scispace - formally typeset
Search or ask a question

Showing papers in "Materials Science Forum in 2012"


Journal ArticleDOI
TL;DR: In this paper, the photocatalytic degradation of different kinds of organic pollutants; mainly surfactants, pesticides, dyes, phenols, chloro compounds, nitrogen containing compounds etc. Mechanisms of their degradation have also been discussed with hydroxyl and allied radicals as the main active oxidizing species.
Abstract: Water pollution is increasing at an ever increasing pace and the whole world is in the cancerous grip of this pollution. Various industries are discharging their untreated effluents into the nearby water resources; thus, adding to the existing water pollution to a great extent. Hence, there is a pressing demand to develop an alternate technology for wastewater treatment and in this context; photocatalysis has emerged as an Advanced Oxidation Process with green chemical approach for such a treatment. This chapter deals with photocatalytic degradation of different kinds of organic pollutants; mainly surfactants, pesticides, dyes, phenols, chloro compounds, nitrogen containing compounds etc. Mechanisms of their degradation have also been discussed with hydroxyl and allied radicals as the main active oxidizing species.

110 citations


Journal ArticleDOI
TL;DR: In this article, the authors used X-ray diffraction (XRD) and optical microscopy, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) techniques to study the interfaces of the friction welded joints.
Abstract: Friction welding is a solid state joining process and it is best suited for joining dissimilar metals. It overcomes the problems associated with the conventional fusion welding processes. The joining of dissimilar metals using fusion welding processes produce brittle intermetallic precipitates at the interface which reduce the mechanical strength. Various aerospace, nuclear, chemical and cryogenic applications demand joints between titanium and stainless steel. Direct joining of these metals results in brittle intermetallics like FeTi and FexTiy, at the weld interface, which is to be avoided in order to achieve improved properties of the joints. Present study involves joining of two industrially important dissimilar metals such as commercially pure titanium and 304 stainless steel by friction welding with electroplated nickel coating as interlayer that can prevent the brittle intermetallic formation. Microstructural details of the interfaces of the friction welded joints were studied by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) technique and X-ray diffraction (XRD). Microhardness survey was carried out across the joints and tensile test was conducted to assess the mechanical properties of the joints. Fractography studies were carried out on the fracture surfaces of the joints to know the region of failure as well as the mode of failure. XRD patterns indicate the presence of intermetallics in the friction welded joints. These two metals were successfully joined by having electroplated nickel as interlayer. The weld interface on titanium side contained Ti-Ni intermetallics layers, in which the hardness of the weld metal showing the higher value than the base metals. Fractography study conducted on the fracture surfaces created due to pull test reveals that the failure is by brittle fracture and occurred at the intermetallics layer. The maximum strength of the joints achieved for 30 μm and 50 μm thick electroplated nickel interlayers are 242 MPa and 308 MPa, respectively.

74 citations


Journal ArticleDOI
TL;DR: In this article, the detrimental laves formation in fusion zone during welding of Inconel 718 is controlled with compound current pulsing technique along with helium shielding gas, solid solution filler wire is used to minimize the niobium segregation.
Abstract: The detrimental laves formation in fusion zone during welding of Inconel 718 is controlled with compound current pulsing technique along with helium shielding gas. Also solid solution filler wire is used to minimize the niobium segregation. Welds were produced in 2mm thick sheets by GTA welding process and subjected to the characterization techniques. The results show, refined fusion zone microstructure, reduced amount of laves phase, minimum niobium segregation and softer fusion zone in the as welded condition.

59 citations


Journal ArticleDOI
TL;DR: In this paper, a case study of a 97 apartment-type building (27.647 m2) located in Portugal, concerning both embodied energy as well as operational energy (heating, hot water, electricity).
Abstract: Energy is a key issue for Portugal, it is responsible for the higher part of its imports and since almost 30% of Portuguese energy is generated in power stations it is also responsible for high CO2 emissions. Between 1995 and 2005 Portuguese GNP rise 28%, however the imported energy in the same period increased 400%, from 1500 million to 5500 million dollars. As to the period between 2005 and 2007 the energy imports reach about 10,000 million dollars. Although recent and strong investments in renewable energy, Portugal continue to import energy and fossil fuels. This question is very relevant since a major part of the energy produced in Portugal is generated in power plants thus emitting greenhouse gases (GHGs). Therefore, investigations that could minimize energy use are needed. This paper presents a case study of a 97 apartment-type building (27.647 m2) located in Portugal, concerning both embodied energy as well as operational energy (heating, hot water, electricity). The operational energy was an average of 187,2 MJ/m2/yr and the embodied energy accounts for aprox. 2372 MJ/m2, representing just 25,3% of the former for a service life of 50 years. Since Portuguese energy efficiency building regulation made under the Energy Performance Building Directive (2002/91/EC-EPBD) will lead to a major decrease of operational energy this means that the energy required for the manufacturing of building materials could represent in a near future almost 400% of operational energy. Replacement up to 75% of Portland cement with mineral admixtures could allow energy savings needed to operate a very high efficient 97 apartment-type building during 50 years.

