these magnetic transitions are accompanied by volume shrinkage and thus reduce the CTE of the WE43 Mg alloy. These results demonstrate that the introduction of the secondary phase with the variation of LMMs for stress response is an effective design strategy for alloys to achieve tunable thermal expansion behavior combined with high strength and moderate compressive deformability.

Superelastic bionic graphene/nanoceramic metamaterials with tunable thermo-mechanical performances

Limited by the intrinsic strong bonds between the composing atoms, engineering materials are plagued by the inevitable trade-offs among thermo-mechanical strength, toughness, and stability. In this work, a graphene/nanoceramic metamaterials (GNC) metamaterial was created by in-situ intercalation of Zr(WO4)2 nanoparticles within the multilayered microcell wall of a 3D hyperbolic graphene template. The bionic lamellar feature of the reduced graphene oxide (RGO)-Zr(WO4)2 sheet makes it highly ductile and stiff at the microscale, while the hyperbolic mesoscopic structure of GNC significantly enhanced the resistance to shear slip-induced fracture. 3D lightweight GNC metamaterials, therefore, exhibited synergic improvement in elastic compressibility (90%), strength (1.4 MPa), and toughness (1.62 N/m) than those of reported materials with similar architectures from either individual component or sandwiched microcell. Moreover, due to the lattice rotation of Zr(WO4)2 effectively regulated by the RGO sheet, the 3D GNC demonstrated tunable thermal expansion coefficient (TEC) as near-zero (−1.1 × 10−6 K−1), negative (−11.6 × 10−6 K−1), positive (1.2 × 10−6 K−1), and even combinations of three schemes. The resultant low thermal conductivity (∼0.007 W m−1 K−1), prior thermal shock resistance (200 K/s), and fireproof make GNC metamaterial show promise for applications in extreme conditions, such as lightweight protective filler, thermal insulator, robust damper, fire-retardant coating, thermal stress regulator, etc.

Interplanar Ferromagnetism Enhanced Ultrawide Zero Thermal Expansion in Kagome Cubic Intermetallic (Zr,Nb)Fe2.

A cubic metal exhibiting zero thermal expansion (ZTE) over a wide temperature window demonstrates significant applications in a broad range of advanced technologies but is extremely rare in nature. Here, enabled by high-temperature synthesis, we realize tunable thermal expansion via magnetic doping in the class of kagome cubic (Fd-3m) intermetallic (Zr,Nb)Fe2. A remarkably isotropic ZTE is achieved with a negligible coefficient of thermal expansion (+0.47 × 10-6 K-1) from 4 to 425 K, almost wider than most ZTE in metals available. A combined in situ magnetization, neutron powder diffraction, and hyperfine Mössbauer spectrum analysis reveals that interplanar ferromagnetic ordering contributes to a large magnetic compensation for normal lattice contraction upon cooling. Trace Fe-doping introduces extra magnetic exchange interactions that distinctly enhance the ferromagnetism and magnetic ordering temperature, thus engendering such an ultrawide ZTE. This work presents a promising ZTE in kagome metallic materials.

Band gap characteristics of multi-functional lattice metamaterials with adjustable thermal expansion and Poisson's ratio

The current development of science and technology has put increased demands on the versatility of metamaterials. In this paper, the band gap characteristics of a lattice metamaterial that can simultaneously modulate thermal expansion and Poisson’s ratio are studied, the dispersion characteristics of elastic waves propagating in periodic lattice metamaterials are analyzed, and the effects of different structures and parameters on the band gap are discussed. The results indicate that the configuration has excellent band gap properties while satisfying the tunable coefficient thermal expansion (CTE)and Poisson’s ratio functions. Through reasonable material selection and shape design, it is expected to achieve a multi-objective win-win for specific thermal expansion properties, Poisson’s ratio, and band gap design, resulting in better tunability and versatility of the metamaterial.

