淡水青虾幼体发育的初步研究

作者观察了淡水青虾在实验室条件下幼体发育的情况。在幼体发育的全过程中,有的个体蜕皮9次,有的蜕皮11、14次。本文是描述蜕皮9次的个体的发育情况。从第一至第九期幼体以及后期幼体都附有详细的附肢图和部分整体图。幼体发育所需的时间随水温而变,在26.5±1.3℃条件下,幼体完成变态达到后期幼体需21天,在30.9±1-2℃仅需16天

有机前驱体法bn纤维的制备和表征

BN fibers with cylindrical hollow structures were prepared from organic polymeric precursors through melt spinning, curing and pyrolysis processes. The microstructure, solid phase and morphologies of the synthesized hollow BN fibers were investigated by XRD, SEM and TEM, respectively. Moreover, the dielectric properties of BN hollow fibers were also measured. The results show that heating temperature and heating rate are the key factors affected the structure and dielectric properties of BN hollow fibers. Moreover, the BN hollow fibers synthesized in the optimized process conditions have good resistance towards oxidation up to 950 C in an oxidation atmosphere, and possess very low dielectric constant (epsilon') and loss tangent (tan delta) less than 3.30 and 0.00064 (7-18 GHz), respectively

Preparation and Characteristic of Hollow BN Fibers Derived from Organic Precursors

BN fibers with cylindrical hollow structures were prepared from organic polymeric precursors through melt spinning, curing and pyrolysis processes. The microstructure, solid phase and morphologies of the synthesized hollow BN fibers were investigated by XRD, SEM and TEM, respectively. Moreover, the dielectric properties of BN hollow fibers were also measured. The results show that heating temperature and heating rate are the key factors affected the structure and dielectric properties of BN hollow fibers. Moreover, the BN hollow fibers synthesized in the optimized process conditions have good resistance towards oxidation up to 950 C in an oxidation atmosphere, and possess very low dielectric constant (epsilon') and loss tangent (tan delta) less than 3.30 and 0.00064 (7-18 GHz), respectively

有机前驱体法bn纤维的制备和表征

BN fibers with cylindrical hollow structures were prepared from organic polymeric precursors through melt spinning, curing and pyrolysis processes. The microstructure, solid phase and morphologies of the synthesized hollow BN fibers were investigated by XRD, SEM and TEM, respectively. Moreover, the dielectric properties of BN hollow fibers were also measured. The results show that heating temperature and heating rate are the key factors affected the structure and dielectric properties of BN hollow fibers. Moreover, the BN hollow fibers synthesized in the optimized process conditions have good resistance towards oxidation up to 950 C in an oxidation atmosphere, and possess very low dielectric constant (epsilon') and loss tangent (tan delta) less than 3.30 and 0.00064 (7-18 GHz), respectively

三氯环硼氮烷改性聚碳硅烷的合成及陶瓷转化

为研究三氯环硼氮烷（TCB）对聚碳硅烷（PCS）性能及陶瓷转化的影响,将一定量的TCB加入PCS中制备TCB改性PCS聚合物,分析了TCB与PCS的反应性及TCB用量对改性PCS结构、陶瓷收率、可加工性和SiC产物微结构的影响,并采用红外光谱、热重、X射线衍射等测试技术对相应产物进行表征.结果表明,PCS中的Si-H键可部分地与TCB中的-Cl反应生成HCl;随着TCB质量分数的增加,PCS中Si—H键相对于Si-CH3的浓度比呈下降趋势.TCB的加入可显著提高PCS的陶瓷收率,TCB质量分数大于8%时,陶瓷收率质量分数约增加10%.TCB质量分数为5%～8%时,可在提高PCS收率的同时使其保持较好的可加工性能,TCB质量分数大于8%时,可加工性能变差.B、N的引入对SiC的微结构有影响：在氩气保护下,经1000℃热处理时,TCB的加入促进SiC晶粒的生长;经1400℃热处理时,TCB的加入抑制SiC晶粒的长大

