Advances in Functionally Graded Ceramics – Processing, Sintering Properties and Applications

In multilayered structures, sharp interface is formed between the layers of dissimilar materials. At this interface, the large difference in thermal expansion coefficients of the two dissimilar materials generates residual thermal stresses during subsequent cooling. These stresses lead to cracking at the interface, and these cracks lead to the deterioration of mechanical properties, and finally crack propagation leads to the delamination of the multilayered structure. Scientific progress in the field of material technology, and the continuing developments of modern industries have given rise to the continual demand for ever more advanced materials with the necessary properties and qualities. The need for advanced materials with specific properties has brought about the gradual transformation of materials from their basic states (monolithic) to composites. Recent advances in engineering and the processing of materials have led to a new class of graded multilayered materials called Functionally Graded Materials (FGMs). These materials represent a second generation of composites and have been designed to achieve superior levels of performance. This chapter looks at the best processing technologies and the uses and applications of the advanced, high quality products generated, and also presents an extensive review of the recent novel advances in Functionally Graded Ceramics (FGCs), their processing, properties and applications. The manufacturing techniques involved in this work have involved many concepts from the gradation, consolidation and different sintering processes. Each technique, however, has its own characteristics and disadvantages. In addition, the FGC concept can be applied to almost all material fields. This chapter covers all the existing and potential application fields of FGCs, such as engineering applications in cutting tools, machine parts, and engine components, and discusses properties of FGCs such as heat, wear, and corrosion resistance plus toughness, and their machinability into aerospace and energy applications

Consistent Coupled Optical and Thermal Analysis of Volumetric Solar Receivers with Honeycomb Absorbers

International audienceIn concentrating solar power plants with central towers, successful design of volumetric solar receivers requires proper understanding of the interaction between optical, heat transfer, and fluid flow phenomena occurring at the microscopic scale of receiver structure material and their effect on the overall solar to thermal efficiency. In the present article, coupled, 3D, optical, heat transfer and fluid flow numerical models have been developed for the analysis and design of honeycomb volumetric receiver modules. The optical model considers the absorptivity and micro dimensions of honeycomb absorber structure and employs a Monte Carlo ray tracing technique to calculate and analyze the absorbed solar heat flux distribution. This, in turn, is employed as a volumetric heat source term at the solid surface for consistent heat transfer and fluid flow modeling using a realistic solution domain and proper boundary conditions. The validated models have been employed to investigate the effects of different types of absorber materials, material absorptivity, and air flow rate on the performance of the solar receiver. It has been shown that positive volumetric effect and high solar-to-thermal efficiency can be obtained by controlling the absorbed radiation heat flux distribution within the honeycomb receiver using surface coating of the absorber material

Bioceramic Scaffolds

Millions of peoples in the world suffer from their bone damage tissues by disease or trauma. Every day, thousands of surgical procedures are performed to replace or repair these tissues. The availability of these tissues is a big problem, and their costs are expensive. The repair of these defects has become a major clinical and socioeconomic need with the increase of aging population and social development. The emerge of tissue engineering (TE) is considered as a glimmer of hope to contribute in solving this problem. It aims at the regeneration of damaged tissues with restoring and maintaining the function of human bone tissues using the combination of cell biology, materials science, and engineering principles. In this chapter, the current state of the tissue engineering in particular bioceramic scaffolds was discussed. Concept of tissue engineering was explored. Bioceramic scaffold materials, their processing techniques, challenges taken into consideration the design of the scaffolds, and their in-vitro and in-vivo studies were highlighted. The scaffolds with extra-functionalities such as drug release ability and clinical applications were mentioned

Treatment of the Wooden Trunks in the Ceiling of the Burial Shaft of the Step Pyramid in Saqqara, Egypt

