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1.
ZrTiO4 thin films were successfully prepared on Pt/Ti/SiO2/Si(100) substrates by a sol-gel process and gel films were heat-treated at various temperatures. The surface morphology,
crystal structure, and dielectric properties of the thin films were investigated. It was possible to obtain ZrTiO4 phase at temperatures above 650 °C for 2 h, which is much lower than the bulk sintering temperature. The microstructure of
well-crystallized ZrTiO4 thin films was a fine-grained microstructure less than 70 nm in grain size and the surface morphology was smooth with 22.4
rms roughness. The dielectric constant and loss of ZrTiO4 thin films were 38 and 0.006, respectively, for thin films with 450 nm thickness heat-treated at 900 °C for 2 h. 相似文献
2.
In the batch type gas injection foaming process, there must exist some melt residual. A differential equation relating the particle content and gas injection depth in the batch type process was presented, by which the melt residual ratio was predicted with the stability criterion as the boundary condition. It was found that the particle diameter increased during the foaming process but the thickness of the foam cell wall can be regarded as a constant. The adsorption coefficient and the injection depth were found to have an inverse relationship, with an exponential of −0.89. Based on the adsorption coefficient at different injection depth, the residual ratio of the melt containing given size particles was able to be predicted. To decrease melt residual needs to increase the particle content and the initial injection depth, and the particle diameter and the critical coverage ratio should be decreased. 相似文献
3.
Mg97Zn1Y2 magnesium alloy was hot-rolled at different temperatures from 390 to 480 °C; the effect of rolling temperature on microstructure
evolution and mechanical properties of Mg97Zn1Y2 magnesium alloy was investigated using x-ray diffraction (XRD), laser optical microscopy (LOP), transmission electron microscopy
(TEM), and tensile test. The results showed that in the multipass process, the rolling temperature had significant effect
on the microstructures and tensile properties for the hot-rolled Mg97Zn1Y alloy. As the rolling temperature was increased, the original strengthening phase-Mg12YZn in as-cast Mg97Zn1Y2 alloy experienced an evolution from dissolution to precipitation, i.e. from chain-shaped Mg12YZn phase together with a little lamellar structure at 420 °C to a maximum volume fraction of lamellar structure at 450 °C,
and finally to a reduced volume fraction of lamellar structure at 480 °C. For Mg97Zn1Y2 alloy hot-rolled in the temperature range of 390-450 °C, the tensile strength was at a high level with yielded strength of
about 300 MPa and ultimate strength of about 320 MPa. The highest yielded strength was 317 MPa after hot-rolling at 450 °C;
the elongation was the highest up to 5.5% after hot-rolling at 420 °C. 相似文献
4.
Ki-Ju Lee Jing-Wen Xu Cheol-Ho Lim Won-Seung Cho 《Metals and Materials International》2008,14(4):433-436
In this study, the thermoelectric properties of 0.1 wt.% Cdl2-doped n-type Bi2Te2.7Sb0.3 compounds, fabrieated by SPS in a temperature range of 250°C to 350°C, were characterized. The density of the compounds was
increased to approximately 100% of the theoretical density by carrying out consolidation at 350°C. The Seebeck coefficient,
thermal conductivity, and electrical resistivity were dependent on a hydrogen reduction process and the sintering temperature.
The Seebeck coefficient and the electrical resistivity increased with the reduction process. Also, electrical resistivity
decreased and thermal conductivity increased with sintering temperature. The results suggest that carrier density and mobility
vary according to the reduction process and sintering temperature. The highest figure of merit, 1.93×10−3 K−1, was obtained for the compound consolidated at 350°C for 2 min. 相似文献
5.
Hibiki Chinen Toshihiro Omori Katsunari Oikawa Ikuo Ohnuma Ryosuke Kainuma Kiyohito Ishida 《Journal of Phase Equilibria and Diffusion》2009,30(6):587-594
Phase equilibria and stabilities of intermetallic phases appearing in the Co-rich portion of the Co-W-Ga ternary alloys were
investigated and isothermal section diagrams at 1200, 1100, 1000, and 900 °C were determined. A fine cuboidal phase with an
L12 structure was observed at 900 and 800 °C, where the composition of the new ternary compound obtained by aging at 900 °C for
the Co-7.4W-12.0Ga alloy was Co-11.2W-11.4Ga (at.%). It was confirmed that this compound is metastable at 900 °C but is more
stable at 800 °C. These results mean that the thermodynamic stability of the metastable Co3W L12 phase, especially in the low temperature region, increases by the addition of Ga. 相似文献
6.
