Fe86Zr5.5 Nb5.5 B3非晶合金的超高压烧结成型

为了获得致密的块状Fe86Zr55Nb55B3纳米晶合金,研究了高压快速烧结工艺参数对样品致密度和α-Fe相晶粒尺寸的影响.结果表明:快淬球磨破碎非晶粉末在5.5 GPa/3min烧结条件下,当Pw=1150 W后,可获得相对密度为98.3%、单相α-Fe纳米晶(16.3 nm)块体合金,且随着Pw和t的增加,样品相对密度和α-Fe相晶粒尺寸均略有增加,样品典型的比饱和磁化强度σs和矫顽力Hc分别为119.6 emu/g,63.8 Oe.     

Fe77Co2Zr9B10Cu2合金的制备及其磁性能

采用单辊快淬法制备了Fe77Co2Zr9B10Cu2合金,在530～750℃等温退火40 min,利用X射线衍射和振动样品磁强计研究了Fe77 Co2 Zr9 B10 Cu2合金的微观结构和磁性能。结果表明:淬态Fe77Co2Zr9B10Cu2合金为非晶、纳米晶双相结构。随着退火温度的升高,α-Fe晶体相从非晶、基体中析出,晶粒尺寸长大,晶化体积分数增加,矫顽力先减小后增大,比饱和磁化强度逐渐增大。实验结果表明,530℃退火后合金的矫顽力最小,在670℃时迅速增大。样品的磁性与其微观结构、晶粒尺寸、晶化体积分数等因素有关.     

Fe_(63)Ni_1Al_5Ga_2P_(9.65)B_(4.6)Si_3C_(6.75)Co_5非晶合金的晶化行为研究

采用XRD、DSC检测技术,采用连续升温晶化和等温退火晶化方法,研究分析了Fe63Ni1Al5-Ga2P9.65B4.6Si3C6.75Co5非晶薄带的晶化动力学行为和晶化过程中晶化相的析出过程。结果表明,该非晶合金的玻璃转变和晶化行为均具有显著的动力学特征。Kissinger法计算得到的Eg、Ex、Ep1、Ep2分别为750、340、432、689kJ/mol,Eg Ex,表明合金具有较好的热稳定性。合金晶化过程为:非晶→非晶+α-Fe→非晶+α-Fe+Fe2P+Fe3P→α-Fe+Fe2P+Fe3P+Fe3C(Al,Si)+Fe5PB2+SiC。合金的晶化类型为初晶型和随后的共晶型反应。     

添加Nb对Fe74Al4Ga2P12B4Si4非晶合金晶化过程的影响

利用X射线衍射(XRD)、差热分析(DSC)和扫描电镜(SEM)方法试验研究了Nb元素对Fe-(Al,Ga)-(P,C,Si,B)系合金非晶晶化的影响.结果表明:Fe73Nb1Al4Ga2P12B4Si4的晶化过程为α-Fe→α-Fe Fe5SiP Al0.7Fe3Si0.3 Fe3B 剩余非晶化相;替代元素Nb的加入提高了材料的晶化温度,改变了Fe74Al4Ga2P12B4Si4的晶化激活能,其中形核激活能(Eg)、晶化起始激活能(Ex)和第一晶化峰激活能(Ep1)都大大增加;另外,Nb的加入显著降低了合金晶化后的晶粒尺寸,并改善了晶粒的均匀度.     

微波场作用下非晶合金Fe73.5Cu1Nb3Si13.5B9的纳米晶化

研究了微波场对晶化的影响.结果表明,将非晶合金Fe73.5Cu1Nb3Si13 5B9在微波场作用下在480℃短时间(5 min)晶化处理,形成体积分数为80%、尺寸约15nm的α-Fe(Si)相;适当延长晶化时间(30 min)使非晶合金完全晶化,α-Fe(Si)相的晶粒不再长大,原子层之间的距离降低至0.2461 nm,磁体具有最大Ms为1.79 T.与激光、激波、脉冲电场和脉冲磁场晶化处理相比,微波场晶化处理可同时获得单一的、更小晶粒尺寸和更高体积分数的α-Fe(Si)晶化相,使合金具有高的饱和磁化强度和优良的软磁性能.微波场有利于非晶合金中的硼原子向空位跃迁,使基体金属相α-Fe(Si)相的形核率增大,促进非晶合金的纳米晶化.     

