Lau Kok-Tee | Universiti Teknikal Malaysia Melaka (original) (raw)

Papers by Lau Kok-Tee

Journal of Telecommunication, Electronic and Computer Engineering, 2016

Boron Nitride (BN) film is increasingly used in various applications like lubrication, releasing ... more Boron Nitride (BN) film is increasingly used in various applications like lubrication, releasing agent, thermosetting insulator material, thermal enhancer etc. Limited studies were done on electrophoretic deposition (EPD) using BN particles for industrial application. EPD is potential coating method for automotive, appliance and general industrial parts, because of its capable to do deposition on the complex geometry shape, achievable controllable thickness, easy setup, and low cost process set-up. BN stability in EPD suspension is important to produce repeatability and reproducibility deposition result. EPD process was characterized by evaluate dispersion medium (water, Acetic acid, Sulphamic acid & Ammonia) and binder (PEG, Silane Coupling Agent, Poly cationic 1 – PC 1, Poly cationic 2 – PC 2). Dispersion medium was evaluated suspension stability at different level of pH, acid (pH 2-pH 6), neutral and base (pH 8 – pH 11). Binder was used to enhance bonding strength of the deposite...

Transactions on Electrical and Electronic Materials, 2020

Studies on shear strength of thin small leadless packages (TSLP) focused predominantly on solder ... more Studies on shear strength of thin small leadless packages (TSLP) focused predominantly on solder and reflow factors. Contact pad’s surface roughness (R a ) and Ni–P thickness factors, though rather important, have not been reported widely. Thus, the current study investigates the effect of TSLP’s contact pad, in terms of R a and Ni–P’s thickness, on shear strength variation of the TSLP after being soldered on PCB. The R a was controlled by using different Cu alloy leadframes, etchant’s pH and etching conveyor speeds. A shear test was conducted on the soldered TSLP using the Dage Series-4000-Bond-Tester as per Infineon’s specifications. The shear test data was supported by failure mode results in the form of scanning electron microscopy images and energy-dispersive X-ray analysis. The present work revealed that TSLP with high contact pad’s R a exhibited a wide shear strength variation. In addition, thicker Ni–P significantly enlarged the shear strength variation of TSLP when the etched surface of the contact pad’s R a is low. After solder reflow, the contact pad’s high R a and Ni–P thickness triggered the formation of more heterogeneous pores in the solder region of the solder joint between TSLP and PCB. This resulted in shear failure at the porous solder region and heterogeneous shear strength of the soldered TSLP.

Journal of Engineering Technology and Applied Physics, 2019

This study is to investigate the dependence of coverlay's adhesive thickness on the laminating pr... more This study is to investigate the dependence of coverlay's adhesive thickness on the laminating press's openingstacking position. Coverlays using acrylic-and epoxy-based adhesives were laminated onto similar size copper clad laminate (CCL) at 140 bars and 195°C for 150 min. Adhesive thickness measurements show opening-stacking positions near to the bottom of laminating press machine produced more consistent adhesive thickness as compared to the top positions.

2016 IEEE 37th International Electronics Manufacturing Technology (IEMT) & 18th Electronics Materials and Packaging (EMAP) Conference, 2016

Cupric chloride etchant was used to removing the unwanted copper alloy carrier of molded units' s... more Cupric chloride etchant was used to removing the unwanted copper alloy carrier of molded units' strips and to expose the Ni bump interconnects. However, an uncontrolled etching process of the carrier led to rough Ni bumps' surface, contributing to cosmetic defect and poor electroless Ni plating's shear strength. The current paper investigates the effect of pH, Cu specific gravity and conveyer speed using cupric chloridebased etchant on the surface roughness of Ni bumps after the etching of respective EFTECH-64-or C194-grade Cu alloy carriers. The DOE input factors on Cu alloy were established with the help of CEDA software. The alkaline etching of C194 resulted in a higher Ni bump's surface roughness as compared to the EFTECH-64 etching. However, under low pH and high specific Cu density parameters, C914 etching produced low surface roughness which comparable to the EFTECH-64 sample due to the consistency of resulted bump's surface roughness at upper and lower levels of etching parameters.

