Papers by Keyword: In Situ Synthesis

Abstract: Vanadium nitride (VN) particulate reinforced Fe-based composite was produced with ferrovanadium, Ferromolybdenum, ferrochromium and nitrogen gas by in situ synthesis process. The microstructure of the composites was characterized by X-ray diffraction and scanning electron microscopy. With the help of differential thermal analysis, reaction process of Fe-V-N system was discussed. The results show that the composite consists of VN and α-Fe phase. VN particles exhibit fine size and homogeneous distribution in Fe matrix. Formation of VN at 674°C is due to the reaction between ferrovanadium and nitrogen gas.

Abstract: In order to systematically study the morphology and distribution of M₇C₃ and TiC which in situ synthesized by plasma arc in the surfacing layer, plasma arc was used to clad the Fe-Cr-Ti-C wear-resistant alloy on low-carbon steel. And high corrosion experiment was applied to the surfacing layer. The hardness, microstructure and phase constitution of the surfacing layer were investigated through the tests of hardness, OM, EDS, SEM and XRD analysis. The results shows that irregular hexagonal (Cross-section) and strip (Side) M₇C₃ and petal-like, granular TiC were in situ synthesized in the surfacing layer. The M₇C₃ and TiC was combined closely. The M₇C₃ grains which closed to the fusion line of the base metal and surfacing layer are fine, but the ones that away from the fusion line are larger caused by the large temperature gradient. Smooth metallurgical bonding layer was formed between the surfacing layer and the base metal, it has a good metallurgical bonding. The phenomenon that carbon diffusion into the base material was clearly, the hardness near the fusion zone was improved effectively.

Abstract: The TiC/Ni composite coating was prepared by Laser Cladding In-situ Synthesis on the surface of damper plate with Ni--Ti-Mo-C -LaF₃ powder．Microstructure and Wear resistance have been studied throughout EPMA、SEM and M—2000 Friction and Wear Tester．It was found that the microstructure got more homogenized grain fineness became finer, TiC distributed better and heterogeneous phase decreased, as adding moderate rare earth LaF3. When the content of LaF₃ was 1%, the highest microhardness was got. While the optimal wear resistance properties were obtained with 2% LaF₃. The laser cladding with excessive LaF₃ has more TiC particle segregation which induces hardness and wear resistance of cladding layer.

Abstract: In situ Al_0.983Cr_0.017 intermetallic compounds reinforced aluminum matrix composite was fabricated by the mechanical stirring casting method in this paper. In addition, microstructure and corrosion resistance of composite was investigated by XRD and SEM. The results show that the Al_0.983Cr_0.017 intermetallic compounds reinforcement distribute in the matrix uniformly. The clean interface between reinforcement and matrix has good interfacial bond. The corrosion resistance of Al_0.983Cr_0.017/Al composite materials presented a U-shaped curve, the best corrosion resistance present in the composite with 12% volume fraction reinforcement. The Al_0.983Cr_0.017 has a high corrosion resistance, which promoted the nucleation of pitting. Furthermore, the reinforcement interrupt the continuity of the matrix, inhibits the further expansion of pitting, which increases the corrosion resistance of composites.

Abstract: The latest development on preparation of SiC-AlN, SiC-mullite and β-Sialon materials using fly ash via in-situ carbothermal reduction process was reviewed. The synthesis mechanisms of SiC based materials and β-Sialon were also discussed.

Abstract: Using the urea intercalated montmorillonite (Urea/MMT) as the precursor, a novel nanocomposite biurea intercalated montmorillonite (Biurea/MMT) was prepared via the in-situ synthesis process through the introduction of hydrazine hydrate (HY). The resulted nanocomposites were characterized by using techniques such as XRD, FTIR, solid state NMR as well as thermal analyses, etc. The influence of the concentration of the HY on the products was also investigated. The XRD results showed the variation of the interlayer spacing of MMT from 1.51 nm to 1.71 nm for Urea/MMT. When the concentration of HY was low, the substitution of urea by HY was taken place which resulted in the decrease of the interlayer distance to 1.27nm. When the concentration increased to greater than 40%, the new phase with basal spacing of 1.75 nm was dominated. It indicated that a novel nanocomposite was synthesized in-situ. The solid state NMR results confirmed the in-situ formation of Biurea/MMT in which the chemical shifts of ¹³C and ¹⁵N of the intercalated biurea were slightly different from the bulk biurea. The intercalated biurea decomposed easily than those bulk powders due to the highly dispersion in the interlayer space of MMT.

