防覆冰涂层构建机理及制备

航空、通信、电力和运输设备的覆冰现象给人们的生产、生活带来许多不便,甚至引起重大经济损失,防覆冰涂层主要通过材料表面特殊物理化学性能与微相形貌来实现抗冰目的,这类材料需要兼具防结冰性和疏冰性,从延长结冰时间和降低冰的附着力两方面来减轻甚至消除冰雪积聚,是目前研究的热点。本文从防覆冰机理入手,深入探讨了防结冰性和疏冰性的影响因素,阐述了防覆冰涂层材料的设计与制备方面的最新进展,并对防覆冰涂层目前存在的问题与发展方向进行了分析和展望。     

超疏水涂层表面粗糙结构对防覆冰性能的影响

结冰给交通、电力输送和航空等领域带来极大的安全隐患,研究防覆冰技术具有重要的应用价值。目前最具前景的防冰方法是涂层防冰,本文介绍了疏水涂层的构建方法,阐述了涂层疏水性和疏冰性之间的关系;重点论证了涂层表面粗糙结构对其防覆冰性能的影响,指出防覆冰涂层研发中存在的问题,并对该领域的发展趋势进行了分析和展望。     

超疏水涂层防覆冰机理及制备

结构物表面严重覆冰有时会威胁人们的生命财产安全,影响经济社会的平稳运行。超疏水涂层具有超大接触角、低滚动角的特性,在防覆冰领域有很好的应用前景。本文重点总结了超疏水涂层防覆冰机理的相关研究结果,并简单综述了聚合物-微粒复合材料类、特殊表面结构类两种典型超疏水型防覆冰涂层的研究进展,指出了目前在超疏水型防覆冰涂层研究中存在的不足,并对其发展趋势进行了展望。     

防冰高分子材料

防冰高分子材料作为一种新型功能高分子材料,在电力、通讯及运输等领域有广泛应用.表面的覆冰现象往往开始于冰的成核,发展于冰的传递,危害于冰的积聚.针对材料表面冰晶形成的环节,揭示冰晶形成的分子机制是设计和开发防冰高分子材料的关键.本文简要介绍了本课题组在防冰高分子材料领域的研究进展,包括设计搭建的基本研究设备,以及具有调控冰成核、控制冰传递、降低冰黏附等不同功能的防冰高分子材料.     

仿生多微纳米梯度界面的液滴动态行为调控

对液滴在界面上动态行为的研究是化学和材料领域的一个重要方向,许多先进的表面和界面技术,比如集水、防覆冰、防雾、微流体控制和传热等,均属于这一范畴.通过模仿自然界中具有特殊微纳米结构和特定化学组成的生物表面,设计并构筑相应具有特殊浸润性的仿生界面,对仿生界面材料的技术应用起到了良好的先导与示范作用.本文结合本课题组的研究...     

仿生控冰材料用于细胞及组织的冷冻保存

冷冻保存是将细胞、组织或器官等生物样品置于超低温环境中, 使其代谢速率大大降低甚至停止, 以达到长期存储的目的, 并能在解冻后恢复其生理功能的科学与技术. 冷冻保存是当前实现生物样品长期存储的唯一有效手段, 是细胞治疗、再生医学以及器官移植等先进医疗技术充分发展的关键瓶颈之一. 然而, 由于细胞、组织中的含水量可高达70%~90%, 在不添加冷冻保护剂的情况下, 降温及复苏过程中伴随的冰晶损伤、渗透压失衡及溶质过度积累等必然会导致冻存失败. 传统冷冻保存策略通过大量使用二甲基亚砜(dimethyl sulfoxide, DMSO)等能与水形成氢键的有机小分子置换出部分胞内水分, 有效避免了胞内形成大冰晶及溶质过度积累等不利因素, 使细胞得以成功冻存. 然而, 该类小分子已被证实破坏蛋白质结构、胞间连接, 并且具有表观遗传毒性; 同时, 传统的冻存策略很难用于组织器官冻存. 因此冷冻保存科学与技术急需冷冻保护材料(剂)的创新, 以摒弃有毒小分子的大量使用, 实现细胞、组织及器官的安全高效冻存. 控冰蛋白是在极寒地区生物体内发现的一类高效冰晶成核与生长控制剂, 可以保护生物不受冰冻损伤. 揭示控冰蛋白作用机制将为仿生构筑高效控冰材料, 开发新型控冰冷冻保存剂提供全新的思路. 本综述将简单回顾冷冻保存的发展历史, 评述传统冷冻保存策略的优缺点; 从新型仿生控冰冷冻保护剂的研究出发, 重点阐述近几十年来控冰蛋白控冰机制的研究进展、仿生控冰材料的创制及其在冷冻保存中的应用; 最后将进一步展望仿生控冰冻存材料未来的发展方向.     

