制备工艺对超细氧化钪透明陶瓷粉体性能的影响

以六次甲基四胺为沉淀剂,研究了不同液相反应温度、陈化时间、洗涤方式及煅烧温度对超细氧化钪粉体性能的影响。在液相反应温度为20和80℃均合成出絮状的前驱沉淀物,前躯体的晶化程度和煅烧产物的粒度均随着反应温度的提高而增加。在陈化溶液环境中,随着陈化时间的增加,粒子逐渐均匀长大。只用水洗涤的粉体产生了轻微团聚的现象,经水-无水乙醇洗涤的粉体分散性得到改善,而用水-无水乙醇-丙酮洗涤的颗粒分散更好。煅烧产物的尺寸随着煅烧温度的提高而增加。     

Nd:YAG纳米粉体的制备和光谱性质

采用共沉淀方法，以碳酸氢铵（NthHC03）为沉淀剂制备得到Nd：YAG前驱物，将其在不同的温度下煅烧并采用红外光谱（FT-IR）、X射线衍射（XRD）、透射电镜（TEM）、荧光光谱分析等技术对样品进行了表征。在900～1000℃下煅烧前驱物，出现YAP和YAM中间相并对共沉淀法中间相出现的原因进行了分析；获得纯YAG晶相的煅烧温度为1100℃，晶粒粒度分布约为40～80nm，具有良好的分散性。光谱研究表明Nd：YAG纳米粉体的发光性能良好，其红外光谱及荧光光谱与单晶无明显的差异。     

碳酸盐前驱物制备Y2O3超细粉及透明陶瓷

以Y(NO3)3和NH4HCO3为原料,通过向Y(NO3)3溶液中滴加NH4HCO3的方式制备了化学组成为Y2(CO3)3·2H2O的先驱沉淀物。研究了先驱沉淀物煅烧过程中的物相变化。先驱沉淀物1100℃煅烧4h后得到了平均粒径为60nm的无团聚Y2O3超细粉体。所得粉体不添加任何添加剂,在1700℃下真空烧结4h得到了透明Y2O3陶瓷。     

超细粉体制备Nd:Y2O3透明陶瓷

采用碳酸氢铵为沉淀剂合成了碱式碳酸钇沉淀前驱体,研究了的前躯体的煅烧工艺对氧化钇粉体性能及烧结氧化钇陶瓷组织、致密化行为以及透光率的影响。在1000℃煅烧6 h获得的超细粉体,经过在氢气介质中1750℃保温3 h烧结后,获得组织均匀,无残余气孔,透光率高的氧化钇陶瓷。     

共沉淀法制备掺钕钇铝石榴石透明激光陶瓷的研究

掺钕钇铝石榴石(Nd∶YAG)多晶透明陶瓷具有良好的化学稳定性、光学性能和耐高温性能,是一种很有前途的激光工作物质。以Al(NO3).9H2O,Y2O3,Nd2O3和NH4HCO3为原料,(NH4)2SO4为静电稳定剂,正硅酸乙酯为添加剂,采用共沉淀法和反滴定方式于1100℃合成出分散均匀、团聚程度轻、YAG立方晶相的Nd∶YAG纳米前驱体粉末,经1700℃真空烧结5 h制备出Nd∶YAG透明陶瓷材料。采用TG-DTA,XRD,TEM,FT-PL和FEG-ESEM等测试手段对Nd∶YAG陶瓷材料进行了表征。研究结果表明:前驱体粉末在800℃时为无定型态,当温度达到890℃时析出大量的YAlO3(YAP)和少量的Y3Al5O12(YAG)晶体,当温度达到1012℃时就全部转化为YAG立方晶相;前驱体纳米粉末中存在团聚。Nd∶YAG陶瓷材料的激光工作波长为1.065μm,和相同组分的单晶相比存在轻微的红移现象;随着透射光波长的增加,透光率逐渐增加,在可见光区透光率约为45%,在近红外光区透光率约为58%。     

