Nanoparticle evolution in flame spray pyrolysis—Process design via experimental and computational analysis

In flame spray pyrolysis (FSP), the evolution of metal oxide nanoparticles relies on quite a number of droplet (liquid) and vapor phase related physical mechanism as for instance precursor evaporation, oxidation, nucleation via gas-to-particle conversion mechanism, and subsequent particle (solid) growth mechanisms based on coagulation, sintering/coalescence, and agglomeration. The liquid precursor and dispersion oxygen feed rates are relevant control parameters of the FSP process for tailoring the nanoparticle size (diameter) and structure as well as the atomizer nozzle configuration. Sophisticated nonintrusive, laser-based in situ and ex situ diagnostics with multiscale spatial resolution (micrometer to meter range) are applied for analyzing droplet formation and size, gas velocity, temperature, species concentration, as well as primary and agglomerate diameters along the flow direction. Computational fluid dynamics (CFD) are coupled with population balance modeling (PBM) to elucidate the nanoparticle dynamics within the reactive spray. It is found that the CFD-PBM approach allows estimations of primary and agglomerate nanoparticle diameters within 80 and 75% accuracy compared to experimental data, suggesting that the methods presented could pave the way for designing next-generations of flame reactors.     

Er2Ti2O7烧绿石基玻璃陶瓷固化体的制备工艺研究

为获得含单一钛酸盐烧绿石的玻璃陶瓷固化体，本文以Er₂Ti₂O₇作为钛酸盐烧绿石代表，在传统的烧结法制备工艺基础上，通过热雾喷解和晶核掺入的技术改进，分别研究了烧结温度、烧结时间、玻璃与陶瓷晶核质量配比等参数对Er₂Ti₂O₇基玻璃陶瓷固化体物相及结构的影响规律。XRD结果表明：在不同的烧结温度、烧结时间和质量配比下，均能获得含单一Er₂Ti₂O₇烧绿石的玻璃陶瓷固化体，Er₂Ti₂O₇前驱体在玻璃中的相稳定性好，未发生相分解，玻璃组分亦未受陶瓷相的影响而析出第二相；玻璃组分对陶瓷颗粒存在张应力作用，玻璃含量越高，Er₂Ti₂O₇的晶胞常数越大；提高烧结温度和烧结时间均有利于增强固化体中Er₂Ti₂O₇的结构有序性，但烧结温度效果强于烧结时间。SEM结果表明：Er₂Ti₂O₇在玻璃基体上呈四方形生长，与玻璃界面清晰，相容性好。固化体的物性测试结果表明，玻璃组分占比将直接影响固化体的表观孔隙率和致密度。根据以上结果可知，新工艺制备的样品具有相纯度高、烧绿石相与玻璃相容性好、两相比例可调等优点，较好地解决了钛酸盐烧绿石在玻璃基体中易发生相分解的问题。     

Economic Indicators

Currency exchanges rates – updated monthly. Economic indicators of industrial production. Countries included: France, Germany, Italy, the United Kingdom, the United States, Canada, Japan (Total G-7), Eurozone and Total EU-28 (Total OECD). Updated monthly. Economic indicators of car registration in the United States, Canada, France, Germany, Italy, Poland, Spain, Turkey, the United Kingdom, Japan, Republic of Korea and Other OECD (Total OECD-30). Updated monthly. Monthly averages of crude steel production in thousand metric tons for the United States, Canada, Brazil, Mexico, Austria, Belgium, Czech Republic, France, Germany, Italy, Netherlands, Poland, Spain, Sweden, Turkey, the United Kingdom, Russia, Ukraine, South Africa, Iran, China, India, Japan, Republic of Korea, Taiwan and Australia.     

Corrosion behavior of austenitic 304L and 316LN stainless steel clad reinforcing bars in cracked concrete

A study has been conducted on the chloride-induced corrosion behavior of 304L and 316LN stainless steel clad reinforcing bars (rebar) in concrete and in synthetic concrete pore solution. Metallographic examination of the as-received clad bars confirmed a strong metallurgical bond at the core/clad interface and some grain growth interdiffusion of species at the interface. Both bars showed a wide variation in coating thickness around the rebar circumference, from a minimum of 0.32 and 0.60 mm to a maximum of 1.4 and 2.8 mm in the 304L clad and 316LN clad, respectively. The electrochemical results and visual examination after autopsy showed that active corrosion was yet initiated on either the solid and clad stainless steel or carbon steel rebar in the sound noncracked concrete specimens. In contrast, corrosion had initiated in the bars embedded in cracked concrete at the base of the crack and extended along or around the bars. In the concrete and synthetic pore solution tests, the current densities of both solid and clad stainless steel rebar exposed to ∼21% chloride brine solution for days between 400 and 1,500 were similar. This was also the case for current densities of the straight and bent stainless steel bars tested in the synthetic pore solution test.     