金属有机框架基防冰膜的制备及其性能

采用点击化学反应在UiO-66-NH_2膜表面原位生长硅油润滑层,制备了金属有机框架(MOF)基防冰膜(OGMCs),通过硅油生长时间调控了表面硅油量,并对不同硅油含量的OGMC的防冰性能进行了研究。利用扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FT-IR)、X射线衍射仪(XRD)、X射线光电子能谱分析仪(XPS)和接触角等技术手段对OGMCs表面进行了表征。结果表明:硅油被成功合成出来,并以共价键方式与MOF膜连接。OGMC保留了MOF膜表面原有的微纳复合结构以及UiO-66的晶体结构。OGMC表面的硅油量随硅油生长时间而增加。但表面冰成核温度和冰粘附力均随硅油生长时间而先下降后升高。硅油量密切影响微纳复合结构表面的防冰性能。当硅油生长时间为12～18 h,表面硅/锆物质的量比在8～12时,表面防冰效果最佳,表面冰成核温度可达到-29.6℃,冰粘附力达到8.8 kPa。     

超浸润光热材料的构筑及其多功能应用研究

随着工业社会的不断发展,不同行业对于超浸润材料的功能提出了更高的要求,超浸润材料向多功能化或智能化转型成为其发展的必然趋势。同时,在人们对环境问题日益重视的背景下,符合环保可持续、高效、低耗的新技术受到关注,具有光热效应的超浸润材料作为实现油水分离、海水淡化及太阳能蒸发等领域的新兴产品而成为研究热点。本文首先介绍了近年来碳基、有机物基、半导体基及复合型超浸润光热材料构筑的研究现状并对其局限性进行了分析,然后梳理并详细论述超浸润光热材料在防覆冰、海水淡化、油水分离等领域的应用进展及其作用机理,进而总结了其目前制备过程中存在的环境危害性等问题,并对功能性与智能型超浸润光热材料的发展趋势及研究路线进行了展望。     

有机硅改性聚氨酯/纳米SiO2复合超疏水涂层的制备

以4,4'-二苯基甲烷二异氰酸酯(MDI)、聚四氢呋喃醚二醇(PTMEG)、羟基封端的聚二甲基硅氧烷(HO-PDMS)、1,4-丁二醇(BDO)为原料,合成了有机硅改性的聚氨酯溶液,通过核磁共振、红外光谱技术对其结构进行表征,并研究了羟基硅油加入量对聚氨酯热稳定性、疏水性的影响.以有机硅改性的聚氨酯溶液为基体、含氟硅烷偶联剂改性的纳米二氧化硅颗粒为填料,喷涂制备超疏水涂层,研究了填料添加量对复合涂层疏水性的影响.结果表明:当硅油加入量为9 wt%,填料加入量为60 wt%时,复合涂层性能最优,水接触角为153.3°,滞后角为6.3°.经过200℃加热1 h后,仍然具有大于150°的水接触角.对复合涂层进行磨损实验与防冰测试,结果表明:该复合涂层在磨损过程中,在基底暴露之前,整个涂层基体都具有超疏水性;并且该涂层能有效降低结冰温度,延长结冰时间,具有良好的防冰性能.     

