磁场作用下有序针状焦的制备

在不同磁场强度下,煤焦油沥青经热聚合、高温煅烧制得了有序度较高的针状焦。研究了磁场对针状焦制备的影响,并采用扫描电镜(SEM)、X射线衍射(XRD)和红外光谱(FT-IR)分析方法表征了针状焦在磁场作用下的结构特征。结果表明:磁场对针状焦制备的影响是正向的,磁场能有效提高针状焦的有序度,改善其纤维组织形貌,并且随着磁场强度的增加,针状焦有序性呈递增趋势。     

原料组成对针状焦结构性能的影响

将不同组成的原料经过延迟焦化和煅烧工艺,制备出一系列针状焦。分别采用偏光显微镜、粉末电阻率测试仪和PCY卧式膨胀仪对针状焦的形貌结构、热膨胀性能以及电导率进行分析。结果表明:经过热过滤和减压蒸馏制得喹啉不溶物(QI)含量为0.09%、甲苯不溶物-喹啉可溶物(TI-QS)含量为57.2%、正庚烷可溶物(HS)含量为41.7%的煤沥青,以其为生焦原料所得的针状焦性能最优,其光学结构为广域流线纤维状结构,热膨胀系数为0.53×10-6/℃,电阻率为5.5μΩ·m,达到优质针状焦的指标。     

煤焦油基针状焦和石油基针状焦晶胀行为的差异

通过高温热解重量分析,高温X射线衍射和四极气体分析研究了煤焦油基针状焦和石油基针状焦的晶胀行为。重量损失差示曲线在1800℃附近出现最大值。在1800℃左右温度下,煤焦油基针状焦的重量损失主要由含氮量减少引起,而石油焦的重量损失是由含氮量和含硫量减小引起的。发生晶胀的时候,针状焦的层间间距减小。这说明晶胀和碳晶格的不可逆收缩有关。还发现煤焦油基普通焦的晶张低于它的含氮量予计的数值。因此,晶胀还可能与焦炭的结构有关。     

不同针状焦对石墨电极性能的影响探讨

选取了3种不同的针状焦,制取小样进行测试,分析针状焦对电极的影响。结果发现原料针状焦的参数决定石墨化小样的性能,CTE、电阻率、抗压强度、真密度将直接决定电极的性能;通过扫描电镜发现,纤维结构纹理清晰,定向排列,片层之间空隙小的针状焦性能表现优异;通过偏光显微镜分析,呈广域型结构的针状焦性能较好。     

烧结温度对不锈钢表面溶胶-凝胶ZrO2纳米薄膜摩擦学性能的影响

采用溶胶-凝胶法,在304不锈钢表面制备了分别经500℃、600℃和700℃下热处理的ZrO2薄膜.利用X射线衍射仪(XRD)、原子力显微镜(AFM)、扫描电镜(SEM)和摩擦磨损测试仪,研究了热处理温度对ZrO2薄膜的表面结构和摩擦学性能的影响.结果表明:随着温度的升高,ZrO2晶体结构逐渐由四方相(t-ZrO2)向单斜相(mZrO2)转变;当热处理温度从500℃升高到700℃时,ZrO2薄膜的平均晶粒度略有增大,但都在80 nm左右,晶粒分布趋于均匀致密,且其表面粗糙度由6.3 nm降低至4.6 nm左右.同时ZrO2薄膜的摩擦系数和磨损率分别从0.22和2.24×10-4mm3/Nm逐渐减小为0.19和1.95×10-4 mm3/Nm,因而薄膜的抗磨减摩性能也显著提高.     

煅烧温度对宝钢针状焦性能影响的研究

通过升温试验研究了煅烧温度对宝钢针状焦性能的影响,相关指标分析分别采用工业分析、元素分析和X射线衍射分析的方法。结果表明:当煅烧温度≥1 400℃时,针状焦的质量得到了大幅度提升,真密度提高至2.156g/cm~3,氮质量分数迅速降低至0.08%,硫质量分数降到0.25%以下,而且可以改善针状焦的晶面结构,使微观碳层趋于平行,面间距减少,更易石墨化。     

石油焦煅烧过程中的行为研究

生焦必须经过煅烧后才能生成熟焦.借助元素分析,FTTR,XRD,DSC,TG等手段,研究了生焦原料性质和煅烧过程对煅后焦的组成结构的影响.研究结果表明,具有适当反应活性的流线性结构的生焦原料,经过1 400℃煅烧后可以获得优质煅后焦.煅烧过程是热解和缩聚过程,是晶体转化和结构重排的过程,也是增加平面度和有序度及降低熵值(△S)的过程.煅烧工艺能够改善石油焦的晶体结构,提高石油焦的热稳定性能.石油焦的晶体转化温度在200～700℃,煅后焦的晶格参数Le为4.7～5.1 nm.d002为0.3453～0.3456 nm.     

ZnO微／纳米纤维的静电纺丝及其表征

以聚乙烯吡咯烷酮(PVP)为络合剂与醋酸锌[Zn(CH3COO)2]反应制得前驱体溶液,用静电纺丝法制备了PVP／Zn(CH3COO)2纤维,经煅烧得到具有微孔结构的氧化锌(ZnO)微／纳米纤维。对所制备纤维分别采用差热-热重分析、红外光谱分析、X射线衍射分析、扫描电镜等手段进行了表征。结果表明: PVP/Zn(CH3COO)纤维表面光滑,直径约300-700 nm,经700℃煅烧后,可得到ZnO微／纳米纤维。     

制备方法对Pr0.6Sr0.4FeO3-δ结构与性能的影响

采用甘氨酸-硝酸盐、Pechini、柠檬酸-硝酸盐以及尿素-硝酸盐等4种不同的湿化学方法,制备了Pr0.6Sr0.4FeO3-δ复合氧化物粉体.用X射线衍射分析了材料中钙钛矿物相的形成过程及其与中温电解质的化学相容性.用扫描电镜研究了样品的微结构.结果表明:不同方法得到的素坯经1 000℃煅烧2 h即形成钙钛矿结构的固溶体.Pechini法制备的非晶产物煅烧后钙钛矿物相的纯度最高.素坯经1200℃煅烧2 h,所得陶瓷体的总气孔率均为43%～49%;体积密度以柠檬酸-硝酸盐法粉体的样品最高,甘氨酸-硝酸盐法最低.在室温到800℃的温度范围内,Pechini法制备的陶瓷体的热膨胀系数为12.15×10-6/K,与电解质Sm0.2Ce0.8O1.9(SDC)及La0.8Sr0.2Ga0.8Mg0.2O3-δ(LSGM)的数值一致.X射线衍射揭示产物与中温电解质SDC及LSGM具有良好的化学相容性.     

偏光显微定量分析针状焦微观结构方法的探讨

针状焦的显微组织结构与热膨胀系数(CTE)有着密切的关系,微观结构越好的针状焦其CTE就越小,反之CTE值就越大,因而它的显微结构能够从侧面反映其CTE指标的好坏。本文介绍了一种偏光显微定量分析方法,得到各类不同显微结构的含量分布;由于消光角的大小与织构的择优取向有关,引入消光角,又能够反映出光学各向异性取向程度,与定性分析相比,它更能直观地以数据形式来描述针状焦的微观结构。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

Highly moisture-proof polysilsesquioxane coating prepared via facile sol-gel process

A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by ¹H MAS NMR. For direct comparison purposes, an SiO₂ coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N₂ absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.