386 resultados para Ni-Zn ferrite
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Using knowledge of geology, geochemistry, coal petrology, mineralogy, by means of a variety of advanced measuring methods such as inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled atomic emission spectrometry (ICP-AES), X-ray powder diffraction (XRD), scanning electron microscopy with energy-dispersive spectrometer(SEM-EDS), sequential chemical extract and density fractions, the characteristics of trace elements and minerals in Jurassic Beipiao coal mine under inland limnetic sedimentary environment and in late Permian Jianxin and Qiaotou coal mines under paralic swamp sedimentary environment were studied. Compared with the average concentration in the world bituminous coals, the Beipiao coal was characterized by relatively high contents of Sc, Ti, Cr, Co, Ni, Zn, Se, Sr, Zr, Y, Ba, REE and Th, and lower contents of V, Rb, Cd, Sn, Pb, Bi and U; while the Jianxin coal was relatively enriched in Li, Sc, Ga, Sr, Y, Nb, Sb, Th and U, with low concentration of Be, Co, Ni, Cu, Ge, Zr, Mo, Cd, Cs, Ba, Pb and Bi; and the Qiaotou coal was enriched in Li, Sc, Sr, Nb, Ta, Zr, REE, Hf, Th and U, with low concentration of Be, V, Co, Ni, Cu, Ge, Mo, Cd, Cs, Ba, Tl, Pb and Bi. The concentrations of Ca, Mg and K in Beipiao coal are higher than those in Jianxin coal and Qiaotou coal, while Fe, S and Ti in Beipiao coal are lower than those in Jianxin coal and Qiaotou coal. The proximate analysis of coal samples was carried out, which indicated that Beipiao coal was medium- to high- ash (5.92-60.68%) with low sulphur coal, and Jianxin coal and Qiaotou coal was medium to high ash (8.85-46.33%) with high sulphur. The reflectivity was measured, which explained that Beipiao coal belonged to high volatile bituminous coal, Jianxin coal was low volatile bituminous coal and Qiaotou coal was low volatile anthracite. Quantitative maceral analyses were studied. The characteristics of rare earth elements (REE) were investigated, which showed that the total contents of REE were higher than that of the world's average content. With the increase of coal's metamorphic grade, the total contents of REE decreased from 98.5 X 10"6 of Beipiao coal to 94.2 X 10"6 of Jianxin coal, and to 75.9 X 10"6 of Qiaotou coal, and 5Eu reduced which indicated that the element Eu depleted. The characteristics of REE was controlled by the metamorphic grade of coal. And REE were mainly absorbed in clay minerals in Beipiao coal samples, while in Jianxin and Qiaotou coal mines, REE were primarily related to clay mineral and pyrite. The variation of trace elements in vertical direction of coal seams was studied, and the results showed that different trace elements differed greatly. The correlation between trace elements and ash were determined. Four major trace elements (aluminium-silicates, sulphide, carbonate and phosphate) accounted for the occurrence and distribution of most elements studied were determined. Coal samples were separated by density fraction, which showed that Cr, Cu, Mo and Pb were closely related to inorganic matters mainly distributed in P >2.6 and dropped remarkably in the density fractions P <2.3 . The occurrences of Co, Cr, Ni, As, Se, Mo, U were studied directly and quantitatively using sequential chemical extract with six steps, which showed that Co. Ni, Mo and U were mainly in the form of mineral, and As, Se chiefly in the form of organic state, while Cr mostly in the form of organic state and mineral. Major mineral phases presented in the Beipiao coal were Kaolinite, illite, quartz, calcite, and small amount of siderite, barite. While major mineral phases in Jianxin and Qiaotou coal were pyrite, kaolinite, and small amount of marcasite, rutile, sphalerite. This is the first time that the chromite in the coal was discovered in China, which indicates that Cr occurrence appeared in the form of chromite. The ratio of Sr/Ba, Sr/Ca and V/Ni in Beipiao coal mine under inland limnetic is smaller than that of in Jianxin and Qiaotou coal mines under paralic swamp. The ratio of K/Na and Th/U of Beipiao coal mine is higher than that of Jianxin and Qiaotou coal mine, which proved that Beipiao coal was not affected by sea water and Jianxin and Qiaotou coal were affected by sea water. Trace elements such as Cr, Ni, Mo in minerals were analyzed by SEM-EDS. The factors controlling the enrichment of trace elements can be divided into syngenetic stage factors and epigenetic stage factors.
