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采用高温煅烧法合成了钙钛矿型铁酸镧(LaFeO3)。探讨了煅烧温度及时间对反应产物的影响,通过X射线衍射(XRD)对LaFeO3进行了表征,确定高温煅烧的最佳条件为800℃下煅烧4 h。通过极限氧指数(LOI)、烟密度等级(SDR)及锥形量热(CONE)测试研究了LaFeO3对软质PVC阻燃及消烟性能的影响,使用热重分析(TGA)考察了LaFeO3对PVC热降解过程的影响。结果表明:LaFeO3能有效地降低PVC燃烧过程中的发烟量,使样品燃烧的热释放速率(HRR)、烟释放速率(SPR)以及总烟释放量(TSP)等明显降低;LaFeO3主要在PVC降解的第二阶段发挥阻燃消烟作用,大量稳定的残炭的生成是LaFeO3具有优异消烟性能的主要原因。 相似文献
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重金属汞是燃煤烟气中一种有毒的痕量元素,由于其大气迁移性和生物累积性极易对生态环境和人类健康产生危害,现已成为燃煤烟气四大污染物之一。燃煤电厂现有污染物控制设备(APCDs)协同脱汞技术得到越来越多的研究和应用。湿法烟气脱硫(WFGD)装置已成为脱除烟气中二价汞的重要设备,且具有较高的脱除效率。但是,WFGD装置吸收的Hg2+,在脱硫浆液中还原性离子的作用下被还原为Hg0形态重新释放到烟气中,从而降低了APCDs的协同脱汞效率。笔者综述了湿法脱硫浆液中汞的再释放机理、影响因素、抑制汞再释放的原理以及汞稳定化添加剂的研究进展,详细阐述了烟气氧含量、脱硫浆液温度、浆液p H值、液气比等脱硫系统运行参数以及浆液中SO23-、Cl-、Ca2+等共存离子对汞再释放特性的影响规律;论述了抑制脱硫浆液中汞再释放添加剂的分类、特性以及常用添加剂与Hg2+相互作用的化学反应机理和影响因素;概述了近年来国内外学者对汞稳定化添加剂的最新研究成果,典型有效的添加剂有H2S、无机硫化物、卤化物、Fenton试剂以及有机硫螯合剂二硫代氨基甲酸盐(DTC)、三巯基均三嗪三钠盐(TMT)、三硫代碳酸钠(STC)等。同时分析了不同添加剂的特性、使用条件、汞稳定化效果及其优缺点;概述了现有试验研究存在的问题并提出完善化发展方向,为进一步抑制脱硫浆液中汞的再释放和汞稳定化添加剂的研究与应用提供参考。 相似文献
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一、前言 采用不同的PVC树脂和添加剂设计不同配方,可以获得各种不同用途的PVC塑料。因此研究新型的PVC树脂添加剂、开发新的PVC塑料配方是发展聚氯乙烯工业的重要途径。 Brabender转矩流变仪为此提供了极大的便利。它作为PVC树脂、添加剂及加工条件的实验仪器已被PVC树脂及添加剂的生产者、塑料加工机械制造者和配方研究人员所广泛应用。 相似文献
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热气候下PVC建筑产品的使用表明,需要具有高温下劲度增加的配方。滑石粉一直用作增加挠曲模量的添加剂,但是,这种方法会产生不受欢迎的冲击强度的降低。本文介绍了高温下硬质PVC配混料的劲度增加,同时其室温冲击性能保持不变的实验室研究结果。 相似文献
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聚氯乙烯热稳定性测试方法的研究 总被引:1,自引:0,他引:1
热稳定性是影响聚氯乙烯(PVC)加工和使用的重要性能之一,PVC热稳定测试方法的研究对PVC热稳定剂的研发起到至关重要的作用.从介绍PVC的降解机理入手,系统介绍和论述了白度法、变色法、刚果红法和电导法等聚氯乙烯稳定性能的测试方法,指出了不同测试方法的优缺点与适用范围.这些方法都以高温下聚氯乙烯降解释放HC l并生成共轭双键导致其颜色变化这一降解机理为依据来测试其稳定性. 相似文献
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优化配方提高PVC树脂热稳定性 总被引:1,自引:1,他引:0
聚氯乙烯树脂是用途广泛的塑料品种之一,它具有价廉、难燃、耐腐蚀、绝缘性等许多优点,因而被大量地应用于工业、农业、建筑、化工等行业。PVC树脂在生产过程中,因聚合工艺配方、原料杂质含量等影响,不可避免地在PVC分子链上形成不同程度的缺陷结构,而PVC树脂是在高温和高剪切条件下进行加工制成塑料制品的,这些缺陷结构使PVC树脂不够稳定,受热时容易分解释放出氯化氢,氯化氢又能促进PVC大分子链脱氯化氢反应,导致聚合物降解,引起产品变色,制品力学性能下降, 相似文献
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《上海化工》1999,(23)
索尔唯公司开发回收PVC新工艺 回收纯聚氯乙烯(PVC)的工艺过程是比较顺利的,但从复合材料中回收PVC则还存在一些难题。 位于布鲁塞尔的比利时索尔唯公司最近开发成功一种回收PVC基复合材料的新工艺,能生成与原产品相同的再生PVC树脂,在回收过程中无废水产生。 上述回收过程被称为Vinyloop法,首先将复合材料磨碎,然后把PVC选择性地溶解在一专用的溶剂中,在70~80℃的温度和低压条件下操作。溶解后的塑料从其他固体组分中分离出来。然后加入专用的添加剂,将PVC沉淀出来,PVC呈大小均匀的颗粒,溶剂可以重复利用。 索尔唯公司已将上述Vinyloop过程在一些含PVC的材料中进行小型规模生产,这些材料有防水布、地板、电缆、医用发泡包装材料和车辆挡泥板等。 现正筹建一家年产5000吨的从建筑用防水布和粗帆布中回收PVC和聚酯的工厂,厂址设在法国,预计于2001年建成投产。再生PVC的成本估计为纯树脂的2/3左右。 相似文献
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Effects of support and additive on oxidation state and activity of Pt catalyst in propane combustion 总被引:1,自引:0,他引:1
