散射光弹性技术在化学钢化玻璃表面应力测量中的应用

在智能手机、平板电脑等电子产品领域,化学钢化超薄玻璃的需求不断增加,而玻璃是易碎材料,要提高或保持强度和抗破碎能力,必须正确认识应力分布。如何有效的测量化学钢化玻璃的表面压应力(CS)和压应力层厚度(DOL),是当下一个迫切需要解决的问题。散射光弹性法是利用通过玻璃内部应力的双折射来改变极化激光束的延迟,并且散射光的强度随着激光束的延迟的变化而改变,最后通过偏振光光路上因激光束的延迟而出现的光程差和偏振特性来计算表面压应力和压应力层厚度。对散射光弹性法测量化学钢化玻璃的表面应力的理论依据、测量技术等进行了介绍。     

化学强化后玻璃应力松驰与再加热温度的对应关系

高铝玻璃通过化学强化后,获得一定的表面应力(CS)和应力层深度(DOL),当它被再次加热(或退火)时,其表面的应力会产生松驰现象,松驰程度与加热温度及玻璃本身的黏温特性有着对应关系;当加热温度达到玻璃自身的转变点(T_g)温度时,应力松驰达到极限,即玻璃表面应力被全部松驰,CS、DOL值回到零。     

钢化玻璃表面应力测量结果不确定度的评定和分析

钢化玻璃属于安全玻璃.钢化玻璃其实是一种预应力玻璃,为提高玻璃的强度,通常使用化学或物理的方法,在玻璃表面形成压应力,玻璃承受外力时首先抵消表层应力,从而提高了承载能力,增强玻璃自身抗风压,耐冷热冲击及抗冲击能力等.故钢化玻璃的表面应力是表征玻璃钢化程度及钢化玻璃质量优劣的一个重要指标.所以能否准确地对表面应力进行测量,并对其测量不确定度进行科学的评估是评价钢化玻璃质量好坏的关键.本文采用GB/T 18144-2000标准规定的方法对钢化玻璃进行了表面应力测量,根据JJF 1059.1-2012《测量不确定度评定与表示》评定和分析了测量结果的不确定度,为同类结果不确定度提供了评定的参考依据.     

物理气相沉积对化学钢化玻璃抗冲击强度的影响

用真空热蒸发沉积、离子束辅助沉积和磁控溅射三种方法在化学钢化玻璃上分别镀制铬薄膜和硫化锌薄膜,并对镀膜的化学钢化玻璃进行落球冲击实验,结果表明:镀膜的化学钢化玻璃的抗冲击强度变弱,不同的物理气相沉积方法对化学钢化玻璃的抗冲击强度影响不同.本文主要分析了薄膜应力和粒子束能量对化学钢化玻璃表面压应力的影响,并探讨化学钢化玻璃抗冲击强度变弱的原因,提出了解决的方法.     

熔盐K2CO3含量对超薄玻璃化学钢化性能的影响研究

采用一步离子交换法制备离子交换钢化玻璃.研究熔盐K2CO3含量对钢化玻璃的性能影响.离子交换时间设定在20 h,离子交换温度设定为380℃,熔盐的K2CO3含量分别设定为0％、1％、2％、3％、4％.离子交换工艺完成后,对化学钢化玻璃进行电子探针测试,表面应力测试,抗折强度测试,显微硬度测试,以分析熔盐K2 CO3含量的改变对化学钢化玻璃所产生的影响.数据结果显示:熔盐的K2CO3含量的变化会对化学钢化玻璃的机械性能产生较大影响.在离子交换过程中K+的扩散系数随着K2CO3含量的增大先增大后减小,Na+的扩散系数随着K2 CO3含量的增大逐渐增大.应力层深度DOL在K2CO3含量为1％时有最大应力深度;表面应力CS在K2CO3含量为3％时有最大值.抗折强度随着K2CO3含量的增大先升高后下降,最大值在K2CO3含量为2％处;显微硬度呈现先升高后下降的趋势,最大值在K2CO3含量为3％处.将交换熔盐的K2CO3含量控制在2％至3％之间能够得到最佳的综合力学性能.     

风冷钢化玻璃应力分布特征及不均匀度评价

钢化玻璃表面应力分布的不均匀性对其钢化品质、安全性都产生重要影响,但风冷钢化玻璃应力分布不均匀是无法消除的,因此需对钢化玻璃应力分布不均匀性给予一定的客观评价.本文基于不同刚化程度玻璃表面应力的测试结果,分析了其应力分布特征,并采用标准偏差对其应力分布不均匀度进行评价,研究结果表明:钢化玻璃表面应力分布总体上是边部应力较大,中间应力偏小,但任一钢化玻璃表面应力分布形态各异,无规律可循.钢化玻璃表面应力分布不均匀度基本在0～0.05范围内,建议采用标准偏差衡量的钢化玻璃表面应力不均匀度应不大于0.05为佳.     

