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1.
In this work, a new method for the preparation of magnesium silicon nitride (MgSiN2) nanopowder was studied using a two-step process in nitrogen gas from Mg/Si starting mixtures. This method is known as mechanical alloying followed by heat treatment. The results showed that the compositions of the combustion products depended on the starting mixtures. In addition, the content of magnesium and silicon in the starting powder should fulfil the condition Mg/Si?=?2 to obtain single phase MgSiN2.Single phase MgSiN2 nanopowder can be fabricated from Mg and Si powders with mole ratio of 2:1 at 1350°C in N2 atmosphere. Composition and structure of reactants and products were examined by X-ray diffraction, field emission scanning electron microscopy and high resolution transmission electron microscopy. 相似文献
2.
《Ceramics International》2016,42(7):7974-7979
In this paper forsterite (Mg2SiO4) nanopowder with particle size in the range of 33 and 112 nm was synthesized by a combination of sol–gel and ball milling methods. Magnesium nitrate and silica were used as the sources of magnesium and silicon in the forsterite nanopowder. Thermogravimetry (TG) analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and dynamic light scattering (DLS) techniques were utilized to characterize the synthesized powders. Single-phase nanocrystalline forsterite powder with mean crystallite size of about 16 nm was obtained from sol–gel method with subsequent ball milling for 5 h and heat treatment at 750 °C for 1 h. A combination of sol–gel and mechanical activation led to the formation of more homogeneous powder and subsequently lower sintering temperature to produce forsterite powder. In vitro biological studies were performed by immersing the forsterite samples in simulated body fluid (SBF). The results showed that nanostructure forsterite is bioactive and possessed apatite formation ability. 相似文献
3.
Effects of Mg‐Doping and of Reinforcing Multiwalled Carbon Nanotubes Content on the Structure and Properties of Hydroxyapatite Nanocomposite Ceramics
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Meriame Bricha Younes Belmamouni Khalil El Mabrouk José M. F. Ferreira 《International Journal of Applied Ceramic Technology》2015,12(2):264-272
Surfactant‐assisted hydrothermal synthesis of magnesium‐doped hydroxyapatite (Ca10?xMgx(PO4)6(OH)2) with 0 ≤ x ≤ 1) was realized in aqueous solution at 90°C. β‐TCP phase was formed in the Mg0.6‐HA sample after heat treatment at 1000°C. Magnesium was found to degrade the sintering ability of Mgx‐HA ceramics. Flexural strength (σf) was found to decrease as a function of Mg‐doped HA. The using of carbon nanotubes as reinforcing agents mitigated the strength loss of Mg‐HA ceramics. The flexural strength of Mg0.6‐HA was then increased by nearly 20% from approximately 33 to 39 MPa with an optimum addition of 3 wt% of multi‐walled nanotubes. 相似文献
4.
《Ceramics International》2016,42(13):14867-14872
A two-step process (milling and then heat treatment) was used for the preparation of α-Si3N4 nanopowder. The influence of the milling time and heat treatment temperature as processing parameters were investigated on the formation of α-Si3N4. Silicon nitride ceramic was produced by spark plasma sintering at 1700 °C for 15 min, using MgSiN2 additive. The optimum sample was produced in a 30 h milling time, heat treatment at 1300 °C, and a 22 °C/min heating rate conditions. X-ray fluorescence analysis showed that the purity of the final product is above 98%. Nanoindentation hardness and Young’s modulus of the SPS-ed sample were measured as 17±2.0 GPa and 290±11.0 GPa, respectively. 相似文献
5.