Gd1.1Lu0.8Eu0.1O3透明陶瓷材料的制备和发光性能

以氨水和碳酸氢铵的混合溶液作为复合沉淀剂,硝酸钆、硝酸镥和硝酸铕为原料,利用共沉淀法获得了碱式稀土碳酸盐前躯体.利用该前躯体经过1000℃煅烧2 h,得到近球形、分散性良好、基本无团聚的Gd1.1Lu0.8Eu0.1O3纳米粉体,晶粒尺寸介于40～50 nm之间,粉体的比表面积为20 m2·g-1,该粉体具有良好的烧结活性.该粉体经干压和等静压成型,不添加任何添加剂和烧结助剂,于1750℃和真空气氛下烧结6 h,获得了相对密度为99.7%的Gd1.1Lu0.8Eu0.1O3透明陶瓷.该透明陶瓷样品在可见光区的最高透过率可达65%,在274 m的紫外光激发下发射出极强的红光,其发射主峰位于610 m,对应于Eu3+的5D0-7F2跃迁.     

钇铝石榴石(YAG)透明陶瓷的研究进展EI北大核心CSCD

钇铝石榴石(Y_(3)Al_(5)O_(12))透明陶瓷具有机械强度高、物化性质稳定,特别是覆盖紫外、可见及红外光透过等优异性能,在固体激光器、导弹穹顶、红外窗口及透明装甲领域有着广泛的应用。本文系统总结了YAG透明陶瓷的制备工艺,包括粉体合成、坯体成型、陶瓷烧结及烧结助剂的选用,对比了不同工艺路线制备YAG透明陶瓷的性能、规格、成本等;就不同稀土离子掺杂对YAG基透明陶瓷性能的影响规律进行了全面阐述;最后通过对现有问题的总结,展望了钇铝石榴石(YAG)透明陶瓷未来的发展趋势。     

氧化铈超细粉体的制备研究

采用共沉淀法，以工业碳酸铈为原料，以工业NH4HCO3为沉淀剂，制备出了平均粒径为一次粒径140nm，二次粒径630nm的CeO2超细粉，并进行了TG-DTA，XRD及TEM的表征研究。结果表明，以工业NH4HCO3作沉淀剂，可以制备CeO2超细粉，沉淀物360℃就可完全分解为CeO2，所制备的CeO2超细粉属于立方晶型，随灼烧温度升高，晶化程度增大。     

低温燃烧法合成掺钕钇铝石榴石（Nd：YAG）纳米粉末

以Nd2O3,Y2O3,Al(NO3)3·9H2O,氨水和柠檬酸为原材料,采用低温燃烧法合成出分散均匀、团聚轻的掺钕钇铝石榴石(Nd∶YAG)纳米粉末,该方法有效地解决了固相合成的高反应温度以及化学沉淀法的颗粒团聚问题。采用TG-DTA,XRD,FT-IR和TEM测试手段对纳米粉末进行了表征,同时测量了(Nd0.01Y0.99)3Al5O12陶瓷素胚以及烧结体的荧光发射光谱。研究结果表明:YAG晶相的形成温度为850℃,在煅烧过程中出现YAP中间相,并于1050℃完全转化为YAG晶相。采用低温燃烧法合成的粉末材料其颗粒尺寸随热处理温度的不同在20~50nm范围波动。(Nd0.01Y0.99)3Al5O12陶瓷体的有效激发发射截面积(σin)为4.03×10-19cm2,比同组成的单晶高44%。     

添加剂对YAG透明陶瓷显微组织的影响

采用固相反应法制备了YAG透明陶瓷，研究了助剂(正硅酸乙酯，TEOS)对YAG显微组织的作用。如果TEOS的质量分数大于3％，会形成大量的液相，导致晶界存在第二相。如果TEOS的质量分数小于0．05％，气孔会陷入晶粒内部。TEOS的合适含量是0．5％。在1750℃真空烧结5h，得到完全透明的YAG陶瓷，在可见光波长范围透过率为63％，在红外波长范围透过率达到70％。     

Lu2O3纳米粉体和透明陶瓷中掺杂Nd3+的局域结构研究

利用扩展X射线吸收精细结构光谱(EXAFS)研究了不同掺杂浓度Nd3+:Lu2O3纳米粉体和透明陶瓷中Nd3+的局域结构.结果表明,在不同条件下Nd3+均以固溶取代Lu3+的方式进入Lu2O3基质晶格,掺杂Nd3+原子的第一配位键长约为0.225 nm,小于Nd2O3纳米粉中Nd-O第一近邻键长0.251 nm,而大于...     