Bilge Yaman Eren Onuklu Nese O. Korpe 《Journal of Materials Engineering and Performance》2017,26(9):4319-4328
Pure Al and alumina (2, 5, 10 wt.% Al2O3)-added Al composite foams were fabricated through powder metallurgy technique, where boric acid (H3BO3) is employed as a new alternative foaming agent. It is aimed to determine the effects of boric acid on the foaming behavior and cellular structure and also purposed to develop the mechanical properties of Al foams by addition of Al2O3. Al and Al composite foams with porosity fraction in the range of 46-53% were achieved by sintering at 620 °C for 2 h. Cell morphology was characterized using a combination of stereomicroscope equipped with image analyzer and scanning electron microscopy. Microhardness values were measured via using Vickers indentation technique. Quasi-static compression tests were performed at strain rate of 10?3 s?1. Compressive strength and energy absorption of the composite foams enhanced not only by the increasing weight fraction of alumina, but also by the usage of boric acid which leads to formation of boron oxide (B2O3) acting as a binder in obtaining dense cell walls. The results revealed that the boric acid has outstanding potential as foaming agent in the fabrication of Al and Al composite foams by providing improved mechanical properties. 相似文献
7.
L.E.G. Cambronero J.M. Ruiz-Roman F.A. Corpas J.M. Ruiz Prieto 《Journal of Materials Processing Technology》2009,209(4):1803-1809
Aluminium foams can be manufactured by two main methods: casting and powder metallurgy. When the latter route is used, a foaming agent (usually TiH2) is mixed with the aluminium or aluminium alloy powders, followed by powder mixture consolidation (usually hot extrusion) into a precursor and finally its foaming treatment. In this research, two calcium carbonate powders were used as foaming agents on an Al–Mg–Si (AA6061) alloy. Their different characteristics (particle size and chemical composition) modified the manufacturing process to achieve the final foam. AA6061 powders were then mixed with 10% calcium carbonate and, after cold isostatic pressing into green cylinders, hot extruded at different temperatures (475–545 °C). The foaming treatment was carried out in a furnace preheated to 750 °C using several heating times. The density changed from 2.03 to 2.10 g/cm3 after cold isostatic pressing to 2.64–2.69 g/cm3 in precursor materials obtained by hot extrusion. Foaming behaviour depends on the carbonate powder as well as the extrusion temperature. Thus, natural carbonate powder (white marble) produces a foam density close to 0.65 g/cm3 after a shorter time than when chemical carbonate is used. The foam structure showed a low degree of aluminium draining, no wall cell cracks and a good fine cell size distribution. Compressive strength of 6.11 MPa and 1.8 kJ/m3 of energy absorption were obtained on AA6061 foams with a density between 0.53 and 0.56 g/cm3. 相似文献
8.
H. S. Nithin Vijay Desai M. R. Ramesh 《Journal of Materials Engineering and Performance》2017,26(11):5251-5261
In this paper, investigation into solid particle erosion behavior of atmospheric plasma-sprayed composite coating of CoCrAlY reinforced with Al2O3 and CeO2 oxides on Superni 76 at elevated temperature of 600 °C is presented. Alumina particles are used as erodent at two impact angles of 30° and 90°. The microstructure, porosity, hardness, toughness and adhesion properties of the as-sprayed coatings are studied. The effects of temperature and phase transformation in the coatings during erosion process are analyzed using XRD and EDS techniques. Optical profilometer is used for accurate elucidation of erosion volume loss. CoCrAlY/CeO2 coating showed better erosion resistance with a volume loss of about 50% of what was observed in case of CoCrAlY/Al2O3/YSZ coating. Lower erosion loss is observed at 90° as compared to 30° impact angle. The erosion mechanism evaluated using SEM micrograph revealed that the coatings experienced ductile fracture exhibiting severe deformation with unusual oxide cracks. Reinforced metal oxides provide shielding effect for erodent impact, enabling better erosion resistance. The oxidation of the coating due to high-temperature exposure reforms erosion process into oxidation-modified erosion process. 相似文献
9.
