Comparison of the activities of C2N and BCNO towards Congo red degradation

An n-type organic carbon nitride semiconductor, C2N, was synthesized by the pyrolysis of uric acid, and its properties were investigated by scanning electron and transmission electron microscopies, X-ray powder diffraction, and vibrational, UV-visible and X-ray photoelectron spectroscopies. This novel material, composed of crystalline flakes, featured a broad absorption centered at 700¿nm, possibly due to charge transfer, and a 2.49¿eV band gap. Its catalytic performance was assessed for the treatment of effluents with the diazo dye Congo red, comparing it with that of boron carbon nitrogen oxide, BCNO. Both wide band gap semiconductors exhibited decolorizing activity in the dark, although the mechanisms were different and were not photocatalytic: BCNO was more effective towards the adsorption-coordination due to the presence of B-O, while C2N was effective towards the adsorption and the advancement of the oxidation reaction. Their kinetic constants (0.19 and 0.02 min-1 for BCNO and C2N, respectively) were comparable to those of intermetallic compounds studied for azo dyes degradation in dark conditions. In view of the high color removal efficiency (97% after 20¿min) and good reusability of BCNO, this study suggests a potential application of this catalyst for wastewater treatment, alone or in combination with C2N

Mechanical, pH and Thermal Stability of Mesoporous Hydroxyapatite

The stability of mesoporous hydroxyapatite (HAP) powder was studied following treatments of ultrasound, pH and heating. HAP was found to be mechanically stable up to (and including) 1 h continuous ultrasonic treatment in water. The HAP structure was also stable to pH, evidenced by practically identical XRD and FTIR spectra over the pH range 2–12. The surface area increased progressively with increasing acidity, reaching a maximum of 121.9 m 2 g −1 at pH 2, while alkaline conditions decreased the surface area to a minimum of 55.4 m 2 g −1 at pH 12. Heating in air had a significant influence on the structural and morphological properties of HAP, which underwent dehydroxylation to form oxyhydroxyapatite (OHAP) at temperatures ≥ 650 °C, and β-tricalcium phosphate (β-TCP) ≥750 °C. The surface area decreased at elevated temperatures due to agglomeration of HAP crystals by sintering, which was associated with an increased particle size

Can Ultrasound or pH Influence Pd Distribution on the Surface of HAP to Improve Its Catalytic Properties in the Dry Reforming of Methane?

The influence of ultrasound and different pH pre-treatments during the metal doping/modification of a hydroxyapatite (HAP) support is investigated. HAP is first synthesised via a hard-template synthetic route using carbon nanorods followed by their full physiochemical characterisation. The HAP was found to be crystalline and comprised a mesoporous structure as observed via XRD and nitrogen adsorption with a BET surface area of 97.57 (±1.16) m2 g−1. Ultrasound-assisted ion exchange (IE) and incipient wetness impregnation (IW) methodologies were employed to decorate the surface of HAP with Pd0 and are compared to previous procedures. The influence of pH upon the distribution of Pd0 throughout the samples during the doping process is also studied. All the prepared samples were evaluated for their catalytic activity towards dry reforming of methane (DRM) and the reaction was monitored via a thermal conductivity detector, coupled with gas chromatography (GC-TCD). It was found that ultrasound-assisted IE significantly accelerated the process from 3 days to 3 h and with the Pd0 metal remaining highly distributed upon the HAP with minor changes in catalytic conversions. Moreover, the ultrasound-assisted IW method successfully improved the Pd0 distribution and catalytic performance. On the other hand, the dispersion of the metal was unaffected after pH treatments in IE with no catalytic improvements observed, in contrast to IW, where considerable increase in metal distribution and subsequently catalytic performance was observed

Whitney Young and the Black Architectural Imagination

This essay considers a speech delivered by Whitney M. Young Jr. in 1968 at the American Institute of Architects’ annual conference. The essay argues that Young’s call for greater diversity and for greater engagement with African American neighborhoods across cities in the U.S. crystalized concepts such as affirmative action and community participation that were not yet named as such, but would become emulated in the three decades that followed. Young’s speech provides new insight into how architecture might engage in conversations around race and the politics of injustice. By focusing on an important Civil Rights leader, the essay highlights the relationship between race and architecture – not only as it existed in 1968 – asking how the discipline can cultivate a contemporary concept of a critical theory of race and architecture.ISSN:2611-934XISSN:2532-645

Black Architectures: Race, Pedagogy, and Practice, 1957–68

Between 1964 and 1968, protests against anti-Black racism and police violence transformed cities across the United States. Against the backdrop of the civil rights movement and the emergent Black Power movement, these so-called “race riots” elicited a diverse groundswell of political responses from architects, city officials, universities and activists alike. On the one hand, this racial unrest sowed the seeds for discriminatory “law and order” measures that increased policing in Black neighborhoods while pathologizing and criminalizing Black neighborhoods. On the other hand, the “riots” encouraged a generation of thinkers, designers, and activists to critique and resist a white-led architecture and design world. This dissertation brushes against the archival grain and the existing scholarship by centering the Black architectural imagination that was very much present, but often underestimated, in this time period. I examine architects and architects-in-training, writers, and cultural producers who imagined Black futurities and created alternative life-worlds within, against, and in spite of the bastions of white elitism in architecture. At the same time, this dissertation reads the interrelationships between architecture, universities, city governance, and racial uprisings to narrate a new architectural history that takes seriously the role that race and racism played in shaping architectural pedagogies in the 1960s. Three case studies form the basis of this investigation: (1) the Civic Design Program at the University of Pennsylvania in Philadelphia; (2) the Yale School of Art and Architecture in New Haven, Connecticut; and (3) an institutional collaboration between Columbia University and the Museum of Modern Art in New York City