PENENTUAN KOMPONEN DAN KOMPOSISI SENYAWA SERTA KARAKTERISTIK AROMA MINYAK ROSEMARY (Rosmarinus officinalis L.) HASIL OKSIDASI MENGGUNAKAN ALIRAN GAS OKSIGEN

Karakteristik aroma minyak atsiri dipengaruhi oleh kandungan senyawa yang mengandung oksigen. Minyak atsiri dengan kandungan senyawa yang mengikat oksigen lebih tinggi memiliki kekuatan fragrance yang lebih kuat dan memiliki potensi kegunaan yang lebih luas. Peningkatan kadar senyawa yang mengikat oksigen dalam minyak atsiri dapat dilakukan dengan oksidasi menggunakan sistem batch. Penelitian ini bertujuan untuk menganalisa perubahan yang terjadi dalam minyak atsiri yang dioksidasi dan pengaruhnya terhadap karakteristik aromanya. Dalam penelitian ini telah dilakukan oksidasi menggunakan aliran O2 terhadap minyak rosemary menggunakan sistem batch pada suhu 115℃. Analisis komposisi senyawa minyak rosemary dilakukan dengan menggunakan Gas Chromatography-Mass Spectrometry (GC-MS), sedangkan analisa karakteristik aroma dilakukan dengan mnggunakan software Perfumer’s Workbook. Hasil analisis GC-MS menunjukkan bahwa kandungan senyawa minyak rosemary terdiri atas ⍺-pinen, 1,8-sineol, linalool, camphor, linalil asetat, isobornil asetat, dan β-terpinil asetat dengan kadar masing-masing senyawa di atas 1%. Oksidasi terhadap minyak rosemary menghasilkan perubahan komposisi dan komponen senyawa utamanya. Jumlah kandungan senyawa yang mengikat oksigen pada minyak rosemary hasil oksidasi mengalami peningkatan, termasuk didalamnya yaitu kandungan senyawa camphor, cis-linalool oksida, trans-linalool oksida, dan isobornil asetat. Selain itu ditemukan juga keberadaan puncak senyawa baru yang mengandung oksigen dengan struktur yang diduga sebagai fenchyl asetat, ⍺-terpinil asetat dan epoksilinalool dalam minyak rosemary hasil oksidasi. Peningkatan kandungan camphor diduga berasal dari oksidasi ⍺-pinen, sementara peningkatan kandungan linalool oksida diduga berasal dari oksidasi senyawa linalool. Selain itu peningkatan isobornil asetat dan pembentukan senyawa fenchyl asetat dan ⍺-terpinil asetat diduga berasal dari reaksi isomerisasi linalil asetat. Analisis karakteristik aroma menunjukkan adanya perubahan karakter minyak rosemary hasil oksidasi. Karakteristik aroma, minyak rosemary sebelum oksidasi didominasi oleh 5 karakter aroma yaitu aroma konifer, iceberg, herb, light chemical floral dan citrus. Sedangkan karakteristik aroma minyak rosemary hasil oksidasi menunjukkan peningkatan karakter aroma konifer, iceberg dan herb dan penurunan karakter aroma light chemical floral, woody, citrus, zolvent, dan fruity. Kata kunci: minyak rosemary, Rosemarinus officinalis L., oksidasi, minyak atsiri, sistem batch, refluks, oksige

Effect of sintering atmosphere on the pore-structure stability of cerium-doped nanostructured alumina

Pore-structure stability of pure and Ce-doped alumina in air and argon atmospheres was studied using DTA, TGA, N2 ads./des. and XRD with a view to understand the importance of the ionic size of the dopant cation on the pore-structure stability of alumina. The ionic size effect was studied by heat treating the Ce-alumina system in both oxidizing and reducing atmospheres to have Ce4+ (87 pm) and Ce3+ (106 pm) respectively. No compound formation between Ce and alumina was observed. In the case of pure alumina there is a drastic reduction in porosity during the transformation to α-alumina. Ce-doped alumina has a higher DSC transformation temperature corresponding to the α-alumina transformation compared to pure alumina. Ce-doped alumina showed higher pore-structure stability compared with pure alumina and the stability was relatively higher in reducing atmosphere (higher Ce3+/Ce4+ ratio, higher effective ionic size) compared with oxidizing conditions (lower Ce3+/Ce4+ ratio, lower effective ionic size)

Preparation and Characterization of High-Temperature Thermally Stable Alumina Composite Membrane