Semi open-cell aluminum foams having channels between individual cells were produced using low cost CaCO3 foaming agent and applying the powder compact melting process. To this end, the aluminum and CaCO3 powder mixtures were cold compacted into dense cylindrical precursors for foaming at specific temperatures under air atmosphere. The effects of several parameters including precursor compaction pressure, foaming agent content as well as temperature and time of the foaming process on the cell microstructure, linear expansion, relative density and compressive properties were investigated. A uniform distribution of cells with sizes less than 100 μm, which form semi open-cell structures with relative densities in the range of 55.4%–84.4%, was obtained. The elevation of compaction pressure between 127–318 MPa and blowing agent up to 15% (mass fraction) led to an increase in the linear expansion, compressive strength and densification strain. By varying the foaming temperature from 800 to 1000 °C, all of the investigated parameters increased except compressive strength and relative density. The results indicated the optimal foaming temperature and time as 900 °C and 10–25 min, respectively. 相似文献
10.
Sung Gyu Pyo 《Metals and Materials International》2008,14(6):767-772
This study is concerned with the effect of CH2I2 iodine catalysis on the film structure and superfilling properties of Chemically Enhanced Chemical Vapor Deposition (CECVD)
Cu process. It was found that, under optimal conditions, treatment of MOCVD Cu deposition with a chemical enhancer increases
deposition rate and intensity and decreases the incubation time and surface roughness. These results imply that the chemical
enhancer has a surfactant effect that promotes two-dimensional layer-by-layer growth. The deposition of CECVD Cu film in the
low temperature region (<150°C) shows superfilling behavior and void-free filling, but shows conformal step coverage in the
intermediate temperature range. The growth of CECVD Cu film does not proceed in a layer-by-layer manner, and becomes agglomerate
in the high temperature region (190°C). Superconformal coverage and the best superfilling performance of CEMOCVD Cu film is
demonstrated with a (hfac)Cu(DMB) precursor of 0.10 um feature size and 17500A height [AR=17.5:1]. 相似文献
11.
Dayanand Paswan Dhananjay Mistry K.L. Sahoo V.C. Srivastava 《Journal of Materials Engineering and Performance》2013,22(8):2201-2209
In the present investigation, an attempt has been made to develop in situ sandwich Fe-based foams using powder forging and rolling. Several metal carbonates are first studied by thermo gravimetric analysis to find out their suitability to be used as foaming agent for iron-based foams. Barium carbonate is found to be the most promising foaming agent among other suitable options studied such as SrCO3, CaCO3, MgCO3, etc. The effects of process parameters such as precursor composition, sintering temperature, foaming temperature and time, and content of foaming agent have been studied. The microstructural characteristics of the sintered precursor have been studied by means of optical and scanning electron microscopy. It was found that a good pore structure can be obtained using 2-3% C in Fe and 3% BaCO3 as foaming agent and by foaming at around 1350 °C for 3-6 min. 相似文献
12.
Mahantayya Mathapati Mrityunjay Doddamani M. R. Ramesh 《Journal of Materials Engineering and Performance》2018,27(4):1592-1600
This research examines the deposition of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings on MDN 321 steel through the process of plasma spray. In this process, the solid particle erosion test is established at 200, 400, 600 °C with 30° and 90° impact angles. Alumina erodent is adopted to investigate the erosive behavior of the coating at higher temperatures. The properties of the Cr3C2-NiCr/cenosphere coating are established based on the microhardness, the adhesive strength, the fracture toughness, and the ductility. To quantify volume loss as a result of erosion, an optical profilometer is used. At higher temperature, decrease in the erosion volume loss of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings is observed. The erosion-resistive property of Cr3C2-NiCr/cenosphere coating is higher than that of MDN 321 steel by 76%. This property is influenced by high-temperature stability of mullite, alumina, and protective oxide layer that is formed at elevated temperatures. The morphology of eroded coating discloses a brittle mode of material removal. 相似文献
13.
