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1.
以TiO2凝胶为模型化合物,利用原位变温X射线衍射(XRD)研究了不同气氛下TiO2的相变过程,对比研究原位和非原位情况下的相变情况.研究表明,各种气氛下,原位和非原位时不同气氛下TiO2相变过程均有不同.其中,最常见的空气气氛下非原位与原位测定的TiO2从无定型向锐钛矿转变的温度相差近200℃.在500℃以前,TiO...  相似文献   

2.
利用X射线衍射(XRD)对金属铀在纯氧环境中50,100,200℃和300℃等温反应过程进行原位分析。定性分析结果显示,50,100,200℃条件下试样表面氧化产物为氟化钙结构的UO2,且UO2生成速度随温度上升迅速加快,200℃下已经观察不到氧化过程;300℃下试样表面首先形成一定厚度的UO2,接着UO2进一步氧化形成U3O8。  相似文献   

3.
随着社会经济的飞速发展,能源短缺问题在世界范围内日益突显。目前,开发利用可再生能源已被我国列为能源发展的优先领域。藻类植物蕴含丰富的生物质能,同时又具有光合效率高、固碳能力强、生长速度快、来源分布广等优势,是公认的可持续绿色清洁能源的发展方向。甘氨酸是藻类水热液化过程中的重要过程反应物,其液化过程中的热动力学性质是认识和优化藻类水热液化技术的基础要素,通过研究甘氨酸水热液化过程可为分析复杂的生物质水热液化反应奠定基础。研究基于熔融石英毛细管反应器(FSCR)高温高压可视反应腔,结合Linkam FTIR600控温台与Andor激光拉曼光谱仪联用,对甘氨酸水溶液在270~290 ℃(压力同于实验环境温度下水饱和蒸气压)条件下的液化过程运用拉曼光谱分析技术开展了原位研究。通过观测5 Wt%甘氨酸溶液中C—C伸缩振动峰(897 cm-1)、C—N 伸缩振动峰(1 031 cm-1)和COO-反对称伸缩峰(1 413 cm-1)在液化过程中的相对拉曼强度变化,深入分析了温度及反应时间对甘氨酸溶液各官能团热分解的影响。运用Avrami的反应动力学模型分析,获取了量化温度对甘氨酸分子中骨架碳链ν(C—C)的特征振动模式热解过程影响的活化能,357 kJ·mol-1,和不同实验温度下的反应速率常数k等一系列相关参数,定量地揭示了甘氨酸液化过程的热动力学性质。实验中发现,在设定相同的液化反应时间(10 min)内,当温度低于290 ℃时,降温后反应腔内能观测到甘氨酸水溶液中ν(C—C),ν(C—N),νas(COO-)的特征峰,而温度高于290 ℃时则不然,表明甘氨酸的完全液化温度约为290 ℃。该研究运用高温高压可视化实验技术,结合原位拉曼光谱分析技术,厘清了甘氨酸水热液化过程中的不同温度下特征官能团拉曼峰强的变化规律,为深入了解藻类水热液化过程机理、推进生物质能的开发利用提供必要的实验依据,具有重要的科学意义和现实意义。  相似文献   

4.
李言荣  刘兴钊  徐进  J.GEERK  R.SMITHY 《物理学报》1997,46(10):2023-2028
用倒筒式直流磁控溅射装置在LaAlO3单晶基片上原位沉积了GdBaCuO(GBCO)薄膜.系统调查了GBCO薄膜的超导性质与溅射温度Ts、溅射压力和靶组成的变化规律,发现在720—820℃较宽的基片温度范围、在较低的溅射气压(40Pa)、较高的溅射速率(0.03nm/s)下均可制备出Tc0>92K,(005)峰摇摆曲线半高宽不大于0.2、膜面非常光滑且具有良好外延特性的c轴嵌镶单晶薄膜.在最佳条件下(Ts=820℃,气 关键词:  相似文献   

