添加剂对0.95MgTiO3-0.05CaTiO3陶瓷性能的影响

采用同相反应法分别制备了V2O5,Co2O3和ZnO氧化物掺杂的0.95MgTiO3-0.05CaTiO3(95MCT)介质陶瓷.研究了V2O5,Co2O3和ZnO氧化物掺杂对95MCT陶瓷烧结特性和介电性能的影响.结果表明:V2O5.Co2O3和ZnO氧化物掺杂的95MCT陶瓷的主晶相为MgTiO3和CaTiO3两相结构,无中间相MgTi2O5出现.V2O5,Co2O3和ZnO氧化物掺杂可以有效地降低95MCT陶瓷的烧结温度,提高致密化程度,降低介电损耗,调节温度系数.ZnO掺杂的95MCT陶瓷性能最好:烧结温度降低至1 250℃,介电常数为21.7,烧结密度可达3.8g、cm3(理论密度的98.4%),介电损耗降低至10-5,温度系数为0.12×10-5/℃.     

掺Li2O-B2O3-SiO2玻璃低温烧结MgTiO3-CaTiO3陶瓷及其微波介电性能

研究了Li2O-B2O3-SiO2玻璃(LBS)对MgTiO3-CaTiO3(MCT)介质陶瓷烧结特性、相组成和介电性能的影响,分析了MCT陶瓷与银电极的共烧行为.结果表明:通过液相烧结,LBS能有效降低MCT烧结温度至890℃.X射线衍射结果显示有Li2MgTi3O8、硼钛镁石以及Li2TiSiO5等新相生成.随着LBS添加量的增大,陶瓷致密化温度和饱和体积密度降低,介电常数εr品质因数与谐振频率乘积Q×f也呈现下降趋势,频率温度系数δf向负值方向移动.添加质量分数为20%的LBS的0.97MgTiO3-0.03CaTiO3陶瓷在890℃烧结4h,获得最佳性能:εr=16.4,Q×f=11 640GHz,τf=-1.5×10-6/℃.陶瓷与银电极共烧界面结合状况良好,无明显扩散.该材料可用于制造片式多层微波器件.     

MgTiO3-Bi4Ti3O12微波介质陶瓷的制备及性能研究

采用传统固相法制备了Bi4Ti3O12掺杂的MgTiO3陶瓷,研究了其对MgTiO3陶瓷烧结特性及微波介电性能的影响。通过测试分析发现,Bi4Ti3O12不仅可以显著降低陶瓷的烧结温度,同时还可以大大提高其介电常数,当Bi4Ti3O12/MgTiO3摩尔比为0.02时,MgTiO3-0.02Bi4Ti3O12陶瓷的最佳烧结温度为1 150℃,介电常数为31.99。     

P2O5-B2O3-V2O5无铅低熔玻璃形成能力和结构

以取代用作封接玻璃和电子浆料粘接相含铅低熔玻璃为目的,实验研究了P2O5-B2O3-V2O5体系玻璃的形成能力,结构和低熔性能.P2O5-B2O3-V2O5体系中,组成在B2O35%～30%、V2O50%～45%、P2O35%～50%(物质的量浓度,下同)区域内的玻璃具有较强的玻璃形成能力,较低的转变温度、良好的重熔流动性和抗析晶性能.优选玻璃组成为:15P2O5-35V2O5-25B2O3-3SiO2-2Al2O3-10ZnO-5SnO-7BaO-3Bi2O3,玻璃转变温度为308℃,在450℃玻璃细粉重熔熔体流动性好,适合用作在450～500℃烧结的封接玻璃和电子浆料的粘接相.红外光谱分析表明:玻璃结构是由大量孤立的[PO4]、[BO3]、[VO2]和[VO3]基团形成的层状结构,在层与层之间有少量的诸如B-O-B、P-O-P、P-O-V、P-O-B等桥氧键连接.     

H3BO3对Li2Zn3Ti4O12微波介质陶瓷低温烧结与微波介电性能的影响

采用传统固相反应法制备了添加H3BO3助烧剂的Li2Zn3Ti4O12 (LZT)陶瓷,分别通过XRD、SEM、排水法及网络分析仪等方法研究了不同H3BO3添加量对所得陶瓷的物相、微观形貌、烧结特性与微波介电性能的影响.结果表明在LZT陶瓷中添加3wt% H3BO3可有效降低烧结温度,在900 ℃/2 h烧结条件下可以获得高致密性及优异的微波介电性:ρ=4.15 g/cm3,εr=17.916,Q×f=61200 GHz,Tf=-52.87×10-6/℃.     

