Hasil Pencarian  ::  Simpan CSV :: Kembali

"Carbon Nanotube (CNT) merupakan material yang memiliki banyak keunggulan, salah satunya adalah nilai konduktivitas termal yang tinggi. Oleh karena itu, CNT sangat banyak digunakan untuk aplikasi perpindahan panas, salah satunya nanofluida. CNT adalah molekul silindris yang terdiri dari lembaran-lembaran atom karbon lapisan tunggal (graphene). CNT dapat berlapisan tunggal atau single-walled CNT (SWCNT) atau multi- walled (MWCNT). Dalam penelitian ini menggunakan MWCNT as-received yang dikarakterisasi dengan menggunakan Energy Dispersive Spectroscopy (EDS) dan Scanning Electron Microscope (SEM). Nanofluida berbasis CNT disintesis dengan menambahkan konsentrasi CNT sebesar 0,01%, 0,03%, dan 0,05% serta surfaktan Polyethylene Glycol (PEG) sebanyak 10%, 20%, dan 30% pada fluida dasar yaitu air distilasi. Penambahan surfaktan bertujuan untuk menjaga kestabilan dari nanofluida. Nanofluida kemudian dilakukan ultrasonikasi selama 15 menit untuk melarutkan dan meningkatkan stabilitas nanofluida. Nanofluida kemudian dilakukan pengujian konduktivitas termal dan zeta potensial yang kemudian dibandingkan dengan analisis literatur. Penambahan konsentrasi CNT pada nanofluida meningkatkan nilai konduktivitas termal nanofluida. Penambahan konsentrasi surfaktan PEG sebanyak 20% dan 30% menurunkan konduktivitas termal nanofluida. Penurunan nilai konduktivitas termal terjadi akibat penambahan surfaktan yang sudah melewati batas optimal. Stabilitas nanofluida diukur dengan nilai zeta potensial. Kestabilan nanofluida berbasis CNT meningkat setelah ditambahkannya surfaktan PEG.

---

Carbon Nanotube (CNT) is a material that’s known to have a high thermal conductivity value. Therefore, CNT is very widely used for heat transfer applications, one of which is to make nanofluids. CNT is a cylindrical molecule consisting layers of single layer carbon atom sheets (graphene). CNTs can be single walled (SWCNT) or multi- walled (MWCNT). In this study, MWCNT as-received was characterized by using Energy Dispersive Spectroscopy (EDS) and Scanning Electron Microscope (SEM). CNT-based nanofluids were synthesized by adding 0.01%, 0.03%, and 0.05% of CNT particles and 10%, 20%, and 30% Polyethylene Glycol (PEG) surfactants to the base fluid, distilled water. The addition of surfactants is to maintain the stability of nanofluids. The nanofluid was ultrasonicated for 15 minutes to increase its stability. The nanofluid was tested for thermal conductivity and zeta potential which were then compared with literature analysis. The addition of CNT to nanofluids increases the value of the nanofluids’ thermal conductivity. The addition of PEG surfactant concentrations by 20% and 30% decreases the thermal conductivity of nanofluids. The decrease in the value of thermal conductivity occurs due to the addition of surfactants that have passed the optimal limit. The stability of nanofluid was measured by the potential zeta value. The stability of CNT-based nanofluids increases after the addition of PEG surfactants."

"ABSTRAKNanopartikel digunakan untuk menghasilkan nanofluida yang mempunyai stabilitas dan dispersi yang baik sehingga menghasilkan konduktivitas termal yang maksimal. Telah dilakukan penelitian pengaruh Polyethylene Glycol (PEG) terhadap transfer panas nanofluida berbasis karbon arang tempurung kelapa dan tempurung kelapa sawit. Karbon dari arang tempurung kelapa dan tempurung kelapa sawit melalui pemrosesan tertentu menjadi partikel karbon aktif. Partikel karbon aktif ditumbuk halus dan direduksi kembali agar dapat mencapai ukuran nano dengan menggunakan alat planetary ball mill dengan metode top-down selama 15 jam dengan kecepetan putaran 500 rpm. Sintesis nanofluida dilakukan dengan mendispersikan nanopartikel karbon dari arang tempurung kelapa dan tempurung kelapa sawit ke dalam fluida air distilasi. Pada penelitian ini dikaji pengaruh penambahan PEG terhadap karakteristik nanofluida berbasis karbon dari arang tempurung kelapa dan tempurung kelapa sawit. Karakterisasi nanopartikel karbon dari arang tempurung kelapa dan tempurung kelapa sawit yang dilakukan adalah menggunakan Field-Emission Scanning Electron Microscope (FE-SEM), dan Energy Dispersive Spectroscopy (EDS) untuk mengamati komposisi dan unsur partikel, morfologi partikel dan ukuran partikel agar dapat dibandingkan. Hasil EDS menunjukan partikel karbon dari arang tempurung kelapa memiliki 60,77 wt% karbon sedangkan partikel karbon dari arang tempurung kelapa sawit mengandung 78,08 wt% karbon dan terdapat banyak unsur pengotor pada kedua nya. Karakterisasi FE-SEM menunjukan partikel karbon membentuk aglomerasi. Karakterisasi nanofluida yang dilakukan adalah pengukuran Particle Size Analyzer (PSA), zeta potensial dan konduktivitas termal. Variabel yang digunakan adalah konsentrasi partikel karbon dari arang tempurung kelapa dan tempurung kelapa sawit masing-masing adalah 0%, 0,1%, dan 0,3% lalu dengan penambahan surfaktan PEG dengan konsentrasi 0%, 10% dan 20%.

