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Abstrak :
ABSTRAK
Sektor industri yang memproduk bahan kimia dan polimer sintetik sangat bergantung pada sumber daya fosil. Sumber daya fosil seperti minyak bumi semakin berkurang sehingga berdampak pada efektivitas biaya dan daya saing polimer. Biomassa lignoselulosa non-pangan seperti jerami padi sangat melimpah di Indonesia dan dapat digunakan sebagai pengganti sumber daya fosil untuk memproduksi prekursor petrokimia. Diketahui bahwa komponen selulosa adalah sumber utama untuk pembentukan levoglucosan LG . Karena kandungan selulosa yang tinggi, potensi jerami padi dapat diubah dengan pirolisis untuk menghasilkan bio-oil dan produk turunan menuju levoglucosan LG harus dikembangkan. Levoglucosan adalah senyawa intermediet penting karena dapat diubah menjadi prekursor bio-polimer asam adipat, bio-etanol, dll. Saat ini masih jarang penelitian yang berfokus pada rute yang menghasilkan LG melalui pirolisis. LG kemudian dapat mengalami reaksi lebih lanjut dan menghasilkan produk turunan. Untuk mendapatkan hasil tertinggi dari LG dalam bio-oil pada akhir pirolisis, suatu kondisi yang dapat menghambat reaksi lebih lanjut dari LG selama pirolisis berlangsung. Faktor sumber biomassa lignoselulosa dan komposisi, suhu, dan waktu tinggal disesuaikan dengan mengatur laju alir gas N2 kemungkinan besar sangat mempengaruhi komposisi produk yang terbentuk pada akhir pirolisis. Dalam penelitian ini, fast-pyrolysis jerami padi dilakukan dalam reaktor unggun tetap 5 gram biomassa pada rentang suhu yang berbeda 450 hingga 600oC , laju alir N2 antara 1200 hingga 1582 ml / menit untuk memaksimalkan hasil LG . Untuk mengkonfirmasi konten LG pada produk pirolisis diukur dengan instrumen GC-MS. Diketahui suhu dan waktu tinggal optimum adalah 500oC dan 1.582 ml/menit untuk mendapatkan yield levoglucosan sebesar 67,64 area kromatogram GC-MS . Kata kunci: biomassa, fast-pyrolysis, levoglucosan, lignoselulosa, waktu tinggal

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ABSTRACT

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The industrial sectors that produce synthetic chemicals and polymers rely heavily on fossil resources. Fossil resources such as petroleum are diminishing thus impacting on the cost effectiveness and competitiveness of polymers. Non food lignocellulosic biomass such as rice straw is very abundant in Indonesia and can be used as a substitute for fossil resources to produce petrochemical precursors. It is known that cellulose component is the main source for LG formation. Due to high contain of cellulose, the potential of rice straw can be transform by pyrolysis to produce bio oils and derivative products towards levoglucosan LG should be developed. Levoglucosan is important intermediet compound as it can be convert to the precursor of bio polymer adipic acid, bio ethanol, etc. Nowadays it rsquo s still rarely research focused on this mechanism route producing LG through pyrolysis. LG then can run into a further reaction and produce derivative products. In order to obtain the highest yield of LG in bio oil at the end of pyrolysis, a condition that may inhibit the further reaction of LG during pyrolysis takes place. The factor of lignocellulosic biomass source and composition, temperature, and holding time adjusted by N2 feed most likely greatly affect the composition of the product formed at the end of pyrolysis. In this study, fast pyrolysis of rice straw was performed in fixed bed reactor 5 grams of biomass under different temperatures ranges 450 to 600 oC , N2 flow rate 1200 to 1582 ml min to maximize the yield of LG. To confirm the content of LG on the pyrolysis product was measured by GC MS instruments. The maximum yield of LG was obtained at an optimal pyrolysis temperature of 500 C, 1.35 s of holding time.

