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1.
Yb_2O_3纳米晶的制备及其若干性质的研究   总被引:6,自引:1,他引:5  
用溶胶 -凝胶法制备了不同粒径的 Yb2 O3纳米晶。XRD分析表明 :所合成的 Yb2 O3纳米晶属于立方晶系 ,空间群为 Ia3。TEM分析表明 :所合成的 Yb2 O3粒子基本呈球形。计算表明 :Yb2 O3的平均晶粒度随焙烧温度的升高而增大 ,而平均晶格畸变率随焙烧温度的升高和晶粒度的增大而减小 ,表明晶粒越小 ,晶格畸变越大 ,微晶发育越不完整。溶解性试验表明 :Yb2 O3晶粒度减小 ,表面活性增加。FTIR光谱分析表明 :纳米 Yb2 O3比普通的 Yb2 O3具有更高的表面活性 ,Yb- O键的吸收强度减弱 ,有微小的蓝移。  相似文献   

2.
水热沉淀法合成SnO_2纳米晶   总被引:4,自引:2,他引:2  
用水热沉淀法合成了不同粒径的 Sn O2 纳米晶 ,属于四方晶系 ,空间群为 P4/ mnm。计算表明 :随焙烧温度的升高 ,Sn O2 晶粒度增大 ;而平均晶格畸变率则随晶粒度的增大而减小 ,表明粒子越小晶格畸变越大 ,晶粒发育越不完整。TEM分析结果表明 :所合成的 Sn O2 纳米粒子基本呈球形 ;随焙烧温度的升高 ,Sn O2 粒子的粒径增大。热失重分析表明 :水热沉淀法所合成的 Sn O2 纳米粉末中杂质含量很少 ,纯度高。  相似文献   

3.
水热沉淀法合成SnO2纳米晶   总被引:7,自引:0,他引:7  
用水热沉淀法合成了不同粒径的SnO2纳米晶,属于四方晶系,空间群为P4/mnm。计算表明:随焙烧温度的升高,SnO2晶粒度增则平均 格畸变率则随昌粒度的增大而减小,表明粒子越小昌格畸变越大,晶粒发育越失重分析表明;水热沉淀法所合成的SnO2纳米粉末中杂质含量很少,纯度高。  相似文献   

4.
纳米CeO2在热处理过程中的结构和性能变化   总被引:7,自引:1,他引:6  
采用XRD方法结合粉体相对密度测定研究了热处理条件对沉淀法合成纳米CeO2的结构和性能的影响. 结果表明: 随焙烧温度升高, CeO2晶粒尺寸显著增大, 晶粒发育趋于完整导致晶格畸变度明显降低, 结构致密程度增加使得晶格常数减小, 粉体烧结程度增大, 相应粉体相对密度随之增加; 较低温度(如300.℃)下, 焙烧时间对CeO2晶粒尺寸无明显影响, 相应晶格畸变度、晶格常数和粉体相对密度变化不大; 较高温度(如700.℃)下, CeO2晶粒尺寸随焙烧时间延长而增大, 且焙烧初期粒子增长较快, 此过程伴随着CeO2晶格畸变度进一步下降, 晶格常数却有所增加, 粉体相对密度略有下降; 认为热处理过程CeO2晶粒生长为扩散生长机制是造成不同焙烧温度下焙烧时间对纳米CeO2结构和性能的影响行为不同的主要原因.  相似文献   

5.
利用X射线衍射对爆轰法制备的纳米晶粒如二氧化钛和纳米发光粉(SrAl2O4Eu2 ,Dy3 )进行了初步研究.通过比较纳米晶粒的XRD微结构参数(晶粒度、晶面指数(hkl)、晶格常数、晶面间距等)和常规粗晶的差异,以及平均畸变度的计算,定量地揭示了爆轰对纳米晶粒微结构的影响.研究表明,爆轰会对合成的纳米氧化物以及复合氧化物的微结构能产生不同的畸变效应.不同的晶粒尺度,不同的前驱体,产生的晶格畸变呈现各向异性晶格膨胀和收缩现象,如液相混合炸药制备的纳米氧化钛产生的平均畸变度是固相炸药制备纳米氧化钛的1.98倍,甚至达到2.72倍,同时随着晶体粒径的增大,平均畸变度减小;而爆轰法制备的SrAl2O4Eu2 ,Dy3 纳米发光粉,在晶粒度变化不大的条件下,经过600~800 ℃的热处理后却产生了先增大后减小的平均畸变度.  相似文献   

