C-axis-oriented Bi3.25La0.75Ti3O12 ferroelectric thin film fabricated by chemical solution deposition

C-axis-oriented Bi_3.25La_0.75Ti₃O₁₂ (BLT) ferroelectric thin films were successfully prepared by chemical solution deposition. According to X-ray diffraction, it is found that the orientation degree increases with the increase of sintering temperature, and at the same time the grain morphology changes from equiaxed to plate-like. Due to the dense morphology and [Bi₂O₂]²⁺ layer of c-preferred orientation of BLT film sintered at 650 °C, it exhibits the lowest leakage current density at room temperature. Additionally, a linear relation between V^0.5 and log(J / T²) is found, suggesting the behavior of leakage current of BLT films obeys the Schottky emission model. P–E loops show that the c-axis-oriented BLT ferroelectric film exhibits low polarization and small coercive field.     

Thermal conductivity of aligned CNT/polymer composites using mesoscopic simulation

Thermal conductivity of CNT/polymer composites depends on alignment, dispersion, volume fraction and size of CNTs as well as polymer size. By coupling smoothed particle hydrodynamics and dissipative particle dynamics, thermal conductivities of random and aligned composites along with their meso morphologies are studied in detail. Thermal conductivity along the alignment of CNT can be significantly enhanced to 16 times that of polymer by increasing volume fraction, dispersion degree and length of CNT, meanwhile thermal conductivity perpendicular to the alignment of CNT is affected modestly by these factors. Enhancement of thermal conductivity of random composites could only be efficiently achieved by increasing the volume fraction of CNT. Particularly, thermal conductivity $\kappa$ is proportional to the square of volume fraction of CNT v in well dispersed random and aligned composites, i.e. $\kappa \propto v^2$.     

Complex mullite structures fabricated via digital light processing of a preceramic polysiloxane with active alumina fillers

By taking advantage of the multi-functional properties of preceramic polymers, their transformation into ceramic material at low sintering temperatures and the processing capabilities of polymer manufacturing processes, mullite components were fabricated by additive manufacturing. A photocurable silicone preceramic polymer resin containing alumina particles was shaped into complex structures via Digital Light Processing. Dense and crack-free, highly complex porous mullite ceramics were produced by firing a mixture of a commercially available photosensitive polysiloxane as the silica source, containing alumina powder as active filler, in air at a low sintering temperature (1300 °C). In particular, the developed formulations, coupled with the additive manufacturing approach, allow for precise control of the architecture of the porous ceramic components, providing better properties compared to parts with stochastic porosity.     

钛酸锶钡/铋锌铌多层复合薄膜的制备及性能

采用溶胶一凝胶法在Pt/Ti/SiO2/Si衬底上制备了钛酸锶钡/铋锌铌多层复合薄膜样品.研究了不同退火温度下多层复合薄膜的结构、微观形貌及介电性能.结果表明:在退火温度高于700℃时,所得复合薄膜中会出现立方焦绿石结构的铋锌铌和钙钛矿结构的钛酸锶钡.750℃退火处理得到的多层复合薄膜,表面致密,无裂纹,其相对介电常数...     

Unveiling crystallization mechanism for controlling nanocrystalline structure in glasses

Controlling nanocrystalline structure in glasses renders the exploration of new composite multiphase (glass-ceramic) materials with novel functionalities that determined by the precipitated nanocrystals and residual glassy matrix. Previous microstructural investigation of glass-ceramics focused only on one aspect of nanocrystalline structures, e.g., nano-polycrystalline or single nanocrystalline. The recognition of the microscopic mechanism of nanostructure formation in glasses is absent. Here, we use advanced microscopic techniques to show the formation of different nanocrystalline structures composed of nano-polycrystals and single nanocrystals in 80GeS₂·20In₂S₃ and 72.5GeS₂·14.5Sb₂S₃·13RbCl glasses, respectively. Crystallization mechanism for controlling the nanocrystalline structure in glasses was revealed to depend on whether the glass network former participates in crystallization process. The results may shed light not only on glass crystallization mechanism, but also on the fundamental nature of the network structure of chalcogenide glasses.     

Magnetic porous carbons with high adsorption capacity synthesized by a microwave-enhanced high temperature ionothermal method from a Fe-based metal-organic framework

Magnetic porous carbons with high surface areas were easily synthesized from a Fe-based metal-organic framework (MOF) by a novel microwave-enhanced high temperature ionothermal method. By choosing a Fe-based MOF called MIL-100(Fe) as both a Fe and C precursor and a porous template, and furfuryl alcohol as a second precursor, a series of γ-Fe₂O₃/C composites with strong magnetism were prepared in 3 min by a microwave-enhanced high temperature ionothermal method. Structure, morphology and magnetic property, as well as porosity of the products, were carefully studied by powder X-ray diffraction, X-ray photoelectron spectroscopy, the BET surface area method, thermogravimetry, vibrating sample magnetometry, scanning electron microscopy, and high resolution transmission electron microscopy. The obtained γ-Fe₂O₃/C composites possess both high surface areas and magnetic characteristics. Their adsorption properties were preliminarily tested by the adsorptive removal of methylene blue from aqueous solution. The results suggest that such magnetic carbon composite exhibited high adsorption capacity (303.95 mg g⁻¹) and fast adsorption kinetics, as well as a perfect magnetic separation performance (M_s = 4.12–19.54 emu g⁻¹), for the MB removal from aqueous solution.     