46 citations


Journal ArticleDOI
TL;DR: In this article, the authors present the latest developments in ultra high voltage 4H-SiC IGBTs and compare P- and N-IGBTs in 4HSiC.
Abstract: We present our latest developments in ultra high voltage 4H-SiC IGBTs. A 6.7 mm x 6.7 mm 4H-SiC N-IGBT with an active area of 0.16 cm2 showed a blocking voltage of 12.5 kV, and demonstrated a room temperature differential specific on-resistance of 5.3 mΩ-cm2 with a gate bias of 20 V. A 4H-SiC P-IGBT exhibited a record high blocking voltage of 15 kV, while showing a differential specific on-resistance of 24 mΩ-cm2. A comparison between P- and N- IGBTs in 4H-SiC is provided in this paper.

45 citations


Journal ArticleDOI
TL;DR: In this article, the volume change associated with carbon partitioning from martensite to austenite was calculated using theoretical models for the carbon partition. But the model was not applied to the case of steel.
Abstract: Annealing of martensite/austenite microstructures leads to the partitioning of carbon from martensite to austenite until the chemical potential of carbon equilibrates in both phases. This work calculates the volume change associated with this phenomenon using theoretical models for the carbon partitioning from martensite to austenite. Calculations are compared with experimentally determined volume changes. This comparison reveals that in the case of steels with higher contents of austenite-stabilizing elements, reported volume changes are satisfactory predicted assuming a low mobilily martensite/austenite interface. In the case of a steel with lower additions of austenite-stabilizing elements, experimentally measured expansions are considerably larger than predicted ones. The large measured volume expansions probably reflect the decomposition of the austenite.

44 citations


Journal ArticleDOI
TL;DR: An AlCoCrCuFeNi high entropy alloy was forged at 950°C to produce a fine equiaxed structure with the average grain/particle size of 1.5 µm as mentioned in this paper.
Abstract: An AlCoCrCuFeNi high entropy alloy was multiaxially isothermally forged at 950°C to produce a fine equiaxed structure with the average grain/particle size of ~1.5 µm. The forged alloy exhibited superplastic behavior in the temperature range of 800-1000°C. For example, during deformation at a strain rate of 10-3 s-1, tensile ductility increased from 400% to 860% when the temperature increased from 800°C to 1000°C. An increase in strain rate from 10-4 to 10-2 s-1 at T = 1000°C did not affect ductility: elongation to failure was about 800%. The strain rate sensitivity of the flow stress was rather high, m = 0.6, which is typical to the superplastic behavior. The equiaxed morphology of grains and particles retained after the superplastic deformation, although some grain/particle growth was observed.

44 citations


Journal ArticleDOI
TL;DR: In this article, the authors present the results of several pozzolanic reactivity methods, applied to different pozzolic materials, including Chapelle method, Fratinni method and Strength Activity Index.
Abstract: Pozzolanicity is a very interesting issue regarding building materials, as a way to enhance mortars and concrete durability. This property results from the reaction between calcium hydroxide and silica and alumina based materials. Different types of natural and artificial pozzolans show pozzolanic activities that differ depending on the materials characteristics. Therefore, the study of this property, namely its reactivity with calcium hydroxide, reveals itself to be important in the selection of the type and content of these materials. This paper presents the results of several pozzolanic reactivity methods, applied to different pozzolanic materials. The selected pozzolanic methods include Chapelle method, Fratinni method and Strength Activity Index. Those tests have been applied to evaluate the reactivity of various kinds of artificial pozzolans. The correlation between the test methods are presented and discussed.

