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以聚锆氧烷为锆源,聚硼硅氮烷兼作硼源、硅源和碳源,通过共混得到ZrB2/SiC液相前驱体,该前驱体经高温裂解得到ZrB2/SiC复相陶瓷.对ZrB2/SiC前驱体的裂解行为、陶瓷产物结构及微观形貌进行了表征.结果表明,ZrB2/SiC前驱体经1400℃裂解后保持无定形状态,1500℃处理后析出t-ZrO2晶体,1600℃时体系发生碳热还原反应生成ZrC,同时析出SiC晶体,1700℃时生成ZrB2,最终陶瓷产物晶相组成为ZrB2/SiC.在1500~2000℃范围内,随着处理温度的升高,陶瓷由致密结构变为多孔结构,最终陶瓷产物由尺寸为100~300 nm的纳米颗粒堆积而成,各元素分布均匀. 相似文献
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采用聚甲基乙烯基硅氮烷与异丙醇铝在90、100和120℃下反应分别合成出Si/Al物质的量的比为3的聚铝硅氮烷。利用红外(FTIR)和核磁(NMR)对前驱体结构进行表征。结果表明:Al-N键的红外振动强度(1 450 cm-1)和核磁铝谱中的AlON2(8ppm)及AlO2N(-1 ppm)基团的强度随合成温度的增加而增加。反应温度越高,形成的Al-N键就越多。这个脱氢耦合合成过程可能是一个三级反应过程,而在最高温120℃下所合成的聚铝硅氮烷的结构最复杂。前驱体的裂解过程通过耦合热重/差热分析(TG/DTA)、FTIR和气相色谱(GC)进行研究。合成温度对陶瓷化过程和陶瓷产率并没有明显的影响。根据DTA曲线可知,475℃发生进一步的交联。另外,GC数据表明裂解时所释放的气体为低分子量硅氮烷、CH4、C2H4、H2和NH3。根据XRD和SEM可知,1200℃裂解后产物为均匀的非晶相。 相似文献
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以三氯化硼和甲基氢二氯硅烷为原料,采用共氨解的方式合成了聚硼硅氮烷前驱体,并采用核磁共振波谱仪、傅里叶红外光谱仪、差式扫描量热仪、热重分析仪、光电子能谱、网络矢量分析仪等仪器对前驱体及其热解产物进行了表征。前驱体在1000 oC、氮气气氛下热解的陶瓷产率为71.1 %。在氨气气氛下热解可以有效降低热解产物中的碳含量,聚硼硅氮烷在900 oC氨气气氛下热解产物的碳含量低于1 %,并且该热解产物具有高的结晶温度、良好的抗氧化性能和介电性能,有望用于耐高温陶瓷基透波复合材料。 相似文献
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聚合物先驱体转化法作为制备SiBCN陶瓷及其复合材料的重要途径,具有成型温度低、产物结构和组成可控等优点.设计合成合适的聚合物先驱体是提高陶瓷产率和性能的关键因素之一,本文采用三氯环硼氮烷(TCB)与乙炔基氯化镁进行反应,合成了乙炔基环硼氮烷,进而与二氯硅烷和二氯甲基乙烯基硅烷进行共氨解反应,制备了聚硼硅氮烷先驱体(PBSZ)并进行了高温裂解.采用综合热分析(TG-DSG)对其陶瓷化过程进行了分析,并采用XRD和SEM对陶瓷化产物的结构进行了表征.PBSZ在室温下是液态,易溶于二氯甲烷和氯仿等溶剂,可加工性优良.基于PBSZ先驱体的SiBCN陶瓷产率超过80%;陶瓷化产物在1400℃以下为无定形状态,在1500℃可形成由α-Si3N4,β-Si3N4,h-BN和SiO2晶体结构组成的陶瓷;陶瓷产物表面致密平整且具有优异的热稳定性和氧化性能,表明聚硼硅氮烷(PBSZ)有望成为高陶瓷产率和高性能陶瓷的重要先驱体. 相似文献
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以二氯甲基硅烷、三氯化硼、六甲基二硅氮烷为起始原料,采用缩聚法合成了新型SiBNC陶瓷前驱体--聚硼硅氮烷(PBSZ),其产率达90%. 通过调节二氯甲基硅烷的用量可获得不同软化点的前驱体. 采用改进的毛细管流变仪,首次对熔融纺丝状态时PBSZ的流变特性进行了研究. 结果表明,PBSZ熔融纺丝时,剪切速率在10~110 s~(-1)范围内时,为切力变稀流体,非牛顿指数为0.83~0.90,表观粘度为440~2 460 Pa·s,粘流活化能约为142 kJ/mol. PBSZ纺丝性能良好,纤维连续无断头长度>1 600 m,纤维直径<20 μm. 相似文献
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R. Peña-Alonso J. Rubio F. Rubio J.L. Oteo 《Journal of Sol-Gel Science and Technology》2003,26(1-3):195-199
Mixed vitreous oxycarbide glasses containing silicon and boron were prepared by pyrolysis of hybrid precursors in N2 at 1100°C. Four different precursors were synthesized through the sol-gel process using TEOS, TEB and PDMS. Poly-condensation between the Si(OH) groups, from the hydrolysed TEOS, and the PDMS was observed by FT-IR spectroscopy. Boron seems not to incorporate into the network until pyrolysis of the precursors that form the oxycarbides. The oxycarbides were porous made of spherical interconnected particles. The porosity and mean pore size of the glasses increased with increasing TEB content. 相似文献
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Control of the Composition and Structure of Silicon Oxycarbide and Oxynitride Glasses Derived from Polysiloxane Precursors 总被引:1,自引:0,他引:1
