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"This research presents the use of the Rietveld method to study the phase composition of cordierite (MG2AL4SI5O18) ceramics prepared from rice husk silica, after the samples were sintered at 1300, 1400 and 1500 °C. The formation of cordierite is temperature-dependent as indicated by the relative phase composition obtained from x-ray diffraction patterns for the cordierite and spinel increased markedly withincreasing temperature, i.e, from 38.98 to 54.15 wt% and from 11.81 to 17.99 wt % following the increase in temperature from 1300-1500 °C, respectively. The above valueswere obtained with the aid of the Rietveld method, carried out until the goodness of fit values (GoF) reached below 2, which is considered a satisfactory value to reveal the real phase composition. Different plots produced by refinement using the Rietveld method also reveal a reasonable fit between the observed and the calculated plot, demonstrating the usefulness of the method for calculating the quantity of phase composition in the sintering process."

"Metode semi-IPN (Interpenetrating Polymer Network) merupakan salah satu metode yang digunakan untuk mensintesis hidrogel superabsorben (HSA) kitosan dan poli(N-vinil-2-pirolidon) (PVP) atau kitosan-PVP. Pada metode semi-IPN, kitosan mengalami reaksi ikat silang dengan asetaldehida membentuk jaringan polimer kitosan terikat silang yang berinteraksi dengan polimer PVP linier. Hasil sintesis HSA kitosan-PVP semi-IPN diharapkan memiliki kekuatan mekanik dan kemampuan swelling yang baik. Kekuatan struktur ikat silang akan meningkat sampai mencapai titik optimum seiring bertambahnya waktu reaksi, konsentrasi agen pengikat silang dan pengaruh rasio kitosan-PVP. Kemampuan swelling HSA kitosan-PVP semi-IPN dengan kekuatan struktur ikat silang yang optimum didapat pada rasio kitosan/PVP 70:30 (b/b%) dengan konsentrasi asetaldehida 2 % dan waktu reaksi 3 jam. HSA kitosan-PVP semi-IPN optimum memberikan persen derajat ikat silang 55,9 % dan kemampuan swelling yang cukup tinggi yaitu 475,6 %. Karakterisasi HSA dilakukan dengan spektrofotometer Fourier Transform Infra Red (FTIR), analisis termal (DSC) dan analisis morfologi (SEM).

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Semi-IPN (Interpenetrating Polymer Network) is one method which can be used to synthesis the superabsorben hydrogel (HSA) of chitosan and poly (N-vinyl-2-pyrrolidone) (PVP) or HSA chitosan-PVP. In the semi-IPN method, chitosan crosslinked with acetaldehyde forming a crosslinked polymer network of chitosan which interacts with linier polymer of PVP. The result of synthesis between HSA chitosan ? PVP semi-IPN is expected to have a good mechanical strength and swelling capability. The strength of crosslinking structure will raise up to its optimum point along with the increase of reaction time, concentration of crosslinker and the influence of chitosan-PVP ratio. Swelling cability of HSA chitosan-PVP semi-IPN with optimum strength of crosslinking structure is obtained in the ratio of chitosan/PVP at 70:30 (w/w %) with 2% acetaldehyde concentration and 3 hours reaction time. The optimum HSA chitosan- PVP semi-IPN provides 55,9% degree of crosslinking and high enough swelling ability at 475,6%. Characterization of HSA is conducted by Fourier Transform Infra Red (FTIR) spectrometer, thermal analysis (DSC) and morphological analysis (SEM)."

"Kermnik merupaf«m material yang memiliki kekerasan yang sangat tinggi sehingga keramik mef!iadi material yang gel«-< (brittle). Umuk meningkatl«m lretangguhan keramik ma1r.a dikembangkan CMCs (Ceramic Matrix Composite."'i otau KIJillposit Mairiks Keramik) Salah satu mmade !lnluk mempraduk.Yi CMC. ada/ah dengan me/alui proses DIMOX DIMOX meropakan metade manufakJur CMCs dengan cara menga!cddasi letn;ran logam. Karakteristik produk CMC.s yang dihasilkan melalui metode ini dipengarul'Ji oleh variahel temperatur. waktu tahan. dopani serta atmosfer tempal berlangungnya proses pembenlukan komposit."

