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"Tujuan dari penelitian ini adalah mengetahui pengaruh suhu vulkanisasi terhadap sifat mekanis dan kinetika vulkanisasi komposit NBR. Formulasi komposit menggunakan dua macam carbon black yaitu N-330 dan N-774. Kinetika vulkanisasi ditentukan dengan alat Moving Die Rheometer, dimana proses vulkanisasi berlangsung dikaitkan dengan torsi dan waktu. Proses pembuatan vulkanisat menggunakan hydraulic press pada suhu 150ºC dan 160ºC. Sifat mekanis komposit NBR yang diamati adalah tegangan putus, perpanjangan putus, kekerasan dan kuat sobek. Kinetika vulkanisasi didekati dengan persamaan Arrhenius dikaitkan dengan mekanisme reaksi dan diasumsikan orde satu. Hasil penelitian menunjukkan bahwa kinetika vulkanisasi dapat didekati dengan persamaan dari data reometer. Surface area carbon black sangat kuat mempengaruhi sifat mekanis dan rate constant (k) dari komposit NBR. Carbon black N 330 merupakan bahan pengisi yang bersifat sebagai penguat dan memberikan sifat mekanis tertinggi dibandingkan carbon black jenis lainnya.

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The aim of this research was to study the effect of vulcanization temperature on mechanical properties and curing kinetics of NBR composites. The composites were formulated by using two types of carbon black i.e. N-330 and N-774. The curing kinetics was determined using Moving Die Rheometer. The network formation processes were related to torque and time. The vulcanizates were obtained by compression molding in a hydraulic press at 150°C and 160°C. The mechanical properties observed include tensile strength, elongation at break, hardness, and tear strength. Kinetics studies were approached by Arrhenius equation and the reaction mechanism was assumed following first order reaction. The results showed that curing kinetics can be approached by the equation from the rheometer data. The surface area of carbon black strongly influenced the mechanical properties and rate constant (k) of NBR composite. Carbon black N-330 can be used as a desirable reinforcing filler which gave a higher mechanical properties than the other type of carbon black"

"Experiments were performed in a piping system to examine the effects of flow rates and Cu2+, a common metal ion in wastewater, on the kinetics of gypsum (CaSO4.2H2O) scale formation. The scaling was monitored by measuring the decrease in Ca2+ concentrations, [Ca2+], of the scaling solution. AAS analysis shows that [Ca2+] reduces progressively after a certain induction time, during which time the concentration remains steady. Thus, the gypsum precipitation which leads to scaling in pipes does not occur spontaneously. Higher impurity concentrations (0 to 10 ppm Cu2+) result in longer induction time (26 to 42 min), which indicate that Cu2+ could inhibit the scale formation. Impurity concentrations and the scale mass generated are negatively correlated. Reduction in scale mass was as high as 61% depending on impurity concentrations and flow rates. Data of [Ca2+] versus time were used to calculate the reaction rate of the gypsum precipitation which led to scaling. It was found that the reaction follows a first order kinetics with respect to [Ca2+], with rate constants ranging between 5.28 and 7.37 per hour, which agree with most published values for mineral scale formation."

"ABSTRAKStudi sifat kemagnetan dan analisis kinetika alloy magnetic berbasis Nd-(Fe,Co)-B telah dilakukan. Ingot dan pita-pita alloy magnetic Nd10(Fel-xCox)14B6 (at %) dengan komposisi x = 0 ; 0.1; 0.2 ; dan 0.5 dibuat masing-masing dengan arc melting furnace dan Teknik melt spinning dengan kecepatan substrat 30 m s pita-pita sampel kemudial dianil dengan temperature 700 C selama 2 sampai 120 menit untuk meningkatkan derajat kristalisasi fasa yang terbentuk adalah Nd2(Fe,Co)14B sebagai fasa utama, dan fasa minar alpha-Fe serta Co. studi XD menunjukkan bahwa volume sel satuan fasa utama berkurang dengan peningkatan subsitusi Co. ukuran butir rata-rata fasa utama dievaluasi dengan menggunakan formula Scherrer dan ditemukan bahwa semua butiran berukuran dalam skala nanometer. Pengukuran sifat kemagnetan menggunakan VSM untuk alloy yang dipelajari diketahui bahwa nilai koersivitas masimum 499 kAm diperoleh untuk alloy dengan komposisi x = 0,1 setelah aniling pada temperature at 700 C selama 2 menit Remanen dari semua pita-pita alloy berkisar antara 0.80-1.10 T Peningkatan nilai remanen disebabkan oleh exchange coupling annatar fasa Nd2(Fe,Co)14B dan partikel alpha-Fe yang berukuran ultra halus (nanometer) di dalam alloy Nd-Fe-B dengan kandungan Nd rendah. Produk energi maksimum dari pita alloy yang telah dianil berkisar antara 28-115 kJ m3. Pengukuran temperature Curie, Tc dengan menggunakan differential scanning calorimeter (DSC) dari pita-pita kristalin menunjukkan bahwa terjadi kenaikan nilai Tc dari 304 C untuk alloy x = 0 sampai 650 C untuk alloy x = 0.5. kinetika kristalisasi dari fasa amorf alloy Nd10(Fe1-xCox)84B6 juga telah dianalisis dengan menggunakan DSC. Energi aktivasi Ec dan konstanta Avrami, n untuk kristalisasi alloy dengan komposisis X = 0 dan x = 01 dihitung dengan menggunakan metode Kissinger yang telah dimodifikasi. Hasil-hasil analisis kinetika menunjukkan bahwa transformasi fasa dikontrol oleh proses difusi dengan laju pertumbuhan dan nukleasi konstan.

