Mechanical and biological performance of rainbow trout collagen-boron nitride nanocomposite scaffolds for soft tissue engineering

We aim to investigate the potential of collagen extracted from rainbow trout for tissue engineering applications. In this regard, nanocomposite scaffolds based on the extracted collagen reinforced with various concentrations of boron nitride (BN) nanoparticles (0, 3, 6, 9, and 12 wt%) were developed. In addition, the role of various concentrations of BN nanoparticles and two-step cross-linking process on the physical and chemical properties of nanocomposite scaffolds were investigated. Our results demonstrated the isolation of Type I collagen with excellent thermal stability but with some structural and chemical differences compared to other sources. The synergic role of BN nanoparticles and two-step cross-linking process resulted in a noticeable improvement in the mechanical properties of collagen-BN scaffolds. Noticeably, incorporation of 6 wt% BN along with a two-step cross-linking process significantly increased the compressive strength (9.5 times) and elastic modulus (four times) of the collagen scaffold. Besides, nanocomposite scaffolds significantly improved proliferation and spreading of MG-63 cell line, confirming their biocompatibility. The results suggested that the incorporation of BN nanoparticles along with a two-step cross-linking process not only could promote the mechanical and thermal performances of collagen scaffolds, but also enhanced high cell viability, and proliferation supporting their potential in tissue engineering applications.     

Poly(tetramethylene oxide)-coated silica nanoparticles incorporated into poly(4,4′-oxydiphenylene-pyromellitimide) matrix

Telechelic poly(teramethylene oxide) with two isocyanate end groups (OCN-PTMO-NCO) was synthesized by the reaction of polytetrahydrofuran (M_n?=?1000?g?mol^?1) and hexamethylene diisocyanate in 1:2 molar ratio. The resulting macrochains were then covalently grafted to the surface of silica nanoparticles (SNPs). Thus, the inorganic nanoparticles could be thoroughly coated by a thick and soft organic shell. Thermogravimetric measurements showed that up to 85?wt.% of the organically modified SNPs (OSNPs) could be formed from the organic part. Different weight ratios of OSNPs were subsequently added to a solution of 4,4′-oxydiphenylamine/pyromellitic dianhydride poly(amic acid) (PAA) in dimethylformamide. Chemical cyclodehydration of the PAA in the presence of homogeneously dispersed OSNPs resulted in poly(4,4′-oxydiphenylene-pyromellitimide) (POPI) nanocomposites, labeled by POPI/OSNP 5, POPI/OSNP 7.5, and POPI/OSNP 10. The nanocomposites obtained were fully characterized by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. According to the diffuse reflectance UV spectroscopy, in comparison with neat POPI, the POPI/OSNP series showed an appreciable redshift in the λ_max values up to 15–20?nm. Moreover, POPI/OSNP series showed significant stability toward heat at temperatures above 540°C. The endothermic phase transitions occurred by the first thermodegradation of the resulting nanocomposites could be obviously seen in the differential thermal analysis.     

Thermodynamic investigation of KCl in the ternary KCl/LiCl/ H2 O mixed electrolyte system based on potentiometric method

The results of a thermodynamic investigation of KCl salt in the ternary KCl+LiCl+H₂O electrolyte system by potentiometric method are reported in this work. The experimental potentiometric data were obtained from a galvanic cell by combining a solvent polymeric (PVC) potassium-selective membrane electrode (K⁺ ISE), containing Valinomycin as ionophore, and an Ag/AgCl electrode. The measurements were performed, at similar constant ionic strengths, in different series of mixed salt solutions, each characterized by a fixed salt molal ratio r$r$ (where r=_m1/_m2=0.1,0.2,1,5,10$r=m_1/m_2=0.1,0.2,1,5,10$, and _m1,_m2$m_1,m_2$ are the molalities of KCl and LiCl, respectively). The non-ideal behaviour of the system was described on the base of the Pitzer ion-interaction model for mixed salts, over the ionic strength ranging from 0.01 up to about 5 mol/kg, at 298.15 K. Based on the obtained Pitzer ion-interaction parameters, the osmotic coefficients, solvent activities, and excess Gibbs free energies were determined for these investigated ternary electrolyte systems.     

