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Abstract: Effect of C particle size on the mechanism of self-propagation high-temperature synthesis (SHS) in the Ni–Ti–C system was investigated. Fine C particle resulted in a traditional mechanism of dissolution-precipitation while coarse C particle made the reaction be controlled by a mechanism of the diffusion of C through the TiC x layer. The whole process can be described: C atoms diffusing through the TiC x layer dissolved into the Ni–Ti liquid and TiC were formed once the liquid became supersaturated. Simultaneously, the heat generated from the TiC formation made the unstable TiC x layer break up. However, with the spread of Ti–Ni liquid, a new TiC x layer was formed again at the interface between spreading liquid and C particle. This process cannot stop until all the C particles are consumed completely. [Copyright &y& Elsevier]

Abstract: Reaction behaviors and products of thermal explosion reaction from Ni–Ti–C system under air and Ar atmosphere were investigated, respectively. The ignition temperature for the thermal explosion reaction under air is much lower than that under Ar atmosphere. Under two atmospheres, increasing the Ni content and Ti particle size can increase the ignition temperature, respectively. Under air, increasing Ni and C particle sizes can decrease the ignition temperature, but the opposite results are achieved under Ar atmosphere. The reaction products are mainly dependent on the C particle size under two atmospheres. [Copyright &y& Elsevier]

Abstract: Influence of reactant (Cr, Ti and B4C) particle size on the SHS reaction products in 30wt.% Cr–Ti–B4C system has been investigated. Particle size of Cr powder has a significant effect on the phase compositions and microstructures of SHS reaction products. The SHS reaction in Cr–Ti–B4C system with nano-size Cr goes more complete and occurs more easily than that in the system with micron-size Cr. Increase in particle size of B4C powder has a little effect on the phase compositions of SHS reaction products, which consist of TiB2, TiC and Cr phases as well as transient phase Cr5B3 and a trace of C, but results in the increase of the amount of Cr5B3. Furthermore, the average sizes of TiB2 and TiC increase from ∼0.5 and ∼1μm to ∼2 and ∼3μm, respectively, as the B4C particle size increases from ∼3.5 to 40μm. Increase in particle size of Ti powder (∼38, ∼48 and ∼74μm) has little influence on the phase compositions of the products, as well as average sizes and morphologies of TiB2 and TiC. [Copyright &y& Elsevier]

Abstract: The effect of Cr content on the self-propagating high temperature synthesis (SHS) reaction of Cr–Ti–C system has been investigated in this research. The thermodynamics calculation indicates that the TiC possesses higher thermodynamic stability than the Cr23C6, Cr7C3 and Cr3C2 phases, and the formation of TiC is the most exothermic. Additionally, the adiabatic combustion temperature (T ad) decreases with the increase of Cr content except for the phase transition regions. The XRD result shows that the type of products synthesized by SHS changes that a higher Cr content corresponds to higher chromium carbide. When Cr content is 10wt.%, only solid solution (Ti,Cr)Css is formed in the products. When Cr content increases to 20wt.%, besides (Ti,Cr)Css, the Cr7C3 phase is also detected. With the Cr content further increasing to 30 and 40wt.%, the products consist of (Ti,Cr)Css, Cr23C6, Cr7C3 and Cr, and therefore, much higher chromium carbide is synthesized. When Cr content reaches 50wt.%, however, the Cr7C3 disappears and the final products become (Ti,Cr)Css, Cr23C6 and Cr. Moreover, when Cr content increases from 10 to 20wt.%, the lattice parameter of (Ti,Cr)Css decreases, while it increases when the Cr content ranges from 20 to 50wt.%. Furthermore, the microstructure shows that the TiC particulate size decreases from ∼8 to ∼2μm with the increase of Cr content from 10 to 50wt.%, and the morphology shape of TiC particulate becomes more and more spherical. [Copyright &y& Elsevier]

