Cyclic cold isostatic pressing and improved particle packing of coarse grained oxide ceramics for refractory applications

This study investigated the cold isostatic pressing of coarse grained alumina refractories applying either a cyclic pressure increase or a cycling at maximum pressure. Additionally the effects of the maximum pressure and the particle size distribution on physical, mechanical and thermomechanical properties were analyzed. The cyclic pressure increase resulted in a slightly higher apparent density and lower apparent porosity. A cycling at maximum pressure decreased the median pore size to some extent. Remarkably, an optimized particle size distribution resulted in a lower apparent porosity, lower median pore size and in a higher Young's modulus before and after thermal shock together with a slightly lower relative decrease of the Young's modulus. A higher pressing pressure which decreased the apparent porosity did not affect the Young's modulus. Thus, apparently the optimized particle size distribution improved the particle packing which was associated with a smaller median pore size. This smaller pore size increased the number of pores relative to the total porosity, which then acted as points of crack initiation and crack deflection limiting the length of propagating cracks in case of thermal shock. Thus, tailoring the pore size distribution is a promising starting point to improve the thermomechanical properties of refractories.     

Periodic reactive flow simulation: Proof of concept for steam cracking coils

Streamwise periodic boundary conditions (SPBCs) have been successful in reducing the computational cost of simulating high aspect ratio processes. Extending beyond the classic assumptions of constant property flows, a novel approach incorporating non‐equilibrium kinetics was developed and implemented for the simulation of an industrial propane steam cracker. Comparison with non‐periodic benchmarks provided validation as relative errors on the main product yields were consistently below 1% for different reactor configurations. A further order‐of‐magnitude reduction of the radial errors on product concentrations was obtained via an intuitive correction method based on the concept of local fluid age. The computational speedup achieved through application of SPBCs was a factor 16–250 compared to the non‐periodic simulations. The presented methodology thus serves as a quick screening tool for the development of novel reactor designs and unlocks the potential for using more elaborate kinetic models or a more fundamental approach toward turbulence modeling. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1715–1726, 2017     

Design and Fabrication of Transparent and Gas‐Tight Optical Windows in Low‐Temperature Co‐Fired Ceramics

Low‐temperature co‐fired ceramics (LTCC) enable the fabrication of microfluidic elements such as channels and embedded cavities in electrical devices. Hence, LTCC facilitate the realization of complex and integrated microfluidic devices. Examples can be applied in many areas like reaction chambers for synthesis of chemical compounds. However, for many applications it is necessary to have an optically transparent interface to the surroundings. The integration of optical windows in LTCC opens up a wide field of new and innovative applications such as the observation of chemiluminescent reactions. These chemical reactions emit electromagnetic radiation and thus offer a method for noninvasive detection. Thin glasses (≤500 μm) were bonded by thermocompression onto a LTCC substrate. As the bonding agent, a glass frit paste was used. Borosilicate glasses, fused silica as well as silicon were successfully bonded onto LTCC. To join materials with a large coefficient of thermal expansion mismatch (i.e., fused silica and LTCC), it is necessary to limit the heat input to the bond interface. Therefore, a heating structure was integrated into the LTCC substrate beneath the bond interface. This bonding process provides a gas‐tight optical port with a high bond strength.     

Single and Polycrystalline Transparent Ceramic Armor with Different Crystal Structure

Contrary to the moderate ballistic advantage of Al₂O₃ ceramics over MgAl₂O₄ polycrystals, the present study shows a reverse ratio of the ballistic strength of alumina and spinel single crystals: Spinel single crystals outperform sapphire and exhibit a similarly high stability as submicrometer Al₂O₃ ceramics. The results correlate with different cleavage of single crystalline spinel and sapphire, changing the fragmentation on ballistic impact.     

Multtphase Materials with Lignin. III. Polyblends with Ethylene-Vinyl Acetate Copolymers

Abstract

Organosolv lignin (OSL) from red oak, and its corresponding hydroxypropyl lignin (HPL) derivative, were blended in the melt with polyethylene and with ethylene-vinyl acetate (EVA) copolymer, and injection molded. Lignin (derivative) content and vinyl acetate (VA) content both served as process variables. All mixtures produced immiscible blends, both by scanning electron microscopy and dynamic mechanical analysis. However, the compatibility of the two polymers increased with VA content. Both lignin products proved to be effective modulus builders, but. HPI, was more effective than OSL at VA contents above 20%. Modulus increased roughly in accordance with the rule of mixing. Inferior tensile strength properties were observed with the EVA copolymer if VA content was below 10%, and superior characteristics were noted in materials containing more than 25% VA and between 5 and 20% HPL.     

Conversion of Ethene to Propene by a Dual Function NiSO4/Re2O7/γ-Al2O3 Catalyst

A NiSO₄/Re₂O₇/γ-Al₂O₃ catalyst was prepared by co-impregnation using an aqueous solution of NiSO₄ and [NH₄][ReO₄], which catalyzes direct conversion of ethene to propene at mild reaction condition (323 K, 1 atm). Catalyst deactivation may be caused by coke formation. The two catalytic components appear to work independently of each other.     

Impact of an Altered Wnt1/β-Catenin Expression on Clinicopathology and Prognosis in Clear Cell Renal Cell Carcinoma

In renal cell carcinoma (RCC), single members of the Wnt/β-catenin signaling cascade were recently identified to contribute to cancer progression. However, the role of Wnt1, one of the key ligands in β-catenin regulation, is currently unknown in RCC. Therefore, alterations of the Wnt1/β-catenin axis in clear cell RCC (ccRCC) were examined with regard to clinicopathology, overall survival (OS) and cancer specific survival (CSS). Corresponding ccRCCs and benign renal tissue were analyzed in 278 patients for Wnt1 and β-catenin expression by immunohistochemistry in tissue microarrays. Expression scores, including intensity and percentage of stained cells, were compared between normal kidney and ccRCCs. Data was categorized according to mean expression scores and correlated to tumor and patients’ characteristics. Survival was analyzed according to the Kaplan-Meier and log-rank test. Univariable and multivariable Cox proportional hazard regression models were used to explore the independent prognostic value of Wnt1 and β-catenin. In ccRCCs, high Wnt1 was associated with increased tumor diameter, stage and vascular invasion (p ≤ 0.02). High membranous β-catenin was associated with advanced stage, vascular invasion and tumor necrosis (p ≤ 0.01). Higher diameter, stage, node involvement, grade, vascular invasion and sarcomatoid differentiation (p ≤ 0.01) were found in patients with high cytoplasmic β-catenin. Patients with a high cytoplasmic β-catenin had a significantly reduced OS (hazard ratio (HR) 1.75) and CSS (HR 2.26), which was not independently associated with OS and CSS after adjustment in the multivariable model. Increased ccRCC aggressiveness was reflected by an altered Wnt1/β-catenin signaling. Cytoplasmic β-catenin was identified as the most promising candidate associated with unfavorable clinicopathology and impaired survival. Nevertheless, the shift of membranous β-catenin to the cytoplasm with a subsequently increased nuclear expression, as shown for other malignancies, could not be demonstrated to be present in ccRCC.