Autogenous Shrinkage and Crack Resistance of Carbon Nanotubes Reinforced Cement‑Based Materials

Yanming Liu,Tao Shi,Yujing Zhao,Yuan Gu,Zhifang Zhao,Jiabin Chen,Bingmiao Zheng,Shichong Shi 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.5

Cracking caused by shrinkage deformation of cement-based materials at early age is a major problem leading to material failure in restrained conditions. Carbon nanotubes (CNTs) are incorporated into cement-based materials, and the autogenous shrinkage and crack resistance of the new composite materials obtained by linear shrinkage and ring tests are studied to solve the destruction of the materials caused by the shrinkage of cement-based materials. The results showed that addition of CNTs significantly inhibited the autogenous shrinkage of cement-based materials with maximum reduction rate above 40%. CNTs also significantly improved the cracking resistance of cement-based materials. The optimal effect was noticed at CNTs content of 0.1 wt%. The incorporation of CNTs not only inhibits the autogenous shrinkage of cement-based materials, but also inhibits the drying shrinkage of cement-based materials to some extent. Therefore, carbon nanotubes have the potential to solve the destruction of materials caused by shrinkage of cement-based materials.

Identification of native charge-transfer status of p-aminothiolphenol adsorbed on noble metallic substrates by surface-enhanced infrared absorption (SEIRA) spectroscopy

Li, Qianwen,Wang, Yanan,Li, Yali,Park, Yeonju,Chen, Yujing,Wang, Xu,Zhao, Bing,Ruan, Weidong,Jung, Young Mee Elsevier 2018 Spectrochimica acta. Part A, Molecular and biomole Vol.204 No.-

<P><B>Abstract</B></P> <P>p-Aminothiophenol (PATP) is a preferred molecule in research on surface-enhanced Raman scattering (SERS) because of its unique characteristics of high spectral activity, easily induced charge-transfer (CT), and sensitivity to molecular structural changes. However, some aspects are still unclear, such as the initial steady state of PATP on noble metallic substrates without strong additional excitation with incident and/or induced electromagnetic radiation. Information about the initial steady state, especially the intrinsic CT state, is of great importance to elucidate the dynamic processes of CT and/or molecular structural changes under additional excitation. To investigate the native state of an adsorbed molecule, a suitable probe method that does not disrupt the native state of the whole system, including both molecules and substrates, is required. SERS is not applied in this context because of its use of high-energy visible and near-infrared light. Herein, a low-energy probe method, surface-enhanced infrared-absorption (SEIRA) spectroscopy, is employed as a suitable method for studying the native adsorption state of PATP on silver nanoisland films. The molecular structure and adsorption state were investigated. The intrinsic CT state received particular attention by analyzing the CT-related vibration of B<SUB>2</SUB> modes. Using Fourier transform infrared (FTIR), transmission SEIRA and reflection SEIRA spectroscopy, we explained why the relative intensities of some bands were different under different conditions. A quasi-standing orientation of PATP adsorbed on the substrates was also confirmed. More importantly, we demonstrated that there is no perceptible CT between PATP and silver nanoisland films; in contrast, CT generally occurs in a disruptive manner in SERS. Density functional theory (DFT) calculations and the selection rules for infrared (IR) transmission and reflection-absorption spectroscopy were used to analyze the spectra throughout the paper. SEIRA proved to be an effective technique to explore the native adsorption state of molecules without the excessive external disturbance induced by excitation. The results are very important in providing insight into molecules in surface-interface chemistry, enhanced spectroscopy and photoelectronics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The native state of PATP was investigated when adsorbed on silver substrates. </LI> <LI> FTIR and SEIRA allow a probe method with less interference on surfaces. </LI> <LI> The intrinsic charge-transfer state was analyzed through the vibration modes of B<SUB>2</SUB>. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>

A Digital Self-Sustained Phase Shift Modulation Control Strategy for Full-Bridge LLC Resonant Converters