Abstract: The SHS reaction behaviors of the Cu–Ti–B4C system with various Cu content were investigated. Theoretical calculation of the adiabatic temperatures reveals that the reaction in the Cu–Ti–B4C system is self-sustainable for the presence of 0–72.22wt.% Cu in the reactants without any preheat. With the increase of Cu content, the adiabatic temperatures, combustion temperatures and wave velocity decrease greatly, while the ignition time shows first a remarkable decrease and then an increase with the minimum value at 20wt.% Cu. Moreover, with the increase of Cu content, the sizes of the TiC and TiB2 grains decrease considerably. [Copyright &y& Elsevier]

Abstract: C particle size plays an important role in the ignition and combustion characteristics of the SHS reaction in the 20wt.% Ni–Ti–C system. When coarse C particles (∼38 and ∼75μm) are used, the SHS reactions consist of two different combustion stages with different brightness intensity of the combustion wave; XRD results indicate that the first and second combustion stages mainly correspond to the formation of Ni–Ti compounds and TiC ceramics, respectively. However, the final reaction is incomplete with a few Ni–Ti compounds and unreacted C. In contrast, when the fine C particle (∼1μm) is used, the SHS reaction consists of only one combustion stage with high brightness intensity of the combustion wave; XRD result indicates that final products consist of TiC and Ni, without any intermediate phase. With the decrease of C particle size, the wave velocities increase, and the ignition time becomes shorter. In addition, the morphology of TiC particulate changes to near-spherical, as C particle size decreases. [Copyright &y& Elsevier]

Abstract: The effect of Ni content on the products of Ni–Ti–B system via self-propagating high-temperature synthesis (SHS) reaction has been investigated in this research. The results show that the products of SHS reactions consist mainly of TiB2 and Ni. Besides, the transient phases of Ni4B3, Ni3B, NiB and Ni3Ti also exist in the final products, which means the SHS reactions of Ni–Ti–B system are incomplete. The change in the content of Ni within the chosen range from 30 to 70wt.% has little effect on the phase compositions of the final products. However, the sizes of TiB2 particulates have been greatly influenced by the Ni content. The average sizes of normal TiB2 particulates are nearly the same and about 4–6μm when Ni contents are 30, 40 and 50wt.%. Furthermore, TiB2 particulates in the products of these three systems present exaggerated growth and their sizes can even reach 10–15μm. The size of TiB2 particulates decreases dramatically to 1–2μm when Ni content increases to 60wt.% while to 0.6μm or less at 70wt.% Ni. The addition of Ni facilitates to form more liquid phases that are beneficial to TiB2 formation during SHS reaction process. The formation mechanism of TiB2 in Ni–Ti–B system can be characterized by the solution, reaction and precipitation processes. This can be further substantiated by the presence of remaining liquids, the typical hexagonal-prism morphology and the growth striation on (0001) crystal face of TiB2 particulates. [Copyright &y& Elsevier]

Abstract: The effect of Fe addition on the SHS reaction products of Fe–Ti–Si system was investigated. When Fe content is 0wt.%, the product only consists of Ti5Si3. As the Fe content ranges from 10 to 30wt.%, besides Ti5Si3 and Fe phases, the transient Fe2Ti is also found in the final products. With a further increasing Fe content of 40 or 50wt.%, however, in addition to Ti5Si3, Fe and Fe2Ti phases, the FeSi phase is also detected. Furthermore, the contents of Fe2Ti and FeSi phases as well as the solubility of Fe in Ti5Si3 also increase with the increasing of Fe content. This indicates that Fe not only serves as a diluent, but also participates in the SHS reaction process. Moreover, addition of Fe has a great effect on the microstructures of SHS reaction products. When Fe content is 10 or 20wt.%, the Ti5Si3 exhibits cobblestone-like shape. When Fe content is increased to 30wt.%, the Ti5Si3 particulates are finer and most of them are surrounded by the bonding agents. As the Fe content is further increased to 50wt.%, it is difficult to distinguish Ti5Si3 particulates from Fe and its compounds. The Ti5Si3 particulate sizes decrease from more than 6 to about 0.6μm or less when Fe content in the preforms ranges from 10 to 50wt.%. This is mainly due to the fact that the combustion temperature decreases with the increasing of Fe content. The addition of Fe provides more liquid phase for the Ti5Si3 formation during SHS reaction process. The formation mechanism of Ti5Si3 in Fe–Ti–Si system can be characterized by the solution, reaction and precipitation processes. This can be confirmed by the presence of bonding agents (remaining liquids), nearly spherical (cobblestone-like) morphology and relatively smooth surface of Ti5Si3 particulates, as well as the presence of growth striation on the surface of Ti5Si3 particulates. [Copyright &y& Elsevier]