2015 16th International Conference on Electronic Packaging Technology (ICEPT), 2015

Palladium coated copper (PCC) wire bonding on roughen preplated leadframe is a preferred electric... more Palladium coated copper (PCC) wire bonding on roughen preplated leadframe is a preferred electrical interconnect in the semiconductor package due to its robustness package performances. PCC wire is replacing bare copper wires to eliminate the copper oxidation problem. Whereas, roughen treated preplated leadframe is used to eliminate post-plating of leadframe as well as to enhance the adhesion of leadframe to the epoxy mold compounds. However, role of the plating thickness of roughen preplated leadframe on the PCC wire has not yet been fully understood. Thus, this paper investigates stitch bonding strength of PCC wire on the AuAg/Pd/Ni/Cu preplated leadframe with different AuAg plating thickness. Stitch pull test results on PCC wire bonding on different preplated leadframe showed higher stitch bonding strength for samples with higher AuAg plating thickness. Optical micrographs showed mechanical failure at bond heel of test sample, due to higher tensile stress during the pull test. Thicker AuAg layers may provide greater cushioning effect against wire deformation at bond heel during stitch bonding process. This in turns increased the stitch bonding strength of the PCC wire bond. STEM micrograph and EDX line-scan profile in all samples showed formation of interdiffusion zone at the PCC wire/ leadframe bonding interface. At the distinct bonding interface, interdiffusion zone extended from Pd layer of PCC wire to Pd layer of leadframe, where Pd species from both sides were intermixed. Whereas at blurred bonding interface, interdiffusion zone was extended further to Pd/Ni interface region. Formation of interdiffusion zone may strengthened wire bond between the PCC wire and the leadframe, thus prevented bond delamination during the stitch pull strength test.

Applied Mechanics and Materials, 2015

Copper (Cu) wire bonding on the pre-plated leadframes with Ni/Pd/AuAg plating has been applied ex... more Copper (Cu) wire bonding on the pre-plated leadframes with Ni/Pd/AuAg plating has been applied extensively in the semiconductor industry for the interconnection of integrated-circuit (IC) packaging due to the lower material cost of Cu and its excellent electrical properties. Furthermore, the Cu wire bonding on the preplated leadframe has advantages, such as the tin whisker prevention and the robust package for automotive application. Nevertheless, a stitch bondability of Cu wire-preplated leadframe is facing several challenges, such as the Cu oxidation, the high hardness of Cu wire and the very thin AuAg plating on the leadframes. This paper discusses the effect of AuAg plating thickness in roughened pre-plated leadframe on the stitch bonding of Cu wires with the leadframe. The stitch bonding integrity was assessed using Dage 4000 shear/pull tool at a key wire bond responses of stitch pull at time zero (T0). Results show that the stitch pull strength of the Cu-leadframe stitch bondi...

Applied Mechanics and Materials, 2015

This study aims to investigate multi-walled carbon nanotube and graphene composite thin films fab... more This study aims to investigate multi-walled carbon nanotube and graphene composite thin films fabricated using cathodic electrophoretic deposition in aqueous solution. The deposition mechanism and films microstructure were investigated using the cyclic voltammetry (CV) and field emission scanning electron microscope. The depositions yield varied by the deposition time and deposition voltage. The composite films were studied for its application in the electrochemical capacitor. The electrochemical performance showed the capacitive behavior of the films in 6 M potassium hydroxide electrolyte. CV scans were verified from 0 to 1 V at different scan rates. The specific capacitance of 29 Fg-1 was achieved at the scan rate of 1 mVs-1.

Applied Mechanics and Materials, 2015

Polymeric poly (vinyliden fluoride) (PVDF) is nontoxic. It possesses a better mechanical flexibil... more Polymeric poly (vinyliden fluoride) (PVDF) is nontoxic. It possesses a better mechanical flexibility and requires a lower synthesis temperature, as compared to the piezoceramic counterparts. In order to achieve a competitive advantage against the current piezoelectric sensor, graphite could replace a more expensive silver-palladium as the electrodes for the piezoelectric PVDF. This paper reports the preliminary results on the synthesis of steel-supported graphite-PVDF/PVDF/graphite-PVDF composite films using the two-step process, consisted of the electrophoretic deposition (EPD) and heat treatment. The composite films were characterized by means of the optical microscopy, scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The heat treated graphite-PVDF electrode deposited by EPD provides adequate mechanical strength for the subsequent depositions of pure PVDF layer and the second layer of graphite-PVDF composite electrode. However, the final heat ...

