Journal of Materials Research and Technology-JMR&T
·
2021
·
IF 5.039
Xiao-jun Wang,Song-tong Xuan,Ming Feng,Yu-ming Tian
The in-situ formed MgAl 2 O 4 –CaAl 12 O 19 (MA–CA 6 ) composites were fabricated in this study. To clarify the influence of the evolution of CA 6 phase on the properties of MA–CA 6 composites, the sintering temperature was carried out at 1200–1700 °C for 2 h. The results show that the growth and development of CA 6 grains improves the densification and flexural strength of MA–CA 6 composites. The formation of MA phase occurs at 1200 °C, while the CA 6 phase is formed by the reaction of CaAl 4 O 7 (CA 2 ) and Al 2 O 3 appears at 1400 °C. The plate-like CA 6 grains intersect with each other, presenting regular hexagonal morphology with a high aspect ratio at 1500 °C. The CaO–Al 2 O 3 –SiO 2 phase acts as an interface phase to regulate the growth and development of MA and CA 6 grains. The CA 6 phase was crystallized from the transient liquid phase CaO–Al 2 O 3 –SiO 2 to significantly increase its thickness at 1600 °C. At the same time, as the sintering temperature rises, the apparent porosity of the sample decreases from 24% at 1400 °C to 4% at 1600 °C, and the flexural strength correspondingly increases from 96.6 MPa to 167 MPa. However, the suitable sintering temperature should not exceed 1600 °C for better properties of the composites.
研究领域:
材料科学
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陶瓷工程
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DOI
高影响因子
DALTON TRANSACTIONS
·
2020
·Vol. 49
·期 11
·3606-3614
·
IF 4.174
Yibing Wu,Yixi Zhuang,Rong-Jun Xie,Kaibin Ruan,Xinhua Ouyang
Red emitters based on CaAl12O19:Mn4+ have been attracting extensive attention due to their advantages of being rare-earth-free and chemically stable. However, their relatively low luminescence efficiencies will seriously hinder their application in light-emitting diodes (LEDs). In this regard, the promising red phosphors of CaAl12O19:Mn4+ were synthesized with enhanced luminous efficiency by introducing the coexisting phase of MgAl2O4. Importantly, an approximately 5 times enhancement of integrated intensity in the emission spectrum was observed for the phosphor with the coexisting phase compared to that with a single phase. Their crystal structures, morphologies and photoluminescence properties and the mechanism of improved luminescence were systematically investigated. Upon exciting them by using near-ultraviolet or blue LEDs, an efficient red emission was achieved with a maximum peak at ∼658 nm. In order to evaluate their potential application, a warm white LED and a plant growth LED were fabricated by using the prepared phosphors in combination with YAG:Ce3+ and InGaN-based blue chips.
研究领域:
材料科学
·
光学工程
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DOI
PubMed
高影响因子
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2018
·Vol. 102
·期 7
·3879-3886
·
IF 2.956
Binbin Dong,Mingye Yang,Feihong Wang,JunWei Wang,LuYuan Hao,Xin Xu,Gang Wang,Simeon Agathopoulos
The rapid development of engineering filtering process suggests that it is imperative to produce membrane substrates with a fine pore size, high gas permeation, and antifouling properties for efficient and long-term application. This study reports on a novel fabrication method of a porous Al 2 O 3 /CaAl 12 O 19 ceramic membrane substrate by a direct foaming method combined with cement solidification and tape-casting technology. The microstructure of the produced ceramic membrane consisted of pores with a size of 50-150 μm, which were interconnected with each other with a large number of small filtering functional pores of <10 μm. By increasing the amount of the foaming agent, the porosity of the porous Al 2 O 3 /CaAl 12 O 19 ceramic membranes was tailored from 64.8% to 80.5%, and the bending strength decreased from 32.1 ± 1.0 to 9.6 ± 0.9 MPa, respectively. The sintered hydrophilic ceramic substrate was successfully modified to a hydrophobic one (with water contact angles of 143°) by pyrolysis of dimethyldichlorosilane and dichloromethylsilane. The resultant membrane displayed high chemical stability and self-cleaning features. The membrane with a porosity of 64.8% had a N 2 permeation of 3.0 (±0.5) × 10 7 L m −2 h −1 at 0.5 bar and a water flux which could be totally suppressed at a liquid entry pressure of 0.45 bar.
