Synthesis of PbS–K2La2Ti3O10 composite and its photocatalytic activity for hydrogen production

Photocatalyst, lead sulfide (PbS )-intercalated layer perovskite-type compound (K2La2Ti3O10), was synthesized via ion-exchange reaction, butylamine pillaring and sulfuration processes under the assistance of the microwave irradiation. The structure of the photoc atalysts was determined by means of powder X-ray diffraction, scanning electron microscope, ultraviolet- visible diffuse reflection spectra and photoluminescence measu rement. And the photocatalytic activity of the composite compound for hydrogen production was also investigated. The experimental results showed that the intercalation of PbS in the layered space of K2La2Ti3O10 greatly improved the absorption edge and the photocatalytic activity. Hydrogen production of the PbS–K2La2Ti3O10 was 127.19 mmol/(g cat) after 3 h irradiation of ultraviolet light.     

Fabrication of Fe–TiC–Al2O3 composites on the surface of steel using a TiO2–Al–C–Fe combustion reaction induced by gas tungsten arc cladding

The aim of the present study was to fabricate Fe–TiC–Al₂O₃ composites on the surface of medium carbon steel. For this purpose, TiO₂–3C and 3TiO₂–4Al–3C–xFe (0 ≤ x ≤ 4.6 by mole) mixtures were pre-placed on the surface of a medium carbon steel plate. The mixtures and substrate were then melted using a gas tungsten arc cladding process. The results show that the martensite forms in the layer produced by the TiO₂–3C mixture. However, ferrite–Fe₃C–TiC phases are the main phases in the microstructure of the clad layer produced by the 3TiO₂–4Al–3C mixture. The addition of Fe to the TiO₂–4Al–3C reactants with the content from 0 to 20wt% increases the volume fraction of particles, and a composite containing approximately 9vol% TiC and Al₂O₃ particles forms. This composite substantially improves the substrate hardness. The mechanism by which Fe particles enhance the TiC + Al₂O₃ volume fraction in the composite is determined.     

The strain ampli tude-controlled cyclic fatigue behavior of Al2O3 fiber reinforced Al–Si alloy composite at elevated temperatures

The strain amplitude-controlled fatigue characteristics of an Al–Si casting alloy and itscomposite reinforced with 17 vol% Al₂O₃ fibers (Al–Si/Al₂O₃) are studied at three different temperatures. Both the alloy and the composite showed different degrees of cyclic softening at elevated temperatures. Increasing the temperature, fatigue damage of either the alloy or the composite occurred with varying mode from brittle fracture of silicon particles to their separation from the aluminum matrix. This is explained by the different thermal expansion coefficients of silicon particles and the aluminum matrix. The reinforcement Al₂O₃ fibers in the composite showed a similar damage behavior with those silicon particles despite temperature variation     

Fabrication and character ization of electrospun TiO2/CuS micro–nano-scaled composite fibers

A process to fabricate a kind of novel micro–nano scaled TiO2/CuS composite fibers by electrospinning technique and chemical precipitation method was developed in the present study. The microstructures and photoelectronic properties of the fibers were characterize d using SEM, FT-IR, UV–vis and fluorescence spectroscopy. The results revealed that the TiO2 portion in the composite fibers was a mixture rutile and anatase phases while TiO2 and CuS had been fully composite. The fibers had smooth surface with a diameter of 50–300 nm. Comparing with pure TiO2 fiber, the TiO2/CuS micro–nano-scaled composite fibers exhibited a strong absorption in the visible light region and the efficiency of photo-induced charge separation were enhanced. This composite system is of widely potential applications in the areas such as solar cells, supercapacity, photocatalysis, etc.     

