红色荧光粉Ca_3Y_2Si_3O_(12):Eu~(3+)的制备及发光特性

采用高温固相法合成了红色荧光粉Ca_3Y_2Si_3O_(12):Eu~(3+)。研究了Eu~(3+)离子掺杂浓度、助熔剂及Gd~(3+)共掺杂对荧光粉发光特性的影响。XRD检测结果显示,荧光粉的主晶相为Ca_3Y_2Si_3O_(12),属单斜晶系。荧光光谱分析表明:硅酸盐荧光粉Ca_3Y_2Si_3O_(12):Eu~(3+)的发射光谱包含2个主峰,峰值分别位于590和614 nm,归属于Eu~(3+)离子从~5D_0→7~F_1和~7F_2的特征跃迁。用614 nm最强峰监测,得到激发光谱为一多峰宽带(200~500 nm)。改变Eu~(3+)离子掺杂浓度发现:随着掺杂量增加,荧光粉发光强度先增加后降低,最佳掺杂量为20 mol%;讨论了几种助熔剂的影响:NaCl、CaF_2作为助熔剂,对荧光粉的发光强度影响不大,H_3BO_3作为助熔剂降低荧光粉的发光强度,而NH_4F能显著提高荧光粉的发光强度;Gd~(3+)可以作为一种很好的共激活剂,敏化Eu~(3+)离子发光。     

Y_2O_3:Eu,Tb纳米荧光粉的制备与发光性能

以氧化钇、氧化铕、氧化铽、硝酸、柠檬酸等为原料,采用溶胶凝胶法制备Y_2O_3:Eu,Tb荧光粉体。通过X射线衍射分析(XRD)研究前驱体煅烧产物随温度变化的过程,用透射电镜(TEM)观察粉体的显微形貌,使用荧光光谱仪分析样品的激发和发射光谱。结果表明,1100℃煅烧3h可以得到结晶良好的纳米粉体,颗粒呈不规则形状,粒径分布在30~100nm之间。Y_(2(1-x))O_3:Tb_(2x)的粉体具有良好的发光性能,最佳掺杂浓度为1.0mol%。Y1.98-2xO_3:Eu0.02,Tb_(2x)粉体的发光同时表现出Eu~(3+)和Tb~(3+)的发光特征,两种离子之间存在能量传递,当Tb~(3+)离子用量大于1.0mol%时,出现浓度猝灭。     

离子交换法制备ZrO_2:Eu~(3+)纳米晶及其发光特性

以强碱性阴离子交换树脂为沉淀剂,采用离子交换法制备了ZrO_2:Eu~(3+)纳米晶,通过XRD,TEM,HRTEM和EDS等对晶体的结构、形貌及化学成分进行了表征,利用3D荧光光谱、激发光谱和发射光谱研究了Eu~(3+)在ZrO_2纳米晶中的发光性质。结果表明,焙烧温度在800℃以下所得的ZrO_2:Eu~(3+)纳米晶主要为四方结构,晶粒尺寸约为5—20 nm,随着焙烧温度的升高,样品的晶结构发生了细微变化,从900℃开始出现了少量单斜晶,由ZrO_2:Eu~(3+)的3D荧光光谱确定了其最佳监测波长和发射波长,在394 nm波长光的激发下观察到纳米ZrO_2中Eu~(3+)的590 nm(~5D_0→~7F_1)和606 nm(~5D_0→~7F_2)特征发射谱,随着相结构细微的变化,发射光谱的形状及强度均发生变化,说明ZrO_2:Eu~(3+)纳米晶的发光性质对其结构非常敏感。     

电子束交替蒸发制备蓄能发光膜及其性能研究

使用真空电子束交替蒸发的方法,在DMD-450型真空镀膜系统中,通过调整Sr_2CO_3、Al_2O_3、Eu_2O_3、Dy_2O_3独立原料靶材的蒸发时间和蒸发周期次数,制得蓝绿色(GF) 和蓝紫色(PF)发光膜.在以铝酸盐为基质的蓄能发光膜中,改变铝与锶的摩尔比,将出现Eu~(2+)的4f~65d~1→4f~7多颜色宽带跃迁和Eu~(3+)的~5D_0→~7F_J窄带跃迁.还原热处理条件对发光膜的发光性能有着重要影响:温度明显影响结晶状态;还原气氛中H_2量对发光膜的发光颜色影响较小,但会影响其相对发光强度.     

