现代连续相变理论在玻璃分相中的应用——碱土金属硅酸盐二元系统分相的普适性及定量计算

本文用现代连续相变理论对稳态分相的碱土金属硅酸盐二元系统SiO_2-RO(R=Mg,Ca,Sr)的分相进行了分析。这些系统的分相值经过对临界点的标度,发现其标度实验值都在同一标度主曲线附近。相应它们临界点两侧的分相曲线,可普适地由以下两表达式定量表示:(x-x_c)/x_c=A(T_c-T)/T_c)~(1/3),(x′-x_c)/x_c=A′(T_c-T)/T_c)~(1/3)。这里A、A′是分相普适常数。本文从这三个系统分相实验值的拟合结果是A=-1.8180,A′=3.2215,并对此结果与从亚稳分相系统得到的普适常数有所不同作了初步分析。预计本文的结果在一定程度上可普适于其它系统的分相。     

玻璃分相

以上情况是将分离相之一当作接近100％SiO_2对待的。如分离相的组成不同,添加组分的效果也可能不同。例如在PbO-TiO_2-SiO_2及Li_2O-SiO_2-P_2O_5系统中加入Al_2O_3反而能引起分相。添加少量Pt能引起Na_2O-P_2O_5系统玻璃分相,但对Na_2O-SiO_2系统的分相没有作用。 由于分相机理不同。玻璃的亚微观结构(分相形貌,也称结构)也不相同。以图16BaO-     

铕离子掺杂碱土金属铝硼硅荧光玻璃的制备与发光性能

采用熔融冷却法在空气条件下制备了含不同碱土金属氧化物的铕离子掺杂铝硼硅酸盐玻璃Al_2O_3–B_2O_3–Si O_2–Eu_2O_3–MO(M=Mg,Ca,Sr,Ba),考察了玻璃的密度、摩尔体积、光学碱度等物理性质,分析了玻璃的结构和发光性能。结果表明:从含Mg到含Ba玻璃,摩尔体积逐渐上升,玻璃化转变温度(T_g)依次下降。在381 nm波长激发下,所有玻璃在469 nm处均存在Eu~(2+)的5d→4f跃迁发射,在615 nm处存在Eu~(3+)的~5D_0→~7F_2跃迁发射,表明玻璃在空气中实现了Eu~(3+)→Eu~(2+)的部分还原,其中在含Sr玻璃中,Eu~(3+)还原程度相对最大,Eu~(2+)发光最强。所有玻璃均为非晶态,结构中存在的[BO_4]、[Al O_4]、[Si O_4]四面体网络结构,有利于屏蔽Eu~(2+)不被氧化。从含Mg到含Ba玻璃,四面体网络Q~4结构单元中桥氧键断裂程度上升,形成更多的Q~3、Q~2结构单元,使玻璃结构对称性、致密性下降。在近紫外光激发下,玻璃发光色坐标均位于白光区域内,表明该系列铕离子掺杂铝硼硅玻璃在白光LED上存在潜在应用。     

碱土替换铝硅酸盐玻璃硬度和玻璃转变温度反向演化的结构起源

为探究过铝区碱土铝硅酸盐玻璃随碱土离子替换硬度(HV)和玻璃转变温度(Tg)的演化规律及结构起源,采用激光加热气动悬浮技术,制备了摩尔组成为xRO·(49–x)Al2O3·51SiO2(x=0～16;R=Mg,Ca,Sr,Ba)的系列碱土铝硅酸盐玻璃样品.采用显微维氏硬度仪、差示扫描量热法(DSC)分别对样品的维氏硬度...     

利用Gibbs自由能推导无机盐及偏磷酸盐共熔区

一、前言随着材料科学的发展,很多特殊性质的玻璃相继出现,这些玻璃与通常使用的玻璃不同,有些是使用卤素化合物组成的,如BaF_2-AlF_3-ZrF_4,HfF_4-ThF_4-BaF_2,氯化物—溴化物玻璃如ZnCl_2-KX(X=Cl,Br,I)和PbBr_2-AgBr-CsBr-CdBr_2,还有硝酸盐玻璃如M(NO_3)_2-RNO_3(M=Mg,Ca,Sr,Ba,R=Li,Na,K,Rb,Cs)。又如近年来发展的新的功能玻璃,使用的系统如K_2O-Ta_2O_5-Al_2O_3,     

(Ba1-xSrx)(Mg1/3 Ta2/3)O3微波陶瓷介电性能研究

Ba(Mg1/3Ta2/3)O3(简称BMT)陶瓷是A(B′1/3B″2/3)O3(A=Ba,Sr;B′=Zn,Mg;B″=Nb,Ta)型复合钙钛矿化合物中的一种,A位由Sr离子取代Ba离子,形成(Ba1-xSrx)(Mg1/3Ta2/3)O3(简称BSMT)固溶体型化合物,也具有复合钙钛矿结构。Sr含量x≥0．6时发生相转变,形成一种新的低温相,这是由于氧八面体畸变造成的。这种低温相结构与BMT六方晶系结构相比具有较低的对称性。低温相的形成．可显著降低BSMT陶瓷的烧结温度．在150℃即可烧结致密(BMT为160℃)。BSMT的微观结构和介电性能(如介电常数ε和介电常数温度系数aε)的变化也与此相转变有关。     

