Nanostructured titanium-45S5 Bioglass scaffold composites for medical applications

Titanium–10 wt.% 45S5 Bioglass scaffold nanocomposites were synthesized by the combination of mechanical alloying and by a “space-holder” sintering process. The porous structure and corrosion properties were investigated. In vitro biocompatibility of these materials was evaluated and compared with a conventional microcrystalline titanium, where normal human osteoblast (NHOst) cells from Cambrex (CC-2538) were cultured on the disks of the materials and cell growth was examined. The morphology of the cell cultures obtained on Ti–10 wt.% 45S5 Bioglass nanocomposite was similar to those obtained on the microcrystalline titanium. On the other hand, on porous scaffold, the cells adhered with their whole surface to the insert penetrating the porous structure, while on the polished surface, more spherical cells were observed with a smaller surface of adhesion. The present study has demonstrated that titanium–10 wt.% 45S5 Bioglass scaffold nanocomposite is a promising biomaterial for bone tissue engineering.     

Fabrication and properties of titanium–hydroxyapatite nanocomposites

Titanium–hydroxyapatite nanocomposites with different HA contents (3, 10, 20 vol%) were produced by the combination of mechanical alloying (MA) and powder metallurgical process. The structure, mechanical and corrosion properties of these materials were investigated. Microhardness test showed that the obtained material exhibits Vickers microhardness as high as 1030 and 1500 HV_0.2, which is more than 4–6 times higher than that of a conventional microcrystalline titanium. Titanium nanocomposite with 10 vol% of HA was more corrosion resistant (i_C = 1.19 × 10⁻⁷ A cm⁻², E_C = −0.41 V vs. SCE) than microcrystalline titanium (i_C = 1.31 × 10⁻⁵ A cm⁻², E_C = −0.36 V vs. SCE). Additionally, the electrochemical treatment in phosphoric acid electrolyte results in porous surface, attractive for tissue fixing and growth. Mechanical alloying and powder metallurgy process for the fabrication of titanium–ceramic nanocomposites with a unique microstructure are developed.     

Synthesis of TiC-TiB2-Ni cermets by thermal explosion under pressure

TiC/TiB₂-based cermets were fabricated in situ by means of the thermal explosion under pressure technique starting from Ti-B₄C powders with the addition of varying contents of Ni metal binder to achieve near-net-shape bulks. The combustion reaction was ignited in a graphite die heated by current. Full conversion of the reactants was obtained by thermal explosion and the process yielded TiC-TiB₂-Ni materials characterised by a fine microstructure. Appreciable differences in terms of microstructure, hardness and fracture toughness by indentation were observed between core and external surface of the products due to fast cooling caused by heat transfer to the die walls. Cermets with a high content of Ni showing high hardness and fracture toughness were obtained, with values of HV₅ = 2182 and K_Ic = 8.8 MPa m^1/2 for 30 wt.% Ni and of HV₅ = 1684 and K_Ic = 12.7 MPa m^1/2 for 47 wt.% Ni.     

Highly conducting poly(methyl methacrylate)/carbon nanotubes composites: Investigation on their thermal, dynamic-mechanical, electrical and dielectric properties

Nanocomposites of poly(methyl methacrylate) (PMMA) containing various multi-walled carbon nanotubes (MWCNT) contents were prepared using melt mixing. Several techniques were employed to study the influence of the MWCNT addition on the thermal, mechanical, electrical and dielectric properties of the PMMA matrix. The electrical percolation threshold (p_c) was found to be 0.5 vol.% by performing AC and DC conductivity measurements. Significantly high conductivity levels (σ_dc) were achieved: σ_dc exceeds 10⁻² S/cm already at 1.1 vol.%, the criterion for EMI shielding (σ_dc > 10⁻¹ S/cm) is fulfilled at 2.9 vol.%, and the highest loaded sample (5.2 vol.%) gave a maximum value of 0.5 S/cm. Dielectric relaxation spectroscopy measurements in broad frequency (10⁻¹−10⁶ Hz) and temperature ranges (−150 to 170 °C) indicated weak polymer-filler interactions, in consistency with differential scanning calorimetry and dynamic-mechanical analysis findings. Weak polymer-filler interactions and absence of crystallinity facilitate the achievement of high conductivity levels in the nanocomposites.     

