Synthesis of boron carbide (B4C) as one of the hardest materials on planet Earth is of particular importance due to its wide range of industrial and engineering applications. For this purpose, boric acid and polymers can be used as the boron and carbon sources, respectively. From the family of saccharides in polymeric materials, glucose has shown the best performance for the synthesis of B4C. In this research, untreated and pretreated (caramelized by heating) glucose precursors were selected and mixed with boric acid for subsequent pyrolysis and synthesis processes. X-ray diffractometry and Fourier transform infrared spectroscopy confirmed that heat-treated glucose is a better carbon precursor for B4C synthesis. In order to evaluate the effect of the amount of boric acid, more than its stoichiometric ratio, additional amounts of boric acid (10-40%) were also examined and the excess amount of 30% was determined as the optimal value.

In order to study the effects of sintering conditions on the properties of TiAl-based materials, two different compositions (TiAl-15 wt% Ti₃AlC₂ and TiAl-25 wt% Ti₃AlC₂) were chosen and manufactured by spark plasma sintering at 900 ºC/7 min and 1000 ºC/15 min. The results showed that increasing the MAX phase content had positive effect on the relative density and mechanical properties, but simultaneous increasing the temperature and holding time is more effective in improvement of properties. For TiAl-15 wt% Ti₃AlC₂ sample, the relative density, Vickers hardness, fracture toughness, and bending strength increased from 92.3%, 3.6 GPa, 10.9 MPa.m^1/2, and 206 MPa to 95.2%, 4.5 GPa, 12.0 MPa.m^1/2, and 336 MPa, respectively, as the sintering temperature and holding time increased from 900 ºC/7 min to 1000 ºC/15 min. In the case of TiAl-25 wt% Ti₃AlC₂ sample, increasing the sintering temperature and holding time from 900 ºC/7 min to 1000 ºC/15 min led to the improvement of relative density, Vickers hardness, fracture toughness, and bending strength from 92.8%, 4.1 GPa, 11.2 MPa.m^1/2, and 270 MPa to 97.5%, 4.6 GPa, 11.8 MPa.m^1/2, and 340 MPa, respectively.

A novel Mg-0.7Ca alloy was prepared by the mechanical alloying (MA) process. Different variables were examined in order to obtain the optimum sample with the best milling behavior and potential sinterability. The structural studies were carried out using X-ray Diffractometer (XRD) and scanning electron microscopy (SEM). Crystallite size and lattice strain of the milled samples were examined by Scherrer and Williamson-Hall methods in order to finalize the investigation. The optimum milling time was found to be 60 minutes. In addition, a starch-containing sample with a fraction of 2.5 weight percent seemed to have the best microstructural properties, based on SEM observations and crystallite size assessments. Due discussions about the effective phenomena during the mechanical alloying were also included.

In this paper, the variables of the pyrolysis operation such as temperature, time, and atmosphere were studied and optimized. At first, the effect of increasing pyrolysis time at lower temperatures was investigated to understand the mutual influence of pyrolysis time and temperature in enhancing the efficiency of B₄C synthesis. Then, three pyrolysis atmospheres were selected to find the optimal conditions: burial method in box furnace (air), pyrolysis in tubular furnace (argon), and pyrolysis in box furnace (air). The pyrolyzed powders were finally located inside the tubular furnace at 1500 °C for 4 h under argon atmosphere to synthesize B₄C ceramics. X-ray diffractometry (XRD) was employed to determine the optimal processing conditions. The temperature of 600 °C and the holding time of 2 h were selected as the optimal pyrolysis conditions. Meanwhile, the burial method was chosen as the best atmosphere despite having a higher percentage of impurity because of the much lower cost compared to the argon atmosphere.

Every day several tons of glass dispose as waste. Glass waste, as a non-degradable waste, causes many environmental problems. Using glass waste powder in concrete as a partial substitute for cement has notable effects on the reduction of environmental pollutants, energy consumption, and concrete production costs. In this study, the impact of using waste glass powder in levels of 5, 10, 15, and 20 wt.% as a substitute for cement on the mechanical properties of concrete was evaluated. Chemical analysis of glass and cement samples was determined using X-ray fluorescence (XRF). The flexural and compressive strength of the samples were measured according to ISO 679, Methods of testing cement – Determination of strength, in 3, 7, 28, and 90 days. The results of the compressive strength test showed that the strength of concrete increases by the amount of used glass powder in the concrete composition. The highest value of compressive strength was obtained by the sample with 15 wt.% of glass powder.

The rapid advancement in information technology, communication, and electronic devices elevates the need to develop suitable materials for microwave absorption (MA) which should have the properties of an ideal microwave absorber. Porous activated carbon from agricultural wastes has piqued the interest of MA researchers due to their distinct properties such as good specific surface area, high dielectric loss, good electrical conductivity, and low density. Herein banana peel activated carbon was prepared by activating banana peel precursor with KOH and carbonizing at different temperatures. The difference in the porous structure with varying carbonization temperature was visible in the FESEM image, validated by BET analysis. The Banana Peel Activated carbon samples exhibited good microwave absorption performance, with BP-AC700 displaying a minimum Reflection Loss (RL) of −40.62 dB at 10.72 GHz & 3.0 mm thickness. In addition, the obtained effective absorption bandwidth of 3.5 GHz spanned through the X band frequency. This exceptional microwave absorption was attained due to the sample's good conductive loss and Porous favourable morphology. This study inspires the development of future facile functional agricultural waste-derived microwave absorbers.

