Mechanical property degradation of high crystalline SiC fiber–reinforced SiC matrix composite neutron irradiated to ∼100 displacements per atom

For the development of silicon carbide (SiC) materials for next-generation nuclear structural applications, degradation of material properties under intense neutron irradiation is a critical feasibility issue. This study evaluated the mechanical properties and microstructure of a chemical vapor infiltrated SiC matrix composite, reinforced with a multi-layer SiC/pyrolytic carbon–coated Hi-Nicalon^TM Type S SiC fiber, following neutron irradiation at 319 and 629?°C to ～100 displacements per atom. Both the proportional limit stress and ultimate flexural strength were significantly degraded as a result of irradiation at both temperatures. After irradiation at 319?°C, the quasi-ductile fracture behavior of the nonirradiated composite became brittle, a result that was explained by a loss of functionality of the fiber/matrix interface associated with the disappearance of the interphase due to irradiation. The specimens irradiated at 629?°C showed increased apparent failure strain because the fiber/matrix interphase was weakened by irradiation-induced partial debonding.     

Poly(4‐vinyl pyridine)‐grafted graphene oxide for drug delivery and antimicrobial applications

Graphene oxide (GO) was covalently functionalized with poly(4‐vinyl pyridine) (P4VP) by atom transfer radical polymerization for drug delivery and antimicrobial applications. The physiochemical properties, chemical structure, composition and morphology of the P4VP‐functionalized GO (GO‐P4VP) were studied. Simple physisorption of a cancer drug, camptothecin (CPT), via π ? π stacking and/or hydrophobic interactions on the GO‐P4VP was tested for drug loading and its release by altering the pH. The GO‐P4VP has low cytotoxicity, and the CPT‐loaded GO‐P4VP exhibited a high potency for killing cancer cells in vitro. Prominent antimicrobial properties against Escherichia coli and Staphylococcus aureus were also observed. Thus, the GO‐P4VP can be utilized as a drug delivery vector with high biocompatibility, solubility and stability in physiological solutions, a suitable payload capacity and excellent bacterial toxicity. Owing to its small size, low cost, large specific area, ready scalability and useful non‐covalent interactions, GO‐P4VP is a novel material for biomedical, industrial and environmental applications. © 2015 Society of Chemical Industry     

Effect of UV-C irradiation on the inactivation of inoculated pathogens and quality of chicken breasts during storage

In this study, we evaluated the inactivation of foodborne pathogens inoculated on chicken breasts by UV-C treatment. Chicken breasts were inoculated with Campylobacter jejuni, Listeria monocytogenes, and Salmonella enterica serovar Typhimurium at 6–7 log CFU/g. The inoculated chicken breasts were then irradiated with UV-C light of dose 0, 0.5, 1, 3, and 5 kJ/m². Microbiological data indicated that the populations of the foodborne pathogens decreased significantly (p < 0.05) with increasing UV-C irradiation. In particular, UV-C irradiation at 5 kJ/m² reduced the initial populations of C. jejuni, L. monocytogenes, and S. typhimurium by 1.26, 1.29, and 1.19 log CFU/g, respectively. After UV-C irradiation, the samples were individually packed using polyethylene terephthalate containers and stored at 4 ± 1 °C for 6 d. The pH of the control increased more than the samples irradiated at 0.5, 1, 3, and 5 kJ/m², while TBARS values increased during storage regardless of UV-C irradiation. UV-C irradiation caused negligible changes in Hunter L, a, and b values. These results suggest that UV-C irradiation can be useful in improving the microbial safety of chicken breasts during storage, without impairing quality.     

聚烯烃接枝马来酸酐接枝率的测定—聚乙烯接枝

以非均相化学接枝法和红外光谱法相结合的方法绘制了定量校正曲线,可用于红外光谱法测定聚乙烯接枝马来酸酐的接枝率。该方法简便快速,准确可靠,重复性好。     

长支链聚乙烯的制备与性能

通过过氧化二异丙苯(DCP)引发三官能单体三羟甲基丙烷三丙烯酸酯(TMPTA)对高密度聚乙烯(HDPE)进行熔融接枝改性,同时利用大分子自由基间的偶合反应制备出长支链聚乙烯(LCBPE)。转矩曲线和傅里叶变换红外光谱测试表明TMPTA成功接枝到HDPE,解释了熔融支化法制备LCBPE的机理。利用多种流变分析方法,如储能模量、损耗角、Cole-Cole图等方法有效区分了LCBPE和HDPE。采用差示扫描量热和X射线衍射分析技术,研究了引发剂用量对LCBPE结晶性能的影响,结果表明,长支链LCB结构的引入使HDPE的熔点、结晶度和起始结晶温度提高,晶体结构和晶型未发生变化,晶粒尺寸增大。利用热台偏光显微镜对HDPE和LCBPE晶体形态进行分析,发现LCBPE相比HDPE晶核增多,晶体生长速度降低。     

