Mochammad Dachyar Effendi

Laboratory biomass-burning aerosol studies use diverse facility designs that complicate comparison. This review introduces a framework linking facility architecture and smoke conditioning to reported organic aerosol mass enhancement.

This study evaluates the performance of ethylene propylene diene monomer (EPDM) composites for rubber sealing applications in a cable-based tsunami system. Rubber composites were prepared using EPDM rubber with varying monomer and filler content to determine the most suitable composite. Mechanical characterization reveals that the composition of EPDM and the amount of filler loading influence the mechanical properties. Dynamic mechanical analysis shows that ethylene and 5-ethylene-2-norbornene (ENB) content influence the glass transition and viscoelastic behavior of the composite. Thermal analysis of rubber composites using EPDM containing 70% ethylene and 5% ENB indicates no change in thermal stability due to prolonged immersion in seawater. Visual inspection using a microscope reveals no cracks on the surface of the rubber seal after the pressure chamber test for rubber composites utilizing EPDM with 70% ethylene and 5% ENB. It was shown that EPDM containing 70% ethylene and 5% ENB, with optimal reinforcement with 80 phr carbon black, exhibits the best performance for rubber sealing applications in subsea environments.

In this research, the production of carbon fiber composite (CFC) with epoxy resin was carried out for biomedical application. The surface of the carbon fibers was previously oxidized with concentrated nitric acid at a temperature of 100 °C for 30–120 min to create a rough surface impression on the carbon fibers to enhance interfacial bonding in the composite, increase surface area, and reduce surface tension. The carbon fiber/epoxy composite was fabricated using the vacuum assisted resin infusion method. Characterization of the oxidized carbon fibers and the composite products was performed using a digital microscope, scanning electron microscope, and Fourier Transform Infrared (FTIR) analysis. FTIR analysis results indicated that the carbon fiber oxidation process introduced new chemical functional groups, such as –CN and –CO groups. Mechanical characterizations included tensile testing of non-oxidized and oxidized carbon fiber and tensile testing of carbon fiber/epoxy composite. The results showed that the composite formed from oxidized carbon fibers/epoxy resin exhibited higher tensile strength compared to non-oxidized CFC. The longer the carbon fiber oxidation process, the higher the tensile strength values obtained.

CaP granules are used for open defect of bone. The important feature in the physical structure of a synthetic ceramic is its porosity. Pore structure is great importance for osteoconduction. The main objective of this study is to investigate the effect of adding carbon black as porogen agent on microstructure of CaP granules of droplet CaP. According to that, certain carbon black (325 mesh) has added into composition of microspheres CaP-alginate gelation with ratio CaP:Carbon black was 0.5, 1, and 1,5 weight ratios respectively. Scanning Electron Microscope (SEM) was used to investigate microstructure of droplet and shown that Irregular shape grain. Internal microstructure appears more open for samples produced without a presence of alginate after sintering process and confirmed by XRD pattern for whole samples. The porosity and pore size increased by increasing CB. On the other hand, no significant change on surface roughness and no transformation phase caused by adding CB. So that, it can be concluded that CB can serve as a porogen agent.

CaP granules as bone graft are used for open defect of bone, where is not necessary mechanical stability they are proposed for no-load bearing applications. The important feature in the physical structure of a synthetic ceramic bone graft is its porosity, pore size, the volume of porosity and interconnections between the pores are three crucial parameters. The pore structure is of great importance for osteoconduction. The level of porosity, pore size distribution and degree of pore interconnectivity significantly influence the extent of bone ingrowth. According to that, this study investigated the effect of sintering holding time on properties of droplet synthetic ha-alginate using dripping technique sintered at 1000 ⁰C with sintering holding time at 1: 2 :3 hours respectively. XRD was used to investigate of phases of the sintered droplet. Scanning Electron Microscope (SEM) was used to investigate the microstructure of beads. In this work, we can conclude that the holding time increased, the crystallinity increased but on the other hand, pore size, porosity, and surface roughness decreased. For all investigated samples. The surface roughness of A102 (0.2 – 2, μm) which is sintered at 1000 ⁰C 2 hours holding time has a better value offered better cell colonialization and has no significant value of porosity (50%) and crystallinity (86.63%) than those of A103 which need more energy for sintering as a consequence.