Interfacial Reactions Between Anorthite (CaAl2Si2O8) and Al 7075 Alloy at 850°C and 1150°C
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Esmaeil Adabifiroozjaei Pramod Koshy Ebad Rastkerdar Charles C. Sorrell 《Journal of the American Ceramic Society》2016,99(5):1694-1708
The present work reports an investigation of the interactions of Al 7075 alloy and anorthite at 850°C (150 h) and 1150°C (24 h). Transmission electron microscopy, electron probe microanalysis, X‐ray diffraction, and scanning electron microscopy coupled with energy‐dispersive spectroscopy were used to identify the mineralogical and microstructural changes at the metal–ceramic interface. At 850°C, the phase formation mechanisms were (a) Si4+–Al3+ interdiffusion between the Al alloy and anorthite to form calcium dialuminate (CA2) and Ca2+–Mg2+ interdiffusion between the Al alloy and calcium dialuminate to form spinel. At 1150°C, spinel + Al2O3 and calcium hexaluminate (CA6) + CA2 were the major and minor phase mixtures, respectively in the corroded area. A thin layer of calcium monoaluminate (CA), gehlenite, and Si was present in the immediate vicinity of anorthite. The early stages of corrosion at 1150°C and 850°C were identical. However, due to thickening of the corroded region (viz., spinel formation) and enhanced evaporation of Mg at the higher temperature, the interdiffusion path evolves from Si4+–Al3+ + Ca2+–Mg2+ to Si4+–Al3+ + Ca2+–Al3+, thus establishing the following phase evolution path at the interface: 相似文献
6.
Esmaeil AdabiFiroozjaei Pramod Koshy Charles Christopher Sorrell 《Journal of the European Ceramic Society》2012,32(8):1463-1471
Interfacial reactions between Al-alloy and andalusite low-cement castables (LCC) containing 5 wt% V2O5 were analyzed at 850 °C and 1160 °C using the Alcoa cup test. Interfacial reaction products and phases formed during heat treatment of the refractory samples were characterized using scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) analysis. V2O5 addition resulted in the formation of glassy phases, which significantly improved the corrosion resistance. These phases were preferentially corroded by the alloy, due to their glassy nature. However, vanadium formed from reduction, formed intermetallic alloys (V–Al–Si–Mg), which formed an interfacial physical barrier to further alloy penetration. 相似文献
7.
Kazuyuki Kohama 《Ceramics International》2021,47(16):22424-22434
Silicon-nitride (Si3N4) components were joined under vacuum at 1100 °C for 10 min using Si–Mg composite fillers with Mg contents (XMg) that ranged from 0 at.% to 59 at.%. The Si3N4/Si3N4 joints were fabricated via Si layer formation at the joint interface; the molten Si–Mg liquid was transformed into a solid Si layer after Mg-evaporation-induced isothermal solidification. The joint tensile strength at room temperature increased considerably when XMg exceeded the liquidus composition of 37 at.% because of the enhanced densification/thinning of the Si layer. In these cases, some Mg atoms reacted with Si3N4 to form a fine-grained MgSiN2-based layer, whereas relatively large (>0.1 μm) and smaller MgO precipitates (<10 nm) were observed in the Si layer. At a high XMg, the MgO precipitates were arranged in a network-like structure, which improved the fracture strength of the Si layer. The joints with a high strength at room temperature were examined using a three-point bending test at 1200 °C in air and endured a maximum fracture stress of ~200 MPa, which confirmed their potential for use in oxidizing atmospheres at least 100 °C above the bonding temperature. 相似文献
8.
《Ceramics International》2016,42(9):11217-11223
Reaction ignition and chemical mechanisms in volume combustion synthesis of TiB2 via TiO2–B2O3–Mg precursors were studied using in-situ differential thermal analysis, X-ray diffraction, scanning electron microscopy and thermochemical modeling. Mg–TiO2 samples ignited at 607 °C through a sudden single step solid-solid reaction while Mg–B2O3 samples ignited at 810 °C after melting of magnesium. X-ray diffraction analysis revealed that reduction of TiO2 occurs in multiple steps and forms intermediate compounds. Results showed that heat released from the first reaction between TiO2 and Mg ignites the reactions between Mg, Ti and B2O3 resulting in the formation of TiB2. Samples with larger TiO2 particle size or a higher sample surface to volume ratio showed a two-step reaction behavior and the released heat in the first solid state reaction was insufficient for the propagation of the reaction throughout the sample. In addition, Mg3B2O6 undesired by-product was formed as a result of this two-step reaction. 相似文献
9.
