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.     

Xe离子束辐照硼硅酸盐玻璃和石英玻璃效应对比研究

玻璃固化体作为放射性废物地质处置的第一道安全屏障,它的耐辐照性能研究至关重要.玻璃固化体主要网络结构硅氧四面体与石英玻璃的硅氧四面体是一致的,所以这里用石英玻璃代替玻璃固化体作为研究对象.本文采用Xe离子在相同条件下辐照石英玻璃和硼硅酸盐玻璃.利用纳米压痕技术和椭圆偏振仪表征了辐照前后样品的硬度、模量以及折射率的变化情况.结果表明:硼硅酸盐玻璃和石英玻璃的硬度均随着辐照剂量的增大而减小,硼硅酸盐玻璃的模量随着辐照剂量的增大而减小;石英玻璃的模量随着辐照剂量的增大而增大.模量的变化可能和密度的变化有关,这点与折射率的结果相符.     

惯性约束聚变靶丸玻璃微观结构的分子动力学模拟北大核心CSCD

使用分子动力学方法模拟惯性约束聚变(ICF)玻璃微球靶丸材料的碱金属硼硅酸盐玻璃,研究了不同SiO2与B2O3和不同Na2O与B2O3物质的量比的微观结构,包括键长、键角、配位数以及空穴的分布情况。通过模拟发现,在不同组分的碱金属硼硅酸盐玻璃中,硅原子的网络体结构相对稳定,硼原子的结构会随着成分的变化发生明显变化。同时,针对实际的ICF实验中对玻璃微球充入惰性气体氩的问题,模拟发现,当SiO2与B2O3物质的量比为40.5,Na2O与B2O3物质的量比为17.4,8.5,4.2时,玻璃中存在有较多的供氩扩散的空穴。     

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.     

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.     

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。     

Eu2+掺杂硼硅酸镁玻璃的发光性能

利用高温固相法合成了Eu2+掺杂的新型蓝色硼硅酸盐发光玻璃,讨论了不同掺杂浓度下硼硅酸镁玻璃体系中Eu-O键共价性的变化以及氧原子周围不同配位环境对MgO-SiO2-B2O3玻璃发光性能的影响.利用X射线衍射仪和荧光光谱仪对该玻璃体系进行了结构表征和性能测试.在紫外-可见光激发下,Eu2+掺杂硼硅酸镁玻璃的荧光发射光谱...     

二价Ba2＋、Pb2＋和四价Ti4＋在硼硅酸盐玻璃系统中 对Li＋／Na＋离子交换的影响

本文讨论了在硼硅酸盐玻璃系统中引入二价 Ba2 、Pb2 和四价 Ti4 后 ,由于 Pb2 和Ti4 配位结构的变化 ,引起 Pb2 、Ti4 场强及其与 O2 -离子间距的变化 ,对 Li /Na 离子交换产生影响 ,从而改变折射率差值 (ΔN )和折射率分布 .     

Eu~(3+)作探针研究铋铕共掺硼硅酸盐玻璃光学特性

利用高温烧结法制备了铕/铋铕共掺硼硅酸盐玻璃系列样品,测量了样品的激发光谱、发射光谱和声子边带谱,利用Eu3+离子作为探针进一步研究了敏化剂Bi3+的掺入对Eu3+发光的影响.结果表明:本文制作的玻璃样品的电子-声子耦合系数比以往报道过的硼铅等玻璃材料的值都要小,但在硼硅酸盐玻璃中掺入Bi3+会使Eu3+的无辐射跃迁概率增加;Bi3+对Eu3+有敏化作用,Bi3+的掺入使材料的共价性增强,对称性降低,这又使得Eu3+的发光整体变强.所以,在硼硅酸盐玻璃体系中,Eu3+发光的增强不仅仅是由于Bi3+对Eu3+的能量传递,而是以上各因素综合作用的结果.     

不同硅含量的硼酸锌盐玻璃的光谱研究

制备了60ZnO-(40-x)B2O3-xSiO2:Tb3+(x=0,10,20)玻璃,测量了红外吸收光谱,分析了玻璃的结构。由于在700cm-1出现较强的振动峰,说明在此硼酸盐玻璃形成了五硼酸盐。硼硅酸盐玻璃中存在着的偏硼酸盐结构,即一个硼氧四面体和四个硼氧三角体连接成五硼酸盐结构基团,并进一步成为无穷链状结构。测量并分析了样品的发射光谱,结果显示玻璃能发出强的绿光(543nm),归属于Tb3+的5D4->7F5的跃迁,随Si含量的增加,发光强度降低。     

High photosensitivity and nanometer-scale phase separation in GeO(2)-SiO(2) glass thin films

Amorphous xGeO(2)-(1-x)SiO(2) thin films exhibit large negative index changes (4-8%) in the high GeO(2) region (x>~0.25) on irradiation with ArF laser pulses. The sign of the index change is opposite the low GeO(2) region X<0.25, and the magnitude of the index change is larger by an order of magnitude than that reported so far. Cross-sectional transmission electron microscope observation has revealed that nanometer-scale phase separation is induced in these highly photosensitive glasses by irradiation with ArF excimer laser light pulses or electron beams. This is a first finding of microphase separation in SiO(2)-GeO(2) glasses by irradiation and provides an essential constraint on the modeling of photonic effects induced by irradiation in these glasses.     

