正铌酸镧陶瓷的形状记忆效应及其畴结构

采用热压烧结工艺制备了多晶正铌酸镧(LaNbO4)陶瓷。对LaNbO4陶瓷的形状记忆效应进行了测量，结果表明：在室温加压变形的试样，在加温到单斜至四方相相变温度以上再冷却后，其形状将回复到其原始状态。透射电镜分析显示，在多晶LaNbO4陶瓷晶粒内大量存在均匀平行捧列的畴结构，畴宽50nm左右。通过选区电子衍射分析鉴定了畴结构和畴间位向关系。X射线衍射分析发现，通过表面打磨施加切应力能使LaNbO4陶瓷发生显著的畴切换。对有关机理进行了讨论。提出陶瓷多晶体中晶界与畴界之间的交互作用导致了其形状记忆效应。     

磷酸四钙粉末的制备研究

讨论了固-固相反应法和湿法反应法制备Ca4(PO)2O粉末的工艺过程,并通过XRD和IR详细研究了2种方法制备的粉末的有关性能.实验表明:通过湿法反应法可以制备高纯的Ca4(PO)2O粉末.     

陶瓷材料新术语诠释(十七)

反应烧结ReactiveSintering将选定的粉末原料压制成生坯,在升温烧结过程中,通过固相、气相或液相间化学反应,生成新相并释放热量,同时坯体逐渐致密化,最终获得要求的烧结体,该过程称为反应烧结。反应烧结有两种类型:1.形成单相固体两种原料(A和B)在高温下发生反应和致密化生成单相的多晶固体(C)。A(粉末)+B(粉末)→C(固相多晶体)如等摩尔数的氧化锌与氧化亚铁粉末混合反应烧结而成亚铁酸锌。ZnO+FeO→ZnFeO由于难以控制反应产物的微观结构,因而无法在工业中反应烧结制造单相陶瓷。2.形成多相固体(或复合材料)烧结时,两种原料(D与E)间…     

一种纳米氧化锌的制备方法

涉及一种以氧化物为基础成分为特征的化合物及其采用水热合成法制备钡锌铌氧化物粉体的方法。钡锌铌氧化物粉体的含量为：m(化学纯的氢氧化钡溶液)：m(醋酸锌)：m(粉末状的五氧化二铌)=3．0：(1．0～1．1)：1．0。先将原料置于高压反应釜中，边搅拌边升温，进行水热反应，把反应产物进行洗涤、抽滤、干燥，获得氧化物粉体。精选了钡锌铌氧化物的化工原料和采用水热合成制备方法的工艺步骤，各种组分反应充分均匀。     

用间乙酰基氯磺酚光度法测定钢中的铌

首次报道新显色剂间乙酰基氯磺酚的合成方法。研究了试剂与铌的显色反应。在1.8～3.0mol/l HCl 介质中,铌与试剂形成蓝色的络合物。在635nm 处有最大的吸收峰,摩尔吸光率为3.35×10~4l·mol~(-1)·cm~(-1)。在0～60微克铌/50ml 范围内符合比耳定律。大多数金属离子不干扰测定。用于钢中微量铌的直接测定,获得了满意的结果。     

沉淀法合成HA粉末过程中球磨处理的作用

采用Ca(OH)2/H3PO4体系的化学沉淀法合成羟基磷灰石粉末,并对反应产物进行球磨处理,以促进合成反应的进行。应用X射线衍射(XRD)、扫描电镜(SEM)、粉末粒度分析等测试方法对HA的组成、晶化过程、颗粒形貌和粒度分布进行表征。研究结果表明,增加球磨处理后得到粉末的XRD图中β-TCP和CaO峰消失,煅烧过程中粉末更易发生晶化,粉末粒度分布变窄,集中在0.3μm～0.5μm。因此球磨处理促进Ca(OH)2/H3PO4体系液固反应进行的程度,提高了羟基磷灰石粉末的纯度,减小粉末粒度并缩小其粒度分布范围。     

