Giant Negative Thermal Expansion Research Articles

Giant Negative Thermal Expansion in Ultralight NaB(CN)4.

Negative thermal expansion (NTE) is crucial for controlling the thermomechanical properties of functional materials, albeit being relatively rare. This study reports a giant NTE (αV ∼-9.2 ⋅ 10-5 K-1 , 100-200 K; αV ∼-3.7 ⋅ 10-5 K-1 , 200-650 K) observed in NaB(CN)4 , showcasing interesting ultralight properties. A comprehensive investigation involving synchrotron X-ray diffraction, Raman spectroscopy, and first-principles calculations has been conducted to explore the thermal expansion mechanism. The findings indicate that the low-frequency phonon modes play a primary role in NTE, and non-rigid vibration modes with most negative Grüneisen parameters are the key contributing factor to the giant NTE observed in NaB(CN)4 . This work presents a new material with giant NTE and ultralight mass density, providing insights for the understanding and design of novel NTE materials.

Unlocking giant negative thermal expansion through reversible conformational changes in regenerated silk fibroin film

Developing thermally contractive polymeric materials with controlled conformational changes that enable more efficient actuation mechanisms has long been an ambitious goal. However, the utilization of naturally derived assemblies with biodegradable and reversible capabilities has, thus far, been hindered by the challenges associated with organizing the hierarchical nanostructures. Herein, hierarchically structured building blocks in regenerated fibroin were utilized to construct a thermal-responsive protein film through a friction-induced assemble strategy. By preserving the protofibrils within the regenerated silk film, we enable the efficient storage and transfer of elastic energy to external loads. The freestanding fibroin film, with pre-extended molecular chains, thus produced exhibited an exceedingly high negative thermal expansion (−1220 ppm K−1) and work capacity (∼203 J kg−1). The comprehensive analysis involving synchrotron infrared spectroscopy, in-situ Raman spectroscopy, and molecular dynamics simulations has confirmed that the actuating mechanism entails a reversible conformational change initiated by H-bonds, which is then amplified into macroscopic deformations by the hierarchical structure. This newly discovered, low-energy-driven mechanism paves the way for the creation of flexible protein assemblies with high-performance actuation capabilities.

Giant Negative Thermal Expansion Materials: Progress of Research and Future Prospects

Giant Negative Thermal Expansion Materials: Progress of Research and Future Prospects

Giant uniaxial negative thermal expansion in FeZr2 alloy over a wide temperature range

Negative thermal expansion (NTE) alloys possess great practical merit as thermal offsets for positive thermal expansion due to its metallic properties. However, achieving a large NTE with a wide temperature range remains a great challenge. Herein, a metallic framework-like material FeZr2 is found to exhibit a giant uniaxial (1D) NTE with a wide temperature range (93-1078 K, {bar{alpha }}_{l}=-34.01times {10}^{-6},{{{{{{rm{K}}}}}}}^{-1}). Such uniaxial NTE is the strongest in all metal-based NTE materials. The direct experimental evidence and DFT calculations reveal that the origin of giant NTE is the couple with phonons, flexible framework-like structure, and soft bonds. Interestingly, the present metallic FeZr2 excites giant 1D NTE mainly driven by high-frequency optical branches. It is unlike the NTE in traditional framework materials, which are generally dominated by low energy acoustic branches. In the present study, a giant uniaxial NTE alloy is reported, and the complex mechanism has been revealed. It is of great significance for understanding the nature of thermal expansion and guiding the regulation of thermal expansion.

Giant negative thermal expansion in Zn2-Cu P2O7 ceramics via microstructure effect

As a novel thermophysical behavior, negative thermal expansion (NTE) has been studied in many materials. However, rare materials have realized giant NTE, and the methods to improve NTE are lacking. Herein, a giant NTE has been achieved in Zn 2- x Cu x P 2 O 7 ceramics via microstructure effect. In the Zn 1.96 Cu 0.04 P 2 O 7 ceramic body, the linear contraction measured by dilatometry reaches to 0.9% (3ΔL/L = 2.7%) when heated from −30 °C to 125 °C, while the intrinsic crystallographic volume contraction derived by X-ray diffraction is only 1.68%. The remarkable NTE enhancement in the ceramic sample is attributed to the microstructure effect. An apparent shrinkage of the voids has been observed by in-situ atomic force microscope (AFM). The voids with large size in the ceramic body is the key factor to enhance NTE. This is the first time to observe direct experimental evidence by AFM for microstructure effect. Microstructure effect is an effective method to produce giant NTE.