ABSTRACT The effects of aluminium (III) chloride (AlCl3), polyethyleneimine (PEI), and poly(diall... more ABSTRACT The effects of aluminium (III) chloride (AlCl3), polyethyleneimine (PEI), and poly(diallyldimethylammonium chloride) (PDADMAC)] as charging agents on the electrophoretic deposition (EPD) of coarse (?20 ?m) titanium (Ti) particles onto low-carbon steel cathodic substrates were assessed through microstructural evaluation, deposit yield, electrophoretic mobility measurements, and electrolytic corrosion. Apart from the capacity to achieve high bonding strength and yield, PDADMAC resulted in lower electrolytic corrosion of the cathode and introduced less anionic contamination than AlCl3 or PEI. The quality of the EPD deposit in terms of its bonding strength and deposit yield depended on the length scale of the charging agents used in addition to the intrinsic nature of the charging agent (ionic functional groups and sites). Minimisation of the PDADMAC addition level and PDADMAC of lower molecular weight are advantageous for surface hardening purposes owing to lower the carbon content introduced into the deposit yield.

We study the effect of various thermo-mechanical treatment on the current transport properties el... more We study the effect of various thermo-mechanical treatment on the current transport properties electrical Bi(Pb)-Sr-Ca-Cu-O tapes with nanopowder CoFe2O4 addition. We found that pinning strength of the tapes without intermediate pressing increases as the sintering temperature increases from 835°C to 855°C, whereas tapes applied with intermediate pressing have lower pinning strength compared with tapes without the pressing. On the contrary, self-field Jc of tapes without intermediate pressing decreases with increasing sintering temperature. Intermediate pressing are found effective to increase self-field Jc. The results obtained will be explained with the help of the XRD spectrums and SEM micrographs on the tapes.

Superconductor Science and Technology, 2002

... transport properties of Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox superconductor tapes KT Lau, SK Chen ... more ... transport properties of Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox superconductor tapes KT Lau, SK Chen and R Abd-Shukor School of Applied Physics, Universiti Kebangsaan Malaysia, 43600 Bangi Selangor DE, Malaysia E-mail: ras@pkrisc.cc.ukm.my ...

Physica C: Superconductivity, 2002

High-T c superconductor tapes with nominal compositions of Bi 1:8 Pb 0:4 Sr 2 Ca 2:2 Cu 3 O 10Àx ... more High-T c superconductor tapes with nominal compositions of Bi 1:8 Pb 0:4 Sr 2 Ca 2:2 Cu 3 O 10Àx (Bi-2223) and (Tl,Cr 0:15)-Sr 2 (Ca 0:9 ,Pr 0:1)Cu 2 O 7Àx (Tl-1212) were fabricated using the powder-in-tube method. The T c zero 's of the tapes, which were subjected to various thermo-mechanical treatments, ranged from 100-103 K for the Bi-2223/Ag tapes and 84-86 K for the Tl-1212/Ag tapes. Their transport critical current densities in low magnetic fields (0.15 T) were compared. All the tapes are dominated by weak links where this is more severe in the Tl-1212/Ag tapes. No significant anisotropic transport properties were observed in Tl-1212/Ag tapes when the magnetic field was applied perpendicular or parallel to the tape plane (i.e. J c ðH ? Þ=J c ðH k Þ ¼ 0:75-1:0). The Bi-2223/Ag tapes however show a pronounced anisotropic transport properties in applied magnetic field (i.e. J c ðH ? Þ=J c ðH k Þ ¼ 0:15-0:65). This can be associated with the microstructural difference between these two types of tapes. Scanning electron micrographs reveal the slightly aligned grains in the Bibased tapes while randomly orientated grains were observed in the Tl-based tapes.

