复合阻燃剂对聚双环戊二烯复合材料聚合动力学和性能的影响

将固/液复合阻燃剂硼酸锌-磷酸三(2-氯乙基)酯-氢氧化镁-氢氧化铝(ZB-TCEP-MH-ATH)引入双环戊二烯(DCPD)溶液中制备了DCPD稳定分散液,并通过前端开环易位聚合(FROMP)制备了阻燃聚双环戊二烯(PDCPD)复合材料。研究了复合阻燃剂的组分及含量对DCPD的聚合动力学、复合材料的热稳定性、力学性能和阻燃性能的影响。结果表明,复合阻燃剂会影响DCPD的反应活性,降低材料的聚合焓和固化度。随着阻燃剂含量的增加,聚合焓降低程度增大,但在相同阻燃体系中,材料的固化度仅受阻燃剂种类的影响,且材料的储能模量和玻璃化转变温度与材料的固化度线性相关。复合阻燃剂的引入会降低PDCPD复合材料的拉伸强度,但明显提高了材料的热稳定性、断裂伸长率、冲击强度和阻燃性,当ZB-TCEP-MH-ATH的含量为55%时,材料的极限氧指数(LOI)达41%,并通过UL-94 V-0级,材料的热释放速率峰值(pHRR)和燃烧增长速率(FIGRA)值分别仅为PDCPD的8.51%和3%,烟生成速率峰值(pSPR)降幅达80.36%,火灾性能指数(FPI)提高了8倍,具有较好的综合性能。

Introducing oxygen vacancies in TiO_(2) lattice through trivalent iron to enhance the photocatalytic removal of indoor NO

The synthesis of oxygen vacancies(OVs)-modified TiO_(2)under mild conditions is attractive.In this work,OVs were easily introduced in TiO_(2)lattice during the hydrothermal doping process of trivalent iron ions.Theoretical calculations based on a novel charge-compensation structure model were employed with experimental methods to reveal the intrinsic photocatalytic mechanism of Fe-doped TiO_(2)(Fe-TiO_(2)).The OVs formation energy in Fe-TiO_(2)(1.12 eV)was only 23.6%of that in TiO_(2)(4.74 eV),explaining why Fe^(3+)doping could introduce OVs in the TiO_(2)lattice.The calculation results also indicated that impurity states introduced by Fe^(3+)and OVs enhanced the light absorption activity of TiO_(2).Additionally,charge carrier transport was investigated through the carrier lifetime and relative mass.The carrier lifetime of Fe-TiO_(2)(4.00,4.10,and 3.34 ns for 1at%,2at%,and 3at%doping contents,respectively)was longer than that of undoped TiO_(2)(3.22 ns),indicating that Fe^(3+) and OVs could promote charge carrier separation,which can be attributed to the larger relative effective mass of electrons and holes.Herein,Fe-TiO_(2)has higher photocatalytic indoor NO removal activity compared with other photocatalysts because it has strong light absorption activity and high carrier separation efficiency.

Electromagnetic wave absorption and mechanical properties of SiC nanowire/low-melting-point glass composites sintered at 580°C in air

Si C nanowires are excellent high-temperature electromagnetic wave (EMW) absorbing materials. However, their polymer matrix composites are difficult to work at temperatures above 300℃, while their ceramic matrix composites must be prepared above 1000℃ in an inert atmosphere. Thus, for addressing the abovementioned problems, SiC/low-melting-point glass composites were well designed and prepared at 580℃ in an air atmosphere. Based on the X-ray diffraction results, SiC nanowires were not oxidized during air atmosphere sintering because of the low sintering temperature. Additionally, SiC nanowires were uniformly distributed in the glass matrix material. The composites exhibited good mechanical and EMW absorption properties. As the filling ratio of SiC nanowires increased from 5wt%to 20wt%, the Vickers hardness and flexural strength of the composite reached HV 564 and 213 MPa, which were improved by 27.7%and 72.8%, respectively, compared with the low-melting-point glass. Meanwhile, the dielectric loss and EMW absorption ability of SiC nanowires at 8.2–12.4 GHz were also gradually improved. The dielectric loss ability of low-melting-point glass was close to 0. However, when the filling ratio of SiC nanowires was 20wt%, the composite showed a minimum reflection loss (RL) of-20.2 dB and an effective absorption (RL≤-10 dB) bandwidth of2.3 GHz at an absorber layer thickness of 2.3 mm. The synergistic effect of polarization loss and conductivity loss in SiC nanowires was responsible for this improvement.

Calcium-Sensing Receptor of Immune Cells and Diseases

Calcium-sensing receptor(CaSR),which was initially found in the parathyroid gland,is ubiquitously expressed and exerts specifi c functions in multiple cells,including immune cells.CaSR is functionally expressed on neutrophils,monocytes/macrophages,and T lymphocytes,but not B lymphocytes,and regulates cell functions,such as cytokine secretion,chemotaxis,phenotype switching,and ligand delivery.In these immune cells,CaSR is involved in the development of many diseases,such as sepsis,cryopyrin-associated periodic syndromes,rheumatism,myocardial infarction,diabetes,and peripheral artery disease.Since its discovery,it has been controversial whether CaSR is expressed and plays a role in immune cells.This article reviews current knowledge of the role of CaSR in immune cells.

