Pengaruh rawatan haba terhadap mikrostruktur katod berliang Ag2O3-Bi2O3 di atas substrat keluli kalis karat telah dikaji. Komposit katod telah diendapkan ke atas substrat dengan menggunakan kaedah pengecatan sluri. Katod yang terhasil dirawat haba pada suhu 400, 500, 600, 700, 800 dan 830oC selama 1 jam dalam tekanan atmosfera. Analisis terma terhadap sluri kering telah dikaji untuk mendapatkan jadual pemanasan bagi penyingkiran komponen organik dengan menggunakan analisis termogravimetri (TGA) dan kalori imbasan kebezaan (DSC). Analisis TGA dan DSC mendapati penyingkiran komponen organik terjadi pada suhu di bawah 418oC dan fasa oksida komposit katod terbentuk pada suhu melebihi 600oC. Mikrostruktur katod terawat haba ditentukan dengan menggunakan mikroskop elektron imbasan (SEM) dan belauan sinar-X (XRD). Keputusan SEM menunjukkan yang saiz ira bagi katod meningkat dengan peningkatan suhu rawatan haba. Analisis pembelauan sinar-X mengesahkan kehadiran fasa δ-Bi2O3 di atas katod. Katod Ag2O3-Bi2O3 yang diendapkan di atas substrat keluli kalis karat dengan proses pengulangan salutan 1, 2, 3, dan 4 kali didapati masing-masing mempunyai keliangan 53%, 51%, 39% dan 28% setelah melalui proses rawatan haba pada suhu 800oC selama 1 jam.
Pencirian keseragaman campuran dan sifat reologi bahan suapan merupakan elemen penting dalam melaksanakan proses pengacuan suntikan seramik. Kesesuaian bahan suapan yang dibangunkan dapat mengurangkan masalah yang timbul ketika proses pengacuan suntikan, penyahikatan dan pensinteran. Justeru itu, kajian ini dijalankan untuk mengenal pasti pembebanan serbuk yang optimum berdasarkan kepada keseragaman campuran dan sifat reologi bahan. Pencirian keseragaman campuran ditentukan berdasarkan kepada nilai tork yang rendah dan berkeadaan mantap. Kajian reologi pula dilakukan dengan menggunakan mesin reometer rerambut. Ujian dijalankan pada julat suhu 150 dan 170oC dengan beban kenaan antara 20 dan 90 kgf. Bahan suapan yang digunakan terdiri daripada kombinasi serbuk seramik alumina-zirkonia bersama bahan pengikat polietilena berketumpatan tinggi, lilin parafin dan asid stearik. Hasil kajian menunjukkan bahan suapan bersifat pseudoplastik dengan pencampuran bahan yang seragam dalam tempoh kurang daripada 30 min. Hasil keputusan juga mendapati pada pembebanan serbuk 57% isi padu adalah yang paling optimum untuk proses pengacuan suntikan seramik berdasarkan kepada nilai kelikatan, indeks hukum kuasa dan tenaga pengaktifan aliran yang rendah.
Kesan suhu pensinteran terhadap sifat mekanik dan mikrostruktur bahan komposit alumina-zirkonia telah dikaji. Jasad
hijau alumina-zirkonia difabrikasi dengan menggunakan kaedah pengacuan suntikan seramik menggunakan sistem
bahan pengikat pelbagai komponen. Jasad perang yang terhasil selepas proses penyahikatan disinter pada suhu 1400,
1450, 1500, 1550, 1600 dan 1650°C selama 2 jam. Selanjutnya nilai ketumpatan, kekerasan dan keliatan patah bagi
jasad tersinter diukur. Mikrostruktur jasad tersinter ditentukan dengan menggunakan mikroskop imbasan elektron
(SEM). Kajian menunjukkan nilai ketumpatan, kekerasan dan keliatan patah bagi jasad tersinter meningkat sejajar
dengan peningkatan suhu pensinteran. Hasil uji kaji juga mendapati pada suhu pensinteran 1650°C sifat mekanik bahan
mencapai keadaan maksimum. Penumpatan jasad tersinter 98% menghampiri ketumpatan teori dengan nilai kekerasan
16.9 GPa dan keliatan patah mencecah 3.95 MPa.m1/2. Keputusan tersebut dapat dikaitkan dengan mikrostruktur bahan
yang padat didorong oleh tumbesaran ira yang lengkap.
