Enhanced photocatalytic hydrogen production by improving the Pt dispersion over mesostructured TiO2

Among other potential applications, mesoporous titania with high surface area and crystalline framework is attractive in photocatalytic hydrogen production. The mesoporous structure with pore walls formed by nanocrystals of anatase would provide a shorter distance of the electron–hole pairs to reach the photocatalyst surface and a higher surface area to deposit modifiers of its photocatalytic activity. In this work, we have successfully applied a hard-templating pathway to obtain ordered mesoporous titania (m-TiO₂) with high surface area and anatase as main crystalline phase. Subsequently, various amounts of metallic Pt have been deposited using different impregnation methods. All reactions performed exhibit, at short times, a rapid increase in the hydrogen production rate until a point in which a nearly constant value is achieved. The material prepared by the “citrate method”, based on reduction and encapsulation with sodium citrate of Pt nanoparticles before the photocatalytic reaction, leads to the highest hydrogen production rates with the shortest time to reach the change on the trend of the activity curve. The reason of this result is that citrate method provides very good dispersion and, specially, because the Pt nanoparticles are deposited and reduced preferentially within the pores of m-TiO₂, leading to stronger interactions than the other two explored dispersion routes (wetness impregnation and photodeposition). Thus, despite introducing less than half of the theoretical amount of Pt, citrate method produces close to twice the amount of hydrogen obtained by the other dispersion routes. This production capacity is even higher when the amount of Pt loaded is increased, with the optimal concentration being determined as 2% (w/w).     

Electrospun composite poly(lactic acid)/polyaniline nanofibers from low concentrations in CHCl3: Making a biocompatible polyester electro-active

Nanofibers of poly(lactic acid) (PLA) blended with polyaniline (PANi) were fabricated via electrospinning at much lower PLA concentrations (∼1wt%) in CHCl₃ than reported before using a more efficient technique of preparing the solutions. The polymer nanofibers had diameters in the range 10 nm–300 nm. Nanofibers prepared with a 3 wt% PLA/PANi solution were conducting and were used to fabricate a diode which was electrically characterized and exhibited a low turn-on voltage and a rectification ratio of 500. The device characteristics were analyzed using the standard thermionic emission model of a Schottky junction and yielded an ideality factor of 1.6 and a barrier height of 0.49 eV. Using a simple circuit, the diode was able to rectify a low frequency alternating current signal with an efficiency of 10%. The ability to engineer insulating PLA into nanofibers that are electro-active extends the range of applications of this biocompatible and biodegradable polyester to include electronic devices that have reduced toxicity.     

Multifractal analysis application to the characterization of fatty infiltration in Iberian and White pork sirloins

This paper applies the multifractal analysis based on the sandbox method to describe the distribution of fatty infiltration in Iberian and White pork meat with the aim of characterization and classification. This work was carried out by making photographs of sirloin cuts of both breeds and then treated with image analysis software. The obtained image data were stored in text format and constituted the input for multifractal analysis. The results obtained show that pork sirloin connective fatty tissue exhibits a multifractal type of scaling. Significant correlations were found between some of the parameters governing the multifractal behavior and fat percentage, especially in the case of Iberian sirloin. The differences found for the relationships between the generalized fractal dimensions and fat percentage provide information for the categorization of the studied meat pieces.     

Entrepreneurial quality and regional development: Characterizing SME sectors in low income areas*

This paper analyses the characteristics of SMEs in less‐developed areas in comparison with more advanced economies. The conceptual framework includes different factors making up the so‐called ‘entrepreneurial quality’ of the SME sector: the personal characteristics of the entrepreneurs (motivations and previous experience), different dimensions of the SMEs’ entrepreneurial orientation, and the patterns of the SMEs’ insertion in national and global value chains. The empirical analysis uses data of SMEs in four different Spanish provinces representing examples of low income economies and comparatively high income ones, respectively. Results show the SMEs in the low income economies to be characterized by a lower entrepreneurial quality.     

Calculation of the Orientation Relationships of Directionally Solidified Eutectic Ceramics by a Modified Coincidence of Reciprocal Lattice Points Model (CRLP)

The Coincidence of Reciprocal Lattice Points (CRLP) method was used to predict, according to geometric considerations, the most favorable orientation relationships (ORs) between the component phases in a family of directionally solidified eutectic ceramics (DSEC) (NiO–YSZ, CoO–YSZ, NiO–CeO₂, NiO–GDC, CoO–CeO₂, and CoO–GDC) grown by the laser floating zone method. The ORs predicted by the CRLP model are consistent with those experimentally found in a previous work by means of Electron Backscatter Diffraction (EBSD). In this article, we also present a modification to the model with the aim of taking into account that the most stable ceramic–ceramic interfaces are usually formed between atomic planes with low Miller indices, due to their higher atomic density and bigger interplanar spacing. Thus, we introduce in the calculation of the overall coincidence volume a weighting factor which is a function of the interplanar spacing. This modified CRLP method has been applied to the aforementioned eutectic ceramics, and the results are presented and discussed in comparison with the traditional CRLP results and the experimental findings.     

