尺寸可控氢氧化镧纳米棒的水热合成及表征

以硝酸镧为镧源、三乙胺为碱源和络合剂,通过简便的水热法成功合成了大量均一的氢氧化镧纳米棒。详细研究了三乙胺的用量、表面活性剂、反应温度和时间对产物形貌及尺寸的影响。基于实验结果,提出了氢氧化镧纳米棒的形成机理。同时制备了稀土掺杂的氢氧化镧纳米棒。利用X射线衍射（XRD）、透射电子显微镜（TEM）、选区电子衍射（SAED）和高分辨透射电子显微镜（HRTEM）对所得产物的物相、结构和形貌进行了表征分析。     

Analysis of Spectral Points of the Operators T [*] T and TT [*] in a Krein Space

Spectra and sets of regular and singular critical points of definitizable operators of the form T ^[*] T and TT ^[*] in a Krein space are compared. The relation between the Jordan chains of the above operators (corresponding to the same eigenvalue) is shown.      

Synthesis, characterization, thermal properties and flame retardancy of a novel nonflammable phosphazene-based epoxy resin

Hexakis(4-hydroxyphenoxy)-cyclotriphosphazene (PN-OH) was synthesized through nucleophilic substitution of the chloride atoms of hexachlorocyclotriphosphazene and reduction of the aldehyde groups, and its chemical structure was characterized by elemental analysis, ¹H and ³¹P NMR, and Fourier transform infrared (FTIR) spectroscopy. A new phosphazene-based epoxy resin (PN-EP) was successfully synthesized through the reaction between diglycidyl ether of bisphenol-A (DGEBA) and PN-OH, and its chemical structure was confirmed by FTIR and gel permeation chromatography. Four PN-EP thermosets were obtained by curing with 4,4′-diaminodiphenylmethane (DDM), dicyandiamide (DICY), novolak and pyromellitic dianhydride (PMDA). The reactivity of PN-EP with the four curing agents presents an increase in the order of DDM, PMDA, novolak and DICY. An investigation on their thermal properties shows that the PN-EP thermosets achieve higher glass-transition and decomposition temperatures in comparison with the corresponding DGEBA ones while their char yields increase significantly. The PN-EP thermosets also exhibit excellent flame retardancy. The thermosets with novolak, DICY and PMDA achieve the LOI values above 30 and flammability rating of UL94 V-0, whereas the one with DDM reaches the V-1 rating. The nonflammable halogen-free epoxy resin synthesized in this study has potential applications in electric and electronic fields in consideration of the environment and human health.     

加合反应对MOCVD生长GaN化学反应路径的影响

针对分隔进口垂直高速转盘式(RDR)MOCVD反应器生长GaN的气相化学反应路径进行数值模拟研究.分别考虑TMG与一个NH3的加合反应(模型1)和TMG: NH3与第二个NH3的加合反应(模型2)两种情况,通过对比两种情况下衬底表面附近主要反应前体的浓度大小,判断GaN生长的主导反应路径.通过分析模拟结果发现:只考虑TMG与一个NH3的加合反应时,GaN生长主要遵循TMG热解路径;在考虑TMG: NH3与第二个NH3的加合反应时,GaN生长主要遵循加合路径.由此可见,TMG: NH3与第二个NH3的反应对于MOCVD生长GaN的化学反应路径的选择具有很大的影响.     

MOCVD生长AlN/GaN化学反应路径的量子化学研究

应用量子化学的密度泛函理论,对MOCVD生长GaN/AlN薄膜的反应路径进行理论计算和分析,特别是针对Ⅲ族TMX(X=Ga,Al)与V族NH3的反应路径与温度的关系进行研究.计算结果表明:当温度T≤473.15 K时,反应自由能△G＜0,TMX与NH3自发生成配位加合物TMX∶ NH3;当T≥573.15 K时,△G＞0,TMX∶ NH3将重新分解为TMX和NH3.在473.15 K≤T≤573.15 K区间,将存在△G=0,即加合反应达到平衡,反应为双向可逆.随着温度的升高,从加合物变为氨基物DMX∶ NH2的反应概率加大.TMX和MMX的直接热解反应均需要高温激活,而DMX变为MMX则较容易发生.当T＞873.15 K时,DMGa变为MMGa的热解反应将自发进行;当T＞1273.15 K时,DMAl变为MMAl的热解反应将自发进行.在自由基CH3参与下,TMX→DMX(X=Ga、Al)的能垒仅为TMX直接热解能垒的一半,约为30 ～ 40 kcal/mol;在自由基H参与下,TMGa和TMAl的热解反应能垒更低,约为16～ 20kcal/mol.因此,自由基H的产生将大大促进TMX的热解.     

