Silver/selenium/chitosan co-substituted bioceramic coatings of Ni–Ti alloy: Antibacterial efficiency and cell viability

The effects of silver (Ag), selenium (Se), and chitosan (Cht) additives on the antibacterial activity and cell viability of NiTi were investigated. Three different hydroxyapatite (HA)-based bioceramic coatings to improve the antibacterial activity and cell viability of NiTi; HA, HA/Ag, and HA/Se–Cht were applied to NiTi substrates by a sol–gel method. The coated samples were characterized by scanning electron microscopy–electron-dispersive spectroscopy and X-ray diffraction and surface hardnesses were measured. The antimicrobial efficiency of the coatings and uncoated surfaces were tested against Escherichia coli-JM 103 and Staphylococcus aureus-ATCC29293. In vitro cell–material interactions using Saos-2 osteoblast cells were characterized by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (mitochondrial activity test) assay for cell viability. A homogeneous, crack-free, and porous surface morphology is achieved in coatings. It has been shown that the Se–Cht additives did not have a significant effect on the surface hardness of the HA coating, but the Ag additive increased the hardness. Through in vitro antibacterial activity and cell viability tests, it was shown that Ag additive to bioceramic coatings significantly increased (p < .05) antibacterial properties but caused a decrease in cell viability. However, although Se–Cht additives did not have a significant effect on antibacterial properties (p < .05), it was observed that they increased cell viability.     

Synthesis of submicron AlN powder using dynamic/thermochemical method

Carbothermal reduction and nitridation (CRN) method, used for the synthesis of nitride-based ceramic powders, is an effective and economic technique that has been widely investigated. In this study, a CRN-based novel approach, denominated as dynamic/thermochemical method (DTM), has been used to synthesize submicron high-purity aluminum nitride (AlN) powders with equiaxed-sized particles. DTM is a modified CRN method in which the reaction takes place in a controlled atmosphere using a rotary tube furnace, allowing the synthesis of fine particle-size powders in a relatively short time. Following the DTM process, homogeneous submicron AlN powders were synthesized from a mixture of aluminum hydroxide (Al(OH)₃) and carbon black at 1450°C for 1.5 h. Furthermore, dynamic synthesis parameters, as well as the use of ammonia (NH₃) and propane (C₃H₈) gas mixtures instead of carbon black and nitrogen, were investigated.     

Effect of Physicochemical Surface Treatments on the Bond Strength and Adhesion of Porcelain Denture Teeth to Heat-Polymerized Acrylic Resin Denture Base Material

The aim of this study was to compare the effect of physicochemical surface treatments on the adhesive bond strength of porcelain denture teeth (PDT) to acrylic resin denture base material (PMMA). Totally, 100 PDT specimens, 50 with retentive palatal pins (+P) and 50 without pins (?P), were selected and assigned to 10 experimental groups (n = 10). Control groups CON-P and CON + P, did not receive any treatment. Groups SB + P and SB-P were sandblasted, groups SB/AE + P and SB/AE-P were sandblasted and acid-etched, groups TSC + P and TSC-P were tribochemically silica-coated, and groups FB + P and FB-P were covered with fibers. Cylindrical PMMA rods were polymerized onto treated palatal PDT surfaces. Force (N) was applied on palatal incisal edges of PDT specimens until debonding of PMMA. Obtained data were statistically analyzed with Kruskal-Wallis and Bonferroni corrected Mann Whitney U tests. The significance level was set at (p < .05). Mean force values of test groups ranged in descending order as follows: TSC+P (132.5 N ± 26.5), SB+P (113.5 N ± 47.5), SB/AE+P (112.2 N ± 26.1), CON+P (103.1 N ± 39.6), TSC-P (90.6 N ± 22.2), FB+P (77.7 N ± 18.3), SB/AE-P (47.6 N ± 10.5), SB-P (18.1 N ± 4.0), CON-P (4.6 N ± 5.4), and FB-P (0.0 N ± 0.0). No significant difference was found between groups with pins (+P) except group FB+P which displayed lower values than CON+P (p < .024), and TSC+P (p < 045). Groups (+P) showed significantly higher bond strength values than groups (?P) except for group TSC-P (p < .09 and p < 1). In groups without pins (P?), differences between groups were significant and ranged as follows: TSC-P>SB/AE-P (p < .0094), SB/AE-P > SB-P (p < .007), and SB-P > CON-P (p < .0013). Groups CON-P and FB-P did not show differences (p ≤ 1). Groups (+P) displayed higher bond strength values than groups (?P). SB-P, SB/AE-P, and TSC-P increased the adhesive bond between PDT and PMMA, respectively. Fiber coating negatively affected the bond.     

