Defect engineering is the core strategy for improving thermoelectric properties. Herein, cation doping along with modulation of cation vacancy has been developed in GeTe-based materials as an effective method to induc...
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Defect engineering is the core strategy for improving thermoelectric properties. Herein, cation doping along with modulation of cation vacancy has been developed in GeTe-based materials as an effective method to induce vacancy-based defects to boost their thermoelectric performance. A series of ternary compounds of Ge9Sb2Te12-x (x = 0, 0.03, 0.06, 0.09, 0.12, 0.15) was prepared by vacuum-melting and annealing combined with the spark plasma sintering (SPS) process. The role of Sb doping and cation vacancy on thermoelectric properties was systematically investigated. It is found that alloying Sb2Te3 into GeTe increases the concentration of cation vacancies, which is corroborated by both positron annihilation measurements and theoretical calculations. The vacancies, stacking faults, and planar defect interactions determine the thermoelectric transport properties. Adjusting the deficiency of Te effectively tunes the concentration of cation vacancies and dopant defects in the structure. In turn, this tunes the carrier concentration close to its optimum. A high power factor of 32.6 mu W cm(-1) K-2 is realized for Ge9Sb2Te11.91 at 725 K. Moreover, large strains induced by the defect structures, including Sb dopant, vacancy, staking faults, as well as planar defects intensify phonon scattering, leading to a significant decrease in the thermal conductivity from 7.6 W m(-1) K-1 for pristine GeTe to Ge9Sb2Te11.85 at room temperature. All of the above contribute to a high ZT value of 2.1 achieved for the Ge9Sb2Te11.91 sample at 775 K.
The construction of donor-acceptor(D-A)molecular structure is an attractive strategy to enhance the photocatalytic performance of polymeric ***,dibenzothiophene(DBT)-4-carbaldehyde as the precursor is introduced into ...
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The construction of donor-acceptor(D-A)molecular structure is an attractive strategy to enhance the photocatalytic performance of polymeric ***,dibenzothiophene(DBT)-4-carbaldehyde as the precursor is introduced into g-C_(3)N_(4)(TCN)prepared by two-step thermal polymerization to construct an intramolecular D-A type copolymer(TCN-DBT_(x)).DFT calculation and experimental results reveal that DBT plays the role of electron donor unit to modify g-C_(3)N_(4).The incorporation of DBT not only adjusts the band gap to improve reduction ability,but also induces an internal electric field with extendingπ-conjugated system for effective charge *** a result,TCN-DBT_(x)exhibits much better photocatalytic performance with an optimal hydrogen production rate of 3334μmol h^(-1)g^(-1),which is 2.5 times that of *** work provides a protocol for preparing high-performance g-C_(3)N_(4)-based photocatalysts toward various applications.
The optimized growth conditions for high density germanium(Ge) nanowires and P-doped Ge nanowires on Si(111) substrate were investigated,the phosphorus(P)-doping in Ge nanowires was also *** liquid solid-low pre...
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The optimized growth conditions for high density germanium(Ge) nanowires and P-doped Ge nanowires on Si(111) substrate were investigated,the phosphorus(P)-doping in Ge nanowires was also *** liquid solid-low pressure chemical vapor deposition(VLS-LPCVD) of Ge nanowires was conducted with different thicknesses of Au film as catalyst,different flow rates of GeH4 as precursor and PH3/Ar as *** morphologies of the Ge nanowires were characterized by scanning electron microscopy(SEM),the P-doping was verified by micro Raman spectroscopy via measuring the P local vibrational peak(342-345 cm^(-1)) and asymmetric broadening of Ge-Ge vibrational peak(about 300 cm^(-1),*** characterization results show that 1 run thickness of Au catalyst is the most suitable condition among thicknesses of 0.1,1,5,and 10 nm for the growth of high density Ge nanowires at 300 and 350℃,and 0.5 sccm is the best flow rate of PH3/Ar to grow high density and large scale P-doped Ge nanowires among flow rates of 0.5,1 and *** P impurity can be doped into Ge nanowires effectively during LPCVD process at 350 ℃.
Hollow nitrogen-doped porous carbon materials covered with different thicknesses of carbon layers were synthesized to assist evaluation of the influence of nitrogen atom on the surrounding carbon *** designed carbon-b...
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Hollow nitrogen-doped porous carbon materials covered with different thicknesses of carbon layers were synthesized to assist evaluation of the influence of nitrogen atom on the surrounding carbon *** designed carbon-based materials were synthesized through pyrolysis of surface-attached block copolymer layers on silica nanoparticles with different thicknesses of the second block of grafted polymer chains,followed by removal of silica *** experimental results reveal that coverage a carbon layer with proper thickness can improve the oxygen reaction reduction activity of nitrogen-doped carbon materials as evidenced by the positive shift of half-wave potential in linear scanning voltammetry response *** conclusions may provide a reference work on understanding the active sites and designing materials with superior electrochemical performance.
Ti2AlC bulk material was synthesized by hot pressing of mixture powders of TiC, Ti, Al and active carbon. The phase compositions of resultant product at different temperature were detected by X-ray diffractometer. The...