Thermal expansion regulation and bandgap analysis of a novel dual-constituent negative Poisson’s ratio lattice metamaterial

Negative Poisson's ratio lattice metamaterials (NPR-LM) have broad application prospects in explosion-proof and impact resistance due to their excellent energy absorption and cushioning properties. The development of science and technology has put forward higher requirements for the versatility of materials, but the currently existing lattice metamaterials are often limited to a single function. In this paper, a novel dual-constituent re-entrant hexagonal lattice metamaterial (DRHLM) with tunable thermal expansion behavior, negative Poisson's ratio (NPR) effect, and outstanding band-gap characteristics are designed based on traditional re-entrant hexagonal metamaterial and bi-layer curved rib. The tunable thermal expansion characteristics and NPR effect of DRHLM are verified by analytic and finite element numerical simulation methods. Finally, the bandgap of DRHLM is studied by using the finite element method, and the influence of the bending angle of the ribs on the bandgap is analyzed for DRHLM configurations with different coefficients of thermal expansion (CTEs) and NPRs. The results show that the designed DRHLM can simultaneously achieve different positive/negative/zero CTE and NPR with outstanding band gap characteristics by reasonably selecting material parameters and geometric parameters. This paper provides a new idea for the design of mechanical metamaterials with various properties and functions.

CeO2–x Nanoparticles Heated to 900 °C Afford Nanomaterials without Thermally Induced Mismatches: Implications for Catalyst Carriers

Nowadays, CeO2–x (0 < x < 0.5) nanoparticles are used for a wide range of applications, most of them using high temperatures. Since the phase diagram of nanoparticles differs from that of the corresponding bulk material and plays a pivotal role in many applications, the phase transition of CeO2–x nanoparticles exposed to a CO atmosphere at 900 °C was probed by in situ XRD measurements. The results show the presence of the fluorite and Cu2Se-like phases at this temperature. During the cooling process to room temperature in the He atmosphere, the Cu2Se-like phase turns metastable and transforms back to the fluorite phase. The phase transition occurs in 1D, with the crystallization mechanism controlled by volume diffusion. The Cu2Se-like phase presents a negative thermal expansion coefficient (α) for the temperature range of 580–300 °C due to the O diffusion from the Cu2Se-like to the fluorite crystal structure. Consequently, tuning the amounts of the fluorite and the Cu2Se-like phase allows reaching a tunable thermal expansion coefficient of the CeO2–x nanoparticles. In particular, the condition for a null thermal expansion coefficient was successfully achieved, which allows the use of smart CeO2–x nanoparticles without inducing thermal mismatches for applications like catalyst carriers.

Design of a transportable miniaturized optical reference cavity with flexibly tunable thermal expansion properties

A 3-cm-long optical reference cavity for transportable miniaturized ultra-stable laser is designed and analyzed using finite element analysis (FEA). Although the tiny cavity is formed in a conventional way, in which a cylinder spacer made of ultra-low expansion (ULE) glass is optically contacted with fused-silica mirror substrates and compensation rings, the compensation rings are specially designed in order to broaden the zero-thermal-expansion temperature tuning range. In addition, the cavity is capable of being rigidly fixed by clamping both end sections of the cylinder spacer along the axis. The thermodynamic analysis shows that a larger tuning span of the zero-thermal-expansion temperature varying from −10 K to + 23 K compared to all-ULE cavity is benefited, resulting in the whole optical reference cavity could work around room temperature. Meanwhile, the statics analysis indicates the design is insensitive to extrusion force and vibration so that it owns a potential of solid performance after transportation.

Lightweight 3D Graphene Metamaterials with Tunable Negative Thermal Expansion.

