排序方式: 共有13条查询结果,搜索用时 109 毫秒
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Zn-Mg-Al型类水滑石纳米颗粒制备及晶体结构 总被引:14,自引:1,他引:14
采用液相非稳态共沉淀法合成了锌镁铝类水滑石(Zn-Mg-Al-HTlc)颗粒,考察了其化学组成、晶体结构、粒子形貌及原料配比的影响等.结果表明,Zn-Mg-Al-HTlc样品中的n(Zn)/n(Zn+Mg+Al)比原料配比低,而n(Mg)/n(Zn+Mg+Al)基本无变化.n(Al)/n(Zn+Mg+Al)(x)在0.22~0.40范围内是纯类水滑石相,超出此范围时出现异相;x<0.22时出现ZnO相;x>0.40时出现Al(OH)3相.所制备的Zn-Mg-Al-HTlc颗粒的晶胞参数a=0.27~0.32nm,c=2.27~2.42nm,层间距在0.75~0.81nm之间,层间通道的高度约0.30nm.样品颗粒均为较规则的六边形片状粒子.XRD-Scherrer公式计算结果表明,粒子的平均晶粒度在30~45nm之间.TEM结果表明,平均颗粒度随x的值趋于减小,x<0.33时平均颗粒度基本小于100nm.x值相近,Zn含量增加,平均颗粒度有增大趋势;n(Zn)/n(Al)相近,Mg含量增加,平均颗粒度有减小趋势. 相似文献
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Large inverse and normal magnetocaloric effects in HoBi compound with nonhysteretic first-order phase transition 下载免费PDF全文
HoBi single crystal and polycrystalline compounds with NaCl-type structure are successfully obtained, and their magnetic and magnetocaloric properties are studied in detail. With temperature increasing, HoBi compound undergoes two magnetic transitions at 3.7 K and 6 K, respectively. The transition temperature at 6 K is recognized as an antiferromagnetic-to-paramagnetic (AFM-PM) transition, which belongs to the first-order magnetic phase transition (FOMT). It is interesting that the HoBi compound with FOMT exhibits good thermal and magnetic reversibility. Furthermore, a large inverse and normal magnetocaloric effect (MCE) is found in HoBi single crystal in the $H|| [100]$ direction, and the positive $\Delta S_{\rm M}$ peak reaches 13.1 J/kg$\cdot$K under a low field change of 2 T and the negative $\Delta S_{\rm M}$ peak arrives at $-18 $ J/kg$\cdot$K under a field change of 5 T. These excellent properties are expected to be applied to some magnetic refrigerators with special designs and functions. 相似文献
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剪切速率对Fe-Al-Mg-MMH/钠质蒙脱土悬浮体触变性的影响 总被引:2,自引:1,他引:2
研究了测定条件对Fe-Al-Mg型混合金属氢氧化物(简称MMH)/钠质蒙脱土(简 称MT)混合悬浮体及纯MT体系触变性的影响,主要考察了高速剪切分散后,剪切速 率(D_L)对粘度(η)~时间(t)变化趋势的影响。发现纯的MT体系和MMH/MT质 量比(R)为0.013的Fe-Al-Mg-MMH/MT体系在所研究的D_L下(10,170,511和1 022 s~(-1))都呈现为正触变性,D_L不影响触变性类型。R = 0.051的体系,低 D_L时(10和170 s~(-1))呈现复合触变性,高D_L时(511和1 022 s~(-1))呈现 正触变性;R = 0.091的体系在低D_L时(10和170 s~(-1))呈现负触变性,在高 D_L时(511和1 022 s~(-1))呈现复合触变性。D_L增加,各体系η逐渐降低。对 D_L影响触变性的机理进行了深入探讨。 相似文献
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pH值对Fe-Al-Mg-MMH/钠质蒙脱土悬浮体触变性的影响 总被引:3,自引:0,他引:3
研究了pH值对Fe-Al-Mg型混合金属氢氧化物/钠质蒙脱土(简称MMH/MT)悬浮体触变性的影响。发现pH值能影响其触变性类型:m(MMH)/m(MT)(下文中以R表示)较低时(0,0.013和0.051),随着pH增高,体系有由负触变性-复合触变性-正触谱性转变的趋势;而R较高的体系(R=0.091),随pH的增高,体系由复合触变性向负触变性转化。探讨了各种触变性产生的原因和pH的影响机理。 相似文献
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研究了测定条件对Fe-Al-Mg型混合金属氢氧化物(简称MMH)/钠质蒙脱土(简 称MT)混合悬浮体及纯MT体系触变性的影响,主要考察了高速剪切分散后,剪切速 率(D_L)对粘度(η)~时间(t)变化趋势的影响。发现纯的MT体系和MMH/MT质 量比(R)为0.013的Fe-Al-Mg-MMH/MT体系在所研究的D_L下(10,170,511和1 022 s~(-1))都呈现为正触变性,D_L不影响触变性类型。R = 0.051的体系,低 D_L时(10和170 s~(-1))呈现复合触变性,高D_L时(511和1 022 s~(-1))呈现 正触变性;R = 0.091的体系在低D_L时(10和170 s~(-1))呈现负触变性,在高 D_L时(511和1 022 s~(-1))呈现复合触变性。D_L增加,各体系η逐渐降低。对 D_L影响触变性的机理进行了深入探讨。 相似文献
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通过磁控溅射进行钕铁硼磁体表面重稀土Tb镀膜,再经过渗扩热处理获得了综合性能近80[Hcj/kOe+(BH)max/MGOe]的超高性能磁体,分析了其内在机制。借助扫描电镜背散射电子成像技术,研究了热处理温度对磁体磁性能和微观组织的影响,并探讨了晶界扩散法矫顽力提高的机理和微观结构变化规律。结果表明,经镀渗处理后磁体的矫顽力明显提高,剩磁无明显降低,温度稳定性得以显著改进,显微组织结构有了明显的优化,形成连续均匀薄层晶界富Nd相组织有效的包裹主相,能够有效降低相邻晶粒的磁耦合效应。Tb富集在2∶14∶1晶粒的表面区域而不是中心,不仅通过增强局部磁晶各向异性场来增加矫顽力,而且还保持了剩磁。 相似文献
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THE INFLUENCE OF Co SUBSTITUTION ON THE MAGNETIC PROPERTIES AND THE GIANT MAGNETO-IMPEDANCE EFFECT OF (Fe1-xCox)84Zr3.5Nb3.5B8Cu1 下载免费PDF全文
The microstructure, magnetic properties and the giant magneto-impedance (GMI) effect of the nanocrystalline (Fe1-xCox)84Zr3.5Nb3.5B8Cu1 ribbons have been studied. With increasing Co concentration, the nanocrystallized grain size and volume fraction of the α-Fe(Co) phase decrease under the same annealing condition, while the coercivity Hc increases from 1.92 A/m at x=0.0 to 30.38 A/m at x=0.8. The effective permeability drops sharply with increasing Co concentration so that the GMI effect goes down. A value of more than 380% for the magneto-impedance(MI) ratio was measured at frequency f=2.5 MHz and the sensitivity can reach 0.9% (A/m)-1 for Fe84Zr3.5Nb3.5B8Cu1 ribbon. When x is equal to 0.8, the MI ratio drops to about 30% and the sensitivity only reaches a value of lower than 0.025% (A/m)-1. The concise analysis in theory is also expounded. 相似文献
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