Using of Taguchi Method for Experimental Design of Crystallization Processes of an Oxidant: Tetraethylammonium Chlorochromate (VI)

Abstract  Crystallization of tetraethylammonium chlorochromate (C₂H₅)₄N[CrO₃Cl], TEACC, with desirable particle size as a performance characteristic was used to illustrate the design procedure. Taguchi design of experiments (DOE) method has been used for to plan a minimum number of experiments and optimization of crystallization processes. Four factors, which influence the crystal size, crystal growth and nucleation, were chosen. These factors are concentration, temperature, type of solvent and method of crystallization. After optimization the results show that concentration is most effective factor that has largest percent of contribution 53.26% and type of solvent is least effective factor that has smallest percent of contribution 4.33%. The optimum conditions are vapor diffusion as method, 0.043 g/15 mL for concentration, 0 °C for temperature and acetonitrile as solvent. These conditions must be produced suitable crystals for single crystal X-ray diffraction experiment. These results confirmed by experimental data and the crystals of the optimum conditions found to have suitable properties for single crystal X-ray diffraction. These crystals had sent for single crystal X-ray diffraction and diffraction data gathered successfully. A red block crystal was mounted on a glass fiber. The X-ray data determined monoclinic system, space group C2(#5), with a = 12.023(3), b = 7.998(2), c = 14.527(4) ?, β = 114.187(4)°, V = 1274.4(6) ?³ and Z = 4. Index Abstract  The Taguchi design of experiments (DOE) method has been used for to plan a minimum number of experiments and optimization of crystallization processes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Crystal structure of the molecular inclusion complex of 5, 17-di-t-butyl-26, 28-disubstituted calix[4]arene with acetone (1:3)

Crystal structure of inclusion complex of 5, 17-di-t-butyl-26, 28-disubstituted calix[4]arene 3 with acetone, [(C₅₄H₅₈N₂O₆·CH₃COCH₃)·2CH₃COCH₃], was determined by X-ray crystallographic analysis. It possesses space group C2/c, with a = 26.277(8), b = 12.967(5), c = 20.355(4) Å, = 124.845(14)°, and D _calc = 1.173 mg/m³ for Z = 4. Crystal data indicate that action of one molecule of compound 3 upon three molecules of acetone forms a clathrate intermolecular inclusion complex.     

Crystal structure of the molecular inclusion complex tetra-p-nitro-tetra-O-butyl calix[4]arene with acetone (1:2)

The crystal structure of the inclusion complex of tetra-p-nitro-tetra-O-butyl calix[4]arene 1 with acetone, [(C₄₄H₅₂N₄O₁₂)·2CH₃COCH₃], was measured by X-ray crystallographic analysis with an imaging plate method. It belongs to the space group C2/c, with a = 13.131(3),b = 21.480(4), c = 19.645(4)Å, = 105.69(3)°, and D_cale = 1.177 mg/m³ for Z = 4. Crystal data indicate that the host molecule 1 exist in a pinched-cone conformation, and the action of one molecule of host upon two molecules of acetone forms a channel type intermolecular inclusion complex.     

Structure of malagashanine,a new alkaloid with chloroquine-potentiating action

The molecular structure of malagashanine (C₂₃H₃₀N₂O₄), a new alkaloid occurring in MadagascanStrychnos species and showing chloroquine-potentiating action, has been determined by single crystal X-ray diffraction. The crystals, in the form of a 11 acetone solvate, are monoclinic, space group P2₁, witha=10.328(2),b=10.554(6),c=11.490(5)Å, =96.67(2)⁰,Z=2. Refinement based on 3650 reflections measured at 294K yieldedR=0.045. The X-ray analysis shows that the ring system in malagashanine differs from that in alkaloids of the strychnobrasiline type in containing only five-and six-membered rings. Thermal analysis of the solvate indicates that the acetone molecules are firmly held in the crystal and the X-ray analysis reveals that they are trapped in crystal voids. Only van der Waals forces and C–H...O hydrogen bonds stabilize the crystal structure.     

4d金属掺杂增强SnO2对丙酮光学传感特性的理论分析

通过检测人体呼出气体中的微量丙酮可以筛查出早期的糖尿病患者,因此寻找能进行微量丙酮气体灵敏探测的材料是一个研究热点。本文计算4d金属杂质Mo、Ru、Rh、Ag掺杂金红石相SnO₂(110)表面吸附丙酮分子后的表面电荷布居(氧化还原性能)、态密度、光学性质以及吸附稳定性,讨论了4d金属杂质掺杂对金红石相SnO₂(110)表面光学气敏传感特性的影响。研究结果发现:各金属杂质对表面的氧化还原性能都有着不同程度的影响;4d电子在费米能级附近形成杂质峰,其中Ru-4d电子引入的杂质峰最大,离费米能级最近,对SnO₂的禁带宽度改善最大;Ru掺杂对于金红石相SnO₂(110)表面在可见光范围内(400~760 nm)的光学性质的改善相对于Mo、Rh、Ag掺杂也有着较大的优势;所有的掺杂表面都能自发吸附丙酮分子,吸附后稳定性为:Ru＞Rh＞Ag＞Mo。结论表明,Ru掺杂的SnO₂作为较为有效的丙酮光学气敏探测材料,有望通过探测人体呼出气体中的丙酮从而达到改善糖尿病的早期发现和诊断的效率。     

Physical aging in PMMA/silica nanocomposites: Enthalpy and dielectric relaxation

We have investigated the physical aging below the glass transition temperature, namely the slow evolution occurring in non-equilibrium glasses, of poly(methyl methacrylate)/silica (PMMA/silica) nanocomposites. To do so we have followed the time evolution of the enthalpy and that of the dielectric strength of PMMA β process during isothermal annealing. The results indicate that physical aging is generally accelerated in all nanocomposites in comparison to pure PMMA, despite the lack of effect of the nanoparticles on PMMA molecular dynamics. Furthermore, the shorter is the interparticle distance, and hence the higher is the area/volume of silica in PMMA, the more pronounced is such acceleration. The acceleration of the physical aging together with the invariance of PMMA dynamics in the nanocomposites in comparison to pure PMMA poses serious questions on the idea that the molecular mobility is the only responsible parameter for the rapidity of physical aging. Thus, an interpretation based on the free volume holes diffusion towards the external surface, in this case represented by the polymer/silica interface, is provided.     

半固态处理对Al-50wt%Si合金初晶硅形貌的影响研究

提高初晶硅的收率是Al-Si合金法制备太阳能级多晶硅的研究热点之一。本文对成分为Al-50wt%Si合金在580℃进行半固态热处理,分析初晶硅的形貌以及Al元素含量的变化。结果表明:随半固态处理时间的增加,初晶硅的尺寸逐渐增大,其原因是在熟化机制的作用下,尺寸为0.15~0.7mm的初晶硅的含量显著增加,这一结果导致初晶硅的收率高于理论收率。同时,经过半固态热处理,片状初晶硅之间的富Al层容易酸洗去除,降低了初晶硅中的Al含量。     

工业晶体生长

本文考察了一些典型的晶体材料及其工业生长技术,如提拉法生长硅单晶,水热法生长水晶,VGF法生长GaAs,下降法生长锗酸铋,壳熔法生长锆石等,探讨了工业晶体生长的特点和发展方向.