Surface modification of an up-conversion luminescence material by overcoating with SiO_2 and its characterization

The surface of an up-conversion luminescence material was modified by overcoating with SiOa, which was synthesized from a hydrolysis progress of telraethoxysilane （TEOS） in alkalescent condition. By analyzing the hydrolyzed mechanism of TEOS, it was found that there was not only physical adsorption but also chemical bonding between the up-conversion material and SiO2. At the same time, some adsorption bands at 1100, 475, 950, and 3500 cm^-1 were found by FI-IR, which were the characteristic bands of Si-OH and Si-O-Si. By analyzing the surface elements of the coated material by XPS, it was found that its surface only included Si, O, and C elements, and not F and Y. In the picture of XRD, there was no additional peak after surface modification, suggesting that the silica shell was amorphous. The small peak at 20 = 23° in the X-ray diffraction pattern of the coated material was caused by the amorphous SiO2 shell, and the TEM image also proved that the surface of the material was successfully modified by overcoating with SiO2. The amount of hydroxyls was then increased on the surface of the material, which made it easy to connect with other active groups.

Surface modification of up-conversion luminescence material Na[Y_(0.57)Yb_(0.39)Er_(0.04)]F_4 with hydrosulfide group

A new method was reported for surface modification of an up-conversion luminescence material with hydrosulfide group. The factors that may influence the surface modification,such as reaction time,amount of catalyzer and modifier,and reaction solvent,were investigated. The optimal conditions were that the reaction time,the quantity of the basic catalyzer,the quantity of modifier and the volume of reaction solvent were 40 min,1.0,1.0,and 40 mL,respectively. The results indicated that hydrosulfide group content modified on the surface of up-conversion luminescence material reached to 0.1430 mmol/g,and this modified up-conversion luminescence material could be widely used in the study of structure of protein and the property of microenvironment.

Comparison study of two aldehyde group finishing agents in surface modification of up-conversion luminescence materials

Surface modification of up-conversion luminescence materials （Na[Y0.57Yb0.39Er0.04]F4 modified by amino groups） by grafting and modifying with aldehyde groups was studied by means of Fourier transform infrared spectroscopy （FTIR）, scanning electron microscopy （SEM）, thermogravimetric analysis （TGA）, and emission spectrum （EM）. The surface modification effect was compared using two different finishhag agents, p-phthalaldehyde and glutaraldehyde. It was found that the surface of up-conversion luminescence materials could be modified by aldehyde groups of the two finishing agents, the systematic dispersibility and the thermostability of the up-conversion luminescence material modified by p-phthalaldehyde were better than those of the material modified by glutaraldehyde, and the luminous intensity of the material modified by p-phthalaldehyde was increased. The AI （the ratio of the suspended segmental quality in the specimen to the total mass of the specimen） of the material modified by p-phthalaldehyde was higher than that of the material modified by glutaraldehyde. It is obviously seen that the embellishment effect of p-phthalaldehyde as a finishing agent was better than that of glutaraldehyde. In addition, the reasons why p-phthalaldehyde is a good finishing agent are also explained.

Luminescence Centers in BaFCl:Ce^(3+) and BaFCl:Gd^(3+) Crystals

Introduction In BaFCl crystal which is of PbFCl type structure in tetragonal system, Ba;ions situate at sites of C;point symmetry, while F;and Cl;ions occupy sites of D;and C;symmetry, respectively. The rare earth ions RE;doped in BaFCl should randomly replace the sites of Ba;ions, and their extra positive charges may be compensated by

The Role of Radiative Surface Modes and Longitudinal Excitons in the Formation of Exciton-Polariton Luminescence Spectra of CdS-Type Crystals

The low-temperature (T = 2 K) exciton-polariton luminescence (EPL) spectra in the vicinity of the exciton-resonance frequency An=1 for CdS-type crystals have been theoretically and experimentally investigated with allowance for the mechanical exciton decay . The results of the numerical calculations of the partial and interference contributions of the bulk and radiative surface spectral modes to the EPL in the geometry of additional s- and p-polarized waves emitted into vacuum are analyzed. It is shown that the contributions of purely longitudinal excitons and their interference with polaritons of the upper dispersion branch near the longitudinal frequency ωL to the EPL are small (∼10% - 30%);nevertheless, they must be taken into account to obtain quantitative agreement with experimental data. Specifically these contributions are responsible for the formation of an additional line (along with the fundamental AT line) in the case of oblique incidence of radiation.

