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应用化学交流论坛举办第九期——发泡材料
No full text3月25日，第九期应用化学交流论坛在图书馆三楼阅览室成功举办。本期论坛以“发泡材料”为主题，邀请中科院生态环境高分子材料重点实验室董丽松研究员、高分子物理与化学国家重点实验室唐涛研究员担任主讲嘉宾。景遐斌研究员、姬相玲研究员、姜伟研究员、栾世方研究员、李胜海研究员、科技发展处孙小红处长以及多位中青年科研骨干、来自东北师大的青年教师等参加了此次活动。论坛活动中大家回顾了应化所发泡材料研究历史，分析了领域的现状，展望了行业的发展前景。参会者介绍了各自所在课题组从事的相关工作及进展情况，在讨论了一些共性科学问题的同时，又从基础理论、应用拓展、产业化推进等方面提出了新的问题和设想。针对目前国家重点研发计划的组织模式，参会者表达了对整合力量组建更大团队的想法，规划与信息处、科技发展处也就所内相关政策做了解释和说明。为取得更好的交流效果，论坛积极尝试各种组织形式。此次论坛活动在资产处图书馆的大力支持下，在更和谐的交流氛围中获得了参会者的广泛好评。“应用化学交流论坛”由所学术委员会牵头，由规划与信息处负责组织实施。目的在于加强所内科研人员相互了解，增进沟通交流，推进相近领域方向人员展开合作，促进跨学科跨领域前沿探索，激发中青年人才创新活力。2016年论坛活动将更加关注材料领域，注重产学研结合，加大“请进来、走出去”力度，打造东北地区最具影响力的学术活动品牌
植酸-金属络合物超亲水薄膜
No full text近年来，超亲水表面由于其广阔的应用前景而被科研工作者们密切关注。通常来讲，超亲水表面是指水滴的表观接触角小于5°的表面。过去十几年里，随着纳米科学技术的不断发展，人们开发了越来越多的制备超亲水表面的方法，但是这些方法仍然存在很多不足之处。例如：设计路线复杂、过程耗时长以及设备昂贵等。而且这些方法通常只适用于特定的基底，大大限制了其应用范围。因此，本论文选用天然物质植酸作为有机框架，三价铁离子作为连接单元，构建了含有大量POOH基团的交联网络薄膜，可以使多种基底表面实现超亲水的功能。 首先，我们将干净的硅基底浸泡在植酸溶液中，几分钟后加入氯化铁溶液，混合的溶液中出现大量白色络合物。再过几分钟，取出硅片，发现该硅基底的接触角由原来的58°变成了0°。随后我们将该方法应用到多种基底上均得到了超亲水的表面。 接下来，我们利用原子力显微镜，研究了植酸浸泡时间，成膜时间，原料浓度等参数对植酸金属薄膜形成及生长产生的影响，发现薄膜生长过程很快达到平衡，厚度仅为10 nm左右。之后我们发现，经过层层沉积的方法，薄膜厚度可以呈线性增长，因此可以通过此方法精确调控薄膜厚度。 最后，我们将植酸金属薄膜应用到油水分离和防雾透明表面上，并对这些应用的实际效果进行了测试。发现经植酸金属薄膜修饰的不锈钢网在油水分离时，具有很高的分离效率和很大的水通量。经植酸金属薄膜修饰的的石英片具有防雾透明的功能，有望被应用到汽车车窗，眼镜，潜水镜以及腹腔镜等镜片上。 以上工作证明，利用植酸金属络合物在固体表面上成膜，是一种简单快速且适用于多种基底的构建超亲水表面的新方法。In recent years, superhydrophilic surface has attracted great attention because of its broad application prospects. Usually, superhydrophilic surface is refer to the surface with water contact angle less than 5°. Over the past ten years, with the development of nano-science and technology, more and more methods for the preparation of superhydrophilic surface have been developed. However, these methods have various limitations, such as complicated routes, time-consuming procedure, and the use of complex instrumentation and so on. Moreover, these methods are generally applied on a given or a type of substrates and can hardly be developed as a general route to be rationally applied on a range of materials, which limits the range of applications. In this regard, we chosed natural phytic acid(PA) as organic ligand and iron (FeⅢ) as the inorganic cross-linker, to build a crosslinked network film that can modify a variety of substrates to be superhydrophilic because of massive POOH groups. Firstly, the cleaned Si substrate was immersed in the PA solution for several minutes, then the FeCl3?6H2O solution was added to this PA aqueous solution. A lot of white complex appeared in the mixed solution at once. After several minutes, the FeⅢ-TA coated Si substrate was removed and the contact angle of the substrate turned to 0° from 58°. After that, we found that this approach can be applied on a series of materials to construct superhydrophilic surfaces. Secondly we analysed the influence of immersion time, deposition time and reagent concentrations on the formation and growth of the FeⅢ-PA film. It is found that the FeⅢ-PA film growth quickly achieve balance. The maximum thickness of the FeⅢ-PA film is only about 10 nm. Then we found that the thickness of the FeⅢ-PA film can be further increased by simply repeating the rapid coating procedure, and this increase present linear rule. Therefore, the film thickness can be precisely regulated by this method. Finally, we successfully made a variety of substrates be superhydrophilic by coating the FeⅢ-PA film. Lastly, we applied the FeⅢ-PA film to the oil-water separation and anti-fog transparent surfaces, and then tested the actual effect of these applications. It is found that the FeⅢ-PA film coated meshes can selectively separate water from various oil-water mixtures with high separation efficiency and high-flux. The FeⅢ-PA film coated quartz slides with anti-fogging and transparent features are highly desired in automobile windshields, eyeglasses, swimming goggles, lenses in laparoscopes and so on. The above work indicates that we provide a versatile strategy with facile, low-cost and environment-friendly features on multiple classes of materials to give surface superhydrophilicity by using the FeⅢ-PA complexes film
应用化学交流论坛举办第五期——生命科学中的化学问题
No full text9月7日，应用化学交流论坛第五期成功举办，本期论坛的主题为"生命科学中的化学问题"。化学生物学实验室曲晓刚研究员应邀担任本期主讲嘉宾，就"生命科学中值得关注的几个重要化学问题"与中青年科技人员进行交流讨论，百人计划入选者张海元研究员担任本期论坛的主持人。 化学生物学实验室高楠副研究员、蒲芳副研究员、张海元研究员，电分析国家重点实验室王宏达研究员，高分子物理与化学国家重点实验室谢志刚研究员分别以"阿尔茨海默症及其化学治疗剂的研究"、"核酸相关功能纳米材料的设计与应用"、"在纳米/生物界面水平理解纳米材料的属性-活性关系"、"单分子技术研究细胞膜结构"、"纳米药物的体内研究"为题，从多个角度就本领域的关键问题及研究热点进行了讲解讨论。 董绍俊院士(TWAS)、宋凤瑞研究员、张吉林研究员、章培标研究员、崔勐研究员、于喜飞研究员、童辉研究员、姜秀娥研究员、徐维林研究员、陶友华研究员、王晓辉研究员及青年科技骨干、研究生等近百人参加了此次论坛活动，并在会后交流沙龙活动中展开热烈讨论。 近年来，化学与生命科学交叉领域成为科学界关注热点，长春应化所在该领域人才队伍不断壮大，本期报告人王宏达研究员和谢志刚研究员分别获得了2015年国家自然科学基金杰出青年基金和优秀青年基金的支持，队伍整体实力更加坚实。 "应用化学交流论坛"由所学术委员会牵头，由规划与信息处负责组织实施。其设立的目的在于加强所内科研人员相互了解，增进沟通交流，推进所内相近领域方向人员展开合作，促进跨学科跨领域前沿探索，激发中青年人才创新活力。论坛每月组织一期，每期结合国家政策、社会需求及研究所发展方向选定一个可广泛参与的议题，组织相近领域方向中青年科技人员3-5人进行约10分钟/人的口头报告，并展开讨论。每期论坛还将邀请研究员代表与中青年科技人员举行座谈，交流科研心得，答疑解惑
两嵌段共聚物增容剂非对称对共混薄膜界面性质的影响
