Tuning the Transport Properties of Gases in Porous Graphene Membranes with Controlled Pore Size and Thickness

Porous graphene membranes emerged as promising alternatives for gas separation applications due to their atomic thickness enabling ultra-high permeance, but suffer from low gas selectivity. Whereas decreasing the pore size below 3 nm is expected to increase the gas selectivity due to molecular sieving, it is rather challenging to generate large number of uniform small pores on the graphene surface. Here, we introduce a pore narrowing approach via gold deposition onto porous graphene surface to tune the pore size and thickness of the membrane to achieve large number of small pores. Through our systematic approach, we determined the ideal combination as pore size below 3 nm obtained at the thickness of 100 nm to attain high selectivity and high permeance. The resulting membrane showed a H2 /CO2 separation factor of 31.3 at H2 permeance of 2.23 × 105 GPU (1 GPU = 3.35 × 10-10  mol s-1 m-2 Pa-1 ), which is the highest value reported to date in the 105 GPU permeance range. This result is explained by comparing the predicted binding energies of gas molecules with the Au surface, -5.3 versus -21 kJ mol-1 for H2 and CO2 , respectively, increased surface-gas interactions and molecular sieving effect with decreasing pore size. This article is protected by copyright. All rights reserved

Polymers based on norbornene derivatives

This study presents the influence of exo,exo-N,N'- hexylene-di(5-norbornene-2,3-dicarboximide) on the degree of cross-linking and glass transition temperature of the polymers obtained from a mixture of dimethyl esters of exo,exo- and endo,endo-5-norbornene-2,3-dicarboxylic acid. It was found that exo,exo-N,N'- hexylene-di(5-norbornene-2,3-dicarboximide) can be used as a cross-linking agent in ROMP. Addition of the cross-linking agent leads to an increase in the degree of cross-linking polymers. The glass transition temperature of polymers increases with concentration increasing of the crosslinking agent

Fast light-switchable polymeric carbon nitride membranes for tunable gas separation

Switchable gas separation membranes are intriguing systems for regulating the transport properties of gases. However, existing stimuli-responsive gas separation membranes suffer from either very slow response times or require high energy input for switching to occur. Accordingly, herein, we introduced light-switchable polymeric carbon nitride (pCN) gas separation membranes with fast response times prepared from melamine precursor through in-situ formation and deposition of pCN onto a porous support using chemical vapor deposition. Our systematic analysis revealed that the gas transport behavior upon light irradiation is fully governed by the polarizability of the permeating gas and its interaction with the charged pCN surface, and can be easily tuned either by controlling the power of the light and/or the duration of irradiation. We also demonstrated that gases with higher polarizabilities such as CO2 can be separated from gases with lower polarizability like H2 and He effectively with more than 22% increase in the gas/CO2 selectivity upon light irradiation. The membranes also exhibited fast response times (<1 s) and can be turned “on” and “off” using a single light source at 550 nm

Fast light-switchable polymeric carbon nitride membranes for tunable gas separation

Switchable gas separation membranes are intriguing systems for regulating the transport properties of gases. However, existing stimuli-responsive gas separation membranes suffer from either very slow response times or require high energy input for switching to occur. Accordingly, herein, we introduced light-switchable polymeric carbon nitride (pCN) gas separation membranes with fast response times prepared from melamine precursor through in-situ formation and deposition of pCN onto a porous support using chemical vapor deposition. Our systematic analysis revealed that the gas transport behavior upon light irradiation is fully governed by the polarizability of the permeating gas and its interaction with the charged pCN surface, and can be easily tuned either by controlling the power of the light and/or the duration of irradiation. We also demonstrated that gases with higher polarizabilities such as CO2 can be separated from gases with lower polarizability like H2 and He effectively with more than 22% increase in the gas/CO2 selectivity upon light irradiation. The membranes also exhibited fast response times (<1 s) and can be turned “on” and “off” using a single light source at 550 nm