"Metode semi-Interpenetrating Polymer Network (semi-IPN) dapat digunakan untuk mensintesis hidrogel. Pada metode ini, jaringan kitosan terikat silang formaldehida akan berinteraksi dengan poli(N-vinil pirolidon) linear. Secara umum, rasio sweling dan derajat ikat silang hidrogel semi-IPN dipengaruhi oleh komposisi kitosan-PVP, konsentrasi formaldehida, dan waktu reaksi. Rasio swelling dan derajat ikat silang dari hidrogel kitosan-poli(N-vinil pirolidon) semi-IPN didapatkan sebesar 553,70% dan 58,82% pada rasio kitosan-poli(N-vinil pirolidon) 70:30 (%b/b), konsentrasi formaldehida 2% (%b/b), dan waktu reaksi 3 jam. Hidrogel kitosan-poli(N-vinil pirolidon) semi-IPN menunjukkan penurunan rasio swelling dan peningkatan derajat ikat silang dibandingkan hidrogel kitosan nonkovalen.

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Semi-Interpenetrating Polymer Network (semi-IPN) method was used to synthesize hydrogel. In this method, chitosan was crosslinked with formaldehyde and blended with Poly(N-vinyl pyrrolidone) to form crosslinked chitosan network that interracts with linear polymer of Poly(N-vinyl pyrrolidone). Generally, swelling ratio and degree of crosslinking of semi-IPN hydrogel were influenced by Poly(N-vinyl pyrrolidone) amount, concentration of formaldehyde, and reaction time. Swelling ratio and degree of crosslinking of semi-IPN hydrogel was obtained at 553,70% and 58,82% in the ratio of chitosan- Poly(N-vinyl pyrrolidone) 70:30 (%w/w), formaldehyde concentration of 2%, and 3 hours of reaction time. Semi-IPN hydrogel of chitosan-Poly(N-vinyl pyrrolidone) has lower swelling ratio and higher degree of crosslinking compared to hydrogel of chitosan."

"Magnesium dan paduannya telah digunakan di berbagai industri karena memiliki rasio kekuatan terhadap berat yang tinggi, modulus elastisitas dan densitas yang rendah, serta sifat mampu bentuk dan manufaktur yang baik. Namun, magnesium memiliki ketahanan korosi dan aus yang rendah. Untuk mengatasi hal tersebut, diperlukan rekayasa permukaan pada paduan magnesium. Plasma Electrolytic Oxidation (PEO) menghasilkan lapisan keramik oksida yang dapat meningkatkan ketahanan korosi dan aus paduan magnesium. Jenis elektrolit yang digunakan karakteristik dan waktu hidup plasma. Dalam penelitian ini, proses PEO dilakukan pada paduan AZ91 dalam elektrolit berbasis campuran silikat, fosfat, dan hidroksida yaitu Na3PO4, Na2SiO3, dan KOH. Proses PEO dilakukan dengan menggunakan rapat arus konstan sebesar 533 A/m2 selama 10 menit. Parameter proses tersebut dipilih untuk memperlama waktu hidup plasma. Pada penelitian sebelumnya, plasma hanya dapat hidup selama 2 menit. Hasil analisis SEM-EDS menunjukkan bahwa lapisan PEO yang dihasilkan memiliki dua tipe warna, yaitu abu-abu dan putih dengan morfologi dan komposisi berbeda. Bagian putih memiliki morfologi yang tidak seragam dan banyak retakan, dibandingkan dengan bagian abu-abu yang memiliki sedikit pori dan retakan. Ketebalan lapisan yang terbentuk sebesar 53 ± 3 μm. Berdasarkan hasil analisis fasa XRD, terdapat fasa kristal dan amorf Mg2SiO4, Mg3(PO4)2, dan MgO pada lapisan PEO. Hasil tersebut dikonfirmasi oleh hasil analisis EDS dengan terdeteksinya unsur-unsur terkait. Bagian putih memiliki konsentrasi Si yang lebih tinggi dibandingkan bagian abu-abu. Bagian abu-abu memiliki daya tahan abrasi yang lebih tinggi dibandingkan lapisan putih yang ditunjukkan dari nilai spesifikasi abrasinya, yaitu 0,684 × 10-5 mm3/mm dibanding 1,48 × 10-5 mm3/mm. Hasil karakterisasi dan uji mekanik menunjukkan lapisan PEO yang terbentuk tebal dan memiliki ketahanan aus yang baik karena plasma dapat hidup sampai 10 menit.

