Ionic transportation and chemical stability of high-endurance porous polyethylene separator for vanadium redox flow batteries

Jung, Ho-Young,Moon, Geon-O,Sadhasivam, T.,Jin, Chang-Soo,Park, Won-Shik,Kim, Hee-Tak,Roh, Sung-Hee Elsevier 2018 Solid state ionics Vol.327 No.-

<P><B>Abstract</B></P> <P>To confirm the viability of a porous polyethylene (PE) separator for using in vanadium redox flow batteries (VRFBs), we conduct a comparative electroanalytical and chemical stability studies of the PE separator and Nafion 212 membrane. We characterize the physicochemical properties of the separator, such as water uptake, dimensional change, and ion conductivity, and analyze its structural and compositional features using thermogravimetric analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy. We also test the chemical stability of the separator against highly oxidative V<SUP>5+</SUP> ions and the cell performance of VRFB using PE separator to assess practical applicability. In chemical stability, the change of VO<SUB>2</SUB> <SUP>+</SUP> ion to VO<SUP>2+</SUP> ion is considerably lowered by the PE separator (0.01 mmol/L) than the Nafion 212 (0.27 mmol/L), which indicates that the PE separator possesses higher chemical stability. The energy efficiency of the VRFB with the PE separator is lower than that obtained with Nafion 212. However, the chemical stability of PE separator is 27 times higher than that of Nafion 212, indicating that its use will promote the long-term operation of the VRFB system. Hence, the PE separator can be considered a cost-effective option for VRFB operation, with appropriate modifications to its thickness, surface properties and pore structure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We assessed a PE separator as a probable alternative to costly Nafion membranes. </LI> <LI> PE separator exhibited comparable efficiencies to those of the Nafion 212. </LI> <LI> PE separator revealed higher chemical stability than Nafion 212 membrane in VO<SUB>2</SUB> <SUP>+</SUP>. </LI> <LI> PE separator is more suitable for long service life of VRFB. </LI> </UL> </P>

Stability of H2O2 as an Oxidizer for Cu CMP

Do-Won Lee,김태군,김상용,장의구,Nam-Hoon Kim 한국전기전자재료학회 2005 Transactions on Electrical and Electronic Material Vol.6 No.1

Chemical mechanical polishing is an essential process in the production of copper-based chips. On this work, the stability of hydrogen peroxide (H2O2) as an oxidizer of copper CMP slurry has been investigated. H2O2 is known as the most common oxidizer in copper CMP slurry. But H2O2 is so unstable that its stabilization is needed using as an oxidizer. As adding KOH as a pH buffering agent, stability of H2O2 decreased. However, H2O2 stability in slurry went up with putting in small amount of BTA as a film forming agent. There was no difference of H2O2 stability between pH buffering agents KOH and TMAH at similar pH value. Addition of H2O2 in slurry in advance of bead milling led to better stability than adding after bead milling. Adding phosphoric acid resulted in the higher stability. Using alumina C as an abrasive was good at stabilizing for H2O2.

Solubility, stability, and bioaccessibility improvement of curcumin encapsulated using 4-α-glucanotransferase-modified rice starch with reversible pH-induced aggregation property

Park, Hye Rin,Rho, Shin-Joung,Kim, Yong-Ro Elsevier 2019 Food hydrocolloids Vol.95 No.-

<P><B>Abstract</B></P> <P>Curcumin is a polyphenolic compound with anti-cancer, anti-inflammatory and anti-oxidant effects. However, its application in the food industry is very limited owing to its low water solubility and chemical stability. In the present study, 4<I>α</I>GTase-treated rice starch (GS) was prepared by treating rice starch with 4-<I>α</I>-glucanotransferase (4<I>α</I>GTase) for 1 h (1 GS) and 96 h (96 GS), and the physicochemical properties of GS were analyzed. Moreover, the capability of GS to improve the encapsulation efficiency and stability of curcumin by forming complexes was investigated in comparison with maltodextrin (MD) and β-cyclodextrin (CD). GS is known to contain cyclic glucans and amylopectin clusters that contribute to its complex forming capability with bioactive compounds. Upon encapsulation with 1 GS and 96 GS, curcumin solubility increased by 2,241- and 2,846-fold, respectively. UV stability of the encapsulated curcumin with 96 GS also improved by 1.83-fold. GS was effective under all pH conditions except for 96 GS under acidic condition, as well as curcumin encapsulated with 1 GS and 96 GS exhibited 11.53- and 11.27-fold increase in bioaccessibility. The increased stability of curcumin within GS may be attributed to the unique molecular structure of GS interacting with curcumin, as suggested by chromatography and Fourier transform infrared spectroscopy. Also, the improved bioaccessibility of curcumin encapsulated with 96 GS even with lower pH stability at acidic pH seems to be partly attributed to reversible pH-induced aggregation of 96 GS. These results suggest that GS could act as a novel food-grade host material to improve the chemical stability of curcumin.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Rice starch was treated by 4αGTase to alter structure and functionality. </LI> <LI> GS treated by 4αGTase for 96 h showed reversible pH-induced aggregation property. </LI> <LI> Curcumin was successfully encapsulated using 4αGTase-treated starch (GS). </LI> <LI> GS was more effective to protect curcumin than maltodextrin and β-cyclodextrin. </LI> <LI> GS highly improved pH, UV stability and bioaccessibility of curcumin. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Enhanced Chemical Stability of D-Cycloserine via Tablet Form Containing Magnesium Oxide as an Alkali Stabilizer