Abstrak :
Pada penelitian ini, sampel pasir besi dengan kandungan ilmenite sebesar 2.8% akan di-roasting dengan sodium karbonat technical grade pada temperatur 500^oC, 600^oC dan 700^oC pada waktu tahan 30, 60 dan 90 menit. Sampel dihaluskan menggunakan ball mill dan disaring pada 200 mesh. Sebelum roasting dimulai, pasir besi ilmenite diaduk hingga merata dengan sodium karbonat menggunakan perbandingan antara pasir besi ilmenite dengan sodium karbonat 1:0.4. setelah waktu tahan terlewati, sampel diquench dengan air demineralisasi lalu dikeringkan. Hasil XRD menunjukkan pada beberapa parameter, hematit berubah menjadi magnetite dan ada yang intensitas ilmenite meningkat. Namun hasil ICP OES belum ada peningkatan kadar titanium. Dilanjutkan dengan separasi magnet menggunakan arus 2A, karena pada arus tersebut kadar ilmenit pada tailing paling tinggi dibanding variasi lain. Hasil akhir ditemukan dari seluruh parameter, temperatur 700^oC dengan waktu tahan roasting 30 menit adalah parameter terbaik dengan banyaknya fasa magnetit dan ilmenit terlihat dari data XRD dan kadar titanium tertinggi pada tailing dari dara ICP-OES. ...... In this research, ilmenite iron sand sample containing 2.8% of ilmenite will be roasted with sodium carbonate technical grade in temperature of  500^oC, 600^oC and 700^oC with holding time from 30, 60 and 90 minutes. We acquired the sample in the form of pellet, so we crushed it with ball mill and sieve the sample with 200 mesh size. Before roasting process begin, we mix the sample with sodium carbonate with ratio of 1:0.4. after roasting process over, we quench the sample with demineralization water and then dry it with oven. XRD results on some of the parameters shows some of the hematite turn into magnetite, we can see from the intensity of those phases and gaining of ilmenite peak. We continue the process to magnetic separation, using 2A parameter. After the separation we characaterize the sample with ICP OES., the results are titanium concentration are not increasing. From all parameters we used, we conclude that roasting temperatur of 700^oC and holding time of 30 minute are the best parameter from this research. Magnetite and ilmenite peak are shown in that parameter, and titanium concentration are the highest from other variations.

Abstrak :
Tingginya permintaan pengujian kualitas air permukaan di laboratorium komersil menyebabkan adanya antrian. Dengan adanya antrian, maka sampel yang diserahkan memiliki kemungkinan tidak langsung diuji sehingga sampel akan mengalami fase yang dinamakan fase waktu tunggu. Penelitian ini bertujuan untuk menganalisis perubahan nilai konsentrasi nitrogen selama rentang waktu tunggu. Selain itu, penelitian ini bertujuan menentukan laju perubahan selama proses nitrifikasi berdasarkan nilai perubahan konsentrasi yang terjadi. Kemudian penelitian ini bertujuan untuk memperkirakan nilai konsentrasi awal dari setiap parameter yang ada di dalam proses nitrifikasi. Adapun metode yang digunakan untuk mengetahui perubahan nilai konsentrasi nitrogen selama waktu tunggu adalah dengan melakukan pengujian laboratorium berdasarkan HACH. Sedangkan penentuan laju perubahan yang terjadi dilakukan dengan menggunakan metode Solver. Analisis perkiraan nilai konsentrasi awal dilakukan dengan pemodelan yang menggunakan solusi persamaan ODE Linear faktor pengintegrasian. Hasil pengujian laboratorium menunjukan adanya perubahan nilai konsentrasi amonia, nitrit, dan nitrat dari sampel yang didiamkan selama rentang waktu 14 hari dengan kondisi tanpa diawetkan dan dengan diawetkan. Rentang persentase perubahan nilai konsentrasi yang terjadi adalah sebesar 0,4% - 100% untuk amonia, 7% - 300% untuk nitrit, dan 18,2% - 960% untuk nitrat. Nilai laju perubahan amonia secara berurutan adalah 0,74/hari dan 0,4/hari untuk sampel tanpa pengawetan dan dengan pengawetan sedangkan nitrit adalah sebesar 0,05/hari dan 0,08/hari. Nilai error terkecil ada pada hari kedua untuk meperkirakan konsentrasi awal. Nilai konsentrasi amonia, nitrit, dan nitrat dengan kondisi tanpa pengawetan dan dengan pengawetan secara berurutan dengan menggunakan hari kedua sebagai waktu acuan adalah 17,29 dan 13,17 mg/L, 2,84 dan 15,26 mg/L, 0,93 dan 1,46 mg/L ......The high demand for surface water quality testing in commercial laboratories causes queues. With the existence of a queue, the samples submitted have the possibility of not being directly tested so that the sample will experience a phase called the holding time phase. This study aims to analyze changes in the value of nitrogen concentrations during the waiting period. In addition, this study tries to determine the level of change during the nitrification process based on the value of the changes in concentration that occur. Then this study aims to develop the concentration of the initial value of each parameter in the nitrification process. The method used to determine changes in the value of nitrogen concentration during the holding time is by conducting laboratory tests based on HACH. While the rate of change that occurs is done using the Solver method. Analysis of the estimated value of the initial concentration was carried out by modeling using the solution of the Linear integrating factor ODE equation. The results of laboratory tests showed that there was a change in the concentration values of ammonia, nitrite, and nitrate from the samples which were left for a period of 14 days with unpreserved and preserved conditions. The proportion of change in concentration value that occured is 0,4% - 100% for ammonia, 7% - 300% for nitrite, and 18,2% - 960% for nitrate. The value of the rate of change of ammonia respectively is 0,74/day and 0,4/day for samples without preservation and with preservation while for nitrite is 0,05/day and 0.08/day. Most of the smallest error value exist on the second day to estimate the initial concentration. The concentration values of ammonia, nitrite and nitrate under the condition of unpreserved and preserved respectively using the second day as a time reference were 17,29 and 13,17 mg/L, 2,84 and 15,26 mg/L, 0,93 and 1,46 mg/L.

