多孔氧化铝陶瓷的制备、表征及性能研究

以蔗糖溶液为低温介质，采用冷冻干燥法和退火工艺制备多孔Al2O3陶瓷。研究了烧结温度和退火时间对多孔陶瓷孔隙结构、开孔率和力学性能的影响。结果表明，随着烧结温度的升高，试样的线性烧成收缩率有明显的升高，开孔率和维氏硬度先缓慢降低，当烧结温度为1600℃时迅速下降。平均晶粒尺寸是影响甚至决定多孔氧化铝陶瓷维氏硬度的主要原因。随着退火时间的延长，多孔陶瓷的孔径显著增大，多孔陶瓷开孔率范围为40.35%～64.58%，退火处理后的孔隙率比未退火处理提高了60.05%。多孔陶瓷的抗压强度随退火时间的延长而降低，而在最长的24h退火时间后，多孔陶瓷的抗压强度仍能达到25.9MPa，可以满足许多应用领域的强度要求。可以通过调节退火时间来控制多孔陶瓷的孔隙结构、开孔率和抗压强度。     

烧结温度对多孔陶瓷压电性能的影响

研究了烧结温度对海藻酸钠离子凝胶法制备3-1型多孔PZT压电陶瓷和凝胶注模法制备3-3型多孔PZT压电陶瓷性能的影响.结果表明:当烧结温度从1150℃升至1250℃,多孔PZT陶瓷的孔隙率降低,晶粒尺寸、介电常数、压电系数、厚度机电耦合系数和抗压强度增大,静水压压电系数与静水压品质因数随之降低.3-1型PZT陶瓷具有定...     

微波两步法烧结氧化铝陶瓷及对韧性的影响

采用微波两步法制备细晶氧化铝陶瓷,研究了烧结温度、保温时间等工艺参数对氧化铝陶瓷致密化、晶粒生长和韧性的影响,并通过与传统两步法烧结对比,分析探讨微波两步法烧结的影响机制。研究发现,微波两步法能有效降低传统两步法的烧结温度,缩短烧结时间;由于微波具有促进扩散的非热效应,微波两步法对晶粒生长的抑制作用表现的不明显,但是在相似的晶粒尺寸下,微波两步法烧结的样品表现出了更优的硬度和韧性。     

泡沫浸渍法制备多孔磷酸钙支架材料

采用泡沫浸渍法制备多孔磷酸钙支架材料,将聚氨酯泡沫体浸渍于磷酸钙水泥浆体中,水泥硬化后,通过在1 200℃烧结,去除其中的聚氨酯泡沫,得到羟基磷灰石基多孔磷酸钙陶瓷.这种多孔磷酸钙陶瓷可多次在室温浸渍于磷酸钙水泥浆体,得到孔隙率高,孔径可控的多孔材料,其贯通性好,抗压强度与松质骨相当.体外细胞培养实验表明,所制得的多孔材料具有良好的生物相容性.     

烧结细晶氧化铝陶瓷的新方法

致密的氧化铝陶瓷可用三种方法烧结得到。从SEM照片可看出：样品比较致密,样品的相对密度大于93％．用两步法和两段法烧结得到的氧化铝陶瓷的晶粒尺寸小于400nm,用常规方法烧结得到的氧化铝陶瓷的晶粒尺寸约为650nm。而且,用两步法和两段法烧结时烧结温度低于常规烧结。实验结果表明：两步法和两段法烧结能得到细晶的氧化铝陶瓷。     

两步烧结法制备纳米氧化钇稳定的四方氧化锆陶瓷

采用共沉淀法制备纳米氧化钇稳定的四方氧化锆（yttria stabilized tetragonal zirconia,3Y-TZP）粉体。利用X射线衍射、N2吸附–脱附等温线,透射电子显微镜对3Y-TZP粉体的物理性能和化学性能进行表征。研究了纳米3Y-TZP粉体的烧结曲线,分析了3Y-TZP素坯在烧结过程中的致密化行为和显微结构,探讨了两步烧结工艺对3Y-TZP纳米陶瓷微观结构的影响。结果表明：采用共沉淀法,在600℃煅烧2h后,可获得晶粒尺寸为13nm、晶型发育良好、团聚较少的纳米3Y-TZP粉体;采用两步烧结法,将素坯升温至1200℃保温1min后,再降温到1050℃保温35h,可获得相对密度大于98%,晶粒尺寸约为100nm的3Y-TZP陶瓷。两步烧结法通过控制煅烧温度和保温时间,利用晶界扩散及其迁移动力学之间的差异,使晶粒生长受到抑制,样品烧结致密化得以维持,实现在晶粒无显著生长前提下完成致密化。     

