辐照导致硼硅酸盐玻璃机械性能变化

为了模拟研究高放废物玻璃固化体在处置过程中因辐照导致的机械性能变化,本文采用5 MeV Xe离子和1.2 MeV电子辐照硼硅酸盐玻璃,利用纳米压痕技术表征了辐照前后样品的硬度和模量,并利用傅里叶变换衰减全反射红外光谱测试,研究了辐照导致玻璃机械性能变化的微观机理.结果表明:当能量沉积达到6.6×10~(21)keV/cm~3时,Xe离子辐照样品的硬度和模量下降都达到饱和,其中硬度下降约24%,模量下降约7.4%;电子辐照后样品的硬度和模量也有轻微下降,但在实验所用剂量范围内硬度和模量下降未出现饱和现象,当吸收剂量达到最大值(1×10~9 Gy)时,硬度和模量分别下降约4.7%和2.9%.分析表明:Xe离子辐照后样品的恢复阻力增大,韧性提高,整体机械性能提升,而电子辐照后样品的机械性能无明显变化.研究结果证明了离子辐照导致玻璃机械性能变化的主要因素是离子在样品中的核能量沉积.     

分子动力学模拟钠硼硅酸盐玻璃电子辐照诱导的结构演化效应

钠硼硅酸盐玻璃作为高放射废物玻璃固化体的候选材料之一,已有大量实验对该类玻璃开展了电子或重离子的辐照效应研究.然而,在理论计算与模拟方面的工作却很少,目前主要集中于重离子的辐照效应,对电子的辐照效应的模拟尚未见报道.本文利用分子动力学工具提出一种新的方法,以实现对电子辐照诱导的玻璃结构演化进行模拟.该方法基于实验中玻璃的结构变化特点,即实验中的拉曼结果已经证实:在大剂量的电子辐照后的玻璃中存在分子氧的事实,由于这些分子氧不会与其他粒子发生相互作用,因而可以通过从体系中逐步地移除一定数量氧原子的方式,以达到模拟大剂量电子辐照的情形,进而得到电子辐照后的玻璃的结构信息.模拟结果显示:随着移除氧原子的数量增加,玻璃中的Si—O—Si平均键角逐渐减小;而且玻璃中的小环数量会因氧的逐渐减少而逐渐增加;玻璃中部分[BO4]结构会转变为[BO3]结构,最终这种转变会达到饱和;大量移除氧之后,玻璃中的钠元素也出现明显的相分离.这些模拟辐照的玻璃结构特性能较好地与实验中的硼硅酸盐玻璃电子辐照诱导的结构变化符合.因此,本文提出的方法有望为通过分子动力学模拟硼硅酸盐玻璃的电子辐照效应提供新思路.     

γ辐照后硼硅酸盐玻璃的吸收光谱研究

玻璃固化体是用来固化放射性废物的硅酸盐。作为放射性废物处理的第一道工程屏障，它的耐辐照性能尤其引人注目。本工作使用硼硅酸盐玻璃模拟玻璃固化体材料，用不同剂量的γ射线辐照硼硅酸盐玻璃模拟天然放射性对固化体的辐照损伤。通过测量和分析辐照后硼硅酸盐玻璃的吸收光谱，证实了辐照后在玻璃中产生了E'缺陷，非桥氧空位色心、过氧自由基以及过桥氧联接等缺陷。此外，还得出了不同微观结构随吸收剂量的演化关系。对于辐照后产生的缺陷，它们的浓度都随吸收剂量的增加而增大。同时，发现玻璃在辐照后其吸收光谱的带隙随着剂量的增加而逐渐变窄；而当吸收剂量大于等于105 Gy时，玻璃的带隙则达到饱和值。Vitrification is one kind of silicates which is used for immobilization of high-level waste (HLW). As the first engineered barrier of HLW disposition, its anti-irradiation characteristic is particularly noticeable. Vitrification is replaced by borosilicate glass to investigate radiation effect, and the irradiation damage generated by natural radioactivity in vitrification is simulated by different doses gamma rays on borosilicate glass. By measuring and analyzing the absorption spectrum of irradiated borosilicate glasses, it is confirmed that E'defect, non-bridging oxygen hole center, peroxy dangling bond and bridge oxygen link, etc. are induced in borosilicate glass after irradiation. Furthermore, the relations between the defects and absorbed doses are shown. For the concentrations of these defects induced by irradiation, all of them increase with absorbed dose. Meanwhile, absorption band gap in borosilicate glass after irradiation decreases with absorbed dose and the band gap becomes saturated when absorbed dose is equal to or greater than 105 Gy.     

