MICROPOROUS AND MESOPOROUS MATERIALS
·
2015
·
IF 3.453
Shengxue Wang,Wei Li,Song Wang,Jinming Jiang,Zhaohui Chen
Hierarchical porous lanthanum zirconate (La 2 Zr 2 O 7 , LZO) monoliths have attracted numerous attentions as adsorption, catalysis, especially in high-temperature and high water-vapor-containing environments. Herein, La 2 Zr 2 O 7 monoliths with hierarchially distributed pores have been synthesized via a spontaneous route based on a non-alkoxide sol–gel process accompanied by phase separation. Nitrates of Zr(IV) and La(III) were used as precursors, propylene oxide and formamide were used as gelation inducers, and polyethylene glycol was used as phase separation inducer. The mechanisms of Zr(IV)/La(III) binary gelation process and competitive reaction between gelation and phase separation have been discussed. Zr(IV)/La(III) binary gels exist in the form of Zr(IV)-rich gel networks coupled with La(III)-rich discrete entities. The size of the pores can be controlled by adjusting the amount of gelation and separation inducers. The surface area of the as-prepared La 2 Zr 2 O 7 monoliths is 89 m 2 /g. La 2 Zr 2 O 7 monoliths are amorphous and heating in air at more than 600 °C leads to the formation of pyrochlore structure La 2 Zr 2 O 7 . With further increase in temperature, the crystalline degree of LZO monoliths increased. After heat treatment, the macroporous skeleton can be well retained. However, the macropores became slightly smaller and the solid skeleton became fragile. Sintering of the continuous skeleton occurred after heat treatment.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
Journal of Materials Chemistry A
·
2023
·Vol. 11
·期 24
·12735-12745
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IF 11.9
Nana Xu,Xiaoshan Zhang,Haiyan Liu,Hui Xu,Shuang Wu,Bing Wang,Yingde Wang
Oxide ceramic fibers with softness and toughness are key materials in emerging fields like wearable devices and membrane technologies. However, the brittle failure of oxide ceramic fibers after thermal cycling leads to the loss of membrane architectures, which limits their long-term applications at high temperature. Here, we report a scalable approach of sol–gel electrospinning to synthesize a flexible and tough pyrochlore La1.85Al0.15Zr2O7 (L5AZO) nanofiber membrane (NFM) involving self-assembled 3D networks. The interactions between the nanoscale constituents lead to the assembled networks with high nodal connectivity and strong crosslinking between nanofibers, which may promote an enhancement of macroscopic mechanical properties by orders of magnitude. Ultrasonic dispersion and an amorphous secondary phase drive the formation of numerous L5AZO nuclei and soft grain boundaries, thus effectively refining grains and inhibiting crystallite growth. Indeed, the L5AZO NFM achieves both a high specific tensile modulus of ∼11.4 MPa cm3 g−1 and fracture toughness of ∼1032 J m−2, as well as high-temperature resistance above 1100 °C, which are advantageous for diverse structural applications. Furthermore, the simple processing technique of the NFM allows it to be fabricated into various functional devices, such as aerogels, thermal camouflage, and filtration membranes at high temperature. The mechanistic insights and manufacturability provided by this flexible and tough oxide NFM may create further opportunities for materials design and technological innovation.
研究领域:
材料科学
·
纳米技术
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2018
·
IF 3.057
Di Jiang,Yanfei Wang,Siqing Wang,Rongjun Liu,Jing Han
The yttrium heavily doped La 2 Zr 2 O 7 solid solutions coatings, with a Y to La molar ratio of 1:1, have been successfully prepared by air plasma spraying technique. The evolution of phase composition, phase structure and thermal conductivity of such coatings with annealing at 1300 °C has been investigated. The results show that, a single pyrochlore structure can be retained for coating after annealing up to 48 h, beyond which the fluorite phase begins to precipitate out. By comparing thermal conductivities to those undoped counterparts at a similar porosity level, we find a considerably flat thermal conductivity versus temperature (k-T) curve, suggesting the existence of a strong phonon scattering source, which is inferred as rattlers. In addition, after the segmentation of the fluorite phase, the thermal conductivity of corresponding coatings rises considerably, indicating that the fluorite phase has a higher thermal conductivity than that of pyrochlore phase. Moreover, while the as-sprayed coatings show a clear indication of radiative thermal conduction beyond 1000 °C, the thermal conductivity of annealed coatings do not show such an uprising trend after 1000 °C, suggesting that the radiative thermal conduction has been greatly suppressed. The reason is proposed as the formation of local dipoles due to local enrichment of certain elements influences the propagation of electromagnetic waves and thus suppresses the radiative thermal conduction.