No full text高分子薄膜在许多方面都有着广泛的应用，例如：民用塑料袋等产品、选择性渗透膜、光电器件、生物医药材料等。随着科学技术的不断发展，单一组分的薄膜已经不能满足人们对高分子薄膜的需求，人们通常将两种或多种均聚物共混来制备性能优异的高分子薄膜。然而，大多数均聚物很难相容，且嵌段共聚物能够改善均聚物共混薄膜体系各组分间的界面性质和相容性，因此，通常向均聚物共混薄膜体系中添加嵌段共聚物作为增容剂。在理论方面，因为高分子链间和链内的相互作用非常复杂，所以在其理论研究中需要引入大量的数学或物理近似；在实验方面，因为单分散的样品合成上非常困难，价格上也非常昂贵，且很难改变体系中粒子间的相互作用参数，所以无法系统而深入地研究这些参数对增容效果的影响。但是，计算机模拟克服了上述困难；事实上，目前计算机模拟已经成为了人们探究高分子物理学领域宏观现象分子机理必不可少的研究方法和手段。通常情况下，高分子共混体系要求计算机模拟的粒子数很大，从而计算模拟的时间很长，往往超出了我们能够接受的范围；但是，如果我们只关注其热力学性质，那么可以选用运算相对较快的格子Monte Carlo模拟方法。另一方面，因为我们模拟的是薄膜体系，因此也消除了一个维度的粒子数限制，从而我们可以利用Monte Carlo模拟方法来研究均聚物/嵌段共聚物/均聚物三元共混薄膜体系的基本热力学性质，特别是，平衡后嵌段共聚物高分子链的基本性质。 在本论文中，为了描述均聚物/嵌段共聚物/均聚物三元共混薄膜体系的基本热力学性质，特别是嵌段共聚物非对称性对其界面性质的影响，我们利用Monte Carlo模拟方法，从分子链水平上研究了非对称两嵌段共聚物增容剂对共混薄膜界面性质的影响，考察了共聚物链长非对称性和A、B两种不同组分间相互作用能的非对称性对界面性质的影响，重点对比了体系中分子链尺寸、密度分布、均聚物间的界面宽度、界面附近嵌段共聚物的取向行为以及中心界面区域内分子链的自由能等物理量受对称性的影响，具体研究工作如下： 1. 两嵌段共聚物链长的非对称性对界面性质的影响：（a）随着均聚物链长的增长，嵌段共聚物的增容效果相对较差，具体表现为嵌段共聚物高分子链的均方回转半径，均方末端距，嵌段间的均方距离等随均聚物链长的增长而变小；（b）当嵌段共聚物链长较长时，对称与非对称高分子的均方回转半径等物理量相当，而当嵌段共聚物较短时，非对称比对称高分子的均方回转半径等物理量小很多，这说明：当链长较长时，高分子链仍然分布于界面；但是当非对称嵌段共聚物较短时，非对称的嵌段共聚物高分子链很容易被链长较长的共聚物组分拽到其本体中，而非界面处；因此，当嵌段共聚物较长时，非对称性对增容效果的影响较小，而当嵌段共聚物较短时，非对称高分子的增容效果差很多。 2. 相互作用强度非对称性对界面性质的影响：（a）当εAB较小时，嵌段共聚物会比较均匀的分布在整个体系中，但是随着相互作用能的增大，聚集在界面附近的嵌段也逐渐增加，同时由于焓的原因，界面也越平整。另外，体系中εAB越大，共聚物在z方向上的拉伸程度越强，取向也越明显。（b）相互作用强度的非对称性（增强某一组分自身的相互作用强度）可使得高分子链的拉伸和取向加强，从而使嵌段共聚物的增容作用增大。Compatibilizing effect of copolymers in binary blends of two homopolymers has been an attracting subject for the researchers. Homopolymers of different types are usually immiscible, and block copolymers containing both types of monomers can be used to modify the interfacial properties of immiscible homopolymer blends. Theorietically, due to the complexity of the interaction in this system, the results from the theory study were usually obtained under the approximate circumstances. Experimentally, preparation of monodisperse samples is difficult and expensive. On the other hand, it is difficult to change the interaction energy between the segment as well as the chain structure. Fortunately, computer simulation can overcome these problems, it is known that the computer simulation has been used to be not only a complement of experimental and theoretical methods, but also a valuA-Ble tool to study the polymer chain dynamics, glass transition, and phase behavior for the polymer system. In this paper, we focus on the thermodynamic properties of homopolymer / block copolymer / homopolymer film system, rather than dynamic behavior, so we use Monte Carlo simulation for this system. In this paper, we employ Monte Carlo simulations to research the effects of chain length on interface of polymer / block copolymer / homopolymer film system. The productive results are as follows. 1. Effects of the chain length asymmetry on interface properties: (a)Compatibilizing effect of diblock copolymers becomes worse as homopolymer chain length increases, which can be showed that square gyration radius, square end-to-end distance and square distance between block center of copolymers all decrease. (b)When the chain length of copolymers is relatively long, physical quantities of symmetry and asymmetry copolymers are similar, such as square gyration radius. When the chain length of copolymers is relatively short, asymmetry copolymers’ physical quantities are smaller than symmetry copolymers’. In other words, copolymers are distributed in interface when chain length are relatively long, and asymmetry copolymers concentrate in homopolymer phase when chain length are relatively short. Therefore, when chain length are relatively long, asymmetry copolymers don’t change compatibilizing effects. And when chain length are relatively short, compatibilizing effects of asymmetry copolymers is worse. 2. Effects of the interaction energy on interface properties: (a)When εAB is smaller, copolymers will distribute in system homogeneously. And when εAB is increasing, proportion of copolymers in interface is also increasing. Meanwhile interface is more flat because of enthalpy effects. Stretching and orientation effects of copolymer also increase as εAB increase. (b) Asymmetry of interaction energy(i.e., increase monomers attraction potential)could increase retching and orientation effects of copolymer, which makes compatibilizing effect better
一种共聚型聚酰亚胺纤维的表面特性及其界面性能