Abstract: The evolution process of TiC formation in the 20wt.% Cu–Ti–C powder mixtures was studied by using differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Ti x Cu y compounds (Ti2Cu, TiCu, Ti3Cu4 and TiCu4) formed initially via solid-state diffusion reactions between Cu and Ti particles; and then Ti2Cu and TiCu can form a Cu–Ti eutectic liquids at about 1233K. The unreacted Ti and C particles dissolved into the Cu–Ti liquids and led to the formation of Cu–Ti–C ternary liquids; subsequently, TiC particulates precipitated out of the saturated liquids. At the same time, also the formation of Ti2Cu occurred at the interface between the Cu–Ti liquids and the unreacted Ti particles. As the temperature increased further, the Ti2Cu melted and more Cu–Ti liquids formed; and then C particles continuously dissolved into the Cu–Ti–C liquids and TiC particulates gradually precipitated out of the saturated liquids. [Copyright &y& Elsevier]

Abstract: The TiB2 particulate reinforced magnesium matrix composites (MMCs) were fabricated by adding a TiB2–Al master alloy processed via self-propagating high-temperature synthesis (SHS) reaction of Al–Ti–B systems with the different molar ratio of Ti to B (n Ti:n B =1:2 and n Ti:n B =1:2.5, respectively) to molten magnesium and using the semisolid slurry stirring technique. When the molar ratio of Ti to B is 1:2 in TiB2–Al master alloy, the TiB2–Al master alloy and TiB2p/AZ91 composites contained a certain amount of transient TiAl3 phase; however, when the molar ratio of Ti to B is 1:2.5, the TiAl3 phase was almost completely eliminated and the distribution of TiB2 particulates generally appeared to be more homogeneous throughout the magnesium matrix. [Copyright &y& Elsevier]

Abstract: The effect of La2O3 in the Al–P–Ti–TiC–La2O3 modifier on primary silicon has been investigated. The results show that La2O3 in the Al–P–Ti–TiC–La2O3 modifier play an important role in modifying primary silicon. According to the present experiment, when the modifier containing La2O3 was added to Al–20wt.% Si alloy at 850°C, La2O3 in the modifier was decomposed (partly or completely). The minimum primary silicon size (approximately average 18μm) modified with Al–P–Ti–TiC–La2O3 modifier is obtained at the holding time of 30min, and the primary silicon size hardly change with the increase in holding time from 30 to 90min. Primary silicon size (approximately average 150μm) in unmodified Al–20wt.% Si alloy is about nine times larger than that (approximately average 18μm) in modified Al–20wt.% Si alloy with Al–P–Ti–TiC–La2O3 modifier at the holding time of 30min. As compared with unmodified Al–20wt.% Si alloy, the Brinell hardness value of modified Al–20wt.% Si alloy with Al–P–Ti–TiC–La2O3 modifier at the holding time of 30min is increased by 39%. [Copyright &y& Elsevier]

Abstract: In the Co39Ni33Al28 alloy, the ferromagnetic shape memory effect was investigated. A martensitic transformation (MT) occurred in the Co39Ni33Al28 alloy when the temperature was lower than the martensitic start transformation temperature, M S =233K. The morphologies and microstructures of the martensitic phase characterized by transmission electron microscope (TEM) showed a new 28-layered (28M) modulated martensite consisting of pinstripes and co-existing with the non-modulated martensite. Anomalies in magnetic properties and strain emerging around the MT have been briefly discussed. [Copyright &y& Elsevier]

