4,078 research outputs found
Preparasi, modifikasi dan karakterisasi katalis bifungsional Sn-H-Zeolit alam Malang
No full textTelah dilakukan preparasi, modifikasi dan karakterisasi katalis Sn-H-Zeolit alam Malang. Zeolit alam diaktivasi dengan menggunakan larutan asam NH4NO3 2 M sehingga dihasilkan H-Zeolit. Logam Sn diimpregnasikan pada sampel H-Zeolit menggunakan variasi konsentrasi SnCl2.2H2O 0,12: 0,24 dan 0,48 M. Metode yang digunakan adalah proses hidrotermal menggunakan suhu 90 °C selama 12 jam, kemudian dikalsinasi pada suhu 500 °C selama 4 jam. Karakterisasi katalis meliputi morfologi permukaan katalis menggunakan SEM-EDAX, analisis kesaman menggunakan adsorpsi ammonia, luas permukaan spesifik katalis menggunakan BET (NOVA-1200) serta kristalinitas katalis menggunakan XRD.
Hasil penelitian menunjukkan bahwa distribusi logam terbaik pada pengemban zeolit adalah pada penggunaan konsentrasi logam SnCl2.2H2O 0,24 M. Nilai keasaman dari hasil variasi terbaik adalah 0,4682 mmol/g, sedangkan luas permukaan spesifiknya adalah sebesar 2,268 m2/g. Dari hasil karakterisasi XRD dapat diketahui bahwa proses modifikasi pada zeolit tidak menyebabkan perubahan struktur dan kristalinitas katalis
Preparation and characterization of suitable insulating and transparent conducting thin films for thin film electroluminescent devices by sol-gel process
No full textThin film electroluminescent (TFEL) displays are attractive because they are light, have low power consumption, wide viewing angle and long lifetime, are extremely rugged and can be used in hostile environments. Recently, there has been a renewed interest in thin film electroluminescent devices because of their promising application to head mounted displays for use in automobiles, aircraft, microsurgery and virtual reality applications. Both conventional and inverted thin film electroluminescent device structures consist of insulating film, transparent conducting film and luminescent layer. In a thin film electroluminescent device, the luminescent layer is sandwiched between two insulating layers. Electrodes outside both insulating layers are used to apply an electric field, with one electrode being transparent.
These thin films are found to be sensitive to preparation conditions and can be prepared by a variety of methods, such as, magnetron sputtering, chemical vapour deposition, reactive electron beam evaporation, reactive thermal deposition, spray pyrolysis, laser ablation and more recently by sol-gel process. Nowadays, the sol-gel process is a wellaccepted technology for the preparation of thin films, monoliths, fibers and monosized powders. Compared to conventional thin film forming processes such as CVD, evaporation or sputtering, sol-gel film formation requires considerably less equipment and is potentially less expensive; however the most important advantage of sol-gel processing over conventional coating methods is the ability to control precisely the microstructure of the deposited film, i.e., the pore volume, pore size and surface area.
The sol-gel process is a method where the substrate to be coated is dipped into a liquid solution containing the active material. When the substrate is removed from the solution a thin layer remains. On exposure to the atmosphere a hydrolysis reaction takes place which solidifies the liquid film.
In this work, all the thin films have been prepared by using sol-gel process. Insulating films of titanium dioxide and tantalum oxide were prepared from titanium and tantalum alkoxides respectively and their characteristics have been investigated. The most important requirements for the insulating layers are high dielectric constant and high electric field strength. The dielectric constants of the films were calculated from the maximum capacitance of the Al/film/Si structure. The maximum dielectric constants for Ti02 and Ta20 5 films were approximately 50 and 82 respectively annealed at 700°C in oxygen. These results suggest that the Ti02 and Ta2Os thin film can be used as a high dielectric constant insulating layer in thin film electroluminescent devices.