铁基非晶磁致低温纳米晶化的相变动力学机理研究

用低频脉冲磁场处理了非晶Fe78Si9B13合金,利用M6ssbauer谱和LDJ9600震动样品磁强计进行了微结构和磁性分析,通过DSC曲线,借助于Kis-singer公式计算了脉冲磁场处理前后样品的纳米晶化过程激活能,探讨了铁基非晶低温纳米晶化的相变动力学机理.结果表明,用脉冲磁场处理非晶Fe78Si9B13合金的晶化激活能由处理前的433.6kJ/mol降到了200kJ/mol以下,大大提高了α-Fe(Si)的形核速率,只有α-Fe(Si)的单相纳米晶体析出,析出相的晶粒尺寸约为10nm,而且脉冲磁场处理过程中,非晶Fe78Si9B13合金试样温升均<10℃,说明脉冲磁场的处理促进了非晶合金的低温纳米晶化.     

热处理对Fe80Zr5Nb4B11非晶合金的结构及磁性能影响

采用单辊快淬法制备Fe80Zr5Nb4B11合金,并在不同温度下对其进行退火,研究热处理对该合金的结构和磁性能的影响.利用X射线衍射(XRD)和透射电镜(TEM)表征合金的结构,利用振动样品磁强计(VSM)测量合金的磁性能.结果表明:随着退火温度的增加,α-Fe晶体相从非晶基体中析出;晶粒尺寸逐渐增大;Fe81Zr5Nb4B10合金的比饱和磁化强度(Ms)在300℃下降,之后保持持续上升的趋势;而矫顽力(Hc)的变化相对复杂,呈现先上升→下降→上升的趋势,这些特征与其微观结构密切相关.     

退火Fe73.5Cu1Mo3Si13.5B9合金的起始磁导率与结构参数的关系

用XRD法测定了Fe73.5Cu1Mo3Si13.5B9非晶合金在退火时析出的α-Fe相的尺寸、点阵参数、体积分量和非晶相的短程有序范围、最近邻原子间距离等结构参数,讨论了它们与相应退火温度下合金的起始磁导率的关系.结果表明,α-Fe粒子在460-560℃范围内不长大,而非晶相结构发生了明显变化.α-Fe相和非晶相的结构对合金的起始磁导率有影响.     

高Fe含量FeCuNbSiB系非晶/纳米晶合金制备及其磁性研究

研究了过渡金属元素(Zr,Nb,Mo)和Cu元素对Fe78Si9B13合金系非晶形成能力、热稳定性和磁性的影响;在Fe74Cu1Nb3Si13B9合金的基础上,通过逐步提高Fe含量,利用单辊甩带法制备Fe(76+x)Cu1Nb3Si(11-x)B9(x=0,2,4)和Fe(79+x)Cu1Nb2Si(6-x)B12(x=0,2,4)非晶/纳米晶合金薄带;利用XRD、DSC、TEM和VSM研究了高Fe含量Fe-Cu-Nb-Si-B系非晶/纳米晶合金的微观结构和磁性,并通过添加Nb元素优化了高Fe含量合金的磁性。研究结果表明:Zr和Nb元素的添加能明显提高Fe78Si9B13合金的非晶形成能力和热稳定性;高Fe含量的Fe-Cu-Nb-Si-B系纳米晶合金为典型的非晶/纳米晶双相结构,合金的饱和磁化强度Ms180 emu/g,且合金的矫顽力Hc在2Oe-9Oe之间,具有良好的软磁性能;Nb元素能显著细化Fe-Cu-Nb-Si-B系合金晶粒尺寸,从而能显著降低合金的矫顽力,改善合金的软磁性能;当Fe含量在80%-83%(原子百分比,下同)之间时,合金具有良好的软磁性能,但当Fe含量达到85%时,会有Fe2B、Fe3B相析出,从而显著恶化其软磁性能。     

