H3BO3对化学共沉淀法制备Sr4Al14O25：Eu^2＋、Dy^3＋的影响

采用化学共沉淀法制备Sr4Al14O25:Eu^2 、Dy^3 长余辉发光粉体。研究了H3BO3的加入对粉体的相组成，晶体结构，发光性能与长余辉特性的影响。结果表明．加入的H3BO3大部分不进入晶格．作为助熔剂有利于Sr4Al14O25相的形成．一小部分H3BO3进入晶格中取代Al^3 离子并且对Sr4Al14O25:Eu^2 、Dy^3 长余辉发光粉体的发光性能与长余辉特性都有显著的提高．然而过量的H3BO3加入则会降低粉体的长余辉特性．本实验所获得H3BO3合适的添加量为0．7mol。     

H3BO3对燃烧法制备SrAl2O4:Eu2+、Dy3+、Pr3+发光性能的影响

以硝酸盐和尿素为基质,采用燃烧法在较低炉温(600～620℃)下制备了SrAl2O4:Eu2+、Dy3+、Pr3+长余辉发光粉体.研究了H3BO3的加入对粉体的相组成、晶体结构、发光性能与长余辉特性的影响.通过对材料的XRD、激发和发射光谱、余辉衰减以及微观形貌分析.结果表明,H3BO3作为一种助溶剂,当其掺杂摩尔百分...     

长余辉发光材料Sr4Al14O25:Eu2+,Dy3+的制备

采用化学沉淀法制备了Sr4Al14O25:Eu2 ,Dy3 蓝绿色长余辉发光粉.通过XRD分析表明:经1100℃和1200℃煅烧制得的发光粉均为单一的Sr4Al14O25晶相,不含其它任何杂相,同时研究了硼酸的加入量对发光粉的物相变化和发射光谱的影响,通过场发射扫描电子显微镜分析了粉体的形貌和粒径.     

长余辉夜光材料Sr4Al14O25:（Eu,Dy）的制备及性能优化（英文）

利用固相反应法制备了Sr4Al14O25:(Eu2+,Dy3+)长余辉夜光材料,并研究了H3BO3含量、固相反应温度和Eu含量对Sr4Al14O25:(Eu2+,Dy3+)长余辉夜光材料性能的影响.实验结果表明,H3BO3含量对蓝绿发射的Sr4Al14O25相的形成至关重要.在固相反应温度为1400℃,H3BO3含量为10at%,Eu/Al原子比为0.03的优化条件下,获得了发射波长为490 nm,余辉时间长达24 h以上的Sr4Al14O25夜光粉.发光强度与Eu含量的关系证明,Sr4Al14O25相的蓝绿发射过程主要受电子从深陷阱到Eu2+能级的转移速度的控制.     

纳米Sr2MgSi2O7:Eu2+,Dy3+的长余辉发光行为

使用溶胶-凝胶技术合成纳米尺度的Sr2MgSi2O7Eu2+,Dy3+长余辉发光材料,比较了该方法与固相法获得的长余辉粉体的光致发光行为和长余辉性能.溶胶-凝胶获得的纯相Sr2MgSi2O7Eu2+,Dy3+长余辉粉体是由纳米尺度的微晶形成的团聚颗粒,具有光致发光行为和长余辉发光特性.其发射峰位于465nm.而固相合成的粉体具有两个发射峰,分别位于404nm和459nm.产生这些差别的原因在于Eu2+在基质晶格中的不同配位情况.固相合成的粉体的余辉发光性能高于溶胶-凝胶粉体,其原因在于高温固相合成在基质内部产生了更高浓度的电子陷阱.     

