Frontiers of Materials Science (v.7, #3)

Recent research situation in tin dioxide nanomaterials: synthesis, microstructures, and properties by Zhi-Wen Chen; Chan-Hung Shek; C. M. Lawrence Wu; Joseph K. L. Lai (203-226).
This review article summarizes the new research in solid-state physical chemistry understanding of the microstructure characteristics of semiconductor tin oxide thin films made in the last years in our group. The work mainly focuses on the fabrication technology of semiconductor tin oxides thin films by using pulsed laser deposition (PLD) as well as the application of this technology on new micro- and nanostructured materials. It is an interdisciplinary work that integrates the areas of physics, chemistry and materials science.
Keywords: tin dioxide; thin film; synthesis; microstructure; nanostructure; property

The effect of selected alloying element additions on properties of Mg-based alloy as bioimplants: A literature review by Li-Nan Zhang; Zeng-Tao Hou; Xin Ye; Zhao-Bin Xu; Xue-Ling Bai; Peng Shang (227-236).
This review investigates the current application limitations of Mg and Mg alloys. The key issues hindering the application of biodegradable Mg alloys as implants are their fast degradation rate and biological consideration. We have discussed the effect of some selected alloying element additions on the properties of the Mg-based alloy, especially the nutrient elements in human (Zn, Mn, Ca, Sr). Different grain sizes, phase constituents and distributions consequently influence the mechanical properties of the Mg alloys. Solution strengthening and precipitation strengthening are enhanced by the addition of alloying elements, generally improving the mechanical properties. Besides, the hot working process can also improve the mechanical properties. Combination of different processing steps is suggested to be adopted in the fabrication of Mg-based alloys. Corrosion properties of these Mg-based alloys have been measured in vitro and in vivo. The degradation mechanism is also discussed in terms of corrosion types, rates, byproducts and response of the surrounding tissues. Moreover, the clinical response and requirements of degradable implants are presented, especially for the nutrient elements (Ca, Mn, Zn, Sr). This review provides information related to different Mg alloying elements and presents the promising candidates for an ideal implant.
Keywords: magnesium alloy; alloying element; corrosion; biodegradation

Silk fibroin-based scaffolds for tissue engineering by Zi-Heng Li; Shi-Chen Ji; Ya-Zhen Wang; Xing-Can Shen; Hong Liang (237-247).
Silk fibroin (SF) from the Bombyx mori silkworm exhibits attractive potential applications as biomechanical materials, due to its unique mechanical and biological properties. This review outlines the structure and properties of SF, including of its biocompatibility and biodegradability. It highlights recent researches on the fabrication of various SF-based composites scaffolds that are promising for tissue engineering applications, and discusses synthetic methods of various SF-based composites scaffolds and valuable approaches for controlling cell behaviors to promote the tissue repair. The function of extracellular matrices and their interaction with cells are also reviewed here.
Keywords: silk fibroin (SF); scaffold; tissue engineering; biomaterial; tissue repair

Poriferan chitin as a template for hydrothermal zirconia deposition by Marcin Wysokowski; Mykhaylo Motylenko; Vasilii V. Bazhenov; Dawid Stawski; Iaroslav Petrenko; Andre Ehrlich; Thomas Behm; Zoran Kljajic; Allison L. Stelling; Teofil Jesionowski; Hermann Ehrlich (248-260).
Chitin is a thermostable biopolymer found in various inorganic-organic skeletal structures of numerous invertebrates including sponges (Porifera). The occurrence of chitin within calcium- and silica-based biominerals in organisms living in extreme natural conditions has inspired development of new (extreme biomimetic) synthesis route of chitin-based hybrid materials in vitro. Here, we show for the first time that 3D-α-chitin scaffolds isolated from skeletons of the marine sponge Aplysina aerophoba can be effectively mineralized under hydrothermal conditions (150°C) using ammonium zirconium(IV) carbonate as a precursor of zirconia. Obtained chitin-ZrO2 hybrid materials were characterized by FT-IR, SEM, HRTEM, as well as light and confocal laser microscopy. We suggest that formation of chitin-ZrO2 hybrids occurs due to hydrogen bonds between chitin and ZrO2.
Keywords: chitin; biocomposite; zirconia; hydrothermal synthesis; ammonium zirconium carbonate

