Journals > > Topics > RESEARCH LETTERS
RESEARCH LETTERS|4 Article(s)
Lu SHEN, Dewen WANG, Rong HUANG, Shiyu DU, and Qing HUANG
An electron irradiation induced fast phase-separation behavior was observed under convention Transmission electron microscopy (TEM) observation of spark plasma sintered AlF3 doped alumina ceramic. Spherical nanocrystalline Al precipitates separated out from original alumina grain surface within several seconds under transmission electron microscopy electron irradiation. By high resolution TEM observation combined with diffraction patterns analysis, it was found that the original alumina grain surface was in highly defected state. After electron irradiation under TEM, the defects on original alumina surface vanished accompanied by the precipitation of nanocrystalline Al particles. By thoroughly analysis of the defect reaction during doping process and the feature of cation sub-lattice of alumina, a defect assisted interstitial atom segregation mechanism was proposed to explain this behavior. According to this mechanism, doped F ions first occupied oxygen vacancy sites with corresponding Al ions at intrinsic interstitial sites. After oxygen vacancies being fully occupied, both F and Al ions tended to settle down at intrinsic octahedron interstitial sites, which resulted in a metastable doping state. Under the act of 1/3 [11ˉ00] partial dislocation of alumina matrix, distorted cation sub-lattice generated double aggregated vacant octahedron sites. When these doublets vacant octahedron sites were occupied by foreign Al ions, stacking faults composed of about three sequences were generated as that observed in high resolution TEM. Meanwhile, the segregated doping Al ions at double aggregated octahedron sites along the stacking faults worked as early stage precipitations. Under electron irradiation, with the ablation of F ions, the unstable segregated Al ions separated out as nano precipitation with the reconstruction of alumina lattice. An electron irradiation induced fast phase-separation behavior was observed under convention Transmission electron microscopy (TEM) observation of spark plasma sintered AlF3 doped alumina ceramic. Spherical nanocrystalline Al precipitates separated out from original alumina grain surface within several seconds under transmission electron microscopy electron irradiation. By high resolution TEM observation combined with diffraction patterns analysis, it was found that the original alumina grain surface was in highly defected state. After electron irradiation under TEM, the defects on original alumina surface vanished accompanied by the precipitation of nanocrystalline Al particles. By thoroughly analysis of the defect reaction during doping process and the feature of cation sub-lattice of alumina, a defect assisted interstitial atom segregation mechanism was proposed to explain this behavior. According to this mechanism, doped F ions first occupied oxygen vacancy sites with corresponding Al ions at intrinsic interstitial sites. After oxygen vacancies being fully occupied, both F and Al ions tended to settle down at intrinsic octahedron interstitial sites, which resulted in a metastable doping state. Under the act of 1/3 [11ˉ00] partial dislocation of alumina matrix, distorted cation sub-lattice generated double aggregated vacant octahedron sites. When these doublets vacant octahedron sites were occupied by foreign Al ions, stacking faults composed of about three sequences were generated as that observed in high resolution TEM. Meanwhile, the segregated doping Al ions at double aggregated octahedron sites along the stacking faults worked as early stage precipitations. Under electron irradiation, with the ablation of F ions, the unstable segregated Al ions separated out as nano precipitation with the reconstruction of alumina lattice.
Journal of Inorganic Materials
- Publication Date: Jul. 21, 2021
- Vol. 36, Issue 1, 95 (2021)
Yaxin LIU, Min WANG, Meng SHEN, Qiang WANG, and Lingxia ZHANG
Oxygen vacancy plays an important role in promoting CO2 adsorption and reduction on photocatalysts. Bi was heavily doped into ceria, forming a solid solution catalyst Ce1-xBixO2-δ meanwhile maintaining the fluorite structure, to increase the oxygen vacancy concentration. The sample Ce0.6Bi0.4O2-δ showed the highest photocatalytic activity with a CO yield of ～4.6 times that of the pristine ceria nanorods. Bi was homogeneously dispersed into the fluorite ceria which was confirmed by XRD and EDX elemental mapping. It has been evidenced by the results of Raman and XPS that Bi introduction boosts the concentration of oxygen vacancy in the solid solution that can facilitate the adsorption/activation of carbonate and bicarbonate intermediates on its surface according to in-situ FT-IR. Oxygen vacancy plays an important role in promoting CO2 adsorption and reduction on photocatalysts. Bi was heavily doped into ceria, forming a solid solution catalyst Ce1-xBixO2-δ meanwhile maintaining the fluorite structure, to increase the oxygen vacancy concentration. The sample Ce0.6Bi0.4O2-δ showed the highest photocatalytic activity with a CO yield of ～4.6 times that of the pristine ceria nanorods. Bi was homogeneously dispersed into the fluorite ceria which was confirmed by XRD and EDX elemental mapping. It has been evidenced by the results of Raman and XPS that Bi introduction boosts the concentration of oxygen vacancy in the solid solution that can facilitate the adsorption/activation of carbonate and bicarbonate intermediates on its surface according to in-situ FT-IR.
