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大同石炭二迭系煤层夹矸,经控温煅烧的偏高岭石具有良好的水化活性。将一定比例的大同偏高岭石粉掺合到水泥中,能显著改善混凝土的力学特性,极大地提高混凝土的密实度和机械强度,使混凝土有良好的工作性能。对比试验发现600℃低温煅烧的大同偏高岭石粉作为水泥掺合料制得混凝土的抗压强度,超过了掺合其他温度煅烧的偏高岭石的抗压强度,掺合20%～30%的600℃煅烧的大同偏高岭石到水泥中,制备的混凝土试样抗压强度表现出优良的机械性能。该研究为大同煤矸石制备高性能混凝土利用提供了科学依据。 相似文献
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以碳酸氢铵为沉淀剂,采用化学共沉淀法合成出多晶Nd：YAG纳米陶瓷粉体．采用XRD,SEM,BET等测试手段对粉体的相组成和微观结构进行表征,研究了煅烧温度、反应温度、Al（NO3）3浓度对粉体形貌、粒径以及分散性的影响．结果表明：前驱体在900℃煅烧2h直接生成Nd：YAG,并且随着煅烧温度的升高,粉体粒径逐渐变大,1100℃时煅烧所得粉体的平均粒径约为70nm．反应温度为30～40℃、硝酸铝溶液浓度为0．1～0．2mol／L时,所得粉体为球形或类球形,分散性最佳． 相似文献
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通过溶胶-凝胶法制备Ti O2粉末,对Ti O2粉末进行了XRD、DRS表征,探讨了二氧化钛的煅烧温度和稀土掺杂对其光催化性能的影响.结果表明,随煅烧温度升高,Ti O2逐渐由无定型向锐钛矿转化,当温度高到700℃开始出现金红石型,制备锐钛矿Ti O2的最佳煅烧温度为500℃.稀土离子掺杂扩展了Ti O2的光响应范围,同时提高了晶体的热稳定性,从而抑制Ti O2晶粒生长,有利于提高二氧化钛光催化活性. 相似文献
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以钛酸四丁酯为钛源,AgNO_3水溶液为介质,室温下水解合成Ag-TiO_2复合材料,然后在不同温度下煅烧;并对材料进行XRD、SEM表征,最后测试其光催化活性.结果表明:煅烧温度能够影响复合材料的形貌、材料后续相变及其光催化活性.煅烧温度为600℃时,TiO_2为锐钛矿型并且形貌均匀、粒径均一;30 W紫外光照下100 min,复合材料对罗丹明B的降解效率为98.51%;煅烧温度为700℃时,TiO_2由锐钛矿型部分转变为金红石型,光催化降解效率开始下降(97.46%);800℃时,TiO_2已全部转化为金红石型,光催化降解效率为94.8%.该合成方法简单、温和、绿色环保、不引入任何模板剂,得到的材料光催化效果佳. 相似文献
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通过试验研究碱激发地聚合物胶凝材料制备技术的优化条件。确定了偏高岭土在马弗炉中经710℃煅烧6h,高岭石结构转化为无定形结构的偏高岭土,有较高的火山灰活性;确定了模数为1.2,波美度为40%的改性水玻璃,其碱度与波美度刚好可以最大限度地激发偏高岭土的地聚合反应,而且也具有很好的工作性能,同时确定了温度为20±3℃,相对湿度95%以上的标准养护制度下最适合碱激发地聚合物强度的发展。 相似文献
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王琼 《湖南科技学院学报》2006,27(11):278-280
运用模板法并结合酸碱对理论来合成多孔材料TiPOx，并时不同条件下所得到的TiPOx材料分别用广角X射线衍射、低角X射线衍射和N2吸脱附等实验进行了表征。实验结果表明：煅烧时间和煅烧气氛等因素对多孔材料的孔结构影响不大，它们并没有改变孔的类型和孔的有序性，影响孔结构的主要因素是煅烧温度，当煅烧温度达到600℃高温时，材料的孔洞发生坍塌，孔的有序性变差。 相似文献
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煤矸石是与煤伴生的岩石;其中氧化铝的含量在22％～30％之间,含量高者可达35％,有较高的利用价值．用浓盐酸浸取煤矸石烧渣可得到结晶氯化铝,可作为较好的净水剂,既可废物利用,又可减少环境污染和占用耕地．一、制备原理煤矸石的主要成分是铝和磋的氧化物,在750—99℃下煅烧．煤矸石中含水高岭石、5水铝矿石等,即可分解脱水生成活性高的γ-Al2O3,用浓盐酸浸取,则γ－Al2O3和盐酸反应生成氨化铝而被溶出,经沉降、洗涤、浓缩、抽滤,即可得产品一结晶氯化铝．二、生产过程1．煅烧将煤矸石投入沸腾炉在750—900“C下银烧4至5小时… 相似文献
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《佳木斯教育学院学报》2018,(1)
钒酸锌纳米材料是一种新型多元过渡族金属氧化物,有着特殊的晶体结构及优异的性能[1]。本实验采用水热合成方法,采用X射线衍射(XRD)、扫描电镜(SEM)等测试手段进行形貌表征和测试分析。结果表明:在不同温度和时间条件下,生成了焦钒酸锌样品且随着温度和时间的升高,样品的形貌由原来的带状产物变少而线状产物变多。当煅烧的温度为600℃时,才能产生钒酸锌样品,形貌得到了重新的结晶并变成颗粒状。 相似文献
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《西安文理学院学报》2021,(4)
煤泥矿物成分主要以粘土质矿物和石英砂为主,有机质主要以—COOH、—OH、—C=O和—OCH:等烯烃类、烷基侧链和杂原子官能团等形式存在,升温过程中有机质在400℃左右分解生成多孔碳.当温度升高至1 200℃时,有机质裂解多孔碳相继与煤泥中石英砂、偏高岭石高温分解生成方石英和莫来石高温分解生成的方石英发生反应生产β-SiC,而添加石英砂煤泥样品则主要发生多孔碳与添加石英砂之间反应,伴随有微量SiC纤维相生成.煤泥中少量长石相和含钙矿物相也相继发生反应促进SiC晶相生成,微量重金属元素分别起到提高材料性能、促进反应烧结等作用. 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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唐芳 《读与写:教育教学刊》2008,5(6)
During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context. 相似文献