Kajian mengenai grafin kini semakin meluas disebabkan sifat kebolehaliran terma yang mampu meningkatkan potensi
bahan komposit. Penambahan grafin dalam matriks kuprum dikaji dengan menggunakan gabungan bahan pengikat
iaitu polietilena glikol (PEG), polimetil metakrilat (PMMA) dan asid stearik. Penggunaan grafin sebagai bahan pengisi
dalam matriks kuprum merupakan pendekatan baru yang bertujuan untuk meningkatkan kebolehaliran terma produk
yang dihasilkan. Namun, penambahan grafin dalam matriks kuprum boleh menyebabkan ketidaksamarataan zarah
komposit kerana penggumpalan zarah-zarah grafin. Oleh itu, kaedah sonikasi dan pengacauan magnetik semasa proses
pra-campuran digunakan bagi menghasilkan bahan suapan yang sebati dan penyerakan grafin yang lebih baik tanpa
penggumpalan. Suhu proses sonikasi telah ditetapkan pada 55˚C dengan masa sonikasi yang berbeza iaitu 30 minit, 60
minit dan 90 minit. Bagi proses pengacauan magnetik, parameter yang digunakan adalah 55˚C, selama 21 jam pada
kelajuan yang berbeza iaitu 300, 350 dan 400 rpm. Analisis imej Pancaran Medan Mikroskopi Elektron Pengimbasan
(FESEM) dan Pemetaan EDX telah dijalankan bagi mengkaji penyerakan grafin dalam komposit kuprum grafin. Keputusan
menunjukkan hasil yang lebih baik diperoleh selepas proses sonikasi dan pengacauan magnetik dijalankan. Penyerakan
terbaik yang lebih seragam dan sebati diperoleh pada masa sonikasi 60 min dan pengacauan magnetik pada kelajuan
sederhana iaitu 350 rpm. Zarah grafin didapati kurang bertumpu pada satu tempat dan penggumpalan semula juga
tidak berlaku. Penyerakan sebati ini menjadikan hubungan antara muka zarah-zarah grafin dan kuprum menjadi lebih
baik seterusnya mampu mengurangkan keliangan bagi penghasilan jasad akhir.
Pembangunan bahan komposit aloi titanium (Ti6Al4V)/wolastonit (WA) semakin mendapat permintaan yang tinggi
terutamanya dalam aplikasi implan tulang. Ti6Al4V adalah sejenis aloi logam yang terkenal dengan sifat mekanik yang
tinggi dan bioserasi manakala seramik WA merupakan bahan biokaca yang bersifat bioaktif dan sesuai untuk dijadikan
bahan implan. Proses pengacuan suntikan serbuk (PIM) adalah proses teknologi serbuk yang boleh menghasilkan jasad
yang kecil dan berbentuk kompleks pada kos yang rendah. Ketumpatan jasad anum yang rendah boleh menyebabkan
kecacatan seperti retakan berlaku semasa proses penyahikatan dan pensinteran dijalankan. Oleh itu, jasad anum yang
optimum terhadap ketumpatan adalah penting bagi menghasilkan komposit yang mempunyai sifat mekanik dan fizikal
yang baik. Kajian ini memberi tumpuan terhadap kesan parameter proses pengacuanan terhadap jasad anum komposit
Ti6Al4V/WA. Nilai pembebanan serbuk ialah 67.0 % isi padu. Serbuk Ti6Al4V dan WA dengan nisbah peratus berat
masing-masing adalah 90:10 dicampurkan bersama 60 % bt. stearin sawit (SS) dan 40% bt. polietilena (PE) untuk
membentuk bahan suapan. Parameter optimum yang diperoleh bagi proses pengacuanan suntikan ditentukan melalui
kaedah Taguchi berdasarkan ketumpatan jasad anum ialah: suhu penyuntikan pada 130°C, suhu acuan pada 50°C,
tekanan penyuntikan pada 13 bar dan masa penyuntikan pada 10 s. Nilai purata ketumpatan tertinggi adalah 3.095 g/
cm3
. Analisis ANOVA menunjukkan suhu acuan memberikan pengaruh paling tinggi iaitu 57.63% bagi mendapatkan jasad
anum yang mempunyai ketumpatan yang tinggi. Uji kaji pengesahan menunjukkan jasad anum yang terhasil berada
dalam julat prestasi optimum yang dijangkakan. Penghasilan jasad anum yang bebas daripada kecacatan adalah penting
bagi menentukan sifat mekanik dan fizikal yang baik pada jasad sinter.
