Preparation and Characterization of Nano-hydroxyapatite/polyvinyl Alcohol Gel Composites

Nano-hydroxyapatite reinforced poly（vinyl alcohol） gel（nano-HA/PVA gel） composites has been proposed as a promising biomaterial,especially used as an articular cartilage repair biomaterial.In this paper,nano-HA/PVA gel composite was prepared by in situ synthesis method and incorporation with freeze-thaw cycle process.The microstructure and morphology were investigated by X-ray diffraction,TEM,SEM and FTIR.The results showed that the size of HA particles synthesized in PVA solution was on the nanometer scale.Both the size and crystallinity of HA particles synthesized in PVA solution decreased compared with that of HA synthesized in distilled water.The nano-HA particles were distributed in PVA matrix uniformly due to the effect of PVA solution as a dispersant while low content of HA particles in the composites.On the contrary,with high content of nano-HA particles in the composites,the particles tended to aggregate.The result of FT-IR analysis indicated that the chemical bond between nano-HA particles and PVA matrix existed.The conformation and degree of tacticity of PVA molecule changed because of the addition of HA particles.Furthermore,the interfacial strength of the composites was improved due to the interaction between nano-HA particle and PVA matrix and this was beneficial to improving the mechanical properties of the composites.

Research on a novel composite gel system for CO_2 breakthrough

A composite gel was prepared for plugging CO2 channeling, which is a serious problem for enhanced oil recovery with CO2. A composite gel which is one of the materials for successful control of CO2 channeling during CO2 injection process was studied in this paper. SEM and nano particle size analysis were used to describe this material’s microstructure. Its effect on CO2 channeling control was evaluated with core flow experiments. Both the rheological test and core plugging experiments indicated that both acrylamide monomer concentration and reaction pressure had positive influences on gel properties. The gel system with an acrylamide monomer concentration of 2% and 5% sodium silicate was proved to have excellent strength, elastic and plugging efficiency, which confirmed huge development potential and wide application of the composite gel system. The high-pressure acid environment arising from the CO2 injection not only reacts with solid silicate to form silicic acid gel, but also facilitates efficient polymerization.

Facile Preparation of PVA-AA/TiO2 Composite Gel Particles and Their Tunable Photo-catalytic Property for the Degradation of Methyl Orange

In the presence of titanium dioxide powder, cross-linking reaction between commercial polyvinyl alcohol(PVA)-based macromonomer and acrylic acid(AA) was initiated with potassium persulfate in an emulsifying system. As a result, PVA-AA/TiO2 composite gel particles were obtained. The morphology and composition of the particles were analyzed with scanning electron microscopy(SEM), energy scattering x-ray spectroscopy(EDS), Fourier infrared spectroscopy(FTIR), and thermogravimetric analysis(TGA). The analysis results confirmed that the particles were the expected ones. TiO2 was dispersed homogeneously within the spheroidal particles. Compared to the control gel, the composite gel particles not only contained Ti element but also showed higher thermal stability. In addition, the photo-catalytic behavior of the particles for the degradation of methyl orange contained in aqueous solution was examined. The particles exhibited photocatalytic characteristic for the degradation of the model dye, which could be modulated by simply varying the amount of cross-linking agent or TiO2. The photo-catalytic degradation percentage of methyl orange maintained at 91%-96% after using the particles three times, which indicated that TiO2 could played its role repeatedly via being fixated within polyvinyl alcohol-based gel.

Novel mechanical behavior of periodic structure with the pattern transformation

Abstract In periodic cellular structures, novel pattern transformations are triggered by a reversible elastic instability under the axial compression. Based on the deformation-triggered new pattern, periodic cellular structures can achieve special mechanical properties. In this paper, the designed architecture materials which include elastomer matrixes containing empty holes or filled holes with hydrogel material are modeled and simulated to investigate the mechanical property of the periodic materials. By analyzing the relationship between nominal stress and nominal strain of periodic material, and the corresponding deformed patterns, the influence of geometry and shapes of the holes on the mechanical property of architecture material is studied in more details. We hope this study can provide future perspectives for the deformation-triggered periodic structures.

