纳米氮化硅陶瓷的抗热震性能研究

研究了由热压法制备的晶粒尺寸为 100nm 左右的氮化硅陶瓷抗热震性能.研究结果表明,纳米氮化硅陶瓷表现出原始短裂纹扩展特征;起始粉末粒度对氮化硅陶瓷的力学性能和抗热震性有一定影响.在纳米尺度范围内,晶粒较粗大的氮化硅陶瓷具有较好的抗热震性能;随起始粉末中仪 α-Si3N4 含量的增加,氮化硅陶瓷的抗热震性能得到明显提高.     

放电等离子体烧结Si_3N_4-BN复合陶瓷性能研究

以Si3N4和BN粉末为原料,Si3N4-BN复合粉末中BN的体积分数分别选定为10%、20%和30%,采用质量分数为2%的Al2O3和6%的Y2O3作为烧结助剂,分别在1500、1600和1650℃,压力50 MPa,保温5 min的条件下,采用放电等离子体烧结法制备了致密Si3N4-BN复合陶瓷。XRD结果和SEM分析表明:当煅烧温度为1650℃时,复合陶瓷中的α-Si3N4已完全转变为β-Si3N4;BN的加入抑制了复合陶瓷中Si3N4晶粒的生长而使结构细化;复合陶瓷的维氏硬度和断裂韧性随BN含量的增加而逐渐降低。     

添加剂对Si粉直接氮化工艺中α-Si3 N4含量的影响

通常情况下,Si粉直接氮化法和自蔓延法所制得Si3N4粉体主要以β-Si3N4为主,而为了使Si3N4陶瓷有更好的烧结性能,需要得到高α相含量的Si3N4粉.本研究以Si粉直接氮化法为基础,通过添加NH4Cl、FeCl3来制备高α相含量的Si3N4粉.经XRD和SEM检测分析发现,添加适量NH4Cl、FeCl3可大幅提高Si3N4粉体中α-Si3N4的含量,最高可达88.3%,但FeCl3的含量过高时,则可显著降低α-Si3N4的含量.研究还发现添加NH4Cl、FeCl3还可降低Si粉发生氮化反应的起始温度.     

氮化硅晶相结构对氮化硅结合碳化硅制品力学性能的影响

研究了氮化硅(Si3N4)晶相结构对氮化硅结合碳化硅制品力学性能尤其是常温抗折强度的影响,分析了其作用机理,研究结果表明,α-Si3N4晶相对碳化硅的结合强度要高于α-Si3N4和β-Si3N4共同作用的结果,随着β-Si3N4量的增加,制品的抗折强度下降明显。     

可加工氮化硅/氮化硼复相陶瓷的制备

以硅(Si)粉、六方氮化硼(h-BN)为原料,在氮气(N2)中用燃烧合成(combustion synthesis,CS)气固反应法,原位生成可加工氮化硅/氮化硼(Si3N4/h-BN)复相陶瓷.考察了h-BN不同体积分数(下同)对Si3N4/h-BN复相陶瓷可加工性的影响.结果表明:在实验条件下,Si粉氮化完全,不存在残余的游离Si.Si3N4/h-BN复相陶瓷中以柱状β-Si3N4为主相,β-Si3N4晶粒之间为针状h-BN相.随着h-BN相含量的增加,Si3N4/h-BN复相陶瓷的可加工性提高,抗弯强度先减小后增加.h-BN含量为25%时,Si3N4/h-BN复相陶瓷的抗弯强度最低.     

放电等离子烧结氮化硅陶瓷刀具材料的摩擦磨损性能

研究了放电等离子烧结氮化硅陶瓷刀具材料(91wt％ α-Si3N4 +5wt％ MgSiN2 +3wt％ Y2O3 +1wt％ CeO2)在干滑动条件下分别与氮化硅陶瓷和轴承钢GCr15的摩擦磨损性能.结果 表明:Si3N4/Si3N4滑动副的摩擦系数和磨损率随着滑动速度的增加而减小,且不同滑动速度下的磨损表面均有明显的犁削特征和剥落,其磨损形式主要为磨粒磨损;Si3N4/GCr15滑动副的摩擦系数和磨损率随着负载的增加先减小后增大,其磨损机理为氧化磨损和粘着磨损.由于氮化硅球的高硬度和轴承钢的相对低硬度,相同条件下Si3N4/Si3N4滑动副的磨损率均大于Si3N4/GCr15.     

低温热压制备半透明α/βSi3N4复相陶瓷

以α-Si3N4粉为原料、MgSiN2粉为烧结助剂,在1563℃热压1h制备出半透明α/βSi3N4复相陶瓷。X射线衍射分析结果表明,半透明α/βSi3N4复相陶瓷由85%(质量分数,下同)α-Si3N4和15%β-Si3N4组成。半透明α/βSi3N4复相陶瓷具有和Mg-α-SiAlON陶瓷相似的透光性质,样品厚度为0.42mm,其透过率随波长增加而增大,波长在3.3μm处透过率最大,达到66%,在2.0～4.5μm波长范围,透过率保持在50%以上,随后透过率迅速降低,在5.0μm处截止。     

β-Si3N4晶种对Si3N4陶瓷力学性能和显微结构的影响

采用无压烧结工艺制备了长柱状β-Si3N4品种.研究了晶种尺寸对Si3N4陶瓷力学性能和显微结构的影响.结果表明:在1750℃通过控制保温时间(1h、1.5h和2h)可获得不同尺寸的长柱状β-Si3N4晶种.Si3N4陶瓷加入晶种后,其相对密度和抗弯强度虽略有降低,但断裂韧性得到大幅提高.平均长度为4.51μm,长径比为5.71的品种对Si3N4陶瓷的增韧效果最佳;且随着其添加量的增加,Si3N4陶瓷的断裂韧性先升高再降低,当掺量为2wt％时断裂韧性达到最高(提高了20％以上).显微结构分析表明,Si3N4陶瓷断裂韧性的提高,与因晶种加入而导致的Si3N4晶粒长径比和大长柱状晶粒含量的增加有关.     

