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In this paper, Si coatings were sprayed onto C/SiC composite substrates by atmospheric plasma spraying (APS). The high-temperature oxidation behavior of the substrate and coating at temperatures of 1100 and 1300 °C was also studied. The C/SiC ceramic matrix composite will be damaged seriously and even failed due to the oxidation of carbon fibers in matrix. The Si coating effectively improved the oxidation resistance of the C/SiC substrate in the high-temperature oxidation test. The effect of the thickness of the Si coatings on the oxidation resistance was investigated. The 150-μm coating is proved to enable the substrate to have the lowest oxidation weight loss and the best oxidation resistance after static oxidation for 5 h. [ABSTRACT FROM AUTHOR]

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Purpose: Heavy metal(loid) contamination has degraded over 20 million ha of global land with soil concentrations far above geo-baseline, consequently posing economic impacts of > 10 billion USD per year. The present study was aimed at mitigating heavy metal-mediated pollution in contaminated soil by using olive mill waste-derived biochar (BC), nutrient-doped BC, silica-embedded BC, and silica-embedded nutrient-doped BC. Methods: The BC was produced from olive mill waste at 500℃. A greenhouse experiment was conducted using agriculture soil artificially spiked by Pb and Cd, using safflower (Carthamus tinctorius L) as a test crop, and soil was amended with synthesized pristine and fabricated BCs at the rate of 1% and 2% (w/w). Results: The results showed that silica-embedded nutrient-doped BC (SNBC) increased plant shoot and root length by 65% and 70%, while fresh and dry biomass were enhanced by 66% and 57%, respectively. Additionally, the uptake of P and K by plant was significantly increased by the addition of BCs, while on contrarily, heavy metal concentration and uptake were reduced in plants grown in NBC- and SNBC-amended soil (2%). Overall plant growth was increased by two-fold by the addition of pristine and fabricated BCs as compared to control. Significant increment in bioconcentration factor suggested the potential of using fabricated amendments for phytoremediation process. Conclusion: In a nutshell, silica-embedded nutrient-doped BC showed excellent potential in mitigating heavy metals (Pb and Cd) toxicity, enhancing nutrient availability, and improving safflower plant growth. [ABSTRACT FROM AUTHOR]

The use of solar energy for drying is considered one of the most environmentally friendly ways to reduce dependence on fossil fuels. The purpose of this experimental study is to determine how absorption plate design affects the evaporation rate of a solar food dryer in Baghdad, Iraq. Tests were performed on four different absorbent panel models. This dryer design consists of a section for heating solar air and one for preserving food. There is insulation at the back of the dining cabinet, which is made of wood. As food samples, orange slices were selected. Except for the absorb plate design, all four models have identical measurements. Matte black aluminum absorbent plate is featured on the Model-1. Both Models 2 and 3 have perforated cylindrical fins arranged uniformly and vertically in Model 2 and horizontally in Model 3. Model 4 uses horizontal fins and an absorber plate coated with 15 % silicon content. A fruit cabinet holds sliced fruit in five movable mesh trays. According to experimental results, the shape of the absorbent plate directly affects the temperature of the outlet air, which in turn affects the rate at which water is evaporated from fruit slices and the overall drying process. Model-1 solar air heaters could be improved by approximately 17 % by coating them with 15 % silicon. The efficiency of Models 2, 3, and 4 is increased by 20 %, 40 %, and 65 % by adding fins and tint over Model 1. Models 1, 2, 3, and 4 had moisture contents of 28 %, 25 %, 20 %, and 18 %, respectively, at 15 p.m. A solar dryer has been demonstrated to be suitable for successfully drying fruits and vegetables in Iraq's atmosphere through practical experiments.

Atmospheric plasma sprayed dense Si coatings have excellent potential for high-temperature oxidation resistance. However, numerous isolated spherical particles on the coating surface result in rapid oxidation and a large local TGO thickness. In the present study, isolated particle healing (IPH) treatment was proposed to eliminate these isolated particles. Then, the related structure evolution and oxidation kinetics of Si coatings were investigated. Finally, the failure mechanism of TGO after oxidation was identified. The results show that the IPH treatment makes isolated particles diffuse, connect with and then immerse themselves into the bulk coating surface, thereby contributing to both surface smoothing and coating densification. Consequently, the localized large thickness in the TGO scale is eliminated, and the overall oxidation rates of the IPH Si coating decrease by ∼24% compared with the as-sprayed coating. The β→α phase transformation of polymorphic cristobalite with a volume reduction of ∼4.5% is the main cause for TGO channel cracking and is not suppressed by IPH treatment, which points out future directions for better antioxidant Si coatings.

