Morphology, drug release behavior, thermal, and mechanical properties of poly(ethylene oxide) (PEO)/poly(vinyl pyrrolidone) (PVP) blends

Study on Autolytic Mechanism and Self-Healing Properties of Autolytic Clinker Microsphere in Alkaline Environment

In this study, the autolytic clinker microsphere with clinker as core and polyvinyl pyrrolidone (PVP) as coating film was prepared. Pretreatment of clinker with silane coupling agent was firstly processed during the preparation. To investigate the autolytic mechanism, the microstructures of the autolytic clinker microsphere at different curing ages were observed using environmental scanning electron microscopy (ESEM), equipped with an energy dispersive spectrometer (EDS). The autolytic stages were also identified based on the microstructural evolution. The influence of pretreatment degree on autolytic behavior was also studied by measurements of micro-morphology and isothermal calorimetry. Experimental results indicated that the compressive strength recovery of specimens was increased by 15–19% due to the addition of autolytic clinker microspheres. The recovery of compressive strength was also improved with the increase of pH value. The improvements in compressive strength recovery of specimens with microspheres were in the range of 15–19%, 15–31%, 25–36%, and 29–50% with the pH value of 7, 8, 10, and 12, respectively. It was also found that inner damage of cement-based matrix had greater recovery when pre-cracked specimens were cured in alkaline environments.

Highly Sensitive Humidity Sensors Based on Polyethylene Oxide/CuO/Multi Walled Carbon Nanotubes Composite Nanofibers

Polymer composites are favorite materials for sensing applications due to their low cost and easy fabrication. In the current study, composite nanofibers consisting of polyethylene oxide (PEO), oxidized multi-walled carbon nanotubes (MWCNT) and copper oxide (CuO) nanoparticles with 1% and 3% of fillers (i.e., PEO–CuO–MWCNT: 1%, and PEO–CuO–MWCNT: 3%) were successfully developed through electrospinning for humidity sensing applications. The composite nanofibers were characterized by FTIR, XRD, SEM and EDX analysis. Firstly, they were loaded on an interdigitated electrode (IDE), and then the humidity sensing efficiency was investigated through a digital LCR meter (E4980) at different frequencies (100 Hz–1 MHz), as well as the percentage of relative humidity (RH). The results indicated that the composite nanofibers containing 1% and 3% MWCNT, combined with CuO in PEO polymer matrix, showed potent resistive and capacitive response along with high sensitivity to humidity at room temperature in an RH range of 30–90%. More specifically, the PEO–CuO–MWCNT: 1% nanocomposite displayed a resistive rapid response time within 3 s and a long recovery time of 22 s, while the PEO–CuO–MWCNT: 3% one exhibited 20 s and 11 s between the same RH range, respectively.

Magnetic-Electrospinning Synthesis of γ-Fe2O3 Nanoparticle-Embedded Flexible Nanofibrous Films for Electromagnetic Shielding

The exploration of a new family of flexible and high-performance electromagnetic shielding materials is of great significance to the next generation of intelligent electronic products. In this paper, we report a simple magnetic-electrospinning (MES) method for the preparation of a magnetic flexible film, γ-Fe₂O₃ nanoparticle-embedded polymeric nanofibers. By introducing the extra magnetic field force on γ-Fe₂O₃ nanoparticles within composite fibers, the critical voltage for spinning has been reduced, along with decreased fiber diameters. The MES fibers showed increased strength for the magnetic field alignment of the micro magnets, and the attraction between them assisted the increase in fiber strength. The MES fibers show modifications of the magnetic properties and electrical conductivity, thus leading to better electromagnetic shielding performance.

Preparation and Self-Healing Properties of Clinker/PVP Microsphere in Cement Paste

This paper presents a new insight into the autolytic mineral self-healing method for cementitious materials. The clinker/PVP (polyvinyl pyrrolidone) autolytic microsphere was prepared via the film coating method with cement clinker as a healing agent and PVP as the autolytic coating film. The morphology and chemical structure of the microsphere were characterized by environmental scanning electron microscopy (FESEM) equipped with energy dispersive spectrometer (EDS) and Fourier transform infrared spectroscopy (FTIR), respectively. The clinker retaining original mineral healing composition was successfully coated with a PVP film confirmed by FTIR. The maximum film thickness was 7.54 μm, which was determined by laser particle size measurement. The autolytic behavior was measured using isothermal calorimetry and successfully controlled by pretreatment degree (i.e., silane coupling agent amount). Experimental results showed that the compressive strength recovery of cement paste with a 30% microsphere was 54% higher than ordinary cement paste specimens. The damage degree of the specimen was also decreased by adding the autolytic microsphere.