Transformation of Brushite (CaHPO4·2H2O) to Whitlockite (Ca9Mg(HPO4)(PO4)6) or Other CaPs in Physiologically Relevant Solutions
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A. Cuneyt Tas 《Journal of the American Ceramic Society》2016,99(4):1200-1206
Brushite (dicalcium phosphate dihydrate, DCPD, CaHPO4·2H2O) and whitlockite [WH, Ca9Mg(HPO4)(PO4)6] are usually found in the mammalian metabolism in the form of diverse pathological calcifications, dental calculi, urinary tract stones, salivary gland deposits, cardiovascular or pulmonary calcified deposits, and even as prostate or cartilage calcifications. The hydrothermal transformation of synthetic brushite crystals into single‐phase whitlockite, octacalcium phosphate, or apatitic calcium phosphate was observed over the time period of 1 to 21 d and at 37°C, 70°C, and 115°C in nonstirred physiologically relevant solutions developed for this work. The strong influence of the physiologically relevant ions such as Mg2+ and HCO3? on hydrothermal transformations is exposed. The formation of the nanoglobules and nanofibrils of X‐ray amorphous calcium phosphate or Mg‐doped calcium phosphate on the surfaces of brushite crystals are observed for the first time in biomimetic solutions containing 10 mm Mg2+ and/or 27 mm HCO3?. The experimental conditions leading to the formation of such nanofibrils on brushite crystal surfaces are also found to stop the further transformation of brushite into any other calcium phosphate (CaP) phases even at high solution temperatures. Samples were characterized by scanning electron microscopy and powder X‐ray diffraction. 相似文献
10.
G. Suárez-Campos D. Cabrera-German J.A. García-Valenzuela M. Cota-Leal J.L. Fuentes-Ríos M. Martínez-Gil H. Hu M. Sotelo-Lerma 《Ceramics International》2019,45(8):10356-10363
The chemical solution deposition of Mg(OH)2 thin films on glass substrates and their transformation to MgO by annealing in air is presented. The chemical solution deposition consists of a chemical reaction employing an aqueous solution composed of magnesium sulfate, triethanolamine, ammonium hydroxide, and ammonium chloride. The as-deposited films were annealed at different temperatures ranging from 325 to 500?°C to identify the Mg(OH)2-to-MgO transition temperature, which resulted to be around 375?°C. Annealing the as-deposited Mg(OH)2 films at 500?°C results in homogeneous MgO thin films. The properties of the Mg(OH)2 and MgO thin films were analyzed by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, UV–Vis spectroscopy, and by circular transmission line model. Results by X-ray diffraction show that the as-deposited thin films have a brucite structure (Mg(OH)2), that transforms into the periclase phase (MgO) after annealing at 500?°C. For the as-deposited Mg(OH)2 thin film, a nanowall surface morphology is found; this morphology is maintained after the annealing to obtain MgO, which occurred with the evident formation of pores on the nanowall surface. The assessed chemical composition from X-ray photoelectron spectroscopy yields Mg0.36O0.64 (O/Mg ratio of 1.8) for the as-deposited Mg(OH)2 film, where the expected stoichiometric composition is Mg0.33O0.67 (O/Mg ratio of 2.0); the same assessment yields Mg0.60O0.40 (O/Mg ratio of 0.7) for the annealed thin film, which indicates the obtainment of a MgO material with oxygen vacancies, given the deviation from the stoichiometric composition of Mg0.50O0.50 (O/Mg ratio of 1.0). These results confirm the deposition of Mg(OH)2 films and the obtainment of MgO after the heat-treatment. The energy band gap of the films is found to be 4.64 and 5.10?eV for the as-deposited and the film annealed at 500?°C, respectively. The resistivity of both Mg(OH)2 and MgO thin films lies around 108?Ω·cm. 相似文献
11.
