共查询到19条相似文献,搜索用时 125 毫秒
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掺杂对纳米氧化铁晶化相的影响 总被引:4,自引:0,他引:4
用X射线衍射、透射电镜和穆斯堡尔谱对由掺杂了不同比例Sb的溶液-凝胶系统制得的α-Fe2O3纳米晶的晶粒度和精细结构进行了研究。结果显示,未掺杂时由Fe(OH)3非晶相干凝胶晶化而得的α-Fe2O3相晶粒较大;掺Sb后,干凝胶晶化时一部分Sb参与形成FeSbO4晶相,另外的Sb原子进入α-Fe2O3晶相中形成间隙式固溶体;系统中掺杂量增多,固溶于α-Fe2O3晶相中的Sb浓度相庆也增大,它们很可能 相似文献
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掺杂聚苯胺磁化率的研究 总被引:6,自引:0,他引:6
分别研究了浓H2SO4掺杂本征态聚苯胺(PAn)、HCl掺杂PAn以及FeCl3掺杂这两种聚安在地的磁化率。通过研究磁化率的变化曲线,我们得到了一些有意义的结果:浓H2SO4掺杂PAa和HCl掺杂PAn的磁化率变化规律不同;FeCl3掺杂浓H2SO4-PAn材料可以获得比FeCl3掺杂HCl-PAn材料更高的磁化率;FeCl3在掺杂HCl-PAn材料和浓H2SO4-PAn材料时,FeCl3在这两种 相似文献
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ZnxFe3—xO4的制备及性能 总被引:4,自引:0,他引:4
采用合适加剂在碱性溶液中制备了FeZn铁氧体,研究了其形成机理及磁性能,提出FeZn铁氧体的形成机理为:An^2++2Fe^3++80H^-→ZnFe2O4+4H2O Fe^2++2Fe^2++80H^-→Fe3O4+4H2O。 相似文献
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Matsuya S Matsuya Y Takagi S Chow LC 《Journal of materials science. Materials in medicine》1998,9(6):325-331
The effect of fluoride on the hydrolysis of tetracalcium phosphate (TTCP; Ca4(PO4)2O) was investigated in 0.1 mol l–1KH2PO4 containing 0–83 mol l–1 KF. Characterization of the final apatite phase formed by the hydrolysis was made with X-ray diffraction and SEM. The initial pH was between 4.5 and 5.4, depending on the solutions, and the pH rapidly increased and was kept constant between 7.3 and 6.5. An increase in KF concentration tended to lower the pH in the final stage of hydrolysis. The calcium concentration was considerably lower than the phosphorus concentration throughout the reaction. The fluoride concentration decreased shortly after the start of hydrolysis. The hydrolysis of TTCP in 0.1 mol l–1 KH2PO4 proceeded to form hydroxyapatite via DCPD when the KF concentration was low. The hydrolysis product was a calcium-deficient non-stoichiometric hydroxyapatite with a Ca/P ratio of about 1.5. With an increase in the KF concentration in the 0.1 mol l–1 KH2PO4 solution, TTCP directly transformed into hydroxyapatite containing F- ions or fluorapatite and with improved crystallinity. The addition of fluoride in the solution initially accelerated the formation of apatite. However, the layer of newly formed apatite adhering to the TTCP particles retarded TTCP dissolution; as a result, hydrolysis was delayed. IR analysis showed that the apatite phase contained HPO2–4 ions in the structure. The formula for the hydrolysis product of TTCP in the presence of fluoride can be expressed as follows: Ca10–x(HPO4)x(PO4)10–x(OH)2–x–yFy. © 1998 Chapman & Hall. 相似文献
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A K SIVADASAN I PACKIA SELVAM SANKARA NARAYANAN POTTY 《Bulletin of Materials Science》2010,33(6):737-740
Phase pure boehmite particles were prepared by microwave assisted hydrolysis of aluminium sheets. These particles were calcined
in air to produce γ Al2O3 particles with specific surface area of ~210 m2/g. The alumina particles were characterized by studying X-ray diffraction, transmission electron microscopy and Fourier transform
infrared spectroscopy. For comparison, the aluminium hydroxide particles were also prepared by normal hydrolysis of aluminium
metal. Normal hydrolysis yielded a mixture of boehmite and bayerite particles whereas microwave assisted hydrolysis produced
phase pure boehmite particles. The importance of using microwave radiation for the hydrolysis of aluminium metal is also manifested
in a shorter reaction time. 相似文献
