Nanostructured β-type titanium alloy fabricated by ultrasonic nanocrystal surface modification

Kheradmandfard, Mehdi,Kashani-Bozorg, Seyed Farshid,Kim, Chang-Lae,Hanzaki, Abbas Zarei,Pyoun, Young-Shik,Kim, Jung-Hyong,Amanov, Auezhan,Kim, Dae-Eun Elsevier 2017 Ultrasonics sonochemistry Vol.39 No.-

<P><B>Abstract</B></P> <P>The surface of β-type Ti-Nb-Ta-Zr (TNTZ) alloy, which is a promising material for biomedical applications, was treated with the ultrasonic nanocrystal surface modification (UNSM) technique to enhance its hardness. As a result, a gradient nanostructured (GNS) layer was generated in the surface; the microstructure of the top surface layer consisted of nanoscale lamellae with a width of about 60–200nm. In addition, there were lamellar grains consisting of nanostructured subgrains having unclear and wavy boundaries. The treated surface exhibited a hardness value of ∼385HV compared to 190HV for the untreated alloy. It was further determined that highly dense deformation twins were generated at a depth of ∼40–150µm below the UNSM-treated surface. These deformation twins led to a significant work hardening effect which aided in enhancing the mechanical properties. It was also found that UNSM treatment resulted in the formation of micropatterns on the surface, which would be beneficial for high bioactivity and bone regeneration performance of TNTZ implants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> UNSM is a method that utilizes ultrasonic vibration to generate nanostructured surface. </LI> <LI> The surface of β-type Ti-Nb-Ta-Zr (TNTZ) alloy was treated with the UNSM technique. </LI> <LI> A gradient nanostructured layer was generated in the surface. </LI> <LI> Top surface layer consisted of nanoscale lamellae with a width of about 60–200nm. </LI> <LI> Hardness of treated surface was ∼385HV compared to 190HV for the untreated alloy. </LI> </UL> </P>

Simultaneous grain refinement and nanoscale spinodal decomposition of β phase in Ti-Nb-Ta-Zr alloy induced by ultrasonic mechanical impacts

Kheradmandfard, Mehdi,Kashani-Bozorg, Seyed Farshid,Kang, Kyeong-Hee,Penkov, Oleksiy V.,Zarei Hanzaki, Abbas,Pyoun, Young-Shik,Amanov, Auezhan,Kim, Dae-Eun Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.738 No.-

<P><B>Abstract</B></P> <P>It was found that ultrasonic nanocrystal surface modification (UNSM) treatment performed on Ti-Nb-Ta-Zr (TNTZ) alloy surface to produce a gradient nanostructured surface layer also resulted in the nano-scale spinodal decomposition of β phase. For the first time, nano-scale spinodal decomposition of β phase induced by ultrasonic mechanical impacts was observed in a short time without any age treatment. The peak shift of XRD to lower angles, (110) β XRD peak splitting, overlapped and asymmetric XRD peaks, satellite reflections in the SAED pattern, and lattice straining in HR-TEM images confirmed nano-scale spinodal decomposition of β phase in the TNTZ alloy induced by UNSM treatment. Nano-scale EDS line-scan probe analysis revealed the β phase separation into nano-scale domains of Ti-rich (β<SUB>1</SUB>) and Ti-depleted (β<SUB>2</SUB>) phases. HR-TEM images showed the semi-coherent arrangement of Ti-rich (β<SUB>1</SUB>) and Ti-depleted (β<SUB>2</SUB>) regions. Nanosized grain formation and spinodal decomposition of β phase were induced simultaneously by UNSM treatment. The nano-scale grains, high dislocation density, and semi-coherent interface between the spinodally separated phases contributed to the high hardness of the UNSM-treated TNTZ alloy specimen.</P> <P><B>Highlights</B></P> <P> <UL> <LI> UNSM is a method that applies ultrasonic impacts to generate nanostructured surface. </LI> <LI> UNSM was applied to the surface of TNTZ alloy. </LI> <LI> Gradient nanostructured layer was produced in the top surface. </LI> <LI> Nano-scale spinodal decomposition of β phase induced by ultrasonic impacts. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Significant improvement in cell adhesion and wear resistance of biomedical β-type titanium alloy through ultrasonic nanocrystal surface modification

Kheradmandfard, Mehdi,Kashani-Bozorg, Seyed Farshid,Lee, Jung Seung,Kim, Chang-Lae,Hanzaki, Abbas Zarei,Pyun, Young-Sik,Cho, Seung-Woo,Amanov, Auezhan,Kim, Dae-Eun Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.762 No.-