煅烧温度对红色长余辉发光材料Sr_3Al_2O_6:Eu~(2+),Dy~(3+)性能的影响

采用溶胶凝胶法合成了Sr3Al2O6:Eu2+,Dy3+长余辉发光材料,利用X射线衍射仪(XRD)对材料的物相进行了分析,采用荧光分光光度计、照度计测定了样品的发光特性。XRD结果表明:随着煅烧温度的升高,SrCO3杂相的衍射峰越来越弱,Sr3Al2O6相的衍射峰越来越强,1200℃时发光基质为纯的Sr3Al2O6相,1250℃时出现新的SrAl2O4杂相。激发光谱和发射光谱结果表明:长余辉发光材料的激发峰位于473nm,发射峰位于612nm,归属于Eu2+的4f65d1→4f7特征发光。温度升至1250℃时,Eu2+的发射峰为612nm和520nm,后者归属于Eu2+在发光基质SrAl2O4中的发光。综合分析得制备Sr3Al2O6:Eu2+,Dy3+发光材料合适的煅烧温度为1200℃,在此温度下,材料具有较好的初始亮度和余辉时间。     

铝锶比对xSrO·yAl_2O_3:Eu~(2+),Dy~(3+)发光性能的影响

系统研究了Eu2+、Dy3+共激活的铝酸锶长余辉发光材料的发光特性与Al/Sr比例的关系,采用高温固相法合成了Al/Sr从1.8到2.7一系列样品,分别利用XRD、荧光分光光度计对材料的物相和发光特性进行了测试和分析,结果表明:基质的物相按SrAl2O4→Sr2Al6O11→Sr4Al14O25的顺序变化,样品的相组成呈明显的过渡性变化,导致样品的发光颜色随Al/Sr比例的增大,从黄绿光向短波长方向移动,先变成蓝光最终到达蓝绿光。     

不同结构稀土掺杂铝酸锶的合成与发光性能研究

采用燃烧法成功合成了稀土掺杂铝酸锶长余辉发光材料.XRD结果表明,当铝锶n(Al)∶n(Sr)=2时,发光基质中只存在SrAl2O4相结构.随着Al∶Sr比值的增大,出现新相Sr4Al14O25.当Al∶Sr比值增大到4时, SrAl12O19相开始形成.而Al∶Sr比值增大到12时,全部为SrAl12O19相.光致发光测量结果表明,发光样品SrAl2O4∶Eu2 ,Dy3 发射谱峰值位于519nm,而发光样品SrAl12O19∶Eu2 ,Dy3 的发射峰位于512nm.余辉检测结果表明,不同结构铝酸锶发光样品的衰减都是由初始的快衰减过程和其后的慢衰减过程组成,但是不同结构铝酸锶发光样品的初始亮度和发光衰减快慢不同.     

硼酸对蓝色铝酸锶长余辉材料的物相及发光特性的影响

采用高温固相法制备了xSrO·yAl2O3:Eu2+,Dy3++m%(摩尔分数)(H3BO3)(m=15,20,23,25,30,35)系列蓝色光致发光材料。X射线衍射(XRD)结果表明:m=15～20之间产品为SrAl2O4,Sr2Al6O11和Sr4Al14O25的混合物,m=23时产品主相为Sr2Al6O11,m=25～35之间产品主相为Sr4Al14O25。利用荧光分光光度计和亮度计研究了材料的发射光谱,衰减曲线,结果显示:随着硼酸量的增加,发射峰值先蓝移后红移,而余辉时间则逐渐变长。从而得到了制备蓝色铝酸锶发光材料Sr2Al6O11:Eu2+,Dy3+的最佳硼酸量,并且对硼酸在材料合成过程中的作用机理进行了探讨。     

电子束还原SrAl_2O_4:(Eu~(2+),Dy~(3+))长余辉材料的力致发光研究

通过高温烧结和电子束还原法制备了SrAl2O4:(Eu2+,Dy3+)长余辉发光材料,并利用球磨获得了SrAl2O4:(Eu2+,Dy3+)长余辉发光粉。通过把发光粉与环氧树脂混合制备了含有SrAl2O4:(Eu2+,Dy3+)长余辉发光粉的夜光胶,利用丝网印刷涂敷技术及热处理在石英玻璃上涂敷了厚度为1000 nm量级的SrAl2O4:(Eu2+,Dy3+)长余辉发光膜。通过小球下落冲击法和一套自制的基于一个雪崩二极管和皮安表的测试装置研究了这种长余辉发光膜的力致发光特性。研究发现,电子束还原法制备的SrAl2O4:(Eu2+,Dy3+)长余辉发光膜具有很好的力致发光特性,具有高达1.25的信背比和很高的信噪比。力致发光强度与小球下落前的初始高度即冲击发生前小球的动能成指数关系,光谱特性及衰减特性与长余辉发光相似。上述结果表明,力致发光是小球冲击能传递给电子并引起电子进入陷阱能级然后释放引起的。     