44 citations


Journal ArticleDOI
TL;DR: In this article, the development of new cast and wrought magnesium alloys using computational thermodynamics tools and experimental approach is summarized, and the Mg-Al-Ca alloys show excellent creep resistance due to the formation of high-temperature (Mg,Al)2Ca phase.
Abstract: This paper summarizes the development of new cast and wrought magnesium alloys using computational thermodynamics tools and experimental approach. The Mg-Al-Ca alloys show excellent creep resistance due to the formation of high-temperature (Mg,Al)2Ca phase. The Mg-Al-Sn alloys are designed for mechanical properties and corrosion resistance through the optimization of Mg17Al12 and Mg2Sn phases in the microstructure. In the Mg-Zn-Ce system, Zn provides strength through solid solution strengthening while Ce increases the ductility via improved texture. Mg-Nd-Zn is a heat-treatable alloy system based on the precipitation hardening of Mg12Nd phase.

43 citations


Journal ArticleDOI
TL;DR: In this article, a two-way tunneling model describing simultaneous oxide trap charging and discharging in SiC MOSFETs is presented, along with a comparison with experimental results.
Abstract: A two-way tunneling model describing simultaneous oxide trap charging and discharging in SiC MOSFETs is presented, along with a comparison with experimental results. This model can successfully account for the variation in threshold-voltage instability observed as a function of bias-stress time, bias-stress magnitude, and measurement time.

42 citations


Journal ArticleDOI
TL;DR: In this article, the effects of chemical composition and cooling rate on the delta ferrite formation in austenitic stainless steels have been investigated and the best agreement was obtained with those proposed independently by Schneider and Schoefer, the latter being recommended in ASTM 800 standard.
Abstract: The effects of chemical composition and cooling rate on the delta ferrite formation in austenitic stainless steels have been investigated. Ferrite fractions measured by a magnetic method were in the range of 0 to 12% and were compared with those calculated by empirical formulas available in the literature. The delta ferrite formation (amount and distribution) was strongly affected by the steel chemical composition, but less affected by the cooling rate. Among several formulas used to calculate the amount of delta ferrite, the best agreement was obtained with those proposed independently by Schneider and Schoefer, the latter being recommended in the ASTM 800 standard.

Journal ArticleDOI
TL;DR: In this paper, the quenching temperature and the isothermal holding temperature for diffusion carbon distribution for three advanced high strength steels with carbon content of 0.43 % were examined.
Abstract: The use of the combined influence of retained austenite and bainitic ferrite to improve strength and ductility has been known for many years from the treatment of multiphase steels. Recently, the very fine films of retained austenite along the martensitic laths have also become the centre of attention. This treatment is called the Q-P process (quenching and partitioning). In this experimental program the quenching temperature and the isothermal holding temperature for diffusion carbon distribution for three advanced high strength steels with carbon content of 0.43 % was examined. The alloying strategies have a different content of manganese and silicon, which leads to various martensite start and finish temperatures. The model treatment was carried out using a thermomechanical simulator. Tested regimes resulted in a tensile strength of over 2000MPa with a ductility of above 14 %. The increase of the partitioning temperature influenced the intensity of martensite tempering and caused the decrease of tensile strength by 400MPa down to 1600MPa and at the same time more than 10 % growth of ductility occurred, increasing it to more than 20%.

Journal ArticleDOI
TL;DR: In this article, the authors used the meniscus formation technique to suppress parasitic reactions such as polycrystal precipitation around the seed crystal, which enabled long-term growth by suppressing parasitic reactions.
Abstract: We have grown high-quality long cylindrical (12 mm thick) 4H-SiC bulk crystals by the meniscus formation technique, which was first applied for the solution growth of bulk SiC. It enabled long-term growth by suppressing parasitic reactions such as polycrystal precipitation around the seed crystal. In addition, we could control the growth angle from −22° to 61° by adjusting the meniscus height. The thickness of the grown cylindrical crystals was 12 mm, which is the largest reported until now, and corresponded to a growth rate of 0.6 mm/h. Smooth morphology growth was maintained on the (000-1) C-face. In cross-sectional transmission optical microscopy images, few solvent inclusions and voids were observed. XRD measurements revealed that the FWHM values of the grown crystals were almost the same as those of the seed crystal.

Journal ArticleDOI
TL;DR: In this paper, the key reliability results from Time-Dependent Dielectric Breakdown (TDDB) and High Temperature Gate Bias (HTGB) measurements indicate that the SiC MOSFETs can demonstrate excellent lifetime and stable operation in the field.
Abstract: Significant advancement has been made in the gate oxide reliability of SiC MOS devices to enable the commercial release of Cree’s Z-FET™ product. This paper discusses the key reliability results from Time-Dependent-Dielectric-Breakdown (TDDB) and High Temperature Gate Bias (HTGB) measurements that indicate that the SiC MOSFETs can demonstrate excellent lifetime and stable operation in the field.

