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"Penelitian ini merupakan rangkaian penelitian lanjutan dari studi iron removal pada sampel pregnant leach solution (PLS) hasil pelindian bijih nikel laterit. Penelitian ini berfokus pada pengendapan unsur nikel dan kobalt yang terkandung di dalam sampel dengan proses hidrometalrugi menjadi produk mixed hydroxide precipitate (MHP). Sebelumnya, sampel PLS sudah dilakukan penghilangan kadar besi dengan penambahan kalsium karbonat sebanyak 2 kali dengan kandungan 25% w/w dan 12,5% w/w yang dilakukan selama 2 jam dan 1 jam pada temperature 90oC. Hasil pengurangan besi yang dilakukan menunjukkan pengurangan kandungan besi dari sampel bijih PLS sebesar 75% dari kandungan semula yang sudah diuji dengan ICP. Selanjutnya penelitian dilanjutkan untuk memproduksi MHP dengan penambahan larutan NaOH sebesar 4M kedalam larutan PLS yang sudah dikurangi kandungan besinya dengan presipitasi sebelumnya. Presipitasi dengan NaOH dilakukan hingga mencapai pH 7 lalu dipanaskan hingga suhu 60oC selama 1 jam. Hasil penelitian yang dilakukan hingga pH 7 menunjukkan hasil yang belum optimal dengan kandungan nikel yang hanya sebesar 5% dari total kandungan setelah dilakukan proses pengurangan kadar besi yang kedua kali. Penelitian ini menemukan beberapa faktor yang mungkin menyebabkan tidak bertambahnya kadar nikel dalam produk MHP setelah dilakukan presipitasi dengan larutan NaOH. Tingkat viskositas yang terlalu tinggi selama titrasi, masih tingginya kadar pengotor yang terkandung dalam larutan pasca pengurangan besi, serta endapan yang tidak kristalin menjadi faktor yang membuat larutan lewat jenuh dan kurang optimalnya hasil pasca penelitian. Waktu penyimpanan larutan pasca titrasi juga menjadi faktor yang membuat kandungan nikel dan kobalt tereduksi dan pengotor tidak terikat sempurna.

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This research is a follow-up research series from the study of iron removal on pregnant leach solution (PLS) samples from the leaching of laterite nickel ore. This research focuses on the deposition of Nickel and Cobalt elements contained in the sample by a hydrometallurgical process to become a mixed hydroxide precipitate (MHP) product. Previously, the PLS sample had iron content removed with the addition of calcium carbonate 2 times with a content of 25% w/w and 12.5% ​​w/w for 2 hours and 1 hour at a temperature of 90oC. The results of the iron reduction carried out showed a reduction in the iron content of the PLS ore samples by 75% of the original content that had been tested with ICP. Furthermore, the research continued to produce MHP with the addition of 4M NaOH solution into the PLS solution which had been reduced in iron content by previous precipitation. Precipitation with NaOH was carried out until it reached pH 7 and then heated to a temperature of 60oC for 1 hour. The results of the research carried out up to pH 7 showed that the results were not optimal with the nickel content only 5% from all the contents after the second process of reducing the iron content was carried out. This study found several factors that might cause the nickel content to not increase in MHP products after precipitation with NaOH solution. Viscosity levels that are too high during titration, high levels of impurities contained in the solution after iron reduction, and non-crystalline precipitates are factors that make the solution supersaturated and post-test results are less than optimal. The storage time of the post-titration solution is also a factor that makes the reduced nickel and cobalt content and impurities not completely bound."

"ABSTRAK Objectives: To comparatively evaluate the incidence of apical transportation during calcium hydroxide paste removal using two rotary systems on 40o curved simulated root canal blocks. Methods: Two groups (n 15: Group1, iRace; Group 2, ProTaper) of simulated root canals (40o curvature) were instrumented until working length wasachieved. Stereomicroscopic post instrumentation images were captured, and the final file was inserted into canal to the working length. Calcium hydroxide paste with iodoform was placed until working length was achieved and removed after 7 days using the master apical file with copious irrigation. Stereomicroscopic images were taken after calcium hydroxide paste removal, with the final file inserted until working length was achieved to assess the incidence of apical transportation. Stereomicroscopic images were obtained and superimposed using Adobe Photoshop 8. Results: Mean angle change after rotary instrumentation and calcium hydroxide paste removalwas observed in both groups and was greater in Group 2 than in Group 1. Superimposed images showed greater root canal deviation in Group 2 than in Group 1. Conclusion: Both file systems showed apical transportation upon calcium hydroxide paste removal from simulated curved root canals. A greater angle deviation and apical transportation was recorded with ProTaper."

