DYES AND PIGMENTS
·
2017
·
IF 3.473
Yunjian Wang,Wanying Wu,Xianliang Fu,Mingzhu Liu,Jing Cao,Congying Shao,Shifu Chen
This work explores the phase transition and its impact on photoluminescent properties of metastable scheelite-type, with and without Eu 3+ doped, CdWO 4 nanophosphors. A series of scheelite structure CdWO 4 :xEu 3+ (x = 0, 0.025, 0.05, 0.075, 0.10) samples were synthesized using a simple solvothermal method. The X-ray diffraction results indicate that the prepared samples were single phase in a tetragonal scheelite-type structure, and completely transformed into pure monoclinic wolframite structure after sintering at 450 °C for 2 h. It was revealed by Rietveld analysis that Eu 3+ doping induced a lattice contraction of both scheelite and wolframite CdWO 4 structures. The impact of Eu 3+ doping on the crystal structure and the band structure were further probed by FT-IR, Raman and UV–Vis spectroscopy. SEM images show that the morphology of the prepared samples also changed in the phase transition and the Eu 3+ doping processes. All samples showed a broad multi-color luminescence emission in the range from 400 to 640 nm under 280 nm excitation. The relative intensities of the blue-green emission originated from CdWO 4 matrix and the red emission ascribed to Eu 3+ can be regulated by both the crystal structure and Eu 3+ doping levels. The energy transfer process between WO 4 groups in scheelite structure CdWO 4 and WO 6 groups in wolframite structure CdWO 4 and Eu 3+ was discussed in detail based on the photoluminescent excitation and emission spectra. The synthetic approach reported here allows the control over CdWO 4 polymorphs and this kind of luminescent material has wide applications in white-LED, chemosensors and bioimaging .
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
NANOTECHNOLOGY
·
2024
·Vol. 35
·期 15
·155401
·
IF 2.9
Hongjing Wang,Tongqing Zhou,Shan Xu,Kai Deng,Hongjie Yu,You Xu,Xiaonian Li,Ziqiang Wang,Liang Wang
The development of effective and stable cathode electrocatalysts is highly desired for fuel cells. Controlling the composition and morphology of Pd-based materials can provide a great opportunity to improve their oxygen reduction reaction (ORR) performance. Here, we report the synthesis of hexagonal close-packed (hcp) Pd2B nanosheet assemblies (Pd2B NAs) via the boronation reaction between as-synthesized Pd NAs and N,N-dimethylformamide. The hcp Pd2B NAs with uniform pore distribution can provide sufficient active sites for ORRs. The insertion of B atoms can induce the phase transition from face-centered cubic structure to hcp structure, as the most thermodynamically stable phase in the Pd-B alloy, which is beneficial for enhancing the ORR stability and toxicity resistance. Therefore, the hcp Pd2B NAs exhibit superior mass activity, specific activity and excellent stability for ORR. The present strategy of boron-intercalation-triggered crystalline transition of Pd-based nanomaterials is valuable for the design of metal–nonmetal catalysts with enhanced performance.
研究领域:
材料科学
·
电化学
·
催化科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CERAMICS INTERNATIONAL
·
2020
·
IF 3.83
Jianbo Xu,Xinchao Qiu,Bowen Zhang,Gangfu Zhong,Maokang Shen,Xiangli Liu,Jun Ou-Yang,Yue Zhang,Benpeng Zhu,Xiaofei Yang,Shi Chen
Hafnium oxide (HfO 2 ) fibers can be widely used in ultra-high temperature ceramics (UHTCs) as reinforced material in order to achieve better antioxidant performance and less cracks and flaking on surface of UHTCs in field of ultra-high temperature thermal protectors. Calcination temperature is one of essential parameters for forming HfO 2 fiber. In this work, one-dimensional (HfO 2 ) fibers were prepared through the electrospinning method and further post-calcination treatment. During the calcination treatment, the monoclinic-HfO2 (m-HfO 2 ) was formed from as-spun HfO 2 fibers at 432 °C, and only a small amount of m-HfO 2 was converted into the tetragonal HfO 2 at 1013 °C, which can increase the fiber density and decrease the grain size. However, the remaining m-HfO 2 was directly converted into the cubic HfO 2 at 1351 °C. The unique temperatures of forming monoclinic, tetragonal, cubic phase were much lower than the phase-transition temperature. The prepared HfO 2 fiber could still maintain fibrous morphology after 10 times cyclic thermal shock in air. Moreover, the fibers calcined at 900 °C and 1200 °C have better thermal shock resistance for their stable phase and fibrous morphology with uniform grain growth after the thermal shock test.
