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Photoluminescence and electrical properties of Eu3+ -doped Na0.5 Bi4.5 Ti4 O15 -based ferroelectrics under blue light excitation
Xing-an JIANG,Xiang-ping JIANG,Chao CHEN,Na TU,Yun-jing CHEN,Ban-chao ZHANG
Front. Mater. Sci.. 2016, 10 (1 ): 31-37.
https://doi.org/10.1007/s11706-016-0328-x
Na0.5 Bi4.5-- x Eux Ti4 O15 (NBT--x Eu3+ ) ceramics with x =0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30 and 0.40 were prepared by conventional ceramics processing. NBT--0.25Eu3+ ceramics show the strongest red and orange emissions corresponding to the 5 D0 → 7 F2 (617 nm) and 5 D0 → 7 F1 (596 nm) transitions, respectively. The strongest excitation band around 465 nm matches well with the emission wavelength of commercial InGaN-based blue LED chip, indicating that Eu3+ -doped NBT ceramics may be used as potential environmental friendly red-orange phosphor for W-LEDs application. As an inherent ferroelectric and piezoelectric material, the electrical properties of this potentially multifunctional electro-optical material have been also studied. The introduction of Eu3+ distinctly increased the Curie temperature (T C ) of NBT--x Eu3+ ceramics from 640°C to 711°C as x ranges from 0 to 0.40. For higher temperature applications, the electrical conductivity was also investigated. The conduction of charge carriers in high-temperature range originates from the conducting electrons from the ionization of oxygen vacancies. High T C and low tanδ makes Eu3+ -doped NBT ceramic also suitable for high temperature piezoelectric sensor applications and electro-optical integration.
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Paramagnetism and improved upconversion luminescence properties of NaYF4 :Yb,Er/NaGdF4 nanocomposites synthesized by a boiling water seed-mediated route
Chao-Qing YANG,Ao-Ju LI,Wei GUO,Peng-Hua TIAN,Xiao-Long YU,Zhong-Xin LIU,Yang CAO,Zhong-Liang SUN
Front. Mater. Sci.. 2016, 10 (1 ): 38-44.
https://doi.org/10.1007/s11706-016-0318-z
In a route boiling water served as reaction medium, a stoichiometric amount of rare-earth compound and fluoride are put into this system to form α-NaYF4 :Yb,Er nuclei. Then prepared sample is heated at elevated temperature to improve the fluorescence intensity, and next a NaGdF4 shell grows on the surface of NaYF4 nuclei. NaYF4 :Yb,Er/NaGdF4 core--shell structured upconversion nanoparticles (CSUCNPs) have been successfully synthesized by above route. The use of boiling water decreases the cubic-to-hexagonal phase transition temperature of NaYF4 :Yb,Er to 350°C and increases its upconversion (UC) luminescence intensity. A heterogeneous NaGdF4 epitaxially growing on the surface of Ln3+ -doped NaYF4 not only improves UC luminescence, but also creates a paramagnetic shell, which can be used as contrast agents in magnetic resonance imaging (MRI). The solution of CSUCNPs shows bright green UC fluorescence under the excitation at 980 nm in a power density only about 50 mW·cm−2 . A broad spectrum with a dominant resonance at g of about 2 is observed by the electron paramagnetic resonance (EPR) spectrum of CSUCNPs. Above properties suggest that the obtained CSUCNPs could be potential candidates for dual-mode optical/magnetic bioapplications.
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Heterogeneous Fenton-like discoloration of methyl orange using Fe3 O4 /MWCNTs as catalyst: process optimization by response surface methodology
Huan-Yan XU,Tian-Nuo SHI,Hang ZHAO,Li-Guo JIN,Feng-Chun WANG,Chun-Yan WANG,Shu-Yan QI
Front. Mater. Sci.. 2016, 10 (1 ): 45-55.