Polypropylene (PP) represents a considerable proportion of polyolefins (PO) used in different industrial applications such as automobile components, textiles, packaging, insulation, medical devices, various housewares and household appliances due to its efficient cost, desirable mechanical, thermal and electrical properties, easy processability and recyclability. Because of its carbonaceous structure, PP is a highly flammable material with a LOI value of 18 that presents serious fire hazard. In this research, Intumescent flame retardant (IFR) and colemanite were added to polypropylene to compose 30% of the total mass of the polymeric compounds and the synergistic effect of colemanite with intumescent flame retardant (IFR) additive in PP was investigated by limiting oxygen index (LOI), glow wire test (GWT), UL-94 test and mechanical properties measurements. The LOI, UL 94 and glow wire test results showed that colemanite had a significant effect on flame retardancy and LOI value which can reach to 37.6 % with loading level of 2 wt.% colemanite at the total amount of flame retardant additives kept constant at 30 wt.%. Additionally, the PP/IFR compounds passed UL 94 V0 rating and both 750 °C and 850 °C glow wire tests and with 2-8 wt.% colemanite loading. According to TGA analyses, the results indicated that colemanite improved the thermal stability of PP/IFR compounds and also promoted the formation of char layer. When colemanite mineral added to polypropylene without IFR system, it has no effect on flame retardancy properties of polypropylene. When all properties have been taken into consideration, colemanite can be used up to 6 wt% in IFR.

Aluminum-doped zinc oxide thin film (Al:ZnO) was derived by the sol-gel dip-coating technique to analyze the doping effect on the film’s crystal structure and optical transparency. The surface structure of the thin film had the particles in the nano-spherical form. Al amount changed surface roughness with the variation of the grain size. The crystal structure of ZnO was wurtzite (in XRD analysis). The surface morphology of the film was also examined with SEM images. The effect of Al doping was investigated to evaluate the necessary amount of Al on the optical properties. The films show high optical transparency (~85%) at specific Al doping amounts (0.8-1.6%).

In this study, the 4^th part of a series of publications on the sintering and characterization of TiAl-Ti₃AlC₂ composite materials, the mechanical properties were measured and discussed. For this purpose, different contents of synthesized Ti₃AlC₂ reinforcement (10, 15, 20, 25, and 30 wt%) were added to metallic Ti and Al powders, then ball-milled and manufactured by spark plasma sintering (SPS) for 420 s at 900 ºC under 40 MPa. Flexural strength, fracture toughness and Vickers hardness were measured by 3-point technique, SENB method, and indentation technique, respectively. Increasing the Ti₃AlC₂ content resulted in improvement of the mechanical properties, so that TiAl-25 wt% Ti₃AlC₂ composite showed the best flexural strength and Vickers hardness (270 MPa and 4.11 GPa, respectively). Increasing amount of Ti₃AlC additive had no significant effect on fracture toughness. Densification improvement, in-situ formation of Ti₂AlC, and limitation of grain growth were recognized as the reasons of mechanical properties enhancement. In contrast, further addition of Ti₃AlC₂ (30 wt%) decreased the mechanical properties due to the reduction of density and formation of more Ti₂AlC agglomerates in grain boundaries.

This study investigates the effects of adding clay and fireclay on the physical and mechanical properties of magnesia-based refractories such as contraction, bending strength, bulk density, and apparent porosity. Domestic raw materials were used for the preparation of samples fired at 1350, 1450, and 1550 °C for 2 h. Adding clay exhibited no significant effect on the density and porosity, whereas adding fireclay had a remarkable influence on the shrinkage. Nevertheless, the effects of clay and fireclay on the strength of magnesia were unnoticeable. X-ray diffraction results showed that, after firing, the main phase compositions of the samples with clay addition were periclase and forsterite. Adding fireclay led to the synthesis of magnesite spinel, which can be attributed to the high alumina content. Based on scanning electron microscopy, no liquid phase was formed indicating that the sintering was a solid-state evolution with the synthesis of forsterite.

The present work aims to prepare a dense cordierite-based glass-ceramic through slip casting and consequent heat treatment procedures. In this regard, sintering conditions were considered as the key variables to improve the properties of the glass-ceramic. For this purpose, glass frit powder was prepared through melting oxide powders (in the system of SiO₂-Al₂O₃-TiO₂-K₂O-CaO-MgO). The mixed powders were then heat treated at 1450 °C for 1 hour and quenched in water. The glass frit powder was slip cast using the appropriate dispersant. Sintering was carried out by one-step, two-step, and three-step procedures. Specimens were characterized in terms of various analysis techniques including dilatometry, X-ray diffractometry, scanning electron microscopy, and mechanical strength measurement. Among the examined specimens, the sample sintered by a three-step approach was considered the optimized one which attained zero porosity. According to the obtained results, cordierite crystals were observable in this glass-ceramic matrix. A low coefficient of thermal expansion and a low dielectric constant were observed for the optimized glass-ceramic sample. The obtained results confirmed that the homogenous distributions of crystalline phases are responsible for the appropriate and desirable properties of the prepared glass-ceramic.

ZrB2-TiC composites with and without nano-sized carbon black as the sintering additive were densified through spark plasma sintering at 1900 °C for 7 minutes under the applied pressure of 40 MPa. The role of carbon black in densification behavior, phase arrangement, microstructural characteristics and mechanical properties of the sintered composites were then investigated. While both of the composite samples were found to be fully sintered, the thermodynamic of the reactive sintering was also studied. Results indicated that whereas the reactive sintering process leads to complete consumption of TiC through the formation of the solid solution as the matrix in both of the composite samples, the presence of carbon black at the initial composition of the samples can result in remained carbon at the final microstructure. Besides the in-situ synthesized zirconium carbide as the major reinforcement phase, such a remained carbon can lead to significantly different mechanical behavior of the composites. Accordingly, the hardness of 21.8 and 24.3 GPa and the indentation fracture toughness of 3.3 and 4.5 MPa.m0.5 were obtained for carbon-black free and doped samples, respectively. The densification, hardening, and toughening mechanisms in both of the composite samples were finally discussed.