Materials Science and Engineering: B, 2011

Materials Science and Engineering: B, 2002

Powders with nominal composition (Tl,Cr0.15)Sr2(Ca0.9,Pr0.1)Cu2O7 (Tl-1212) and Tc∼90 K were used... more Powders with nominal composition (Tl,Cr0.15)Sr2(Ca0.9,Pr0.1)Cu2O7 (Tl-1212) and Tc∼90 K were used to fabricate Ag-sheathed superconducting tapes employing the powder-in-tube (PIT) method. The tapes were subjected to intermediate mechanical rolling or pressing. Conditions that enhance the transport critical current density (Jc) of the tapes were investigated. Optimum annealing temperature and period together with uniaxial pressing are necessary to increase Jc of

Journal of Physics: Conference Series, 2008

This paper reports on the flux pinning capability of micron size Fe3O4 in Bi-Sr-Ca-Cu-O supercond... more This paper reports on the flux pinning capability of micron size Fe3O4 in Bi-Sr-Ca-Cu-O superconductor tapes. Ag sheathed high temperature superconductor tapes with starting compositions (Bi,Pb)2Sr2Ca2Cu3O10 (2223) and(Bi,Pb)2Sr2Ca2Cu3O10-(Fe3O4)0.01 were fabricated using the powder in tube method.The Bi-Sr-Ca-Cu-O powders were prepared by using the co-precipitation technique.The effects of Fe3O4 addition on the microstructure, phase formation, critical temperature and transport critical current density, Jc were studied. The Jc value of the Fe3O4 added tapes is higher (6,090 A/cm2 at 77 K and 24,500 A/cm2 at 30 K, in zero field) than the non-added tapes (3,730 A/cm2 at 77 K and 13,3180 A/cm2 at 30 K, in zero field). A sudden decrease of Jc in low magnetic fields (B < 0.12 T) when applied parallel (B||) and perpendicular (B^) to the tapes surface was observed. The destruction of weak links played an important role in the early Jc suppression. The rate of decrease of Jc was observed to decrease when the magnetic field was increased further. Improvement in the flux pinning was observed in (Bi, Pb)2Sr2Ca2Cu3O10-Fe3O4)0.01 tapes. This study shows that magnetic particles such as Fe3O4 can act as effective pinning centers leading to the enhancement of Jc in the system.

Journal of Applied Physics, 2006

... In this paper, we report the effect of magnetic nanorod a)Author to whom any correspondence s... more ... In this paper, we report the effect of magnetic nanorod a)Author to whom any correspondence should be addressed; electronic mail: ras@pkrisc.cc.ukm.my JOURNAL OF APPLIED PHYSICS 99, 123904 (2006) 0021-8979/2006/99(12)/123904/4/$23.00 ...

Electrophoretic deposition (EPD) is a potential coating technique for surface hardening of steel ... more Electrophoretic deposition (EPD) is a potential coating technique for surface hardening of steel when combined with a subsequent rapid sintering process. This process requires synergy between suspension particles and charging agent, particularly when the particles involved are noncolloidal in nature. The present work will investigate the effect of three commercially-available cationic charging agents; aluminium (III) chloride (AlCl3), polyethyleneimine (PEI) and poly (diallyldi-methylammonium chloride) (PDADMAC) on the EPD of coarse Ti particles onto steel. Surface microstructure, deposit yield, electrophoretic mobility and electrical conductivity were used to characterize Ti particles and obtained Ti deposit. The key finding of the present study is the bonding strength of charging agent-adsorbed coarse Ti particles deposits predominantly controlled their deposit yield. Electrophoretic mobility of the Ti particles only played a lesser role in the deposit yield because of strong hind...

Journal of Telecommunication, Electronic and Computer Engineering, 2018

This paper discusses on the design and fabrication steps of piezopolymer using poly(vinylidene fl... more This paper discusses on the design and fabrication steps of piezopolymer using poly(vinylidene fluoride) trifluoroethylene, P(VDF-TrFE) thick film on the flexible substrate using screen-printed method. Polyethylene terephthalate, PET film was used as a substrate to hold P(VDFTrFE) thick film in between sandwiched layers of electrodepiezopolymer-electrode. The P(VDF-TrFE) thick film is then annealed at 100 °C and polarized at 100 V for the film and inspected under EDS, FESEM and XRD for the characterization process. The flexible piezoelectric P(VDFTrFE) thick film is able to generate maximum output peak power of 4.36 µW at an external load of 1kΩ with generated maximum peak-to-peak voltage about 3.0 V for energy harvesting applications when using impact force test from freefall drop plasticine of 0.2 N was applied to the thick film.