Gd<Superscript>3+</Superscript> doped Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles with proper magnetic and supercapacitive characteristics: A novel synthesis platform and characterization

A novel electrochemical procedure was developed for the facile preparation of Gd-doped iron oxide nanoparticles (GdIO-NPs). A simple galvanostatic deposition (i=10 mA cm^-2) was done in an additive-free aqueous solution containing FeCl₂·4H₂O, Fe(NO₃)₃·9H₂O and GdCl₃·6H₂O. The XRD, FE-SEM, EDS and TEM characterizations showed that the product is composed of 15% GdIO-NPs with 10 nm in size. VSM analysis proved that the GdIO-NPs are superparamagnetic. The cyclic voltammetry and charge-discharge tests showed that the prepared GdIO-NPs are capable to deliver specific capacity as high as 190.1 F g^-1 at 0.5A g^-1 and capacity retention of 95.1% after 2000 cycling. Based on the results, it was concluded that the developed electrochemical strategy acts as an efficient procedure for the preparation of lanthanide doped MNPs with proper magnetic and supercapacitive characters.     

A numerical study on the damping capacity of metal matrix nanocomposites

In the present study, the damping capacity of metal matrix nanocomposites (MMNCs) is predicted using a micro-mechanical modeling approach. The model is based on finite element analysis of a unit cell, which mimics a pure metallic lattice with stiff reinforcing nanoparticles. The dissipated energy of nanocomposite is predicted numerically by applying a harmonic load on the unit cell model. The influences of the grain size, boundary phase thickness and reinforcement size on the energy dissipation were calculated by the developed finite element model. Also, the damping capacities of three typical particulate reinforced nanocomposites have been simulated by the proposed model. The relationship between damping capacity and dislocations were also discussed with respect to the Granato–Lücke (G–L) theory. The results calculated from the developed model show good agreement with the G–L theory, which demonstrates the feasibility of damping calculation with the proposed method.     

Thermodynamic Aspects of Nanostructured CoAl Intermetallic Compound during Mechanical Alloying

The nanostructured CoAl intermetallic compound was produced by mechanical alloying (MA) of the Co50Al50 elemental powder mixture in a planetary high energy ball mill. The ordered B2-CoAl structure with the grain size of about 6 nm was formed via a gradual reaction after 10 h of MA. A thermodynamic analysis of the process was also done. The results showed that the intermetallic compound of CoAl had the minimum Gibbs free energy compared to solid solution and amorphous states indicating the initial MA product was the most stable phase in the Co-Al system which was changed to a partially disordered structure with a steady long-range order of 0.82 at further milling. This amount of disordering caused the enthalpy of final product to show an increase of about 5.1 kJ·mol-1. Calculation of enthalpy related to the triple defect formation revealed that the enthalpy required for Al anti-sites formation was about 3 times greater than that for Co anti-sites formation.     

TERNARY NaCl+LiCl+H2O MIXED ELECTROLYTE SYSTEM: DETERMINATION OF ACTIVITY COEFFICIENTS BASED ON POTENTIOMETRIC METHOD

The mean activity coefficients for NaCl in a ternary electrolyte system were determined by the potentiometric method, at 25°C, using a solvent polymeric (PVC) sodium-selective membrane electrode (Na⁺ ISE), containing N,N'-dibenzyl-N,N'-diphenyl-1,2-phenylenedioxydiacetamide as ionophore, and combined with an Ag/AgCl electrode. The potentiometric measurements were performed at the same ionic strengths in different series of mixed salt solutions, each characterized by a fixed salt molal ratio r (where r = m₁/m₂ = 1, 10, 50, 100). The nonideal behavior of the ternary NaCl(m₁) + LiCl(m₂) + H₂O electrolyte system was described based on the Pitzer ion-interaction model for mixed salts over the ionic strength ranging from 0.01 up to about 4 mol/kg. Two- and three-particle Pitzer interaction parameters for a mixed electrolyte system were determined based on potentiometric data, and the critical role of potentiometric selectivity coefficient (K₁₂) of ISE as limiting factor in the potentiometric measurements was analyzed.     

