机械力化学在陶瓷材料研究中的应用

机械力化学是机械合金化技术研究中的最新进展，在球磨过程中机械力化学使颗粒和晶粒细化产生裂纹、比表面积增大、晶格缺陷增多、晶格发生畸变和结晶程度降低，乃至诱发低温化学反应，可制备出高活性陶瓷粉体和性能优异的陶瓷基材料。本介绍了机械力化学在陶瓷材料研究中的最新研究进展，同时讨论了不同球磨工艺条件对材料制备过程的影响，并对其未来发展进行了展望。     

助磨剂在陶瓷粉体机械粉碎过程中的助磨作用

从机械力化学角度探讨了陶瓷粉体机械粉碎过程中助磨剂的助磨作用机理。分析了助磨剂的表面吸附及粉碎过程中影响其作用效果的因素 ,进而指出助磨剂开发研究的趋势     

机械力化学作用对CaO-B2O3-SiO2系陶瓷微观结构及相组成和相变规律的影响

采用X射线衍射、扫描电镜和差热热重分析等手段研究了机械力化学作用对CaO-B_2O_3-SiO_2(CBS)混合粉末及其陶瓷的微观结构、相组成和相变过程的影响。结果表明:高能球磨中的机械力化学作用能够细化晶粒、提高球磨混合粉体的反应活性和诱导室温化学反应。CBS混合粉末高能球磨120 h可合成出C_2B(2CaO·B_2O_3)中间相,该球磨粉末950℃烧成后的主晶相为CB(CaO·B_2O_3),C_6S_4(6CaO·4SiO_2)和CS(CaO·SiO_2)。该种材料的介电常数ε≈5,介电损耗<2×10~(-3)(1 MHz),有望用于低介高频电子元件领域。     

Cephalopod‐Inspired High Dynamic Range Mechano‐Imaging in Polymeric Materials

Cephalopods, such as squid, cuttlefish, and octopuses, use an array of responsive absorptive and photonic dermal structures to achieve rapid and reversible color changes for spectacular camouflage and signaling displays. Challenges remain in designing synthetic soft materials with similar multiple and dynamic responsivity for the development of optical sensors for the sensitive detection of mechanical stresses and strains. Here, a high dynamic range mechano‐imaging (HDR‐MI) polymeric material integrating physical and chemical mechanochromism is designed providing a continuous optical read‐out of strain upon mechanical deformation. By combining a colloidal photonic array with a mechanically responsive dye, the material architecture significantly improves the mechanochromic sensitivity, which is moreover readily tuned, and expands the range of detectable strains and stresses at both microscopic and nanoscopic length scales. This multi‐functional material is highlighted by creating detailed HDR mechanographs of membrane deformation and around defects using a low‐cost hyperspectral camera, which is found to be in excellent agreement with the results of finite element simulations. This multi‐scale approach to mechano‐sensing and ‐imaging provides a platform to develop mechanochromic composites with high sensitivity and high dynamic mechanical range.     

Atomistic understanding of surface wear process of sodium silicate glass in dry versus humid environments

Understanding surface reactions of silicate glass under interfacial shear is critical as it can provide physical insights needed for rational design of more durable glasses. Here, we performed reactive molecular dynamics (MD) simulations with ReaxFF potentials to study the mechanochemical wear of sodium silicate glass rubbed with amorphous silica in the absence and presence of interfacial water molecules. The effect of water molecules on the shear-induced chemical reaction at the sliding interface was investigated. The dependence of wear on the number of interfacial water molecules in ReaxFF-MD simulations was in reasonable agreement with the experimental data. Confirming this, the ReaxFF-MD simulation was used to find further details of atomistic reaction dynamics that cannot be obtained from experimental investigations only. The simulation showed that the severe wear in the dry condition is due to the formation of interfacial Si_substrate–O–Si_{counter_surface} bond that convey the interfacial shear stress to the subsurface and the presence of interfacial water reduces the interfacial bridging bond formation. The leachable sodium ions facilitate surface reactions with water-producing hydroxyl groups and their key role in the hydrolysis reaction is discussed.     