No full text聚酰亚胺纤维作为一种新型高性能有机纤维，具有优异的力学性能、耐热性、环境稳定性及介电性能，与目前广泛使用的玻璃纤维、芳纶纤维等相比，具有更低的密度或更高的使用温度等优势，故有望在树脂基先进复合材料、高性能绳索、线缆等高技术领域得到广泛的应用。本论文以一种共聚型高强高模聚酰亚胺纤维为研究对象，对其表面特性、表面改性及其与两种树脂的界面性能进行了详细研究，加深了对纤维表面特性和界面性能的认识，得到了简单的酸碱处理对纤维力学性能和表面及界面性能的影响规律，为纤维的实际应用奠定坚实基础。 首先，从力学性能、耐热性、表面特性和与树脂的界面剪切强度等几个方面，将共聚型聚酰亚胺纤维与PBO、K-49、F-12几种商品化高性能有机纤维进行了对比，结果发现，共聚型PI纤维的力学性能优于芳纶K-49纤维，但劣于PBO和F-12纤维；耐热性良好，玻璃化转变温度约为266 °C；300 °C和370 °C高温热老化性能优于F-12纤维，但劣于PBO和K-49纤维；聚酰亚胺纤维表面含氧活性基团含量低，表面自由能较小，与环氧树脂和聚酰亚胺树脂的界面粘合性差，界面剪切强度高于PBO纤维，但低于芳纶纤维。 其次，采用简单的酸碱处理方法对这种共聚型聚酰亚胺纤维表面进行了表面改性，详细研究了KOH、NaOH、H2SO4和HNO3四种溶液的处理时间、处理温度和处理溶液浓度对纤维力学性能和表面特性的影响，优化了处理条件。发现处理后的纤维力学性能下降，表面出现沟槽而变得粗糙，表面氧元素含量及含氧活性基团含量与未处理的纤维相比大幅度增加，且纤维表面自由能中的极性分量所占比重提高。采用较优化处理条件时，纤维力学性能受影响较小，KOH、NaOH、H2SO4和HNO3四种溶液处理后的聚酰亚胺纤维与环氧树脂和聚酰亚胺树脂基体的界面粘合性改善，改性后的纤维与环氧树脂的界面剪切强度可提高14%~37%，与聚酰亚胺树脂的界面剪切强度可提高78%~115%。可看到后者界面剪切强度得到了相当大的提高。As a new high performance organic fibre, polyimide (PI) fibre exhibits excellent mechanical properties, outstanding resistance to heat and environment as well as good dielectric properties. Additionally, its density is much lower compared with currently widely used high performance fibres, such as glass fibre and aramid fibre. Therefore, it is a promising material applied in high technology industries like advanced polymer matrix composites, high performance ropes or cables, etc. To provide a solid basis for PI fibre’s practical utilisation, surface properties, surface modification, and interfacial adhesion with two resins of a high-strength high-modulus PI copolymer fibre were investigated in detail. As a result, a deeper understanding of its surface properties, interfacial adhesion, and the influence of a simple treatment method with acid or alkaline on its mechanical properties, surface properties and interfacial adhesion were obtained. Firstly, PI fibre was compared with commercial high performance polymer fibres PBO, K-49 and F-12 from the aspects of mechanical properties, heat-resistant performance, surface properties and interfacial adhesion. The results indicated that the mechanical properties of the PI copolymer fibre used herein is superior to K-49 fibre but inferior to PBO and F-12 fibre. Also, the PI fibre showed excellent heat resistant performance with a glass transition temperate of 266 °C. Its thermal aging performance at 300 °C and 370 °C was better than F-12 fibre but worse than PBO and K-49 fibre. Meanwhile, the fibre’s smooth surface was attached with few functional groups, and the surface free energy was relatively low. Consequently, the interfacial adhesion with epoxy or polyimide resin was poor, and interfacial shear strength (IFSS) was lower than aramid fibres K-49 and F-12 but higher than PBO fibre. Then, a simple treatment method with acid or alkaline was employed to modify the PI copolymer fibre’s surface. The effects of treatment time, temperature and concentration of KOH, NaOH, H2SO4 and HNO3 solution on PI copolymer fibre’s mechanical properties and surface properties were fully studied, and treatment conditions were optimised. Compared with untreated fibre, several changes occurred afterwards: its mechanical properties declined; fibre surface became rougher with ditches; both oxygen element and carbon-oxygen functional groups contents of fibre surface increased evidently; the polar component of surface free energy occupied more proportion. After PI fibre was treated with KOH, NaOH, H2SO4 and HNO3 solution under the optimised treatment conditions which ensure the excellent mechanical properties of PI fibre, the interfacial adhesion of PI fibre with epoxy and polyimide resin was improved. IFSS of PI fibre/epoxy resin and polyimide resin after acid or alkaline surface modification can be raised by 14%~37%, and 78%~115, respectively. Obviously IFSS of the latter was enhanced significantly
Cf/SiC表面RE2SiO5/LaMgAl11O19(RE=Yb,Er)新型热障涂层的抗氧化行为与失效机理研究
No full textCf/SiC抗氧化抗烧蚀性能较差, 涂层防护是克服Cf/SiC性能不足的有效途径。现代超音速武器装备要求Cf/SiC表面涂层能够经受2273K火焰灼烧并对基底提供良好的热防护。本文设计了新型稀土复合氧化物热障涂层，通过等离子喷涂技术制备涂层，有效地解决了Cf/SiC在2273K火焰灼烧时的热防护难题，为突破新一代高超音速武器装备对Cf/SiC高温热防护需求瓶颈奠定一定的理论基础。 通过高温固相反应合成了Er2SiO5，Yb2SiO5和LaMgAl11O19 (LMA)粉末，并采用大气等离子喷涂技术对粉末进行喷涂，成功地在C/SiC表面制备了RE2SiO5/LMA (RE=Yb, Er)双陶瓷层热防护涂层。涂层与基体以及陶瓷层之间界面结合良好，涂层分布均匀，RE2SiO5内陶瓷层组织致密。 发现在~2273 K高温火焰循环灼烧下，RE2SiO5/LMA (RE=Er, Yb)涂层显著地提高了Cf/SiC基体的抗氧化性能。11次热循环后，未喷涂Cf/SiC样品氧化失重率高达20.6%，而单面喷涂了Er 2SiO5/LMA和Yb 2SiO5/LMA涂层的Cf/SiC样品，其氧化失重率仅分别为4.5%和4.1%。Cf/SiC本身的孔洞和裂纹导致了样品轻微氧化。11次热循环后，涂层与基体之间界面结合良好。 揭示了Cf/SiC表面RE2SiO5/LMA(RE=Yb,Er)涂层热循环失效机理如下：首先，RE2SiO5和LMA双陶瓷层之间原子相互扩散导致界面发生化学反应，使涂层发生液相烧结，形成了致密组织结构；其次，基体氧化生成的气体由于涂层的致密组织结构，来不及从涂层中逸出，形成了气泡；随后，随着气体产生，烧结涂层中气泡长大，使涂层产生了鼓包和裂纹，这显著加速了涂层和基体之间的剥离和裂纹的蔓延，从而造成涂层失效。 发现Cf/SiC表面Yb2SiO5/LMA涂层的热循环寿命主要取决于Yb2SiO5陶瓷层厚度。当Yb2SiO5层厚度从50μm增加至100μm时，涂层热循环寿命从130次降低为35次，而当Yb2SiO5层厚度继续增加至200μm时，涂层热循环寿命降低为仅有2次。揭示了Yb2SiO5层厚度对涂层热循环寿命的影响机理。Yb2SiO5 与基体的热膨胀不匹配以及1415oC时Yb2SiO5的体积收缩决定了涂层的热循环寿命。当Yb2SiO5层较薄时（如≤50μm），Yb2SiO5层热膨胀不匹配和体积收缩产生的热应力较小，涂层失效是由于涂层烧结和气泡长大引起的，涂层寿命较长；而当Yb2SiO5层较厚时（如≥100μm），由于Yb2SiO5层与基体的热膨胀不匹配和体积收缩形成了较大的界面残余热应力，涂层寿命显著降低。 揭示了RE2SiO5/LMA(RE=Er,Yb)涂层可以在短时间内（如几十分钟）对Cf/SiC复合材料提供良好的热防护。