Enhancement of Thermoelectric Properties in Cold Pressed Nickel Doped Bismuth Sulfide Compounds

Fitriani Fitriani,Suhana Mohd Said,Shaifulazuar Rozali,Mohd Faiz Mohd Salleh,Mohd Faizul Mohd Sabri,Duc Long Bui,Tadachika Nakayama,Ovik Raihan,Megat Muhammad Ikhsan Megat Hasnan,Mohamed Bashir Ali Ba 대한금속·재료학회 2018 ELECTRONIC MATERIALS LETTERS Vol.14 No.6

Nanostructured Ni doped Bi 2 S 3 (Bi 2−x Ni x S 3 , 0 ≤ x ≤ 0.07) is explored as a candidate for telluride free thermoelectric material,through a combination process of mechanical alloying with subsequent consolidation by cold pressing followed with asintering process. The cold pressing method was found to impact the thermoelectric properties in two ways: (1) introductionof the dopant atom in the interstitial sites of the crystal lattice which results in an increase in carrier concentration, and (2)introduction of a porous structure which reduces the thermal conductivity. The electrical resistivity of Bi 2 S 3 was decreasedby adding Ni atoms, which shows a minimum value of 2.35 × 10 −3 Ω m at 300 °C for Bi 1.99 Ni 0.01 S 3 sample. The presenceof porous structures gives a signifi cant eff ect on reduction of thermal conductivity, by a reduction of ~ 59.6% compared toa high density Bi 2 S 3 . The thermal conductivity of Bi 2−x Ni x S 3 ranges from 0.31 to 0.52 W/m K in the temperature range of27 °C (RT) to 300 °C with the lowest κ values of Bi 2 S 3 compared to the previous works. A maximum ZT value of 0.13 at300 °C was achieved for Bi 1.99 Ni 0.01 S 3 sample, which is about 2.6 times higher than (0.05) of Bi 2 S 3 sample. This work showan optimization pathway to improve thermoelectric performance of Bi 2 S 3 through Ni doping and introduction of porosity.

Formation of a Carbon Interphase Layer on SiC Fibers Using Electrophoretic Deposition and Infiltration Methods

Fitriani, Pipit,Sharma, Amit Siddharth,Lee, Sungho,Yoon, Dang-Hyok The Korean Ceramic Society 2015 한국세라믹학회지 Vol.52 No.4

This study examined carbon layer coating on silicon carbide (SiC) fibers by utilizing solid-state and wet chemistry routes to confer toughness to the fiber-reinforced ceramic matrix composites, as an alternative to the conventional pyrolytic carbon (PyC) interphase layer. Electrophoretic deposition (EPD) of carbon black nanoparticles using both AC and DC current sources, and the vacuum infiltration of phenolic resin followed by pyrolysis were tested. Because of the use of a liquid phase, the vacuum infiltration resulted in more uniform and denser carbon coating than the EPD routes with solid carbon black particles. Thereafter, vacuum infiltration with controlled variation in phenolic resin concentration, as well as the iterations of infiltration steps, was improvised to produce a homogeneous carbon coating having a thickness of several hundred nanometers on the SiC fiber. Conclusively, it was demonstrated that the carbon coating on the SiC fiber could be achieved using a simpler method than the conventional chemical vapor deposition technique.

Effects of sintering additives on the microstructural and mechanical properties of the ion-irradiated SiC_f/SiC

Fitriani, Pipit,Sharma, Amit Siddharth,Yoon, Dang-Hyok Elsevier 2018 Journal of nuclear materials Vol.503 No.-

<P><B>Abstract</B></P> <P>SiC<SUB>f</SUB>/SiC composites containing three different types of sintering additives <I>viz.</I> Sc-nitrate, Al<SUB>2</SUB>O<SUB>3</SUB>-Sc<SUB>2</SUB>O<SUB>3</SUB>, and Al<SUB>2</SUB>O<SUB>3</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB>, were subjected to ion irradiation using 0.2 MeV H<SUP>+</SUP> ions with a fluence of 3 × 10<SUP>20</SUP> ions/m<SUP>2</SUP> at room temperature. Although all composites showed volumetric swelling upon ion irradiation, SiC<SUB>f</SUB>/SiC with Sc-nitrate showed the smallest change followed by those with the Al<SUB>2</SUB>O<SUB>3</SUB>-Sc<SUB>2</SUB>O<SUB>3</SUB> and Al<SUB>2</SUB>O<SUB>3</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> additives. In particular, SiC<SUB>f</SUB>/SiC containing the conventional Al<SUB>2</SUB>O<SUB>3</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> additive revealed significant microstructural changes, such as surface roughening and the formation of cracks and voids, resulting in reduced fiber pullout upon irradiation. On the other hand, the SiC<SUB>f</SUB>/SiC with Sc-nitrate showed the highest resistance against ion irradiation without showing any macroscopic changes in surface morphology and mechanical strength, indicating the importance of the sintering additive in NITE-based SiC<SUB>f</SUB>/SiC for nuclear structural applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> SiC<SUB>f</SUB>/SiC with Sc-nitrate, Al<SUB>2</SUB>O<SUB>3</SUB>-Sc<SUB>2</SUB>O<SUB>3</SUB>, and Al<SUB>2</SUB>O<SUB>3</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> additives were ion-irradiated. </LI> <LI> Changes in microstructure and mechanical properties were compared. </LI> <LI> SiC<SUB>f</SUB>/SiC with Sc-nitrate was more irradiation resistant than with Al<SUB>2</SUB>O<SUB>3</SUB>-Sc<SUB>2</SUB>O<SUB>3</SUB> and Al<SUB>2</SUB>O<SUB>3</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> additions. </LI> </UL> </P>

