Argentophilicity induced anomalous thermal expansion behavior in a 2D silver squarate

A 2D bilayer coordination polymer has been found to exhibit colossal interlayer PTE and in-plane NTE owing to argentophilic interactions.

Achieving High Performances of Ultra-Low Thermal Expansion and High Thermal Conductivity in 0.5PbTiO3-0.5(Bi0.9La0.1)FeO3@Cu Core-Shell Composite

Achieving high performances of ultra-low thermal expansion (ULTE) and high thermal conductivity remains challenging, due to the strong phonon/electron-lattice coupling in ULTE materials. In this study, the challenge has been solved via the construction of the core-shell structure in 0.5PbTiO₃-0.5(Bi_0.9La_0.1)FeO₃@Cu composites by the electroless plating, which can simultaneously combine the advantages of the negative thermal expansion material of 0.5PbTiO₃-0.5(Bi_0.9La_0.1)FeO₃ in controlling thermal expansion, and copper metal in high thermal conductivity. By changing the volume fraction of copper, the coefficient of thermal expansion of composites can be adjusted continuously from positive to negative. In particular, a ULTE (ΔT = 400 K) has been achieved in the composite of 35 vol % Cu. Intriguingly, a 3D thermal conductive network copper structure is formed for thermal conducting, which can double the thermal conductivity of the 35 vol % Cu composite from the methods by the traditional mixing (32 W·m^-1·K^-1) up to the core-shell structure (60 W·m^-1·K^-1). The present work not only provides a composite material with excellent comprehensive properties but also proposes a general chemical method to resolve the problem of low thermal conductivity in most ULTE materials.

Magnetic structure and uniaxial negative thermal expansion in antiferromagnetic CrSb

Negative thermal expansion (NTE) has been found in a growing number of ferromagnetic and ferrimagnetic materials; however, it remains a challenge to discover antiferromagnetic (AFM) NTE materials. Here, we report the uniaxial NTE properties of AFM intermetallic CrSb systematically, and reveal its uniaxial NTE mechanism for the first time. The present AFM intermetallic CrSb shows uniaxial NTE at high temperature and over a broad temperature window (αa = -6.55 × 10-6 K-1, 360-600 K). The direct experimental evidence of neutron powder diffraction reveals that NTE is induced by the AFM ordering of the Cr atom. The present study demonstrates that due to the transition from an AFM ordered structure to a paramagnetic disordered configuration, the negative contribution to the thermal expansion from the magnetovolume effect overwhelms the positive contribution from anharmonic phonon vibration. This study is of interest to find antiferromagnetic NTE materials.

Negative-Pressure-Induced Large Polarization in Nanosized PbTiO3

Ferroelectric materials usually undergo decay with particle size decreasing into the nanoscale. At the critical value, the crystal structure undergoes a transition from the ferroelectric to paraelectric phase and the ferroelectricity vanishes. It is a big issue to sufficiently maintain strong ferroelectricity at the nanoscale. Herein, it is reported that synthesized 0D freestanding PbTiO₃ nanoparticles (NPs) present negative pressure along the c axis (Δc/c_bulk × 100% = -2.406), inducing large spontaneous polarization P_S (71.2 µC cm^-2 in 12 nm). Further local structural studies by atomic pair distribution functions and extended X-ray absorption fine structure indicate the structural evolution of nanosized PbTiO₃ . High-angle annular dark-field STEM images reveal the existence of preponderant PbO-terminations on the surface of the PbTiO₃ NPs. Ab initio calculation reveals the enhanced hybridization between Pb and O ions, which gives rise to the negative pressure and tensile stress to stabilize the high tetragonality and large polarization. The present work demonstrates an untraditional route to enhance the ferroelectricity and related properties in functional nanostructured materials, being of significance to nanodevices.

Bone microstructure of adult patients with non-surgical hypoparathyroidism assessed by high-resolution peripheral quantitative computed tomography

There is limited evidence regarding changes in bone microstructure in patients with hypoparathyroidism. In the current study, we used a non-invasive technique to assess bone structure in hypoparathyroidism patients and discovered site-specific changes which were mainly influenced by age and menstrual status. Such changes were more prominent in the trabeculae as well as in non-surgical as opposed to post-surgical patients.

INTRODUCTION

Hypoparathyroidism (hypoPT) is a rare disease characterized by the lack of parathyroid hormone. There is limited evidence regarding changes in bone microstructure in patients with non-surgical hypoPT. We investigated bone microstructure of patients with non-surgical hypoPT using a non-invasive technique.