Dalam kertas ini dibentangkan hasil kajian sifat fizikal dan terma komposit elektrolit berasaskan samarium terdop seria (Ce0.8Sm0.2O1.9, SDC) dan karbonat (67%mol Li2CO3/ 33%mol Na2CO3). Komposit SDC-(Li/Na)2CO3 adalah pengalir berion yang berpotensi digunakan sebagai bahan elektrolit sel fuel oksida pepejal bersuhu rendah (LT-SOFC). Pencirian komposit elektrolit ini meliputi morfologi, luas permukaan bahan, analisis terma dan keliangan pelet elektrolit. Komposit elektrolit SDC-(Li/Na)2CO3 disediakan dalam dua langkah: (1) penyediaan serbuk samarium terdop seria melalui kaedah sol-gel dan (2) pencampuran samarium terdop seria dan karbonat dalam pelbagai komposisi yang berbeza melalui kaedah tindak balas keadaan pepejal. Pelet elektrolit dihasilkan dengan tekanan mampatan 25, 50, 150 and 200 MPa pada suhu pensinteran 500, 600, 700 dan 800oC. Keputusan XRD menunjukkan bahawa penambahan karbonat tidak mengubah struktur fasa SDC. Keputusan FESEM menunjukkan bahawa sebatian karbonat adalah amorfus dan tersebar dengan baik dalam matriks SDC. Semakin tinggi kandungan karbonat dalam komposit, luas permukaan serbuk komposit didapati semakin kecil. Keputusan analisis terma menunjukkan bahawa takat lebur fasa karbonat berkurang dengan berkurangnya kandungan karbonat. Keliangan optimum yang sesuai bagi elektrolit LT-SOFC iaitu 3.38% dan 4.85% telah dicapai masing-masing untuk sampel dengan kandungan karbonat 20% (SDC8020) dan 30% (SDC7030) dengan suhu pensinteran 600oC dan tekanan mampatan 200 MPa.
Moldability of metal injection molding (MIM) is dependent on the outward appearance of the resultant feedstock. Properties of the binders used will influence the properties of the feedstock. Stainless steel powder 316L with mean size 22 μm and the binder system consists of three major fractions of paraffin wax, thermoplastic natural rubber and stearic acid with a powder loading of 65 vol. % was investigated. Comparison was also made with existing palm stearin in the binder system replacing the paraffin wax. Kinetic solvent extractions were done to determine the differences between the binder systems. The feedstock was then injected into tensile bar using vertical injection machine. The results showed that there is a slightly time extension during the solvent extraction as a comparison. The feedstock has been successfully injection molded at 190-200°C. Study of thermal analysis such as DSC and TGA has been done as a preparation for the thermal debinding and sintering process. This study demonstrated that a backbone polymer; thermoplastic natural rubber performs best in term of flow stability and compact quality and also saves in processing time.
Oksida perovskit La1-xSrxCo0.2Fe0.8O3-δ (LSCF) dengan x = 0.3-0.5 telah dihasilkan melalui kaedah sol-gel. Ia merupakan pengalir berion campuran yang sangat baik sebagai bahan katod untuk sel fuel oksida pepejal bersuhu sederhana (IT-SOFC). Serbuk yang terhasil dicirikan dengan menggunakan teknik pembelauan sinar-X (XRD) dan keputusannya menunjukkan bahawa hablur perovskit yang tulen terhasil sepenuhnya setelah dikalsin pada suhu 900°C. Kesan suhu pensinteran ke atas pelet LSCF dikenal pasti dengan menggunakan Mikroskop Elektron Imbasan (SEM). Keputusan menunjukkan
bahawa perovskit LSCF mempunyai keliangan yang optimum sebanyak 30% setelah disinter pada suhu 900°C. Keliangan optimum ini membolehkan tindak balas penurunan oksigen berlaku dengan lebih mudah. Analisis FTIR yang dijalankan menunjukkan kehadiran ikatan Fe-O dalam serbuk LSCF dan tiada bendasing yang wujud dalam serbuk LSCF.