Abstrak :
This research is to study the effects of _firing temperature and holding time on characteristics of Directed Metal Oxidation (DIMOAQ Ceramic Matrix Composites (CMCs) SiC /' A1 product. In this research, the firing temperature and holding time used are varied from 900° C to 1300° C with holding time 10 and 20 hours for each temperature. The characterizations of composite products are examined such as density and porosity test, micro hardness test, microstructure examination and chemical composition test. The results show that SiC preform has been infiltrated by Al liquid at tiring temperature of 1100"C for 20 hours. Composite product with the highest density (3,54 gram / cm3) can be obtained at firing temperature of 1100°C for 20 hours. Porosity tents to increase with increasing firing temperature. Composite product with highest micro hardness (1820 VHM can be obtained at firing temperature of 1300°C for 10 hours. At the some firing temperature, composite at products micro hardness for 20 hours tower than composite product with holding time I0 hours. Distribution of SiC particles spread over quite uniform on SiC/A1 composites product. Around SiC particles can be found Al, spinel (MgAl2O2). Al2O2, and possibility Mg,Si.

Abstrak :
Air limbah domestik merupakan air limbah yang berasal dari aktivitas hidup sehari-hari manusia yang berhubungan dengan pemakaian air. Untuk mengetahui karakteristik air limbah diperlukan pengujian segera setelah sampel diambil, namun pada realitanya seringkali sampel tidak dapat langsung diuji dan membutuhkan waktu tunggu penyimpanan sebelum diuji di laboratorium. Penelitian ini bertujuan untuk menganalisis pengaruh waktu tunggu terhadap perubahan konsentrasi dan laju penurunan konsentrasi, serta memprediksi konsentrasi awal berdasarkan perubahan konsentrasi BOD dan COD. Penentuan koefisien laju penurunan dilakukan menggunakan fitur “Trendline” jenis eksponensial dari grafik scatter plot pada Microsoft Excel, sedangkan analisis prediksi konsentrasi awal dilakukan dengan pemodelan menggunakan solusi persamaan diferensial reaksi orde pertama. Hasil penelitian menunjukkan bahwa konsentrasi BOD menurun seiring waktu tunggu, sedangkan konsentrasi COD mengalami peningkatan setelah turun terlebih dahulu. Diperoleh rata-rata koefisien laju penurunan BOD sebesar 0,278/hari pada sampel tanpa pengawetan dan 0,13/hari pada sampel dengan pengawetan, sedangkan rata-rata koefisien laju penurunan COD sebesar 0,046/hari pada sampel tanpa pengawetan dan 0,0185/hari pada sampel dengan pengawetan. Hasil pemodelan untuk memprediksi konsentrasi awal BOD reliabel hingga hari ke-2 penyimpanan pada sampel tanpa pengawetan dan hari ke-2,25 penyimpanan pada sampel dengan pengawetan. Sementara itu, hasil pemodelan untuk memprediksi konsentrasi awal COD reliabel hingga hari ke-21 penyimpanan pada sampel dengan pengawetan, namun tidak reliabel sama sekali pada sampel tanpa pengawetan. ......Domestic wastewater originates from daily human activities involving the use of water. To determine the characteristics of wastewater, testing is required immediately after sample collection. However, samples often cannot be tested immediately and require a holding period before laboratory testing. This study aims to analyze the impact of holding time on the concentration changes and the degradation rate, as well as to predict the initial concentration based on changes in BOD and COD concentrations. The determination of the degradation rate coefficient was performed using the "Trendline" feature with an exponential type from the scatter plot graph in Microsoft Excel, while the analysis of the initial concentration prediction was conducted through modeling using the solution of the first-order reaction differential equation. The results showed that BOD concentration