Synthesis of Activated Carbon from Rice Husk Using Microwave Heating Induced KOH Activation

Nguyen, Tuan Dung,Moon, Jung-In,Song, Jeong-Hwan,Kim, Taik-Nam Materials Research Society of Korea 2012 한국재료학회지 Vol.22 No.6

The production of functional activated carbon materials starting from inexpensive natural precursors using environmentally friendly and economically effective processes has attracted much attention in the areas of material science and technology. In particular, the use of plant biomass to produce functional carbonaceous materials has attracted a great deal of attention in various aspects. In this study the preparation of activated carbon has been attempted from rice husks via a chemical activation-assisted microwave system. The rice husks were milled via attrition milling with aluminum balls, and then carbonized under purified $N_2$. The operational parameters including the activation agents, chemical impregnation weight ratio of the calcined rice husk to KOH (1:1, 1:2 and 1:4), microwave power heating within irradiation time (3-5 min), and the second activation process on the adsorption capability were investigated. Experimental results were investigated using XRD, FT-IR, and SEM. It was found that the BET surface area of activated carbons irrespective of the activation agent resulted in surface area. The activated carbons prepared by microwave heating with an activation process have higher surface area and larger average pore size than those prepared by activation without microwave heating when the ratio with KOH solution was the same. The activation time using microwave heating and the chemical impregnation ratio with KOH solution were varied to determine the optimal method for obtaining high surface area activated carbon (1505 $m^2$/g).

Performance of Electric Double Layers Capacitor Using Activated Carbon Materials from Rice Husk as Electrodes

Nguyen, Tuan Dung,Ryu, Jae Kyung,Bramhe, Sachin N.,Kim, Taik-Nam Materials Research Society of Korea 2013 한국재료학회지 Vol.23 No.11

Activated carbon (AC) was synthesized from rice husks using the chemical activation method with KOH, NaOH, a combination of (NaOH + $Na_2CO_3$), and a combination of (KOH + $K_2CO_3$) as the chemical activating reagents. The activated carbon with the highest surface area (around $2000m^2/g$) and high porosity, which allows the absorption of a large number of ions, was applied as electrode material in electric double layer capacitors (EDLCs). The AC for EDLC electrodes is required to have a high surface area and an optimal pore size distribution; these are important to attain high specific capacitance of the EDLC electrodes. The electrodes were fabricated by compounding the rice husk activated carbons with super-P and mixed with polyvinylidene difluoride (PVDF) at a weight ratio of 83:10:7. AC electrodes and nickel foams were assembled with potassium hydroxide (KOH) solution as the electrolyte. Electrochemical measurements were carried out with a three electrode cell using 6 M KOH as electrolyte and Hg/HgO as the reference electrode. The specific capacitance strongly depends on the pore structure; the highest specific capacitance was 179 F/g, obtained for the AC with the highest specific surface area. Additionally, different activation times, levels of heating, and chemical reagents were used to compare and determine the optimal parameters for obtaining high surface area of the activated carbon.

Optical Properties of Opal Glass on the Various Contents of Chemical Composition

Nguyen, Tuan Dung,N., Bramhe Sachin,Kim, Ji Ho,Kim, Taik-Nam Materials Research Society of Korea 2013 한국재료학회지 Vol.23 No.1

Opal glass samples having different chemical compositions were synthesized and transparent glass was obtained after melting. The effects of $TiO_2$, $BaF_2$, and $CeO_2$ content on the color of the opal glass were studied by observing images of the opal samples and analyzing the results via ultraviolet visible spectroscopy and color spectrometry. The aesthetic properties of the opal glass were determined by studying the transmittance of visible light in the 400 nm to 700 nm range. The basic chemical composition of opal glass was $SiO_2$ 52.9 wt%, $Al_2O_3$ 12.35 wt%, $Na_2CO_3$ 15.08 wt%, $K_2CO_3$ 10.35 wt%, $Ca_3(PO)_4$ 4.41 wt%, $MgCO_3$ 1.844 wt%, $LiCO_3$ 2.184 wt%, and $TiO_2$ 0.882 wt%. The glass samples were prepared by varying the weight percentage of $TiO_2$, $BaF_2$, and $CeO_2$. The transmittance of visible light was decreased from 95 % to 75 % in the glass samples in which $TiO_2$ content was increased from 0 to 3.882 wt%. In the blue spectrum region, as the content of $TiO_2$ increased, the reflectance value was observed to become higher. This implies that $TiO_2$ content induces more crystal formation and has an important effect on the optical properties of the glass. The opalescence of opal samples that contained $CeO_2$ or $BaF_2$ is stronger than that in the samples containing $TiO_2$. Opal glass samples comprising $TiO_2$ had tetragonal lattice structures; samples including $CeO_2$ as an additive had cubic lattice structures (FCC, $CeO_2$).

