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      • KCI등재

        Influences of characteristics of the alkaline activator on the compressive strength and microstructure of the fly ash-based geopolymer pastes

        Qingbo Tian,Daquan Sun,Zeyu Gu,Zhijie Lv 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.3

        The effects of Na2O content, water to binder (W/B) ratio, and the modulus (Ms) of alkaline activator solution on a fly ash-basedgeopolymer paste (FGP) were investigated. The microstructure of the pastes was observed and characterised by Scanningelectron microscope and X-ray diffraction. The results showed that the increase of Na2O content and Ms resulted in an increasein compressive strength: an increase in the W/B ratios led to a decreased compressive strength. It was found that the highcompressive strength was achieved as Ms of the alkaline activator was 1.5, and the content of this activator was 8.0-12.0% bythe proportion of Na2O to fly ash. The compressive strength of these pastes was between 26.5-39.6 MPa at 28 days when theywere cured at 85 ºC for 1 h followed by curing under standard conditions. OH− concentration, determined by Na2O content,Ms, and water content, seemed to be a crucial parameter influencing the compressive strength. There was an optimal OH−concentration range, in which the appropriate strength of geopolymer paste would be achieved. An increased alkaline contentpromoted the reaction between the mineral phases of the fly ash with the alkaline activator and the formation of an additionalsodium aluminosilicate hydrate (N-A-S-H) gel.

      • KCI등재

        Effect of characteristics of submicrometer powder on the sintering behaviors of Al2O3 ceramic

        Qingbo Tian,Jinshan Dai,Zhijie Lv,Tongguang Zhai 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.7

        The sintering behaviors of high purity Al2O3 ceramics prepared from a submicron-scale powder were investigated. The effectsof ball milling on the evolution of alumina powders’ compressibility, sinterability, grain growth and microstructure duringsintering process were studied. It was observed that the relative density of the Al2O3 ceramics increased with increasingcompaction pressure on the green compacts and the sintering temperature. However, the applied pressure had less influenceon the relative density of ceramics sintered from green compact with narrower size distribution and finer powder. The fastgrain growth of the Al2O3 ceramics occurred in different temperature ranges and was influenced by milling time and formingmethods. The effect of milling on the microstructural evolution of alumina during sintering was also discussed.

      • KCI등재

        Overexpression of the potato StEPF2 gene confers enhanced drought tolerance in Arabidopsis

        Yanli Wang,Tian Xie,Chunli Zhang,Juanjuan Li,Zhi Wang,Hongbing Li,Xiping Liu,Li-Na Yin,Shi-Wen Wang,Sui-Qi Zhang,Xiping Deng,Qingbo Ke 한국식물생명공학회 2020 Plant biotechnology reports Vol.14 No.4

        Epidermal patterning factor 2 (EPF2) is a negative regulator of stomatal development, and is essential for plant growth, development, and environmental stress responses. However, the role of EPF2 in potato (Solanum tuberosum) has not been investigated to date. Here, we cloned and characterized the potato EPF2-like gene (StEPF2). StEPF2 is predominantly intercellular space localized and its transcripts were rhythmically expressed, and showed the highest expression in apical unexpanded leaves. Expression of StEPF2 was markedly down-regulated in response to abscisic acid and sodium chloride treatments; however, upon the application of polyethylene glycol, the expression of StEPF2 peaked at 4 h and then decreased gradually. Overexpression of StEPF2 in Arabidopsis (OE) substantially reduced stomatal density and photosynthetic rate, but had little effects on plant growth. Under drought stress, OE lines maintained higher photosynthetic rates, photosystem II efficiency, and instantaneous water use efficiency than wild-type (WT) plants. Moreover, OE lines showed less water loss and hydrogen peroxide accumulation in detached leaves compared with WT plants. Thus, our results suggest that StEPF2 acts as a negative regulator of stomatal development in potato, indicating that the role of EPF2 is conserved across plant species. Overall, StEPF2 represents an important target for the development of drought-tolerant potato cultivars via genetic engineering.

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        Influence of graphene oxide on the heat resistance of high strength concrete

        Guangming Meng,Yuwu Sui,Shu Liu,Qingbo Tian,Xinling Cui,Yuejian Wu 한양대학교 청정에너지연구소 2022 Journal of Ceramic Processing Research Vol.23 No.6

        The effect of Graphene Oxide (GO) on the thermal properties of high-strength concrete has been less studied. The mechanicalproperties, compactness, mineral composition and microstructure of the high-strength concrete with GO addition wereexamined by heat treatments at different temperatures. The results showed that the enhancement of the residual flexuralstrength with GO addition was greater than that of the residual compressive strength; GO addition had a significant effecton the mechanical properties of concrete treated at less than 500 ℃; Differential Scanning Calorimeter (DSC) test showed thatthe high-strength concrete with GO addition required more heats for its decomposition after 500 ℃; The internal pores/cracksof the high strength concrete with GO addition were reduced after the heat treatment at a high-temperature because theproducing of new crystals can improve the residual properties of the high-strength concrete.

      • KCI등재

        Effect of kaolin pretreatment on the structure and properties of metakaolin phosphate-based geopolymers

        Xin Yu,Chengxin Ren,Wenlong Xu,Lina Xu,Qingbo Tian 한양대학교 청정에너지연구소 2024 Journal of Ceramic Processing Research Vol.25 No.1

        This study focused on the preparation of metakaolin-based phosphate-activated geopolymers (MKPGs) using kaolin pretreatedat 950 °C for varying times as a precursor. It was found that kaolinite quickly transformed into amorphous metakaolin (MK)and then transitioned from a disordered phase to an ordered phase, resulting in precipitation of kyanite and mullite withincreasing calcination time. The formation of the kyanite phase had an adverse effect on geopolymerization, which causeda decrease in the strength of the MKPGs. The precipitation of the mullite phase hindered the geopolymerization reactionbetween phosphoric acid and MK, and the geopolymer failed to solidify. As the calcination time increased from 10 min to 60min, the compressive strength of the geopolymers increased and then decreased. The maximum strength of the geopolymerscreated from MK calcined for 30 min was 132.1 MPa.

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