The effects of support and additive on the oxidation state and catalytic activity of Pt catalyst in the low temperature propane combustion were systematically investigated on Pt/MgO, Pt/Al2O3 and Pt/SiO2–Al2O3. The catalytic activity varied much with both support materials and additives. The catalyst on the more acidic support showed higher activity, and the catalytic activity on every support materials increased as the electronegativity of additives increased, while some additives decreased the activity. The oxidation state of platinum, estimated by white line intensity of Pt LIII-edge XANES spectrum, also varied with the support and additives, and additives with higher electronegativity greatly prevented the platinum from its oxidation under oxidising atmosphere. Among almost all the catalysts with various supports and various additives, a clear relationship was observed between the oxidation state of platinum and the catalytic activity; the more metallic platinum showed higher activity. Thus, it was concluded that the total electrophilic/electrophobic property derived from those of the support and additive controls the oxidation state of platinum, which intensively affects the catalytic activity; i.e. higher electrophilic property provides less oxidised platinum, resulting in high catalytic activity. The mechanism of this effect was also discussed on the basis of thermochemical data, and it was proposed that the electrophobic materials promote the noble metal oxidation since the noble metal oxo-anion such as PtOδ− is more stabilised with electrophobic cation. 相似文献
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Jiawei Meng Huiyi Fang Hongyu Wang Yun Wu Chuncheng Wei Shuang Li Xin Geng Xiaowei Li Jipeng Zhang Guangwu Wen Peng Wang 《International Journal of Applied Ceramic Technology》2023,20(3):1350-1370
Diboride-based ultra-high temperature ceramics (UHTCs) are a special class of ceramics with excellent comprehensive properties, which have extensive potential applications in extreme environments. However, their practical applications are limited, mainly due to the poor fracture toughness and thermal shock resistance. Refractory metals have high melting points, good ductility, and high toughness, which have huge potential to improve the properties of diboride-based ceramics. As a special class of additives, they have been adopted to promote densification, improve microstructure, and properties. However, diboride-based ceramics containing refractory metals have not received adequate attention due to relatively weak practical effects on property improvement. The present review highlights the progress and existing problems of transition metal diborides with refractory metal additives, including W, Ta, Mo, Nb, Hf, V, Cr, and Zr, focusing mainly on the microstructure change and property improvements, followed by challenges and possible future development strategies. 相似文献