"Indonesian Journal of Dentistry 2006; Edisi Khusus KPPIKG XIV: 111-116Apexification is the preparation of the endodontic treatment for a tooth with pulpal necrosis and incomplete developed apex. The aim of this treatment is to stimulate further apex development and formation of calcified tissue at the apex, so that conventional endodontic treatment could be performed. One of the most suitable material for apexification is calcium hydroxide since it has an excellent biocompatibility, antimicrobial property, and ability to stimulate hard tissue formation. In this case, apexification was performed on a 9 years old boy with incompletely developed apex and necrosis 36 tooth. Thereis, no subjective or clinical symptoms after 6 months. Although in the radiograph, apical closure was not clearly detected, apical stop was obtained in clinical examination. Subsequently, the 36 tooth was restored with onlay."

"Nanopartikel Ni(OH)2 digunakan secara luas sebagai material katoda pada superkapasitor asimetrik karena memiliki sifat elektrokimia yang baik dan mudah didapat. Nanopartikel Ni(OH)2 diproduksi dengan metode hidrotermal. fasa dari hasil sintesis Ni(OH)2 dikarakterisasi menggunakan XRD, tercipta pola difraksi dari fasa Ni(OH)2 tanpa terlihat impurity dari pola difraksi. Didapat ukuran partikel hasil sintesis-Ni(OH)2 sebesar 16.285 +- 4.215 nm dari karakterisasi TEM. Untuk menambah sifat konduktivitas panas, dicampurkan β-Ni(OH)2 dengan karbon mesopori, dan dideposisi pada permukaan glassy carbon electrode. Karakterisasi menggunakan SEM-EDX dan XPS, menghasilkan spektrum perbandingan atom Ni : O sebesar 1 : 2 yang memperkuat dugaan terbentuknya Ni(OH)2. Karakterisasi pendahuluan menggunakan cyclic voltammetry menjelaskan bahwa penambahan material karbon mesopori tidak mendominasi karakter dari Ni(OH)2. Lalu, didapat hasil kapasitas spesifik dalam fungsi discharging sebesar 280C/g, 120 C/g, 30 C/g, dan 10 C/g untuk arus spesifik sebesar 1 A/g, 2 A/g, 5 A/g,dan 10A/g berturut-turut. Serta didapatkan nilai energi spesifik sebesar 39.72; 36.67; 22.92; 15.28 Wh/kg, dan nilai daya spesifik sebesar 0.55; 1.1;2.75; 5.5 kW/kg untuk arus spesifik 1 ;2; 5; 10 A/g secara berturut-turut. Hasil kapasitas spesifik dari Ni(OH)2 masih bertahan 96.59% pada siklus ke 3000.

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Ni(OH)2 nanoparticle is widely used as cathode material in asymmetric supercapacitors due to its good electrochemical properties and affordable prices. Ni(OH)2 nanoparticles are synthesized via hydrothermal method. The phase from the as synthesized Ni(OH)2 was characterized using XRD, creating a diffraction pattern from the phase of Ni(OH)2 without any visible impurity from the diffraction pattern. The obtained particle size of Ni(OH)2 was 16.285+- 4.215 nm were measured by TEM characterization. To increase heat conductivity property, Ni(OH)2 was mixed with mesoporous carbon, and deposited on the surface of the glassy carbon electrode. Characterization using SEM-EDX and XPS, resulting in a comparison of determining the ratio of Ni : O at 1 : 2 which strengthens the suspicion of the formation of Ni(OH)2. Preliminary characterization using cyclic voltammetry explains mesoporous carbon material does not dispel characters from Ni(OH)2. the results of specific capacity are 280 C/g, 120 C/g, 30 C/g, and 10 C/g for specific currents of 1 A/g, 2 A/g, 5 A/g, and 10A/g consecutively. Specific energy values obtained were 39.72;36.67; 22,92;15.28 Wh/kg, and specific power values of 0.55; 1.1;2.75;5.5 kW/kg for specific currents 1;2;5;10 A/g respectively. The results of the specific capacity of Ni (OH) 2 still survive at 96.59% in the 3000 cycle."