Electrical conductivity of yttrium-doped SrTiO3: influence of transition metal additives

The electrical conductivity of yttrium-doped SrTiO₃ with transition metals added as acceptor dopants (V, Mn, Fe, Co, Ni, Cu, Zn, Mo, Mg, Zr, Al, or Ga) was measured by the dc four-probe method at 600-900°C in reducing atmospheres. The replacement of 5 mol% titanium by acceptors leads to a decrease of conductivity of Sr_1−1.5xY_xTiO_3−δ. The degree of the decrease depends strongly on the type of dopant. Of the 5 mol% acceptor-doped compositions, the system Sr_0.85Y_0.10Ti_0.95Co_0.05O_3−δ had the highest conductivity of 45 S/cm at 800°C and oxygen partial pressure of 10⁻¹⁹ atm. The oxidation kinetics of yttrium-doped SrTiO₃ was significantly retarded by the addition of cobalt or manganese dopants. The ionic conductivity of SrTiO₃ doped with 5 mol% acceptors at Ti-sites was estimated from the total conductivity to lie in the vicinity of 10⁻⁴ S/cm, depending on oxygen partial pressure and temperature.     

Polyethersulfone-expanded graphite nanocomposites: Charge transport and impedance characteristics

Polyethersulfone (PES)-expanded graphite nanocomposites have been prepared by solution blending route after sonicating expanded graphite in dichloromethane. It has been observed that ultrasonication results in nanosheets formation leading to a low percolation threshold of 3 wt.%. At 5 wt.% filler loading the conductivity is of the order of 10⁻² S/cm. Hopping type of charge transport occurs at 3.2 wt.% expanded graphite in PES below which capacitive effects couple. The effective dielectric constant at low frequency increases with filler concentration. Impedance measurement has been carried out to evaluate interfacial capacitance which, for 3.2 wt.% expanded graphite addition in PES, increases to 110 pF from 32 pF for 1 wt.% expanded graphite in the polymer. DSC analysis shows an increment of 12 °C in the T_g of PES with 3 wt.% expanded graphite suggesting interaction between the polymer and filler.     

Synthesis and characterization of a new monophosphate (5-Cl-2,4-(OCH3)2C6H2NH3)H2PO4

Chemical preparation, crystal structure and NMR spectroscopy of a new organic cation 5-chloro(2,4-dimethoxy)anilinium monophosphate H₂PO₄ are given. This new compound crystallizes in the monoclinic system, with the space group P2₁/c and the following parameters: a = 5.524(2) Å, b = 9.303(2) Å, c = 23.388(2) Å, β = 90.66(4), V = 1201.8(2) Å³, Z = 4 and D_x = 1.573 g cm⁻³. Crystal structure has been determined and refined to R = 0.031 and R_w = 0.080 using 1702 independent reflections. Structure can be described as an infinite (H₂PO₄)_nⁿ⁻ corrugated chains in the a-direction. The organic groups (5-Cl-2,4-(OCH₃)₂C₆H₂NH₃)⁺ are anchored between adjacent polyanions through multiple hydrogen bonds. This compound is also investigated by IR, thermal, and solid-state, ¹³C, ³¹P MAS NMR spectroscopies.     

Materials with layered structures XIII: electrical and optical properties of layered chalcogenides in the system CoIn2S4-CoIn2Se4

The system CoIn₂S_4xSe_4(1−x) has been investigated by X-ray powder methods on samples quenched at 700 °C. The spinel type phase has a phase width of 1≥x>0.9. A new layered compound is formed for 0.9>x>0.45 which crystallizes with the α-FeGa₂S₄-type with a=392.6 pm and c=1270.3 pm (x=0.5) for the hexagonal cell. Platelike crystals of the layered phase are obtained by transport reactions with iodine in a temperature gradient 750→700 °C. The band gaps of these crystals measured by optical absorption vary from 1.2 to 1.4 eV. The electrical conductivities of the crystals are found in the order of 10⁻⁵ Ω⁻¹ cm⁻¹.     

