锂离子电池正极材料Li_3V_(2-2x)/3Mg_x(PO_4)_3/C的制备及电性能研究

本文主要通过水热法制备了锂离子电池正极材料Li3V2-2x/3Mgx(PO4)3/C,并研究了掺杂金属元素Mg对Li3V2(PO4)3晶体结构和电性能的影响。结果表明,当Mg含量x=0.45(质量分数,下同)时,且在温度为750℃焙烧6 h的条件下所制备的样品具有较好的晶体结构、微观形貌和电化学性能。镁掺杂量在一定范围内变化不会影响磷酸钒锂本身的单斜结构。在3.0~4.8 V、0.1 C倍率下,Li3V1.70Mg0.45(PO4)3/C复合材料首次放电比容量高达154.4 mAh·g-1,首次库伦效率为94.32%,在不同倍率下循环25次之后的容量依然可以达到112.8 mAh·g-1。掺杂镁的样品与未掺杂的样品相比,容量和循环倍率性能均有了很大程度的提高。     

固溶体Er_(2-x)Ho_x(WO_4)_3的热膨胀性能研究

用固相化学反应法制取了Er2-xHox(WO4)3(x=0.0～0.4,1.2～2.0)系列固溶体,利用XRD实验及Rietveld结构精修分析研究了Er2-xHox(WO4)3系列固溶体的晶体结构和热膨胀性能,结果表明Er2-xHox(WO4)3(x=0.0～0.4,1.2～2.0)系列化合物沿着三个晶向是呈异性负热膨胀性能。     

镍电极掺杂[x(Y2O3)+y(Er2O3)]的MH/Ni电池性能研究

研究了在镍电极活性物质中掺杂一定量的[x(Y2O3) +y(Er2O3)](x+y=1,其中x=0,0.5,1.0)对MH/Ni电池的性能影响.利用不同环境温度(25℃～55℃)下恒流充放电、高温(65℃)放电态搁置等方法测试了电池的性能.结果表明,常温下镍电极掺杂[x(Y2O3)+y(Er2O3)]的MH/Ni电池的放电容量和放电平台比未掺杂的电池稍低,但随温度的升高,它的放电容量和高温储存性能等均明显优于未掺杂的电池,镍电极掺杂[x(Y2O3) +y(Er2O3)]提高了MH/Ni电池的高温性能.常温下,电池以1C,100%DOD循环200周后,镍电极掺杂[x(Y2O3) +y(Er2O3)]的MH/Ni电池容量损失较少,利用X射线衍射(XRD)、交流内阻分析结果表明,镍电极活性物质循环后的相结构差别不大,但掺杂的电池循环前后内阻变化较小.综合实验结果,当x=0.5时,电池的性能最佳.     

尖晶石结构ZnAl_(2-x)Fe_(x)O_(4)纳米颗粒微观结构与光学性能北大核心

采用水热法和热处理工艺成功制备了不同Fe含量的掺杂尖晶石结构ZnAl_(2-x)Fe_(x)O_(4)纳米颗粒(x=0、0.025、0.05和0.10),研究了Fe掺杂比例对样品微观结构和光学性能的影响。X射线衍射(XRD)表明ZnAl_(2-x)Fe_(x)O_(4)纳米颗粒具有立方尖晶石结构,随着掺杂浓度的增加,平均晶粒尺寸减小,晶格参数增大。场发射透射电子显微镜(FE-TEM)表明样品形貌呈规则球形颗粒,颗粒大小均匀。X射线光电子能谱(XPS)表明掺杂的Fe离子替代Al^(3+)进入ZnAl_(2)O_(4)晶格,主要占据ZnAl_(2-x)Fe_(x)O_(4)样品的八面体位置。紫外可见光谱(UV-vis)表明样品的带隙随着Fe离子浓度的增加而减小,并发生红移。光致发光光谱(PL)发现样品表现出猝灭现象。傅里叶红外光谱(FT-IR)表明Fe^(3+)取代Al^(3+)没有改变ZnAl_(2)O_(4)尖晶石的结构。CIE色度图显示所有样品均呈黄绿色区域发射。     

