热压烧结法制备碳化钛/氧化铝复合材料

把TiC颗粒和金属Al以AlTiC中间合金的形式引入Al2O3陶瓷中,用过渡液相热压烧结法制备了TiC/Al2O3复合材料,并对其微观结构与力学性能进行了研究。结果表明:在1450℃,30MPa条件下,热压烧结制备的TiC/Al2O3复合材料中TiC与Al2O3能稳定共存,材料的断裂韧性和Vickers硬度均有明显提高。材料的Vickers硬度平均超过23.5GPa,断裂韧性超过8.7MPa·m1/2,密度低于纯Al2O3的。由于添加相AlTiC和Al2O3的成本均较低,因而找到了一种低成本制造高性能TiC/Al2O3复合材料的方法。     

矾土基MgAlON复合材料的制备及性能研究

选用登封轻烧矾土(Al2O3含量为85wt％)、电熔镁铝尖晶石、高纯电熔镁砂、Al粉和少量的活性材料氮化气氛下制备矾土基MgAlON复合材料,考察了MgAlON含量及烧成温度对制备矾土基MgAlON复合材料性能的影响.结果表明:随着MgAlON加入量的增加,显气孔率、线变化率及增重率逐渐增大,材料体积密度逐渐减少,常温抗折强度呈上升趋势;随着烧成温度的提高,试样的体积密度略有减小,显气孔率增大,常温抗折强度逐渐增大,1500℃下氮化烧成的制品性能最好;矾土基MgAlON复合镁铝尖晶石材料比矾土基MgAlON复合镁质材料密度大,强度高,氮化效果好.     

BaO-Al2O3-B2O3-SiO2系微晶玻璃低温共烧陶瓷研究

采用烧结法制备了BaO-Al2O3-B2O3-SiO2系微晶玻璃低温共烧陶瓷。通过差热分析仪、影像式烧结点试验仪、X射线衍射仪等方法研究了玻璃组成以及烧结制度对微晶玻璃结构和性能的影响。结果表明:随着B2O3替代Al2O3量的增加,玻璃转变温度和烧结温度逐渐降低,析晶能力增强,有利于重硅酸钡晶体的析出,但不利于钡长石晶体的析出。烧结制度对析出晶体的种类和数量有很大影响。在850℃烧结2 h,微晶玻璃低温共烧陶瓷的气孔率低于1%,热膨胀系数在(7.05～12.78)×10-6/℃之间变化。     

真空热压烧结制备高性能B4C/Al复合材料

B4C/Al复合材料因其优异的性能,受到了人们广泛关注.以Al粉和B4C粉体为原料,采用真空热压烧结法,在高于Al熔点温度时,制备出了碳化硼含量10wt%的铝基复合材料.研究结果表明:烧结温度为700 ℃,烧结压力为30 MPa,保温时间为45 min时,获得的B4C/Al复合材料力学性能最佳,其相对密度为98.2%,硬度为2.53 GPa,抗弯强度为350 MPa.球磨混料使Al颗粒表面生成少量Al2O3,在烧结过程中,Al2O3与B2O3发生固-液反应形成共融物,改善了B4C/Al之间的界面结合强度,从而获得力学性能优异的B4C/Al复合材料.     

Al2O3-AlON复合材料的烧结性能和显微结构

研究了在保护气氛下1600℃烧成的Al2O3-AlON复合材料的烧结性能、物相组成和显微结构.结果表明在刚玉材料中加入AlON,烧结性能得到改善,物相组成主要为刚玉和尖晶石型构造的氧氮化铝,两者之间形成紧密结合结构,并有少量MgAlON微晶填充在大颗粒间的孔隙中,形成致密结构.     