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与农村土壤相比,阿伯丁市城市土壤(路边土、公园土)的微生物特征发生了显著的改变,微生物基底呼吸作用明显增强,但微生物生物量却显著降低,微生物生理生态参数Cmic/Corg、qco2值明显升高,Biolog数据显示城市土壤对能源碳的消耗量和速度显著升高。对重金属元素研究表明,与农村土相比城市土壤中重金属Pb、Zn、Cu、Ni已经有明显积累,化学形态研究表明Pb主要与氧化铁有关,Ni、Zn以残渣态为主,Cd以有效态为主,而Cu除有效态外,其它结合形态基本具有同等重要的意义。主成分分析表明,有效态Pb是控制城市土壤与农村土壤微生物特征差异的主要因素,其次为Zn,Cu和Ni的有效态和有机态亦有一定的作用效应。
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微量金属元素的微藻生物地球化学主要通过研究微藻与微量金属元素的各种相互作用,在时空上了解微藻在微量金属元素的分布、迁移和富集等过程中所起的作用,以及由此引起的微藻本身的成分、结构、形态和功能在不同地球化学环境中的变异等。地球化学环境变化及由此产生的生态环境效应是目前研究的科学热点之一。工业革命以来,人为活动强烈地改变了地球表层的局部乃至全球的微量金属元素含量,对生物的正常生长乃至人类的健康构成了潜在的威胁。作为初级生产力,浮游藻类在水生生态系统中占有重要地位;它通过生物积累、光合作用及生物矿化,驱动着C、N、Si、P、O、,S、Fe等元素在水体内部的生物地球化学循环;微藻对环境变化敏感,能够很好的响应微量金属元素生物地球化学行为的变化。目前有关湖泊微量金属元素地球化学及浮游植物生态学的研究较多,但浮游植物和微量金属元素相互作用规律的系统研究较少,对湖泊微量金属元素复杂的生物地球化学行为的解释仍缺乏实验依据。本论文研究了高原湖泊阿哈湖、百花湖和红枫湖的微量金属元素和微藻的时空分布特征,探讨了两者之间的相互关系;研究了小球藻和衣藻对微量金属元素的生物吸收和生物吸附特征:研究了微量金属元素对微藻生理生化因子(生长速度和碳酸醉酶胞外酶)的影响;分析了微藻和微量金属元素的相互作用规律,为湖泊微量金属元素生物地球化学行为的解释提供科学依据。通过上述研究,获得了以下几点认识:1.阿哈湖、百花湖和红枫湖的微藻生物量在2002年出现了两个高峰,一个在春季,一个在秋季;这是水温、光照、营养源和捕食等多种因素综合作用的结果。百花湖和红枫湖的微藻以蓝藻和绿藻为主;阿哈湖的微藻春季以蓝藻和绿藻为主,秋季以硅藻为主。阿哈湖和红枫湖的叶绿素a含量在垂直方向随深度增加呈下降趋势,表层浮游藻类较多。2.阿哈湖、百花湖和红枫湖2002年过滤水中微量金属Co、Ni、Cu、zn、M。含量的月变化各不相同;其变化是微藻和降水等多种因素综合作用的结果。降水(酸雨)腐蚀湖泊流域的碳酸盐岩,其中的微量金属元素被溶解,随河流输入湖泊,影响了微量金属元素在湖水中的含量(如三个湖中的cu,阿哈湖中的Mo)。百花湖和红枫湖的蓝藻和绿藻的生物量变化与微量金属元素C。、Cu、zn、M。的含量变化正相关,可能是因为这些微量金属元素在某些程度上限制了蓝藻和绿藻的生长;阿哈湖的硅藻的生物量变化与微量金属元素的含量变化负相关,可能是由于硅藻对它们的富集造成了两者之间的负相关关系。浮游藻类通过吸附、吸收和富集溶解态微量金属元素,影响其在垂直方向的分布。溶解态微量金属元素在垂直方向的分布趋势并不完全相同,其垂直分布特征是本身的浓度大小、浮游藻类和湖底微生物等诸多因素共同作用的结果。3.微藻对微量金属元素生物吸附的平衡时间因对微藻处理方式的不同而不同。单离子体系和多离子体系中衣藻对同一微量金属的吸附情况不同,多离子体系中微量金属元素对吸附作用位点的相互竞争造成了这种差异。多离子体系中,死藻细胞对Cd、zn、cu、Co、Mn的吸附量的大小顺序与它们的原子量的大小顺序一致,这可能是在各种微量金属元素的相互竞争中,死的藻细胞优先选择原子量大的金属;活藻细胞对Cd、Fe、C。、Zn(Ni)的吸附量的大小顺序与它们的离子密度的大小顺序正好相反,这可能是由于活的藻细胞的生物调节作用使其优先选择离子密度小的金属。4.在单离子体系和多离子体系中,不论是活的藻细胞还是死的藻细胞,小球藻对各种微量金属的吸附量大于或相当于衣藻的吸附量;小球藻和衣藻对各种微量金属的吸附量一般随金属浓度的升高而增大。