Ecological opportunity enabled invertebrate radiations in ancient Lake Ohrid

Ancient Lake Ohrid is the oldest and biologically most diverse freshwater lake in Europe. The recent deep-drilling campaign SCOPSCO provided detailed insights into the lake’s limnological history over the past 1.36 my. However, it remains unclear what factors triggered the onset of radiations and whether diversification rates remained constant throughout their evolution. We therefore inferred time-calibrated molecular phylogenies for eight invertebrate groups endemic to Lake Ohrid and performed diversification-rate analyses for the four most species-rich groups. The molecular-clock analyses indicate that few groups possibly originated in springs or rivers in the ‘proto-Balkans’ during the pre-lake phase. The onset of all other radiations, however, can be correlated to one of the three limnological phases in the Ohrid Graben and in Lake Ohrid since 1.9 mya. We therefore assume that the onset of radiations was triggered by an increased ecological opportunity arising from massive environmental changes in the course of the lake deepening. The diversification-rate analyses further indicate that the groups examined diversified with a constant rate. Although the reconstruction of the early evolutionary history of these groups remains challenging, our data suggest that the relatively stable conditions in Lake Ohrid together with its high buffer capacity likely prevented significant changes in diversification rates over time.     

Void Formation and Plastic Deformation Mechanism of a Cold-Rolled Dual-Phase Steel During Tension

The void formation and plastic deformation micromechanisms of a cold-rolled DP600 steel during tensile loading were studied by scanning electron microscopy(SEM) and electron backscatter diffraction(EBSD).The SEM observations revealed that the main void nucleation mechanism in the DP600 steel is decohesion at the ferrite-martensite interfaces.The voids were mostly observed between the closely spaced martensite islands situated at the boundaries of relatively finer ferrite grains.The EBSD results indicated a strain gradient developed from the ferrite-martensite and ferrite-ferrite interfaces into the interior of ferrite grains during the tensile deformation,which led to a stress concentration at these interfaces.Moreover,it was demonstrated that local misorientation inside the finer ferrite grains surrounded by martensite islands was higher than that for the coarser ferrite grains,which made the former more prone to void initiation.     

Isothermal crystallization of PLA: Nucleation density and growth rates of α and α' phases

From a technological point of view, poly(lactic acid) (PLA) is one of the most important polymers produced from renewable sources, due to its versatility, relatively acceptable processability, and low cost. However, a significant limitation exists in its slow crystallization kinetics, which results in amorphous products having low mechanical properties and thermal resistance. For this reason, quantitative knowledge of the phenomenon of crystallization kinetics is fundamental. In this work, the crystallization kinetics in quiescent conditions of a commercial grade of PLA was analyzed in terms of nucleation and growth rates by direct morphological observations at different crystallization temperatures (T_c) and by calorimetric analysis in isothermal and non-isothermal conditions. The optical analysis showed a spherulitic morphology with radial growth of the lamellae. The analysis of the growth rate evidenced the α/α'-crystals polymorphism with a transition temperature of ~120°C. Based on experimental observation, the crystallization kinetics of the two crystalline phases were assessed.     

Regulating existing power plants under the U.S. Clean Air Act: Present and future consequences of key design choices

In June 2014, the U.S. EPA released its proposed rules to regulate carbon dioxide emissions from existing fossil fuel power plants, triggering considerable debate on the proposal’s design and its environmental and economic consequences. One question not addressed by this debate is this: What if the EPA regulations turn out to be inadequate to address future mitigation goals? That is, what will the landscape for future policies look like if these regulations turn out to be just an interim measure? This analysis compares potential short- and long-term consequences of several key regulatory design choices, including mass-based versus rate-based standards, tradable versus non-tradable standards, and differentiated versus single standards. It finds that long-term consequences may be significant in terms of the legacy they leave for future policy revisions: tradable standards lead to lower electricity prices and become weaker over time; differentiated tradable standards lead to relatively greater investment in coal retrofits; non-tradable standards lead to relatively greater retirement of coal capacity. It may be the case that key policy choices entail one set of trade-offs if proposed EPA rules are viewed as relatively permanent and final and another set of tradeoffs if the rules are viewed as an interim solution.