Saqqara is one of the most famous archaeological sites in Egypt and all over the world. It was the main necropolis of Memphis which was the capital of Egypt for the most part of the Old Kingdom period. Saqqara is also famous for the Step Pyramid which is the oldest stone structure in ancient Egypt. It was built by king Djoser who was the first king in the Third Dynasty. It is thought that the south entrance of the Step Pyramid was opened during the Saite period. During that period, a lot of restoration work was done to many places in Saqqara, one of whose places was the Step Pyramid, especially the south entrance, when they saw that there were cracks in the bedrock ceiling, that some limestone columns were used to support it. It seems that the ceiling of the burial shaft had a problem since that time. So, some wooden trunks were used to support the ceiling, especially in the places where there was a collapse. Those trunks were in bad condition, because they were affected by deterioration factors especially the brown rotten that caused the wood to be turned into cubes in different sizes. It is known that the ancient Egyptians used both local and imported wood, especially wood that was imported from Lebanon. So, it was important to identify the wood species to indicate if it was local or imported. Transmitted light optical microscope was used to identify the wood species. It is indicated that the species is Acacia Nilotica which has been common in Egypt from ancient times till now. There were deterioration products that could be seen on the wooden trunks such as cracks in different sizes and different depths, wood turned into cubes in different sizes. And then, and the surface of the wood was fragile and squishy, and some parts of the wooden trunks were covered with mortar that used for restoration in the Saite period or for supporting the ceiling during the current restoration project. Restoration work was done through three main steps. First, cleaning was done mechanically and chemically. Consolidation by using Nano cellulose and Plexisol P550, filling by using cotton injected with Paraloid B72 20% and Microballoon. FTIR analysis was done after using Nano cellulose and it indicated the percentage of cellulose in the wood was increased after using Nano cellulose for consolidation

Rice husk templated water treatment sludge as low cost dye and metal adsorbent

AbstractThe preparation of adsorbents at low cost as alternatives to the expensive ones in the treatment processes of water and wastewater is the interest of the researchers worldwide. Here, a novel cheap mesoporous adsorbent was prepared via the recycling of wastes namely water treatment sludge and rice husk (RH) as textural modifier. Surface area and pore dimensions were optimized against RH ratio. The mesoporous sludge was employed in adsorption of rosaniline dye, Pb2+, Ni2+ and chlorine from aqueous solutions under dynamic experimental conditions. It was found that the initial dye concentration and textural structure of the adsorbent played important roles in adsorption capacity. The reusability test shows the ease desorption of dye with slightly alkaline water (pH=8) indicating the stability and reusability of the ceramic adsorbent for several times. For metallic cations, the characteristics (ionic radius and ΔHhyd) of ions affect the adsorption affinity. Chlorine adsorption is controlled by the cation exchange capacity(CEC)

The effect of wind turbines on subsynchronous resonance

With the rapid growth of the penetration of wind power into the power system, fixed series compensation is considered as an economic solution to increase power transfer capability. This will render the power system vulnerable to Sub-Synchronous Resonance (SSR). This thesis conducts research on the effect of wind turbines represented by Fixed Speed Induction Generator-Based Wind Turbines (FSIG-WTs) and Fully Rated Converter-Based Wind Turbines (FRC-WTs) on damping SSR. Firstly, SSR is investigated through mathematically modelling IEEE First Benchmark Model (FBM) using MATLAB package. Modal analysis is used to study SSR over a wide range of series compensation percentages. Secondly, the effect of incorporating FSIG-WTs into FBM on SSR is studied over a wide range of series compensation percentage and different power size of FSIG-WTs. Furthermore, the ability of the grid-side converters of the FRC-WTs connected with the FBM to damp SSR occurrence in the steam turbine shafts is evaluated using two different types of control. An optimal controller based on a Linear Quadratic regulator (LQR) has been designed as an auxiliary controller of the grid-side converter of FRC-WTs. A full-order observer was designed to estimate the unmeasured state variables to enable a vii full-state feedback. Finally, eigenvalue sensitivity was studied to choose the most suitable feedback signal for an SSR damping controller. Lead/Lag compensation controller based on the residue method is designed as an auxiliary controller within the grid-side converters of FRC-WTs. Eigenvalue analysis and time domain simulations over widely varying levels of series compensation have been carried out. The simulation studies were carried out in MATLAB and PSCAD. Connecting FSIG-WTs to the FBM increases the range of series compensation level at which SSR can occur. Therefore, it was shown that FSIG-WTs have an adverse effect on the SSR occurring at the multi-mass synchronous generator. If the system is visible, LQR as an auxiliary damping controller within the grid-side converters of FRC-WTs is an effective controller to damp SSR over a wide range of series compensation percentages. Based on eigenvalue sensitivity technique, synchronous generator speed deviation is the most suitable feedback signal for damping SSR occurrence in the steam turbine shafts