The modified spectral index r(α); the Westcott gLu(Tn) factor and absolute neutron temperature Tn were determined for the handling of non-1/ν (n, γ) reaction based on the Westcott formalism using k0-neutron activation analysis (k0-NAA) method at the Malaysian Nuclear Agency (MNA) research reactor. The r(α) was determined by the bare bi-isotopic monitor method using measurement of radionuclides of 97Zr and 95Zr. The 176Lu as non-1/ν and 197Au as 1/ν monitors were utilized for determination of gLu(Tn). The r(α) and gLu(Tn) values ranged from 0.0715 to 0.1417 with a RSD of 15.24% and from 1.7832 to 2.0149 with a RSD of 3.58%, respectively. The accuracy of the method was evaluated based on the calculated absolute neutron temperature (Tn) value. The calculated average value of Tn was 40.56±9.32°C while the value reported by MNA was 40°C, which represents an acceptable level of consistency.
In this study, injection molding parameters, including green strength, surface quality and green part density, were optimized using the L18 Taguchi orthogonal array. The L25 Taguchi method was used to optimize the green density of solvent debinding parameters. The feedstock consisted of stainless steel powder (SS316L), with powder loading fractions of 63, 63.5 and 64 v/o. The binder compositions used in the study were polyethelene glycol (PEG-73 wt. %), polymethyl methacrilate (PMMA-25 wt. %) and stearic acid (2 wt. %). The Taguchi method was used to optimize the injection parameters. The obtained optimum parameters were as follows: mold temperature of 65oC, injection temperature of 145oC, injection pressure of 650 bar, injection flow rate of 20 m3/s, holding time of 5 s and powder loading of 64% v/o. Analysis of variance results showed that mold temperature has the greatest influence in the production of good green part surface quality and that powder loading gave the best green part strength. Immersion time and temperature were used to optimize for solvent debinding parameters. By optimizing the solvent debinding parameters, an immersion temperature of 61oC and immersion time of 5 h produced the highest density which is the optimum value gain in this study.
Elektrolit dwi lapisan samarium terdop seria (sDc)lytria terstabil bismut (YsB) dikaji adalah untuk menghasilkan sel fuel oksida pepejal bersuhu sederhana (rr-soFc). Matlamat penyelidikan ialah mengkaji kesan suhu pengkalsinan terhadap penghasilan struktur elektrolit dwi lapisan SDCIYSB untuk IT-SOFC. Elektrolit dwi lapisan SDC dan YSB dihasilkan melalui kaedah sol-gel dan kaedah tindak balas keadaan pepejal. Serbuk SDC dikalsin pada suhu 800, 1000 dan 1200°C selama 5 jam dan serbuk YSB dikalsin pada suhu 550, 650 dan 750°C selama 2 jam. Analisis pembelauan sinar-X (xRD) mendapati serbuk SDC yang dihasilkan pada suhu 800-1200°C selama 5 jam mempunyai struktur Sm02Ce0.801.90, manakala YSB mempunyai struktur Y0.25Bi0.75015 pada suhu 750°C selama 2 jam. Peningkatan suhu pengkalsinan SDC pada suhu 800, 1000 dan 1200°C selama 5 jam menunjukkan peningkatan pada saiz hablur iaitu 42.4, 58.7 dan 79.9 nm. Peningkatan suhu pengkalsinan YSB sehingga suhu 750°C menyebabkan berlakunya perubahan struktur YSB daripada bentuk tetragon menjadi kiub fluorit dengan saiz hablur 28.86 nm. Hasil perbandingan ujian prestasi sel pada suhu pengoperasian sederhana (650°C), penggunaan elektrolit dwi lapisan (sDaYsR) dengan suhu pengkalsinan SDC-1200°C dan YsB-750°C menghasilkan prestasi sel paling tinggi dengan ketumpatan kuasa 81.55 mW/cm2 dan ketumpatan arus 225.36 mA/cm2.