超声波辐射合成4-(4-氯苯基)-6-甲基-5-乙氧羰基-3,4-二氢嘧啶-2(H)-酮

研究了超声波辐射合成4-(4-氯苯基)-6-甲基-5-乙氧羰基-3,4-二氢嘧啶-2(H)-酮,确定了最优合成工艺条件:n(4-氯苯甲醛)∶n(乙酰乙酸乙酯)∶n(尿素0.03 mol)=1.0∶1.2∶1.5,催化剂氨基磺酸用量0.6 g,超声波功率120 W,辐射时间45 min,产物产率为98.4%。     

Preparation of ion‐exchange membranes by hydrolysis of radiation‐grafted polyethylene‐g‐polyacrylamide membranes

Polyethylene‐g‐polyacrylamide membranes were prepared by graft polymerization of acrylamide onto polyethylene films using a preirradiation method. The ion‐exchange membranes were obtained by the hydrolysis of grafted films so as to transform amide groups into carboxyl groups. The fraction of amide groups transformed into carboxyl groups was limited to ～0.5. The characterization and thermal behavior of membranes with different degrees of grafting were evaluated by FTIR, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) measurements. The heat of fusion and the crystallinity of polyethylene decreased considerably in the hydrolyzed membranes depending on the degree of grafting. It was found that the grafting of acrylamide led to the reduction in crystallinity due to disruption of the crystallites (crystal defects) and dilution of the inherent crystallinity (dilution effect). The contribution of the hydrolysis step to the crystallinity decrease was negligible. The thermal stability of the membranes as obtained from TGA showed considerable enhancement after hydrolysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 149–154, 2003     

Study of the retrogradation behaviour of rice cake using rapid visco analyser,Fourier transform infrared spectroscopy and X‐ray analysis

Retrogradation of gelatinised starch is the main phenomenon that influences the texture of MiGao (rice cake). The hardness of the MiGao increased during stored at 25 °C for 5 days. Rapid visco analyser (RVA), Fourier transform infrared (FT‐IR) spectroscopy and X‐ray were quantified to analysis the retrogradation behaviour of MiGao. The most significant change in the pasting curve was the increase in peak viscosity over time measured with an RVA. FT‐IR indicated changes in crystallinity of the MiGao crumb. The X‐ray diffraction patterns could be classified as typical of A‐type starch for the fresh MiGao. With aging, the B‐type structure increases, while the A‐type structure remains virtually unchanged. All the results suggested that the main mechanism underlying the changes in properties is suggested to be slow amylopectin crystallisation.     

Improvement of green cathodoluminescence of zinc oxide stacked films prepared by high-power excimer laser irradiation of sol-gel-derived precursors

Zinc oxide (ZnO) stacked films were prepared by repeating a procedure involving KrF excimer laser irradiation at various energy fluences (E_f) of sol-gel-derived precursors. All the stacked films are wurtzite-type and highly c-axis oriented on glass substrates. The green cathodoluminescence (CL) efficiency of the films is strongly influenced by the preparation conditions. Especially, laser E_f and stacking number are important control factors. The stacked film prepared under optimized preparation conditions consists of large grains and indicate low electric resistivity. The green CL efficiency of the stacked film is 0.0139 lm/W, which is higher than those of ZnO thin films prepared by a single stacking.     

反应挤出熔融接枝改性淀粉/PE-LD发泡材料的制备及性能研究

将热塑性淀粉分别与6种小分子单体及引发剂熔融挤出制备接枝改性淀粉。红外光谱和接枝率的研究表明,采用熔融挤出接枝的方法可以使小分子单体与淀粉发生接枝反应,丙烯酸与淀粉的接枝率最高为2.4%;采用XRD、哈克流变仪和偏光显微镜等分析了熔融接枝改性淀粉/低密度聚乙烯(PE-LD)共混物的结晶性能、流动性能和发泡性能。结果表明,接枝改性增加了淀粉和 PE-LD 的相容性,使淀粉基发泡材料的密度降低、泡孔均匀度提高,其中用丙烯酸接枝的淀粉/PE-LD 发泡材料的各项性能均较好,丙烯酸的最佳用量为3份。