国家钢化玻璃均质化标准将出台

对钢化玻璃进行均质处理，目的是要大大降低钢化玻璃的自爆率。普通退火玻璃经过热处理工艺成为钢化玻璃，钢化玻璃的表面形成了压应力层，使得玻璃的机械强度、耐热冲击强度得到了提高，并具有了特殊的碎片状态。     

第一步离子交换时间对化学钢化玻璃的性能影响

本文主要研究化学钢化玻璃中第一步离子交换的时间对化学钢化玻璃的性能影响.制备出不同的离子交换时间的化学钢化玻璃.分析第一步交换时间对钢化玻璃的弯曲强度、Weibull模数、表面应力大小、深度以及K+离子扩散所产生的影响.结果表明:随着第一步离子交换时间的延长,弯曲强度逐渐降低,Weibull先升高后降低,在40h时达到最高值;表面应力大小会随着时间的延长而降低,应力深度会增加;K+离子扩散曲线符合菲克第二定律的拟合曲线.扩散深度随着时间增加而增加,并且会在玻璃内部产生富集峰.     

抛光对浮法超薄碱铝硅酸盐玻璃化学强化翘曲影响研究

将抛光气氛面(A)、抛光锡面(B)和原片(C)超薄浮法铝硅酸盐玻璃在相同化学强化条件(420℃/5h)下化学强化,分析比较化学强化指标(CS、DOL)、翘曲变形量(Wv)、气氛面与锡面的化学组成,发现A的气氛面Na_2O含量高于锡面,B和C的气氛面Na_2O含量均低于锡面;A气氛面CS大于锡面,B、C气氛面CS均小于锡面,A、C气氛面DOL均略大于锡面,B气氛面DOL略小于锡面,但是DOL相差很小;三种样品的翘曲值依次为BCA,且翘曲方向均为向空气面凸起。另外将未经处理的原片在相同条件下(420℃/4h)进行强化,然后分别抛光气氛面(D)和锡面(E),并分析比较化学强化指标(CS、DOL)、翘曲变形量(Wv)。发现D气氛面CS小于锡面,向气氛面凸起,且翘曲值大于未抛光的样品;E气氛面CS大于锡面,向锡面凸起,且翘曲值小于未抛光的样品。实验结果表明浮法超薄铝硅酸盐玻璃两面CS值差异是引起化学强化翘曲变形的一个重要原因。根据本研究结果,控制超薄浮法铝硅酸盐玻璃气氛面CS值大于锡面是减少化学强化翘曲变形值的有效手段。     

钢化应力与硫化镍结石对钢化玻璃自爆率的影响

通过设定不同钢化应力、硫化镍粒径及距中心面位置、玻璃厚度,计算出不同条件下钢化玻璃内部应力,得到了残余应力分布曲线及自爆临界曲线,并结合80例钢化玻璃自爆源样品测试,讨论了降低自爆率的途径.结果表明:玻璃厚度不变时,随着表面压应力值的增大,自爆临界曲线的截止粒径逐渐变小,截止位置也趋近中心面;表面压应力不变时,截止粒径及截止位置不受玻璃厚度影响;若排除临界尺寸0.046 mm以上的结石,自爆率可由现在的0.3％降低至0.003％.     

超薄铝硅玻璃离子交换工艺研究

高强度超薄盖板玻璃是电子信息产品的重要组成部分,化学强化(离子交换)是提升超薄盖板玻璃力学性能的主要技术途径。在离子交换过程中,玻璃易产生应力弛豫等现象,导致化学强化玻璃难以具备较高的表面压应力、较大的应力层深度与较高的维氏硬度。本文采用两步法离子交换工艺,研究了熔盐、离子交换温度与时间等因素对强化后超薄铝硅玻璃应力层分布及维氏硬度等性能的影响。结果表明,本文所研发的两步法离子交换工艺,可以使玻璃兼具较高的表面压应力、较大的应力层深度与较高的表面维氏硬度。离子交换后,铝硅玻璃的表面压应力可达900 MPa以上,应力层深度可达70 μm以上,同时表面维氏硬度达7.2 GPa以上。     

Fracture Analysis of Chemically Strengthened Glass Disks

The increase in fracture strength in chemically strengthened, soda-lime glass disks compared with nonstrengthened ones is investigated analytically and experimentally. An empirical stress-relaxation function is proposed to predict the stress profile through the disk as a result of ion exchange, with parameters determined from experimental data. The function accounts for stress increase due to concentration rise and decrease caused by stress relaxation, which depends on concentration, treatment time, and exchange temperature. The surface-flaw closure distance caused by the compressive stress profile is computed using an existing model. The size of the most severe surface flaw for chemically strengthened disks is computed using fracture mechanics, assuming knowledge of the experimental failure strength. The predicted flaw size is slightly smaller than that calculated for a similar sample of nonstrengthened disks and the strengthening is underpredicted by a factor of 2. Reasons for the discrepancies are discussed.     

