查看更多>>摘要：Bi_2Te_3 based thermoelectric device is the only commercialized thermoelectric module. The thermal stability of the interface between the thermoelectric materials and barrier layer or electrode plays pivotal role for the stability and reliability of micro thermoelectric devices especially for power generation. In this work, the thermal stability, bonding strength and structure evolution of the interface between Bi_2Te_3 based materials (both n type and p type materials) and Ni barrier layer were systematically investigated. The interface between Ni and Bi_2Te_3 based materials demonstrates an ohmic contact with the contact resistivity of 3.64 μΩ cm~2 and 5.31 μΩ cm~2 for p-type and n-type element respectively. The bonding strength of p-type and n-type element with electrode is 13.43 MPa and 17.62 MPa, respectively. Upon annealing at 423 K for 7 days, due to the mass diffusion between Ni and Bi_2Te_3 based materials, a thin Ni-Te layer is formed. With further extending the annealing time at 423 K to 42 days, the thickness of the diffusion layer increases to 3 μm. The growth of diffusion layer enhances the bonding strength to 19.81 MPa. However, this is accompanied with a sharp increase in the contact resistivity to 14.48 μΩ cm~2 for n-type element and to 6 μΩ cm~2 for p-type element with Ni barrier. The increase in the contact resistance deteriorates the output power of thermoelectric module especially for the micro-device from 2.60 mW to 2.48 mW under the temperature gradient of 20 K. This work points out that for the application of Bi_2Te_3 based thermoelectric device in power generation above 423 K, appropriate barrier layer is indispensable and plays significant role for the performance of the device.
查看更多>>摘要：Birefringent materials are of great important as opto-electronic functional devices in solid laser system. Investigations on the design of new birefringent materials with large birefringence is meaningful. In this study, structure-birefringence relationship between AgGaS_2 (AGS) and NaGaS_2 (NGS) was systematically investigated. In the structures, the high ionic Na~+ cations broke the three dimensional (3D) [GaS] network to 2D layers, which results in the regular packing of GaS_4 tetrahedra and further the birefringence (-0.09, nearly twice that of AGS at -1064 nm). Meanwhile, the blue-shift of the UV cutoff edge to 307 nm and a wide band gap of 3.9 eV has been observed in NGS. The property characterizations were carried out using the as-grown NGS single crystal with a size of 4 × 4 × 0.3 mm~3 by high temperature flux method. The results indicate that NGS may be a promising IR birefringent material and the cation substitiition-oriented design strategy could be used to regulate the structure and optical properties of materials.
查看更多>>摘要：Hybrid nanostructures composed of a plasmonic noble metal and a semiconductor have been studied intensively because of their unusual properties and wide range of potential applications. However, preparing these hybrid nanostructures with a precisely controlled shape, composition, heterostructure, and internal structure remains a challenge. Here, we describe a method for synthesizing new metal-semiconductor? bimetal hybrid nanostructures. Specifically, Ag-Ag_2S nanoplates were first prepared by site-controlled sulfidation, and these nanoplates were then used as seeds to synthesize Ag-Ag_2S@Ag-Au hybrid nanostructures with unique porous architectures through seed-mediated growth and a galvanic replacement reaction. The composition of the ternary alloy combined with the unique porous structure of the hybrid nanostructures resulted in excellent broadband absorption in the UV-Vis-NIR region (300-1100 nm), and hence a black color, without an additional post-treatment process. When used as photothermal conversion materials, the hybrid nanostructures showed good photothermal conversion activity, with a maximum efficiency of 76.1% under irradiation with an 808 nm near-infrared laser. A mechanism for the high photothermal conversion activity is proposed on the basis of experimental and simulation results.