Journal of Telecommunication, Electronic and Computer Engineering, 2016

Boron Nitride (BN) film is increasingly used in various applications like lubrication, releasing ... more Boron Nitride (BN) film is increasingly used in various applications like lubrication, releasing agent, thermosetting insulator material, thermal enhancer etc. Limited studies were done on electrophoretic deposition (EPD) using BN particles for industrial application. EPD is potential coating method for automotive, appliance and general industrial parts, because of its capable to do deposition on the complex geometry shape, achievable controllable thickness, easy setup, and low cost process set-up. BN stability in EPD suspension is important to produce repeatability and reproducibility deposition result. EPD process was characterized by evaluate dispersion medium (water, Acetic acid, Sulphamic acid & Ammonia) and binder (PEG, Silane Coupling Agent, Poly cationic 1 – PC 1, Poly cationic 2 – PC 2). Dispersion medium was evaluated suspension stability at different level of pH, acid (pH 2-pH 6), neutral and base (pH 8 – pH 11). Binder was used to enhance bonding strength of the deposite...

Transactions on Electrical and Electronic Materials, 2020

Studies on shear strength of thin small leadless packages (TSLP) focused predominantly on solder ... more Studies on shear strength of thin small leadless packages (TSLP) focused predominantly on solder and reflow factors. Contact pad’s surface roughness (R a ) and Ni–P thickness factors, though rather important, have not been reported widely. Thus, the current study investigates the effect of TSLP’s contact pad, in terms of R a and Ni–P’s thickness, on shear strength variation of the TSLP after being soldered on PCB. The R a was controlled by using different Cu alloy leadframes, etchant’s pH and etching conveyor speeds. A shear test was conducted on the soldered TSLP using the Dage Series-4000-Bond-Tester as per Infineon’s specifications. The shear test data was supported by failure mode results in the form of scanning electron microscopy images and energy-dispersive X-ray analysis. The present work revealed that TSLP with high contact pad’s R a exhibited a wide shear strength variation. In addition, thicker Ni–P significantly enlarged the shear strength variation of TSLP when the etched surface of the contact pad’s R a is low. After solder reflow, the contact pad’s high R a and Ni–P thickness triggered the formation of more heterogeneous pores in the solder region of the solder joint between TSLP and PCB. This resulted in shear failure at the porous solder region and heterogeneous shear strength of the soldered TSLP.

Journal of Engineering Technology and Applied Physics, 2019

This study is to investigate the dependence of coverlay's adhesive thickness on the laminating pr... more This study is to investigate the dependence of coverlay's adhesive thickness on the laminating press's openingstacking position. Coverlays using acrylic-and epoxy-based adhesives were laminated onto similar size copper clad laminate (CCL) at 140 bars and 195°C for 150 min. Adhesive thickness measurements show opening-stacking positions near to the bottom of laminating press machine produced more consistent adhesive thickness as compared to the top positions.

2016 IEEE 37th International Electronics Manufacturing Technology (IEMT) & 18th Electronics Materials and Packaging (EMAP) Conference, 2016

Cupric chloride etchant was used to removing the unwanted copper alloy carrier of molded units' s... more Cupric chloride etchant was used to removing the unwanted copper alloy carrier of molded units' strips and to expose the Ni bump interconnects. However, an uncontrolled etching process of the carrier led to rough Ni bumps' surface, contributing to cosmetic defect and poor electroless Ni plating's shear strength. The current paper investigates the effect of pH, Cu specific gravity and conveyer speed using cupric chloridebased etchant on the surface roughness of Ni bumps after the etching of respective EFTECH-64-or C194-grade Cu alloy carriers. The DOE input factors on Cu alloy were established with the help of CEDA software. The alkaline etching of C194 resulted in a higher Ni bump's surface roughness as compared to the EFTECH-64 etching. However, under low pH and high specific Cu density parameters, C914 etching produced low surface roughness which comparable to the EFTECH-64 sample due to the consistency of resulted bump's surface roughness at upper and lower levels of etching parameters.

