共查询到16条相似文献,搜索用时 517 毫秒
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制备了B2O3-Na2O-CaO-SiO2四元系若干玻璃样品,通过实验拉曼光谱和量子化学从头计算相结合的方法,对其微观结构进行了定性定量研究。结果表明,随着B2O3的加入,硅酸盐转变为硼硅酸盐结构。当质量比CaO/SiO2=1时,B主要以[BO3]的形式参与网络形成,并在B2O3含量为6 Wt%时迹象明显。拉曼光谱精细结构解谱的结果表明,B的加入使结构复杂化,体系中Q1相对含量减少,Q3相对含量增加,整体由以Q2为主变为以Q2、Q3为主。 相似文献
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锂、硼、硅酸盐玻璃体系的11B核磁共振研究 总被引:1,自引:1,他引:0
利用11B的核磁共振谱研究了锂、硼、硅酸盐(Li2O·B2O3·SiO2)三元玻璃体系,测量并分析了BO4单元与对称和非对称的BO3单元的比例。分析结果表明,三元体系的结构单元亦可适用于锂、硼玻璃的二元体系的FDB模型说明,其差异在于前者中的Li2O由B2O3与SiO2按比例分享。 相似文献
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本文用X射线和差热分析方法对BaO-Li2O-B2O3三元系中的两个截面:BaB2O4-Li2B2O4和BaB2O4-Li2O作了研究。在BaB2O4-Li2B2O4赝二元系中发现了一个新的化合物4BaB2O4·Li2B2O4。化合物在930±3℃由包晶反应形成,并与Li2B2O4形成共晶反应。共晶温度为797±3℃,共晶点组分为79mol%Li2B2O4。在BaB2O4-Li2O截面中也存在化合物4BaB2O4·Li2B2O4,其包晶反应温度从930±3℃随Li2O含量增加下降到908±3℃。在组分60mol%Li2O处形成另一个新的化合物2BaB2O4·3Li2O。该化合物在630±3℃也是由包晶反应形成,并与Li2O和Li2CO3分别形成共晶反应,共晶温度分别为400±3℃和612±3℃。在BaB2O4-Li2B2O4和BaB2O4-Li2O体系中都没有观察到固溶体。用计算机程序分别对化合物4BaB2O4·Li2B2O4和2BaB2O4·3Li2O的X射线粉末衍射图案进行了指标化,其结果:4BaB2O4·Li2B2O4的空间群为Pmma,a=13.033?,b=14.630?,c=4.247?,每个单胞包含两个化合式单位;2BaB2O4·3Li2O的空间群为Pmmm,a=4.814?,b=9.897?,c=11.523?,每个单胞也含有两个化合式单位。
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木文研究了Al2O3对B2O3-0.7Li2O-0.7LiCl非晶态的形成和电学性能的影响,我们发现:加入适量的Al2O3后,无需借助液氮骤冷技术,直接将熔体倾倒在室温下的紫铜板上就很容易形成大块非晶锂离子导体B2O3-0.7Li2O-0.7LiCl-xAl2O3。Al2O3的加入使B2O3-0.7Li2O-0.7LiCl的电导率有所降低,但在高温下不太明显,电导激活能略微升高,实验发现:Al2O3含量x=0.03是较合适的剂量,较容易形成大块非晶态,对电导率的影响也不大。
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采用高温原位拉曼光谱技术,研究了Li2B4O7从常温至1 373 K温度范围内的拉曼光谱。在升温过程中,晶体的拉曼光谱出现展宽和红移现象,且强度降低。晶体熔化时,由2个[BO4]和2个[BO3]组成的[B4O9]环状结构转变成(B3O6)3- 六元环和[BO3]结构,[BO4]结构减少直至消失。基于密度泛函理论,计算了Li2B4O7晶体的拉曼光谱,对其振动模式进行了分析归属。利用量子化学从头计算法计算了由[B3O6-BO3]为基础相互连接形成的x(Li2B4O7)(x=2, 3, …, 9)的环状团簇模型的拉曼光谱,对Li2B4O7熔体的结构进行了模拟分析。计算结果表明Li2B4O7熔体的阴离子基元为三个(B3O6-BO3)组成的大三元环超级结构。 相似文献
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Sealing quality lithium zinc silicate (LZS) glasses of compositions (wt.%) (a) LZSL- Li2O: 12.65, ZnO: 1.85, SiO2: 74.4, Al2O3: 3.8, K2O: 2.95, P2O5: 3.15, B2O3: 1.2 (low ZnO), and (b) LZSH- Li2O: 8.9, ZnO: 24.03, SiO2: 53.7, Na2O: 5.42, P2O5: 2.95, B2O3: 5 (high ZnO) were prepared by conventional melt-quench technique and converted to glass-ceramics by controlled crystallization process. The electrical properties of these samples were measured using ac impedance spectroscopy technique over a frequency range of 10 Hz-15 MHz at several temperatures in the range of 323-673 K. The ac conductivity, dc conductivity, dielectric constant and loss factor were obtained from these measurements. The dc conductivity (σdc) follows the Arrhenius behaviour with temperature. It is observed that σdc in LZSL glass is significantly higher than in the LSZH glass and the activation energies for σdc for LZSL and LZSH glasses are 0.59 and 1.08 eV, respectively. It further observed that the conductivity value decreases nearly one order of magnitude on conversion to glass-ceramics. The behaviour is explained on the basis of distributions and nature of alkali ions and network structures in these samples. 相似文献
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M.M. Elkholy 《Journal of luminescence》2010,130(10):1880-1892