In this study, silicon coating was deposited on melt-infiltrated SiC composites using atmospheric plasma spraying and then annealed at 1100 and 1250 °C for 1–10 h to investigate the effect of annealing on the layer. The microstructure and mechanical properties were evaluated using scanning electron microscopy, X-ray diffractometry, transmission electron microscopy, nano-indentation, and bond strength tests. A silicon layer with a homogeneous polycrystalline cubic structure was obtained without phase transition after annealing. After annealing, three features were observed at the interface, namely β-SiC/nano-oxide film/Si, Si-rich SiC/Si, and residual Si/nano-oxide film/Si. The nano-oxide film thickness was ≤100 nm and was well combined with SiC and silicon. Additionally, a good bond was formed between the silicon-rich SiC and silicon layer, resulting in a significant bond strength improvement from 11 to >30 MPa. [ABSTRACT FROM AUTHOR]

Silicon (Si) has been identified as a key nutrient in plants to lower the pressures of environmental stress. In pot experiment, seeds of different maize hybrids (Pioneer-1543, Monsanto-6103 and Monsanto-6724) were coated with different concentrations of Si viz. 0, 5, 10, 15 and 20 mg kg− 1 seed using H2SiO3. Salinity was imposed by adding NaCl (120 mM) into the soil. Saline stressed (without Si coating) plants were observed with a significant decrease in growth and yield, Chl a and b, soluble contents of sugars and proteins, contents of free amino acids and phenols, leaf relative water content (LRWC), superoxide dismutase, catalase, peroxidase and brings only increased in proline contents. However, plants developed from Si coated seeds were recorded with significant improvements in growth and different physiological parameters. Moreover, among Si coated maize, coating with 20 mg Si proved maximum growth and yield in saline condition, which was came with the improvement in photosynthetic contents, osmoprotectants and antioxidant. Furthermore, Si coated plants have significantly lower proline compare than saline stress alone. Taken above results together, it is concluded that Si has significant role in reducing adverse behavior of NaCl in maize growth through bringing a improvement in leaf relative water contents, keeping normal working of chl a and b that enhanced the osmoprotectants concentration rather than proline and motivate the antioxidant system. Thus, our study suggested that Si coating is a viable strategy that can be implemented to bring a significant improvement in maize under saline condition. [ABSTRACT FROM AUTHOR]

To facilitate the optimal application of carbon fiber (CF) reinforced hydroxyapatite (HA) bio-ceramics as load-bearing bone substitutes, we adopted the magnetron sputtering method to prepare a Si coating on CF surface and then prepared Si-coated CF (Si-CF) with controllable alignment reinforced HA composites via pressureless and hot-press sintering. CFs were evenly distributed in the HA matrix according to the designed layers and alignment states using a special mold and technology. The results showed that uniform and continuous Si coatings with a thickness of approximately 0.2 μm covered the surface of CF. The bending strength of three-layer Si-CF reinforced HA (3Si-CF/HA) bio-ceramics fabricated by pressureless sintering was 33 MPa, which is 45% higher than that of three-layer CF reinforced HA (3CF/HA) bio-ceramics. Three-layer Si-CF reinforced HA bio-composites fabricated by hot-press sintering (H/Si-CF/HA) had a bending strength of 80.9 MPa, which is more than five times that of 3CF/HA bio-ceramics. The corresponding fracture toughness of H/Si-CF/HA was 2.53 MPa m1/2, which is 27.14% higher than that of 3Si-CF/HA composites. Compared with CF reinforced by HA, Si-coated CF could reduce the contact between CF and the O 2 produced by the decomposition of HA. The chemical reaction between Si and O 2 produces SiO 2. The barrier layer provided by the Si and SiO 2 coatings can prevent oxidative damage of CF during sintering and maintain the original reinforcing and toughening effects of CF. Axial pressure strengthened the bond between CF and the HA matrix in the H/Si-CF/HA composites sintered at high temperature. The pores and activated grain boundaries of the composites were reduced, and their degree of densification was improved. Therefore, the bending strength and fracture toughness of H/Si-CF/HA composites were improved and are able to satisfy the requirements of load-bearing bones. [ABSTRACT FROM AUTHOR]

Two fuel plates, containing Si and ZrN coated U-Mo fuel particles dispersed in an Al matrix, were irradiated in the BR2 reactor of SCK•CEN to a burn-up of ∼70% 235 U. Five samples were prepared by INL using focused ion beam milling and transported to SCK•CEN for transmission electron microscopy (TEM) investigation. Two samples were taken from the Si coated U-Mo fuel particles at a burn-up of ∼42% and ∼66% 235 U and three samples from the ZrN coated U-Mo at a burn-up of ∼42%, ∼52% and ∼66% 235 U. The evolution of the coating, fuel structure, fission products and the formation of interaction layers are discussed. Both coatings appear to be an effective barrier against fuel matrix interaction and only on the samples having received the highest burn-up and power, the formation of an interaction between Al and U(Mo) can be observed on those locations where breaches in the coatings were formed during plate fabrication. [ABSTRACT FROM AUTHOR]

