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931.
Characteristic behavior in the graft copolymerization of acrylamide/N-(1,1-dimethyl-3-oxybutyl)acrylamide (AM/DAAM) comonomers onto dextran by Ce(IV)-induced initiation was investigated. From a preliminary study, it was found that ceric ammonium nitrate polymerized AM/DAAM comonomer mixtures and diacetone acrylamide, but not acrylamide alone in the aqueous solution. The effect of grafting conditions on the graft copolymerization product was studied with the aid of aqueous size exclusion chromatography and the anthrone reagent. The selectivity of formation of the graft copolymer over random copolymer was found to increase as the reaction temperature and AM/DAAM ratio increased and as both the Ce(IV)/Dextran molar ratio and HNO3 concentration decreased. After establishing optimum grafting conditions, graft copolymer samples were prepared, and their aqueous solution behavior studied as functions of structure, temperature, and added salts. 相似文献
932.
Young-Soo Lee Do-Hyeon Park Hee-Taik Kim Kyong-Ok Yoo 《Korean Journal of Chemical Engineering》1995,12(1):23-28
Much SO2, another perilous air pollutant, was emitted during the oxidative regeneration of sulfided sorbent by H2S. In order to prevent emission of SO2, we carried out oxidative regeneration with the physical mixture of CaO and sulfided sorbent and investigated the effect
of regeneration temperature and oxygen concentration on the reactivity of CaO with S02. The effluent gases were analyzed by G.C. and the properties of sorbent were characterized by XRD. SEM, TG/DTA and EPMA.
Deterioration of reactivity of CaO with S02 resulted in increment of emission of SO12 due to the structural changes of CaO above 750°C and that at 850°C was more severe. Furthermore EPMA and XRD analysis revealed
that product layer diffusion through the solid product, CaSO4, was the rate limiting step for CaO sulfidation. The reaction of CaO w:.th SO2 was first order approximately and that was accelerated by high O2 concentration. 相似文献
933.
934.
Nanofiber‐Based Hydrocolloid from Colloid Electrospinning Toward Next Generation Wound Dressing 下载免费PDF全文
Nanofiber‐based hydrocolloid scaffold is prepared by colloid electrospinning of thermoplastic polyurethane (TPU)/sodium carboxymethyl cellulose (S.CMC) in tetrahydrofuran (THF)/dimethylformamide (DMF). The most suitable process of electrospinning for successful formation of fibers is investigated by controlling the concentration of polymeric solution and co‐solvent ratio. In order to accomplish high wettability, the amount of colloid (S.CMC) and the co‐solvent ratio (THF/DMF), which affects the morphology of fibers, are adjusted. Finally, the open wound healing effect is confirmed using nanofiber‐hydrocolloid from in vivo animal studies. A detailed study of the wound healing process is also demonstrated for the first time.
935.
Effect of Sintering Temperature on Thermoelectric Properties of p‐Bi2Te3 Alloys Produced by Gas Atomization 下载免费PDF全文
Babu Madavali Hyo‐Seob Kim Min‐Gyu Choi Gi‐Chan Park Jar‐Myung Koo Hyeon‐Taek Son Soon‐Jik Hong 《International Journal of Applied Ceramic Technology》2016,13(2):245-251
In this research, p‐type Bi2Te3–75% Sb2Te3 thermoelectric alloy powders were produced by gas atomization and subsequently sintered by hot pressing at different temperatures. The grain growth of the hot‐pressed samples was observed with increasing sintering temperature from 380°C to 460°C. The compressive strength increased with increasing hot‐pressing temperature due to the high relative density of bulk samples obtained at high temperatures. The effect of sintering temperature on thermoelectric (TE) properties was studied. The maximum power factor 3.48 mW/mK2 was obtained for the sample hot pressed at 420°C due to the resulting high electrical conductivity and enhanced Seebeck coefficient values. 相似文献
936.
Mechanical Properties of Submicrometer‐Grained Transparent Yttria Ceramics by Hot Pressing with Hot‐Isostatic Pressing 下载免费PDF全文
Lin Gan Young‐Jo Park Haneul Kim Jin‐Myung Kim Jae‐Woong Ko Jae‐Wook Lee 《International Journal of Applied Ceramic Technology》2016,13(4):678-684
Here, we report the fabrication and mechanical properties of submicrometer‐grained (0.29–0.58 μm) transparent yttria ceramics by hot pressing combined with hot‐isostatic pressing. The effects of the grain size on the microhardness and the fracture toughness were studied. An unusual decrease of the fracture toughness with an increase in the grain size was revealed, which may be attributed to the different grain size dependence of the fracture behavior of the ZrO2‐doped yttria ceramics compared to that of other yttria ceramics. The microhardness and fracture toughness of the transparent yttria ceramics were found to be better than those of the large‐grained yttria ceramics. 相似文献
937.
Structural and Piezoelectric Properties of (Na1−xKx)NbO3 Platelets and Their Application for Piezoelectric Nanogenerator 下载免费PDF全文
HaiBo Xu Young‐Jin Ko Tae‐Gon Lee Su‐Jin Park Myoung‐Sub Noh Bo‐Yun Kim Jeong Seog Kim Sahn Nahm 《Journal of the American Ceramic Society》2016,99(10):3476-3484
(Na1?xKx)NbO3 (NKN) platelets synthesized at 600°C for 12 h have an Amm2 orthorhombic structure. However, the structure of NKN platelets synthesized at 500°C is a mixture of R3m rhombohedral and Amm2 orthorhombic structures. The formation of a rhombohedral structure is attributed to the presence of OH? and H2O defects in the NKN platelets. The piezoelectric strain constant (d33) of NKN platelets synthesized at 600°C for 12 h is 100 pmV?1, whereas that of NKN platelets synthesized at 500°C is lesser (50 pmV?1) due to the presence of these defects. Piezoelectric nanogenerators (PNGs) are fabricated using composites consisting of NKN platelets and polydimethylsiloxane. A large output voltage of 25 V and output current of 2.7 μA were obtained for the PNG with NKN platelets synthesized at 600°C for 6 h. This PNG shows a high output electrical energy of 3.0 μW at an external load of 5.1 MΩ. 相似文献
938.
Hyunjun Kim Brahim Akdim James Park Woo-Yong Jang Randall S. Hay Augustine M. Urbas Christopher Woodward 《Journal of the American Ceramic Society》2021,104(11):5659-5670
High-throughput computation, based on density functional theory (HT-DFT), is used to predict the bounds for optical transparency, from the ultraviolet to the infrared, for materials in the pyrochlore family. The HT-DFT approach adopted here uses an initial screening from Materials-Project database, with millions of calculated properties. Band gaps and phonon spectra were calculated from selected pyrochlore crystal structures taken from the Materials Project database. Short and long wavelength bounds for optical transparency were calculated for chemistries with stable, cubic structures. The calculations predict that La2Ce2O7 has one of the broadest range of transparency for the pyrochlore family. Based on these calculations, dense polycrystalline samples of La2Ce2O7 were produced by sintering and hot-isostatic pressing. Transparency was characterized by methods that did not require large samples with high optical quality, obtaining 7.15 and 7.5 µm at 95% and 90% normalized transmittance, respectively. Bandgap calculations suggest a lower bound of UV transparency cut-off of 0.3 µm. The infrared wavelength cut-off is higher than that reported for other pyrochlores, and higher than for yttria, zirconia, or other common infrared transparent ceramics. We discuss our prediction and characterization methods as well as the suitability of pyrochlores for mid- and far-infrared optical applications. 相似文献
939.
940.