A red-emitting phosphor of Li₅La₃Ti₂O₁₂:Eu³⁺ with garnet-like structure and near-UV/blue light excitation

Zhang, Suyin,Zhang, Pengyue,Liu, Xin,Yang, Zhexi,Huang, Yanlin,Seo, Hyo Jin Elsevier 2018 Journal of luminescence Vol.203 No.-

<P><B>Abstract</B></P> <P>A series of novel red-emitting phosphor of Li<SUB>5</SUB>La<SUB>3–3x</SUB>Eu<SUB>3x</SUB>Ti<SUB>2</SUB>O<SUB>12</SUB> (x = 0.01–0.25) were synthesized via the facile solid-state reaction method. The Rietveld refinements verified that all the samples crystallized in a garnet-like cubic structure. The band gap energy of Li<SUB>5</SUB>La<SUB>3</SUB>Ta<SUB>2</SUB>O<SUB>12</SUB> is 3.87 eV, which can be greatly narrowed by Eu<SUP>3+</SUP>-doping. This benefits the red-shift of optical absorption from UV- to near-UV light region. Importantly, the sample presents dominant absorption in near-UV (390–395 nm) and blue-light (460–465 nm) region. Li<SUB>5</SUB>La<SUB>3–3x</SUB>Eu<SUB>3x</SUB>Ta<SUB>2</SUB>O<SUB>12</SUB> (x = 0.01–0.15) has a bright red-luminescence with the strongest <SUP>5</SUP>D<SUB>0</SUB> → <SUP>7</SUP>F<SUB>2</SUB> transition at 613 nm. The energy transfer was discussed on the Eu<SUP>3+</SUP>-doping concentration. The experimental red-emitting lamps were fabricated using a 395 and a 460 nm LED-chips, respectively, in combination with the single phosphor of Li<SUB>5</SUB>La<SUB>3–3x</SUB>Eu<SUB>3x</SUB>Ta<SUB>2</SUB>O<SUB>12</SUB> (x = 0.2) driven by 2 mA current. The results indicate that the phosphor could be a promising candidate used in solid-state lightings and displays.</P>

Enhanced Coercivity of Sintered NdFeB Magnets Prepared by Dy Addition

Zhang Pengyue,Ge Hong-liang,Pan Minxiang,Wu Qiong,Yang Hangfu,Jiao Zhiwei,Liu Tingting,Fu Rui 한국자기학회 2010 한국자기학회 학술연구발표회 논문개요집 Vol.2010 No.12

Magnetic and Structural Properties of MnBi<SUB>1-x</SUB>Ti<SUB>x</SUB> Alloys

Suyin Zhang,Pengyue Zhang,HuanChang Jiang,Yaojun Shi,Nengjun Yu,Hongliang Ge 한국자기학회 2014 Journal of Magnetics Vol.19 No.3

MnBi1-xTix (x = 0, 0.4, 0.7, 1) alloys were prepared by arc-melting, followed by heat treatment. X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) were used to measure and investigate the phase structure and magnetic properties. The temperature dependent magnetization curves indicate that the phase transitions between LTP and HTP MnBi occur with heating or cooling in MnBi1-xTix (x ≤ 0.7) samples. However, MnTi samples are in Mn₂Ti single-phase, with very low magnetic properties. Furthermore, the coercivity exhibits a positive temperature coefficient. The results show that the optimal content of Ti for the coercivity of MnBi1-xTix alloy is x = 0.4. For MnBi sample, the coercivity reaches a maximum value of 1.13 T at 550 K. However, the remanence and energy product show apparent decrease with the addition of Ti in MnBi1-xTix alloys.