Anisotropic thermal expansion of silicon monolayer in biphenylene network.

Materials with a negative thermal expansion property are of great importance in the emerging family of two-dimensional materials. For example, mixing two materials with negative and positive coefficients of thermal expansion avoids volume changing with temperature. In this work, based on first-principles calculations and Grüneisen's theory, we investigated the thermal expansion properties of a silicon monolayer in biphenylene networks. Our results show that the thermal expansion is greatly negative and anisotropic, as the linear thermal expansion coefficient along the a-direction is significantly smaller than the one along the b-direction, even at high temperatures. At 300 K, the thermal expansion coefficients along the two lattice directions are -17.010 × 10-6 K-1 and -2.907 × 10-6 K-1, respectively. By analyzing the Grüneisen parameters and the elastic compliance, we obtained an understanding of the giant negative thermal expansion of the material. Rigid unit modes are also responsible for the negative thermal expansion behavior. Our work provides fundamental insights into the thermal expansion of silicon monolayer in biphenylene networks and should stimulate the further exploration of the possible thermoelectric and thermal management applications of the material.

Lattice dynamics and spin–phonon coupling in the noncollinear antiferromagnetic antiperovskite Mn[formula omitted]NiN

Antiferromagnetic antiperovskites, of the form Mn3BN (B= Ni, Cu, Zn, Sn, Ir, and Pt), have shown an outstanding behavior in which, giant negative thermal expansion and chiral magnetic structures are intertwined. As such, aiming to shed light on the magnetostructural behavior, related to the magnetic ordering and crystalline structure of this type of materials, we studied theoretically, based-on first-principles calculations, the lattice dynamics and spin–phonon coupling in the Manganese-based antiperovskite Mn3NiN, as a prototype in the Mn3BN family. We found a strong spin–lattice coupling by means of the understanding of the phonon-dispersion curves obtained when including the chiral noncollinear magnetic structures. To do so, we highlight the importance of the exchange–correlation scheme selected and its influence on the structural, electronic, magnetic, and vibrational degrees of freedom. Finally, we found two unstable vibrational modes at the M- and R-points when the magnetic ordering is switched to ferromagnetic from the chiral Γ4g and Γ5g. These octahedral-associated modes with spin–phonon coupling parameters, λ, as large as 10.74 cm−1 and −2.53 cm−1 for the R5−, and M2+, respectively. The latter coupling is observed as a key signature of the strong spin–lattice interaction.

Design of zero thermal expansion and high thermal conductivity in machinable xLFCS/Cu metal matrix composites

Materials having good comprehensive performances, such as zero thermal expansion (ZTE), high thermal conductivity, and machinability are in great demand for electronics, precision instruments, and aerospace applications. However, the challenge is that very few materials meet such requirements. In this study, a multicomponent reinforcement with negative thermal expansion (NTE) is designed for metal matrix composites (MMCs) to achieve wide-temperature-range ZTE, high thermal conductivity, and certain machinability. Taking advantage of the giant NTE in La(Fe,Co,Si)13 system, its originally narrow NTE temperature range can be broadened in the multicomponent material (xLFCS). When xLFCS is used as a reinforcement in MMCs and combined with copper, the thermal expansion coefficient of the xLFCS/39.7 vol%Cu composite can be adjusted to nearly zero (−0.2 × 10−6 K−1) over a wide temperature range of 200–320 K. The thermal conductivity of this composite is 44.1 W m−1 K−1, which is about seven times that of LFCS itself. In addition, compared with other ZTE metal-based materials, the present composite has good machinability. This work reports a metal matrix composite with high thermophysical properties and proposes an easy-to-operate method for broadening the temperature range of NTE or ZTE.