Fabrication of tubular SiC_f/SiC using different preform architectures by electrophoretic deposition and hot pressing

Fitriani, Pipit,Sharma, Amit Siddharth,Septiadi, Arifin,Park, Ji-Yeon,Yoon, Dang-Hyok Elsevier 2017 Ceramics international Vol.43 No.10

<P><B>Abstract</B></P> <P>This paper reports the processing feasibility of electrophoretic deposition combined with hot pressing in the fabrication of dense tubular SiC<SUB>f</SUB>/SiC composites using a cylindrical mold. A simulation of pressure distribution using ANSYS software was performed by varying the angular inclinations in a cylindrical mold with an ‘out → in’ configuration so as to ensure a maximum and uniform conversion of vertical hot press force to the lateral side of a centrally-located preform through graphite powder. The simulation revealed an inhomogeneous pressure distribution along the height of the preform, which could be minimized by mold optimization to achieve a more uniform tube density. To verify this, two different preform architectures such as 0/90° woven 2-D fabric rolled in a jelly state and filament winding with two plies having an inter-ply angle of 55° were hot-pressed using a mold fabricated based on the simulation after infiltrating the matrix phase by electrophoretic deposition. The density of the tube could be increased with more uniform microstructures. Although the tube using a filament winding preform exhibited a lower flexural strength (105MPa) and relative density (90%) than those with the preform rolled in a jelly state (221MPa, 95%), the results revealed a high degree of fiber pull-out due to the PyC coating on the SiC fiber.</P>

Effects of post-sintering annealing on the microstructure and toughness of hot-pressed SiC_f/SiC composites with Al₂O₃-Y₂O₃ additions

Fitriani, Pipit,Yoon, Dang-Hyok,Sharma, Amit Siddharth Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.16

<P><B>Abstract</B></P> <P>This study examined the effects of post-sintering heat treatment on enhancing the toughness of SiC<SUB>f</SUB>/SiC composites. Commercially available Tyranno<SUP>®</SUP> SiC fabrics with contiguous dual ‘PyC (inner)-SiC (outer)’ coatings deposited on the SiC fibers were infiltrated with a SiC + 10wt% Al<SUB>2</SUB>O<SUB>3</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> slurry by electrophoretic deposition. SiC green tapes were stacked between the slurry-infiltrated fabrics to control the matrix volume fraction. Densification of approximately 94% ρ<SUB>theo</SUB> was achieved by hot pressing at 1750°C, 20MPa for 2h in an Ar atmosphere. Sintered composites were then subjected to isothermal annealing treatment at 1100, 1250, 1350, and 1750°C for 5h in Ar. The correlation between the flexural behavior and microstructure was explained in terms of the in situ-toughened matrix, phase evolution in the sintering additive, role of dual interphases and observed fracture mechanisms. Extensive fractography analysis revealed interfacial debonding at the hybrid interfaces and matrix cracking as the key fracture modes, which were responsible for the toughening behavior in the annealed SiC<SUB>f</SUB>/SiC composites.</P>

Joining of SiC_f/SiC using a Ti₃AlC₂ filler and subsequent elimination of the joining layer

Fitriani, Pipit,Yoon, Dang-Hyok Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.18

<P><B>Abstract</B></P> <P>This study examined the joining of SiC fiber-reinforced SiC matrix composites (SiC<SUB>f</SUB>/SiC) using a Ti<SUB>3</SUB>AlC<SUB>2</SUB> MAX phase filler and the possibility of eliminating the joining layer via solid-state diffusion upon the decomposition of Ti<SUB>3</SUB>AlC<SUB>2</SUB>. The base SiC<SUB>f</SUB>/SiC was fabricated by electrophoretic deposition (EPD) combined with hot pressing after adding a 10 wt% Al<SUB>2</SUB>O<SUB>3</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> sintering additive. Two types of base SiC<SUB>f</SUB>/SiC with a density of 93% and 96% were prepared by hot pressing at 1750 °C without and with SiC tape insertion, respectively, followed by joining at 1700 or 1900 °C for 5 h under 3.5 MPa in an Ar atmosphere. The SiC<SUB>f</SUB>/SiC with tape insertion showed feasible elimination of the joining layer after joining at 1900 °C, whereas the composite joined at 1700 °C revealed the presence of a joining filler due to incomplete decomposition of the Ti<SUB>3</SUB>AlC<SUB>2</SUB> filler. All samples showed fracturing at the joining interface during the flexural test, showing a joining strength of 180–255 MPa depending on the preparation conditions. The properties of the SiC<SUB>f</SUB>/SiC joints were explained by the surface roughness, microstructure, and phase evolution upon decomposition of the Ti<SUB>3</SUB>AlC<SUB>2</SUB> filler.</P>