The reactions involved in the preparation of silicon oxycarbide and oxynitride glasses by pyrolysis of polysiloxane precursors respectively under argon and ammonia are reviewed. The influence of the composition and structure of the precursor and of these pyrolysis reactions on the pyrolysis yield, the composition, and the structure of the glass is discussed. The free-carbon content of the glass depends on the substituents in the precursor and on the nature of the pyrolysis atmosphere. The composition of the oxynitride or the oxycarbide phase depends on the O/Si ratio of the precursor. The structure of these phases is not directly related to the structure of the precursors, but rather depends on their composition and on the pyrolysis temperature. 相似文献
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富氮生物质原料热解过程中NOx前驱物释放特性研究 《燃料化学学报》2016,44(12):1464-1472
利用热重分析-傅里叶红外光谱联用(TG-FTIR)和水平管式炉-X射线光电子能谱(XPS)研究了两种富氮生物质原料(大豆秸秆(SBS)和纤维板(FB))热解过程中NO_x前驱物(NH_3、HCN和HNCO)的释放特性,考察温度、升温速率及燃料含N物质结构对其NO_x前驱物释放行为的影响。结果表明,燃料中的N来源不同(天然固有与人工添加)造成其转化差异:SBS释放的NO_x前驱物主要为NH_3而FB为NH_3、HCN(快速)和HNCO(慢速);FB气相N主要随挥发分析出,而SBS则相反,在二次反应阶段析出;两种燃料中N的转化随温度变化,低温下富集于半焦N,600℃以上时更多向非半焦N转移,NO_x前驱物以NH_3为主,高温及高升温速率利于HCN生成,若以减排NO_x为目的,热解温度控制在600℃为佳;两种燃料中N的结构均为胺类N(N-A),热解时部分N-A向半焦中杂环N转化,同时伴随杂环N分解;高温下吡啶N和吡咯N分解分别主要产生HCN和NH_3。 相似文献
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采用质谱技术实时研究了金属有机源DIPTe和DMCd在MOCVD反应器中热裂解的性质。着重分析了可能发生的气相反应及热裂解机理,并探讨了在CdTe,HgCdTe实际生长条件下两个有机源之间可能发生的相互作用及其对热裂解温度的影响。 相似文献
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药渣热解过程NO_x前驱物生成特征及规律研究 总被引:1,自引:0,他引:1
药渣热解过程NOx前驱物生成特征及规律研究 《燃料化学学报》2017,45(3):279-288
以凉茶药渣(HTW)和青霉素菌渣(PMW)为对象,结合热重(TGA)和X射线光电子能谱(XPS)表征,在水平管式反应器上对比研究了热解NO_x前驱物的生成特征,考察了热力因素和燃料理化特性的影响。结果表明,蛋白质N为主要原料N结构,HTW占全部,PMW超过80%,决定了主导NO_x前驱物为NH_3;热力因素不改变此主导性,但会影响前驱物生成路径,改变组分比例及总产率,其强弱顺序为:高温快速高温慢速低温快速≈低温慢速;基于高温快速热解,大粒径和低含水率可分别降低总产率5%-11%和4%-6%;燃料组分影响NH_3产率,低温或慢速下,N结构差别使PMWHTW;高温快速下,灰分元素差异使PMWHTW;半焦N结构及N分布表明,典型热解条件下总产率为20%-45%,与药渣种类无关,可为其清洁利用提供参考。 相似文献
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W.-C. Xie X.-H. Gu Z.-C. Tan J. Tang G.-Y. Wang C.-R. Luo L.-X. Sun 《Journal of Thermal Analysis and Calorimetry》2007,87(2):505-510
To develop thermal stable flavor, two glycosidic
bound flavor precursors, geranyl-tetraacetyl-β-D-glucopyranoside
(GLY-A) and geranyl-β-D-glucopyranoside
(GLY-B) were synthesized by the modified Koenigs–Knorr reaction. The
thermal decomposition process and pyrolysis products of the two glycosides
were extensively investigated by thermogravimetry (TG), differential scanning
calorimeter (DSC) and on-line pyrolysis-gas chromatography mass spectroscopy
(Py-GC-MS). TG showed the T
p
of GLY-A and GLY-B were 254.6 and 275.7°C. The T
peak
of GLY-A and GLY-B measured by DSC were 254.8 and 262.1°C respectively.