Magnesium based alloys, especially Mg–Ca alloys, are biocompatible substrates with mechanical properties similar to those of bones. The biodegradable alloys of Mg–Ca provide sufficient mechanical strength in load carrying applications as opposed to biopolymers and also they avoid stress shielding and secondary surgery inherent with permanent metallic implant materials. The main issue facing a biodegradable Mg–Ca alloy is the fast degradation in the aggressive physiological environment of the body. The alloy's corrosion is proportional with the dissolution of the Mg in the body: the reaction with the water generates magnesium hydroxide and hydrogen. The accelerated corrosion will lead to early loss of the alloy's mechanical integrity. The degradation rate of an alloy can be improved mainly through tailoring the composition and by carrying out surface treatments. This research focuses on the ability to adjust degradation rate of Mg–Ca alloys by an original method and studies the biological activity of the resulted specimens. A new Mg–Ca alloy, with a Si gradient concentration from the surface to the interior of the material, was obtained. The surface morphology was investigated using scanning electron microscopy (VegaTescan LMH II, SE detector, 30 kV), X-ray diffraction (X’Pert equipment) and energy dispersive X-ray (Bruker EDS equipment). In vivo degradation behavior, biological compatibility and activity of Mg–Ca alloys with/without Si gradient concentration were studied with an implant model (subcutaneous and bony) in rats. The organism response to implants was characterized by using radiological (plain X-rays and computed tomography), biochemical and histological methods of investigation. The results sustained that Si gradient concentration can be used to control the rate of degradation of the Mg–Ca alloys for enhancing their biologic activity in order to facilitate bone tissue repair. [ABSTRACT FROM AUTHOR]

Abstract: Oxidization of diamond in the sintering process of diamond/glass composites results in low compressive fracture strength (CFS) of the grit and uncontrolled expansion with many irregular pores in the composites, which causes low bending strength of the composites. In this paper, a Si barrier layer on the diamond surface was introduced for the first time in diamond/glass composites in order to resolve the above issues. The effects of Si coating on the properties of diamond grit and diamond/glass composites were studied. The results showed that the Si film prepared at 600°C for 10cycles has high thermal stability and excellent oxidization resistance, and could effectively protect grit from being oxidized. Uncoated diamond grit in the composites began to be oxidized at 812°C, while oxidation of Si-coated grits could not be found below 1000°C. Compared with uncoated grit, Si-coated grit had higher CFS after sintering at 850°C. In the composites sintered at 850°C, replacing uncoated grit with Si-coated grit, resulted in a decrease of volume expansion from 217.2% to −28.6%, and an increase in bending strength from 9.5MPa to 51.9MPa. [Copyright &y& Elsevier]

Uniform Ag and Si layers were successfully prepared on the surface of graphite films (GF) to improve thermal conductivity (TC) by physical vapor deposition method (PVD). The results demonstrate that the unique cubic crystal structure of Ag layer with different deposition time show good interface bonding and no carbide product of Ag/GF composites. Meanwhile, the dense Si coating contribute to the enhancement of the thermal diffusion ability. The Ag/GF composites with the deposition time of 2 h possess the best comprehensive property with the TC of 9.93 (W/m·K), which is approximately 73.30% higher than untreated GF. The TC of Si/GF composites reach the maximum TC of 11.12 W/(m·K) and increase about 101.81% due to the nano-Si layer comparing with untreated GF. Those composites with high performance make them promising thermal management laminated materials. • Designing of three-dimensional structure of nano-plating benefits the surface property of heat export and displays strong bonding force with matrix (graphite film). • The TC of Si/GF composite increase about 101.81% due to the nano-Si layer. The performance of Ag/GF composites show an increase of 73.30% in TC. • Application of the Ag/GF and Si/GF composites make it potentially as one of the most promising thermal management materials for the stability of equipment. [ABSTRACT FROM AUTHOR]

Abstract: Amorphous Si film was prepared by plasma enhanced chemical vapor deposition (PECVD) of SiH4 on WE43 alloy for biomedical application. The microstructure and the composition of the film were investigated by glancing angle X-ray diffraction (GAXRD), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. The immersion test indicated that Si film could efficiently slow down the degradation rate of WE43 alloy in simulated body fluid (SBF) at 37±1°C. MTT assay suggested that the extract of the Si coated WE43 alloys was harmless to murine fibroblast cells (L 929). Hemolysis test and blood platelets adhesion test were conducted, and the results show that the hemolysis of WE43 alloy decreased after being coated by Si and the platelets attached on the Si film were at the inactivated stage with a round shape. [Copyright &y& Elsevier]