质子辐照硼硅酸盐玻璃盖片的物理效应分析

作为航天器电源系统的重要组成部分,太阳电池需要更高的转换效率和可靠性以及更长的使用寿命。通过在太阳电池表面覆盖抗辐照玻璃盖片,可以增强太阳电池对粒子辐射的防护,延长太阳电池的服役寿命,使航天器获得可靠的能源供应。硼硅酸盐玻璃就是一种理想的太阳电池玻璃盖片材料。采用蒙特卡罗方法,结合SRIM软件模拟研究质子辐照硼硅酸盐玻璃的损伤物理机理。基于粒子与物质相互作用的理论以及基本公式,通过分析不同入射能量的质子在硼硅酸盐玻璃中的阻止本领、电离能损、位移能损、空位的产生情况,对辐照损伤的物理机制进行研究。结果表明:能量为30~120 keV的质子辐照损伤主要发生在硼硅酸盐玻璃表面;质子沉积、空位分布等均为Bragg峰型分布;电离能损是能量损失的主要部分,随入射能量的增加而增大,导致电子的电离和激发;位移能损在玻璃内部随能量降低而增大,导致硼、氧和硅等空位缺陷的产生;电离效应和缺陷的产生是硼硅酸盐玻璃色心形成的重要原因。     

硼硅酸盐玻璃的电子辐照效应

在高放废物长期地质处置过程中,作为第一层工程屏障的固化体玻璃会受到持续的电子辐照,研究其电子辐照效应对高放废物的长期安全处置具有重要的意义。在透射电子显微镜(TEM)上对硼硅酸盐玻璃样品进行原位电子辐照实验。在电子束的作用下,两种硼硅酸盐玻璃均很快发生相分离现象,这主要是由于电离作用导致Na的迁移或逃逸引起网络体结构重组的结果。引入简单的结构模型解释了两种不同组分硼硅酸盐玻璃相分离的不同,结果表明,相分离的不同与玻璃组分中Na成分的多少密切相关。     

ZK类重冕玻璃生产工艺总结

一、概述重冕玻璃属于BaO(ZnO)-B_2O_3一SiO_2系统,是以(SiO_4)硅氧四面体为骨架的无碱硼硅酸盐玻璃。它的折射率N_D在1.57～1.67左右,阿贝数V_D在52.0～64.O左右。由于它的折射率较高,玻璃中必须含有较大量的BaO(30～50%),同时引入ZnO,以改善玻璃的析晶性能和化学稳定性;引入Al_2O_3也有助于改善玻璃的化学稳定性。ZK类玻璃含BaO量高,对粘土质耐火材料侵蚀十分严重,因此,我厂采用铂坩埚在     

钠钛硅酸盐精细结构及其拉曼活性分子振动的量子化学从头计算研究

本文选取了Na_2O-TiO_2-SiO_2体系不同成分的团簇模型,采用量子化学从头计算方法计算其拉曼振动频率和相对散射活性。本文分析了钛硅酸盐中硅氧四面体([SiO_4])的局域环境变化对特征拉曼振动频率的影响,对硅氧四面体应力指数进行了拓展与修正,研究表明钠钛硅酸盐拉曼光谱高波数区硅氧四面体非桥氧对称伸缩振动频率随相应的硅氧四面体应力指数的增加而增加,并表现出良好的线性相关性。采用拉曼光谱和~(29)Si NMR对Na_2TiSiO_5玻璃进行解谱、定量分析和比较,并认为869 cm~(-1)处的谱峰归属为Q_(1(Si))中非桥氧的对称伸缩振动。     

磷硅酸盐微结构及其拉曼光谱的量子化学计算

构建了系列典型的磷硅酸盐团簇结构模型,应用量子化学从头计算方法研究了磷硅酸盐的精细结构,选用Restricted Hartree-Fock(RHF)方法以及6-31G(d)基组优化空间几何构型,并计算了其拉曼光谱,同时引入硅氧四面体应力指数(SIT)分析和讨论了磷氧四面体对硅氧四面体微环境的影响。研究表明,磷硅酸盐高频区硅氧四面体非桥氧的对称伸缩振动频率不仅与非桥氧所处的硅氧四面体本身的种类有关,同时也与其邻接四面体种类及成环状况有关;磷氧四面体具有较强的键角调节和应力传导能力,使得硅氧四面体的振动频率相对键角不敏感;硅氧四面体非桥氧的对称伸缩振动频率随硅氧四面体应力指数(SIT)的增加而增加,并呈线性关系。     