Study of the hot deformation behaviour in Ti-5Al-5Mo-5V-3Cr-1Zr

Structural applications of near beta titanium alloys are gradually increasing in the aerospace industry because of their high specific mechanical properties and good corrosion resistance. Furthermore, a wide range of microstructures can be obtained by thermomechanical processes. This work determines by the use of EBSD technique the mechanism of restoration active in the near beta titanium alloy Ti-5Al-5Mo-5V-3Cr-1Zr for deformations in both α + β and β field near to the β transus temperature (T_β = 803 °C). Hot compression tests are carried out up to 0.7 true strain by means of a Gleeble^® 1500 machine at strain rates of 0.01, 0.1 and 1 s⁻¹. Dynamic recovery of β phase and rotation of the α grains take place predominantly in the α + β field. Further deformation produces continuous dynamic recrystallization of the β phase influenced by the strain rate. Dynamic recovery is observed during deformation above the T_β, where the misorientation is increasing towards the grain boundaries forming new small grains with a substructure at high strain rates and larger deformation. The stress exponent and the apparent activation energy for the sinh constitutive equations are determined and the microstructural features are correlated with the Zener-Hollomon parameter.     

Structural study by X-ray diffraction and transmission electron microscopy of the misfit compound (SbS1−xSex)1.16(Nb1.036S2)2

In the Sb-Nb-S-Se system, a new misfit layer compound (MSL) has been synthesized and its structure was determined by combining single crystal X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. It presents a composite crystal structure formed by (SbS_1−xSe_x) slabs stacking alternately with double NbS₂ layers and both can be treated as separate monoclinic subsystems. The (SbS_1−xSe_x) slabs comprise a distorted, two-atom-thick layer with NaCl-type structure formed by an array of {SbX₅} square pyramids joined by edges (X: S, Se); the NbS₂ layers consist of {NbS₆} trigonal prisms linked through edge-sharing to form sheets, just as in the 2H-NbS₂ structure type. Both sublattices have the same lattice parameters a = 5.7672(19) Å, c = 17.618(6) Å and β = 96.18(3)°, with incommensurability occurring along the b direction: b₁ = 3.3442(13) Å for the NbS₂ subsystem and b₂ = 2.8755(13) Å for the (SbS_1−xSe_x) subsystem. The occurrence of diffuse scattering intensity streaked along c^* indicates that the (SbS_1−xSe_x) subsystem is subjected to extended defects along the stacking direction.     

Synthesis and crystal structure of a novel lithium bismuth phosphate, Li2Bi14.67(PO4)6O14

A lithium bismuth phosphate, Li₂Bi_14.67(PO₄)₆O₁₄, has been synthesized for the first time by the solid-state method. The crystal structure was determined by single crystal X-ray diffraction at 150 K. Li₂Bi_14.67(PO₄)₆O₁₄ crystallizes in the monoclinic system C2/c (No. 15), with a = 30.8189(4) Å, b = 5.2691(3) Å, c = 24.5302(3) Å, β = 122.84(2)°, V = 3346.81(1) Å³ and Z = 2. The structure along the b axis consists of layers of [Bi₂O₂] units as the basic building block. These are separated by isolated PO₄ and LiO₄ tetrahedra. The oxygen co-ordination around two of the phosphorus atoms is disordered. Solid-state ⁷Li NMR studies confirm the presence of lithium in the structure. The material shows ionic conductivity of the order of 10⁻⁵ S cm⁻¹ at 600 °C.     

Very-low temperature specific heat of Torlon

The specific heat of Torlon has been measured in the 0.15-4.2 K temperature range. Data below 1 K can be represented by c(T) = P₁T^1+δ + P₂T³, with P₁ = (5.41 ± 0.08)·10⁻⁶J K^−(2+δ) g⁻¹, P₂ = (2.82 ± 0.03) ·10⁻⁵JK⁻⁴g⁻¹ and δ = 0.28 ± 0.01, as predicted by the tunnelling theory. Above 1 K, the behaviour of c(T) is similar to that of other amorphous materials and can be expressed as: c(T) = P · T^Ω with P = (2.68 ± 0.07)·10⁻⁵JK^Ω+1g⁻¹ and Ω = 3.32 ± 0.02.     

