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1.
催化剂对合成碳化硅晶须的影响   总被引:7,自引:0,他引:7  
以炭黑和SiO2微粉为原料,用双重加热技术合成了碳化硅晶须,考查了催化剂的种类、用量和加入方式对合成碳化硅晶须的影响。研究表明:以Fe2O3为催化剂,用量为原料SiO2总量的2%,在1250℃下、1.5h内可以获得平均直径为0.6μm、平均长度为30μm、生成率达80%的碳化硅晶须。  相似文献   

2.
介绍了一种低成本、大批量生产碳化硅晶须的新方法。以炭黑和SiO2微粉为原料、以氯化钴作催化剂、利用粉末电热体加热技术在较低的合成温度1500℃下、较短的合成时间2h内得到了平均直径为0.52μm、平均长度为16μm、生成率达63%(质量分数)的碳化硅晶须。实验结果表明:与常规加热法相比,粉末电热体加热法不但具有设备投资少、制作简单、操作方便的优点,而且碳化硅晶须的合成温度低、时间短、产量大,易于实现规模化生产。  相似文献   

3.
溶胶-凝胶和碳热还原法合成碳化硅晶须的研究   总被引:5,自引:0,他引:5  
以工业硅溶胶和炭黑为主要原料,用溶胶-凝胶和碳热还原法合成了SiC晶须,获得的产物中碳化硅质量分数高于95%,碳化硅晶须质量分数高于74%,碳化硅晶须为直线形,具有光滑的表面,直径为0.2-0.5μm,长径比约为50-200,对影响碳化硅晶须产率和微观结构的主要因素进行了研究,结果表明:采取原料中碳含量稍多于理论值,并且严格控制反应温度,使得碳化硅的生成速度与碳化硅晶须的形成速度相匹配的措施对于提高产物中的碳化硅晶须含量是非常有效的。  相似文献   

4.
以硅溶胶和炭黑为原料,金属硅、三氧化二铁和硅铁合金为催化剂,采用碳热还原法合成碳化硅晶须,通过XRD及SEM对合成产物的物相及形貌进行分析,探讨了合成温度、催化剂种类、催化剂加入量对合成碳化硅晶须的影响.结果表明:在原料中加入催化剂,合成碳化硅晶须的最佳温度为1550℃;以Si-Fe合金为催化剂合成碳化硅晶须的效果明显好于以Fe2O3和金属硅为催化剂合成效果;Si-Fe合金加入量(占SiO2质量分数)为1%时,晶须生成率高,成直线形,长度10 ~ 50μm,直径0.1 ~0.3 μm.  相似文献   

5.
以硅灰、白炭黑、硅溶胶为硅源,炭黑为碳源,采用碳热还原法合成碳化硅晶须,通过XRD及SEM对合成产物的物相及形貌进行分析,探讨了合成温度(分别为1 400、1 450、1 500、1 550℃)、硅源、n(C)∶n(SiO2)对合成碳化硅晶须的影响.结果表明:n(C)∶n(SiO2)为2.4~3.6,合成温度为1 500 ℃,保温3 h时,硅溶胶与炭黑反应没有生成碳化硅晶须,硅灰、白炭黑与炭黑反应均生成碳化硅晶须;以硅灰为硅源合成碳化硅晶须的质量及数量明显优于以白发黑为硅源合成碳化硅晶须;合成碳化硅晶须的最佳n(C)∶n(SiO2)为3.3.  相似文献   

6.
闫岩  宋波  于萍 《无机盐工业》2007,39(6):41-43
以硅酸钠和硫酸为原料,采用沉淀法工艺,控制釜底液碱浓度0.2~0.3moL/L、反应温度80-95℃、反应时间30-90min、反应pH8-10、熟化时间10-30min,助剂质量浓度15-30g/L,合成透明牙膏组合物用二氧化硅摩擦剂。着重考察了釜底液碱浓度、助剂质量浓度等对二氧化硅性能的影响。此种二氧化硅摩擦剂的比表面积为30-54m^2/g,邻苯二甲酸二丁酯(DBP)吸收值为0.9-1.4mL/g,平均粒径为6~10μm,辐射牙釉质磨损(RDA)值低于150,pH为6-7,水分质量分数为3%-5%。此种二氧化硅引入到透明牙膏中,体系透光率为40%-85%。  相似文献   

7.
碳热还原氮化合成TiN的研究   总被引:2,自引:1,他引:1  
以锐钛矿(中位径0.38μm)、金红石(中位径4.58μm)和鳞片石墨(粒度<0.15mm)、炭黑(平均粒度0.02μm)、可膨胀石墨(粒度<0.15mm)为原料,固定配比nC∶nTiO2为5∶1时分别组成不同的原料组合,并以锐钛矿和鳞片石墨为原料,改变配比nC∶nTiO2分别为3∶1、4∶1、5∶1、6∶1、7∶1和8∶1进行配料,在管式电炉、流动N2中分别于1300℃和1400℃制备了TiN,并进行了合成产物的氧化脱碳试验;采用XRD测定TiN的特征峰(d200=0.212nm)强度,以表征TiN的合成率,研究了原料粒度、反应物活性、反应温度等因素对TiN合成率的影响。结果表明:选用粒度较细或晶格活性大的原料,提高反应温度,均有利于提高TiN粉末的合成率;合成TiN粉末的最佳原料组合是可膨胀石墨和锐钛矿;以鳞片石墨和锐钛矿为原料时,其配比为nC∶nTiO2=6∶1时TiN合成率最高;合成产物中均含有一定量的碳,采用普通的加热氧化法不能除碳,其原因是TiN的氧化温度低于石墨的。  相似文献   

8.
《涂料技术与文摘》2006,27(5):39-40
申请的涂料含层状鳞片二氧化硅(平均直径0.1~2.0μm,厚度0.01~0.5μm,比表面积60~220m/g,硅羟基浓度20~70μmol/m)和聚乙烯醇(如固含量≥95mo1%,成膜后吸水量≤80%,Mn 10 000~80000)。该涂料适用于食品或药物包装和喷墨印刷纸张的受墨涂层成膜物。例如,一种涂料含75:25(%)的Exceval HR 3010(聚乙烯醇,固含量99.0%~99.6%)和SunlovelyLFS HN 050(浮型二氧化硅,平均直径0.5μm)。  相似文献   

9.
在热力学分析的基础上,以B粉和A1粉为原料,直接制备A1B12粉末。通过X射线衍射和扫描电子显微镜分析研究了工艺对合成产物相组成和显微结构的影响,确定了合成过程的最佳工艺参数。结果表明密封法最有利于控制氧化物杂质生成。用密封法合成A1B12粉末的最佳工艺参数为:合成温度1400℃,恒温时间60min,试样中A1的质量分数17.2%,埋粉中A1的质量分数20%。产物主晶相为α—A1B12杂质相为MgAl2O4。A1B12粉体平均粒径4.32μm,比表面积611.76m^2/kg。  相似文献   

10.
唐昆 《炭黑译丛》2007,(11):1-3,14
本发明涉及炭黑的生产,该工艺是加热炭黑生成原料以得到炭黑产品。 炭黑生产工艺是大家所熟悉的,这类工艺大多包括生成高温燃烧气流,然后将炭黑生成原料喷入高温燃烧气流中,以得到含炭黑产物的高温燃烧气流。随后冷却所得气流,最后将所得炭黑与高温燃烧气流分离并进行回收。  相似文献   

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12.
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   

13.
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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15.
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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18.
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   

19.
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。  相似文献   

20.
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.  相似文献   

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