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1.
Xuezhi Wang Xue Sun Zhelun Ma Tianbiao Yu Wanshan Wang 《Ceramics International》2018,44(18):22301-22307
Vitrified bond CBN grinding wheels are being widely used due to their superior performance. Also, advantages of vitrified grinding wheels are high elastic modulus, stable chemical property, and low thermal expansion coefficient. Brittleness and low strength are key factors restricting the development of vitrified bond CBN grinding wheels. In this paper, the sintering in a high magnetic field was innovatively introduced into the manufacturing of vitrified bond CBN grinding wheels, and the effects of sintering in a high magnetic field on properties on vitrified bond and vitrified CBN composites were systematically investigated. Vitrified bond was characterized using three-point bending, scanning electron microscopy, X-ray diffraction. It was observed that microstructure of vitrified bond could be changed, grain orientation could be controlled and average grain size could be decreased in a high magnetic field, while vitrified bond strength could be simultaneously improved. High quality vitrified bond could be obtained by appropriately adjusting the strength and direction of high magnetic field. Results demonstrated that vitrified bond properties were improved when the magnetic field strength was 6?T. In order to highlight the high magnetic field effect on the vitrified CBN composites, the ordinary CBN abrasives and nickel plated CBN abrasives were used respectively. Microstructures, bending strengths of vitrified CBN composites were compared in different high magnetic fields. When the magnetic field strength was appropriate (less than 6?T), the binding characteristic of vitrified bond CBN composites with nickel plated CBN abrasives was greatly improved. The highest bending strength value of vitrified CBN composites was 79.5?MPa in 6?T high magnetic field. 相似文献
2.
The effect of polycrystalline mullite fibers (PMFs) on the properties of vitreous bonds and vitrified CBN composites was investigated. The results show that the addition of PMFs can increase the porosity of composites and reduce the fluidity of binders. The vitrified composites incorporating 6.4 wt% PMFs display excellent mechanical strength, which is enhanced by 21.2% compared with that of composites without PMFs sintered at the optimal sintering temperature. Meanwhile the thermal expansion coefficient of vitrified bond reduces from 6.256×10−6 °C−1 to 4.805×10−6 °C−1 with increasing fraction of PMFs. The improvement of mechanical strength is associated with the change of cracking mechanisms of the composites with fibrous crystals and the existence of several observed mechanisms, including fiber pull-out, fiber bridging and rupture. 相似文献
3.
Xue Sun Tianbiao Yu Xuezhi Wang Maoqiang Xu Wanshan Wang 《Ceramics International》2018,44(14):16307-16313
Vitrified bond CBN composites, with different amounts of TiO2 doping, were prepared by conventional sintering and high magnetic field sintering processes. Mechanical properties, cross-sectional morphology, refractoriness, fluidity and structural characterization have been carried out to understand the role of TiO2 addition and sintering conditions. Results show that TiO2 addition significantly affected bending strength, refractoriness and fluidity of vitrified bonds. In addition, high magnetic field sintering improved bending strength and the microstructure of vitrified bond CBN composites. Due to high magnetic field sintering, CBN grains were completely covered by vitrified bond and exhibited fewer pores. In addition, high magnetic field promoted the growth of specific grains, such as SiO2, whereas suppressed grain growth of other crystal phases, such as NaAlSi3O8. 相似文献
4.
《Ceramics International》2020,46(13):21202-21210
Differences in structure and properties of Na2O–Al2O3–B2O3–SiO2 vitrified bonds and vitrified diamond composites prepared by sol-gel and melting methods were methodically discussed. Results showed that the vitrified bond prepared by sol-gel method contained more [AlO4] tetrahedron and owned higher bending strength, with the maximum value reaching 137 MPa, 31.73% higher than that prepared by melting method (104 MPa). As the sintered temperature rose, coefficient of thermal expansion of the vitrified bond prepared by sol-gel method increased first and then decreased, acquiring a maximum value of 5.75 × 10−6 °C −1 at 720 °C, which was still much lower than the minimum value of vitrified bond prepared by melting method (7.02 × 10−6 °C −1). The vitrified diamond composite prepared by sol-gel method possessed lower sintering shrinkage than that prepared by melting method, and could be applicable to the production of grinding tools with high dimensional accuracy. What's more, the maximum bending strength of vitrified diamond composites obtained by sol-gel method was 106 MPa, 24.7% higher than that of vitrified diamond composites prepared by melting method (85 MPa). 相似文献
5.
