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991.
Bangchao Zhong Qifeng Shi Chao Yang Yuanfang Luo Demin Jia 《International Journal of Polymer Analysis and Characterization》2016,21(1):1-10
A novel rubber antioxidant, vitamin C-lanthanum complex, was prepared and applied in styrene-butadiene rubber (SBR)/silica composites. The anti-aging behavior of SBR/silica composites with vitamin C-lanthanum complex was systematically investigated by mechanical property retention after aging, oxidation induction time, exothermic enthalpies of thermal oxidation, and thermo-oxidative degradation kinetics. The highlight of this work lies in the fact that several thermal analysis techniques were successfully applied to fully evaluate the thermal-oxidative aging of SBR/silica composites and the vitamin C-lanthanum complex was found to endow SBR/silica composites with better protection against aging than commercial antioxidants, which may be beneficial for better characterization of rubber aging and fruitful for the preparation of highly aging-resistant rubber composites, respectively. 相似文献
992.
建立固相萃取与电感耦合等离子体原子发射光谱法(ICP–AES)测定环境水样中Cr(Ⅲ)含量的方法。合成了功能化铁氧体磁性材料作为固相萃取剂,优化了固相萃取条件。当样品溶液的p H值为2.5时,固相萃取剂能在5 min内完成Cr(Ⅲ)的富集。使用1 mol/L HNO3在3 min内即可解吸附分离Cr(Ⅲ),饱和吸附容量为15.2μg/mg,研究了共存离子的影响。Cr(Ⅲ)含量在1~50μg/L范围内与发射光谱强度呈良好的线性关系,线性相关系数为0.999 9,检出限为0.09μg/L,测定结果的相对标准偏差为2.2%(n=8),回收率为97.7%~104.8%。该方法高效、快速,测定结果准确可靠,可用于测定环境水样品中的痕量Cr(Ⅲ)。 相似文献
993.
以乙酰丙酮盐为前驱体,三乙二醇为溶剂,采用多元醇法制备了纳米Ni0.5-xCoxZn0.5Fe2O4(x=0,0.1,0.2,0.3和0.4)铁氧体.通过X射线衍射仪(XRD)、透射电子显微镜(TEM)、傅里叶变换红外光谱仪(FTIR)和振动样品磁强计(VSM)等对样品的结构、形貌和磁性能进行了表征.结果表明,所得纳米Ni0.5-xCoxZn0.5Fe2O4铁氧体的分散性较好,尺寸均一.在室温下产物的剩磁和矫顽力均较小,表现出亚铁磁性.纳米Ni0.3Co0.2Zn0.5Fe2O4铁氧体的饱和磁化强度达到41.34 A·m2·kg-1,其在交变磁场中升温可达到55℃,表现出较好的磁热性能. 相似文献
994.
Ravi Kumar Ganta A. Ramgopal Chatragadda Ramesh K. Raghu Babu M. Murali Krishna Kumar B. Venkateswara Rao 《合成通讯》2016,46(24):1999-2008
A simple, efficient, ecofriendly, and cost-effective method has been developed for the synthesis of 16 spiropyrazolo pyrimidine derivatives (5a–5p) by a four-component, one-pot reaction of pyrimidine-2,4,6(1H,3H,5H)-trione, 3-oxo-3-phenylpropanenitrile, hydrazine, and isatins (4a–4f) by using nanocopper ferrite catalyst (20?mol%) in water with excellent yields (73–91%). The isatin with electron-withdrawing groups gave products in high yields (5h and 5p). The present methodology offers an environmentally benign, cost-effective, high-yielding method with recyclable catalyst. The drug likeness or “drugability” of all the synthesized compounds were tested through rule of five (RO5) parameters. Compounds 5f, 5h, 5n, and 5p have shown one RO5 violation each. The compounds were screened for their antibacterial activity against human pathogenic bacteria wherein two of the synthesized compounds were found to possess significant antibacterial activity. Compounds showing RO5 violations had negligible antibacterial activity. 相似文献
995.
