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961.
The crystal structure and microwave dielectric properties of Zn0.9Ti0.8?xSnxNb2.2O8 (x = 0.00, 0.05, 0.10, 0.15) ceramics sintered at temperatures ranging from 1100 °C to 1140 °C for 6 h were investigated. A single phase with ixiolite structure was obtained. With the increase of Sn content, the dielectric constant decreased attributed to the decrease of dielectric polarizability. The Qf value decreased with the decrease of packing fraction and grain size. The temperature coefficient of resonant frequency (τf) increased due to the increase of the bond valence of Zn0.9Ti0.8?xSnxNb2.2O8 ceramics. The excellent microwave dielectric properties of ? = 35.05, Qf = 49,100 GHz, τf = ?27.6 × 10?6/°C were obtained for Zn0.9Ti0.8?xSnxNb2.2O8 (x = 0.05) specimens sintered at 1120 °C for 6 h. 相似文献
962.
The excess amounts of K and Na in precursor solutions are very important for the phase structure and performance of (K0.48Na0.52)NbO3 (KNN) thin films because of their volatilization loss. However, there are no identical opinions have been reported that could describe which element is easily volatile. In this paper, different excessive amounts of K and Na are added simultaneously in precursor solutions, the lead-free KNN thin films are prepared by metallorganic compound decomposition (MOD) method. Through comparison of phase structures, dielectric properties, J–E characteristic and ferroelectric P–E hysteresis loops, the effects of chemical componential fluctuation of K and Na on properties of KNN thin films are discussed systematically. 相似文献
963.
Kang‐Zhen Xu Hang Zhang Ping Liu Jie Huang Ying‐Hui Ren Bo‐Zhou Wang Feng‐Qi Zhao 《Propellants, Explosives, Pyrotechnics》2012,37(6):653-661
1,4‐Dihydro‐5H‐(dinitromethylene)‐tetrazole ammonium salt ((NH4)2DNMT), a high nitrogen energetic compound, was synthesized and structurally characterized by single‐crystal X‐ray diffraction. The thermal behavior of (NH4)2DNMT was studied with DSC and TG‐DTG methods. The kinetic equation of the thermal decomposition reaction is: dα/dT=1013.17/3β(1−α)−2 exp(−1.388×105/RT). The critical temperature of thermal explosion is 182.7 °C. The specific heat capacity of (NH4)2DNMT was determined and the molar heat capacity is 301 J mol−1 K−1 at 298.15 K. The adiabatic time‐to‐explosion of (NH4)2DNMT was calculated to be 277 s. The detonation velocity and detonation pressure were also estimated. All results showed that (NH4)2DNMT presents good performance. 相似文献
964.
965.
Johannes Schilling Christian Horend André Bardow 《American Institute of Chemical Engineers》2020,66(5):e16903
The key to many chemical and energy conversion processes is the choice of the right molecule, for example, used as working fluid. However, the choice of the molecule is inherently coupled to the choice of the right process flowsheet. In this work, we integrate superstructure-based flowsheet design into the design of processes and molecules. The thermodynamic properties of the molecule are modeled by the PC-SAFT equation of state. Computer-aided molecular design enables considering the molecular structure as degree of freedom in the process optimization. To consider the process flowsheet as additional degree of freedom, a superstructure of the process is used. The method results in the optimal molecule, process, and flowsheet. We demonstrate the method for the design of an organic Rankine cycle considering flowsheet options for regeneration, reheating, and turbine bleeding. The presented method provides a user-friendly tool to solve the integrated design problem of processes, molecules, and process flowsheets. 相似文献
966.
Xiang Ren Jingyuan Sun Zhengliang Huang Yao Yang Sihang Tian Jingdai Wang Yongrong Yang 《American Institute of Chemical Engineers》2020,66(5):e16909
Nowadays, the droplet–particle collision characteristics in the gas-phase ethylene polymerization process are still unclear. The high-speed photography and a quasi-circle imaging approach are employed to study the collision interaction characteristics between liquid droplets and polyethylene particles. The liquid film evolution is studied through variations of the film thickness on the particle north pole, the dynamic contact angle, center angle and film thickness at the maximum extension. Results have found that for n-hexane the threshold temperature of the recoil happening increases with increasing initial Weber number, but for 1-hexene it is stable. Over 70°C evaporation and splash occurs immediately. Under low Weber numbers, the water droplet stays for damping oscillations, the reference stable height of which is linearly related to temperatures. Moreover, three regimes of film thickness variation with time are identified and mathematically described, while Regime 3 characteristics are found strongly dependent on the liquid species, Weber number, and particle temperature. 相似文献
967.
