纳米氧化锌/低密度聚乙烯膜中锌向食品的迁移研究

目的研究纳米氧化锌/低密度聚乙烯膜(low density polyethylene film,LDPE)中锌(Zn)向食品的迁移行为,探究其迁移规律。方法选取2种食品模拟物(3%乙酸及超纯水)及真实食品(食用白醋及瓶装水),在3种不同实验温度下(70、40及20℃),研究锌向食品模拟物的迁移规律。采用扫描电子显微镜(scanning electron microscope,SEM)和原子力显微镜(atomic force microscope,AFM)表征纳米ZnO/LDPE膜的表面形貌。结果锌向酸性模拟物中的迁移率远远大于水性模拟物中的迁移率,其中锌向酸性模拟物中的最大迁移率分别为22.7%,20.3%及18.6%(ZL-1,ZL-2及ZL-2#),向水性模拟物中的最大迁移率分别为9.9%,5.7%及4.9%(ZL-1,ZL-2及ZL-2#);锌向酸性食品的迁移量(1.59~5.03 mg/g)同样高于向水性食品的迁移量(2.98~24.60μg/g);随着纳米ZnO的初始含量变大迁移率变小;而偶联剂的加入对锌的迁移有一定的抑制作用。随着纳米ZnO浓度的增加,在薄膜中观察到纳米ZnO的不规则形貌。结论纳米ZnO/LDPE膜不适合在高温下包装食物,且其在酸性食品中的安全隐患高于水性食品。     

Effects of CuO addition on the sinterability and electric properties in PbNb2O6-based ceramics

PbNb₂O₆ (PN)-based ceramics with tungsten bronze structure are promising piezoelectric materials in high-temperature devices such as piezoelectric vibration transducers. However, the PN-based ceramics usually exhibit a low bulk density, which greatly limits their practical applications. In this work, CuO was used as the sintering aid to form a liquid-phase bridge, leading to an obvious increase of the bulk density of PN-based ceramics by 11% (from 5.25 to 5.85 g cm⁻³) and the improvement of the piezoelectric constant (d₃₃) (from 168 to 190 pC/N) and the Curie temperature (T_C) from 367 to 395 °C. The positive influence of CuO on densification has been proved by SEM and fracture toughness. The XRD patterns confirmed that there was no secondary phase introduced by CuO addition. The Raman spectra revealed that part of Cu²⁺ ions has probably diffused into host lattice of the PN and preferred to occupy on A-sites. These results not only demonstrate the high potential of the CuO added PN-based ceramics for high-temperature piezoelectric applications, but also reveal the corresponding structure-properties relationship as well as provide a way to improve the sinterability, d₃₃, and T_C simultaneously.     

Photocatalytic desulfurization of dibenzothiophene by NiCo2O4 nanospinel obtained by an oxidative precipitation process modeling and optimization

This paper reports for the first time, synthesis of NiCo₂O₄ nano spinel by green oxidative precipitation and its performance in photocatalytic desulfurization of dibenzothiophene (DBT) from gas oil model at different process conditions under visible light. The as-produced nanostructure was characterized by X-ray diffraction, Fourier transform infrared, UV–VIS diffuse reflective spectroscopy, energy-dispersive X-ray spectrometry and scanning electron microscopy. The experiments for the study of different photocatalytic conditions were designed by response surface methodology and a second-order regression model was developed with a determination coefficient (R²) of 0.9769. Pareto analysis predicted that the relative importance of process factors for DBT removal is as follows: irradiation time?>?reaction temperature?>?photocatalyst dosage?>?DBT concentration. The promising results for DBT removal were concluded by photo desulfurization over the nano spinel. The study confirmed that nano spinels could be an alternative and cheap photocatalyst for desulfurization from the oil products.     

离子液体水热法辅助合成稀土Ce掺杂ZnO纳米材料的制备及其应用研究

以1-甲基咪唑和氯代正丁烷为原料,合成1-丁基-3-甲基咪唑氯盐离子液体;以醋酸锌[Zn(Ac)2]、硫酸锌(ZnSO4)和氯化锌(ZnCl2)为锌源,在1-丁基-3-甲基咪唑氯盐离子液体和丙氨酸体系中与硝酸铈反应,经水热合成法制备得到Ce掺杂的纳米ZnO。采用扫描电子显微镜(SEM)、紫外-可见光吸收光谱(UV-Vis)、X射线衍射仪(XRD)、X射线光电子能谱分析(XPS)和红外光谱(FT-IR)对产品进行表征。以亚甲基蓝(MB)为目标降解物,采用UV-Vis检测,考察了Ce掺杂的纳米ZnO的光催化活性。研究表明,焙烧温度对光催化的晶体结构和光催化活性产生较大的影响;2%Ce/ZnO、焙烧温度为500℃、催化时间为30 min、亚甲基蓝用量0.05 g、pH值为10时降解率可达99.5%以上。     

Development of the method of production of the ultrafine macrohomogeneous composite powder

ABSTRACT

A method of ultrafine macro-homogeneous composite powder – B₄C–ZrO₂ production using a planetary mill was developed. From the macro-homogeneous composite high-density ceramics, B₄C–ZrB₂ was produced by the method of reactive sintering (in situ) at 2000°C under the pressure of 41–42?MPa. The effect of ZrO₂ grain size and of its distribution in the matrix on the consolidation parameters, and the microstructure of the obtained ceramics was studied.     

Tinospora cordifolia mediated facile green synthesis of cupric oxide nanoparticles and their photocatalytic,antioxidant and antibacterial properties

The study reports a facile method for the green synthesis of copper oxide nanoparticles (CuO Nps) by a solution combustion method using Tinospora cordifolia water extract. The Nps were characterized by XRD, SEM, TEM and UV–visible studies. XRD data indicates the formation of pure monoclinic crystallite structures of CuO Nps. SEM images show that the particles have sponge like structure with large surface area and the average crystallite sizes were found to be ~6–8 nm. These observations were confirmed by TEM analysis. Photocatalytic activity studies of CuO Nps reveal that they act as very good catalyst for the effective degradation of methylene blue (MB) in the presence of UV and Sun light. Also, the degradation of MB was found to be pH dependent. The Nps found to inhibit the activity of 1,1-Diphenyl-2-picrylhydrazyl (DPPH) free radicals effectively. CuO Nps exhibit significant bactericidal activity against Klebsiella aerogenes, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus. The study reveals a simple, ecofriendly and robust method for the synthesis of multifunctional CuO nanoparticle employing underutilized medicinal plants.     

Influence of additive materials on the roughness of AISI D2 steel in electrical discharge machining (EDM) environment

The quality of the machined surface resulted from the electrical discharge machining (EDM) environment is not efficient according to the previous studies. One of the significant problems is the impedance of dielectric fluid, where it is contributing to focusing the plasma channel in a limited area. Hence, this behavior leads to appearing deep craters on the machined zone. The researchers have attempted to enhance the average of surface roughness by employing powder particles or surfactant as the additive materials in the dielectric fluid. Unfortunately, these studies did not present a comparison between these additive materials in this environment. Therefore, the present study aims to compare the performance of the average of surface roughness (R_a) for AISI D2 steel by utilizing Nano chromium powder (NCP) and Span-20. The present work has proved that the behavior of the average of surface roughness for this steel is dropping at the maximum level of Nano chromium powder concentration and pulse duration as compared to the behavior with the Span-20. Moreover, the best roughness was produced by this steel with Nano chromium powder at 2 g/L and 20 μs for this powder and the pulse duration.