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ABTRACT

Magnetic studies and kinetic analysis on melt spun ribbon of Nd-(Fe,Co)-B based permanent magnets have been done. Ingot and ribbon samples of Nd10(Fel-xCox)14B6 (at %) with x = 0 ; 0.1; 0.2 ; and 0.5 compositions were prepared by arc melting furnace and melt spinning with substrate velocity of 30 mis respectively. The ribbon samples were subsequently annealed at 700 C for 2-120 minutes to promote crystallization. The phases present in the samples are Nd2(Fe,Co)14B type as main phase, alpha-Fe, and Co as the addition. X-ray diffraction studies indicate that the volume of unit cell of main phase tends to decrease by Co substitution. The mean grain size of main phase was also evaluated by line broadening analysis, using the Scherrer formula and found that all the grains were in nanometer scale. From magnetic measurements by VSM for the alloys under studied, it is found that the maximum coercivity of 499 kA per m was observed in the ribbon alloy of x = 0.1 composition after annealing at 700 C for 2 minutes. Remanence of all as-spun and heat treated ribbons are in the range of 0.80 to 1.10 T (above the theoretical value based on Stoner-Wohlfarth theory.L12; Js = saturation magnetization). The enhancement of remanence raised due to exchange coupling between nanosized Nd2(Fe,Co)14B and cc -Fe particles in the Nd-Fe-B alloys with lower Nd content. Maximum energy products of the annealed ribbon are in the range of 28 to 115 kJ per m3. The Curie temperature, T, measurement of crystallized melt spun ribbon by Differential Scanning Calorimeter (DSC) show an increase the value of L from - 304 C for alloy x = 0 to -650 C for alloy x = 0.5. The kinetic of crystallization process of amorphous Nd1o(Fe1-x Cox)14B6 alloy have also been analyzed by DSC employed modified Kissinger method from which activation energy, Ec and Avrami constant, n for the crystallization were determined for alloys with composition x = 0 and x = 0.1. Results of kinetic analysis show that the phase transformation is a diffusion-controlled transformation with initial growth of particles nucleated at a constant rate."

"Synthetic biodiesel using biocatalyst is an emerging and attracting alternative process to replace the conventional process. However, biocatalyst is easy to be deactivated by alcohol, which is a reactant in biodiesel synthesis reaction. Therefore, it is needed to develop new method to maintain the activity and stability of the biocatalyst during reaction. New method to be developed is by changing the reaction route which is using alcohol to the reaction route which is not using alcohol. Route reaction of non alcohol can be done by changing the alkyl alcohol with alkyl acetate. Both have the same function as alkyl supply during the reaction. In this paper, the research results of the synthesis biodiesel via route of non alcohol using biocatalyst Novozym 435 are presented In this reaction, methyl acetate is reacted with triglyceride from used fried oil in batch reactor. The reactants and products were analyzed using HPLC. The Results showed that Novozym 435 can convert trioleat up to 93.24% under the condition of 4% wt substrate of the biocatalyst concentration, oil/alkyl mole ratio equal to 1/I2 in 50 hour reaction. Stability test indicate that the activity of the immobilized biocatalyst still remain after three reaction cycles."

"There are many researches to solve the effects of global warming caused by great amount of CO2 in the air. One of the effective alternatives to reduce this gas in atmosphere is by using micro alga Spirulina platensis due to its ability of CO2 fixation and the very useful biomass that it produced. Spirulina platensis contains high protein and can cure diseases such as cancer and cholesterol reduction. In considering of these benefits, this research focused on increasing the biomass production of Spirulina platensis by alteration of light illumination during microbial growth. The cultivation holds in a series of photo-bioreactors at 29"C and I atm where each of photo-bioreactor has volume of 500 ml., using Conwy medium as nutrition. 3% CO2 is the carbon source for the cultivation with superficial velocity 1.2 m/h. Phillips Halogen lamp 20W/12V/50Hz is the source for illumination. The cultivation using constant intensity of light illumination was also be done as a control. Cultivation of Spirulina platensis with alteration illumination method successfully increased the biomass production 55.1 % higher than constant intensity of light illumination. The energy of producing biomass in alteration of light illumination method lower than continuous intensity illumination which was only 21.6 % than constant intensity of light illumination. Kinetic studies of this microbial growth at alteration of light illumination also concluded that specific growth rate and bicarbonate concentration as essential compound followed Ierusalemsky kinetic model equation."

