Proses penyemperitan merupakan salah satu proses pra-pencampuran yang dapat membantu meningkatkan tahap serakan
bahan pengalir dalam komposit polimer pengalir (CPC). Tahap keberaliran elektrik dilihat tidak begitu memuaskan
walaupun telah melalui proses serakan melalui pengacuan mekanik. Kajian ini dijalankan bagi mengoptimumkan
proses penyemperitan bahan gentian karbon terkisar (MCF) dan polipropilena (PP) iaitu suhu penyemperitan dan halaju
putaran melalui kaedah reka bentuk eksperimen (Taguchi). Susunan orthogonal Taguchi L9 digunakan bagi menentukan
aras yang paling optimum serta menjalankan analisis varian bagi memperoleh nilai keberaliran elektrik yang paling
baik. Pengoptimuman parameter pada suhu penyemperitan 210ºC hingga 250ºC dan halaju putaran 50 hingga 90 rpm
menggunakan komposisi bahan sebanyak 80 % bt. MCF dan 20 % bt. PP dengan tahap keberaliran elektrik meningkat
pada tahap maksimum 3.67 S/cm. Pengoptimuman parameter ini menunjukkan bahawa reka bentuk eksperimen yang
terhasil mampu menghasilkan nilai keberaliran elektrik yang tinggi serta mempunyai sifat mekanik yang baik.
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.
Kaedah tindak balas permukaan (RSM) telah digunakan untuk mengoptimumkan penyediaan biokomposit rHDPE berpenguat sekam padi sebagai pengisi. Sekam padi adalah sisa pertanian yang mempunyai ciri-ciri kayu dan digunakan secara pesat dalam bidang komposit kayu plastik. Kesan parameter suhu, tekanan serta masa proses tekanan panas ke atas kekuatan tegangan telah dikaji. Reka bentuk Box Bechken telah digunakan untuk menentukan parameter optimum biokomposit yang mempunyai kekuatan tegangan yang tinggi. Model tertib kedua telah dibangunkan untuk meramalkan kekuatan tegangan berdasarkan reka bentuk komposit. Didapati bahawa komposit sesuai digunakan apabila model regresi kuadratik dengan pekali penentu bilang (R2) yang tinggi. Keadaan proses menekan yang optimum dicapai pada suhu 180°C, tekanan 1000 psi dan masa 9 min dengan pekali penentu berbilang mencapai 97%. Di bawah keadaan yang optimum ini, komposit yang mengandungi 10, 20, 30, 40 dan 50% gentian RH telah disediakan. Kekuatan tegangan dan modulus tegangan biokomposit menunjukkan peningkatan apabila kandungan gentian RH ditambah.
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.
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.
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.
Penggunaan proses pengendapan elektroforetik (EPD) telah menunjukkan potensi yang memberangsangkan dalam pembangunan komponen katod untuk sel tunggal sel fuel oksida pepejal (soFc). Sehubungan itu, kesan saiz elektrod lawan dan masa pengendapan terhadap ketebalan dan kualiti filem komposit katod LSCF-SDC karbonat pada substrat seria terdop samarium (sDc) karbonat telah dikaji untuk membuktikan kebolehlaksanaan kaedah ini. Kesan perubahan parameter tersebut terhadap penghasilan filem LSCF-SDC karbonat dikenal pasti dengan menetapkan nilai pH ampaian dan voltan kenaan. Parameter masa pengendapan diubah suai dengan lima masa yang berbeza iaitu antara 10 - 30 min, manakala dua saiz elektrod lawan yang digunakan ialah 25 x 25 mm2 dan 50 x 50 mm2. Filem komposit katod kemudian disinter pada suhu 600°C selama 90 min. Pencirian mikrostruktur dan ketebalan filem LSCF ini diperoleh menggunakan mikroskop imbasan elektron (sEm). Penggunaan saiz elektrod lawan yang besar (50 x 50 mm2) didapati mampu menghasilkan filem komposit katod yang lebih tebal . Selain itu, kesan perubahan parameter (masa pengendapan dan saiz faring elektrod lawan) dikenal pasti melalui analisis berat dan ketebalan filem LSCF-SDC karbonat. Filem katod berketebalan 4.6 - 30.8 ,um telah berjaya diendap pada tempoh pengendapan yang digunakan. Ketebalan katod komposit LSCF-SDC karbonat yang diperoleh berada dalam julat ketebalan yang telah dihasilkan oleh pengkaji terdahulu melalui kaedah pembentukan yang sama ke atas bahan katod lain. Keputusan kajian menunjukkan bahawa kaedah pengendapan elektroforetik bagi pembentukan katod komposit amat berpotensi untuk kajian yang lebih intensif.
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.
Kertas kajian ini membincangkan kesan suhu pensinteran ke atas prestasi elektrokimia katod komposit sel bahan api oksida pepejal LSCF-SDCC. Katod komposit LSCD-SDCC disediakan dengan nisbah berat 50:50 dan dihasilkan melalui kaedah pengedapan elektroforetik (EPD). Kaedah EPD dijalankan ke atas kedua belah sisi substrat SDCC untuk menghasilkan sel simetri. Sel simetri yang terhasil adalah menggunakan suhu sinter yang berbeza (550°C hingga 750°C) sebelum analisis ke atas mikrostruktur dan ujian prestasi elektrokimia dijalankan. Kesan suhu sinter ke atas keliangan permukaan dikaji menggunakan analisis spektrometer serakan tenaga sinar-X, mikroskop elektron imbasan pancaran medan dan J-image. Kemudian, hubungan antara rintangan pengutuban, Rp dengan suhu sinter diukur menggunakan spektroskop elektrokimia impedans. LSCF-SDCC yang telah disinter pada suhu 600°C memberikan nilai Rp terendah iaitu 0.68 Ω pada suhu operasi 650°C. Kajian ini mencadangkan bahawa suhu sinter antara julat 550-650°C sebagai suhu pensinteran terbaik untuk menghasilkan katod komposit LSCF-SDCC berprestasi tinggi.
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.
316L stainless steel is a common biomedical material. Currently, biomedical parts are produced through powder injection molding (PIM). Carbon control is the most critical in PIM. Improper debinding can significantly change the properties of the final product. In this work, thermal debinding and sintering were performed in two different furnaces (i.e. laboratory and commercially available furnaces) to study the mechanical properties and corrosion resistance. Debounded samples were sintered in different atmospheres. The samples sintered in inert gas showed enhanced mechanical properties compared with wrought 316L stainless steel and higher corrosion rate than those sintered in the vacuum furnace. The densification and tensile strength of the hydrogen sintered samples increased up to 3% and 51%, respectively, compared with those of the vacuum-sintered samples. However, the samples sintered in inert gas also exhibited reduced ductility and corrosion resistance. This finding is attributed to the presence of residual carbon in debonded samples during debinding.
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).