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"Bronze (Cu - Sn) are the most commonly used materials for self lubricating bearings produced by powder metallurgy process. The characteristics and the performance of these bearings are highly dependent on the chemical composition and the microstructure, especially the fraction of open porosity. While the microstructure fully dependent on the control of the compaction and sintering process. In this study, the effects of three parameters were investigated : (1) the Sn content (5 % , 10 % and 15 %); (2) the compaction pressure (200 MPa, 300 MPa and 400 MPa); and (3) the sintering temperature (800°C, 850°C and 900°C) on the characteristics of Cu-Sn P/M alloys. The increase in compaction pressure will increase the green density and the green strength, while the increase in Sn content will decrease the green strength. In general, the increase in sintering temperature will decrease the sintered density followed by the swelling of the sintered. The increase in sintering temperature also decrease the macrohardness and the compressive strength. The amount of porosity and the second phase , 8 phase - Cu31Sna, formed during sintering is increased with the increase in Sn content and then followed by the increase in grain size."

"Zirkonium-Niobium paduan (Zr-Nb paduan) memiliki potensi untuk menggantikan implant Titanium kontemporer dengan mempertimbangkan sitotoksisitas nya, suseptibilitas magnetik dan ketahanan korosi. Metalurgi serbuk sebagai salah satu metode pembentukan dapat digunakan dalam produksi implant dengan desain rumit dan struktur mikro yang fleksibel, baik dalam komposisi dan porositas. Pemadatan dan sintering dilakukan untuk menghasilkan produk yang padat dengan porositas. Pengamatan morfologi porositas akan diamati dengan mikroskop optik dan jumlah porositas dalam paduan akan diamati dengan pengujian porositas. Sedangkan struktur kristal diamati dengan dan X-Ray Diffraction (XRD). Konstituen fasa mikro sangat tergantung pada komposisi Niobium. Pengujian kekerasan menunjukkan peningkatan seiring dengan penambahan jumlah Niobium. Sementara itu penambahan Niobium akan menurunkan jumlah porositas dan mengubah morfologi porositas menjadi berbentuk jaring. Penambahan Niobium dalam jumlah besar membutuhkan temperature sintering yang jauh lebih tinggi dibandingkan paduan dengan jumlah Niobium lebih kecil.

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Zirconium-Niobium alloy (Zr-Nb alloy) has potency to replace the contemporary Titanium bioimplant by considering its cytotoxicity, magnetic susceptibility and corrosion resistance. Powder metallurgy as one of the forming methods could be used in production of bioimplant with intricate design and flexible microstructure, both in composition and porosity. Compaction and sintering is carried out to produce solid product with remained porosity. Resulting porosity of Zr-Nb alloy produced by powder metallurgy method will be characterized by density measurements and optical microscopy. Crystalline structure is observed by X-Ray Diffraction (X-RD). The microphase constituent is highly dependent on Niobium composition. The density of alloy will decrease as the addition of Niobium. In contrary, the hardness of alloy will increase as the addition of Niobium."

"In general, the Nd-Fe-B as-cast ingot is homogenized for a long time before the hydrogenation, disproportionation, desorption and recombination (HDDR) process, to produce good magnetic properties. Since the homogenizing process is expensive, this work examined the possibility of replacing it with a water quenching process for Nd-Fe-B magnetic powder. The magnetic powders were soaked at 1100oC for 4 hours, followed by water quenching prior to HDDR. The resulting powder had magnetic properties that were almost similar to magnetic powder that was homogenized prior to HDDR. The remanence values of the water-quenched alloy and the homogenized alloy were 7.8 KG and 8.9 KG, respectively, while the coercivity values were 12.6 KOe and 10.3 KOe, respectively. In general, the magnetic properties of both samples were not much different. The microstructure of Nd2Fe14B phase combined with a very slight Nd rich phase in micro grain boundary likely caused the coercivity enhancement."

"ABSTRACTPaduan memori bentuk berbasis tembaga adalah bahan alternatif untuk menggantikan paduan Ni-Ti komersial karena paduannya ekonomis dan mudah dibuat. Penggunaan paduan memori bentuk berbasis tembaga seperti paduan terner Cu-Zn-Al biasanya memiliki beberapa kendala seperti stabilisasi fase yang dapat dihindari dengan menggunakan metode pendinginan alternatif. Oleh karena itu, penelitian ini mempelajari efek metode pendinginan pada karakteristik martensit dan pemulihan regangan paduan Cu-28Zn-3.5Al (wt.%). Plat as-cast dihomogenisasi pada 850 oC selama 2 jam sebelum larutan diperlakukan pada 850 oC selama 30 menit diikuti dengan pendinginan menggunakan direct quench (DQ), up quench (UQ) dan metode step quench (SQ). Karakterisasi pada paduan dilakukan dengan menggunakan uji komposisi OES, pengamatan struktural menggunakan mikroskop optik dan SEM, analisis mikro EDS, uji XRD, uji kekerasan, uji DSC, dan uji tekuk untuk mengamati pemulihan regangan. As - cast dan as - homogenisasi terdiri dari α [A1] dan β [D03] fase biner dengan α [A1]: β [D03] rasio 46:54, bersama dengan kekerasan fase α [A1] dari 106.73 HV dan β [D03] kekerasan fase 195,82 HV. Perlakuan panas langsung (DQ) dan naik (UQ) menghasilkan β ′ [M18R] dengan jarak interlamelar 9,08 dan 6,08, masing-masing, sedangkan pendinginan langkah menghasilkan fasa β [D03] dan α [A1] dengan β [D03]: α [ A1] dari 94: 6. Kekerasan paduan pada pendinginan langsung, pendinginan naik dan pendinginan adalah 175,46 HV, 186,90 HV, dan 195,49 HV. Sedangkan regangan pemulihan quench langsung, quench dan step quench adalah 52,76, 58,4 dan 5,86%. Up quench memiliki suhu transformasi austenit dan martensit yang selesai dalam periode yang lebih pendek daripada pendinginan langsung yang karenanya mengakomodasi sifat memori bentuk yang lebih baik.