Tianbiao Yu Zhelun Ma Xuezhi Wang Boxue Song Wanshan Wang 《Ceramics International》2018,44(8):9312-9317
Properties of vitrified bond with varying Ni doping amounts were extensively investigated. Effects of Ni addition on microstructures and properties of vitrified bond cubic boron nitride (CBN) composites prepared in strong magnetic field were investigated for applications in CBN grinding tools. Vitrified bond was characterized using three-point bending, scanning electron microscopy, X-ray diffraction and other methods. The refractoriness, fluidity, and bending strength of vitrified bond were evaluated. Bending strengths, microstructures, and phase compositions of vitrified bond CBN composites achieved using conventional and strong electromagnetic sintering techniques were compared. Results show that the addition of Ni to vitrified bond CBN composites improved the fluidity and bending strength of the vitrified bond. Strong electromagnetic sintering improved the mechanical strength and pore structure of vitrified bond CBN composites. Moreover, the introduction of the strong magnetic field facilitated Ni migration and aggregation in vitrified bond, rotated abrasives, and formed new substances, thus increasing the stability of vitrified bond CBN composite thermal material. Also, strong magnetic field inhibit grain growth of non-magnetic and ferromagnetic materials with fine-grain effect. 相似文献
6.
In this paper, synthesis of novel super hard and high performance composites of titanium silicon carbide–cubic boron nitride (Ti3SiC2–cBN) was evaluated at three different conditions: (a) high pressure synthesis at ~ 4.5 GPa, (b) hot pressing at ~ 35 MPa, and (c) sintering under ambient pressure (0.1 MPa) in a tube furnace. From the analysis of experimental results, the authors report that the novel Ti3SiC2–cBN composites can be successfully fabricated at 1050 °C under a pressure of ~ 4.5 GPa from the mixture of Ti3SiC2 powders and cBN powders. The subsequent analysis of the microstructure and hardness studies indicates that these composites are promising candidates for super hard materials. 相似文献
7.
Al2O3-cBN/Ni composites were consolidated by spark plasma sintering (SPS) using α-Al2O3 and Ni nanoparticle precipitated cBN (cBN/Ni) powders. The Ni nanoparticles, 10-100 nm in diameter and 0.5-2.2 mass% in content, were precipitated on cBN powder by rotary chemical vapor deposition. The effect of sintering temperature (TSPS) and Ni content (CNi) on the densification, phase transformation, microstructure and hardness of the Al2O3-cBN/Ni composites were investigated. The highest relative density of Al2O3-30 vol% cBN composite was 99% at TSPS = 1573 K and CNi = 1.7 mass%. At TSPS = 1673 K, the relative density decreased due to the phase transformation of cBN to hBN. The Vickers hardness of Al2O3-30 vol% cBN/Ni at TSPS = 1573 K and CNi = 1.7 mass% showed the highest value of 27 GPa. 相似文献
8.
《Ceramics International》2022,48(11):15565-15575
The vitrified bond CBN grinding wheels are characterized by high efficiency, high precision, and low environmental pollution. In recent years, the vitrified bond CBN grinding wheel has been widely used in manufacturing industries such as aerospace, automotive, and machine tools. In this study, a novel vitrified bond formulation containing nano SiO2 and nano CeO2 is selected to prepare the grinding wheel. The grinding experiments on 45# steel and YG20 alloy indicate that the grinding performance of the nano vitrified bond grinding wheel is significantly better than that of the conventional vitrified bond grinding wheel. The introduction of nano SiO2 and nano CeO2 greatly improves the machining performance of the vitrified bond CBN grinding wheel. 相似文献
9.
