光固化快速成型中光敏树酯的光学特性对成型的影响

研究了光固化快速成型中光敏树酯的光化学过程、光敏树脂与固化光源的匹配性以及对光吸收特性和固化特征,分析了这些因素对成型过程的影响,为快速成型机的实际应用提供了参考.     

微细光束固化的蒙特卡罗建模

光固化是光束与光敏树脂之间的光化学反应,其作用过程对光固化加工分辨率有着直接影响.基于光子输运理论,利用蒙特卡罗方法追踪光子往树脂中的运动轨迹,对曝光光束人射、传输过程进行抽样,建立了微细光束固化模型;利用遗传算法并结合光同化实验重构获得了树脂材料的光学参数;利用该崮化模型,模拟计算了微细会聚紫外光束(λ=365 nm)单点曝光同化过程和固化单元点的形状和大小,分析了不同曝光最对固化结果的影响规律,计算结果与实验结果一致.研究表明,该模型可以有效地对微细光束与光敏树脂作用的复杂过程进行仿真,并能对不同入射光和曝光工艺条件下的固化物进行模拟计算,为微细光固化机理的研究和工艺优化提供了基础.     

光敏树脂固化机理研究

本文探讨了高新技术──快速成型技术中关键材料:光敏树脂的光固化机理。着重分析了光敏预聚物和光敏引发剂的光交联固化机理,并对光固化过程进行了讨论。     

用于光学位移传感器的新型数字编码光栅尺的制作（英文）

介绍了数字编码光栅尺的结构设计并提出一种制作方法.采用紫外对准光刻、全息光刻及湿法腐蚀结合在(100)硅片上制作母光栅尺,并以具有紫外固化特性的聚氨酯丙烯酸酯为材料,将母光栅尺复制到硬基底上.实验表明,该工艺可重复性高,复制光栅尺的衍射效率高于母光栅尺的90%,并能承受航空环境-55℃~70℃的高低温冲击.光栅尺的制作准确度满足传感器的要求,信号响应准确率100%.该方法可对具有准确度高、图形复杂、工作环境恶劣等特点的微纳米结构的制作提供借鉴.     

臂型网格结构增强石墨烯电调制太赫兹透射

为提高单层石墨烯薄膜电控太赫兹调制器的调制深度,提出一种臂型金属网格微结构与石墨烯结合的太赫兹波透射调制器件.通过臂型金属网格结构激发的共振耦合场增强石墨烯与太赫兹波的相互作用,使石墨烯在外加电压调制下对太赫兹波透射幅度的调制深度获得大幅提升.通过有限元仿真分析了金属结构参数对石墨烯与太赫兹波相互作用增强规律的影响,理论结果表明,臂型网格结构使石墨烯对太赫兹波透射幅度调制深度从7.7%提升到了28.2%.在理论结果的基础上,基于光刻工艺完成了器件的结构制作,实验测试中获得了24%的太赫兹幅度调制深度,且调制深度曲线与理论仿真规律基本一致.     

高效全固化263nm紫外激光脉冲的产生

运用半导体泵浦的Nd:YLF调Q倍频激光器输出的527nm波长激光和BBO晶体直接进行了外腔谐波倍频的实验研究.采用较小的基波光束尺寸和长聚焦相结合的方法实现了高效全固化263nm紫外激光脉冲的大功率输出.基波功率为6.0W时,紫外263nm激光输出780mW,转换效率达13%,实验中还发现紫外输出光束质量很好.     

两种含硅炔基树脂的固化行为研究

综合采用红外光谱（FTIR）、核磁碳谱 (13C NMR)、差示扫描量热（DSC）,热失重测试(TGA)等多种表征手段,研究了聚硅芳炔（PAR）和聚硅乙炔（PMR）两种含硅炔基树脂的固化行为,讨论了树脂固化物的结构与热稳定性的关系。结果表明：PAR和PMR树脂的固化机理不同,PAR主要通过炔基间的加成和Diels-Alder反应实现分子间的固化交联,并最终形成由苯环和稠芳环组成的芳构网络;PMR则主要通过硅氢基、炔基、烯基之间的加成反应实现固化,并成形饱和的碳硅Si—C(sp3)网络结构。固化成型的芳构网络和Si—C(sp3)网络结构分别赋予了PAR和PMR树脂固化物良好的热稳定性能,它们的热分解温度T_d5均大于600 ℃,900 ℃残重率均达到85%以上。     