"Partikel halus batubara dikategorikan sebagai partikel batubara dengan kadar air yang tinggi dan ukuran 25-500 μm. Dewatering adalah bagian dari proses pembersihan batubara yang digunakan untuk mengurangi kadar air batubara dan dianggap sebagai proses yang paling mahal dibandingkan dengan aspek lainnya. Oleh karena itu, penelitian ini menerapkan bahan kimia tambahan untuk meningkatkan performa filtrasi. Proses vacuum filtration digunakan dengan mengaplikasikan tekanan sebesar 40 kPa dan komposisi batubara dengan padatan sebesar 15%. Penelitian ini dilakukan untuk menganalisis kinetika filtrasi dan karakteristik cake yang dihasilkan, sehingga efektivitas dari bahan kimia yang digunakan dapat ditentukan. AERODRI® 104, surfaktan anionik, teramati sebagai bahan kimia yang paling efektif, dengan menunjukkan kinerja yang optimal pada dosis rendah dibandingkan dengan AERODRI® 105 sebagai ester. Penemuan lebih lanjut juga menunjukkan bahwa, ketika dosis meningkat lebih dari dosis optimal, filtrasi menjadi kurang efektif.

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Fine coal particles are categorised as coal particles with a high moisture content and a size from 25 to 500 μm. Dewatering is a part of coal cleaning process that used to reduce the moisture content of coal and considered as the most expensive process compared to other aspects of coal cleaning. Hence, it is planned to apply chemical additives to enhance filtration. Vacuum filtration was utilised with a pressure of 40 kPa and a coal composition of 15% solids. The experiment was conducted to analyse the filtration kinetics and the cake properties produced, thus, the effectiveness of the chemical can be determined. AERODRI® 104, an anionic surfactant, is observed to be the most effective chemical, showing optimum performance at low dosage compared to AERODRI® 105 as an ester. Further discovery also indicates that, when the dosage is increased over the optimal dosage, the filtration becomes less effective."

"Penelitian ini bertujuan untuk mengetahui pengaruh kinetika pembentukan flok pada pengolahan air limbah pewarna buatan menggunakan proses koagulasi-flokulasi. Tawas dan Anionik Polyacrylamide (APAM) digunakan sebagai koagulan dan flokulan. Analisis kinetika yang digunakan adalah persamaan kinetika Avrami menggunakan fraksi penghilangan kekeruhan dan warna pada suhu 303 K, 323 K, dan 343 K untuk memngetahui kinetika pembentukan flok. Hasil uji jar menunjukan data optimum pada suhu 303 K dengan pH 6,5, dosis koagulan dan flokulan masing masing 30 ppm dan 1 ppm. Proses koagulasi-flokulasi selama 120 menit menunjukan penghilangan parameter kekeruhan (NTU) dan parameter warna (Gardner scale) masing-masing 90,8% dan 85,2 %. Data proses koagulasi-flokulasi pada parameter kekeruhan dan parameter warna masing masing mengikuti kinetika persamaan Avrami: Y(T,t)_kekeruhan=1- exp{[-0,21exp(-(598,80)/(T))t(0,85)]}Y(T,t)warna=1- exp{[-174,84exp(-(2928,20)/T)t(0,90)]}

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The goal of this research is to better understand the kinetics of floc formation in artificial dye wastewater treatment utilizing the coagulation-flocculation method. Alum is used as a coagulant, while Anionic Polyacrylamide is used as a coagulant aid. To understand floc formation kinetics, the Avrami equation is utilized to examine turbidity and color removal at 303 K, 323 K, and 343 K. Jar test procedures were also performed in this study to identify the optimal tubidity and color removal. The best results were obtained at 303 K and a pH of 6,5. The optimal coagulant and flocculant dosages are 30 ppm and 1 ppm, respectively. At 120 minutes, turbidity removal (NTU) and color removal (Gardner Scale) were 90,8% and 85,2%, respectively. Data on turbidity and color parameters for coagulation-flocculation process respectively follow the kinetics of the Avrami equation:

Y(T,t)turbidity=1-exp{[-0,21exp(-(598,80)/(T))t(0,85)]}

Y(T,t)color=1-exp{[-174,84exp(-(2928,20)/T)t(0,90)]}"