《Ceramics International》2015,41(8):9916-9922
The effects of Y2O3 addition on the structure and properties of Li2O–ZnO–Al2O3–SiO2 (LZAS) vitrified bonds were firstly investigated for CBN grinding tools application. Glasses and glass-ceramics were characterized using differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy and infrared spectroscopy. The thermal expansion coefficient (TEC), microhardness, bending strength and chemical durability of the obtained products were also evaluated. Results showed that Y2O3 acted as the network former in the track of SiO4 tetrahedrals. Introducing Y2O3 in the glasses increased the glass transition temperature and crystallization temperature. The crystallization of the main β-quartzss phase increased with increase of Y2O3 content. The morphology of the crystals was dependent on the Y2O3 content. The TEC (5.15×10−6/°C) of vitrified bond containing 1.0 mol% Y2O3 (Y1.0) was very close to the TEC (5.0×10−6/°C) of CBN grains. Moreover, Y1.0 vitrified bond exhibits a high microhardness (5.98 GPa), a high bending strength (202 MPa) and a good chemical durability (20 days, DR=2.8×10−9 g/cm2 min), suggesting that it would be a promising material for CBN grinding tool. 相似文献
10.
In this study, conducting banana fibers (BF) were obtained through in situ oxidative polymerization of pyrrole (Py) on the BF surface using ferric chloride hexahydratate (FeCl3·6H2O) as an oxidant. Suitable reaction conditions are outlined for the polymerization of Py: oxidant/monomer molar ratio, Py concentration and polymerization time of 2/1, 0.05 mol.L−1 and 30 min, respectively. Under these conditions, high‐quality conducting fibers containing polyPy and BF (PPy‐BF) were obtained with an electrical resistivity as low as 0.54 Ω.cm. The PPy‐BF was blended with different concentrations of polyurethane (PU) by mixing the two components in a vacuum chamber and then applying compression molding. The electrical resistivity of composites with 25 wt% of PPy‐BF was around 1.8 × 105 Ωcm, which is approximately 108 times lower than that found for pure PU. Moreover, PU/PPy‐BF composites exhibited higher mechanical properties than pure PU and PU/PPy, indicating that these conducting fibers can also be used as reinforcement for polymer matrices. The properties of the PPy‐BF obtained by the method described herein open interesting possibilities for novel applications of electrically conducting fibers, from smart sensors to new conducting fillers that can be incorporated into several polymer matrixes to develop conducting polymer composites with good mechanical properties.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers 相似文献
11.
Chu Kuen Ong Sudip Ray Ralph P. Cooney Neil R. Edmonds Allan J. Easteal 《应用聚合物科学杂志》2008,110(1):632-640
Composite sheets of polyethylene and polypyrrole‐coated wollastonite were prepared by extrusion and compression molding. Four compatibilizers were also evaluated, poly(ethylene‐co‐methyl acrylate) (EMA), maleated polyethylene (MAPE), poly(ethylene‐co‐vinyl alcohol) (EVOH), and poly(vinyl alcohol) (PVOH). The composite materials were characterized using X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy (SEM), Raman spectroscopy, and mechanical properties determined by tensile tests. SEM micrographs showed that significantly improved interactions occurred between the PE matrix and polypyrrole‐coated wollastonite particles in the presence of EMA, MAPE, and EVOH. Raman spectroscopy confirmed that the polypyrrole coating on the wollastonite particles was not thermally degraded during melt processing. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
12.
《应用陶瓷进展》2013,112(2):123-127
AbstractThis article describes the synthesis of a CeO2 fine powder by thermal decomposition of cerium oxalate and cerium nitrate powders using a microwave furnace. Plate-like crystalline CeO2 particles were obtained using the cerium oxalate precursor powder. Using the cerium nitrate powder as a precursor, spherical crystalline CeO2 particles were obtained with a primary particle diameter of 30?nm and secondary particle size of 550?nm. 相似文献
13.