EDTA辅助水热法制备NaGd_(0.79-x)Y_xF_4:Yb~(3+),Er~(3+)固溶体上转换性能的研究（英文）

通过EDTA辅助的水热法合成了Yb~(3+)/Er~(3+)共掺NaGd0.79-xYxF4固溶体。XRD与TEM结果表明成功制备出直径约为20nm的纳米颗粒。通过光谱显示,系列样品在980nm激光激发下,观察到了位于540,656nm的发光,分别归因于Er~(3+)离子2H11/2,4S3/2→4I15/2与4F9/2→4I15/2跃迁,并且通过调节Y~(3+)/Gd~(3+)比例,显著增强了Er~(3+)的上转换发光强度。与此同时,Y~(3+)完全取代Gd~(3+)时,Er~(3+)上转换发光强度最强。EDX结果表明,Yb~(3+)在NaGdF4与NaYF4基质中具有不同的固溶度,并进一步讨论了可能的上转换发光机理。     

Cr~(3+),Nd~(3+):GSGG激光陶瓷原料制备及性能

采用化学共沉淀法制备Cr~(3+)与Nd~(3+)不同配比的Cr~(3+),Nd~(3+):GSGG激光陶瓷的前驱粉体,在不同的温度下对其进行煅烧得到多晶粉体原料,采用X射线衍射、热分析仪、场发射扫描电镜和红外荧光综合测试系统对煅烧后多晶原料的物相转变、微观形貌和发光性能进行研究,确定复合掺杂离子的最佳掺杂浓度。结果表明,前驱粉体在1000℃下煅烧可获得分布均匀的GSGG纳米粉体,Cr~(3+)与Nd~(3+)之间存在能量传递机制,能够增强发光。     

La~(3+)掺杂TiO_2粉体的化学沉淀法制备条件优化

采用化学沉淀法制备La~(3+)掺杂TiO_2粉体,并用正交实验方法对制备工艺进行优化,通过SEM、XRD、XPS和UV-Vis对TiO_2粉体的形貌、结构、光吸收性能进行了表征。结果表明:煅烧温度和La~(3+)掺杂量对TiO_2粉体光吸收性能具有显著影响;不同煅烧温度得到的La~(3+)掺杂TiO_2均以锐钛矿结构为主;升高煅烧温度可以增强La~(3+)掺杂TiO_2在紫外光波段的吸光强度;La~(3+)掺杂可以改善TiO_2粉体的团聚,减小TiO_2的禁带宽度,同时导致TiO_2表面吸附一定数量的羟基。最优的制备条件为:煅烧温度800℃,La~(3+)掺杂量0.6%(摩尔分数),反应温度为90℃,反应液pH值为8,此条件下获得的TiO_2粉体可见光性能最优。     

