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以Al(OH)3和H3BO3为原料,分别以MnO2、Fe2O3为助熔剂制备硼酸铝晶须,研究助熔剂对晶须形貌的影响。研究发现,在1350℃煅烧6h,试样的物相为硼酸铝(9Al2O3·2B2O3)。以MnO2为助熔剂的试样晶须的直径为1μm~6μm,长径比较小;以Fe2O3为助熔剂的试样晶须的直径为0.2μm~1μm,长径比〉10。 相似文献
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探讨了一种合成氧化镁晶须的新的工艺方法。首先以活性氧化镁和氯化镁为原料合成了前驱体碱式氯化镁晶须,接着将碱式氯化镁焙烧成氧化镁晶须。分别用X射线衍射仪(XRD)、扫描电镜(SEM)、热重分析仪(TGA)和化学分析,分析了中间体碱式氯化镁和产品氧化镁晶须的成分、形貌和热化学行为。探讨了各个工艺条件对产物的影响,探索出最佳的工艺条件:活性氧化镁与氯化镁的物质的量比在0.08左右,氯化镁溶液的浓度为3mol/L,反应温度40~50℃,陈化时间在48-72h,陈化温度50℃。在此条件下制得了形貌良好的前驱物碱式氯化镁晶须。将碱式氯化镁晶须焙烧,控制升温速率在2—5℃/min,采取分段升温方式升温至600℃,即可制得氧化镁晶须。制得的晶须长度在100μm左右,直径约0.5μm。 相似文献
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四针状氧化锌晶须的制备 总被引:5,自引:0,他引:5
用锌粉氧化的方法,通过控制反应器内的气相过饱和度,可以获得不同尺度的四针状氧化锌晶须(T-ZnOW)。合成出的ZnO的晶须纯度高,晶体结构完整,晶须尺度可控(针长为10-60μm,根部尺寸约为1-6μm)。晶须的生长机理为气-固(VS)机理。 相似文献
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为提高煤气化炉用碳化硅-尖晶石复合材料的力学性能,以SiC颗粒(≤2.5 mm)、尖晶石细粉(≤90μm)、α-Al2O3微粉(d50≈5μm)和金属Al粉(≤74μm)为主要原料,在氮气气氛中进行热处理,制备了SiC-MgAl2O4-Al复合材料。分析了200~1 600℃不同热处理温度对复合材料显微结构、物相组成和力学性能的影响。结果表明:1)当热处理温度大于1 000℃时,复合材料中的Al开始逐渐反应生成Al-O-C-N晶须,可显著提升材料的力学性能。2)常温和热态抗折强度随着复合材料内Al-O-C-N晶须含量的增多和尺寸的增大而提高。通过调整热处理温度可调控材料内Al-O-C-N晶须的物相组成、含量和形貌等,从而实现对复合材料物相组成与显微结构的调控,提升材料的力学性能。 相似文献
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《耐火材料》2018,(5)
为了获得长度较长、长径比大的莫来石晶须,以w(Al_2O_3)98%、d_(50)=3μm的α-Al_2O_3微粉为铝源,w(SiO_2)95%、d_(50)=2μm的熔融石英和工业级硅溶胶为硅源,工业级Al F_3·3H_2O为助剂,PAA为发泡剂,采用发泡法-溶胶凝胶成型工艺制备莫来石晶须,研究了Al F_3·3H_2O添加量(w)分别为2.5%、5%、7.5%、10%和15%以及热处理温度分别为1 200、1 300、1 400、1 500和1 600℃时对试样莫来石化及生成晶须形貌的影响,并用XRD、SEM对热处理后试样的物相组成及显微结构进行了分析。结果表明:1)制备莫来石晶须的最佳工艺条件是Al F_3·3H_2O添加量为7.5%(w),热处理条件为1 500℃保温6 h;2)生成的莫来石晶须长度可达360μm,直径3~9μm,长径比40~120;3)莫来石晶须的生长机制遵循气-固(VS)机制。 相似文献
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M. S. J. Simmonds W. M. Blaney F. Delle Monache M. Marquina Mac-Quhae G. B. Marini Bettolo 《Journal of chemical ecology》1985,11(12):1593-1599
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. 相似文献
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Cheng-Le Zhao Shane Porzio Alan Smith Haiyan Ge H. T. Davis L. E. Scriven 《Journal of Coatings Technology and Research》2006,3(2):109-115
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. 相似文献
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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. 相似文献
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Peter A. Edwards Grant Striemer Dean C. Webster 《Journal of Coatings Technology and Research》2005,2(7):517-527
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. 相似文献
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Dongjiang Yang Yao Xu Lei Zhang Shangru Zhai Dong Wu Yuhan Sun 《Journal of Coatings Technology and Research》2006,3(2):127-131
A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by 1H MAS NMR. For direct comparison purposes, an SiO2 coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N2 absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals. 相似文献
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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. 相似文献