Penambahan bahan semen tulang kedalam rongga tulang dapat menjadi salah satu alternatif untuk mencegah kerusakan tulang akibat osteoporosis. Kelemahan utama dari bahan implant ortopedik berbasis hydroksiapatit sinter adalah bahan dalam bentuk solid dimana dalam aplikasi pembedahan, sulit untuk mengisi rongga tulang dengan ukuran tertentu. Alternatif yang nyaman untuk bahan pengisi tulang suspensi adalah dengan menggunakan bahan Injectable bone substitute. Dalam studi ini dipelajari komposisi material Injectable Bone substitute dengan matrik berupa polimer CMC-gelatin dan HA/TCP sebagai filler. Dilakukan variasi rasio Hidroksiapatit (HA) / tri-calcium phosphate (TCP) (70:30; 50:50; 40:60)  untuk  mempelajari pengaruhnya terhadap sifat-sifat fisik dan mekanik campuran. Hasil uji FTIR menunjukkan gugus fungsi fosfat (PO₄^3-) gugus fungsi karboksil dan gugus fungsi NH2 yang merujuk kepada bahan penyusunnya. Peningkatan porositas karena perubahan morfologi dikonfirmasi oleh gambar mikroskop polaritas. Hasil uji tekan menunjukkan berkurangnya  nilai kuat tekan dengan bertambahnya konsentrasi TCP dalam campuran. Semua kelompok uji menunjukkan kemiripan struktural dengan tulang cancellous dalam sifat porositas dan kekuatan mekanik.

Indonesia is known to have abundant mineral resources and some of them have not been properly utilized. Frozen rock from Gayo area, Aceh is suspected to have a feldspar content that can be used as a raw material for the manufacture of ceramics. This study is intended to determine the content of Gayo rocks and their compatibility as ceramic materials. For that purpose, has been identified the existing mineral content in these rocks and then made the composition of stoneware ceramic raw materials with triaxial blend method. different sintering temperature (800, 900, 1000, 1100 and 1250 oC respectively) has been conducted to known the efffect of sintering temperature on ceramic body. From the experiment, it is known that Gayo stone contains 69%of feldspar with specific gravity is 2.6963 + 0.1290 gram / cm3. In the sample test, the results obtained at the sintering temperature of 1250oC achieved 1.09% water absorption, a number which is included in the water impregnation area for stoneware ceramics according to the provisions of ISO 10543-3 / ASTM C373 ie <3%, .The prototype of ceramic objects made with rotary technique showing good quality (not cracked, shapedo not change, solid ceramic body

Indonesia is known to have abundant mineral resources and some of them have not been properly utilized. Frozen rock from Gayo area, Aceh is suspected to have a feldspar content that can be used as a raw material for the manufacture of ceramics. This study is intended to determine the content of Gayo rocks and their compatibility as ceramic materials. For that purpose, has been identified the existing mineral content in these rocks and then made the composition of stoneware ceramic raw materials with triaxial blend  method. different sintering temperature (800, 900, 1000, 1100 and 1250 oC respectively) has been conducted to known the efffect of sintering temperature on ceramic body. From the experiment, it is known that Gayo stone contains 69%of feldspar with specific gravity is 2.6963 + 0.1290 gram / cm3. In the sample test, the results obtained at the sintering temperature of 1250oC achieved 1.09% water absorption, a number which is included in the water impregnation area for stoneware ceramics according to the provisions of ISO 10543-3 / ASTM C373 ie <3%, .The prototype of ceramic objects made with rotary technique showing good quality (not cracked, shapedo not change, solid ceramic body

Biopolymer coated porous hydroxyapatite (HA) scaffolds were prepared for tissue engineering trough freeze drying method and impregnation. in this study, to mimic the mineral and organic component of natural bone, synthetic hydroxapatite (HA) scaffolds coated by polymer were prepared. Highly porous Hap scaffolds, fabricated by synthetic HA impregnation method on polyurethane foam, were coated with polymer coating solution, consisting of chitosan, Gelatin, and bilayered chitosan-gelatin prepared by aging and impregnating technique. For the purpose of comparison, The bare scaffolds without polymer coating layer were investigated. The Bare scaffolds were highly porous and interconnected with a pore size of around 150 µm–714 µm, has porosity at around 67,7% -85,7%, and has mechanical strength at around 0.06 Mpa - 0.071 Mpa, which is suitable for osteoblast cell Proliferation. Chitosan coated porous HA scaffold and gelatin coated porous HA scaffold had mechanical strength at around 0.81-0.85 Mpa, and 1.32-1.34 Mpa, respectively, with weight ratio of biopolymer and Hap was around 18%-22%. To compare these results, the coating on the bare scaffold with gelatin and chitosan had been conducted. Based on the result of FTIR, it could be concluded that coating procedure applied on porous hydroxy apatite (HA) coated by gelatin, chitosan coated HA scaffold, and bilayered Gelatin-chitosan coated porous HA scaffold, confirming that for allsampleshad no significant chemical effect on the coating structure. The compressive strength of bilayered Gelatin-chitosan coated HA scaffold had middle values between the rest, at around 1,06-1.2 Mpa for the samples at the same weight ratio of biopolymer: HA (around 18% - 22%). These results also confirming that coating by gelatin on porous hydroxyapatite was highest compresive strength and can be applied to improve mechanical properties of porous hydroxyapatite bare scaffold