B₄C–Fe–based cermets with various Ni concentrations were produced by tube furnace sintering using the powder metallurgy method. The prepared cermets were sintered at 1000 °C under the argon shroud. Ultrasonic properties such as ultrasonic wave velocities, ultrasonic longitudinal and shear attenuation values, Young's (elastic) modulus, and Poisson’s ratio were determined by the pulse-echo method using 2 MHz and 4 MHz probes. The obtained ultrasonic properties were used to characterize the properties of the samples. It was observed that ultrasonic wave velocities and Young's modulus decreased with increasing Ni concentration. At the same time, ultrasonic attenuation values and Poisson ratio increased with increasing Ni concentration. According to the results, the amount of Ni has an effective role in the structure of the cermets.

At present, the composition and crystalline structure of transition metal nitrides or carbides (MXenes) and their derivatives are continuously expanding due to their unique physicochemical properties, especially in the photocatalytic field. Advances over the past four years have led to improved preparation of new MAX phases, resulting in new MXenes with excellent photo-thermal effect, considerable specific surface area, long-term stability and optimum activity. Since MXenes have good electrical conductivity and their bandgap is adjustable under the visible light range, this group is one of the best promising candidates for hydrogen production from photo-splitting of water as an environment-friendly method of converting sunlight to chemical energy. Progress in noble metal-free photocatalyst associated with more understanding of the fundamental mechanism of photocatalysis has enabled a proper choice of cocatalyst with better efficiency. In this study, the photocatalytic production of hydrogen through MXens as a support and co-catalyst on metal sulfide is summarized and discussed. Recent advances in the design and synthesis of MXenes-based metal sulfide nanocomposites to increase the efficiency of photocatalytic hydrogen production are then highlighted. Finally, the challenges and future prospects for the development of MXenes-based metal sulfide composites are outlined.

The paper reports, the effect of water sorption on the microstructural and flexural properties of the flax fiber/ polylactic acid (PLA) biocomposites compared to the composites with maleic anhydride (MAH) as coupling agents and alkali treatment. In the current study, five different biocomposites which are 15 % wt. flax/PLA, 25 % wt. flax/PLA as control group and15 % wt. flax/PLA, 25 % wt. flax /PLA, and 35% wt. flax / PLA with 5 % wt. MAH was produced. Ten different soaking times were studied to understand the water absorption behavior of the biocomposites. To investigate mechanical properties of the biocomposites impact test was applied on the dry and 750 h, 1850 h water sorption composites. A three-point bending test was performed on the dry and 1850 h water sorption biocomposites to determine flexural properties. Short flax fiber-reinforced PLA matrix biocomposites were compounded using extrusion and manufactured by injection molding. Flax fiber surface was treated using sodium hydroxy solution to advance the interface interaction between fiber-matrix and surface performance of the fiber and matrix. According to the results, alkali treatment improved the water gain resistance of the composites since its enhancement of the interfacial bonding. Alkali-treated composites with maleic anhydride showed the better impact and flexural strength than composites without alkali-treated after 1850 h water sorption.

Understanding the behavior of ultra-high temperature ceramics (UHTCs) against oxidation is of particular importance in high-temperature applications. In this study, ZrB₂–SiC–HfB₂ UHTC composites were fabricated by spark plasma sintering (SPS) method at different temperatures, times, and pressures to investigate the effects of sintering process variables on their oxidation resistance. Before the oxidation tests, the as-sintered samples contained ZrB₂ and SiC phases with (Zr,Hf)B₂ solid solution. The samples were subjected to oxidative conditions at 1400 °C and their relative mass changes were measured as a function of oxidation time up to 20 hours. FESEM and EDS equipment were used for microstructural and elemental analyzes of cross-sections of different oxide layers. Due to the oxygen diffusion, ZrO₂ and SiO₂ phases appeared alongside (Zr, Hf)O₂ in the surface layers. After identifying the several oxides and SiC-depleted layers in the oxidation-affected zone, a schematic model for the arrangement of such layers was proposed.

Boron carbide is the third hardest material in the world after diamond and cubic boron nitride, which is one of the most strategic engineering ceramics in various industrial applications. The aim of this research is to synthesize B₄C by reacting boric acid as boron source with polymers from the saccharide family as carbon sources, and to determine the best saccharide as precursor. For this purpose, glucose (monosaccharide), sucrose (disaccharide), and cellulose (polysaccharide) were used and examined. The samples were prepared by appropriate mixing of the starting materials, pyrolysis at 700 °C, and synthesis at 1500 °C. The results of Fourier transform infrared (FT-IR) spectroscopy and X-ray diffractometry (XRD) showed that among the studied saccharide polymers, glucose is the best carbon source candidate for the synthesis of B₄C. To describe precisely, the specimen prepared with glucose and boric acid had more boron carbide and less hydrocarbon.

In this paper, the 3^rd part of a series of publications on the sinterability and characteristics of TiAl–Ti₃AlC₂ composites, the microstructure development during the synthesis and sintering processes was studied by scanning electron microscopy (SEM). Chemical evaluation of various phases in the developed microstructures was performed using energy-dispersive X-ray spectroscopy (EDS) in different ways such as point, line scan and two-dimensional elemental map analyses. For this purpose, five samples were fabricated with different percentages of Ti₃AlC₂ MAX phase additive (10, 15, 20, 25 and 30 wt%). Ball-milling and spark plasma sintering (SPS: 900 °C/7 min/40 MPa) of as-purchased Al and Ti powders with already-synthesized Ti₃AlC₂ additive were selected as composite making methodology. SEM/EDS analyses verified the in-situ manufacturing of TiAl/Ti₃Al intermetallics as the matrix during the SPS process and the presence of Ti₃AlC₂ as the ex-situ added secondary phase. Moreover, the in-situ synthesis of Ti₂AlC, another member of MAX phases in Ti-Al-C system, was also detected in titanium aluminide grain boundaries and attributed to a chemical reaction between TiC (an impurity in the initial Ti₃AlC₂ additive) and TiAl components.