2015 16th International Conference on Electronic Packaging Technology (ICEPT), 2015

Palladium coated copper (PCC) wire bonding on roughen preplated leadframe is a preferred electric... more Palladium coated copper (PCC) wire bonding on roughen preplated leadframe is a preferred electrical interconnect in the semiconductor package due to its robustness package performances. PCC wire is replacing bare copper wires to eliminate the copper oxidation problem. Whereas, roughen treated preplated leadframe is used to eliminate post-plating of leadframe as well as to enhance the adhesion of leadframe to the epoxy mold compounds. However, role of the plating thickness of roughen preplated leadframe on the PCC wire has not yet been fully understood. Thus, this paper investigates stitch bonding strength of PCC wire on the AuAg/Pd/Ni/Cu preplated leadframe with different AuAg plating thickness. Stitch pull test results on PCC wire bonding on different preplated leadframe showed higher stitch bonding strength for samples with higher AuAg plating thickness. Optical micrographs showed mechanical failure at bond heel of test sample, due to higher tensile stress during the pull test. Thicker AuAg layers may provide greater cushioning effect against wire deformation at bond heel during stitch bonding process. This in turns increased the stitch bonding strength of the PCC wire bond. STEM micrograph and EDX line-scan profile in all samples showed formation of interdiffusion zone at the PCC wire/ leadframe bonding interface. At the distinct bonding interface, interdiffusion zone extended from Pd layer of PCC wire to Pd layer of leadframe, where Pd species from both sides were intermixed. Whereas at blurred bonding interface, interdiffusion zone was extended further to Pd/Ni interface region. Formation of interdiffusion zone may strengthened wire bond between the PCC wire and the leadframe, thus prevented bond delamination during the stitch pull strength test.

Applied Mechanics and Materials, 2015

Copper (Cu) wire bonding on the pre-plated leadframes with Ni/Pd/AuAg plating has been applied ex... more Copper (Cu) wire bonding on the pre-plated leadframes with Ni/Pd/AuAg plating has been applied extensively in the semiconductor industry for the interconnection of integrated-circuit (IC) packaging due to the lower material cost of Cu and its excellent electrical properties. Furthermore, the Cu wire bonding on the preplated leadframe has advantages, such as the tin whisker prevention and the robust package for automotive application. Nevertheless, a stitch bondability of Cu wire-preplated leadframe is facing several challenges, such as the Cu oxidation, the high hardness of Cu wire and the very thin AuAg plating on the leadframes. This paper discusses the effect of AuAg plating thickness in roughened pre-plated leadframe on the stitch bonding of Cu wires with the leadframe. The stitch bonding integrity was assessed using Dage 4000 shear/pull tool at a key wire bond responses of stitch pull at time zero (T0). Results show that the stitch pull strength of the Cu-leadframe stitch bondi...

Applied Mechanics and Materials, 2015

This study aims to investigate multi-walled carbon nanotube and graphene composite thin films fab... more This study aims to investigate multi-walled carbon nanotube and graphene composite thin films fabricated using cathodic electrophoretic deposition in aqueous solution. The deposition mechanism and films microstructure were investigated using the cyclic voltammetry (CV) and field emission scanning electron microscope. The depositions yield varied by the deposition time and deposition voltage. The composite films were studied for its application in the electrochemical capacitor. The electrochemical performance showed the capacitive behavior of the films in 6 M potassium hydroxide electrolyte. CV scans were verified from 0 to 1 V at different scan rates. The specific capacitance of 29 Fg-1 was achieved at the scan rate of 1 mVs-1.

Applied Mechanics and Materials, 2015

Polymeric poly (vinyliden fluoride) (PVDF) is nontoxic. It possesses a better mechanical flexibil... more Polymeric poly (vinyliden fluoride) (PVDF) is nontoxic. It possesses a better mechanical flexibility and requires a lower synthesis temperature, as compared to the piezoceramic counterparts. In order to achieve a competitive advantage against the current piezoelectric sensor, graphite could replace a more expensive silver-palladium as the electrodes for the piezoelectric PVDF. This paper reports the preliminary results on the synthesis of steel-supported graphite-PVDF/PVDF/graphite-PVDF composite films using the two-step process, consisted of the electrophoretic deposition (EPD) and heat treatment. The composite films were characterized by means of the optical microscopy, scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The heat treated graphite-PVDF electrode deposited by EPD provides adequate mechanical strength for the subsequent depositions of pure PVDF layer and the second layer of graphite-PVDF composite electrode. However, the final heat ...