---

ABSTRACT

Nanoparticles are used to produce nanofluids which have a good stability and good dispersion resulting in maximum thermal conductivity. This research study conduct the effect of Polyethylene Glycol (PEG) on heat transfer carbon-based nanofluids based on coconut shell ash particles and palm shell ash particles. Coconut shell carbon and palm shell ash carbon through certain process to become activated carbon particles. The activated carbon particles are finely ground and reduced again to reach nano size by using a planetary ball mill with a top-down method for 15 hours with a speed of 500 rpm rotation. Synthesis of nanofluids was carried out by dispersing carbon shells and coconut shell nanoparticles into distilled water fluid. In this study the effect of PEG on the characteristics of carbon-based nanofluids based on coconut shell and palm shell ash. Characterization of carbon nanoparticles of coconut shell and palm shell is done using Field-Emission Scanning Electron Microscope (FE-SEM), and Energy Dispersive Spectroscopy (EDS) to use materials and particles, morphology and particle size to be used. The EDS results showed that the coconut shell carbon particles had 60.77% carbon while the coconut shell carbon particles contained 78.08% by weight of carbon and both contained many impurities. The FE-SEM characterization shows carbon particles to form agglomeration. The nanofluid characterization carried out was the measurement of Particle Size Analyzer (PSA), zeta potential and thermal conductivity. The variables used are the composition of carbon particles of coconut shell and oil palm shell are 0%, 0.1%, and 0.3%, then the composition of surfactant PEG with concentrations of 0%, 10% and 20%.

"

"The present study investigates the aqueous stability of polyethylene glycol and oleic acid- based anionic surfactants through the dynamic light scattering (DLS) and zeta potential methods, for application in enhanced oil recovery (EOR). Polyethylene glycol dioleate sulfonate (PDOS) surfactant solutions were prepared in concentrations of 0.05, 0.1, 0.3, 0.5, and 1 wt% in deionized water. Aqueous stability of PDOS was assessed by measuring the droplet size over five days, using nano particle analyzer HORIBA SZ-100 at 25oC. Results show that good aqueous stability of PDOS was achieved at concentrations of 0.1 to 1 wt%, but with the droplet size becoming unstable at the lowest concentration of 0.05 wt%. The polydispersity indices were classified into polydisperse distribution type recorded as 0.3 to 0.5 at concentrations of 0.05 and 0.1 wt% and 0.2 at concentrations of 0.3 to 1 wt%. The critical micelle concentration (CMC) of PDOS was 0.3% and the interfacial tension of PDOS surfactant above the CMC was around 10-3 dyn/cm. The zeta potential of PDOS surfactant without the addition of salt in concentrations of 0.05, 0.1, 0.3, 0.5, and 1 wt% was highly stable up to -96.8, -90.5, -89.6, -82.3, and -64.4 mV, respectively. With the addition of salt they were moderately stable at a concentration of 1 wt%. The conductivity increased with increasing concentration. The zeta potential of PDOS with the addition of salt was moderately stable in a concentration of 1%. Although PDOS with concentration of 0.05% showed a high value of zeta potential with the addition of salt, there is no guarantee that the PDOS surfactant solution will be stable for five days."