Highly conductive and transparent aluminum-doped zinc oxide thin films have been prepared from the solution of zinc acetate and aluminum nitrate in ethanol by the sol-gel process. The effect of changing the aluminum-to-zinc ratio from 0 to 5 at. % and annealing temperature from 0 to 700°C in air, oxygen and nitrogen has been investigated. The resistivities of thin films were measured as a function of annealing temperature and also as a function of aluminum dopant concentration in the solution. As-deposited films have high resistivity and high optical transmission. Annealing of the as-deposited films in atmosphere leads to a substantial reduction in resistivity. The films have a minimum value of resistivity of 1.3xl0'4 Q-cm for 0.8 at. % aluminum-doped zinc oxide annealed at 500°C in nitrogen and a maximum transmission of about 88% when deposited on glass substrates. X-ray diffraction measurements employing CuKa radiation were performed to determine the crystallinity of the ZnO:Al films which showed that the films were polycrystalline with a hexagonal structure when annealed at higher temperatures in air, oxygen and nitrogen.
Transparent conductive indium tin oxide (ITO) thin films have been prepared by a solgel
process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. 0-20 % by weight Sn-doped indium oxide (ITO) films were prepared by heat-treatment at above 400°C. The electrical, optical and structural properties of ITO thin films were investigated. The electrical resistivity was measured by using four-point probe method. The ITO thin films containing 10 wt.% Sn showed the minimum resistivity of p = 8.0xl0'4 Q-cm annealed at 500°C in nitrogen. The films have an optical transparency up to 89% at 900 nm. X-ray diffraction measurements employing CuKa radiation were performed to determine the crystallinity of the ITO films which showed that the ITO films were polycrystalline with a cubic bixbyite structure annealed in air, oxygen and nitrogen.
Aluminum doped zinc oxide thin films have been deposited on titanium dioxide and
tantalum oxide films on glass by sol-gel process. The resistivity of ZnO:Al thin films
deposited on titanium dioxide and tantalum oxide films on glass have a minimum value
of 2.5xl0'3 Q-cm and 9.6xl0'4 Q-cm respectively annealed at 500°C in nitrogen. ZnO:Al
thin films deposited on titanium dioxide film on glass have a higher resistivity than that
deposited on glass. This increase in resistivity on titanium dioxide film is due to the
diffusion of titanium into the zinc oxide layer.
Indium tin oxide thin films have been deposited on titanium dioxide and tantalum oxide
films on glass for thin film electroluminescent devices. The resistivity of ITO films
deposited on titanium dioxide and tantalum oxide films has a minimum value of 9.5x1 O'4
Q-cm and 9.0x10'4 Q-cm respectively annealed at 500°C in nitrogen which are as low as
the resistivity of ITO films deposited on glass. This combination of transparent conductive ITO thin films and titanium dioxide or tantalum oxide insulating layer can be
used for thin film electroluminescent devices
Pemanfaatan katalis Zeolit alam terimpregnasi logam Sn dalam reaksi Isomerisasi Glukosa dengan variasi suhu reaksi
No full textINDONESIA:
Zeolit alam ditemukan berlimpah dalam beberapa wilayah di Indonesia, salah satunya dari daerah Malang. Dengan jumlah yang berlimpah ini maka zeolit alam malang perlu dimanfaatkan salah satunya sebagai katalis. Penelitian ini bertujuan untuk mengetahui karakteristik katalis zeolit teraktivasi dan zeolit modifikasi serta untuk mengetahui aktivitas katalitiknya pada reaksi isomerisasi glukosa. Zeolit alam diaktivasi menggunakan NH4NO3 2 M menghasilkan katalis HZA. Sedangkan modifikasi menggunakan logam Sn 0,24 M yang diimpregnasikan pada HZA menghasilkan katalis Sn-HZA. Pada tahap tersebut dilakukan proses hidrotermal dengan suhu 90ºC selama 12 jam dilanjutkan kalsinasi dengan suhu 500ºC selama 4 jam. Karakterisasi meliputi analisis XRD, SEM-EDAX, analisis keasaman metode adsorpsi amoniak dan analisis luas permukaan metode adsorpsi methylen blue. HZA dan Sn-HZA diaplikasikan pada reaksi isomerisasi glukosa dengan metode batch. Konversi glukosa diperoleh melalui analisis polarimeter pada setiap jam ke-0, 1, 2, 3 dan 4 dengan variasi suhu 110, 120 dan 130 °C. Larutan hasil analisis polarimeter yang menghasilkan konversi terbesar dianalisis dengan HPLC. Analisis XRD menunjukkan bahwa tidak terjadi perubahan struktur pada zeolit setelah proses aktivasi dan modifikasi. Analisis dengan SEM-EDAX menunjukkan bahwa morfologi permukaan zeolit tidak rusak dan logam Sn yang berhasil diipregnasikan sebesar6,94 %. Keasaman HZA dan Sn-HZA yang diperoleh sebesar 1,4850 mmol/gr dan 2,3145 mmol/gr. Sedangkan luas permukaan H-ZA dan Sn-HZA sebesar 11,4077 m2/gr dan 11,4738 m2/gr. Penggunaan katalis Sn-HZA dengan suhu reaksi 120 °C dapat memberikan konversi glukosa dan selektivitas fruktosa terbesar yaitu 14,0737 % b/v dan 0,646 % b/v.