5.
原位红外光谱法是近十几年来新兴的一种动态研究方法。该方法结合了原位实时监控和红外光谱精确分析物质化学结构的优点,通过实时跟踪材料在不同温度下的化学变化,测定材料的微观结构与温度的关系。本实验采用原位红外光谱技术研究了HMX炸药在5℃/min升温条件下的热分解过程,得到如下结论。  相似文献   

6.
传统研究材料热稳定性的方法包括热失重(TG)(热介电法、热电阻)、真空安定性(VST)、差热分析(DTA)、差示扫描量热法(DSC)等。其中,TG是测量炸药重量变化与温度的函数关系,ST是测量真空状态下炸药热分解所产生的气体量,DTA和DSC是测量炸药在不同温度下,由于发生相变所表现出的变化(吸热或放热)。以上这些方法得到的是炸药热性质的宏观信息,而无法反映炸药在不同温度下的微观化学变化。原位红外光谱法是一种新兴的动态研究方法。该方法结合ir原位实时监控和红外光谱精确分析物质化学结构的优点,通过实时跟踪材料在不同温度下的化学变化,测定材料的微观结构与温度的关系。  相似文献   

7.
在氢气氛下合成了新化合物Ru2H4(CO)2(PPh3)4,建立了可至液氮温度的原位红外测试装置,在室温至液氮温度下进行了外多氢化合物的结构研究。发现RuT4(CO)PPh3)3在室温下会发生分子氢与原子氢的结构流变,Ru2H4(CO)(PPh3)4则随温度变化而出现桥氢与端氢的结构转化现象。  相似文献   

8.
Al-0.03at% Mg合金在倒扭摆上-65℃在原位进行拉伸,形变量为0.5%,然后在升温过程中测量内耗,于-30℃及60℃附近观测到内耗峰,随后从80℃的降温过程中仍在相同温度观测到内耗峰。研究了不同温度下的内耗-振幅曲线,在降温过程中出现内耗峰的温度范围内观测到了振幅内耗峰,并由此计算得到等效激活能分别为0.32及0.22eV。初步认为,当低温冷加产生的位错弯结在外力作用下作沿边往复运动时,“镁原子-空位”对和镁原子被拖曳运动是分别引起-30℃峰和60℃峰的可能的原因。 关键词:  相似文献   

9.
杨春  冯玉芳  余毅 《物理学报》2009,58(5):3553-3559
采用基于第一性原理的从头计算分子动力学方法,计算了300—800℃下AlN吸附过程与系统能量、动力学轨迹以及扩散系数.研究表明,吸附过程由物理吸附、化学吸附和表面稳定态三个阶段组成,在吸附成键过程中,温度越高,粒子平均表面扩散能力增强.N原子的扩散系数大于Al原子的扩散系数,尤其是在物理吸附阶段.在较高温度条件下(大于700℃),N的解吸附作用明显增强,不利于AlN的稳定吸附生长,500—700℃之间的温度有利于AlN在α-Al23(0001)表面的稳定吸附生 关键词: 2O3(0001)表面')" href="#">α-Al23(0001)表面 扩散 吸附生长 从头计算分子动力学  相似文献   

10.
 以化学水解法合成的β-FeOOH纳米微粉(平均粒径在12 nm左右)为原料,分别在0.0~4.5 GPa和200~350 ℃的压力和温度范围进行冷压和热压处理。实验结果表明,冷压对β-FeOOH纳米固体的结构没有明显影响,但却使它的热致相变(从β-FeOOH相到α-Fe2O3相)温度从常压下的203.8 ℃提高到4.5 GPa压力下的274 ℃,接近常规体相材料的相变温度。而在一定的热压条件处理下,首次发现了从β-FeOOH相到α-FeOOH相的结构转变,并在4.5 GPa、200 ℃的热压条件下得到了转变过程中的一个新的亚稳相。从压力和温度对纳米微粒的作用角度,对上述实验结果进行了讨论。  相似文献   