This paper reports the development of a new process for the synthesis and sintering of forsterite nanopowder via microwave-assisted high energy ball milling of a powder mixture containing silica gel and Mg(OH)2. X-ray diffraction (XRD), FTIR spectrometer, BET, scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) techniques were utilized to characterize the as-milled and annealed samples. X-ray diffraction results showed that highly ordered forsterite can be obtained through the calcination of the as-milled powder over 900 °C. In addition, SEM and TEM observations of the synthesized powders showed that the particle size of the powder lies in the nanometer range, also being compared with the BET results (about 45 to 64.5 nm). Microwave sintering (MS) of the forsterite nanopowder produced with high energy ball milling and subsequent microwave heating resulted in remarkable enhancement in densification in comparison with conventional sintering (CS) at lower temperatures. 相似文献
12.
《Ceramics International》2023,49(10):15544-15552
The influence of hydrogen on a (Co0·2Cu0·2Mg0·2Ni0·2Zn0.2)O HEO with a rock salt structure was studied. Two forms of this HEO (nanopowder and sinter) were prepared via mechanochemical synthesis (MS) and additional heat treatment, respectively. The chemical stability of the synthesized samples in a pure hydrogen atmosphere was investigated using Sievert's technique. High-pressure hydrogenation at 250 °C had no noticeable effect on the HEO sinter. The sintered sample was chemically, structurally, and morphologically stable, as confirmed via the XRD, Raman spectroscopy, SEM, and XPS techniques. Thermogravimetric analysis (TGA) showed the sinter to be stable in an argon gas mixture with 5 vol% of hydrogen and over the temperature range of up to 400 °C. 相似文献
13.
Mi Tian Congxiao Shang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(1):69-74
BACKGROUND: Magnesium hydride is considered to be a promising hydrogen storage material because of its high gravimetric and volumetric storage capacities. However, its slow kinetics and high desorption temperature of > 300 °C limit practical applications. In this work, TiC nanoparticles were selected to modify the hydrogen storage properties of MgH2. Composite mixtures (MgH2 + TiC) were prepared using both cryogenic milling and high‐energy ball milling. RESULTS: The resulting morphology and crystallite structure of the composites were identified by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The milled samples show good mixing of the hydride and carbide particles, with MgH2 particles around 0.09–1 µm and TiC particles 10–20 nm. The (MgH2 + TiC) composites consist of γ‐MgH2, β‐MgH2 and TiC. MgH2 nano‐crystallites of 25 nm were formed after cryomilling. Thermogravimetry reveals that the composites release ~6.5 mass % hydrogen from 190–400 °C at a heating rate of 10 °C min?1 under He flow, with the onset and peak temperatures at 190 and 280 °C, respectively, for the (MgH2 + TiC) after 8 h cryomilling and 60 h ball milling. CONCLUSION: Results indicate that TiC is an effective catalyst for hydrogen desorption of MgH2. Copyright © 2010 Society of Chemical Industry 相似文献
14.
ZrB2–SiC–G Composite Prepared by Spark Plasma Sintering of In‐Situ Synthesized ZrB2–SiC–C Composite Powders
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YeHong Cheng Yushi Qi Ping Hu Shanbao Zhou Guiqing Chen Jiadong An Kunfeng Jin Wenbo Han 《Journal of the American Ceramic Society》2016,99(6):2131-2137
To avoid introduction of milling media during ball‐milling process and ensure uniform distribution of SiC and graphite in ZrB2 matrix, ultrafine ZrB2–SiC–C composite powders were in‐situ synthesized using inorganic–organic hybrid precursors of Zr(OPr)4, Si(OC2H5)4, H3BO3, and excessive C6H14O6 as source of zirconium, silicon, boron, and carbon, respectively. To inhabit grain growth, the ZrB2–SiC–C composite powders were densified by spark plasma sintering (SPS) at 1950°C for 10 min with the heating rate of 100°C/min. The precursor powders were investigated by thermogravimetric analysis–differential scanning calorimetry and Fourier transform infrared spectroscopy. The ceramic powders were analyzed by X‐ray diffraction, X‐ray photoelectron spectroscopy, and scanning electron microscopy. The lamellar substance was found and determined as graphite nanosheet by scanning electron microscopy, Raman spectrum, and X‐ray diffraction. The SiC grains and graphite nanosheets distributed in ZrB2 matrix uniformly and the grain sizes of ZrB2 and SiC were about 5 μm and 2 μm, respectively. The carbon converted into graphite nanosheets under high temperature during the process of SPS. The presence of graphite nanosheets alters the load‐displacement curves in the fracture process of ZrB2–SiC–G composite. A novel way was explored to prepare ZrB2–SiC–G composite by SPS of in‐situ synthesized ZrB2–SiC–C composite powders. 相似文献
15.