ENGLISH:
Natural zeolites are found abundance in Indonesia, such as in Malang. Due to this amount, it needs to be utilized such as to be catalyst. The aims of this study are to investigate the characteristic of the activated zeolite catalyst and modification zeolite, and also to investigate the catalytic activity in the isomerization of glucose. Natural zeolite was activated by NH4NO3 2 M obtained catalyst HZA. While modification using 0,24 M Sn metal impregnated on HZA obtained catalyst Sn-HZA. At this stage, hydrothermal process carried out at temperature of 90 °C for 12 hours followed by calcination at temperature of 500 °C for 4 hours. The characterization includes the XRD analysis, SEM-EDAX analysis, acidity by ammonia method, and surface area by adsorption of methylene blue method. Glucose conversion was obtained through analysis of polarimeter at hour-0, 1, 2, 3, and 4 with temperature variation of 110, 120, and 130 °C. Solution which had the highest conversion resulted by polarimeter was analyzed by HPLC. XRD analysis showed that there were no changes in the structure of zeolite after activation and modification process. SEM-EDAX analysis showed that morphology of the zeolite surface is not damaged and Sn metal was successfully impregnated 6,94 %. The activity of HZA and Sn-HZA was 1,4850 mmol/g and 2,3145 mmol/g. while the surface area of HZA and Sn-HZA was 11,4077 m2/g and 11,4738 m2/g. Using the Sn-HZA catalyst with the reaction temperature of 120 °C provides the highest conversion of glucose and fructose selectivity. It were 14,0733% w/v and 0,646% w/v
First-Principles Study on Structural and Electronic Properties of Cubic (Pm3m) And Tetragonal (P4mm) ATiO₃ (A=Pb, Sn) / Nurakma Natasya Md Jahangir Alam …[et al.]
No full textThis work focuses on exploring lead-free ferroelectric materials that have a comparable unique ns2 solitary pair electrons with Pb (II), for example, Sn (II) using the first-principles study. All counts were performed dependent on ultrasoft pseudopotential of Density Functional Theory (DFT) that has been executed in the Cambridge Serial Total Energy Package (CASTEP). The convergence test for cut-off energy and k-point was performed to measure the accuracy of the calculations. It is shown that the structures have threshold energy of 350 eV and k-point of 4x4x4 with Monkhorst Pack. The structural properties for both cubic and tetragonal structures ATiO3 (Pb, Sn) have shown the comparable value of the lattice parameter that was in agreement with previous work. Generalised gradient approximation (GGA) PBE displays the most exact qualities for cross-section parameters concerning exploratory qualities for both cubic PbTiO₃ while GGA-PBEsol functional is the best functional approximation for tetragonal PTO. The electronic band structure and density of states show the presence of hybridizations between anion O 2p and cation Pb 6s/Sn 5s unique solitary pair in tetragonal PTO and SnTO stage. The calculations have shown that both cubic and tetragonal structure of ATiO3 (A=Pb, Sn) has an indirect bandgap of 1.169 eV, 1.164 eV, 1.703 eV, and 1.016 eV respectively. It is shown that tetragonal structures have a higher value of bandgap compared to cubic structures
Preparasi, Modifikasi, dan Karakterisasi Katalis Bifungsional Sn-H-Zeolit Alam Malang
No full textABSTRAK
Telah dilakukan preparasi, modifikasi dan karakterisasi katalis Sn-H-Zeolit alam Malang. Zeolit alam diaktivasi dengan menggunakan larutan asam NH4NO3 2 M sehingga dihasilkan H-Zeolit. Logam Sn diimpregnasikan pada sampel H- Zeolit menggunakan variasi konsentrasi SnCl2.2H2O 0,12: 0,24 dan 0,48 M. Metode yang digunakan adalah proses hidrotermal menggunakan suhu 90 °C selama 12 jam, kemudian dikalsinasi pada suhu 500 °C selama 4 jam. Karakterisasi katalis meliputi morfologi permukaan katalis menggunakan SEM- EDAX, analisis kesaman menggunakan adsorpsi ammonia, luas permukaan spesifik katalis menggunakan BET (NOVA-1200) serta kristalinitas katalis menggunakan XRD.