TRIGA fuel burn-up calculations and its confirmation

The Cesium (Cs-137) isotopic concentration due to irradiation of TRIGA Fuel Elements FE(s) is calculated and measured at the Atominstitute (ATI) of Vienna University of Technology (VUT). The Cs-137 isotope, as proved burn-up indicator, was applied to determine the burn-up of the TRIGA Mark II research reactor FE. This article presents the calculations and measurements of the Cs-137 isotope and its relevant burn-up of six selected Spent Fuel Elements SPE(s). High-resolution gamma-ray spectroscopy based non-destructive method is employed to measure spent fuel parameters. By the employment of this method, the axial distribution of Cesium-137 for six SPE(s) is measured, resulting in the axial burn-up profiles. Knowing the exact irradiation history and material isotopic inventory of an irradiated FE, six SPE(s) are selected for on-site gamma scanning using a special shielded scanning device developed at the ATI. This unique fuel inspection unit allows to scan each millimeter of the FE. For this purpose, each selected FE was transferred to the fuel inspection unit using the standard fuel transfer cask. Each FE was scanned at a scale of 1 cm of its active length and the Cs-137 activity was determined as proved burn-up indicator. The measuring system consists of a high-purity germanium detector (HPGe) together with suitable fast electronics and on-line PC data acquisition module. The absolute activity of each centimeter of the FE was measured and compared with reactor physics calculations. The ORIGEN2, a one-group depletion and radioactive decay computer code, was applied to calculate the activity of the Cs-137 and the burn-up of selected SPE. The deviation between calculations and measurements was in range from 0.82% to 12.64%.     

The Effect of Crystallinity of Carbon Source on Mechanically Activated Carbothermic Synthesis of Nano-Sized SiC Powders

The relevance of the structure of carbon materials and milling on the carbothermic reduction of silica to produce nano-sized silicon carbide (SiC) was studied. Graphite (crystalline) and metallurgical coke (mainly amorphous) were chosen as carbon precursors that were mixed with amorphous pure nano-sized SiO₂ and milled for different times. The SiC yield at 1450 °C for l h was influenced by the degree of milling. Extending the milling time increased SiC formation in both cases. Although some extensive milling converted both sources of carbon into amorphous phase, the amount of synthesized SiC from graphite was about 4.5-3 times higher than coke with increased extent of milling. Graphite is converted from stable crystalline state into the amorphous phase, so it absorbs more activation energy of milling and fresher active centers are created, while the already amorphous coke absorbs less energy and thus less fresh active centers are created. This energy difference acts as a driving force, resulting in higher yield of nano-sized SiC when graphite is used as carbon source.     

Mechanosynthesis of nanostructured magnetic Ni-Zn ferrite

Nanocrystalline Ni-Zn ferrite (NiZnFe₂O₄) was directly produced by high energy ball milling of stoichiometric mixture of ZnO, NiO, Fe₂O₃ powders. X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), simultaneous thermal analysing (STA), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM) were carried out to characterize the structural, chemical and magnetic aspects of NiZnFe₂O₄ compound. The formation of NiZnFe₂O₄ phase appeared to involve two stages; development of Zn ferrite by diffusion of ZnO in Fe₂O₃ followed by diffusion of NiO in Zn ferrite to form Ni-Zn ferrite. The crystallite size of final product after 60 h of ball milling time was estimated to be 18 nm which increased to 45 nm after annealing at 800 °C for 4 h. After annealing of ball milled powders, the saturation magnetization was increased and coercivity was decreased as lattice defects and internal strain reduced.