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本文主要针对预氧化聚碳硅烷纤维的恒温烧结过程进行了基础方面的研究。采用XPS、TG -DTG -DTA、IR对预氧化聚碳硅烷原纤维进行标定 ;采用日本精密天平连续跟踪纤维质量变化情况 ,探讨了烧结过程中温度对纤维失重及收缩的影响 ;采用IR、SEM和数码相机分析了纤维恒温烧结过程中微观结构和宏观形貌的变化情况 ,并对预烧结纤维进行了二次烧结 相似文献
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本文主要针对预氧化聚碳硅烷纤维的恒温烧结过程进行了基础方面的研究。采用XPS、TG-DTG-DTA、IR对预氧化聚碳硅烷原纤维进行标定;采用日本精密天平连续跟踪纤维质量变化情况,探讨了烧结过程中温度对纤维失重及收缩的影响;采用IR、SEM和数码相机分析了纤维恒温烧结过程中微观结构和宏观形貌的变化情况,并对预烧结纤维进行了二次烧结。 相似文献
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对聚碳硅烷(PCS)原丝在不同氧化交联温度区间生成的逸出产物进行红外、核磁和GC-MAS分析,并结合交联丝的红外分析,推测氧化交联的机理。结果表明,PCS的氧化交联主要是其Si—H氧化生成Si—OH,后者进而彼此缩合生成Si—O—Si交联结构;氧化交联温度高于150℃时,其部分Si—CH3也开始氧化生成Si—OH并进而交联;同时,在氧化交联过程还发生PCS侧链的热裂解,所形成小分子也通过Si—OH彼此结合,形成较大分子,且其分子量随交联温度的提高而提高。因此,要及时排除氧化交联过程废气,以免逸出产物黏附在纤维表面而导致粘结。 相似文献
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合成了聚碳硅烷树脂,以该树脂为原料制备了SiC纤维。用电镜、红外光谱、X射线衍射、差热分析、热失重等方法对SiC纤维进行了研究,并对以聚碳硅烷树脂作为浸渍物质涂覆石墨进行了初步研究。 相似文献
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以超支化液态聚碳硅烷(LPCS)与固态聚碳硅烷(纯PCS)的共混物作先驱体,熔融纺丝;所得原丝再在热空气气氛中氧化交联,在高温氮气气氛中热裂解,得到碳化硅纤维。研究表明,15%(质量分数)LPCS的加入,可使纯PCS先驱体的纺丝温度,从285℃降低到225℃;纺丝性能和纤维表面质量明显提高;还可以提高氧化交联的效率,降低交联温度,从而减少纤维部分融并、粘结的弊端;虽然纤维的室温力学强度有所降低,但抗氧化性能提高,1400℃氧化交联后,力学性能几乎不变;而纯PCS的力学性能却降为原来的50%。 相似文献
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插层化合物在膨化过程中的热分解动力学 总被引:1,自引:0,他引:1
采用红外傅立叶变换光谱仪与热重分析仪联动装置在线检测HNO3-CH3COOH—GIC、H2SO4-GIC及H2SO4-CH3COOH—GIC等插层石墨的相变及热分解过程,同时通过快速扫描得到相应时间段内分解产物的红外光谱,并运用Kissinger—Ozawa原理计算了几种典型膨化反应的动力学参数。研究结果揭示了膨化过程的热分解机理,当升温速率在20℃/min~80℃/min范围时,由实验数据计算出膨化反应表观活化能不大于120kJ/mol。 相似文献
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研究了聚碳硅烷(PCS)熔体在Y型喷丝孔中的挤出胀大机理、膨胀模型以及膨胀比对Y型碳化硅纤维异形度的影响.结果表明:采用圆形喷丝孔时PCS的膨胀比为1.02~1.15,Y型喷丝孔时膨胀比为1.02~1.43,在与圆形喷丝孔成形条件相当的情况下,Y型喷丝孔的膨胀比比圆形孔的高出约15%,Y型口模周边的剪切应力分布不均、剪切应力内外差异和区域差异是造成其膨胀比增大的根本原因.PCS熔体温度降低或软化点提高,其出口挤出胀大效应增大.由于模口膨胀的影响,Y型PCS纤维的异形度比喷丝孔异形度下降10%~20%. 相似文献
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《Advanced Powder Technology》2014,25(6):1709-1714
This paper was aimed at the thermal decomposition and kinetics of the byproducts from MgO flue gas desulfurization. The effects of particle size and charcoal on thermal decomposition of the byproducts were investigated by the thermogravimetric analysis method, and the non-isothermal kinetic parameters of the byproducts were evaluated with the Coats–Redfern method. The results showed that the mass loss increased with the decrement of the particle size. However, the effect of the particle size on the mass loss of each thermal decomposition stage was different. Increasing the amount of charcoal powder in the byproducts had an obvious effect on the temperature characteristics of the thermal decomposition of magnesium sulfate, resulting in a reduced thermal decomposition temperature which could facilitate the thermal decomposition process. The equations G(α) = 1−(1−α)1/2, G(α) = [−ln(1−α)]2, and G(α) = 1−(1−α)1/3 were the quite appropriate kinetic mechanisms describing the thermal decomposition process of MgCO3, MgSO3, and MgSO4, respectively. 相似文献
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Beyers H Malan SF van der Watt JG de Villiers MM 《Drug development and industrial pharmacy》2000,26(10):1077-1083