Impurity induced band-gap narrowing in p-type CuIn1 − xGax(S,Se)2

Green's functions modelling of the impurity induced effects in p-type CuIn_1 − xGa_xS₂ and CuIn_1 − xGa_xSe₂ (x = 0.0, 0.5, and 1.0) reveals that: (i) the critical active acceptor concentration for the metal non-metal transition occurs at N_c ≈ 10¹⁷-10¹⁸ cm^− 3 for impurities with ionization energy of E_A ≈ 30-60 meV. (ii) For acceptor concentrations N_A > N_c, the hole gas of the metallic phase affects the band-edge energies and narrows the energy gap E_g = E_g⁰ − ΔE_g. The energy shift of the valence-band maximum ΔE_v1 is roughly twice as large as the shift of the conduction-band minimum ΔE_c1. (iii) ΔE_v1 depends strongly on the non-parabolicity of the valence bands. (iv) Sulfur based compounds and Ga-rich alloys have the largest shifts of their band edges. (v) A high active acceptor concentrations of N_A = 10²⁰ cm^− 3 implies a band-gap narrowing in the order of ΔE_g ≈ 0.2 eV, thus E_g = E_g⁰ − 0.2 eV, and an optical band gap of E_g^opt ≈ E_g⁰ − 0.1 eV.     

Crystal structure and spectroscopic investigations of an organic monophosphate

Single crystals of (p-ClC₆H₄NH₃)H₂PO₄ are synthesized in water by interaction of H₃PO₄ and (p-ClC₆H₄NH₂). This compound crystallizes in the orthorhombic system with the Pbca space group. Its unit-cell parameters are a = 9.724(3), b = 7.861(1), c = 25.078(6) Å, V = 1917.1(6) Å³ and Z = 8. The crystal structure has been solved and refined to R = 0.039, using 4298 independent reflections. The atomic arrangement can be described by inorganic layers parallel to ab plane, between which the organic cations are located. This compound exhibits a reversible phase transition at 403 K. The electrical conductivity measurements show that the (p-ClC₆H₄NH₃)H₂PO₄ has a conductivity value which goes from σ = 0.88 × 10⁻⁶ Ω⁻¹ cm⁻¹ at room temperature (293 K) to 3.31 × 10⁻⁴ Ω⁻¹ cm⁻¹ at 433 K. Its characterisation by TA, NMR and IR is reported too.     

Synthesis and crystal structure of triphosphate RbPrHP3O10

Crystals of RbPrHP₃O₁₀ have been grown by the flux technique and characterized by single-crystal X-ray diffraction. RbPrHP₃O₁₀ crystallizes in the triclinic space group with lattice parameters: a = 7.0655(5), b = 7.7791(4), c = 8.6828(6) Å, α = 74.074(3), β = 74.270(3), γ = 82.865(2)°, V = 441.09(5) ų, Z = 2. The crystal structure has been solved yielding a final R(F²) = 0.0443 and R_w(F²) = 0.1426 for 1955 independent reflections (F_o² ≥ 2σ(F_o²)). The structure of RbPrHP₃O₁₀ consists of PrO₈ polyhedra and P₃O₁₀⁵⁻ groups sharing oxygen atoms to form a two-dimensional framework; the PrO₈ polyhedra form infinite chains by edge-sharing. Each Rb⁺ ion is bonded to 10 oxygen atoms, these ions are located between chains formed of (HP₃O₁₀)⁴⁻. The energies of the vibrational modes of the crystal were obtained from measurements of the infrared spectrum.     

Crystal structure and ionic conductivity of ruthenium diphosphate ARu2(P2O7)2, A=Li, Na, and Ag, with a tunnel structure

Crystal structure and ionic conductivity of ruthenium diphosphates, ARu₂(P₂O₇)₂ A=Li, Na, and Ag, were investigated. The structure of the Ag compound was determined by single crystal X-ray diffraction techniques. It crystallized in the triclinic space group P−1 with a=4.759(2) Å, b=6.843(2) Å, c=8.063(1) Å, α=90.44(2)°, β=92.80(2)°, γ=104.88(2)°, V=253.4(1) Å³. The host structure of it was composed of RuO₆ and P₂O₇ groups and formed tunnels running along the a-axis, in which Ag⁺ ions were situated. The ionic conductivities have been measured on pellets of the polycrystalline powders. The Li and Ag compounds showed the conductivities of 1.0×10⁻⁴ and 3.5×10⁻⁵ S cm⁻¹ at 150 °C, respectively. Magnetic susceptibility measurement of the Ag compound showed that it did not obey the Curie-Weiss law and the effective magnetic moment decreased as temperature decreased due to the large spin-orbital coupling effect of Ru⁴⁺ ions.     