Ultrafine, cemented tungsten carbide (WC) possesses exceptional hardness, wear resistance and high strength in various applications. In this study, WC was produced through micro powder injection molding (μPIM), which is also applicable for metals and ceramics in producing complex parts with high-dimensional accuracy. Different inhibitors, such as VC, Cr2C3, NbC, or TaC, were added to improve the mechanical properties of WC and control its grain growth. The effects of a grain growth inhibitor were investigated by adding VC in WC–10%Co–nVC, where n = 0 to 1.2 wt. %. The mechanical properties of the sintered part, such as hardness and flexural strength, were determined. The morphology and elemental distribution of the samples were studied by field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. X-ray diffraction was employed to study the phases of the obtained samples. The results showed that the sample with 0.4 wt. % VC (optimal amount) sintered at 1410°C exhibited the highest theoretical density, hardness and flexural strength of 95.2%, 1973±31 HV and 2586±172 MPa, respectively. The average grain size measured was 519±27 nm. VC acted as a grain growth inhibitor during sintering, thereby improving the mechanical properties.
Feedstock preparation, as well as its characterization, is crucial in the production of highly sintered parts with minimal defect. The hard metal powder - particularly, cemented carbide (wc-co) used in this study was investigated both physically and thermally to determine its properties before the mixing and injection molding stage. Several analyses were conducted, such as scanning electron microscopy, energy dispersive X-ray diffraction, pycnometer density, critical powder volume percentage (cPvP), as well as thermal tests, such as thermogravimetric analysis and differential scanning calorimetry. On the basis of the CPVP value, the feedstock, consisting of wc-co powder, was mixed with 60% palm stearin and 40% polyethylene at an optimal powder loading, within 2 to 5% lower than the CPVP value. The CPVP spotted value was 65%. The feedstock optimal value at 61% showed good rheological properties (pseudoplastic behavior) with an n value lower than 1, considerably low activation energy and high moldability index. These preliminary properties of the feedstock serve as a benchmark in designing the schedule for the next whole steps (i.e. injection, debinding and sintering processes).
Micro powder injection molding (vim) is a promising process that may satisfy the demand on miniaturization parts to micro domain in mass production with low manufacturing cost. Three mol% yttria stabilized zirconia (Ysz) with nano-sized powder and binder system consists of polyethylene glycol (PEG), polymethyl methacrylate (PMMA) and stearic acid (sA) were used. Nano-size powders with higher surface area generally require more binder to form a feedstock. As such, determination of the optimum powder loading of the feedstock for 1UPIM process is important. The rheological characteristics of different YSZ feedstocks with powder loading of 52 53 and 54 vol.% were investigated in terms of flow behavior as a function of viscosity and shear rate. Fairly low values of flow behavior exponent ranging from 025 to 0.39 (n<1) resulted in pseudoplastic flow behavior of the examined Yszfeedstock. The 52 vol.% feedstock exhibited the lowest viscosity resulting in highest activation energy and lowest moldability index of 1.862x10-6, while the 54 vol.% feedstock regardless to its high viscosity, yielded a low activation energy of 4.14 kJImol and high moldability index of 4.59x10-6. Based on rheological properties obtained, a powder loading of 54 vol.% has desirable feedstock characteristics for iumm process and exhibited molding ability for micro detail filling. The relationship between the optimum rheological properties obtained and the actual injection process was also determined. The results showed that the green parts were able to be injected without defects such as short shot or flashing.
owder injection molding (PIM) is able to produce porous titanium alloy/hydroxyapatite composite through the space holder technique. Thermal debinding and sintering processes were the main challenges due to different properties of metal and ceramic in producing such composite. This study focused on the effect of different space holders on the physical and mechanical properties of debound and sintered porous titanium aloi/hydroxyapatite composite. The feedstock is containing of 80 wt. % of titanium alloy/hydroxyapatite with 20 wt. % of space holders such as sodium chloride (NaCl) and polymethylmethacrylate (PMMA), respectively. The binders were then removed from the injected samples by two stages of debinding; solvent and thermal debinding. The sintering was performed at three different temperatures 1100oC, 1200oC and 1300oC at a heating rate of 10oC /min and holding time of 5 h. It was found that the samples containing PMMA space holder was fractured after sintering. While, the samples containing NaCl space holder successfully formed pores and not fractured. At sintering temperature of 1300oC, the density, compressive strength and porosity volume percentages for the sintered sample containing NaCl space holder were 3.05 g/cm3, 91.7 MPa. and 11.9 vol%, respectively.