水体细菌微生物多波长透射光谱快速准确获取方法研究

为实现水体细菌微生物快速在线监测,搭建了多波长透射光谱快速测量实验系统,利用该系统分别测量了重铬酸钾标准溶液紫外波段及中性滤光片可见波段的透射光谱,并与紫外-可见分光光度计测得的透射光谱进行对比分析,验证了实验系统测量透射光谱的准确性;以水体中常见的金黄色葡萄球菌作为研究对象,利用搭建的实验系统获取金黄色葡萄球菌溶液在220～900 nm波段的前向小角度透射光谱,进一步验证了实验系统测量细菌微生物透射光谱的准确性和快速性。结果表明,由实验系统和紫外-可见分光光度计测得的重铬酸钾标准溶液,与中性滤光片紫外波段及可见波段透射光谱的线性拟合相关系数分别为0.999 7和0.999 5,光密度误差分别在5.00%和4.58%以内,说明两个系统测量光谱的一致性较好,所搭建的实验系统测量标准样品紫外-可见透射光谱准确度较高;对于金黄色葡萄球菌,实验系统测得的透射光谱经过校正后,与紫外-可见分光光度计测得的透射光谱线性拟合的相关系数为0.999 97,两者相比的光密度误差在0.74%以内;系统重复30次细菌光谱信号采集获得平均透射光谱单次测量时间为15 s,说明该实验系统相对于紫外-可见分光光度计能够快速准确获取水体细菌微生物多波长透射光谱,在保证测量结果准确的同时缩短了光谱测量时间,为水体细菌微生物快速检测提供技术支持。     

用于光学位移传感器的新型数字编码光栅尺的制作

介绍了数字编码光栅尺的结构设计并提出一种制作方法.采用紫外对准光刻、全息光刻及湿法腐蚀结合在(100)硅片上制作母光栅尺,并以具有紫外固化特性的聚氨酯丙烯酸酯为材料,将母光栅尺复制到硬基底上.实验表明,该工艺可重复性高,复制光栅尺的衍射效率高于母光栅尺的90％,并能承受航空环境-55℃～70℃的高低温冲击.光栅尺的制作准确度满足传感器的要求,信号响应准确率100％.该方法可对具有准确度高、图形复杂、工作环境恶劣等特点的微纳米结构的制作提供借鉴.     

杂化溶胶改性紫外光固化胶粘剂的研究

 以自制的杂化溶胶对紫外光固化丙烯酸酯胶粘剂进行改性，得到了具有高粘接强度，对丙酮、乙醇、氯仿等具有明显的耐溶剂性的紫外光固化胶粘剂。实验发现：活性稀释剂中含有较多的羟基、羧基时，此胶粘剂对玻璃的粘接强度较高；胶层粘接力随杂化溶胶用量的增加先增大，后减小，当杂化溶胶中的固体质量为光敏树脂的60％时，胶粘剂的剪切强度达到最大（12MPa）。     

长亚甲基链段改性固化剂的制备与性能

采用二官能度环氧树脂对己二胺进行改性,得到了含多段长亚甲基链段的柔性固化剂。利用红外光谱表征其基本结构。采用环氧树脂E-44与之进行固化,通过不同温度下固化时间对力学强度影响的分析,初步确定其最佳固化条件为80 ℃,6 h。通过热重分析检测不同固化比例下固化产物的热稳定性,并采用差示扫描量热法研究该固化剂的固化动力学参数、反应活性、最佳固化温度及时间。对其固化物拉伸剪切强度进行测试,测试结果表明:在固化比例为1:0.5时,在-196 ℃、室温、60 ℃下的拉伸剪切强度分别为16.84,14.73和13.52 MPa,基本满足实际应用的需求。     

Influence of Curing Pressure on the Structure and Properties of Epoxy Adhesive Films