Abstract: The reactive infiltration synthesis of steel matrix composite reinforced with in situ TiB2–TiC particulates by the self-propagating high-temperature synthesis (SHS) reaction of the Ni–Ti–B4C system during casting was investigated. The as-cast microstructures of the in situ processed composites reveal a uniform distribution of TiB2–TiC particulates with a fine size of ∼5.0μm. Although, microstructural characterization shows the absence of macro-pores and blowholes, the Ni content in the system has a significant effect on the presence of micro-porosity in the composites. Moreover, the results show that the densities of the composites are lower than those of medium carbon steel and high-speed (HS) steel. Although, the hardness values of the composites are significantly higher than that of medium steel and lower than that of HS steel, the wear resistance values of the composites are higher than those of medium steel and HS steel. [Copyright &y& Elsevier]

Abstract: The modification effect of KBF4 on the primary and eutectic Mg2Si in Mg–Si alloy is better than that of K2TiF6. This may be the reason of the presence of B in melts. However, the modification effect of KBF4 is greatly weakened by the simultaneous addition of K2TiF6 due to the decreasing of B content in the melts by the formation of TiB and TiB2. [Copyright &y& Elsevier]

Magnesium metal matrix composites (MMCs) reinforced with various fractions of 10, 15 and 20 vol.% B4C particulates fabricated by powder metallurgy (P/M) technique were investigated. Microstructure characterization of the composites revealed necklace distribution of B4C particulates in the matrix material and the presence of minimal micro-porosity. The X-ray diffraction (XRD) showed the formation of MgO and MgB2 in B4C/Mg composites. Moreover, the results revealed that the hardness and wear resistance of the composites were higher than those of as-cast Mg ingot and increased with increasing amount of B4C particulates from 10 to 20 vol.%. [Copyright &y& Elsevier]

The materials combining high-entropy alloys with good mechanical properties and magnetic materials with a significant magnetocaloric effect are among the best candidates for magnetic refrigeration. For this purpose, the high-entropy alloys (MnNiSi) 1- x (FeCoGe) x (x = 0.4, 0.42, 0.45, and 0.47) were designed in this study. The effects of the Si/Ge ratio on the magnetocaloric effect and mechanical properties were also investigated. The results show that high-entropy alloy (MnNi) 0.6 Si 0.62 (FeCo) 0.4 Ge 0.38 possesses a Vickers hardness value of 580.6HV2 and compressive strength of 267 MPa with respect to a significant entropy change of 48.5 J·kg−1K−1 under a magnetic field of 5 T near the Curie temperature of 308.8 K. In order to clearly understand the origin of this excellent comprehensive performance, the influence mechanism of crystal structure and configurational entropy were explored. Furthermore, the first-principles calculations indicated that the magnetic properties mainly originate from Mn atoms located in 3 d sites and are influenced by the interaction between the Mn and Fe atoms. Additionally, the total magnetic moment and electron density are taken into account to reveal their influence on magnetocaloric properties. [Display omitted] • An MnNiSi-based magnetocaloric high-entropy alloys with excellent comprehensive properties were obtained. • The MnNiSi-based alloys have good mechanical properties (the Vickers hardness of 580.6 HV2 and compressive strength of 267 MPa). • The magnetocaloric effects of the MnNiSi-based alloys is 48.5 J·kg−1K−1 under 0–5 T at T C = 309 K. • The physical mechanism about good mechanical properties and magnetocaloric effects is revealed from the crystal structure, configurational entropy and electronic structure. [ABSTRACT FROM AUTHOR]

Abstract: The microstructural evolution of Mg–5Si–1Al alloy during partial remelting was firstly investigated in the present study. The experimental results indicated that it was difficult to acquire the designed microstructures only by a single partial remelting, since either the globular primary Mg2Si or the granular eutectic Mg2Si phase can be produced in this process. However, the desired microstructures consisting of both globular primary and granular eutectic Mg2Si phases are successfully produced by secondary partial remelting. [Copyright &y& Elsevier]

