Microstructure and thermoelectric properties of p-type Bi-Sb-Te-Se thin films prepared by electrodeposition method

P-type Bi-Sb-Te-Se thermoelectric thin films with thickness of 8 μm have been prepared by cathodic electrodeposition technique on Au substrate from nitric acid solution system at room temperature. Cyclic voltammetry was used for determination of the deposition potentials of the thin films. In order to enhance the crystallinity, as well as the thermoelectric properties of the deposited films, they were annealed at 523 K for 2 h under nitrogen atmospheric pressure condition. X-ray diffraction (XRD), environmental scanning electron microscopy, and energy-dispersive spectroscopy (EDS) were employed to characterize the thin films. Seebeck coefficients and resistivities of the films were also evaluated. The results revealed that Bi, Sb, Te and Se could be co-deposited to form Bi-Sb-Te-Se semiconductor compound in the solution containing Bi^III, Sb^III, Te^IV and Se^IV and the compositions of the films were sensitive to the electrodepositing potentials. The XRD results suggested that the crystal structure of the thin films were changed from amorphous state to polycrystalline after annealing. The EDS data indicated that the composition of the films was consistent with XRD results. The annealed Bi-Sb-Te-Se thin films exhibited the Seebeck coefficients of 116-133 μV/K and a maximum power factor of 0.62 mW·K^− 2·m^− 1.     

Removal of ammonium from wastewater using calcium form clinoptilolite

The paper concerns the removal of ammonium ions from aqueous solution using a modified clinoptilolite-Ca(2+)-formed clinoptilolite (CaY) prepared from natural clinoptilolite. The batch study results show that the pH has an effect on ammonium adsorption capacity as it can influence both the character of the exchanging ions and the clinoptilolite itself; the CaY has a high selectivity to NH(4)(+) and the exchange decreases with increasing temperature; ammonium ion uptake onto CaY was suitably described by the Langmuir model. The column results indicated that the effluent of simulated wastewater treated with CaY could meet the integrated wastewater discharge standard of China, and CaY can be circulated through regenerating by Ca(OH)(2).     

Mercury-promotion of platinum catalysis of dehydrogenation and dehydrochlorination

Mercury in very low concentrations (i.e. when there is up to about one Hg atom in one hundred Pt atoms) promotes the dehydrogenation activity of supported Pt towards cyclohexane and to a lesser extent cyclohexene. However, dehydrochlorination activity towards monochlorocyclohexane is relatively unaffected by Hg additions. Interestingly, cyclohexene is a significant intermediate from dehydrochlorination at high Hg concentrations; consideration is given to reaction mechanisms. The low concentrations at which Hg promotes catalytic activity suggests that it may disrupt the lattices of the Pt crystallites producing surface sites of low coordination and high activity.     

Synthesis and characterization of quaternized carboxymethyl chitosan/poly(amidoamine) dendrimer core–shell nanoparticles

With the aim to develop a novel water-soluble modified chitosan nanoparticle with tuned size and improved antibacterial activity, quaternized carboxymethyl chitosan/poly(amidoamine) dendrimers (CM-HTCC/PAMAM) were synthesized. Firstly low-generation amino-terminated poly(amidoamine) (PAMAM) dendrimers were prepared via repetitive reactions between Michael addition and amidation, which were then employed for modifying quaternized carboxymethyl chitosan (CM-HTCC). Prior to the reaction of CM-HTCC with PAMAM, carboxylic groups in CM-HTCC were activated with EDC/NHS in order to enhance the reaction efficiency. FT-IR, ¹H NMR, elemental analysis and XRD were performed to characterize CM-HTCC/PAMAM dendrimers. Turbidity measurements showed that CM-HTCC/PAMAM dendrimers had good water-solubility. TEM images indicated that CM-HTCC/PAMAM dendrimers existed as smooth and spherical nanoparticles in aqueous solution. The results of antibacterial activity explored that CM-HTCC/PAMAM dendrimer nanoparticles displayed higher antibacterial activity against Gram-negative bacteria Escherichia coli (E. coli), whereas they showed much less efficiency against Gram-positive bacteria Staphylococcus aureus (S. aureus) compared to quaternized chitosan (HTCC).     

The chemistry of structural defects in CuInSe2

The composition of CuinSe₂ can be described by two parameters, non-stoichiometry and non-molecularity. The concentration variation of the structural defects on thermal annealing is predicted as a function of two component activities. Even though the electrical properties can be interpreted within the model of vacancy defects, the establishment of any defect model must await their identification by structure-sensitive techniques.     

