B4C(W,Ti)C陶瓷复合材料的制备及其性能

采用热压烧结工艺制备了B4C/(W,Ti)C陶瓷复合材料.研究表明:B4C/(W,Ti)C陶瓷材料烧结时将产生化学反应,反应产物为TiB2和W2B5.B4C/(W,Ti)C陶瓷材料的性能与(W,Ti)C的含量密切相关,随(W,Ti)C含量的增加,材料的致密度、抗弯强度和断裂韧性逐渐增加,硬度逐渐减小;当保温时间低于50min时,材料的致密度、抗弯强度和硬度显著降低;B4C/(W,Ti)C陶瓷复合材料的最佳性能参数为:抗弯强度693MPa,维氏硬度23.5GPa,断裂韧性3.9MPa·m1/2.磨损实验表明,B4C/(W,Ti)C陶瓷材料在低速小载荷的实验条件下,耐磨性能优异,在高速大载荷的实验条件下,磨损过程中局部点的高温导致试样表面发生氧化,加剧了材料的磨损.     

热燃烧温度对超重力场自蔓延离心熔铸TiB_2-TiC-(Ti,W)C组织及性能的影响

通过在(Ti+B_4C)燃烧体系中引入WO_3+Al高能铝热剂,采用自蔓延离心熔铸方法制备TiB_2-TiC-(Ti,W)C复相陶瓷材料。结果表明,陶瓷是由规则的TiB_2片晶、TiC球晶以及(Ti,W)C固溶体组成,并发现少量Al_2O_3夹杂存在于陶瓷熔体中。随着铝热剂含量的增加,不仅提高了绝热燃烧温度,增进了陶瓷致密化,而且提高了陶瓷熔体中的W含量,提高了陶瓷硬度。TiB_2片晶诱发的裂纹偏转和桥接增韧大幅度提高了陶瓷的抗弯强度和断裂韧性。材料的硬度、抗弯强度和断裂韧性分别为24.6 GPa、584 MPa与20.3 MPa·m~(1/2)。当铝热剂添加过量,TiB_2相的含量下降,导致陶瓷力学性能有所下降。     

高能球磨和热压烧结制备SiC/Ti_3SiC_2复相陶瓷及其性能

以Ti,Si和C粉为主要原料,利用高能球磨及热压烧结制备了SiC/Ti3SiC2复相陶瓷。研究了工艺条件尤其是烧结温度和压力对合成产物相组成、微观结构及性能的影响,并结合X射线衍射、扫描电镜等检测结果探讨了Ti-Si-C体系反应合成机理。结果表明:通过高能球磨18h,在25MP和1300oC热压,可得到均匀、致密的SiC/Ti3SiC2复相陶瓷材料。Si含量对SiC/Ti3SiC2材料的相组成及性能有较大影响。起始原料中的Ti,Si,C和Al的质量比为3:1.2:2:0.2时,材料性能提高明显,其弯曲强度、断裂韧性、密度和相对密度分别为526.65MPa,8.67MPa·m1/2,4.058g/cm3,89.78%。显微结构的观察表明,SiC/Ti3SiC2复合材料的断裂具有沿晶和穿晶混合断裂特征。SiC颗粒增韧抑制了微裂纹在Ti3SiC基体中的扩展。     

Al2O3/Cr3C2/(W,Ti)C陶瓷材料的力学性能及微观结构

用热压烧结工艺在1 700℃,28 MPa保温保压30 min及N2气氛条件下,制备了添加不同含量Cr3C2和(W,Ti)C颗粒的Al2O3/CraC2/(W,Ti)C复合陶瓷材料.对复合陶瓷的力学性能进行测试.用环境扫描电镜、透射电镜和能谱分析仪对复合陶瓷的显微结构进行观察.结果表明与纯Al2O3相比,70Al2O3/10Cr3C2/20(W,Ti)C复合陶瓷材料的显微组织更均匀细化,具有良好的综合力学性能,其断裂韧性自纯Al2Oa陶瓷的4.0 MPa·m1/2提高到8.92 MPa·m1/2.分析发现其内部位错机制、纳米颗粒的淀析、裂纹扩展路径偏转、沿晶断裂、韧窝及解理撕裂等是材料断裂韧性提高的主要原因.     

Al2O3/ZrB2/ZrO2复合陶瓷材料的制备与性能

将ZrB2和ZrO2添加入到Al2O3基体中,采用熟压法制备了Al2O3/ZrB2/ZrO2复合陶瓷材料,ZrB2和ZrO2的体积含量分别为(92.2±0.1)%和(7.8±0.1)%.对复合材料的硬度、断裂韧性和抗弯强度进行了测试和分析.结果表明:当ZrB2/ZrO2体积分数为20%时,所制备的复合陶瓷的综合力学性能最优,其相对密度,抗弯强度和断裂韧度分别达到96.3%,520.5MPa和6.1 MPa·m1/2.Al2O3/ZrB2/ZrO2复合陶瓷断面的断裂模式为沿晶断裂和穿晶断裂混合模式.通过高温氧化试验发现Al2O3/ZrB2/ZrO2复合材料在500～700℃时开始氧化.     