La_(0.5)Sm_(0.2)Sr_(0.3)MnO_3/Ag_x二相复合体的结构及磁电阻

用固相反应法制备La0.5Sm0.2Sr0.3MnO3/(Ag2O)x/2(x=0.00,0.04,0.08,0.25,0.30)样品,通过X射线衍射谱线(XRD),扫描电子显微镜(SEM)照片及SEM能谱(EDS),ρ-T曲线,研究样品的输运行为及磁电阻效应。结果表明:少量掺杂时Ag全部挥发。掺杂量较多时,挥发后多余的Ag主要以金属态包覆在母体颗粒的表面,使体系形成两相复合体。掺Ag为30%摩尔比时,样品的电阻率较低掺杂样品的电阻率降低一个数量级,在300K、0.5T磁场下,磁电阻明显增强,达到9.4%,这与颗粒母体界面结构的改善有关,也与材料电阻率的降低有关。     

共沉淀法制备白光LED用CaMO_4:Eu~(3+),Bi~(3+)(M=Mo,W)红色荧光粉及其发光性能的研究

采用共沉淀法制备了Ca_(0.93-x)(Mo_(0.9)W_(0.1))O_4∶Eu_(0.07)~(3+),Bi_x~(3+)(0≤x≤0.05)系列样品,通过XRD、SEM及荧光光谱仪对粉体的晶体结构、形貌及荧光性能进行测试和表征。结果表明,Bi~(3+)、Eu~(3+)及WO_4~(2-)的掺杂没有改变CaMoO_4原有的四方晶系体心结构,且样品粒径分布较均匀,无明显团聚现象。随着Bi~(3+)的掺杂,Ca_(0.93-x)(Mo_(0.9)W_(0.1))O_4∶Eu_(0.07)~(3+),Bi_x~(3+)样品的激发光谱带边会发生红移,且激发强度呈现先增强后减弱的趋势,其发射光谱也具有相应的规律,Bi~(3+)的最佳掺杂浓度为x=0.02 mol,在395 nm激发下,样品的发光强度提升至134%;较之商用红色荧光粉Y_2O_2S∶Eu~(3+),Ca_(0.91)(Mo_(0.9)W_(0.1))O_4∶Eu_(0.07)~(3+),Bi_(0.02)~(3+)样品显现出更好的色纯度和发光强度,适合于近紫外LED用红色荧光粉。     

钙钛矿化合物SrFe_(1-x)Cu_xO_(3-δ)(0≤x≤0.3)的制备及磁性

采用溶胶-凝胶法制备钙钛矿结构化合物Sr Fe1-xCuxO3-δ(0≤x≤0.3)的多晶样品,通过X射线衍射(XRD)结合Rietveld结构精修方法研究该化合物的晶体结构,并使用物性综合测量系统(PPMS)研究其磁性能。精修结果表明掺Cu可使样品发生结构转变,x=0的样品为I4/mmm点群的正方结构,而x=0.1,0.2,0.3的样品均为Pm 3 m点群的立方结构,晶格常数随Cu含量的增加而减小。磁性测量的结果表明Cu含量越高,造成铁磁和反铁磁相互作用的竞争越激烈,形成自旋玻璃态;x=0.1,0.2,0.3的样品转变温度低于x=0的样品,但随Cu含量增加,x=0.1,0.2,0.3的样品转变温度逐渐升高;随Cu含量增加,Fe/Cu位的有效磁矩减小。     

V掺杂对La_(0.45)Ca_(0.55)MnO_3电荷有序态及输运性质影响的研究

采用标准固相反应法制备了La0.45Ca0.55Mn1-xVxO3(x=0.00,0.06,0.10,0.12)多晶样品。通过XRD、ρ-T曲线、M-T曲线和ρ-T拟合曲线,研究了Mn位V5+离子掺杂对体系的电荷有序相及输运性质的影响。实验结果表明:随着V5+离子的掺杂量的增加,电荷有序相(CO)逐渐削弱,当x=0.10时,CO相基本融化但还有部分残留,当x=0.12时CO相完全融化;对低掺杂(x=0.00,0.06)样品,表现出复杂磁相:随温度降低,发生顺磁-电荷有序-反铁磁相变,40 K附近,在反铁磁背景下产生再入型自旋玻璃态;随掺杂量增加,体系的电阻率逐渐减小,当掺杂量x≥0.10时,样品发生金属-绝缘体相变,其相变温度随着掺杂量的增加而向高温移动。对于金属型导电机制满足自旋波散射和电-磁子之间的散射,而绝缘体导电机制有两种情况:x≤0.10的样品满足变程跃迁模型ρ=ρ0exp(T0/T)1/4,x=0.12的样品则满足小极化子绝热最近邻跃迁模型ρ=ATexp(Eα/κBT),通过掺杂实现了从变程跃迁到绝热小极化子最近邻跃迁。     

