Corrosion behavior of tempered dual-phase steel embedded in concrete

Dual-phase(DP) steels with different martensite contents were obtained by appropriate heat treatment of an SAE1010 structural carbon steel,which was cheap and widely used in the construction industry. The corrosion behavior of DP steels in con-crete was investigated under various tempering conditions. Intercritical annealing heat treatment was applied to the reinforcing steel to obtain DP steels with different contents of martensite. These DP steels were tempered at 200,300,and 400°C for 45 min and then coo...     

Identification of Ti incorporation into β-SiAlON crystal structure through transmission electron microscopy techniques

In this paper, we report the transmission electron microscopy (TEM) observations on the incorporation of Ti transition metal element into β-SiAlON crystal structure in a bulk β-SiAlON–TiN composite material. Considering our energy dispersive X-ray (EDX) and electron energy loss (EEL) spectroscopy results acquired by using nanometre-scale focused electron probe in scanning transmission electron microscopy (STEM) mode, the Ti-K characteristic X-ray lines and Ti-L_3,2 edges were detected in the chemical composition of the β-SiAlON grains. These results clearly reveal that Ti can enter into the β-SiAlON crystal structure. It is anticipated that this data will provide the new engineering insights on the production of transition metal element doped SiAlON-based materials for different applications.     

Myoglobin adsorption onto poly(glycidyl methacrylate) microbeads with surface functionalized iminodiacetic acid

In this study, poly(glycidyl methacrylate) [PGMA] microbeads with surface modified iminodiacetic acid (IDA) were used for myoglobin (Mb) adsorption from buffer solutions at different pHs and ionic strengths in a packed-bed column. Attenuated Total Reflectance Fourier Transformed Infrared (ATR-FTIR) spectroscopy and scanning electron microscopy (SEM) measurements before and after the adsorption process confirmed the structural stability of adsorbed Mb. The effects of initial concentration, flow-rate, pH and ionic strength on the adsorption were investigated. The results showed that the maximum amount of protein was adsorbed at a pH 7.0, which is the protein isoelectric point. The adsorption is rationalized in terms of local electrostatic forces acting between the protein and the IDA modified PGMA surface as well as hydrophobic interactions close to the protein isoelectric point, whereas at low pH the global changes give rise to protein–protein repulsion and at high pH protein-support material repulsion.     

Co-doped willemite ceramic pigments: Technological behaviour,crystal structure and optical properties

Cobalt-doped willemite is a promising blue ceramic pigment, but some important aspects concerning crystal structure, optical properties and technological behaviour are still undisclosed. In order to get new insight on these features, willemite pigments (Zn_2?xCo_xSiO₄, 0 < x < 0.3) were synthesized by the ceramic route and characterized from the structural (XRPD with Rietveld refinement), optical (DRS and colorimetry), microstructural (SEM, STEM, TEM, EDX, EELS) and technological (simulation of the ceramic process) viewpoints. The incorporation of cobalt in the willemite lattice, taking preferentially place in the Zn1 tetrahedral site, induces an increase of unit-cell parameters, metal–oxygen distances, and inter-tetrahedral tilting. It causes shifting and enhanced splitting of spin-allowed bands of Co²⁺ in tetrahedral coordination, implying slight changes of crystal field strength Dq and Racah B parameter, but increasing spin-orbit coupling parameter λ. Willemite pigments impart deep blue hue to ceramic glazes and glassy coatings with a colouring performance better than commercial Co-bearing colorants in the 800–1200 °C range. Detailed SEM-TEM investigation and microanalysis proved that no diffusion phenomena occur at the pigment–glassy coating interface and that willemite pigments are chemically inert during firing at 1050 °C.     

The mechanism for the colour change of iron chromium black pigments in glazes through transmission electron microscopy techniques

Black iron-chromium (Fe-Cr) bearing oxide pigments are generally utilised as effective colourants in a wide variety of applications. However, in the case of their use within ZnO-containing glazes, they yield an undesirable brown colour instead of expected black colour. In order to understand the colour change in this system, we report the use of focused ion beam (FIB) sample preparation technique followed by the use of analytical transmission electron microscopy (TEM) characterisation techniques. According to the results, the formation of a reaction layer between the pigment and glaze was identified with an average composition of Zn_0.48Fe_0.79Cr_1.32O₄. Additionally, the valance of Fe was determined as 3+ in the pigment grain, whereas 2+ in the reaction layer and the glaze, respectively. Therefore, it was concluded that the colour change is occurring as result of the valence variation of Fe, the formation of Zn_0.48Fe_0.79Cr_1.32O₄ compound and the outward diffusion of Fe into the glaze.     