在单离子体系中,衣藻和小球藻对每种微量金属的生物吸收速度随浓度的变化趋势相似,一般是随金属浓度升高吸收速度先增加后减小,但增加和减小分界线处吸收速度对应的金属浓度大小各不相同;小球藻和衣藻对Mn、Fe、C。、Cu、zn(藻必需的微量金属营养元素)的吸收速度大于对Ni、Cd的吸收速度;这主要是因为同一藻类维持新陈代谢所需各种金属的量不同,对不同微量金属毒害的承受程度(生物调节能力)也不同;不同藻类对同一微量金属的需求量和毒害的承受程度也不相同。在单离子体系小球藻和衣藻对各种微量金属的吸附和吸收中,随着浓度的增加,吸收过程比吸附过程更快的达到饱和状态。5.各种微量金属对小球藻和衣藻生长的影响情况因金属种类和藻的种类的不同而不同。Cd·Cu、Ni、zn对小球藻和衣藻生长的毒害较大,而且对衣藻的影响比小球藻的影响大·随各种微量金属浓度的增加,小球藻和衣藻生长速度的变化趋势一般表现为先增大后减小,和它们对各种微量金属的吸收速度的变化趋势一致:可见吸收到藻细胞体内的微量金属的量和它们对细胞生长的影响有密切.的关系,藻细胞的生物调节在这个变化趋势中起了重要的作用。6.阿哈湖和红枫湖微藻碳酸醉酶胞外酶活性明显高于衣藻的CA。活性,主要是因为c入的活性与环境中HcO3一的浓度有关。cd、zn、cu和Pb对微藻c人的活性的抑制效应因金属浓度的不同而不同,而且抑制作用因微藻种类的不同而不同。微量金属元素对CA活性的影响主要通过三个途径:①.直接与CA这一含zn蛋白酶作用;②.间接影响藻细胞内CAe的新陈代谢:③.直接改变cA。的生物活性(例如Pb)。低浓度的Fe、Mn、Co 、Ni和cd刺激了衣藻碳酸配酶胞外酶(cAe)的活性,高浓度的各种金属抑制cAe的活性;cu和zn对衣藻cAe的抑制作用比其它金属离子的强。衣藻对Fe和Mn影响CAe的生物调节作用明显,其次是Co和Ni。7.微藻是影响高原湖泊微量金属元素地球化学行为的重要因素,影响情况因微藻种类而有所差异。微藻能强烈地改变环境中微量金属元素的含量,微量金属元素含量的变化也影响了微藻的生理生化功能。微藻和微量金属的相互作用因微藻和金属种类的不同而不同;这种种类差异性是造成微量金属元素生物地球化学行为复杂性的主要原因之一。
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Nanocrystalline Zn0.95 - xNi0.05AlxO (x = 0.01, 0.02, 0.05 and 0.10) diluted magnetic semiconductors have been synthesized by an auto-combustion method. X-ray diffraction measurements indicate that all Al-doped Zn0.95Ni0.05O samples have the pure wurtzite structure. Transmission electron microscope analyses show that the as-synthesized powders are of the size 40 - 45 nm. High-resolution transmission electron microscope, energy dispersive spectrometer and X-ray photoemission spectroscope analyses indicate that Ni2+ and Al3+ uniformly substitute Zn2+ in the wurtzite structure without forming any secondary phases. The Al doping concentration dependences of cell parameters (a and c), resistance and the ratio of green emission to UV emission have the similar trends. (c) 2007 Elsevier B.V. All rights reserved.