"Reaksi thermal dari campuran kaolin dengan magnesium hidroksida dan kaolin dengan magnesium karbonat diamati untuk mendapatkan keramik cordierite tanpa penambahan zat aditif. Komposisi campuran ditentukan berdasarkan rumus molekul 2MgO.2Al2O3.5SiO2. Pembakaran campuran bahan-bahan pada perbandingan mol berdasarkan formula tersebut diharapkan dapat menghasilkan bentuk fasa amorf pada temperatur sekitar 900°C, yang merupakan temperatur dekomposisi. μ-Cordierite kemudian mengkristal pada temperatur sekitar 950°C, dan perlahan-lahan berubah menjadi keramik α-cordierite. Campuran reaktan dipress menjadi benda uji dan dibakar untuk mendapatkan keramik α-cordierite pada temperatur 1300 oC dan 1350°C. Keramik cordierite sebanyak 80,41 - 86,62 % dihasilkan dari campuran kaolin dengan magnesium karbonat dan metakaolin dengan magnesium karbonat pada temperatur pembakaran 1300 oC dan 1350 oC. Uji katalitik dilakukan terhadap cordierite untuk mendekomposisi gas NO, di mana 44,17 % NO terdekomposisi pada temperatur 400°C.

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Thermal reaction of mixed kaolin with magnesium hydroxide and kaolin with magnesium carbonate were studied to produce cordierite ceramic without additives. Its composition was determined based on the molecular formula of 2MgO.2Al2O3.5SiO2. The firing of those mixed materials at mole ratios of this formula was expected to produce μ-cordierite at temperature of 900°C due to its thermal decomposition. The μ-Cordierite was then crystallized at temperature around 950°C, and was gradually transformed into α-cordierite. This study was conducted by prssing the reactants mixtures as specimens which were then fired to obtain α-cordierite ceramic at 1300°C and 1350°C. Cordierite of 80.41-86.62 % were resulted from the mixture of kaolin with magnesium carbonate and metakaolin with magnesium carbonate at the firing temperature of 1300 oC and 1350°C. The catalityc activity of cordierite was tested to decompose NO was tested, in which 44,17% NO could be decomposed at 400°C."

"Nanocomposites of zinc-aluminium-anthranilate (ZAAN) have been synthesized at different concentrations of anthranilic acid by co-precipitation method. These materials have been examined in detail by powder X-ray powder diffraction (PXRD) which showed the expansion of the basal spacing from 0.89 to ca. 1.33 nm and the shifting of the 003 peak towards the lower 2q angle. This indicates that the anthranilate anion was successfully intercalated into the interlayer gallery. However, FTIR analysis showed nitrate anion was also co-intercalated in the interlayer. The resulting nanocomposites show Type IV adsorption-desorption isotherms indicated the mesoporous structure of the material. BET surface area was found to be slightly different compared to zinc-aluminium-nitrate-layered double hydroxide (ZANO) after the intercalation process took place. Both ZANO and ZAAN have similar surface morphology, namely a flaky-like structure, but they are of different sizes."

"Hydroxyapatite (HAP) is a member of the apatite group of minerals, and its chemical formula is Ca10(PO4)6(OH)2. HAP is a Calcium phosphate including hydroxide, and its Ca/P ratio is represented as 1, 67 HAP is being utilized in medical and dental fields including as artificial bones and artificial tooth roots. There are five methods for preparing apatite compounds, but the wet method is most popular, simple and available for mass production. The purpose of this experiment of HAP is to know the technique of synthesizing HAP and to get the data/information about the influence of pH and sintering temperature towards the HAP characteristic. Modification wet method is used in this experiment. The result of DTA, DTA curves of pH 7, pH 9 and pH 11 indicate that the last peak are at 825° C, 835° C and 815° C. The XRD result indicates that almost the entire peak exists are dominant phase and the relative intensity indicate that crystal structure of dominant phase are similar using the Hanawalt method. The physical and mechanical characteristic indicates that at pH 9 with sintering temperature 1100° C, shows the greatest density (3,1327 g/cm3), the smallest porosity (9,2212 % ) and the greatest bending strength (54,9813 MPa) compared with the result at other pH. The conclusion of this experiment are : the synthesis HAP technique "Wet Method" is good enough; the best pH is pH 9 with sintering temperature 1100° C; the connection pattern between pH and character result of HAP sampel is not similar if compared with the connection pattern between sintering temperature and the character result of HAP sample. Sintering process begins at 1000°C, but we cannot know when the sintering temperature ended. The suggestion is doing advance experiment using Rietveld method which needed to know the atomic position in crystal structure of HAP and to know the dominant phase percentage and the minor phase percentage too. We also have to know when sintering process ended with other experiment using sintering temperature of 1200° C and 1300° C.

