颗粒第二相改性热固性树脂的增韧机理谱

本文分析了颗粒第二相改性热固性树脂的各种增韧机制及其影响因素,提出应用增韧机理谱来描述这类材料的增韧行为.文中还介绍了增韧机理谱在若干实际体系中的应用.     

颗粒增韧陶瓷裂纹扩展微观过程

对于第二相颗粒增韧的复相陶瓷，颗粒热膨胀系数ａｐ与基体热膨胀系数ａｍ之间的匹配关系是决定增韧效果的主要因素。当两相弹性模量相当，颗粒粒径小于应力诱导微开裂的粒径，且ａｐ〉ａｍ时，残余热应力场的存在将会使扩展的裂纹在颗粒周围基体中产生较大的裂纹偏转，由此产生明显的增韧效果；而当ａｐ〈ａｍ时，扩展的裂纹将首先达到两相的界面，此时裂纹有可能沿两相界面偏转，也有可能穿过颗粒，这取决于颗粒的表面能、粒径、形     

金属颗粒增韧氧化铝陶瓷研究现状

概述了金属颗粒增韧氧化铝陶瓷的研究进展,对氧化铝/金属复合材料的研究现状、增韧机理及制备方法进行了介绍,并对氧化铝/金属复合材料的主要发展方向进行了分析预测。     

ZrO2增韧陶瓷的研究进展

综述了ZrO2陶瓷及添加氧化物稳定剂对四方相氧化锆的稳定性影响，以及ZrO2陶瓷材料的种类，增韧机理及其主要应用领域，并展望了氧化锆增韧陶瓷的研究发展趋势。     

氧化铝陶瓷增韧研究进展

介绍了氧化铝陶瓷增韧技术及其机理,包括相变增韧、晶须和纤维增韧、颗粒弥散增韧、微结构设计增韧、纳米技术增韧、耦合协同增韧;探讨了氧化铝陶瓷材料增韧技术的研究现状和今后的发展方向。     

陶瓷增韧技术的研究进展

介绍了颗粒增韧、纤维和晶须增韧、相变增韧、复合增韧、自增韧、纳米增韧等陶瓷增韧技术的研究现状以及相应的增韧机理，探讨了今后陶瓷增韧技术的发展方向。     

热塑性树脂增韧环氧树脂研究进展

介绍了热塑性树脂/环氧树脂共混体系的的制备方法,相分离机理以及相结构的影响因素,综述了国内外热塑性树脂增韧环氧树脂的研究进展。并对其增韧机理进行了论述。     

酚醛树脂的增韧方法及增韧机理分析

综述了酚醛树脂的主要增韧方法,详细地分析和总结了各种增韧方法的增韧机理。结果表明:增韧方法可以归结为内增韧和外增韧两大类,不同的增韧方法对应不同的增韧机理。     

氧化铝陶瓷增韧技术及机理

介绍了氧化铝陶瓷增韧技术及其机理(包括相变增韧、晶须和纤维增韧、颗粒弥散增韧、微结构设计增韧、纳米技术增韧、耦合协同增韧),探讨了氧化铝陶瓷材料增韧技术的研究现状和今后的发展方向。     

含氟聚醚醚酮增韧环氧树脂相形貌与性能研究

采用SEM观察了热塑性含氟结构聚醚醚酮(6FPEEK)共混增韧环氧树脂的浇铸体脆断断口相形貌,测试了浇铸体的力学性能及动态机械性能,通过统计和数学分析建立了冲击韧性(αk)、热塑颗粒粒径(d)和粒间距(D)间的半定量关系。结果表明,该体系可得到连续相为环氧树脂而分散相为热塑颗粒的相结构,热塑相颗粒尺寸较为统一,且随热塑性树脂含量的增加而增大;6FPEEK含量增加对拉伸强度的影响不大,环氧树脂和热塑性塑料的结合界面差导致了冲击韧性在6FPEEK质量分数达到9.09%时出现峰值而后下降;该增韧体系的增韧机理可能为刚性粒子增韧。     