In this study, the structural chemistry of Fe³⁺ doped Li₂O–Al₂O₃–SiO₂–TiO₂ (LAST) glasses has been analyzed utilizing UV-Vis spectroscopy. Optical parameters like absorption and extinction coefficients, indirect and direct optical band gaps, Urbach energy as well as Fermi energy level of samples were estimated via their absorption spectra. Then, it was tried to make a relationship between the variation of mentioned parameters and structural chemistry of different doped samples. Results of the investigation illustrated that even a little change in the microstructure of glassy samples has an effect on optical parameters and accordingly it could be sensible. Furthermore, it was revealed that Fe³⁺ ions have the role of network forming in the structure of glass by increasing the formation of bridging oxygens (BOs) in the matrix.

In this research, the radiation-heterogeneous processes of water decomposition on the surface of zirconium dioxide nanoparticles (n-ZrO₂) were studied. The kinetics of buildup of molecular hydrogen during the radiolytic processes of water decomposition was also examined. The production of H₂ and H₂O₂ through water radiolysis was investigated to develop a computational model and disclose the kinetic behavior of water radiolysis. The enthalpy of ZrO₂ nanoparticles was studied at the temperature range T=1200-2900 K, in which ZrO₂ nanoparticles has a two-phase transition. Some of the electrons were transported to the surface of the nanoparticles during the physical and physicochemical stages of the process and emitted into the water. At the same time, the migration of energy carriers in radioactively active oxide compounds changed at different intervals depending on the composition, structural stability, and electro-physical properties of the oxides.

Fe-32Mn-6Si alloy was produced using the mechanical alloying (MA) process of high purity powders under an inert argon gas atmosphere. The aim of this investigation is the in-depth study of the microstructure and phase transformation during the milling-sintering process of Fe-32Mn-6Si shape memory alloys. During the milling process, a significant amount of amorphous phase was created as well the crystalline martensite and austenite phases. The amorphous phase was increased by milling time enhancement and then it was decreased due to the mechano-crystalization phenomenon. It was detected that the microhardness of the alloyed powder directly depends on the amount of the amorphous phase. Furthermore, the particle size of as-milled powder firstly decreased and then increased, when the amorphous phase cojoined gradually during the milling process the transformation of martensite into austenite. The lattice strain was increased considerably during the milling process which was a reason for martensite phase creation resulting in the high shape memory properties. The amount of pre-strain for Fe-32Mn-6Si alloy was calculated to be 3.3%. Furthermore, the optimum sintering temperature was approved to be 950 ^°C by reduction of the percentage of pores and suitable densification.

Zinc oxide nanoparticles (ZnO) exhibit numerous characteristics such as biocompatibility, UV protection, antibacterial activity, high thermal conductivity, binding energy, and high refractive index that make them ideal candidates to be applied in a variety of products like solar cells, rubber, cosmetics, as well as medical and pharmaceutical products. Different strategies for ZnO nanoparticles’ preparation have been applied: sol-gel method, co-precipitation method, etc. The sol-gel method is an economic and efficient chemical technique for nanoparticle (NPs) generation that has the ability to adjust the structural and optical features of the NPs. Nanostructures are generated from an aqueous solution including metallic precursors, chemicals for modifying pH using either a gel or a sol as a yield. Among the various approaches, the sol-gel technique was revealed to be one of the desirable techniques for the synthesis of ZnO nanoparticles. In this review, we explain some novel investigations about the synthesis of zinc oxide nanoparticles via sol-gel technique and applications of sol-gel zinc oxide nanoparticles. Furthermore, we study recent sol-gel ZnO nanoparticles, their significant characteristics, and their applications in biomedical applications, antimicrobial packaging, drug delivery, semiconductors, biosensors, catalysts, photoelectron devices, and textiles.

In recent decades, the use of photocatalysts in the evolution of hydrogen (H₂) has received much attention. However, the use of the well-known titanium oxide and another photocatalyst as a base for noble metals is limited due to their major weakness in electron-hole pair separation. The use of cocatalysts can be a good way to overcome this problem and provide better performance for the evolution of hydrogen. In this review, suitable high-efficiency cocatalysts for solar hydrogen production have been thoroughly reviewed. New strategies and solutions were examined in terms of increasing the recombination of charge carriers, designing reactive sites, and enhancing the wavelengths of light absorption. Several new types of cocatalysts based on semiconductors in noble groups and dual metals have been evaluated. It is expected that these photocatalysts will be able to reduce the activation energy of reaction and charge separation. In this regard, the existing views and challenges in the field of photocatalysts are presented. The characteristics of monoatomic photocatalysts are reviewed in this manuscript and the latest advances in this field are summarized. Further, the future trends and upcoming research are also briefly discussed. Finally, this review presents noble metal-based photocatalysts for providing suitable photocatalysts on a larger scale and improving their applicability.

This study aimed to investigate the effect of sintering temperature on Ti₃SiC₂ samples' microstructure and mechanical properties, including three-point flexural strength, Vickers hardness, and fracture toughness. Therefore, Ti₃SiC₂ samples were sintered under a vacuum atmosphere at a pressure of 35 MPa for 30 minutes at two temperatures of 1500 and 1550 °C by hot pressing. The microstructure obtained from the fracture cross-section of the samples shows that by increasing the sintering temperature to 1550 °C the microstructure of this sample becomes larger than the sintered sample at 1500 °C. Also, increasing the sintering temperature to 1550 °C causes the decomposition of Ti₃SiC₂ to TiC, which can be seen in the X-ray diffraction pattern (XRD). In addition, the relative density of the sintered sample at 1550 °C is 98.08% which is higher than that of the sintered sample at 1500 °C with the result of 89%. On the other hand, the three-point flexural strength (227.5 MPa), the Vickers hardness (~9 GPa), and the fracture toughness (8.6 MPa.m^1/2) of the sintered sample at 1500 °C are higher due to the fine-grained structure.