decreases over the holding time, whereas COD concentration increases after initially decreasing. The average degradation rate coefficient for BOD was found to be 0.278/day in samples without preservation and 0.13/day in preserved samples, while the average degradation rate coefficient for COD was 0.046/day in samples without preservation and 0.0185/day in preserved samples. The modeling results for predicting the initial BOD concentration were reliable up to the 2nd day of storage for samples without preservation and the 2.25th day for preserved samples. Meanwhile, the modeling results for predicting the initial COD concentration were reliable up to the 21st day of storage in preserved samples but not reliable at all in samples without preservation.

Abstrak :
Keramik merupakan material yang memiliki kekerasan yang sangat tinggi dan getas (getas). Untuk meningkatkan ketangguhan keramik,maka dikembangkan CMCs (Ceramic Matix Composite). Salah satu metode untuk memproduksi CMCs adalah dengan melalui proses DIMOX, yaitu cara mengoksida leburan logam dalam atmosfer dapur. Karakteristik produk CMCs yang dihasilkan melalui metode ini dipengaruhi oleh variabel waktu tahan, temperatur, dopant serta atmosfer tempat berlangsungnya proses pembentukan komposit. Penelitian ini bertujuan untuk mempelajari proses pembuatan CMCs C/Al melalui proses DIMOX dan pengaruh waktu tahan terhadap karakteristik produk CMCs yang dihasilkan. Pada penelitian ini dilakukan variasi waktu tahan, dimana digunakan waktu tahan 8, 10, 15, 20, 24 jam pada temperatur 1100 °C. Karakterisasi terhadap produk komposit yang dihasilkan dilakukan melalui pengujian densitas dan porositas, pengujian kekerasan mikro, pengamatan struktur mikro dengan menggunakan mikroskop optik dan SEM serta pegujian komposisi kimia. Infiltrasi prabentuk C oleh leburan Al dapat terjadi secara optimum pada waktu tahan 24 jam. Produk CMCs dengan densitas yang tertinggi, sebesar 3,17 gram/cm3, diperoleh pada waktu tahan 24 jam. Porositas produk CMCs cenderung meningkat seiring dengan penambahan waktu tahan. Produk CMCs dengan kekerasan mikro tertinggi, sebesar 14300 Mpa pada waktu tahan 24 jam. Laju keausan produk CMCs tertinggi, sebesar 2.03x10^-6 m3/mm terdapat pada waktu tahan 24 jam. Partikel C terdistribusi cukup merata pada produk CMC C/Al. Pada produk CMCs pada daerah sekitar partikel C dapat ditemui adanya Al, spinel (MgAl2O4), Al2O3. ......Ceramic is material which possed a very high hardness and brittle. To increase its toughness, then CMCs is developed. One of method to produce CMCs is DIMOX process. DIMOX involved oxidized molten metal in furnace atmosphere. The charateristic of CMCs product is effected by variables processes such as : holding time, temperature, dopant and the atmosphere where the process is held. The aim of this research is to study the making process of CMCs C/Al itself through DIMOX process and the effect of holding time with variable : 8, 10, 15, 20, 24 hours at 1100 °C. The characterizations of CMCs are examined by density, porosity, hardness, wear and microstructure analysis. It is found that Infiltration preform graphite by molten Al is optimal at the holding time of 24 hours. This variable produced highest density at 3,17 gr/cm3. The porosity of CMCs product tends to increase with increment of holding time. The highest porosity that obtained at holding time of 24 hours is 6.15 %. The highest hardness that can be obtained at holding time of 24 hours is 14300 MPa. This variable also produced the lowest wear rate, it is 2.03x10^-6 mm3/mm. Distribution of graphite particles spread over C / Al composite product and around graphite particles can be found Al, spinel ( MgAl2O4 ), and Al2O3. Based on EDS analysis, there are three phase in systems of CMCs product, they are C/Al, Al2O3/Al, and C/Al2O3.