Journal of Inorganic Materials
- Publication Date: May. 20, 2021
- Vol. 36, Issue 1, 88 (2021)
Yueting SHAO, Yingjie ZHU, Liying DONG, and Anyong CAI
Xuan paper is an indispensable carrier for Chinese calligraphy and painting works. It has won the reputation of “the King of Paper” because of its superior durability and anti-mildew performance. Xuan paper was inscribed on the Representative List of the Intangible Cultural Heritage of Humanity by the Educational, Scientific and Cultural Organization of the United Nations in 2009. In this study, we developed a new type of nanocomposite “Xuan paper” made from ultralong hydroxyapatite nanowires and cellulose fibers with excellent anti-mildew performance. The whiteness of the as-prepared nanocomposite “Xuan paper” with HAP weight ratio of 25% is 76.1%, which is higher than that of the commercial unprocessed Xuan paper (71.9%) or the commercial processed Xuan paper (70.3%). The nanocomposite “Xuan paper” has superior performance in inhibiting the growth of three kinds of moulds (Chaetomium globosum, Trichoderma viride (long branch) and Aspergillus niger) compared with the blank control and commercial Xuan paper. During the incubation process, the mildew grows on the surface of the traditional Xuan paper, however, no obvious growth of mildew is observed on the surface of the nanocomposite “Xuan paper”. It is expected that the nanocomposite “Xuan paper” is favorable for its long-term safe preservation and application in calligraphy and painting arts. Xuan paper is an indispensable carrier for Chinese calligraphy and painting works. It has won the reputation of “the King of Paper” because of its superior durability and anti-mildew performance. Xuan paper was inscribed on the Representative List of the Intangible Cultural Heritage of Humanity by the Educational, Scientific and Cultural Organization of the United Nations in 2009. In this study, we developed a new type of nanocomposite “Xuan paper” made from ultralong hydroxyapatite nanowires and cellulose fibers with excellent anti-mildew performance. The whiteness of the as-prepared nanocomposite “Xuan paper” with HAP weight ratio of 25% is 76.1%, which is higher than that of the commercial unprocessed Xuan paper (71.9%) or the commercial processed Xuan paper (70.3%). The nanocomposite “Xuan paper” has superior performance in inhibiting the growth of three kinds of moulds (Chaetomium globosum, Trichoderma viride (long branch) and Aspergillus niger) compared with the blank control and commercial Xuan paper. During the incubation process, the mildew grows on the surface of the traditional Xuan paper, however, no obvious growth of mildew is observed on the surface of the nanocomposite “Xuan paper”. It is expected that the nanocomposite “Xuan paper” is favorable for its long-term safe preservation and application in calligraphy and painting arts.
Journal of Inorganic Materials
- Publication Date: Jan. 20, 2021
- Vol. 36, Issue 1, 107 (2021)
Dongqiang ZHANG, Huihui LU, Na SU, Guixian LI, Dong JI, and Xinhong ZHAO
Solvent-free synthesis of zeolites has received extensive attention in recent years, because it is advantageous over conventional hydrothermal synthesis. Nevertheless, SAPO-34, a micropore zeolite, prepared by this method does not satisfy the catalytic lifetime requirements of the methanol-to-olefins (MTO) reaction. Herein, an improved solvent-free approach was developed to synthesize SAPO-34 catalysts with enhanced MTO reaction performance, in which acid-etched seed crystals were introduced to modulate the physico-chemical properties of the zeolite via crystallization kinetics regulation. The results indicated that the SAPO-34 samples prepared from seed-containing precursor gels show considerably higher crystallinity, larger surface area, but lower strong acid site density than the parent sample. In particular, the catalytic lifetime of the SAPO-34 catalyst prepared from activated seeds was remarkably prolonged to 480 min, which was significantly superior to that of the parent sample (40 min). The result confirmed the validity of the seeding approach for modifying the zeolite properties via the solvent-free synthesis and the potential of the approach in improving catalytic performance. Solvent-free synthesis of zeolites has received extensive attention in recent years, because it is advantageous over conventional hydrothermal synthesis. Nevertheless, SAPO-34, a micropore zeolite, prepared by this method does not satisfy the catalytic lifetime requirements of the methanol-to-olefins (MTO) reaction. Herein, an improved solvent-free approach was developed to synthesize SAPO-34 catalysts with enhanced MTO reaction performance, in which acid-etched seed crystals were introduced to modulate the physico-chemical properties of the zeolite via crystallization kinetics regulation. The results indicated that the SAPO-34 samples prepared from seed-containing precursor gels show considerably higher crystallinity, larger surface area, but lower strong acid site density than the parent sample. In particular, the catalytic lifetime of the SAPO-34 catalyst prepared from activated seeds was remarkably prolonged to 480 min, which was significantly superior to that of the parent sample (40 min). The result confirmed the validity of the seeding approach for modifying the zeolite properties via the solvent-free synthesis and the potential of the approach in improving catalytic performance.
Journal of Inorganic Materials
- Publication Date: Jan. 20, 2021
- Vol. 36, Issue 1, 101 (2021)
Topics
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20