"Grafin merupakan material yang marak dikembangkan karena memiliki berbagai keunggulan dari material lain, diantaranya adalah konduktivitas termal yang tinggi. Namun, proses sintesis grafin memakan biaya yang tinggi. Maka, perlu dikembangkan metode yang lebih sederhana yaitu sintesis Grafin Oksida (GO). GO adalah material hasil proses oksidasi serta eksfoliasi dari material grafit. Dalam penelitian ini, fluida berbasis GO disintesis dengan metode Hummers termodifikasi. Struktur GO dikarakterisasi dengan menggunakan Energy Dispersive Spectroscopy (EDS), Scanning Electron Microscope (SEM), dan X-Ray Diffraction (XRD). Kemudian, fluida berbasis GO dipersiapkan dengan menambahkan konsentrasi mikropartikel GO sebesar 0,01%, 0,03%, dan 0,05% dengan surfaktan Polyethylene Glycol (PEG) sebanyak 10% dan 20% untuk menjaga stabilitas fluida. Mikropartikel dan surfaktan didispersikan dalam larutan dasar yaitu air dengan proses ultrasonikasi selama 2 jam. Setelah terdispersi, dilakukan pengujian Particle Size Analyzer (PSA), zeta potensial, dan analisis literatur konduktivitas termal. Mikropartikel GO memiliki karakteristik hidrofilik maka akan terdispersi di dalam air dengan baik. Penambahan konsentrasi 10% dan 20% surfaktan PEG menurunkan stabilitas fluida pada pengujian zeta potensial karena penambahan konsentrasi terlalu tinggi. Pada analisis literatur, menunjukan penambahan konsentrasi mikropartikel GO tanpa surfaktan dapat meningkatkan konduktivitas termal. Dengan penambahan konsentrasi surfaktan yang optimal, konduktivitas termal fluida akan cenderung naik hingga titik terbentuknya Critical Misell Concentration (CMC), lalu konduktivitas termal fluida akan turun. Penggunaan PEG sebagai fluida dasar lebih banyak ditemukan pada penelitian, karena PEG memiliki momen dipol yang besar sehingga tingkat kepolarannya semakin tinggi.

---

ABSTRACTGraphene is a material that vividly developed because it has various advantages than other materials, such as high thermal conductivity. However, the process of synthesis graphene cost is high. Then, need to be developed in a simpler method, namely the synthesis of Graphene Oxide (GO). GO is a material result of the process of oxidation and exfoliation of the material graphite. In this study, fluids-based GO was synthesized by the method of Hummers modified. The structure of GO was characterized by using Energy Dispersive Spectroscopy (EDS), Scanning Electron Microscope (SEM), and X- Ray Diffraction (XRD). Then, fluids-based GO prepared by adding the concentration of the microparticles GO of 0.01%, and 0.03%, and 0.05% with surfactant Polyethylene Glycol (PEG) as much as 10% and 20% to maintain the stability of fluids. Microparticles and surfactant dispersed in a solution of basic water by the process of ultrasonication for 2 hours. After dispersed, the testing performed Particle Size Analyzer (PSA), zeta potential, and analysis of the literature thermal conductivity. Microparticles GO has the characteristics of hydrophilic then it will be good dispersible in water. The addition of a concentration of 10% and 20% surfactant PEG lowering stability fluids in testing the zeta potential due to the addition concentration is too high. On the analysis of the literature, showing the addition concentration of the microparticles GO without a surfactant can enhance the thermal conductivity. With the addition of the optimal surfactant concentration, thermal conductivity fluids will tend to rise to the point of Critical Micelle Concentration (CMC) has formed, and the thermal conductivity fluids will go down. The use of PEG as a base fluid are more common in research, because PEG has a great dipole moment so that the level of polarity become higher also."

"Baja meupakan material yang penting yang digunakan dalam berbagai sektor kebutuhan. Rekayasa struktur baja merupakan salah satu langkah yang dapat dilakukan agar mendapatkan sifat baja yang sesuai. Perlakuan panas dan pendinginan cepat menggunakan nanofluida merupakan salah satu metode rekayasa struktur yang dapat dilakukan untuk mengeraskan baja. Pada penlitian ini membahas penggunaan nano fluida sebagai media pendingin pada perlakuan baja S45C. Fluida yang digunakan disintesis dengan mendispersikan surfaktan polyethylene glycol dengan variabel konsentrasi 0; 3; 5; dan 7% v/v dan partikel hasil daur ulang limbah PCB dengan variabel konsentrasi 0; 0,1; 0,3; 0,5% w/v didalam air distilasi,. Proses sintesis partikel PCB meliputi crushing, leaching dengan HCL 1M, pirolisis pada suhu 500oC, dan ball milling dengan total durasi 20 jam. Hasil pengujian Particle Size Analyzer (PSA) pada partikel menunjukkan adanya peningkatan ukuran partikel dari 268 nm menjadi 1035 nm saat di milling selama 10 jam kemudian turun menjadi 572 nm saat di milling selama 20 jam. Ukuran yang diperoleh tidak mencapai ukuran nano (1-100 nm) sehingga partikel tergolong kedalam partikel mikron. Untuk mengevaluasi pengaruh konsentrasi surfaktan polyethylene glycol dan partikel PCB pada fluida, dilakukan pemanasan Baja S45C pada suhu 900oC yang kemudian didinginkan cepat menggunakan fluida partikel mikron. Hasil yang diperoleh dari perlakuan pada baja meliputi kurva pendinginan, nilai kekerasan HRC dan foto mikrostruktur. Kurva pendinginan yang diperoleh memperkirakan fasa akhir yang didapatkan baja adalah ferrite, pearlite, bainite dan martensite. Adapun struktur mikro yang dihasilkan oleh baja menunjukan fasa pearlite, bainite, martensite dengan nilai kekerasan diatas 50 HRC serta kekerasan tertinggi mencapai 56,3 HRC