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Ti2AlC bulk material was synthesized by hot pressing of mixture powders of TiC, Ti, Al and active carbon. The phase compositions of resultant product at different temperature were detected by X-ray diffractometer. The microstructures of the samples were observed by SEM. Finally, the mechanical properties and thermal properties of the sample at 1400 ℃ were measured. The results show that high purity Ti2AlC material with little Ti3AlC2 can be synthesized by hot pressing 0.5TiC/1.5Ti/1.0Al/0.5C at 1 400 ℃. Ti2AlC exhibits high mechanical properties and metallic electrical properties. Its fracture toughness is 7.0 MPa·m1/2, its flexural strength is 384 MPa at room temperature, and its electrical conductivity is 2.56×106 Ω1·m-1 at room temperature.
The(TiNbTaZrHf)C high entropy carbide(HEC)was successfully synthesized by complete commercial transition metal powders,obtained fine sintered bulks without additives by in-situ reaction element synthesis method.(TiNbT...
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The(TiNbTaZrHf)C high entropy carbide(HEC)was successfully synthesized by complete commercial transition metal powders,obtained fine sintered bulks without additives by in-situ reaction element synthesis method.(TiNbTaZrHf)C bulk shows a face centered cubic rock salt structure with homogeneous single-phase FCC structure in composition and *** optimum sintering temperature is about 1900℃at which the best mechanical properties are *** mechanical properties of(TiNbTaZrHf)C ceramic block are better than those of binary transition metal carbides,and it has obvious high entropy *** a small amount of Al as sintering additive,the mechanical properties of(TiNbTaZrHf)C ceramics continue to improve,the bending strength of the samples at each temperature is increased by at least 38%,and the highest is 486 *** elastic modulus and hardness of the sample at 1900℃are also slightly increased by 4%and 14%,*** above conclusions illustrate that the properties of high entropy ceramics are greatly improved by in-situ reaction sintering.
BiVO4 photocatalysts were synthesized by a surfactant free hydrothermal method without any further treatments,and characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron mic...
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BiVO4 photocatalysts were synthesized by a surfactant free hydrothermal method without any further treatments,and characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),ultraviolet-visible diffuse reflectance spectroscopy(UV-vis DRS),Raman spectroscopy,and Brunauer-Emmett-Teller(BET) surface area *** photocatalytic activity was evaluated for the degradation of the methylene blue(MB) under visible light *** from the structural and morphological characterization,it is stated that the obtained samples present monoclinic phase,and the pH value has significant influence on the *** enhanced photocatalytic performance was associated with its crystallinity,unique morphology,band gap energy,BET specific surface area,surface charge and adsorption *** recycle experiments results show that the BiVO4 photocatalysts have excellent photo-stability,and we deduced a possible mechanism by examining the effects of the active species involved in the photocatalytic process for MB photocatalytic degradation.
We reported the synthesis of nitrogen-doped carbon using surface-attached polyelectrolyte layers as precursors. The synthesized material has a large surface area of 800 m^2·g^-1 with uniformed pore distribution. ...
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We reported the synthesis of nitrogen-doped carbon using surface-attached polyelectrolyte layers as precursors. The synthesized material has a large surface area of 800 m^2·g^-1 with uniformed pore distribution. Benefitfed from the high pyridinic nitrogen content, the synthesized nitrogen-doped porous carbon material exhibits promising electrocatalytic activity toward oxygen reduction reactions in acidic medium and very high stability against continuous cyclic voltammetry scans. The experimental results demonstrate that surface-attached polyelectrolyte layers are promising carbon and nitrogen sources for the formation of heteroatom-doped porous carbon materials.
Porous carbon spheres represent an ideal family of electrode materials forsupercapacitors because of the high surface area,ideal conductivity,negligible aggregation,and ability to achieve space efficient ***,the devel...
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Porous carbon spheres represent an ideal family of electrode materials forsupercapacitors because of the high surface area,ideal conductivity,negligible aggregation,and ability to achieve space efficient ***,the development of new synthetic methods towards porous carbon spheres still remains a great ***,N-doped hollow carbon spheres with an ultrahigh surface area of2044 m^(2)/g have been designed based on the phenylenediamine-formaldehyde *** applied in symmetric supercapacitors with ionic electrolyte(EMIBF_4),the obtained N-doped hollow carbon spheres demonstrate a high capacitance of 234 F/g,affording an ultrahigh energy density of 114.8 Wh/*** cycling stability has also been *** impressive capacitive performances make the phenylenediamine-formaldehyde resin derived N-doped carbon a promising candidate electrode material for supercapacitors.
A recombinant protein ChiSifiCa,which was originally designed for regulation of calcium carbonate,was utilized to direct the mineralization of PbI_(2).By the regulation of ChiSifiCa protein,PbI_(2)nanoparticles compos...
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A recombinant protein ChiSifiCa,which was originally designed for regulation of calcium carbonate,was utilized to direct the mineralization of PbI_(2).By the regulation of ChiSifiCa protein,PbI_(2)nanoparticles composed of crystalline nanoflakes and amorphous nanorods were fabricated under environmental benign *** PbI_(2)was successfully applied for preparation of perovskite precursors to fabricate solar *** regulation of ChiSifiCa on PbI_(2)improves the power conversion efficiency of corresponding perovskite solar cells to 16%.The present study may open a new avenue in the design and synthesis of materials with novel structures and functions.
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