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
产品关联
DOI
高影响因子
Polymer Chemistry
·
2021
·Vol. 12
·期 5
·736-743
·
IF 5.582
Enjie He,Kai Tu,Jiannan Cheng,Huanjun Lu,Lifen Zhang,Zhenping Cheng,Xiulin Zhu
Main-chain liquid crystalline polymers seldom develop into a columnar phase, let alone mesophase transitions between the columnar phase and other phases as the temperature changes. Herein, we present a new series of main-chain liquid crystalline copolymers which consist of strictly alternating rod-like aryl ester core, alkyl chain and perfluoroalkyl segments synthesized by photoinduced step transfer-addition and radical-termination (START) polymerization. The mesophases can be adjusted by changing the length of alkyl chains or perfluoroalkyl segments, which have been fully investigated and simulated in terms of molecular arrangements of molecules. Importantly the resultant liquid crystalline copolymers can present rare reversible phase transitions from a hexagonal columnar phase to a rectangular columnar phase and finally to a smectic phase with temperature increasing.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2025
·
IF 3.8
Huifeng Hu,Qihang Wang,Jin Chen,Zhuanfei Liu,Weiming Wang,Zhengyi Fu,Zhaoyong Zou
Cold sintering of dense ceramic materials at a significant lower temperature compared to conventional high-temperature sintering has attracted broad interests in recent years. During biomineralization process, hydrated amorphous phases are often used as precursors by living organisms to produce biominerals under ambient conditions. However, the crystallization and densification mechanisms of amorphous phases under pressure have not been thoroughly explored. Here, we found that water played a critical role in controlling the crystallization pathways of amorphous calcium carbonate, leading to the formation of two hydrated crystalline phases, ikaite or monohydrocalcite (MHC), depending on the pressure, temperature, and external water content. Furthermore, ikaite and MHC were used as hydrated crystalline precursors for fabrication of anhydrous aragonite ceramic through in situ phase transformation and densification under pressure at low temperature (80°C). The hardness, Young's modulus, and flexural strength of the aragonite ceramic formed from MHC could reach 4.0 GPa, 70.0 GPa, and 55 MPa, respectively, which were comparable to those of nacre. Our study provides a new bioprocessing-inspired cold sintering strategy for the fabrication of ceramics via metastable hydrated phases.
研究领域:
材料科学
·
生物矿化
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
ACS Applied Polymer Materials
·
2024
·
IF 4.4
You Wu,Zhonglei Li,Heyu Wang,Zhong Zheng,Boxue Du
As an environmentally friendly polymer material, isotactic polypropylene (pp), possesses excellent dielectric properties while it can be recycled, so it is regarded as having promising application prospects in the field of high voltage power cable insulation. However, the increasing operating voltage rating also puts higher demands on its insulation reliability. In this study, an intrinsic modulation method for pp insulation based on mesoscopic structure modulation by crystal phase transformation is proposed, which not only effectively improved the dielectric properties but also enhanced the mechanical toughness synergistically. The transformation of the crystal phase from the α-crystal to β-crystal within the PP/β-NA samples was successfully achieved by the solution blending method. The crystallization efficiency is greatly promoted, and the crystal structure is further improved at the same time. As the proportion of β-crystal gradually increases, the elongation at break could be raised to 451% at maximum. The difference in dielectric parameters between the crystal and amorphous regions is caused by the variation in the molecular chain density and arrangement, which is also the main reason for further triggering the high-intensity partial discharges and large-area electrical tree degradation in the amorphous region between the spherocrystal boundary at the mesoscopic scale. Compared with the premodification, the introduction of β-crystal effectively alleviated the problem of electric field distortion. Among them, the modified PP-β-0.2 sample had 16.8 kV/mm lower maximum electric field, 2258 fewer total partial discharges, 420 μm2 less electrical tree cumulative damage area, and 28% higher breakdown strength. Accordingly, it also has promising applications in the manufacturing of high-voltage power cable insulation.