Hydroxyapatite (HAP) is the constituent of calcium phosphate based bone cement and it is extensively used as a bone substitute and drug delivery vehicle in various biomedical applications. In the present study we investigated the release kinetics of ciprofloxacin loaded HAP and analyzed its ability to function as a targeted and sustained release drug carrier. Synthesis of HAP was carried out by combustion method using tartaric acid as a fuel and nitric acid as an oxidizer. Powder XRD and FTIR techniques were employed to characterize the phase purity of the drug carrier and to verify the chemical interaction between the drug and carrier. The synthesized powders were sieve separated to make two different drug carriers with different particle sizes and the surface topography of the pellets of the drug carrier was imaged by AFM. Surface area and porosity of the drug carrier was carried out using surface area analyzer. The in-vitro drug release kinetics was performed in simulated body fluid, at 37.3°C. The amount of ciprofloxacin released is measured using UV-visible spectroscopy following the characteristic λ max of 278 nm. The release saturates around 450 h which indicates that it can be used as a targeted and sustained release carrier for bone infections.
Keywords: ceramic drug delivery system; antibiotic; hydroxyapatite (HAP); porosity; targeted release

Novel crosslinked alginate/hyaluronic acid hydrogels for nerve tissue engineering by Min-Dan Wang; Peng Zhai; David J. Schreyer; Ruo-Shi Zheng; Xiao-Dan Sun; Fu-Zhai Cui; Xiong-Biao Chen (269-284).
Artificial tissue engineering scaffolds can potentially provide support and guidance for the regrowth of severed axons following nerve injury. In this study, a hybrid biomaterial composed of alginate and hyaluronic acid (HA) was synthesized and characterized in terms of its suitability for covalent modification, biocompatibility for living Schwann cells and feasibility to construct three dimensional (3D) scaffolds. Carbodiimide mediated amide formation for the purpose of covalent crosslinking of the HA was carried out in the presence of calciumions that ionically crosslink alginate. Amide formation was found to be dependent on the concentrations of carbodiimide and calcium chloride. The double-crosslinked composite hydrogels display biocompatibility that is comparable to simple HA hydrogels, allowing for Schwann cell survival and growth. No significant difference was found between composite hydrogels made from different ratios of alginate and HA. A 3D BioPlotter™ rapid prototyping system was used to fabricate 3D scaffolds. The result indicated that combining HA with alginate facilitated the fabrication process and that 3D scaffolds with porous inner structure can be fabricated from the composite hydrogels, but not from HA alone. This information provides a basis for continuing in vitro and in vivo tests of the suitability of alginate/HA hydrogel as a biomaterial to create living cell scaffolds to support nerve regeneration.
Keywords: hyaluronic acid (HA); alginate; hydrogel scaffold; nerve injury; tissue engineering

The effect of surface mechanical attrition treatment (SMAT) of commercially pure titanium (CP-Ti) using 8mm Ø alumina balls was studied. SMAT induced plastic deformation, increased the surface roughness, reduced the grain size and decreased the contact angle (from 64° to 43°) with a corresponding increase in surface energy (from 32 to 53 mJ/m2). Untreated CP-Ti and those treated using alumina balls for 900 s reveals no apatite growth until the 28th day of immersion whereas those treated for 1800 and 2700 s exhibit apatite growth in selective areas and the extent of growth is increased with increase in immersion time in SBF. The study reveals that SMAT using alumina balls is beneficial in imparting the desired surface characteristics, provided the surface contamination is limited, which would otherwise decrease the apatite forming ability.
Keywords: nanostructured material; surface modification; scanning electron microscopy (SEM); surface mechanical attrition treatment (SMAT)

