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"This research was done to investigate influence of the base metal surface roughness on the BAg-8 spreading behavior and to get a proper surface roughness number for large area brazing. The filler metal was melted at 830o C for 15 minutes on a S50C surface for with various roughness levels. After solidified, the spreading area was observed and characterized in macro and micro scale. The results show that physically the filler spreading consists of two kinds of spreading forms: true and apparent filler spreading with composition of the both being almost same; 77% Ag and 23% Cu. For some roughness numbers, irregularities in uniformity of the heating and cooling process on the filler and dissolving of contaminant into the molten filler caused the true spreading that tend to separate became several parts and tend to flow out from initial placement. Increasing of the surface roughness tends to increase the capillarity effect and to decrease imbalance in the surface tension. Optimum surface roughness was obtained at Rz = 0.92. At this number, the ratio, as well as fitness of the true spreading with initial condition, was at the maximum. During the application process, this condition is predicted as being able to prevent or avoid weaknesses in the joint, thereby increasing the joint strength and its appearance quality."

"Plasma Electrolytic Oxidation (PEO) merupakan pelapisan permukaan logam dengan plasma anodisasi untuk menghasilkan lapisan tahan karat dan keras. Sifat lapisan yang dihasilkan dikendalikan oleh parameter proses seperti arus dan waktu pembentukan. Proses PEO dilakukan dengan 2 variasi yaitu variasi waktu dan variasi arus dalam larutan 0,5 M Na3PO4. Pada variasi waktu, arus yang digunakan adalah 0,5 A dengan waktu 1, 3, dan 5 menit. Sedangkan pada variasi arus digunakan arus 0,2; 0,3; 0,4 A dan dilakukan pada waktu konstan selama 3 menit. Temperatur elektrolit dijaga tetap 30°C dan diaduk dengan magnetic stirrer dengan kecepatan konstan 300 rpm. Perubahan morfologi sebagai fungsi arus dan waktu diamati menggunakan scanning electron microscope dan energy dispersive X-ray spectroscopy (SEM-EDS). Analisis fasa dilakukan dengan X-ray Diffraction (XRD). Perubahan kekerasan diamati melalui uji kekerasan micro-Vickers. Perubahan sifat korosi diuji dengan metode electrochemical impedance spectroscopy (EIS) dan potentiodynamic polarization (PDP). Hasil karakterisasi menunjukkan fasa kristal yang terbentuk pada lapisan PEO adalah fasa Mg3(PO4)2 yang diidentifikasikan pada puncak 35°, 37°, 49° dan 62° pada pola XRD. Nilai kekerasan lapisan PEO yang terbentuk pada 1, 3 dan 5 menit masing-masing adalah 315,67; 427,67; dan 382,67 HV sedangkan pada arus 0,2; 0,3; dan 0,4 A diperoleh nilai kekerasan lapisan masing-masing sebesar 355; 421,67; dan 459 HV. Hasil uji polarisasi menunjukkan peningkatan ketahanan korosi yang ditunjukkan dengan berkurangnya rapat arus korosi. Semakin kecil rapat arus korosinya maka laju pembentukkan korosi semakin berkurang. Pada variasi waktu 1, 3 dan 5 menit nilai rapat arus korosinya adalah 3,24 x 10-5; 7,76 x 10-7; dan 1,11 x 10-6 A/cm2 sedangkan pada variasi arus 0,2; 0,3; dan 0,4 A nilai rapatarus korosinya adalah 2,26 x 10-6; 3,12 x 10-6; dan 7,60 x 10-7 A/cm2. Hasil EIS menunjukkan bahwa nilai R1 semakin besar yang artinya ketahanan resistansi polarisasi semakin besar dengan meningkatnya waktu dan arus pembentukan. Pada variasi waktu 1, 3 dan 5 menit nilai R1 adalah 42,35; 564,7; dan 574,4 Ω.cm2 sedangkan pada variasi arus 0,2; 0,3; dan 0,4A nilai R1 adalah 254,5; 169; 627,5 Ω.cm2 setelah dicelupkan selama 3 jam.