Sn2p2s6: An All-Inorganic Lead-Free Reversible Thermochromic Ferroelectric with Giant Negative Thermal Expansion and High Near-Infrared Reflectance

Sn2p2s6: An All-Inorganic Lead-Free Reversible Thermochromic Ferroelectric with Giant Negative Thermal Expansion and High Near-Infrared Reflectance

Evidence of negative thermal expansion in supercooled tantala

A density anomaly, i.e. a temperature region with negative thermal expansion (NTE) bounded by a density maximum and a density minimum at lower temperatures, is revealed and characterised in tantala for the first time by Molecular Dynamics simulations. The NTE region is evidenced in the metastable supercooled liquid and rather close to the glass transition. Since NTE is suppressed by poor structural equilibration, highlighting these phenomena is highly challenging due to the need for fulfilling competing constraints of slow cooling and avoidance of the crystallization. We find that the density anomaly is signalled by a decrease of the partial coordination numbers nTa,Ta and nO,O when lowering the temperature. The NTE magnitude is comparable to the ones of both stable water and solid-state materials with giant NTE.

Giant negative thermal expansion of polycrystalline Ti2O3 induced by microstructural effects

Discovery of giant negative thermal expansion (NTE) of Ti2O3 is reported herein. Ti2O3 undergoes a phase transition from a low-temperature (low-T) insulating state to a high-T metallic state gradually at temperatures of 400–600 K, accompanied by highly anisotropic thermal deformation of the crystallographic unit cell. This anisotropic deformation induces large bulk NTE in the sintered body, although the unit-cell volume estimated from diffraction experiments shows positive thermal expansion in this T range. Results of this study also demonstrate that partial replacement of Ti with Nb increases the total volume change related to bulk NTE and show that it lowers the operating-T range of NTE to include room temperature. The development of NTE materials particularly addressing such microstructural effects is effective and promising.

Evidence for a coupled magnetic-crystallographic transition in La0.9Ce0.1Fe12B6

Competition between antiferromagnetic (AFM), paramagnetic (PM), and ferromagnetic (FM) states in ${\mathrm{La}}_{0.9}{\mathrm{Ce}}_{0.1}{\mathrm{Fe}}_{12}{\mathrm{B}}_{6}$ compound is investigated by means of temperature- and magnetic field-dependent x-ray diffraction, magnetization, linear thermal expansion, and magnetostriction experiments. It is shown that both AFM and PM phases get converted into the FM phase via a first-order metamagnetic transition, which is accompanied by a huge forced-volume magnetostriction $\mathrm{\ensuremath{\Delta}}V/V(25\phantom{\rule{0.16em}{0ex}}\mathrm{K},\phantom{\rule{0.16em}{0ex}}6\phantom{\rule{0.16em}{0ex}}\mathrm{T})=1.15%$. X-ray powder diffraction reveals a magnetic field-induced crystallographic phase transition from a $R\overline{3}m$ rhombohedral (AFM, PM) to a $C2/m$ monoclinic (FM) structure. A peculiarly anisotropic lattice expansion as well as giant negative thermal expansion with a volumetric thermal expansion coefficient ${\ensuremath{\alpha}}_{V}=\ensuremath{-}193\ifmmode\times\else\texttimes\fi{}{10}^{--6}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{--1}$ are observed. These findings point to the significance of magnetoelastic effects in this metamagnet and illustrate the strength of the coupling between lattice and spin degrees of freedom in the ${\mathrm{La}}_{0.9}{\mathrm{Ce}}_{0.1}{\mathrm{Fe}}_{12}{\mathrm{B}}_{6}$ intermetallic compound.