ABSTRACT The effects of aluminium (III) chloride (AlCl3), polyethyleneimine (PEI), and poly(diall... more ABSTRACT The effects of aluminium (III) chloride (AlCl3), polyethyleneimine (PEI), and poly(diallyldimethylammonium chloride) (PDADMAC)] as charging agents on the electrophoretic deposition (EPD) of coarse (?20 ?m) titanium (Ti) particles onto low-carbon steel cathodic substrates were assessed through microstructural evaluation, deposit yield, electrophoretic mobility measurements, and electrolytic corrosion. Apart from the capacity to achieve high bonding strength and yield, PDADMAC resulted in lower electrolytic corrosion of the cathode and introduced less anionic contamination than AlCl3 or PEI. The quality of the EPD deposit in terms of its bonding strength and deposit yield depended on the length scale of the charging agents used in addition to the intrinsic nature of the charging agent (ionic functional groups and sites). Minimisation of the PDADMAC addition level and PDADMAC of lower molecular weight are advantageous for surface hardening purposes owing to lower the carbon content introduced into the deposit yield.

We study the effect of various thermo-mechanical treatment on the current transport properties el... more We study the effect of various thermo-mechanical treatment on the current transport properties electrical Bi(Pb)-Sr-Ca-Cu-O tapes with nanopowder CoFe2O4 addition. We found that pinning strength of the tapes without intermediate pressing increases as the sintering temperature increases from 835°C to 855°C, whereas tapes applied with intermediate pressing have lower pinning strength compared with tapes without the pressing. On the contrary, self-field Jc of tapes without intermediate pressing decreases with increasing sintering temperature. Intermediate pressing are found effective to increase self-field Jc. The results obtained will be explained with the help of the XRD spectrums and SEM micrographs on the tapes.

Superconductor Science and Technology, 2002

... transport properties of Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox superconductor tapes KT Lau, SK Chen ... more ... transport properties of Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox superconductor tapes KT Lau, SK Chen and R Abd-Shukor School of Applied Physics, Universiti Kebangsaan Malaysia, 43600 Bangi Selangor DE, Malaysia E-mail: ras@pkrisc.cc.ukm.my ...

Physica C: Superconductivity, 2002

High-T c superconductor tapes with nominal compositions of Bi 1:8 Pb 0:4 Sr 2 Ca 2:2 Cu 3 O 10Àx ... more High-T c superconductor tapes with nominal compositions of Bi 1:8 Pb 0:4 Sr 2 Ca 2:2 Cu 3 O 10Àx (Bi-2223) and (Tl,Cr 0:15)-Sr 2 (Ca 0:9 ,Pr 0:1)Cu 2 O 7Àx (Tl-1212) were fabricated using the powder-in-tube method. The T c zero 's of the tapes, which were subjected to various thermo-mechanical treatments, ranged from 100-103 K for the Bi-2223/Ag tapes and 84-86 K for the Tl-1212/Ag tapes. Their transport critical current densities in low magnetic fields (0.15 T) were compared. All the tapes are dominated by weak links where this is more severe in the Tl-1212/Ag tapes. No significant anisotropic transport properties were observed in Tl-1212/Ag tapes when the magnetic field was applied perpendicular or parallel to the tape plane (i.e. J c ðH ? Þ=J c ðH k Þ ¼ 0:75-1:0). The Bi-2223/Ag tapes however show a pronounced anisotropic transport properties in applied magnetic field (i.e. J c ðH ? Þ=J c ðH k Þ ¼ 0:15-0:65). This can be associated with the microstructural difference between these two types of tapes. Scanning electron micrographs reveal the slightly aligned grains in the Bibased tapes while randomly orientated grains were observed in the Tl-based tapes.

