Agus Geter Edy Sutjipto

Low Temperature Fluidized Bed Nitriding of Austenitic Stainless Steel

In the present investigation, low temperature nitriding has been attempted on AISI 316L austenitic stainless steel by using a laboratory fluidized bed furnace. The nitriding was performed in temperature range between 400°C and 500°C. X-ray diffraction, metallography, and corrosion tests were used to characterize the resultant nitrided surface and layers. The results showed that fluidized bed process can be used to produce a precipitation-free nitrided layer characterized by the S phase or expanded austenite on austenitic stainless steel at temperatures below 500°C. But there exists a critical temperature and an incubation time for effective nitriding, below which nitriding is ineffective. The corrosion behaviour of the as-nitrided surfaces is significantly different from that previously reported for low temperature plasma nitriding. This anomaly is explained by the formation of iron oxide products and surface contamination during the fluidized process.

The Effect of CaO Addition on the Microstructural, Mechanical and Dielectric Properties of Pure MgO Ceramic

High purity MgO is a common ceramic material used as a protecting layer in an alternating current plasma display panel (AC-PDP). In this work, pure MgO was added by CaO for a better protecting layer. The effect of CaO addition was discussed according to the changes in the microstructure, mechanical strength and the ability of the sample to withstand surface breakdown (flashover) with various CaO addition in the powder mixture. In addition, it was found that 2.5 wt% CaO-addition shows a better electrical discharge. Since secondary electron emission coefficient contributes in the electrical discharge, it could be predicted that the 2.5 wt% CaO added MgO has a higher secondary electron emission constant and becomes a promising candidate for a protecting layer in AC-PDP.

Virtual Simulation and Remote Desktop Interface for CNC Milling Operation

Advanced development of computer network through Internet brings the technology to Manufacturing. Increasing the demand for effectively use of the production facility requires the tools for sharing the manufacturing facility by remote operation of the machining process. This paper introduces the methodology of machining technology for direct remote operation of networked milling machine. The tools including virtual simulation using CAD model, remote desktop protocol and Setup Free Attachment for remote operation of milling process are proposed. Accessing and monitoring of machining operation is performed by remote desktop interface and 3D virtual simulations. Capability of remote operation is supported by an auto setup attachment with a reconfigurable pin type setup free technology installed on the table of CNC milling machine to perform unattended machining process. The system is designed using a computer server and connected to a PC based controlled CNC machine for real time monitoring. A client will access the server through internet communication and virtually simulate the machine activity. The result has been presented that combination between real time virtual simulation and remote desktop tool is enabling to operate all machine tool functions and as well as workpiece setup.

Relationship between average slope of textured substrate and poly-Si thin film solar cells performance

Abstract This paper presents a nanoscopic characterisation of a series of textured substrates with a structure of Ag-grid/ZnO/p-i-n/ZnO/Ag/SnO2/glass for poly-Si thin film solar cells performed by atomic force microscopy, in order to find the optimum texture substrate and realise the light trapping. The relationship between average slopes (tanθ) and photovoltaic performance are studied based on the experimental results. The experimental results show that the textured ZnO/Ag/SnO2/glass with tanθ of 0·13 yields the maximum conversion efficiency for J sc and V oc. Although the poly-Si deposited on highly textured substrate (σ>37 nm) shows excellent light trapping properties, however, in its microstructure shows a crystal deterioration and exhibits n-type characteristic, yielding poor photovoltaic performances.

Use of Porous Alumina Bioceramic to Increase Implant Osseointegration to Surrounding Bone

A new experimental porous glass ceramic coating for dental implants was prepared with a new formula consisted of a sintered glass ceramic based on alumina, silica glass and boron trioxide. The resultant sintered objects were anodized by one step anodization method at a constant potential of 40V and at a temperature of 22°C. X-ray diffraction analysis was performed to investigate the phase structure of the new material in addition to SEM investigation for surface texture and pores size and distribution. The new experimental material was subjected to failure under universal testing machine for compressive strength. The results showed a promising material to use as coating for implants as X-ray diffraction exhibited an amorphous phase diagram for the material structure whereas SEM results revealed that the pores in the specimens prepared by anodization method were highly ordered and the mean average pore size was 6.5-8.5 nm. The compressive strength test showed that the test-porous glass ceramic coating has a mean numerical value of up to 7.5 MPa which indicates an ambitious result for the new material.