Journal ArticleDOI
TL;DR: A physically-based model for nucleation during discontinuous dynamic recrystallization (DDRX) has been developed and is coupled with polyphase plasticity and grain growth models to predict the macroscopic stress and grain size evolution during straining as mentioned in this paper.
Abstract: A physically-based model for nucleation during discontinuous dynamic recrystallization (DDRX) has been developed and is coupled with polyphase plasticity and grain growth models to predict the macroscopic stress and grain size evolution during straining. The nucleation model is based on a recent description for static recrystallization and considers the dynamically evolving substructure size. Model predictions are compared with literature results on DDRX in pure Cu as a function of initial grain size, deformation temperature and strain-rate. The characteristic DRX features such as single to multiple peak stress transitions and convergence towards a steady-state stress and grain size are quantitatively reproduced by the model.

Journal ArticleDOI
TL;DR: The effect of metal dopant on the structural, textural and photocatalytic properties of titanium dioxide has been reviewed in this article, where different synthesis route for doping of metal ions in titanium dioxide have been emphasised.
Abstract: Titanium dioxide (Titania; TiO2) is one of the most widely used metal oxide semiconductor in the field of photocatalysis for removal of pollutants. It has been noted that titanium dioxide is a research friendly material as its physico-chemical and catalytic properties can be easily altered as per specific application. Since many years, researchers have tried to modify the properties of titanium dioxide by means of doping with metals and non-metals to improve its performance for photocatalytic degradation (PCD) applications. The doping of various metal ions like Ag, Ni, Co, Au, Cu, V, Ru, Fe, La, Pt, Cr, Ce, etc. in titanium dioxide have been found to be influencing the band gap, surface area, particle size, thermal property, etc. and therefore the photocatalytic activity in PCD. Moreover, photocatalytic activity of doped titanium dioxide has been observed in visible light range (i.e., at wavelength >400 nm). In this review, different synthesis route for doping of metal ions in titanium dioxide have been emphasised. The effect of metal dopant on the structural, textural and photocatalytic properties of titanium dioxide has been reviewed.

Journal ArticleDOI
TL;DR: In this paper, a SiC PiN rectifier module consisting of five parallel large area 6.4 mm x 6. 4 mm rectifiers is connected as a free-wheeling diode with a Si IGBT and 1100 V/100 A switching transients are recorded.
Abstract: Sharp avalanche breakdown voltages of 12.9 kV are measured on PiN rectifiers fabricated on 100 µm thick, 3 x 1014 cm-3 doped n- epilayers grown on n+ 4H-SiC substrates. This equates to a record high 129 V/µm for a > 10 kV device. Optimized epilayer, device design and processing of the SiC PiN rectifiers result in a > 60% blocking yield at 10 kV, ultra-low on-state voltage drop and differential on-resistance of 3.75 V and 3.3 mΩ-cm2 at 100 A/cm2 respectively. Open circuit voltage decay (OCVD) measured carrier lifetimes in the range of 2-4 µs are obtained at room temperature, which increase to a record high 14 µs at 225 °C. Excellent stability of the forward bias characteristics within 10 mV is observed for a long-term forward biasing of the PiN rectifiers at 100 A/cm2. A PiN rectifier module consisting of five parallel large area 6.4 mm x 6.4 mm 10 kV PiN rectifiers is connected as a free-wheeling diode with a Si IGBT and 1100 V/100 A switching transients are recorded. Data on the current sharing capability of the PiN rectifiers is also presented.

Journal ArticleDOI
TL;DR: In this article, the effect of processing on structure and texture in titanium alloys has been reviewed, focusing on the understanding of this relationship that has evolved over the last decade and tracing the strong dependence of thermomechanical pathways on the final structure and textures.
Abstract: We review the effect of processing on structure and texture in titanium alloys, focusing on the understanding of this relationship that has evolved over the last decade. Thermomechanical processing cycles for these alloys involve deformation and heat treatment in single phase β and two phase, α+β, phase fields, and involves a complex interplay between deformation and recrystallization textures of the individual phases, textures arising from the crystallographic relationship between the two phases, and the scale of microstructure evolution. We explore these interactions and trace the strong dependence of thermomechanical pathways on the final structure and texture.