Mg2+、Zr4+离子掺杂对Li4Ti5O12电化学性能的影响

以固相反应法合成了尖晶石型Li4Ti5O12电极材料,进行了金属离子掺杂以提高其导电性及综合性能,以适应用于大电流充放电的目的。采用XRD、室温恒流充放电循环、交流阻抗和循环伏安等测试手段,考察了A位掺杂Mg(Li4-xMgxTi5O12,x=0.15),B位掺杂Zr(Li4ZrxTi5-xO12,x=0.15)对Li4Ti5O12结构和电化学性能的影响。结果表明:掺杂少量的Mg2+、Zr4+未引起材料结构的变化,明显降低了Li4Ti5O12电荷转移阻抗,使导电性得到有效提高。0.1 C放电倍率下放电,未掺杂及掺杂Mg2+、Zr4+的Li4Ti5O12首次放电容量分别为159.8、144.9、161.2mAh/g,循环40次后,容量分别保持为113.8、130.6、133.6 mAh/g。与未掺杂的Li4Ti5O12相比,掺杂后的电极材料极化减小、循环容量及稳定性提高。     

Phase behaviour and solution properties of sulphobetaine polymers

Aqueous polyelectrolytes have been extensively studied and comprehensively described in numerous books and reviews. In contrast, systematic investigations of aqueous polyzwitterions are few. This paper describes the detailed phase behaviour and solution properties of a homopolymer based upon a recently available sulphobetaine monomer, N-(3-sulphopropyl)-N-methacrylooxyethyl-N,N-dimethyl ammonium betaine (SPE). In addition, such properties are probed at the molecular level by static and dynamic light scattering, as well as laser Raman spectroscopy. Poly[N-(3-sulphopropyl)-N-methacrylooxyethyl-N,N-dimethyl ammonium betaine], P(SPE), of 4.35 × 10⁵M_w shows remarkable phase behaviour. It exhibits both an upper critical solution temperature (UCST) and an ‘apparent inverted’ lower critical solution temperature (LCST), i.e. a 1-phase region flanked by two 2-phase regions. Moreover, the UCST occurs at an order of magnitude lower polymer concentration than predicted by theory or demonstrated by experiment with conventional polymers. The aqueous solubility of (SPE) depends upon polymer molecular weight, as well as the concentration and structure of added salts. ‘Soft’ salt anions and cations are more effective solubilizers than ‘hard’ anions and cations. Furthermore, solutions of P(SPE) display ‘antipolyelectrolyte behaviour’, i.e. viscosities which increase with increasing salt concentrations. Static light scattering experiments indicate that the solvent quality for P(SPE) increases with increasing salt concentration. Dynamic light scattering measurements show that the polymer diffusion coefficients decrease and the chain dimensions increase with increasing salt concentrations. Moreover, laser Raman spectroscopy indicates that the local environment around the zwitterion functionalities is also modified by changes in salt concentration. Based upon such molecular level probes, models have been proposed to account for the P(SPE) phase behaviour and solubility. Thus, P(SPE) is depicted as a collapsed coil in water because of intra-group and intra-chain associations. The unusual phase behaviour of P(SPE) in water is rationalized in terms of a shift from intra- to interinteractions. In turn, NaCl breaks up the intra-associations and promotes polymer solubility.     

Correlation between electrochemical reactions with bare surfaces and corrosion fatigue crack growth in steels

The results of this preliminary correlation demonstrate the relationship between electrochemical reactions with bare metal surfaces and CF crack growth for steels in aqueous environments, and is very encouraging. These findings provide further support for the hypothesis of surface/electrochemical react control, and indicate the effectiveness of the in-situ fracture technique in providing unambiguous measurements of bare-surface reaction kinetics. For quantitative modeling, efforts will be needed to provide measurements of current and charge densities, and to address the issue of actual surface areas of cracks. Additional research is in progress and will be reported.     

Elevated temperature combined erosion-corrosion of steels

The effects of erodent particle size and elevated temperatures on the combined erosion-corrosion behavior of a series of chromium-containing steels were investigated in an oxidizing gas stream.It was determined that corrosion was the dominant mechanism at all test conditions for all alloys. Particle impacts enhanced the growth rate of multilayered iron oxide and Fe-Cr oxide spinel scales and markedly changed the morphology of the scale surface and the thickness of the various scale layers.