METHODS

Patients with hypoPT were assessed using high-resolution peripheral quantitative computed tomography (HR-pQCT) and compared to age- and sex-matched healthy controls randomly selected from a pre-existing HR-pQCT database in a cross-sectional study. Preliminary comparison between patients with different etiologies of hypoPT was performed. Associations between bone microstructure and clinical parameters were investigated using correlation and regression analyses.

RESULTS

A total of 94 patients with non-surgical hypoPT were recruited. Patients displayed an increase in trabecular volumetric BMD of the tibia (170.57 ± 34.32 vs. 156.48 ± 40.55 mg HA/cm³, p = 0.011) and increase in trabecular number of both the radius (1.48 ± 0.29 vs. 1.36 ± 0.22 mm^-1, p = 0.003) and tibia (1.42 ± 0.23 vs. 1.24 ± 0.22 mm^-1, p < 0.001) compared to healthy controls. Trabecular number was higher for non-surgical hypoPT compared to post-surgical hypoPT (1.37 ± 0.25 and 1.17 ± 0.13 mm^-1, p = 0.022). Trends towards increase in cortical volumetric BMD were only present for post-menopausal female and male patients above the age of 50. For female patients, cortical volumetric BMD and area increased with age and decreased after menopause. For males, age had little influence on bone microstructure, but cortical porosity increased with longer treatment durations.

CONCLUSIONS

Results from this pilot study suggested that both cortical and trabecular bone were altered in this group of patients with hypoPT. Etiology for hypoPT might influence bone microstructure, mainly on trabeculae. Age, menstrual status, and treatment duration were likely to influence bone microstructure in hypoPT.

Relationship among the Crystal Structure, Texture, and Macroscopic Properties of Tetragonal (Pb,La)(Zr,Ti)O3 Ferroelectrics Investigated by In Situ High-Energy Synchrotron Diffraction

In situ diffraction investigations have played an important role in experimentally revealing the mechanism of piezoelectric and ferroelectric properties. In this study, a pure tetragonal ferroelectric ceramic of La-doped PbZr_0.5Ti_0.5O₃ (LaPZT50) was investigated to eliminate the complex influence of phase coexistence. The electric field evolutions of the crystal structure, domain switching, and lattice deformation of the tetragonal phase have been revealed by in situ high-energy synchrotron X-ray diffraction. We found that the crystal structure of LaPZT50 is quite stable, showing a negligible change in the Pb-O bond length, unit cell volume, and spontaneous polarization upon application of an in situ external electric field. Importantly, the maximum macroscopic polarization of tetragonal LaPZT50 is defined by the 111-oriented grains. As determined by the intensity difference, the switching of non-180° domains plays a more significant role in contributing to the macroscopic strain than lattice deformation. These results further imply that the phase coexistence around the morphotropic phase boundary facilitates domain wall motion in the tetragonal phase and improves the ferroelectric and piezoelectric properties.

Negative and zero thermal expansion in α-(Cu2-xZnx)V2O7 solid solutions

Negative or zero thermal expansion (NTE or ZTE) of materials is intriguing for controllable thermal expansion. We report a series of orthorhombic α-Cu2-xZnxV2O7 (x = 0, 0.1, 0.2), in which the volumetric coefficients of thermal expansion are successfully tuned from -10.19 × 10-6 K-1 to -1.58 × 10-6 K-1 in the temperature range of 100-475 K by increasing the content of Zn2+. It has been revealed that the transverse vibrations of oxygen bonded with vanadium are dominant in the contraction of the bc plane, leading to the overall volume NTE in α-Cu2V2O7. The introduction of Zn2+ densifies the crystal structure, which is presumed to suppress the space of transverse vibrations and results in the ZTE in α-Cu1.8Zn0.2V2O7. This work presents an effective method to realize ZTE in anisotropic framework systems.

Classification and treatment strategies for condylar fractures in children

In this study, we aimed to describe a classification method (position and displacement (PD) classification) and the corresponding treatment strategies for condylar fractures in children, based on the anatomical position and displacement of the fractures. Moreover, we aimed to explore the effect of the treatment strategies for condylar fractures in children. Such fractures were classified into the following three types by PD classification: condylar head fracture (type A), mildly displaced condylar neck and base fracture (type B), and severely displaced condylar neck and base fracture (type C). According to this classification, we proposed the corresponding treatment strategy of closed treatment for types A and B fractures and open treatment for type C fractures. Eighty-four patients who had 123 condylar fractures (type A = 97, type B = 16, type C = 10) were included in this study. Type A fractures showed the restoration of normal function with favourable remodelling in the condyles. Types B and C fractures had good function and symmetry in the condylar angle and height of the condylar neck. The PD classification and corresponding treatment strategies may serve as a better option for the clinical treatment of condylar fractures in children.