In this study, a 3D graphene metamaterial (GM) showing negative thermal expansion is prepared using a strategy of hyperbolically oriented freezing under a dual temperature gradient along orthogonal directions after the π-π stacking-derived assembly of 2D graphene sheets. As the fundamental construction element of the 3D GM, the graphene sheet displays anomalous shrinking deformation with a thermal expansion coefficient of (-6.12 ± 0.28) × 10-6 that is triggered by thermally induced out-of-plane vibrations of the CC bonds. A combination of numerical simulations and experimental investigations validates that anomalous negative thermal expansion (NTE) behavior can be effectively delivered to scalable 3D GM candidates at larger dimensions beyond the basic 2D graphene sheets at the microscale. The multiscale design and optimization of the structural characterization of the 3D GM further realize the desirable regulation of the NTE performance with the NTE coefficient ranging from negative ((-7.5± 0.65) × 10-6 K-1 ) to near-zero values ((-0.8 ± 0.25) × 10-6 K-1 ). This is attributed to the NTE-derived release regulation of the primary stress/strain of the microstructure, and the 3D GM exhibits high thermal stability while preserving the desirable structural robustness and fatigue resistance under thermo-mechanical coupling conditions. Therefore, this 3D GM offers promising potential for applications as protective skin, thermal actuator, smart switcher, and packing filler.

Tunable thermal expansion and bandgap properties of the bi-material-directional honeycomb metamaterial

The excellent shape stability of thermally expanded metamaterials and the good bandgap properties of acoustic metamaterials have a wide range of promising applications in aerospace and sensors. Here, a bi-material-directional honeycomb metamaterial (BHM) with tunable coefficient of thermal expansion (CTE) and bandgap properties is proposed. The theoretical analysis and numerical simulations are employed to reveal the thermal deformation mechanism of the BHM. In addition, the analytical expression of the effective Young’s modulus is established by considering both tensile and bending deformation. Based on the Bloch theorem, the band structures of the BHM are calculated by the finite element method. Parameter analysis confirms that the CTE and bandgap of the BHM can be simultaneously regulated and drastically adjusted by changing the geometric parameters and material combinations. Meanwhile, the coupling relationship of the effective CTE, Young’s modulus, and total effective bandgap width are investigated. The results show that the BHM can have tunable CTE function and large total effective bandgap width by selecting suitable parameters while satisfying stiffness requirements. This study achieves a dual objective of specific CTE properties and bandgap design through rational material selection and shape design, which makes the metamaterials have better tunability and multifunctionality.

Modelling and verification of a novel bi-material mechanical metamaterial cellular structure with tunable coefficient of thermal expansion

The tunable thermal expansion characteristic of metamaterials is beneficial to solve the problems caused by drastic temperature changes. Here, we propose a novel bi-material mechanical metamaterial cellular structure (NBMCS) that can adjust the coefficient of thermal expansion (CTE). Under some parameters restrictions, the structure can realize the regulation of its CTE in a wide range from -115 ppm/℃ to 83.6 ppm/℃ with Al alloy/Low carbon steel combination. A general thermoelasticity equation that builds the relationship among the temperature, the external force, and the displacement is derived, which is then assembled into a theoretical model of NBMCS. Through theoretical analysis and numerical simulations, the underlying mechanism among the CTE of NBMCS, geometric parameters, elastic modulus ratio, and CTE ratio is revealed. Experiments are carried out based on industrial camera and DIC method, which verify the theoretical modelling. Finally, the tunable range of CTE and elastic modulus for three different material combinations are compared. • A novel metamaterial structure with tunable coefficient of thermal expansion. • A general thermoelasticity equation for the structure is established. • Simulation and experiments are carried out to verify the theoretical modeling.