<P><B>Abstract</B></P> <P>A novel β-type Ti–29Nb–13Ta–4.6Zr (TNTZ) alloy with a low Young's modulus, high bio-corrosion resistance, and excellent biocompatibility has been recently introduced for implant applications. Here, ultrasonic nanocrystal surface modification (UNSM) treatment was applied to TNTZ alloy to improve its wear resistance and biofunctionality. Application of UNSM to a TNTZ alloy resulted in the generation of a nanostructured surface layer. The wear resistance of the UNSM-treated specimen was observed to be more than 7 times higher than that of the untreated one. Cell culture tests indicated that MC3T3 cells adhered and spread more readily on the UNSM-treated specimen than on the untreated one. MTT assays after 1 and 4 days in culture also indicated enhancement of cell proliferation on the UNSM-treated specimen than that of the untreated one. Live/dead assay revealed no significant cytotoxicity in either substrate. The significant improvement of cell adhesion, spreading, and proliferation on the UNSM-treated TNTZ alloy specimen were attributed to both grain refinement and micro-patterned surface effects. These results demonstrate that UNSM-treatment not only improves the wear resistance of TNTZ alloy, but also enhances its biocompatibility, which makes it a strong candidate for applications in medical implants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> UNSM treatment was applied to a β titanium alloy to generate nanostructured surface. </LI> <LI> The wear resistance of the UNSM-treated specimen was significantly improved. </LI> <LI> Treated specimens showed significant improvement of cell adhesion and proliferation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A Study on the Wear Characteristics of Titanium Alloy with respect to Surface Roughness

Mehdi Kheradmandfard,D. E. Kim(김대은) 한국트라이볼로지학회 2016 한국트라이볼로지학회 학술대회 Vol.2016 No.4

Ion-beam irradiation of DLC-based nanocomposite: Creation of a highly biocompatible surface

Penkov, Oleksiy V.,Kheradmandfard, Mehdi,Khadem, Mahdi,Kharaziha, Mahshid,Mirzaamiri, Rouhollah,Seo, Kuk-Jin,Kim, Dae-Eun Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.469 No.-

<P><B>Abstract</B></P> <P>Ion-beam irradiation of diamond-like carbon (DLC) by He ions was studied. Molecular dynamics simulation was performed to understand the effects of irradiation on the nano-topography and chemical state of the coatings and determine the optimal irradiation conditions. Then, the experiment was conducted to validate the results of the simulation and correlate surface modifications to biomedical properties. It was demonstrated that the irradiation led to the formation of a low-density and low-sp<SUP>3</SUP> content surface layer. The structural and chemical properties of the final surface were nearly independent of the initial sp<SUP>3</SUP> content and irradiation energy. The biocompatibility of DLC-based nanocomposite coatings was significantly improved by ion-beam irradiation. Nanocomposite coatings were irradiated by 1 keV He ions. Irradiation with a dose of 4.2 × 10<SUP>15</SUP> ion/cm<SUP>2</SUP> increased the adhesion of MG63 cells dramatically from 10 to ∼100%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MD models of DLC with various sp<SUP>3</SUP> content were developed. </LI> <LI> MD simulation of ion-beam irradiation of DLC was performed. </LI> <LI> DCL-based nanocomposites were irradiated by He ion beam. </LI> <LI> Effect of the ion-beam irradiation n cell adhesion was assessed. </LI> <LI> Correlations between MD simulation and experiment were established. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Highly durable and biocompatible periodical Si/DLC nanocomposite coatings

Penkov, Oleksiy V.,Khadem, Mahdi,Lee, Jung-Seung,Kheradmandfard, Mehdi,Kim, Chang-Lae,Cho, Seung-Woo,Kim, Dae-Eun The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.10

<P>Functional nanocomposite coatings comprised of periodically stacked nanolayers of diamond-like carbon (DLC) and amorphous silicon were developed for biomedical applications. The periodical nanocomposite structure provided high surface durability while silicon aided in reducing the residual stress. The structural, mechanical, tribological, and biomedical properties of the Si/DLC coatings deposited by magnetron sputtering were investigated systematically. The effect of the negative substrate bias on the structure and properties of the coatings was also assessed. The coatings demonstrated high durability and high biocompatibility. The bias voltage and bias mode affected both the hardness and residual stress of the Si/DLC coatings. Particularly, application of 60 V negative bias during the DLC layer deposition resulted in the lowest wear rate. FEM simulations showed that the wear resistance of the coatings was dictated by the hardness as well as the adhesion between the coatings and a chromium sub-layer. The periodical alternation of Si and DLC nanolayers led to a significant improvement of MC3T3 cell adhesion compared to the previously published data for Si-DLC composites.</P>