Cf/SiC composites are susceptible to ablation and oxidation in the high-temperature oxidizing environment, and it has been proven that the coating protection is a better approach to improve the oxidation and ablation resistance of Cf/SiC composites. With the development of modern hypersonic weapons, it is desired that the coating could endure a flame with temperature up to 2273 K and protect Cf/SiC from degradation by the flame. In this project, the novel thermal barrier coatings based on rare-earth oxides composites were designed and deposited on Cf/SiC substrate by atmospheric plasma spraying, which had a good protection for the Cf/SiC substrate against the flame. It is expected that this study could provide valuable theoretical basis for the breakthrough of bottleneck of the high temperature thermal protection required by the new generation of hypersonic weapons for the Cf/SiC composites. The Er2SiO5, Yb2SiO5 and LaMgAl11O19 (LMA) powders were produced by solid state reactions at high temperatures. The synthesized powders were subjected to atmospheric plasma spraying and thus the RE2SiO5/LMA (RE=Er, Yb) coatings were successfully fabricated on the C/SiC composites. Good interfacial bonding was present between the substrate and coatings as well as between the ceramic layers in the coatings, the coatings uniformly distrubuted on the substrate, and the inner ceramic layer of RE2SiO5 seemed to be dense. The RE2SiO5/LMA (RE=Yb, Er) coatings significantly improved the oxidation resistance of the Cf/SiC composites exposed to gas flame with temperature about 2273 K. The weight losses for the samples coated on one–side with the Er2SiO5/LMA and Yb2SiO5/LMA coatings were only 4.1% and 4.5% after 11 cycles, respectively. For the uncoated sample, the weight loss was as high as 20.6%. The holes and cracks in the green C/SiC composites should be responsible for the slight oxidation of the coated sample. Good interfacial bonding between the substrate and the coatings was retained after 11 cycles. The failure mechanism of RE2SiO5/LMA (RE=Yb,Er)coatings on the Cf/SiC substrate during thermal cycling is presumed to be as follows: firstly, liquid sintering occurred in the coating, which may be as a successive result of the reactions resulted from the interdiffusion of atoms between RE2SiO5 layer and LMA layer, and therefore, a dense microstructure of the coating was obtained. Secondly, the produced gases from the oxidation of the substrate did not promptly escape from the sintered coating due to the dense microstructure, which brought the formation of the bubbles; subsequently, the growing bubbles because of the increasing gases in them made the sintered coating give rise to the bumps and cracks, which significantly accelerated the delamination of the coating from the substrate and thus the induced propagating of the cracks, as a result, the coating was peeled off. The thermal cycling life of Yb2SiO5/LMA coating is significantly dependent on the Yb2SiO5 layer thickness, which decreased from 130 cycles to 35 cycles when the Yb2SiO5 layer thickness increased from 50 ?m to 100 ?m. Further increasing Yb2SiO5 layer thickness to 200 ?m made the thermal cycling life decrease to 2 cycles. The influencing mechanism of Yb2SiO5 layer thickness for the thermal cycling life was clarified. The CTE mismach between the substrate and Yb2SiO5 layer and the volume contraction of Yb2SiO5 after 1415 oC are the crucial factors manipulating the thermal cycling life of the coating. For thin Yb2SiO5 layer (e.g. ≤50 ?m), the thermal stress by the CTE mismach and the volume contraction of Yb2SiO5 is considered to be very small, the failure of Yb2SiO5/LMA coating resulted from the reaction sintering of the coating and the formation of bubbles between the substrate and the coating, and so the thermal cycling life of the coating is long. For thicker Yb2SiO5 layer (e.g. ≥100 ?m), the larger interface thermal stress was produced between the substrate and Yb2SiO5 layer because of the CTE mismach and the volume contraction of Yb2SiO5, which significantly decreased the thermal cycling life of the coating. The RE2SiO5/LMA (RE=Yb,Er) coatings are attractive for short–term applications (e.g. tens of minutes) of C/SiC composites exposed to gas flame with high temperature (e.g. ~2273 K)
高韧性全生物降解高分子复合材料的制备与性能研究
No full text白色污染和石油资源的快速消耗成为影响人类社会可持续发展的重大问题，引起了全球的高度重视，大力发展以可再生资源为原料的生物降解高分子材料成为普遍共识。然而，时至今日，与传统石油基高分子材料相比，多数生物降解高分子材料在性能上仍存在不足，成本也还偏高，严重制约了其广泛应用。在这一研究背景下，本论文将多种可生物降解的高分子材料进行共混，制备出高韧性的全生物降解复合材料，具体研究内容与结论如下： 1.高抗冲全生物降解聚（3-羟基丁酸酯）/聚碳酸亚丙酯/碳酸丙烯酯共混物的制备与性能研究。为提高聚（3-羟基丁酸酯）（PHB）的抗冲击性能，将聚碳酸亚丙酯（PPC）和碳酸丙烯酯（PC）与PHB进行熔融共混。结果表明，PC的含量越高，PPC的塑化程度越高，塑化PPC的模量也就越小，其在基体中的分散形貌也越规整、粒子尺寸也越小。分散相的模量低和粒子尺寸小是PHB的抗冲击性能提高的两条根本原因。当塑化PPC中增塑剂的质量分数达到25 wt%时，共混物的冲击强度可达34.9±3.4kJ/m2，几乎是纯聚（3-羟基丁酸酯）冲击强度（3.7±0.3 kJ/m2）的十倍。 2.高抗冲低成本全生物降解聚乳酸/聚醚酰胺/热塑性淀粉醋酸酯共混物的制备与性能研究。将玉米淀粉酯化改性后，再将其塑化产物热塑性淀粉醋酸酯与聚乳酸、聚醚酰胺共混。力学测试结果显示，聚乳酸/聚醚酰胺/热塑性淀粉醋酸酯共混物的冲击强度、拉伸强度、断裂伸长率都随着酯化度的增加而先升后降，在酯化度为0.04时达到最高值。透射电子显微镜照片显示，共混物中形成了以聚醚酰胺为外壳、热塑性淀粉醋酸酯为内核的核壳结构分散相粒子，并且当酯化度为0.04时，核壳粒子的尺寸最小最均一。研究结果还发现，在保证材料的抗冲击性能比较接近的前提下，使用廉价的淀粉或淀粉醋酸酯可以显著减少昂贵的聚醚酰胺弹性体的使用量，进而有效地降低了这一全生物降解高分子复合材料的成本。 3.高抗冲全生物降解聚乳酸/聚醚酰胺/热塑性交联淀粉共混物的制备与性能研究。对玉米淀粉进行交联改性，再将交联淀粉塑化，随后，制备了高韧性的聚乳酸/聚醚酰胺/热塑性交联淀粉三元共混物。共混物的冲击强度、拉伸强度、断裂伸长率都随着交联剂投入量的增加而先升后降，当交联剂的用量为淀粉干重的0.5 wt%时达到最大值。电子显微镜照片显示，分散相的形貌同样受到交联剂用量的影响，当交联剂用量为0.5 wt%时，分散相粒子的尺寸最小。 4.全生物降解聚乳酸/聚醚酰胺/热塑性双重改性淀粉共混物的制备与性能研究。对玉米淀粉进行先交联再酯化或先酯化再交联的双重改性，并将双重改性产物塑化。在各组分比例相同的情况下，聚乳酸/聚醚酰胺/热塑性双重改性淀粉共混物的冲击强度没能超越聚乳酸/聚醚酰胺/热塑性淀粉醋酸酯共混物的冲击强度。 5. 高韧性全生物降解聚乳酸/聚碳酸亚丙酯共混物的制备与性能研究。通过加入催化剂钛酸四丁酯，提高聚乳酸与聚碳酸亚丙酯之间的酯交换反应进行程度，从而提高了二者的相容性，共混物的韧性也随之提高。催化剂钛酸四丁酯的加入量、聚乳酸/聚碳酸亚丙酯二者的比例对共混物的韧性都有重要影响。