Stiffness characteristics for bi-directional tunable thermal expansion metamaterial based on bi-material triangular unit

The stiffness and coefficient of thermal expansion (CTE) are of great significance for lightweight metamaterials that adapt to variations in temperature. Toward this goal, bi-directional tunable thermal expansion metamaterial based on bi-material triangular unit is reported and fabricated using multi-layer assembly strategy. The CTE and stiffness of the designed metamaterial can be programmed in two directions, which provides a method for existing metamaterials can only be regulated in a single direction. To describe the mechanical properties, theories of the effective CTE and stiffness are established considering bending, tensile, and shear deformations and verified by numerical analysis. The mechanical response, especially stiffness, of the multi-material metamaterial is experimentally verified. By rationally modulating the cell architectures, the high relative stiffness and tunable CTE can be realized. In particular, the proposed metamaterial achieves a wide range of tunable CTEs from -31.16 ppm/°C to 56.43 ppm/°C. The exclusive integrated functions of the metamaterials including low density, considerable stiffness, and tunable CTE are superior compared with common materials. The coupling design of the CTE, stiffness, and relative density further demonstrates that this work has a positive effect on the development of metamaterials in aerospace applications and other fields.

Large tunable thermal expansion in ferroelastic alloys by stress

Metallic materials inherently possess small coefficients of thermal expansion (CTE). Engineering the CTEs of metals to achieve large values is demanded in many applications but has proved challenging. Here, we propose a strategy to obtain large CTEs in ferroelastically-transformable alloys through uniaxial stress control by utilizing the alloys' inherenty strong temperature dependence of Young's modulus (dE/dT). In nanostructured NiTi alloy with large elastic limit and large dE/dT, we tune the CTE from a large negative value of -53.2×10 −6 K −1 to a large positive value of +40.4×10 −6 K −1 by applying 1 GPa tensile stress. Such stress effect on CTE is 40 times those of non-ferroelastic metals and the created tunable CTE span is one order of magnitude larger than the typical span (10×10 −6 K −1 ) obtained via the existing chemical modification and hydrostatic pressure control. Through in-situ neutron diffraction experiment and theoretical calculation based on Reuss approximation, we show that the observed large thermal expansion under stress mainly comes from the elastic strain change with temperature due to the large dE/dT of the NiTi and can be generally achieved in ferroelastic alloys. In contrast to the stress-insensitive thermal expansion of most metals, the unique stress-sensitive thermal expansion of ferroelastic alloys may enable new solutions to problems arising from thermal expansion problems.

Designing high-entropy rare-earth zirconates with tunable thermophysical properties for thermal barrier coatings

The development of rare-earth zirconates with tunable thermal expansion coefficient (TEC) and thermal conductivity is of great importance in the area of thermal barrier coatings. In general, TEC can be tailored by the average electronegativity difference, and the thermal conductivity can be customized by the atomic mass difference and/or ionic radius. Based on this thermophysical properties design principle, a series of high-entropy rare-earth zirconate ceramics were synthesized and characterized, and the obtained results indicate that: (1) the TEC is negatively correlated with the average electronegativity difference of cation and anion concerning its corresponding compound; (2) the thermal conductivity is negatively correlated with the atomic mass difference and ionic radius difference concerning its corresponding compound; (3) the synthesized ceramics have excellent high-temperature long-term thermal phase stability, larger TEC (RT-1500 °C, 10.20 ~ 10.39 × 10-6 K-1), lower thermal conductivity (1500 °C, 1.17 ~ 1.37 W·m-1·K-1), and higher fracture toughness (1.61 ~ 1.69 MPa·m1/2) compared with lanthanum zirconate. The tailorable design principle involved in this work sheds new insights for designing alternative ceramics with pre-assigned thermophysical properties for the next-generation thermal barrier coatings.

Metallic glass based composites with precise tunable thermal expansion

Thermal expansion properties of materials are of fundamental interest and regulation of thermal expansion is significant for practical applications, but remains a challenge. We developed a moderate and efficient route for the preparation of metallic glass matrix composites, enabling precise tuning of thermal expansion properties over a wide range. Admixtures with dissimilar thermal expansion properties were successfully bonded to metallic glasses because of the unique thermoplasticity. The prepared composites achieve continuous regulation of the coefficient of thermal expansion over a broad range (9.6 ppm/K to 34 ppm/K), and high precision (0.065 ppm/K corresponds to one percent of the volume) can be realized. In addition, composites with nearly zero thermal expansion properties (average 0.19 ppm/K) in the wide temperature region (223 K to 473 K) were successfully prepared. Our approach provides a flexible and moderate pathway to achieve precise customization thermal expansion properties, promising a shift from laborious searching to precise tailoring of materials.

