Phase and State Transitions in Granular Starches Studied by Dynamic Differential Scanning Calorimetry

Phase and state transitions of granular starches heated in water are studied by dynamic differential scanning calorimetry (DDSC). The DDSC results of various granular starches show a stepwise heat capacity (C_p) change in the storage C_p curve, which starts at the beginning of melting or immediately preceding gelatinization and ends before the melting reaches its peak temperature. Annealing reduces the magnitude of this stepwise change in storage C_p. After the amorphous phase is selectively removed by acid, the stepwise storage C_p is greatly reduced. The stepwise storage C_p increase is not observed when recrystallized linear short chains from enzyme‐debranched waxy maize starch are heated in water. The results show that the stepwise change in C_p observed on the granular starch is a unique property associated with the phase transition of granular structure and reflects a glass transition of the rigid amorphous regions in starch granules. The glass transition of the mobile amorphous phase in granular starch is believed to extend over a broad range of temperatures before gelatinization. A small glass transition below 0°C is directly detected by DDSC and is attributed to part of the mobile amorphous fraction in granular starch.     

低碳合金钢经高压处理后加热过程中固态相变的研究

利用差示扫描量热(DSC)测出了低碳合金钢经高压处理后不同加热速率下组织中珠光体向奥氏体转变的温度和时间.并计算了其相变激活能.所得结果为研究低碳合金钢经高压处理后组织中珠光体向奥氏体转变提供一定的参考数据.     

Polymorphic transformation of 1,3-distearoyl-sn-2-linoleoyl-glycerol

Polymorphic transformation behavior of sub-α₁, sub-α₂, α, and γ in 1,3-distearoyl-sn-2-linoleoyl-glycerol (SLS) has been studied with X-ray diffraction, differential scanning caloremetry, and Fourier-transform infrared spectroscopy. Synchrotron radiation X-ray beam was employed to observe rapid transformation processes from the sub-α and α forms to the γ form. The chain length structures were double in sub-α₁, sub-α₂, and α, whereas γ was of triple chain-length structure. The subcell packing was pseudohexagonal for the two sub-α forms, hexagonal for the α form, and parallel type for the γ form. In comparison with 1,3-distearoyl-sn-2-oleoyl-glycerol (SOS), the occurrence behavior of sub-α, α, and γ of SLS was the same as that of SOS. However, the absence of β′ and β was unique for SLS. The chain-chain interactions between the linoleoyl moieties may stabilize the γ form, prohibiting the transformation into β′ and β forms. The presence of two cis double bonds may cause this stabilization, revealing the disordered chain conformation of the unsaturated chains.     

用等温DSC曲线的全熔分解时间评价HMX与材料的反应性

用测定全熔分解时间(TCMD)的等温DSC法检验了各种材料与HMX的反应性,结果表明,TCMD是一个精确筛选HMX组分和HMX接触材料的判据。     

超有光聚酯切片的热性能

利用DSC热分析进行了超有光聚酯切片热性能的研究。结果表明,和常规半消光PET切片相比,超有光聚酯切片冷结晶温度较高,结晶热焓较低,结晶度较小;其熔融热焓较大,说明熔融结晶时结晶尺寸较大;过冷程度较小,可纺性差。     

三羟甲基乙烷、新戊二醇及其二元体系相变动力学的DSC研究

用DSC技术研究了新戊二醇（NPG）,三羟甲基乙烷（PG）及其二元体系的固－固,固－液相变的动力学,运用Kissinger及Ozawa方法计算了相变过程的活化能及反应级数,两种方法计算结果一致,固－固相变温度和峰温与升温速度呈线性关系。     

Materials for intelligent sun protecting glazing

The aim of this review is to present the last 10 years of development in sun protection by use of electrochromic devices, thermotropic gels and polymer dispersed liquid crystalline systems. Furthermore, the properties of new lyotropic liquid crystalline and thermotropic hydrogels are discussed. Thermochromic hydrogels, which change their colour by changes in the temperature, also are presented. The relationship between gel composition, optical behaviour and thermodynamic properties as investigated by differential scanning calorimetry (DSC) is also demonstrated.     