The effects of different curing pressures on the structure and properties of bisphenol A type epoxy adhesive film (METLBOND 1515-4, Cytec Industries Inc. Germany) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), nano-indentation analysis, and tensile testing. When the curing pressure was increased from 0?MPa to 0.5?MPa FTIR showed that more rigid carbonyl groups were found in the polymers. In addition, the microscopic and macroscopic mechanical properties of the cured adhesive films were improved. Nano-indentation analysis showed that the elastic modulus of the cured product increased significantly, from 2.92?GPa to 3.49?GPa. However, the tensile tests showed that the breaking-elongation increased only slightly, from 3.10% to 3.73%, when the curing pressure was increased from 0?MPa to 0.5?MPa. DMA results showed that the crosslinking densities of the cured epoxy films were improved by the increased curing pressure. These results indicated that a higher modulus of the cured product could be gained by increasing the curing pressure appropriately.     

光固化成型中紫外光源-光纤耦合研究

CPS(Compact Prototyping System)光固化成型系统中,以紫外灯作为光源,通过光纤传输紫外光到液面,进行扫描成型.光源通过椭球反射镜集光,在焦点处与光纤耦合,提高了光源-光纤的耦合效率,在实际的光源-光纤耦合中,光纤的装配存在着角度误差、离焦误差、离轴误差三种形式,这些误差影响传输光束的传输效率.在光纤的输出端,聚焦透镜将紫外光汇聚,光斑尺寸更小,能量更加集中.CPS成型机中使用的紫外光的能量并不是均匀分布的,光斑的中心能量高,边缘能量低,不同的能量分布影响树脂固化的形貌和质量.     

聚氨酯改性TDE-85/MeTHPA环氧树脂的力学性能研究

 采用自制的聚氨酯预聚体(PUP)制备聚氨酯(PU)改性TDE-85/ MeTHPA环氧树脂体系,探讨了聚醚二元醇(PPG)分子量的大小、PUP加入量等因素对PU改性TDE-85/ MeTHPA环氧树脂体系力学性能的影响。研究结果表明,PU改性TDE-85/ MeTHPA环氧树脂的拉伸强度和冲击强度随着合成的PUP加入量的增加先呈上升趋势,达到最大值后又开始下降。采用的PPG分子量不同,得到的改性材料的力学性能相差悬殊。当PPG分子量为1 000,PUP质量分数为15%时,改性材料的拉伸强度达到69.39 MPa,冲击强度达到23.56 kJ/m²,力学综合性能显著提高。     

Preparation and Characterization of Silicon-containing Polyarylacetylene/montmorilloite Nanocomposites

Dimethylphenylpropargyl ammonium bromide (DMPPAB) was synthesized and used to modify pristine montmorillonite (MMT) by a cation exchange process. The organically modified montmorillonite (OMMT) was verified and used to mix with a silicon-containing polyarylacetylene (PSA) as well as MMT. The PSA/MMT and PSA/OMMT nanocomposites were prepared by solution under sonication and melting intercalation processes, respectively, and then cured by a step heating process. The thermal and flexural properties of the cured PSA and nanocomposites were studied by thermogravimetric and dynamic mechanical analysis. The results showed that the intercalation of DMPPAB into the MMT galleries made the d-spacing enlarge. During PSA curing, the cure heat of PSA caused the MMT and OMMT to delaminate and exfoliate in the PSA matrix. The glass transition temperature of the cured PSA and nanocomposites were higher than 500?°C. The inner acetylenic groups in the PSA resin could further crosslink above 300?°C. The temperature at 5% mass loss of the cured PSA decreased by 4.6% with 3% mass fraction of OMMT loading, and the char yield of the cured PSA changed only slightly. The flexural strength of the cured PSA was augmented with addition of MMT or OMMT, but the flexural modulus of the cured PSA decreased slightly. The flexural strength of the cured nanocomposite increased from 20.1?MPa to 30.1?MPa when 3% mass fraction of OMMT was added into the PSA matrix.     