Abstrak :
Tujuan dari penelitian ini adalah untuk meneliti pengaruh 0,25 % Molibdenum (Mo) yang dikandung dalam besi tuang nodular terhadap sifat mekanis Austempered Ductile Iron (ADI). Variasi temperatur dan waktu tahan digunakan dalam proses perlakuan panas. Dengan 0,25 % Mo dalam besi tuang, ADI yang dibuat, menghasilkan suatu nilai tegangan tarik yang besar dan menurunkan elongasi bila kita bandingkan dengan as-cast (paduan dan non paduan besi tuang tanpa perlakuan panas). Nilai energi impak terbesar didapat pada temperatur austenisasi 9000 C dan austempering 3750 C dengan waktu tahan selama 60 menit. Struktur berubah menjadi ausferrit.

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The aim of this research is to investigate the effects of 0.25 % Mo (Molybdenum) which is contained in the ductile cast iron on mechanical properties of Austempered Ductile Iron (ADI). The various temperatures and the holding times are used in the heat treatment processes. Using a given 0.25 % Mo in the ductile iron, ADI's alloyed developes a higher ultimate tensile stress value and decreases the elongation if we compare with the as cast (non alloy ductile iron). The higher impact energy value obtained at 9000 C austenization and 375o C austempering temperatures during 60 minutes holding times. The structure changes into ausferrit.

Abstrak :
This study aimed to determine the effect of using acrylonitrile butadiene styrene in place of conventional wax material on treatment pattern removal in the investment casting process. There are three controllable process variables that can affect treatment pattern removal, which include temperature increase, holding time and the number of layers of ceramic shell that have been considered for comparison. Comparison among the effects of temperature increase, holding time and numbers of ceramic shell layers on the ceramic shell was analyzed using ANOVA. It was found that temperature increase (Tx), holding time (t) and number of layers of ceramic shell (N) contribute significantly to the length of the crack (l) on the ceramic shell. The crack in the ceramic shell?s surface was analyzed using scanning electron microscope photos. Less layers number cause the increase of crack length. The combination between temperature upraise and longer holding time cause cracking delay. The experimental is conducted by using 3 (three) variants for each of layers number, temperature and holding time. The layers number is ranging between 7-9 layers. Temperature increase from room temperature until 1300oC. The layers number variant is ranging between 180-300 seconds. It was concluded that a longer holding time will result in a more intact ceramic shell, as longer holding times yield short crack lengths.

Abstrak :
This study aimed to determine the effect of using acrylonitrile butadiene styrene in place of conventional wax material on treatment pattern removal in the investment casting process. There are three controllable process variables that can affect treatment pattern removal, which include temperature increase, holding time and the number of layers of ceramic shell that have been considered for comparison. Comparison among the effects of temperature increase, holding time and numbers of ceramic shell layers on the ceramic shell was analyzed using ANOVA. It was found that temperature increase (Tx), holding time (t) and number of layers of ceramic shell (N) contribute significantly to the length of the crack (l) on the ceramic shell. The crack in the ceramic shell’s surface was analyzed using scanning electron microscope photos. Less layers number cause the increase of crack length. The combination between temperature upraise and longer holding time cause cracking delay. The experimental is conducted by using 3 (three) variants for each of layers number, temperature and holding time. The layers number is ranging between 7-9 layers. Temperature increase from room temperature until 1300oC. The layers number variant is ranging between 180-300 seconds. It was concluded that a longer holding time will result in a more intact ceramic shell, as longer holding times yield short crack lengths.