SiO_2掺杂对Mn_(2.38)Ni_(0.5)Cu_(0.12)O_4系NTC热敏陶瓷老化性能的影响

以SiO2为掺杂剂,运用XRD、SEM和电性能测试等手段,研究了掺杂对Mn2.38Ni0.5Cu0.12O4系NTC热敏陶瓷样品相结构、电性能以及老化性能的影响。研究发现:SiO2的掺杂可以使Mn2.38Ni0.5Cu0.12O4热敏电阻的老化值从未掺杂时的10%降低到6%左右,提高了其电学稳定性,此类掺杂材料将会拓宽含Cu NTC热敏陶瓷的生产和应用范围。     

NiMnFeO4的制备与性能研究

采用(NH4)2C2O4为沉淀剂,基于共沉淀法制备了NiMnFeO4 NTC热敏陶瓷,用TG、XRD、SEM、电导率测量等方法对前驱体、氧化物粉体及NTC陶瓷样品的进行了表征。结果表明,用此种方法制备的NTC陶瓷,其结构均匀、致密;烧结后经随炉冷却的样品,在150％老化l000h后,电阻漂移小于1％;而在1150℃下淬火的样品在同样的条件下,电阻漂移大于4％。     

柠檬酸凝胶法制备Mn-Ni-Fe基负温度系数热敏陶瓷

采用柠檬酸凝胶法制备锰-镍-铁基前驱体,在300℃煅烧干燥的前驱体得到纳米粒度粉末,压制成圆片坯体后在1100～1300℃烧结得到负温度系数(negative temperature coefficient,NTC)热敏陶瓷样品。研究了粉体和烧结样品的相结构、微观形貌、电性能和热敏特性。结果表明:合成粉体的纳米颗粒为单相Mn1/3Ni2/3Fe2O4尖晶石,粉体具有高化学均匀性。烧结的Mn1/3Ni2/3Fe2O4陶瓷样品具有均匀的微观结构,陶瓷样品的烧结密度和材料敏感指数β随着烧结温度的增加而增加。测量温度为50～150℃范围时,1300℃烧结的Mn1/3Ni2/3Fe2O4样品,其β可高达4300K。     

NiMnFeO_4的制备与性能研究

采用 (NH4) 2 C2 O4为沉淀剂 ,基于共沉淀法制备了NiMnFeO4NTC热敏陶瓷 ,用TG、XRD、SEM、电导率测量等方法对前驱体、氧化物粉体及NTC陶瓷样品的进行了表征。结果表明 ,用此种方法制备的NTC陶瓷 ,其结构均匀、致密 ;烧结后经随炉冷却的样品 ,在 15 0℃老化 10 0 0h后 ,电阻漂移小于 1% ;而在 115 0℃下淬火的样品在同样的条件下 ,电阻漂移大于 4 %。     

掺杂对Ni-Mn-O系NTC热敏陶瓷及其电学性能的影响

以Ni0.66Mn2.34O4为负温度系数(negative temperature coefficient,NTC)的热敏陶瓷基体,分别掺入Mg2+、Zn2+、Al3+、Fe3+或Ni2+等不同离子,以考察对结构和电性能的影响.X射线衍射结果表明:所有样品均为单相尖晶石结构,并计算出晶胞参数和近似的阳离子分布.电性能测量结果表明:当掺杂离子进入尖晶石结构B位时,对电阻率有较大影响;当掺杂离子进入尖晶石结构A位时,则对电阻率的影响较小.通过选择合适的掺杂离子可以调节其电性能参数.     

ZrO2纳米颗粒的添加对ZrO2/HA复合陶瓷物相和力学性能的影响

将液相掺杂CeO2和Fe2O3的钇稳定四方ZrO2纳米粉作为着色剂添加到微米ZrO2/HA体系中,1400℃烧结制备了ZrO2/HA纳米复合陶瓷.利用X射线衍射分析了复合陶瓷的物相组成;三点弯曲法、单边切口梁法及压痕法测试了陶瓷的力学性能;讨论了纳米氧化锆的添加对复合陶瓷力学性能及物相组成的影响,分析纳米氧化锆导致复合陶瓷力学性能改变的原因.根据复合陶瓷断裂前后单斜相氧化锆的含量变化,证实氧化锆纳米粉的添加不仅有利于复合陶瓷中四方相氧化锆的稳定存在,而且可以提高基体相变四方相氧化锆的含量,相变增韧作用加强.力学性能测试结果显示:体系中适量纳米氧化锆的存在可以提高材料的抗弯强度和断裂韧性20%以上,密度和硬度少量增加,但由于没有新物相引入,对弹性模量未造成影响.     

