Preparation of ZnO nanomaterials and their photocatalytic degradation of organic pollutants

Nano zinc oxide(ZnO)has excellent performance and low cost,but ZnO has a wide band gap and its electron-hole is difficult to achieve effective separation,which greatly limits its photocatalytic activity.This paper introduces the structural properties of ZnO and the mechanism of photocatalytic degradation of organic pollutants,and summarizes the preparation of ZnO nanomaterials and the application studies in improving its photocatalytic properties,in order to promote the research and development of ZnO nanomaterials.

CONSTITUTIVE RELATION AND STIFFNESS DEGRADATION OF CRACKED ANISOTROPIC COMPOSITE LAMINATES(II)─DETERMINATION OF RESOLVED STIFFNESS AND INVESTIGATION OF STIFFNESS DEGRADATION FOR CRACKED LAMINATES

The study on properly degradation of damaged,.onlj,osile laminates is extendedto anisotropic laminates with matrix cracking. In (II) of the paper, a solution forpartitioned stiffness is given to complete the constitutive relations developed in (I) Thestiffness degradation in cracked laminates is calculated and the results arediscussed.

Degradability of biodegradable plastic films and its mulching effects on soil temperature and maize yield in northeastern China

Plastic film is an important resource in agricultural production,but it takes hundreds of years to degrade completely in natural environment.The large-scale use of plastic film will inevitably lead to serious environmental pollution.One way to solve the problem is to develop a substitutable mulching film,such as a biodegradable film that can ultimately be decomposed to water,carbon dioxide,and soil organic matter by micro-organisms.In this study,a 2-year experiment was conducted to determine the degradation properties of a biodegradable plastic film,including degradation rate,surface microstructure,tensile strength and elongation at break,and the effects of different mulching treatments on soil temperature and maize yield.The mulching experiment was conducted with three different biodegradable plastic films with different degradation rates,using a common plastic film and a non-mulched treatment as control.With the addition of the additives for degradation in the biodegradable plastic films,the degradation rates increased significantly,which were 7.2%-17.8%in 2017 and 18.1%-35.2%in 2018 after maize harvesting.However,the degradation occurred mainly on the ridge side.The decrease in tensile strength and elongation was proportional to the degradation rate of the degradable film.The SEM results indicated that the surface microstructures of the biodegradable films were loose and heterogeneous after maize harvesting.Biodegradable plastic film mulching increased the soil temperature at soil depths of 5 cm,15 cm,and 25 cm,over the maize’s entire growth period,by 3.1℃-3.2℃ in 2017 and 1.2℃-2.1℃ in 2018 compared with the non-mulched treatment.The biodegradable plastic film increased the maize yield by 10.4%-14.3%in 2017 and 11.6%-24.7%in 2018.The soil temperature and maize yield increases were statistically significant;however,with respect to maize qualities,there were no statistically significant increases among the five treatments.This study shows that biodegradable plastic film can be used as a substitute for common plastic film.However,the ingredients in biodegradable plastic films should be improved further to ensure that they can be degraded completely after crop harvest.

A comprehensive review on metallic biomaterials for airway stenosis repair

In recent years,the incidence of airway stenosis in respiratory diseases increases year by year.Among many treatment methods,tracheal stent implantation is a very effective way.Metallic stents have been the first choice for tracheal stent implantation due to their excellent mechanical properties,low rate of migration,and minimal effect on the ciliary movement of the trachea.In this paper,the research progress of metal tracheal stents is introduced in detail from three aspects of mechanical properties,degradation properties,and biocompatibility,including traditional inert metallic tracheal stents and new degradable metallic tracheal stents,and its future research and development are prospected:although the current research on biodegradable metal tracheal stents is still in its infancy,with only some studies of magnesium-based,iron-based,and zinc-based tracheal stents,they are considered as the best material for preparing future metal tracheal scaffolds considering their biodegradability and biocompatibility.