The Seasonal Festivals and Special Days in Uzbekistan

Özbekistan’ın bağımsızlığına kavuşmasından sonra Sovyetler döneminde yasaklanan ya da hor görülen birçok örf ve adet hem resmi zeminde hem de halk arasında daha coşkulu kutlanmaya başlanmıştır. Özbeklerin yaşadığı Türkistan bölgesinin geçirdiği tarihi süreç günümüzde Özbek folklorundaki birçok uygulamanın ortaya çıkışında etkili olmuştur. Özbeklerin hayatında merasimler, mevsimsel, ailevi (gündelik hayat) ve dini merasimler şeklinle üç ana gruba ayrılır. Bu merasimlerden mevsimlere bağlı olanları Özbek toplumunun kültürel hayatında önemli yer tutmaktadır. Mevsime bağlı merasimler, kışa bağlı merasimler, bahara bağlı merasimler ve güz mevsimine bağlı merasimler şeklinde görülmektedir. Nevruz, Mehrcan, Sede, Gül Seyilleri, Hasıl Bayramı gibi bayram ve şenliklerde eski Türk inançlarının ve Özbekler öncesinde bölgeye yerleşmiş olan yerleşik unsurların ve komşu bölgelerdeki kültürlerin etkisini görmek mümkündür. Nevruz Orta Asya ve Orta Doğu halklarının eski geleneksel yeni yıl bayramıdır. Yine Lale Seyli Özbek halkının eski ve milli şenliklerinden biri olup, Harezm, Buhara ve Baysun’da Kızıl Gül (Gul-ı Surh), Kokand, İsfara, Taşkent, Çust gibi bazı yörelerde Lale Seyli, bazı yerlerde ise Bayçiçek şenliği gibi isimler ile düzenlenmiştir. Lale şenliği Nevruz bayramından sonra nisanın sonu mayısın başlarında laleler açıldığı dönemde gerçekleştirilmektedir. Bahar şenlikleri dışında güz mevsimlerinde de kutlanan özel gün ve şenlikler vardır. Bunlardan biri hasat bayramı olup günümüzde şehir merkezlerinde de kutlanmaya başlanmıştır.A lot of customs and traditions which were neither forbidden or despised in Soviet era began to be celabrated more enthusiasticly both in formal life and among the public after the Independence of Uzbekistan. The historical process experienced by Turkestan era and also where Uzbeks live affected to arise many practice in Uzbek folklore.Ceremonies in Uzbek life divided into three title as seasonal, daily and religious. Among these ceremonies, seasonal ceremonies take important place in Uzbek’s societies’ cultuel life. This seasonal ceremonies ara attached to winter, spring and autumn periods. It is possible to observe old Turkic beliefs, cultures of neighborhood regions and cultures of people who settled Turkestan before Uzbeks in the Nowruz, Mehircan, Sade, Gul Seyli holidays and festivals. Nowruz is an old traditional new year holiday of societies who live in Middle Asia and Middle East. Besides, Lale Seyli that is one of the old and national festival of the Uzbeks has been orginized in Khorezm, Bukhara and Baysun under the name of Kızıl Gul (Gul-ı Surh), in Kokand, İsfara, Tashkent and &Ccedil;ust under the name of Bay&ccedil;i&ccedil;ek and Lale Seyli. Tulip ceremony however, have been hold after Nowruz holiday that coincide with end of April and beginning of May when tulips were bloomed.Except for spring ceremonies, there were celabrated special days and ceremonies in automn. One of them is harvest ceremony and it is began to be celabrated in city centers today

The Seasonal Festivals and Special Days in Uzbekistan

WOS: 000354339900010A lot of customs and traditions which were neither forbidden or despised in Soviet era began to be celabrated more enthusiasticly both in formal life and among the public after the Independence of Uzbekistan. The historical process experienced by Turkestan era and also where Uzbeks live affected to arise many practice in Uzbek folklore.Ceremonies in Uzbek life divided into three title as seasonal, daily and religious. Among these ceremonies, seasonal ceremonies take important place in Uzbek's societies' cultuel life. This seasonal ceremonies ara attached to winter, spring and autumn periods. It is possible to observe old Turkic beliefs, cultures of neighborhood regions and cultures of people who settled Turkestan before Uzbeks in the Nowruz, Mehircan, Sade, Gul Seyli holidays and festivals. Nowruz is an old traditional new year holiday of societies who live in Middle Asia and Middle East. Besides, Lale Seyli that is one of the old and national festival of the Uzbeks has been orginized in Khorezm, Bukhara and Baysun under the name of Klzil Gul (Gul-1 Surh), in Kokand, isfara, Tashkent and cust under the name of Baygigek and Lale Seyli. Tulip ceremony however, have been hold after Nowruz holiday that coincide with end of April and beginning of May when tulips were bloomed. Except for spring ceremonies, there were celabrated special days and ceremonies in automn. One of them is harvest ceremony and it is began to be celebrated in city centers today