氮化硼合成的工艺及性能研究

本论文采用硼酸和三聚氰胺按照一定的配比合成氮化硼的前驱体高聚物,氮化硼前驱体高聚物溶于甲酸溶液。将氮化硼前驱体高聚物在23 kV,正负极距离为15 cm条件下纺出细度均匀的纤维。对合成的前驱体高聚物放在马弗炉中按照10℃/min的升温速度升至800℃,保温一定时间得到氮化后的产物,氮化后产物成白色,硬度较大。利用扫描电镜、傅里叶红外光谱仪和TG-DSC热重分析仪对氮化后产物的性能特征进行了测试。     

环保型催化材料氮化钼的合成与表征

采用溶胶-凝胶法制备了负载型氮化钼的前驱体,采用流化氮化新工艺制备了氮化钼。通过单因素和正交实验,确定了较优氮化条件:升温速率为1.2℃/min,H2∶N2=4.0∶1,空速70×103h-1,氮化终温为650℃,活性组分MoO3含量为10%。并采用BET、XRD、SEM等对制备的氮化钼及前驱体进行了表征。     

氮化硼纤维合成工艺与结构表征

硼酸和三聚氰胺以一定配比合成氮化硼前驱体高聚物.将该前驱体超声溶于甲酸溶液,在静电纺丝电压25 kV,正负极距离18 cm的条件下,可通过静电纺丝法制备直径均匀的纤维.将该电纺纤维放入马弗炉,以10℃/min升温速率加热至600℃和850℃,保温不同时间,可制备白色BN纤维.利用SEM、TEM、TG-DSC、XPS和IR对BN纤维的结构,性能进行详细表征.结果表明,前驱体高聚物具有良好的静电纺丝性能,提高煅烧温度、延长煅烧时间可制备较纯的氮化硼纤维.     

新型催化材料氮化钼的批量制备与结构表征

环境法规关于硫、氮含量的严格规定要求对燃料进行深度脱硫脱氮,氮化钼作为一种催化材料具有良好的脱硫脱氮活性和较高的选择性。但其制备条件苛刻,为加快其应用进程,采用溶胶—凝胶法制备了负载型氮化钼的前驱体,采用流化床反应器、三级脱水、循环未反应氮化剂的流化氮化新工艺实现了氮化钼的批量合成。采用正交实验的方法确定了最优氮化条件:空速7 000 h-1、H2/N2为4、升温速率为1.2℃/min、氮化终温为650℃,活性组分含量为10%。并采用BET、XRD、SEM等对制备的氮化钼及其前驱体进行了结构表征。     

无机前驱体法制备连续氮化硼纤维及其结构表征

采用无机前驱体法制备氮化硼（BN）纤维,先将熔融B2O3拉丝低温（1000℃）NH3下氮化后高温（1750℃）N2下氮化得到均匀的BN纤维.利用XRD,FTIR,XPS,FE-SEM,HR-TEM,XRF和ICP等测试方法对1750℃氮化温度下的BN纤维物相组成、微观结构、元素成分进行了系统表征.结果表明：经过1750℃二次氮化后的BN纤维物相主要为六方氮化硼（h— BN）,氮化基本完全,纤维直径5～8μm,结构致密但结晶不完全,部分出现无定形BN（a-BN）.     

溶剂热温度对制备氧化锆晶须的影响

本文采用溶剂热工艺合成氧化锆前驱体,然后将前驱体与熔盐混合制备氧化锆晶须。借助XRD、FE-SEM、Raman、TEM等测试手段研究了溶剂热温度对氧化锆前驱体物相以及制备氧化锆晶须的影响。结果表明:随着容弹温度的升高,前驱体中氧化锆晶体的发育也越来越好;容弹温度为120℃时,能够获得大量平均长径比达15且沿[001]方向生长的单斜氧化锆晶须。     

利用方解石制备文石型碳酸钙晶须的研究

以方解石碳酸钙为原料,以氯化镁为晶型控制剂,制备文石型碳酸钙晶须。研究了搅拌速率、反应温度、Ca(OH)2浓度、镁钙比、反应时间对文石型碳酸钙晶须制备的影响,并讨论其生长机理。通过SEM和XRD对产品形貌、结构及组成做了表征。得到最佳工艺条件:镁钙物质的量比为2、反应温度为110℃、二氧化碳通入量为100 m L/min、氢氧化钙浓度为0.5 mol/L、搅拌速度为150 r/min、反应时间为1 h,在此条件下所制备的碳酸钙晶须直径为1~4μm,长度为15~30μm。     