铌酸钾的合成及其光催化性能

以草酸铌和醋酸钾为原料,加水研磨干燥后得到前驱体,前驱体分别在500℃和800℃焙烧3 h合成高纯相和高结晶度的铌酸钾粉末。红外光谱分析表明,草酸铌和醋酸钾发生离子交换反应生成前驱体K[NbO(C_2O_4)_2]·xH_2O。500℃合成的铌酸钾颗粒粒径约50 nm,800℃合成的颗粒粒径在100 nm以上。以制备的铌酸钾粉末为光催化剂,在高压汞灯照射下,对亚甲基蓝溶液进行光催化降解。实验表明,500℃焙烧合成的铌酸钾粉末具有光催化性能,而800℃焙烧合成的不具有催化性能。催化动力学分析表明,亚甲基蓝溶液的光催化降解反应符合一级动力学方程。     

4-(5-甲醛基-2-噻吩基)-7-(2-噻吩基)[2,1,3]苯并噻二唑的合成

采用两种不同的途径合成了4-(5-甲醛基-2-噻吩基)-7-(2-噻吩基)[2,l,3]苯并噻二唑。研究结果表明,DMF/POCl3体系较n-BuLi/DMF体系产率更高。改变两种合成途径的反应条件,或用单醛化产物进一步醛化,均未发现二醛取代产物的生成。     

双酰亚胺型均苯四甲酸及复合酸镧盐的合成与应用

采用水热法制备了4,4'-亚甲基-二苯基-二-(1″,2″)-酰亚胺-二-(4″,5″)-苯二甲酸酐(简称酰亚胺四酸酐)以及双硬脂酸单4,4'-亚甲基-二苯基-二-(1″,2″)-酰亚胺-二-(4″,5″)-苯二甲酸二镧(简称复合酸镧盐La-1),应用红外光谱与热失重法对其结构进行表征,并将La-1应用于聚酰胺66(PA 66)以改善PA 66热氧化稳定性,且与硬脂酸镧(La-2)、均苯四甲酸镧(La-3)、双硬脂酸单均苯四甲酸二镧(La-4)进行比较。结果表明:通过正交实验得出,酰亚胺四酸酐合成的最优反应条件为酰亚胺化反应温度135℃,时间5 h,二甲苯与产物水质量比6∶1,均苯四甲酸酐(PMDA)与4,4'-二氨基二苯甲烷(DDM)摩尔比2.3∶1.0;傅里叶变换红外光谱表征所合成的酰亚胺四酸酐和La-1为目标产物;La-3的热分解温度大于550℃,高于PA 66的热分解温度,La-1,La-2,La-3的热稳定性均弱于纯PA 66;La-3,La-4对PA 66的抗黄变性效果比La-1,La-2的要好,这是由于硬脂酸长链热稳定性差及芳香酸镧中的邻苯二甲酸结构中残存羟基量对PA 66热氧化稳定性造成影响的缘故。     

对甲苯磺酸催化乙二醇合成二氧六环

1,4-二氧六环又称二烷 ,是常用的溶剂 ,以对甲苯磺酸为催化剂 ,乙二醇可按下式合成二氧六环。2CH2 OHCH2 OHp- CH3C6 H4SO3H· H2 O O O +2 H2 O　　在 1 0 0 m L 圆底烧瓶中加入 0 .4mol( 2 4 .0 m L,2 4 .8g)乙二醇和 0 .0 2 0 mol对甲苯磺酸及几粒沸石 ,安装成蒸馏装置 ,加热控制蒸馏头温度不超过 1 30℃进行反应 ,生成的二氧六环以馏出液形式收集于收集瓶中 ,直到反应瓶内变黑、冒烟 ,则停止反应。将馏出液用固体 Na OH(或KOH)干燥过夜 (若析出液层 ,则应吸出并补加Na OH或 KOH)。然后倾入蒸馏瓶中进行蒸馏 ,收集 94～ …     

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.