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91.
Norimah Yusof Ros Anita Ahmad Ramli Foziah Ali 《Radiation Physics and Chemistry》2007,76(11-12):1882-1884
A study was carried out to determine optimum decontamination dose for a locally manufactured coconut cream powder. Samples were gamma irradiated (0–15 kGy) and ageing process was achieved using GEER oven at 60 °C for 7 days, which is equivalent to one-year storage at room temperature. Iodine value (IV), ranging from 4.8 to 6.4, was not affected by radiation doses and storage, however peroxide value and thiobarbituric acid (TBA) generally increased with radiation doses. In most samples, peroxide value (meq/kg) reduced after storage, whilst the TBA (mg malonaldehyde/kg), indicator for product quality, slightly increased. The sensory evaluation conducted using 25 taste panellists indicated that scores on odour, creamy taste and overall acceptance for all irradiated samples at more than 5 kGy were significantly lower (P<0.05) than the control. However, the panellists could not detect any significant differences among the irradiation doses (P>0.05). All stored products were significantly different in colour, creamy taste, odour and overall acceptance (P<0.05) when compared to the non-stored non-irradiated control. Microbiological count of the samples prior to irradiation was in the range of 1×102–1.7×103 cfu/g with no detection of Salmonella sp. and Escherichia coli. No microbial colonies were detected after irradiation. Based on the TBA and overall sensory acceptance, gamma irradiation of 5 kGy was found to be the optimum dose and lower doses can be considered to decontaminate coconut cream powder. 相似文献
92.
93.
P. Berastegui S. HullF.J. Garc? Garc? J. Grins 《Journal of solid state chemistry》2002,168(1):294-305
The structures of the oxyorthogermanate La2(GeO4)O and the apatite-structured La9.33(GeO4)6O2 have been refined from powder neutron diffraction data. La2(GeO4)O crystallizes in a monoclinic unit cell (P21/c) and is cation stoichiometric in contrast to previous reports. La9.33(GeO4)6O2 crystallizes in a hexagonal unit cell (P63/m) and the powder diffraction data show anisotropic peak broadening that is observed in electron diffraction patterns as incommensurate diffuse spots at hkq reciprocal planes (with q=1.6-1.7) and can be attributed to a correlated disorder in the “apatite channels”. This compound was doped up to a nominal composition close to M2La8(GeO4)6O2 with M=Ca, Sr, Ba. The dopant ions preferentially occupy the 4f sites as the number of La vacancies decreases. The measured ionic conductivity of La9.33(GeO4)6O2 is about 3 orders of magnitude larger than for La2(GeO4)O at high temperatures and decreases with increasing dopant content from the highest value of about 0.16 S cm−1 at 1160 K. 相似文献
94.
A novel carrier of ultradispersed diamond black powder (UDDBP) was used to support metallocene catalyst. Al2O3 was also used as carrier in order to compare with UDDBP. Supported catalysts for ethylene polymerization were synthesized by two different reaction methods. One way was direct immobilization of the metallocene on the support, the other was adsorption of MAO onto the support followed by addition of the metallocene. Four supported catalysts Cp2ZrCl2/UDDBP, Cp2ZrCl2/Al2O3, Cp2ZrCl2/MAO/UDDBP and Cp2ZrCl2/Al2O3/MAO were obtained. The content of the zirconium in the supported catalyst was determined by UV spectroscopy. The activity of the ethylene polymerization catalyzed by supported catalyst was investigated. The influence of Al/Zr molar ratio and polymerization temperature on the activity was discussed. The polymerization rate was also observed. 相似文献
95.
CuO超细粉体的形貌与红外特性研究 总被引:16,自引:0,他引:16
CuO作为一种多功能精细无机材料,在印染、陶瓷、玻璃及医药等领域的应用已有数十年的历史,作为催化剂的主要活性成分,近年来在氧化、加氢、C1化学合成、NOx还原、CO及碳氢化合物燃烧、精细化工等多种催化反应中也得到了广泛的应用。可以推测,当CuO材料的粒度达到纳米级时,将使它的功能更加独特,应用更为广泛。因此CuO纳米材料的制备方法、聚集状态、与其他组分或载体的作用状况及催化活性等成为当前功能材料发展的研究热点之一犤1~8犦。我们在前文中报道了直接热解Cu2(OH)2CO3所得CuO粒径小、分布均匀、比表面积大,… 相似文献
96.