LUMINESCENCE CENTERS OF Eu^(2+) IN KCaF_3:Eu^(2+)

The nature of the emission center of Eu^(2+) in KCaF_3:Eu^(2+) strongly depends on the preparative condi- tions.Experimental results show that there are two different d→f transition emission bands,and the origin of these two emission bands,their interrelationship and the effect of doping concentration on them have been dis- cussed.A Eu^(2+)-Eu^(3+) valency change process has been proposed.

Photostimulated Luminescence and F-centers of Sr_3Ca_2(PO_4)_3X:Eu^(2+)(X=F,Cl,Br)

This paper reports the F-centers and photostimulated luminescence of Eu^(2+)-activated Sr_3Ca_2(PO_4)_3X crystals.The influence of various halide ions on the F-centers and their energy level is discussed.The mechanism for the photostimulated luminescence and valence change of Eu ion in that process have been investigated.

An Evaluation of Manure Management Strategies, Phosphorus Surface Runoff Potential and Water Usage at an Arkansas Discovery Dairy Farm

Manure management is an essential component of dairy production. Nutrient-laden, field-applied dairy manure often serves as a fertilizer source, but can also pose environmental threats if not properly managed. The Haak dairy farm, located in Decatur, Arkansas, was granted a permit by the Arkansas Department of Environmental Quality (ADEQ) to employ a unique method in treating and storing cattle manure generated during the milking process. This method includes minimizing water use in wash water, dry scraping solids to combine with sawdust for composting and pumping effluent underground into a sloped concrete basin that serves as secondary solid separator before transporting the manure effluent into an interception trench and an adjacent grassed field to facilitate manure nutrient uptake and retention. The Arkansas Discovery Farm program (ADF) is conducting research to evaluate the environmental performance of the dairy’s milk center wash water treatment system (MCWW) by statistical analysis, characterization of phosphorus (P) migration in soil downslope from the inception trench, temperature measurements, and nutrient analysis of a stored dry stack manure/sawdust mixture. Goals included determining possible composting effectiveness along with comparisons to untreated dairy manure and quantifying the use of on-farm water. Results from this research demonstrated that: 1) The MCWW was effective at retaining manure-derived nutrients and reducing field nutrient migration as the MCWW interception trench had significantly higher total nitrogen (TN) (804.2 to 4.1), total phosphorus (TP) (135.6 to 1.5), and water extractable phosphorus (WEP) (55.0 to 1.0) concentrations in milligrams per liter (mg⋅L-1) than the downhill freshwater pond respectively;2) temperature readings of the manure dry stack indicated heightened levels of microbial and thermal activity, but did not reach a standard composting temperature of 54°C;3) manure dry stack nutrient content was typically higher than untreated dairy manure when measured on a “dry basis” in ppm, but was lower on an “as is basis” in ppm and kg/metric ton;and 4) water meter readings showed that the greatest use of on-farm water was for farm-wide cattle drinking (18.77), followed by water used in the milking center (3.45) and then followed by human usage (0.02) measured in cubic meters per day (m3⋅d-1). These results demonstrate that practical innovations in agricultural engineering and environmental science, such as the Haak dairy’s manure treatment system, can effectively reduce environmental hazards that accompany the management of manure at this dairy operation.