复合添加TiO2和ZrO2对MgO-MA材料性能的影响

以电熔镁砂、高纯烧结镁砂、烧结富镁尖晶石和α-Al2O3为主要原料,在实验室制备了可替代水泥回转窑烧成带用镁铬砖的方镁石-镁铝尖晶石(MgO-MA)质耐火材料,研究了复合添加1.2%(w)的非晶TiO2粉和2.3%(w)的单斜ZrO2粉对MgO-MA材料性能的影响。结果表明:复合添加TiO2和ZrO2能促进MgO-MA材料的烧结;复合添加TiO2和ZrO2的MgO-MA材料的晶界处生成了CaTiO4和Mg2Zr5O12固溶相,有利于提高MgO-MA材料的挂窑皮性能。     

添加ZrO_2提高镁尖晶石复合耐火材料的机械性能和抗热震性

研究了添加ZrO2对镁尖晶石耐火材料的机械性能和抗热震性及微观结构特征的影响。镁尖晶石中加入ZrO2可以使其机械性能、Rst值和抗热震效果提高约1.5倍。提高镁尖晶石ZrO2复合耐火材料的机械性能和抗热震性的基本参数确定如下：（1）互连的微裂纹扩展距离短;（2）微裂纹遇到气孔或ZrO2颗粒会终止或发生偏转;（3）断裂面上同时出现大量晶间裂纹和一些穿晶裂纹;（4）加入ZrO2后,堆密度增加;（5）MgO粒度锐减。热机械性能的提高证明了镁尖晶石ZrO2复合耐火材料在高温条件下强度损失低、抗热震性好、在工业应用中使用寿命更长。     

掺杂La2O3对刚玉基复相陶瓷的烧结和力学性能的影响

刚玉基复相陶瓷材料具有高硬度、高强度及耐磨性等优异的力学性能,是结构陶瓷领域研究的热点之一,具有广阔的应用前景.以α-Al2O3、SiC和ZrO2为原料,掺杂少量稀土氧化物La2O3,采用无压埋烧工艺,制备了稀土掺杂刚玉基复相陶瓷.通过XRD、SEM等手段研究La2O3添加量对复相陶瓷微观结构和性能的影响.结果表明:掺杂La2O3可将复相陶瓷的烧结温度降低至1540℃,经1540℃烧结的掺杂复相陶瓷强度和硬度分别为183 MPa和18.46 GPa.La2O3位于晶界处抑制晶粒长大,促进晶粒细化,利于样品的致密化,同时其晶界强化作用有利于复相陶瓷强度的提高.     

B位前躯体法制备PZT/ZrO2纳米复相压电陶瓷的力学性能研究

采用改进的聚合物法制备B位前驱体PZT/ZrO2纳米复相陶瓷.采用TEM观察到马氏体相变和热失配产生的应力条纹和应力斑,发现ZrO2粒子截断电畴和使电畴弯曲的现象.应力场有效吸收裂纹扩展能量,加之ZrO2粒子强化基体晶界,PZT/ZrO2纳米复相陶瓷得到了强韧化.SEM分析显示陶瓷断裂模式随ZrO2加入向穿晶断裂模式转变.抗弯强度和断裂韧性随Zr2加入量增加明显提高,可达141.6 MPa和2.3 MPa·m1/2.     

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.     

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.     

ICP-MS法测定地球化学样品中As、Cr、Ge、V等18种微量痕量元素的研究

建立了测定地球化学样品中包括As、Cr、Ge、V等18种微量、痕量元素的ICP-MS方法。地化试样用HF-HNO3混酸分解后,以1 1 HNO3溶解干渣。由于制样不使用盐酸,避免了Cl对As、Cr、Ge、V的质谱干扰。用国家一级地球化学标准物质GBW 07309制备溶液优化仪器工作参数,并用于校准。方法测定限(6s)为:0.007~6.4μg/g,精密度(RSD%,n=12)为:29%~9.4%,经过国家一级地球化学标准物质的分析验证,结果与标准值吻合。方法已应用于国土资源调查的试样分析。     

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.     

基于ATRP法制备的触角状亲水性羟胺树脂的吸硼性能的研究

以大分子引发剂氯乙酰化聚苯乙烯微球(PS-acyl-Cl)经原子转移自由基聚合(ATRP)法引发丙烯酰胺(AM)和甲基丙烯酸缩水甘油酯(GMA)单体的共聚接枝,制得一种触角状亲水性环氧载体(PS-acyl-g-P(AM-co-GMA)),再经二乙醇胺(DEA)的环氧基开环胺化反应,得到一种含多个-NCH2CH2OH螯合配基的多齿-五元螯合环的触角状亲水性羟胺树脂(PS-acyl-g-P(AM-co-GMA)-DEA)。将此树脂用于硼吸附研究,结果表明,PS-acyl-g-P(AM-co-GMA)-DEA树脂对硼的吸附满足Langmuir方程,为单分子层吸附;饱和吸附量约为37.7 mg·g-1,且树脂5 min即可达到吸附平衡,与其它已报道的吸硼树脂相比,该树脂具有更高的吸附量和吸硼速率。吸附动力学研究表明,树脂吸附硼的过程主要由颗粒扩散过程控制。重复使用5次后该树脂的吸附量基本不变,解吸率均在90%以上,重复使用性能良好。