---

Steel is classified as an important materials that used in various sector of applications. Engineering the microstructure of steels is an important step that can be used to obtain the desired properties of steel. Quenching, especially with nanofluids is one of the great options to alter the microstructure of steel, specifically through steel hardening treatments. In this study, the use of nanofluid as steel quenchant id discussed. Synthesized fluid obtained by dispersing polyethylene glycol as a surfactant with 4 variation of concentration (0; 3; 5; 7% v/v) and PCB recycled particle with also 4 concentration variation (0; 0.1; 0.3; 0.5% w/v) to the distilled water. Recycling / synthesis process of PCB particle include crushing, leaching with 1 Molar Hydrochloric Acid, pyrolysis at 500oC, and ball milling for up to 20 hours. Results obtained from the particle size analyser (PSA) indicate an increase in particle size from 268 nm to 1035 nm within 10 hours milling and reduced to 572 nm when milled for 20 hours. Particle retrieved after the recycling process classified as micron sized particle because the final size doesn’t meet the criteria of nanoparticles (1-100 nm). To evaluate the effects of polyethylene glycol and PCB based particle concentration on the dispersed fluids, a hardening treatment is conducted by heating S45C steels to 900oC for 1 hour then quenched with the dispersed fluid. Information that can be obtained from the process are the cooling curves, rockwell hardness, and microstructure of steels. Obtained cooling curves predict the final phase that may be present at steels are ferrite, pearlite, bainite, martensite. The microstructure of steels after quenching in general consist of pearlite, bainite, martensite. Meanwhile, overall steels rockwell hardness obtained after quenching is above 50 HRC with maximum value of 56,3 HRC.

"

"Aliran turbulen dari larutan polimer PEG 4000 untuk permukaan pipa stainless steel telah diteliti. Eksperimen ini menggunakan pipa stainless steel berdiameter luar 5 mm dan diameter dalam pipa 3 mm. Nilai dari kekasaran tersebut telah diukur tersebut dengan nilai kekasaran (k) 1.12 μm. Pipa tersebut diuji dengan konsentrasi polimer polyethylene glycol (PEG) 4000 200, 400 dan 600 ppm. Hasil menunjukkan bahwa karakteristik aliran dipengaruhi oleh penambahan konsentrasi polimer. Pada aliran turbulen tanpa additive kenaikan koefisien gesek terjadi akibat dari kondisi kekasaran dinding. Penambahan additive ke dalam air terlihat efektif pada permukaan pipa stainless steel. Penambahan 200 ppm additive polimer PEG 4000 pada bilangan Reynolds 8078 dapat menurunkan gesekan pada pipa stainless steel sebesar 65,27 persen, sedangkan dengan penambahan 200 ppm additive PEG 4000 penurunan gesekannya 20 persen.

---

Turbulent flow of dilute polymer polyethylene glycol (PEG)4000 solutions in stainless steel pipes was studied. This experiment use stainless steel pipe with outside diameter (OD) 5mm and inside diameter (ID) 3mm. Inside pipe roughness is measured with relative roughness (k) 1.12 μm and 250, 500 and 1000 ppm for additive concentration. The results show that flow properties are influenced by polymer addition and surface roughness. In the turbulent flow regime without additive, the increasing of friction coefficient appeared to be effected by wall condition alone. Addition of polymer to water is effective for rough in stainless steel pipe. For example with addition of 600 ppm of polymer polymer polyethylene glycol (PEG)4000 reduced drag in stainless steel pipe by 65,27 percent at Reynolds number 8078, whereas in 200 ppm addition tested drag was reduced only 20 percent."