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Plasma Electrolytic Oxidation (PEO) is a coating for metal surface by plasma anodization to produce corrosion resistant and hard coating. The resulting coating properties were controlled by process parameters such as formation current and time. The PEO process in this research uses 2 variation: time and current formation in 0,5 M Na3PO4 solution. At the time variation, the current used is 0,5 A with time of 1, 3 and 5 minutes. Whereas in the current variation used 0,2;0,3 and 0,4 A for 3 minutes. The electrolyte temperature was kept at 30 oC and stirred with a magnetic stirrer at 300 rpm. Morphological changes were investigated by using scanning electron microscope and energy dispersive X-ray spectroscopy (SEM-EDS). Phase analysis was performed by X-ray Diffraction (XRD). Hardness changes were observed using micro-Vickers hardness test. Changes in corrosion properties were investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). The phases formed in the PEO layer is Mg3(PO4)2 which identified at the peaks of 35°, 37°, 49° and 62° in the XRD pattern. Hardness of AZ31 alloys at 1, 3 and 5 minutes was 315,67 HV, 427,67 HV and 382,67 HV whilte at currents 0,2;0,3 and 0,4 A is 355 HV, 421,67 HV dan 459 HV. The polarization test results showed an increase in corrosion resistance which is approved by the reduced corrosion current density. The smaller the corrosion current, the rate of corrosion formation decreases. At the time variation of 1, 3 and 5 minutes the value of the corrosion current density is 3,24 x 10-5, 7,76 x 10-7, and 1,11 x 10-6 A/cm2 whereas in the variation of current 0,2; 0,3; and 0,4 A thecorrosion current density is 2,26 x 10-6; 3,12 x 10-6; and 7,60 x 10-7 A/cm2. EIS results showed that the higher value of R1 means the greater the polarization resistance. At the time variation of 1, 3 and 5 minutes the value of R1 are 42.35. 564.7, 574.4 Ω.cm2 whereas in the current variation of 0,2;0,3 and 0,4 A the value of R1 are 254.5, 169, 627.5 Ω.cm2 after being immersed for 3 hours."

"Telah dibangun sistem akuisisi data dan pencitraan morfologi permukaan logam 2 dimensi dengan resolusi perpindahan di bawah 0.1mm dan kapasitas ADC 24 Bit. Sampel dapat digerakan 2 dimensi menggunakan stepper motor lead screw T8 pada satu arah dan stepper motor lead screw T3 pada arah lainnya. Stepper motor T8 memiliki panjang ulir 25cm, lead 8, pitch 2mm dan perpindahan per step hingga 0.0044mm/step dalam kondisi microstep 1/16. Stepper motor T3 memiliki panjang ulir 5cm, lead 4, pitch 4mm dan perpindahan per step hingga 0.0371mm/step dalam kondisi microstep 1/4. Terdapat probe pengukur permukaan logam yang dapat dikendalikan dengan stepper motor lainnya dengan panjang ulir 5cm dengan perpindahan per step hingga 0.0371mm/step dalam kondisi microstep 1/4. Analog-to-Digital Converter ADC ADS1232 digunakan untuk mengukur tegangan yang akan diakusisi melalui Arduino Nano. Arduino Nano berkomunikasi dengan komputer yang menjalankan GUI melalui protokol komunikasi serial. GUI diprogram menggunakan bahasa pemrograman python dan package Tkinter. Data yang diakuisisi ini akan diolah dan diplot 3 dimensi dengan sumbu x dan y merupakan perpindahan dari kedua Stepper Motor dan sumbu z merupakan pembacaan ADC yang menggambarkan ketinggian dari permukaan logam. Untuk membuktikan kinerja sistem ini digunakan simulasi yang berdasarkan DAC MCP4725. DAC MCP4725 akan diprogram untuk memberikan besaran yang menggambarkan ketinggian dari permukaan logam dengan menerima input x dan y dari serial yang dikirim menggunakan program python dengan GUI Tkinter.

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A data acquisition system and 2-dimensional metal surface morphology imaging have been developed, featuring displacement resolution under 0.1mm and 24-bit ADC capacity. Samples can be moved in 2 dimensions using a T8 stepper motor lead screw in one direction, and a T3 stepper motor lead screw in another. The T8 stepper motor has a thread length of 25cm, lead 8, pitch 2mm, and displacement per step up to 0.0044mm/step under 1/16 microstep conditions. The T3 stepper motor has a thread length of 5cm, lead 4, pitch 4mm, and displacement per step up to 0.0371mm/step under 1/4 microstep conditions. There is a metal surface measuring probe that can be controlled by another stepper motor with a 5cm thread length, moving up to 0.0371mm/step under 1/4 microstep conditions. The Analog-to-Digital Converter (ADC) ADS1232 is used to measure the voltage to be acquired through an Arduino Nano. The Arduino Nano communicates with a computer running a graphical user interface (GUI) through a serial communication protocol. The GUI is programmed using Python and the Tkinter package. The acquired data will be processed and plotted in 3 dimensions, with the x and y axes representing the displacement from both stepper motors and the z-axis representing the ADC reading, which describes the height of the metal surface. To demonstrate the performance of this system, a simulation based on the DAC MCP4725 is used. The DAC MCP4725 will be programmed to provide values that depict the height of the metal surface, receiving x and y inputs from the serial sent using a Python program with a Tkinter GUI."