Synergistic catalysis of bifunctional polyacrylonitrile fiber for the synthesis of (E)-α,β-unsaturated esters from aldehydes by decarboxylative Doebner–Knoevenagel reaction

Pengyu Li,Liwei Mi,Yuanyuan Liu,Wenqin Zhang,Xian-Lei Shi 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.81 No.-

A series of monofunctional and bifunctional polyacrylonitrilefiber catalysts have been successfullyprepared to catalyze the decarboxylative Doebner–Knoevenagel reaction of aldehydes and monoethylmalonate for the syntheses of the (E)-α,β-unsaturated esters. Among which, the catalyst PANPDFII/I showsthe best synergistic catalytic activity with high yields (89–96%), stereoselectivities (Z:E > 99:1) andreusability (up to 8 times). The influences of the N position on aminopyridine moiety, solvent andtemperature on the catalytic system were investigated in detail. This catalytic system can process well inhigher or lower polar organic solvents instead of moderate polar solvents, which is an interestingphenomenon in organic catalysis, and the reasons are explained in this work. Furthermore, a DMAP (4-dimethylaminopyridine) and piperazine synergistic catalytic mechanism in the micro-environment ofthefiber catalyst has been conceived to explain the high catalytic performance of this catalytic system. Besides, thefiber catalyst PANPDFII/I shows high application potential in industry for its good performancein scaled-up experiment, as well as its advantages of the easy preparation, high mechanical strength,flexibility and high stability in air.

Ensemble learning-based hierarchical retrieval of similar cases for site planning

Wang Pengyue,Guo Maozu,Han Yunsong,Zhao Lingling,Zhou Xiaoping,Zhang Dayu 한국CDE학회 2021 Journal of computational design and engineering Vol.8 No.6

Site planning not only involves the arrangement of a large number of elements but also considers the complexity of urban systems; hence, the design process involves large workloads and is time consuming. Retrieving similar existing cases helps architects optimize or accelerate the design process. This paper proposes a computational approach that provides valuable references by retrieving similar cases. Three types of attributes are extracted to represent a given parcel: land-use attributes, geometric attributes (area, orientation, etc.), and environmental attributes (greening rate, surrounding facilities, etc.). The complete hierarchical retrieval process is divided into three phases. The first phase selects cases whose land-use attributes are consistent with the target parcel. Then, the similarity distances between the given target parcel and the selected cases are calculated using geometric attributes. The eXtreme Gradient Boosting (XGBoost) classifier is adopted to determine which case is similar to the target parcel. Finally, similarity scores of the retrieved cases are calculated based on the environmental attributes to provide more options during the actual design. In total, 1189 cases with different land-use types in Beijing were collected for the case base. The comparative experimental results confirmed that the proposed ensemble learning-based hierarchical retrieval of similar cases approach improves the accuracy of retrieval results. Furthermore, we use a real-world target parcel to demonstrate the superiority and flexibility of the retrieval process.

The Magnetic and Magnetocaloric Properties of the Perovskite La<SUB>0.7</SUB>Ca<SUB>0.3</SUB>Mn<SUB>1-x</SUB>Ni<SUB>x</SUB>O₃

Sihao Hua,Pengyue Zhang,Hangfu Yang,Suyin Zhang,Hongliang Ge 한국자기학회 2013 Journal of Magnetics Vol.18 No.1

This paper studies the effects of the Mn-site substitution by nickel on the magnetic properties and the magnetocaloric properties of La0.7Ca0.3Mn1-xNixO₃ (x = 0, 0.05 and 0.1). The orthorhombic crystal structures of the samples are confirmed by the room temperature X-ray diffraction. The dependence of the Curie temperature (TC) and the magnetic entropy change (ΔSM) on the Ni doping content was investigated. The samples with x = 0 had the first order phase transition, while the samples with x = 0.05 and 0.1 had the second order phase transition. As the concentration of Ni increased, the maximum entropy change (|ΔSM|max) decreased gradually, from 2.78 Jㆍ㎏?¹ㆍK?¹ (x = 0) to 1.02 Jㆍ㎏?¹ㆍK?¹ (x = 0.1), in a magnetic field change of 15 kOe. The measured value of TC was 185 K, 150 K and 145 K for x = 0, 0.05 and 0.1, respectively. The phase transition temperatures became wider as x increased. It indicates that the Mn-site substitution by Ni may be used to tailor the Curie temperature in La0.7Ca0.3Mn1-xNixO₃.

