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61.
Study on the relationship between the particle size distribution and the effectiveness of the K‐powder fire extinguishing agent 下载免费PDF全文
The relationship between the particle size distribution and the extinguishing effectiveness of the new K‐powder fire extinguishing agent has been studied experimentally, to explore the reason of the great extinguishing efficiency exhibited by the new K‐powder fire extinguishing agent on Class B fire (liquid fuel fire). The results of the experiment showed that the extinguishing effectiveness increased along with the decrease of the particle size distribution. In addition, a sharp discontinuity appeared around the limiting size, about 40 μm. The powder with the particle size below 40 μm exhibited highly effective extinguishing with the minimum effective extinguishing concentration Cxr = 23 g·m?3, while the powder with the particle size above 40 μm exhibited little fire extinguishing efficiency. Compared with other fire extinguishing agents produced by different substances, the new K‐powder fire extinguishing has the bigger limiting size. That means, in the same particle size distribution, the new K‐powder fire extinguishing agent contains more highly effective powder than others contain, and is more effective. 相似文献
62.
Paweena Prapainainar Sumanut Maliwan Kannikar Sarakham Zehui Du Chaiwat Prapainainar Stuart M. Holmes Paisan Kongkachuichay 《International Journal of Hydrogen Energy》2018,43(31):14675-14690
In this work, composite membranes for a direct methanol fuel cell (DMFC) were prepared using a spraying method to improve cell performance especially at a high methanol concentration. Nafion polymer and mordenite as a filler were used for the composite membrane preparation using a spraying method and a conventional solution casting method and the membranes from the two methods were compared. SEM images showed that a more homogeneous composite membrane could be obtained using the spraying method. The effect of mordenite content was also studied. The membranes were consequently characterized and tested in DMFC operation. The results were compared to those prepared using the solution casting method at 30, 50, and 70 °C with methanol concentrations of 2, 4, and 8 M. It was found that the membrane with 5 wt.% mordenite from the spraying method showed a vast improvement in DMFC performance. When the cell was operated at 70 °C, the maximum power density of 5 wt.% mordenite from the spraying method was higher than that of commercial membrane and 5 wt.% from the solution casting method. Power densities from the 5 wt.% sprayed membrane were higher by around 29%, 40%, and 60% at 2, 4, and 8 M methanol concentration, respectively. 相似文献
63.
64.
Crystal Structures and Phase Behavior of Sulfadiazine and a Method for the Preparation of Aggregates with Good Performance 下载免费PDF全文
Songgu Wu Shichao Du Mingyang Chen Kangli Li Lina Jia Dejiang Zhang Estevao G. J. Macaringue Baohong Hou Junbo Gong 《化学工程与技术》2018,41(3):532-540
The solvate and the solvent‐free form of sulfadiazine (SD) were investigated. SD was found to exist in one solvent‐free form and the N‐methylpyrrolidone (NMP) solvate form. The NMP solvate was shown to be a channel‐type compound. The intrinsic properties of the solvents were used to evaluate the effects of solubility on the phase transformation of SD and the NMP solvate. The SD phase could transform to the NMP solvate by NMP‐mediated phase transformation, which was governed by crystallization of the NMP solvate. The crystalline NMP solvate could transform to the solvent‐free solid state through solid‐solid transformation upon heating or water penetration‐mediated phase transformation. The rate of this water penetration‐mediated phase transformation of the NMP solvate to SD was unusually fast. It can be used to obtain SD aggregates of well‐defined shape and good powder properties. 相似文献
65.
Yan Xiong Xianwu Du Mingyu Xiang Hao Wang Weimin Wang Zhengyi Fu 《Journal of the European Ceramic Society》2018,38(12):4167-4172
The densification behaviors of pure B4C and B4C-ZrO2 mixtures were compared during hot pressing. The results showed that in-situ formed ZrB2 effectively enhanced the densification process of B4C-ZrO2 mixtures, more significantly during the intermediate stage. Within the relative density ranging from 0.75 to 0.90, the B4C-15?wt%ZrO2 mixture (B15Z) achieved the maximum densification rate as twice much as that of pure B4C. The stress exponent n>3 indicated plastic deformation was the dominant densification mechanism of B15Z. The viscosities of plastic flow were evaluated using Murray-Rodger-William equation and the viscosity of B15Z was only a quarter of that in pure B4C. The sintering activation energy was calculated to be 305.9?kJ/mol for pure B4C and 197?kJ/mol for B15Z, respectively. It was proposed that the lower viscosity of plastic flow and activation energy accelerated the sliding and propagating motions of plastic flow, by which underlain the enhanced densification behaviors of B4C-ZrO2 mixtures. 相似文献
66.
Xueli Du Yuelong Wang Rongna Shi Zhiyong Mao Zhihao Yuan 《Journal of the European Ceramic Society》2018,38(10):3512-3517
The PbClxS1-x and Pb1-xBixS (x? =?0–0.05) bulks were fabricated with a facile method of hydrothermal synthesis and microwave sintering, and the effect of anionic and cationic donors on the thermoelectric performance of PbS was investigated. Although Cl? and Bi3+ both effectively improved the thermoelectric properties of n-type PbS, more excellent thermoelectric performance was obtained from Cl? doped samples because of higher electrical property and lower thermal conductivity at higher temperature (T? >?600?K). The thermoelectric figure of merit (ZT) reaches 1.04 for PbCl0.015S0.985 at 800?K and increases with temperature increasing without sign of saturation, which is probably the highest value ever reported for single-phase polycrystalline n-type PbS. The results also indicate that the hydrothermal synthesis and microwave sintering can realize anion doping as well as cation doping for n-type PbS at low cost, and PbS should be a robust alternative for PbTe thermoelectric materials. 相似文献
67.