合成工艺对氮化硅铁物相和结构的影响

以硅铁合金(FeSi75)为原料,分别采用闪速燃烧合成工艺和自蔓延高温合成工艺制备氮化硅铁样品,利用X射线衍射仪和扫描电镜对样品进行了表征,探讨了合成工艺对氮化硅铁物相和显微结构的影响。采用闪速燃烧工艺合成的氮化硅铁相组成为β-Si3N4,α-Si3N4,Fe3Si和少量SiO2;而采用自蔓延高温合成的氮化硅铁由β-Si3N4,α-Si3N4,Fe3Si和Si2N2O组成。闪速燃烧合成的氮化硅铁样品中存在大量长径比较高的柱状氮化硅晶体,Fe3Si位于柱状结晶所包裹材料的内部;自蔓延高温合成的氮化硅铁显微结构为致密的氮化硅块体,在块体表面覆盖有氧氮化硅膜,块体的间隙存在晶形细小的氮化硅晶体,含铁组分镶嵌在致密的块体中。闪速燃烧合成的氮化硅铁结构疏松,活性较强;自蔓延高温合成的氮化硅铁结构致密,性质稳定。     

纳米Si3N4／PP复合材料的力学性能研究

研究了纳米氮化硅（Si3N4）粒子对其填充的聚丙烯（PP）力学性能的影响,结果发现纳米Si3N4/PP复合材料的力学性能表现出了许多与常规纳米粒子改性PP的不同之处。复合材料的拉伸强度随纳米Si3N4粒子含量增加而基本呈直线上升趋势,而冲击强度变化不大,纳米Si3N。粒子对PP并无明显增韧效果;少量（5％）纳米Si3N4粒子便能显著提高复合材料弯曲强度。     

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.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料，介绍了2005—2006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生产量以及各国塑料制品的进出口情况。作为对比，介绍了中国塑料的生产情况。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（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序，对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008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、不饱和聚酯树脂、环氧树脂)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.     

Inorganic/organic nanocomposite coatings: The next step in coating performance

Inorganic/organic hybrid materials have considerable promise and are beginning to become a major area of research for many coating usages, including abrasion and corrosion resistance. Our primary approach is to prepare the inorganic phase in situ within the film formation process of the organic phase. The inorganic phase is introduced via sol-gel chemistry into a thermosetting organic phase. By this method, the size, periodicity, spatial positioning, and density of the inorganic phase can be controlled. An important aspect of the inorganic/organic hybrid materials is the coupling agent. The initial task of the coupling agent is to provide uniform mixing of the oligomeric organic phase with the sol-gel precursors, which are otherwise immiscible. UV-curable inorganic/organic hybrid systems have the advantages of a rapid cure and the ability to be used on heat sensitive substrates such as molded plastics. Also, it is possible to have better control of the growth of the inorganic phase using UV curing. It is our ultimate goal to completely separate the curing of inorganic and organic phases to gain complete control over the morphology, and hence optimization of “all” the coating properties. Thus far, it has been found that concomitant UV curing of the inorganic and organic phases using titanium sol-gel precursors afforded nanocomposite coatings which completely block the substrate from UV light while maintaining a transparent to visible light. Also, it has been found that the morphology of the inorganic phase is highly dependent on the concentration and reactivity of the coupling agent. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago, IL.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Some Large Wood-Boring Beetles in Southeastern USA

Ethanol and α-pinene were tested as attractants for large wood-boring pine beetles in Alabama, Florida, Georgia, North Carolina, and South Carolina in 2002–2004. Multiple-funnel traps baited with (−)-α-pinene (released at about 2 g/d at 25–28°C) were attractive to the following Cerambycidae: Acanthocinus nodosus, A. obsoletus, Arhopalus rusticus nubilus, Asemum striatum, Monochamus titillator, Prionus pocularis, Xylotrechus integer, and X. sagittatus sagittatus. Buprestis lineata (Buprestidae), Alaus myops (Elateridae), and Hylobius pales and Pachylobius picivorus (Curculionidae) were also attracted to traps baited with (−)-α-pinene. In many locations, ethanol synergized attraction of the cerambycids Acanthocinus nodosus, A. obsoletus, Arhopalus r. nubilus, Monochamus titillator, and Xylotrechus s. sagittatus (but not Asemum striatum, Prionus pocularis, or Xylotrechus integer) to traps baited with (−)-α-pinene. Similarly, attraction of Alaus myops, Hylobius pales, and Pachylobius picivorus (but not Buprestis lineata) to traps baited with (−)-α-pinene was synergized by ethanol. These results provide support for the use of traps baited with ethanol and (−)-α-pinene to detect and monitor common large wood-boring beetles from the southeastern region of the USA at ports-of-entry in other countries, as well as forested areas in the USA.