微纳米水合盐相变材料Na2CO3·7H2O的仿生合成及热学性质研究

以定量滤纸为生物模板制备了具有定量滤纸形貌的Na2CO3晶体,经过低温下的吸水和结晶过程合成了相变材料Na2CO3·7H2O。并借助扫描电子显微镜(SEM)、X-射线粉末衍射仪(XRD)和差示扫描量热仪(DSC)对产物的形貌、晶型以及热学性质进行了表征。同时,考察了掺杂NaCl对合成的相变材料Na2CO3·7H2O的热学性能的影响。结果表明:产物纯度高,且很好地遗传了模板(滤纸)的形貌;Na2CO3.7H2O表现出了良好的储能效果,相变热可达216.8J/g;掺杂NaCl(20mol%)可使Na2CO3.7H2O的相变温度降低5.5℃,而相变热仍然高达177.9J/g。     

微纳米水合盐相变材料Na2SO4·10H2O的仿生合成与表征

以定量滤纸为生物模板成功制备了具有滤纸形貌的微纳米Na2SO4晶体,经过吸水和低温的结晶过程合成了相变材料Na2SO4·10H2O.并借助扫描电子显微镜(SEM)、X-射线粉末衍射仪(XRD)和差示扫描量热仪(DSC)对产物进行了表征.结果表明,产物纯度很高,且很好地遗传了模板的形貌.同时,最终合成的相变材料Na2SO...     

相变温度可调的无机混盐体系相变储能材料

现阶段,利用无机水合盐制备相变储能材料已成为一大研究热点,但是单组份无机水合盐相变储能材料的相变温度高,较难适用于温室大棚、室内节能材料等低温应用领域。为了解决这一问题,将CaCl2·6H2O、MgCl2·6H2O以及H2O混合配制出了CaCl2-MgCl2-H2O混盐体系,并采用Thistory方法和差示扫描量热法研究了混盐的体系组成、成核剂添加量等因素对材料相变性能的影响。制备的CaCl2-MgCl2-H2O混盐相变材料可以在25℃以下完全熔解,并且通过改变混盐体系的组成可使材料凝固温度在10℃~20℃范围内可调。此外,本研究在一定程度上解决了无机水合盐相变储能材料在相变过程中的过冷和相分离现象。     

无机水合盐相变材料Na2SO4·10H2O的研究进展

介绍TNa2SO4·10H2O用作相变材料的储能特性,综述了针对Na2SO4·10H2O过冷和相分离现象的解决方法以及Na2SO4·10H2O某些共晶盐的研究,同时简要概括了各因素对Na2SO4·10H2O结晶速度的影响,展望了NazSO4·10H2O未来的发展方向.Na2SO4·10H2O作为相变材料的研究主要集中在成核剂和增稠剂的选择,Na2SO4·10H2O的无机共晶盐表现出较好的储热性能,可以尝试研究在微、纳米级多孔限域作用下的无机水合盐及其共晶盐的储热性能.     

混合水合盐作为储热相变材料的热物性能研究

目的研究不同质量比的Mg Cl2·6H2O和Mg(NO3)2·6H2O的混合水合盐作为储热相变材料的热物性能。方法制备不同混合质量比的Mg Cl2·6H2O和Mg(NO3)2·6H2O,用温度记录仪测其步冷曲线,得到相变温度和过冷度,再用高低温交变箱测试长期循环性能,最后用DSC对相变材料循环前后的相变潜热进行测试比较。结果质量比为5∶5的Mg Cl2·6H2O和Mg(NO3)2·6H2O的混合水合盐相变材料表现出良好的热物性,具有相变温度适合、过冷度小、相变潜热大和长期循环性能稳定等特点,可以作为潜在的储热相变材料。     

CH3COONa·3H2O相变储能性能研究

三水醋酸钠(CH3COONa.3H2O)由于潜热较高而常作为相变储能材料被众多学者研究;而其适宜的熔点,使其能适用于家用热水储能系统等。然而,三水合醋酸钠在相变过程中存在着严重的过冷和相分离的问题。本文以三水合醋酸钠作为相变基体材料,经研究、比较分别以羧甲基纤维素、明胶作为增稠剂,添加各种成核剂后的各体系的相变储能性能,从而得出羧甲基纤维素比明胶作为该体系的增稠剂的效果好得多,Na2SiO3.9H2O、Na2B4O7.10H2O的成核效果较好。     

熔融自发浸渗制备多孔陶瓷复合相变储能材料

研究了融盐Na2SO4与石英质多孔陶瓷预制体的自发熔融浸渗制备工艺,成功地制备出无机盐/陶瓷基(Na2SO4/SiO2)复合相变储能材料,观察和分析了该材料的物相组成与显微结构特征,对该材料的各项热物理性能和机械性能进行了测量.结果表明:自发熔融浸渗工艺比混合烧结工艺更适合于制备无机盐陶瓷基复合相变储能材料.     