热处理温度对磷渣-煤矸石微晶玻璃结构和性能的影响

以磷渣和煤矸石为原料,采用一步烧结法制备了性能优良的CaO?Al2O3?SiO2(CAS)系微晶玻璃,用差示扫描量热法(DSC),X射线衍射(XRD)和扫描电子显微镜(SEM)等对其进行分析和表征,研究了热处理温度对微晶玻璃晶相组成、微观结构和宏观性能的影响规律。结果表明,固废利用率达100%,微晶玻璃性能良好;以磷渣和煤矸石为原料在1250℃下熔融2 h、于850℃热处理保温2 h可制备主晶相为假硅灰石Ca3(Si3O9)的微晶玻璃,其抗折强度、显微硬度和体积密度分别为74.4 MPa,566.9 HV和2.75 g/cm3。随热处理温度升高,微晶玻璃主晶相由Ca3(Si3O9)相转变为硅灰石CaSiO3相,晶体形态由球状向针状、短柱状改变,对提高微晶玻璃抗折性能有利,而显微硬度和体积密度均先增加后降低。     

MgAlON-MgAl_2O_4复合材料的制备与性能研究

为了制备具有良好性能的MgAlON-MgAl_2O_4复合材料以替代含铬耐火材料,以电熔镁铝尖晶石(粒度1~3、≤1和≤0.074 mm)、活性α-Al_2O_3粉(2~5μm)、Al粉(≤0.074 mm)、Mg O粉(≤0.044 mm)为原料,采用原位生成MgAlON的方法制备了MgAlON-MgAl_2O_4复合材料。通过调整配料中α-Al_2O_3粉+Al粉+Mg O混合粉(三者的质量比固定为76∶12∶12)的加入量(在整个固态配料中的质量分数分别为15%、20%、25%和30%)来调整MgAlON的设计生成量,研究了MgAlON设计生成量对MgAlON-MgAl_2O_4复合材料致密度、常温强度、物相组成和显微结构等的影响。结果表明:1)随着α-Al_2O_3-Al-Mg O混合粉加入量的增加,复合材料中MgAlON相生成量增多;但当α-Al_2O_3+Al+Mg O混合粉加入量达到30%(w)时,复合材料中有副产物Al4O4C生成。2)随着α-Al_2O_3+Al+Mg O混合粉加入量从15%(w)增加到25%(w),复合材料中MgAlON晶粒发育程度逐渐变好,与MgAl_2O_4颗粒的结合也逐渐紧密;但当α-Al_2O_3+Al+Mg O混合粉加入量达到30%(w)时,复合材料基质中有明显微气孔出现,致密性和均匀性变差。3)随着α-Al_2O_3+Al+Mg O混合粉加入量的增加,复合材料的烧后体积密度和显气孔率变化不大,常温耐压强度和常温抗折强度变化明显,烧成线变化率由微收缩变为微膨胀。4)综合考虑,α-Al_2O_3+Al+Mg O混合粉加入量为25%(w)的试样的性能最佳。     

Al2O3／TiAl复合材料的制备与性能研究

采用热压烧结法制备Al2O3／TiAl复合材料,研究了不同Al2O3体积分数对Al2O3／TiAl复合材料的相对密度、弯曲强度、断裂韧性以及耐磨性的影响。研究结果表明,掺入20％Al2O3时,复合材料的相对密度达到最小,随着烧结温度的不断升高,Al2O3／TiAl复合材料的相对密度不断增加。当Al2O3含量为15％时,弯曲强度与断裂韧性达到最佳,其值分别为865．9Mpa和17．60MPam^1/2。随Al2O3体积分数的增加,Al2O3／TiAl复合材料的摩擦系数不断增加,而磨损失重则呈先降低后增大的变化趋势,当Al2O3含量为15％时,在不同载荷作用下,材料的磨损失重均最小。     

基础成分对绿色微晶玻璃色度及性能的影响

以CaO-Al2O3-SiO2玻璃为基础,以CuO+Cr2O3为着色剂,通过烧结法制备了绿色微晶玻璃,采用X射线衍射、扫描电子显微镜、色度计、熟膨胀仪和硬度计研究了Al2O3、Na2O和ZnO含量对绿色微晶玻璃晶相结构、色度及性能的影响.结果表明:在所研究的成分范围内,Al2O3、ZnO和Na2O含量的变化不改变绿色微...     

Al2O3-SiC复相陶瓷材料制备方法的研究现状

简要论述了Al2O3-SiC复相陶瓷材料的常用制备方法,如无压烧结法、热压烧结法、气压烧结法和溶胶-凝胶法等,重点介绍了碳热还原法。对以不同原料制备Al2O3-SiC复相陶瓷材料的碳热还原法进行了比较,指出了这方面研究的不足之处和下一步研究的方向。     

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.     

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。     

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.     

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.     

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.