研究领域:
材料科学
·
热力学
·
涂层技术
✓ 已验证
DOI
高影响因子
CHEMISTRY-A EUROPEAN JOURNAL
·
2020
·Vol. 26
·期 64
·14654-14664
·
IF 4.857
Yi Cao,Peiyuan Tang,Yue Han,Wenfeng Qiu
Graphical Flexible film : Flexible thin films of La 2 Y x Zr 2− x O 3 (LNF- x ) ( x= 0, 0.1, 0.3, 0.5) nanofibers are synthesized and characterized. The LNF-0.1//LNF-0.1 flexible device shows good electrochemical performance and is of great significance in the field of next-generation flexible energy-storage devices and applications in portable and wearable electronics. With the rapid development of wearable electronics devices, there is increasing demand for the development of new flexible energy storage devices with high security, and this has become a hot research topic. Although flexible supercapacitors are considered to be high-performance energy-storage equipment because of their fast charging/discharging ability, long cycle life, good reliability, wide operating temperature range, and so on, there are still many drawbacks that need to be overcome. Herein, the La 2 Zr 2 O 7 (LZO) thin film is synthesized as a new energy-storage material by using a facile electrospinning method and calcination at low temperature. In addition, the mechanism of producing the flexibility of this film is determined by TG, IR, and XRD analyses. As previous studies have suggested that the charge storage of the LZO film can be attributed to the mechanism of oxygen intercalation, the Y element is doped into the LZO film to increase the concentration of oxygen vacancies. The changes in structural and electrochemical properties of La 2 Y x Zr 2− x O 3 (0≤ x ≤0.5) nanofibers (LNF- x ) with increasing Y content are studied carefully to obtain the best doping sample. The LNF-0.1 sample shows the highest areal capacitance of 605.3 mF cm −2 at 2 mA cm −2 , so a symmetrical flexible device is fabricated with LNF-0.1 electrodes. This device has a high energy density (76.7 μW h cm −2 at 2 mW cm −2 ), good cycling stability, and excellent mechanical flexibility. This study thus provides a new research trend for portable and wearable electronics.
研究领域:
材料科学
·
能源技术
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2021
·
IF 5.302
Xiaoyi Chen,Xiaohui Li,Bo Gao,Wenwen Kong,Pengjun Zhao,Aimin Chang
A novel negative temperature coefficient material based on lanthanum zirconate ceramics was proposed for high-temperature applications. This material was synthesized through a solid-state reaction by sintering at 1923 K for 10 h in air. The X-ray diffraction and scanning electron microscopy results confirmed that La 2 Zr 2 O 7 ceramics exhibited a pyrochlore phase with a relative density of 98.2 %. The resistance–temperature characteristics of the material revealed that La 2 Zr 2 O 7 ceramics exhibited an NTC feature within the broad temperature range of 973–1773 K in addition to maintaining high thermal constant B , and resistivity to ensure good sensitivity at high temperatures. These properties, along with high ceiling temperature, unique oxygen insensitivity, and excellent ageing coefficient of <0.7 % at 1773 K, render La 2 Zr 2 O 7 ceramics a promising candidate as thermistor materials with high-temperature NTC.
研究领域:
材料科学
·
热电学
✓ 已验证
产品关联
DOI
高影响因子
International Journal of Applied Ceramic Technology
·
2024
·
IF 1.8
Pengju Chen,Peng Xiao,Tian Tian,Yang Li
Ytterbium silicate (Yb 2 Si 2 O 7 ) and lanthanum zirconate (La 2 Zr 2 O 7 ) ceramic powders were synthesized by the sol–gel method. A novel tri-layer La 2 Zr 2 O 7 /Yb 2 Si 2 O 7 /SiC environmental barrier coating was prepared on the surface of C/SiC composites to improve the service temperature of the coating (above the Si melting point, 1683 K). Results show that both Yb 2 Si 2 O 7 and La 2 Zr 2 O 7 ceramic powders had extremely high purity and were accompanied by a large number of nanoparticles. The tri-layer La 2 Zr 2 O 7 /Yb 2 Si 2 O 7 /SiC coating can efficiently prevent the oxidation failure of C/SiC composites in 1773 K air environment for more than 100 h with slight weight loss of 5.71 × 10 −3 g·cm −2 and the matching weight loss rate of 5.71 × 10 −5 g·cm −2 ·h −1 . No significant chemical reaction was observed between Yb 2 Si 2 O 7 middle and La 2 Zr 2 O 7 outer coatings during the oxidation process at 1773 K, indicating that the tri-layer La 2 Zr 2 O 7 /Yb 2 Si 2 O 7 /SiC coating had better oxidation stability in 1773 K air environment.