Materials Science and Engineering: B, 2011

Materials Science and Engineering: B, 2002

Powders with nominal composition (Tl,Cr0.15)Sr2(Ca0.9,Pr0.1)Cu2O7 (Tl-1212) and Tc∼90 K were used... more Powders with nominal composition (Tl,Cr0.15)Sr2(Ca0.9,Pr0.1)Cu2O7 (Tl-1212) and Tc∼90 K were used to fabricate Ag-sheathed superconducting tapes employing the powder-in-tube (PIT) method. The tapes were subjected to intermediate mechanical rolling or pressing. Conditions that enhance the transport critical current density (Jc) of the tapes were investigated. Optimum annealing temperature and period together with uniaxial pressing are necessary to increase Jc of

Journal of Physics: Conference Series, 2008

This paper reports on the flux pinning capability of micron size Fe3O4 in Bi-Sr-Ca-Cu-O supercond... more This paper reports on the flux pinning capability of micron size Fe3O4 in Bi-Sr-Ca-Cu-O superconductor tapes. Ag sheathed high temperature superconductor tapes with starting compositions (Bi,Pb)2Sr2Ca2Cu3O10 (2223) and(Bi,Pb)2Sr2Ca2Cu3O10-(Fe3O4)0.01 were fabricated using the powder in tube method.The Bi-Sr-Ca-Cu-O powders were prepared by using the co-precipitation technique.The effects of Fe3O4 addition on the microstructure, phase formation, critical temperature and transport critical current density, Jc were studied. The Jc value of the Fe3O4 added tapes is higher (6,090 A/cm2 at 77 K and 24,500 A/cm2 at 30 K, in zero field) than the non-added tapes (3,730 A/cm2 at 77 K and 13,3180 A/cm2 at 30 K, in zero field). A sudden decrease of Jc in low magnetic fields (B < 0.12 T) when applied parallel (B||) and perpendicular (B^) to the tapes surface was observed. The destruction of weak links played an important role in the early Jc suppression. The rate of decrease of Jc was observed to decrease when the magnetic field was increased further. Improvement in the flux pinning was observed in (Bi, Pb)2Sr2Ca2Cu3O10-Fe3O4)0.01 tapes. This study shows that magnetic particles such as Fe3O4 can act as effective pinning centers leading to the enhancement of Jc in the system.

Journal of Applied Physics, 2006

... In this paper, we report the effect of magnetic nanorod a)Author to whom any correspondence s... more ... In this paper, we report the effect of magnetic nanorod a)Author to whom any correspondence should be addressed; electronic mail: ras@pkrisc.cc.ukm.my JOURNAL OF APPLIED PHYSICS 99, 123904 (2006) 0021-8979/2006/99(12)/123904/4/$23.00 ...

Electrophoretic deposition (EPD) is a potential coating technique for surface hardening of steel ... more Electrophoretic deposition (EPD) is a potential coating technique for surface hardening of steel when combined with a subsequent rapid sintering process. This process requires synergy between suspension particles and charging agent, particularly when the particles involved are noncolloidal in nature. The present work will investigate the effect of three commercially-available cationic charging agents; aluminium (III) chloride (AlCl3), polyethyleneimine (PEI) and poly (diallyldi-methylammonium chloride) (PDADMAC) on the EPD of coarse Ti particles onto steel. Surface microstructure, deposit yield, electrophoretic mobility and electrical conductivity were used to characterize Ti particles and obtained Ti deposit. The key finding of the present study is the bonding strength of charging agent-adsorbed coarse Ti particles deposits predominantly controlled their deposit yield. Electrophoretic mobility of the Ti particles only played a lesser role in the deposit yield because of strong hind...

Journal of Telecommunication, Electronic and Computer Engineering, 2018

This paper discusses on the design and fabrication steps of piezopolymer using poly(vinylidene fl... more This paper discusses on the design and fabrication steps of piezopolymer using poly(vinylidene fluoride) trifluoroethylene, P(VDF-TrFE) thick film on the flexible substrate using screen-printed method. Polyethylene terephthalate, PET film was used as a substrate to hold P(VDFTrFE) thick film in between sandwiched layers of electrodepiezopolymer-electrode. The P(VDF-TrFE) thick film is then annealed at 100 °C and polarized at 100 V for the film and inspected under EDS, FESEM and XRD for the characterization process. The flexible piezoelectric P(VDFTrFE) thick film is able to generate maximum output peak power of 4.36 µW at an external load of 1kΩ with generated maximum peak-to-peak voltage about 3.0 V for energy harvesting applications when using impact force test from freefall drop plasticine of 0.2 N was applied to the thick film.