Resonance Frequency and NMR Relaxation Times in Two Inequivalent <Superscript>133</Superscript>Cs in Cs<Subscript>2</Subscript>CuBr<Subscript>4</Subscript> and Cs<Subscript>2</Subscript>ZnBr<Subscript>4</Subscript> Single Crystals

The resonance frequencies and relaxation mechanisms of Cs₂CuBr₄ and Cs₂ZnBr₄ were examined by static nuclear magnetic resonance (NMR) method. Here, the two inequivalent Cs(1) and Cs(2) sites surrounded by Br ions were distinguished. The saturation recovery traces for ¹³³Cs nuclei in Cs₂CuBr₄ with the paramagnetic ions, and those in Cs₂ZnBr₄ without the paramagnetic ions were each fitted by four exponential functions. From these results, the spin–lattice relaxation times T₁ in the laboratory frame of ¹³³Cs nuclei in the two crystals were obtained, and Cs(1) surrounded by 11 bromide ions has a longer relaxation time than Cs(2) surrounded by 9 bromide ions.     

基于拜占庭故障模式的空天飞行器GNC系统架构研究

针对空天飞行器对GNC系统的高可靠性需求,开展了基于拜占庭故障模式的GNC系统架构研究,采用四机三总线架构设计方案,通过系统内总线实现输入数据及输出数据多机冗余比对,防止拜占庭故障的发生,提升了系统可靠性,实现了系统自检测和故障的准确定位及隔离,并具有在线故障诊断、故障自修复功能,同时解决了高动态、强干扰环境下系统自主性较差的问题,提升了GNC系统可靠性和容错性;经分析,该系统架构能够满足空天飞行器在轨、再入复杂任务需求。     

抗白血病药物克拉屈滨的合成

报道了抗白血病药物克拉屈滨的合成新方法:在NaH作用下,廉价易得的6-氯嘌呤高选择性地在β位和1-氯-2-脱氧-3,5-二-O-对氯苯甲酰基-D-核糖缩合;β-缩合物的2位在三氟乙酸酐和四丁基硝酸铵作用下引入硝基;在NH₄Cl/EtOH作用下,2-硝基转化为2-氯;最后在饱和NH₃/CH₃OH溶液中完成保护基脱除和6-氯氨解两步反应,以4步共43.5%的总收率得到抗白血病药物克拉屈滨。 该方法完全避免了α异构体的生成,原料廉价易得,分离纯化不需柱层析,且反应扩大到100 g规模时,收率无下降,具有较好的应用前景。     

用于核聚变装置的W/Cu 穿管部件的制备与辐照性能研究

采用了两步热等静压法制备W/Cu 穿管部件,即先用热等静压(930℃,100MPa,2h)在钨块的孔内壁上覆一层无氧铜作为中间层,然后再用热等静压工艺(600℃,100MPa,2h)把W/Cu 复合块与CuCrZr 管串接起来。经过高热负荷辐照测试,部件经受住了1000 次10MW•m⁻² 高热负荷的辐照,满足使用要求。     

基于类间方差的MODIS森林火灾火点检测方法

提出一种基于火点与背景的类间方差和烟雾掩膜的红外光谱火点检测算法。该算法的潜在火点判定阈值设为305K,再利用MODIS热红外光谱通道亮温数据的类间方差值将森林火灾火点从背景中区分出来,并对低温闷烧火点采用烟雾掩膜进行识别。应用该算法对福建省和黑龙江地区的林火数据进行探测处理,与传统MODIS火点检测方法比较分析表明,该算法使用简单高效,在不同环境适应性较强,可以更准确地检测到高温明火点和一些低温闷烧火点,降低了火点的误报率和小火点的漏报率,检测效果更理想。