Jung Suk Kim,이상민,김동식,김동욱,김경수,조관형,Dong Xun Li,진성규,최한곤 대한화학회 2020 Bulletin of the Korean Chemical Society Vol.41 No.1

The purpose of this study was to improve the chemical stability of D-cycloserine via tablet form containing an alkali stabilizer. The influence of alkalizing agents on the stability of D-cycloserine was investigated at 60 °C/75% RH for 2?days. The drug stability was evaluated with the D-cycloserine-loaded tablets prepared with various amounts of magnesium oxide using direct compression method. Compared to D-cycloserine powder and a commercial D-cycloserine-loaded product, the long-term drug stability on the chosen tablet was assessed at 40, 60, and 40 °C/75% RH during 6?months. Amongst the stabilizers investigated, magnesium oxide most improved the stability of D-cycloserine at the accelerated stress condition. The magnesium oxide/drug ratio of 1 and 2 showed higher remaining drug concentrations than those less than 0.5; however, two formers gave no significant difference in the remaining drug concentrations. Amongst the tablets tested, the formulation composed of D-cycloserine, magnesium oxide, and talc at the weight ratio of 250/250/5 most increased the stability of D-cycloserine. Additionally, due to the alkali and water-proofing property of magnesium oxide, this tablet improved the stability of D-cycloserine compared to the drug powder and commercial product. Hence, this novel tablet with enhanced drug stability would be a candidate for oral pharmaceutical product of D-cycloserine.

Experimental analysis of the impact of ionic concentration and type on shale’s stability: dilute vs. concentrated salt solutions

Alkhaldi M. M.,AL-Bazali T. M. 한국자원공학회 2023 Geosystem engineering Vol.26 No.4

Wellbore instability in shale formations is one of the most bothersome problems leading to significant changes in shale’s petrophysical, mechanical, and chemical properties, and could cost billions of dollars annually. Drilling fluid’s ionic composition is one of the factors affecting wellbore stability. This paper investigates the impact of chemical osmosis, ionic diffusion, and diffusion osmosis on the stability of shale, identify the critical salt concentration, and examine the impact of ionic type and concentration on shale’s stability. Experimental methods include utilisation of two different shale cores (I and II), in which each core is cut into several samples, to conduct linear expansion and gravimetric measurement tests using different salt solutions (KCl, NaCl, and CaCl2) of various salt concentrations. Results show that the critical salt concentrations of shale I and II is 8 w/w%. Chemical osmosis is found to be a reliable method for water extraction out of shale if the critical salt concentration value is not surpassed. Beyond this value, ionic diffusion and diffusion osmosis in shale I and II were adversely affecting shale’s stability through swelling. The swelling and gravimetric ions and water uptake tests showed that shale is a leaky semi-permeable membrane, and that chemical osmosis could be jeopardised by ionic transport into shale. In this study, the cation type (Na+, K+, Ca+2) that makes up the salt was varied. The impact of cation type on the stability of shale was clear as the anion type was fixed. Since both cations and anions tend to diffuse into shale in the presence of a concentration gradient, it is proposed for future work to study the combined impact of cation and anion types on shale’s stability by varying the anion and cation types.

Approaches to Improvement in the Stability of Polymer Electrolyte Membranes

신동원,( Abdul Kodir ),( Juniko Nur Pratama ),신성희,배병찬 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

Polymer electrolyte membrane fuel cell (PEMFC) is an eco-friend energy device. It has high energy efficiency and wide power ranges. Polymer electrolyte membrane (PEM) is one of key components in PEMFC. Electrochemical performance of PEM has been improved, whereas long-term durability of PEM needs to be further improved. There are two kinds of stability issues in PEM. One is chemical stability and the other is mechanical stability. In this study, we investigated the effect of radical scavengers on the chemical stability of PEM, while the mechanical stability of PEM was improved by fabricating reinforced composite membrane. Radical scavengers improved chemical stability of both perfluorosulfonic acid polymers and hydrocarbon-based polymers. In addition, reinforced composite membranes had better mechanical properties than dense membranes.