研究领域:
材料科学
·
电气工程
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
FUEL
·
2024
·
IF 6.7
Chenxuanzi Wang,Mingxuan Zhong,Yongcheng Cai,Zewei Zhang,Bo Xiao,Tingting Xu,Xun Wang
The chemical looping reforming coupled with CO 2 splitting (CLR-CS) offers a promising solution for syngas production and simultaneous decomposition of CO 2 . In this study, the Sr-Fe based oxygen carriers (OCs) were evaluated in CLR-CS using ethanol as fuel. The presence of Sr significantly improved the oxidation performance of iron oxides. The Sr element in fresh Sr-Fe based OCs mainly formed two crystal phases, including SrFe 12 O 19 and Sr 4 Fe 6 O 13 . Increasing the amount of Sr element made it easier to form Sr 4 Fe 6 O 13 crystal phase. The Sr 4 Fe 6 O 13 was favorable for syngas production, due to the higher surface oxygen vacancy formation energy with a range of 3.13–3.37 eV. However, the lower oxygen transfer capacity (OTC) of Sr 4 Fe 6 O 13 resulted in a lower CO yield in the of stage of CO 2 decomposition. Compared with Sr 4 Fe 6 O 13 , SrFe 12 O 19 exhibited the higher OTC and the higher reactivity of lattice oxygen, which was preferable to produce more CO 2 in the stage of ethanol reforming in fuel reactor. During the cycle tests, the crystalline phase of SrFe 12 O 19 didn’t regenerate under the CO 2 atmosphere but transformed into Sr 4 Fe 6 O 13 . It was attributed to the lower energy barrier of CO 2 oxidation on the oxygen defect surface of Sr 4 Fe 6 O 13 . The phase transformation of SrFe 12 O 19 accompanied the formation of Fe 3 O 4 . The excessive Fe 3 O 4 had poor stability and inactivated easily due to sintering and agglomeration in Sr1Fe4 and Sr1Fe6 samples. The Sr1Fe2, namely the molar ratio of SrO to Fe 2 O 3 of 1:2, exhibited the better performance for syngas (0.291 Nm 3 /kg OC) and CO (0.141 Nm 3 /kg OC) coproduction at 800 °C. Additionally, the Sr1Fe2 presented an excellent cyclic stability in 30 cycles due to the suitable proportion of Sr 4 Fe 6 O 13 and iron oxides formed, which maintained a high syngas yield and avoided sintering of iron oxides. Overall, the Sr1Fe2 is a promising OC candidate in CLR-CS process.
研究领域:
能源科学
·
材料科学
✓ 已验证
DOI
高影响因子
JOURNAL OF POROUS MATERIALS
·
2015
·Vol. 23
·期 2
·489-495
·
IF 1.108
Pan Yani,Zhang Jingji,Xu Yu,Gao Yafeng,Chen Zhi,Wang Jiangying
Sulfonated mesoporous ZrO 2 was prepared by a facile one-pot hydrothermal process, using a mixture of ZrOCl 2 ·8H 2 O and sodium dodecyl sulfonate in a NaOH solution, and subsequent calcination of the inorganic/organic intermediate. The influence of NaOH concentration, hydrothermal and calcination temperature on the structural and textural properties of the final products was investigated. Increasing the NaOH concentration gave rise to the transformation from tetragonal to monoclinic and then to tetragonal phase, whereas the increase of hydrothermal temperature led to the tetragonal-to-monoclinic phase transformation. As the NaOH concentration and hydrothermal temperature were increased, a narrow pore size distribution was turned into a multi-modal pore size distribution resulting from regular mesopores and interparticle voids. Accordingly, the incorporated sulfonate anions were oxidized into sulphate anions. After the calcination of 550 °C, the sulfonated products possessed tetragonal crystalline phase with average pore diameter of 4.2 nm and surface area of 108 m 2 g −1 .
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF MOLECULAR LIQUIDS
·
2024
·
IF 5.3
Hongyu Guo,Linfang Liang,Jiayi Guo,Liangbin Lin,Fafu Yang
The metal-coordination self-assemble system played an important role on constructing novel supramolecular smart-response materials. Although the single and double-response materials based on metal-induced self-assembly had been studied extensively, the triple responses for this kind of supramolecular material was seldom reported. In this work, the first metal-induced self-assemble system with triple responses on photophysical, liquid crystalline and gel properties was presented based on Hg 2+ -coordination tetraphenylene dimer ( Bis-TPE ). Bis-TPE was prepared by bridging two alkyl-substituted tetraphenylene with amido chain. It possessed the fluorescence response from the strong emission for Bis-TPE to the faint emission for Bis-TPE -Hg 2+ complex. The self-assemble mechanism of Bis-TPE -Hg 2+ was clarified as that Hg 2+ was located in the cavity of the amido-ether chain of Bis-TPE . The Hg 2+ -induced mesomorphic transition was also observed from smectic mesophase for Bis-TPE to hexagonal columnar mesophase for Bis-TPE -Hg 2+ complex. The unique Hg 2+ -induced gel transition was further distinguished from low-order spherical morphology for Bis-TPE to high-order fibrous morphology for Bis-TPE -Hg 2+ complex. The maximum fluorescence wavelength exhibited the giant shift from 494 nm for Bis-TPE in gel to 606 nm for Bis-TPE -Hg 2+ in gel. This kind of triple responses on photophysical, liquid crystalline and gel properties for metal-coordination self-assemble system was described for the first time, affording a new idea on design of new multiple-response materials with unique properties.
