共查询到20条相似文献,搜索用时 312 毫秒
1.
在硫酸钠熔盐中合成莫来石的热力学研究 总被引:5,自引:0,他引:5
以硫酸铝和二氧化硅为原料,以硫酸钠为介质合成莫来石粉体.利用差示扫描量热法研究了合成过程中的热量变化.由理论数据与实验数据分别经过计算得到的反应热变化基本一致,从而确定了合成反应的温度范围应在950~1 000℃之间.利用X射线衍射仪和场致发射扫描电子显微镜等手段对合成粉体的相组成、结构和形貌进行了研究.结果表明:在1 000℃保温3 h合成的莫来石粉体基本无其他相存在,其粉体呈针状晶须,直径约50~100 nm,长度约3~8 um.该方法工艺简单,合成温度较其它方法低200~400℃. 相似文献
2.
水热合成NaNbO3粉体的研究 总被引:1,自引:1,他引:0
采用Nb2O5,NaOH为反应原料,在180℃~200℃下通过水热法合成出结晶度高、晶粒发育完整的NaNbO3粉体。利用X射线衍射分析(XRD)对产物的物相结构进行了表征,并用扫描电子显微镜(SEM)观察了晶粒的结晶形貌、尺寸以及分布情况。研究结果表明:合成的NaNbO3粉体为正交相结构,晶胞参数a=5.569,b=15.523,c=5.505;水热合成温度影响体系的反应速度,温度越高反应速度越快;晶粒的尺寸随着反应时间的增加而增大。 相似文献
3.
《硅酸盐学报》2016,(12)
以硅粉和液态酚醛树脂为原料,硝酸镍为催化剂前驱体,采用催化反应的方法制备了碳化硅粉体。研究了反应温度、催化剂用量、保温时间和碳硅摩尔比等对合成碳化硅粉体的影响,采用X射线衍射、场发射扫描电子显微镜和透射电子显微镜分析了产物的物相组成和显微结构。结果表明:无催化剂时,β-SiC的合成条件为1 350℃保温3 h,所合成的β-SiC大部分为颗粒状,仅有极少量晶须生成;当添加0.50%的Ni作催化剂、n(C):n(Si)=1.2:1.0时,1 300℃保温3h即可合成纯相的β-SiC,且制备的试样中有大量β-SiC晶须生成。β-SiC晶须的生长机理主要为固-液-气-固机理。 相似文献
4.
5.
以CaCO3和ZrO2为原料,CaCl2为熔剂,在熔盐条件下合成CaZrO3粉体,考察了原料配比、保温时间和煅烧温度对合成过程的影响,通过X射线衍射分析和扫描电子显微镜对合成产物的物相组成和颗粒形貌进行了分析。结果表明,提高CaCO3和熔盐的量有利于合成反应的进行。最佳工艺条件为CaCO3、ZrO2、CaCl2摩尔比为1.2:1.0:1.2,烧成温度和保温时间分别为900℃和3 h。在最佳工艺条件下制备出的CaZrO3粉体粒度为1.0~2.0μm,分散性好,颗粒呈四方体状。以CaCl2为熔盐时,合成CaZrO3的反应机制为"模板生长"和"溶解–析出"两种形式共存。 相似文献
6.
7.
以草酸钠和氢氧化钽为原料,少量水为溶剂,在红外灯下充分研磨烘干后得到前驱体。利用热重分析(TG)技术对前驱体进行分析。将制备的前驱体分别在500℃、600℃、700℃、800℃下焙烧3 h,得到的产物均为单相的NaTaO3粉体。通过X-射线衍射仪(XRD)、扫描电镜(SEM)及FTIR对产物进行表征。在500℃焙烧下得到的NaTaO3粉体,XRD分析计算其晶粒直径为43 nm,通过扫描电镜(SEM)证实其颗粒小于100 nm。在FT-IR谱图中615cm-1处存在Ta-O键的特征吸收峰,经紫外-可见漫反射光谱(UV-Vis)表征、计算得出NaTaO3粉体的能隙为3.96 eV。 相似文献
8.
9.
利用氯化钾作熔盐,采用熔盐方法利用高温煅烧制备了Bi3NbTiO9陶瓷粉体,研究了煅烧温度,保温时间和粉体合成之间的关系。结果表明:氧化钾能够有效降低Bi3NbTiO9粉体的合成温度和提高粉体的合成速率。熔盐方法获得纯Bi3NbTiO9相的温度要比固相方法降低约150℃。和保温温度相比较,保温时间对晶粒尺寸的影响有限。 相似文献
10.