WS2–WC–WO3 nano-hollow spheres as an efficient and durable catalyst for hydrogen evolution reaction

Van Nguyen Tuan,Do Ha Huu,Tekalgne Mahider,Van Le Quyet,Nguyen Thang Phan,Hong Sung Hyun,Cho Jin Hyuk,Van Dao Dung,Ahn Sang Hyun,Kim Soo Young 나노기술연구협의회 2021 Nano Convergence Vol.8 No.28

Transition metal dichalcogenides (TMDs), transition metal carbides (TMCs), and transition metal oxides (TMOs) have been widely investigated for electrocatalytic applications owing to their abundant active sites, high stability, good conductivity, and various other fascinating properties. Therefore, the synthesis of composites of TMDs, TMCs, and TMOs is a new avenue for the preparation of efficient electrocatalysts. Herein, we propose a novel low-cost and facile method to prepare TMD–TMC–TMO nano-hollow spheres (WS 2 –WC–WO 3 NH) as an efficient catalyst for the hydrogen evolution reaction (HER). The crystallinity, morphology, chemical bonding, and composition of the composite material were comprehensively investigated using X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The results confirmed the successful synthesis of the WS 2 –WC–WO 3 NH spheres. Interestingly, the presence of nitrogen significantly enhanced the electrical conductivity of the hybrid material, facilitating electron transfer during the catalytic process. As a result, the WS 2 –WC–WO 3 NH hybrid exhibited better HER performance than the pure WS 2 nanoflowers, which can be attributed to the synergistic effect of the W–S, W–C, and W–O bonding in the composite. Remarkably, the Tafel slope of the WS 2 –WC–WO 3 NH spheres was 59 mV dec −1 , which is significantly lower than that of the pure WS 2 NFs (82 mV dec −1 ). The results also confirmed the unprecedented stability and superior electrocatalytic performance of the WS 2 –WC–WO 3 NH spheres toward the HER, which opens new avenues for the preparation of low-cost and highly effective materials for energy conversion and storage applications.

Correction to: WS2–WC–WO3 nano‑hollow spheres as an efficient and durable catalyst for hydrogen evolution reaction

Van Nguyen Tuan,Do Ha Huu,Tekalgne Mahider,Van Le Quyet,Nguyen Thang Phan,Hong Sung Hyun,Cho Jin Hyuk,Van Dao Dung,Ahn Sang Hyun,Kim Soo Young 나노기술연구협의회 2021 Nano Convergence Vol.8 No.33

Following publication of the original article [1], the affiliation of the authors was incorrectly published in the article. The affiliation which was shown in supplementary information is correct. This has been corrected with this erratum.

Pancreaticoduodenectomy with superior mesenteric artery first-approach combined total meso-pancreas excision for periampullary malignancies: A high-volume single-center experience with short-term outcomes

Thanh Khiem Nguyen,Ham Hoi Nguyen,Tuan Hiep Luong,Kim Khue Dang,Van Duy Le,Duc Dung Tran,Van Minh Do,Hong Quang Pham,Hoan My Pham,Thi Lan Tran,Cuong Thinh Nguyen,Hong Son Trinh,Yosuke Inoue 한국간담췌외과학회 2024 Annals of hepato-biliary-pancreatic surgery Vol.28 No.1

Backgrounds/Aims: Pancreaticoduodenectomy (PD) is the only radical treatment for periampullary malignancies. Superior mesenteric artery (SMA) first approach combined with total meso-pancreas (MP) excision was conducted to improve the oncological results. There has not been any previous research of a technique that combines the SMA first approach and total MP excision with a detailed description of the MP macroscopical shape. Methods: We prospectively assessed 77 patients with periampullary malignancies between October 2020 and March 2022 (18 months). All patients had undergone PD with SMA first approach combined total MP excision. The perioperative indications, clinical data, intra-operative index, R0 resection rate of postoperative pathological specimens (especially mesopancreatic margin), postoperative complications, and follow-up results were evaluated. Results: The median operative time was 289.6 min (178−540 min), the median intraoperative blood loss was 209 mL (30−1,600 mL). Microscopically, there were 19 (24.7%) cases with metastatic MP, and five cases (6.5%) with R1-resection of the MP. The number of lymph nodes (LNs) harvested and metastatic LNs were 27.2 (maximum was 74) and 1.8 (maximum was 16), respectively. Some (46.8%) patients had pancreatic fistula, but mostly in grade A, with 7 patients (9.1%) who required re-operations. Some 18.2% of cases developed postoperative refractory diarrhea. The rate of in-hospital mortality was 1.3%. Conclusions: The PD with SMA first approach combined TMpE for periampullary malignancies was effective in achieving superior oncological statistics (rate of MP R0-resection and number of total resected LNs) with non-inferior short-term outcomes. It is necessary to evaluate survival outcomes with long-term follow-up.