Effects of the γ-irradiation strength and basalt additive content on the mechanical performance and dielectric response of polypropylene films

In this study, we investigated the effects of high-dose γ-ray irradiation on the mechanical and dielectric properties of polypropylene (PP)–basalt thick films. PP–basalt thick-film composites with various basalt contents from 0.5 to 10.0% were prepared by a hot-press method. The samples were exposed to γ radiation at different doses in the range 3–25 kGy. The mechanical properties of the samples, such as the Young's modulus, tensile strength, percentage strain at break, and energy at break, were examined in the context of the γ-irradiation process. Although the maximum elasticity was obtained for the unirradiated 0.5% basalt-added composite, the 6 kGy γ-irradiated PP–1.0% basalt sample exhibited the highest elasticity properties among all of the composites. The best mechanical properties, including the ultimate tensile strength and energy at break values, were achieved for the 12 kGy γ-irradiated neat PP. The dielectric properties of the PP–basalt composites were also investigated in the 100 Hz to 15 MHz frequency region at room temperature. According to the analysis of the dielectric properties, the 3 kGy γ-irradiated neat PP may have potential for microelectronic device applications that require low dielectric constant and dielectric loss materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47414.     

Structural and optical properties of MgМоO4 prepared by mechanochemical technique

MgMoO₄ with hexagonal particles were prepared by combining high energy ball milling with heat treatment technique. The influence of the mechanochemical activation/heat-treatment on the phase, structural and morphology transformation were investigated by X-ray powder diffraction analysis (XRD), infrared spectroscopy (IR), differential scanning calorimetry (DSC), particle size distribution (PSD) and scanning electron microscope (SEM). Optical properties of the final product were studied by UV–Vis and photoluminescence (PL) measurements. Mechanochemical activation of the initial oxides for 10 h ball milling leads to a full amorphization of MoO_3, only. The heat-treatment at different temperatures after 10 h milling time results to the phase formation of MgMoO₄. The reaction started at 400 °C for 5 h and completed at 800 °C for 5 h. The calculated energy band gap value as prepared MgMoO₄ is 2.03 eV and exhibits photoluminescence emission above 600 nm. The CIE chromaticity coordinates (x = 0.53 and y = 0.43) were found to lie in the orange region.     

Crystallization and hydrogen absorption in a Ni32Nb28Zr30Fe10 melt spun alloy and correlation with icosahedral clusters

The crystallization and the hydrogen absorption properties of a Ni₃₂Nb₂₈Zr₃₀Fe₁₀ melt spun ribbon were investigated. X-ray diffraction measurements reveal that a small fraction of the ribbon is in a crystalline state, whereas the main component is amorphous. The bulk crystallization process of the alloy ribbon occurs in two steps above 770 K, as measured by differential scanning calorimetry. At each step of the crystallization process, an unusually low activation energy of the order of 180 kJ/mol, was observed. Hydrogen absorption pressure-composition isotherms measured between 598 K and 673 K showed that the enthalpy of hydrogenation is quite high (～85 kJ/mol), as compared to that of analogous ribbons. The isotherms of these ribbons do not exhibit any plateau, similarly to other amorphous materials, but they exhibited extremely slow kinetics for hydrogen absorption. To simulate the local atomic structure involving cluster formation in amorphous Ni₃₂Nb₂₈Zr₃₀Fe₁₀ alloy, DFT-MD approach was used to construct an amorphous supercell of this alloy with 108 atoms. Calculations predicted that a fully amorphous structure of Ni₃₂Nb₂₈Zr₃₀Fe₁₀ can form. The low activation energy of crystallization observed before hydrogenation is due to the presence of only 3 full icosahedra without any Ni-centered icosahedra, that could provide resistance against crystallization. Moreover, a cluster analysis of the Ni₃₂Nb₂₈Zr₃₀Fe₁₀ alloy after hydrogenation showed interaction of hydrogen atoms with only two icosahedra out of four found in this case, and this could be the probable reason for the extremely slow kinetics of hydrogen absorption.