11.
聚氨酯的FTIR光谱与热分析研究   总被引:8,自引:1,他引:7  
采用原位傅里叶变换红外光谱法, 研究了聚酯型聚氨酯和聚醚型聚氨酯在空气气氛中从室温到400 ℃之间的热解反应, 实时考察了其在不同温度条件下分解残留物的基团特性. 利用热分析技术考察了它们在不同气氛下从室温到700 ℃之间的热解反应. 探讨了在有氧条件下的热解反应机理. 结果表明聚酯型聚氨酯在空气中存在硬段和软段先后分解的两个阶段, 而聚醚型聚氨酯则是硬段与软段同时分解. 热分解结果也显示, 硬段相同的聚氨酯, 聚酯型聚氨酯的起始失重温度高于聚醚型聚氨酯, 显示聚酯型的热稳定性强于聚醚型. 同时聚氨酯在空气中的起始失重温度比在氮气中提前, 说明氧气的存在能促进聚氨酯主链上C-C和C-O键的断裂.  相似文献   

12.
采用快速热解法以及傅里叶变换红外光谱(FTIR)和气相色谱/质谱(GC/MS)检测技术,研究了2-氢七氟丙烷在驻留时间为30 s,反应温度分别为400,500,600,700和800 ℃时的热分解过程.结果发现:反应温度对2-氢七氟丙烷的热分解有明显的影响,2-氢七氟丙烷在400,500和600 ℃时是稳定的,在700℃时明显地开始分解,800℃时发生了强烈的分解.与此同时,在800℃时,在反应器的管壁上观察到了大量的焦炭,并在热分解产物中发现了1,2-二(三氟甲基)全氟茚满、全氟(1-亚乙基茚满)和八氟化萘等三种环状化合物,这表明2-氢七氟丙烷在高温热分解过程中并不只是发生了简单的分解,环化和聚合过程也是会发生的.  相似文献   

13.
We have successfully resolved the degradation problem of CsLiB(6)O(10) (CLBO) by means of elevated crystal temperature. CLBO crystals were continuously operated at 160 degrees C in ordinary room humidity. No degradation of performance was observed after more than 1 month. We believe that heating CLBO crystal above 130 degrees C can relieve stresses introduced by crystal hydration, cutting, polishing, and thermal shock owing to laser power absorption. Thus long-term operation of CLBO crystal is achieved for effective application of laser frequency conversion. Output stability from CLBO is also further enhanced at elevated crystal temperature.  相似文献   

14.
The reaction of triphenylmethane and triphenylcarbinol with nitrobenzene under thermal or ultrasonic activation was studied. It was shown beyond doubt that the thermal reaction of the aforementioned systems at 210 degrees C occurs through electron transfer. The sonochemical reactions occur at 40 degrees C, although slowly, while heating at the same temperature leaves the system unchanged. Electron transfers are also involved but an unexpected reductive process was evident.  相似文献   

15.
Several thermal treatments in the temperature range from 270 °C to 320 °C (each of 10 min) were tested as a final preparation procedure of LiF:Mg,Cu,Si to improve the protocol of TL readout with less residual signal for the LiF:Mg,Cu,Si TLD. This high sensitivity LiF:Mg,Cu,Si TLD exhibited thermal stability much better than that of the well known LiF:Mg,Cu,P. For LiF:Mg,Cu,Si, a readout temperature up to 300 °C did not affect the TL sensitivity and glow curve structure for 12 cycles of exposure and readout following an initial thermal treatment at 295 °C for 10 min. The residual TL signal also remained negligible.  相似文献   

16.
采用基于密度泛函理论(DFT)的第一性原理平面波超软赝势方法,系统研究了Ti_3(Ge_(1-x)Si_x)C_2(x=0, 0.5, 1)固溶体的晶体结构、弹性性质以及热力学性能.研究结果表明,Ti_3(Ge_(1-x)Si_x)C_2体系均具有力学和热力学稳定结构,并且为脆性材料;Ti_3(Ge_(1-x)Si_x)C_2固溶体的力学性能随Si含量的增加而提高;Ti_3(Ge_(1-x)Si_x)C_2固溶体在室温下具有稳定的晶格结构和较高的晶格热导率,有望用于一些需要良好散热性能电子元器件的封装材料.  相似文献   