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Yuki Nakashima You Zhou Keisuke Tanabe Souhei Arima Kiyoshi Hirao Tatsuki Ohji Manabu Fukushima 《International Journal of Applied Ceramic Technology》2023,20(2):1071-1080
We prepared sintered reaction-bonded silicon nitride ceramics by using yttria and magnesia as sintering additives and evaluated effects of the nitridation temperature on their microstructure, bending strength, fracture toughness, and thermal conductivity. The effects of the nitridation temperature were large, but different depending on the property. The ratio of β-phase in the nitrided compacts significantly increased with increasing the nitridation temperature, whereas their microstructures had no clear difference. Although the bending strength varied, it maintains a high value of 800 MPa. Fracture toughness was almost constant regardless the temperature. The thermal conductivity improved as the β-phase in the nitrided compact increases. This resulted in a decrease of the lattice oxygen content and increase of the thermal conductivity. Therefore, elevating the nitridation temperature and consequently the β-phase ratio should be a promising strategy for achieving compatibly high strength and high thermal conductivity, which are generally known to be in a trade-off relationship. 相似文献
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本研究对已确定的一种改性双马来酰亚胺胶液加入适量热固性树脂或橡胶,测其粘接强度表明,在一定条件下,粘接性得到了明显改善。文中还对效果较好的体系,进行了添加量、固化温度、被粘材料以及存放时间等因素对粘接性影响的探索。 相似文献
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测试了助剂对PVC/MBS体系塑化性能及流变性能的影响。结果表明:①改性树脂AS的加入,能够明显改变PVC/MBS体系的塑化行为,缩短塑化时间,类似于PVC内润滑剂的流变效果,当AS用量提高到4份时,PVC/MBS体系表现出塑化过快、塑化扭矩过高的特征;②随着润滑剂用量的增加,PVC/MBS体系的塑化扭矩降低,塑化时间延长;试验温度升高,PVC/MBS体系的黏度减小,平衡扭矩降低。 相似文献
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文章讨论了影响乳胶漆外观品质的因素,从颜填料细度、乳液、乳胶漆助剂和生产工艺四个方面分析了它们对乳胶漆外观品质的影响;并提出了乳胶漆外观品质的控制方法,只有搭配好乳胶漆配方中乳液、颜填料、助剂等诸要素和使用正确的生产工艺,才能生产出好的外观品质的乳胶漆,这对于乳胶漆生产过程中的质量品质控制有积极的指导意义。 相似文献
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外加剂对熔融石英陶瓷烧结性能的影响 总被引:6,自引:1,他引:6
为改善熔融石英陶瓷材料的低温烧结性能 ,选用石英玻璃粉为主要原料 ,研究了H3 BO3 、B4C、Si、SiC、CeO2 和Y2 O3 六种外加剂对熔融石英陶瓷烧结性能的影响。结果表明 :添加Si、SiC、CeO2和Y2 O3 时对熔融石英陶瓷的低温烧结的促进作用较小 ;H3 BO3 和B4C能有效地促进熔融石英陶瓷的烧结 ,加入相同量的H3 BO3 和B4C外加剂时 ,B4C对材料烧结性能的影响明显强于H3 BO3 。H3 BO3 的高温分解产物和B4C的氧化产物均为B2 O3 ,高温下B2 O3 能增加材料中的液相生成量 ,加快材料的扩散传质 ,从而促进材料的烧结。 相似文献