研究领域:
材料科学
·
环境工程
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DOI
高影响因子
CERAMICS INTERNATIONAL
·
2023
·
IF 5.2
Xiaoping Jiang,Yue Guo,Lixi Wang,Qitu Zhang
The integration of dynamic photoluminescence and photochromism to achieve dual-modal characteristics can substantially elevate the security of anticounterfeiting measures. In this study, a novel bifunctional phosphor, namely CaAl 12 O 19 :Eu, Tb possessing dynamic photoluminescence and photochromism, is developed by the sol-gel combustion method. As the duration of exposure to 254 nm ultraviolet radiation increases, the CaAl 12 O 19 :Eu, Tb phosphors exhibit exceptional dynamic luminescent characteristics and pronounced color changes. Furthermore, this exposure results in a photochromic phenomenon on the surface of the samples, causing a shift from white to light brown. With an increase in Tb doping concentration, distinct and diverse chromatic variations easily discernible are observed by the naked eye. In addition, the mechanisms underlying the dynamic photoluminescent and photochromic characteristics are analyzed herein. Furthermore, the application of the bifunctional phosphor CaAl 12 O 19 :Eu, Tb for advanced dual-modal multicolor anticounterfeiting is explored, offering enhanced security against duplication attempts.
研究领域:
材料科学
·
光学
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DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
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2021
·Vol. 32
·期 23
·27513-27523
·
IF 2.478
He Youyi,Liu Jun,Gao Yalei,Yan Lijuan,Lv Fengzhen,Liu Fuchi,Long Lizhen
Mn 4+ -activated phosphors have become a hotspot in the development of inorganic red phosphors due to the fascinating photoluminescent properties. Herein, the synergetic manipulation of the flux effect and charge compensation was employed to improve the performance of Mn 4+ -activated CaAl 12 O 19 red phosphors. The crystallinity was improved by appropriate Zn 2+ -doping, while nonradiative transition between Mn 4+ ions is reduced by charge compensation of the formation of Mn 4+ –Mg 2+ pairs with Mg 2+ dopants. Thus, the emission of Mn 4+ -activated CaAl 12 O 19 red phosphors has been remarkably enhanced. The low probability of nonradiative transition between Mn 4+ ions was demonstrated by the thermal stability analysis. To depict the luminescent process, the crystal-field strength ( D q ), and Racah parameters ( B and C ) were calculated to determine the sequence of the energy levels. Meanwhile, the warm WLEDs with high CRI and low CCT were obtained using the prepared phosphors as red-emitting composition. Our results clearly suggested that the synergetic strategy by combining the flux effect and charge compensation is an effective method to enhance the luminescence of CaAl 12 O 19 :Mn 4+ , and CaAl 12 O 19 :Mn 4+ /Zn 2+ /Mg 2+ red-emitting phosphors, which have potential application value in warm WLEDs.
研究领域:
材料科学
·
光学工程
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DOI
高影响因子
CERAMICS INTERNATIONAL
·
2023
·
IF 5.2
Xiaoping Jiang,Yue Guo,Lixi Wang,Qitu Zhang
Dynamic photoluminescence and photochromism are two critical technologies applied in advanced anti-counterfeiting and encryption. In this work, an innovative phosphor of CaAl 12 O 19 :Eu 2+/3+ combining the features of dynamic photoluminescence and photochromism is developed for the first time. After being irradiated by a portable 254 nm ultraviolet lamp, the photoluminescent color of the phosphor can dynamically change from red to magenta in dark field, and the surface color can dynamically alter from white to light brown in bright field. Based on these two appealing features, an application in advanced anti-counterfeiting and encryption is designed which can write, encrypt, and erase information successfully, thus guaranteeing information security. Furthermore, a composite material of CaAl 12 O 19 :Eu 2+/3+ /PDMS is fabricated for application in advanced anti-counterfeiting and encryption in both dark and bright fields, which is difficult to be replicated.