6.
块体纳米晶镍的制备及力学性能研究   总被引:1,自引:0,他引:1  
采用直流电弧等离子体蒸发+预压烧结法制得块体纳米晶镍。对纳米晶镍的晶粒度、孔隙率进行了表征,对其压缩强度、应变速率敏感性及压缩对晶格畸变、晶粒尺寸的影响进行了研究。结果表明,纳米晶镍的晶粒尺寸随烧结温度的升高而增大,725℃烧结时块材相对致密度达97%。压缩强度随晶粒尺寸减小而增大,且与压缩速率成正比;最大抗压断裂强度达到600MPa,表现出较低的加工硬化和良好的塑性压缩形变能力,断口为沿晶断裂;压缩会引起晶格畸变量的减小和晶粒的细化。  相似文献   

7.
采用室温固相反应法制备了CeO2纳米晶.XRD分析表明,所合成的CeO2纳米晶属于立方晶系.TEM分析表明,CeO2纳米粒子呈球形,粒度随焙烧温度的增加而增大.热失重分析表明,样品的热失重主要受温度的影响,而焙烧时间的影响不大.相对密度分析表明,随CeO2纳米晶粒度的增大,粉末的密度略有增加.  相似文献   

8.
固相合成Co3O4纳米晶及晶化动力学研究   总被引:1,自引:1,他引:0  
以Co(NO3)2·6H2O和NH4HCO3为原料,利用固相反应合成无定形前驱体,再经焙烧合成Co3O4纳米晶.用X射线衍射(XRD)分析了不同焙烧温度对合成Co3O4晶粒尺寸的影响.研究结果表明按Scherrer公式估算合成Co3O4纳米晶的晶粒尺寸在10~40nm,焙烧温度越高,晶粒尺寸越大;根据前驱体不同升温速率下的差热(DTA)曲线,用Kissinger和Ozawa法计算合成Co3O4纳米晶的活化能分别为132.77kJ/mol和141.17kJ/mol,差别不大;根据晶粒生长动力学理论计算Co3O4晶粒长大的活化能为15.44kJ/mol,表明热处理过程Co3O4纳米晶粒的长大主要以界面扩散为主.  相似文献   

9.
采用射频溅射法制备了纳米“铁磁金属-半导体基体”Fe-In2O3颗粒膜,研究了颗粒膜中纳米Fle颗粒的晶格结构和尺度效应.结果表明:Fe-In2O3颗粒膜中纳米Fe颗粒晶格发生畸变,原子间距随颗粒尺寸的减小而增大;纳米Fe颗粒的比饱和磁化强度MS和Curie温度TC随颗粒尺寸减小而降低.探讨分析了Fe-In2O3颗粒膜中纳米Fe颗粒的MS和TC随颗粒尺寸变化的原因.  相似文献   

10.
以乙醇为分散剂和保护剂,采用反向化学共沉淀法,制备了Y2O3-ZrO2纳米晶。结果表明:所制备的纳米晶为说办晶系;Y2O3-ZrO2纳米晶呈球形,当焙烧温度为900℃时,粒予粒径约30nm,粒径分布均匀,无明显硬团聚体存在;Y2O3-ZrO2纳米晶为多晶结构:Y2O3-ZrO2的晶化温度为489.19℃;Y2O3-ZrO2纳米晶的相对密度随粒径增大而增大。  相似文献   

