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采用二次烧结方法,并控制颗粒级配,制备了不同氧化铁添加剂含量的氧化钙试样,测量了试样的抗水化性能。结果表明,加入氧化铁能提高氧化钙材料的抗水化性能,加入3Wt%氧化铁能制备出具有较好的抗水化性能的氧化钙坩埚。 相似文献
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M. V. Borrachero J. Payá M. Bonilla J. Monzó 《Journal of Thermal Analysis and Calorimetry》2008,91(2):503-509
The thermogravimetric analysis (TG) technique is widely used in the characterization of diverse types of construction materials
related to binders, such as plasters, limes and cements. For calcium sulphate dihydrate (gypsum) two serial dehydration steps
are very near in temperature decomposition and overlapping in the thermogravimetric events is observed. The goal of this research
is to develop new thermogravimetric analysis procedures that allow obtaining more precise information in the characterization
of plasters. The resolution of both dehydration events has been increased using two different strategies: on one hand, the
production in the experience of a water vapour self-generated atmosphere by the use of sealed aluminium pan with a pinholed
lid. On the other hand, the use of high resolution thermogravimetric analysis (HRTG), based on the variation of the heating
rate as a function of the rate of mass loss observed at once. The results obtained for both strategies of improvement of the
TG curves, showed that they are two procedures that let to obtain a total resolution of the two dehydration steps for gypsum. 相似文献
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本文研究了在B_2O_3—Al_2O_3—PbO玻璃中引入SiO_2、Sb_2O_3、Ga_2O_3后,TF光学玻璃化学稳定性及相对部分色散P_(g·F)。论证了B_2O_3—Al_2O_3—PbO光学玻璃光学性质、化学组成和结构关系。TF光学玻璃在3.51铂坩埚熔制。 相似文献
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The solubility of Ag2O was measured for the Na2O–B2O3 and Na2O–B2O3–Al2O3 system with the rotating crucible method and static method, respectively, under air atmosphere at temperatures ranging from 1273 to 1423 K. The contamination of melts from crucibles could be avoided by the rotating crucible method, with which it became possible to measure the solubility of Ag2O for the Na2O–B2O3 system above the melting point of Ag for the first time. It was found that the addition of Na2O decreases the solubility of Ag2O while the addition of Al2O3 had little effect on the solubility. The effect of Na2O and Al2O3 on the solubility of Ag2O is expressed by interaction coefficients and is analyzed in terms of the basicity of melts. The solubility of Ag2O in Na2O–B2O3–Al2O3 melts increased with increased temperature. This phenomena was explained by a small enthalpy change in oxidation of silver. 相似文献
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近化学计量比铌酸锂晶体组分过冷与临界生长速率研究 总被引:1,自引:1,他引:0
本文在用双坩埚提拉法生长近化学计量比LiNbO3晶体的过程中观察到了组分过冷的实验数据,同时根据Tiller-Chalmers稳定性判据公式半定量计算了近化学计量比LiNbO3晶体临界生长速率的理论值,得到一般电阻加热双坩埚提拉法生长近化学计量比LiNbO3晶体的临界生长速率为0.1mm/h数量级.通过临界生长速率解释了一系列晶体生长的实验结果.提出了一些工艺措施来避免组分过冷,根据这些工艺获得了无包裹体的近化学计量比LiNbO3晶体. 相似文献
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采用自主设计改造的温梯炉,成功生长了不同浓度Ho3+、Y3+掺杂的CaF2及SrxCa1-xF2晶体,晶体尺寸约为ϕ15 mm×55 mm,生长周期约为6 d,能够实现7种不同浓度晶体的同步生长,并选取其中的4%(原子数分数)Ho,4%Y∶CaF2晶体进行分析,吸收测试表明,该晶体448 nm和643 nm处吸收峰的吸收截面分别是1.13×10-20 cm2和0.84×10-20 cm2, J-O理论分析得到了晶场强度参数Ωt(t=2、4、6)、辐射跃迁几率、荧光分支比和辐射寿命。在448 nm氙灯激发下,经计算得到该晶体在546 nm、650 nm 和752 nm处的发射截面分别为10.450×10-21 cm2、8.737×10-21 cm2和5.965×10-21 cm2,测得5F4和5F5能级的寿命分别为33.5 μs和17.7 μs。在640 nm LD泵浦激发下,经计算得到该晶体2 031 nm处发射截面为5.375×10-21 cm2,2 847 nm处发射截面为10.356×10-21 cm2,测得5I7和5I6 能级的寿命分别为4.37 ms 和1.85 ms。以上结果表明,多孔坩埚温梯法能够大大提高激光晶体稀土离子掺杂浓度筛选的效率,加快新型激光晶体材料的研发速度。 相似文献
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H. Saeedi M. Asadian Sh. Enayati N. Mirzaei I. Mashayekhi Asl J. Sabbaghzadeh 《Crystal Research and Technology》2011,46(12):1229-1234
In this paper, we report the growth of neodymium doped Gadolinium Gallium Garnet (Nd: GGG) crystal using Czochralski (CZ) method, and study the effects of crucible bottom deformation and thermal insulator thickness on the growth process and crystal quality. Garnet structure and <111> crystallography orientation of the crystal were confirmed by the X‐Ray diffraction (XRD) analysis. Macroscopic defects, residual stresses, quality, and homogeneity of the crystals were investigated by means of parallel plane polariscope and laser fizeau interferometer respectively and the results compared together. Experimental observations show that the crucible bottom deformation from flat to convex, and decreasing the thickness of zirconia insulator under the crucible result in the formation of lateral cores and increasing the crystal inhomogeneity and tensions, leading to the decrease of the crystal quality. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Choice of crucible material is a key issue during the growth of AlN crystal. The stabilities at high temperature and life-spans of boron nitride (BN) crucible,tantalum (Ta) crucible and tungsten (W) crucible were compared. Tantalum crucible behaved worse at high temperature and life-span was shortened as compared with the other two crucible materials. It was very crisp and easy to crack. In contrast,self-seeded AlN crystals with different morphologies could be obtained at different high temperatures using BN crucible. The boron nitride crucible was stable below 2200 ℃,above which it would decompose. Thus it was unsuitable for the bulky AlN crystal growth. Tungsten crucible could endure the temperatures higher than 2200℃. Unfortunately we could only get AlN polycrystallines using tungsten crucible. After 50~100 hours’ run,the crucible was destroyed completely due to the multiple deep cracks. XRD results of destroyed tungsten crucible indicated that the main phases are tungsten carbide and tungsten nitride. 相似文献