新疆尖山菱镁矿制备轻烧氧化镁的煅烧工艺

以新疆尖山菱镁矿为原料,采用普通马弗炉和微波马弗炉两种加热设备,通过设计正交实验,研究煅烧温度、煅烧时间、升温速率和原料粒径对所制备的轻烧氧化镁的活性和纯度的影响.采用柠檬酸法表征轻烧氧化镁的活性,水合法测定活性氧化镁的含量.结果表明:无论采用哪种加热方式,煅烧温度对轻烧氧化镁活性和纯度的影响最大.采用微波马弗炉加热时,煅烧时间、升温速率和原料粒径对轻烧氧化镁的活性和纯度影响较小,制备条件宽松,尤其当原料粒径不均一时,采用微波加热方式更有利于轻烧氧化镁的制备.     

悬浮态煅烧菱镁矿制备高活性轻烧氧化镁

为探讨悬浮态煅烧菱镁矿制备高活性轻烧氧化镁的可行性,将粒度74μm的菱镁矿粉放置于实验室自行研制的小型模拟悬浮态煅烧装置内煅烧,在温度分别为650、750、850和950℃,保温时间分别为30、60、180和300 s的条件下对菱镁矿进行快速煅烧而制备轻烧氧化镁,采用XRD、SEM分析煅烧产物的物相组成和显微结构,根据Scherrer公式计算MgO晶粒的尺寸,通过柠檬酸显色法分析MgO活性。结果表明:采用悬浮态煅烧菱镁矿可在短时间内制备出高活性轻烧氧化镁;煅烧温度为850℃、保温时间为180 s时制备出的MgO活性最高,其活性指数为3.33,柠檬酸显色时间为30 s。     

利用菱镁矿制备高活性氧化镁

以菱镁矿为原料,先在850℃下煅烧2h获得轻烧氧化镁,然后水化成氢氧化镁,干燥后在不同温度(分别为450℃、500℃、550℃、600℃)和保温时间(分别为1h、1.5h、2h)下轻烧,通过分解氢氧化镁制备了高活性氧化镁。结果表明:氢氧化镁在500℃时完全分解成氧化镁;轻烧温度和保温时间对氧化镁活性(用吸碘值表征)有较大的影响,随着温度的升高,氧化镁活性逐渐降低,而在相同温度下,随着保温时间的延长,氧化镁的活性降低;在加热温度为500℃,保温时间为1h的条件下轻烧分解氢氧化镁,能得到吸碘值达191.42mg·g-1的活性氧化镁。     

煅烧和消化工艺对白云石活性的影响

以白云石为原料,采用柠檬酸测定法,通过控制煅烧温度、保温时间、消化温度和消化时间等因素,研究了煅烧和消化工艺对白云石活性的影响及最佳的煅烧和消化条件.结果表明:煅烧温度为950℃,保温时间为1.5 h时,煅烧产物中的氧化镁活性最好;以最佳煅烧条件下得到的白云灰粉进行消化反应,消化温度为80 ℃、消化时间为30 min时,得到的消化产物活性最高.工艺简单、操作方便,对进一步利用白云石制备氢氧化镁和氧化镁产品具有重要的参考价值.     

轻烧氧化镁活性对镁砂烧结性能及显微结构的影响

为利用轻烧氧化镁制备高性能烧结镁砂,以大石桥产破碎至≤0.074 mm的菱镁矿粉为原料,分别于700、800、900和1 000℃保温30 min煅烧获得4种不同活性的轻烧氧化镁,再将不同活性的轻烧氧化镁分别于1 550、1 600、1 650和1 700℃保温3 h进行二步煅烧制备了烧结镁砂,探讨了轻烧氧化镁活性对镁砂烧结性能、物相组成和显微结构的影响。结果表明:高活性轻烧氧化镁具有更高的缺陷能,从而具有更大的烧结驱动力,可以促进Mg O晶体的发育,提高镁砂的烧结性能,但过高的活性会导致镁砂的致密度降低;利用900℃煅烧的轻烧氧化镁经1 700℃保温3 h二步煅烧制备的烧结镁砂的体积密度可以达到3.41 g·cm-3,并且晶粒发育良好,排布均匀、紧密。     