Synthesis and characterization of poly (styrene‐b‐[(butadiene)1−x‐(ethylene‐co‐butylene)x] ‐b‐styrene) star‐like molecular polymers produced by partial hydrogenation of SBS

This article reports the synthesis and characterization of four arm star‐shaped poly(styrene‐b‐[(butadiene)_1?x‐(ethylene‐co‐butylene)_x]‐b‐styrene) (SBEBS) copolymers. A series of SBEBS copolymers with different compositions of the elastomeric block were produced by hydrogenating a given poly(styrene‐b‐butadiene‐b‐styrene) (SBS) copolymer using a catalyst prepared from bis(η⁵‐cyclopentadienyl)titanium(IV) dichloride and n‐butyllithium. The characterization was accomplished by proton nuclear magnetic resonance spectroscopy (¹H NMR), infrared spectroscopy (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The results indicate that there is a selective saturation of the polybutadiene block over the polystyrene block; this selectivity was determined by the Ti/Li molar ratio and the concentration of Ti. It was observed that the saturation rate of the 1,2‐vinyl was higher than that of the 1,4‐trans and 1,4‐cis poly(butadiene)‐b isomers. The DSC and DMA results indicate that the degree of hydrogenation had a profound effect on the polymer's relaxation behavior. All samples exhibited a biphasic system behavior with two distinct transitions corresponding to the elastomeric and polystyrene blocks. SBEBS copolymers with higher saturation levels (>33%) exhibited a crystalline character. The TGA results indicated a characteristic weight loss temperature in all samples, with slightly higher thermal degradation stabilities in the materials with higher degrees of saturation. POLYM. ENG. SCI., 54:2332–2344, 2014. © 2013 Society of Plastics Engineers     

新城区的生态林荫道

项目地点:西班牙马德里项目类型:景观设计开工日期:2005年4月该项目获2005年豪瑞可持续建筑大奖赛欧洲地区提名奖     

Influence of liquid lead and lead-bismuth eutectic on tensile, fatigue and creep properties of ferritic/martensitic and austenitic steels for transmutation systems

In this paper, the tensile, fatigue and creep properties of the Ferritic/Martensitic (F/M) steel T91 and of the Austenitic Stainless (AS) Steel 316L in lead-bismuth eutectic (LBE) or lead, obtained in the different organizations participating to the EUROTRANS-DEMETRA project are reviewed. The results show a remarkable consistency, referring to the variety of metallurgical and surface state conditions studied. Liquid Metal Embrittlement (LME) effects are shown, remarkable on heat-treated hardened T91 and also on corroded T91 after long-term exposure to low oxygen containing Liquid Metal (LM), but hardly visible on passive or oxidized smooth T91 specimens. For T91, the ductility trough was estimated, starting just above the melting point of the embrittler (T_M,E = 123.5 °C for LBE, 327 °C for lead) with the ductility recovery found at 425 °C. LME effects are weaker on 316L AS steel. Liquid Metal Assisted Creep (LMAC) effects are reported for the T91/LBE system at 550 °C, and for the T91/lead system at 525 °C. Today, if the study of the LME effects on T91 and 316L in LBE or lead can be considered well documented, in contrast, complementary investigations are necessary in order to quantify the LMAC effects in these systems, and determine rigorously the threshold creep conditions.     

NUMERICAL SIMULATION OF THE EFFECTS OF BUOYANCY FORCES AND FLOW CONTROL DEVICES ON FLUID FLOW AND HEAT TRANSFER PHENOMENA OF LIQUID STEEL IN A TUNDISH

Fluid flow and heat transfer of liquid steel in a tundish of a continuous slab caster was numerically simulated. The importance of natural flow convection was established through a dimensionless number given by the ratio Gr/Re². Buoyancy forces proved to be as important as inertial ones, especially in the extremes of the tundish far from the entering liquid jet. The usual flow control devices like weirs and dams were not as effective as turbulence inhibitors, a kind of impact pad with lips, interior squared angles, and a square cross section. The simulations indicated that this device helps to decrease fluid turbulence in the zone of the entering liquid jet and has damping effects of step inputs of cold or hot steel, allowing for better control of the casting temperature.