11.
The Ba0.985Na0.015Ti0.985Nb0.015O3, Ba0.6Na0.4Ti0.6Nb0.4O3 and Ba0.3Na0.7Ti0.3Nb0.7O3 compositions of the (1 − x) BaTiO3xNaNbO3 (BTNNx) system have been studied by X-ray diffraction and by measurements of dielectric properties. The specimens with composition BTNN (x = 0.015, 0.40 and 0.70) have been refined by the JANA program from X-ray powder diffraction data. Ceramic samples with composition (1 − x) BaTiO3 + xNaNbO3 (where x = 0.015, 0.40 and 0.70) were prepared by calcinations from appropriate mixture of BaCO3, TiO2, Na2CO3 and Nb2O5. The calcined powder was sintered at temperature range 1200–1400 °C. As the composition x increased from 0.015 (and 0.70), the ferroelectric ceramics (x = 0.015, FE) with tetragonal phase changed to the ferroelectric relaxors (RFE, x = 0.40). RFE ceramics showed a peculiar diffuse phase transition and dielectric relaxation at the low temperature (down to 180 K) due to a frustration between RFE and FE state. These ceramics present the classical ferroelectric character when 0 ≤ x < 0.075 and 0.55 < x ≤ 1 and relaxor character when 0.075 ≤ x ≤ 0.55.  相似文献   

12.
Influence of 1 h annealing in vacuum on magnetic, electrical and plastic properties of Fe76Nb2Si13B9, Fe75Ag1Nb2Si13B9 and Fe75Cu1Nb2Si13B9 melt spun ribbons were carefully investigated. It was shown that in all cases soft magnetic properties can be significantly enhanced by applying 1-h annealing at characteristic temperatures Top. This optimization annealing causes that permeability increases more than 15-times and magnetic losses (tangent of loss angle) achieves a minimum in relation to the as quenched state. Using structural examinations (X-ray and HRTEM) it was shown that for the Fe75Cu1Nb2Si13B9 alloy the optimized microstructure corresponds to a nanocrystalline αFe(Si) phase whereas in other alloys to a relaxed amorphous phase free of iron nanograins. As a consequence of this fact the Fe76Nb2Si13B9 and Fe75Ag1Nb2Si13B9 alloys show higher plasticity in comparison to the nanocrystalline Fe75Cu1Nb2Si13B9 alloy. Temperatures of the first stage of crystallization, and related diffusion parameters were determined using measurements of resistivity versus temperature with different heating rates.  相似文献   

13.
针对草酸盐配位共沉淀热分解还原法制备超细铁镍合金粉过程中Fe2+-Ni2+-NH3-NH4+-C2O42--H2O体系的溶液平衡建立热力学分析模型,并根据模型进行相关计算,揭示反应体系中各物质随pH值、氨及草酸浓度的变化关系。结果表明:溶液中的Fe主要以[Fe(C2O4)n]2 2n络合物形式存在,而铁氨络合物含量很低。当氨含量较低时,溶液中的Ni主要以[Ni(C2O4)n]2 2n存在;氨含量较高时,在酸性条件下,溶液中的Ni主要以[Ni(C2O4)n]2 2n存在,在碱性条件下,则主要以[Ni(NH3)n]2+存在。低pH值下,Ni的沉淀率较Fe的高,而高pH值下,Ni的沉淀率则较Fe的低。  相似文献   

14.
We applied our model to the enthalpy of mixing data of the binary systems Na2O-SiO2, Na2O-GeO2, Na2O-B2O3, Li2O-B2O3, CaO-B2O3, SrO-B2O3, and BaO-B2O3. The most stable composition in the liquid, that is where the enthalpy of mixing is most negative, is with a metal-oxygen ratio of 4 to 3, for monovalent metals (Na and Li) and 3 to 4 for divalent metals (Ba and Ca) in liquid silicates or borates. The same applies to the CaO-SiO2, CaO-Al2O3, PbO-B2O3, PbO-SiO2, ZnO-B2O3, and ZnO-SiO2 systems. The oxygen to metal ratio, its constant value in various types of systems, reflects and describes the structure of the liquid. Using the analyzed enthalpies of mixing data and the available phase diagrams, we calculated the enthalpies of formation of the various binary compounds. The results are in excellent agreement with data in the literature that were obtained from direct solid-solid calorimetry.  相似文献   

15.
Results of a powder X-ray diffraction investigation of new ternary compounds are reported. The compounds Y6CoBi2 [a=0.8312(1) nm, c=0.4144(1) nm], Ho6CoBi2 [a=0.8246(2) nm, c=0.4095(1) nm], and Tm6CoBi2 [a=0.8155(2) nm, c=0.4066(1) nm] crystallize in the hexagonal Zr6CoAs2-type structure (space group P6b2m No. 189). The Zr6CoAs2-type structure is a superstructure of the Fe2P-type structure.  相似文献   