Electrical conductivity of Gd doped BiFeO3-PbZrO3 composite by Santosh Kumar Satpathy; Nilaya Kumar Mohanty; Ajay Kumar Behera; Banarji Behera; Pratibindhya Nayak (295-301).
The composite, 0.5(BiGd0.15Fe0.85O3)-0.5(PbZrO3), was synthesized using the solid-state reaction technique. The formation of the compound was confirmed by XRD with an orthorhombic structure at room temperature. The impedance parameters were studied using an impedance analyzer in a wide range of frequency (102–106 Hz) at different temperatures. The Nyquist plot suggests the contribution of bulk effect and a slight indication of grain boundary effect and the bulk resistance decreases with a rise in temperature. The presence of temperature-dependent relaxation process occurs in the material. Electrical modulus reveals the presence of the hopping mechanism in the materials. The value of exponent n, pre-factor A and σ dc were obtained by fitting ac conductivity data with Jonscher’s universal power law. The activation energies calculated from the ac conductivity were found to be 0.50, 0.46, 0.44, 0.43, 0.42 and 0.38 eV at 1, 10, 50, 100, 500 kHz and 1 MHz respectively in the temperature region of 110°C–350°C. The dc conductivity was found to increase with the rise in temperature. The activation energy calculated from complex impedance plot and from the fitted Jonscher’s power law are very close, which results similar type of charge carrier exist in conduction mechanism of the material.
Keywords: solid state reaction; XRD; impedance; electrical conductivity

Characterization of carbon black modified by maleic acid by Vijayshankar Asokan; Pawel Kosinski; Tore Skodvin; Velaug Myrseth (302-307).
We present here a method for modifying the surface of carbon black (CB) using a simple heat treatment in the presence of a carboxylic acid as well as water or ethylene glycol as a solvent. CB was mixed with maleic acid and either water or ethylene glycol, and heated at 250°C. Unlike the traditional surface modification processes which use heat treatment of carbon with mineral acids the present modification method using a carboxylic acid proved to be simple and time efficient. CB from two different vendors was used, and the modified samples were characterized by TGA, BET surface area measurement, XRD, particle size and zeta potential measurements, and FTIR. It was found that several material properties, including thermal stability and surface area, of the modified CB are significantly altered relative to the parental carbon samples. This method provides a rapid and simple route to tailor new materials with desired properties.
Keywords: carbon black (CB); carboxylic acid; ethylene glycol; thermal stability; surface area

Large scale synthesis of FeS coated Fe nanoparticles as reusable magnetic photocatalysts by He Feng; Ping-Zhan Si; Xiao-Fei Xiao; Chen-Hao Jin; Sen-Jiang Yu; Zheng-Fa Li; Hong-Liang Ge (308-311).
The FeS coated Fe nanoparticles were prepared by using high temperature reactions between the commercial Fe nanoparticles and the S powders in a sealed quartz tube. The simple method developed in this work is effective for large scale synthesis of FeS/Fe nanoparticles with tunable shell/core structures, which can be obtained by controlling the atomic ratio of Fe to S. The structural, magnetic and photocatalytic properties of the nanoparticles were investigated systematically. The good photocatalytic performance originating from the FeS shell in degradation of methylene blue under visible light and the high saturation magnetization originating from the ferromagnetic Fe core make the FeS/Fe nanoparticles a good photocatalyst that can be collected and recycled easily with a magnet. An exchange bias up to 11 mT induced in Fe by FeS was observed in the Fe/FeS nanoparticles with ferro/antiferromagnetic interfaces. The enhanced coercivity up to 32 mT was ascribed to the size effect of Fe core.
Keywords: magnetic photocatalyst; exchange bias; FeS coated Fe nanoparticle