纳米ZrO2-微米Al2O3复合陶瓷中"内晶型"结构的形成与机理

考察了不同烧结状态的氧化错增韧氧化铝陶瓷(zirconia—toughened alumina,ZTA)的晶粒长大与“内晶型”形成的关系。烧结过程中,ZTA陶瓷中晶粒生长与温度、保温时间、第二相ZrO2含量有关,其中温度的影响最为显著。第二相粒子有沿主晶相晶界移动聚集的趋向。内晶结构的形成机理可概括为第二相粒子被夹在主相两晶粒之间不能移动,在随后的主晶相长大过程中,两晶粒共同晶界发生迁移或晶粒“合并”,将第二相粒子纳入晶粒内部。而没有被主相颗粒挤住的可移动的第二相粒子则聚集成较大的晶问第二相颗粒。     

第三相的加入对气液传质过程的影响

系统地介绍了气液传质过程中,固体小颗粒或第二分散液相(有机相)所形成的第三相的加入对传质过程的影响.分别论述了在不同的气-液接触器(搅拌釜、鼓泡塔)中,固体小颗粒和第二分散液相的加入对体系的传质系数、传质速率及界面面积等的影响,叙述并讨论了传质机理及模型的最新进展.     

La2O3掺杂SnO2陶瓷的烧结机理探讨

利用共沉淀法制备La2O3掺杂二氧化锡陶瓷。通过观察晶粒及晶界情况分析了烧结机理。结合相图指出在烧结初期以固体烧结为主,随着烧结的进行出现少量液相,进一步促进了烧结,在烧结后期从主晶相中分离出第二相。     

关于氮化铝陶瓷导热性的讨论

本从声子机理出发，探讨了影响氮化铝陶瓷导热性的主要因素；提出了提高导热率的努力方向，即结构上努力减少晶格缺陷（主要是杂质固溶）和晶界缺陷（包括第二相析出，晶界玻璃相，气孔），并使相的分布尽量合理；指出了提高A1N陶瓷导热率的可能途径，即严格控制A1N粉末质量，选择合理的烧结助剂，采用还原气氛烧成等。     

金属基及陶瓷基金属陶瓷的强化机理

简述了金属陶瓷的金属基体及陶瓷基体的引入第二相强化,重点论述了与陶瓷增强体强化金属基体、金属增强体强化陶瓷基体相关的内容;为更直观的描述强化的机理,绘制了金属基及陶瓷基金属陶瓷的各种强化方式示意图,最后针对金属陶瓷的强化效果影响因素做了简要的分析,并提出了相关展望。     

分散第二液相对增强气液传质的研究进展

系统介绍了分散第二液相对气液传质的增强作用 ,提出了增强因子和铺展系数的概念 ,叙述和讨论了传质增强机理及模型的最新进展 ,并针对该领域的研究现状提出了一些展望。     

Investigation on the phase stability of cubic perovskite BaCo0.7Fe0.2Nb0.1O3-δ oxygen-permeable membrane

The phase stability of the cubic perovskite-type oxide BaCo_0.7Fe_0.2Nb_0.1O_3?δ (BCFNO) has been examined by means of X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). And, the timescale on the second phases has been established by using the TOPAS 4.2. Compared with Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ (BSCFO), for samples annealed at T?=?1023?K for t?=?64 d, the rhombohedral and hexagonal phases formed on the surface of cubic perovskite BCFNO surface simultaneously and the amount of them is smaller. As for the rhombohedral phase, it comes out firstly along the grain boundary, and whose amount in equilibrium is about 5％. In contrast to the rhombohedral phase, the hexagonal phase is more likely to form at lower temperature which lead to the microcracks. In brief, obtaining the eligible phase stability is crucial for the industrial application of the oxygen permeation membrane.     

