共查询到20条相似文献,搜索用时 125 毫秒
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Ravi Mohan Prasad Yuji Iwamoto Ralf Riedel Aleksander Gurlo 《Advanced Engineering Materials》2010,12(6):522-528
The hydrogen and carbon monoxide separation is an important step in the hydrogen production process. If H2 can be selectively removed from the product side during hydrogen production in membrane reactors, then it would be possible to achieve complete CO conversion in a single‐step under high temperature conditions. In the present work, the multilayer amorphous‐Si‐B‐C‐N/γ‐Al2O3/α‐Al2O3 membranes with gradient porosity have been realized and assessed with respect to the thermal stability, geometry of pore space and H2/CO permeance. The α‐Al2O3 support has a bimodal pore‐size distribution of about 0.64 and 0.045 µm being macroporous and the intermediate γ‐Al2O3 layer—deposited from boehmite colloidal dispersion—has an average pore‐size of 8 nm being mesoporous. The results obtained by the N2‐adsorption method indicate a decrease in the volume of micropores—0.35 vs. 0.75 cm3 g?1—and a smaller pore size ?6.8 vs. 7.4 Å—in membranes with the intermediate mesoporous γ‐Al2O3 layer if compared to those without. The three times Si‐B‐C‐N coated multilayer membranes show higher H2/CO permselectivities of about 10.5 and the H2 permeance of about 1.05 × 10?8 mol m?2 s?1 Pa?1. If compared to the state of the art of microporous membranes, the multilayer Si‐B‐C‐N/γ‐Al2O3/α‐Al2O3 membranes are appeared to be interesting candidates for hydrogen separation because of their tunable nature and high‐temperature and high‐pressure stability. 相似文献
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W. Wessel F. Zeismann A. Brueckner‐Foit 《Fatigue & Fracture of Engineering Materials & Structures》2015,38(12):1507-1518
Fatigue crack growth at room temperature and its relation to the local microstructure is studied for four different γ‐TiAl‐alloys with microstructures ranging from coarse and fully lamellar to fine and partly lamellar. It is shown that the number of cycles to failure depends strongly on the efficiency of the first barrier to crack extension, as crack growth rates may increase rapidly once this barrier has been breached by a specific crack. The crack extension behaviour for two typical barriers (colony boundary and twin boundary) is studied using high‐resolution optical and scanning electron microscopy. 相似文献
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Development and processing of high‐temperature materials is the key to technological advancements in engineering areas where materials have to meet extreme requirements. Examples for such areas are the aerospace and spacecraft industry or the automotive industry. New structural materials have to be “stronger, stiffer, hotter, and lighter” to withstand the extremely demanding conditions in the next generation of aircraft engines, space vehicles, and automotive engines. Intermetallic γ‐TiAl‐based alloys show a great potential to fulfill these demands. 相似文献
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Limei Cha Thomas Schmoelzer Zaoli Zhang Svea Mayer Helmut Clemens Peter Staron Gerhard Dehm 《Advanced Engineering Materials》2012,14(5):299-303
In situ heating transmission electron microscopy (TEM) was used to investigate the initial stage of γ‐TiAl lamellae formation in an intermetallic Ti–45Al–7.5Nb alloy (in at.%). The material was heat treated and quenched in a non‐equilibrium state to consist mainly of supersaturated, ordered α2‐Ti3Al grains. Subsequently, specimens were annealed inside a TEM up to 750 °C. The in situ TEM study revealed that ultra‐fine γ‐TiAl laths precipitate in the α2‐matrix at ≈730 °C which exhibit the classical Blackburn orientation relationship, i.e. (0001)α2//(111)γ and [$11{\bar {2}}0$ ]α2//<110]γ. The microstructural development observed in the in situ TEM experiment is compared to results from conventional ex situ TEM studies. In order to investigate the precipitation behavior of the γ‐phase with a complementary method, in situ high energy X‐ray diffraction experiments were performed which confirmed the finding that γ‐laths start to precipitate at ≈730 °C from the supersaturated α2‐matrix. 相似文献
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Coaggregation of κ‐Casein and β‐Lactoglobulin Produces Morphologically Distinct Amyloid Fibrils
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Jared K. Raynes Li Day Pauline Crepin John A. Carver 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(14)
The unfolding, misfolding, and aggregation of proteins lead to a variety of structural species. One form is the amyloid fibril, a highly aligned, stable, nanofibrillar structure composed of β‐sheets running perpendicular to the fibril axis. β‐Lactoglobulin (β‐Lg) and κ‐casein (κ‐CN) are two milk proteins that not only individually form amyloid fibrillar aggregates, but can also coaggregate under environmental stress conditions such as elevated temperature. The aggregation between β‐Lg and κ‐CN is proposed to proceed via disulfide bond formation leading to amorphous aggregates, although the exact mechanism is not known. Herein, using a range of biophysical techniques, it is shown that β‐Lg and κ‐CN coaggregate to form morphologically distinct co‐amyloid fibrillar structures, a phenomenon previously limited to protein isoforms from different species or different peptide sequences from an individual protein. A new mechanism of aggregation is proposed whereby β‐Lg and κ‐CN not only form disulfide‐linked aggregates, but also amyloid fibrillar coaggregates. The coaggregation of two structurally unrelated proteins into cofibrils suggests that the mechanism can be a generic feature of protein aggregation as long as the prerequisites for sequence similarity are met. 相似文献
