Orientation Dependence of Hardness and Reduced Modulus of Single Crystal Sapphire Surface Measured by Nanoindentation
Toshiro Okawa,
Ian Thomas Clark,
Katsuhiko Tashiro,
Hideo Honma,
Kazuhiro Yoshihara,
Osamu Takai
Issue:
Volume 8, Issue 5, September 2019
Pages:
76-80
Received:
15 September 2019
Accepted:
26 September 2019
Published:
10 October 2019
Abstract: Nowadays, industrial products are downsized, and the structure of materials is controlled with the nanometer precision, and it becomes very important to measure the mechanical properties of local area of bulk material. Especially the hardness and the elastic modulus are important mechanical properties. The orientation dependence of hardness and reduced modulus of single crystal sapphire surface was investigated by nanoindentation. The conventional technique to measure the hardness of materials using an optical micrometer cannot evaluate mechanical properties of a local region of several µm or less. However, nanoindentation can measure mechanical properties of very small surface area of materials, and is expected to detect the micro structure dependence of mechanical properties. Nanoindentation uses very small indenter made of diamond, and measures the indentation depth. The measured depth is converted to the indented area size using the area function. The area function of the indenter can be obtained using a standard material (fused quartz) in advance. Therefore nanoindentation can measure the indented area size without using an optical micrometer. In this report, it was shown that the nanoindentation could detect the structure dependence of mechanical properties of materials. The specimen was a single crystal sapphire with c - axis surface, and the indenter was Berkovich type diamond tip. It was confirmed that the nanoindentation hardness was the lowest, and the reduced modulus was the largest, when the ridge line of indenter was oriented to the m - axis of single crystal. The nanoindentation could detect the structure dependence of a local area of mechanical properties materials.
Abstract: Nowadays, industrial products are downsized, and the structure of materials is controlled with the nanometer precision, and it becomes very important to measure the mechanical properties of local area of bulk material. Especially the hardness and the elastic modulus are important mechanical properties. The orientation dependence of hardness and red...
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Innovative Approach to Flame Retardant Cotton Fabrics with Phosphorus Rich Casein via Layer-by-Layer Processing
Sechin Chang,
Brian Condon,
Jade Smith,
Sunghyun Nam
Issue:
Volume 8, Issue 5, September 2019
Pages:
81-89
Received:
6 September 2019
Accepted:
25 September 2019
Published:
23 October 2019
Abstract: Flame retardant behaviour was imparted using the layer-by layer assemblies of phosphorus rich casein milk protein with eco-friendly inorganic chemicals on cotton fabrics. The cotton twill fabrics were prepared using two solutions; a mixture of positively charged branched polyethylenimine (BPEI) with urea and diammonium phosphate (DAP), and negatively charged casein. Layer-by-layer assemblies for flame retardant properties were applied using the pad-dry-cure method, and each coating formula was rotated for 20 bi-layers. The effectiveness to resist flame spread on treated fabrics was evaluated using vertical (ASTM D6413-08) and 45° angle flammability test (ASTM D1230-01) methods. In most case, char lengths of fabrics that passed the vertical flammability tests were less than 50% of the original length, and after-flame and after-glow times were less than one second. Thermal properties were tested the extent of char produced by untreated and treated fabrics at 600°C by thermogravimetric analysis (TGA). Micro-scale combustion calorimeter (MCC) and Limiting oxygen indices (LOI, ASTM D2863-09) were also assessed. All untreated fabrics showed LOI values of about 21% oxygen in nitrogen. LOI values for the treated casein with BPEI/urea/DAP fabrics were greater than 29-34% between 5.80-9.59 add on wt%. Their structural characterizations were revealed by TGA/FT-IR and SEM methods. The treated fabrics exhibited improved thermal stability, as evidenced by increased ignition times and lower heat release rates. The results of this study show that flame retardant nanocoatings can be readily applied to textile fabrics using a continuous process that is ideal for commercial and industrial applications.
Abstract: Flame retardant behaviour was imparted using the layer-by layer assemblies of phosphorus rich casein milk protein with eco-friendly inorganic chemicals on cotton fabrics. The cotton twill fabrics were prepared using two solutions; a mixture of positively charged branched polyethylenimine (BPEI) with urea and diammonium phosphate (DAP), and negative...
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Characterization of the Palmyra Petiole as a Biovegetal Material of Artisanal Construction in Chad
Ngargueudedjim Kimtangar,
Djidengar Lazare,
Deudjonbe Baruc,
Beda Tibi,
Nzie Wolfgang
Issue:
Volume 8, Issue 5, September 2019
Pages:
90-97
Received:
14 August 2019
Accepted:
9 October 2019
Published:
23 October 2019
Abstract: The palmyra is a wood particularly famous for its resistance to xylophages and various bad weather. But the determining factors of this resistance are unknown. This base material is available in the form of lignocellulosic waste generated in large quantities, following its grooming, maintenance and felling. This lignocellulosic waste is not valued in Chad. Its petiole is the biovegetal material widely used in Chad for the artisanal manufacture of furniture and other works. The present study concerns the determination of its physical, chemical and mechanical characteristics. We used chemical analyzes, physical tests and mechanical tests in three-point flexion, intension and in compression. Its contents in cellulose, lignin and Hemicellulose obtained justify its resistance to physical and chemical degradation and its attack by termites. The values of its mechanical characteristics obtained place it between the category D50 and D60 of hardwoods. Those of its physical properties place it among the light woods. This study, the first on the knowledge of the scientific and technical properties of the palmyra of Chad, opens perspectives on a new field of study on the behaviour of this abundant natural raw material with a view to its valorisation and its rational use in various fields, such as pulp and building construction and public works.
Abstract: The palmyra is a wood particularly famous for its resistance to xylophages and various bad weather. But the determining factors of this resistance are unknown. This base material is available in the form of lignocellulosic waste generated in large quantities, following its grooming, maintenance and felling. This lignocellulosic waste is not valued ...
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