Statement of Problem: Mechanical strength and durability of dental composites are the main topics studied in this field of science today. This study examined fumed silica-based composite as a strong and durable restorative material through flexural and cycling test methods.Objectives: The purpose of this study was to evaluate the effect of silanization, ageing, cycling and hybridizing on mechanical properties of fumed silica-based resin composite.Materials and Methods: Composites were made of light-cured copolymer based on Bisphenol A glycolmethacrylate (Bis-GMA) and Triethylene glycoldimethacrylate (TEGDMA) at proportion of 50:50 which reinforced by fumed silica filler. For each composite sample, 5 specimen bars were made using Teflon mould (2 x 2 x 25 mm3). The samples with 12 wt% fumed silica (FS) were considered as a base line group. The samples were exposed to cyclic cold water (FS-CCW) and hot water (FS-CHW). The effect of silanization and adding more filler was studied together with samples containing 12 wt% (FS-S (12), 16 wt% (FS-S (16) and 20 wt% (FS-S (20) fumed silica filler. The filler was silanized with ( g-MPS). The degree of conversion was assessed with Fourier Transform Infra-Red spectroscopy. Flexural properties were evaluated with the Three-Point Bending test. Flexural data were analyzed with Excel software. Hardness was measured with an Atomic Force Microscope (AFM).Results: The degree of conversion of the resin reached 74% within 24 hrs. Salinization allowed more filler to be wetted by resin. Addition of silanized particles from sample FS-S (12) to sample FS-S (20) improved the mechanical strength. Hybridizing fumed silica with nano-silica (FS-N) had no significant effect on the strength, but nano-hardness improved greatly. Ageing and cycling had adverse effects on the strength of the sample FS. The flexural strength of FS-CHW was 72% less than FS sample.Conclusions: Sample FS-N with low diluent and filler percentage complied with the requirements of flexural strength was established by ISO 4049/2009 and may be cost benefit to be used as a dental composite for clinical application.

Background and Objective: Chemical attacks through concrete pores destroy concrete structures and reduce their structural integrity in sulfate environments. The durability of concrete in harsh environments is a crucial issue worldwide. Specifically, environments like coastalareas, saline-alkali lands and salt lakes contain many sulfate ions, which could penetrate into the concrete foundation facilities like pier, bridge and tunnel. It is generally accepted that the ingression of sulfate ions in concrete causes serious deterioration, such as cracking, expansion and strength loss. This phenomenon is mainly attributed to the formation of gypsum and ettringit. Ordinary Portland Cement (OPC) concrete has long been used in construction of civil infrastructure and its deterioration over time due to sulphate attack has been widely observed and documented. Investigations have revealed that the degradation of OPC concrete takes place due to reactions between cement hydration products and sulphate-bearing solutions. Degradation of concrete strength due to sulphate attack takes place when the calcium and hydroxide ions dissolve out of the matrix, causing an increase in porosity and permeability of the concrete surface. Maintaining the durability of concrete structures against corrosion in acidic environments is an important challenge. Investigating concrete microstructure makes it possible to understand concrete porosity and structural composition in micro-and nano-scales, and makes concrete more concentrated, durable and strong. Accordingly, the present study is a microstructural analysis of the long-and short-term impacts of the conditions of different sulfate environments on concrete strength parameters. Material and method: This study evaluated about 200 concrete samples. The samples were preserved for 3 months in simulated environments with 0. 1%, 0. 25%, 0. 5%, 1%, 2. 5%, 5% and 7. 5% sulfuric acid concentrations. Compressive strength, weight percentage, ultrasonic wave, permeability and pH change tests were then performed after 1, 3, 7, 14, 28 and 90 days on all the samples in the preserving environment. Images from the scanning electronic microscope (SEM) test were used for microstructural analysis. Result and discussion: The results indicate that the strength of samples preserved in the sulfate environment compared to the control sample depended on the amount of sulfate. In the majority of sulfate attacks, the most vulnerable compounds to react with waterborne sulfate ions are calcium hydroxide (CH) and phases containing aluminium, such as AFM (e. g. monosulfate) and unreacted C3A. After 28 days, the compressive strength of samples preserved in the 5% concentration sulfuric acid sulfate environment was reduced by about 63% compared to control samples. This reduction in compressive strength is inversely related to the results from the ultrasonic test of samples preserved in the 5% percent concentration sulfate environment. The environment’, s wave velocity increased by 27% after 90 days. Consequently, expansion and cracking result in severely compromised structural integrity of the attacked concrete. Cracking also leads to further propagation of the attack. The increase in ultrasonic wave velocity of samples was accompanied by a loss of strength and mass due to destruction of concrete strength structures, including the C-S-H nanostructure, and formation of ettringite due to exposing samples to sulfate.