Xin Zhong Yaran Niu Liping Huang Hong Li Xuebin Zheng Chuanxian Ding Jinliang Sun 《Journal of Thermal Spray Technology》2017,26(1-2):203-210
In the present work, Yb2Si2O7 powder was synthesized by solid-state reaction using Yb2O3 and SiO2 powders as starting materials. Atmospheric plasma spray technique was applied to fabricate Yb2Si2O7 coating. The phase composition and microstructure of the coating were characterized. The density, open porosity and Vickers hardness of the coating were investigated. Its thermal stability was evaluated by thermogravimetry and differential thermal analysis (TG-DTA). The thermal diffusivity and thermal conductivity of the coating were measured. The results showed that the as-sprayed coating was mainly composed of crystalline Yb2Si2O7 with amorphous phase. The coating had a dense structure containing defects, such as pores, interfaces and microcracks. The TG-DTA results showed that there was almost no mass change from room temperature to 1200 °C, while a sharp exothermic peak appeared at around 1038 °C in DTA curve, which indicated that the amorphous phase crystallized. The thermal conductivity of the coating decreased with rise in temperature up to 600 °C and then followed by an increase at higher temperatures. The minimum value of the thermal conductivity of the Yb2Si2O7 coating was about 0.68 W/(m K). 相似文献
14.
We fabricated a micro gas sensor for hydrogen sulfide (H2S) gas using MEMS technology and the sol-gel process, and synthesized SnO2-CuO as a sensing material by the sol-gel method. Synthesized particles of SnO2-CuO were characterized with an average particle size of about 40 nm as measured by FE-SEM imagery and XRD peaks. The sensing
material was coated on the micro platform and annealed at 400 °C. The maximum gas sensitivity (Rs= Rg/Ra) was 0.005 at 300 °C for 1.0 ppm — H2S. The gas sensitivity showed linear behavior with increasing H2S concentration. 相似文献
15.
Zhenbang Wei Yong Jiang Limeng Liu Laner Wu Zhenkun Huang 《Journal of Phase Equilibria and Diffusion》2016,37(2):149-154
Phase formation sequence of the yttrium aluminates in the Y2O3-Al2O3-SiC ternary system as temperature increases were investigated via x-ray diffraction (XRD). Results showed that YAM (monoclinic), YAP (perovskite) and YAG (garnet) were the yttrium aluminates presented in the solid-state reacted samples at a fixed Al2O3:SiC ratio of 1:1. Formation of the yttrium aluminates depended on the temperature. The YAM, YAP and YAG started to form below 1150 °C, at 1300 °C, and at 1450 °C, respectively. Accordingly, two behavior phase diagrams of the Y2O3-Al2O3-SiC ternary system were recognized, one is in the temperature range of 1150-1300 °C and the other is in 1300-1450 °C, respectively. Thereafter, the phase equilibrium was reached in the temperature range of 1450-1700 °C. Effects of SiC on the phase formation processes in the ternary system were discussed. 相似文献
16.
The present study investigates the early stages in the oxidation process of Sanicro 28 (Fe31Cr27Ni) stainless steel when exposed to an alkali salt (KCl, NaCl or K2CO3) for 2 h at 450 and 535 °C. After the exposure, the oxidized samples were analyzed with a combinatory method (CA, XPS and SEM–EDX). It was found that all three salts were corrosive, and the overall oxidation reaction rate was much higher at 535 °C than at 450 °C. There were clear differences in terms of the impact of cations (Na+, K+) and anions (Cl?, CO3 2?) on the initial corrosion process at both temperatures. When focusing on the cations, the presence of potassium ions resulted in a higher rate of chromate formation than in the presence of sodium ions. When studying the effect of anions, the oxidation of iron and chromium occurred at higher rates in the presence of both chloride salts than in the presence of the carbonate salt, and chloride salts seemed to possess higher diffusion rate in the gas phase and along the surface than carbonate salts. Moreover, at the higher temperature of 535 °C, the formed chromate reacted further to chromium oxide, and an ongoing oxidation process of iron and chromium was identified with a significantly higher reaction rate than at 450 °C. 相似文献
17.