Py-GC-MS was used for the simply qualitative analysis of the pyrolysis
products at 300 and 400°C. The results indicated that: 1) A large amount
of geraniol and few by-products were produced at 300°C, the by-products
were significantly increased at 400°C; 2) The characteristic pyrolysis
product was geraniol; 3) The primary decomposition reaction was the cleavage
of O-glycosidic bound of the two glycosides flavor precursors. The study on
the thermal behavior and pyrolysis products of the two glycosides showed that
this kind of flavor precursors could be used for providing the foodstuff with
specific flavor during heating process. 相似文献
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In recent years it has been realized by geochemists that pyrolysis techniques can provide successful and rapid analyses of sedimentary organic material, including petroleums, coals, oil shales and their precursors. This article represents an introductory overview of the literature of the last 25 years pertaining to geochemical pyrolysis studies. The overview introduces non-geochemists to the many areas in academic and industrial geochemistry to which pyrolysis in general, and analytical pyrolysis in particular, are applicable. 相似文献
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Ehsan Jazaeri Liyuan Zhang Xungai Wang Takuya Tsuzuki 《Cellulose (London, England)》2011,18(6):1481-1485
The possibility of fabricating carbon nanofibers from cellulose nanofibers was investigated. Cellulose nanofiber of ~50 nm
in diameter was produced using ball milling in an eco-friendly manner. The effect of the drying techniques of cellulose nanofibers
on the morphology of carbon residue was studied. After pyrolysis of freeze-dried cellulose nanofibers below 600 °C, amorphous
carbon fibers of ~20 nm in diameter were obtained. The pyrolysis of oven-dried precursors resulted in the loss of original
fibrous structures. The different results arising from the two drying techniques are attributed to the difference in the spatial
distance between cellulose nanofiber precursors. 相似文献
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以城市污泥(SS)、中药药渣(HTW)和硅藻(DT)为对象,在水平管式反应器上对比研究了水热处理前后样品在热解过程中NO_x前驱物的生成特征,并结合热重(TGA)和X射线光电子能谱(XPS)表征分析了该耦合过程对NO_x前驱物的影响机制。结果表明,在240℃下进行水热预处理能直接或间接地影响样品燃料N在不同热解阶段时的转化路径,从而在整体层面上降低NO_x前驱物的释放量,例如当热解温度为900℃时,源于水热焦燃料N的NO_x前驱物为55.0%(SS_(240))、48.1%(HTW_(240))和51.2%(DT_(240)),比未经处理样品的NO_x前驱物释放量分别少9.5%(SS)、6.0%(HTW)和15.4%(DT),但若以原料燃料N为基准,源于水热焦的NO_x前驱物则比未经处理样品的NO_x前驱物释放量分别少90.1%(SS)、41.9%(HTW)和59.8%(DT),并且对NH_3的抑制效果高于HCN。进一步根据热失重曲线及其半焦N官能团的演变规律可以推测,水热预处理对NO_x前驱物的两条影响机制,即含N官能团的脱除(对于初次反应的NH_3释放)与含N官能团的稳定化(对于二次反应的HCN释放),可为废弃物的清洁利用提供理论参考。 相似文献