In the recent few decades, the rapid consumption of non-renewable oil resource and increasingly serious disposal problem of the non-degradable plastics stimulate people to develop biodegradable polymer material from renewable resources, and big processes have been made. However, there are still some deficiencies in the properties of many biodegradable polymers, and the prices are also higher than the petroleum based polymers. Therefore, the widespread use of biodegradable polymers is limited seriously. In this context, several kinds of biodegradable polymer were selected to prepare full-biodegradable polymer composites with good toughness and low cost. Details of the research contents and the results are summarized as follows: 1. Toughening of full-biodegradable poly (3-hydroxybutyrate)/ plasticized poly (propylene carbonate) blends. In order to improve the poor impact resistance of poly (3-hydroxybutyrate) (PHB), poly (propylene carbonate) (PPC) and plasticizer propylene carbonate (PC) were used together to toughen PHB. The impact strength of PHB/PPC/PC blends could be significantly increased up to 34.9±3.4 kJ/m2 when the PC content reached 25 wt%, which was almost 10 times of the impact strength of neat PHB (3.7±0.3 kJ/m2). On the other hand, as the PC content increased, the Young’s modulus of plasticized PPC decreased and the particle size of the dispersed phase in the matrix became more uniform and smaller. Both the low Young’s modulus and smaller uniform particle size of plasticized PPC were the fundamental reasons of the improvement of toughness of PHB/PPC/PC blends. 2. Toughening of polylactide with polyether-block-amide and thermoplastic starch acetate. Native corn starch was esterified with acetic anhydride and plasticized with glycerol. Subsequently, the thermoplastic starch acetate (TPSA) was blended with polylactide (PLA) and polyether-block-amide-graft-glycidyl methacrylate (PEBA-g-GMA) to obtain full biodegradable PLA/PEBA-g-GMA/TPSA blends with high notched impact resistance and low cost. Comparing with PLA/PEBA-g-GMA blend, as much as 9 wt% expensive PEBA-g-GMA elastomer could be substituted by the slightly acetylated thermoplastic starch for achieving equivalent high impact strength in the PLA/PEBA-g-GMA/TPSA blend. More interesting was that the mechanical properties depended on the esterification degree of starch acetate. The impact strength, tensile strength and elongation at break increased to the peak value with increasing the esterification degree from 0 to 0.04, thereafter they decreased with further increasing the esterification degree. The morphological results showed that the TPSA particles were smaller and more uniform for optimum esterification degree: 0.04, leading to the peak value of mechanical properties. 3. Toughening of polylactide with polyether-block-amide and thermoplastic cross-linked starch. Native corn starch was cross-linked with epichlorohydrin (ECH) and plasticized with glycerol. Subsequently, the thermoplastic cross-linked starch (TPCLS) was blended with polylactide (PLA) and polyether-block-amide-graft-glycidyl methacrylate (PEBA-g-GMA) to obtain full biodegradable PLA/PEBA-g-GMA/TPCLS blends with high notched impact resistance and low cost. It was also found that the impact strength, tensile strength and elongation at break of the ternary blends increased to the peak value with increasing the addition amount of the cross-linking agent ECH from 0 to 0.5 wt%, thereafter it decreased with further increasing the ECH amount. The morphological results showed that the TPSA particles were smaller and more uniform for optimum ECH addition amount (i.e. optimum cross-linking degree of starch), leading to the peak value of mechanical properties. 4. Toughening of polylactide with polyether-block-amide and thermoplastic cross-linked starch acetate. Double modification was performed on native corn starch by two steps (first cross-linking and then esterification or first esterification and th
纳米粒子/聚合物复合体系的结构和流变性能研究
No full text纳米粒子/聚合物复合材料在国民经济的诸多领域有着广泛应用，因而受到了人们的密切关注。聚合物纳米复合材料的结构和流变性能与其加工和最终应用密切相关，因此，深入理解聚合物纳米复合材料的聚集态结构形成规律及其流变性质影响因素，进而获得结构与流变性能之间的关系，对于聚合物纳米复合材料的设计和性能优化具有重要的指导意义。在本论文中，我们针对几种典型的纳米粒子/聚合物复合体系，着重探索了纳米粒子形状、纳米粒子间相互作用、聚合物的支化度以及聚合物的分子量等因素对复合物聚集态结构以及流变性质的影响规律，进而预测了复合体系中微结构与流变性能之间的关系。具体研究内容及结果如下： 1、研究了聚合物的分子量（Mw）对具有一维线状结构的碳纳米管（MWNT）/聚二甲基硅氧烷（PDMS）复合物和具有二维片层结构的氧化石墨烯（GO）/PDMS复合物的结构和流变性能的影响。研究发现，随着PDMS分子量的增加，MWNT和GO在聚合物中的分散状态均变好，且复合物形成网络结构的临界浓度均随着PDMS分子量的增加而升高。进一步对复合物施加剪切，发现在弱剪切条件下，当PDMS分子量低于其临界缠结分子量（Mc）时，复合物具有负法向应力差（ΔN）；而当PDMS分子量高于其Mc时，复合物具有正ΔN。为了明晰负法向应力差产生的机理，我们利用光学剪切池在相同剪切速率条件下原位观察了复合物的结构，发现低分子量PDMS（Mw < Mc）复合物中的团聚体在弱剪切下沿涡度方向取向，从而导致负ΔN的出现；而高分子量PDMS（Mw > Mc）复合物在弱剪切下没有明显的结构变化。同时，由于高分子量的PDMS本体在剪切条件下呈现正ΔN，因而，在复合物中出现的正ΔN也可能是由于高分子链的非线性拉伸所致。进一步减小流变仪的平板间距，即对体系施加平行板受限时，MWNT/部分高分子量PDMS（Mw > Mc）复合物在弱剪切下也能够形成涡度取向条带结构，进而导致体系产生负ΔN。然而，在同样条件下，平行板受限却不能诱导GO在高分子量PDMS（Mw > Mc）中的团聚体形成涡度取向结构，因而该体系中没有观测到负ΔN。 2、研究了纳米粒子间的相互作用及其形状等因素对纳米粒子/聚合物复合体系的结构和流变性能的影响。我们首先系统地改变了石墨烯基纳米粒子（GP）的表面氧含量，获得了具有不同表面相互作用的GP。发现GP在低分子量PDMS（Mw < Mc）中的分散程度随粒子表面氧含量的增加呈现非单调变化。这是由于在高氧含量的GP之间易形成氢键相互作用，而在低氧含量的GP间易形成π-π相互作用，这两种较强的吸引相互作用使得粒子易于聚集，形成较大尺寸的聚集体。