SiO_(2) nanofiber composite gel polymer electrolyte by in-situ polymerization for stable Li metal batteries

Gel polymer electrolytes(GPEs) are promising alternatives to liquid electrolytes applied in high-energydensity batteries.Here superior SiO_(2) nanofiber composite gel polymer electrolytes(SNCGPEs) are developed via in-situ ionic ring-opening polymerization of 1,3-dioxolane(DOL) monomers in SiO_(2) nanofiber membrane(PDOL-SiO_(2)) for lithium metal batteries.The oxygen atoms of PDOL together with Si-O of SiO_(2) construct a more efficient channel for Li^(+) migration.Consequently,the lithium ion transference number(t_(Li^(+)) and ionic conductivity(σ) at 30℃ of PDOL-SiO_(2) are 0.80 and 1.68×10^(-4)S/cm separately.PDOL-SiO_(2) manifests the electrochemical decomposition potentials of 4.90 V.At 0.5 mA/cm^(2),Li|PDOL-SiO_(2) |Li cell shows a steady cycling performance for nearly 1400 h.LFP|PDOL-SiO_(2) |Li battery can steadily cycle at 0.5 C with a capacity retention rate of 89% after 200 cycles.While cycling at 2 C,the capacity retention rate can maintain at 78% after 300 cycles.This contribution provides a innovative strategy for accelerating Li^(+)transportation via designing PDOL molecular chains throughout the SiO_(2) nanofiber framework,which is crucial for high-energy-density LMBs.

Photocatalytic properties of P25-doped TiO_2 composite film synthesized via sol–gel method on cement substrate

TiO2 films have received increasing attention for the removal of organic pollutants via photocatalysis. To develop a simple and effective method for improving the photodegradation efficiency of pollutants in surface water, we herein examined the preparation of a P25-TiO2 composite film on a cement substrate via a sol–gel method. In this case, Rhodamine B（Rh B）was employed as the target organic pollutant. The self-generated TiO2 film and the P25-TiO2 composite film were characterized by X-ray diffraction（XRD）, N2 adsorption/desorption measurements, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and diffuse reflectance spectroscopy（DRS）. The photodegradation efficiencies of the two films were studied by Rh B removal in water under UV（ultraviolet） irradiation. Over 4 day exposure, the P25-TiO2 composite film exhibited higher photocatalytic performance than the self-generated TiO2 film. The photodegradation rate indicated that the efficiency of the P25-TiO2 composite film was enhanced by the addition of the rutile phase Degussa P25 powder. As such, cooperation between the anatase TiO2 and rutile P25 nanoparticles was beneficial for separation of the photo-induced electrons and holes. In addition, the influence of P25 doping on the P25-TiO2 composite films was evaluated. We found that up to a certain saturation point, increased doping enhanced the photodegradation ability of the composite film. Thus, we herein demonstrated that the doping of P25 powders is a simple but effective strategy to prepare a P25-TiO2 composite film on a cement substrate, and the resulting film exhibits excellent removal efficiency in the degradation of organic pollutants.

High thermal conductivity and remarkable damping composite gels as thermal interface materials for heat dissipation of chip

The emerging applications of composite gels as thermal interface ma-terials(TIMs)for chip heat dissipation in intelligent vehicle and wear-able devices require high thermal conductivity and remarkable damp-ing properties.However,thermal conductivity and damping proper-ties are usually correlated and coupled each other.Here,inspired by Maxwell theory and adhesion mechanism of gecko’s setae,we present a strategy to fabricate polydimethylsiloxane-based composite gels in-tegrating high thermal conductivity and remarkable damping prop-erties over a broad frequency and temperature range.The multiple relaxation modes of dangling chains and the dynamic interaction be-tween the dangling chains and aluminum fillers can efficiently dis-sipate the vibration energy,endowing the composite gels with ultra-high damping property(tanδ>0.3)over a broad frequency(0.01-100 Hz)and temperature range(-50-150°C),which exceeds typi-cal state-of-the-art damping materials.The dangling chains also com-fort to the interfaces between polymer matrix and aluminum via van der Waals interaction,resulting in high thermal conductivity(4.72±0.04 W m-1 K-1).Using the polydimethylsiloxane-based composite gel as TIMs,we demonstrate effective heat dissipation in chip oper-ating under vigorous vibrations.We believe that our strategy could be applied to a wide range of composite gels and lead to the devel-opment of high-performance composite gels as TIMs for chip heat dissipation.