Furosemide, a high ceiling diuretic, decomposes on heating and is very sparingly soluble in water. The aim of this study was to identify the thermal decomposition product(s) of furosemide and to calculate the activation energy needed for this reaction. This was done to gain a better understanding of the unusually low water solubility of this drug. The main thermal decomposition product was identified by nuclear magnetic resonance (NMR), mass spectrometry (MS), and infrared (IR) analysis as 4-chloro-5-sulfamoylanthranilic acid (saluamine), and the activation energy, calculated from thermogravimetric analysis (TGA) measurements, for this reaction was 47.7 (±1.93) kcal/mol. The experimentally measured activation energy was well below the normal 59 ± 4 kcal/mol needed for the cleavage of the C-N bond to form saluamine. This could possibly be explained by the weakening of the C-N bond through the I-effect of the furane ring and the delocalization of the electrons of the aniline nitrogen in the chlorosulfamoyl benzoic acid entity of furosemide. This decomposition of furosemide indicates the breaking of intramolecular bonds before those of intermolecular bonds (separation of individual furosemide molecules). Strong inter- and intramolecular bonds are a probable cause for the poor water solubility of furosemide because, when some of the inter- and intramolecular bonds that form part of the hydrogen bond network disappeared, as in the structurally related decomposition product saluamine, the aqueous solubility increased. 相似文献
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Study on thermal decomposition characteristics of AIBN 总被引:1,自引:0,他引:1
It is found that the results such as observed in the differential scanning calorimeter (DSC), which show the major thermal decomposition (TD) of a self-reactive material, lack the detail to reveal what happens at the initial stage of a reaction. The reaction at this stage is corresponding to the handling condition of storage or transportation, often possibly having the potential to be developed to a runaway reaction. This paper examined and compared the thermal behaviors of AIBN at various working conditions in calorimeters and Dewar vessels. The mechanism that affects the initial reaction and self-heating behavior of the given material was clarified. Near its onset decomposition temperature, physical processes, such as sublimation or melting interfered the initial reaction of AIBN. The mutuality of the physical effect and the chemical reaction made AIBN behave differently under different measuring conditions, and as the result, quasi-autocatalysis or TD possibly occurs in the same sample at the handling temperature range. The heat accumulation storage tests in two Dewar vessels presented completely different self-heating behaviors due to this mechanism and heat transfer capability of the vessels. 相似文献
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G. Ya. Gerasimov Yu. M. Pogosbekyan 《Journal of Engineering Physics and Thermophysics》2009,82(1):92-97
A set of experiments on determination of the parameters of the gas release from a mold have been performed. The thickness
of the casting, the thickness of the mold wall, the process time, and the temperature of the charged metal (liquid gray cast
iron) were varied. The investigated molding sands were prepared from quartz sand and organic binders: M19-62 (urea resin),
FF-1S (furanic resin), and PK-104 (phenolic resin). On the basis of the experimental data obtained the kinetic parameters
of the thermal decomposition of the considered resins have been determined.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 92–97, January–February, 2009. 相似文献