Bulk Al-Al3Zr composite prepared by mechanical alloying and hot extrusion for high-temperature applications

Bulk Al/Al₃Zr composite was prepared by a combination of mechanical alloying (MA) and hot extrusion processes. Elemental Al and Zr powders were milled for up to 10 h and heat treated at 600℃ for 1 h to form stable Al₃Zr. The prepared Al₃Zr powder was then mixed with the pure Al powder to produce an Al-Al₃Zr composite. The composite powder was finally consolidated by hot extrusion at 550℃. The mechanical properties of consolidated samples were evaluated by hardness and tension tests at room and elevated temperatures. The results show that annealing of the 10-h-milled powder at 600℃ for 1 h led to the formation of a stable Al₃Zr phase. Differential scanning calorimetry (DSC) results confirmed that the formation of Al₃Zr began with the nucleation of a metastable phase, which subsequently transformed to the stable tetragonal Al₃Zr structure. The tension yield strength of the Al-10wt%Al₃Zr composite was determined to be 103 MPa, which is approximately twice that for pure Al (53 MPa). The yield stress of the Al/Al₃Zr composite at 300℃ is just 10% lower than that at room temperature, which demonstrates the strong potential for the prepared composite to be used in high-temperature structural applications.     

In-situ fabrication of Al(Zn)-Al2O3 graded composite using the aluminothermic reaction during hot pressing

In this study, the fabrication of multilayer Al(Zn)–Al₂O₃ with different volume fractions of Al₂O₃ was investigated. Al and ZnO powders were milled by a planetary ball mill, after which five-layer functionally graded samples were produced through hot pressing at 580℃ and 90 MPa pressure for 30 min. Formation of reinforcing Al₂O₃ particles occurred in the aluminum matrix via the aluminothermic reaction. Determination of the ignition temperature of the aluminothermic reaction was accomplished using differential thermal and thermogravimetric analyses. Scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffractometery analyses were utilized to characterize the specimens. The thermal analysis results showed that the ignition temperatures for the aluminothermic reaction of layers with the highest and lowest ZnO contents were 667 and 670℃, respectively. Microstructural observation and chemical analysis confirmed the fabrication of Al(Zn)–Al₂O₃ functionally graded materials composites with precipitation of additional Zn in the matrix. Moreover, nearly dense functionally graded samples demonstrated minimum and maximum hardness values of HV 75 and HV 130, respectively.     

Novel approaches to produce Al2O3– TiC/TiCN– Fecomposite powders directly from ilmenite

Al2O3 –TiC/TiCN–Fe composite powders were successfully prepared directly from ilmenite at 1300–1400℃.The effects of Al/C ratio,sintering atmosphere,and reaction temperature and time on the reaction products were investigated.Results showed that the nitrogen atmosphere was bene cial to the reduction of ilmenite and the formation of Al2O3 –TiC/TiCN–Fe composite powders.When the reaction temperature was between 600 and 1100℃,the intermediate products,TiO2,Ti3O5 and Ti4O7 were found,which changed to TiC or TiCN at higher temperature.Al/C ratio was found to affect the reaction process and synthesis products.When Al addition was 0.5 mol,the Al2O3 phase did not appear.The content of carbon in TiCN rose when the reaction temperature was increased.     

La2O3-Al2O3-SiO2 glass-infiltrated 3Y-TZP all-ceramic composite for the dental restorative application

The 3 mol％ yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) powder had three particle size distributions,while the fine one was lower than 100 nm.The 3Y-TZP compact was prepared by dry-press...     

Bulk Al–Al_3Zr composite prepared by mechanical alloying and hot extrusion for high-temperature applications

Bulk Al/Al_3Zr composite was prepared by a combination of mechanical alloying(MA) and hot extrusion processes. Elemental Al and Zr powders were milled for up to 10 h and heat treated at 600℃ for 1 h to form stable Al_3Zr. The prepared Al_3Zr powder was then mixed with the pure Al powder to produce an Al–Al_3Zr composite. The composite powder was finally consolidated by hot extrusion at 550℃. The mechanical properties of consolidated samples were evaluated by hardness and tension tests at room and elevated temperatures. The results show that annealing of the 10-h-milled powder at 600℃ for 1 h led to the formation of a stable Al_3Zr phase. Differential scanning calorimetry(DSC) results confirmed that the formation of Al_3Zr began with the nucleation of a metastable phase, which subsequently transformed to the stable tetragonal Al_3Zr structure. The tension yield strength of the Al-10wt%Al_3Zr composite was determined to be 103 MPa, which is approximately twice that for pure Al(53 MPa). The yield stress of the Al/Al_3Zr composite at 300℃ is just 10% lower than that at room temperature, which demonstrates the strong potential for the prepared composite to be used in high-temperature structural applications.     

