Zhongkuan Luo

Sonochemical synthesis of cobalt aluminate nanoparticles under various preparation parameters.

Cobalt aluminate (CoAl(2)O(4)) nanoparticles were synthesized using a precursor method with the aid of ultrasound irradiation under various preparation parameters. The effects of the preparation parameters, such as the sonochemical reaction time and temperature, precipitation agents, calcination temperature and time on the formation of CoAl(2)O(4) were investigated. The precursor on heating yields nanosized CoAl(2)O(4) particles and both these nanoparticles and the precursor were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The use of ultrasound irradiation during the homogeneous precipitation of the precursor reduces the duration of the precipitation reaction. The mechanism of the formation of cobalt aluminate was investigated by means of Fourier transformation infrared spectroscopy (FT-IR) and EDX (energy dispersive X-ray). The thermal decomposition process and kinetics of the precursor of nanosized CoAl(2)O(4) were investigated by means of differential scanning calorimetry (DSC) and thermogravimetry (TG). The apparent activation energy (E) and the pre-exponential constant (A) were 304.26 kJ/mol and 6.441 x 10(14)s(-1), respectively. Specific surface area was investigated by means of Brunauer Emmett Teller (BET) surface area measurements.

Molecular dynamics study on ion diffusion in LiFePO4 olivine materials.

Molecular dynamics (MD) simulations have been employed to investigate the ionic diffusion and the structure of LiFePO 4 cathode material. The results correspond well with the published experimental observations. The simulation results indicated that the diffusion of lithium ions was thermally activated and more significant than those of other ions. Compared with other cathode materials, the shifts of ions were less significant in LiFePO 4. This suggested that LiFePO 4 was more thermally stable. The snapshots of the positions of lithium atoms over a range of the steps provided a microscopic picture and the picture showed the lithium ions migrated through one-dimension channels.

Effect of processing conditions on sonochemical synthesis of nanosized copper aluminate powders

Nanosized copper aluminate (CuAl(2)O(4)) spinel particles have been prepared by a precursor approach with the aid of ultrasound radiation. Mono-phasic copper aluminate with a crystallite diameter of 17nm along the (311) plane was formed when the products were synthesized using Cu(NO(3))(2) x 6H(2)O and Al(NO(3))(3) x 9H(2)O as starting materials, with urea as a precipitation agent at a concentration of 9M. The reaction was carried out under ultrasound irradiation at 80 degrees C for 4h and a calcination temperature of 900 degrees C for 6h. The synthesized copper aluminate particles and the effect of different processing conditions such as the copper source, precipitation agents, sonochemical reaction time, calcination temperature and time were analyzed and characterized by the techniques of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and Fourier transformation infrared spectroscopy (FT-IR).

A hierarchical micro/mesoporous carbon fiber/sulfur composite for high-performance lithium–sulfur batteries

A carbon matrix with an appropriate porous structure plays a vital role in developing high-performance sulfur/carbon cathodes of lithium–sulfur batteries. In this work, a hierarchical porous carbon fiber (HPCF) with a few mesopores and abundant micropores was prepared via electrospinning with a SiO2 template and subsequent KOH activation. The HPCF with an ultra-high surface area and a large pore volume can construct a loose network structure to promise high sulfur utilization and sufficient sulfur loading. Mesopores can provide pathways for the infiltration of electrolyte to ensure fast transport of lithium ions during electrochemical reactions, whereas micropores can effectively suppress the diffusion of polysulfides by their strong adsorption capability. Due to such advantages, the proposed cathode, with 66 wt% sulfur content, can yield a high reversible capacity of 1070.6 mA h g−1 at 0.5C, and a stable cycle performance with a capacity retention of 88.4% after 100 cycles.

A stable electrolyte makes a nonaqueous Li–O2 battery truly rechargeable

As a result of their ultra-high specific energy and potential use in electric vehicles and grid energy storage, rechargeable nonaqueous lithium–air (Li–O2) batteries are becoming more and more popular among academia, corporations, and research institutes. Unfortunately, the cycle numbers of nonaqueous rechargeable Li–O2 batteries are seriously restricted by the electrolyte. To deal with this problem, a novel Li–O2 battery that contains a sulfolane-based electrolyte is shown. Even though it only has a simple structure, it still exhibits amazing performance at different air temperatures (a valid discharge specific capacity of ∼1000 mA h g−1 is obtained after 110 cycles at air temperatures between 17 °C and 29 °C). This kind of Li–O2 battery inspires us to build lithium–air batteries with true rechargeability.

