Effects of Chemical-Electrical and Mechanical Parameters on Electrical-induced Chemical Mechanical Polishing of GaN

Overcoming the low fabricating efficiency of traditional chemical mechanical polishing (CMP) for Gallium nitride (GaN) is a challenge owing to its high hardness, high brittleness, and chemical inertness. Here, electrochemical etching is proposed to increase the material removal rate and acquire a high-quality surface on GaN wafers. To reveal the synergistic etching mechanism of oxidizing agent and corrosion inhibitor on the GaN wafers, electrochemical etching experiments were carried out. The optimal etching solution contained 4 wt% H2O2 and 10 mmol/L purified terephthalic acid. Experiments with various polishing parameters were comparatively investigated to verify the auxiliary effect of etching and determine the ideal parameters. Cathodoluminescence spectroscopy shows that the electrochemical etching removes the SSDs completely and the CMP process with befitting parameters does not induce supernumerary SSDs.

ANALISIS PENGENDALIAN PERSEDIAAN AUX RAW MATERIAL MENGGUNAKAN METODE MIN-MAX STOCK DI PT. MITSUBISHI CHEMICAL INDONESIA

PT. Mitsubishi Chemical Indonesia merupakan perusahaan yang bergerak di bidang industri polyester yang memproduksi Purified Terephthalic Acid (PTA) terbesar di Indonesia. PTA adalah suatu senyawa yang tidak tersedia di alam yang dibuat dari sintesa kimia. Terdapat auxiliary raw material yang diperlukan untuk membantu proses produksi PTA agar dapat berjalan dengan lancar, seperti Hydrobromic Acid (HBr) dan Soda Ash Dense (Na2CO3). Perusahaan belum memiliki jumlah safety stock padahal perusahaan harus mengendalikan persediaan auxiliary raw material agar dapat menghindari kekurangan dan kelebihan bahan baku yang menyebabkan perusahaan dapat mengeluarkan biaya lebih banyak. Hasil perhitungan memperlihatkan bahwa metode min-max stock menunjukan jumlah safety stock bahan baku Hydrobromic Acid yaitu sebesar 17,5 ton dan untuk Soda Ash Dense yaitu sebesar 5,41 ton. Penentuan jumlah persediaan antara kebijakan perusahaan dengan hasil perhitungan metode min-max stock memiliki beberapa perbedaan. Dari perbedaan tersebut, perusahaan dapat menghemat total biaya persediaan sebesar Rp 7.550.000,00 untuk Hydrobromic Acid dan Rp 11.221.224,16 untuk Soda Ash. Frekuensi pemesanan yang terlalu sering dengan ukuran pemesanan yang besar menyebabkan total biaya persediaan menjadi tinggi. Dari hasil tersebut perusahaan perlu menerapkan metode min-max stock untuk mengendalikan persediaan bahan baku supaya dapat menghemat biaya pengeluaran. Abstract[Inventory Control Analysis of Aux Raw Material Using Min-Max Stock Method in Mitsubishi Chemical Indonesia Company] Mitsubishi Chemical Indonesia is a company engaged in the polyester industry that produces the largest Purified Terephthalic Acid (PTA) in Indonesia. PTA is a compound that is not available in nature, so it is made by chemical synthesis. There are auxiliary raw materials that are needed to help the PTA production process, so it can run well, such as Hydrobromic Acid (HBr) and Soda Ash Dense (Na2CO3). The company don’t have the safety stock even though the company should control the aux raw material inventory to avoid the company to run out of stock or overstock, that causes the company to spend a lot of money. The calculations result shows that the amount of the safety stock for Hydrobromic Acid is 17.5 tons and for Soda Ash is 5.41 tons. The determined number of inventories between company policy and the calculation of the min-max stock method have several differences. From those differences, the company can save the total inventory cost amounted at IDR 7.550.000,00 for Hydrobromic Acid and IDR 11.221.224,16 for Soda Ash. High frequency of orders with a large order size can cause the total inventory cost to be high. From that result, the company needs to apply a min-max stock to control inventory and to save money on expenses.Keywords: inventory; min-max stock method; out of stock; overstock; TIC

Treatment of Purified Terephthalic Acid Wastewater by Ozone Catalytic Oxidation Method

In this study, a Cu–Ce@Az ozone catalyst with multiple active components was prepared through the impregnation method to treat purified terephthalic acid (PTA) wastewater, and characterized by X-ray diffraction, X-ray fluorescence spectroscopy, scanning electron microscopy, specific surface area analysis, X-ray energy spectroscopy, X-ray photoelectron spectroscopy, and other methods. The Cu–Ce@Az ozone catalyst had a developed pore structure with a large specific surface area and crystal structure. After calcination, the metallic elements Cu and Ce existed in the state of oxides CuO and CeO2. The effects of reaction time, solution pH, catalyst dosage, and ozone dosage on the catalytic oxidation performance of the Cu–Ce@Az ozone catalyst were studied. Adding tert-butanol reduced the removal rate of COD from the PTA wastewater through the catalytic oxidation system, which proves that a Cu–Ce@Az ozone catalyst treatment process of PTA wastewater follows the free-radical reaction mechanism. The results of 3D fluorescence spectroscopy analysis show that the organic matter in the PTA wastewater was converted into tryptophan organic matter and aromatic organic matter after the reaction of the catalytic oxidation system. Ultraviolet absorption spectroscopy analysis indicated that in unsaturated chemical bonds, some conjugated structures and benzene ring structures of organic matter in the PTA wastewater were destroyed.

Impact of MTA blend % in melt spinning process and polyester properties

In Polyethylene terephthalate (PET) processing the raw materials are purified terephthalic acid (PTA), moderately purified terephthalic acid (MTA), monoehalene glycol (MEG). The processing of PTA is very difficult and costly. For reducing PTA percent we are using different percentages of MTA blend in PET processing. MTA affected the properties of polyester and melt spinning process. The properties such as elongation, tenacity, molecular chain length, b-color and IV, thermal properties, % carboxyl groups will change with MTA percentage. MTA percentage also affects fiber breakage percentage s, the melting point of PET. FTIR results show a change in chemical composition. Particle size, 4-CBA content of MTA affects the properties of the fiber.