摘要
受限于传统表征方法的能力,在建立硅酸盐水泥最主要的水化产物——水化硅酸钙(C-S-H)理论模型时获取的化学组成、结构参数等信息多是基于水泥颗粒群的测试结果。由于C-S-H的组成和结构极易受水化环境影响,C-S-H结构和组成的量化研究有待进一步优化。光镊技术作为一种可实现微小粒子无损捕获的技术,已被用于多个领域的单颗粒研究。将光镊技术引入水泥基材料领域,观测单个水泥颗粒的水化,有利于实现其水化条件的精准控制,降低不同颗粒间的相互影响。利用光镊技术从微米和纳米尺度直接获取C-S-H的形貌特征、化学组成及结构参数等信息,为进一步优化C-S-H纳米结构模型提供理论依据。按照捕获精度的不同,光镊技术经历了三个主要发展阶段:(1)常规远场光镊。多适用于捕获微米级粒子。其捕获对象以生物细胞为主,逐渐向有机和无机材料领域拓展。(2)近场光镊。利用近场光学的倏逝场,突破了传统衍射极限限制,实现了微米及亚微米尺度粒子的捕获。(3)纳米孔径光镊。主要基于自诱导反作用力(SIBA)效应,使得捕获精度提升至纳米尺度,降低了激光功率,减小了热损伤,丰富了光镊技术可操控的对象。目前三种光镊技术的捕获介质满足液体、气体与真空环境,捕获对象包含有机粒子、无机粒子和金属粒子等,理论上可满足各领域的研究要求。光镊技术能否捕获微粒与激光波长、光束功率、捕获介质、微粒性质等诸多因素相关。微粒性质主要与其折射率有关,折射率越大越有利于产生拉力,即梯度力。本文统计了已经实现捕获的部分微粒的性质,其物质折射率涵盖0.30~2.86。对水泥颗粒而言,其折射率在1.7左右,静止空气的捕获介质不会影响水泥水化,毫瓦级的捕获功率不足以损伤水泥颗粒,因此理论上可实现稳定捕获。本文综述了光镊技术的研究现状,重点探讨了其应用对象、操作环境以及操作精度的异同,提出了光镊技术在水泥基材料中的应用前景。
Calcium silicate hydrate(C-S-H),as the main hydration product of Portland cement,is limited by the ability of traditional characterization methods when establishing theoretical models.However,the information,which is used to establish the theoretical model like chemical composition and structural parameters,is based on the results of cement particle groups.Since the composition and structure of C-S-H are susceptible to the change of hydration condition,the average results need to be further optimized to accurately explain C-S-H.Optical tweezers technology have been used in single particle research of many fields,because it can capture small particles nondestructively.Introducing optical tweezers into the research of cement-based materials can manipulate the individual cement particle and observe its hydration,which is beneficial to achieving the precise control of cement hydration conditions and reducing the interaction effect between different particles.By using optical tweezers,morphological characteristics,composition and structure of C-S-H at the micro-nano scale can be directly explored under specific hydration conditions.This is of significance for establishing a theoretical model of C-S-H which is closer to the actual system.Optical tweezers have gone through three main development stages according to the difference of capture accuracy as follow:(i)Far-field optical tweezers are more suitable for capturing micron-sized particles.The capture objects mainly include microbial cells and gradually expand the field of organic and inorganic materials.(ii)Near-field optical tweezers are suitable for capturing micron and sub-micron particles.They break through the classical optical diffraction limit through the evanescent field of near field optics.(iii)Nano-aperture optical tweezers are based on the self-induced back-action(SIBA)effect,which increases the capture accuracy of optical tweezers to nanoscale.Nano-aperture optical tweezers can reduce the laser power,decrease the thermal damage and enrich the capture objects.At present,the capture medium of the three optical tweezers includes liquid,gas and vacuum,while the capture objects extend to organic particles,inorganic particles and metal particles,making it applied to the particles in various fields in theory.The parameters of optical tweezers to capture particles include many factors such as laser wavelength,beam power,capture medium and particle properties.For the particle,capture is mainly related to its refractive index.The larger the refractive index is,the more helpful it is to produce“pull force”(gradient force).This paper counts the properties of some particles that have been captured,and the refractive index ranges from 0.30 to 2.86.For cement particles,the refractive index is about 1.7.The capture medium of air will not affect cement hydration,and the laser power for capture is at milliwatt level which is not enough to damage the cement particles.Thus it is realizable to achieve the capture of cement particles stably.This paper reviews the research about optical tweezers.Their application objects,capture medium and capture accuracy are focused,and the application of optical tweezers in cement-based materials is explored.
作者
周玥
朱哲誉
徐玲琳
王中平
周龙
ZHOU Yue;ZHU Zheyu;XU Linglin;WANG Zhongping;ZHOU Long(School of Materials Science and Engineering,Tongji University,Shanghai 201804,China;Key Laboratory of Advanced Civil Engineering Materials,Ministry of Education,Tongji University,Shanghai 201804,China)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2022年第8期95-101,共7页
Materials Reports
基金
国家自然科学基金(51772212)。
关键词
水泥基材料
水化硅酸钙(C-S-H)
光镊技术
纳米孔径光镊
cement-based materials
calcium silicate hydrate(C-S-H)
optical tweezers technology
nano-aperture optical tweezers