An expert system for the humidity and temperature control in HVAC systems using ANFIS and optimization with Fuzzy Modeling Approach

The aim of this study is to design a HVAC system which damper gap rates have been controlled by PID controller. One of the dampers was controlled by using the required temperature for the interested indoor volume while the other damper was controlled by using the required humidity for the same indoor volume. The realized system has a zone with variable flow-rate by considering the ambient temperature and humidity. In the authors’ previous theoretical work, PID parameters were theoretically obtained by using fuzzy sets for the same HVAC system. Optimization with Fuzzy Modeling Approach of PID parameters has been performed to maximize the performance of the system. The obtained PID parameters in the previous theoretical work were used in this study. Besides, the damper gap rates of a HVAC system with only one zone were predicted by using Artificial Neural Fuzzy Interface System (ANFIS) method. The input-output data sets of this system were first stored and then these data sets were used to obtain its intelligent model and control based on ANFIS. Efficiency of the developed ANFIS method was tested and a mean 99.98% recognition success was obtained. This paper shows that the values predicted with the ANFIS can be used to predict damper gap rate of HVAC system quite accurately. Therefore, faster and simpler solutions can be obtained based on ANFIS.     

Capacitor-Discharge Joining of Oxide Ceramics

A capacitor-discharge joining technique has been used to fabricate alumina–metal–alumina and zirconia–metal– zirconia joints using thin foils of aluminum, titanium, or amorphous Al_x Ni_y Y_z alloys as interlayers. The technique involves passing a high-energy pulse through a conductive interlayer, so converting the interlayer into a liquid-vapor "energized foil" which wets and bonds the pieces of ceramic being joined. The bond strengths of the joints were mea-sured by shear testing which showed that the highest bond strengths for both alumina and zirconia substrates were obtained when an amorphous Al_x Ni_y Y_z interlayer was used. An investigation of the interfacial structure of the joints revealed that there is a distinct reaction layer between the ceramic substrate grains and the amorphous Al_x Ni_y Y_z interlayer.     

Complexity and performance of an Augmented Lagrangian algorithm

Algencan is a well established safeguarded Augmented Lagrangian algorithm introduced in [R. Andreani, E. G. Birgin, J. M. Martínez, and M. L. Schuverdt, On Augmented Lagrangian methods with general lower-level constraints, SIAM J. Optim. 18 (2008), pp. 1286–1309]. Complexity results that report its worst-case behaviour in terms of iterations and evaluations of functions and derivatives that are necessary to obtain suitable stopping criteria are presented in this work. In addition, its computational performance considering all problems from the CUTEst collection is presented, which shows that it is a useful tool for solving large-scale constrained optimization problems.     

Effect of heat treatment on the creep behavior of α/β SiAlON sintered with multication oxide sintering additives

SiAlONs are important materials for high-temperature applications and creep properties of SiAlONs are largely controlled by the amount and type of sintering additives. It has been established that heat treatment can reduce the amount of amorphous intergranular phase through crystallization. However, there is no study on the creep behavior of heat-treated SiAlON ceramics containing multication sintering additives. Therefore, the aim of the study was to investigate the effect of heat treatment on the creep properties of multication containing (Y-Sm-Ca oxides) α/β-SiAlON ceramics. The heat treatments of the sintered samples were carried out at 1600°C for 2 hours. The creep tests were carried out in the range 1300-1400°C under different loads (50-150 MPa). The existing phases and the microstructures of samples before and after creep were investigated using XRD and SEM techniques. It was found that heat treatment resulted in a better creep performance compared to as-sintered samples. The activation energy and stress exponent for heat-treated SiAlONs were also calculated as 708 ± 45 kJ/mol and 1.4, respectively. Compared to the sintered sample values, the results suggested that the acting creep mechanism of grain-boundary sliding and cavitation was reduced with the heat treatment.