Effect of Ca-compound on low temperature synthesis of AIN ultrafine powders by carbothermal reduction nitride route from sol-gel precursor 下载免费PDF全文
YANG Qinghua WANG Huanping ZHANG Wenjuan CHEN Shuwen HUA Youjie WANG Shifeng XU Shiqing 《化工学报》2012,63(6)
以硝酸铝、葡萄糖和硝酸钙为原料,通过溶胶-凝胶工艺获得了组分均匀的Al2 O3、C和CaO前驱体,进而利用碳热还原反应合成超细氮化铝粉体,探讨了钙助剂对氮化铝合成温度及粉体颗粒生长的影响规律.结果表明:钙助剂的添加,通过与前驱体中氧化铝在较低温度下发生反应,先后生成CaAl4 O7、Ca3 Al10O18、CaAl2 O4和Ca12Al14O33等铝酸钙相;上述铝酸钙相能在较低温度下形成液相,可有效促进氮化铝的合成和粉体颗粒的生长,从而在1400℃合成纯相氮化铝.当原料中钙铝摩尔比为0.0262时,在1350℃氮化得到了粒径60~80 nm的氮化铝粉体,仅有少量铝酸钙相存在;当氮化温度上升至1400℃时,铝酸钙相因挥发而消失,得到粒径100~180 nm的单相氮化铝粉体. 相似文献
11.
乙烯酮(双乙烯酮)是十分重要的化工中间体,其下游产品较多。江苏某化工厂开发生产乙烯酮(双乙烯酮)下游产品三十多个,年生产规模三万多吨,是国内以乙烯酮(双乙烯酮)为中间体生产精细化学品的综合骨干企业。针对乙烯酮(双乙烯酮)下游产品废水特点,该厂结合企业实际,开展了产品优化,结构调整,清洁生产,资源循环利用,节水降耗等工作,从源头削减了污染物的生产。同时投资二千多万元新建预处理装置三套,6000m3/d废水生化处理装置一套,使全厂乙烯酮(双乙烯酮)下游产品的废水得到了有效的治理。 相似文献
12.
D. G. Gordeev L. F. Gudarenko M. V. Zhernokletov V. G. Kudel’kin M. A. Mochalov 《Combustion, Explosion, and Shock Waves》2008,44(2):177-189
A semi-empirical equation of state for metals is described. Its capabilities are demonstrated by the example of the equation
of state for aluminum. New experimental data are presented on the location of the isentrope of aluminum for unloading from
the state at p = 229.71 GPa on the shock adiabat to an aerogel (SiO2) of density 0.08 g/cm3.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 61–75, March–April, 2008. 相似文献
13.
15.
16.
Jorge Marcelo Romero Soledad Bustillo Hugo Enrique Ramirez Maisuls Nelly Lidia Jorge Manuel Eduardo Gómez Vara Eduardo Alberto Castro Alicia H. Jubert 《International journal of molecular sciences》2007,8(7):688-694
A thermochemical rather simple experimental technique is applied to determine the enthalpy of formation of Diperoxide of ciclohexanone. The study is complemented with suitable theoretical calculations at the semiempirical and ab initio levels. A particular satisfactory agreement between both ways is found for the ab initio calculation at the 6–311G basis This set level. Some possible extensions of the present procedure are pointed out. 相似文献
17.
The objective of the study was to explore the effect of the degree of deacetylation (DD) of the chitosan used on the degradation rate and rate constant during ultrasonic degradation. Chitin was extracted from red shrimp process waste. Four different DD chitosans were prepared from chitin by alkali deacetylation. Those chitosans were degraded by ultrasonic radiation to different molecular weights. Changes of the molecular weight were determined by light scattering, and data of molecular weight changes were used to calculate the degradation rate and rate constant. The results were as follows: The molecular weight of chitosans decreased with an increasing ultrasonication time. The curves of the molecular weight versus the ultrasonication time were broken at 1‐h treatment. The degradation rate and rate constant of sonolysis decreased with an increasing ultrasonication time. This may be because the chances of being attacked by the cavitation energy increased with an increasing molecular weight species and may be because smaller molecular weight species have shorter relaxation times and, thus, can alleviate the sonication stress easier. However, the degradation rate and rate constant of sonolysis increased with an increasing DD of the chitosan used. This may be because the flexibilitier molecules of higher DD chitosans are more susceptible to the shear force of elongation flow generated by the cavitation field or due to the bond energy difference of acetamido and β‐1,4‐glucoside linkage or hydrogen bonds. Breakage of the β‐1,4‐glucoside linkage will result in lower molecular weight and an increasing reaction rate and rate constant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3526–3531, 2003 相似文献
18.
19.
醋酸纤维素取代基分布与性质的关系 总被引:9,自引:0,他引:9
分析了以吡啶为溶剂的醋酸纤维素的13C-NMR核磁共振谱,得出了三种不同位置羟基的取代度。结合X—射线和DSC分析,初步说明具有相同取代度但未经水解和经过水解的醋酸纤维素(CA) 性质上的差异是由于三个羟基上的取代度分布不同及消晶程度差异所致。 相似文献
20.
1 INTRODUCTIONBecause of importance of equations of state (EOS)in science and industry,hundreds forms of EOS havebeen presented since latter 19th century.It seems impossible to develop a general equation covering vari-ous kinds of EOS.But for cubic EOS,several generalequations have been reported already. Martin presented the first general equation whichis following p=RT/V-α(T)/(υ β)(υ γ) δ(T)/υ(υ β)(υ γ) (1) Kumar et a1.presented an equation called the most general form of a density-cubic or, alterna tively,volume-cubic mathematical equation,the form of which is as follows 相似文献