Magnetic-field-induced structural phase transition and giant magnetoresistance in La0.85Ce0.15Fe12B6

Magnetoelastic coupling, structural, magnetic, electronic transport, and magnetotransport properties of ${\mathrm{La}}_{0.85}{\mathrm{Ce}}_{0.15}{\mathrm{Fe}}_{12}{\mathrm{B}}_{6}$ have been studied by a combination of macroscopic [magnetization, electrical resistivity, and magnetoresistance (MR)] and microscopic temperature- and magnetic-field-dependent x-ray powder diffraction measurements. The itinerant-electron system ${\mathrm{La}}_{0.85}{\mathrm{Ce}}_{0.15}{\mathrm{Fe}}_{12}{\mathrm{B}}_{6}$ exhibits an antiferromagnetic (AFM) ground state and multiple magnetic transitions, AFM-ferromagnetic (FM) and FM-paramagnetic (PM), triggered by changes in both temperature and magnetic fields. At low temperatures, the field-induced first-order AFM-FM metamagnetic phase transition is discontinuous, manifesting itself by extremely sharp steps in magnetization as well as in MR and is accompanied by large magnetic hysteresis. A remarkably large negative MR of \ensuremath{-}73% was discovered. In addition, the time evolution of the electrical resistivity displays a colossal spontaneous jump when both the applied magnetic field and temperature are constant. Diffraction data reveal a magnetic-field-induced structural phase transition associated with the AFM-FM and PM-FM transformations. The lattice distortion is driven by magnetoelastic coupling and converts the crystal structure from rhombohedral ($R\overline{3}m$) to monoclinic $(C2/m)$. The AFM and PM states are related to the rhombohedral structure, whereas the FM order develops in the monoclinic symmetry. A huge volume magnetostriction of \ensuremath{\sim}0.9% accompanies this symmetry-lowering lattice distortion. Meanwhile, a highly anisotropic thermal expansion involving giant negative thermal expansion with an average volumetric thermal expansion coefficient ${\ensuremath{\alpha}}_{V}=\ensuremath{-}195\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ was observed. The consistency seen in these different experimental data constitutes direct evidence of the strong correlations between charge, magnetic, and crystallographic degrees of freedom in this material.

Origin and Absence of Giant Negative Thermal Expansion in Reduced and Oxidized Ca2RuO4

Negative thermal expansion (NTE) is an intriguing physical phenomenon. Layered Ca2RuO4 exhibits giant NTE over a wide temperature range from 200 to 400 K, which makes it attractive for fundamental research and industrial applications. However, a clear physical understanding is lacking for the appearance of NTE over such a wide temperature range and the oxygen-content-dependent switch from NTE to positive thermal expansion (PTE). Herein, we present insights into the average crystal structure, local structure, and electronic and orbital states of Ca2RuO4. Surprisingly, a previously overlooked monoclinic distortion is identified by electron diffraction and synchrotron X-ray diffraction (SXRD). X-ray absorption fine structure (XAFS) and synchrotron X-ray pair distribution function (PDF) analyses show large local distortions in monoclinic Ca2RuO4. Moreover, local stress on Ru cations is confirmed by the existence of over-bonding states, which relaxes along with NTE. Theoretical calculations indicate that dxy orbital ordering and disordering in the monoclinic structure are the origins of NTE. Moreover, interstitial oxygen plays a critical role in stabilizing elongated RuO6 and locally breaks the dxy orbital ordering, facilitating the occurrence of PTE. This work elucidates the electronic and orbital states in NTE materials with defective lattices and provides a different route to designing unconventional NTE materials.

Giant negative thermal expansion in a textured MnCoSi alloy

In the present work, textured stoichiometric MnCoSi alloys were fabricated by slow-cooling thermal treatment. Microstructure and crystallographic characterization revealed that the textured MnCoSi alloy consists of three different oriented orthorhombic TiNiSi-type martensite variants with their aOrth-axis lying in the cross-section of the rod-like MnCoSi alloy. A giant reversible linear negative thermal expansion (NTE) as much as 9350 ppm was achieved along the aOrth-axis of the textured MnCoSi alloy at a wide operation temperature span from 50 K to 400 K, owing to the antiferromagnetic arrangement. The linear NTE value slightly decreases from 9350 ppm to 9200 ppm with increasing the external magnetic field up to 2 T, which indicates that the present MnCoSi alloy demonstrates a stable NTE effect under external magnetic field. Moreover, during the martensitic transformation, the linear NTE along the aOrth-axis of the textured MnCoSi alloy could be up to 70,000 ppm at about 1200 K.