"Phosphate Sludge (PS) waste has been a problem in metal surface finishing industry. The waste cannot be dumped in landfill due to the metal content. Valorisation of the waste will be beneficial in a way that it conserves natural reserves and reduces energy consumption. This paper describes the attempt of utilization of PS by mixing it in kaolin in preparation of ceramic bricks. A series of experiments showed that mixtures containing between 25–50 mass % PS sintered at 1200oC attained the highest compressive strength of >25 MPa. X-ray diffractions (XRD) showed that the presence of PS hindered the formation of mullite, the phase that contribute to strength in Al2O3–SiO2 kaolin system. In the mixture of 1:1 kaolin: PS fired at 1200oC, cristobalite was formed, instead of mullite, as observed in the XRD patterns."

"Telah dilakukan Studi Awal Probe Pemindai Permukaan Logam Berbasis Perubahan Kapasitansi dengan tegangan konstan. Tegangan konstan ini dapat divariasikan dalam rentang 0-1000 V. Probe dihubungkan dengan rangkaian integrator dengan resistor feedback 1 GΩ menggunakan operational amplifier OPA128JM yang memiliki impedansi input 1 TΩ dan arus bias input hingga 300 fA. Output dari rangkaian integrator ini dihubungkan dengan rangkaian penguat tegangan yang dapat melakukan penguatan hingga 987.6 kali. Probe dapat digerakkan di mana pada arah sumbu-x menggunakan stepper motor 17HS3401 dengan angle sebesar 1.8°/step yang dioperasikan menggunakan driver dengan sistem mikrostep sebesar sixteenth step. Konversi gerak rotasi-linier dari stepper motor menggunakan lead screw T8L8P2 dengan 4 start sehingga memiliki resolusi pergerakan linier sebesar 0.0044 mm/step. Adapun penggerak arah sumbu-z dapat memosisikan probe pada permukaan logam menggunakan stepper motor SPS-15RF dengan angle sebesar 18°/step yang dioperasikan menggunakan driver dengan sistem mikrostep sebesar quarter step. Konversi gerak rotasi-linier dari stepper motor menggunakan lead screw T3L4P4 dengan 1 start sehingga memiliki resolusi pergerakan linier sebesar 0.0371 mm/step. Untuk menghasilkan tegangan konstan menggunakan EMCO C10 dengan sumber tegangan 12 V dengan daya sebesar 1 watt.

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An Initial Study of a Capacitance Change-Based Metal Surface Scanning Probe operating at constant voltage has been conducted. The constant voltage can be varied within a range of 0-1000 V. The probe is connected to an integrator circuit with a 1 GΩ feedback resistor using an operational amplifier OPA128JM, which has an input impedance of 1 TΩ and an input bias current of up to 300 fA. The output from this integrator circuit is connected to a voltage amplifier circuit that can amplify up to 987.6 times. The probe can be moved in the x-axis direction using a 17HS3401 stepper motor with an angle of 1.8°/step, operated using a driver with a sixteenth step microstep system. The rotation-linear motion conversion from the stepper motor uses a T8L8P2 lead screw with 4 starts, resulting in a linear motion resolution of 0.0044 mm/step. The z-axis direction actuator can position the probe on the metal surface using an SPS-15RF stepper motor with an angle of 18°/step, operated using a driver with a quarter-step microstep system. The rotation-linear motion conversion from the stepper motor uses a T3L4P4 lead screw with 1 start, resulting in a linear motion resolution of 0.0371 mm/step. To generate a constant voltage, an EMCO C10 is used with a 12 V power source and a power of 1 watt."

"This collection of ideas and results on topics of curve and surface design is intended for research in the academic environment as well as for practical use in industrial applications. Main emphasis is on minimal energy splines and geometric spline curves, and on techniques beyond tensor product surfaces."