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Magnesium and its alloys have been used in various industries due to their high strength-to-weight ratio, low modulus of elasticity and density, as well as good formability and manufacturability. However, magnesium has low corrosion resistance and wear resistance. To overcome these challenges, surface engineering is required for magnesium alloys. Plasma Electrolytic Oxidation (PEO) produces a ceramic oxide layer that can enhance the corrosion resistance and wear resistance of magnesium alloys. The type of electrolyte used determines the characteristics and lifetime of the plasma. In this study, the PEO process was performed on the AZ91 alloy using an electrolyte based on a mixture of silicate, phosphate, and hydroxide, namely Na3PO4, Na2SiO3, and KOH. The PEO process was carried out using a constant current density of 533 A/m2 for 10 minutes. These process parameters were chosen to prolong the plasma lifetime. In previous studies, the plasma could only last for 2 minutes. The results of SEM-EDS analysis showed that the produced PEO layer had two different colors, namely gray and white, with different morphologies and compositions. The white part exhibited non-uniform morphology and numerous cracks compared to the gray part, which had fewer pores and cracks. The thickness of the formed layer was measured to be 53 ± 3 μm. Based on XRD phase analysis, crystal and amorphous phases of amorf Mg2SiO4, Mg3(PO4)2, and MgO were detected in the PEO layer. These findings were confirmed by EDS analysis, which detected related elements. The white part had a higher concentration of Si compared to the gray part. The gray part exhibited higher abrasion resistance compared to the white layer, as indicated by the abrasion specification values, which were 0,684 × 10-5 mm3/mm and 1,48 × 10-5 mm3/mm, respectively. The characterization and mechanical testing results indicated that the formed PEO layer was thick and had good wear resistance due to the plasma lifetime reaching 10 minutes."

"The effect of Fe substitution on AI of garnet ceramic with chemical formula Y3Fe5_5XAl5 O12, where x (synthesis) of 0, 0.05, 0.15, and 0.25, has been investigated. Sample in this study were synthesized using wet oxydation method, Hot Kerosene Drying (HKD). All constituents were used in liquid form from YCI3.6H2O, AIC13, and Fe2O3 and HCI, which were reagents with purity better than 99%. Thermal 'analysis (DTA) was used to investigate calcination and sintering temperature. The resultant powders were calcined at 1250°C and sintered 1350°C and 1400°C. The X-ray diffractogram, which were obtained at room temperature, were refined using crystallographic software package GSAS. The samples contain at least 85% garnet phase with the remaining Fe2O3 impurity phase. In those garnet phases, 0 atom slightly shift. As a concentration increases theoretical densities decreases. For increasing x (synthesis) above, the theoretical densities and unit cell volume, respectively are of 5.148 grlcm3, 4.951 grlcm3, 4.946 grlcm3, 4.918 grlcm3 and 1.890x10-21 cm3, 1.885x10' 1 cm3, 1.874x10-2i cm3, 1.856x10-21 cm3 for the sample sintered at 1350°C. Similarly, at 1400°C, the theoretical densities and unit cell volume, respectively, are of 5.136 grlcm3, 5.100 grlcm3, 5.021 grlcm3, and 1.891x10-21 cm3 1.885 x10-21 cm3 1.875x10-21 cm3 without x (synthesis) of 0.25 . The formula of resultant garnets, respectively, are of Y3Fe4.88O12, Y3Fe3.77A11.23012, Y3Fe3.61A11,39012, and Y3Fe3.25Al1.7512 for the samples sintered at 1350°C. Similarly, at 1400°C, The formula of resultant garnets, respectively, are of Y3Fe4.33O12, Y3Fe4.51A10.89O12, Y3Fe3A12O12. Based on macroscopic measurements, the average bulk density and porosity respectively, are of 3.458 grlcm3 and 27.32%, which confirms the X-ray diffraction (microscopic) measurement.