Role of "Dumbbell" Pairs of Fe in Spin Alignments and Negative Thermal Expansion of Lu2Fe17-Based Intermetallic Compounds

Knowledge of negative thermal expansion (NTE) is an interesting issue in the field of materials science and engineering. It has been proposed that the unique dumbbell pairs of Fe (dumbbells) are highly entangled in the NTE behaviors of R₂Fe₁₇ (R = rare earth) compounds but still remain controversial. Here, a facile method is employed to explore the role of dumbbells in spin alignments and NTE by the nonstoichiometric design of Lu_2-xFe₁₇ compounds. The powder synchrotron X-ray diffraction, magnetometry, and neutron powder diffraction investigations indicate that a decrease of the Lu content can enhance the dumbbell concentration and motivate an incommensurate magnetic structure simultaneously. However, increasing the dumbbell concentration makes little difference in the amplitude of the ordered magnetic moments of Fe sublattices, which reveals an equivalent NTE behavior for Lu_2-xFe₁₇ compounds. This work gives insight into the role that dumbbells played in spin alignments and NTE for Lu₂Fe₁₇-based compounds, correcting the previously proposed conjecture and probably conducive to adjusting the related magnetic performances of R₂Fe₁₇ compounds in the future.

Large nonlinear optical effect in tungsten bronze structures via Li/Na cross-substitutions

By a simple cross-substitution of A-site Li/Na in tetragonal tungsten bronze (TTB) structures, we successfully synthesized a new niobate compound, Pb2.15(Li0.25Na0.75)0.7Nb5O15, with a superstructure. This compound exhibits a strong second harmonic generation (SHG) up to ∼47 × KDP. The large SHG response is related to strengthened local distortion, manifesting cross-substitution as a possibly general route to improve the NLO effect in stiff and low symmetric structures.

Structural Distortion and Dielectric Permittivities of KCoO2-Type Layered Nitrides Ca1-xSrxTiN2

Among the KCoO₂-type phases, the orthorhombic layered nitride CaTiN₂ is a newly reported high dielectric permittivity material (ε_r ∼ 1300-2500 within 10⁴-10⁶ Hz from 80 to 450 K) while the tetragonal SrTiN₂ is reported to display an unintentional metallic conduction property. In this work, a Ca_1-xSr_xTiN₂ solid solution was synthesized, in which the insulating SrTiN₂ end member and some Sr-doped CaTiN₂ samples were successfully obtained, and therefore, the dielectric properties of the Ca_1-xSr_xTiN₂ solid solution were investigated. The Sr substitution for Ca drove an orthorhombic-to-tetragonal phase transformation in Ca_1-xSr_xTiN₂, which reduced the dielectric permittivity significantly. The tetragonal SrTiN₂ displays a much lower dielectric permittivity (ε_r ∼ 20-70 in 10⁵-10⁶ Hz and 10-300 K) than that of CaTiN₂. The comparison on the dielectric permittivities and structures of CaTiN₂ and SrTiN₂ indicates that the structural distortion arising from the splitting of N planes between Ti layers within the TiN₂ pyramidal layers could be a plausible structural origin of the high bulk dielectric permittivity of CaTiN₂.

Large-scale Two-dimensional MoSx Catalyst Prepared under Mild Conditions for Enhancing Electrocatalytic Hydrogen Evolution Reaction

As an electrocatalyst with abundant resources and great potential, molybdenum disulfide is regarded as one of the most likely alternatives to expensive noble-metals catalysts. However, it is still a challenge to achieve large scale production of few-layer MoS₂ with enhancing activity of electrocatalytic hydrogen reaction at ambient conditions. Herein, we developed a simple environmentally friendly two-step method, which included intercalation reaction and a subsequent electrochemical reduction reaction for mass preparation of defect-rich desulfurized MoS_x (D-MoS_x ) nanosheets with plentiful sulfur vacancies. The ratio of sulfur-molybdenum atoms can be adjusted from 2 : 1 to 1.4 : 1 by regulating the desulfurization voltage. It was found that the HER catalytic activity of the D-MoS_x was enhanced compared with that of pristine MoS₂ (P-MoS₂ ), the current density of D-MoS_x (desulfurization at -1.0 V) at -0.3 V versus RHE was about 169% of the P-MoS₂ , and the Tafel slope decreased to 136 mV dec^-1 . This method can be widely applied to large-scale preparation of other two-dimensional materials.