Abstract: The In Situ Synthesized Tic Particle Reinforced High Chromium Fe-Based Ceramics Composite Coating Was Fabricated on the Substrate of Q235 Steel by Plasma Cladding Process Using Fe-Cr-Ti-C Composite Powder as Reactive Material. Microstructure of the Coating Was Observed by Scanning Electron Microscope (SEM), the Phases Were Determined by X-Ray Diffraction (XRD), and the Wear Resistance Was Evaluated under Dry Sliding Wear Test Conditions at Room Temperature. Results Indicate that the Composite Coating Consists of the Reinforcing Tic Carbide, (Cr,Fe)₇C₃ Eutectic as Well as Austenite, and Is Metallurgically Bonded to the Q235 Steel Substrate. the Gradient Distribution of Tic Carbides Is Observed. Tic Particles Present in the Granular Shape in the Fusion Zone and Central Zone while Present in the Dendritic Shape on the Surface of the Composite Coating. Hardness of the Coating from Surface to Fusion Zone Varies a Little; the Average Hardness of the Coating Is about HV_0.2750 which Is 3.2 Times as much as that of the Base. the Wear Mass Loss of Q235 Base Material Is 13 Times Higher than that of the Composite Coating.

Abstract: Magnesium alloys have high specific strength, specific stiffness, excellent thermal conductivity and casting properties, which have a great prospects development in the industry, However, its low plasticity and ductility limited its application. Magnesium matrix composites can effectively improve its performance. Magnesium alloy die-casting is the main forming process, the conventional high-pressure die-casting (HPDC) defects in multi-cavity type, easy to volume gas, non-heat-treated. Compared with HPDC, the rheo-diecasting (RDC) process has been greatly developed for near-net shape components. In this paper, Mg2Si /AM60 composites is fabricated by in-situ synthesis and semi-solid magnesium matrix composites which are rheoformed in the die-casting machine are prepared by mechanical stirring. The results indicate that the microstructure of composites is non-dendritic and Chinese script type Mg2Si are fine distributed. The fundamental morphology of microstructure by HPDC is dendrite and liquid-phase distributed between dendrite irregularly. The RDC samples have close-to-zero porosity, less segregation, the most of semi-solid of microstructure in rheo-diecasting is spherical or as-spherical structure.

Abstract: The complexes of europium with two schiff base ligands [2-carboxybenzaldehyde- diethylenetriamine (1), 2-carboxybenzaldehyde-triethylenetetramine (2)] were in-situ synthesized. The formation of complexes was confirmed by the luminescence spectra. The luminescence spectra of two europium complexes were investigated in solid and in DMSO solution, respectively. The results show that two europium complexes exhibit low luminescence emission. And organic solvent DMSO could quench the luminescence of europium complexes.

Abstract: Tabular alumina, α-Al₂O₃ powder, TiO₂ powder and metal aluminum powder in purity of 99%(by mass) were uesd to prepare the Al₂O₃-TiN composite ceramics by mechanical mixing and thermal reduction of aluminum in situ reaction sintering in the flow of nitrogen gas under atmospheric pressure;the influences of phase composition and microstructure changes at 1200°C-1500°C nitridation reaction in situ,different amount of TiN formations and sintering temperature on the properties of the samples were analyzed by thermal analysis, XRDand SEM. The results show that: TiO₂ was reduced by Al and then nitrided as TiN in the test temperature, the porosity has been increasesd while the bulk density has been decreased with the increased content of TiN formation because of the process of nucleation growth and the strong exothermic of the reaction.The mechanical properties of the composites are relatively better of TiN generated 10%content,because the structure of the skeleton formed by corundum was filled of part matrix evenly and was integrated closely by the matrix.