《Ceramics International》2019,45(13):16275-16278
We have reported the successful growth of Mg2GeO4 nano-crystals by simple thermal evaporation technique. The Mg and Ge metal powders were evaporated on the Si substrate and kept the oxygen flow rate of 100 sccm. The modulation of structural, morphological, thermoelectric and electrical properties was performed by controlling the thermal energy of carriers using different annealing temperatures. XRD data showed a peak at 61.80 which was related to (212) plane of Mg2GeO4. XRD data further suggested that sample annealed at 700 °C has stable crystal structure while sample annealed at 800 °C posses degraded structure because the presence of highest density of donors defects. This defect concentration causes an increase in the conductivity of annealed samples as evident by the Hall data. This argument was also supported by Raman spectroscopy which showed that sample annealed at 700 °C has strongest Mg2GeO4 Raman peak. SEM images also verified the smooth surface of the sample annealed at 700 °C. The temperature dependent (25–100 °C) Seebeck effect measurements were performed to calculate the Seebeck coefficient of Mg2GeO4 nano-crystals at different measurement temperatures. The highest value of room temperature Seebeck coefficient (397 μV/0C) for the sample annealed at 800 °C is due the high density of carrier concentration. 相似文献
16.
Liga Stipniece Inga Narkevica Kristine Salma‐Ancane 《Journal of the American Ceramic Society》2017,100(4):1697-1706
Nanocrystalline Mg‐ or Sr‐containing hydroxyapatite powders were synthesized through low‐temperature chemical precipitation. The most significant factor for reduction in particle sizes included adjusting the reaction temperature between 0°C and 50°C. Syntheses products were characterized using several analytical tools to determine purity and influence of added amount (up to 15 mol%) of Mg or Sr on the composition and structure. Qualitative analysis by Fourier transform infrared spectroscopy and low intensity, broad X‐ray diffraction peaks indicated the presence of nanocrystalline and/or amorphous hydroxyapatite in all the products. Moreover, a significant decrease in the crystallinity was observed with increasing Mg (up to 2.8 ± 0.3 wt%) and Sr (up to 9.6 ± 1.0 wt%) concentration. N2 adsorption and scanning electron microscopy characterizations confirmed the nanocrystalline nature of the synthesized products. The synthesized products had nanosized spherical‐like particle morphology with the specific surface area ranging from 89 ± 7 to 150 ± 20 m2/g. 相似文献
17.
《Carbon》2014
Microstructural and mechanical behavior of heat treatable Al–Mg–Si (6XXX series) alloy composites reinforced with multi-wall carbon nanotubes (MWCNTs) fabricated by powder metallurgy process were investigated by SEM-EDS, XRD, tensile test and Vicker’s hardness test. As-extruded P/M 6063 alloy composites with CNT reinforcements indicated a small increment of mechanical strength compared to the monolithic 6063 alloy with no CNT before T6 heat treatment. When T6 heat treatment was applied to the specimens, the 6063 composite with CNTs showed a noticeable decrease of yield stress (YS) improvement, compared to the monolithic Al alloy. It means that Mg2Si precipitates hardening effect by the artificial aging treatment was insufficient for the composite containing CNTs. This was mainly because Mg alloying elements were diffused around CNTs and consumed to form Al2MgC2 compounds, and resulted in the incomplete matrix strengthening behavior by Mg2Si precipitation after the aging treatment. 相似文献
18.