氨水共沉淀法制备Nd∶Y2O3透明陶瓷纳米粉体

以Y2O3粗粉、Nd2O3、硝酸和氨水为原料,通过共沉淀法制备了Nd:Y2O3透明陶瓷纳米粉体,利用热重/差热分析(TG/DTA)、红外光谱(FTIR)、粉末X射线衍射(XRD)、透射电镜(TEM)以及能谱分析(EDS)等方法对合成的Nd:Y2O3纳米粉体进行了表征.结果表明,在前驱物中添加适量SO42-离子能减轻煅烧得到的Nd:Y2O3纳米粉体粒子的团聚,使Nd:Y2O3纳米粒子的粒度均匀并呈球形分布.在600～1000℃煅烧3 h所得粉体粒子的粒径在20～40 nm之间,具有较好的分散性.     

Preparation and Optical Properties of Submicron SiO2 Spheres Doped with YAG:Nd3+ Nanocrystallites

The sol-gel technology has been applied to obtain SiO₂ spheres of submicron size. The spheres have been doped with YAG:Nd³⁺ nanocrystallites. The nanocrystallites have been obtained from aqueous solutions of citric acid, yttrium, aluminum and neodymium chlorides. The obtained gels have been heated up to 800°C. Emission spectra as well as the excited state lifetimes have been measured at room and liquid nitrogen temperatures. The structural characterization has been performed by means of transmission and scanning electron microscopies (TEM, SEM) and powder diffraction (XRD) measurements. We have observed that the YAG:Nd³⁺ nanocrystallites demonstrate pronounced dependence of the emission intensities on the excitation power as compared to the YAG:Nd³⁺ crystallites embedded into the submicron SiO₂ spheres. The results suggest that silica spheres/YAG:Nd³⁺ composites are expected to be good hosts for microlaser systems.     

Ce,Pr掺杂的YAG微晶玻璃的制备及光谱性能

以Y2O3-Al2O3-SiO2-Li2O-K2O-Na2O玻璃作为Ce,Pr掺杂基质玻璃,制备出白光LED用Ce:YAG和Ce,Pr:YAG微晶玻璃.使用X射线衍射仪、场发射扫描电子显微镜、荧光光度计对微晶玻璃的晶相、微观形貌、光谱性能及荧光寿命进行了研究.结果表明:掺杂铈或铈镨共掺杂的基质玻璃在1400℃热处理得到...     

单纵模Nd:YAG激光泵浦H2气中的受激喇曼散射

Strong backward first Stokes (BS) in H2 is observed when a single longitudinal mode fundamental frequency Nd:YAG laser (1.06 μm, pulsed width about 9 ns, linewidth 0.003 cm-1) is used as the pump source. Using a pump energy of 120 mJ, photon conversion efficiency of FS and BS was determmed to be 66% and 15% respectively in 1.5 MPa H2, while in 4.0 MPa H2 the respective values are 46% and 39%. Due to their propagation in opposite directions, there is tension between FS and BS, which leads to a relaxation of the oscillation that splits both FS and BS pulses into two peaks, with the BS pulses being narrowed to about 1 ns. Surprisingly, the BS peak power reaches twice that of the pump, which can never happen in the FS case. Furthermore, the beam quality of BS is much better than that of both FS and pump. At 4 MPa of H2 pressure and a 10 Hz cycle rate, the thermal release of the Raman process deteriorates the FS beam quality, without noticeably affecting that of BS. According to this calculations, within the present experimental conditions, the stimulated Raman scattering process does not reach the steady state. Because of this, all of the experimental results can be explained explained by a related transient state, theory of stimulated Raman scattering.     