Lingyu Li Zhiyun Li Xiutao Li Xiqing Xu Anran Guo Jiachen Liu Haiyan Du 《Journal of the European Ceramic Society》2018,38(10):3595-3602
Directional ice-templated ceramics have unique lamellar porous channels between ceramic walls which run from bottom to top of the samples. This highly oriented morphology results in the anisotropy in mechanical properties both parallel and perpendicular to freezing direction. In this research, fiber-enhanced ice-templated porous ceramics were fabricated by introducing fibers into alumina slurry for freezing. The trans-lamellar fiber bridges connecting adjacent ceramic walls were formed by adjusting the aspect ratio of fibers and freezing velocity, which greatly enhanced the compressive response in two directions and weakened the anisotropy in mechanical properties of the directional ice-templated ceramics. The results showed that the of fiber bridges increased with the increase of fiber aspect ratio and the longitudinal and transverse mechanical properties increased by 73.5% and 232.6%, respectively. 相似文献
68.
Teng Zheng Laihui Luo Peng Du Anmeng Deng Weiping Li 《Journal of the European Ceramic Society》2018,38(2):575-583
The (0.98-x)(0.6Pb(Mg1/3Nb1/3)O3-0.4PbTiO3)-xPb(Yb1/3Nb1/3)O3-0.02Pb(Er1/2Nb1/2)O3 ((0.98-x)(PMN-PT)-xPYN:Er3+) ceramics were prepared through a solid-state reaction method. The phase structure, piezoelectric response, ferroelectric performance and upconversion emission of the ceramics were systematically investigated. The phase structure, the electrical and optical properties are strongly related to the content of PYN. The optimized piezoelectric response and upconversion emissions of the ceramics were achieved near x = 0.12, which locates in the morphotropic phase boundary (MPB) composition. Furthermore, the temperature sensing behaviors of the resultant compounds based on the thermally coupled levels of 2H11/2 and 4S3/2 of Er3+ ions in the temperature range of 133–573 K were studied by utilizing the fluorescence intensity ratio technique. Additionally, the thermal effect, which is induced by the laser pump power, of the studied ceramics is also investigated and the produced temperature is enhanced from 268 to 348 K with the pump power rising from 109 to 607 mW. 相似文献
69.
Tao Li Zehui Du Nobumichi Tamura Mao Ye Saikumar Inguva Wei Lu Xierong Zeng Shanming Ke Haitao Huang 《Journal of the European Ceramic Society》2018,38(4):1488-1497
(1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 ((1-x)PZN-xPT in short) is one of the most important piezoelectric materials. In this work, we extensively investigated (1-x)PZN-xPT (x = 0.07–0.11) ferroelectric single crystals using in-situ synchrotron μXRD, complemented by TEM and PFM, to correlate microstructures with phase transitions. The results reveal that (i) at 25 °C, the equilibrium state of (1-x)PZN-xPT is a metastable orthorhombic phase for x = 0.07 and 0.08, while it shows coexistence of orthorhombic and tetragonal phases for x = 0.09 and x = 0.11, with all ferroelectric phases accompanied by ferroelastic domains; (ii) upon heating, the phase transformation in x = 0.07 is Orthorhombic → Monoclinic → Tetragonal → Cubic. The coexistence of ferroelectric tetragonal and paraelectric cubic phases was in-situ observed in x = 0.08 above Curie temperature (TC), and (iii) phase transition can be explained by the evolution of the ferroelectric and ferroelastic domains. These results disclose that (1-x)PZN-xPT are in an unstable regime, which is possible factor for its anomalous dielectric response and high piezoelectric coefficient. 相似文献
70.
Tingen Zhu Wenping Li Qiqing Wang Yanbo Hu Kaifang Fan Jiafa Du 《Mine Water and the Environment》2020,39(1):57-67
A method to calculate the height of a water-conducting fractured zone (HWCFZ) was developed based on the plate and shell theory, and the development of the HWCFZ in bedrock and Q2l loess strata is discussed in detail. First, the subsidence-deflection curve equation of the overlying stratum is theoretically derived, and then the ultimate deflection and free space height of rock strata are calculated. Moreover, the strata tensile strain is calculated by using integral calculus. In addition, the failure state of the rock is analyzed by comparing the theoretically calculated tensile strain with the experimentally measured yield tensile strain, allowing one to attain the maximum value of HWCFZ. This approach was tested at the Jinjitan coal mine; the theoretically predicted, experimentally measured, and numerically computed maximum HWCFZ values were 189.5, 187.3, and 188.5 m, respectively, demonstrating the accuracy of the proposed method. These results are highly significant for safe and environment-friendly coal mining in northwest Shaanxi, China. 相似文献