Journal ArticleDOI
TL;DR: In this article, the influence of hot-working conditions on recrystallization behavior of high-manganese austenitic steels was investigated and the microstructure evolution in successive stages of deformation was determined using light microscopy.
Abstract: The high-manganese austenitic steels are an answer for new demands of automotive industry concerning the safety of passengers by the use of materials absorbing high values of energy during collisions. The chemical compositions of two high-manganese austenitic steels containing various Al and Si concentrations were developed. Additionally, the steels were microalloyed by Nb and Ti in order to control the grain growth under hot-working conditions. The influence of hot-working conditions on a recrystallization behaviour was investigated. Flow stresses during the multistage compression test were measured using the Gleeble 3800 thermo-mechanical simulator. To describe the hot-working behaviour, the steel was compressed to the various amount of deformation (4x0.29, 4x0.23 and 4x0.19). The microstructure evolution in successive stages of deformation was determined in metallographic investigations using light microscopy. The flow stresses are much higher in comparison with austenitic Cr-Ni and Cr-Mn steels and slightly higher compared to Fe-(15-25) Mn alloys. Making use of dynamic and metadynamic recrystallization, it is possible to refine the microstructure and to decrease the flow stress during the last deformation at 850°C. Applying the true strains of 0.23 and 0.19 requires the microstructure refinement by static recrystallization. The obtained microstructure – hot-working relationships can be useful in the determination of powerful parameters of hot-rolling and to design a rolling schedule for high-manganese steel sheets with fine-grained austenitic structures.

Journal ArticleDOI
TL;DR: In this paper, an experimental attempt to separate the two physically different effects has been made by conducting photoluminescence (PL) mapping experiments which allowed simultaneous measurements of partial dislocation velocity and SF-originated PL intensity the latter of which is related to the driving force for stacking faults expansion through the density of free excitons planarly confined in the SF.
Abstract: Anomalous expansion of stacking faults (SFs) induced in 4H-SiC under electronic excitations is driven by an electronic force and is achieved by enhanced glide of partial dislocations. An experimental attempt to separate the two physically different effects has been made by conducting photoluminescence (PL) mapping experiments which allowed simultaneous measurements of partial dislocation velocity and SF-originated PL intensity the latter of which is proposed to be related to the driving force for SF expansion through the density of free excitons planarly confined in the SF.

Journal ArticleDOI
TL;DR: In this paper, an integrated bipolar OR-NOR gate based on emitter coupled logic (ECL) is demonstrated in 4H-SiC. Operated from 27 up to 300 °C on −15 V supply voltage, the logic gate exhibits stable noise margins (NMs) of about 1 V in the entire temperature range.
Abstract: An integrated bipolar OR-NOR gate based on emitter coupled logic (ECL) is demonstrated in 4H-SiC. Operated from 27 up to 300 °C on –15 V supply voltage the logic gate exhibits stable noise margins (NMs) of about 1 V in the entire temperature range.

Journal ArticleDOI
TL;DR: A critical analysis of the available literature has been made and some general conclusions have been drawn related to the above mentioned parameters as discussed by the authors, and the photocatalytic degradation pathways for carboxylic acids are also discussed to understand this process thoroughly.
Abstract: Among the new oxidation methods in advanced oxidation processes, heterogeneous photocatalysis based on UV/ titanium dioxide is one of the emerging technologies for degrading and totally mineralizing toxic and highly stable carboxylic acids from waste water has attracted great attention in last decade. The aliphatic and aromatic carboxylic acids are widely used as reactants or produced as main products or byproducts in various chemical process industries. These chemical process industries generates waste water containing significant amount of carboxylic acids, which need to be removed from waste water before disposal to natural water bodies due to the environmental restrictions and their hazardous effects on flora and fauna. This paper reviews photocatalytic degradation (PCD) process for various carboxylic acids in detail, including basic mechanism of titanium dioxide, effect of carboxylic acid structure and various reaction parameters like effect of initial concentration and kinetic study, catalyst loading, pH, adsorption and deactivation of the photocatalyst. A critical analysis of the available literature has been made and some general conclusions have been drawn related to the above mentioned parameters. The photocatalytic degradation pathways for carboxylic acids are also discussed to understand this process thoroughly.