Reactivity between carbon cathode materials and electrolyte based on industrial and laboratory data

Interaction between electrolyte and carbon cathodes during the electrolytic production of aluminium decreases cell life. This paper describes the interaction between carbon cathode materials and electrolyte, based on industrial and laboratory data. It also reports on the degree of expansion of semi-graphitic and graphitised materials when exposed to a sodium rich environment. Phase relations in the slow cooled bath electrolyte, spent industrial cathodes and laboratory scale cathode samples were similar: all contained Na₃AlF₆, NaF, CaF₂ and NaAl₁₁O₁₇. Al₄C₃, AlN and NaCN were only detected in the spent industrial cathodes. The inability to locate Al₄C₃ in the laboratory scale samples could be due to very low concentrations of Al₄C₃ which could not be detected by XRD, or to the limited direct contact between the produced aluminium and carbon material. X-ray diffraction analysis confirmed that sodium intercalation into graphite did not take place. Wear of the examined carbon cathodes proceeded due to penetration of electrolyte and sodium into the cathode, followed by reactions with carbon and N₂ whereby AlN and NaCN formed. Once electrolysis started the carbon cathodes expanded rapidly, but slowed down after approximately an hour. Sodium expansion decreased with degree of graphitisation of the carbon cathode material.     

Influence of Ag on TCR and MR of La0.7(Ca0.27Sr0.03)MnO3:Ag0.2 ceramics subjected to cross magnetic fields

In this account, polycrystalline La_0.7(Ca_0.27Sr_0.03)MnO₃:Ag_0.2 (LCSMO:Ag) ceramics were synthesized by the sol-gel method followed by solid-state doping. The Ag amounts doped into grain boundary and cell lattice could be adjusted by changing the sintering temperature from 1000 °C to 1500 °C. The temperature coefficient of resistivity (TCR) and magnetoresistance (MR) of the obtained LCSMO:Ag ceramics were tested under cross magnetic field with directions parallel and perpendicular to the flat of bulk. The difference between TCR and MR values reached their maxima at sintering temperature of 1450 °C, meaning that degree of lattice distortion reached maximum value. The combined data from X-ray diffraction (XRD) and scanning electron microscopy (SEM) demonstrated that Ag was doped into the grain boundary and lattice cell, and Ag played an important role during the process. The influence of Ag-doping on TCR and MR suggested that degree of lattice distortion can be adjusted by doping, leading to change in isotropic ceramics into anisotropic ceramics without damage. Application of parallel magnetic fields shifted the application temperature to room temperature, and response sensitivity of the ceramics to magnetic field further increased. Overall, these findings look promising for future applications in photoelectric and magnetic devices.     

Artificial magnetism in a carbon diamond nanolattice with the spin orientation effect

In this paper, we investigate the spin orientation effects on the magnetic properties of the Carbon diamond nanolattice (CDNL) by using Kaneyoshi approach (KA) within the effective field theory. In our calculations, we use the normalized lattice constant (na = 3.566 = a/1 A⁰) which is obtained from the real lattice constant (a = 3.566 A⁰) of the CDNL. The CDNL has three different magnetic atoms according to nearest-neighbor, and they are defined as corner atoms (m_c), face atoms (m_f) and inner atoms (m_i). For m_c, m_f and m_i, the CDNL has eight spin orientations as +++ (↑↑↑), −++ (↓↑↑), ++− (↑↑↓), −+− (↓↑↓), −−+ (↓↓↑), −−− (↓↓↓), +−− (↑↓↓) and +−+ (↑↓↑), respectively. We find that the CDNL has two kinds of critical temperature behaviors, we call them as high critical temperature behavior (HCTB) for the first four spin orientations and low critical temperature behavior (LCTB) for the second four spin orientations. However, the CDNL exhibits ferromagnetic (FM), antiferromagnetic (AFM), superconductivity (SC), discontinuous diamagnetic (DM) and discontinuous paramagnetic (PM) hysteresis behaviors according to the spin orientation of its atoms. Therefore, we suggest that it is possible to obtain different magnetic behaviors and artificial magnetism from the Carbon and Carbon-based materials with the spin orientations of their atoms.