Components Constituting the Audit Expectation Gap: The Vietnamese Case

Tuan Anh DANG,Dung Khanh Ngoc NGUYEN 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.1

The present study seeks to investigate the degree of awareness that constitutes the audit gap expectations (AEG) to determine which audit responsibilities can be narrowed or even eliminated. The author had surveyed a sample comprising four groups including auditors, auditees, the financial community, and other interest groups. In this survey, 1400 questionnaires were sent to the respondents, and the total number of responses was 454. The collected data was processed using statistical software SPSS, version 22. The Chi-Square test was used to analyze the effect of professional differences on AEG. The results of this study indicate that AEG cannot be eliminated due to the occupational impact of each survey group (about 46%), but it can be narrowed down to 54%, including a reduction of 11% in the knowledge gap (lack of public knowledge), 13% in the reasonable expectations gap (unqualified audit quality), 30% in the deficient standards gap (limited auditing standards). These results could be attained by improving training, communicating, and adding more responsibilities. This is the first study that provides another method of measuring the contribution of the knowledge gap through professional differences and professional gaps that make up each of the AEG’s components.

A Gateway for Multi-device Communication between Mechatrolink-III and RS-485

Tuan Thanh Dang,Jin Ho Kim,Dung Duc Nguyen,Jae Wook Jeon 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10

The gateway plays an important role in networks with different communication protocols because it enables devices in these networks to communicate with each other. Designing a gateway for multiple -devices with one physical device helps us to reduce costs and take full advantage of the higher-speed communication protocol. The lack of realtime capacity is a problem in this design approach. In this paper, we propose a gateway between Mechatrolink-III and multi RS-485 that satisfies real-time condition and reuses monitoring software over the entire network. The concept of the proposed gateway is based on an advanced feature of the Mechatrolink-III protocol that supports multi-slave devices. The lower speed RS-485 protocol is used as a demonstration for transmitting and receiving the proposed gateway. The identification of each slave differs over the entire network. The Mechatrolink-III slaves and RS-485 slaves have the same point of view as the monitoring software.

Synthesis and Properties of Magnetic-Semiconductor Fe₃O₄/TiO₂ Heterostructure Nanocomposites for Applications in Wastewater Treatment

Tien-Dung Chu,Thi-Thuy-Phuong Doan,Duy-Truong Quach,Xuan-Tuyen Nguyen,Tuan-Son Nguyen,Duc-Thang Pham,Dong-Hyun Kim 한국자기학회 2020 Journal of Magnetics Vol.25 No.1

In this research, a simple method has been presented to synthesize the magnetic - semiconductor Fe₃O₄/TiO₂ heterostructure nanocomposites via three steps: firstly, synthesis of Fe₃O₄ nanoparticles by co-precipitation method; thereafter, formation of Fe₃O₄/TiO₂ composites by sol-gel method; finally, annealing to form Fe₃O₄/TiO₂ anatase (denoted as Fe₃O₄/TiO₂-A) and Fe₃O₄/TiO₂ rutile (denoted as Fe₃O₄/TiO₂-R) heterostructure nanocomposites, respectively. The results of X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray spectroscopy show that the Fe₃O₄/TiO₂-A and Fe₃O₄/TiO₂-R heterostructure nanocomposite samples contain both magnetite (Fe₃O₄) and semiconductor TiO₂ (anatase or rutile phase, respectively). The asprepared nanocomposite samples exhibit superparamagnetic properties at room temperature with high saturation magnetization (Ms) above 19.5 emu/g at the applied magnetic field of 11 kOe. Moreover, the Fe₃O₄/TiO₂-A and Fe₃O₄/TiO₂-R heterostructure nanocomposites with a low band gap energy of 2.89 eV and 2.81 eV, respectively, are promising to enhance the performance of photocatalytic activities in the visible light region for application in wastewater treatment.

Establishment of a loop-mediated isothermal amplification (LAMP) assay for the detection of phytoplasma-associated cassava witches’ broom disease

Nam Tuan Vu,Juan Manuel Pardo,Elizabeth Alvarez,Ham Huy Le,Kris Wyckhuys,Kim-Lien Nguyen,Dung Tien Le 한국응용생명화학회 2016 Applied Biological Chemistry (Appl Biol Chem) Vol.59 No.2

Cassava (Manihot esculenta Crantz) is one of the most important food crops in the tropics; however, bacterial phytopathogens pose a serious threat to its farming. Cassava Witches’ Broom Disease (CWB) is caused by the infection of phytoplasma and is manifested as reduction in tuber yield and starch content at harvest of 10 and 30 %, respectively. Although polymerase-chain reaction provides the gold standard in diagnostics, this method requires significant investments in infrastructure and training. Here, we developed a loop-mediated isothermal amplification (LAMP) assay that allows specific detection of phytoplasma from field-collected samples. Three primer sets were designed, of which two detected phytoplasma DNA sequence encoding 16S rRNA (16S rDNA), the other detected cassava actin. Following a 1 h LAMP reaction at 63 °C, a positive reaction can be visualized by agarose gel electrophoresis, hydroxynaphthol blue color change, or the presence of a precipitate. In a pilot field study, the assay was able to rapidly distinguish between healthy and CWB-infected cassava. With further development, a LAMP for routine on-site screening of cassava crops can be envisioned.