Developing novel structural modelling methods for optical glasses

有机化学键，如C-O， C-H和O-H，在特定的中红外（中红外）频率上强烈吸收光。这使得每个分子都有了独特的“化学指纹”，可以被检测到。可以测量这些相互作用的传感器的开发将在各种领域得到应用，从监测制造环境中的污染，检测药物和爆炸物，到确保食品和饮料生产线不受污染，以及在手术期间监测癌症边缘。然而，现有的硅基纤维技术只能将光传输到近红外，为了利用这种“指纹”方法进行化学鉴定，需要新的中红外透射玻璃。对中红外光技术的研究往往集中在设备开发上，利用一小部分已知表现出适当行为的玻璃成分。然而，非最佳材料特性可能会导致不必要的问题，从通过光纤的光强度损失到改变光特性的非线性光学（NLO）效应。在构建工作装置时需要解决这些问题，但如果起始材料被特别设计以显示所需的功能特性，则可以避免这些问题。该项目的目的是解决连接玻璃成分与结构和功能特性的基本知识差距。当前的构图开发必然是一种反复试验的过程，需要大量的时间和金钱投入。对光学玻璃中成分-结构-性质关系的更好理解将为预测新玻璃提供路线图，为确定光学应用的最佳成分提供捷径。一旦建立，研究方案可以应用于改善其他应用的玻璃性能，如能源、生物医学设备、建筑玻璃和核废料形式。该项目的目标将通过研究碲酸盐（TeO2）和硫系（Sb2Se3）玻璃家族的玻璃成分来实现。之所以选择这种玻璃，是因为它们可以将光传输到中红外，并表现出强烈的NLO效应，可以通过许多潜在的有用方式与光相互作用。这项研究将分为两个阶段。第一阶段将是测量玻璃的功能特性。众所周知，玻璃的功能特性，如软化和熔化温度、密度、折射率和透光窗口，取决于原子结构。研究的第二阶段将是通过使用一系列技术获得的数据的直接和计算分析，对玻璃结构进行定量分析。这些将包括中子和x射线散射、x射线吸收光谱学、拉曼散射和核磁共振。初步结果表明，碲玻璃成分的微小变化改变了碲的局部环境，改变了最近邻的数量。相比之下，硫系玻璃组成的变化可以导致锑周围最近邻居类型的变化。最近邻居的数量和类型会对玻璃的性能产生很大的影响，影响我们如何制作、塑造和使用玻璃。然而，我们目前对这些变化的理解是定性的，而不是定量的，特别是在应用所需的复杂的多组分玻璃中。对精心选择的组合物系列的结构和功能特性的确定将使牢固的关系得以发展。这些将用于预测具有特定性能的新玻璃成分，从而满足特定应用的精确功能性能要求。这些新材料的应用将导致在中红外中工作的新设备的发展发生重大变化。

Organic chemical bonds, such as C-O, C-H and O-H, absorb light strongly at specific mid-infrared (mid-IR) frequencies. This gives every molecule a distinctive 'chemical fingerprint' that can be detected. The development of sensors that can measure these interactions would have applications in a diverse range of fields, from monitoring pollution in manufacturing environments and detecting drugs and explosives, to ensuring food and drink production lines are not contaminated and monitoring cancer margins during surgery. However, established silica-based fibre technologies only transmit light to the near-IR, and to exploit this "fingerprinting" method for chemical identification new mid-IR transmissive glasses are required. Research into mid-IR light technologies tends to focus on device development, utilising a small set of glass compositions that are known to exhibit adequate behaviour. However, non-optimal material properties can result in unnecessary problems, from loss of light intensity through a fibre to non-linear optical (NLO) effects that change the light characteristics. These need to be addressed when constructing a working device, but could be avoided if the starting material were specifically designed to exhibit the functional properties needed. The aim of this project will be to address the fundamental gap in knowledge that links glass composition to structure and functional properties. Current compositional development is, perforce, trial-and-error and requires a significant investment in time and money. A better understanding of composition-structure-property relationships in optical glasses will provide a road map to allow new glasses to be predicted, providing a short cut to determining optimised compositions for optical applications. Once established, the research protocols can be applied to improve glass performance for other applications such as energy, biomedical devices, architectural glasses and nuclear waste forms.The aim of this project will be achieved by studying glass compositions in the tellurite (TeO2) and chalcogenide (Sb2Se3) glass families. These glasses have been chosen because they transmit light into the mid-IR and exhibit strong NLO effects that can interact with light in a number of potentially useful ways. The research will be comprised of two stages. The first stage will be to measure the functional properties of the glasses. It is well-established that the functional properties of a glass, such as softening and melting temperatures, densities, refractive indices and light transmittance windows, depend upon atomic structure. The second stage of the study will be a quantitative analysis of glass structures through the direct and computational analysis of data obtained using a range of techniques. These will include Neutron and X-ray scattering, X-ray Absorption Spectroscopy, Raman Scattering and Nuclear Magnetic Resonance. Preliminary results show that small changes in the composition of tellurite glasses alter the local environment of tellurium, changing the number of nearest neighbours. In comparison, variations in the composition of chalcogenide glasses can lead to changes in the types of nearest neighbours around antimony. The number and type of nearest neighbours can have a large impact on the glass properties, affecting how we make, shape and use the glass. However, our current understanding of these changes is qualitative, rather than quantitative, particularly in the complex multicomponent glasses required for applications.A determination of structure and functional properties for carefully chosen compositional series will allow robust relationships to be developed. These will be used to predict new glass compositions that exhibit specific properties, allowing the precise functional property requirements of a specific application to be fulfilled. The application of these new materials will result in a step change in the development of new devices that operate in the mid-IR.