In this research, the 2^nd part of a series of papers on the processing and characterization of TiAl–Ti₃AlC₂ composites, the phase evolution during the manufacturing process was investigated by X-ray diffraction (XRD) analysis and Rietveld refinement method. Metallic Ti and Al powders with different amounts of previously-synthesized Ti₃AlC₂ additives (10, 15, 20, 25 and 30 wt%) were ball-milled and densified by spark plasma sintering (SPS) under 40 MPa for 7 min at 900 °C. Before the sintering process, XRD test verified that the powder mixtures contained metallic Ti and Al as well as Ti₃AlC₂ and TiC (lateral phase synthesized with Ti₃AlC₂) phases. In the sintered composites, the in-situ synthesis of TiAl and Ti₃Al intermetallics as well as the presence of Ti₃AlC₂ and the formation and Ti₂AlC MAX phases were disclosed. The weight percentage of each phase in the final composition of the samples and the crystallite size of different phases were calculated by the Rietveld refinement method based on the XRD patterns. The size of Ti₃AlC₂ crystallites in sintered samples was compared with the crystallite size of synthesized Ti₃AlC₂ powder.

In this study, the UHTC-based composite layers where applied on the graphite substrates using SPS method to protect them against ablation. The protective layers had some defects and problems such as crack, fracture, separation, melting, and weak adhesion to the substrate. Several factors such as the thickness of composite layer, the number of protective layers, the SPS conditions (temperature, applied pressure, soaking time and mold), the chemical composition of the layers, the type of the substrate and the mismatch between the thermal expansion coefficients of the substrate and the applied layer(s) affected the quality and connection of the protective layer to the graphite substrate. The amount of additive materials influenced the melting phenomenon in the composite layer; for example, further MoSi2 in the layer led to more melting. The mismatch between the thermal expansion coefficients of the graphite substrate and the composite layer caused stresses during the cooling step, which resulted in cracks in the applied layer. Hence, proximity in the thermal expansion coefficients seems to be necessary for the formation of an acceptable adhesion between the layer and the substrate.

CaTi1-x(Nb1/2Al1/2)xO3 with x=0.1-0.5 ceramics were processed through solid state sintering. X-rays diffraction (XRD) patterns of the compositions showed that the samples have orthorhombic crystal structure with symmetry (Pbnm). The symmetry was further confirmed using Raman spectroscopy. A total of 13 Raman modes were detected, which were in agreement with the XRD results. Microstructure analysis of the samples showed porosity in the samples, presumably due to the substitution of Al, having high melting point. As the concentration of Al and Nb increased, relative permittivity (er), quality factor (Q×fo) and temperature coefficient of resonance frequency decreased. Optimum microwave dielectric properties were achieved for the composition x=0.5 sintered at 1650 °C for 8 h i.e., er ~27.09, Q×fo ~17378 GHz and tf ~ -2.5 ppm/°C.

Understanding the phase formation mechanisms in self-propagating high-temperature synthesis from the thermodynamical aspect of view is important. In this study, the phase formation of the ternary system of nickel-titanium-silicon was studied by using the HSC software V6.0, and phase formation is predicted by calculating the adiabatic temperature of exothermic reaction between reagents. Then, by using X-ray diffractometer analysis, the results of the simulation were evaluated by experimental achievements. Results showed a good correlation between thermodynamical calculation and prediction with experimental. It could be concluded that the equilibrium mechanism is the dominant mechanism in phase formation in the SHS synthesis method. NiTiSi solid solution phase is obtained from the reaction between Ti5Si3 and Ni2Si and Ni.

A significant proportion of mined natural corundum (ruby and sapphire) contain fractures, which negatively affects a gemstone’s clarity and value. Over the past decades, heat treatment techniques have been developed for either fracture healing, or filling to make such gems marketable. The clarity enhancement processes are mainly based on techniques which are either not durable, as in the case of lead silicate fillers, or do not yield perfect transmittance through a fracture, as in the case of borax based fluxes. Therefore, the gemstone treatment community is actively in pursuit of better techniques for clarity enhancement in corundum. Given that application of pressure is a recent advancement in the heat treatment processes of natural sapphire, it is essential to explore the possibilities regarding different outcomes such treatments can have. In this perspective paper, we have briefly described how application of pressure during heat treatments can lead to in-situ sintering of transparent polycrystalline ceramics within the fractures of corundum, which can result in clarity enhancement. Spinel-structure based fillers can be tailored to mimic corundum in terms of tribological, chemical and optical properties. Therefore, gemstones treated with such fillers will be durable, unlike currently used glass-based filler material. We also provide a possible explanation for ghost-fissures in sapphires heated under pressure, as being a by-product of in-situ sintering process of ceramic fillers that are thermodynamically compatible with Al2O3. The prospect of transparent polycrystalline ceramics in the gem and jewelry industry opens a new field of research in this area, given that ceramic fillers can outperform currently used methods and material for clarity enhancement in gemstones. In essence, we present a novel application for sintered transparent polycrystalline ceramics.

In the current work, high density polyethylene (HDPE) composites were fabricated via Friction Stir Processing (FSP). A two-phase Fe-Fe3O4 powder was used as the reinforcing agents. The extremely low cost powder was obtained from shot-blasting of as-forged low carbon steel components. X-ray diffraction (XRD) was used to phase analysis and evaluation of the purity of the as-received powder. The size distribution of the powder was determined by Laser Particle Size Analysis (LPSA). Also, Scanning Electron Microscopy (SEM) was employed to investigate the particles morphology. The processing used a cylindrical tool to impose the severe plastic deformation and material stirring in order to improve the mechanical properties and particles distribution. The tribological and mechanical properties of the fabricated samples were examined. According to the results, both the friction coefficient and specific wear rate of FSPed samples reduced remarkably. The hardness and tensile strength of the FSPed composites were higher than the FSPed HDPE samples; however, their elongations were lower.