Xinhui Li Wen Ma Jing Wen Yu Bai Li Sun Baodong Chen Hongying Dong Yingchai Shuang 《Journal of Thermal Spray Technology》2017,26(3):371-377
The solution precursor plasma spray (SPPS) process is capable of depositing highly durable thermal barrier coatings (TBCs). In this study, an aqueous chemical precursor feedstock was injected into the plasma jet to deposit SrZrO3 thermal barrier coating on metal substrate. Taguchi design of experiments was employed to optimize the SPPS process. The thermal characteristics and phase evolution of the SrZrO3 precursor, as well as the influence of various spray parameters on the coating deposition rate, microhardness, microstructure, and phase stability, were investigated. The experimental results showed that, at given spray distance, feedstock flow rate, and atomization pressure, the optimized spray parameters were arc current of 600 A, argon flow rate of 40 L/min, and hydrogen flow rate of 10 L/min. The SrZrO3 coating prepared using the optimized spray parameters had single-pass thickness of 6.0 μm, porosity of ~18%, and microhardness of 6.8 ± 0.1 GPa. Phase stability studies indicated that the as-sprayed SrZrO3 coating had good phase stability in the temperature range from room temperature to 1400 °C, gradually exhibiting a phase transition from t′-ZrO2 to m-ZrO2 in the SrZrO3 coating at 1450 °C with increasing time, while the SrZrO3 phase did not change. 相似文献
18.
Qiong Wu Xiaojuan Ji Haoran Peng Xianjing Ren Yueguang Yu 《Journal of Thermal Spray Technology》2016,25(4):757-762
Ce-modified La2Zr2O7 powders, i.e., La2Zr2O7 (LZ), La2(Zr0.7Ce0.3)2O7 (LZ7C3), and La2(Zr0.3Ce0.7)2O7 (LZ3C7), were used to produce thermal barrier coatings by atmospheric plasma spray process. The chemical compatibility of the CeO2-doped La2Zr2O7 with the traditional YSZ was investigated in LZ-YSZ powder mixtures and LZ-YSZ bilayer coatings by x-ray diffraction and scanning electron microscope. The powder mixtures and coatings were aged at 1200 and 1300 °C for 100 h. The results showed that LZ and LZ7C3 presented single pyrochlore structure after the heat treatments at both 1200 and 1300 °C. For LZ3C7, however, fluorite structure was observed at 1300 °C, indicating a poor phase stability of LZ3C7 at the elevated temperature. The results further showed that La2(Zr0.3Ce0.7)2O7 reacted with YSZ in the bilayer ceramic coatings due to the diffusion of cerium, zirconium, and yttrium. While for La2Zr2O7(LZ) and La2(Zr0.7Ce0.3)2O7, a better chemical compatibility with YSZ was shown. 相似文献
19.
E. I. Kuznetsova M. V. Degtyarev N. A. Zyuzeva I. B. Bobylev V. P. Pilyugin 《The Physics of Metals and Metallography》2017,118(8):773-781
The influence of plastic deformation carried out by high pressure torsion at room temperature on the microstructure of the YBa2Cu3O y (123) compound prepared by standard ceramic technology and annealed at low temperature (200°C) in a water-saturated atmosphere has been studied. It has been shown that the directional growth of recrystallized lamellar-shaped grains initiated by the 124–123 phase transformation takes place upon recovery (after deformation) annealing at 930°C in ceramics subjected to additional low-temperature annealing, which leads to the formation of the texture. A rodlike structure has been observed in samples prepared by standard technology, after deformation and recovery annealing (930°C). 相似文献
20.
Low-Co La1.8Ti0.2MgNi8.9Co0.1 alloys were prepared by magnetic levitation melting followed by annealing treatment. The effect of annealing on the hydrogen storage properties of the alloys was investigated systematically by X-ray diffraction (XRD), pressure-composition isotherm (PCI), and electrochemical measurements. The results show that all samples contain LaNi5 and LaMg2Ni9 phases. LaCo5 phase appears at 1,000 °C. The enthalpy change of all hydrides is close to ?30.6 kJ·mol?1 H2 of LaNi5 compound. Annealing not only increases hydrogen capacity and improves cycling stability but also decreases plateau pressure at 800 and 900 °C. After annealing, the contraction of cell volume and the increase of hydride stability cause the high rate dischargeability to reduce slightly. The optimum alloy is found to be one annealed at 900 °C, with its hydrogen capacity reaching up to 1.53 wt%, and discharge capacity remaining 225.1 mAh·g?1 after 140 charge–discharge cycles. 相似文献