The comparative study of Active Screen Plasma Nitriding (ASPN) treatment of two Finemet-type alloys with the compositions of Fe73:5Si13:5B9Nb3Cu1 and Fe77Si11B9Nb2:4Cu0.6 was investigated in different temperatures ranging from 410°C to 560°C. Differential Scanning Calorimetry (DSC), X-Ray Diffractometery (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), electrical resistivity, microhardness measurements and magnetic characterization by a Vibrating Sample Magnetometer (VSM) were utilized to characterize the treated samples. The comparison of the DSC data for the alloys suggested that the smaller amount of Nb as a growth inhibitor shifted the crystallization temperatures towards lower temperatures. Thus, the crystalline volume fraction and grain size in each temperature for Fe77Si11B9Nb2.4Cu0.6 alloy increased compared to Fe73.5Si13.5B9Nb3Cu1 alloy. The size of iron nitrides on the surface of the ribbons with the lower Si content was larger. The electrical resistively for the annealed and nitrided Fe77Si11B9Nb2.4Cu0.6 alloy was lower compared to the annealed and nitrided Fe73.5Si13.5B9Nb3Cu1 alloy, due to the larger grain size and lower Si content of Fe(Si) phase in Fe77Si11B9Nb2.4Cu0.6 alloy. The VSM results showed that the maximum saturation magnetization and coercivity at 440°C were obtained in Fe77Si11B9Nb2.4Cu0.6 alloy after nitriding under 75% H2 and 75% N2 gas mixture, respectively.

The current study assesses the effect of fibrous clay minerals’ amendments and arbuscular mycorrhiza incubation on heavy metal uptake and translocation in Eucalyptus grandis and Ailanthus altissima plants. For doing so, Eucalyptus and ailanthus trees have been grown in a soil sample, contaminated with heavy metal iron ore mining and collected from southern Iran. The area under study is arid, with the majority of trees being ailanthus and eucalyptus. Amounts of Cd, Pb, Zn, Cu, and Mn have initially been at toxic levels which declined after cultivation. Fibrous clay minerals have been added to soils as a natural adsorbent to adsorb heavy metals like Pb, Cd, Zn, and Mn. Accumulation of the elements in the roots and shoots has been in the following order: Cu>Zn>Mn>Cd>Pb>Fe. The organ metal concentrations have not statistically translocated from roots to shoots of plants, except for Zn and Cu whose concentrations have been significantly higher in roots. Eucalyptus is well capable of extracting elements from contaminated soils, compared to ailanthus, particularly in case of Cu and Cd. The percentage of mycorrhizal colonization proves to be more in pots with ailanthus plants grown in contaminated soil, suggesting enhanced effect of high metal concentrations on plant infection by G. mosseae. AMF assists soil remediation by enhancing the growth and retention of toxic elements by ailanthus, while no substantial change has been observed between inoculated and non-inoculated eucalyptus plants by AFM, regarding translocation of elements to plants. The possibility of increasing metal accumulation in roots is interesting for phytoremediation purposes, since most high-producing biomass plants, such as eucalyptus, retain heavy metals in roots.