Explorations in the Dynamics of Crystalline Solids and the Evolution of Crystal Formation Processes

This article describes a few selected areas of research within the field of structural chemistry, with emphasis on aspects that have been influenced and inspired by the seminal work of Jack Dunitz. The topics covered include the study of dynamic properties of crystalline materials, focusing on the use of solid-state ²H NMR spectroscopy to unravel details of dynamic hydrogen-bonding arrangements in crystalline alcohols and amino acids, as well as the use of in situ Raman microspectrometry to explore molecular transport processes through porous crystals. A case study involving the determination of both structural properties and dynamic properties of a material (ammonium cyanate) that is not amenable to structural characterization by single-crystal X-ray diffraction is also presented. On the theme of exploring the time evolution of crystallization pathways, the recent development and application of in situ solid-state NMR techniques for mapping time-dependent changes that occur in the solid phase during crystallization processes are discussed. Finally, the article contemplates the prospects for deriving a fundamental physicochemical understanding of crystal nucleation processes, which is identified as perhaps the most significant challenge in structural chemistry in the next few decades.     

Formation of Bubbles by Electrochemical Processes in Glass

Bubble formation at both electrodes in the systems metal | glass | oxide, metal is investigated by short-circuiting, or application of an electromotive force. The systems investigated included noble metals, soda-lime-silicate glass, and simple or complex oxides which operate as electronic or ionic conductors. Oxygen was considered as the main gaseous component produced by an electrochemical process. The analysis of the current-potential curves defining the kinetics of the electrochemical processes on the surface of two electrodes, points to the possible existence and the importance of bubble formation when two electrodes are short-circuited.     

Positron Annihilation Lifetime Spectra in a Metakaolin-Based Geopolymer

Significant nanoporosity as indicated by positron annihilation lifetime spectroscopy (PALS) has been observed in a metakaolin-based geopolymer. The nanoporosity was indicated by a component of the PALS spectrum having a lifetime of 1.5–2 ns, characterizing a pore diameter size of ∼0.5 nm. Progressive heating to 600°C decreased the intensity of this spectral component from ∼10% to 2.5%. Positron annihilation in free pore water appears to be only a minor contributor to this spectral component. The Barrett–Joyner–Halenda (BJH) method pore distribution data, derived from BET nitrogen adsorption isotherms, showed the presence of considerable meso- and macroporosity in the samples. However, these porosities were not evident in the PALS spectrum. Heating from 150° to 600°C progressively changed the smallest detectable pore size via the BJH method from 3.3 to 7.1 nm.     

浮法玻璃锡石缺陷的形成机理和控制措施

阐述锡石的产生机理,重点分析锡槽中氧、硫、水污染要素的主要途径,提出了锡石的预防、控制方法。     

Effect of Nontraditional Additives on the Processes of Silicate and Glass Formation

The results of studying the effect of nontraditional additives, namely, metallic aluminum and zinc powders on the process of silicate and glass formation using polythermal and thermogravimetric analysis, are described. The specifics of the glass-melting process for decorative glasses using the nontraditional additives are considered. __________ Translated from Steklo i Keramika, No. 5, pp. 7 – 10, May, 2005.     

氧化锌导电陶瓷钇掺杂效应的正电子寿命谱研究

用正电子湮没谱方法,研究了掺杂Y2O3的ZnO导电陶瓷在不同掺杂量,不同烧结温度和烧结时间对材料结构的影响。实验结果表明：Y2O3掺杂量增加,ZnO导电陶瓷材料完整性变差;烧结温度增加,ZnO陶瓷产生空洞为主的缺陷,烧结时间增加,微空洞缺陷数目明显增加,本研究对正电子湮没机制与氧化锌陶瓷导电特性的关联也进行了探讨。     

绿色玻璃瓶罐中黑点缺陷成因探讨

绿色玻璃瓶罐中产生的黑点缺陷,通过光学显微镜及扫描电子显微镜-能谱(SEM-EDS)分析,找出了缺陷形成的原因。化学成分分析结果证实黑点缺陷主要为硅和碳元素。经过机理及成因分析,判断其主要为配合料比例失调、窑炉气氛还原性过强等因素所致,通过采取相应的措施,最终解决了黑点缺陷问题。     

Study of Radiation-Induced Processes in Electron-Irradiated Alkali-Silicate Glass

The formation of a localized charge upon irradiation of colorless silicate glass containing Na, K, and Ba is investigated. Irradiation is performed in the sterilizing mode in air at room temperature using an Elektronika U-003 electron accelerator (average power 4 MeV). The integral fluence is accumulated in 6 stages of sequential irradiation from 1.8 × 10¹³ to 1.8 × 10¹⁵ e/cm², which corresponds to exposure doses ranging from 0.3 to 30 MR. The irradiation creates a permanent dark brown coloration of the glass, which protects the medicinal products from sunlight. The absorption spectra demonstrates a red shift of the absorption edge from 300 to 500 nm depending on the accumulated exposure dose, which is typical for charged metal-containing nanoparticles of 20 to 30 nm.     