温度对CaO-MgO-Al_2O_3-SiO_2系纳米晶玻璃陶瓷结构影响的拉曼光谱研究

采用熔融法制备了CaO-MgO-Al2O3-SiO2系纳米晶玻璃陶瓷材料。在-190~310℃温度范围,利用显微共聚焦拉曼光谱测量分析了该体系纳米晶玻璃陶瓷硅氧四面体结构的变化规律。结果表明,随着温度的降低具有不同非桥氧键的硅氧四面体结构单元变化并不一致,位于三维硅氧四面体结构边缘的具有二个非桥氧键的硅氧四面体(Q2)和具有三个非桥氧键的硅氧四面体(Q1),以及完全独立于三维硅氧网络结构外的具有四个非桥氧键的硅氧四面体(Q0)受温度影响明显,其拉曼光谱均向高波数移动,键的力常数变强,硅氧键长变短。为丰富外环境对纳米晶玻璃陶瓷材料结构与性能影响的研究提供了实验依据,也为控制该体系纳米晶玻璃陶瓷材料的膨胀系数提供了一定的实验依据。     

Ar离子辐照导致微球玻璃机械性能的变化

为研究离子辐照导致空心玻璃微球机械性能的变化，利用Ar离子辐照与空心玻璃微球组分相同的微球玻璃薄片，结合不同温度下的等时退火处理，采用纳米压痕测试方法研究了辐照前后玻璃机械性能的变化。测试结果表明:辐照后玻璃的硬度和模量均呈下降趋势，恢复阻力明显升高；退火后的未辐照样品硬度和模量呈上升趋势，恢复阻力在误差范围内没有发生变化; 退火后的模量呈下降趋势，恢复阻力呈下降趋势；在退火温度约为300 ℃时，辐照样品退火后的恢复阻力与未辐照样品基本相同。     

Direct joining of glass substrates by 1 kHz femtosecond laser pulses

When a femtosecond laser pulse is focused at the interface of two transparent substrates, localised melting and quenching of the two substrates occur around the focal volume, bridging them due to nonlinear absorption. The substrates can then be joined by resolidification of the materials. We investigate the optimum irradiation conditions needed to join borosilicate glass substrates and fused silica substrates using a 1 kHz 800 nm Ti:sapphire amplifier. We characterised the joint strength and the transmittance through joint volumes as a function of laser energy and translation velocity. We found that a joining strength as large as 14.9 MPa could be obtained in both fused silica and borosilicate glass. Annealing the joint samples led to an increase in the joint strength. PACS 42.65.Jx; 42.70.Ce; 81.20.Vj     

Intrinsic dosimetry: Elemental composition effects on the thermoluminescence of commercial borosilicate glass

Intrinsic dosimetry is the method of measuring total absorbed dose received by the walls of a container holding radioactive material. By considering this dose in tandem with the physical characteristics of the radioactive material housed within the container, this method can provide enhanced pathway information for interdicted radioactive samples. Thermoluminescence (TL) dosimetry was used to measure ionizing radiation dose effects on stock borosilicate glass. Differences in TL glow curve shape and intensity were observed for glasses from different geographical origins. The different TL signatures strongly correlated with the concentration of alkaline earth metals and the ratio of sodium to the total amount of alkali metal present in the borosilicate glass.     

Gamma radiation induced changes in nuclear waste glass containing Eu

Gamma radiation induced changes were investigated in sodium-barium borosilicate glasses containing Eu. The glass composition was similar to that of nuclear waste glasses used for vitrifying Trombay research reactor nuclear waste at Bhabha Atomic Research Centre, India. Photoluminescence (PL) and electron paramagnetic resonance (EPR) techniques were used to study the speciation of the rare earth (RE) ion in the matrix before and after gamma irradiation. Judd-Ofelt (J-O) analyses of the emission spectra were done before and after irradiation. The spin counting technique was employed to quantify the number of defect centres formed in the glass at the highest gamma dose studied. PL data suggested the stabilisation of the trivalent RE ion in the borosilicate glass matrix both before and after irradiation. It was also observed that, the RE ion distributes itself in two different environments in the irradiated glass. From the EPR data it was observed that, boron oxygen hole centre based radicals are the predominant defect centres produced in the glass after irradiation along with small amount of E’ centres. From the spin counting studies the concentration of defect centres in the glass was calculated to be 350 ppm at 900 kGy. This indicated the fact that bulk of the glass remained unaffected after gamma irradiation up to 900 kGy.     