基岩断层面黏滑和蠕滑时岩石表层光释光信号模拟

重建断层的黏滑(seismic slip)和蠕滑(creep)历史对于更好地了解断层活动和地震危险性评估至关重要。近年来,利用大地测量技术研究活动断层的蠕滑和黏滑过程成为一个研究热点。然而,在地质历史时期(如百年尺度以上),如何判断活动断层的滑动方式(黏滑或蠕滑),并获取其滑动速率仍然是一项挑战。文中基于近十年来发展的岩石表层光释光测年方法,结合内蒙古狼山断裂花岗岩样品的光释光晒退参数进行理论模拟,得到了基岩正断层发生黏滑、蠕滑和崩积楔侵蚀等情形的光释光晒退模型。模拟结果表明,该方法能够有效区分断层的黏滑和蠕滑,获得相应的活动期次和位移量,并且有潜力记录崩积楔侵蚀。文中还分析了该方法区分断层活动方式、期次的时间分辨率和获得位移量的空间分辨率。

基于阳极氧化铝模板增强NaYF4:Yb^(3+)/Er^(3+)上转换发光研究

采用共沉淀法制备了Yb^(3+)/Er^(3+)共掺杂的稀土掺杂上转换纳米晶.并对样品的相结构和形貌进行表征.结果表明:制备的NaYF_(4):Yb^(3+),Er^(3+)具有六方晶相,形貌均一.利用两步阳极氧化法制备了阳极氧化铝模板.通过扫描电子显微镜对样品形貌进行表征,结果表明:制备的阳极氧化铝模板周期性良好,孔径均一.在近红外980 nm激发下,阳极氧化铝模板实现了对上转换纳米晶发光强度的增强,使NaYF_(4):Yb^(3+),Er^(3+)的红绿光发射强度分别增强了4.4倍和9.0倍.运用时域有限差分法探究其增强机制,结果表明主要增强机制为阳极氧化铝模板的局域表面等离子共振效应.接着探究了不同入射角度下模板的发光强度,发现随着入射角度的增大,上转换纳米晶红绿光的发光强度均先减小后增大.本研究为上转换纳米晶在防伪领域和太阳能电池领域的应用提供了参考.

Al纳米颗粒高频局域等离激元效应对BCzVBi深蓝光有机发光器件发光效率的影响

蓝紫光有机电致发光器件难以提升发光效率.本文以BCzVBi作为深蓝荧光材料,把Al纳米颗粒引入ITO/:PEDOT:PSS/TAPC/BCzVBi:BCPO/TmPyPb/Liq/Al有机发光器件的TmPyPb电子传输层,尝试用A1纳米颗粒的高频局域等离激元效应来改善此问题.在室温真空蒸镀Al膜,厚度为1 nm时,形成尺寸在10 nm量级的分散纳米颗粒.将这种颗粒膜插入TmPyPb层内距离BCzVBi:BCPO发光层x=4,8,12 nm处,与没有Al层的对比器件相比,器件的电流密度和发光亮度都会因载流子迁移率变差而下降.但在x=8 nm,两者都显著回升.其机理可能在于,x<8 nm,会产生过强的荧光淬灭,而x>8 nm,到达Al颗粒的荧光衰减过多,又难以产生足够强的局域等离子体振荡.在x=8 nm,达到最大亮度的电压(9 V)没有变化,最大亮度从4200 Cd/m^(2)降到3500 Cd/m^(2),但电流密度也从335.19 mA/cm^(2)减小到145.71 mA/cm^(2),使得电流效率反而从0.88 Cd/A提高到2.36 Cd/A,从而把外量子效率提升了170%,效率滚降比则从78%降到30.5%,压减61%.在电流密度高达270 mA/cm^(2)时,电流效率和外量子效率也能提升66.5%.这些结果表明,Al纳米颗粒高频局域表面等离激元确实能够有效增强深蓝光有机发光二极管的发光性能.