化学强化玻璃的发展现状及研究展望

化学强化玻璃因其表面压应力层使玻璃的机械强度提高,被广泛用于电子产品显示屏领域。本文对钠钙玻璃、铝硅玻璃、磷铝硅玻璃、锂铝硅玻璃等的化学强化进行了综述,对进一步通过优化骨干网络结构来提高玻璃本征强度获得更高机械强度的玻璃做出了可行性探索。总结了目前化学强化玻璃面临的问题及发展方向,为相关科学研究和工业生产提供参考。     

Na+浓度对化学增强钠铝硅酸盐玻璃性能的影响

熔盐中少量的Na⁺并不会对玻璃的离子交换效果产生明显影响,但当熔盐中Na⁺浓度不断增大时,化学增强钠铝硅酸盐玻璃的性能开始受到影响。本文采用一步法离子交换工艺研究了熔盐中Na⁺浓度对不同厚度化学增强钠铝硅酸盐玻璃表面压应力、应力层深度和弯曲强度等性能的影响。研究表明:熔盐中Na⁺浓度不断增大时,化学增强钠铝硅酸盐玻璃的表面压应力、弯曲强度下降;弯曲强度下降最多可达175 MPa,此时玻璃的表面压应力下降了57.4 MPa;熔盐中Na⁺浓度变化未对化学增强钠铝硅酸盐玻璃的应力层深度和可见光透过率产生明显影响。     

Thermal history and its implications: A case study for ion exchange

Glasses containing monovalent species can be chemically strengthened by the replacement of smaller ions in the glass with larger external ions in the near glass surface. This type of ion exchange puts glass surface under high compressive stress (CS). Glass mainly fails from tension with the presence of surface flaws. Chemical strengthening can change the stress at the flaw tip from tension to compression and further stop the flaw from propagating. Glass damage resistance is therefore significantly improved. For the same glass composition, glass thermal histories can affect the magnitude and depth of the CS generated during ion exchange. In this study, the impact of thermal history on glass physical properties and ion exchange attributes in one alkali-containing glass formed by fusion draw process was investigated. Multiple thermal treatments were done to rewrite the glass thermal histories. Glass density, refractive index, and ion-exchange properties as a function of the thermal treatment were studied. It is concluded that ion exchange-related properties change dramatically with the glass thermal history.     

Structure and physical properties evolution of ITO film during amorphous-crystalline transition using a highly effective annealing technique

Three kinds of amorphous ITO (a-ITO) films were deposited on chemically strengthened glass by DC magnetron sputtering at room temperature. A rapid infrared annealing (RIA) device was built, and an infrared fast crystallization process was developed. Not only the effects of RIA on the structural, optical, and electrical properties of ITO films, but also the effects of RIA on the mechanical properties of chemically strengthened glass substrates were investigated compared with those of conventional furnace annealing (CFA). The rules of the structural and physical properties during amorphous-crystalline transition are basically the same by RIA and CFA. However, the RIA time is only 10% of the CFA time, and the compressive stress reduction of chemically strengthened glass is only 4.2% at 500 °C, which is 38.5% by CFA. These results demonstrate that very effective RIA technology could replace the traditional annealing method (CFA), which can greatly reduce production costs and significantly improve production efficiency.     

Selective Stress Relaxation on Chemically Strengthened Glass Sheets for Conventional Wheel Cutting

We introduce, for the first time to the best of our knowledge, the use of variable frequency microwave (VFM)‐assisted second ion exchange to selectively modify the compressive stress CS in chemically strengthened glass sheets, which allows for separation of these glass sheets into smaller pieces using a conventional cutting tool. The CS in paste‐coated zones, in the regions where it is desired for separation of the glass sheets, was successfully manipulated via VFM‐assisted second ion exchange, substituting the larger alkali ions in glass by smaller ions of the paste. Its effect on chemically strengthened glass was characterized using a strain viewer, an optical microscope, and an electron probe microanalyzer. We also report on the scribability and breakability across the stress relaxation zones. The results reveal a CS loss of only 3%, from 677 to 656 MPa, in the paste‐uncoated zones, and complete CS relaxation, down to 0 MPa, in the paste‐coated regions. The areas of relaxed CS enable the separation of the strengthened glass sheets using conventional wheel cutting.     

热处理对离子交换高碱铝硅酸盐玻璃性能的影响

将离子交换高碱铝硅酸盐玻璃在340~460℃热处理1 h,研究热处理对离子交换玻璃性能的影响。测试了热处理后玻璃的表面应力、应力层深度、强度和硬度。结果表明:随着热处理温度的升高,玻璃的表面应力及强度明显下降,应力层深度有所增加,而硬度略微下降。     

Coupling of diffusion and chemical stress: The case of ion exchange in glass

The chemical strengthening of glass results from an ion exchange process in which smaller alkali ions in a glass are replaced with larger alkali ions from a molten salt bath. This interdiffusion process leads to a buildup of chemical stress in the glass. However, traditional modeling of the ion exchange process has not fully accounted for interaction effects between mass diffusion and the chemical stress developed during the process. In this study, we develop the general theory of coupling between diffusion and stress, resulting in a single flux equation with a concentration- and stress-dependent interdiffusion coefficient. We apply the theory to the specific cases of chemically strengthened soda lime silicate and aluminosilicate glasses, demonstrating the impact of interaction terms on concentration profiles and interdiffusion coefficient. Following a phenomenological approach, this study demonstrates the effect of the interdiffusion on stress generation and vice versa to account for deviations from the simple expressions published hitherto in the literature.