研究领域:
材料科学
·
涂层技术
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2023
·
IF 5.2
Ze Zhu,Xiaoqian Zhang,Ying Peng,Zhenfeng Guo,Yongshuai Xie,Benxue Liu,Guanghui Zhang,Luyi Zhu,Xinqiang Wang,Yonggang Jiang,Jian Feng
Rare earth zirconates have incomparable chemical thermophysical properties , yet the difficulty of preparation methods limit their application as fibrous material. In present work, a spinnable La 2 Zr 2 O 7 precursor, named as carboxylate lanthanum-zirconium (COLZ), was developed using carboxylic acids as structural and functional ligands. When COLZ is in its liquid state, it can be readily processed into desired shapes, allowing preparation of high aspect ratio precursor fibers with dense and bonding-strong internal structures. The spinnability was explained by the transformation from solid to liquid state under external forces, in which dynamic bridging of carboxylate and hydroxyl between nano-sized colloidal particles play a key role. Due to weakly acidic ligands, organics in COLZ can be easily removed, making direct heat treatment at the target temperature possible, which is beneficial for massive production. The strategy of developing spinnable precursor could also be applied to prepare other rare earth zirconate fibers or new multi-oxide fibers.
研究领域:
材料科学
·
化学工程
·
纳米技术
·
热管理
✓ 已验证
产品关联
DOI
高影响因子
Materialia
·
2024
·
IF 3
Guanlin Lyu,Shuoyan Zhai,Xiaohui Zhao,Wei Pan
The focus of this work is to investigate the strain-induced recrystallization behavior on the surface of La 2 Zr 2 O 7 ceramic through annealing. Unlike in metallic materials, the recrystallization phenomenon resulting from surface mechanical treatment in ceramics has not been extensively explored. In this study, we examine the strain-induced recrystallization in La 2 Zr 2 O 7 that has undergone surface deformation and subsequent annealing at different temperatures. It reveals the presence of recrystallized grains in the region of the surface that was deformed, following the annealing process. To better understand the driving force for the recrystallization behavior, we analyze the variation of stored deformation energy in La 2 Zr 2 O 7 using Raman spectroscopy. The study also highlights the microstructural evolution, revealing that shear bands, characterized by a high density of dislocations, serve as preferential sites for the nucleation of recrystallized grains. Finally, we discuss the mechanism of strain-induced recrystallization in ceramic materials.
研究领域:
材料科学
·
陶瓷
·
固体物理学
✓ 已验证
产品关联
DOI
高影响因子
Materials Science and Engineering B-Advanced Functional Solid-State Materials
·
2022
·
IF 3.407
Debao Liu,Chao Zhang,Yahui Xue
La 2 Zr 2 O 7 ceramic aerogels (LZO CAs) were successfully fabricated via sol-gel method followed by heat treatment process. The morphology, microstructure, and phase composition of the as-prepared samples were systematically studied using various technological means. The results indicated that the as-prepared LZO CAs present a typical three-dimentional (3-D) porous network with a single-phase pyrochlore crystal structure. In addition, the as-prepared LZO CAs presented high specific surface area of 594.85 m 2 /g, low thermal conductivity of 0.033 W/(m·K) at room temperature, and remarkable high temperature heat-insulating property. This work offers a novel strategy for the development of other rare-earth zirconates ceramic aerogels which can be used as high temperature insulations.
研究领域:
材料科学
·
陶瓷
·
热绝缘
✓ 已验证
DOI
高影响因子
SURFACE & COATINGS TECHNOLOGY
·
2013
·
IF 1.941
Kuo Jiang,Songbai Liu,Yu Luo,Qiang Li,Haiyang Wang
A polyglycol-assisted spreading deposition (PASD) method has been used to prepare the high-quality ZrO 2 thin film on single crystalline Si (111) substrate. The structure and composition of the films were studied by SEM, XRD and UV Raman techniques. Characterization results indicated that the ZrO 2 films were composed of nano-sized small particles and have a crack-free, dense and homogeneous microstructure. After a heat treatment of 10 min at 700–900 °C, the films showed a mixture of monoclinic and tetragonal ZrO 2 phases. And the grain sizes of monoclinic and tetragonal phases in the ZrO 2 films were 5–16 nm and 10–18 nm, respectively. In addition, the thin films of Y 2 O 3 -stabilized ZrO 2 (YSZ), La 2 Zr 2 O 7 , and the multilayer thin films of La 2 Zr 2 O 7 /YSZ were also fabricated by the PASD method.
研究领域:
材料科学
·
陶瓷
·
薄膜
·
表面科学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）