https://doi.org/10.1007/s11706-016-0326-z
Fe3 O4 /MWCNTs nanocomposites were prepared by chemical oxidation coprecipitation method and developed as highly efficient heterogeneous Fenton-like catalyst. XRD results revealed that Fe3 O4 nanoparticles deposited onto MWCNTs surface remained the inverse spinel crystal structure of cubic Fe3 O4 phase. The FTIR characteristic peaks of MWCNTs weakened or disappeared due to the anchor of Fe3 O4 nanoparticles and Fe–O peak at 570 cm−1 was indicative of the formation of Fe3 O4 . TEM observation revealed that Fe3 O4 nanoparticles were tightly anchored by MWCNTs. The Fenton-like catalytic activity of Fe3 O4 /MWCNTs nanocomposites for the discoloration of methyl orange (MO) was much higher than that of Fe3 O4 nanoparticles. The process optimization of this heterogeneous Fenton-like system was implemented by response surface methodology (RSM). The optimum conditions for MO discoloration were determined to be of 12.3 mmol/L H2 O2 concentration, 2.9 g/L catalyst dosage, solution pH 2.7 and 39.3 min reaction time, with the maximum predicted value for MO discoloration ratio of 101.85%. The corresponding experimental value under the identical conditions was obtained as 99.86%, which was very close to the predicted one with the absolute deviation of 1.99%.
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Hot rolling and annealing effects on the microstructure and mechanical properties of ODS austenitic steel fabricated by electron beam selective melting
Rui GAO,Wen-jun GE,Shu MIAO,Tao ZHANG,Xian-ping WANG,Qian-feng FANG
Front. Mater. Sci.. 2016, 10 (1 ): 73-79.
https://doi.org/10.1007/s11706-016-0327-y
The grain morphology, nano-oxide particles and mechanical properties of oxide dispersion strengthened (ODS)-316L austenitic steel synthesized by electron beam selective melting (EBSM) technique with different post-working processes, were explored in this study. The ODS-316L austenitic steel with superfine nano-sized oxide particles of 30–40 nm exhibits good tensile strength (412 MPa) and large total elongation (about 51%) due to the pinning effect of uniform distributed oxide particles on dislocations. After hot rolling, the specimen exhibits a higher tensile strength of 482 MPa, but the elongation decreases to 31.8% owing to the introduction of high-density dislocations. The subsequent heat treatment eliminates the grain defects induced by hot rolling and increases the randomly orientated grains, which further improves the strength and ductility of EBSM ODS-316L steel.
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A new rabbit model of implant-related biofilm infection: development and evaluation
Cheng-Bing CHU,Hong ZENG,Ding-Xia SHEN,Hui WANG,Ji-Fang WANG,Fu-Zhai CUI
Front. Mater. Sci.. 2016, 10 (1 ): 80-89.
https://doi.org/10.1007/s11706-016-0324-1
This study is to establish a rabbit model for human prosthetic joint infection and biofilm formation. Thirty-two healthy adult rabbits were randomly divided into four groups and implanted with stainless steel screws and ultra-high molecular weight polyethylene (UHMWPE) washers in the non-articular surface of the femoral lateral condyle of the right hind knees. The rabbit knee joints were inoculated with 1 mL saline containing 0, 102 , 103 , 104 CFU of Staphylococcus epidermidis (S. epidermidis ) isolated from the patient with total knee arthroplasty (TKA) infection, respectively. On the 14th postoperative day, the UHMWPE washers from the optimal 103 CFU group were further examined. The SEM examination showed a typical biofilm construction that circular S. epidermidis were embedded in a mucous-like matrix. In addition, the LCSM examination showed that the biofilm consisted of the polysaccharide stained bright green fluorescence and S. epidermidis radiating red fluorescence. Thus, we successfully create a rabbit model for prosthetic joint infection and biofilm formation, which should be valuable for biofilm studies.
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In vitro evaluation of electrospun gelatin–glutaraldehyde nanofibers
Jianchao ZHAN,Yosry MORSI,Hany EI-HAMSHARY,Salem S. AL-DEYAB,Xiumei MO
Front. Mater. Sci.. 2016, 10 (1 ): 90-100.
https://doi.org/10.1007/s11706-016-0329-9
The gelatin–glutaraldehyde (gelatin–GA) nanofibers were electrospun in order to overcome the defects of ex-situ crosslinking process such as complex process, destruction of fiber morphology and decrease of porosity. The morphological structure, porosity, thermal property, moisture absorption and moisture retention performance, hydrolytic resistance, mechanical property and biocompatibility of nanofiber scaffolds were tested and characterized. The gelatin–GA nanofiber has nice uniform diameter and more than 80% porosity. The hydrolytic resistance and mechanical property of the gelatin–GA nanofiber scaffolds are greatly improved compared with that of gelatin nanofibers. The contact angle, moisture absorption, hydrolysis resistance, thermal resistance and mechanical property of gelatin–GA nanofiber scaffolds could be adjustable by varying the gelatin solution concentration and GA content. The gelatin–GA nanofibers had excellent properties, which are expected to be an ideal scaffold for biomedical and tissue engineering applications.
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