灌注液体型光滑多孔表面制备及应用

仿猪笼草效应的灌注润滑液的光滑多孔表面(SLIPS)是将润滑液如全氟聚醚、硅油、离子液体等灌注到微/纳粗糙结构基材中制备的。SLIPS材料表面可达到分子尺度的光滑,能显著减小液滴滑动角和滞后角,具有全方位疏液、自修复、透明度高、温度和压力稳定性好等诸多优点,能够高效抑制各种基材包括油脂、血液、冰以及生物膜的黏附,在自清洁涂料、海洋防污、生物医用领域具有广阔的应用前景。近年来SLIPS材料因其具有的特殊表面润湿性能而备受研究者的关注,本文详细介绍了SLIPS材料的构建机理和制备方法,包括浸润法和溶胀法等。综述了SLIPS材料在防污、促进滴状冷凝、防霜防覆冰、油水分离等方面的最新进展,并对SLIPS目前存在的问题与发展方向进行了分析和展望。     

Superhydrophobic surfaces: are they really ice-repellent?

This work investigates the anti-ice performance of various superhydrophobic surfaces under different conditions. The adhesion strength of glaze ice (similar to that deposited during "freezing rain") is used as a measure of ice-releasing properties. The results show that the ice-repellent properties of the materials deteriorate during icing/deicing cycles, as surface asperities appear to be gradually damaged. It is also shown that the anti-icing efficiency of superhydrophobic surfaces is significantly lower in a humid atmosphere, as water condensation both on top of and between surface asperities takes place, leading to significantly larger values of ice adhesion strength. This work thus shows that superhydrophobic surfaces are not always ice-repellent and their use as anti-ice materials may therefore be limited.     

Highly cross-linked UV-cured siloxane copolymer networks as icephobic coatings

Preventing ice growth on infrastructure, vehicles, and appliances remains a significant engineering challenge. Damage caused by ice growth on these installations can be expensive to repair, and their failure can be dangerous. Materials such as cross-linked polymer networks make effective anti-ice coatings and can prevent ice growth: reducing the cost of infrastructure repairs and limiting downtime. A link between cross-link density and ice adhesion has been demonstrated, such that lower cross-link density materials tend toward lower ice adhesion. Here we describe a method of lowering cross-link density by incorporating the covalently bound comonomers methyl methacrylate, lauryl methacrylate, and styrene into UV-cured PDMS-based polymer networks. Cross-link density, hardness, surface roughness, and ice adhesion on these materials are tested, showing the influence of comonomer proportions on their properties. Durability is found to increase with the addition of 5, 10, and 25 wt% comonomer, with little to no effect on ice adhesion until 25 wt%, where increases in ice adhesion are observed. Coatings show promisingly low ice adhesion of ~50 kPa, maintaining this low adhesion for up to 50 deicing cycles.     

聚合物在仿生合成中的应用研究进展

仿生合成技术通过模拟生物矿化机理,以有机物为模板控制无机物的生成,制备具有特殊结构及性能的无机材料.聚合物是仿生合成中较多采用的有机模板之一,用来控制无机粒子的成核、生长及排列,能够在温和条件下合成具有多级结构、特殊形貌和优异性能的有机,无机复合材料.本文综述了聚合物在仿生合成中的应用研究进展,并指出了存在的问题及发展方向.     