Metallic foams are a new class of materials that have a great potential to be used in various functional and structural applications. Due to their competitive price compared to aluminium, metallic foams are anticipated to become an alternative material for light-weight structures. In this study, stainless steel foams are fabricated using a powder space holder method. The materials used include stainless steel powder, a novel space holder glycine and binders consisting of palm stearin and of polyethylene (PE). The stainless steel foams are sintered at 1100o C, 1200o C and 1300o C with sintering times of 1, 2 and 3 h, respectively, to investigate the effects of the sintering parameters on the compressive yield strength of the stainless steel foams. The results showed that all of the stainless steel foams produced exhibit the general behaviours of metal foams. The sintering time is the most significant parameter that influences the compressive yield strength of stainless steel foams. Increasing the sintering temperature and sintering time will increase the compressive yield strength. The interaction between the sintering temperature and sintering time is found to be not statistically significant.
Natural fibres potentially offer better reinforcement to improve the mechanical and physical properties of polymer composites. However, these natural materials at this stage are not fully explored yet due to the fibres themselves have limited heat resistance and are quite sensitive to moisture. This limitation will weaken the adhesion when interacting with thermoplastic matrices during the processing of composites. Therefore, the main purpose of this study is to investigate inherent strength characteristics among kenaf (core and bast) fillers as a reinforcement in polypropylene composites at various geometries and loadings via the injection moulding process. The composite materials consisted of kenaf with the geometric core filler of the 20 mesh (992 µm), 40 mesh (460 µm) and bast filler (166.9 µm) were mixed with polypropylene based on the filler loadings of 10 up to 40 wt. %. The results showed that bast filled composites had the highest tensile strength of 19.52 MPa at 30 wt. %, compared to core filled composites. Instead, 20 mesh core filled composites were obtained had the highest flexural strength which values were 25 MPa and 29 MPa at 20 wt. % and 30 wt. %, respectively. While 40 mesh core filled composites had the highest values of 25.35 MPa at 40 wt. % of filler loading compared to bast filled composites. SEM micrograph images showed the good interfacial bonding of core filler which surrounded by PP leading to diffusion and permeation of bonding. In conclusion, the use of kenaf (core and bast) fillers as a reinforcement in composite materials is reasonable to maximise the use of fibre from natural sources.
Composite materials have increasingly become crucial in manufacturing engineering products and producing commodity
materials in the major industries including; automotive, aerospace, marine, construction, agriculture and health science.
However, several improvements regarding the strength, dimensional stability and the cost of production are required.
In this study, composite of Kenaf, multi-wall carbon nanotube (MWCNT) and polypropylene (PP) with maleic anhydridegrafted
polypropylene (MAPP) are examined. The results highlight that increasing MAPP loading, in turn, increases the
value of the mechanical properties. The composites are produced by blending kenaf/MWCNT/PP using a Sigma blade
mixer and injection moulding. Injection moulding is a significant operation used to produce plastic products. In the
study, Kenaf core fibre was mixed with MWCNT and polypropylene, in addition to MAPP. The MAPP is added by applying
different percentage (1, 2, 3 and 4 wt. %) during the blending process. The main objective of the study was to analyse the
effects of MAPP concentrations on the mechanical properties of the Kenaf/MWCNT/PP composite. The results of the study
established that MAPP 3 wt. % concentration with MWCNT 3 wt. % loading and Kenaf 30 wt. % filler provide optimum
results for the composites. There was approximately, a 21% enhance in tensile strength of Kenaf 30 wt. %/MWCNT, 3 wt.
%/MAPP, 3 wt. %/PP observed compared to the (without) MAPP composite. The composites with coupling agent stimulate
better filler dispersion between Kenaf, MWCNT and PP observed using a scanning electron microscope (SEM) and fieldemission
scanning electron microscope (FESEM).