Fabrication of CuSiC Composite by Powder Metallurgy Route

Copper-based composite now is a potential material for various applications, while powder metallurgy processing technique is an alternative for high temperature processing materials and net shape component. In this research, Cu-based composite containing 10-50 vol% SiC fibers was fabricated by employing the powder metallurgy route. The mixtures of SiC fibers and Cu particles were blended in a ball milling machine with the addition of ethanol at 150rpm. Then, the mixtures were uniaxially compacted into a ɸ13.5mm cylindrical pallet and followed by sintering in vacuum furnace from 800-950°C for 4 hours. The density of the composite decrease with increasing SiCf and density as high as 87% for 10vol% SiCf/Cu matrix sintered at 800°C had been achieved. The Vickers hardness of 774MPa also had been achieved for 10vol% SiCf/Cu matrix but sintered at 900°C.

Microstructure and Electrical Properties of AZO Films Prepared by RF Magnetron Sputtering

AZO is an ideal replacement transparent conducting oxide (TCO) for ITO to all corresponding applications. The typical applications include: transparent electrodes for solar cells, flat panel displays, LCD electrodes, electro-magnetic compatibility (RF-EMI shielding) coatings, touch panel transparent contacts, static discharge dissipation. The production of useful and commercially attractive thin films using different deposition processes is very important parameter to investigate. A systematic study of the sputtering condition and their influenced on electrical and structural were studied. In this work, AZO films were deposited by RF magnetron sputtering at 200 °C. The result shows that the deposited time has influenced the characteristic of deposited AZO films. For a longer deposition time, thin film shows a uniform grain growth. The resistivity found minimum at the deposition time of 45 minutes. It can be considered that by reducing of the grain boundaries which enable the electron carries to conduct smoothly.

Discharge, microstructural and mechanical properties of ZrO2 addition on MgO for plasma display panel materials

Abstract One of the major parts in the plasma display panel is its protecting layer. MgO thin film has been widely used as a protective layer for dielectric materials. Adding another material to the MgO base material is an alternative method for improving its property as protective layer. A study on reducing the surface discharge potential of a single pure MgO protecting layer by the addition of ZrO2 with several compositions is presented in this paper. The microstructural and mechanical properties are also described. The discharge properties were measured utilising the flashover treeing for material characterisation, produced by a scanning electron microscope. The mechanical properties were measured using the pure bending moment. The MgO and ZrO2 powders with 99·95 and 99% purity were used for powder mixtures of various desired compositions. In this work, investigation was carried out for sintered samples at 1250°C for 24 h. From observation, ZrO2 addition into high purity MgO has influenced the properties of MgO. Since secondary electron emission coefficient contributes in increasing the electrical field of the surface, it could be found that 5 wt-%ZrO2 added MgO has the highest secondary electron emission coefficient because the charging and discharging process happened within a shorter time.

An SEM Flashover: Technique to Characterize Wide Band Gap Insulators

This paper introduces the use of a scanning electron microscope (SEM) to evaluate the insulation property of wide band gap insulators. An SEM may be used not only to observe a surface image but also to provide a fine electron beam for charging an uncoated-insulator surface at once. The charging can create an electric field distribution in the surface. The increase of electric field at the surface may exceed a critical value when a surface breakdown/flashover occurs. An insulation property can be evaluated by varying the duration of charging/electron bombardment which is needed to initiate an optically-visible flashover treeing formation (hereinafter time to flashover treeing/TTF). In this paper, high purity MgO as a wide band gap insulator material was used as a main investigated sample. Varying addition of high purity SiO2 was used to change insulator property of the MgO. Under a certain SEMs energy and magnification, SiO2 addition has change the duration of charging up to surface breakdown. Therefore, this technique may be useful for investigating an insulation property of materials under electron bombardment such as MgO in a plasma display panel, high voltage insulator, and other insulator materials for space technology

MFI Zeolite Membrane from Rice Husk for Biofuels Production

High silica MFI zeolite membrane was synthesized by hydrothermal method at 313 K on asymetri pore structure alpha alumina substrate, utilizing natural rice husk as the sources of silica. The top layer of substrate was about 0.1 µm. The calcination was conducted at 773 K to remove the organic template. This membrane has a good stability at high temperature and in organic solvent. The membrane structure was identified by X-ray diffraction (XRD). The permeation of some pure gases was carried out to detect pinhole or cracking by studying mass transfer mechanism in the membrane. The pervaporation performance of as-synthesized membrane showed good results. This process was able to produce fuel grade bioethanol (99.2%) with the separation factor about 14.