Five TiAl–Ti3AlC2 composite samples containing (10, 15, 20, 25 and 30 wt% Ti3AlC2 MAX phase) were prepared by spark plasma sintering technique at 900 °C for 7 min under 40 MPa. For this purpose, metallic titanium and aluminum powders (aiming at the in-situ formation of the TiAl matrix phase) were ball-milled with predetermined contents of Ti3AlC2 MAX phase, which already was synthesized using the same metallic powders as well as graphite flakes. Displacement-time-temperature variations during the heating and sintering steps, displacement rate versus temperature, displacement rate versus time, and densification behavior were studied. Two sharp changes were detected in the diagrams: the first one, ~16 min after the start of the heating process due to the melting of Al, and the second one, after ~35 min because of the sintering progression and the applied final pressure. The highest relative densities were measured for the samples doped with 20 and 25 wt% Ti3AlC2 additives. More Ti3AlC2 addition resulted in decreased relative density because of the agglomeration of MAX phase particles.

Among the ongoing research on photocatalysis under visible-light, it has been shown that doped or hybrid catalysts are more active than a single catalyst alone. However, problems including visible light absorption, a low quantity of energetic sites on surfaces, and rapid recombination of the photo-electron hole pair produced by light have prohibited photocatalysts from being used in a practical and widespread manner. To overcome these problems, synthesis of nanostructure hybrid catalyst using several methods has attracted much attention. Several procedures have been suggested for the preparation of photocatalysts with the desired structure and morphology. Preparation methods similar to partial modification may lead to diverse structures and qualities. In this regard, the development of efficient, low-cost photocatalysts and rapid synthesis is the most important issues that should be considered. This review discusses various methods and mechanisms that work with the modification of vanadium compounds as photocatalysts to progress their photocatalytic efficiency. In addition, the effects of synthesis temperature, solution pH and concentration on the photocatalytic performance are also described in detail.

In this research, Cr2O3 ceramic nano-sized powder particles were prepared using ball milling and then were granulated to reach the proper size for spraying. Afterward, Cr2O3 nano-coatings were deposited by atmospheric plasma spraying (APS) process onto stainless steel substrates. To optimize APS parameters, spraying was carried out under six conditions with different parameters. Microstructures of the elemental/milled powder and coatings were characterized via a field emission scanning electron microscope (FESEM) equipped with energy-dispersive spectroscopy (EDS). In this research, Cr2O3 coatings were deposited under different spraying conditions to understand the effect of APS parameters on the splat formation, deposition efficiency, and porosities of the coatings. After parameter optimization, spraying was performed under a high deposition efficiency of 46.0±1.3%. The optimized Cr2O3 coatings showed porosity content, Knoop microhardness, and adhesive strengths of 8.7±2.2%, 823±27 HK0.2, and 49±4 MPa, respectively; making them a good candidate for industrial use.

Birefringence is a major source of difficulty in sintering of transparent polycrystalline alumina ceramics, especially as the grain size exceeds a few hundred nanometers, which ultimately leads to complete opacity, mainly due to scattering of light. Recent studies have made it clear that by application of a strong magnetic field, alumina grains can be aligned along a particular crystallographic orientation, which minimizes scattering due to birefringence, and enhances transparency. Defects that cause spin delocalization are known to induce a paramagnetic behavior in alumina ceramics. Therefore, such defects have become a focal point of research for magnetic field assisted sintering of transparent polycrystalline alumina, in order to reduce the necessary magnetic field strength during production process. In light of recent studies on paramagnetic potentials of transition metal doped alumina, we have applied Spin Polarized Density Functional Theory (SP-DFT) calculations on manganese and chromium doped and co-doped alumina to calculate the magnetic moments, density of states and defect formation energies, which should be expected from this system of dopants, along with their interactions with oxygen vacancies. The results clearly indicate that formation of a point defect comprised of chromium and manganese positioned substitutionally at adjacent aluminum sites, in vicinity of an oxygen vacancy can induce a magnetic moment equivalent to 5 Bohr magnetons (μβ), outperforming previously reported defects. Based on this study we find it likely that chromium and manganese co-doping in alumina can further reduce the required magnetic field strength for production of transparent polycrystalline alumina.

In this paper, the copper-based nanocomposites with TiO2 nanoparticles were synthesized by the self-propagating high-temperature synthesis (SHS) process. The effect of the different amounts of excess copper, in comparison with the stoichiometric ratio (CuO:Ti ratios of 1:1, 2:1, and 3:1), on the phase formation of achieved samples was studied. A thermodynamical study showed that increasing the excess copper powder reduces the adiabatic temperature, which helps the phase formation. The maximum Brinell hardness (89) was obtained for the sample with the CuO:Ti ratio of 1:1. Finally, the wear behavior of the synthesized nanocomposites was evaluated by the pin on disk test, and the variation of friction coefficient and lost weight were measured. The friction coefficient decreased by the formation of phases and distribution of titanium oxide particles during the SHS process in the presence of the stoichiometric ratio of CuO:Ti. Therefore, the wear behavior was improved. The lowest depth of wear trace was measured 0.68 where the ratio of CuO: Ti was 1:1.

In this paper, the synthesis of the copper matrix nanocomposite and the effect of adding TiB2 nanoparticles on the copper matrix was investigated. Three different amounts of TiB2 nanoparticles 5, 10, and 15 wt% were added and sintering was carried out at 900 oC for 4 hours under argon atmosphere. The phase formation of achieved nanocomposites was studied by X-ray diffractometer and the morphology of the synthesized samples was studied by field emission scanning electron microscopy and atomic force microscopy. The polarization and electrochemical impedance spectroscopy (EIS) at 3.5 wt% NaCl solution at room temperature was were carried out to evaluate the corrosion behavior of synthesized samples. Results show that adding the TiB2 nanoparticles decrease the corrosion resistance by the formation of galvanic couples, but the effect of amounts of porosities on the corrosion resistance is higher. It is revealed that the variation of the surface roughness is in direct relation to the value of polarization current density.