Journal ArticleDOI
TL;DR: In this article, a 6x150mm/10x100mm Warm-Wall Planetary Vapor-Phase Epitaxial (VPE) Reactor was used for SiC epitaxial growth.
Abstract: Initial results are presented for SiC-epitaxial growths employing a novel 6x150-mm/10x100-mm Warm-Wall Planetary Vapor-Phase Epitaxial (VPE) Reactor. The increased areal throughput offered by this reactor and 150-mm diameter wafers, is intended to reduce the cost per unit area for SiC epitaxial layers, increasing the market penetration of already successful commercial SiC Schottky and MOSFET devices [1]. Growth rates of 20 micron/hr and short

Journal ArticleDOI
TL;DR: In this paper, the authors discuss the entire scope from the preparation of the used powders, the different manufacturing steps and their optimization potential up to the final tape-cast product and the influence of the use of pore forming agents, heat treatment or other parameters during processing.
Abstract: Tape casting is widely used in industrial scale for production of multilayer ceramic capacitors or substrates for different applications. In 2009, it was successfully introduced as standard shaping technology for 3 (BSCF) are shown. The entire scope from the preparation of the used powders, the different manufacturing steps and their optimization potential up to the final tape-cast product will be discussed. The influence of the use of pore forming agents, heat treatment or other parameters during processing will be described in detail. Finally, the option of sequential tape casting of different materials for graded structures as a future step in shaping technology will be presented for different applications.

Journal ArticleDOI
TL;DR: In this article, the authors explore the basic features of this model in the simulation of the excess vacancy evolution during technological heat treatments, and the focus of this article lies on the effect of vacancy supersaturation during different heat treatment steps, such as quenching, heating, natural and artificial aging.
Abstract: 6xxx Al alloys owe their superior mechanical properties to the precipitation of finely dispersed metastable β´´ precipitates. These particles are formed in the course of optimized heat treatments, where the desired microstructure is generated in a sequence of precipitation processes going from MgSi co-clusters and GP zones to β´´ and β´ precipitates and finally to the stable β and Si diamond phases. The entire precipitation sequence occurs at relatively low temperatures (RT to approx. 200 °C) and is mainly controlled by the excess amount of quenched-in vacancies, which drive the diffusional processes at these low temperatures. Very recently a novel model for the prediction of the excess vacancy evolution controlled by the annihilation and generation of vacancies at dislocation jogs, grain boundaries and Frank loops was developed and implemented in the thermo-kinetic software MatCalc. In the present work, we explore the basic features of this model in the simulation of the excess vacancy evolution during technological heat treatments. The focus of this article lies on the effect of vacancy supersaturation during different heat treatment steps, such as quenching, heating, natural and artificial aging.

Journal ArticleDOI
Yuki Nakano1, Ryota Nakamura1, Hiroyuki Sakairi1, Shuhei Mitani1, Takashi Nakamura1 
TL;DR: In this article, the double-trench MOSFET was proposed to improve the oxide destruction at the trench bottom during high drain-source voltage application, which has both source trenches and gate trenches.
Abstract: The trench gate structure MOSFET, with its lack of JFET resistance, is one of the structures able to achieve low on-state resistance [1,2]. In 2008, this group succeeded in fabricating 790V SiC trench MOSFETs with the lowest Ron,sp (1.7 mΩcm2) at room temperature. However these devices had issues regarding oxide destruction at the trench bottom during high drain-source voltage application. In order to improve this problem, this group developed the double-trench MOSFET structure. This structure has both source trenches and gate trenches. This paper compares two kinds of trench MOSFETs: the conventional, single trench structure and a double-trench structure. Also, the latest characteristics are presented.

Journal ArticleDOI
TL;DR: In this article, the authors present a foresight project to identify the priority innovative technologies and strategic research trends in the scope of surface structure and properties formation of engineering materials and biomaterials whose development in the country will be of key importance within next 20 years.
Abstract: Throughout history, a substantial or often leap technological progress, was determined by the availability of new engineering materials, which usually stimulated the improvement in the quality of life. The development of engineering materials constitutes one of the most significant elements in the field of science and technology, and innovative policy in Poland and Europe as regards the knowledge-based economy (KBE). The enhancement of the product functional properties, required by the new strategies of engineering materials development, as well as materials processing technologies is frequently connected with appropriate formation of the engineering materials surface layer structure and properties. Functional properties of many products depend not only on the possibility of transferring the mechanical load across the whole element section or its physicochemical properties, but, most often, they depend mainly on the surface layer structure and properties. The application of foresight methodology in the assessment of the state and prospects regarding the development of technology related to the formation of the materials surface structure and properties provides the possibility to manage knowledge in this field. It can be achieved through a formalization of the explicit and tacit knowledge gathering and use in order to increase production competitiveness, effectiveness, and innovation, improve the quality of life and achieve sustainable development. The objectives accomplished in such a way contribute to the increase in intellectual capital by enhancing the effectiveness of using the existing knowledge, creating new knowledge, as well as increasing the level of understanding and disseminating knowledge. The implemented foresight project will result in identifying the priority innovative technologies and strategic research trends in the scope of surface structure and properties formation of engineering materials and biomaterials whose development in the country will be of key importance within next 20 years.