研究领域:
材料科学
·
光学
·
信息安全
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DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
·
2019
·Vol. 30
·期 12
·11419-11428
·
IF 2.195
Zhao Caiyue,Xu Yudong,Wang Lei,Chen Xinyi,Hu Wenjie,Dai Zhaoxiang,Hu Mengyuan,Liu Kai,Shi Min
In this study, Bi 3+ and Mn 4+ co-doped CaAl 12 O 19 phosphors were prepared via high-temperature solid-state reaction method, and their crystal structure, particle morphologies, luminescence properties, charge compensation mechanism and crystal field effect were investigated in detail. A most remarkable tuning effect can be achieved when the Bi 3+ concentration is 5% in CaAl 12 O 19 :Bi 3+ , 0.05% Mn 4+ and the electric multipolar interaction is inferred to be the main mechanism for concentration quenching effect. It is also found that, as charge compensators rather than sensitizers, Bi 3+ ions can effectively tailor the emissions in a wide range through partial reducing Mn 4+ to Mn 2+ . The charge compensation physics presumably involves the shift of Fermi energy level ( E F ) and variations of valence states of manganese ions after Bi 3+ introduction. Moreover, the authors calculated the splitting energy (Δ) and Racah parameters ( B and C ) for Mn 4+ in octahedral sites and Mn 2+ in tetrahedral sites by combining excitation spectra with Tanabe-Sugano diagram. The experimental results will be of certain helpfulness in developing phosphors used in white LED.
研究领域:
材料科学
·
光学
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产品关联
DOI
高影响因子
JOURNAL OF COLLOID AND INTERFACE SCIENCE
·
2024
·
IF 9.4
Xiaoping Jiang,Yue Guo,Lixi Wang,Qitu Zhang
Multi-mode dynamic anti-counterfeiting materials can provide complex anti-counterfeiting performance and ensure the anti-counterfeiting strategy becomes more secure. Herein, a new type of multi-mode anti-counterfeiting encryption material of CaAl 12 O 19 :Eu, Er with different Er doping concentration was developed by sol–gel method. Interestingly, the CaAl 12 O 19 :Eu, Er phosphor and its composite have multi-mode anti-counterfeiting characteristics of multi-color down-conversion luminescence, up-conversion luminescence, dynamic luminescence, and photochromism. Effect of different Er doping concentration on the down-conversion luminescence, up-conversion luminescence, dynamic luminescence, and photochromism of CaAl 12 O 19 :Eu, Er was systematically investigated, and the relevant mechanisms were discussed. These anti-counterfeiting features can be simultaneously applied in both bright and dark fields, which can achieve high-level anti-counterfeiting in both spatial and temporal dimensions. The CaAl 12 O 19 :Eu, Er phosphors cannot be easily replaced by other materials with the same anti-counterfeiting properties. They display good application foreground in the field of anti-counterfeiting encryption.