铜模吸铸法制备的Fe74Al4Sn2P10Si4B4C2块体非晶与块体纳米晶合金

利用铜模吸铸法制备了直径φ1.0mm和2.0mm的Fe74Al4Sn2P10Si4B4C2块体非晶合金和直径2.0mm的Fe74Al4Sn2P10Si4B4C2块体纳米晶合金圆棒.利用X射线衍射、差示扫描量热仪(DSC)和差热分析仪(DTA)对Fe74Al4Sn2P10Si4B4C2块体非晶合金的结构和热性质进行了测定.该非晶合金的超冷液相区△Tx为16.7K,约化玻璃转变温度Tg/Tm和Tg/T1分别为0.60和0.57.Fe74Al4Sn2P10Si4B4C2合金接近共晶成分,在10K/min的冷却速率下其过冷度可达86.7K.利用透射电子显微镜(TEM)观察了制备态的Fe74Al4Sn2P10Si4B4C2纳米晶合金圆棒的结构,为非晶基体上均匀分布的尺寸10～20nm的α-Fe晶粒.Fe74Al4Sn2P10Si4B4C2合金能达到较大的过冷度,具有较高的约化玻璃转变温度(接近共晶合金成分)和过冷合金熔体的二步相析出有利于块体非晶合金和块体纳米晶合金的形成.铜模吸铸法既可制备块体非晶合金,也可制备块体纳米晶合金,是一种很有吸引力的制备块体非晶合金和块体纳米晶合金的方法,并进一步证实利用快速凝固法可以直接制备块体纳米晶合金.     

Dielectric properties of Bi4(GeO4)3 and Bi4(SiO4)3

Dielectric constant, dielectric loss and conductivity of Bi₄(GeO₄)₃ and Bi₄(SiO₄)₃ single crystals have been measured as a function of frequency and in the temperature range from liquid nitrogen temperature to 400° C. The values of the static dielectric constant at room temperature are 16·4 and 13·7 for Bi₄(GeO₄)₃ and Bi₄(SiO₄)₃ respectively. The plots of log (σ) against reciprocal temperature at different frequencies of these crystals merge into a straight line beyond 250°C and the activation energies calculated in this region are found to be 0·95 eV and 1·2 eV for Bi₄(GeO₄)₃ and Bi₄(SiO₄)₃ respectively.     

Acousto-optic interaction in alpha-BaB(2)O(4)and Li(2)B(4)O(7) crystals

Experimental studies and analysis of acousto-optic diffraction in alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are given. Ultrasonic wave velocity, elastic compliance and stiffness coefficients, and piezo-optic and photoelastic coefficients of alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals are determined. The acousto-optic figure of merit has been estimated for different possible geometries of acousto-optic interaction. It is shown that the acousto-optic figures of merit for alpha-BaB(2)O(4) crystals reach the value M(2)=(270 +/- 70) x 10(-15) s(3)/kg for the case of interaction with the slowest ultrasonic wave. The directions of propagation and polarization of those acoustic waves are obtained on the basis of construction of acoustic slowness surfaces. The acousto-optic diffraction is experimentally studied for alpha-BaB(2)O(4) and Li(2)B(4)O(7) crystals.     

Synthesis of Cu11(OH)14(CrO4)4 nanobelts

Cu₁₁(OH)₁₄(CrO₄)₄ nanobelts have been synthesized by hydrothermal method in the absence of any surfactants. The as-synthesized products are characterized by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. The average thickness, widths and lengths of the nanobelts are about 15 nm, 40 nm, and several micrometers, respectively. It is interesting that Cu₁₁(OH)₁₄(CrO₄)₄ nanobelts are very sensitive to electron beam illumination. The influences of the reaction temperature on the morphologies of the resulting products have been investigated.     