Kai Zheng,Dongfang Zhou,Jianbing Li,Li Li,Yujing Zhao 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3

A digital self-sustained phase shift modulation (DSSPSM) strategy that allows for good soft switching and dynamic response performance in the presence of step variations is presented in this paper. The working principle, soft switching characteristics, and voltage gain formulae of a LLC converter with DSSPSM have been provided separately. Furthermore, the method for realizing DSSPSM is proposed. Specifically, some key components of the proposed DSSPSM are carefully investigated, including a parameter variation analysis, the start-up process, and the zero-crossing capture of the resonant current. The simulation and experiment results verify the feasibility of the proposed control method. It is observed that the zero voltage switching of the switches and the zero current switching of the rectifier diodes can be easily realized in presence of step load variations.

Calcined Attapulgite Clay as Supplementary Cementing Material: Thermal Treatment, Hydration Activity and Mechanical Properties

Tao Shi,Yanming Liu,Yanlin Zhang,Yingjia Lan,Qifan Zhao,Yujing Zhao,Haobo Wang 한국콘크리트학회 2022 International Journal of Concrete Structures and M Vol.16 No.2

The present paper studied the effects of calcination temperatures (200–800 °C) on the appearance, mineral composition, and active SiO2 content in attapulgite and investigated the effects of attapulgite before and after calcination on the chemically bonded water content, the degree of reaction of cement paste, and the mechanical properties such as the flexural strength, compressive strength, and splitting-tensile strength of cement mortar. The results indicate that the calcination temperature changes the mineral composition of attapulgite, thereby affecting the hydration activity of cement-based materials. The attapulgite calcined at 500 °C (AT500) has the best enhancement on the hydration activity of cement-based materials. The calcination at 500 °C is most beneficial to the dissolution of SiO2, and the content of SiO2 reaches 20.96%. The contents of chemically bonded water in the samples incorporated with calcined attapulgite reduced and that of the samples incorporated with AT500 at 28 d is the same as that of the control group. The reaction degree of AT500 is 78.61% at 28 days. Calcined attapulgite clay can reduce the energy consumption of the cement industry and promote the sustainable development of attapulgite clay.

Study on Preparation of Core-Spun Yarn Surgical Sutures by Compositing Drug-Loaded Nanofiber Membrane with PLA and Its Controllable Drug Release Performance

Zhichao Yang,Shuqiang Liu,Jingjing Li,Gaihong Wu,Man Zhang,Fu Li,Lu Jia,Yujing Zhang,Huimin Li,Xia Liu,Jingjing Zhao,Huiqin Zhang,Shiyu Li 한국섬유공학회 2023 Fibers and polymers Vol.24 No.12

Polylactic acid (PLA) surgical suture is considered to be one of the most ideal materials for tissue closure due to its rich raw materials and excellent biological properties. However, surgical sutures face great challenges due to problems such as wound infection and tissue reaction in practical applications. In order to improve the clinical applicability of surgical sutures, we constructed a new drug-loading system for core-spun surgical sutures. The shell was composed of nanofibrous membranes composed of polyglycolic acid (PGA) and polycaprolactone (PCL) and ciprofloxacin (CIP) antibacterial drugs, and the core layer adopts PLA filament. By adjusting the composition ratio of PGA and PCL in the shell, a new mode of regulating the release rate and release cycle of the suture was constructed. According to different wound healing time, different drug release cycles of surgical suture were selected. In the study, the structure of the core-spun yarn can be clearly observed by scanning electron microscope, the higher the shell PGA content and drug loading, the faster the drug release rate. When the carrier ratio PGA/PCL was 80/20 and the drug loading was 3%, the drug release rate was the fastest and the drug release was high; finally, antibacterial experiments showed that the suture had excellent antibacterial effect and could effectively kill Staphylococcus aureus and Escherichia coli. The successful preparation of core-spun yarn surgical suture provides a new idea for the study of new antibacterial surgical suture.