Microstructure and mechanical properties of a hot-extruded Al-based composite reinforced with core–shell-structured Ti/Al_3Ti

An Al-based composite reinforced with core–shell-structured Ti/Al_3Ti was fabricated through a powder metallurgy route followed by hot extrusion and was found to exhibit promising mechanical properties. The ultimate tensile strength and elongation of the composite sintered at 620°C for 5 h and extruded at a mass ratio of 12.75:1 reached 304 MPa and 14%, respectively, and its compressive deformation reached 60%. The promising mechanical properties are due to the core–shell-structured reinforcement, which is mainly composed of Al_3Ti and Ti and is bonded strongly with the Al matrix, and to the reduced crack sensitivity of Al_3Ti. The refined grains after hot extrusion also contribute to the mechanical properties of this composite. The mechanical properties might be further improved through regulating the relative thickness of Al–Ti intermetallics and Ti metal layers by adjusting the sintering time and the subsequent extrusion process.     

Microstructure and properties of Ag–Ti3SiC2 contact materials prepared by pressureless sintering

Ti₃SiC₂-reinforced Ag-matrix composites are expected to serve as electrical contacts. In this study, the wettability of Ag on a Ti₃SiC₂ substrate was measured by the sessile drop method. The Ag–Ti₃SiC₂ composites were prepared from Ag and Ti₃SiC₂ powder mixtures by pressureless sintering. The effects of compacting pressure (100–800 MPa), sintering temperature (850–950℃), and soaking time (0.5–2 h) on the microstructure and properties of the Ag–Ti₃SiC₂ composites were investigated. The experimental results indicated that Ti₃SiC₂ particulates were uniformly distributed in the Ag matrix, without reactions at the interfaces between the two phases. The prepared Ag–10wt%Ti₃SiC₂ had a relative density of 95% and an electrical resistivity of 2.76×10-3 mΩ·cm when compacted at 800 MPa and sintered at 950℃ for 1 h. The incorporation of Ti₃SiC₂ into Ag was found to improve its hardness without substantially compromising its electrical conductivity; this behavior was attributed to the combination of ceramic and metallic properties of the Ti₃SiC₂ reinforcement, suggesting its potential application in electrical contacts.     

Structural and electrical properties of HCl-polyaniline-Ag composites synthesized by polymerization using Ag-coated (NH4)2S2O8 powder

Ag nanoparticles were sputter-deposited on ammonium persulfate ((NH₄)₂S₂O₈) powder to obtain (NH₄)₂S₂O₈-Ag powder, which was used to synthesize the HCl-doped polyaniline-Ag (HCl-PANI-Ag) composite via a polymerization procedure. The Ag nanoparticles were dispersed in the HCl-PANI matrix, and their sizes mainly ranged from 3 to 6 nm. The Ag nanoparticles did not affect the structure of emeraldine salt in the composite, and they increased the ordered crystalline regions in the HCl-PANI matrix. The HCl-PANI-Ag composite had a conductivity of (6.8 ±0.1) S/cm, which is about four times larger than that of the HCl-PANI. The charge transport mechanism in the composite is explained by the three-dimensional Mott variable-range hopping (3D-Mott-VRH).     

Effect of La2O3 on microstructure, mechanical and tribological properties of Ni-W coatings

In this paper, a Ni-W-La2O3 composite coating was prepared by the electrodeposition method. Microhardness tester and environmental scanning electron microscope equipped energy dispersive spectroscopy were employed to investigate the microhardness and the surface morphology of the composite coatings respectively, and the high temperature friction behavior and corrosion resistance of the coatings against molten glass were investigated by using a high temperature tribometer. The results show that La2O3 can refine the microstructure effectively, and make the element distribution uniform, which leads to the increase of average microhardness. La2O3 particulates can reduce the friction coefficient between the composite coating and glass during the sliding process at about 973 K largely, and the corrosion resistance of the La2O3 added Ni-W coatings is effectively improved compared with that of the non-added one, furthermore the mechanism of friction-reducing and anti-corrosion is also discussed.     