"ABSTRAKLatar Belakang: Pemeriksaan kolonoskopi memerlukan persiapan dan usaha yang kompleks dengan melibatkan modifikasi diet dan pemilihan laksatif untuk meningkatkan kualitas bersihan kolon. Penggunaan berbagai regimen dan cara pemberian pencahar masih menjadi bahan diskusi para ahli hingga sekarang. Polyethylene glycol merupakan salah satu regimen pencahar yang dapat diberikan dalam dosis terbagi maupun dosis tunggal dalam satu waktu.Tujuan: Mengetahui perbedaan bersihan kolon pada polyethylene glycol dosis tunggal dengan dosis terbagi pada persiapan kolonoskopiMetode: Uji klinis acak tersamar tunggal dilakukan di Divisi Gastroenterologi, Departemen Ilmu Penyakit Dalam Rumah Sakit dr. Cipto Mangunkusumo pada periode Juni hingga Agustus 2018. Pasien yang dilakukan tindakan kolonoskopi dijadikan sampel dengan pemilihan secara konsekutif. Pasien dengan obstruksi kolon, penyakit jantung, gangguan fungsi ginjal, gangguan fungsi hati berat, riwayat reseksi usus besar, alergi terhadap polyehtylene glycol, dan pasien yang tidak bersedia mengikuti penelitian tidak diikutsertakan dalam penelitian. Penilaian bersihan kolon dilakukan oleh beberapa staf gastroenterologi yang telah ditunjuk menggunakan Boston Bowel Preparation Score (BBPS) tanpa mengetahui cara pemberian preparat saat persiapan kolonoskopi pasien.Hasil: Sebanyak 76 subyek penelitian, 38 pada kelompok pemberian dosis tunggal dan 38 pada kelompok pemberian dosis terbagi, diikutsertakan dalam uji klinis. Tidak terdapat perbedaan bermakna antara metode pemberian polyethylene glycol terhadap tingkat bersihan kolon pada pasien kolonoskopi.Simpulan: Bersihan kolon pada regimen pemberian polyethylene glycol dosis terbagi dan dosis tunggal pada persiapan kolonoskopi memiliki nilai efikasi yang sama.

---

ABSTRACTIntroduction: Colonoscopic examination is a unique examination requiring various plans and efforts including diet modifications and laxative choices in order to maximize colon adequacy. A plethora of regiments and methods have been served as a discussion topic for experts. Polyethylene glycol is one of the laxative regiments used in multiple administration method, either split dose or single doseAim: Comparing bowel cleanliness between polyehtylene glycol given in single dose and split dose on patients undergoing colonoscopic preparation.Methods: Single blinded study was done in Gastroenterology Division, Internal Medicine Department of Doctor Cipto Mangunkusumo National General Hospital during June to August 2018. Patients undergoing colonoscopic preparations weree chosen as research samples using consecutive method. Patients with colon obstruction, heart disease, kidney function decline, severe liver damage, history of colon resection, allergic to polyehtylene glycol, or disagree to join the study was excluded. Bowel cleanliness was assessed by multiple gastroenterologist staff using Boston Bowel Preparation Score (BBPS) without knowing patients laxative regimentResults: There were 76 study samples, 38 of each study groups, included in this study. There were no significant difference of efficacy between polyehtylene glycol administration method with bowel cleanliness in colonoscopic examination patients.Conclusion: Bowel cleanliness on polyehtylene glycol given in split dose and single dose were of similar efficacy"

"Natural-based surfactant such as methyl esther sulfonate, which is derived from palm oil, has increasingly become the focus of study for the last decade to improve oil recovery due to the abundant raw materials availability and the need for oil as a source of energy. Surfactant MES development with the targeted fluid reservoir characteristics has been conducted in the laboratory scale as well as in the field scale. In this study, the addition of polyethylene glycol mono-oleate as co-surfactant to enhanced oil recovery in the "L" oillfield in Central Java was investigated in the laboratory scale through compatibility observation, IFT measurement, thermal stability and core flooding tests. The result showed that the presence of PMO improved the solubility of surfactant mixture in the water which formed one phase milky solution. Decreasing IFT as the crucial factor for surfactant flooding was also achieved until 10-3 dyne/cm and thermally stable for two months. Furthermore, core flooding experiments to study the performance of surfactant to recover oil production showed that the mixture of MES and PMO are able to enhance oil recovery until 55.35%S and have potential to be used as chemicals for chemical flooding in the targeted oilfield."