Surface Crystal Formation During Acid Corrosion of Phosphate-Doped Lead Silicate Glass

The effect of small P₂O₅ additions on the acid corrosion behavior of lead silicate glass was studied at 22°C. Crystals of penta-lead phosphosilicate, a phase heretofore synthesized only by high-temperature melt techniques, formed on the surface of the phosphate-doped glass during the corrosion process. No crystals were observed to form on the pure lead silicate glass. Crystallization appears to result from the controlled release of phosphorus and lead at the glass surface and/or from the reactive catalytic properties of a silica gel surface film. Apparent lead diffusion rates into the acid solution for the phosphate-doped lead silicate glass are much less (by a factor of 11,3) than for the pure lead silicate glass. Application of these findings is suggested in two areas: formulation of low cation-release glass and glaze compositions and the synthesis of high-temperature phases in aqueous solution at ambient temperatures.     

基于线阵CCD的玻璃缺陷检测方法的研究

玻璃缺陷检测已成为提高玻璃质量的重要技术之一,它在检测出不合格玻璃产品的同时,还能将缺陷信息传递给玻璃生产的各个流程,再对各个环节加以改进。为能够生产出高质量的玻璃,以及准确获取玻璃缺陷信息,本文提出了一种基于莫尔条纹的玻璃缺陷检测新方法。这种检测方法不但能够检测出微小缺陷,并进行分类,同时还能有效地检测出玻璃的光学畸变。     

安瓿玻管析晶的探讨

玻璃析晶是玻璃拉管工艺中存在的技术性难题,本文从理论方面分析玻璃析晶必须具备温度和时间两个因素,根据生产工艺要求提出消除析晶的方法。     

多分束产品耳朵纱解决方案的探讨

通过对公司多分束合股纱产品“耳朵纱”问题的形成原因进行分析,找出各种影响因素,制定解决方案并实施。现场验证效果良好,有效保证了公司多分束产品的正常生产,提升了产品品质。     

铅晶质玻璃在不同环境下的铅析出性能研究

铅水晶玻璃具有折射率高、透过率高等优异性能,被广泛应用于工艺品、高档餐具、首饰等,但其中氧化铅成分存在潜在析出的风险,因此对使用者的健康有一定的影响。通过制备3种不同Pb_3O_4质量分数的铅水晶玻璃样品,分别研究了80℃条件下样品在白酒、洗洁精中浸泡后的铅析出情况,并通过失重法、光学显微镜以及元素分析(ICP)测试,对铅水晶玻璃在侵蚀过程中的铅析出速率和表面形貌等进行了测定。研究结果表明,铅水晶玻璃在不同溶液中长时间浸泡会导致铅析出,析出量和析出速率与其Pb_3O_4质量分数有关,其中低、中铅玻璃相对稳定,高铅玻璃的铅析出量大幅提升。     

简述玻璃缺陷种类及产生原因

通过对玻璃产品产生的各类缺陷(气态、固态、玻璃态)的分析,找出其产生原因,指出了解决缺陷的办法。     

Formation and Properties of a Lead-Barium-Aluminum Phosphate Glass

A lead-barium-aluminum phosphate glass has been prepared by a wet chemical process. The phosphate glass exhibits high transmission in the visible region of the spectrum and into the mid-infrared and can strongly absorb in the ultraviolet at wavelengths of less than 344 nm. In addition, the glass has a relatively high index of refraction and a good chemical durability. Therefore, the phosphate glass can be used for general-purpose optical applications.     

浮法玻璃生产中出现硅质缺陷时的处理方法

浮法玻璃生产过程中,出现两种不太常见的硅质缺陷,通过排查其生成原因,探索解决方法和总结经验。     

单层氮化硼空位缺陷的形成与稳定性的研究

本文利用密度泛函理论方法研究了单层氮化硼中多原子空位缺陷的结构和稳定性。研究发现缺陷多为对称结构,并且存在幻数现象。通过对不同尺寸缺陷离解能的回归分析,发现对于尺寸较大的缺陷,周围的氮原子数越多,缺陷越稳定,该结论很好的解释了实验中观察到的现象。