基于点云的铣刀螺旋槽截面预测模型

基于点云离散的思想,将铣刀棒料离散为点云集合,将砂轮简化为回转面及中心矢量表达的二维模型,建立判断棒料截面点云与砂轮回转面是否包含的磨削切除预测模型,并利用预测截面点云集合计算螺旋槽相关参数。采用OCC建立实际仿真磨削的点云切除过程模块,实现对预测螺旋槽截面的显示以及结构参数的精确计算。通过改变砂轮结构位置参数,给出螺旋槽截面相关参数变化规律,并对其中具体实例进行了结果显示。

旋转测量状态下光斑中心定位方法

目前,对管道内腔为自由曲面的截面轮廓进行高精度测量是行业难题。拟将多个不同测量范围的激光位移传感器放置于管道内腔中,采用旋转的方式对内腔进行测量,将得到的测量数据进行归一化处理后获得被测管道内腔截面轮廓形状。分析测量过程中激光光斑的变化情况,针对光斑图像的多峰、散斑、平顶与形状变化等现象,提出了一种基于传统灰度重心法进行粗定位的距离倒数加权多项式插值亚像素光斑中心定位方法。采用中值滤波对光斑图像进行预处理,通过自适应阈值分割法从环境背景光强中分离出光斑中心定位区域。通过MATLAB仿真与灰度重心法、加权灰度重心法与高斯拟合法传统光斑中心定位方法相比,结果表明,光斑中心定位精度达到0.01 pixel,在激光光斑中心定位精度和稳定性方面有一定的改善,明显优于传统的光斑中心定位算法。

支撑面稳定度在不同视觉输入条件下对轻度认知障碍老年人平衡能力的影响

背景:支撑面稳定度与视觉输入是影响静态平衡的重要因素,但目前对轻度认知障碍老年人平衡能力的研究大多集中在稳定的硬支撑面,对其在不同视觉输入条件下不稳定支撑面上的静态平衡控制尚未可知。目的:探讨轻度认知障碍老年人不同视觉输入条件下在软、硬支撑面上的静态平衡能力。方法:选择21名轻度认知障碍老年人和19名认知正常老年人为研究对象,使用Kistler三维测力台分别对其进行睁眼双脚硬支撑面站立、睁眼双脚软支撑面站立、闭眼双脚硬支撑面站立、闭眼双脚软支撑面站立4种测试,每次测试站立持续时间为30 s,采集2组人群不同视觉条件下在软、硬支撑面站立时的足底压力中心数据,并进行对比。结果与结论:①有视觉输入条件下,轻度认知障碍老年人在软、硬支撑面上足底压力中心的总摇摆路径(软支撑面:P=0.003)、内外总摇摆路径(软支撑面:P=0.001,硬支撑面:P<0.001)和95%椭圆置信面积(软支撑面:P=0.001,硬支撑面:P<0.001)显著高于认知正常老年人;②无视觉输入条件下,轻度认知障碍老年人在软支撑面上足底压力中心的均方根距离(P=0.014)、内外均方根距离(P=0.014)和95%椭圆置信面积(P=0.001)显著高于认知正常老年人,而在硬支撑面上组间无显著性差异(P>0.05);③结果表明:相比于正常老年人在软、硬支撑面能够充分利用视觉感觉输入维持身体平衡,轻度认知障碍老年人表现出平衡功能的缺失。尤其是在视觉受到干扰时,轻度认知障碍老年人更加依靠足踝本体感觉维持平衡,提示轻度认知障碍老年人应该着重加强足踝本体感觉训练。

基于响应面和MOGA的卧加主轴多目标优化设计

主轴作为卧式加工中心中最重要的功能部件,对其进行优化设计来提高卧式加工中心的动态性能和运动精度具有重要意义。根据主轴的有限元分析结果,以主轴前端半径和长度、后端半径和长度以及拉刀杆外径为设计变量,总质量最小、总体最大变形最小和1阶固有频率最大为优化目标,利用CCD试验设计方法获得初始样本点,再使用Kriging模型建立响应面。最后利用多目标遗传算法(MOGA)进行优化。结果表明:所提方法实现了主轴质量减少29.6%,总变形量减少30.8%,1阶固有频率增加5.4%。