(Sr_(1-x)Me_x)_(1.95)SiO_4:0.05Eu荧光粉光谱调控机制

采用高温固相法制备(Sr_(1-x)Me_x)_(1.95)SiO_4:0.05Eu系列荧光粉,研究不同大(Ba~(2+))、小(Mg~(2+))半径离子基体固溶对其物相、发光中心配位结构、Eu离子价态的影响,探究其光谱精细调控机制。结果表明,Sr_2SiO_4粉末中随着温度升高α-Sr_2SiO_4相增加、β-Sr_2SiO_4相减少;Mg~(2+)(小半径离子)掺杂可以提高α-Sr_2SiO_4相稳定性,但容易出现Mg_2SiO_4,粉末中始终为混合物;Ba~(2+)(大半径离子)掺杂可以提高α-Sr_2SiO_4相稳定性,粉体发生β-Sr_2SiO_4+α-Sr_2SiO_4→α-Sr_2SiO_4-α-Sr_2SiO_4+Ba_2SiO_4→Ba_2SiO_4转变,且随β-Sr_2SiO_4、α-Sr_2SiO_4、Ba_2SiO_4的顺序其Si-O-Me(Ⅰ)-O-Me(Ⅱ)链逐渐由锯齿状变为平直状、Me-O键长拉长。Eu离子激活的β-Sr_2SiO_4、α-Sr_2SiO_4、Ba_2SiO_4粉体在254 nm (365 nm)激发下有明亮的绿色荧光发射(且依序强度增强、光谱整体略微蓝移)和微弱的红光发射;当光学基体发生β-Sr_2SiO_4→α-Sr_2SiO_4转变时,发射光谱中Eu~(2+)(Ⅰ)蓝移Eu~(2+)(Ⅱ)红移(Si-O-Sr(Ⅰ)-O-Sr(Ⅱ)由锯齿形链成为平链,且Sr-O键拉长),发生α-Sr_2SiO_4→Ba_2SiO4转变则Eu~(2+)(Ⅰ)、Eu~(2+)(Ⅱ)均发生蓝移(仅发生Me-O键拉长);3种粉体热释光谱中均存在Eu~(2+)和Eu~(3+)缺陷能级,且Eu~(2+)缺陷浓度更高。Eu 3d的精细X射线光电子谱表明随着β-Sr_2SiO_4→α-Sr_2SiO_4→Ba_2SiO_4转变其Eu离子以Eu~(2+)存在的可能性增大,对应的电子顺磁共振也证实这一结果。由此可见,采用Ba~(2+)离子固溶掺杂Sr_2SiO_4,可在一定浓度范围得到单相粉末,实现光学基体的β-Sr_2SiO_4→αSr_2SiO_4→Ba_2SiO_4相变,调控Si-O-Me(Ⅰ)-O-Me(Ⅱ)链型及Me-O键长,调节Eu离子价态和配位场,进而实现其绿色荧光粉荧光强度、发射波段精确调控。     

共沉淀法制备Eu~(3+)掺杂La_3PO_7荧光材料及其性能

采用共沉淀法合成Eu~(3+)掺杂La_3PO_7荧光材料,利用X射线衍射(XRD)、扫描电镜(SEM)、傅里叶红外光谱(FT-IR)和荧光光谱等对合成产物的物相结构和光学性能进行研究,并对合成体系的p H值、Eu~(3+)掺杂量的影响进行分析。结果表明:采用共沉淀法可制备单一相单斜晶系的La_3PO_7:Eu~(3+)晶体。所制备La_3PO_7:Eu~(3+)样品可被280 nm波长紫外光有效激发,在617nm处发射出属于Eu~(3+)的5D0-7F2跃迁的强烈红色光。当Eu~(3+)掺杂量高于4%时(摩尔分数)观察到浓度淬灭现象,其浓度猝灭机理为离子间交换相互作用。     

Gd~(3+)/Ga~(3+)共掺杂石榴石型Yb_3Al_5O_(12)材料的制备及热物理性能

采用柠檬酸溶胶-凝胶法制备了Gd~(3+)/Ga~(3+)双掺杂的石榴石型Yb_(3-x)Gd_xAl_(5-x)Ga_xO_(12)固溶体陶瓷材料(x=0,0.1,0.2,0.3,0.4,0.5;YGAGO)。结果表明:Gd~(3+)/Ga~(3+)共掺杂的YGAGO保持了石榴石相结构;随着Gd~(3+)/Ga~(3+)掺杂量的增加,固溶体样品的衍射峰位整体向低角度偏移;SEM形貌表明Yb_3Al_5O_(12)材料的微观形貌由纳米级晶粒和高密度晶界构成;大离子Gd~(3+)与Ga~(3+)分别对Yb_3Al_5O_(12)晶体结构中Yb~(3+)与Al~(3+)晶格位的取代,不仅因引入的点缺陷明显降低了材料的热导率,同时还造成石榴石型Yb_3Al_5O_(12)晶体结构的松弛,利于热膨胀系数的提高。随着Gd~(3+)/Ga~(3+)掺杂量的增加,晶体中点缺陷浓度不断升高,声子平均自由程不断减小,使得YGAGO的热导率在x=0.5时达到最低值(λ=1.67W/(m·K),T=1273 K),热膨胀系数达到最高值(α_1=11.71×10~(-6)K~(-1),T=1273 K)。     

Structural, mechanical and corrosion properties of TiOxNy/ZrOxNy multilayer coatings