轻烧氧化镁活性对烧结镁砂性能的影响

以大石桥某矿产菱镁矿为原料,分别于650℃、700℃、950℃和1200℃保温2 h煅烧,获得四种不同活性的轻烧氧化镁;用不同活性的轻烧氧化镁制备烧结镁砂并对其性能进行表征。结果表明:650℃、1200℃煅烧的轻烧氧化镁虽然活性较低,但是制备的烧结镁砂致密度较高,方镁石晶粒尺寸较大,利用1200℃煅烧的轻烧氧化镁制备的烧结镁砂性能更佳。     

轻烧氧化镁的微观特征及其活性

活性是轻烧氧化镁的主要应用特性，它与轻烧氧化镁的微观结构密切相关。将新疆某粗晶菱镁矿粉在700～1 100℃煅烧制得轻烧氧化镁，对不同温度轻烧氧化镁的晶胞参数、晶粒尺寸、结晶度、比表面积、孔径分布、比孔容、平均孔径、活性和显微结构等进行表征，利用TG结合非等温反应动力学理论研究轻烧氧化镁的微粒结构，分析该微粒结构随温度变化的机理及其对轻烧氧化镁活性的影响。结果表明：从700℃至1 100℃，轻烧氧化镁晶胞参数a0缩小并趋于稳定，晶粒尺寸逐渐增大，比表面积逐渐减小，但其活性变化并不遵从这一规律，在800℃时活性最高；粗晶菱镁矿粉的热分解受相界面上的化学反应所控制，分解产物—轻烧氧化镁“假象”微粒由氧化镁微晶和贯通的气孔网络结构组成；随煅烧温度升高，氧化镁微晶的烧结影响轻烧氧化镁“假象”微粒结构，进而影响其活性；800℃轻烧试样晶粒尺寸较小，结晶度较低，比孔容较大，且由于晶格调整使其平均孔径最大，大的孔径有利于溶液进入微粒内部，促进反应进行，因此其活性最高。     

探究温度制度对制备ZrSiO4-CdSxSe1-x包裹色料的影响

笔者研究了化学共沉淀法制备ZrSiO4-CdSxSe1-x包裹色料的工艺,进一步探究了温度制度（煅烧温度、升温速率和保温时间）对其合成的包裹色料的影响,并利用扫描电镜、色差仪对实验样品进行表征和分析。实验表明：当煅烧温度为950℃时,升温速率为30℃/min,保温时间为40min,色料在透明釉的呈色效果最佳,色度值坐标...     

烧成制度对溶胶-共沉淀合成锆镨黄色料的影响

采用溶胶-共沉淀法合成锆镨黄色料,分别探讨了煅烧温度、升温速率和保温时间对合成色料的物相组成、显微形貌与色度值的影响。实验结果表明:以4℃/min的升温速率煅烧至750℃并保温时间1 h,合成的色料性能最佳,此时主晶相为硅酸锆,还有少量的二氧化锆;煅烧温度和保温时间的增加致使硅酸锆含量先增加后减少,色度值随着硅酸锆含量的变化也先提高后降低;而随升温速率的提高,硅酸锆的含量增加,并在8℃/min时完全转化为硅酸锆;随温度、升温速率和保温时间的增加,部分硅酸锆晶体的显微形貌由颗粒状发育为块状和柱状。     

煅烧条件对白云石质磷尾矿热分解规律的影响

对贵州川恒磷尾矿的热分解进行了研究,考察了煅烧温度、煅烧时间、升温速率对磷尾矿分解规律的影响。结果表明,在煅烧温度为950℃,煅烧时间为30min,升温速率为10℃/min,原料粒径为200目的条件下,CaO质量分数为32.92%,MgO质量分数为22.91%;测得活性CaO使用盐酸量为23.8mL,活性MgO质量分数为59.04%。熟料达到制备白云石质耐火材料原料的标准,为磷尾矿的综合利用提供了一定的理论依据。     

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.     

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.     

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。