Crystal structure, thermal expansion and electrical properties of a new compound Al0.33DyGe2

A new ternary compound Al_0.33DyGe₂ has been synthesized and studied from 298 K to773 K by means of X-ray powder diffraction technique. The crystal structural refinement of Al_0.33DyGe₂ has been performed by using the Rietveld method. The ternary compound Al_0.33DyGe₂ crystallizes in the orthorhombic of the defect CeNiSi₂-type structure (space group Cmcm, a = 0.41018(2)nm, b = 1.62323(6)nm, c = 0.39463(1)nm, Z = 4 and D_calc = 8.004 g/cm³). The average thermal expansion coefficients α_a, α_b and α_c of Al_0.33DyGe₂ are 1.96 × 10^− 5 K^− 1, 0.93 × 10^− 5 K^− 1 and 1.42 × 10^− 5 K^− 1, respectively. The bulk thermal expansion coefficient α_V is 4.31 × 10^− 5 K^− 1. The resistivity is observed to fall from 387 to 308 µΩ cm between room temperature and 25 K.     

Synthesis and crystal sructure of a new dihydrogenomonophosphate (4-C2H5C6H4NH3)H2PO4

Chemical preparation, crystal structure, calorimetric, and spectroscopic investigations are given for a new organic-cation dihydrogenomonophosphate, (4-C₂H₅C₆H₄NH₃)H₂PO₄ in the solid state. This compound crystallizes in the orthorhombic space group Pbca with the following unit cell parameters: a=8.286(3) Å, b=9.660(2) Å, c=24.876(4) Å, Z=8, V=1991.2(7) Å³, and D_X=1.442 g cm⁻³. Crystal structure was solved with a final R=0.054 for 3305 independent reflections. The atomic arrangement coaled described as H₂PO₄⁻ layers between which are located the 4-ethylanilinium cations.     

Preparation of polybenzoxazine-functionalized Fe3O4 nanoparticles through in situ Diels–Alder polymerization for high performance magnetic polybenzoxazine/Fe3O4 nanocomposites

Hybrids and nanocomposites of polymer and magnetic Fe₃O₄ nanoparticles have been utilized as magnetically-responsive materials and magnetically-directed nanoparticles. In this work, we prepare polymer-functionalized Fe₃O₄ nanoparticles through in situ Diels–Alder polymerization using maleimide-functionalized Fe₃O₄ nanoparticle as a precursor. Polybenzoxazine-functionalized Fe₃O₄ nanoparticles (MNP-PBz) have been obtained and characterized with Fourier Transform Infrared, X ray photoelectron, and Raman spectroscopies. The high saturation magnetization value of 51.9 emu g⁻¹ of the MNP-PBz nanoparticles demonstrates its superparamagnetism. Moreover, MNP-FBz has been utilized as a nanofiller for preparation of cured PBz/MNP-PBz nanocomposites, which contain various MNP-PBz contents of 67, 50, 33, and 17 wt.%. The sample of PBz/MNP-PBz-67 shows a storage modulus of 8.0 GPa, a saturation magnetization value of 37.6 emu g⁻¹, and a glass transition temperature above 380 °C. As a result, the PBz/MNP-PBz nanocomposites could be classified as magnetically-responsive high performance materials.     

Crystal structure and EPR study of Mn-doped β-tricalcium phosphate

Mn-doped β-tricalcium phosphate was prepared by solid state reaction at 1100 °C. The crystal structure of Ca_2.85Mn_0.15(PO₄)₂, was determined by single crystal X-ray diffraction and found to be rhombohedral, R3c. Unit cell parameters are: a = 10.3419(3); c = 37.025(3) Å (hexagonal setting), Z = 21. Structure refinement data show that from the five Ca positions the Ca(4) site is only half filled and that the Mn²⁺ ions occupy the hexacoordinated Ca(5) site solely. EPR spectroscopy reveals that manganese in solid solutions Ca_3−xMn_x(PO₄)₂ (x = 0.1; 0.28; 0.6) is divalent and supports the structure refinement results that Mn occupies the Ca(5) site with a geometry very near to a regular octahedron.