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Facile Synthesis of γ‐In2Se3 Nanoflowers toward High Performance Self‐Powered Broadband γ‐In2Se3/Si Heterojunction Photodiode
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Shuo Chen Xuemei Liu Xvsheng Qiao Xia Wan Khurram Shehzad Xianghua Zhang Yang Xu Xianping Fan 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(18)
An effective colloidal process involving the hot‐injection method is developed to synthesize uniform nanoflowers consisting of 2D γ‐In2Se3 nanosheets. By exploiting the narrow direct bandgap and high absorption coefficient in the visible light range of In2Se3, a high‐quality γ‐In2Se3/Si heterojunction photodiode is fabricated. This photodiode shows a high photoresponse under light illumination, short response/recovery times, and long‐term durability. In addition, the γ‐In2Se3/Si heterojunction photodiode is self‐powered and displays a broadband spectral response ranging from UV to IR with a high responsivity and detectivity. These excellent performances make the γ‐In2Se3/Si heterojunction very interesting as highly efficient photodetectors. 相似文献
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Yunxiang Sun Aleksandr Kakinen Yanting Xing Pouya Faridi Aparna Nandakumar Anthony W. Purcell Thomas P. Davis Pu Chun Ke Feng Ding 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(18)
The self‐assembly of human islet amyloid polypeptide (hIAPP) into β‐sheet‐rich nanofibrils is associated with the pathogeny of type 2 diabetes. Soluble hIAPP is intrinsically disordered with N‐terminal residues 8–17 as α‐helices. To understand the contribution of the N‐terminal helix to the aggregation of full‐length hIAPP, here the oligomerization dynamics of the hIAPP fragment 8–20 (hIAPP8‐20) are investigated with combined computational and experimental approaches. hIAPP8‐20 forms cross‐β nanofibrils in silico from isolated helical monomers via the helical oligomers and α‐helices to β‐sheets transition, as confirmed by transmission electron microscopy, atomic force microscopy, circular dichroism spectroscopy, Fourier transform infrared spectroscopy, and reversed‐phase high performance liquid chromatography. The computational results also suggest that the critical nucleus of aggregation corresponds to hexamers, consistent with a recent mass‐spectroscopy study of hIAPP8‐20 aggregation. hIAPP8‐20 oligomers smaller than hexamers are helical and unstable, while the α‐to‐β transition starts from the hexamers. Converted β‐sheet‐rich oligomers first form β‐barrel structures as intermediates before aggregating into cross‐β nanofibrils. This study uncovers a complete picture of hIAPP8‐20 peptide oligomerization, aggregation nucleation via conformational conversion, formation of β‐barrel intermediates, and assembly of cross‐β protofibrils, thereby shedding light on the aggregation of full‐length hIAPP, a hallmark of pancreatic beta‐cell degeneration. 相似文献
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Sustainable Solid‐State Supercapacitors Made of 3D‐Poly(3,4‐ethylenedioxythiophene) and κ‐Carrageenan Biohydrogel
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Georgina Fabregat L'udmila Hodásová Luis J. del Valle Francesc Estrany Carlos Alemán 《Advanced Engineering Materials》2018,20(7)
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S. Holdcroft 《Advanced materials (Deerfield Beach, Fla.)》2001,13(23):1753-1765
π‐Conjugated polymers show promise as active materials in application areas such as microelectronics, electro‐optics, opto‐electronics, and photonics. A critical feature in this emerging technology is device fabrication and the reproducible deposition of active material. This review focuses on current trends in the spatial deposition of conjugated polymers. 相似文献
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M. Fröhlich A. Ebach‐Stahl R. Braun C. Leyens 《Materialwissenschaft und Werkstofftechnik》2007,38(9):667-673
Engine designers show continued interest in γ‐TiAl based titanium aluminides as light–weight structural materials to be used at moderately elevated temperatures. Although alloy development has made significant progress in terms of mechanical properties and environmental resistance, protective coatings have been developed that help to extend the lifetime of these alloys significantly. The major challenge of coating development is to prevent the formation of fast growing titania. Furthermore, changes of coating chemistries at high temperatures have to be considered in order to avoid rapid degradation of the coatings due to interdiffusion between substrate and coating. The paper describes recent work of the authors on different coatings produced by means of magnetron sputter technique. Thin ceramic Ti‐Al‐Cr‐Y‐N layers tested at 900 °C exhibited poor oxidation resistance. In contrast, intermetallic Ti‐Al‐Cr, Si‐based and aluminum rich Ti‐Al coatings were tested at exposure temperatures up to 950 °C for 1000h resulting in reasonable and partially excellent oxidation behaviour. 相似文献
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