不同碳含量对C/SiC陶瓷材料的力学性能及加工性的影响

主要针对SiC基陶瓷作为高温玻璃夹具材料的可行性进行研究。采用机械化学结合无压烧结制备碳颗粒改性SiC陶瓷基复合材料(Cp/SiC),对其进行了XRD、SEM表征,分析了不同碳含量对C/SiC陶瓷烧结样品的体收缩率、密度、抗弯强度、显微硬度、断裂韧性和机加工性的影响。同时运用模糊数学理论,建立了模糊综合评价模型。我们偿试通过陶瓷的断裂韧性、硬度和抗弯强度等物理力学性能,对陶瓷的可加工性进行预测。结果表明:(1)烧结后的C/SiC复相陶瓷中的SiC发生了晶型转变,并且α-SiC比β-SiC的结晶度更好;(2)在碳含量为0~20%时,碳含量为10%的C/SiC复相陶瓷的显微组织最致密,而且碳与SiC的结合情况较好;(3)随着碳含量的增加,C/SiC烧结体的密度、体收缩率和抗弯强度都逐渐变小;(4)随着碳含量的增加,C/SiC复相陶瓷机加工性逐渐增强。     

ZrB2-SiC复相陶瓷的制备及其力学性能研究

以ZrB2和SiC粉为原料,采用Si3N4球为球磨介质,通过热压烧结制备了ZrB2-SiC复相陶瓷.并对ZrB2-SiC复相陶瓷进行了相对密度、力学性能检测和微观结构分析.结果表明:随着ZrB2球磨时间和SiC含量的增加,该复相陶瓷相对密度先增加后略有降低,ZrB2最佳球磨时间为8小时,SiC最佳含量为20vol.%.ZrB2+20vol.%SiC复相陶瓷的相对密度达到98.3%,抗弯强度达到631±4MPa,断裂韧性达到5.4±0.2 MPa·m1/2.随着球磨时间的增加,ZrB2+20vol.%SiC复相陶瓷的断裂方式由穿晶断裂向沿晶断裂转变.     

Ti（C，N）基金属陶瓷的制备与性能研究

采用真空热压烧结工艺制备了Ti（C,N）基金属陶瓷复合材料。借助于SEM和XRD分别分析了其显微结构和组分,并测试了其力学性能和相对密度。实验结果表明：其晶粒较细、均匀,具有明显的黑芯-灰壳结构,气孔较少,致密度较高。断裂机理主要是沿晶断裂,部分为混合型断裂（穿晶断裂和沿晶断裂）。金属相存在着明显的撕裂棱。其维氏硬度22．74GPa,断裂韧性10．1MPa·m^1／2,抗弯强度1192．83MPa,相对密度达到了99．12％。     

不同含量Ce对Ti(C,N)基金属陶瓷的结构和性能的影响

采用固溶型Ti(C,N)、Mo2C、WC、Co、Ni、Ce作为原料粉末,通过粉末冶金真空液相烧结Ce改性的Ti(C,N)基金属陶瓷材料,并对金属陶瓷复合材料的微观形貌和性能进行分析。研究结果表明,添加稀土Ce后,Ti(C,N)基金属陶瓷的硬质相变得细小且均匀,微观组织中的空隙和缺陷也减少了;随着Ce含量的增加,金属陶瓷材料的维氏硬度、抗弯强度以及断裂韧性均呈现出先增大后逐渐减小的趋势,当Ce的含量增加到0.5 wt%时,金属陶瓷材料的维氏硬度、抗弯强度以及断裂韧性达到最佳,分别为102.3 HRA、902.2 MPa、11.5 MPa·m1/2。     

AlN-Pr2O3液相烧结SiC陶瓷

以AlN、Pr2O3做为SiC陶瓷液相烧结的复合助剂,选定不同的助剂含量(5wt％～ 20wt％)和不同的助剂摩尔比例(Pr2O3/AlN=1/3、1/1、3/1),在1800～2000℃温度下,采用热压和无压烧结的方法制备SiC陶瓷样品,并对这些陶瓷样品的性能进行了研究.实验结果表明,助剂比1/3组的样品显示出更有效地促进SiC陶瓷致密化,该组样品无压烧结最大相对密度为87％,热压烧结具有最高的相对密度96.1％、维氏硬度23.4 GPa、抗弯强度549.7MPa、断裂韧性5.36 MPa·m1/2,显微结构中可观察到晶粒拔出现象,断裂模式为沿晶断裂.     

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.     

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.     

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.     

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。