苯乙烯-马来酸酐共聚物表面改性SiC浆料的流变性研究

通过自由基聚合反应,合成了含有苯乙烯-马来酸酐共聚物的改性剂.通过表面改性将上述改性剂接枝在粉体表面,研究了不同因素对改性SiC浆料流变特性的影响.结果表明,表面改性使SiC浆料的粘度显著降低,且浆料呈现出近似Newton流体行为.通过控制影响改性SiC浆料流变性的因素,在改性剂中WD-20与SMA配比为1:1,改性剂用量为1、wt%,pH=9,加入分散剂TMAH的量为0.6wt%的条件下,成功地制备出了固相含量为58vol%,粘度低于1Pa·s的SiC陶瓷浆料.     

碳化硅悬浮浆料粘度损失研究

用硅烷偶联剂对1.2μSiC粉接枝改性,和100μSiC粉调制浆料,研究了SiC粉表面Zeta电位和浆料固相体积含量、粘度增量之间的关系;在碱性条件下,SiC表面水解是导致Zeta电位变化和浆料粘度损失的原因。考察了润湿剂烷基聚氧乙烯醚(Alcohol Ethoxylate,AEO)对浆料Zeta电位和粘度损失的影响,...     

碳化硅陶瓷水基浆料的流变性研究

主要研究了分散剂、pH、颗粒级配等因素对SiC水基浆料流变性能的影响,并分析了其原因。结果表明,各分散剂对SiC浆料粘度影响效果的大小顺序依次为:四甲基氢氧化铵(TMAH)>六偏磷酸钠(SHMP)>聚乙二醇(PEG)。TMAH、SHMP、PEG三种分散剂的最佳用量分别为0.8wt.%、0.6wt.%、1.0wt.%,最佳pH为13,最佳颗粒级配(F220/F1200,下同)为1.5,当固相体积分数超过50%后SiC浆料的粘度急剧增加。通过优化工艺参数,制备出了流动性较好,固相体积分数为50%、粘度为500mPa.s的SiC陶瓷浆料。     

甘氨酸钠对SiC粉体的表面改性及其浆料流变性研究

以强电解质甘氨酸钠(SG)为改性剂,考察其在SiC粉体表面的吸附状况,制备高分散SiC粉体,同时研究其浆料流变性。结果表明,采用固相球磨和恒温处理工艺,0.15%甘氨酸钠改性后的SiC粉体Zeta电位绝对值明显高于改性前,pH值为10.0时,从38.9 mV增加到62.2 mV。TOC(总有机碳)对粉体洗涤液中有机物含量的测试表明,微量甘氨酸钠的平衡吸附可有效降低SiC浆料粘度,提高其固含量和稳定性。     

六甲基二硅氮烷改性纳米二氧化钛工艺研究

以纳米二氧化钛为原料,水为溶剂,采用湿法工艺对纳米二氧化钛表面进行了改性研究,分别探讨了改性剂种类、改性剂用量、乳液质量分数、反应温度和反应时间对纳米二氧化钛表面改性效果的影响.结果表明,纳米二氧化钛经六甲基二硅氮烷改性处理后,在有机溶剂中的润湿性明显改善;六甲基二硅氮烷用量、乳液质量分数、反应时间、反应温度对纳米二氧化钛表面改性均有影响.较佳工艺条件:六甲基二硅氮烷质量分数为15%,乳液质量分数为30%,反应温度为90 ℃,反应时间为1 h.通过对纳米二氧化钛润湿性的测定表征纳米二氧化钛的改性效果.     

纳米碳化硅在环氧树脂中的分散工艺研究

采用加入分散剂和超声波分散2种方法改进纳米SiC在环氧树脂中的分散,研究了分散剂种类和用量、分散方法对纳米SiC在环氧树脂中分散的影响。结果表明:分散剂DISPERBYK-2009的降粘效果最好,SiC/EP浆料的粘度下降达57.3%,浆料粘度随分散剂用量的增加呈现先降后升态势。通过添加粉体质量分数5%的分散剂DISPERBYK-2009并采用超声波分散15 min,实现了纳米SiC在环氧树脂中的均匀分散,成功制备了粒子细小、均匀分布的纳米SiC/EP复合材料。     

稀土复合偶联剂对氢氧化镁的表面改性研究

对超细无机阻燃粉体氢氧化镁进行表面改性可大大改善其与有机高聚物的相容性和加工流动性.选择稀土偶联剂/螯合磷酸酯钛偶联剂作为氢氧化镁的复合改性剂,采用湿法改性处理氢氧化镁.通过表面分析技术测定改性氢氧化镁粉体表面性质;利用差热分析技术(DTA)测定其热起始分解温度;利用傅里叶变换红外光谱仪(FT-IS)证实了氢氧化镁表面改性层的存在.通过实验,得到稀土偶联剂/螯合磷酸酯钛偶联剂复合改性剂表面处理氢氧化镁的最佳工艺条件:浆料质量分数为30%,改性剂稀土偶联剂与螯合磷酸酯钛偶联剂质量比为1.9∶ 1,改性剂用量为2.5%,改性温度为80 ℃,搅拌速率为760 r/min,改性时间为30 min.在此条件下,改性氢氧化镁的吸油值从0.499 7 g/g降至0.336 5 g/g,活化指数从0上升到99.86%,热起始分解温度从341.1 ℃升至366.5 ℃.     

SiC粉体表面改性对其成形坯体含水量的影响

研究了阳离子型表面活性剂溴化十六烷基吡啶对SiC粉体进行表面改性的效果。表面活性剂吸附在SiC粉体表面后,其表面zeta电位升高至27mV;用旋转粘度计表征了表面活性剂的加入对SiC浆料流变性的影响,当HBH的加入量为0.2%时,SiC浆料的触变性最小。当HBH的加入量为0.08%时,SiC浆料的含水量最低,约为8.3%,此时对应的生坯密度为2.42g/cm3。     

分散剂用量对碳化硅浆料流变性能的影响

使用四甲基氢氧化铵(TMAH)作为分散剂,研究了分散剂用量对SiC浆料流变性能的影响,并分析了其原因。结果表明：TMAH能够显著提高SiC粉体的zeta电位,降低浆料粘度,从而显著优化浆料的流变性能。在pH为10左右,加入质量分数为0．3％和o．6％NTMAH后zeta电位分别提高了11.7mV和21mV。实验中,在不同体积分数SiC浆料中,加入0．6%TMAH时能够达到最优性能,浆料粘度都达到最低。过量的分散剂则会增加浆料中的离子浓度而导致双电层厚度减小,从而恶化浆料的流变性。     

柠檬酸钠表面改性重钙粉体的研究

研究了柠檬酸钠用量、反应温度、反应时间、浆料浓度对重钙粉体表面改性的影响。结果表明,柠檬酸钠用量为重钙粉体的6.0%(质量分数),改性温度65℃,改性时间45 min,浆料浓度为12.5%时,重钙粉体沉降体积降为0.65 mL/g,活化度可达到67.9%,吸油值降为230 mg/g,粘度值降低为120 mPa.s,pH值8.50。     

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.     

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。     

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.     

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.     

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。