Polyurethane/Siloxane Hybrid Polymers with Chemiluminescent Mechanophores as Stress Probes

A series of mechanoluminescent polyurethane/siloxane hybrid polymers are synthesized through mild polycondensation and sol–gel hydrolysis process with 1,2‐dioxetane as the mechanophore. With joint advantages of polyurethanes and silicon‐containing polymers, these hybrid polymers exhibit good mechanical strength, high elasticity, and water resistance properties. Herein, 1,2‐dioxetane acts as an autoluminescent probe of chain scission, which could emit visible and sensitive signals of the covalent bond breaking in these hybrid polymers under mechanical force. Thus, chain scission and chain slipping events during the failure process of these polymers can be effectively discriminated. The current work will offer exciting opportunities to study the failure process of hybrid polymers with unprecedented temporal and spatial resolutions.     

Chemical Genetics Approach to Engineer Kinesins with Sensitivity towards a Small‐Molecule Inhibitor of Eg5

Due to their fast and often reversible mode of action, small molecules are ideally suited to dissect biological processes. Yet, the validity of small‐molecule studies is intimately tied to the specificity of the applied compounds, thus imposing a great challenge to screens for novel inhibitors. Here, we applied a chemical‐genetics approach to render kinesin motor proteins sensitive to inhibition by the well‐characterized small molecule S‐Trityl‐l ‐cysteine (STLC). STLC specifically inhibits the kinesin Eg5 through binding to a known allosteric site within the motor domain. Transfer of this allosteric binding site into the motor domain of the human kinesins Kif3A and Kif4A sensitizes them towards STLC. Single‐molecule microscopy analyses confirmed that STLC inhibits the movement of chimeric but not wild‐type Kif4A along microtubules. Thus, our proof‐of‐concept study revealed that this chemical‐genetic approach provides a powerful strategy to specifically inhibit kinesins in vitro for which small‐molecule inhibitors are not yet available.     

Polymer mechanochemistry: the design and study of mechanophores

The burgeoning field of polymer mechanochemistry has garnered significant interest in recent years. Mechanochemical transformations are those that are promoted by exogenous forces, and polymer mechanochemistry concentrates on the use of polymer chains to translate mechanical forces to chemical systems. Acoustic fields, particularly ultrasound, have proven to be highly efficient progenitors of tensile stresses within macromolecules and are frequently used to facilitate mechanochemical phenomena. Mechanochemical activation often arises when mechanophores, or functional groups that respond to mechanical perturbation in a controlled manner, are appropriately positioned within a polymer chain to experience tensile forces. A variety of interesting transformations have been realized when well‐designed mechanophores have been properly outfitted with polymer chains, including: thermally inaccessible isomerizations and cycloreversions, symmetry‐forbidden electrocyclic ring openings and activation of latent catalysts. Herein, the chemistry of known mechanophores is summarized and augmented with implications for new opportunities in synthesis and materials science. The focus of this mini‐review is limited to mechanophores that have been specifically adapted for polymer mechanochemistry under acoustic activation. Copyright © 2012 Society of Chemical Industry     

机械化学法降解甲基红

以甲基红分解为探针反应,以碱土金属氧化物为主要磨料,研究了球磨速度、球磨时间、投料比等因素对甲基红分解的影响.将甲基红质量分数为2.5%和0.25%的MgO、CaO磨料分别于行星式球磨机中共磨,诱发其发生化学降解反应,采用紫外-可见分光光度计测定反应后剩余甲基红质量分数.分析表明:甲基红初始浓度越低,降解率越高;随着转速和时间的增加,降解率不断提高,6 h后球磨甲基红质量分数为0.25%的MgO、CaO磨料,降解率分别可达78%和65%;此外,添加TiO2和(NH4)2S2O8,分别利用其热催化效应和氧化性可提高甲基红的降解程度,最高降解率可达91%.利用气-质连用检测仪及X射线衍射仪对甲基红降解过程作了进一步研究.     

The Microstructure and Chemical Bonds of β-C2S Under the High Energy Ball Grinding Function

Using the laser granularity survey technology , logy, X-ray powder diffraction, scanning electron microscopy （SEM） and infrared spectrum anal）sis methods, we studied the microscopic structure and chemical bonds changes of β-C2 S monomineral under the high energy ball grinding function. The result indicates that, continuously under the mechanical power, β-C2 S crystal size would decrease, the micro strain and the effective Beff parameter would increase, and the amorphous phases would be presented. Furthermore, the mechanical power would cause Si-O bond broken and reorganized, the specific surface area would increase, the energy of micro-powder agglomeration vibration would be enhanced and the crystal would be disordered. Finally, β- C2 S was caused to have the mechanochemical change and the activity enhancement.