铈、钐掺杂YAG微晶玻璃制备及光谱性能

以Y2O3-A l2O3-S iO2-L i2O-K2O-Na2O玻璃作为Ce,Sm掺杂基质玻璃,制备出白光LED用YAG:Ce和YAG:Ce,Sm微晶玻璃。利用X射线衍射、荧光光度计对微晶玻璃的晶相、光谱性能及荧光寿命进行了研究。结果表明:掺杂铈或铈钐共掺杂基质玻璃在1400℃热处理得到的几乎是纯YAG晶相;并且YAG:Ce和YAG:Ce,Sm微晶玻璃在454 nm有特征激发峰,说明它们能被蓝光芯片有效激发;在蓝光芯片激发下,YAG:Ce微晶玻璃在480~700 nm产生有效发射,发射光谱中心波长531 nm,同时铈钐共掺微晶玻璃在566,602,615,650 nm都有窄的发射峰,可以提高LED s的显色性、降低色温;此外,浓度掺杂实验表明钐的较好掺杂浓度范围是Ce:Sm为10∶2~10∶10;YAG:Ce和YAG:Ce,Sm微晶玻璃的荧光衰减曲线表明,YAG:Ce微晶玻璃的荧光寿命要长于YAG:Ce,Sm微晶玻璃。     

Preparation of Ultrafine Ceramic Powder Used for Making PTCR Ceramics by Sol-gel Method

Amorphous gel powder containing Ba, Sr, Ca, Ti, Si, Mn, Li and Y elements has been prepared by a modified sol-gel method, the ultrafine PTCR (Positive Temperature Coefficient of Resistance) powder was obtained through calcination for 2 h at 800℃ in air. According to XRD, DSC, BET and SEM. it can be concluded that it's crystal structure is cubical perovskite phase at room temperature, it's average crystallite size is about 28.4nm (using the Debye-Scherrer formula) or about 40 nm (using BET) or about 50nm(using SEM), it's specific surface area is 24.80 m²/g, and which is two twice as much as that of the sample prepared by old sol-gel method^[l,2], it's particle size displays normal distribution with average particle size of 437.2nm.     

蓝色长余辉材料CaAl2O4:Eu2+,Nd3+的合成及其发光性能

采用高温固相法合成了系列单相Ca(1-x-y)Al2O4:Eu2+x,Nd3+y(0≤x≤0.045,0≤y≤0.0037)粉末样品,并表征了其发光特性.研究结果表明,样品的发射光谱为最大发射峰位于440nm的宽带谱,属于Eu2+的4f65d→4f7跃迁.通过对Eu2+,Nd3+掺杂量与样品发光性能之间关系的研究发现,Eu2+和Nd3+最佳掺杂量分别为x=0.00125和y=0.0025,并且Nd3+对改善蓝色长余辉材料CaAl4:Eu2+的余辉性能具有重要的作用.在最佳掺杂条件下,样品的余辉时间可达1000min,初始亮度大于1200mcd/m2,60min后发光粉的亮度仍然在10mcd/m2以上.利用正电子湮灭技术和热释光技术,研究了Eu2+和Nd3+对CaAl2O4:Eu2+,Nd3+材料的发光性能的影响.     

Employment of Carbon Nanomaterials for Welding Polyethylene Joints with a Nd:YAG Laser

Single-lap polymeric joints can be obtained using laser welding overlapping two polymeric sheets, with one laser transparent and the other laser adsorbent. In this study we employed crystalline carbon nanomaterials (in amounts of 0.2, 0.5, and 1.0 wt.%) as filler to enhance the absorption of polyethylene (UHMWPE type). A Nd:YAG laser operating at 1064 nm was used as a power source to make the welded joints. Morphological, mechanical, and calorimetrical tests were carried out to study the strength of the joints made. Serious attention was paid to find the best compromise between exposure time to laser light and filler amount. We found that in the optimal conditions (with 0.2 wt.% filler and 60 s exposure time) the joint exhibits a good shear strength with a regular welded area. In fact, the best conditions guarantee proper absorption power of the laser light and deep interpenetration of the chains between the two polymeric sheets without any damage.