Fabrication of Metal Matrix Composite Containing Manganese Nitride Showing Giant Negative Thermal Expansion by Compressive Torsion Processing

Fabrication of Metal Matrix Composite Containing Manganese Nitride Showing Giant Negative Thermal Expansion by Compressive Torsion Processing

Extraordinary negative thermal expansion of two-dimensional nitrides: A comparative ab initio study of quasiharmonic approximation and molecular dynamics simulations

Thermal expansion behavior of two-dimensional (2D) nitrides and graphene were studied by ab initio molecular dynamics (MD) simulations as well as quasiharmonic approximation (QHA). Anharmonicity of the acoustic phonon modes are related to the unusual negative thermal expansion (NTE) behavior of the nitrides. Our results also hint that direct ab initio MD simulations are a more elaborate method to investigate thermal expansion behavior of 2D materials than the QHA. Nevertheless, giant NTE coefficients are found for $h$-GaN and $h$-AlN within the covered temperature range 100--600 K regardless of the chosen computational method. This unusual NTE of 2D nitrides is reasoned with the out-of-plane oscillations related to the rippling behavior of the monolayers.

2D Metamaterials: Designing Mechanical Metamaterials with Kirigami‐Inspired, Hierarchical Constructions for Giant Positive and Negative Thermal Expansion (Adv. Mater. 3/2021)

2D Metamaterials: Designing Mechanical Metamaterials with Kirigami‐Inspired, Hierarchical Constructions for Giant Positive and Negative Thermal Expansion (Adv. Mater. 3/2021)

Designing Mechanical Metamaterials with Kirigami-Inspired, Hierarchical Constructions for Giant Positive and Negative Thermal Expansion.

Advanced mechanical metamaterials with unusual thermal expansion properties represent an area of growing interest, due to their promising potential for use in a broad range of areas. In spite of previous work on metamaterials with large or ultralow coefficient of thermal expansion (CTE), achieving a broad range of CTE values with access to large thermally induced dimensional changes in structures with high filling ratios remains a key challenge. Here, design concepts and fabrication strategies for a kirigami-inspired class of 2D hierarchical metamaterials that can effectively convert the thermal mismatch between two closely packed constituent materials into giant levels of biaxial/uniaxial thermal expansion/shrinkage are presented. At large filling ratios (>50%), these systems offer not only unprecedented negative and positive biaxial CTE (i.e., -5950 and 10 710ppm K-1 ), but also large biaxial thermal expansion properties (e.g., >21% for 20 K temperature increase). Theoretical modeling of thermal deformations provides a clear understanding of the microstructure-property relationships and serves as a basis for design choices for desired CTE values. An Ashby plot of the CTE versus density serves as a quantitative comparison of the hierarchical metamaterials presented here to previously reported systems, indicating the capability for substantially enlarging the accessible range of CTE.

Enhanced negative thermal expansion of boron-doped Fe43Mn28Ga28.97B0.03 alloy

Enhanced negative thermal expansion (NTE) properties are achieved by introducing a little amount of boron in the Fe43Mn28Ga28.97B0.03 alloy. As a result, this alloy shows a giant NTE coefficient of αl = −79.7 × 10−6 K−1 in a wide temperature range from 277 K to 136 K. Compared to the NTE characteristics in Fe43Mn28Ga29, the NTE operation temperature window has expanded by 74% with the corresponding coefficient of thermal expansion increased by 57% within the NTE temperature window for the boron-doped Fe43Mn28Ga28.97B0.03. In-situ synchrotron high-energy X-ray diffraction results suggest that by boron substitution, the large unit cell volume change across martensitic transformation and the wide phase transition temperature interval are responsible for the pronounced NTE behavior in Fe43Mn28Ga28.97B0.03. Moreover, for the Fe43Mn28Ga28.97B0.03 NTE material, the compressive strength and strain are significantly improved compared with that of Fe43Mn28Ga29. The present study indicates that Fe43Mn28Ga28.97B0.03 with enhanced NTE across martensitic transformation may be used for practical application as thermal-expansion compensators.