高气孔率及低热导率多孔莫来石陶瓷的制备(英文)

采用叔丁醇基凝胶注模工艺制备多孔莫来石陶瓷,研究了固含量和烧结工艺对多孔莫来石陶瓷显微结构、气孔率、气孔尺寸及分布、压缩强度和室温热导率的影响。结果表明,固含量相同时,随着烧结温度的升高,多孔莫来石陶瓷的气孔率不断降低,而抗压强度则不断增加;当固含量为15%、烧结温度为1 350℃时,多孔莫来石陶瓷的气孔率最高为71.7%,平均气孔孔径为3.49μm,而热导率则低至0.103W/(m·K)。通过改变烧结温度和初始固含量可调整多孔莫来石陶瓷的微观结构和性能。     

(Zr0.8Sn0.2)TiO4(ZST)微波介质陶瓷微波烧成工艺研究

分别采用传统的电热烧结和微波烧结制备了ZST微波介质陶瓷,研究了烧结温度对介质陶瓷烧结性能、微观结构、相组成和微波介电性能的影响。结果表明:与传统电热烧结相比,在所得材料密度近似的情况下,微波烧结能降低烧结温度约70℃、缩短烧结时间2.5h,所获材料密度分布的标准差大大减小;微波烧结后材料由(Zr0.8Sn0.2)TiO4斜方晶单一晶相组成,随温度升高,无新相产生;微波烧结所得材料的晶粒尺寸均匀、结构致密;材料的介电常数和品质因数随着微波烧结温度的提高而增大,对应数值分别比传统烧结方式提高17.5%和14.3%左右。     

海藻酸钠凝胶–发泡法制备Al2O3多孔陶瓷

以海藻酸钠为凝胶体系、脂肪醇聚氧乙烯醚硫酸钠(AES)为发泡剂,采用凝胶注模与发泡法相结合的技术制备了Al₂O₃多孔陶瓷坯体,并利用无压烧结工艺进行材料的烧结。研究了固相含量及发泡剂含量与Al₂O₃多孔陶瓷坯体的气孔率与抗压强度之间的关系,探讨了烧结温度对Al₂O₃多孔陶瓷烧结体的显微结构及力学性能的影响规律,并研究了海藻酸钠体系的凝胶固化机制。结果表明,海藻酸钠与Ca2+反应形成网络结构,实现了Al₂O₃陶瓷粉体的固化成型。25%(体积分数)固相含量及3.0%(质量分数)发泡剂含量为最佳含量,有利于制备气孔率高、气孔孔径均匀的多孔陶瓷坯体。随着烧结温度升高,Al₂O₃多孔陶瓷烧结体气孔率下降,抗压强度上升,过高的烧结温度引起Al₂O₃晶粒异常长大,抗压强度降低。     

多孔重结晶碳化硅陶瓷的烧结颈结构调控与力学性能

结合气固反应和重结晶烧结,制备了烧结颈结构可控的多孔重结晶SiC陶瓷。首先以微米SiC颗粒作为骨架,通过SiO气体和纳米炭黑的高温气固反应得到纳米碳化硅均匀分布的预烧结体;再对预烧结体进行重结晶处理,通过纳米SiC颗粒的低温蒸发凝聚获取高纯度的SiC多孔陶瓷。研究了重结晶过程中烧结温度对多孔SiC陶瓷的烧结颈、显微形貌、以及力学性能的影响规律。结果表明:SiC晶粒之间的烧结颈参数(烧结颈直径/微米SiC晶粒直径,d/d0)决定了多孔材料的抗弯强度。随着烧结温度增加,纳米SiC颗粒的饱和蒸气压升高,加速了蒸发–凝聚的进行,物质传输总量增加,多孔SiC材料的d/d0值增加,抗弯强度迅速升高,达到峰值后,基本保持不变或者略有下降。温度高于2100℃时,骨架SiC微米颗粒会发生分解反应产生残碳,导致材料的抗弯强度降低。原位合成的纳米SiC含量为20%,在Ar气氛中于2000℃保温1h后,材料组织性能最优,烧结颈面积的平均值为15.91μm~2,d/d_0值为99.7%,气孔率为42.4%,抗弯强度高达75.7MPa,其性能优于商用柴油颗粒物过滤材料。     

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。