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Hydroxyapatite ( HAP ) adalah suatu calcium phosphate yang mengandung hydroxyde dengan ratio Ca/P = 1,67 dengan formula kimia Ca10(P04)6(OH)2. Dalam bidang kedokteran dan kedokteran gigi HAP antara lain digunakan sebagai tulang buatan dan akar gigi buatan. Pada saat sekarang, terdapat berbagai metode untuk pembuatan HAP. "Wet Method" merupakan metode yang paling populer, paling mudah dan dapat digunakan untuk produksi masal. Tujuan penelitian adalah dikuasainya teknik proses sintesis dan karakterisasi HAP serta diketahuinya pengaruh perubahaan pH (7, 9 dan 11) dan suhu sintering ( 9000 C, 1000° C dan 1100° C ) terhadap karakterisasi sampel HAP. Metode sintesis HAP yang digunakan adalah "Wet Method" Hasil DTA sampel HAP pada pH 7, pH 9 dan pH 11 menunjukkan adanya puncak terakhir berturut-turut pada suhu 825° C, 835° C dan 815° C. Hasil analisis XRD menunjukkan bahwa hampir semua puncak adalah fasa dominan HAP dan intensitas relative menunjukkan struktur kristal fasa dominan adalah sama. Penentuan fasa dengan menggunakan metode Hanawalt. Posisi atom pada struktur kristal HAP dan prosentase fasa dominan dan .fasa minor tidak dapat ditentukan dengan metode Hanawalt. Hasil uji sifat-sifat fisik dan mekanik sampel HAP pada pH 9 dan suhu sintering 11000 C menunjukkan densitas terbesar (3,1327 g/cm3), porositas terkecil (9,2212 %) dan kekuatan patah terbesar (54,9813 MPa) dibandingkan hasil pengujian pada pH lain. Kesimpulan hasil penelitian adalah bahwa teknik sintesis HAP dengan modifikasi "Wet Method" cukup memuaskan; pH terbaik untuk sintesis HAP adalah pH 9 dengan suhu sintering 11000 C; hubungan pH dengan hasil karakterisasi sampel HAP menunjukkan pola yang tidak sama dengan pola hubungan suhu sintering dengan hasil karakterisasi sampel HAP; proses sintering mulai terjadi pada suhu 1000° C sedangkan akhir proses sintering belum dapat dimonitor. Diperlukan penelitian lanjutan dengan suhu sintering 1200° C dan 1300° C serta penelitian lanjutan dengan metode Rietveld untuk menentukan posisi atom pada struktur kristal HAP dan untuk menentukan prosentase fasa dominan dan fasa minor."