Hasil penelitian menunjukkan bahwa distribusi logam terbaik pada pengemban zeolit adalah pada penggunaan konsentrasi logam SnCl2.2H2O 0,24 M. Nilai keasaman dari hasil variasi terbaik adalah 0,4682 mmol/g, sedangkan luas permukaan spesifiknya adalah sebesar 2,268 m2/g. Dari hasil karakterisasi XRD dapat diketahui bahwa proses modifikasi pada zeolit tidak menyebabkan perubahan struktur dan kristalinitas katalis.
ABSTRACT
Have done preparation, modification and characterization of catalysts Sn-H- natural Zeolite Malang. Natural zeolites were activated by using 2 M NH4NO3 acid solution to produce H-zeolites. Sn metal is impregnationded on H-zeolite samples using concentration variation SnCl2.2H2O 0.12: 0,24 and 0,48 M. The method used is a hydrothermal process using a temperature of 90 °C for 12 hours, and then calcined at a temperature of 500 °C for 4 hours. Characterization of catalysts include catalysts surface morphology using SEM-EDAX, equality analysis using ammonia adsorption, specific surface area of the catalyst using the BET (NOVA-1200) and the crystallinity of the catalysts using XRD.
The results showed that the distribution of the best metal on a zeolite carrier is on the use of metal concentrations SnCl2.2H2O 0,24 M. Acidity values of yield variation is best to 0,4682 mmol/g, while the specific surface area is equal to 2,268 m2/g. From the results of XRD characterization can be seen that the process of modification on zeolite does not cause changes in the structure and crystallinity of the catalyst
Ordering of organic molecules on templated surfaces
No full textThis thesis describes the controlled growth of molecular nanostructures using modified metallic and semiconductor surfaces. The Ag/Si(lll)-(root3 x root3),the Sn/Cu(100) surface alloy system and the Bi/Si(100) nanolines and (2xn) surfaces were all investigated as suitable substrates for the controlled growth of pentacene, (C22H14) or trimesic acid, (C6H3(COOH)3) organic molecules. The following techniques were used in this study; Scanning Tunnelling Microscopy (STM), Low Energy Electron Diffraction (LEED), Normal Incident X-Ray Standing Waves (NIXSW) and Temperature Programmed Desorption (TPD).
The room temperature growth and ordering of trimesic acid on the AgfSi(ll1)-(root3 x root3) surface was investigated. An oblique unit cell was determined and a model proposed for the highly ordered close-packed domains.
The discovery of a new submonolayer phase on Sn/Cu(100) and the re-examined known phase are discussed. New models for these reconstructions are proposed. Adsorption of trimesic acid at room temperature on the clean substrate the lowest Sn coverage phase were studied. Two new Sn coverage dependent structures were discovered and bonding schemes in upright and flat orientations are discussed.
