机械合金化-放电等离子烧结制备Ti_2SnC块体

以单质Ti、Sn和C粉体为反应原料,利用机械合金化-放电等离子法烧结制备Ti2SnC块体材料,研究了机械合金化-放电等离子烧结工艺对Ti_2SnC块体物相及性能的影响。通过研究发现:球磨粉体进行放电等离子烧结后,制备具有较高致密度及硬度的Ti_2SnC块体材料,烧结块体中Ti_2SnC的含量较高,衍射峰强度比值(ITSC/ITC)约为2.4,且块体材料具有较低的摩擦系数。在不同压力下烧结发现,在较高压力下烧结,所得块体中Ti_2SnC的含量较高,当烧结温度在1000℃时,其密度也接近Ti_2SnC的理论密度。     

放电等离子烧结制备Ti_3SiC_2导电陶瓷及性能表征

以Ti粉、Si粉和C粉为反应原料,采用机械合金化和放电等离子制备Ti_3Si C2导电陶瓷块体材料,并对试样进行性能表征。研究表明:随着烧结温度的提升,块体的相对密度和硬度随之增加,当烧结温度为1100℃时,块体的相对密度约为98.9%,当温度继续提升时,Ti_3Si C2开始分解,致使块体相对密度下降;烧结温度为1300℃时,块体硬度值达到最佳值,约为6.7 GPa。     

Al对等离子放电烧结法合成Ti3SiC2的影响研究

以元素为原料，Al为助剂，采用等离子放电烧结(SPS)工艺合成Ti3SiC2块体材料，通过X射线衍射分析和对SPS过程参数的研究表明：适量A1能促进Ti3SiC2的反应合成，提高合成材料的纯度，但Al也会使Ti3SiC2的热稳定性降低。     

放电等离子烧结工艺合成Ti3SiC2的研究

以元素单质粉为原料，当原料配比为n(Ti):n(Si):n(Al):n(C)=3:(1.2-x):x:2，其中：x=0.05-0.2时，在1200－1250℃温度下经放电等离子烧结成功制备了高纯、致密Ti3SiC2固溶体材料。原料中掺加适量Al能改善Ti3SiC2的合成反应并提高制备材料的纯度。当x=0.2时，所合成的固溶体形貌为板状结晶，分子式近似为Ti3Si0.8Al0.2C2，晶格参数a=0.3069nm,c=1.767nm。在1250℃温度下烧结，得到平均厚度达5μm，发育完善均匀的致密多晶体材料。材料Vickers硬度为3.5-5.5GPa，具有与石墨相似的加工性能。     

不同原料体系对无压烧结合成Ti3SiC2的影响及其腐蚀行为

通过液相磁力搅拌混合原料粉末,压片后无压烧结合成了三元Ti3SiC2,研究不同原料配比Ti/Si/C,Ti/SiC/C/和TiC/Si/Ti对合成Ti3SiC2的影响,同时为了比较,在相同条件下加入少量Al或Sn,研究其对Ti3SiC2的合成过程及最终产物的影响,并探讨Ti3SiC2的合成机理.结果表明:3Ti/1.2Si/2C/0.1Al在1400 ℃无压烧结合成了较高纯度的Ti3SiC2,Al粉的加入可以降低混合粉末的起始反应温度,有利于三元层状化合物Ti3SiC2的合成和纯度的提高,其合成机制为,在铝粉形成的熔池中,经形核钛和硅反应生成钛硅金属间化合物,钛与石墨反应生成碳化钛,随后扩散,长大,随着温度的升高,反应生成三元层状Ti3SiC2.而以TiC或SiC为Ti或Si源制备的Ti3SiC2含杂质较多,不适用于无压烧结合成Ti3SiC2.合成的Ti3SiC2在HF溶液中经200 ℃溶剂热反应后,产物主要为两种不同晶型的SiC和AlF3立方体,且随着反应时间的延长,AlF3的含量增加,结晶更完善.     

放电等离子烧结钛/氧化铝的界面反应

研究了用放电等离子烧结的Ti/Al2O3在1 200℃和30MPa条件下界面反应特性,用X射线衍射和电子探针微区分析了界面反应类型.结果表明:Ti/Al2O3界面反应为反应扩散型,即氧化铝首先发生分解,分解出的Al原子扩散进入Ti中,扩散距离约为62 μm,界面处Al原子的摩尔分数x高达42.49%,Ti与Al在界面区发生反应,在贫Al区生成Ti3Al相,贫Ti区生成TiAl相等界面产物,O原子固溶于Ti中.     

放电等离子合成Ti_4AlN_3块体的相形成及显微结构

采用放电等离子烧结和热处理工艺制备相对密度为99.6%的Ti4AlN3块体材料。用X射线衍射、扫描电子显微镜和能谱仪等分析测试手段研究Ti4AlN3的相形成及显微结构。结果表明：在900℃以下,Ti和Al反应生成金属间化合物TiAl3;在900～1200℃,TiAl3和TiN反应生成Ti2AlN;在1200～1300℃...     

烧结工艺对Ti/Al2O3复合材料性能的影响

利用放电等离子烧结技术探讨了烧结工艺对40%(体积分数)Ti/Al2O3复合材料性能的影响。实验结果表明,复合材料的性能受烧结温度的影响最为显著,过度延长保温时间会使晶粒发生异常长大,材料性能降低。烧结温度1300℃,保温时间8min制备的复合材料力学性能最佳,其弯曲强度、断裂韧性、显微硬度和相对密度分别为1002.22MPa,19.73MPa·m1/2,18.14GPa和99.74%。     

放电等离子制备Ti3AlC2/TiB2复合材料及性能

采用放电等离子烧结(spark plasma sintering,SPS)工艺制备了Ti3AlC2/TiB2复合材料,并研究了复合材料的性能.研究表明:在1 250℃,30MPa烧结8min,可以获得相对密度达98%以上的致密Ti3AlC2/TiB2块体材料;在Ti3AlC2中添加TiB2能大幅度提高材料性能,当TiB2含量为30%(体积分数,下同)时,Ti3AlC2/30%TiB2复合材料的Vickers硬度达到10.39GPa,电导率为3.7×106 S/m;当TiB2含量为10%时,抗弯强度为696MPa,断裂韧性为6.6MPa·m1/2.用电子显微镜对复合材料的显微结构分析表明:Ti3AlC2/TiB2复合材料的晶粒为层状结构.     

铝对3Ti/SiC/C体系自蔓延高温合成Ti_3SiC_2的影响

采用3Ti/SiC/C粉体为原料,通过自蔓延高温合成技术制备了Ti3SiC2材料。探讨Al助剂对制备Ti3SiC2的作用。研究结果发现C-SiC-3Ti粉体能够产生SHS反应,产品由TiC、Ti5Si3和Ti3SiC2三相组成,Ti3SiC2含量约46%。添适当Al可显著促成Ti3SiC2相合成。选用3Ti/SiC/C/0.3Al粉体作原材料,产物中Ti3SiC2含量高达92.5wt%。     

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.