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用微波加热反应-变速滴加共沉淀法合成了[Mg-Al-CO3]纳米层状双氢氧化物,并以[Mg-Al-CO3]纳米层状双氢氧化物为前体,用微波加热反应-离子交换法制备了PO43-,P2O74-柱撑Mg-Al层状双氢氧化物。该法合成的[Mg-Al-CO3]纳米层状双氢氧化物的粒径约为10-40nm。讨论了微波和变速滴加碱液的速度对纳米层状双氢氧化物的合成的影响。用FT-IR、TEM与XRD对产物进行了表征,结果表明在微波加热反应的条件下可在短时间内用PO43-,P2O74-彻底交换CO32-。 相似文献
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Shin HC Park SH Ahn HG Chung M Kim BW Kim SJ Seo SG Jung SC 《Journal of nanoscience and nanotechnology》2011,11(2):1597-1600
The photo-catalytic decomposition of rhodamine B was examined in aqueous nano TiO2 particles dispersions to assess effects of the microwave radiation assisted photo-catalytic process driven by UV radiation. The results of photo-catalytic degradation of rhodamine B showed that the decomposition rate increased with the microwave intensity, UV intensity, TiO2 particle dosages and the circulating fluid velocity. Addition of oxygen gas in the photo-catalytic degradation of rhodamine B increased the reaction rate. The effect of addition of H2O2 was not significant when photo-catalysis was used without additional microwave radiation or when microwave was irradiated without the use of photo-catalysts. When H2O2 was added under simultaneous use of photo-catalysis and microwave irradiation, however, considerably higher degradation reaction rates were observed. This study demonstrates that the microwave irradiation can play a very important role in photo-catalytic degradation. 相似文献
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磷酸盐基耐高温粘结涂层的性能及功能填料对其性能的影响 总被引:1,自引:0,他引:1
本文以Al(OH)3和H3PO4为原料,研究了磷酸盐粘结剂的最佳合成条件,探讨了P/Al配比和反应温度对Al(H2PO4)3的形成以及填料的加入对粘结剂耐热性的影响,利用XRD和TG-DSC对粘结剂晶体结构和涂层热性能进行了分析。结果表明:P/Al比例为3∶1.4,合成温度在120~200℃范围内,可获得性能较好的Al(H2PO4)3粘结剂。填料的加入有利于粘结剂表面吸附水的蒸发和磷酸盐基体分子间结晶水的脱除,提高了涂层的热稳定性和耐高温性能。 相似文献
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The densification of MgO and MgO-TiC ceramics by hollow cathode plasma and microwave sintering techniques was studied. The resultant fractional densities were compared to those of conventionally sintered samples. It was demonstrated that indirect heating and sintering of MgO by microwave radiation was possible. Higher fractional densities were obtained in MgO by microwave sintering in comparison to conventional sintering under the same conditions. In the case of MgO-TiC composites, chemical reaction led to Mg2TiO4 formation in all samples. Plasma sintering suppressed this reaction and exhibited reduced sinterability upon TiC addition. On the other hand, small amounts of TiC additions aided the conventional sintering of MgO, resulting in better mechanical properties. Furthermore, commercial grade MgO was sintered to higher densities than relatively pure research grade MgO. Hardness and fracture toughness values are reported. 相似文献
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Immobilization of aqueous cadmium by addition of phosphates 总被引:5,自引:0,他引:5
In situ immobilization of heavy metals in polluted soils using phosphates leads to formation of products which are highly insoluble and thermodynamically stable over a broad pH and Eh range. In this research effectivity of Cd ions immobilization (initial [Cdaq]-4.800 mM) from aqueous solutions by different phosphorus compounds (K2HPO4, NH4H2PO4 and "Polifoska 15" fertilizer) was compared at pH in the range 4.00-9.00 and for reaction times 2-1440 h. The highest reduction of cadmium concentration (>99%), owing due to the formation