17.
Permanent long-period gratings were written using arc discharges in two aluminosilicate fibers, one of which was doped with erbium. Reversible gratings were also mechanically induced in both fibers. The thermal behavior of the arc-induced gratings was investigated at up to 1100 degrees C. It was found that the shift of the resonant wavelengths exhibited a well-defined linear dependence on temperature up to 700 degrees C.  相似文献   

18.
We report what is to our knowledge the first characterization at high temperatures of long-period fiber gratings written in Ge-free air-silica microstructure fiber. The gratings written with the electric-arc technique suffer a low shift of the resonance wavelengths when the temperature is increased from 20 degrees C to 1200 degrees C. This shift is studied and compared with that of a long-period fiber grating written in a standard single-mode fiber by the same technique. Good thermal stability of the grating and of the fiber after annealing at 1200 degrees C for 1 h is demonstrated.  相似文献   

19.
Richard C  Lee HS  Guyomar D 《Ultrasonics》2004,42(1-9):417-424
This paper deals with the emission performance of 1-3 piezoelectric composite power transducers made with a hard PZT (Navy III) and epoxy resins with a high glass-rubber transition temperature. Following the "dice and fill" technique, various composite transducers with 30 and 50% PZT volume fractions were fabricated with an air backing and no front matching layer with resonance operating frequencies around 500 kHz. The transducers were first evaluated under isothermal conditions, with a low emission duty cycle. Efficiencies as high as 95% were monitored as a function of the instantaneous input power up to a 60 W/cm(2) density. The effect of the polymer matrix mechanical losses and the fabrication conditions is then discussed. For the transducer thermal stability, the case of long duty cycle or continuous emission was considered in a second evaluation. In this case the transducer working temperature and axial radiated pressure were monitored as functions of the input power density up to 40 W/cm(2). It is shown that the transducer efficiency and working temperature were strongly dependent on the type of resin used but also on the PZT material, even for hard PZT compositions. A composite transducer configuration with strongly improved thermal stability was investigated demonstrating a working temperature higher than 90 degrees C and an extended power range (30-40 W/cm(2)). The composite thermal breakdown mechanism was analyzed and the effect of the curing-induced thermo-mechanical stresses on the PZT mechanical losses was considered in relation to the composite working temperature. Measurements of the composite mechanical losses versus the temperature were obtained and related to the variation of the PZT mechanical losses with the stresses due to the composite transducer temperature change. It is found that the thermally induced stress can strongly influence the PZT ceramic mechanical losses and that it can be the reason for a thermal breakdown taking place at a temperature much lower than the epoxy resin transition.  相似文献   

20.
Accurate measurement of tissue relaxation characteristics is dependent on many factors, including field strength and temperature. The purpose of this study was to evaluate the relationship between sample temperature, viscosity and proton spin-lattice relaxation time (T1) and spin-spin relaxation time (T2). A review of two basic models of relaxation the simple molecular motion model and the fast exchange two state model is given with reference to their thermal dependencies. The temperature dependence for both T1 and T2 was studied on a 0.15 Tesla whole body magnetic resonance imager. Thirteen samples comprising both simple and complex materials were investigated by using a standard spin-echo (SE) technique and a modified Carr-Purcell-Meiboom-Gill (CPMG) multi-echo sequence. A simple linear relationship between T1 and temperature was observed for all samples over the range of 20 degrees C to 50 degrees C. There is an inverse relationship between viscosity and T1 and T2. A quantity called the temperature dependence coefficient (TDC) is introduced and defined as the percent rate of change of the proton relaxation time referenced to a specific temperature. The large TDC found for T1 values, e.g. 2.37%/degrees C for CuSO4 solutions and 3.59%/degrees C for light vegetable oils at 22 degrees C, indicates that a temperature correction should be made when comparing in-vivo and in-vitro T1 times. The T2 temperature dependence is relatively small.  相似文献   

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