Shear amplification of orientation in Nylon 11/clay nanocomposites during melt casting and resulting electrical properties

In this study, the effect of organically modified clay on the orientation enhancement in Nylon 11 in melt casting was investigated. Nylon 11 was mixed with 1 and 3 wt% Cloisite 20A using twin screw extrusion and they were cast into films with varying take-up speeds. The addition of clay in Nylon 11 helped increase orientation levels substantially in melt cast films, both as a function of clay concentration as well as take-up speeds. This was primarily due to shear amplification effect caused by the movement of adjacent clay nanoparticles due to the shear flow gradient within the die. At low clay concentrations, the sub-T_m stretchability, and electrical breakdown strength improve as the presence of clay reduces inter/intrachain hydrogen bonding. At higher clay concentrations, both orientation and electrical breakdown levels decrease. The latter is primarily caused by increased percolation path of charge carriers. Nevertheless, clay nanoplatelets were very effective in their role as melt processing aids, as they enhance orientation levels of Nylon 11 thin films by shear amplification effect where they increase local chain orientation of chains trapped between clay platelets while their orientation relaxation is suppressed.     

Effect of shade and thermo-mechanical viscosity stimulation methods on the rheological properties of nanohybrid resin composite

The aim of the present study is to measure the rheological properties of nanohybrid resin composite of three shades in pre-polymerized phase using different thermomechanical stimulations. Nanohybrid composite (Kerr Herculite XRV Ultra) in enamel, dentin, and incisal shades was included. Rheological measurements were made with a rotational rheometer in dynamic oscillation mode using three methods: (a) Strain Sweep test explored a range of deformation γ₀ from 0.025 to 3% with a frequency ω = 1 Hz (temperature set at 25 and 65?°C), (b) Frequency Sweep test explored frequencies between 1 and 100 rad/s applying a deformation γ₀ = 0.5% (temperature set at 25; 45; 65?°C), and (c) Ramp Temperature test explored a heating phase from 25 to 75?°C then a cooling phase back to 25?°C applying a γ₀ = 0.5% and a ω = 10 rad/s. Data were analyzed using a three-way ANOVA and Tukey’s test (α = 0.05). Viscosity measurement (p < 0.05) and shade of the composites (p < 0.05) significantly affected the results. Viscosity turned out to be subordinate to strain amplitude, frequency, temperature, and axial force applied during each test. Enamel shade was the most viscous whereas dentin shade was 8% less viscous (p < 0.05). The incisal shade was significantly less viscous (70%) than enamel (p < 0.05). Pre-heating decreased viscosity of incisal shade (30%) above 50?°C but this value was 90 and 98%, respectively, for strain and frequency sweep test. Preheating had a side effect as in the cooling phase, viscosity increased from 66 to 450% exceeding the value recorded at the beginning of the test. Preheating was not effective to reduce viscosity, and may reveal some side effects. The composite tested might not be pre-heated above 45?°C.     

Surface modification of textiles by glow discharge technique: Part II: Low frequency plasma treatment of wool fabrics with acrylic acid

In this study, wool fibers are modified by low frequency plasma polymerization of acrylic acid regarding to its' hydrophobic character due to cuticular cells at their surfaces. Variables of the plasma glow discharge processes were power (40–100 W) and exposure time (5–45 min). The effect of plasma modification in the performance properties of wool were investigated on the basis of hydrophilicity of wool, average wrinkle recovery angle, and breaking strength. The surface chemical structures of fabrics were examined with x‐ray photoelectron spectroscopy. The hydrophobic wool fabric became hydrophilic after all plasma treatments except one (40W–5 min). Average wrinkle recovery angle of the treated fabrics were between 157 and 178°, while that of untreated fabric was 180°. The treated fabrics had a little bit lower angles according to the untreated fabric. However, even the lowest value as 157° means that the fabric has a good crease resistance property. The breaking strengths of fabrics were increased up to 26% after the plasma treatments. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and Characterization of Novel Surfactants: Combination Products of Fatty Acids,Hydroxycarboxylic Acids and Alcohols

