Porous carbon nanotubes/cobalt nanoparticles (CNTs/Co) composite with dodecahedron morphology was synthesized by in situ pyrolysis of the Co-based zeolitic imidazolate framework in a reducing ...atmosphere. The morphology and microstructure of the composite can be well tuned by controlling the pyrolysis conditions. At lower pyrolysis temperature, the CNTs/Co composite is composed of well-dispersed Co nanoparticles and short CNT clusters with low graphitic degree. The increase of pyrolysis temperature/time promotes the growth and graphitization of CNTs and leads to the aggregation of Co nanoparticles. The optimized CNTs/Co composite exhibits strong dielectric and magnetic losses as well as a good impedance matching property. Interestingly, the CNTs/Co composite displays extremely strong electromagnetic wave absorption with a maximum reflection loss of −60.4 dB. More importantly, the matching thickness of the absorber is as thin as 1.81 mm, and the filler loading of composite in the matrix is only 20 wt %. The highly efficient absorption is closely related to the well-designed structure and the synergistic effect between CNTs and Co nanoparticles. The excellent absorbing performance together with lightweight and ultrathin thickness endows the CNTs/Co composite with the potential for application in the electromagnetic wave absorbing field.
The monodispersed ultrasmall Fe
3
O
4
nanoparticles (NPs) have been anchored on reduced graphene oxide (rGO) nanosheets through a one-step method. Hybriding Fe
3
O
4
particles with rGO sheets ...benefits adjusting the permittivity and permeability of the composite, balancing the dielectric loss and magnetic loss. The Fe
3
O
4
/rGO composite with a thickness of 3.0 mm exhibits an optimum absorption of − 71.86 dB at a low filler loading of 20 wt%, superior to most Fe
3
O
4
/graphene composites. The effective absorbing bandwidth covers 4.1 GHz. These results indicate that the Fe
3
O
4
/rGO composites prepared by facile synthesis can be ideal candidates as microwave absorbers with lightweight and excellent microwave absorption properties.
Monodispersed titanium oxide nanospheres were synthesized via the controlled hydrolysis method in this study firstly. Then the rapid mixing method was used to in situ oxidation polymerize aniline, ...which can modify the surface of titanium oxide nanospheres to form a core/shell nanostructure. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and rotational viscometer were used to investigate its structure, morphology and properties. The different type and dosage of surfactants, different acids, crystal forms of titanium oxide and different dosages of aniline were studied to analysis the impact on the TiO2/PANI nanocomposites. The suitable type and dosage of surfactants, the ratio of aniline to titania were the key to synthesize the nanocomposite, which can include nanoring, nanofiber or nanoparticles core/shell composite depending the synthesis condition. The titania/polyaniline composite showed typical electrorheological (ER) behavior, which demonstrated its potential applications as an ER smart material.
While a large number of well-known knowledge bases (KBs) in life science have been published as Linked Open Data, there are few KBs in Chinese. However, KBs in Chinese are necessary when we want to ...automatically process and analyze electronic medical records (EMRs) in Chinese. Of all, the symptom KB in Chinese is the most seriously in need, since symptoms are the starting point of clinical diagnosis.
We publish a public KB of symptoms in Chinese, including symptoms, departments, diseases, medicines, and examinations as well as relations between symptoms and the above related entities. To the best of our knowledge, there is no such KB focusing on symptoms in Chinese, and the KB is an important supplement to existing medical resources. Our KB is constructed by fusing data automatically extracted from eight mainstream healthcare websites, three Chinese encyclopedia sites, and symptoms extracted from a larger number of EMRs as supplements.
Firstly, we design data schema manually by reference to the Unified Medical Language System (UMLS). Secondly, we extract entities from eight mainstream healthcare websites, which are fed as seeds to train a multi-class classifier and classify entities from encyclopedia sites and train a Conditional Random Field (CRF) model to extract symptoms from EMRs. Thirdly, we fuse data to solve the large-scale duplication between different data sources according to entity type alignment, entity mapping, and attribute mapping. Finally, we link our KB to UMLS to investigate similarities and differences between symptoms in Chinese and English.
As a result, the KB has more than 26,000 distinct symptoms in Chinese including 3968 symptoms in traditional Chinese medicine and 1029 synonym pairs for symptoms. The KB also includes concepts such as diseases and medicines as well as relations between symptoms and the above related entities. We also link our KB to the Unified Medical Language System and analyze the differences between symptoms in the two KBs. We released the KB as Linked Open Data and a demo at https://datahub.io/dataset/symptoms-in-chinese .