PTA clad (Cr,Fe)7C3/γ-Fe in situ ceramal composite coating

A wear-resistant (Cr, Fe)₇C₃/γ-Fe in situ ceramal composite coating was fabricated on the substrate of 0.45wt%C carbon steel by a plasma-transferred arc cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness, and dry-sliding wear resistance of the coating were evaluated. The results indicate that the microstructure of the coating, which was composed of (Cr, Fe)₇C₃ primary phase uniformly distributed in the γ-Fe, and the (Cr, Fe)₇C₃ eutectic matrix was metallurgically bonded to the 0.45wt%C carbon steel substrate. From substrate to coating, the microstructure of the coating exhibited an evident epitaxial growth character. The coating, indehiscent and tack-free, had high hardness and appropriate gradient. It had excellent wear resistance under the dry sliding wear test condition.     

Phosphate enrichment mechanism in CaO–SiO2–FeO–Fe2O3–P2O5 steelmaking slags with lower binary basicity

The addition of silica to steelmaking slags to decrease the binary basicity can promote phosphate enrichment in quenched slag samples. In this study, we experimentally investigated phosphate enrichment behavior in CaO–SiO₂–FeO–Fe₂O₃–P₂O₅ slags with a P₂O₅ content of 5.00% and the binary basicity B ranging from 1.0 to 2.0, where the (%Fe_tO)/(%CaO) mass percentage ratio was maintained at 0.955. The experimental results are explained by the defined enrichment degree R_C2S-C3P of solid solution 2CaO·SiO₂–3CaO·P₂O₅ (C₂S–C₃P), where R_C2S-C3P is a component of the developed ion and molecule coexistence theory (IMCT)–N_i model for calculating the mass action concentrations N_i of structural units in the slags on the basis of the IMCT. The asymmetrically inverse V-shaped relation between phosphate enrichment and binary basicity B was observed to be correlated in the slags under applied two-stage cooling conditions. The maximum content of P₂O₅ in the C₂S–C₃P solid solution reached approximately 30.0% when the binary basicity B was controlled at 1.3.     

In situ(α-Al_2O_3+ZrB_2)/Al composites with network distribution fabricated by reaction hot pressing

In situ(α-Al_2O_3+ZrB_2)/Al composites with network distribution were fabricated using low-energy ball milling and reaction hot pressing. Differential thermal analysis(DTA) was used to study the reaction mechanisms in the Al–Zr O2–B system. X-ray diffraction(XRD) and scanning electron microscopy(SEM) in conjunction with energy-dispersive X-ray spectroscopy(EDX) were used to investigate the composite phases, morphology, and microstructure of the composites. The effect of matrix network size on the microstructure and mechanical properties was investigated. The results show that the optimum sintering parameters to complete reactions in the Al–Zr O2–B system are 850°C and 60 min. In situ-synthesized α-Al2O3 and Zr B2 particles are dispersed uniformly around Al particles, forming a network microstructure; the diameters of the α-Al2O3 and Zr B2 particles are approximately 1–3 μm. When the size of Al powder increases from 60–110 μm to 150–300 μm, the overall surface contact between Al powders and reactants decreases, thereby increasing the local volume fraction of reinforcements from 12% to 21%. This increase of the local volume leads to a significant increase in microhardness of the in situ(α-Al2O3–Zr B2)/Al composites from Hv 163 to Hv 251.     