北虫草液体菌种培养基优化及胞外多糖抗氧化性初探

针对北虫草人工栽培中菌丝液体发酵培养菌丝长速慢,产量不高的问题。研究引入了用于人工栽培的北虫草菌种(Cordyceps militaris),对其液体发酵培养基进行了优化并提取北虫草胞外多糖测定其抗氧化活性。结果表明,单因素筛选实验及Plackett-Burman分析表明最佳碳源、氮源、无机盐分别为蔗糖、酵母粉、磷酸二氢钾。爬坡试验进一步得出,当蔗糖浓度为25 g·L^(-1)、酵母粉为6 g·L^(-1)、磷酸二氢钾为2 g·L^(-1)时,北虫草生物量达到较大值2.113 g·L^(-1)。最后经中心组合试验设计和响应面法分析得出,最佳培养基配方为:蔗糖26.364 g·L^(-1)、酵母粉6.699 g·L^(-1)、磷酸二氢钾2.093 g·L^(-1),此时菌丝干重达到最大值为2.314 g·L^(-1)。验证实验表明结果准确,产量提升了107.34%。对胞外多糖提取物的DPPH自由基及ABTS自由基清除率,超氧阴离子自由基与脂质过氧化抑制率测定试验表明清除率与样品浓度呈正相关。

考虑中心距安装误差下的齿面磨损特性分析

以重合度为1~2之间的定轴渐开线直齿轮为研究对象,基于Archard磨损模型数值仿真齿面磨损的分布规律,研究齿轮中心距安装误差对齿轮啮合过程的影响,揭示中心距安装误差对齿面磨损的影响机理。结果表明:在0.1%的中心距误差下,中心距的增大会使齿轮的重合度下降,啮合区域变小,啮入点的位置远离齿根,从而减小齿面磨损。

两种耐水处理长余辉材料制备发光混凝土的性能对比研究

荧光粉的水解不稳定性会降低发光混凝土的力学强度和发光性能。本研究采用SiO_(2)包覆和疏水处理两种方法对长余辉荧光粉进行耐水处理并制备发光混凝土,对掺入不同耐水处理的荧光粉制备的发光混凝土进行抗压强度、发光性能和微观形态测试,揭示荧光粉对发光混凝土性能改善的作用机理。结果表明:与SiO_(2)包裹法处理相比,疏水处理荧光粉能够获得更优异的耐水性能;与SiO_(2)包裹法处理相比,疏水处理荧光粉发光混凝土28 d抗压强度提高了8.0%~25.7%,强度最高达80.2 MPa,最佳掺量为5%~10%(质量分数),过量添加则会产生不利影响;与未耐水处理荧光粉的发光混凝土相比,两种耐水处理荧光粉发光混凝土的微观结构密实度、抗压强度和发光性能均显著提高。

基于等离子体增强上转换发光的窄带1550 nm光探测

近红外光(NIR)探测技术在军事、通信和工业应用中发挥着重要的作用,巨大的市场需求带动了NIR光电探测器(PDs)研究的快速发展。具有双光子或多光子泵浦特性的稀土掺杂上转换纳米颗粒(UCNPs)可以将NIR光子转换为可见光子或紫外光子,并被禁带宽度更宽的半导体吸收,进而制备出性能优异的上转换PDs。然而,NIR窄带上转换PDs的实现仍然面临一些困难,例如稀土离子荧光量子效率低、需要高泵浦阈值才能实现可探测的上转换发光。在此,我们利用NaYF4∶4%Er UCNPs与钙钛矿半导体层相结合,实现了1550 nm的窄带上转换PDs。通过使用具有局域表面等离子体共振效应的银纳米棒层(Ag NRs)增强了UCNPs的上转换发光,从而降低了上转换PDs的泵浦阈值。基于Ag NRs/NaYF4∶4%Er UCNPs/MAPbI3复合结构的PDs的最佳响应度(R)和探测率(D*)分别约为48.5 mA/W和5.7×10^(8) Jones。与纯UNCP/MAPbI3 PDs相比,R和D*均提高了一个数量级。我们成功地构建了一种简单的策略来制造出稳定的近红外窄带PDs。

长余辉材料在发光路面上的应用及研究进展

文章首先介绍了长余辉材料的发光机理,探讨了它的主要应用,并分析了目前存在的一些问题.然后,提出了一些有关长余辉材料的发展建议,以期为相关领域的研究人员提供一些指引和帮助.最后,总结了长余辉材料的发展趋势,并对未来的发展前景进行了展望.