自锐性金刚石树脂砂轮磨削性能的研究

本文通过对比磨削试验，研究了自锐性金刚石(CSD)树脂砂轮的磨削性能。试验结果表明，由于CSD形状小规则，有许多凹入角和粗糙表面，树脂结合剂对CSD的把持力较普通金刚石强，所以在磨削各参数相同的条件下，自锐性金刚石砂轮与普通金刚石砂轮相比，其磨削比提高60％以上。且由于CSD的内部为许多单个亚晶粒所组成的镶嵌的颗粒，因此在应力作用下，只有很小的不规则的碎片崩掉，从而在每个颗粒的表面上留下许多新的小切削刃，故其加工工件的表面粗糙度值较低。     

Effect of photoaligning azo dye structure on liquid crystal anchoring energy

A method of controlling anchoring energy of surface interaction of liquid crystal photoaligning substances is considered to enhance the liquid crystal display performances. An important parameter of the dye's molecular structure that determines the ratio of polar and azimuthal anchoring energy is the ability to form dimers. The values of dimerization thermodynamic potentials have been found. The probability of the formation of dye molecules dimers is evaluated. The bonds conjugation transfer via intermolecular hydrogen bond is revealed, and anisotropy of polarizability of the hydrogen bond is evaluated. The effect of dimerization on polar and azimuthal anchoring energy of liquid crystal — azo dye system — is shown.     

预应力筋与沥青基材料的黏结性能研究

预应力筋与沥青基材料的黏结性能研究对采用沥青基材料灌浆的后张预应力结构具有重要的意义。以沥青基材料为研究对象,建立计算模型,在沥青基材料黏弹性本构关系的基础上,推导出预应力筋-沥青基材料黏结受力理论解。通过该理论解,得到钢绞线、钢绞线-基体界面以及沥青基材料基体等的应力分布特征。探讨了施加荷载、预应力筋与基体的半径比、沥青基材料温度以及荷载施加时间等因素对预应力筋-沥青基材料之间黏结性能的影响规律。通过与已有成果的对比,验证了本文所推导公式的正确性。本文的研究结果,可为采用沥青基材料灌浆的后张预应力结构的设计计算提供理论依据。     

Optimizing the Oxygen-Catalytic Performance of Zn–Mn–Co Spinel by Regulating the Bond Competition at Octahedral Sites

By using the more electro-negative Mn³⁺ ion to partially replace Co³⁺ at the octahedral site of spinel ZnCo₂O₄, i.e., forming ternary Zn–Mn–Co spinel oxide, the electrocatalytic oxygen reduction/evolution activity is found to be significantly increased. Considering the physical characterization and theoretical calculations, it demonstrated that the bond competition played a key role in regulating the cobalt valence state and the electrocatalytic activity. The partial replacement of octahedral-site-occupied Co³⁺ by Mn³⁺ can effectively modulate the adjacent Co–O bond and induce the Jahn–Teller effect, thus changing the originally stable crystal structure and optimizing the binding strength between the active center and reaction intermediates. Certainly, the Mn-substituted ZnMn_1.4Co_0.6O₄/NCNTs exhibit higher electrocatalytic oxygen reduction reaction (ORR) activity than that of ZnCo₂O₄/NCNTs and ZnMn₂O₄/NCNTs, supporting that the Co–O bond covalency determines the ORR activity of spinel ZnCo₂O₄. This study offers the competition between adjacent Co–O and Mn–O bonds via the B_Oh–O–B_Oh edge-sharing geometry. The ion substitution at octahedral sites by less electronegative cations can be a new and effective way to improve the electrocatalytic performance of cobalt-based spinel oxides.     

Surface Oxygen Coordination of Hydrogen Bond Chemistry for Aqueous Ammonium Ion Hybrid Supercapacitor

Aqueous ammonium ion hybrid supercapacitor (A-HSC) combines the charge storage mechanisms of surface adsorption and bulk intercalation, making it a low-cost, safe, and sustainable energy storage candidate. However, its development is hindered by the low capacity and unclear charge storage fundamentals. Here, the strategy of phosphate ion-assisted surface functionalization is used to increase the ammonium ion storage capacity of an α-MoO₃ electrode. Moreover, the understanding of charge storage mechanisms via structural characterization, electrochemical analysis, and theoretical calculation is advanced. It is shown that NH₄⁺ intercalation into layered α-MoO₃ is not dominant in the A-HSC system; rather, the charge storage mainly depends on the adsorption energy of surface “O” to NH₄⁺. It is further revealed that the hydrogen bond chemistry of the coordination between “O” of surface phosphate ion and NH₄⁺ is the reason for the capacity increase of MoO₃. This study not only advances the basic understanding of rechargeable aqueous A-HSC but also demonstrates the promising future of surface engineering strategies for energy storage devices.     