Results on the deposition and characterization of TiO_xN_y/ZrO_xN_y multilayers, with bilayer periods of 20 and 400 nm, are presented. The coatings were deposited on TiNiNb alloy substrates by the pulsed magnetron sputtering method. The elemental composition, hardness, adhesion and corrosion resistance of the coatings were analyzed.As resulted from the XPS analysis, the individual layers consisted of a mixture of titanium or zirconium oxynitrides and corresponding oxides. X-ray analysis revealed that the coatings were amorphous. Only slight differences between the microhardness and adhesion values of the coatings with small and large bilayer period Λ were found. The experiments also showed that the multilayered coatings improved the corrosion resistance of the uncoated alloy and reduced the amount of ion release in artificial body fluids.     

MOCVD growth and characterizations of BxAl1−xAs and BxAl1−x−yInyAs alloys

Zinc-blende B_xAl_1−xAs and B_xAl_1−x−yIn_yAs alloys have been grown on exactly oriented (0 0 1)GaAs substrates by low pressure metalorganic chemical vapor deposition (LP-MOCVD). The influence of susceptor coating, growth temperature and gas-phase boron mole fraction on boron incorporation into AlAs has been comprehensively investigated. It has been found that boron incorporation into AlAs could be enhanced and the optimal growth temperature range of B_xAl_1−xAs alloys changed from 580 °C to 610 °C when SiC-coated graphite susceptors were replaced by the non-coated ones. In this study, the maximum boron composition x of 2.8% was achieved for the pseudomorphically strained B_xAl_1−xAs alloys. AFM measurements show that RMS roughness of B_xAl_1−xAs alloys increased sharply with the increase of gas-phase boron mole fraction. Raman spectra of B_xAl_1−xAs alloys show a linear increase of the BAs shift with boron composition x. Based on BAlAs deposition, bulk B_xAl_1−x−yIn_yAs (x = 1.9%) quaternary alloy was grown lattice-matched to GaAs successfully. Moreover, 10-period BAlAs/GaAs and BAlInAs/GaAs MQW heterostructures were also demonstrated.     

生物医用NiTi形状记忆合金腐蚀研究进展

镍钛形状记忆合金(NiTi-SMA)具有较好的耐腐蚀和机械性能,在口腔和临床医学中有着大量而广泛的应用。NiTi-SMA腐蚀后释放Ni²⁺会引发细胞毒性和过敏反应,进一步提高NiTi-SMA的耐蚀性是目前生物医学材料领域发展的核心之一。本文对近年来国内外有关口腔医学和临床医学中常用NiTi-SMA的腐蚀研究现状进行了总结,同时也对NiTi-SMA增材制造及表面改性技术进行了评述,以期为开发高性能抗腐蚀生物医用NiTi-SMA提供一定的指导意义。     

Li掺杂Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li(1/7-x))O3高熵陶瓷的制备及介电性能研究

近年来,在高熵合金基础上发展起来的高熵陶瓷逐渐引起了研究者的广泛关注,其出现为开发高性能的无机非金属材料提供了新的设计思路。本文采用固相法制备了BaMO3基钙钛矿型高熵陶瓷Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li(1/7-x))O3 (x = 0, 2.3%, 5.3%, 8.3%, 11.3%),并研究了Li含量对高熵陶瓷物相结构、微观形貌及介电性能的影响。结果表明,Li含量对陶瓷结构的影响不大,陶瓷均保持立方钙钛矿结构,且无杂相产生;陶瓷的晶粒尺寸相对较均匀。当x = 0时,即B位七元等摩尔比Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li1/7)O3高熵陶瓷,其介电常数达到了最大值2920 (@100 Hz),相较于已报道的不掺Li的六元高熵钙钛矿陶瓷Ba(Ti1/6Sn1/6Zr1/6Hf1/6Nb1/6Ga1/6)O3提升了近50倍。     

Hydrothermal synthesis of superconductors Ba1−xKxBiO3 and double perovskites Ba1−xKxBi1−yNayO3

Superconductors Ba_1−xK_xBiO₃ and body-centered double perovskites Ba_1−xK_xBi_1−yNa_yO₃ have been selectively synthesized by a facile hydrothermal route. The appropriate ratio and adding sequence of initial reagents, alkalinity, reaction temperature and time are the critical factors that influence the crystal growth of the compounds. The purity and homogeneity of the crystals were detected by the ICP, SEM, EDX and TEM studies. Magnetic measurements show that the superconducting transition temperatures T_C of Ba_1−xK_xBiO₃ decrease from 22 K (for x = 0.35) to 8 K (for x = 0.55) with increasing the K doping level.     

