Materials Science Forum Vol. 761

Abstract: This study evaluated the microstructure and mechanical properties enhancement of cross roll rolled Ni-10Cr alloy, comparing with conventional rolled material. Cold rolling was carried out to 90% thickness reduction and subsequently annealed at 700 °C for 30 min to obtain the fully recrystallized microstructure. Particularly, cross roll rolling was carried out at a tilted roll mill condition of 5º from the transverse direction in RD – TD plane. Application of cross roll rolling on Ni-10Cr alloy contributed to the notable grain refinement due to higher effective strain than that of conventional rolling, consequently, average grain size was refined from 135 µm in initial material to 4.2 µm in cross roll rolled material. Furthermore, //ND texture in CRR material was well developed than that of CR material, which contributed to the mechanical properties and formability enhancement.

Abstract: Antibacterial polypropylene cross-sectional shape fibers were melt spun with adding nano ZnO and modified chitosan. Two types of fiber cross-section, round and worm cross-sectional shape were studied including with nano ZnO and modified chitosan loading. Antibacterial properties, surface area, and fiber crystalization were investigated. The surface area of the fiber and antibacterial properties were directly related to the cross-sectional shape. The greater antibacterial properties was found at lower modified chitosan loading compared ZnO.

Abstract: Linear assembly of densely packed oxidized nanodiamonds (OxNDs) was achieved in polyepoxide-based nanohybrid films. A homogeneous suspension of pre-polymer of polyepoxide and OxNDs was cast onto a polyamide-spacer and subjected to an electric field in order to induce relocation and stretched-assembles of the fillers before the mixture became cross-linked. The OxNDs suspended readily, forming linear assemblies of OxNDs (LAOxNDs) of varying thicknesses, and aligned vertical to the film surfaces. Nanohybrid films with assemblies of LAOxNDs led to a significant enhancement in thermal conductivity while maintained the electrical insulation property of the polyepoxide. Mechanisms for the formation and structural variation of LAOxNDs in the matrix are elaborated regarding the improvement in physical properties. The present ambient-oxidation process and field-induced application are simple, but effective in enhancing the thermal properties of the polymer-based hybrids, and hence, promising for applications in the semiconductor industry, such as thermal interface materials.

Abstract: Plasma sprayed hydroxyapatite (HA) coatings on titanium alloy substrates have been used extensively due to their excellent biocompatibility and osteoconductivity. However, the low bonding strength between HA and Ti substrates is still problematic in the long-term implantation lifespan. In this paper, HA/Ta composite coatings with various Ta contents (20% and 60%) were fabricated by vacuum plasma spraying (VPS). The microstructure, phase composition of the coatings was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The results revealed that the coatings had a rough surface and lamellar structure including some pores. ASTM C-633 standard was used for the measurement of bonding strength, which was found increasing with the increase of Ta contents in the composite coatings. The bonding strength of the composite coating containing 60% Ta (H4T6) reached to 37.2 MPa, which is about 1.9 times that of HA coating. In vitro bioactivity evaluated in simulated body fluids (SBF) showed that bonelike apatite layer was formed on the composite coatings surface, which indicated the good bioactivity of the HA/Ta composite coatings.

Abstract: Abstract: Calcium silicate (CS) ceramics have good biocompatibility, high bonding strength with titanium alloy substrates, and are potential candidates for implant coating materials. The osteo-integration of coated implants with host bone tissue is greatly affected by the degradation of these coating materials in biological fluid. In this paper, zirconia adopted calcium silicate (CaO-ZrO2-SiO2, CZS) ceramic powder was synthesized. Plasma spraying was used to prepare the coating with Ti-6Al-4V as substrates. Human bone marrow-derived stromal cells (hBMSCs) culture system was used to evaluate the cytocompatibility of the CS and CZS coatings. Results showed that more cells were adhered to the CZS coating with high proliferation ratio than those on CS. The dissolution of CS and hereby elevated pH value were contributed to the decreased cell adhesion and proliferation.