Dimethyl ether (DME) is a synthetically produced alternative fuel to diesel-based fuel and could be used in ignition diesel engines due to increasing energy demand. DME is considered extremely clean transportation and green fuel because it has a high cetane number (around 60), low boiling point (−25 °C), and high oxygen amount (35 wt%) which allow fast evaporation and higher combustion quality (smoke-free operation and 90% fewer NOx emissions) than other alternative CO2-based fuels. DME can be synthesized from various routes such as coal, petroleum, and bio-based material (i.e., biomass and bio-oil). Dimethyl ether can be produced from CO2 to prevent greenhouse gas emissions. This review aims to summarize recent progress in the field of innovative catalysts for the direct synthesis of dimethyl ether from syngas (CO+H2) and operating conditions. The problems of this process have been raised based on the yield and selectivity of dimethyl ether. However, regardless of how syngas is produced, the estimated total capital and operating costs in the industrial process depend on the type of reactor and the separation method.

This research is dedicated to the role of different amounts of hexagonal BN (hBN: 0, 1.5, 3, and 4.5 wt%) on the pressureless sinterability of ZrB2–25 vol% SiC ceramics. Phenolic resin (5 wt%) with a carbon yield of ~40 % was incorporated as a binder to the powder mixtures and after initial cold pressing, the final sintering process was performed at 1900 °C for 100 min in a vacuum furnace. The as-sintered specimens were characterized by X-ray diffractometry, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results disclosed that the incorporation of 1.5 wt% hBN could increase the relative density to ~92%, while the sample with zero hBN content just reached ~81% of full densification. Appropriate hBN content not only facilitated the particle rearrangement during the cold pressing, but also removed the harmful oxide impurities during the final sintering. Nevertheless, the addition of higher amounts of hBN remarkably lessened the densification because of more delamination of the non-reacted hBN flakes and release and entrapment of more gaseous by-products induced by the reacted hBN phases.

The microbial corrosion of reinforced concrete sewers was inhibited by synthesized cuprous oxide (Cu2O) nanoparticles. The antibacterial characteristics of Cu2O on Acidithiobacillus thiooxidans were investigated by temporal variation of pH, turbidity, and bacterial counting. Three reinforced concrete samples with different weight percentages of electrodeposited Cu2O (0.06 wt%, 0.055 wt %, 0.05 wt %) were used. The bacterial counting showed that the number of bacteria in samples with 0.06, 0.055, and 0.05 wt% of Cu2O was 4.82, 4.42, and 2.94 times lower than the blank sample (BS), respectively. After bacterial growth, the optical density measurement showed that the percentage of turbidity enhancement for samples with 0.06, 0.055, and 0.05 wt% of Cu2O were 108%, 118%, 165%, respectively, while it was 412% for the BS. Moreover, the pilot stage's pH monitoring revealed that the electrodeposited Cu2O lowered the concentration of hydronium between 7 to 81 times compared to the BS. Experiments indicated that slight changes in the amount of electrodeposited Cu2O lead to significant changes in samples' ability to hinder bacterial growth and microbial-induced corrosion.

The hydroxyapatite layer was deposited on the commercial magnesium alloy of AZ91 by electrophoretic deposition route, and the corrosion behavior of applied layers was studied by polarization and electrochemical impedance spectroscopy at the Simulated Body Fluid (SBF) solution. The best corrosion resistance improvement was obtained for the sample synthesized at 40 V within 4 minutes. Also, the morphology of coated samples was studied by atomic force microscopy (AFM) and the surface parameters were measured. It could be concluded that the calculated values for surface parameters including surface roughness, maximum peak height, maximum pit depth, and maximum peak have a meaningful relationship with corrosion resistance.

In this research, various types of nitride additives were incorporated into titanium diboride attaining dense TiB2-based ceramics by field-assisted sintering technique. The addition of different types of nitride additives, namely Si3N4, BN, AlN, and TiN, significantly improved the sinterability of TiB2, achieving near fully dense ceramics. The X-ray diffraction analysis and microstructural evaluation confirmed the presence of the h-BN compound in all specimens. In the TiB2-Si3N4 ceramic, Si3N4 additive reacted with B2O3 oxide, in-situ generating h-BN, and SiO2 phases. Although the h-BN phase was produced in the TiB2-AlN specimen, the main proportion of AlN remained in the sample as an unreacted ex-situ phase. In terms of the TiB2-TiN ceramic, some of the nitrogen and boron atoms could leave the TiN and TiB2 crystalline structures, contributing to the in-situ formation of h-BN.

Five carbonaceous nano-additives (graphite, graphene, carbon black, carbon nanotubes, and diamond) had different impacts on the sinterability, microstructural evolution, and properties of titanium carbide. In this research, the sintering by spark plasma was employed to produce the monolithic TiC and carbon-doped ceramics under the sintering parameters of 1900 ºC, 10 min, 40 MPa. The carbon black additive had the best performance in densifying the TiC, thanks to its fine particle size, as well as its high chemical reactivity with TiO2 surface oxide. By contrast, the incorporation of nano-diamonds resulted in a considerable decline in the relative density of TiC owing to the graphitization phenomenon, together with the gas production at high temperatures. Although carbon precipitation from the TiC matrix occurred in all samples, some of the added carbonaceous phases promoted this phenomenon, while the others hindered it to some extent. Amongst the introduced additives, carbon black had the most contribution to grain refining, so that a roughly halved average grain size was attained in comparison with the undoped specimen. The highest values of hardness (3233 HV0.1 kg), thermal conductivity (25.1 W/mK), and flexural strength (658 MPa) secured for the ceramic incorporated by 5 wt% nano carbon black.