PEDOT-PSS coated sulfur/carbon composite on porous carbon papers for high sulfur loading lithium–sulfur batteries

Increasing the sulfur loading in the cathode of a lithium–sulfur battery is an important way to improve its capacity for practical applications. To achieve this, the present work proposes using PEDOT-PSS to encapsulate sulfur/carbon black (S/BP) by a facile solution mixing method and the formed composite is then coated on a porous carbon paper. It is believed that the formation of a core/shell structure in the PEDOT@S/BP composite can promote the electron transport and effectively impede the diffusion of polysulfides, and the porous carbon paper is able to retain the electrolyte containing the dissolved polysulfides in the cathode and alleviate the adverse effect of sulfur volumetric expansion. Due to such advantages, the proposed cathode, with a high sulfur loading of 3 mg cm−2, can yield a high reversible capacity of 1041 mA h g−1 and an excellent cycle stability with a capacity retention of 868 mA h g−1 after 100 cycles and an average coulombic efficiency of 99.4%.

Mechanical properties and in vivo study of modified-hydroxyapatite/polyetheretherketone biocomposites

Polyether ether ketone (PEEK) has received much attention for its excellent mechanical properties and biocompatibility. Here, the silane coupling agent KH560 [γ-(2,3-epoxypropoxy)propyltrimethoxysilane] is used for graft modification of bioactive HA (hydroxyapatite) particles and for preparing HA/PEEK composites via a hot-press molding method. The prepared HA/PEEK composites were tested for their mechanical properties with SEM (scanning electron microscopy), infrared spectroscopy, and thermo-analysis. The results show that silane coupling KH-560 modifies HA successfully and that the tensile strengths of HA/PEEK and m-HA/PEEK composites indicate an increasing and then a decreasing tendency with increasing HA contents. The non-modified HA/PEEK composites display the same trend as the modified specimens with lower tensile strength and consist of sharp points. When the HA content is 5wt.%, the tensile strength of m-HA/PEEK composite reaches its maximum, which is 23% higher than that of pure PEEK specimens. The in vivo experiments of m-HA/PEEK used a biomechanical push-out test, SEM, optical microscopy, and an Image-Pro Express C image analysis system. The growth of the bone tissues around the m-HA/PEEK composites with an HA content of 5wt.% is better than that of specimens with different HA contents. This finding shows the nano-scale effect of the bioactive filler HA in PEEK substrates, which obviously contributes to the growth of the surrounding bone issues in vivo. This study could provide theoretical support for the further promotion and application of high-performance engineering plastics such as PEEK in biomedical fields.

Electrochemical performance of a nonaqueous rechargeable lithium-air battery

Nonaqueous rechargeable lithium-air battery has so high specific capacity and specific energy that it is being widely researched by academia, corporation, and different research institutes. When used in dried air and absorbing oxygen form the air, this battery is called lithium-air battery, and its specific capacity based on cathode active material (oxygen) is infinite. However, its cycle performance is very limited as reported by the state-of-the-art researches. This cycle problem is mainly caused by instability of electrolyte. Based on electroanalysis of materials’ electrochemical property, a stable electrolyte solvent (sulfolane) and a lithium salt LiBF4 are selected as electrolytes in this work. Coupled with other eligible battery materials and careful assembly, the lithium-air battery exhibits favorable cycle performance. Above all, this lithium-air system is evaluated objectively in this paper.

Doped Titanium Dioxide Films Prepared by Pulsed Laser Deposition Method

TiO2 was intensively researched especially for photocatalystic applications. The nitrogen-doped TiO2 films prepared by pulsed laser deposition (PLD) method were reviewed, and some recent new experimental results were also presented in this paper. A new optical transmission method for evaluating the photocatalystic activity was presented. The main results are (1) PLD method is versatile for preparing oxide material or complex component films with excellent controllability and high reproducibility. (2) Anatase nitrogen-doped TiO2 films were prepared at room temperature, 200°C, and 400°C by PLD method using novel ceramic target of mixture of TiN and TiO2. UV/Vis spectra, AFM, Raman spectra, and photocatalystic activity for decomposition of methyl orange (MO) tests showed that visible light response was improved at higher temperature. (3) The automatic, continuous optical transmission autorecorder method is suitable for detecting the photodecomposition dynamic process of organic compound.

Catalytic performance of a pyrolyzed graphene supported Fe–N–C composite and its application for acid direct methanol fuel cells

In this work, a graphene supported Fe–N–C composite catalyst, synthesized by pyrolysis of graphene oxide (GO), graphitic carbon nitride (g-C3N4), ferric chloride (FeCl3) and carbon black (Vulcan XC-72), was evaluated for oxygen reduction reaction (ORR) in acid media. The introduction of carbon black was to separate the graphene sheets to enhance the specific surface area and thus improve the catalytic activity of the catalyst. The experimental results showed that the composite catalyst could yield an average electron transfer number of 3.85 and its onset and half-wave potentials for acidic ORR were only 56 and 69 mV smaller than those of Pt/C (40 wt% Pt) catalyst, respectively. The as-prepared catalyst was applied in an acid direct methanol fuel cell as the cathode catalyst and a peak power density of 11.72 mW cm−2 at 30 °C was demonstrated when feeding the anode and cathode with a 1 M methanol solution and air, respectively, suggesting its promising application.