This study investigates changes in the concentration and types of free radicals in the process of coal heating, first rising and then falling. Hailar lignite, Panjiang bituminous coal, and Yangquan ...anthracite were selected as coal test samples. The results show that the lignite’s concentration of free radical changes during heating is greater than that of bituminous coal or anthracite. It clearly shows that lignite is more prone to spontaneous combustion. In the heating and cooling portion of the experiment, the concentration of free radicals during the cooling process was much more than that of free radicals at the same temperature during the heating process. These results obtained from this research study can provide a reference for the prevention and control of the spontaneous combustion of coal with changes in temperature. This study provides a theoretical basis for the prevention and control of spontaneous combustion of coal and the selection of retarding agents and methods in the process of flame retarding by testing the free radical changes of coal at different temperatures. Also, it provides a reference for preventing and controlling coal oxidation with the change in temperature, first rising and then falling.
Developing lightweight and highly efficient electromagnetic wave (EMW) absorbing materials is crucial but challenging for anti-electromagnetic irradiation and interference. Herein, we used ...multiwalled carbon nanotubes (MWCNTs) as templates for growth of Co-based zeolitic imidazolate frameworks (ZIFs) and obtained a Co–C/MWCNTs composite by postpyrolysis. The MWCNTs interconnected the ZIF-derived Co–C porous particles, constructing a conductive network for electron hopping and migration. Moreover, the Co–C/MWCNTs composite was aligned in paraffin matrix under an external magnetic field, which led to a stretch of the MWCNTs along the magnetic field direction. Due to the anisotropic permittivity of MWCNTs, the magnetic alignment considerably increased the dielectric loss of the Co–C/MWCNTs composite. Benefiting from the conductive network, the orientation-enhanced dielectric loss, and the synergistic effect between magnetic and dielectric components, the magnetically aligned Co–C/MWCNTs composite exhibited extremely strong EMW absorption, with a minimum reflection loss (RL) of −48.9 dB at a filler loading as low as 15 wt %. The specific RL value (RL/filler loading) of the composite was superior to that of the previous MOF-derived composite absorbers. It is expected that the proposed strategy can be extended to the fabrication of other lightweight and high-performance EMW-absorbing materials.
The development of a high-performance electromagnetic microwave (EMW) absorber is pivotal for the practical realization of EMW pollution issues. However, the design of EMW absorbers with ultra-high ...reflection loss (RL < −70 dB) at ultrathin matching thickness (<2 mm) still faces daunting challenges. Herein, a NiCo2O4 nanosheets-covered Ti3C2Tx MXene (NiCo2O4 NSs-MXene) heterostructure with multi-layered MXene and vertically grown ultrathin NiCo2O4 nanosheets prepared by detachment process, reflux reaction, and heat-treatment is introduced as a new EMW absorber; this heterostructure enables a shocking EMW absorption performance with RL value of −72.3 dB at a thickness of 1.7 mm. The effective absorption bandwidth (EAB, RL < −10 dB) can also reach a relatively impressive 3.6 GHz. Furthermore, the NiCo2O4 NSs-MXene heterostructure shows large dielectric loss derived from conductive loss, interface polarization, and dipolar polarization. The high magnetic loss in the heterostructure originates from natural resonance and eddy current loss. Hence, the synergistic effect of dielectric loss, magnetic loss, and impedance matching promote the superior EMW absorption performance of NiCo2O4 NSs-MXene heterostructure. This achievement paves the way for the exploitation of heterostructure as an ultrathin and super-strong EMW absorption performance.
Display omitted
•A unique g-C3N4/Fe3CNC/Co-NC heterostructure is prepared by simple mixing and two-step pyrolysis.•After the structural and phase reconfiguration, small Fe3C@NC and Co@NC core-shell nanoparticles are ...anchored on porous g-C3N4 bridges.•The g-C3N4/Fe3CNC/Co-NC heterostructure delivers remarkable electromagnetic wave absorption.
Developing electromagnetic wave (EMW) absorbers with low-cost, lightweight, strong absorption capacity, thin matching thickness, and wide effective absorption bandwidth (EAB) is still a significant challenge. Herein, we report a unique g-C3N4/Fe3CNC/Co-NC heterostructure by simple mixing and two-step pyrolysis of melamine, Fe3O4, and ZIF-67. After the structural and phase reconfiguration, N-doped carbon layer-coated Fe3C nanoparticles (NPs) assembled nanoshells (Fe3C@NC) and N-doped graphitic carbon-coated metallic Co NPs (Co@NC) are formed, and the core-shell NPs are interconnected by porous g-C3N4 bridges. Profiting from the successful construction of the unique g-C3N4/Fe3CNC/Co-NC heterostructure and the synergetic effect of multi-component, multiple core-shell structure, and strong interaction, the as-fabricated g-C3N4/Fe3CNC/Co-NC inherits the excellent EMW absorption performance with a RL value of -25.4 dB at a thin matching thickness of 2.6 mm. The EAB can reach up to 8.64 GHz at a thickness of 2∼5 mm. This study provides the contribution of structural and phase reorganization to the field of EMW absorption.
Display omitted
PDF