"Korosi adalah sebuah produk yang dihasilkan oleh sebuah reaksi kimia antara mineral dengan oksigen dalam bentuk oksida yang sangat merugikan. Proses terjadinya korosi permukaan pada peralatan yang di bungkus isolasi tahan panas sulit dideteksi secara fisik dari luar sehingga kerusakan baru diketahui apabila sudah terjadi kegagalan pada saat peralatan atau sistim sudah mengalami kebocoran.Penelitian terhadap produk korosi beserta material isolasi tahan panas di daerah produk korosi dilakukan untuk mengidentifikasi mekanisme korosi yang terjadi pada permukaan pipa. Dengan menggunakan alat uji laboratorium XRF, XRD dan TG-DTA dapat diketahui kandungan material pada produk korosi beserta material isolasi tahan panas yang terpasang serta perilaku peruraian kandungan material sehingga dapat dibandingkan dengan material aslinya.Korosi permukaan pada pipa kondensat ASTM A53-B yang teijadi dilapangan adalah akibat adanya air (H2O) yang diserap oleh material isolasi tahan panas calcium silicate (CaSiOj) sehingga membentuk calcium hydroxide (Ca(OH)2), disamping itu kondisi operasional sistim yang mengalami perubahan temperatur berulang-ulang (cyclic) juga memiliki kontribusi mempercepat terjadinya proses korosi. Air yang masuk melalui celah pelapis luar material isolasi tahan panas akan menimbulkan senyawa baru dan mengakibatkan terjadinya korosi permukaan pipa seperti yang didapatkan dari pengujian sample didapatkan calcium yang terkandung dalam produk korosi.

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Corrosion is product of a Chemical reaction between mineral and oxygen in term of destructive oxide. Visually, surface corrosion in most of equipment which covered by thermal insulation material are undetectable, consequently that any failures will be recognize only after leakage take in place.

Study of the corrosion product including thermal insulation material around corrosion product had been done to identify corrosion mechanism at pipe surface. By using laboratory test apparatus XRF, XRD and TG-DTA is able to identify corrosion Chemical product, thermal insulation material and thermal behavior as result of corrosion under insulation experiment.

Surface corrosion at existing condensate pipe ASTM A53-B is reaction product of water (H2O) and calcium silicate (CaSiO3) which produced calcium hydroxide (Ca(OH)i). In addition cyclic operation temperatures here proven to accelerate the corrosion process and water that found as absorbed by thermal insulation materials generates a new Chemical product which was found as calcium hydroxide at corrosion product."

"Korosi adalah sebuah produk yang dihasilkan oleh sebuah reaksi kimia antara mineral dengan oksigen dalam bentuk oksida yang sangat merugikan. Proses terjadinya korosi permukaan pada peralatan yang di bungkus isolasi tahan panas sulit dideteksi secara fisik dari luar sehingga kerusakan baru diketahui apabila sudah terjadi kegagalan pada saat peralatan atau sistim sudah mengalami kebocoran.Penelitian terhadap produk korosi beserta material isolasi tahan panas di daerah produk korosi dilakukan untuk mengidentifikasi mekanisme korosi yang terjadi pada permukaan pipa. Dengan menggunakan alat uji laboratorium XRF, XRD dan TG-DTA dapat diketahui kandungan material pada produk korosi beserta material isolasi tahan panas yang terpasang serta perilaku peruraian kandungan material sehingga dapat dibandingkan dengan material aslinya.Korosi permukaan pada pipa kondensat ASTM A53-B yang teijadi dilapangan adalah akibat adanya air (H2O) yang diserap oleh material isolasi tahan panas calcium silicate (CaSiOj) sehingga membentuk calcium hydroxide (Ca(OH)2), disamping itu kondisi operasional sistim yang mengalami perubahan temperatur berulang-ulang (cyclic) juga memiliki kontribusi mempercepat terjadinya proses korosi. Air yang masuk melalui celah pelapis luar material isolasi tahan panas akan menimbulkan senyawa baru dan mengakibatkan terjadinya korosi permukaan pipa seperti yang didapatkan dari pengujian sample didapatkan calcium yang terkandung dalam produk korosi.

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Corrosion is product of a Chemical reaction between mineral and oxygen in term of destructive oxide. Visually, surface corrosion in most of equipment which covered by thermal insulation material are undetectable, consequently that any failures will be recognize only after leakage take in place.

Study of the corrosion product including thermal insulation material around corrosion product had been done to identify corrosion mechanism at pipe surface. By using laboratory test apparatus XRF, XRD and TG-DTA is able to identify corrosion Chemical product, thermal insulation material and thermal behavior as result of corrosion under insulation experiment.

Surface corrosion at existing condensate pipe ASTM A53-B is reaction product of water (H2O) and calcium silicate (CaSiO3) which produced calcium hydroxide (Ca(OH)i). In addition cyclic operation temperatures here proven to accelerate the corrosion process and water that found as absorbed by thermal insulation materials generates a new Chemical product which was found as calcium hydroxide at corrosion product."