Order–disorder structural tailoring and its effects on the chemical stability of (Gd, Nd)2(Zr, Ce)2O7 pyrochlore ceramic for nuclear waste forms

Wang Yan,Wang Jin,Zhang Xue,Li Nan,Wang Junxia,Liang Xiaofeng 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.7

Series of unequal quantity Nd/Ce co-doped ceramic nuclear waste forms, (Gd, Nd)2(Zr, Ce)2O7, were prepared to tailor its ordered pyrochlore or disordered fluorite structure. The phase transition, microtopography, and elemental composition of the ceramic samples were systematically investigated, especially the effect of order-disorder structure on the chemical stability. It was confirmed that unequal quantity of Nd/Ce could synchronously replace the Gd/Zr-sites of Gd2Zr2O7. And the phase transition of order-disorder structure could be successfully tailored by regulating the average cationic radius ratio of (Gd, Nd)2(Zr, Ce)2O7 series. The elements of Gd, Nd, Zr, and Ce are uniformly distributed in the ordered or disordered structures. The MCC-1 leaching results showed that (Gd, Nd)2(Zr, Ce)2O7 pyrochlore ceramic nuclear waste forms had excellent chemical stability, whose elements' normalized leaching rates were as low as 104 -107 g‧m2 ‧d1 after 7 days. In particular, the chemical stability of disordered structure was superior to that of ordered structure. It was proposed that the force constant and the closest packing were changed with the structure transformation resulting the chemical stability difference

Stability of H₂O₂ as an Oxidizer for Cu CMP

Lee, Do-Won,Kim, Tae-Gun,Kim, Nam-Hoon,Kim, Sang-Yong,Chang, Eui-Goo The Korean Institute of Electrical and Electronic 2005 Transactions on Electrical and Electronic Material Vol.6 No.1

Chemical mechanical polishing is an essential process in the production of copper-based chips. On this work, the stability of hydrogen peroxide ($H_{2}O_{2}$) as an oxidizer of copper CMP slurry has been investigated. $H_{2}O_{2}$ is known as the most common oxidizer in copper CMP slurry. But $H_{2}O_{2}$ is so unstable that its stabilization is needed using as an oxidizer. As adding KOH as a pH buffering agent, stability of $H_{2}O_{2}$ decreased. However, $H_{2}O_{2}$ stability in slurry went up with putting in small amount of BTA as a film forming agent. There was no difference of $H_{2}O_{2}$ stability between pH buffering agents KOH and TMAH at similar pH value. Addition of $H_{2}O_{2}$ in slurry in advance of bead milling led to better stability than adding after bead milling. Adding phosphoric acid resulted in the higher stability. Using alumina C as an abrasive was good at stabilizing for $H_{2}O_{2}$.

Chemical/morphological transition behavior of lithium phosphorus oxynitride solid-electrolyte in air: An analytical approach based on X-ray photoelectron spectroscopy and atomic force microscopy

Yun, Dong-Jin,Lim, Sungjin,Won, Jung Yeon,Kim, Kihong,Lee, HyungIk,Hwang, Junsik,Chung, JaeGwan,Kim, Yong Su,Kwon, Young-Nam,Lee, Eunha,Baik, Jaeyoon,Yang, Woo-Young Elsevier 2018 Journal of Power Sources Vol.399 No.-

<P><B>Abstract</B></P> <P>Lithium phosphorus oxynitride and lithium phosphate layers are prepared by controlling nitrogen composition using an optimized chemical vapor deposition process. Besides the predictable lithium phosphate layer decomposition process, progressive changes are observed in the lithium phosphorus oxynitride layer in air over time. These changes influence both the performance and stability of Lithium phosphorus oxynitride, utilized as solid-electrolytes or interface barriers in batteries. Therefore, to clarify the transition mechanism of them in air, a unique experiment is designed based on x-ray photoelectron spectroscopy. The results indicate that changes in the chemical structures of lithium phosphorus oxynitride and lithium phosphate occurred alongside morphological variations. Lithium phosphorus oxynitride layers undergo steady attacks by reactive gases in air, such as O<SUB>2</SUB>, CO<SUB>2</SUB>, and H<SUB>2</SUB>O, resulting in an increased number of imperfect or dangling bonds and internal chemical reactions that in turn cause morphological changes. In addition, a graphene layer is employed to reduce the reactions of Lithium phosphorus oxynitride layers with reactive gases. The results show that the graphene-coated domains have relatively lower degradation rate than other regions. Overall, our results reveal the stability problems of lithium phosphorus oxynitride and lithium phosphate by demonstrating significant changes in the chemical/morphological structures exposed to air.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The nitrogen composition effects on LiPON stability are clarified. </LI> <LI> The degradation mechanism of LiPON solid-electrolyte in air is illustrated. </LI> <LI> X-ray spectroscopy and atomic force microscopy explain well the degradation process. </LI> <LI> Graphene layer can slow down the aging process of LiPON solid-electrolyte. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Study on Volume Stability of Chemical Foaming Cement Paste

Wen-bin Liu,Xiong Zhang 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.7

The paper is aimed at investigating the mechanism and cause of volume instability of chemical foaming cement paste. Volume stability were studied by introducing ultimate shear stress of the technical parameter. The research shows that the ultimate shear stress should be between 25 Pa and 40 Pa when the paste was mixed for 30 minutes, and the ultimate shear stress reached 75 Pa when the paste was mixed for 2 hours. The paste is not easy to collapse, sink. By force analyzing of the paste, mathematical model of the paste was established. The ultimate shear stress was controlled by water-binder ratio, quick setting agent and foam stabilizer. The result shows that the water-binder ratio is 0.54~0.58, the setting accelerator is 2% of cement content, and the foam stabilizer is 1.6% of cement content, which played an important role in the volume stability of the paste.