研究领域:
超分子化学
·
材料科学
·
配位化学
✓ 已验证
DOI
高影响因子
Journal of Environmental Chemical Engineering
·
2022
·
IF 7.968
Peng Zhao,Nengjie Feng,Bangjie Tan,Zhuobin Huo,Geng Liu,Hui Wan,Guofeng Guan
The exposed crystal facets are crucial to heterogeneous catalysis . Herein, the facet controlled Ce 1−x La x O δ (0 ≤ x ≤ 0.30) nanocomposites have been constructed elaborately via a hydrothermal route and used for soot abatement. The catalysts were characterized by XRD , TEM, Raman, FT-IR, XPS , H 2 -TPR, and so forth. With the increasing content of La 3+ , part of CeO 2 crystals transformed from nanocubes to nanorods , inducing distinct effects on the catalytic activity . When the concentration of La 3+ was lower than 10 %, the exposed facet in the catalyst was (200). After La 3+ were further introduced, the facet degraded to (111). La 3+ at low concentration would enhance activity by facilitating lattice oxygen delivery and inducing abundant surface oxygen species, especially O - , which were vital to surface sensitive soot oxidation . Nevertheless, excessive La 3+ ions would inhibit CO 2 desorption due to the generation of La 2 O 2 CO 3 , a strong alkali as a result of phase separation. Among all the catalysts, Ce 0.95 La 0.05 O δ showed the best catalytic performances for soot combustion, with T 50 of 375 °C.
研究领域:
材料化学
·
环境催化
·
纳米材料
·
能源化学
·
表面科学
✓ 已验证
DOI
高影响因子
JOURNAL OF WUHAN UNIVERSITY OF TECHNOLOGY-MATERIALS SCIENCE EDITION
·
2020
·Vol. 35
·期 2
·441-448
·
IF 0.64
Xiong Yan,Zhang Yucheng,Liu Wei,Liu Yang,Tan Junjun
A citrate-assisted hydrothermal method was utilized for the preparation of Sr-substituted hydroxyapatite (HA) nanoparticles. The influences of Sr-substituting degree on the phase identifications, microstructures and colloidal stability of the resultant products were studied. The experimental results show that the crystalline structures and morphologies of final resultants are significantly changed by controlling the Sr-substituting degree. As the Sr-substituting degree increases, the colloidal stability of samples first increases and then decreases rapidly; the morphology of the product first changes from nanorods to short nanorods rod and then becomes nanowires. Uniform HA hexagonal nanorods with high aspect ratio (>4.0) and excellent aqueous colloidal stability were prepared by 6 h hydrothermal reaction at 180 °C without Sr substitution. The dispersion underwent the phase transition from isotropic to liquid-crystalline state upon the increasing concentration of 25wt% and the complete liquid-crystalline phase was achieved when at the concentration above 31wt%. These novel findings provide new insights into the role of Sr substitution on both the citrate-assisted hydroxyapatite crystallization and tailoring of colloidal stability. Moreover, HA liquid crystal behavior was successfully observed, which lays a foundation for the fabrication of macroscopically assembled hydroxyapatite-based biomimetic materials for biomedical applications.
研究领域:
材料科学
·
生物医学工程
·
纳米技术
✓ 已验证
产品关联
DOI
高影响因子
DALTON TRANSACTIONS
·
2021
·Vol. 50
·期 25
·8927-8937
·
IF 4.39
Ying Liu,Na Wang,Zhongqiao Sun,Yide Han,Junli Xu,Yan Xu,Junbiao Wu,Hao Meng,Xia Zhang
MOF/polymer hybrid membranes integrate the surface activity of MOFs and the advantages of PVDF membranes, and can be used as adsorption membranes in the efficient removal of target organics. In this work, a new hybrid membrane of ZIF-67/PVDF with varying ZIF-67 dosages has been fabricated through a facile mechanical blending followed by a lyotropic phase transition. Methods including field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), FT-IR analyses and surface hydrophobicity/hydrophilicity measurements are applied to characterize the structure, physicochemical properties and membrane performances. Two synthetic triarylmethane dyes, cationic malachite green (MG) and anionic fuchsin acid (FA), are chosen as the main adsorption targets to evaluate the adsorption capacities of the resulting ZIF-67/PVDF hybrid membranes. Interestingly, all of the ZIF-67/PVDF hybrid membranes exhibit distinctly favorable efficiencies and selectivities toward MG and FA compared to pristine PVDF, which proves the positive roles of ZIF-67 in the adsorption ability of the hybrid membranes. The adsorption conditions are optimized and the adsorption kinetics and thermodynamics are analysed to study the adsorption mechanism. The reusability and the structural stability of the hybrid membranes undergoing cyclic adsorption processes are also discussed. To the best of our knowledge, this is the first time that good adsorption capacities for MG and FA for these MOF/PVDF membranes have been reported. This work highlights the prospective applications of MOF/PVDF hybrid membranes in the rapid and effective removal of target organics in the treatment of waste water.
研究领域:
环境科学
·
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）