苯代三聚氰胺增韧改性三聚氰胺树脂的制备及光谱分析

利用三聚氰胺、甲醛和苯代三聚氰胺增韧剂在碱性条件下制备了改性三聚氰胺甲醛树脂(BG-MF)，并将其浸渍牛皮纸使用直接浸渍方法来制得层积板。研究加入不同添加量的苯代三聚氰胺对共缩聚树脂结构、结晶性、力学性能、耐燃烧、耐沸水等性能的影响。核磁共振氢谱图(1H-NMR)结果显示，改性后树脂BG-MF在化学位移δ7.0~7.6处出现了尖锐的特征峰，主要归属于苯代三聚氰胺中的苯环的氢质子峰；红外光谱(FTIR)结果显示，BG-MF红外结果除了与三聚氰胺甲醛树脂(MF)具有相同的特征吸附峰外，在1 557和774 cm-1出现了新的特征吸收峰，主要归属于苯代三聚氰胺中的苯环骨架的特征吸收峰，说明苯代三聚氰胺参与缩聚反应。X射线衍射图谱分析说明BG加入后晶型有轻微变化，主要是由于MF中含有N元素，有大量的氢键产生，进而形成不规则的部分微小晶体。改性后树脂用于浸渍层积板的制备，DMA测试结果显示，当BG含量达到15%时在137.2 ℃储能模量为20 228 MPa，比未改性MF树脂的峰顶储能模量17 050 MPa提高了18.6%，表明改性后树脂胶接强度提高。从拉伸实验结果可以看出，苯代三聚氰胺含量约为15%时，增韧效果最好。氧指数从36.2升高到38.4，表明苯代三聚氰胺的加入其阻燃性能有所增强。     

CLAM钢冲击和拉伸性能测试与研究

对中国低活化马氏体钢——CLAM钢的冲击和拉伸性能进行了测试。结果表明:CLAM钢的塑。脆转变温度在-100℃左右,低于国际上其它几种典型的低活化马氏体钢;在室温和600℃时抗拉强度分别为668和334MPa,类似于EUROFER97的性能。约8μm的晶粒尺寸是CLAM钢具有较好冲击和拉伸性能的主要原因之一。The impact and tensile tests were carried out on the China Low Activation Martensitic steels （CLAM）. The results show: the Ductile-Brittle Transition Temperature （DBTY） is about - 100 ℃, which is lower than those of some other RAFMs; The ultimate strength are 668 MPa at room temperature and 334 MPa at 600℃, which are comparable to those of EUROFER97. The finer grain size of about 8 μm was considered as one of reasons for the superior mechanical properties of CLAM.     

Localization of electromagnetic waves in three-dimensional fractal cavities

Three-dimensional fractals called the Menger sponge, with a fractal dimension D=log(20/log(3, were fabricated from epoxy resin by stereolithography. Clear attenuation of both reflection and transmission intensity was observed at 12.8 GHz for a cubic specimen with an edge size of 27 mm that was constructed up to the third stage of the self-similar patterns. The electromagnetic field was found to be confined in the central part of the specimen at this frequency. The localization is not caused by the presence of a photonic band gap as in photonic crystals but should be attributed to a singular photon density of states realized in the fractal structure. This is the first report on such localization of electromagnetic waves in three-dimensional fractal cavities.     

Author Index to Volume 8

Pull-out experiments have been carried out with Kevlar fibres embedded in epoxy resin. Friction accompanied debonding, and had to be allowed for in the analysis. The debonding stress was about equal to the matrix strength for 80°C cured epoxies. However, debonding appears to be a brittle fracture process, and the works of fracture corresponding to the apparent interface strengths are very low, ranging from ca. 20-40 Jm^-2 depending on the surface treatment and degree of cure of the resin. Water immersion for 2300 h at room temperature reduced the apparent strengths and works of fracture with some of the surface treated fibres, but not with the untreated fibres. Interface pressures during debonding were 10-15 MPa for the 20°C cured specimens and 20-30 MPa for the 80°C cure. Water soaking markedly reduced the friction coefficients. Post-debonding friction was high, but estimates of the parameters was probably unreliable due to the fibre having a somewhat thick end due to fibrillation when being cut.