而在中等氧含量的GP之间不存在较强吸引相互作用，因而其分散程度较好。在弱剪切下，中等氧含量的GP复合物没有明显的结构变化；而对于最高和最低氧含量的GP复合物体系，由于粒子间吸引作用较强，导致其碰撞的捕获效率高，因而出现剪切诱导的团聚以及一定程度的涡度取向。为了进一步理解纳米粒子间相互作用对复合体系结构与流变性质的影响，我们将不同亲疏水性的盘状纳米粒子（疏水的有机改性蒙脱土（OMMT）、亲水的GO和高岭土（Kaolin））分散到低分子量硅油（SO）中，发现OMMT在SO中分散较好，而GO和Kaolin分散较差。在剪切条件下，三种复合物均出现了负ΔN。进一步研究表明，OMMT和GO复合物具有液晶相结构，而Kaolin复合物中并不存在液晶相结构。因而，三者产生负ΔN的机理不同：OMMT/SO中液晶相的翻滚运动以及GO/SO和Kaolin/SO中团聚体的涡度取向导致复合体系负ΔN的产生。为了获得纳米粒子形状对复合体系结构及流变性质的影响规律，我们研究了表面元素组成相似的中空碳球、多臂炭黑、石墨烯以及碳纳米管体系在低分子量PDMS（Mw < Mc）中的分散、结构和流变性质。结果表明，各向同性的中空碳球均匀分散在PDMS中，剪切下复合物没有明显的结构变化，其ΔN几乎为零。而其它各向异性的碳质纳米粒子复合物中均存在不同大小的团聚体，并出现了不同程度的涡度取向以及负ΔN。由此可见，碳质纳米粒子出现负ΔN主要源自于聚集体在剪切下的涡度取向。 3、研究了聚合物的支化结构对石墨烯/聚乙烯复合体系的粘弹性、热稳定性和力学性能的影响。我们选择分子量相近但支化结构不同的线性HDPE，短链接枝LLDPE和长链接枝LDPE作为模型聚合物。发现支化度对纳米粒子在聚合物中的分散状态产生较大影响。石墨烯可以被LLDPE插层，因此微观尺度上分散良好，并且随着石墨烯含量的增加，石墨烯/LLDPE的零切粘度和模量均出现极小值。石墨烯被HDPE和LDPE插层不明显，因而光学显微镜下可以观察到大团聚体的存在，同时复合物的零切粘度和模量随石墨烯含量的增加而单调增加。为了明晰复合材料粘度的降低是否影响其力学性能，我们用拉伸力学测试仪测得了复合材料的拉伸力学曲线。发现少量（1 wt %）石墨烯的加入使LLDPE复合物的拉伸强度、断裂伸长率和杨氏模量得到较大提高（分别提高了14%，31%和40%）。然而，由于石墨烯/HDPE和石墨烯/LDPE中存在大的团聚体，其拉伸强度和断裂伸长率随石墨烯的加入而降低。另一方面，由于石墨烯可捕获LLDPE和LDPE热降解过程中的自由基，从而促进聚乙烯的氧化交联，因而使其热稳定性提高~33 °C，然而石墨烯对HDPE热稳定性的提高并不明显。综上，改变聚合物的支化结构对于提高纳米复合材料的运输性和可加工性具有重要影响。 4、研究了聚合物的分子量对石墨烯/聚环氧乙烷（PEO）的粘弹性和松弛行为的影响。研究发现，石墨烯在高分子量的PEO（Mw > Mc）中被剥离或插层，微观分散良好；随着PEO分子量的降低，石墨烯的微观分散状态变差。石墨烯可以降低高分子量PEO（Mw > Mc）的零切粘度和模量，提高低分子量PEO（Mw ≤ Mc）的零切粘度。为了明晰零切粘度的变化与聚合物松弛行为的关系，我们用介电松弛谱和DSC研究了石墨烯对高分子量PEO松弛行为的影响。发现石墨烯的加入导致PEO的玻璃化转变温度降低，脆性减弱，表明石墨烯与PEO间为非吸引相互作用。片层剥离的石墨烯厚度小，可以改变聚合物的堆积和运动，降低PEO的协同运动并使PEO解缠结，因而可以导致复合物宏观粘度的降低。Nanoparticle/polymer composites have received extensive attention due to their various applications in immense fields. The structure and rheological properties of composites are closely related with their transport, processing and final application. Thus exploring effective factors influencing the structure and rheological properties of composites and the relationship between microstructure and rheological properties of composites are important for the design and improving the properties of composites. In this dissertation, we examined the effective factors affecting the structure and rheological properties of composites and the relationship between structure and rheological properties of composites. Specifically, we conducted the following studies: 1. We explored the influence of molecular weight (Mw) of polydimethylsiloxane (PDMS) on the structure and rheological properties of multi-walled carbon nanotube (MWNT)/PDMS and graphene oxide (GO)/PDMS composites. With the increase of the molecular weight of PDMS, the dispersion state of MWNT and GO gets better and the critical concentration for the formation of network structure increases. Under bulk shear, the normal stress differences (ΔN) of samples with low molecular weight of PDMS (below the critical entangled molecular weight Mc) are negative, while the ΔN of samples with high molecular weight of PDMS (Mw > Mc) is positive. To understand the mechanism for the negative ΔN, optical shearing cell equipped with a microscope was used to explore the structural change of composites under shear. The vorticity alignment of aggregates was observed in samples with low molecular weight of PDMS (Mw < Mc), which resulted in the negative ΔN. No obvious structural change was found in samples with high molecular weight of PDMS (Mw > Mc) and the nonlinear stretching of entangled PDMS chain partially resulted in the positive ΔN. Under confinement, vorticity aligned bands were observed in some MWNT/high molecular weight PDMS (Mw > Mc) composites, which induced the negative ΔN. However, under confinement, no vorticity aligned bands and negative ΔN were found in GO/high molecular weight PDMS (Mw > Mc) composites. 2. The effects of particle shape and inter-particle interaction on the structure and rheological properties of nanoparticle/polymer composites were investigated. By changing the surface chemistry of graphene-based particles (GP), we observed the nonlinear change of dispersion state of GP with the surface oxygen content. The strong interparticle hydrogen bonding or π-π attractive interaction between GP with the highest and lowest oxygen content results in the bad dispersion of particles, while the weak attractive interaction between GP with modest oxygen contents leads to the good dispersion of particles. Under weak shear, shear induced aggregation and vorticity alignment of large aggregates were observed in suspensions of GP particles with the highest and lowest oxygen contents, while no obvious structural change was observed in suspensions of GP particle with modest oxygen contents. The higher interparticle attractive energy between GP with the highest and lowest oxygen contents induces the higher capture efficiency in collision and the higher upper limit of aggregate size. Organically modified montmorillonite (OMMT), GO and kaolinite (Kaolin) with different hydrophobicity were dispersed in silicone oil (SO). OMMT disperses well in SO, while GO and Kaolin disperse badly in SO. Under crossed-polarizered microscope, liquid crystalline phase was observed in OMMT and GO suspensions, while it was absent in Kaolin/SO suspension. Under weak shear, the tumbling motion of the liquid crystalline phase of OMMT suspension and the some extent of vorticity alignment of GO and Kaolin suspensions result in the negative ΔN. The influence of particle shape on the structure and rheological properties of carbon-based particle/PDMS suspensions were explored as the surface chemistry of parti