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Telah dilakukan penelitian terhadap keramik garnet dengan rumus kimia Y3Fes-5 AI5xO12. Nilai sintesis x adalah 0; 0,05; 0,15 dan 0,25. Sintesa dilakukan dengan metoda oksidasi basah, yaitu Hot Kerosene Drying (HKD). Bahan dasar yang digunakan adalah YCI3.6H20, AICI3, Fe203, dan HCl dengan kemurnian diatas ± 99%. Setelah sintesa dilakukan analisa termal (DTA) untuk mengetahui temperatur kalsinasi dan temperatur sintering: Sampel dikalsinasi pada pada temperatur 1250°C dan disintering pada temperatur 1350°C dan 1400°C. Analisa difraksi dilakukan pada masing-masing sampel dan diolah dengan perangkat lunak GSAS. Didapatkan persentase garnet yang terbentuk diatas 85% untuk seluruh sampel, dengan fasa pengotor adalah Fe203. Posisi atom-atom penyusun garnet hasil sampel yang disintesa menunjukkan tidak ada perubahan, kecuali pada atom 0 ada sedikit pergeseran posisi atom. Densitas teoritis menurun dengan semakin tingginya konsentrasi Al pada garnet. Dari harga nominal x diatas didapatkan densitas teoritis dan volume per unit selnya berturut-turut: 5,148 gr/cm3, 4,951 gr/cm3, 4,946 grlcm3, 4,918 gr/cm3 dan 1,890x10-1 cm3, 1,885x10-21 cm3, 1,874x10-1 cm'', 1,856x10'21 cm3 untuk temperatur sintering 1350°C serta 5,136 Tice, 5,100 grlcm3, 5,021 grlcm3, dan 1,891x10-21 cm3, 1,885 x10'21 cm3, 1,875x10-1 cm3 untuk temperatur 1400°C (tanpa nilai sintesis x=0,25). Sedangkan rumus kimia garnet yang terbentuk berturut-turut adalah Y3Fe4,88012, Y3Fe3.77A11.23012, Y3Fe3.61A1i.39012, Y3Fe3.25A11.75012 untuk temperatur sintering 1350°C dan Y3Fe4888012, Y3Fe4.51AI0.89012, Y3Fe3A12O12 untuk temperatur sintering 1400°C. Dihitung pula secara makroskopik densitas bulk dan porositas, dengan harga rata-rata 3,458 grlcm3 untuk densitas bulk serta 27,32% untuk porositas."

"This is research about color measurements of ceramic glaze with measure the reflectance of glaze ceramic sample that used spectrophotometer UV-VIS and color different calculation, to get quantitative color standard in the ceramic product and to look for the color matching method in each batch of ceramic glaze product that compared with product standard. Ceramic sample used four base colors, these are Blue 4571, Green AV-I500, Yellow DKC-9, and Red 270066, that make variable between the percentage of two base colors in the glaze ceramic composition that applied on the ceramic body and ceramic engobe. Illuminant used Illuminant CIE A, observer standard is CIE 1931 (2°), in the wavelength range 400 - 700nm, with spectrophotometer UV-VIS. The spectrophotometer data (R vs X) result is converted in the tristimulus value (X,Y,Z), chromaticity value (x,y,z) and CIE L*a*b* data with the color different calculation formula, then we can conclude the quantitative color standard and make the plot in color map of chromaticity diagram and the plot in color area of CIE L*a*b*. Color matching method made by measuring sample in each batch of ceramic glaze product and compared by color standard that used the total color different calculation with condition AE < 0.5. The research results will implement in the big ceramic industry to improve the ceramic product and ceramic quality development.

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Dalam penelitian ini diteliti pengukuran warna glasir keramik dengan mengukur reflektansi sample keramik berglasir menggunakan spektrofotometer UV-VIS dan perhitungan perbedaan warna, untuk mendapatkan standar warna secara kuantitatif pada produk keramik dan mencari metode colour matching pada setiap batch produk glasir keramik dibandingkan dengan standar produk yang sudah ditetapkan. Pembuatan sample keramik menggunakan empat warna dasar, yaitu Biru 4571, Hijau AV-1500, Kuning DKC-9, dan Merah 270066, yang divariabelkan berdasarkan persentase pencampuran diantara dua warna dasar di dalam suatu komposisi glasir keramik, yang diaplikasikan di atas permukaan badan keramik dan engobe keramik. Illuminant yang digunakan adalah illuminant CIE A, dengan standar observer CIE 1931 (2"). pada daerah panjang gelombang 400 - 700 nm, dengan spektrofotometer UV-VIS. Data spektrolotometri ( R vs X ) yang didapat, dikonversikan ke dalam nilai tristimulus (X,Y,Z) . nilai kromatisitas (x,y,z), dan data CIE L*a*b* dengan menggunakan rumus perhitungan warna, kemudian ditentukan standar warna secara kuantitatif dan dibuat plot pets warna dalam diagram kromatisitas dan posisinya claim ruang warna CIE L*a*b*. Metode colour Matching ditentukan dengan mengukur sample setiap hatch glasir keramik dan dibandingkan dengan standar warna menggunakan perhitungan total perbedaan wama dengan syarat matching jika E < 0.5. Hasil penelitian ini akan diimpelentasikan dalam industri- industri besar keramik untuk lebih meningkatkan pengembangan produk dan kualitas keramik."