Photostriction of CH3NH3PbBr3 Perovskite Crystals

Organic–inorganic hybrid perovskite materials exhibit a variety of physical properties. Pronounced coupling between phonon, organic cations, and the inorganic framework suggest that these materials exhibit strong light–matter interactions. The photoinduced strain of CH₃NH₃PbBr₃ is investigated using high‐resolution and contactless in situ Raman spectroscopy. Under illumination, the material exhibits large blue shifts in its Raman spectra that indicate significant structural deformations (i.e., photostriction). From these shifts, the photostrictive coefficient of CH₃NH₃PbBr₃ is calculated as 2.08 × 10^?8 m² W^?1 at room temperature under visible light illumination. The significant photostriction of CH₃NH₃PbBr₃ is attributed to a combination of the photovoltaic effect and translational symmetry loss of the molecular configuration via strong translation–rotation coupling. Unlike CH₃NH₃PbI₃, it is noted that the photostriction of CH₃NH₃PbBr₃ is extremely stable, demonstrating no signs of optical decay for at least 30 d. These results suggest the potential of CH₃NH₃PbBr₃ for applications in next‐generation optical micro‐electromechanical devices.     

Constitution of the Ni3Cr-Ni3Al-Ni3W system

Isothermal sections of the Ni-Cr-Al-W system have been investigated at 75 at % Ni and temperatures of 1523 and 1273 K, by means of phase compositional analysis, X-ray diffraction and microscopical examination. The alloys studied lay in the range 2.5 to 10 at % Cr, 12.5 to 20 at% Al, 2.5 to 6.25 at % W, The phases formed were, and the bcc solid solution based on tungsten (designated ₂). The maximum extent of the region was found to be 3 at % each of chromium and tungsten. Preferential partitioning of tungsten to occurred. Study of an Ni-10Cr-12.5Al-2.5W alloy aged at 1273 and 1073 K, after quenching from 1573 K, showed that changes in and compositions and lattice parameters occur as a function of ageing time.     

(La2/3Ca1/3)(Mn(3-x)/3)Fex/3)O3体系磁电阻行为的研究

通过系统地测量（La_2/3Ca_1/3）（Mn_{（3-x）／3}Fe_x／3）O₃（x＝0、0.1、0．2、0．3的体系样品的电阻率-温度关系以及一定温度下磁电阻率与磁场的关系,发现随x的变化其磁电阻率峰和电阻率峰均发生位移,磁电阻率峰值增大,并伴生磁电阻率峰展宽效应．作者认为由于Fe的替代,引起体系中Mn³⁺／Mn⁴⁺比率及磁矩的变化,加之外场对磁有序结构的调制作用,从而影响了Mn³⁺－O^－Mn⁴⁺的双交换作用,最终导致磁电阻行为发生变化．     

PbZrO3-CdTiO3 solid solutions

The structural, nonlinear optical, and dielectric properties of (1-x)PbZrO₃ ·xtCdTiO₃ solid solutions were studied. The phase relations in the composition rangesx = 0–0.3 and 0.85-1.0 were established. The results suggest that the ferrielectric ordering in CdTiO₃ persists up to 730 K.     