Substitution of Pb for Bi in the recently characterized mixed-valence lead-platinum oxide PbPt2O4 was attempted and a Pb1−xBixPt2O4 solid solution was obtained for 0≤x≤0.3. Powder X-ray diffraction study showed that all substituted compounds crystallize with similar triclinic unit cell and PbPt2O4 lattice parameters. The structural model of Pb0.7Bi0.3Pt2O4 was refined from powder X-ray diffraction data using the Rietveld method and the results indicate the same crystal structure than PbPt2O4 with one mixed Pb/Bi atomic site. Neutron diffraction realized on the two limit compositions of the solid solution (x=0 and 0.3) allowed to confirm the PbPt2O4 and Pb0.7Bi0.3Pt2O4 stoichiometries. Mean oxidation degree of Pt atoms in the [PtO4] infinite chains decreases from +3 for PbPt2O4 to +2.7 for Pb0.7Bi0.3Pt2O4. Conductivity measurements show a metallic behavior for all the compositions except the limit composition x=0.3 for which a semiconducting behavior appears. 相似文献
97.
XRF分析铁矿粉的标准选择判据研究和应用 总被引:2,自引:0,他引:2
本文对XRF法分析铁矿的基体校正元素进行了研究,并建立了标准选择判据,编制的计算软件可以自动地从大量标样中选择适合该样品分析的标准。该法可用于粉末压片制样的分析,方法快速,准确度和精密度均符合生产要求。 相似文献
98.
A coalesced high-intensity dc discharge is maintained between three cathodes and a single anode, stabilized by using resistors on each cathode leg. Jets of plasma gas are produced from either the cathode area or the anode area of the device. Cathode jets are generated by the self-induced pumping at the cathode tips and augmented by central gas injection. Arc voltage-current characteristics show classical convection-stabilized arc behavior. Anode heat transfer rates may be substantially increased by central gas injection toward the anode. Temperature fields in the coalesced, axially symmetric portion of the arc are determined spectrometrically and compared to those of a classical single-cathode free-burning arc. 相似文献
99.
重钙粉作为填充剂被广泛应用于橡胶加工过程,但由于其表面具有极性,分散性较差,导致与橡胶材料界面结合较差,影响了橡胶产品的抗拉强度、断裂伸长率等力学性能。 本文采用沉淀法,在CaCl2-H2O-NH3-CO2体系中生成碳酸钙直接结晶于重钙粉颗粒表面,实现对重钙粉的表面包覆,将n(CaCl2):n(重钙粉)=1:100、5:100、10:100的包覆重钙粉填充到天然橡胶和再生胶中,橡胶的力学性能与填充未包覆重钙粉的橡胶相比有了一定的提升。 通过比较,在填充量较大(8.5%、15%)时,包覆重钙粉橡胶产品在硬度、定伸应力等力学性能上要好于轻钙粉橡胶产品;在填充量(5%、8.5%)时,包覆重钙粉橡胶产品的抗拉强度、断裂伸长率接近于白炭黑,硬度高于白炭黑橡胶产品。 相似文献
100.
Sara Busi Jarmo Ropponen Jussi Valkonen Kari Rissanen 《Journal of solid state chemistry》2004,177(10):3757-3767
Series of new aromatic R2R′2N+Br− (R=benzyl, 4-methylbenzyl, 2-phenylethyl, 3-phenylpropyl; R′=ethyl, methyl, isopropyl) or RR′2NH+Br−-type (R=benzyl, R′=isopropyl) quaternary ammonium bromides were prepared by using novel synthetic route in which a formamide (N,N-diethylformamide, N,N-dimethylformamide, N,N-diisopropylformamide) is treated with aralkyl halide in presence of a weak base. The compounds were characterized by 1H-NMR and 13C-NMR spectroscopy and mass spectrometry. Structures of the crystalline compounds were determined by X-ray single crystal diffraction, and in addition the powder diffraction method was used to study the structural similarities between the single crystal and microcrystalline bulk material. Three of the compounds crystallized in monoclinic, two in orthorhombic and one in triclinic crystal system, showing ion pairs, which are interconnected by weak hydrogen bonds and weak π-π interactions between the phenyl rings. Three of the compounds appeared as viscous oil or waxes. Finally, TG/DTA and DSC methods were used to analyze thermal properties of the prepared compounds. The lowest melting points were obtained for diethyldi-(2-phenylethyl)ammonium bromide (122.2 °C) and for diethyldi-(3-phenylpropyl)-ammonium bromide (109.1 °C). In general, decomposition of the compounds started at 170-190 °C without identifiable cleavages, thus liquid ranges of 30-70 °C were observed for some of the compounds. 相似文献