Ana Carolina Rodríguez-Negrette María José Rodríguez-Batiller Victor Alonso García-Londoño Virginia Borroni Roberto Jorge Candal María Lidia Herrera 《Journal of the American Oil Chemists' Society》2020,97(11):1215-1228
Physical chemical properties of cupuassu fat were modified by dry fractionation. Stearin and olein fractions were obtained at 29, 26, and 24 °C. Polymorphic behavior of unfractionated cupuassu fat (UCF) and its fractions were studied in situ by small-angle (SAXS) and wide-angle (WAXS) X-ray scattering using synchrotron light. Polymorphic transitions were followed in real time tempering samples with a thermal cycle. For UCF, the main polymorphic form crystallized under selected conditions was the β’2. α and β’1-forms appeared in trace amounts. β2-form was obtained after storage at 25 °C for 3 months. Stearins obtained at 26 (S-26) and 24 °C (S-24) showed a similar polymorphic behavior. However, S-26 with improved physical properties might be more suitable for chocolate production or as a trans-fat alternative than UCF. Stearin fraction obtained at 29 °C (S-29) had a complex polymorphic behavior. The α-form was the first polymorphic form detected followed by β’2-form. There was a polymorphic transition from α to β’1-form but no transition between β’-forms. They were independent to each other showing fractionation in two different solid solutions. Increased contents of the triacylglycerols (TAG) SOA and SOB together with lower contents of SOO compared to UCF led to co-crystallization because there was no complete compatibility among all TAG present in S-29. β1-form crystallized after storage forming crystals with a double-layer arrangement and a characteristic morphology. This form could be useful for accelerating crystallization process in melted liquid systems. 相似文献
968.
Elisa Garza Montelongo María G. Sánchez Anguiano Leonor M. Blanco Jerez Eduardo D. Pereira Ulloa Bernabé L. Rivas Quiroz Perla Elizondo Martínez 《应用聚合物科学杂志》2020,137(40):49204
Poly(ethylene terephthalate)-based molecularly imprinted polymers (MIPs) were synthesized, and their recognition capability was evaluated. Adsorption isotherm was described by the Langmuir model and the maximum adsorption capacity of MIPTy reached 172.4 mg g−1 in water at pH 6.2. A recognition coefficient of 1.17 was obtained. A solid-phase extraction cartridge was manufactured and its behavior was evaluated for tylosin extraction from aqueous and milk samples. An off-line SPE-UV method was applied. An acceptable linearity was obtained in the range of 1–20 μg ml−1 and the average recovery at three spike levels in milk samples was higher than 92%. The limit of quantification was 2.6 × 10−2 μg ml−1. The manufactured SPE cartridge has a great potential for clean-up processes in complex media. The cartridge offers a fast and sensitive option to the existing sorbents for extracting this drug from milk samples. 相似文献
969.
Yin-tao Li Shi-feng Zhang Shan-qiang Wang Zhi-yu He Yuan-lin Zhou Hui Ren 《应用聚合物科学杂志》2020,137(41):49234
Hydrophobically associating copolymers using acrylamide (AM), acrylic acid (AA), and Styrene (St) as comonomers were successfully prepared by self-emulsified microemulsion polymerization, in which low-molecular-weight AM/AA/St copolymers as surfactant and AM as cosurfactant. The structure and chemical composition of AM/AA/St copolymers were characterized by Fourier transform infrared, nuclear magnetic (NMR), and differential scanning calorimeter. The content of PSt in the copolymers is determined by 1H nuclear magnetic resonance spectra, suggesting that the self-made polymer surfactant can disperse uniformly the St monomers to improve the copolymerization efficiency. Furthermore, the polymerization mechanism of the self-emulsified microemulsion method is explored preliminarily. During the synthesis of the copolymers, the purified copolymer solution is obtained in one step without using a small molecular emulsifier such as sodium dodecyl sulfate, in order to avoid the complicated post-treatment process of the small molecular emulsifier. The copolymers revealed good hydrophobic association properties and low surface tension. 相似文献
970.
Xiatong Qin Weihao Liu Genqi Liu Chenrui Ren Chenhui Liu Huanhuan Li Yunlei Cao 《应用聚合物科学杂志》2020,137(42):49299
A novel molecularly imprinted two-dimensional (2-D) photonic crystal hydrogels (MIPH) for sensitive and label-free recognition of 2,4-dichlorophenol (2,4-DCP) was prepared. The 2-D photonic crystal template was fabricated by using air-water interface self-assembly method. And then the template was embedded with molecularly imprinted polymer, which was synthesized with 2,4-DCP as imprinted molecules, dimethyl sulfoxide as solvent, acrylic acid and acrylamide as functional monomers, N,N-methylene bis acrylamide as cross-linker, azobisisobutyronitrile as initiator. The imprinted molecules were removed by 0.01 M ammonia solution. The results indicated that the 2,4-DCP molecularly imprinted 2-D photonic crystal hydrogels has good response and recognition ability to 2,4-DCP. When the molar ratio of cross-linking density of MIPH is 2.3% and the molar ratio of imprinting molecule is 5.0%, the change of Debye ring diameter is the largest. The diameter of Debye ring increased by 7.1 mm when the concentration of 2,4-DCP changed from 0 to 1 × 10−6 M, and the particle spacing of MIPH reduced 38 nm. In addition, the diameter of the Debye ring hardly changed in the solution of analogues of 2,4-DCP such as, phenol, 2-chlorophenol, 2,4,6-trichlorophenol and so on, indicating that the MIPH has highly sensitivity and specificity. 相似文献