机械力化学研究现状及其在小麦制粉中的应用前景

小麦制粉是将小麦籽粒经粉碎碾磨、分级、混配等工艺制成小麦粉的加工过程。现有的小麦制粉理论认为在制粉过程中,籽粒受到机械力作用后只对其物理性质如粒度、损伤淀粉含量等产生影响,而越来越多的研究表明,粒度的差异不足以解释制粉过程中出现的面粉品质差异。机械力化学是研究固体因受机械力作用而发生的化学或者物理化学变化,这些变化包括物质破碎、粒度减小、晶型变化、化学键变化等,其还能降低部分化学反应所需能量,使反应更易发生,目前已应用于材料表面改性、物理降解等领域。本文综述了机械力化学理论、原理模型,以及机械力化学在合成、降解和改性方面的应用,介绍了小麦制粉基本理论和当前实践过程中遇到的困扰,以及机械力化学在淀粉和蛋白质等谷物大分子成分方面的研究现状,并对机械力化学理论在小麦制粉研究中的应用作出展望。     

Self-Propagating Reactions in the Ti–Si System: A SHS-MASHS Comparative Study

In this work, we report on the self-propagating reaction in Ti–Si blends, observed by SHS and MASHS (mechanical activated SHS) techniques. In spite of the differences between the two reacting methods, correlations were found between the key parameters of the two modes of activation. Moreover, this comparative study enabled us to gain some hints on the reaction mechanism. The combustive behavior of powder mixtures with stoichiometries corresponding to the intermetallics present in the Ti–Si phase diagram (TiSi₂, TiSi, Ti₅Si₄, and Ti₅Si₃) was studied. The SHS characteristics, such as combustion temperature, propagation rate, and ignition temperature was strongly dependent on both the initial stoichiometry and milling time. Particular attention was paid to the influence of the initial stoichiometry and milling conditions on the reaction mechanism. A single-step dissolution-precipitation mechanism was found for the composition Ti : Si = 5 : 3. On the other hand, at the composition Ti : Si = 1 : 2, the mechanism shows two steps, the first, active at the leading front of the combustion front, involving only solid phases, and the second, active in the afterburn region, involving solid–liquid interaction.     

机械力化学过程及效应(Ⅰ)--机械力化学效应

介绍了机械力化学这门新兴交叉学科的概念及发展,阐述了机械力化学是指固体物质在机械力作用下可能引起的化学和物理化学过程,如密度变化、晶体的结晶度和结构变化、含水物质的脱水,在某些体系中混合物组分间可能发生化学反应等,并以无机非金属材料在机械力作用下引起物质的化学效应实例作了综合介绍。     

机械化学的研究发展现状与展望

介绍了机械化学的发展简史和基本特征,简述了机械化学过程中粉体(晶体)结构变化、粉体物理化学性质变化和粉体机械化学反应的研究现状,展望了机械化学、特别是其中的机械活化的研究发展前景.     

粉碎方式对TiO2粉体的影响

为了研究研磨作用方式对粉碎样品的粒径和晶型转变的影响,以汽车颜料TiO2为原料,分别用离心环隙式磨机和QM-BP型行星式球磨机对质量分数为30%的TiO2进行了湿法超细粉碎试验。XRD分析结果表明:离心环隙式磨机粉磨6h,近90%的锐钛矿型TiO2转变成金红石型TiO2,且粒径达到22.9nm。而行星球磨机粉磨20h,其粒径仅达到86.5nm,且无晶型转变。研究结果表明:新型机的特殊研磨方式不仅能够获得纳米级的颗粒,而且通过机械力化学效应使TiO2的相变温度从900℃降到100℃以下。     

机械化学合成纳米材料的研究进展

分析了机械化学的特性,着重论述了利用固相机械化学法合成磁性材料、储氢材料、特种陶瓷、梯度功能材料、形状记忆合金、超导材料、尖晶石型功能材料、氧化物等功能材料的研究现状,以及利用机械化学法合成这些纳米材料的特点,指出了机械化学合成技术的发展前景。     

机械化学促成可调谐光-电多功能响应二维杂化钙钛矿材料

二维有机-无机杂化钙钛矿因在光伏、光电子等领域的巨大应用潜力而备受关注.此外,该类材料具有突出的结构可调性和材料稳定性,为功能性质的设计调控及器件应用提供了丰富的材料设计平台.然而,将多种物理通道的性质整合实现材料的多功能性仍具有挑战性,而对其进行快速有效的调节更是难上加难.迄今为止,尚未成功实现可调谐的光电多通道响应...     

高能机械化学法制备微纳米Mo—Si粉体

以Mo粉和Si粉为原料,通过自行设计的高能机械化学球磨机在室温下制备出了微纳米Mo-Si粉体,利用X射线衍射（XRD）和扫描电子显微镜（SEM）进行物相分析和粒度分析,结果表明,在不同的反应阶段会生成MoSi2和Mo5Si3,并且生成物之间相互有一定的转化,反应生成率接近100％,制备出的微纳米Mo—Si粒度在100nm左右,在Mo和Si的高能机械化学反应中,适当地提高球料比和转速可以加快反应的进程。     

Preparation of aluminosilicate precursor by mechanochemical method from gibbsite-fumed silica mixtures

Aluminosilicate (mullite) precursor was prepared by mechanochemical treatment of gibbsite and fumed silica mixtures. The effect of grinding on its structure and thermal behaviour was examined by²⁷Al and²⁹Si MAS NMR, XRD, DTA-TG and FTIR. Thermal treatment of this precursor led to the crystallization of mullite at about 1200°C via a spinel-phase.²⁷Al and²⁹Si MAS NMR spectroscopies show lowering of mullitization temperature, which is associated with increased homogeneity of the precursor. Mechanochemical treatment of gibbsite and fumed silica mixtures resulted in the formation of a more homogeneous aluminosilicate precursor.     

Going with the Flow: Tunable Flow‐Induced Polymer Mechanochemistry

Mechanical forces can drive chemical transformations in polymers, directing reactions along otherwise inaccessible pathways, providing exciting possibilities for developing smart, responsive materials. The state‐of‐the‐art test for solution‐based polymer mechanochemistry development is ultrasonication. However, this does not accurately model the forces that will be applied during device fabrication using processes such as 3D printing or spray coating. Here, a step is taken toward predictably translating mechanochemistry from molecular design to manufacturing by demonstrating a highly controlled nozzle flow setup in which the shear forces being delivered are precisely tuned. The results show that solvent viscosity, fluid strain rate, and the nature of the breaking bond can be individually studied. Importantly, it is shown that the influence of each is different to that suggested by ultrasonication (altered quantity of chain breakage and critical polymer chain length). Significant development is presented in the understanding of polymer bond breakage during manufacturing flows to help guide design of active components that trigger on demand. Using an anthracene‐based mechanophore, the triggering of a fluorescence turn‐on is demonstrated through careful selection of the flow parameters. This work opens the avenue for programmed chemical transformations during inline manufacturing processes leading to tunable, heterogeneous final products from a single source material.