Microstructure and mechanical properties of a hot-extruded Al-based composite reinforced with core-shell-structured Ti/Al3Ti

An Al-based composite reinforced with core-shell-structured Ti/Al₃Ti was fabricated through a powder metallurgy route followed by hot extrusion and was found to exhibit promising mechanical properties. The ultimate tensile strength and elongation of the composite sintered at 620℃ for 5h and extruded at a mass ratio of 12.75:1 reached 304 MPa and 14%, respectively, and its compressive deformation reached 60%. The promising mechanical properties are due to the core-shell-structured reinforcement, which is mainly composed of Al₃Ti and Ti and is bonded strongly with the Al matrix, and to the reduced crack sensitivity of Al₃Ti. The refined grains after hot extrusion also contribute to the mechanical properties of this composite. The mechanical properties might be further improved through regulating the relative thickness of Al-Ti intermetallics and Ti metal layers by adjusting the sintering time and the subsequent extrusion process.     

CaO-Al2O3-SiO2系烧结微晶玻璃的结晶过程

To control the quatity, grain size and morphology of crystals in glass-ceramics, relative crystallinity of CaO-Al₂O₃-SiO₂ sintered glass-ceramics was determined using XRD method. The crystallization at different temperature range was studied by SEM. The results indicate that sintering at low temperature (below 900　℃), crystals originate at the interface of glass particles and grow toward the inside of particles. There was no crystallization taken place within particles and the crystallinity was relatively low. Higher crystallinity can be obtained at mid temperature range (900～1　050　℃) when crystallization takes place both at and within the interface of glass particles. The crystallinity tends to decrease at high temperature range (1　050～1　100　℃) due to the rapid sintering and drop of driving force for phase transformation.     

利用氧化基粉煤灰粉和医疗废弃物颗粒开发无电镀镍基复合涂层 (Ni–P/粉煤灰和Ni-P/Ni–P/SiO2–Al2O3)

Recycling and reusing materials from waste have become a nexus in the development of sustainable materials, leading to more balanced technologies. In this study, we developed a composite coating by co-depositing recycled ceramic particles, pulverised fly ash (PFA) and medical ceramics (MC), into a nickel–phosphorus matrix using a typical electroless plating process. Scanning electron microscopy (SEM) images indicated well-dispersed particles in the Ni–P matrix. However, compared with the MC particles, the PFA particles were distributed scantily with a lower content in the matrix, which could be due to the less impingement effect during the co-deposition. A modified microstructure with refined grains was obtained for the PFA-incorporated composite coating, as seen in the SEM micrograph. The X-ray diffraction result of the MC-incorporated composite coating showed the formation of Ni_xSi_y phases in addition to the typical Ni₃P phases for the heat-treated electroless Ni–P coatings. Upon heat treatment, the PFA-reinforced composite coating, due to a modified microstructure, exhibited a higher microhardness up to HK_0.05 818, which is comparable to that of the traditional SiC particle-embedded composite coating (HK_0.05 825). The findings can potentially open up a new strategy to further advance the green approach for industrial surface engineering.     

Activity coefficient of NiO in SiO2-saturated MnO–SiO2slag and Al2O3-saturated MnO–SiO2–Al2O3slag at 1623 K

As a part of the fundamental study related to the reduction smelting of spent lithium-ion batteries and ocean polymetallic nodules based on MnO–SiO₂slags,this work investigated the activity coefficient of NiO in SiO₂-saturated Mn O–Si O₂slag and Al₂O₃-saturated Mn O–SiO₂–Al₂O₃slag at 1623 K with controlled oxygen partial pressure levels of 10^-7,10^-6,and 10^-5Pa.Results showed that the solubility of nickel oxide in the slags increased with increasing oxygen partial pressure.The nickel in the Mn O–Si O₂slag and Mn O–Si O₂–Al₂O₃slag existed as Ni O under experimental conditions.The addition of Al₂O₃in the Mn O–Si O₂slag decreased the dissolution of nickel in the slag and increased the activity coefficient of Ni O.Furthermore,the activity coefficient of Ni O(γN_(i O)),which is solid Ni O,in the Si O₂saturated Mn O–Si O₂slag and Al₂O₃saturated Mn O–Si O₂–Al₂O₃slag at 1623 K can be respectively calculated asγN_(i O)=8.58w(Ni O)+3.18 andγN_(i O)=11.06w(Ni O)+4.07,respectively,where w(Ni O)is the Ni O mass fraction in the slag.