Journal ArticleDOI
TL;DR: In this paper, the conversion process from a threading screw dislocation into a few Frank partial dislocations in basal planes was investigated by synchrotron X-ray topography.
Abstract: Solution growth is considered to be a powerful method for high quality SiC crystals. This work reports that the conversion process from a threading screw dislocation into a few Frank partial dislocations in basal planes was investigated by synchrotron X-ray topography. This process was effectively assisted by step-flow growth on off-oriented (0001) seed crystals. The Frank partials were not extended into the crystal grown toward the [0001] direction perpendicular to the basal plane. Thus, the conclusion of this study suggests the use of off-oriented seed crystal is important to improve crystal quality.

Journal ArticleDOI
TL;DR: In this article, the results related to the replacement of sand by sewage sludge ash were presented for chemical composition (XRF analysis), crystalline phases (XRD analysis), and pozzolanic activity.
Abstract: The production of sewage sludge from waste water treatment plants is increasing all over the world. Disposal of sewage sludge ash is a serious environmental problem. If we think of the areas needed for sludge ash disposal, we clearly understand the importance of reusing sewage sludge ash in concrete. This paper presents results related to the replacement of sand by sewage sludge ash. The sludge was characterized for chemical composition (XRF analysis), crystalline phases (XRD analysis) and pozzolanic activity. The effects of incineration on crystal phases of dry sludge were investigated. Two (W/C) ratios (0.55 and 0.45) and three sludge percentages (5%, 10% and 20%) by cement mass were used. The mechanical performance of SSAC at different curing ages (3, 7, 28 and 90 days) was assessed by means of mechanical tests. Results show that sewage sludge ash leads to a reduction in density and mechanical strength. Results also show that concrete with 20% of sewage sludge ash and W/C=0.45 has a 28 day compressive strength of almost 30MPa.

Journal ArticleDOI
TL;DR: In this article, the authors provide a comprehensive picture of the photo catalytic reduction of carbon dioxide and artificial photo synthesis to yield hydrogen and hydrocarbons like methane, methanol etc.
Abstract: Photo catalytic reduction of carbon dioxide or artificial photo synthesis to yield hydrogen and hydrocarbons like methane, methanol etc., has emerged as a subject/process of intensive study due to its potential applications towards abatement of atmospheric CO2 levels and conversion to fuels and chemicals. This Chapter provides a comprehensive picture of the process that has posed several scientific and technological challenges, like activation of most stable molecules-CO2 and water, extremely low conversion rates, complex reaction pathways involving multi electron transfer steps and short catalyst life. All the major aspects/developments on this process like, the salient features and technological aspects, thermodynamic and kinetic characteristics, various types of photo-active catalysts-, like, titania based catalysts and titania with various dopants and modifiers, various metal oxides/sulfides/nitrides/ layered titanates, binary and ternary oxides of Nb, Ta, Ga & In mixed oxide catalysts, metal complexes, and supra molecular catalysts-, sensitization by macro cylic ligands, influence of process parameters, catalyst structure-property-activity correlations, aspects of deactivation of catalysts, reaction mechanistic aspects and sequential surface reaction pathways, recent trends and future directions have been covered. Design and development of efficient catalyst systems and achieving higher yield of desired products (higher selectivity) and extending the catalyst life are the key issues being pursued by the researchers. The process is in nascent stage and further improvements are needed as CO2 conversion rates are extremely small, with products formed in terms of 1-10 micro moles/hr. One of the means of improving the process efficiency is to carry out electrochemical reduction of CO2 using solar electric power, with an integrated Photo electrochemical cell (PEC). Yet another option is to reduce CO2 to methanol with hydrogen produced using solar powered PEC.