Joining of SiC monoliths using a thin MAX phase tape and the elimination of joining layer by solid-state diffusion

Fitriani, Pipit,Septiadi, Arifin,Hyuk, Jeong Dong,Yoon, Dang-Hyok Elsevier 2018 Journal of the European Ceramic Society Vol.38 No.10

<P><B>Abstract</B></P> <P>This paper reports the joining of SiC monoliths using a thin MAX phase tape filler, such as Ti<SUB>3</SUB>AlC<SUB>2</SUB> and Ti<SUB>3</SUB>SiC<SUB>2</SUB>, and the subsequent phenomena leading to the elimination of the joining layer via solid-state diffusion of the MAX phase into the SiC base material, particularly with the decomposition of the Ti<SUB>3</SUB>AlC<SUB>2</SUB> filler. The base SiC monolith, showing ≥ 99% density, was fabricated by hot pressing SiC powder after adding 5 wt. % Al<SUB>2</SUB>O<SUB>3</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> sintering additive. A butt-joint configuration was prepared and joined by hot pressing under a pressure of 3.5 MPa. The effects of the experimental parameters, including the type and thickness of the joining filler, temperature as well as the holding time, were examined carefully in terms of the microstructure, phase evolution and joining strength. The joining interface could be eliminated from the SiC base when the SiC monoliths were joined at 1900 °C using a thin Ti<SUB>3</SUB>AlC<SUB>2</SUB> tape, showing a high joining strength ∼300 MPa. Moreover, fracture during the mechanical test occurred mainly at the base material rather than the joining interface, indicating excellent joining properties. These findings highlight the elimination of the joining interlayer, which might be ideal for practical applications because the absence of a joining filler helped preserve the excellent SiC mechanical properties of the joint.</P>

Fabrication of tough SiC_f/SiC composites by electrophoretic deposition using a fabric coated with FeO-catalyzed phenolic resin

Fitriani, Pipit,Septiadi, Arifin,Yoon, Dang-Hyok,Sharma, Amit Siddharth Elsevier 2017 Journal of the European Ceramic Society Vol.37 No.4

<P><B>Abstract</B></P> <P>A hybrid processing route based on vacuum infiltration, electrophoretic deposition, and hot-pressing was adopted to fabricate dense and tough SiC<SUB>f</SUB>/SiC composites. The as-received Tyranno SiC fabric preform was infiltrated with phenolic resin containing 5wt.% FeO and SiC powders followed by pyrolysis at 1700°C for 4h to form an interphase. Electrophoretic deposition was performed to infiltrate the SiC-based matrix into the SiC preforms. Finally, SiC green tapes were sandwiched between the SiC fabrics to control the volume fraction of the matrix. Densification close to 95% ρ<SUB>theo</SUB> was achieved by incorporating 10wt.% Al<SUB>2</SUB>O<SUB>3</SUB>-Sc<SUB>2</SUB>O<SUB>3</SUB> sintering additive to facilitate liquid phase sintering at 1750°C and 20MPa for 2h. X-ray diffraction and Raman analyses confirmed the catalytic utility of FeO by the formation of a pyrolytic carbon phase. The flexural response was explained in terms of the extensive fractography results and observed energy dissipating modes.</P>

Formation of a Carbon Interphase Layer on SiC Fibers Using Electrophoretic Deposition and Infiltration Methods

Pipit Fitriani,아밋시다하스샤르마,이성호,윤당혁 한국세라믹학회 2015 한국세라믹학회지 Vol.52 No.4

This study examined carbon layer coating on silicon carbide (SiC) fibers by utilizing solid-state and wet chemistry routes to confer toughness to the fiber-reinforced ceramic matrix composites, as an alternative to the conventional pyrolytic carbon (PyC) interphase layer. Electrophoretic deposition (EPD) of carbon black nanoparticles using both AC and DC current sources, and the vacuum infiltration of phenolic resin followed by pyrolysis were tested. Because of the use of a liquid phase, the vacuum infiltration resulted in more uniform and denser carbon coating than the EPD routes with solid carbon black particles. Thereafter, vacuum infiltration with controlled variation in phenolic resin concentration, as well as the iterations of infiltration steps, was improvised to produce a homogeneous carbon coating having a thickness of several hundred nanometers on the SiC fiber. Conclusively, it was demonstrated that the carbon coating on the SiC fiber could be achieved using a simpler method than the conventional chemical vapor deposition technique.

Synthesis of Au nanoparticle-decorated TiO₂ for Photo/Photoelectrocatalysis Application

( Rosyadi Anisa Fitriani ),유효종 한국공업화학회 2023 한국공업화학회 연구논문 초록집 Vol.2023 No.1