This study describes the synthesis of doped polyaniline in its emeraldine salt form (PANI-ES) with carboxylic groups containing multi-walled carbon nanotubes (c-MWNTs) via in situ polymerization. Both Raman and FTIR spectra indicate that carboxylic acid groups formed at both ends and on the sidewalls of the MWNTs. Based on the π-π* electron interaction between aniline monomers and MWNT and hydrogen bonding interaction between the amino groups of aniline monomers and the carboxylic acid group of c-MWNT, aniline molecules were adsorbed and polymerized on the surface of MWNTs. Structural analysis using FESEM and HRTEM showed that PANI-ES/c-MWNT composites are core (c-MWNT)-shell (doped-PANI-ES) tubular structures with diameters of several tens to hundreds of nanometers, depending on the PANI content. The conductivities of these PANI-ES/c-MWNT composites are 50-70% higher than those of PANI without MWNT. 相似文献
14.
This study reports the synthesis of doped polyaniline in its emeraldine salt form (PANI-ES) with carboxylic acid and acylchloride groups contained multi-walled carbon nanotubes (designated as c-MWNTs and a-MWNTs) by in situ polymerization. Both Raman spectra and HRTEM images indicate that carboxylic acid and acylchloride groups formed at both ends and on the sidewalls of the MWNTs. Based on the π-π* electron interaction between aniline monomers and functionalized MWNT and hydrogen bonding interaction between the amino groups of aniline monomers and the carboxylic acid/acylchloride groups of functionalized MWNT, aniline molecules were adsorbed and polymerized on the surface of MWNTs. Structural analysis by FESEM and HRTEM showed that PANI-ES/c-MWNT and PANI-ES/a-MWNT composites are core (c-MWNT or a-MWNT)- shell (doped-PANI-ES) tubular structures with diameters of several tens to hundreds of nanometers, depending on the PANI content. The conductivities of 0.5 wt% functionalized MWNT containing PANI-ES/c-MWNT and PANI-ES/a-MWNT composites are 60-70% higher than that of PANI without MWNT. 相似文献
15.
《Ceramics International》2015,41(7):8710-8716
The combination of the attractive properties of graphene with excellent characteristics of other functional nanomaterials has become a popular pathway for achieving applications in multiple fields. Herein, reduced graphene oxide (RGO)/CeO2 nanocomposites with enhanced capacitive performance were designed and synthesized by a facile two-step approach with a self-assembly method followed by thermal treatment. The structure, morphology and composition of the resulting RGO/CeO2 nanocomposites were systematically investigated. The presence of RGO can prevent the aggregation and control the structures of the CeO2 nanocrystals in the annealing process. The nanocomposites as electrode materials for supercapacitor exhibited an enhanced capacitive performance due to the synergic effect between RGO nanosheets and CeO2 nanocrystals. The excellent capacitive performance of the RGO/CeO2 nanocomposites offer great promise for supercapacitor applications. 相似文献
16.
Composites of polyaniline (PANI) nanorods and multiwalled carbon nanotubes (MWNTs) coated with PANI were prepared by in situ polymerization with perchloric acid as a dopant. Transmission electron microscopy images showed that the coexisting composites of PANI nanorods and MWNTs coated with PANI were formed at low MWNT contents. The interaction between MWNTs and PANI was proved by Fourier transform infrared and ultraviolet–visible spectra. The electrical conductivity of a dedoped PANI/MWNT composite with a 16.3 wt % concentration of MWNTs reached 3.0 × 10?3 S/cm, which was 6 orders of magnitude higher than that of dedoped PANInanorods. The results also showed that coexisting composites of PANI nanorods and MWNTs coated with PANI had high electrochemical activity and good cyclic stability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
17.