Abstract: Copper nanoparticles have been prepared by pulsed wire discharge (PWD) using copper wire in deionized water at various relative energy (K) from 0.8 to 5.5, which is ratio of the charged energy of capacitor in the electrical circuit to the vaporization energy of the wire. From the X-ray diffraction analysis of the prepared nanoparticles in deionized water at various K, the nanoparticles prepared at all conditions were identified as Cu and Cu₂O. The Cu content in prepared nanoparticles was increased with the decrease in K, and changed from 77 to 95 [%]. Additionally, the deposited energy in the arc discharge after the wire heating was decreased with decreasing K. From these results, we considered that the Cu content was increased with decreasing the deposited energy in the arc discharge during particle formation.

Abstract: Tantalum (Ta) can be use a suture for operation and implant material in order not to react with body fluid and stimulate a human body. In this study, the stable oxide of a tantalum, tantalum oxide layer produced by oxidation of the tantalum nitride, TaN powders by high temperature oxidation were investigated in order to determine the possibility of its a distributed aid for biomaterial composite such as an artificial root etc. The sample, TaN powder oxidized at high temperature exhibited a steady mass gain with increasing oxidation temperature. Based on the results of the XRD, tantalum oxide, Ta2O5 was detected on the samples. It is considered, the TaN showed a good oxidation film produced by high temperature oxidation.

Abstract: A metallurgical method for preparing oxide nano-rod array structure was developed with internal oxidation of Ni(Al) solid solution obtained by aluminizing Ni with a pack cementation technique. The present method was applied in order to fabricate nano-rod array on the micro-channel surface of microreactor. A micro-channel with 1 mm in depth, 1mm in width and 10 mm in length was fabricated on the Ni disk by an electric discharge machining and electropolishing. The Ni disk with a micro-channel was annealed at 1300°C for 12 h in vacuum. The sample was aluminized by a pack cementation using pack powder mixture consisting of 10 mass% of Ni3Al, 88 mass% of Al2O3 and 2 mass% of NaCl at 1100°C for 12 h in a flow of argon gas. The sample was oxidized from 1000 to 1200°C for 6 h with the Co/CoO buffer. Ni matrix in internally oxidized zone was removed by electropolishing to expose nano-rods. Al2O3 nano-rod array located on the micro-channel surface was successfully fabricated with the proposed technique. Diameter and height of nano-rods were ranged from 100 to 300 nm and from 1.5 to 3 µm, respectively.

Abstract: The material study on bioactivitying artificial bone is lacking results for improve the quality of life (QOL) for individuals to fulfill their happy life in the society, which requires artificial bone to be replaced with neonatal bone by absorbing, regenerating the bone, which is not possible. Hydroxyapatite Ca₁₀(PO₄)₆(OH)₂, (HAp) has excellent biomaterial for biomedical and dental applications because of its superior properties. However, HAp had poor mechanical properties such as low hardness and fracture toughness. In this study, HAp containing titanium and titanium hydride (TiH₂) sintered bodies were studied in order to investigate the possibility of its advanced biomaterials application. The nano particle size starting powders were milled by using mortar and muddler equipment. The sintered bodies were prepared by pressureless sintering at argon-hydrogen gas atmosphere. The samples were evaluated for bioactive performance by using simulated body fluid (SBF) solution for. The HAp-Ti, the HAp-TiH₂ composite material is attractive as a bioceramics compared with HAp ceramics.

Abstract: The glycerides of castor oil (GCO) were copolymerized with isophorone diisocyanate (IPDI) to generate glyceride-based polyurethane (GCPU), meanwile blending with hydroxyapatite (HA) powder to fabricate porous composite scaffolds. The effect of HA content on mechanical properties of the resulting polymer scaffolds and the in vitro cell response of HA/GCPU scaffolds were investigated, by use of mechanical testing, FTIR, SEM and MTT assay. The results showed that the compressive strength increased with HA content, and the HA/GCPU scaffold with 40 wt% HA reached about 4.6 MPa, much higher than the scaffold without HA (only 605 kPa). The SEM observation, live-dead staining assay and MTT assay demonstrated the excellent biological properties of HA/GCPU scaffolds, which support cell adhesion and proliferation. This novel class of HA/GCPU porous scaffolds have prospect and advantage for bone repair and regeneration.