Ice nucleation by particles immersed in supercooled cloud droplets

The formation of ice particles in the Earth's atmosphere strongly affects the properties of clouds and their impact on climate. Despite the importance of ice formation in determining the properties of clouds, the Intergovernmental Panel on Climate Change (IPCC, 2007) was unable to assess the impact of atmospheric ice formation in their most recent report because our basic knowledge is insufficient. Part of the problem is the paucity of quantitative information on the ability of various atmospheric aerosol species to initiate ice formation. Here we review and assess the existing quantitative knowledge of ice nucleation by particles immersed within supercooled water droplets. We introduce aerosol species which have been identified in the past as potentially important ice nuclei and address their ice-nucleating ability when immersed in a supercooled droplet. We focus on mineral dusts, biological species (pollen, bacteria, fungal spores and plankton), carbonaceous combustion products and volcanic ash. In order to make a quantitative comparison we first introduce several ways of describing ice nucleation and then summarise the existing information according to the time-independent (singular) approximation. Using this approximation in combination with typical atmospheric loadings, we estimate the importance of ice nucleation by different aerosol types. According to these estimates we find that ice nucleation below about -15 °C is dominated by soot and mineral dusts. Above this temperature the only materials known to nucleate ice are biological, with quantitative data for other materials absent from the literature. We conclude with a summary of the challenges our community faces.     

Molecular dynamics simulations of ice nucleation by electric fields

Molecular dynamics simulations are used to investigate heterogeneous ice nucleation in model systems where an electric field acts on water molecules within 10-20 ? of a surface. Two different water models (the six-site and TIP4P/Ice models) are considered, and in both cases, it is shown that a surface field can serve as a very effective ice nucleation catalyst in supercooled water. Ice with a ferroelectric cubic structure nucleates near the surface, and dipole disordered cubic ice grows outward from the surface layer. We examine the influences of temperature and two important field parameters, the field strength and distance from the surface over which it acts, on the ice nucleation process. For the six-site model, the highest temperature where we observe field-induced ice nucleation is 280 K, and for TIP4P/Ice 270 K (note that the estimated normal freezing points of the six-site and TIP4P/Ice models are ～289 and ～270 K, respectively). The minimum electric field strength required to nucleate ice depends a little on how far the field extends from the surface. If it extends 20 ?, then a field strength of 1.5 × 10(9) V/m is effective for both models. If the field extent is 10 ?, then stronger fields are required (2.5 × 10(9) V/m for TIP4P/Ice and 3.5 × 10(9) V/m for the six-site model). Our results demonstrate that fields of realistic strength, that act only over a narrow surface region, can effectively nucleate ice at temperatures not far below the freezing point. This further supports the possibility that local electric fields can be a significant factor influencing heterogeneous ice nucleation in physical situations. We would expect this to be especially relevant for ice nuclei with very rough surfaces where one would expect local fields of varying strength and direction.     

Liquid crystal compound anti-ice surface

In some cold areas/regions, ice accumulation is harmful to aircrafts, highways and power lines. To overcome this challenge, many researchers have focused on developing anti-icing surfaces. In this paper, liquid crystal compound Cholest-5-en-3-ol(3β)-4-(2-propenyloxy)benzoate was synthesised, and a liquid crystal surface (LC surface) is prepared by heating the liquid crystal compound to 250°C and then cooling it. We determined ice-phobic properties of LC surface using differential scanning calorimetry (DSC) and polarised optical microscope (POM). A phenomenon that the freezing of water droplet on the LC surface is delayed was found. Compared with the two measurement methods, we obtained similar result that water freezing temperature was delayed nearly by 8°C on average on the LC surface. A process of ice/frost formation is observed using POM. The results displayed that the glass wafer without LC was covered completely by ice/frost, whereas on the LC surface at the same temperature no ice/frost was formed. Characteristics of LC surface were observed by field emission scanning electron microscope (FESEM) and Fourier transform infrared (FT-IR) imaging system. We suggest that the reason behind anti-ice surface is related to surface molecules and this is an important factor which may have an effect on anti-icing property.     