Interactions of gamma rays with undoped and Mn-doped sodium phosphate glasses

Ultraviolet and visible spectroscopic measurements were used to investigate prepared undoped and Mn-doped sodium phosphate glasses before and after successive gamma irradiation. The effects of both glass composition and MnO₂ content on the generation of radiation-induced defects were investigated. Undoped sodium phosphate glass shows strong UV absorption, which is attributed to the presence of trace iron impurities present in the raw materials. Mn-doped glasses reveal an additional visible broad band centered at about 500 nm due to Mn³⁺, which has recently been related to the ⁵E_g →⁵T_2g transition. The radiation-induced bands are correlated with the generation of liberated electron–hole pairs during the process of gamma irradiation and the possibility of photochemical reactions especially with trace iron impurities and manganese ions. The intensity and the position of the induced bands are observed to depend on the type and composition of glass, concentration of the dopant and also on the irradiation dose. Manganese ions when present in relatively higher content have been found to show a shielding behavior towards the effects of progressive gamma irradiation causing a retardation of the growth of the induced defects. Infrared and Raman spectra of the undoped and Mn-doped glasses were measured to investigate the structural phosphate groups present and the effect of MnO₂ on the network structure. An ESR investigation was carried out to confirm the state of manganese ions in the prepared sodium phosphate glasses.     

Space-selective phase separation inside a glass by controlling compositional distribution with femtosecond-laser irradiation

Space-selective phase separation was induced inside Na₂O–SiO₂ glasses by changing the glass composition locally from a miscible composition to an immiscible one via femtosecond-laser irradiation at a high repetition rate. The formation of a nanoscale co-continuous structure due to phase separation was confirmed by scanning electron microscopy after heat treatment, polishing until the laser-modified area was exposed, and subsequent etching. The configuration of the structure could be controlled by changing the heat-treatment time.     

The Microstructure of Soda-Lime Silicate Glasses Detected by Electron Microscopy

Transmission electron microscopy and selected area electron diffraction performances were used to characterise the microstructure of a multicomponent soda-lime silicate glass, the composition of which corresponds to the miscibility gap in the SiO₂—Na₂O system. It has been stated that phase separation already exists in as prepared specimens, and the Na₂O-rich phase occurs in the form of nearly spherical droplets. The microstructure of these glasses was modified by high-temperature annealing in air and hydrogen, by irradiation with soft X- and gamma-irradiation and by mechanical stretching. In this way the quantity, size, shape and distribution of these particles was changed. A variety of induced changes affects the structure-sensitive properties of commercial soda lime silicate glasses, which can be potentially useful for new applications.     

紫外激光照射引起的硅酸铅玻璃结构的变化

采用紫外-可见吸收光谱和电子自旋共振谱(ESR)对硅酸铅玻璃薄膜和体材料受紫外激光照射前后的结构变化进行了研究。研究发现：266 nm的紫外激光照射硅酸铅玻璃体材料时,能使其Urbach能量增大,即玻璃结构的无序性增大。电子自旋共振谱研究表明,266 nm激光照射不会在硅酸铅玻璃中产生顺磁缺陷中心, 也不会对硅酸铅玻璃薄膜在235 nm附近的吸收峰产生影响,但用248 nm紫外激光照射则观察到了235 nm吸收峰的光漂白现象。     

HT—6B等离子体对金属玻璃的辐照效应

金属玻璃是由熔态经急冷淬火形成的非晶态金属,具有很高的力学强度和良好的抗腐蚀、耐辐照性能。关于中子、质子、电子和He、Ar离子等分别对金属玻璃的辐照损伤效应已有一些研究报道。托卡马克装置中的等离子体辐照是一种十分复杂的过程,它包括有质子、电子、光子、氘核和少量杂质重离子与中性粒子的混合辐照。本工作研究了某些金属玻璃在托卡马克装置真空器壁处经等离子体辐照以后的结构变化,探索金属玻璃用于托卡马克核聚变装置真空器壁的可能性。     

XPS and Raman studies of electron irradiated sodium silicate glass

The microstructure modifications of sodium silicate glass induced by 1.2-MeV electron irradiation are studied by x-ray photoelectron spectroscopy and Raman spectroscopy. Depth profile analyses are also performed on the irradiated glass at 109 Gy. A sodium-depleted layer with a thickness of a few tens of nanometers and the corresponding increase of network polymerization on the top surface are observed after electron bombardment, while the polymerization in the subsurface region has a negligible variation with the irradiation dose. Moreover, the formation of molecular oxygen after electron irradiation is evidenced, which is mainly aggregated in the first two-micron-thick irradiated glass surface. These modifications are correlated to the network relaxation process as a consequence of the diffusion and desorption of sodium species during electron irradiation.     

氟锆酸盐光纤玻璃中的析晶和分相现象

氟化物光纤玻璃中的夹杂物,分相颗粒和微晶颗粒等缺陷,造成光纤的散射损失,影响了实际制备工作.本文利用大视场光学显微镜,X射线衍射,透射电子显微镜和差热分析,研究了ZBLA氟化物玻璃中的分相和析晶现象,观察到了以成核生长机理进行的分相颗粒,析晶颗粒的成分是β-BaF_2·ZrF_4和α-BaF_2·2ZrF_4,通过DTA分析确定了这些相的析晶活化能.     

Femtosecond Laser Induced Rewritable Optical Memory in Silicate Glasses

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