A series of Mn–Zn Ferrite nanoparticles (<15 nm) with formula MnxZn1−xFe2O4 (where x=0.00, 0.35, 0.50, 0.65) were successfully prepared by citrate-gel method at low temperature (400 °C). X-ray diffraction analysis confirmed the formation of single cubic spinel phase in these nanoparticles. The FESEM and TEM micrographs revealed the nanoparticles to be nearly spherical in shape and of fairly uniform size. The fractions of Mn2+, Zn2+ and Fe3+ cations occupying tetrahedral sites along with Fe occupying octahedral sites within the unit cell of different ferrite samples are estimated by room temperature micro-Raman spectroscopy. Low temperature Mossbauer measurement on Mn0.5Zn0.5Fe2O4 has reconfirmed the mixed spinel phase of these nanoparticles. Room temperature magnetization studies (PPMS) of Mn substituted samples showed superparamagnetic behavior. Manganese substitution for Zn in the ferrite caused the magnetization to increase from 04 to18 emu/g and Lande's g factor (estimated from ferromagnetic resonance measurement) from 2.02 to 2.12 when x was increased up to 0.50. The FMR has shown that higher Mn cationic substitution leads to increase in dipolar interaction and decrease in super exchange interaction. Thermomagnetic (M–T) and magnetization (M–H) measurements have shown that the increase in Mn concentration (up to x=0.50) enhances the spin ordering temperature up to 150 K (blocking temperature). Magnetocrystalline anisotropy in the nanoparticles was established by Mossbauer, ferromagnetic resonance and thermomagnetic measurements. The optimized substitution of manganese for zinc improves the magnetic properties and makes these nanoparticles a potential candidate for their applications in microwave region and biomedical field. 相似文献
996.
Erbium substituted cobalt ferrite (CoFe2−xErxO4; x=0.0–0.2, referred to CFEO) materials were synthesized by sol-gel auto-combustion method. The effect of erbium (Er3+) substitution on the crystal structure, dielectric, electrical transport and magnetic properties of cobalt ferrite is evaluated. CoFe2−xErxO4 ceramics exhibit the spinel cubic structure without any impurity phase for x≤0.10 whereas formation of the ErFeO3 orthoferrite secondary phase was observed for x≥0.15. All the CFEO samples demonstrate the typical hysteresis (M–H) behavior with a decrease in magnetization as a function of Er content due to weak superexchange interaction. The frequency (f) dependent dielectric constant (ε′) revealed the usual dielectric dispersion. The ε′–f dispersion (f=20 Hz to 1 MHz) fits to the modified Debye's function with more than one ion contributing to the relaxation. The relaxation time and spread factor derived are ∼10−4 s and ∼0.61(±0.04), respectively. Electrical and dielectric studies indicate that ε′ increases and the dc electrical resistivity decreases as a function of Er content (x≤0.15). Complex impedance analyses confirm only the grain interior contribution to the conduction process. Temperature dependent electrical transport and room temperature ac conductivity (σac) analyses indicate the semiconducting nature and small polaron hopping. 相似文献
997.
998.
999.
Carp O Patron L. Marinescu G. Pascu G. Budrugeac P. Brezeanu M. 《Journal of Thermal Analysis and Calorimetry》2003,72(1):263-270
The influence of the coordination architecture (materialized by ligand binding mode and content) on the thermal behaviour
of coordination compounds containing copper, iron and oxalic anion as ligand was investigated. It was established that the
metal-metal connections influence stronger, comparative with ligand content, the stoichiometry of the thermal decompositions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
1000.
镧对黄瓜幼苗叶片细胞透性及膜脂的影响 总被引:7,自引:1,他引:7
研究了不同浓度的La3 对黄瓜(Cucumis sativus L.)幼苗叶片相对含水量、膜透性、膜脂脂肪酸组分和氧化产物量的影响. 结果表明, La3 对黄瓜幼苗叶片的相对含水量无明显影响; La3 浓度为2 mmol·L-1时, 膜的相对透性明显上升, 而0.002~0.2 mmol·L-1 La3 处理的叶片细胞质膜通透性的变化不明显; 利用高压气相色谱法测定了叶片膜脂脂肪酸组分的变化, 表明用不同浓度La3 处理后, 组成及总的含量无显著改变, 但脂肪酸配比发生了变化; La3 处理的黄瓜幼苗叶片膜脂过氧化程度与它的浓度相关. 当La3 的浓度为0.002~0.02 mmol·L-1时, 丙二醛(MDA)的含量发生了减少, 而2 mmol·L-1 La3 使得叶片产生的MDA的含量增加了. 低浓度La3 减轻了膜脂过氧化程度, 而高浓度La3 恰恰相反, 加重了膜脂过氧化的程度. 相似文献