Packaging and degradability properties of polyvinyl alcohol/gelatin nanocomposite films filled water hyacinth cellulose nanocrystals

Cellulose nanocrystals isolated from water hyacinth fiber(WHF)have been studied as a reinforcement for polyvinyl alcohol(PVA)-gelatin nanocomposite.Central composite design was used to study and optimize effects of the PVA,gelatin and cellulose nanocrystal(CNC)concentration on tensile strength and elongation of formed films.The results of this study showed that WHF CNC had a diameter range of 20-50 nm produced films reaching 13.8 MPa tensile strength.Thermal stability of the films was improved from 380℃ to 385℃ in addition of CNCs and maximum storage modulus of 3 GPa were observed when 5 wt%CNC was incorporated.However,water absorption,water vapour permeability(WVP)and moisture uptake of the films decreased in addition of CNC to the PVA-gelatin blends.Moisture uptake decreased from 22.50%to 19.05%while the least WVP when 10 wt%CNC added was 1.64×10^(-6)g/(m·h·Pa).These results show possibility for industrial application of WHF CNC and PVA-gelatin blends in biodegradable films for on-the-go food wrappers.

In vivo biocompatibility and degradability of a Zn-Mg-Fe alloy osteosynthesis system

Zinc is generally considered to be one of the most promising materials to be used in biodegradable implants,and many zinc alloys have been optimized to improve implant biocompatibility,degradation,and mechanical properties.However,long-term degradation leads to the prolonged presence of degradation products,which risks foreign body reactions.Herein,we investigated the in vivo biocompatibility and degradation of a biodegradable Zn-Mg-Fe alloy osteosynthesis system in the frontal bone,mandible,and femur in beagles for 1 year.Results of the routine blood,biochemical,trace element,and histological analyses of multiple organs,peripheral blood CD4/CD8a levels,and serum interleukin 2 and 4 levels showed good biocompatibility of the Zn-Mg-Fe alloy.Zinc content analysis revealed zinc accumulation in adjacent bone tissue,but not in the liver,kidney,and spleen,which was related to the degradation of the Zn-Mg-Fe alloy.The alloy demonstrated a uniform slowing degradation rate in vivo.No degradation differences in the frontal bone,mandible,and femur were observed.The degradation products included zinc oxide[ZnO],zinc hydroxide[Zn(OH)_(2)],hydrozincite[Zn_(5)(OH)_(6)(CO_(3))_(2)],and hopeite[Zn_(3)(PO_(4))_(2)⋅4H_(2)O].The good biocompatibility and degradation properties of the Zn-Mg-Fe alloy render it a very attractive osteosynthesis system for clinical applications.

Chlorination pattern effect on thermodynamic parameters and environmental degradability for C_(10)-SCCPs: Quantum chemical calculation based on virtual combinational library

Short-chain chlorinated paraffins（SCCPs） are still controversial candidates for inclusion in the Stockholm Convention.The inherent mixture nature of SCCPs makes it rather difficult to explore their environmental behaviors.A virtual molecule library of 42,720 C10-SCCP congeners covering the full structure spectrum was constructed.We explored the structural effects on the thermodynamic parameters and environmental degradability of C10-SCCPs through semi-empirical quantum chemical calculations.The thermodynamic properties were acquired using the AM1 method,and frontier molecular orbital analysis was carried out to obtain the EHOMO,ELUMO and ELUMO-EHOMO for degradability exploration at the same level.The influence of the chlorination degree（NCl on the relative stability and environmental degradation was elucidated.A novel structural descriptor,μ,was proposed to measure the dispersion of the chlorine atoms within a molecule.There were significant correlations between thermodynamic values and NCl,while the reported NCl-dependent pollution profile of C10-SCCPs in environmental samples was basically consistent with the predicted order of formation stability of C10-SCCP congeners.In addition,isomers with largeμ showed higher relative stability than those with small μ.This could be further verified by the relationship between μ and the reactivity of nucleophilic substitution and · OH attack respectively.The C10-SCCP congeners with less Cl substitution and lower dispersion degree are susceptible to environmental degradation via nucleophilic substitution and hydroxyl radical attack,while direct photolysis of C10-SCCP congeners cannot readily occur due to the large ELUMO-EHOMO values.The chlorination effect and the conclusions were further checked with appropriate density functional theory（DFT） calculations.