Abstract: The Mg–30B2O3 modifier with the composition of Mg and B2O3, sintered in the temperature range between 250 and 450°C, has been developed as a low-cost and effective modifier for hypereutectic Mg–Si alloys. With 0.2–1.0wt.% B (introduced in the form of Mg–30B2O3), the morphology of the primary Mg2Si transforms from coarse dendrite shape into fine polyhedral shape with the size about 10μm. The modification mechanism of B2O3 is attributed to the adsorption and poisoning manners due to the presence of B in the melts by the decomposition of B2O3. [Copyright &y& Elsevier]

Abstract: Addition of Al can lead to the invalidation of KBF4 modification on the primary Mg2Si in Mg–5Si alloys and thus promote the preferred growth of the primary Mg2Si dendrite crystal. This may be due to the decrease or exhaustion of B in the melts by the formation of AlB x . [Copyright &y& Elsevier]

The synthesis of in situ formed TiB2/Mg composite utilizing the self-propagating high-temperature synthesis (SHS) reaction that occurred between the molten magnesium and green preforms consisting of Al, Ti and B powders was investigated. The result shows that it is feasible that the smelting temperature of the magnesium matrix alloy is selected at 860 °C, which is slightly higher than the exothermic reaction temperature of 852 °C on the DTA curve, prepared for the SHS reaction in the Al–Ti–B system. An as-cast microstructure of the composite reveals a relatively uniform distribution of TiB2 particulates with hexagonal or rectangular size of ∼2.0 μm. Furthermore, an analysis of the powders extracted from the TiB2/Mg composite confirms that a small amount of blocky TiAl3 phase is also present in the composite. [Copyright &y& Elsevier]

The effect of Al content on the self-propagating high-temperature synthesis (SHS) reaction of the Al–Ti–C preform in molten magnesium was investigated. As the Al content in the preforms was increased over the range of 20–40 wt.%, the TiC particulate sizes decreased from ∼5.0 to ∼1.0 μm. Microstructural characterization of the TiC/Mg (AZ91D) composite showed relatively uniform distribution of TiC particulates in the matrix material and the presence of minimal micro-porosity. [Copyright &y& Elsevier]

Abstract: The effects of different processing parameters, such as heating rate, isothermal temperature and isothermal holding time, on the semisolid microstructures of the AZ91D alloy during partial remelting had been investigated in the present paper. The experimental result showed that the high heating rate shortened the growth process of renascent recrystal grains in the deformed alloys, which ultimately attributed to refine the globular α-Mg grains in the evolved semisolid microstructure. The liquid volume fraction f L of the semisolid slurry gradually enlarged with the elevating of isothermal temperature during partial remelting. The isothermal temperature between 560°C and 580°C for 30min was adequate for the AZ91D to produce an ideal semisolid slurry with liquid fraction range between 32% and 52%. During the partial remelting, it would experience a relatively long holding time that the liquid and solid phases reached a state of dynamic equilibrium in the semisolid slurry. For the AZ91D alloy, the isothermal holding time of 30min was relatively adequate for the present experiment. During the partial remelting, the primary irregular grains gradually spherodized under a function of interface curvature. Oswald ripening mechanism, a dissolution and reprecipitation diffusion-controlled growth, could account for the coarsening of globular grains in the present experiment. The spheroidization and coarsening evolution processes of solid particles in the semisolid slurry were deduced and elucidated by the corresponding simulant formulae in the present paper. [Copyright &y& Elsevier]