查看更多>>摘要：The chemistry of metal borohydrides and their derivatives has expanded signficantly during the past decade involving new compositions, structures, and the diversity of associated properties. Here we provide an overview of interesting results mainly from the past few years, discussed relative to previously published results. A range of new synthesis strategies has been developed to obtain pure samples, which has allowed very detailed structural, physical, and chemical investigations. A short overview of mono- and dimetallic borohydrides is provided, including a description of the complete series of rare-earth metal borohydrides and the recently discovered ammonium metal borohydrides, where the latter has attracted interest due to an extreme hydrogen content. Metal borohydrides appear to be the most promising class of materials to achieve high cationic conductivity of divalent metals, and particularly derivatives of metal borohydrides with neutral molecules show promise as future electrolytes for new types of solid-state batteries. Furthermore, metal borohydrides display a wide range of other properties, including optical, magnetic, semi conduction and possibly superconducting properties, and are also used as a new approach for carbon capture and conversion. The aim of the present review is to highlight new trends in properties and provide an outlook with possible future applications. Here, we focus on the more recently discovered materials.
查看更多>>摘要：Recently, additive manufacturing (AM), being part of IR4.0, received great attention for the fabrication of customized implants with outstanding quality, which are used in hard tissue replacement. For an orthopedic application, the titanium alloy implants, especially those that use Ti-6Al-4V manufactured by selective laser melting (SLM), should facilitate maximum osteointegration between the implant and corresponding bone. However, the superior mechanical characteristics, poor surface integration, antibacterial performance, and readiness of SLM Ti-6Al-4V for use in advanced implants are still not comparable to those of anatomical bone. This review focused on the current issue of stress-shielding limitations in SLM Ti-6Al-4V owing to failures in load-bearing applications. The surface treatment and modification strategy that might improve the osseointegration of the implant were discussed. The corrosion resistance of SLM Ti-6Al-4V which could significantly affect antibacterial capability, improve cell adherence and apatite formation on the bone remodeling surface was also addressed. Finally, the current challenges, prospects and applications for SLM Ti-6Al-4V development were presented.
查看更多>>摘要：In the present study, the amorphous Ti-Ni-Zr-Cu thin ribbons were successfully prepared through rapid spinning technology. The crystallization temperature of Ti-Ni-Zr-Cu thin ribbon increased with the increasing of heating rate. The activation energy of crystallization for Ti-Ni-Zr-Cu thin ribbon is calculated to be 156 kj/mol, which is remarkably lower than that of the reported Zr-Cu based metal glass due to the smaller negative enthalpy of mixing atomic pairs. The phase constituents of annealed Ti-Ni-Zr-Cu thin ribbons were largely related to the annealing temperatures. The phase constitutes of Ti-Ni-Zr-Cu thin films annealed at the temperatures lower than 850 °C is almost equal, but the lattice constant of various phases is gradually reduced with the increasing of annealing temperatures. In proportion, Ti-Ni-Zr-Cu thin ribbons annealed at the temperatures lower than 750 °C show the higher Vickers hardness, while a noteworthy reduction of Vickers hardness is observed in Ti-Ni-Zr-Cu thin ribbon annealed at 850 °C. Besides, the annealing temperature has a significant effect on the specific heat and corrosion properties, which can be attributed to the distinction of phase constituents.
Evgeny V. ZharikovValentina B. DudnikovaNina G. Zinovieva
8页
查看更多>>摘要：The content of all matrix elements, including oxygen, was determined by X-ray spectral microanalysis in series of single crystals of sodium-gadolinium molybdates (NGM) grown from melt by Czochralski technique. All grown NGM crystals, including those grown from stoichiometric charge, are non-stoichiometric and contain a molybdenum deficiency of about 3% in average. The NGM congruently melting composition has been determined. For crystals grown from melt of equimolar (stoichiometric) composition, the content of cationic vacancies in the (Gd + Na) sublattice is close to zero, while the composition of crystal differs from the initial melt. As the Gd excess increases, the content of cationic vacancies in the (Gd + Na) sublattice increases up to 10%. It has been found that cation-deficient NGM crystals are also ahion-deficient. The concentration of oxygen vacancies varies from 0.5% to 5% of the amount of anion sites. Possible mechanisms responsible for the formation of cationic and anionic vacancies in NGM crystals are discussed.