A mechanistic approach to evaluate the potential of the debonding distress in asphalt pavements

The debonding distress in asphalt pavement structures is a critical problem that affects the performance of asphalt concrete pavements. It occurs at the layer interface due to the poor bond quality between adjacent asphalt concrete layers and/or when stresses at the layer interface exceed the strengths of the material at the interface. The debonding of the adjacent layers, especially the top surface layer of an asphalt pavement, is a contributing factor to the premature cracking of pavements. Hence, the debonding distress can lead to a reduction in the life of the pavement. This paper presents an analytical and experimental framework to evaluate the potential for debonding at the layer interface of asphalt concrete pavements. Computational analysis was performed to determine the critical stress and strain states in layered asphalt pavements under moving vehicle loads using the Layered ViscoElastic pavement analysis for Critical Distresses (LVECD) computer program developed at North Carolina State University. This computational analysis enables a greater understanding of the critical stress that is involved in debonding and the ways that such stress is affected by pavement design parameters and environmental conditions. In addition, a prediction model was developed that can determine the shear bond strength at the interface of asphalt concrete layers with different tack coat materials at various temperatures, loading rates and normal confining stresses. The systematic and mechanistic framework developed in this study employs the maximum shear ratio concept as a shear failure criterion and provides a tool to evaluate the effects of various loading, environmental and pavement factors on the debonding potential of asphalt pavements. The overall advantages of the mechanistic framework and approach using the LVECD analysis tool will help lead to better understanding of the debonding mechanism, proper selection of the tack coats, and economic benefit in highway pavement maintenance and rehabilitation costs.     

Polyethylene Glycol–CaCl2 Coordination Compounds as a Novel Form‐Stable Phase Change Material with Excellent Thermophysical Properties

Polyethylene glycols (PEGs) have been extensively studied as phase change materials (PCMs). To overcome the problem of liquid leakage, the authors firstly report a novel form‐stable phase change material (FSPCM) using coordination compound. The structure, morphology, thermal property, and thermal stability of the self‐prepared samples are determined. The obtained results confirm the existence of coordination bonds between PEG and Ca²⁺ species, and no liquid leakage is observed for the synthesized PEG–CaCl₂ composites at temperatures as high as 120 °C. The PEG8000–CaCl₂ (1:2) FSPCM exhibits a relatively large latent heat of 147.7 J g^?1, corresponding to 87.8% of that of pure PEG. From the dynamical viewpoint, the activation energy of crystallization process is increased by only 5.2% for the PEG8000–CaCl₂ composite due to the formation of coordination bonds; however, the activation energy is reduced by 18.3% during melting process. After adding 3 wt% conductive carbon black, the heat storage performance of the PEG phase change material can be optimized. The PEG‐CaCl₂ composite would be a promising material for thermal energy storage applications and can be used in various engineering fields.

     

Selective Nanoscale Fabrication with Roughness Reduction of Polycrystalline Silicon by Physically Induced Fluorine Bonds Using Atomic Force Microscope

Polycrystalline silicon (poly-Si) is widely used as a gate layer in integrated circuits, transistors, and channels through nanofabrication. Nanoremoval and roughness control are required for nanomanufacturing of various electronic devices. Herein, a nanoscale removal method is developed to overcome the limitations of microcracks, complex procedures, and time-consuming conventional fabrication and lithography methods. The method is implemented with a mechanically induced poly-Si phase transition using atomic force microscope (AFM). Mechanical force induces the covalent bonds between silicon and fluorine atoms which cause the phase transition of poly-Si. Then, the bond structure of the Si molecules is weakened and selectively removed by nano-Newton-scale force using AFM. A selective nanoscale removal with roughness control is implemented in 0.5 mM TBAF solution after mechanical force (43.58–58.21 nN) is applied. By the magnitude of nano-Newton force, the removal depth of poly-Si is controlled from 2.66 to 21.52 nm. Finally, the nanoscale fabrication on poly-Si wafer is achieved. The proposed nanoremoval mechanism is a simple fabrication method that provides selective, nanoscale, and highly efficient removal with roughness control.