Magnetic and Magnetocaloric Properties of Perovskite Pr<SUB>0.5</SUB>Sr<SUB>0.5-x</SUB>Ba<SUB>x</SUB>MnO₃

Sihao Hua,Pengyue Zhang,Hangfu Yang,Suyin Zhang,Hongliang Ge 한국자기학회 2013 Journal of Magnetics Vol.18 No.4

This paper studies the effects of A-site substitution by barium on the magnetic and magnetocaloric properties of Pr0.5Sr0.5-xBaxMnO₃ (x = 0, 0.04, 0.08 and 0.1). The tetragonal crystal structures of the samples are confirmed by room temperature X-ray diffraction. The dependence of the Curie temperature (TC) and the magnetic entropy change (ΔSM) on the Ba doping content has been investigated. The samples of all doping contents undergo the second order phase transition. As the concentration of Ba increased, the maximum entropy change (|ΔSM|max) increased gradually, from 1.15 J kg<SUP>?1</SUP> K<SUP>?1</SUP> (x = 0) to 1.36 J kg<SUP>?1</SUP> K<SUP>?1</SUP> (x = 0.1), in a magnetic field change of 1.5 T. The measured value of TC is 265 K, 275 K, 260 K and 250 K for x = 0, 0.04, 0.08 and 0.1, respectively. If combining these samples for magnetic refrigeration, the temperature range of ~220 K and 290 K, where |ΔSM|max is stable at ~1.27 J kg<SUP>?1</SUP> K<SUP>?1</SUP> and RCP = 88.9 Jㆍg<SUP>?1</SUP> for ΔH = 1.5 T. Pr0.5Sr0.5-xBaxMnO₃ compounds, are expected to be suitable for magnetic-refrigeration application due to these magnetic properties.

Magnetic Microstructures and Corrosion Behaviors of Nd-Fe-B-Ti-C Alloy by Ga Doping

Qiong Wu,Pengyue Zhang,Hongliang Ge,Aru Yan,Dongyun Li 한국자기학회 2013 Journal of Magnetics Vol.18 No.3

The influences of Gallium doping on the magnetic microstructures and corrosion behaviors of Nd-Fe-B-Ti-C alloys are investigated. The cooling rate for obtaining fully amorphous structure is raised, and the glassforming ability is improved by the Ga addition. The High Resolution Transmission Electron Microscopy image shows that the α-Fe and Fe3B soft magnetic phases become granular surrounded by the Nd2Fe14B hard magnetic phase. The rms and (Δ?)rms value of Nd-Fe-B-Ti-C nanocomposite alloy thick ribbons in the typical topographic and magnetic force images detected by Magnetic Force Microscopy(MFM) decreases with 0.5 at% Ga addition. The corrosion resistances of Nd9Fe73B₁₂.6C ₁.₄Ti₄-xGax (x = 0, 0.5, 1) alloys are enhanced by the Ga addition. It can be attributed to the formation of more amorphous phases in the Ga doped samples.

Hydraulic and Mechanical Coupling Analysis of Rough Fracture Network under Normal Stress and Shear Stress

Tianjiao Yang,Shuhong Wang,Pengyu Wang,Ze Zhang 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.2

The hydraulic and mechanical coupling characteristics of fracture networks under normal stress and shear stress were studied in this paper. The hydraulic and mechanical coupling model of the fracture network comprehensively considers the normal stress, shear stress, seepage pressure and roughness characteristics. Based on the boundary conditions and reasonable assumptions, COMSOL Multiphysics software was used to develop the hydraulic and mechanical coupling finite element model of the fracture network with different intersection points under normal stress and shear stress, focusing on the study of the effect of normal stress and shear stress on the fracture permeability. The degree of permeability change caused by the normal stress and shear stress is different. The shear stress has a significant influence on the fracture permeability, and when the normal stress is low, the relationship between the fracture permeability and shear stress can be described by a linear relationship. Then, the influence of the number of intersection points in the fracture network on the average fracture width, average water pressure, average seepage velocity and seepage passage of the fractured rock mass was analyzed. The number of intersections in the fracture network has little influence on the average fracture gap width and average water pressure but has a great influence on the flow velocity. The analysis in this paper is very helpful to understand the seepage characteristics in rough fractures under normal stress and shear stress.

The effect of Ga-doping on the structure and magnetic properties of MnBi

Yang Yang,Qiong Wu,Pengyue Zhang,Hongliang Ge,Jong-Woo Kim,Chul-Jin Choi 한국자기학회 2017 한국자기학회 학술연구발표회 논문개요집 Vol.2017 No.11