聚合物的碳化反应及其应用
No full text伴随着大量聚合物材料的广泛应用，如何处理日益增长的废旧聚合物，特别是塑料，成为影响我国乃至全世界可持续发展的重要因素之一。由于聚合物中含有碳元素（比如聚烯烃中碳元素高达85.7%），将聚合物或者废旧聚合物转化成高附加值的碳材料是一种新的聚合物回收方法。我们课题组在2005年提出了“组合催化剂”策略，发现固体酸或者氯化物与Ni2O3的组合催化剂可以高效催化聚烯烃碳化制备碳纳米管（CNTs）。但是，还存在许多问题需要解决，比如碳化机理不清楚、碳材料形貌较差、碳化效率不高以及缺乏对碳材料应用的探索。事实上，众多国内外以聚合物回收为目的的碳化研究小组都存在类似的问题。因而，还需要进一步研究聚合物的碳化反应。另一方面，由于实际的废旧塑料包含了多种类型的塑料，比如聚丙烯（PP）、聚乙烯（PE）、聚苯乙烯（PS）、聚对苯二甲酸二甲酯（PET）和聚氯乙烯（PVC），同时还有许多类型的填料。那么，为了研究废旧混合塑料转化成高附加值的碳材料，就必须弄清楚单独的和混合的塑料的碳化反应规律，同时还需要弄清楚填料对于碳化反应的影响。更为重要的是目前关于回收聚合物碳化产物的应用还缺乏研究，探索其在环境污染治理、能源存储、催化和阻燃等领域的应用就非常必要。 本论文研究了聚合物碳化反应，制备了零维碳材料（包括中空碳球（HCS）、核壳结构的Co@C球和Fe3O4-微米碳球杂化材料）、一维碳材料（包括CNTs、碳纳米纤维（CNFs）、“杯叠”碳纳米管（CS-CNTs）、多孔“杯叠”碳纳米管（P-CSCNT）、盘子状碳纤维（PL-CF）和CF/CNT杂化材料）和二维碳材料（包括碳纳米薄片（CNS）和多孔碳薄片（PCNS）），并且探索了它们在锂离子电池、光催化降解染料、吸附污染物（重金属离子、油和染料）、吸附二氧化碳、存储氢气以及提高聚合物阻燃性能方面的应用。不仅丰富了“组合催化剂”策略，还提出了“快速碳化”和“模板碳化”新的聚合物碳化策略。具体内容如下： 1、系统研究聚合物催化碳化制备HCS及其杂化材料。首先，研究PS的碳化反应规律，利用钴催化剂/有机改性蒙脱土（OMMT）组合催化剂，制备了介孔的HCS。接着，通过调节Co3O4催化剂的量，首次将混合塑料转化成尺寸可控的HCS。在此基础上，考察四种常见的填料对于HCS生长的影响，发现填料与钴催化剂的相互作用是填料影响HCS的主要因素。此外，成功将五组份混合废旧塑料转化成介孔HCS，并且探索了其在锂离子电池方面的应用。之后，发现如果不加入OMMT，一步就能将混合塑料转化成尺寸均一的磁性核壳结构的Co@C球。它在光催化降解染料刚果红（CR）中表现出较高的催化效率、很好的回收性能、重复使用性能以及较好的长效稳定性能。 2、在利用“组合催化剂”催化非成碳聚合物碳化制备CNTs的基础上，探索新的成碳聚合物碳化策略—“催化碳化”，从而调控成碳聚合物的碳化反应。系统研究了Fe2O3对于氯化聚氯乙烯（CPVC）的碳转化率、产率、形貌和组成的影响。发现Fe2O3被还原成Fe3O4，并且以微晶的形式镶嵌在微米碳球表面。证明了Fe2O3可以催化CPVC微球表面快速脱氯化氢以及随后的交联反应，从而避免了CPVC微球的熔融粘接。制备的Fe3O4-微米碳球杂化材料在光催化降解染料CR方面有着较高的效率、回收性能、重复使用性能和长效稳定性，表明其在环境污染治理方面有着潜在的应用。更为重要的是，根据“形状复制”的碳化反应原理，还可以制备功能性纳米球、纤维和棒状等各种形貌的碳材料或者碳基杂化材料。 3、系统研究了氯化物/Ni2O3组合催化剂中氯化物对于聚合物碳化反应的影响。首先研究了Cl/Ni摩尔比对碳材料的产率和形貌的影响。考察了Cl/Ni摩尔比对碳材料活性位点和PP降解产物的影响。然后将制备Cu-Ni/C杂化材料用于催化“Click”反应，产率高达97%。因而，提供了新的制备金属-碳杂化材料的方法。接着，发现PVC也可以充当氯源，与Ni2O3协同催化线性低密度聚乙烯（LLDPE）碳化制备磁性Ni/C杂化材料。PVC的种类对于Ni/C杂化材料的产率影响不大，但是PVC的含量决定了Ni/C杂化材料的产率。随着PVC含量的增加，Ni/C杂化材料的产率快速增加，而后减少。当PVC含量较低时，生成了较长的CNTs；当PVC含量较高时，得到的是较短的CNFs和无定形碳。这主要是由于PVC分解生成的氯自由基促进了LLDPE大分子自由基的脱氢和芳构化反应。Ni/C杂化材料被用于吸附亚甲基蓝（MB），表现出较快的吸附速率、较高的吸附量和磁性吸附等三大特点。此外，发现活性炭与Ni2O3组合协同催化PP碳化制备CNTs，分析了CNTs生长机理，证明了活性炭表面的官能团是协同催化的关键因素。首次提出了基于苯环的层层组装的CNTs生长机理，为将塑料或者废旧塑料转化成CNTs提供了理论指导。 4、为了改善碳材料形貌，从催化剂设计角度出发，用溶胶-凝胶-燃烧法合成了NiO纳米粒子成碳催化剂。首先，考察了OMMT/NiO组合催化PP碳化制备CS-CNTs，发现OMMT的含量对于CS-CNTs的产率和形貌起到决定性的作用。CS-CNTs的石墨层排列与轴向存在20–25o夹角。证明了少量的OMMT可以促进PP碳正离子的脱氢和芳构化从而生成大量的小分子碳氢化合物和芳烃化合物，这些降解产物促进NiO纳米粒子的熔结和重建生成双锥结构的NiO。接着，重建的NiO催化剂再催化这些降解产物碳化生成较长且表面平整的CS-CNTs。在此基础上，系统考察了卤化物/NiO组合催化剂催化PP碳化制备碳纳米材料（CNM）。证明了组合催化剂的催化效率为氟化物/NiO << 氯化物/NiO < 溴化物/NiO < 碘化物/NiO。这主要是因为卤素自由基催化PP大分子自由基的脱氢和芳构化能力为F << Cl < Br < I。此外，将CS-CNTs酸处理制备酸化的CS-CNTs（CS-CNT-H）。它表现出较高的吸附重金属离子和有机染料的性能，这表明CS-CNT-H在废水处理方面有着潜在应用。Langmuir模型更适合于拟合吸附数据，吸附动力学数据则由Pseudo second-order模型拟合更为准确。 5、在（4）基础上，系统研究了NiO尺寸（18–227 nm）对于CS-CNTs生长的影响，发现在OMMT/NiO催化PP碳化制备CS-CNTs过程中NiO纳米粒子的熔结和重建过程是CS-CNTs生长的关键步骤。尺寸较小的NiO促进较长且表面平整的CS-CNTs的形成。这主要是由于尺寸较小的NiO更容易发生熔结和重建。40 nm的NiO最适合于CS-CNTs生长，制备“海绵”状的CS-CNTs。它具有较高的吸附油的性能、较好的重复使用性能、较高的机械强度以及磁性。另外，研究了催化剂中晶格氧在PP碳化过程中的作用，发现CNM的产率随着晶格氧含量的增加而增加。当晶格氧含量很低时，得到的是较粗而弯曲的PL-CFs。增加晶格氧后，得到的是较细、弯曲且较短的CNFs。但是当晶格氧含量很高时候，得到的是较长、直且表面平整的CS-CNTs。晶格氧不仅促进镍纳米粒子重建成双锥结构、抑制催化剂团聚成大颗粒，还促进聚合物降解产物的碳化。这部分工作有助于进一步了解塑料的碳化反应机理以及将废旧塑料转化成高附件值的碳材料。 6、探讨了聚合物种类、HZSM-5含量以及镍催化剂种类对于CNM的产率和形貌的影响。随着HZSM-5含量的增加，CNM的产率先增加而后变化不明显。聚合物种类和镍催化剂种类对于CNM的产率并不明显，但是对于CNM的形貌有着显著影响。另外，相比于PP，LLDPE降解产物中芳烃含量较高，从而使得LLDPE作为碳源时生成的CNM中含有较少的石墨化结构以及较多的无定形碳。这部分工作为将混合塑料转化成高附加值碳材料奠定基础。在此基础上，研究了PE的链结构对于PE碳化反应的影响。发现不论PE的结构，PE的产率都随着CuBr含量的增加而增加，达到最大值后逐渐减低。LLDPE作为碳源时，得到的是较长且表面平整的CS-CNTs，但是低密度聚乙烯或者高密度聚乙烯作为碳源时到的是较短、弯曲且表面粗糙的CNFs。这主要是归因于不同链结构的PE在CuBr催化作用下生成不同的降解产物。 7、在制备CS-CNTs的基础上，首次提出了利用碱处理的办法来制备P-CSCNT。P-CSCNT包含了许多尺寸在几纳米到十几纳米、连接P-CSCNT表面和内部且与轴向存在一定夹角的孔通道。与CSCNTs比较，P-CSCNT具有较高的比表面积（558.7 m2/g）、较大孔容（1.993 cm3/g）以及较多的表面官能团。此外，P-CSCNT表现出较高的MB吸附量。Langmuir模型可以很好地拟合吸附数据，P-CSCNT的MB最大吸附量可达319.1 mg/g。这主要归因于P-CSCNT较高的比表面积和较大的孔容，以及多种类型的吸附机理。更为重要的是，P-CSCNT表现出很好的回收性能和重复使用性能。这表明P-CSCNT在废水治理中有着潜在应用。这部分工作为P-CSNT的大规模应用奠定了基础。 8、除了“组合催化剂”和“快速碳化”策略，提出了聚合物碳化的第三种策略—“模板碳化”。即利用OMMT作为模版，将塑料转化成CNS，经过KOH活化后制备了PCNS，并且探索了PCNS在能源存储和环境污染治理方面的应用。CNS的产率随着OMMT/废旧PP的重量比的增加而增加。制备的CNS具有褶皱的形貌，层数在几层到十几层，并且石墨层并不连续同时具有很多缺陷。此外，制备的CNS有着较高的纯度以及一定量的表面官能团。