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Excitation energies and electron impact excitation strengths from the ground states of Ni-, Cu- and Zn-like Au ions are calculated. The collision strengths are computed by a 213-levels expansion for the Ni- like Au ion, 405-levels expansion for the Cu-like Au ion and 229-levels expansion for the Zn-like Au ion. Configuration interactions are taken into account for all levels included. The target state wavefunctions are calculated by using the Grasp92 code. The continuum orbits are computed in the distorted-wave approximation, in which the direct and exchange potentials among all the electrons are included. Excellent agreement is found when the results are compared with previous calculations and recent measurements.
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Spinel ferrite, MFe2O4 (M = Co, Ni), ribbons with nanoporous structure were prepared by electrospinning combined with sol-gel technology. The ribbons were formed through the agglomeration of magnetic nanoparticles with PVP as the structure directing template. The length of the polycrystalline ribbons can reach millimeters, and the width of the ribbons can be tuned from several micrometers to several hundred nanometers by changing the concentration of precursor. The nanoporous structure was formed during the decomposition of PVP and inorganic salts.
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The electrochemical behavior of a series of undecatungstozincates monosubstituted by first-row transition metals, ZnW11M(H2O)O-39(n-) (M=Cr, Mn, Fe, Co, Ni, Cu or Zn), was investigated systematically and comparably in aqueous solutions by electrochemical and in situ UV-visible-near-IR spectroelectrochemical methods. These compounds exhibit not only successive reduction processes of the addenda atoms (W) in a negative potential range, but some of them also involve redox reactions originating from the substituted transition metals (M) such as the reduction of Fe-III and Cu-II at less negative potentials and the oxidation of Mn-II at a more positive potential. Some interesting results and phenomena, especially of the transition metals, were found for the first time. Moreover, possible reaction mechanisms are proposed based on the experimental results.
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With XRD, R-T, and ac chi measurements a comparative study on the doping effects of 3d elements in Bi(1.5)Pb(0.2)Sr(2)Ca(2)Cu(2.8)M(0.2)O(y) (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, or Zn) has been carried out. The effects of the former five members are significantly different, both on phase formed and on T-c, from the latter four. It seems that the effect on phase stabilization correlates with the valency of the doped cation. In connection with the instability of the 2223 phase, the correlation has been discussed.
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Magnetic nanoparticles of nickel substituted cobalt ferrite (NixCo1-xFe2O4:0 <= x <= 1) have been synthesized by co-precipitation route. Particles size as estimated by the full width half maximum (FWHM) of the strongest X-ray diffraction (XRD) peak and transmission electron microscopy (TEM) techniques was found in the range 18-28 +/- 4 nm. Energy dispersive X-ray (EDX) analysis confirms the presence of Co, Ni, Fe and oxygen as well as the desired phases in the prepared nanoparticles. The selective area electron diffraction (SAED) analysis confirms the crystalline nature of the prepared nanoparticles. Data collected from the magnetization hysteresis loops of the samples show that the prepared nanoparticles are highly magnetic at room temperature. Both coercivity and saturation magnetization of the samples were found to decrease linearly with increasing Ni-concentration in cobalt ferrite. Superparamagnetic blocking temperature as determined from the zero field cooled (ZFC) magnetization curve shows a decreasing trend with increasing Ni-concentration in cobalt ferrite nanoparticles. (C) 2009 Elsevier B.V. All rights reserved.
