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1.
E. K. Merabet H. K. Yuen W. A. Grote K. L. Deppermann 《Journal of Thermal Analysis and Calorimetry》1994,42(5):895-906
A new sensitive isothermal titration microcalorimeter using polyvinylidene difluoride (PVDF) as detector has been developed. Heat pulses of less than 0.4 μJ can be detected and the baseline noise level (p-p) is 40 nW. The calorimeter is constructed with one reaction cell (0.7 ml) insulated by several radiation shields inside a vacuum chamber. The performance of the instrument was examined by measuring the heat of protonation of Tris with HCl. The enthalpy of reaction was found to be ?49±1 kJ·mol?1, in good agreement with the reported value of ?47.5 kJ·mol?1. 相似文献
2.
The ferroelectric lead germanate (Pb5Ge3O11) and its isomorphous compounds are important because of their uses as pyroelectric and electro-optic devices. Comparison
of inter-planar d-spacings of Pb5Ge3−x
Si
x
O11 (x=0, 0.3, 0.7 and 1.00) suggests that there is no change in basic structure of Pb5Ge3−x
Si
x
O11 when Si is substituted for Ge in small quantity (x<1). The dielectric properties of the Si-substituted compounds have been studied as a function of temperature (30 to 200°C).
The ferroelectric-paraelectric phase transition has been observed at 185°C. The Si doping causes (a) Curie point to shift
towards low temperature, (b) peak value of the dielectric constant to decrease and (c) phase transition diffuse. The fast
increase in dielectric constant of pure Pb5Ge3O11 with temperature (beyond transition temperature) may be attributed to the development of space charge polarization in the
system. 相似文献
3.
Long-range effects on the pyroelectric coefficient of a ferroelectric superlattice consisting of two different ferroelectric materials are investigated based on the transverse Ising model.The effects of the interfacial coupling and the thickness of one period on the pyroelectric coefficient of the ferroelectric superlattics are studied by taking into account the long-range interaction.It is found that with the increase of the strength of the long-range interaction,the pyroelectric coefficient decreases when the temperature is lower than the phase transition temperature;the mumber of the pyroelectric peaks decreases gradually and the phase transition temperature increases,It is also found that with the decrease of the interfacial coupling and the thickness of one period.the phase transition temperature and the number of the pyroelectric peaks decrease. 相似文献
4.
5.
现有的激光能量计传感器灵敏度系数都与其所处环境温度有关,在-50℃~70℃的温度范围内,灵敏度偏差较大,直接影响测量结果。为了达到消除环境温度的影响,采取在不同环境温度下对热释型能量计的灵敏度进行校准的研究方法。该校准方法与普通激光能量计的校准方法的不同之处在于对热释电型能量计进行校准时,温度由室温扩展到-50℃~70℃的温度范围。利用环境试验箱,每隔10℃固定一个温度点,进行激光能量的测量实验,得到各个温度点所对应的灵敏度修正系数,再借助最小二乘法建立起各个温度点上能量计灵敏度系数同环境温度的函数关系,从而实现了-50℃~70℃的温度范围内激光能量的准确计量。研制能直接工作于非常规工作环境下的热释电型激光能量计,对解决激光能量测量的外场需求有一定现实意义。 相似文献
6.
FTIR-RAIRS and ATR techniques are shown to provide a powerful means of investigating the molecular behaviour responsible for the pyroelectric properties of organic monolayer assemblies on silicon and aluminised glass. Spectral changes, associated with either proton transfer or head group rearrangement, are well correlated with the level of pyroelectric response for two different devices. The technique promises to be extremely important for the elucidation of the microscopic properties of molecular electronic devices. 相似文献
7.
在制造红外热释电探测器阵列过程中,需要利用超薄钽酸锂(LiTaO3)晶片作为红外热释电探测器件的敏感层。通常LiTaO3晶片的厚度远厚于红外热释电探测器件要求的厚度,所以需要采用键合减薄技术对LiTaO3晶片进行加工处理。键合减薄技术主要包括:苯并环丁烯(BCB)键合、铣磨、抛光、加热剥离、刻蚀BCB。加工后得到面积为10mm×10mm、厚度为25μm的超薄单晶LiTaO3薄膜,晶片厚度、表面粗糙度和面形精度比较理想。测得了LT晶片减薄后的热释电系数为1.6×10-4Cm-2K-1。得到的单晶LiTaO3薄膜满足红外热释电探测器敏感层的要求。 相似文献
8.
Jonas
rtegren Philippe Busson Ulf W. Gedde Anders Hult Anders Eriksson Mikael Lindgren Per-Otto Arntzn David S. Hermann Per Rudquist Sven T. Lagerwall 《Macromolecular Symposia》1999,148(1):179-195
Highly oriented pyroelectric liquid-crystalline polymers were prepared by photopolymerization under the influence of a static electric field from binary mixtures of two acrylate monomers exhibiting chiral smectic C mesomorphism. Both monomers contained nitro groups to yield second order nonlinear optical properties (second harmonic generation) and one of the monomers had two functional groups to yield a crosslinked polymer. The room temperature second order nonlinear susceptibility of the polymers showed during the first two hours a 10 % decrease after which it remained constant during the next 48 days. At elevated temperatures there was a significant difference in the nonlinear optical properties over time between crosslinked and uncrosslinked polymers. The uncrosslinked polymer showed a pronounced loss of second order nonlinear optical activity with time at ≥38°C. The crosslinked polymer showed a much smaller and basically a temperature independent decrease rate in the second order nonlinear optical properties at all the ageing temperatures (23-130°C). Both the loss in mesogen order parameter, very evident for the uncrosslinked polymer, and conformational changes occurring within the mesogens (β mechanism), may account for the observations made. 相似文献
9.
A method to study domain structure in ferroelectrics, using pyroelectric effect is described. Variation of pyroelectric signal
from the surface of a triglycine sulphate crystal plate has been studied by scanning the surface of the crystal with a low
wattage He-Ne laser beam. The integrated pyroelectric signal is due to two components, namely, (1) the primary component arising
out of the change in spontaneous polarization with temperature and (2) the delayed component arising out of the possible polarization
reversal. The component of an electric field along the ferroelectric axis due to thermal hemisphere within the crystal plate
formed by the laser beam has been calculated and shown to exceed coercive field, making polarization reversal possible. The
delayed pyroelectric signal is a measure of polarization reversal within the patch illuminated and its observed variation
over the surface yields information of the domain structure. 相似文献
10.
You Ming-Chang 《International Journal of Infrared and Millimeter Waves》1986,7(6):919-925
The configurations of the coupling network, which can effectively aecrease the effect of the noise sources within the amplifier on the equivalent input noise of the whole pyroelectric detector-amplifier system, are studied. The influences of feedback upon the noise properties of the basic amplifiers are analyzed. The procedures of designing low-noise pyroelectric detector-amplifier systems are followed. 相似文献