查看更多>>摘要：Molybdenum disulfide (MoS_2) nanosheets were prepared by the method of liquid phase ultrasonic separation. It is coated on the surface of single mode-no-core-single mode (SNS) fiber structure by drip coating method, which realizes the detection of formic acid gas under room temperature. The corresponding sensing performance has been discussed in the concentration range of 0-250 ppm and 0-1100 ppm, respectively. The good selectivity, repeatability and response/recovery characteristics have been experimentally demonstrated and used for exploring an effect method to greatly improve the sensitivity of the formic acid gas sensor. This passive optical fiber probe has the promising potential application in medical and industrial production process for determining the formic acid concentration at room temperature.
查看更多>>摘要：Due to the increase in pollution, and incredibly polluted water resources, access to safe water has become one of the major human activities in the present age. Also, existing organic compounds from industrial wastewater in water sources are a concern for human health. So in this work, Sr_2Fe_2O_5/Dy_3Fe_5O_(12) (SFO/DFO) nanocomposite were fabricated via a green auto-combustion sol-gel method using Hordeum vulgare L extract as a natural fuel. Proper control over the dimensions and morphology of nanocomposite was achieved by changing the parameters consisting of fuel types (natural and chemical) and calcination temperature. The results showed that every parameter affects the particle size and morphology of products, and by controlling these factors, the optimum sample can be obtained. The photocatalytic ability of SFO/ DFO nanocomposite was performed for the destruction of organic dyes. This nanocomposite was used to investigate the photocatalytic properties under UV light in the aqueous solution of methylene blue (MB), Erythrosine, and acid red dyes. The results of the photocatalytic process showed 82% discoloration for the methylene blue (MB). Three compounds, including Ethylenediaminetetraacetic acid, 1,4-Benzoquinone, and Benzoic acid, were used as scavengers to investigate the mechanism of the photocatalytic process. The results showed that the mechanism of the photocatalytic process proceeds through hydroxide radicals, which Benzoic acid scavenges. The electrochemical redox behavior of MB on SFO/DFO/CPE (carbon-paste electrode) was studied using cyclic voltammetry (CV). Besides, according to the VSM result, SFO/DFO nanocomposite is ferromagnetic.
查看更多>>摘要：Cubic spinel Li_4Ti_5O_(12) is a desired anode material for lithium-ion batteries (LIBs) due to high stability (the feature of "zero strain") and good safety. Moreover, Li_4Ti_5O_(12) has a good affinity with sulfur for restraining lithium polysulfides (LiPSs) by the Ti-S bond in lithium-sulfur batteries (LSBs). Interestingly, extra cobalt element is introduced to form Li_2CoTi_3O_8, which not only increases theoretical capacity for LIBs but also enhances the adsorption of sulfur for LSBs. In this paper, Li_2CoTi_3O_8 nanoparticles are synthesized via a sol-gel method. As the anode for LIBs, Li_2CoTi_3O_8 displays a desired specific capacity (335.3 mAh g~(-1) at 0.2 A g~(-1)) and a better rate-capability (188.5 mAh g~(-1) at 5 A g~(-1); no capacity decay over 400 cycles), which is superior to electrochemical performances of the reported same substances. Besides, Li_2CoTi_3O_8 nanoparticles are designed as both the sulfur host material and the modified separator in LSBs for the first time. Under the LCTO-coated separator, the Li_2CoTi_3O_8/S electrode achieves a first capacity of 1048 mAh g~(-1) at 0.5 C and the stable capacity retention (732.7 mAh g~(-1) after 100 cycles). The enhanced performance of the Li_2CoTi_3O_8 electrode is the result of synergistic effect of dispersed particles and larger contact area for LIBs and LSBs.
NSTL
Elsevier