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ABSTRACTCopper-based form memory alloys are an alternative material to replace commercial Ni-Ti alloys because they are economical and easy to make. The use of copper-based form memory alloys such as the Cu-Zn-Al ternary alloy usually has several constraints such as phase stabilization which can be avoided by using alternative cooling methods. Therefore, this study studies the effects of the cooling method on the characteristics of martensite and strain recovery of Cu-28Zn-3.5Al alloys (wt.%). As-cast plates were homogenized at 850 oC for 2 hours before the solution was treated at 850 oC for 30 minutes followed by cooling using direct quench (DQ), up quench (UQ) and step quench (SQ) methods. Characterization of the alloy was carried out using the OES composition test, structural observations using optical microscopy and SEM, EDS micro analysis, XRD test, hardness test, DSC test, and buckling test to observe strain recovery. As-cast and as-homogenization consist of α [A1] and β [D03] binary phase with α [A1]: β [D03] ratio of 46:54, along with α [A1] phase hardness of 106.73 HV and β [D03 ] 195.82 HV phase hardness. Direct heat treatment (DQ) and rise (UQ) produce β ′ [M18R] with interlamatic distances of 9.08 and 6.08, respectively, whereas cooling steps produce phases β [D03] and α [A1] to β [D03] ]: α [A1] of 94: 6. Hardness of the alloy in direct cooling, rising cooling and cooling is 175.46 HV, 186.90 HV, and 195.49 HV. While the direct recovery quench strain, quench and step quench are 52.76, 58.4 and 5.86%. Up quench has austenitic and martensitic transformation temperatures that are completed in a shorter period than direct cooling which therefore accommodates better shape memory properties."

"Sintesis semikonduktor Cu2SnS3 (CTS) sebagai penyerap semikonduktor telah berhasil dilakukan dengan metode fisika menggunakan planetary ball mill energi tinggi dan bola ZrO2 (zirkonia) dengan variasi waktu milling dan komposisi unsur. Hasil penggilingan kemudian dianil pada suhu 450oC selama 30 menit. Keberadaan fasa CTS semakin meningkat setiap bertambahnya waktu milling, dengan waktu milling terlama 240 menit menghasilkan pola difraksi yang paling mendekati referensi dan tertinggi dari semua sampel. Penambahan Sn pada sampel yang kaya Sn mempengaruhi kelancaran hasil uji difraksi, namun mengurangi fasa CTS yang terbentuk dan meningkatkan pembentukan senyawa pengotor. Nilai energi celah pita yang lebih tinggi pada sampel kaya Sn bukan disebabkan oleh absorbansi CTS, melainkan oleh fase pengotor yang diduga memiliki kemampuan sebagai penyerap akibat proses fisik dan penambahan unsur Sn pada pengujian. Sampel. Hasil uji Difraksi sinar-X tinggi dan nilai energi celah pita adalah 1,1-1,2 eV yang sesuai dengan literatur. Hasil pengujian mikroskop elektron scanning diperoleh yang menunjukkan terjadinya penyatuan butir dan rongga CTS akibat proses fisis dan annealing.The synthesis of Cu2SnS3 (CTS) semiconductor as a semiconductor absorber has been successfully carried out by physical methods using high energy planetary ball mill and ZrO2 (zirconia) balls with variations in milling time and elemental composition. The milled results were then annealed at 450oC for 30 minutes. The presence of the CTS phase increases with every increase in milling time, with the longest milling time of 240 minutes producing the diffraction pattern that is closest to the reference and the highest of all samples. The addition of Sn to Sn-rich samples affects the smoothness of the diffraction test results, but reduces the CTS phase formed and increases the formation of impurities. The higher band gap energy value in Sn-rich samples was not caused by the absorbance of CTS, but by the impurity phase which was thought to have the ability as an absorbent due to the physical process and the addition of Sn elements in the test. Sample. The results of the X-ray diffraction test are high and the band gap energy value is 1.1-1.2 eV which is in accordance with the literature. Scanning electron microscope test results were obtained which showed the occurrence of coalescence of CTS grains and cavities due to physical processes and annealing."