溶胶-凝胶法制备Y_2Zr_2O_7:Tm~(3+)及其发光性能研究

以柠檬酸为络合剂采用溶胶-凝胶法制备了(Y1-xTmx)2Zr2O7(x=0.005,0.01,0.03,0.05)荧光粉.采用X-射线衍射分析仪(XRD)、扫描电子显微镜(SEM)和荧光光谱仪分别检测了Y2Zr2O7∶Tm3+的晶体结构、颗粒形貌以及样品的荧光光谱.XRD图谱表明,所得到的产物Y2Zr2O7∶Tm3+为单一相的萤石结构,而且Tm3+的掺杂并没有改变其晶体结构.荧光光谱的测试表明,在359 nm波长的紫外光激发下,1000℃下烧结的(Y1-xTmx)2Zr2O7(x=0.01)样品的发光性能最好,发射峰对应于Tm3+的1D2→3F4跃迁和1G4→3H6跃迁,并对其发光机理进行了探讨.样品在454nm处的发光强度随Tm3+离子掺杂浓度的增加先升高后降低,即出现了浓度猝灭的现象,当Tm3+掺杂浓度摩尔百分比为1%时,样品的发光强度达到最大.     

钙位掺杂对钴酸钙阴极性能影响的研究

固相法制备了钴酸钙阴极材料,考察在钙位用异价元素取代掺杂对材料性能的影响.结果 表明:少量异价元素取代,材料的物相结构保持不变;Sm掺杂材料Ca3-xSmxCo4O9(x=0.2)和Na掺杂材料Ca3-xNaxCo4O9(x=0.2)相比于未掺杂材料具有较低的极化电阻;Sm掺杂材料电导率比未掺杂阴极材料、Na掺杂材料都...     

La~(3+)掺杂WO_3的制备及其光催化分解水活性的研究

研究了不同掺杂量和焙烧温度对La3+掺杂WO3催化材料催化分解水析氧活性的影响,通过XRD检测表征了La3+掺杂WO3的相组成与掺杂量的关系。实验结果表明,400℃条件下制备的0.05%La3+/WO3催化剂的催化活性最高,与未掺杂WO3相比,其光催化析氧速率增加1.44倍。微量La3+的掺杂能够有效提高WO3的光催化活性。La3+的掺杂可以抑制WO3由单斜晶型向六方晶型的转变。     

三氧化钨催化氧化环己醇制环己酮

无需酸性配体、相转移剂,以30%H2O2为氧源,甲醇为溶剂,单独使用三氧化钨催化氧化环己醇制环己酮,可达到较高产率。当三氧化钨用量为1 mmol,甲醇5 mL,(WO3)∶(环己醇)∶(H2O2)的摩尔比为1∶100∶150时,温度90℃,反应3 h,环己酮的产率达88.0%。WO3催化剂重复使用5次,环己酮的产率仍可达80%以上。并用FTIR分析证明了三氧化钨催化氧化环己醇制环己酮反应过程中催化剂的结构稳定性和重复使用性。     

Effects of Samarium Doping on Optical Properties of Zn0.9(Co1-xSmx)0.1O Diluted Magnetic Semiconductor

Transparent ZnO and Zn0.9(Co1-xSmx)0.1O (x=0.0, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0) films were prepared by sol-gel method. For the prepared Zn0.9(Co1-xSmx)0.1O systems, the influences of dopant concentration of Sm on the structural and optical properties were investigated. Three additional absorption peaks around 570, 620, and 660 nm wavelengths were observed in low Sm content films, which is attributed to the d-d transitions of Co2 ions in tetrahedral crystalline. The redshift of band gap in doped samples was discussed in detail.     