Biotechnological applications of fungal endophytes associated with medicinal plant Asclepias sinaica (Bioss.)

AbstractFungal endophytes associated with medicinal plants have potential role to promote plant growth through different mechanisms. However, the biological and ecological roles of fungal endophytes still totally unexplored. In this study, three different fungal endophytes were isolated from the medicinal plant of Asclepias sinaica and identified as Penicillium chrysogenum Pc_25, Alternaria alternata Aa_27 and the third fungal strain was described as sterile hyphae Sh_26. It was recorded that, these endophytes had various ability to produce several extracellular enzymes including amylase, pectinase, cellulase, gelatinase, xylanase and tyrosinase. Their antimicrobial activities against different specific test organisms were investigated as well. In addition, both endophyte isolates i.e. Sh_26 and Aa_27 were found to promote root growth higher than Pc_25 and control treatments. These fungal isolates had a considerable impact on plant growth parameters including root elongation as a result of ammonia and IAA production

Silver nanoparticles treated activated carbon as effective sorbent for the removal of acid Red 1 dye from aqueous media: Kinetic and equilibrium studies

429-436Silver nanoparticles (AgNPLs) impregnated onto activated carbon (AC) as an effective solid adsorbent has been used for the uptake of acid red 1 (AR) from aqueous solution. In acid medium at pH ≤ 4.0, the removal of AR is found favourable than at pH ≥ 4.0. The data approve well with Fruendlich model and pseudo second-order kinetic. Adsorption capacity calculated from Langmuir is 107.5 mg/g. Thermodynamic activation parameters suggest endothermic and spontaneous process. Silver nanoparticles enhanced uptake of AR by AC. The liquid-film and intra-particle diffusion types examined the adsorption mechanism. Removal of AR from AC-AgNPLs surface carried out to illustrate the recapture of the adsorbent and adsorbate for the economic value of the remediation system. The solid phase extractor is excellent recovered for six consecutive sorption–adsorption round elucidate its rise reused

A systematic review and meta-analysis of mindfulness based interventions and yoga in inflammatory bowel disease

Background: Mindfulness interventions are increasingly used as a part of integrated treatment in inflammatory bowel disease (IBD) but there are limited data and a lack of consensus regarding effectiveness. Objectives: We explored the efficacy of mindfulness interventions compared to treatment as usual (TAU), or other psychotherapeutic interventions, in treating physical and psychosocial symptoms associated with IBD. Methods: We conducted a systematic review and meta-analysis of relevant randomized controlled trials (RCTs). We included a broad range of mindfulness interventions including mindfulness-based interventions and yoga, with no restrictions on date of publication, participants’ age, language or publication type. We searched the following electronic databases: MEDLINE, EMBASE, PsycINFO, CINAHL and WHO ICTRP database. We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines in conducting the review. Results: We included eight studies in the meta-analysis. Mindfulness interventions showed a statistically significant effect on stress in both the short(SMD = −0.48; 95%CI:–0.97, 0.00; P =.05), and long term(SMD = −0.55; 95%CI:-0.78, −0.32;