of cadmium phosphates, was observed for all used phosphorus sources within pH range of 6.75-9.00. Uptake of cadmium for pH< or =5.00 did not exceed 80% and was lowest in the reaction with "Polifoska 15" fertilizer (28.25%). Identification of phases formed in the reactions using XRD, FTIR and SEM-EDS-EBSD was carried out. It was noticed that crystallinity of formed solid decreased with pH increase. Formation of Cd5H2(PO4)4.4H2O was observed in acidic conditions (pH< or =5.00), at pH approximately 7.00 mixture of following cadmium phosphates Cd(H2PO4)2, Cd3(PO4)2 and Cd5H2(PO4)4.4H2O was formed. Amorphic cadmium phosphates were noticed in alkaline conditions (pH>8.50). 相似文献
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Phosphate (PO(4)(3-)) solutions in water and heavy water have been studied by Raman and infrared spectroscopy over a broad concentration range (0.0091-5.280 mol/L) including a hydrate melt at 23 degrees C. In the low wavenumber range, spectra in R-format have been constructed and the R normalization procedure has been briefly discussed. The vibrational modes of the tetrahedral PO(4)(3-)(aq) (T(d) symmetry) have been assigned and compared to the calculated values derived from the density functional theory (DFT) method for the unhydrated PO(4)(3-)(T(d)) and phosphate-water clusters: PO(4)(3-).H(2)O (C(2v)), PO(4)(3-).2H(2)O (D(2d)), PO(4)(3-).4H(2)O (D(2d)), PO(4)(3-).6H(2)O (T(d)), and PO(4)(3-).12H(2)O (T), a cluster with a complete first hydration sphere of water molecules. A cluster with a second hydration sphere of 12 water molecules and 6 in the first sphere, PO(4)(3-).18H(2)O (T), has also been calculated. Agreement between measured and calculated vibrational modes is best in the case of the PO(4)(3-).12H(2)O cluster and the PO(4)(3-).18H(2)O cluster but far less so in the case of the unhydrated PO(4)(3-) or phosphate-water cluster with a lower number of water molecules than 12. The asymmetric, broad band shape of v(1)(a(1)) PO(4)(3-) in aqueous solutions has been measured as a function of concentration and the asymmetric and broad band shape was explained. However, the same mode in heavy water has only half the full width at half-height compared to the mode in normal water. The PO(4)(3-) is strongly hydrated in aqueous solutions. This has been verified by Raman spectroscopy comparing v(2)(H(2)O), the deformation mode of water, and the stretching modes, the v(1)OH and v(3)OH of water, in K(3)PO(4) solutions as a function of concentration and comparison with the same modes in pure water. A mode at approximately 240 cm(-1) (isotropic R spectrum) has been detected and assigned to the restricted translational mode of the strong hydrogen bonds formed between phosphate and water, P-O...HOH. In very concentrated K(3)PO(4) solutions (C(0) > or = 3.70 mol/L) and in the hydrate melt, formation of contact ion pairs (CIPs) could be detected. The phosphate in the CIPs shows a symmetry lowering of the T(d) symmetry to C(3v). In the less concentrated solutions, PO(4)(3-)(aq) solvent separated ion pairs and doubly solvent separated ion pairs exist, while in very dilute solutions fully hydrated ions are present (C(0) < or = 0.005 mol/L). Quantitative Raman measurements have been carried out to follow the hydrolysis of PO(4)(3-)(aq) over a very broad concentration range. From the hydrolysis data, the pK(3) value for H(3)PO(4) has been determined to be 12.45 at 23 degrees C. 相似文献