水合二氧化钛纤维的制及其相变过程研究

对KDC法制备的四肽酸钾纤维进行水合，酸洗处理后可得到水合二氧化钛纤维，对其进行差热分析和热失重测试，并借助XRD加以验证，发现随着温度的升高，水合二氧化钛纤维发生一系列的相变过程：H2Ti4O9·1．2H2O→H2Ti8O17→TiO2(B)→中间相 →锐钛矿相→金红石相，并初步讨论了水合二氧化钛纤维的形成机理。     

生物模板法制备微纳米二氧化锡

以SnCl4.5H2O为起始原料,采用不同的生物模板(定量滤纸、鸡蛋内膜),通过浸渍和煅烧,在常压空气气氛中成功地制备出具有不同生物形态的微纳米SnO2。采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征样品的相组成和微观结构。结果表明:两种模板所制得的产物纯度很高,且很好地复制了原模板的形貌。同时,研究了制备条件诸如煅烧温度和反应物浓度对产物结构、形貌和尺度的影响,并初步探讨了不同生物形态的微纳米SnO2形成的机理。     

水合二氧化钛纤维的制备及其相变过程研究

对KDC法制备的四钛酸钾纤维进行水合、酸洗处理后可得到水合二氧化钛纤维．对其进行差热分析和热失重测试,并借助XRD加以验证,发现随着温度的升高,水合二氧化钛纤维发生一系列的相变过程：H2Ti4O9·1．2H2O→H2Ti8O17→TiO2（B）→中间相→锐钛矿相→金红石相．并初步讨论了水合二氧化钛纤维的形成机理．     

Path-independent phase unwrapping of subsampled phase maps

A technique for unwrapping subsampled phase maps is presented. The subsampled phase map is obtained by standard phase-shifting methods that use subsampled interferograms. The technique then estimates the wrapped local curvature of the subsampled phase map. This local curvature is then low-pass filtered with a free-boundary low-pass filter to reduce phase noise. Finally the estimated local curvature of the wave front is integrated by the use of a least-squares technique to obtain the searched continuous wave front.     

The phase representation of covariant phase observables

Abstract

Covariant phase observables are obtained by defining simple conditions for mappings from the set of phase wavefunctions (unit vectors of the Hardy space) to the set of phase probability densities. The existence of phase probability density for any phase wavefunction, the existence of interference effects and the natural phase shift covariance are those simple conditions. The non-localizability of covariant phase observables is proved.     

Full-field phase error compensation method based on relationship between unwrapped phase and phase error

The three-dimensional reconstruction in phase-measuring profilometry (PMP) usually involves the phase error caused by the gamma effect of the projector. In this study, the relationship between the unwrapped phase and the phase error of every pixel is analysed, and an effective full-field phase error compensation method based on this relationship is proposed for the reduction of every pixel error. In our optimized PMP system, the full-field phase error can be detected by directly fitting the unwrapped phase of the reference plane. In addition, the relationship between the unwrapped phase and the phase error can be established by creating a phase-error lookup table for the phase error compensation of every pixel. The experimental results demonstrate the effectiveness of the proposed method in practical PMP, and the measurement errors can be reduced by a factor of least 10.     

Sensing wave-front amplitude and phase with phase diversity

We show in benchtop experiments that wave-front phase estimation by phase diversity can be significantly improved by simultaneous amplitude estimation. Processing speed, which will be important for real-time wave-front control applications, can be enhanced by use of small-format detectors with pixels that do not fully sample the diffraction limit. Using an object-independent phase-diversity algorithm, we show that, for both pointlike and extended objects, the fidelity of the phase and amplitude estimates degrades gracefully, rather than catastrophically, as the sampling becomes coarser. We show in simulation that the same algorithm also improves the fidelity of image reconstruction of complex targets.     

Studying transient phase dynamics using the phase resetting method

A new method is proposed for the investigation of transitions from synchronous dynamics of coupled oscillators to asynchronous regimes attained upon synchronization breakage by a sequence of short phase resetting pulses. The possibility to use the proposed method for determining the coefficient of coupling between interacting systems from an analysis of the signals generated by these systems is considered.     

Lensless phase microscopy using phase retrieval with multiple illumination wavelengths

A phase retrieval method for microscopy using multiple illumination wavelengths is proposed. A fast algorithm suitable for calculations with high numerical aperture is used for the iterative retrieval of the object wavefront. The advantages and limitations of the technique are systematically analyzed and demonstrated by both simulation and experimental results.     

Nonequilibrium phase transitions

A brief review is provided of the subject of nonequilibrium phase transitions occurring in various systems in different disciplines. All these systems exhibit a similar kind of ordering phenomena at a macroscopic level and can therefore be classified in terms of appropriate order parameters. Typical order parameter equations are discussed in the light of Landau’s phenomenological theory of phase transitions. The instabilities occurring in a few chemical reactions are discussed in some detail and the role of fluctuations pointed out. Mention is also made of the possibility of viewing some metallurgical phenomena as examples of nonequilibrium phase transitions.