Urchin-Like Fe3 Se4 Hierarchitectures: A Novel Pseudocapacitive Sodium-Ion Storage Anode with Prominent Rate and Cycling Properties

Transition metal chalcogenides have received great attention as promising anode candidates for sodium-ion batteries (SIBs). However, the undesirable cyclic life and inferior rate capability still restrict their practical applications. The design of micro-nano hierarchitectures is considered as a possible strategy to facilitate the electrochemical reaction kinetics and strengthen the electrode structure stability upon repeated Na⁺ insertion/extraction. Herein, urchin-like Fe₃ Se₄ hierarchitectures are successfully prepared and developed as a novel anode material for SIBs. Impressively, the as-prepared urchin-like Fe₃ Se₄ can present an ultrahigh rate capacity of 200.2 mAh g^-1 at 30 A g^-1 and a prominent capacity retention of 99.9% over 1000 cycles at 1 A g^-1 , meanwhile, a respectable initial coulombic efficiency of ≈100% is achieved. Through the conjunct study of in situ X-ray diffraction, ex situ X-ray absorption near-edge structure spectroscopy, as well as cyclic voltammetry curves, it is intriguing to reveal that the phase transformation from monoclinic to amorphous structure accompanied by the pseudocapacitive Na⁺ storage behavior accounts for the superior electrochemical performance. When paired with the Na₃ V₂ (PO₄ )₃ cathode materials, the assembled full cell enables high energy density and decent cyclic stability, demonstrating potential practical feasibility of the present urchin-like Fe₃ Se₄ anode.

Discovering Large Isotropic Negative Thermal Expansion in Framework Compound AgB(CN)4 via the Concept of Average Atomic Volume

Exploring isotropic negative thermal expansion (NTE) compounds is interesting, but remains challenging. Here, a new concept of "average atomic volume" is proposed to find new NTE open-framework materials. According to this guidance, two NTE compounds, AgB(CN)₄ and CuB(CN)₄, have been discovered, of which AgB(CN)₄ exhibits a large NTE over a wide temperature range (α_v = -40 × 10^-6 K^-1, 100-600 K). The analysis by extended X-ray absorption fine structure spectroscopy and first-principles calculation indicate that (i) the NTE driving force comes from the transverse vibrations of bridge chain atoms of C and N, corresponding to the low-frequency phonon modes; and (ii) the same transverse vibration direction of C and N atoms is a key factor for the occurrence of strong NTE in AgB(CN)₄. The present concept of "average atomic volume" can be a simple parameter to explore new NTE compounds especially in those open-framework materials.

Manipulating Spin Alignments of (Y,Lu)1.7Fe17 Intermetallic Compounds via Unusual Thermal Pressure

External pressure has been successfully employed to achieve desirable spin alignments in the field of materials science but is seriously restricted by the difficulty of reaching high pressure with conventional methods. The search for simple and effective ways to apply pressure on the lattice is challenging but intriguing. Here we report a new strategy to manipulate the spin alignments of (Y,Lu)_1.7Fe₁₇ intermetallic compounds through unusual thermal pressure. The spin alignments of Fe initially lie parallel inside the basal plane and then turn spirally between adjacent layers with a zone axis along the c direction under higher Lu concentration. The synchrotron and neutron powder diffraction investigations clearly reveal that the direction of spin alignments is highly correlated to large lattice contraction induced by negative thermal expansion (NTE), an unusual thermal pressure, along the c direction. The critical lattice parameter c to form spiral spin alignments is determined unambiguously. This work presents a feasible way to adjust spin alignments through NTE, which might be conducive to the future design of particular spin alignments instead of physical pressure for functional magnetic materials.

Transforming Thermal Expansion from Positive to Negative: The Case of Cubic Magnetic Compounds of (Zr,Nb)Fe2

Negative thermal expansion (NTE) is an intriguing property for not only fundamental studies but also technological applications. However, few NTE materials are available compared with the huge amount of positive thermal expansion materials. The discovery of new NTE materials remains challenging. Here we report a chemical modification strategy to transform thermal expansion from positive to negative in cubic magnetic compounds of (Zr,Nb)Fe₂ by tuning the magnetic exchange interaction. Furthermore, an isotropic zero thermal expansion can be established in Zr_0.8Nb_0.2Fe₂ (α_l = 1.4 × 10^-6 K^-1, 3-470 K) over a broad temperature range that is even wider than that of the prototype Invar alloy of Fe_0.64Ni_0.36. The NTE of (Zr,Nb)Fe₂ is originated from the weakened magnetic exchange interaction and the increased d electrons of Fe by the Nb chemical substitution, so that the magnetovolume effect overwhelms the contribution of anharmonic lattice vibration.