OMMT不仅充当了聚合物降解催化剂With the wide application of polymer materials in our daily life, the treatment of ever-increasing waste polymer materials, especially waste plastics, has been the major factor which influences the sustainable development in both our country and the world. Converting the polymer materials and waste polymer materials into high value-added carbon materials is a potential way to largely recycle them. In 2005, our group put forward the strategy of "combined catalysts", and found the combination of solid acids or chlorinated compound with Ni2O3 could effectively catalyze the carbonization of polyolefins into carbon nanotubes (CNTs). However, many questions are still needed to be solved, for example, the carbonization mechanism of polyolefins is not clear, the morphology of carbon materials should be improved and adjusted, the efficiency of carbonization should be enhanced, and the applications of carbon materials should be explored. Actually, all the groups which study the carbonization of waste polymer materials around the world confront with the same questions. Therefore, much work should been done to better understand the carbonization of polymer materials. On the other hand, the real waste plastics consisted of many kinds of plastics, such as polypropylene (PP), polyethylene (PE), polystyrene (PS), poly(ethylene terephthalate) (PET) and poly(vinyl chloride) (PVC), along with a lot of fillers. Hence, in order to transform the waste mixed plastics into high value-added carbon materials, the carbonization of single and mixed plastics should be studied and also the effects of fillers on the carbonization should be clear. In this dissertation, the carbonization of polymer materials were studied, carbon materials including zero dimensional carbon materials (such as carbon spheres (HCS), core/shell Co@C spheres and Fe3O4/carbon microspheres), one dimensional carbon materials (such as CNTs, carbon nanofibers (CNFs), cup-stacked CNTs (CS-CNTs), porous CS-CNTs (P-CSCNT), plate-like carbon fibers (PL-CF) and CF/CNT hybrid) and two dimensional carbon materials (such as carbon nanosheet (CNS) and porous CNS (PCNS)) were synthesized, and were explored in the applications of Li-ion batteries, photo-degradation of dyes, adsorption of pollutants (such as heavy metal ions, oils and organic dyes), adsorption of carbon dioxide, storage of hydrogen and the improvement of the flame retardancy of polymer materials. These results not only enriched the strategy of "combined catalysts", but also put forward the two new strategies of fast carbonization and template carbonization. Detail work is as follows: 1. Zero-dimensional carbon materials and their hybrids were synthesized by catalytic carbonization of polymer materials. Firstly, the carbonization mechanism of PS was studied, and the mesoporous HCS was synthesized by the combined catalysts of cobalt catalyst and organically-modifiedmontmorillonite (OMMT). Subsequently, HCS with controllable size was prepared from mixed plastics (PP, PE and PS) by adjusting the amount of Co3O4. Based on this result, the effect of four fillers on the formation of HCS was studied, and the interaction between filler and cobalt catalyst was found to be the crucial factor influcing the formation of HCS. At the same time, the waste five-component plastics (PP, PE, PE, PET and PVC) were converted into mesoporous HCS, which was used in Li-ion batteries. Afterwards, without OMMT, mixed plastics consisting of PP, PE and PS were catalyzed by Co3O4 into uniform magnetic core/shell Co@C spheres via a one-pot approach. It showed high performance in the photo-degradation of Congo red (CR) with good recycling, good reusability and stability. 2. On the basis of the strategy of "combined catalysts" to convert polymer materials into CNTs, a new strategy of "fast carbonization" was put forward to promote the carbonization of charring polymer materials. The effect of Fe2O3 on the yield, carbon conversion, morphology and composition of ca
UV-Emitting Upconversion-Based TiO2 Photosensitizing Nanoplatform: Near-Infrared Light Mediated in Vivo Photodynamic Therapy via Mitochondria-Involved Apoptosis Pathway
No full textPhotodynamic therapy (PDT) is a promising anti-tumor treatment that is based on the photosensitizers that inhibit cancer cells by yielding reactive oxygen species (ROS) after irradiation of light with specific wavelengths. As a potential photosensitizer; titanium dioxide (TiO2) exhibits minimal dark cytotoxicity and excellent ultraviolet (UV) light triggered cytotoxitity, but is challenged by the limited tissue-penetration of UV light. Herein, a novel near-infrared (NIR) light activated photosensitizer for PDT based on TiO2-coated upconversion nanoparticle (UCNP) core/shell nanocomposites (UCNPs@TiO2 NCs) is designed. NaYF4:Yb3+,Tm3+@NaGdF4:Yb3+ core/shell UCNPs can efficiently convert NIR light to UV emission that matches well with the absorption of TiO2 shells. The UCNP5@TiO2 NCs endocytosed by cancer cells are able to generate intracellular ROS under NIR irradiation, decreasing the mitochondrial membrane votential to release cytochronne c into the cytosol and-then activating caspase 3 to induce cancer cell apoptosis. NIR light triggered PDT of tumor-bearing mice with UCNPs@TiO2 as photosensitizers can suppress tumor growth efficiently due to the better tissue penetration than UV irradiation. On the basis of the evidence of in Vitro and in vivo results, UCNPs@TiO2 NCs could serve as an effective photosensitizer for NIR light mediated PDT in antitumor therapy