Nanostructured Ag(4)O(4) films with enhanced antibacterial activity

Ag(4)O(4) (i.e.?silver(I)-silver(III) oxide) thin films with tailored structure and morphology at the nanoscale have been grown by reactive pulsed laser deposition (PLD) in an oxygen-containing atmosphere and they are shown to exhibit a very strong antibacterial activity towards Gram-negative bacteria (E. coli) and to completely inhibit the growth of Gram-positive bacteria (S. aureus). The formation of this particular high-valence silver oxide is explained in terms of the reactions occurring during the expansion of the ablated species in the reactive atmosphere, leading to the formation of low-stability Ag-O dimers and atomic oxygen, providing reactive species at the substrate where the film grows. PLD is shown to allow control of the structure (i.e.?crystallinity and grain size) and of the morphology of the films, from compact and columnar to foam-like, thus allowing the deposition of nanocrystalline films with increased porosity and surface area. The antibacterial action towards E. coli is demonstrated and is shown to be superior to that of nanostructured Ag-based medical products. This can be related to the release of Ag ions with high oxidation number, which are known to be very reactive towards bacteria, and to the peculiar morphology at the nanoscale resulting in a large effective surface area.     

Separation of H(2)SO(4) + CuSO(4) mixture by diffusion dialysis

Diffusion dialysis of aqueous solution of H(2)SO(4) + CuSO(4) has been investigated in a two-compartment cell with an anion-exchange membrane Neosepta-AFN. The experiments have proved that sulfuric acid permeates well through the membrane used, while cupric sulfate is efficiently rejected. This operation is very effective at high acid concentrations and low concentrations of cupric sulfate. Furthermore, it has been found that even at the highest concentration of CuSO(4), the rejection coefficient is higher than 0.965. The flux of CuSO(4) calculated from the time dependences of the CuSO(4) concentration is negatively influenced by increasing acid concentration.     

Controlled synthesis of LaPO(4) and CePO(4) nanorods/nanowires

LaPO(4) and CePO(4) nanorods/nanowires with controlled aspect ratios have been successfully synthesized using a hydrothermal microemulsion method under mild conditions. It has been shown that the obtained LaPO(4) has a monoclinic structure, while CePO(4) exists in the hexagonal structure. Uniform nanorods/nanowires with diameters of 20-60?nm and lengths ranging from several hundreds of nanometres to several micrometres were obtained. The aspect ratios of the obtained 1D nanostructures can be fine-tuned by simply changing the [H(2)O ]/[surfactant] molar ratios. The possible growth mechanism of LaPO(4) and CePO(4) nanorods/nanowires was explored in detail.     

Dielectric properties of K2Zn2(SO4)3 and (NH4)2 Mg2(SO4)3

Dielectric constant (ɛ), dielectric loss (tan δ) and conductivity (σ) for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ have been measured over the frequency range 100 Hz — 100 kHz and in temperature range 30°C — 400°C. The values of static dielectric constant at room temperature are 7.67 and 4.80 for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively. The plots of log σ against reciprocal temperature at different frequencies of these samples merge into a straight line beyond 250°C and the activation energies calculated in this region are found to be 0.67 eV and 1.98 eV for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively.     

Nanomechanical characterization of one-step combustion-synthesized Al(4)B(2)O(9) and Al(18)B(4)O(33) nanowires

Two kinds of aluminum borate nanowires, Al(4)B(2)O(9) and Al(18)B(4)O(33), were successfully synthesized by a one-step combustion method through control of the Al:B atomic ratio and synthesis temperature. Both nanowires are single crystalline but have distinguishing growth habits. Nanoindentation tests were performed directly on individual nanowires to reveal their mechanical properties. A 70% reduction in elastic modulus was found in Al(18)B(4)O(33) nanowires compared with their bulk counterpart. Al(18)B(4)O(33) nanowires exhibited higher hardness and elastic modulus than Al(4)B(2)O(9) nanowires.     

4-羧酸正辛酯基-4′-正辛氧基偶氮苯液晶的性能研究

以4-羧基-4′-羟基偶氮苯为母体,与正溴辛烷同时发生酯化和醚化反应,合成了一种新型偶氮苯液晶化合物——4-羧酸正辛酯基-4′-正辛氧基偶氮苯,其结构采用红外光谱(FT-IR)和核磁共振氢谱(1 H NMR)进行表征。采用360nm和440nm的紫外-可见光交替照射,该偶氮苯液晶在乙醇溶液中能够发生顺反光异构化反应,经重复照射10次,其紫外吸收峰均能回复至最初状态。通过差示扫描量热仪(DSC)和偏光显微镜(POM)研究发现,该偶氮苯液晶为热致互变液晶,显示扇形织构的近晶相,并且易于汇集形成马尔他十字液晶相。