研究领域:
材料科学
·
光学
·
防伪技术
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产品关联
DOI
PubMed
高影响因子
JOURNAL OF FLUORESCENCE
·
2025
·
IF 3.1
Guan Chuheng,Jia Yumeng,Shi Zhongxiang,Wang Jing,Dong Yingnan,Wang Zhihui
The present paper details the preparation of CaAl 12- x O 19 : x Mn 4+ (CAO: Mn 4+ ) red phosphors based on CaAl 12 O 19 using a high-temperature solid-state method through Mn ion doping. A range of analytical techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectroscopy, to comprehensively investigate the crystal structure, microstructure and photoluminescence characteristics of the samples. The results demonstrate that the doped Mn 4+ ions enter the octahedral sites of Al 3+ , and the lattice constants of the matrix does not change significantly because the ionic radius of the doped Mn 4+ ions is equivalent to the size of the Al 3+ ions. On this basis, the lattice size and lattice strain were calculated using the W-H equation. The results show that as the doping concentration gradually increases, both the lattice size and strain exhibit a slowly increasing trend. The prepared phosphor exhibited a polyhedral morphology, characterised by two hexagonal prisms with irregular hexagonal end faces, a substantial particle size, and optimal dispersion. When exposed to near ultraviolet light at a wavelength of 349 nm, the photoluminescence spectrum displays narrow-band emission characteristics, with the central wavelength of the emission peak at 654 nm and the full width at half maximum (FWHM) of 40.706 nm. The emission peak is attributed to the transition from 2 E g to 4 A 2g of Mn 4+ in a strong crystal field. With the increase of Mn 4+ doping concentration, the fluorescence intensity first increases and then decreases, and the fluorescence intensity is the highest when the doping concentration is 1.2 mol%. The analysis yielded three emission peaks, which were separated by the peak separation method. These peaks correspond to the emission of Mn 4+ at three different octahedral points of Al 3+ . The integrated area ratio of the three peaks indicates that Mn 4+ is predominantly present on the symmetrical sites. Thermal stability analysis demonstrates that the emission intensity of the phosphor decreases rapidly due to three factors. Firstly, the size of the Mn 4+ ions is smaller than the octahedral gap size. Secondly, the energy is higher. Thirdly, no radiation transition intensifies with the increase of temperature. The colour purity calculation indicates that the red phosphor prepared has a colour purity of over 99%. At the same time, the color temperature is below 6000k, which renders it suitable for indoor plant cultivation.
研究领域:
材料科学
·
发光材料
·
固态化学
·
光学材料
·
荧光粉技术
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Science of Advanced Materials
·
2017
·
IF 1.671
Zheng Jiayu,Li Liyi,Peng Mingying
Unusually, valent Bi2+ ions doped into solids can exhibit near ultraviolet or blue excitation and red emissions. Previously the ion has only been found stabilized in compounds such as borate, sulfate or phosphate, and has not yet been reported in other types of compounds.
In this work, we found that Bi2+ can also survive in CaAl12O19. Time resolved emission spectra reveal that there are two types of Bi2+ ions in the compound due to the substitution of calcium lattice sites. Both types of Bi2+ ions show
blue excitations and red emissions, with energy transfer occurring from the longer wavelength emission center to the shorter wavelength emission center. As bismuth content x increases, Bi2+ luminescence intensifies at first, but is then quenched afterwards when x exceeds
0.3 mol%. The dominant mechanism of quenching was found to be due to electric quadrupole–quadrupole rather than exchange interactions. This work suggests that CaAl12O19:Bi2+ is a potential red phosphor for application in white light LEDs (WLEDs).
研究领域:
材料科学
·
光学材料
·
固态化学
·
光子学
·
LED技术
✓ 已验证
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2026
·
IF 6.7
Xiaoping Jiang,Yifan Shen,Yiren Wu,Jinpeng Ding,Zhiyu Qu,Pengde Han,Lixi Wang,Qitu Zhang
Dual-mode anti-counterfeiting materials with photochromic and dynamic luminescent properties can improve the security of anti-counterfeiting and encryption. This study aimed to synthesize CaAl 12 O 19 :Eu, Ce phosphors with photochromic and dynamic photoluminescent properties. With the extension of 254-nm UV radiation time, the surface of the CaAl 12 O 19 :Eu, Ce phosphors changed in color from white to brownish yellow and was bleached by heating at 520 °C for 5 min, exhibiting excellent fatigue resistance and thermal stability. After co-doping Eu and Ce in CaAl 12 O 19 , the photochromic performance significantly improved, with the ΔR value increasing by 2.6- and 1.8-fold that of the CaAl 12 O 19 :1.0%Eu and CaAl 12 O 19 :1.0%Ce samples, respectively. After 254-nm UV irradiation, the CaAl 12 O 19 :Eu, Ce samples showed time-dependent dynamic luminescence characteristics, changing in color from orange-red to magenta. The mechanisms responsible for the photochromic and dynamic luminescence properties were further investigated. Overall, owing to their photochromism and dynamic photoluminescence, the CaAl 12 O 19 :Eu, Ce/polydimethylsiloxane composites could be applied in advanced anti-counterfeiting and information encryption with higher security in both the bright and dark fields.
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高影响因子
危险品化学品经营许可证（带存储）