Thermally insulating and fire-resistant carbon composite foams are prepared by consolidating natural cotton fibre dispersed in aqueous sucrose solution by filter-pressing followed by drying and carbonization.The compr...Thermally insulating and fire-resistant carbon composite foams are prepared by consolidating natural cotton fibre dispersed in aqueous sucrose solution by filter-pressing followed by drying and carbonization.The compressive strength(5 kPa to 1.4 MPa)and thermal conductivity(0.069 to 0.185 W m^(-1)K^(-1))depend on the foam density(0.06 to 0.31 g cm^(-3))which is modulated by varying the sucrose solutions concentration(100 to 700 g L^(-1)).Partially flexible to the rigid transition of the carbon composite foams occurs at sucrose concentration above 200 g L^(-1).The tubular carbon fibre formed from cotton is welded at their contact points by the amorphous carbon produced from sucrose leading to partial flexibility at low sucrose concentration and advancement of fibre-to-fibre bonding area at higher sucrose concentration results in rigid foam.The porosity in the inter-fibre space and lumen of the carbonized cotton fibre contributes to the low thermal conductivity.The carbon composite foams prepared at a sucrose solution concentration of 500 g L^(-1) and above are amenable to machining using conventional machines and tools.The rigid carbon foams show EMI shielding effectiveness and specific shielding effectiveness in the ranges of 21.5 to 38.9 d B and 108-138 dB cm^(3) g^(-1),respectively.展开更多
A quadrupole Penning trap for spectroscopy and investigations of non-neutral plasmas was designed and built. In this work we provide details of the trap design and a discussion of a simple design and procedure for con...A quadrupole Penning trap for spectroscopy and investigations of non-neutral plasmas was designed and built. In this work we provide details of the trap design and a discussion of a simple design and procedure for convenient electron loading from an aligned filament. Electrons from thermionic emission which form a low-energy diffuse beam are trapped in weak magnetic fields. They are detected through a non-destructive electronic detection scheme, the details of which are discussed. The detection signal is diminished when the electron beam energy is increased while the electron flux is kept constant. This is explained by considering the energy shift in the distribution function of electrons emitted from the filament and entering the trap. We present a calculation of the number of trapped electrons from the shape of the detection signal. This calculation, based on a model of a driven damped harmonic oscillator to describe the axial motion of the electrons, compares favourably with the numbers obtained by measurements of the space charge induced shift in the trap potential.展开更多
As the field of metal halide perovskites matures,a range of compositionally different perovskite films has found a place in efficient optoelectronic devices.These films feature variable local structural stability,carr...As the field of metal halide perovskites matures,a range of compositionally different perovskite films has found a place in efficient optoelectronic devices.These films feature variable local structural stability,carrier diffusion,and recombination,while there is still a lack of easy-to-implement generic protocols for high-throughput characterization of these variable properties.Correlation clustering imaging(CLIM)is a recently developed tool that resolves peculiarities of local photophysics by assessing the dynamics of photoluminescence detected by wide-field optical microscopy.We demonstrate the capability of CLIM as a high-throughput characterization tool of perovskite films using MAPbI3(MAPI)and triple cation mixed halide(TCMH)perovskites as examples where it resolves the interplay of carrier diffusion,recombination,and defect dynamics.We found significant differences in the appearance of metastable defect states in these two films.Despite a better surface quality and larger grain size,MAPI films showed more pronounced effects of fluctuating defect states than did TCMH films.As CLIM shows a significant difference between materials known to lead to different solar cell efficiencies,it can be considered a tool for quality control of thin films for perovskite optoelectronic devices.展开更多
文摘Thermally insulating and fire-resistant carbon composite foams are prepared by consolidating natural cotton fibre dispersed in aqueous sucrose solution by filter-pressing followed by drying and carbonization.The compressive strength(5 kPa to 1.4 MPa)and thermal conductivity(0.069 to 0.185 W m^(-1)K^(-1))depend on the foam density(0.06 to 0.31 g cm^(-3))which is modulated by varying the sucrose solutions concentration(100 to 700 g L^(-1)).Partially flexible to the rigid transition of the carbon composite foams occurs at sucrose concentration above 200 g L^(-1).The tubular carbon fibre formed from cotton is welded at their contact points by the amorphous carbon produced from sucrose leading to partial flexibility at low sucrose concentration and advancement of fibre-to-fibre bonding area at higher sucrose concentration results in rigid foam.The porosity in the inter-fibre space and lumen of the carbonized cotton fibre contributes to the low thermal conductivity.The carbon composite foams prepared at a sucrose solution concentration of 500 g L^(-1) and above are amenable to machining using conventional machines and tools.The rigid carbon foams show EMI shielding effectiveness and specific shielding effectiveness in the ranges of 21.5 to 38.9 d B and 108-138 dB cm^(3) g^(-1),respectively.
文摘A quadrupole Penning trap for spectroscopy and investigations of non-neutral plasmas was designed and built. In this work we provide details of the trap design and a discussion of a simple design and procedure for convenient electron loading from an aligned filament. Electrons from thermionic emission which form a low-energy diffuse beam are trapped in weak magnetic fields. They are detected through a non-destructive electronic detection scheme, the details of which are discussed. The detection signal is diminished when the electron beam energy is increased while the electron flux is kept constant. This is explained by considering the energy shift in the distribution function of electrons emitted from the filament and entering the trap. We present a calculation of the number of trapped electrons from the shape of the detection signal. This calculation, based on a model of a driven damped harmonic oscillator to describe the axial motion of the electrons, compares favourably with the numbers obtained by measurements of the space charge induced shift in the trap potential.
基金support of Marie Skłodowska-Curie postdoctoral fellowship(No.101151427,SPS_Nano)from the European Union’s Horizon Europe program,short stay abroad grant(K257023N)travel grant(K147824N)from Research Foundation-Flanders(FWO)。
文摘As the field of metal halide perovskites matures,a range of compositionally different perovskite films has found a place in efficient optoelectronic devices.These films feature variable local structural stability,carrier diffusion,and recombination,while there is still a lack of easy-to-implement generic protocols for high-throughput characterization of these variable properties.Correlation clustering imaging(CLIM)is a recently developed tool that resolves peculiarities of local photophysics by assessing the dynamics of photoluminescence detected by wide-field optical microscopy.We demonstrate the capability of CLIM as a high-throughput characterization tool of perovskite films using MAPbI3(MAPI)and triple cation mixed halide(TCMH)perovskites as examples where it resolves the interplay of carrier diffusion,recombination,and defect dynamics.We found significant differences in the appearance of metastable defect states in these two films.Despite a better surface quality and larger grain size,MAPI films showed more pronounced effects of fluctuating defect states than did TCMH films.As CLIM shows a significant difference between materials known to lead to different solar cell efficiencies,it can be considered a tool for quality control of thin films for perovskite optoelectronic devices.