A Novel NASICON-Type Na4 MnCr(PO4 )3 Demonstrating the Energy Density Record of Phosphate Cathodes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have attracted incremental attention as a promising candidate for grid-scale energy-storage applications. To meet practical requirements, searching for new cathode materials with high energy density is of great importance. Herein, a novel Na superionic conductor (NASICON)-type Na₄ MnCr(PO₄ )₃ is developed as a high-energy cathode for SIBs. The Na₄ MnCr(PO₄ )₃ nanoparticles homogeneously embedded in a carbon matrix can present an extraordinary reversible capacity of 160.5 mA h g^-1 with three-electron reaction at ≈3.53 V during the Na⁺ extraction/insertion process, realizing an unprecedentedly high energy density of 566.5 Wh kg^-1 in the phosphate cathodes for SIBs. It is intriguing to reveal the underlying mechanism of the unique Mn²⁺ /Mn³⁺ , Mn³⁺ /Mn⁴⁺ , and Cr³⁺ /Cr⁴⁺ redox couples via X-ray absorption near-edge structure spectroscopy. The whole electrochemical reaction undergoes highly reversible single-phase and biphasic transitions with a moderate volume change of 7.7% through in situ X-ray diffraction and ex situ high-energy synchrotron X-ray diffraction. Combining density functional theory (DFT) calculations with the galvanostatic intermittent titration technique, the superior performance is ascribed to the low ionic-migration energy barrier and desirable Na-ion diffusion kinetics. The present work can offer a new insight into the design of multielectron-reaction cathode materials for SIBs.

Controllable Ferromagnetism in Super-tetragonal PbTiO3 through Strain Engineering

The coupling strain in nanoscale systems can achieve control of the physical properties in functional materials, such as ferromagnets, ferroelectrics, and superconductors. Here, we directly demonstrate the atomic-scale structure of super-tetragonal PbTiO₃ nanocomposite epitaxial thin films, including the extraordinary coupling of strain transition and the existence of the oxygen vacancies. Large strain gradients, both longitudinal and transverse (∼3 × 10⁷ m^-1), have been observed. The original non-magnetic ferroelectric composites notably evoke ferromagnetic properties, derived from the combination of Ti³⁺ and oxygen vacancies. The saturation ferromagnetic moment can be controlled by the strain of both the interphase and substrate, optimized to a high value of ∼55 emu/cc in 10-nm thick nanocomposite epitaxial thin films on the LaAlO₃ substrate. Strain engineering provides a route to explore multiferroic systems in conventional non-magnetic ferroelectric oxides and to create functional data storage devices from both ferroelectrics and ferromagnetics.

Predicting the intervention threshold for initiating osteoporosis treatment among postmenopausal women in China: a cost-effectiveness analysis based on real-world data

This study built a micro-simulation Markov model to determine the treatment threshold of osteoporosis in postmenopausal women in Mainland China. Treatment with zoledronate is cost-effective when FRAX-based (Fracture risk assessment tool) fracture probability is over 7%.

INTRODUCTION

The purpose of this study is to estimate FRAX-based fracture probabilities in Mainland China using real-world data, at which intervention could be cost-effective.

METHODS

We developed a micro-simulation Markov model to capture osteoporosis states and relevant morbidities including hip fracture, vertebral fracture, and wrist fracture. Baseline characteristics including incidences of osteoporosis and distribution of risk factors were derived from the Peking Vertebral Fracture study, the largest prospective cohort study of postmenopausal women in Mainland China. We projected incidences of fractures and deaths by age groups under two treatment scenarios: 1) no treatment, and 2) zoledronate. We also projected total quality-adjusted life-years (QALY) and total costs including fracture management and osteoporosis drugs for cost-effectiveness analysis. Cost-effective intervention thresholds were calculated based on the Chinese FRAX model.

RESULTS

Treatment with zoledronate was cost-effective when the 10-year probability of major osteoporotic fracture based on FRAX was above 7%. The FRAX threshold increased by age from 51 to 65 years old, and decreased in elder age groups, ranging from 4% to 9%.

CONCLUSIONS

Using real-world data, our model indicated that widespread use of zoledronate was of both clinical and economic benefit among Chinese postmenopausal women. Using a FRAX-based intervention threshold of 7% with zoledronate should permit cost-effective access to therapy to patients and contribute to reducing the disease burden of osteoporosis in Mainland China.