Relaxation mechanism in several kinds of polyethylene estimated by dynamic mechanical measurements, positron annihilation, X-ray and C solid-state NMR

Relaxation processes of several kinds of polyethylene films and fibers with different molecular orientational degrees and crystallinities were extensively investigated by the dynamic mechanical relaxation, positron annihilation and ¹³C nuclear magnetic relaxation (¹³C NMR). From complex dynamic tensile modulus, the activation energies of α₁ and α₂ relaxations were determined to be 97-118 and 141-176 kJ/mol, respectively. The activation energy of β relaxation was 114-115 kJ/mol. These values were similar to those of α₁ relaxation reported already. For γ relaxation mechanisms, there existed two mechanisms, γ₁ and γ₂, the activation energies being 9-11 and 23-25 kJ/mol, respectively. The values were independent of the molecular orientation and crystallinity. The two local motions indicate that non-crystalline phase composes of two regions of non-crystalline phase, rubber-like amorphous phase and interfacial-like amorphous phase. From ¹³C NMR measurements of ¹³C longitudinal relaxation time for the non-crystalline phase, the activation energy was 20.7 kJ/mol. This value is close to the activation energy (23-25 kJ/mol) of the γ₂ relaxation estimated by the dynamic mechanical measurement. The result by ¹³C NMR did not provide two kinds of activation energy, indicating combined influence of the two correlation times. Even so, the activation energies obtained by ¹³C NMR indicated that the γ₂ relaxation mainly is due to the motion of the C-C central bond of a short segment (e.g. three to four CH₂) within interfacial-like amorphous phase. The γ and β relaxation peaks by the dynamic mechanical measurements corresponded to the first and second lifetime transition of ortho-positronium indicating, in turn, a drastic change in free volume by local mode relaxation.     

SHS转炉补炉料的物相组成及显微结构特征

利用自蔓延高温合成(SHS)原理,选择工业铝粉作为发热剂,菱镁矿为供氧剂,通过铝热反应,研制出了一种以镁砂为骨料,以镁铝尖晶石和炭质材料作为结合相的新型SHS转炉补炉料.对不同环境温度下补炉料的物相组成及显微结构进行了研究,并对合成尖晶石的固相反应原理及SHS产物相的烧结机制进行了探讨.结果表明补炉料中颗粒状的骨料方镁石与SHS反应产物尖晶石、非晶质碳、少量刚玉相和硅酸盐玻璃相共同构成含有气孔的交织结构,形成尖晶石、碳桥和陶瓷相与方镁石骨料的多重结合;SHS反应过程分碳酸盐矿物的分解反应、铝热氧化还原反应(即SHS反应)和合成尖晶石的固相烧结反应三步进行,其烧结受扩散机理控制.     

纤维素热裂解反应机理数值模拟

A detailed mechanism analysis of cellulose pyrolysis was carried out according to the previous experimental results. On the basis of the Brodio-Shafizadeh model, a modified two-stage model was proposed to simulate the formation and decomposition of active cellulose (AC) and several main organic compounds, such as levoglucosan (LG), hydroxyl-acetaldehyde (HAA), acetol and furfural etc. During pryolysis, the temperature rise of cellulose can be divided into three stages. In the second stage, cellulose undergoes a main decomposition process in which the reaction temperature remains rather low because of the endothermic cracking of glucosidic bond of AC during the formation of LG. The components density of bio-oil, including LG and other competitive compounds, increased rapidly with the increase of temperature during the first stage. However, in the main decomposition process, LG density in bio-oil had an obvious decrease, while the competitive products appeared to increase gradually, which means the ring-opening and reforming reaction of pyranoid ring are superior to LG formation in high temperature.The secondary reaction of volatile components occurs largely in gaseous phase rather than in the solid phase. Short residence time of volatile materials in high temperature region will be advantageous to a high production of LG,which may otherwise decompose quickly under high temperature. An optimum yield of LG could be obtained when radiant source temperature is in the range of 730---920K and gas residence time is less than 1 s. In addition, the reaction temperature has a stronger effect than gas residence time on the formation of HAA, acetol, formaldehyde and furfural etc.