Preparation and characterization of CNTs-TiO2 composites 总被引:1,自引:0,他引:1
Carbon nanotubes-based TiO2 composites were fabricated by hydrolysis, and the transmission electron microscopy(TEM) results showed that carbon nanotubes were partly coated with TiO2. X-ray photoelectron spectroscopy (XPS) results of purified carbon nanotubes indicated that there were some polar oxygenated groups such as C-O, C=O and O-C=O which might stimulate formation of the composites, and enhance the interfacial combination of TiO2 with carbon nanotubes. The formation of TiO2 and its compounding with CNTs happened almost simultaneously in this process. The method is a convenient route to fabricate CNTs-based TiO2 composites with different ratios. 相似文献
18.
Symalla M. O. Drochner A. Vogel H. Philipp S. Göbel U. Müller W. 《Topics in Catalysis》2007,42(1-4):199-202
The storage of NO, NO/O2-mixtures and NO2 on CeO2 and BaO/CeO2 was investigated by in situ DRIFT-spectroscopy. The NOx-storage capacity, as well as the kinetic and the mechanism of the NOx-storage process are influenced by the temperature and the BaO-loading as well as the oxygen partial pressure. The addition
of oxygen into NO containing gas mixtures results in the oxidation of the stored nitrite to nitrate species. Adsorption of
NO2 leads to in the formation of nitrite and nitrate species, where the nitrite species are completely oxidized to nitrate in
the progress of storage. 相似文献
19.
采用溶胶-凝胶法,制备了铈硅包覆金红石型钛白粉,通过正交实验考察了浆液浓度、分散剂用量和两种包膜剂含量对铈硅包覆金红石型钛白粉性能的影响。采用Nano-ZS型粒度仪、扫描电镜(SEM)、透射电镜(TEM)和能谱(EDS)等测试手段,对金红石型钛白粉的Zeta电位、表面形貌和元素进行了表征。结果表明:在水浴温度为80 ℃左右、转速为600 r/min、浆液质量浓度为400 g/L、分散剂质量分数为0.1%、二氧化铈质量分数为3%、二氧化硅质量分数为4%的条件下,金红石型钛白粉表面包覆了两层均匀而致密的二氧化硅和二氧化铈膜;罗丹明B光催化降解实验证实,铈硅包覆明显改善了金红石型钛白粉的光催化屏蔽性。 相似文献
20.
Al-xNi-yCeO2 (x = 6, 10, 15, 20 and y = 0, 5, 10 wt%) composites were produced by a powder metallurgical production route. Powder mixtures of Al, Ni and CeO2 were fabricated via mechanical alloying (MA) for 4 h in a Spex-type high-energy ball mill. Both the mechanically alloyed (MAed) and non-MAed (as-blended mixtures) powders were pre-compacted in a hydraulic press under 650 MPa and then pressurelessly consolidated at 630 °C for 2 h under an inert atmosphere. The effects of MA process and the amounts of Ni and CeO2 on the microstructural, mechanical and tribological properties of the sintered composites were determined. Based on the SEM and XRD investigations, the MAed powders illustrated a homogenous structure, comprising flaky particles with smaller crystallite sizes and greater lattice strain. According to the XRD analysis, Ni formed Al–Ni intermetallic compounds in the matrix of sintered composites that act as secondary reinforcement phases. The SEM observations conducted on the MAed samples demonstrated more uniformly and finely distributed Al3Ni and CeO2 phases in the microstructure of the MAed samples, unlike the non-MAed ones. The hardness values of sintered composites increased due to the MA process and increasing Ni and CeO2 amounts, and the hardness value of the MAed Al20Ni–10CeO2 sample reached 179 HV. The ultimate compressive strength and failure strain of the MAed Al6Ni–10CeO2 sample were 441 MPa and 11.3%. In the Al20Ni–10CeO2 sample, the compressive strength and failure strain were 391 MPa and 5.5%, respectively. Additionally, the reciprocating wear test results illustrated that both wear resistance and hardness values of the composites increased as the amounts of Ni and CeO2 increased, and the Al20Ni–10CeO2 sample exhibited the highest wear resistance as 0.175 × 10-3 mm3/Nm. 相似文献