CaO-SiO2-B2O3系陶瓷的低温快烧制备与性能

以CaCO3,SiO2,H3BO3为原料,采用无压烧结法,分别在3个不同的烧成条件下,低温快速烧成制备了CaO-SiO2-B2O3系陶瓷样品,所得样品在室温下快速冷却.测定了该体系的烧结性能和样品的体积电阻率,并探讨了其变化规律.结果表明:按照一定比例复合添加ZnO和MgO,对CaO-SiO2-B2O3系陶瓷具有明显的助烧作用;在添加量少于6.0%(质量分数,下同),同比例复合添加ZnO,MgO时较相应单一添加ZnO(为同比例复合添加ZnO,MgO时质量的1/2)所得样品的体积电阻率大.当添加6.0%ZnO,6.0%MgO时,在3种烧成条件下,均可制得体积密度较大、吸水率较小、体积电阻率较大(>1011 Ω·cm)的致密烧结体.     

ZB/SiO_2体系玻璃陶瓷的低温烧结与介电性能研究

采用水淬法制备3Zn O-2B_2O_3(3Z2B)玻璃,利用液相参与烧结机理制备了锌硼(3Z2B)玻璃陶瓷。研究了不同SiO_2添加量下的3Z2B/SiO_2体系玻璃陶瓷的相组成、显微结构及介电性能。研究结果表明,SiO_2的添加,有效地降低了3Z2B/SiO_2体系玻璃陶瓷的介电常数,玻璃陶瓷在650℃烧结30 min可致密化。当SiO_2添加量为15 wt%时,650℃烧结的样品的介电性能最优,在10 MHz频率测试下的εr为6.1,tgδ为1.5×10-3。样品中主要晶相有α-Zn(BO2)2、Zn3B2O6、SiO_2,无硅酸盐相生成,说明SiO_2与3Z2B玻璃在烧结过程中不发生反应。     

BaO-Al2O3-B2O3-SiO2玻璃/SiO2高膨胀低温共烧陶瓷研究

用BaO-Al2O3-B2O3-SiO2玻璃与二氧化硅复合的方法制备了高膨胀系数低温共烧陶瓷。实验首先制备一组玻璃材料,通过热膨胀测试、DTA等方法研究了玻璃的热学性能,然后用玻璃与石英、方石英和鳞石英晶体按一定比例复合制得高膨胀低温共烧陶瓷。通过烧结试验、XRD等分析方法研究了复相陶瓷材料的烧结收缩性能、晶相组成、热膨胀系数和介电常数。结果表明:50%BaO-7.5%Al2O3-30%B2O3-12.5%SiO2玻璃具有较低的转变温度(520℃)。该玻璃与鳞石英晶体以1:1的比例复合,850℃/10min烧结可以获得热膨胀系数为12.18×10-6K-1、介电常数为5.37的低温共烧陶瓷。     

添加Sb_2O_5,ZnO和玻璃对(Zr_(0.7)Sn_(0.3))Ti_4陶瓷高频介电性能的影响

用氧化物混合方法制备了主晶相为 (Zr0 .7Sn0 .3)TiO4的高频陶瓷材料。添加Sb2 O5,ZnO和玻璃有效降低了陶瓷的烧成温度和介质损耗。添加 0 .5 %Sb2 O5(摩尔分数 ) ,1.5 %ZnO(质量分数 )和 3.0 %玻璃 (质量分数 )的陶瓷组成在 115 0℃烧结 ,在测试频率 1MHz下的介电性能为 :介电常数ε≈ 38,损耗角正切tanδ=0 .6× 10 - 4 ,介电常数温度系数αε=0± 30× 10 - 6 /℃ ,体电阻率 ρv≥ 10 1 3Ω·cm。用此种陶瓷材料可在中温烧结制成多层陶瓷电容器 (multilayerceramiccapacitor,MLCC)     

BaBA玻璃烧结剂对Li_2ZnTi_3O_8陶瓷结构及性能影响

采用SEM、网络分析仪等分析测试手段研究了BaBA玻璃对Li_2ZnTi_3O_8陶瓷微观结构与微波介电性能的影响。研究结果表明:BaBA玻璃添加量为10%,烧结温度为920℃时,样品烧结最致密;BaBA玻璃添加量为5%,940℃烧结时,介电常数达到最高为23.89,密度达到最高为3.833g/cm~3;同一烧结温度下,BaBA玻璃添加量越多,样品介电常数越小,介电损耗越大。     

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.     

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.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.