Ice nucleation in aqueous electrolytes by light scattering observation

Nucleation of ice is studied in supercooled aqueous electrolytes, after quenching, by light scattering experiments. According to salt concentration heterogeneous nucleation can occur on cracks, decorating and locking most of them. In contrast the homogeneous nucleation results are in agreement with Turnbull's theory if the equilibrium temperature for crystallization is identified with the homogeneous nucleation temperature. The mean field scaling law is obtained for the steady state frequency of the ice nucleation per unit volume which gives some estimate for the quantity β^1/3related to the melting of ice and its interface with the solution near 140–145 K. The scaling law is also obtained for the transient nucleation period.     

无机材料的仿生合成

生物矿化重要的特征之一是细胞分泌的有机基质调制无机矿物的成核和生长, 形成具有特殊组装方式和多级结构特点的生物矿化材料(如骨、牙和贝壳)。仿生合成就是将生物矿化的机理引入无机材料合成, 以有机物的组装体为模板, 去控制无机物的形成,制备具有独特显微结构特点的无机材料, 使材料具有优异的物理和化学性能。仿生合成已成为无机材料化学的研究前沿。本文综述了无机材料仿生合成的发展现状。     

Homogeneous ice nucleation from aqueous inorganic/organic particles representative of biomass burning: water activity, freezing temperatures, nucleation rates

Homogeneous ice nucleation plays an important role in the formation of cirrus clouds with subsequent effects on the global radiative budget. Here we report on homogeneous ice nucleation temperatures and corresponding nucleation rate coefficients of aqueous droplets serving as surrogates of biomass burning aerosol. Micrometer-sized (NH(4))(2)SO(4)/levoglucosan droplets with mass ratios of 10:1, 1:1, 1:5, and 1:10 and aqueous multicomponent organic droplets with and without (NH(4))(2)SO(4) under typical tropospheric temperatures and relative humidities are investigated experimentally using a droplet conditioning and ice nucleation apparatus coupled to an optical microscope with image analysis. Homogeneous freezing was determined as a function of temperature and water activity, a(w), which was set at droplet preparation conditions. The ice nucleation data indicate that minor addition of (NH(4))(2)SO(4) to the aqueous organic droplets renders the temperature dependency of water activity negligible in contrast to the case of aqueous organic solution droplets. The mean homogeneous ice nucleation rate coefficient derived from 8 different aqueous droplet compositions with average diameters of ～60 μm for temperatures as low as 195 K and a(w) of 0.82-1 is 2.18 × 10(6) cm(-3) s(-1). The experimentally derived freezing temperatures and homogeneous ice nucleation rate coefficients are in agreement with predictions of the water activity-based homogeneous ice nucleation theory when taking predictive uncertainties into account. However, the presented ice nucleation data indicate that the water activity-based homogeneous ice nucleation theory overpredicts the freezing temperatures by up to 3 K and corresponding ice nucleation rate coefficients by up to ～2 orders of magnitude. A shift of 0.01 in a(w), which is well within the uncertainty of typical field and laboratory relative humidity measurements, brings experimental and predicted freezing temperatures and homogeneous ice nucleation rate coefficients into agreement. The experimentally derived ice nucleation data are applied to constrain the water activity-based homogeneous ice nucleation theory to smaller than ±1 order of magnitude compared to the predictive uncertainty of larger than ±6 orders of magnitude. The atmospheric implications of these findings are discussed.     

Free energy landscapes for homogeneous nucleation of ice for a monatomic water model

We simulate the homogeneous nucleation of ice from supercooled liquid water at 220 K in the isobaric-isothermal ensemble using the MW monatomic water potential. Monte Carlo simulations using umbrella sampling are performed in order to determine the nucleation free energy barrier. We find the Gibbs energy profile to be relatively consistent with that predicted by classical nucleation theory; the free energy barrier to nucleation was determined to be ~18 k(B)T and the critical nucleus comprised ~85 ice particles. Growth from the supercooled liquid gives clusters that are predominantly cubic, whilst starting with a pre-formed subcritical nucleus of cubic or hexagonal ice results in the growth of predominantly that phase of ice only.