三氯环硼氮烷改性聚碳硅烷的合成及陶瓷转化

为研究三氯环硼氮烷（TCB）对聚碳硅烷（PCS）性能及陶瓷转化的影响,将一定量的TCB加入PCS中制备TCB改性PCS聚合物,分析了TCB与PCS的反应性及TCB用量对改性PCS结构、陶瓷收率、可加工性和SiC产物微结构的影响,并采用红外光谱、热重、X射线衍射等测试技术对相应产物进行表征.结果表明,PCS中的Si-H键可部分地与TCB中的-Cl反应生成HCl;随着TCB质量分数的增加,PCS中Si—H键相对于Si-CH3的浓度比呈下降趋势.TCB的加入可显著提高PCS的陶瓷收率,TCB质量分数大于8%时,陶瓷收率质量分数约增加10%.TCB质量分数为5%～8%时,可在提高PCS收率的同时使其保持较好的可加工性能,TCB质量分数大于8%时,可加工性能变差.B、N的引入对SiC的微结构有影响：在氩气保护下,经1000℃热处理时,TCB的加入促进SiC晶粒的生长;经1400℃热处理时,TCB的加入抑制SiC晶粒的长大

三氯环硼氮烷改性聚碳硅烷的合成及陶瓷转化

为研究三氯环硼氮烷(TCB)对聚碳硅烷(PCS)性能及陶瓷转化的影响,将一定量的TCB加入PCS中制备TCB改性PCS聚合物,分析了TCB与PCS的反应性及TCB用量对改性PCS结构、陶瓷收率、可加工性和SiC产物微结构的影响,并采用红外光谱、热重、X射线衍射等测试技术对相应产物进行表征.结果表明,PCS中的Si-H键可部分地与TCB中的-Cl反应生成HCl;随着TCB质量分数的增加,PCS中Si—H键相对于Si-CH3的浓度比呈下降趋势.TCB的加入可显著提高PCS的陶瓷收率,TCB质量分数大于8%时,陶瓷收率质量分数约增加10%.TCB质量分数为5%～8%时,可在提高PCS收率的同时使其保持较好的可加工性能,TCB质量分数大于8%时,可加工性能变差.B、N的引入对SiC的微结构有影响:在氩气保护下,经1000℃热处理时,TCB的加入促进SiC晶粒的生长;经1400℃热处理时,TCB的加入抑制SiC晶粒的长大

一种漂浮铰接式波能装置的水动力学研究

A kind of hinged wave energy device with a floating body and a submerged body was studied. In order to get the hydrodynamic coefficient and wave excitation force of the device with complicated shape, the software HydroStar based on 3-D surface element me

C/C-ZrB_2-ZrC-SiC超高温复相陶瓷基复合材料的性能

以聚合有机锆烷、聚合有机硼氮锆烷与聚碳硅烷组成的共溶前驱体为原料,采用化学气相渗透和聚合物浸渍裂解工艺制备了C/C-ZrB2-ZrC-SiC超高温陶瓷基复合材料,对其物相组成、微观结构、力学性能和抗烧蚀性能进行了研究.结果表明,所制材料基体由ZrB2和ZrC纳米颗粒均匀弥散分布于连续的SiC相中构成.随热解炭含量增加,材料的弯曲强度和断裂韧性皆呈先上升再下降的趋势,其含量为22.3%(φ)的材料的力学性能最优,弯曲强度和断裂韧性分别为127.9MPa和6.23MPam1/2,且具有假塑性断裂特性.材料在1800～2200℃等离子弧中1000s的线烧蚀率小于1.67μm/s,质量烧蚀率小于1.66mg/s

碳化锆陶瓷有机前驱体的热解过程

合成了碳化锆陶瓷有机前驱体,研究了其在热解过程中化学成分和物相组成变化,探讨了从有机高分子向无机陶瓷转化的机理,对碳热还原反应进行了热力学分析。结果表明,前驱体在600℃以下完成了有机结构的断裂、裂解碎片的重排与挥发,600℃以上裂解产物不再具备有机特征;随热解温度升高,无定型碳和单斜相ZrO2逐渐生成,大于1200℃时可检测到立方相ZrC,1400℃时单斜相ZrO2基本消失;1500℃时完成碳热还原反应,在远低于热力学反应温度的条件下生成了高度结晶的纳米尺寸的立方相碳化锆陶瓷