"Pengembangan material biologis mampu luruh alami sebagai aplikasi perancah pembuluh darah telah banyak dilakukan. Pada penelitian sebelumnya Fe-Mn-C berstruktur busa dengan 5% kalium karbonat (K2CO3) berhasil dikembangkan dengan fasa austenit dan laju degradasi yang cukup baik. Namun kandungan karbon yang terbentuk masih sangat tinggi dengan membentuk fasa grafit (C) menyebabkan kekerasan yang terlalu tinggi dan meninggalkan sifat magnet yang akan mengganggu saat pemeriksaan MRI (Magnetic Resonance Imaging). Variasi komposisi unsur karbon (0%, dan 0,5%C) dilakukan untuk memperbaiki sifat mekanik dan membentuk fasa austenit sepenuhnya guna diperoleh sifat yang non magnetic. Pemaduan mekanik material serbuk dilakukan dengan metode rotary mixing dengan komposisi target Fe-35Mn dan Fe-35Mn-0,5C. Sinter dilakukan pada temperatur 850oC selama 3 jam dan dilanjutkan dengan sinter dekomposisi pada temperatur 1100oC selama 1,5 jam di atmosfer inert gas Nitrogen (N). Hasil sinter kemudian dilakukan karakterisasi sifat fisik, kimia, mekanik, dan perilaku korosinya. Fasa yang terbentuk adalah fasa austenit, dan fasa mangan oksida dengan laju degradasi yang baik dan tidak bersifat magnet.

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Development of degradable biomaterial for coronary stent applications has been carried out. Degradable biomaterial Fe-Mn-C with foam structure with 5% potassium carbonate (K2CO3) was successfully developed with austenite phase and good degradation rate. However, the carbon content still too high and produce graphite phase (C) causing the hardness becomes too high and will produce the magnetic properties that interfere with the examination process of MRI (magnetic resonance imaging). Variations of carbon composition (0%, and 0.5% C) has been done to improve mechanical properties and form a fully austenite phase to produce non-magnetic properties. Mechanical alloying of powder material done by rotary mixing method with a target composition of alloy are Fe-35Mn and Fe-35Mn-0,5C. Sintering was performed in inert gas atmosphere of nitrogen (N) at temperature of 850oC for 3 hours and continued at 1100oC for 1.5 hours. Several characterization was performed on sintered sampel such as physical, chemical, and mechanical properties also degradation behavior. Austenite and manganese oxide phase with a good rate of degradation and not magnetic properties are formed in this degradable biomaterial Fe-Mn-C."

"Telah berhasil dilakukan sintesis semikonduktor Cu2SnS3 (CTS) sebagai absorber semikonduktor yang dilakukan dengan metode fisik menggunakan mesin high energy planetary ball mill dan bola-bola ZrO2 (zirconia) dengan variasi waktu milling dan komposisi unsur. Hasil milling kemudian dilakukan annealing pada temperatur 450oC selama 30 menit. Kehadiran fasa CTS meningkat pada setiap peningkatan waktu milling, dengan waktu milling terlama selama 240 menit menghasilkan pola difraksi yang paling mendekati referensi dan paling tinggi dari semua sampel. Penambahan unsur Sn pada sampel Sn-rich berpengaruh terhadap kehalusan hasil uji difraksi, akan tetapi mengurangi fasa CTS yang terbentuk dan meningkatkan pembentukan senyawa pengotor. Nilai energi celah pita yang lebih tinggi pada sampel Sn-rich bukan dihasilkan oleh absorbansi CTS, melainkan oleh fasa-fasa pengotor yang diduga memiliki kemampuan sebagai absorber sebagai hasil dari proses fisik dan penambahan unsur Sn pada sampel uji. Didapatkan hasil uji X-ray Diffraction yang tinggi serta nilai energi celah pita sebesar 1,1-1,2 eV yang sesuai dengan literatur. Didapatkan hasil uji scanning electron microscope yang menandai terjadinya penyatuan butir-butir CTS dan voids sebagai hasil dari proses fisik dan annealing.

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The semiconductor syntesis of Cu2SnS3 has been succesfully carried as a semiconductor absorber by physical method using high energy planetary ball mill machine and ZrO2 (zirconia) balls with milling time and powder composition variations. The results from this process then annealed in an electric furnace in 450oC for 30 minutes. The presence of CTS phase increased simultaneously with the increase of milling time, with the longest milling time 240 minutes produced the closest and the highest x-ray diffraction pattern compared to the literatures of all samples. The addition of Sn element in Sn-rich samples affected the refinement of x-ray diffraction patterns, however reduced the CTS phases formed and shown increased impurity phases. The higher value of bandgap energies from Sn-rich samples may be not produced by the absorbance of CTS, but of the impurities as the other results from physical process and the addition of Sn element to the test samples. X-ray diffraction test confirm the high peak of CTS with 1,1-1,2 eV bandgap energy. Scanning electron microscope showed fusion of CTS grains and voids as the result of physical and annealing process."