Nb_2O_5对高介电常数玻璃微观结构和性能的影响

采用熔融淬冷法制备了50Si O_2·30RO·(20–x)MO_2·x Nb O_(2.5)(R=Ca,Ba,Sr;M=Ti,Zr)(x≤10)高介电常数玻璃。采用Archimedes法测试了玻璃的密度,采用析晶梯度炉测试了玻璃的失透上限温度,采用纳米划痕测试了玻璃弹性模量,采用X射线光电子能谱和核磁共振分析了不同Nb_2O_5含量的玻璃的结构。结果表明:随着Nb_2O_5含量的增加,桥氧数量先增加后减少,形成的[Nb O_6]铌氧八面体会与[Si O_4]顶角相连以增强网络结构;[Si O_4]的存在形态主要为Q~3和Q~4,表明其网络结构更牢固;密度和摩尔体积逐渐增大;失透上限温度先下降再上升;弹性模量先增加后降低。     

烧结温度对粉煤灰-高钛高炉渣微晶泡沫玻璃孔结构与性能的影响

以粉煤灰、高钛高炉渣和废玻璃为主要原料,CaCO_3为发泡剂,Na_2B_4O_7·5H_2O为助熔剂,Na_3PO_4·12H_2O为稳泡剂,通过"一步法"粉末烧结制备了微晶泡沫玻璃。借助DSC、XRD和SEM等分析测试手段研究了烧结温度对微晶泡沫玻璃物相组成、气孔结构、体积密度、孔隙率、吸水率及抗压强度的影响。结果表明:烧结温度变化对样品的物相种类影响不显著,析出的晶体主要为透辉石Ca(Mg,Al)(Si,Al)_2O_6,普通辉石Ca(Mg,Fe)Si_2O_6以及富铝普通辉石Ca(Mg,Fe,Al)(Si,Al)_2O_6,同时还含有少量的硅灰石Ca_3Si_3O_9。随着烧结温度的升高,微晶泡沫玻璃的气孔结构变得越来越均匀。然而,940℃时由于小气孔的合并产生了孔径达到2～4 mm的大孔,导致样品的力学性能很低。综合而言,当烧结温度为900℃时,样品孔径大小合适且均匀性好,所制得的泡沫微晶玻璃具备最优综合性能。     

生物玻璃在模拟生理溶液中的失重规律和界面反应产物间关系的研究

七十年代初,Hench及其合作者对CaO-Na_2O-SiO_2-P_2O_5玻璃进行过系统的研究,并首先研究成功组成(重量％)为:Na_2O24.5,CaO24.5,P_2O_56.0,SiO_245的生物玻璃45S5。进一步研究发现,在45S5某础上改变成分,添加K_2O、CaF_2、B_2O_3、MgO、     

天然沸石及其应用

天然沸石是一族架状构造的含水铝硅酸盐矿物,所含金属阳离子主要是Na、Ca及少量Sr、Ba、Mg等,其硅铝比(Si/Al)和阳离子通常都是变值,它们的化学组成通常用下式表示: (Na.K)_x (Mg.Ca.Sr.Ba),[Al_x+2ySi_n-(x+2_y)·O_2n]·mH_2O 目前已知的天然沸石有40种左右,随着研究工作的进展,新的沸石种类在不断地发现。沸石种类     

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.     

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.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008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、不饱和聚酯树脂、环氧树脂)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.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料，介绍了2005—2006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生产量以及各国塑料制品的进出口情况。作为对比，介绍了中国塑料的生产情况。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（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序，对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。     

Inorganic/organic nanocomposite coatings: The next step in coating performance

Inorganic/organic hybrid materials have considerable promise and are beginning to become a major area of research for many coating usages, including abrasion and corrosion resistance. Our primary approach is to prepare the inorganic phase in situ within the film formation process of the organic phase. The inorganic phase is introduced via sol-gel chemistry into a thermosetting organic phase. By this method, the size, periodicity, spatial positioning, and density of the inorganic phase can be controlled. An important aspect of the inorganic/organic hybrid materials is the coupling agent. The initial task of the coupling agent is to provide uniform mixing of the oligomeric organic phase with the sol-gel precursors, which are otherwise immiscible. UV-curable inorganic/organic hybrid systems have the advantages of a rapid cure and the ability to be used on heat sensitive substrates such as molded plastics. Also, it is possible to have better control of the growth of the inorganic phase using UV curing. It is our ultimate goal to completely separate the curing of inorganic and organic phases to gain complete control over the morphology, and hence optimization of “all” the coating properties. Thus far, it has been found that concomitant UV curing of the inorganic and organic phases using titanium sol-gel precursors afforded nanocomposite coatings which completely block the substrate from UV light while maintaining a transparent to visible light. Also, it has been found that the morphology of the inorganic phase is highly dependent on the concentration and reactivity of the coupling agent. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago, IL.