A review on perfluoroalkyl acids studies:Environmental behaviors,toxic effects,and ecological and health risks

Perfluoroalkyl acids(PFAAs)are emerging persistent organic pollutants that are globally distributed in the environment.In the present review,the occurrence of PFAAs and their behavior in aquatic ecosystem were summarized,and the health and ecological risk assessment and the multimedia fate simulation were investigated.PFAAs are most likely to exist in the aqueous phase,and PFAAs in atmosphere are also able to enter water bodies through diffusion and wet and dry deposition and eventually become widely distributed in various environmental media.The air-solid partition is considered to be one of the major factors in the long-distance transportation of the pollutants.The pKa values and organic carbon fraction of the sediment could influence the partition of PFAAs between water and sediment.Otherwise,PFAAs have teratogenic,mutagenic and other toxic effects and they could be accumulated by biota,and magnified through trophic level.The ecological and health risks of PFOA and PFOS were assessment.In order to explore the partition mechanism and reduce the uncertainty of the simulation of the transport,transformation and fate,the experimental methods on physicochemical properties of PFAAs should be developed.Moreover,further studies on toxicities of PFAAs are necessary for health and ecological risk assessment.

Vacancy-engineering-mediated activation of excitonic transition for boosting visible-light-driven photocatalytic oxidative coupling of amines

The light absorption properties of semiconductor-based photocatalysts to a large extent determine the relevant catalytic performance.Traditional strategies in broadening the light absorption range are usually accompanied with unfavorable changes in redox ability and dynamics of photoinduced species that would confuse the comprehensive optimization.In this work,we propose a nontrivial excitonic transition regulation strategy for gaining sub-bandgap light absorption in low-dimensional semiconductor-based photocatalysts.Using bismuth oxybromide(BiOBr)as a model system,we highlight that the light absorption cut-off edge could be effectively extended up to 500 nm by introducing Bi vacancies.On the basis of theoretical simulations and spectroscopic analyses,we attributed the broadening of light absorption to the promotion of excitonic transition that is generally forbidden in pristine BiOBr system,associated with Bi-vacancy-induced excited-state symmetry breaking.In addition,Bi vacancy was demonstrated to implement negligible effects on other photoexcitation properties like excited-state energy-level profiles and kinetics.Benefiting from these features,the defective sample exhibits a notable advantage in gaining visible-light-driven photocatalytic reactions.

Engineering Exciton-Phonon Interactions for Suppressing Nonradiative Energy Loss in Energy-Transfer-Initiated Photocatalysis

The prevalent excitonic effects in low-dimensional semiconductors enable energy-transfer-initiated photocatalytic solar-to-chemical energy conversion.However,the generally strong interactions between excitons and lattice vibrations in these low-dimensional systems lead to robust nonradiative energy loss,which inevitably impedes photocatalytic performance of energy-transfer-initiated reactions.Herein,we highlight the crucial role of engineering exciton-phonon interactions in suppressing nonradiative energy losses in low-dimensional semiconductor-based photocatalysts.By taking bismuth oxybromide(BiOBr)as an example,we demonstrate that phonon engineering could be effectively implemented by introducing Bi-Br vacancy clusters.Based on nonadiabatic molecular dynamics simulations and spectroscopic investigations,we demonstrate that the defective structure can promote exciton-low-frequency phonon coupling and reduce exciton-high-frequency optical phonon coupling.Benefiting from the tailored couplings,nonradiative decay of excitons in defective BiOBr is significantly suppressed,thereby facilitating exciton accumulation and hence energy-transfer-initiated photocatalysis.

Atomically Precise Pd Species Accelerating CO_(2) Hydrodeoxygenation into CH_(4) with 100%Selectivity

High-rate CO_(2)-to-CH_(4)photoreduction with high selectivity is highly attractive,which is a win-win strategy for mitigating the greenhouse effect and the energy crisis.However,the poor photocatalytic activity and low product selectivity hinder the practical application.To precisely tailor the product selectivity and realize high-rate CO_(2)photoreduction,we design atomically precise Pd species supported on In_(2)O_(3)nanosheets.Taking the synthetic 1.30Pd/In_(2)O_(3)nanosheets as an example,the aberration-correction high-angle annular dark-field scanning transmission electron microscopy image displayed the Pd species atomically dispersed on the In_(2)O_(3)nanosheets.Raman spectra and X-ray photoelectron spectra established that the strong interaction between the Pd species and the In_(2)O_(3)substrate drove electron transfer from In to Pd species,resulting in electron-enriched Pd sites for CO_(2)activation.Synchrotronradiation photoemission spectroscopy demonstrated that the Pd species can tailor the conduction band edge of In_(2)O_(3)nanosheets to match the CO_(2)-to-CH_(4)pathway,instead of the CO_(2)-to-CO pathway,which theoretically accounts for the high CH_(4)selectivity.Moreover,in situ X-ray photoelectron spectroscopy unveiled that the catalytically active sites had a change from In species to Pd species over the 1.30Pd/In_(2)O_(3)nanosheets.In situ FTIR and EPR spectra reveal the atomically precise Pd species with rich electrons prefer to adsorb the electrophilic protons for accelerating the*COOH intermediates hydrogenation into CH_(4).Consequently,the 1.30Pd/In_(2)O_(3)nanosheets reached CO_(2)-to-CH_(4)photoconversion with 100%selectivity and 81.2μmol g^(−1)h^(−1)productivity.