The incorporation of 1 wt% hexagonal BN (hBN) into ZrB2–30 vol% SiC could noticeably better the fracture toughness, hardness, and consolidation behavior of this composite. This research intended to scrutinize the effects of various amounts of hBN (0–5 wt%) on different characteristics of ZrB2–SiC materials. The hot-pressing method under 10 MPa at 1900 °C for 120 min was employed to sinter all designed specimens. Afterward, the as-sintered samples were characterized using X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and Vickers technique. The hBN addition up to 1 wt% improved relative density, leading to a near fully dense sample; however, the incorporation of 5 wt% of such an additive led to a composite containing more than 5% remaining porosity. The highest Vickers hardness of 23.8 GPa and fracture toughness of 5.7 MPa.m1/2 were secured for the sample introduced by only 1 wt% hBN. Ultimately, breaking large SiC grains, crack bridging, crack deflection, crack branching, and crack arresting were introduced as the chief toughening mechanisms in the ZrB2–SiC–hBN system.

Five titanium-based alloys containing 4, 8, 12, 16, and 20 wt% molybdenum additive were fabricated by spark plasma sintering process at 1200 ˚C. The samples were scrutinized in terms of relative density, phase evolution, and microstructural development. The relative density reached 99.9% with the molybdenum addition up to 16 wt% but slightly dropped in the sample with 20 wt% additive. In the specimens with 4 wt% Mo, molybdenum solved completely in the matrix and three different phase morphologies were observed, namely continuous α-Ti, laminar α-Ti, and very thin laminar β-Ti. With increasing Mo content to 20 wt%, widespread single β-Ti appeared alongside remained Mo and α-Ti. Ductile fracture mode was dominant in the samples with low Mo contents whilst it changed to brittle in the specimens with higher content of molybdenum.

A BN-TiB2-TiN composite was produced via reactive sintering of the hexagonal BN (hBN) with 20 wt% Ti. Spark plasma sintering (SPS) was used as the fabrication method and the sample was characterized by X-ray diffractometry, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. According to the results, the Ti was utterly consumed during the SPS, led to the in-situ TiB2 and TiN0.9 formations. Additionally, the microstructural study revealed the nucleation and growth of new hBN platelets from the initial fine hBN particles. Anyway, the final composite reached a relative density of 95%, because of the remaining free spaces between the hBN platelets. It was found that some nitrogen and boron atoms could leave the TiN and TiB2 microstructures, respectively, and diffuse into the opposing phase.

Sintering of ceramics is an energy-consuming process that needs high temperatures, therefore, in the present work; solar energy is used to produce high temperatures for the sintering aim of different materials. Solar energy concentrators increase the intensity of incident energy to the receiver provides high temperatures. Ultrahigh-temperature ceramics (UHTCs) due to their high melting point can also be a good alternative for receiver materials. In the present work, ZrB2 is introduced as an alternative material for solar receivers which can withstand high temperatures of sintering. The governing equations, including heat radiation and conduction ones are solved numerically using the finite element method. Transient heat transfer in the concentrator-collector system is investigated to check the feasibility of high temperatures needs for sintering at the receiver. The highest temperature of 1680 °C was achieved after 15 minutes at the focal point of the concentrator when the solar heat flux of 6.86 w/mm2 used for the location of the city of Ardabil in Iran. The obtained temperature can be used to sintering of some groups of materials.

The impact of Si3N4 content on the hardness and microstructural developments of ZrB2-SiC material has been investigated thoroughly in the present investigation. Having prepared the raw materials in a jar mill, the ZrB2-SiC samples containing various amounts of Si3N4 were hot-pressed at 1850 °C. Furthermore, XRD, FESEM, and HRTEM were utilized to evaluate the microstructure of samples. The formation of in-situ h-BN was proved by the mentioned methods. Also, it was shown that the Vickers hardness of ZrB2-SiC increases up to 20 GPa in presence of 4.5 wt% Si3N4 which is 3 GPa more than the sample without Si3N4. Results show that the positive effect of increased relative density on hardness is more than the negative effect of h-BN soft phase formation.

The present work aims to investigate the geometrical parameters of the graphite die on energy consumption needed for sintering of a ZrB2 sample. The Maxwell and electrical charge conservation equations are solved to obtain the electrical potential and current of the system. The governing equations are discretized by the Galerkin method and solved using the finite element method. The electric current distribution is obtained at each geometry and the temperature contours are obtained. The results showed that the height of die has a direct effect on power consumption. This can be attributed to the increased electric resistance and consequent increased Joule heating. On the other hand, increasing the die height resulted in more uniform temperature distribution through the sintered sample.

Researchers are currently considering membranes separation processes due to their eco-friendly, process simplicity and high efficiency. Selecting a suitable and efficient operation is the primary concern of researchers in the field of separation industries. In recent decades, polymeric and inorganic membranes in the separation industry have made significant progress. The polymeric and inorganic membranes have been challenged due to their competitiveness in permeability and selectivity factors. A combination of nanoparticle fillers within the polymer matrix is an effective method to increase polymeric and inorganic membranes’ efficiency in separation processes. Mixed matrix membranes (MMMs) have been considered by the separation industry due to high mechanical and physicochemical, and transfer properties. Moreover, gas separation, oil treatment, heavy metal ions removal, water treatment and oil-water separation are common MMMs applications. Selecting suitable polymer blends and fillers is the key to the MMMs construction. The combination of rubbery and glassy polymers with close solubility parameters increases the MMMs performance. The filler type and synthesis methods also affect the morphological and transfer properties of MMMs significantly. Zeolites, graphene oxide (GO), nanosilica, carbon nanotubes (CNTs), zeolite imidazole frameworks (ZIFs) and metal-organic frameworks (MOFs) are used in the MMMs synthesis as fillers. Finally, solution mixing, polymerization in situ and sol-gel are the primary synthesising MMMs methods.