A crack- and pinhole-free composite membrane consisting of an α-alumina support and a modified γ-alumina top layer which is thermally stable up to 1100°C was prepared by the sol–gel method. The supported thermally stable top layer was made by dipcoating the support with a boehmite sol doped with lanthanum nitrate. The temperature effects on the microstructure of the (supported and unsupported) La-doped top layers were compared with those of a common γ-alumina membrane (without doping with lanthanum), using the gas permeability and nitrogen adsorption porosimetry data. After sintering at 1100°C for 30 h, the average pore diameter of the La-doped alumina top layer was 17 nm, compared to 109 nm for the common alumina top layer. Addition of poly(vinyl alcohol) to the colloid boehmite precursor solution prevented formation of defects in the γ-alumina top layer. After sintering at temperatures higher than 900°C, the common alumina top layer with addition of poly(vinyl alcohol) exhibits a bimodal pore distribution. The La-doped alumina top layer (also with addition of poly(vinyl alcohol)) retains a monopore distribution after sintering at 1200°C

Tunnel magnetoresistance in alumina, magnesia and composite tunnel barrier magnetic tunnel junctions

Using magnetron sputtering, we have prepared Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions with tunnel barriers consisting of alumina, magnesia, and magnesia-alumina bilayer systems. The highest tunnel magnetoresistance ratios we found were 73% for alumina and 323% for magnesia-based tunnel junctions. Additionally, tunnel junctions with a unified layer stack were prepared for the three different barriers. In these systems, the tunnel magnetoresistance ratios at optimum annealing temperatures were found to be 65% for alumina, 173% for magnesia, and 78% for the composite tunnel barriers. The similar tunnel magnetoresistance ratios of the tunnel junctions containing alumina provide evidence that coherent tunneling is suppressed by the alumina layer in the composite tunnel barrier.Comment: 3 pages,4 figures, 1 tabl

Investigation of the surface structure and activity of molybdenum oxide-containing catalysts : I. An infrared study of the surface structure of molybdena-alumina catalysts

A comparison has been made of the infrared spectra of alumina with molybdenum oxide-alumina in both the oxidized and reduced forms. In the case of molybdena-alumina prepared via adsorption of gaseous MoO2(OH)2, the spectra show that a practically complete monolayer of Mo6+ oxide covers the alumina. After reduction with hydrogen the hydroxyls of the carrier appear. From the reversibility of reduction and oxidation under mild conditions it has been established that the reduced oxide is present as an interrupted monolayer

Improved masers for X-band and Ku band

Slow-wave structure of traveling-wave maser utilizes comb system which is comprised of ruby on one side and alumina on other; alumina also supports isolator material. Radiation at pump frequency is coupled to ruby through shaped alumina strips. Contact between ruby bars and comb completes conductance path for heat transfer

The effect of thermal annealing on the properties of thin alumina films prepared by low pressure MOCVD

Thin amorphous alumina films were prepared on stainless steel, type AISI 304, by low pressure metal-organic chemical vapour deposition. The effect of thermal annealing in nitrogen (for 2, 4 and 17 h at 600, 700 and 800 °C) on the film properties, including the protection of the underlying substrate against high temperature corrosion and the chemical composition of the film, were investigated.\ud \ud Corrosion experiments performed at 450 °C in a hydrogen sulphide-containing gas, showed that the thermal annealing process had a detrimental effect on the protective properties of the alumina films. From FTIR and Auger measurements, it was found that the amorphous alumina, containing boehmite, converted to ¿-alumina during the annealing process

Sinter forging of zirconia toughened alumina

Sinter forging experiments have been carried out on powder compacts of zirconia toughened alumina (ZTA) Ceramics Alumina-15 wt% zirconia was prepared by a gel precipitation method and calcined at temperatures of 900 or 1100°C. Full densification of ZTA ceramics was obtained within 15 min at 1400°C and 40 MPa. A homogeneous microstructure can be observed with an alumina grain size of 0.7 mgrm and a zirconia grain size of 0.2 mgrm. Almost no textural evolution occurred in the microstructure. During sinter forging the densification behaviour of the compacts was improved by an effective shear strain, for which values of more than 100% could be obtained. As a result of the shear deformation the densification of ZTA in the agr alumina phase stage shifted to lower temperature. During pressureless sintering the gamma to agr alumina transformation temperature was dependent of the preceding calcination temperature, while during sinter forging this phase transformation was independent of calcination temperature and took place at a lower temperature

Degradation of alumina and zirconia toughened alumina (ZTA) hip prostheses tested under microseparation conditions in a shock device

This paper considers the degradation of alumina and zirconia toughened alumina vs. alumina for hip implants. The materials are as assumed to be load bearing surfaces subjected to shocks in wet conditions. The load is a peak of force; 9 kN was applied over 15 ms at 2 Hz for 800,000 cycles. The volumetric wear and roughness are lower for ZTA than for alumina. The long ZTA ageing did not seem to have a direct influence on the roughness. The ageing increased the wear volumes of ZTA and it was found to have a higher wear resistance compared to alumina.Comment: International Conference on BioTribology (ICoBT 2011), Londres, 18 au 21 septembre 2011, Londres : United Kingdom (2011