Lithium borate (LiB) glasses in the system (100−x)B2O3-xLi2O with x=20, 30, 40, 50, 60 and 70 mol% were prepared. The glasses were doped with different concentrations of the order of 10−1, 10−2, 10−3, 10−4 and 10−5 of MgO and their thermoluminescent (TL) response was investigated. The irradiations were performed using γ rays from a 60Co source in the dose range from 0.1 to 25 kGy. The material displayed good sensitivity for γ-rays and intensity of TL signals is dependent on γ-ray dose and Li2O content. For each dose level and investigated temperature range (50-350 °C), exactly single isolated glow peak appears in the temperature range of 165-205 °C depending on both Li2O concentrations and time of exposure. The shape of the glow peak has altered significantly with increase in the gamma ray dose or Li2O concentrations. The glass composition with x=50 mol% doped with 10−3 mol% of MgO presented the best TL response. The results of the present study indicated that the recorded single and isolated high temperature peak is a good candidate for TL dosimetric investigations. This indicates that 50 B2O3-50Li2O-doped with 10−3 mol% of MgO is possibly used as materials for radiation dosimetry in the dose range of 0.1-20 kGy. 相似文献
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Lithium borate (Li2B4O7) is a low Zeff, tissue equivalent material that is commonly used for medical dosimetry using the thermoluminescence (TL) technique. Nanocrystals of lithium borate were synthesized by the combustion method for the first time in the laboratory. TL characteristics of the synthesized material were studied and compared with those of commercially available microcrystalline Li2B4O7. The optimum pre-irradiation annealing condition was found to be 300 °C for 10 min and that of post-irradiation annealing was 300 °C for 30 min. The synthesized Li2B4O7 nanophosphor has very poor sensitivity for low doses of gamma up to 101 Gy whereas from 101 to 4.5×102 Gy this phosphor exhibits a linear response and then from 4.5×102 to 103 Gy it shows supralinearity. Thermoluminescence properties of Li2B4O7 nanophosphor doped with Cu has also been investigated in this paper. It shows low fading and a linear response over a wide range of gamma radiation from 1×102 to 5×103 Gy. Therefore the synthesized lithium borate nanophosphor doped with Cu may be used for high dose measurements of gamma radiations. 相似文献
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A. Levasseur J.C. Brethous P. Hagenmuller R. Berger G. Vignaud 《Solid State Communications》1979,32(2):115-119
An EPR study of fast Li+ ion vitreous conductors belonging to the B2O3-Li2O-LiCl system has been carried out. The samples have been subjected to X-ray irradiation at room temperature. Two types of paramagnetic centers have been observed. The first one is the Cl2- species (Vk center) present in the part of the vitreous domain which corresponds to low LiCl concentrations, it vanishes when Li+ and Cl- begin to order. The second one is of the B.O.H.C. type often present in alkali borate glasses. Its presence shows the similarity between the boron-oxygen network of the alkali borate glasses and of our samples containing alkali chloride. 相似文献
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A. Levasseur M. Kbala J.C. Brethous J.M. Réau P. Hagenmuller M. Couzi 《Solid State Communications》1979,32(10):839-844
New vitreous electrolytes with fast lithium ion carriers have been obtained in the B2O3 - Li2O - Li2SO4 system. The variation of the ionic conductivity is discussed. Raman spectroscopy indicates that sulfate ions are diluted in the vitreous matrix without detectable interaction with the surrounding. 相似文献