The reaction of hydroxycarboxylic acids, such as citric, malic and tartaric species with an excess of fatty acid chlorides produces the corresponding O-acylated hydroxycarboxylic anhydrides in one step and in a near quantitative yield. These molecules are excellent electrophiles which react readily with a variety of nucleophiles including alcohols, diols and polyols. Their reaction with triethylene glycol and triethylene glycol monomethyl ether leads to two series of novel anionic surfactants, which are unsymmetrical gemini surfactants. The determination of their properties (CMC, foaming, HLB) revealed that these molecules are—depending on the chain length of the fatty acid—excellent emulsifiers, and that they also display interesting antimicrobial activity. These novel functional surfactants are of interest for applications in food and personal care products and for the formulation of pharmaceuticals.     

Linkage isomerism for 4-methylimidazole and a new coordination mode of pyrazine-2,3-dicarboxylate ligand in {[Cd(pzdc)(4-mim)(5-mim)2]·½H2O}n coordination polymer

A novel one dimensional coordination polymer of Cd(II)-pyrazine-2,3-dicarboxylate with a new coordination mode of pyrazine-2,3-dicarboxylate ligand (pzdc), {[Cd(pzdc)(4-mim)(5-mim)₂]·½H₂O}_n (1) (4(5)-methylimidazole = 4(5)-mim), has been synthesized and characterized by elemental, thermal analysis, IR spectrum and single crystal X-ray diffraction technique. In complex 1, the Cd(II) ion has a distorted octahedral geometry, in which the pzdc moiety acts as a bridging ligand. Linkage isomerism of the coordinated 4(5)-methylimidazole ligand was observed in 1. The two adjacent one-dimensional chains connected by interchain hydrogen bonds among the N-H groups of methylimidazoles and carboxylate oxygens of pzdc, leading to a three-dimensional framework. The hydrogen bonds account for the coexistence of two unique coordination forms of methylimidazoles in the same coordination sphere.     

Reuse of glass waste in the manufacture of ceramic tableware glazes

Today, various studies are carried out to spread the understanding of sustainability. The sustainability of production processes gains importance in corporate areas. In this study, the use of glass waste instead of frit used in glaze compositions in the ceramic industry was evaluated. The chemical and physical properties of glass wastes on samples were examined. The glaze formulations were prepared using 3%, 5%, and 8% by weight of glass waste instead of frit. Glass wastes were added to glaze compositions and 12 different glaze formulation studies were carried out. Transparent, Opaque, and Matte test glazes were prepared with glass waste added glaze formulations, and these glazes were applied to ceramic bodies. SEM (scanning electron microscope) analysis of standard glaze and glass waste added glazes was performed to determine the microstructural and morphological characterizations. Also, surface whiteness, brightness, L*a*b values, glaze flows, harcort test results, and final water absorption values were compared. As a result of the studies, it has been determined that it is appropriate to use 3% glass waste by weight instead of the frit in the production of ceramic tableware.     

Evaluating the role of uniformity on the properties of B4C–SiC composites

Fully dense boron carbide-silicon carbide composites were successfully produced by spark plasma sintering method at 1950 °C under 50 MPa applied pressure. The effect of dry and wet mixing methods on uniformity was observed. Density, elastic modulus, microstructure, Vickers hardness and fracture toughness were evaluated. The results showed that dry mixing did not provide uniformity on composites properties. On the other hand wet mixing provided uniformity in microstructure and consistency in material properties. The hardness of the sample containing 50 wt% B₄C was measured to be 30.34 GPa hardness value was found at 50 wt% B₄C content sample. The increase in the B₄C content of the composites decreased the Young's modulus, shear modulus, bulk modulus and fracture toughness. The highest values were found at 10 wt% B₄C sample which were 415 GPa (E), 177 GPa (G), 209 GPa (K), and 2.89 MPa m^1/2 fracture toughness (K_Ic).