配合物NH4[Ln（H2O）9][（VⅣO）2（μ2-O）（nta）2]（Ln=Sm,Y）的合成及钐配合物的晶体结构

在水溶液中合成了两个钒-稀土配合物NH4[Ln(H2O)9][(VIVO)2(μ2-O)(nta)2](Ln=Sm,Y),其中钒-钐配合物为单晶体,钒-钇配合物为多晶态粉末。单晶X-射线衍射分析表明,钒-钐配合物属单斜晶系,C2/c空间群,晶胞参数a=2.336(4),b=1.0907(9),c=1.0823(10)nm,β=93.21(2)°,V=2.753(6)nm3,Z=4。配合物包含了一个二核的钒阴离子[(VIVO)2(μ2-O)(nta)2]4-(H3nta=氨三乙酸)和一个九配位的钐阳离子[Sm(H2O)9]3+,两者通过氢键连接成三维超分子结构。     

Preparation and electrochemical properties of Y-doped Li3V2（PO4）3 cathode materials for lithium batteries

Y-doped Li3V2(PO4)3 cathode materials were prepared by a carbothermal reduction(CTR) process. The properties of the Y-doped Li3V2(PO4)3 were investigated by X-ray diffraction (XRD) and electrochemical measurements. XRD studies showed that the Y-doped Li3V2(PO4)3 had the same monoclinic structure as the undoped Li3V2(PO4)3. The Y-doped Li3V2(PO4)3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra (EIS). The optimal doping content of Y was x=0.03 in Li3V2-xYx(PO4)3 system. The Y-doped Li3V2(PO4)3 samples showed a better cyclic ability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Y-doping. The improved electrochemical performances of the Y-doped Li3V2(PO4)3 cathode materials were attributed to the addition of Y3+ ion by stabilizing the monoclinic structure.     

Luminescence Properties of Sm^3＋ doped Bi2ZnB2O7

The phosphors of （Bi1- x Smx ） 2ZnB2O7 （ x = 0. 01, 0. 03, 0. 05, 0. 07, and 0. 09） were synthesized by conventional solid state reaction. The purity of all samples was checked by X-ray powder diffraction （XRD）. XRD analysis shows that all these compounds are of a single phase of Bi2ZnB2O7, indicating that the Bi^3＋ in Bi2ZnB2O7 can be partly replaced by the Sm^3＋ without the change of crystal structure. The excitation and emission spectra at room temperature show the typical 4f-4f transitions of Sm^3＋ . The dominant excitation line is around 404 nm due to ^6H5/2→^4K11/2 and the emission spectrum consists of a series of lines at 563, 599, 646, and 704 nm due to ^4G5/2→^6H5/2, ^6H7/2, ^6H9/2, and ^6H11/2, respectively. The optimal concentration of Sm^3＋ in Bi2ZnB2O7 is about 3mol% （relative to lmol Bi^3＋ ） and the critical distance Rc was calculated as 2.1 nm. The temperature dependence of the emission intensity of Bi1.94Sm0.06ZnB2O7 was examined in the temperature range between 100 and 450 K. The quenching temperature where the intensity has dropped to half of the initial intensity is 280 K. The lifetime for Sm^3＋ in Bi1.94Sm0.06ZnB2O7 is fitted as a value of 0.29 and 1.03 ms.     

Zn~（2＋）催化氟虫腈水解的产物及其结构表征

在溶剂热条件下,利用路易斯酸Zn2＋对氟虫腈（5-氨基-1-（2,6-二氯-4-三氟甲基苯基）-4-三氟甲基亚磺酰基吡唑-3-腈）进行原位水解反应,得到其结晶产物5-氨基-1-（2,6-二氯-4-三氟甲基苯基）-4-三氟甲基亚磺酰基吡唑-3-羧酸.对该化合物进行了元素分析、红外、紫外-可见光谱测定及X-射线单晶衍射等表征.晶体结构解析表明该化合物属单斜晶系,空间群为P2（1）/n,晶胞参数为：a=12.7457（8）,b=8.8244（6）,c=15.7322（11）,α=90°,β=100.2310（10）°,γ=90°,Z=4,V=1741.3（2）3,F（000）=856.化合物中存在的弱相互作用力分子间氢键将其形成一个稳定的三维层状结构.紫外-可见光谱分析表明该化合物在220 nm和281 nm处有最大吸收峰.     

Synthesis, Crystal Structure and Fluorescent Properties of a New One-Dimensional Polymer [Sm（ sal ） 4 （ phen）2 Na ] n

A growing attention has been paid to the investi gation of fluorescence enhancement of the lanthanidessince the lanthanides have low absorptivity and poorquantum yields. Fluorescence enhancement has gener ally been achieved through ligand sensitization in re cent years[1~4]. In emission process, an organic lig and is first excited by absorption of light, followed byenergy transfer from the ligand to the excited levels ofa lanthanide, which then emits. Moreover, the fluo rescence of th…     

Preparation and Structure of

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