氮化铝晶须的制备工艺研究

以三聚氰胺和硝酸铝为主要原料,通过前驱体法制备了氮化铝晶须,研究了不同原料配比、不同浓度对制备前驱体和晶须的影响,并通过X射线衍射(XRD)、扫描电子显微镜(SEM)和光学显微镜对晶须和前驱体进行物相及形貌分析。结果表明:当三聚氰胺/硝酸铝=1∶3,浓度为0.2mol/L时,制备的氮化铝晶须前驱体细长且尺寸均匀,直径为1～2μm,长度约为80μm。制备的氮化铝晶须为表面光滑的长柱状,直径约为1μm,长度为10～20μm。     

SiC晶须的微波加热合成

首先以硅溶胶(w(siO2)=30%,平均粒径为10～20 nm)和活性炭(平均粒径<10um,w(C)=99.5%)为原料,六偏磷酸钠为分散剂,混匀后在真空下于110℃烘干24 h制成反应前驱体,然后将其破碎成不同粒度的细粉,在多模谐振腔微波炉中分别加热至1 300～1 600℃保温15～60 min制备了SiC晶须,研究了热处理温度、保温时间以及反应前驱体的粒度对晶须产率的影响.结果表明:(1)当热处理温度为1 300～1 400℃时,产物主要为方石英及少量β-SiC,SiC晶须的产率较低;温度达到1 500℃以后,产物主要为SiC晶须及少量SiC颗粒,且在1 500℃下保温时间从15 min延长到30 min时,SiC晶须产率显著增加;温度提高到1 600℃时,生成了等轴SiC颗粒及SiC晶须.(2)1 500℃保温30 min为比较适合的微波加热合成条件,晶须产率能达到80%以上.(3)较小的反应前驱体颗粒有利于SiC晶须的生成.     

碳化硼-立方氮化硼复合陶瓷的高压制备及性能研究

利用六面顶液压机,以铝、钴为烧结助剂,在压力5.5 GPa,温度1 470℃,保温时间5 min的条件下制备出碳化硼-立方氮化复合陶瓷。并通过XRD衍射仪、SEM扫描电镜、维式硬度仪对其进行了物相分析、微观形貌表征和硬度测量,并研究了不同含量的立方氮化硼对碳化硼复合陶瓷力学性能的影响。实验结果表明,当碳化硼和立方氮化硼的比例为7∶3时,复合陶瓷具有较好的综合性能,维式硬度为41.6 GPa、密度为2.45 g/cm³、磨耗比为2.5。将立方氮化硼作为增强材料不仅保持了碳化硼的硬度还兼顾了轻质性能。而铝、钴作为烧结助剂不仅降低了烧结温度还抑制了立方氮化硼向六方氮化硼的转变。     

Sapindaceae,cyanolipids, and bugs

Scentless plant bugs (Heteroptera: Rhopalidae) are so named because adults of the Serinethinae have vestigial metathoracic scent glands. Serinethines are seed predators of Sapindales, especially Sapindaceae that produce toxic cyanolipids. In two serinethine species whose ranges extend into the southern United States,Jadera haematoloma andJ. sanguinolenta, sequestration of host cyanolipids as glucosides renders these gregarious, aposematic insects unpalatable to a variety of predators. The blood glucoside profile and cyanogenesis ofJadera varies depending on the cyanolipid chemistry of hosts, and adults and larvae fed golden rain tree seeds (Koelreuteria paniculata) excrete the volatile lactone, 4-methyl-2(5H)-furanone, to which they are attracted.Jadera fed balloon vine seeds (Cardiospermum spp.) do not excrete the attractive lactone. Loss of the usual heteropteran defensive glands in serinethines may have coevolved with host specificity on toxic plants, and the orientation ofJadera to a volatile excretory product could be an adaptive response to save time.Mention of a commercial product does not consititute an endorsement by the USDA.     

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.     

2008～2009年世界塑料工业进展

收集了2008年7月～2009年6月世界塑料工业的相关资料,介绍了2008～2009年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况。按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、环氧树脂、不饱和聚酯树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍。     

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.     

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.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

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.