Phase equilibria in the system LaMnO3 + δ-SrMnO3-LaFeO3-SrFeO3 − d

We have revealed the formation of a continuous series of orthorhombic LaMn_{1 ? y} Fe_yO₃ solid solutions (0<y<1); La_{1 ? x} Sr_xFeO₃ solid solutions in the composition range 0 < x ≤ 0.8, with an orthorhombic structure at 0 < x ≤ 0.6 and a cubic structure at 0.6 < x ≤ 0.8; and a tetragonal SrMn_{1 ? y} Fe_yO₃ phase in the range 0.6 ≤ y ≤ 1. The composition stability limits of the perovskite phase La_{1 ? x} Sr_xMn_{1 ? y} Fe_yO₃ have been determined, and the 1100°C isotherm of the La₂O₃-SrO-Mn₃O₄-Fe₂O₃ system in air has been constructed.     

Multicolor up-conversion emissions of Tm3+/Er3+/Yb3+ tri-doped YF3 phosphors

Tm3+/Er3+/Yb3+ tri-doped yttrium fluoride (YF3) phosphors were prepared by a facile hydrothermal method. X-ray topographic analysis found that the phosphors were crystallized products. Their sizes and morphologies were characterized by scanning electron microscopy (SEM, Hitachi S-4800), which indicated that most of the YF3 phosphors were hundreds of nanometers in size. Up-conversion (UC) spectra were recorded under 980-nm diode laser excitation at room temperature with a fluorescence spectrometer (Hitachi F-4500). Plenty of UC emissions of Tm3+ and Er3+ were observed from ultraviolet to red. For Tm3+ ions, a five-photon process (approximately 291 nm and approximately 347 nm), a four-photon process (approximately 362 nm and approximately 452 nm), and a three-photon process (approximately 475 nm) were identified in the UC spectra. The UC emissions from the Er3+ were: approximately 380 nm, approximately 408 nm, approximately 521 nm, approximately 537 nm, and approximately 652 nm. Therefore, cyan-white light can be observed by the naked eye at 980-nm excitation, even under low excitation power density. By comparing the UC spectra of the phosphors annealed at different temperatures, we found that the intensity of the UC luminescence increased as annealing temperature increased. Furthermore, the spectral dependencies on Tm3+ doped concentrations were studied. The energy transfer processes and fluorescence dynamics in the tri-doped system are currently being investigated.     

3 Cr3 Mo3 VNb 在热冲孔中的应用研究

高合金钢热冲孔冲头寿命关系到模具与产品成本、生产效率、自动化设备的使用,因此,应注重冲头的选材、材料制备与冲头制造工艺。 用 3 Cr3Mo3 VNb 作为高合金钢热冲孔冲头,为提高模具寿命,在材料制备上,优化了成分,采用电渣重熔冶炼,减少杂质,毛坯锻造两次,用大锻造比锻造,冲头热处理用真空炉,三次回火,热处理硬度取 HRC42 ~ 46 ,冲头表面处理采用镀铬工艺,开展了热冲孔工艺试验。 结果表明,用3 Cr3Mo3 VNb 可使冲孔冲头寿命平均达到 800 件以上。     

Processing and properties of Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3 ceramic relaxors

The shrinkage phenomenon during the reaction-sintering of PMN-PZT from low-temperature pre-reacted 3PbO + MgNb₂O₆ + PZT powder mixtures has been studied. It was assumed that the pre-reaction treatment leads to the formation of a pyrochlore phase containing very active MgO small particles, and that the strong shrinkage occurring up to 800 °C took place by the diffusion of Mg²⁺ cations into the pyrochlore phase particles, thus controlling the reaction-sintering shrinkage phenomenon. Above that temperature the densification was enhanced by a liquid-phase sintering process. The ceramics sintered at 1050 °C for 2 h showed 96% of the theoretical density, and the dielectric constant of such a sintered ceramic showed a maximum value of 17 000 at 1 kHz. It was also found that the dielectric constant decreased with increasing grain size. Although the role of PZT in enhancing the dielectric constant of otherwise low-purity PMN ceramics is not clear, the increase in K is assumed to be a solid-solution effect. The presence of impurities and the PbO stoichiometry could be influencing the not too high dielectric constant value of PMN-PZT ceramics.