Papers by Keyword: Solid-Phase

Abstract: Niobia is used as a sintering additive in alumina processing because it lowers the sintering temperature. This work investigated the influence of sintering dwell time at 1400^oC on the properties of 4 wt% niobia doped alumina. The sintered ceramics were characterized by scanning electron microscopy (SEM), and X rays diffraction (XRD) with Rietveld refinement. Measurements of density, average grain size, hardness, and elastic constants were also performed. The results showed that the porosity depend on the time sintering and this influence on the elastic properties. Longer sintering times improved densification and with this the Young's Modulus.

Abstract: This work investigated the sintering behavior of alumina doped with 4wt% niobia. Three sintering temperatures were investigated: 1400°C, 1450°C and 1500°C. The first temperature leads to solid-phase assisted sintering (SSS) while the other ones develop liquid-phase assisted sintering (LPS). The presence of liquid phase in the second case is due to an eutectic reaction occurring at 1440°C ± 20°C in the alumina-niobia system. The sintering behavior was assessed by measuring the final densities. The results indicated that the 1400°C solid-state sintering, comparatively, was better. This paper proposes that defects associated to the substitution of Al⁺³ by Nb⁺⁵ in the alumina cation sub-lattice, fostered diffusion and SSS. Sintering at 1500°C presented the lowest density, apparently due to niobate (liquid phase) loss, at this temperature as observed by XRD results.

Abstract: Oligonucleotides are essential components of many applications in molecular biology. The synthesis chemistry is robust and commercial oligonucleotide synthesizers have taken advantage of the chemistry to provide oligonucleotides of high quality and purity. This paper established nucleic acid synthesis platform to carry out the synthesis of the labeled nucleic acid probes based on the DNA synthesizer and solid-phase synthesis technology. We chose to study the automated synthesis starting from DMT protected FAM labeled amidite attached to controlled pore glass (CPG) support and the standard trityl-off oligonucleotide synthesis cycle was performed, yielding the solid-supported oligonucleotide. The reported automated solid-phase oligonucleotide synthesis procedure successfully employs the common iterative synthesis, deblocking, activation, coupling, capping, oxidation, and isolation steps in standard oligonucleotide synthesis. The automated synthetic approach can also be applied to oligonucleotides of different length, composition of nucleotide, demonstrating the universality of the method. Moreover, the synthesis involved the use of commercially available, safe, stable, and inexpensive reagents, particularly advantageous and attractive for their use in automated solid-phase synthesis. The synthesis allows custom tailoring of their structure to the requirements of biological assays within hours, as opposed to traditional approaches that require weeks or months of work in the laboratory. Therefore it will become much easier to investigate biological interactions and optimize for objectives such as the receptor mediated targeting of oligonucleotides.

Abstract: In an attempt to optimize the friction spot joining process of Al alloys for automobiles (Al 5000 and Al 6000 series, thickness 1mm), effects of joining parameters such as tool rotating speed, plunging depth and dwelling time on the weld joints properties were evaluated. Experimental tests were carried out for lap joined Al plates. A wide range of joining conditions could be applied to join Al alloys for automobiles without defects in the weld zone except for certain welding conditions with an insufficient heat input. The microstructures and hardness variations in the weld regions are discussed. The microstructures of welds, corresponding to the pin hole, have dynamic-recrystallized grain similar to stir zone in FSW weld. In hardness distribution, minimum hardness region was located about 6-mm away from the weld center, corresponding to the shoulder radius of the tool. For each weld the results from tensile-shear tests are also presented. For sound joints without defects, tensile shear strength of weld joints was higher approximately 230% than acceptable criteria of tensile shear strength of electrical resistance spot-welded joints for aluminum (MIL-W-6858D).