Abstract: The effect of predeformation on the α-Mg grains in the AZ91D alloys was investigated in different stages during the semisolid processing. The result showed that, with the increase of compressive ratio, the α-Mg dendrites in the as-cast microstructures gradually oriented themselves in the direction that was vertical to the compressive direction, and exhibited an obvious directional character. During the sequent heat treatment at 310°C for 20min, the recrystallization was induced in the deformed alloys by the increasingly accumulated systemic strain energy. The metallographical observation showed that the average size of recrystal α-Mg grains gradually reduced with the increase of compressive ratio. The reason might be that the nucleation to growth ratio of the renascent recrystal α-Mg grains gradually increased in the recrystallization process. Due to the recrystallization mechanism, the predeformation made the α-Mg grains particularly rounder and finer after the semisolid isothermal heat treatment at 560°C for 20min. The average diameter of the globular α-Mg grains in the semisolid microstructures also reduced with the increase of compressive ratio and this descending trend was almost similar to that in the recrystal microstructures, which further demonstrated that the recrystallization had an inevitable role on the evolution process of globular grains during SIMA process. While the compressive ratio surpassed 20%, the above descending trend was not so evident as that below 20%. In addition, the effect of predeformation on the tensile strength and elongation of the semisolid AZ91D alloys was also discussed in the present paper. [Copyright &y& Elsevier]

Abstract: The semisolid microstructure evolution process of the predeformed AZ91D alloy during heat treatment was studied. After being compressed by a ratio of 20.6% in height at 220°C, all the dendrites oriented in the same way. With increasing heat-treatment temperature, the dissolution of eutectic β-Mg17Al12 first took place, resulting in the primary dendritic grains coarsening into interconnected non-dendritic grains. With heating continuously, a large amount of polygon recrystallization grains occur in the microstructure. Subsequently, the residual interdendritic β-Mg17Al12 at the edges of the primary grains and the new recrystallization grains melted in succession at higher heat-treatment temperature and the primary grains separated into small polygon grains. After being heat-treated at the semisolid temperature, the amount of liquid increased until the solid–liquid system reached its equilibrium state, and the grains spheroidized. [Copyright &y& Elsevier]

Due to its explosive, colorless and volatile nature, detection of ethanol is critical in daily life, industrial production and medical treatment. Metal oxide semiconductors (MOS) gas sensors have caught the attention of researchers due to their low cost and convenient detection. Indium oxide (In 2 O 3) is a typical wide band gap n-type semiconductor metal oxide widely used in detecting H 2 S, NO 2 , H 2 , and ethanol. This paper summarizes the strategies used in the last decade to improve the performance of gas sensors based on In 2 O 3 sensitive materials for ethanol detection. These strategies include modifying the morphology of indium oxide sensitive materials, doping and loading, building heterojunctions, and using composite new materials. In addition, the sensing mechanism for ethanol detection by gas sensors is presented. [ABSTRACT FROM AUTHOR]

Abstract: The crystal structure and magnetic properties for the ordered double perovskite oxides Sr2−x K x FeMoO6 (0≤ x ≤0.04) are investigated. X-ray powder diffraction studies reveal that all the samples are single phase and have the I4/m symmetry. The anti-site defect (AS) in double perovskite oxides of Sr2−x K x FeMoO6 may be adjusted by alkali metal element of K doping. The unit cell magnetization at 280K is 1.12μB for x =0 and 1.26μB for x =0.04, respectively. The cation-ordering and the Felyph name="sbnd" />Mo bond-angle play the competition roles on the magnetism in the doping system. [Copyright &y& Elsevier]

Abstract: In the present study, the effect of Nd on primary silicon and eutectic silicon in hypereutectic Al-20wt.%Si alloy has been investigated. It has been concluded that Nd in Al–P–Ti–TiC–Nd modifier can modify not only eutectic silicon but also primary silicon in hypereutectic Al-20wt.%Si alloy. Statistical analysis shows that primary and eutectic silicon crystallite sizes (approximately 60μm and 40μm in length, respectively) in modified Al-20wt.%Si alloy with Al–P–Ti–TiC modifier are about seven- and two-times larger than those (approximately 22μm and 18μm in length, respectively) in modified Al-20wt.%Si alloy with Al–P–Ti–TiC–Nd modifier, respectively. [Copyright &y& Elsevier]