BifSi(100)-(2xn) surface was exploited as a template for the ordered growth of pentacene, which exhibited orientation specific adsorption. The Bi/Si(100)-(2xn) single domain surface created on vicinal silicon was used to test the suitable of Daresbury 4.2 beamline for NIXSW Imaging experiments and the quality of the results are discussed
A trio of gamma-ray burst supernovae : GRB 120729A, GRB 130215A/SN 2013ez, and GRB 130831A/SN 2013fu
No full textWe present optical and near-infrared (NIR) photometry for three gamma-ray burst supernovae (GRB-SNe): GRB 120729A, GRB 130215A/SN 2013ez, and GRB 130831A/SN 2013fu. For GRB 130215A/SN 2013ez, we also present optical spectroscopy at t − t0 = 16.1 d, which covers rest-frame 3000–6250 Å. Based on Fe ii λ5169 and Si ii λ6355, our spectrum indicates an unusually low expansion velocity of ~4000–6350 km s-1, the lowest ever measured for a GRB-SN. Additionally, we determined the brightness and shape of each accompanying SN relative to a template supernova (SN 1998bw), which were used to estimate the amount of nickel produced via nucleosynthesis during each explosion. We find that our derived nickel masses are typical of other GRB-SNe, and greater than those of SNe Ibc that are not associated with GRBs. For GRB 130831A/SN 2013fu, we used our well-sampled R-band light curve (LC) to estimate the amount of ejecta mass and the kinetic energy of the SN, finding that these too are similar to other GRB-SNe. For GRB 130215A, we took advantage of contemporaneous optical/NIR observations to construct an optical/NIR bolometric LC of the afterglow. We fit the bolometric LC with the millisecond magnetar model of Zhang & Mészáros (2001, ApJ, 552, L35), which considers dipole radiation as a source of energy injection to the forward shock powering the optical/NIR afterglow. Using this model we derive an initial spin period of P = 12 ms and a magnetic field of B = 1.1 × 1015 G, which are commensurate with those found for proposed magnetar central engines of other long-duration GRBs
Silica supported Sn catalysts with tetrahedral Sn sites for selective isomerization of glucose to fructose
No full textLewis acid catalyzed isomerization of glucose to fructose is an important reaction for production of renewable chemicals. Here, we show the synthesis of an active and selective Lewis acid catalyst for this reaction by controlling Sn dispersion on SBA15. Sn loading of 1 wt. % over SBA15 (Sn/SBA15) maximized the formation of tetrahedral Sn species on the catalyst surface. Increasing the loading or changing support caused formation of SnO2 clusters which reduced fructose selectivity. A mechanism based on condensation of Sn with silanol group of SBA15 is proposed. The catalyst showed high selectivity of 93 % after 2 h with 57 % fructose yield. The Lewis acid catalyzed isomerization of glucose was proven by isotopic tracer study using D-glucose-2-d. The catalyst deactivated in the third cycle owing to byproduct deposition, but the activity was restored by recalcining the catalyst
Sn-Based Electrocatalyst Stability: A Crucial Piece to the Puzzle for the Electrochemical CO<sub>2</sub>Reduction toward Formic Acid
No full textNowadays, Sn-based electrocatalysts for the electrochemical CO2 reduction reaction (eCO2RR) toward formic acid have been reported to reach industrially relevant current densities and Faradaic efficiencies approaching 100%. However, electrocatalyst stability remains inadequate and appears to be a crucial piece to the puzzle, as lifetimes in the range of several thousands of hours should be reached for practical application and economic viability. Here, we provide insights into stability issues related to Sn-based electrocatalysts and electrolyzers for formic acid production. By determining the chemical and physical phenomena that occur during the electrochemical reduction reaction on the surface and bulk of Sn-based catalysts, we intend to elucidate the most common degradation mechanisms that impair long-term electrocatalytic activity of these catalysts. Moreover, highlighting the importance of correctly selected process conditions and an optimized reactor design allows us to unveil all necessary aspects for a stable Sn-based eCO2RR toward formic acid.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Large Scale Energy Storag
Influences of Nanostructures of Sn and Ir for the Oxygen Evolution Reaction in Polymer Electrolyte Membrane Water Electrolysis
No full textThe influence of nanostructures and interaction of Sn and Ir in oxygen evolution catalysts in a polymer electrolyte membrane electrolyzer were investigated. For this aim, two synthesis methods, namely, the one-step solution combustion method and the precipitation-deposition method with sodium borohydride reduction, were evaluated to prepare distinct nanostructures. Sn addition to Ir-based oxygen evolution reaction catalysts has been reported to yield materials with higher activity; however, in our case, this was observed only for Sn/Ir catalysts prepared by the precipitation-deposition method. The nanolayer of Sn/SnO2 deposited over metallic Ir particles was identified to enhance the interfacial contacts, resulting in synergistic interactions. By deconvolution of the polarization curves into constituting contributions, the performance improvement was attributed to the higher exchange current density of the Sn/Ir powder as a consequence of a higher number of surface reaction sites created by the Sn-Ir interactions.ChemE/Catalysis Engineerin
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