Magnetic phase diagrams of the TbRh2−xPdxPdxSi2 and TbRu2−xPdxSi2 systems

The a.c. susceptibility and high field magnetization on TbRh_2−xPd_xPd_xSi₂ and TbRu_2−xPd_xSi₂ compounds were investigated up to 140 kOe. The (T,x) magnetic phase diagrams were determined. For both systems, an increase in the Pd content causes a decrease in the Néel temperature and changes the magnetization curves.     

High strength and good ductility of casting Al-Cu alloy modified by PrxOy and LaxOy

A modified Al-Cu alloy with high tensile strength and ductility of about 574.0 MPa and 10.4%, respectively, was obtained by adding multiple rare earth oxides (Pr_xO_y and La_xO_y) as modifier. Compared with the unmodified Al-Cu alloy, the tensile strength and ductility of the modified sample were increased by 24.3% and 42.5%, respectively. The improvement both in the strength and ductility may attribute to the finer crystal grains and dendrites, more homogeneously distributed θ′ phase precipitates and the intermetallic compounds formed at the crystal grain boundaries as well as in the space of the dendrites.     

Si3N4/Ti/Cu/Ni/Cu/Ti/Si3N4二次部分瞬间液相连接强度

采用Ti/Cu／Ni中间层对Si3N4陶瓷进行二次部分瞬间液相(PTLP)连接，研究连接工艺参数对Si3N4／Ti/Cu／Ni连接强度的影响，同时研究了连接强度随试验温度的变化规律。结果表明，在该试验条件下，室温连接强度随着二次连接温度的提高和二次保温时间的延长而提高，改变连接工艺参数对Si3N4／Ti/Cu／Ni二次PTLP连接界面反应层厚度无明显影响；连接强度在试验温度400℃时达到最大，随后随试验温度升高，连接强度降低，但在800℃前，其高温强度具有很好的稳定性。     

Thermoelectric properties of Sn1−x−yTiySbxO2 ceramics

Thermoelectric properties of Sn_1−x−yTi_y Sb_xO₂ ceramics were investigated in detail. The addition of Sb into SnO₂ matrix increased the electric conductivity, σ. The increase in the σ value should be caused by the increase in the carrier concentration. The Seebeck coefficients of all the samples were negative, which means that these samples have n-type conduction. The samples of this study have porous structure. The maximum Z value of all the samples measured in this study was 2.4 × 10⁻⁵ K⁻¹.     

Power factor of La1−xSrxFeO3 and LaFe1−yNiyO3

The electrical conductivity (σ), Seebeck coefficient (S), and power factor (σS²) of perovskite-type LaFeO₃, La_1−xSr_xFeO₃ [0.1 ≤ x ≤ 0.4] and LaFe_1−yNi_yO₃ [0.1 ≤ y ≤ 0.6] were investigated in the temperature range of 300–1100 K to explore their possibility as thermoelectric materials. The electrical conductivity of LaFeO₃ showed semiconducting behavior, and its Seebeck coefficient changed from positive to negative around 650 K with increasing temperature. The electrical conductivity of LaFeO₃ increased with the substitutions of Sr and Ni atoms, while its Seebeck coefficient decreased. The Seebeck coefficient of La_1−xSr_xFeO₃ was positive, whereas that of LaFe_1−yNi_yO₃ changed from positive to negative with increasing Ni content. The substitutions of Sr and Ni were effective in increasing the power factor of LaFeO₃; 0.0053 × 10⁻⁴ Wm⁻¹ K⁻² for LaFeO₃ (1050 K), 1.1 × 10⁻⁴ Wm⁻¹ K⁻² for La_1−xSr_xFeO₃ (x = 0.1 at 1100 K) and 0.63 × 10⁻⁴ Wm⁻¹ K⁻² for LaFe_1−yNi_yO₃ (y = 0.1 at 1100 K).