(Ho0.25Lu0.25Yb0.25Eu0.25)2SiO5 high-entropy ceramic with low thermal conductivity, tunable thermal expansion coefficient, and excellent resistance to CMAS corrosion

Low thermal conductivity, compatible thermal expansion coefficient, and good calcium—magnesium—aluminosilicate (CMAS) corrosion resistance are critical requirements of environmental barrier coatings for silicon-based ceramics. Rare earth silicates have been recognized as one of the most promising environmental barrier coating candidates for good water vapor corrosion resistance. However, the relatively high thermal conductivity and high thermal expansion coefficient limit the practical application. Inspired by the high entropy effect, a novel rare earth monosilicate solid solution (Ho0.25Lu0.25Yb0.25Eu0.25)2SiO5 was designed to improve the overall performance. The as-synthesized (Ho0.25Lu0.25Yb0.25Eu0.25)2SiO5 shows very low thermal conductivity (1.07 W·m−1·K−1 at 600 °C). Point defects including mass mismatch and oxygen vacancies mainly contribute to the good thermal insulation properties. The thermal expansion coefficient of (Ho0.25Lu0.25Yb0.25Eu0.25)2SiO5 can be decreased to (4.0–5.9)×10−6 K−1 due to severe lattice distortion and chemical bonding variation, which matches well with that of SiC ((4.5–5.5)×10−6 K−1). In addition, (Ho0.25Lu0.25Yb0.25Eu0.25)2SiO5 presents good resistance to CMAS corrosion. The improved performance of (Ho0.25Lu0.25Yb0.25Eu0.25)2SiO5 highlights it as a promising environmental barrier coating candidate.

Tunable negative thermal expansion in La(Fe, Si)13/resin composites with high mechanical property and long-term cycle stability

Materials with tunable negative thermal expansion (NTE) are highly demanded in various functional devices. La(Fe, Si)13-based compounds are promising NTE materials due to their outstanding NTE properties. However, their poor mechanical properties and related short service life restrict their practical applications. In this work, epoxy resin with positive thermal expansion is used to synthesize La-Fe-Si/resin composites. The NTE of La-Fe-Si/resin composites can be manipulated by optimizing the La-Fe-Si particle size and resin content, and tailoring resin content could tune the NTE more effectively. The average linear coefficient of thermal expansion of the composites decreases from -275.0 × 10-6 K-1 to -4.9 × 10-6 K-1 over the magnetic transition temperature range as the resin content increases from 3 wt.% to 80 wt.%. In addition, zero thermal expansion is achieved in the La-Fe-Si/resin composite with 20 wt.% resin. The resin would reinforce the binding force by filling the pores between the particles. The La-Fe-Si/resin composite with 80 wt.% resin exhibits highly improved mechanical properties; for example, its compressive strength of 205 MPa is 75% higher than that of the La-Fe-Si/resin composite with 3 wt.% resin. The prepared La-Fe-Si/resin composites can be machined into different shapes for practical applications, such as thin plates, strips, and rods. Furthermore, the La-Fe-Si/resin composites can undergo 1000 thermal cycles without NTE performance degradation and mechanical integrity loss, indicating durable cycle stability. Hence, significantly tunable NTE with high mechanical properties and long-term cycle stability makes La-Fe-Si/resin composites present great application potential as NTE materials.

Metallic Glass Based Composites with Precise Tunable Thermal Expansion

Metallic Glass Based Composites with Precise Tunable Thermal Expansion