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Geochemical processes in estuarine and coastal waters often occur on temporally and spatially small scales, resulting in variability of metal speciation and dissolved concentrations. Thus, surveys, which are aimed to improve our understanding of metal behaviour in such systems, benefit from high-resolution, interactive sampling campaigns. The present paper discusses a high-resolution approach to coastal monitoring, with the application of an automated voltammetric metal analyser for on-line measurements of dissolved trace metals in the Gulf of Cadiz, south-west Spain. This coastal sea receives metal-rich inputs from a metalliferous mining area, mainly via the Huelva estuary. On-line measurements of dissolved Cu, Zn, Ni and Co were carried out on-board ship during an eight-day sampling campaign in the study area in June 1997. A pumping system operated continuously underway and provided sampled water from a depth of ca. 4 m. Total dissolved metal concentrations measured on-line in the Gulf of Cadiz ranged between <5 nM Cu (<3 nM Ni) ca. 50 km off-shore and 60–90 nM Cu (5–13 nM Ni) in the vicinity of the Huelva estuary. The survey revealed steep gradients and strong tidal variability in the dissolved metal plume extending from the Huelva estuary into the Gulf of Cadiz. Further on-line measurements were carried out with the automatic metal monitor from the bank of the Odiel estuary over a full tidal cycle, at dissolved metal concentrations in the μM range. The application confirmed the suitability of the automated metal monitor for coastal sampling, and demonstrated its adaptability to a wide range of environmental conditions in the dynamic waters of estuaries and coastal seas. The near-real time acquisition of dissolved metal concentrations at high resolution enabled an interactive sampling campaign and therefore the close investigation of tidal variability in the development of the Huelva estuary metal plume.
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A new high-performance material, poly(sulfone-imide) was prepared by Ni(0)-catalyzed coupling of aromatic dichlorides containing imide structure and 4,4'-dichlorodiphenylsulfone. The copolymers were produced with high yield and moderate to high inherent viscosities of 0.52-1.13 dL/g. Wide-angle X-ray diffractograms revealed that the polymers were amorphous. Most of the polymers exhibited good solubility and could be readily dissolved in various solvents such as N-methyl-2-pyrrolidinone(NMP) and N,N-dimethylacetamide (DMAc). These polysulfone-imides had glass-transition temperatures between 317 and 345 degreesC and 10% weight loss temperatures in the range of 450476 degreesC in nitrogen atmosphere. The tough polymer films, obtained by casting from cresol solution, had a tensile strength range of 21 158 MPa and a tensile modulus range of 2.1-3.3 GPa.
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The speciation and distribution of Zn(II) and the effect of Gd(III) on Zn(II) speciation in human blood plasma were studied by computer simulation. The results show that, in normal blood plasma, the most predominant species of Zn(II) are [Zn(HSA)] (58.2%), [Zn(IgG)](20.1%), [Zn(Tf)] (10.4%), ternary complexes of [Zn(Cit)(Cys)] (6.6%) and of [Zn(Cys)(His)H] (1.6%), and the binary complex of [Zn(CYS)(2)H] (1.2%). When zinc is deficient, the distribution of Zn(II) species is similar to that in normal blood plasma. Then, the distribution changes with increasing zinc(II) total concentration. Overloading Zn(II) is initially mainly bound to human serum albumin (HSA). As the available amount of HSA is exceeded, phosphate metal and carbonate metal species are established. Gd(III) entering human blood plasma predominantly competes for phosphate and carbonate to form precipitate species. However, Zn(II) complexes with phosphate and carbonate are negligible in normal blood plasma, so Gd(III) only have a little effect on zinc(II) species in human blood plasma at a concentration above 1.0x10(-4) M.
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The rational synthesis and the structural and magnetic characterization of a nickel cluster are presented. The compound comprises a rhomblike Ni4O16 group encapsulated between two-heptadentate tungstoarsenate ligands [AsW9O34](9-). The crystal structure of K-10[Ni-4(H2O)(2)(AsW9O34)(2)](.)4H(2)O was solved in monoclinic, P2(1)/n symmetry, with a = 12.258(3) Angstrom, b = 21.232(4) Angstrom, c = 15.837(3) Angstrom, beta = 92.05(3)degrees, V = 4119.1(14) Angstrom(3), Z = 2, and R = 0.0862. The crystal structure of the Ni(II) derivative was compared with that of the Cu(II), Zn(II), Co(II) and Mn(II) derivatives. The Ni4O14(H2O)(2) unit in the compound shows no Jahn-Teller distortion. On the other hand, the Ni(II) derivative shows ferromagnetic exchange interactions within the Ni4O16 group (J = 7.8 cm(-1), J' = 13.7 cm(-1)) and an S = 4 ground state, the highest spin state reported in a heteropoly complex. Its redox electrochemistry has been studied in acid buffer solutions using cyclic voltammetry. It exhibited two steps of one-electron redox waves attributed to redox processes of the tungsten-oxo framework. The new catalyst showed an electrocatalytic effect on the reduction of NO2-.