《Ceramics International》2020,46(2):1472-1486
The current study aims to investigate the microstructural properties, diametral tensile strength, Weibull modulus, and surface roughness (Ra) of the zirconia-mullite composites. The simultaneous effect of duration of the mechanical activation (MA) process of starting materials, as well as TiO2 and ZnO additions on the mentioned properties, were studied. X-ray diffraction analysis showed that mullite was the main crystalline phase in 6–24 h mechanically activated-TiO2 containing samples which were subsequently heat treated at 1450 °C. Prolonging the duration of the MA process to 72 h led to the crystallization of the tetragonal zirconia as one of the main crystalline phase in the mentioned samples. As the heat treatment temperature increased to 1550 °C, the dependence of the type of the crystalline phases on the milling time eliminated and mullite became the main crystalline phase in 6–72 h MA processed samples. The transformation of starting materials to mullite and t-zirconia was not progressed effectively in ZnO containing samples which were heat treated at 1450 °C. However, by increasing the temperature of the heat treatment process to 1550 °C, both mullite and zirconia were efficiently crystallized in 6–72 h MA processed ZnO containing ones. Scanning electron microscopy results revealed that prolonging the duration of the milling process of the additive containing mixtures from 6 to 72 h could eliminate the acicular morphology of the mullite phase. 72 h mechanically activated ZnO containing sample which was later heat-treated at 1550 °C had the highest noticeable diametral tensile strength of 270 ± 15 MPa. The Weibull modulus of composite samples increased from 10.07 to 12.37 and 20.95 by the addition of TiO2 and ZnO to the starting mixture, respectively. Finally, it was found that prolonging the milling time increased the Weibull modulus remarkably and decreased the Ra values as a result of the homogeneity development in the composite samples. 相似文献
19.
Copper ferrite (CuFe2O4) was synthesised from an equimolar mixture of copper and iron oxides by mechanosynthesis and subsequent heat treatment. After mechanosynthesis, depending on the milling time, the powder consists in a mixture of phases. The heat treatment at 600 °C did not lead to a complete reaction of the mechano-activated precursors. After the heat treatments at 800 and 1000 °C, the complete formation of copper ferrite for almost all the milling times was noticed. The crystal structure of the copper ferrite was found to be cubic for all the samples heat treated at 1000 °C and a mixture of tetragonal and cubic for the samples heat treated at 800 °C. The amount of copper ferrite with cubic structure predominates in the samples with prolonged milling duration and a decrease of the tetragonal distortion by increasing the milling time occurs. The crystallisation of CuFe2O4 in cubic structure for the samples milled for prolonged time is influenced by the powder contamination with iron. The magnetisations of the samples obtained after heat treatment at 1000 °C were found to be larger compared to the ones of the samples heat treated at 800 °C. The iron contamination, milling duration and heat treatment temperature influence the cations distribution, thus leading to the saturation magnetisation of the copper ferrite samples ranging from 11.9 μB/f.u. to 16.4 μB/f.u. 相似文献
20.
The chemical interaction study of AO–SiO2–B2O3–Y2O3 (A = Ba, Sr) (BaY, SrY) glass with high‐temperature electrolyte yttria‐stabilized zirconia (YSZ 8 mol%) is reported as a function of different heat treatment durations. The as‐prepared glass with 10 mol% of yttria shows limited amount of crystallization at 800 °C. Due to this yttria‐based glasses BaY and SrY have been chosen to make diffusion couples with high‐temperature electrolyte and interconnect material. These diffusion couples have been heat treated at 850 °C, for 100, 200, and 500 h. The heat‐treated diffusion couples have been characterized using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Microstructural analysis of diffusion couples shows absence of any undesired oxides and detrimental reaction products at the interface. The glass has shown good bonding characteristics and absence of cracks, pores, or any kind of delamination from YSZ. Apart from this, SrY and BaY glass seals have also shown good adhesion characteristics with Crofer 22 APU, even after 500 h at 850 °C. The morphology and microstructure of the glass matrix suggest limited amount of devitrification in the glass. 相似文献