高功率脉冲电子束辐照SiO$lt;sub$gt;2$lt;/sub$gt;的光学和激光损伤性能

研究了不同剂量的60 kW高功率脉冲电子束辐照对高纯熔石英玻璃的微观结构、光学性能和激光损伤特性的影响规律. 光学显微图像表明, 辐照后熔石英样品由于热效应导致表面破裂, 裂纹密度和尺寸随辐照剂量增加而增大, 采用原子力显微镜分析表面裂纹的微观形貌, 裂纹宽度约1 um, 同时样品表面分布着大量尺寸约0.1–1μm的碎片颗粒. 吸收光谱测试表明, 所有样品均在394 nm处出现微弱的吸收峰, 吸收强度随着电子束辐照剂量增大呈现先增加后减小的趋势. 荧光光谱测试发现辐照前后样品均有3个荧光带, 分别位于460, 494和520 nm, 荧光强度随辐照剂量的变化趋势与吸收光谱一致. 利用355 nm激光研究了不同剂量电子束辐照对熔石英激光损伤阈值的影响, 结果表明熔石英的损伤阈值随着辐照剂量的增加而降低. 在剂量较低时, 导致熔石英激光损伤阈值下降的原因主要是色心缺陷; 剂量较高时, 导致损伤阈值降低的原因主要是样品表面产生的大量微裂纹和碎片颗粒对激光的调制和吸收. 关键词： 熔石英 电子束辐照 色心 激光损伤阈值     

Fused silica as a composite nanostructured material

A method for calculating the refractive index of optical fused silica by applying the model of effective permittivity of composite homogeneous media is proposed and realized. The calculation was performed using the tabular data of the refractive index of crystalline α quartz and the ratio of the quartz glass and α quartz densities. It was suggested that fused silica contains nanosized pores with a glass filling number q immersed in a matrix with a density differing from the α quartz density by a factor of κ, where κ is slightly less than unity. It was established that the Maxwell-Garnett model makes it possible to calculate the refractive index of quartz glass and its dispersion in the transparency range (404 nm ≤ λ ≤ 671 nm) with a deviation less than 0.0002 from the tabular values. The calculated and experimental values coincide at q = 0.155 and κ = 0.986.     

Fabrication of microchannels in glass using focused femtosecond laser radiation and selective chemical etching

We use the combination of femtosecond laser dielectric modification and selective chemical etching to fabricate high-quality microchannels in glass. The photoinduced modification morphology has been studied in fused silica and in borosilicate glass BK7, using ultra-high spatial resolution techniques of selective chemical etching followed by atomic force or scanning electron microscopy. The analysis shows that the high differential etch rate inside the modified regions, is determined by the presence of polarization-dependent self-ordered periodic nanocracks or nanoporous structures. We also investigate the optimum irradiation conditions needed to produce high-aspect ratio microchannels with small symmetric cross-sections and smooth walls. PACS 42.62.-b; 42.65.Re; 81.05.Kf; 87.80.Mj     

基于AFM的固液界面表面电荷密度测量方法

固液界面的表面电荷会影响微纳流体系统的流体阻力,因此如何测量固液界面的表面电荷密度以及分析表面电荷的产生机理对于研究表面电荷对流体阻力的影响具有较大的意义。提出了一种基于接触式AFM的固液界面表面电荷密度测量方法。基于该方法测量了浸在去离子水和0.01 mol/L的NaCl溶液中的高硼硅玻璃和二氧化硅样本的表面电荷密度,并研究了溶液pH值对表面电荷的影响。研究结果表明高硼硅玻璃和二氧化硅由于表面硅烷基的电离带负电。溶液pH值和离子浓度的增加都会增加浸在去离子水和0.01 mol/L的NaCl溶液中高硼硅玻璃和二氧化硅的表面电荷密度的绝对值。     

Dosimetry techniques

The formation and annealing of defects in ion implanted silicon dioxide layers and in connection with them the refractive index change are of high interest for the production of electronic and integrated optical devices.

Several studies have shown that the ion implantation in fused silica leads to a compaction of the material and in consequence to an increasing of the refractive index.^1–6 On the other hand the defect formation in crystalline quartz is connected with a decreasing of the refractive index up to nearly the same value for ion implanted quartz and fused silica layers in the high dose region.^1,5 On the base of this effects optical waveguides had been produced by ion implantation in both material.^2,7–12 However, the nature of the mechanisms responsible for the defect formation and for the changes of the optical properties are not well understood.

This paper reports on the ion dose and annealing temperature dependence of several defects in connection with the refractive index change.