16.
采用溶胶-凝胶法和低温燃烧技术制备Ce1-xSmxO2(x=0,0.1,0.2,0.3)和掺杂Sm和(2%-8%)Al2O3的二氧化铈;研究其合成、结构、致密化、导电性和热膨胀等性能,并利用XRD研究其结构和相组成。结果表明,于1300°C烧结球团,获得致密的陶瓷,于1250°C在Ce0.8Sm0.2O0.2中加入2%和4%的Al2O3以促进烧结。利用扫描电子显微镜观察烧结后球团的表面形貌,使用双探针交流阻抗谱研究总离子电导率。  相似文献   

17.
Single crystals of RbBa3Ca4Cu3V7O28 were prepared above the melting point of the reaction mixture. It crystallizes with hexagonal symmetry, space group C6V4-P63mc, a 11.1751, c 12.434 Å, Z = 2. RbBa3Ca4Cu3V7O28 is the second member of a new structure type of the copper-oxovanadates. Ba2+ shows an unusual 12-fold coordination. The two calcium positions are coordinated by trigonal prisms and octahedra respectively. The copper coordination is characterized by a stretched square pyramid. The Cu2+ ions are outside the centre nearly in plane of the pyramids.

Zusammenfassung

Einkristalle von RbBa3Ca4Cu3V7O28 wurden oberhalb des Schmelzpunktes der Reaktionsmischung erhalten. Die Verbindung kristallisiert hexagonal, Raumgruppe C6V4-P63mc, a 11.1751, c 12.434 Å, Z = 2. RbBa3Ca4Cu3V7O28 ist das zweite Beispiel für einen neuen Strukturtyp der Kupfer-Oxovanadate, mit 12-fach koordinierten Ba2+ -Ionen. Die zwei Calciumpositionen sind trigonal prismatisch bzw. oktaedrisch koordiniert. Die Koordination der Cu2+-Ionen ist durch eine gestreckte Pyramide charakterisiert. Cu2+ ist auβerhalb des Polyederzentrums nahezu in der quadratischen Fläche der Pyramide angeordnet.  相似文献   


18.
19.
The composite ceramics of Ba0.55Sr0.4Ca0.05TiO3-CaTiSiO5-Mg2TiO4 (BSCT-CTS-MT) were prepared by the conventional solid-state route. The sintering performance, phase structures, morphologies, and dielectric properties of the composite ceramics were investigated. The BSCT-CTS-MT ceramics were sintered at 1100 °C and possessed dense microstructure. The dielectric constant was tailored from 1196 to 141 as the amount of Mg2TiO4 increased from 0 to 50 wt%. The dielectric constant and dielectric loss of 40 wt% Ba0.55Sr0.4Ca0.05TiO3-10 wt% CaTiSiO5-50 wt% Mg2TiO4 was 141 and 0.0020, respectively, and the tunability was 8.64% under a DC electric field of 8.0 kV/cm. The Curie peaks were broadened and depressed after the addition of CaTiSiO5. The optimistic dielectric properties made it a promising candidate for the application of tunable capacitors and phase shifters.  相似文献   

20.
在Q235低碳钢板上利用电弧喷涂工艺进行喷涂,以制得Fe65Cr20Mo7B3.5SiMn1.5W3涂层。喷涂材料为自行配制的丝材,按照35%的填充率将配好的粉填充到U型不锈钢外皮中,经过多道拉拔、挤压工艺制成Φ2mm的粉芯丝材。采用X射线衍射仪、扫描电镜、能谱分析仪、透射电镜对涂层的物相和组织形貌及成分进行了表征;采用差示扫描量热仪、显微硬度仪等设备对涂层的热稳定性及显微硬度进行了检测和分析。试验结果表明:涂层组织形貌呈典型的层状组织结构,由变形良好的带状粒子相互搭接堆积而成。涂层含有50.63%的非晶相,同时含有纳米级的晶相。涂层组织均匀、结构致密、孔隙率低,并且涂层硬度高达1040.5HV0.3,属硬质涂层,具有良好的热稳定性。  相似文献   

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