排序方式: 共有34条查询结果,搜索用时 15 毫秒
1.
《Ceramics International》2023,49(18):29433-29448
Stable slurries for Si3N4-bonded SiC refractories for direct ink writing (DIW) were successfully prepared from a mixture of non-spherical silicon carbide (SiC) and silicon (Si) powders with an average particle size of D50 = 41.98 μm. The rheological properties and printability of slurries prepared using polyvinyl alcohol (PVA; 4–16 wt %) or hydroxypropyl methylcellulose (HPMC, 0.5–2 wt.%) were investigated with the effect of sintering temperature on the mechanical performance, phase, and microstructure of Si3N4-bonded SiC refractory products. The results indicated that slurries prepared with the HPMC solution showed better printability than those prepared with the PVA solution because colloidal films formed by HPMC in slurries play a role in encasing particles, preventing solid−liquid separation and contributing to plasticity and lubrication, which guarantees the smooth extrusion and homogeneity of slurries. The successful printing of SiC–Si slurries is not only related to proper viscosity, yield value, and shear thinning characteristics but it is also crucial for maintaining the homogeneity of slurries under extrusion pressure. Optimal SiC–Si slurries containing 52 vol % SiC–Si and 1.5 wt% HPMC exhibited proper viscosity, shear thinning, and homogeneity characteristics during printing. The obtained specimens achieved the best printing performance with height and section retention rates of 98.7% and 97.6%, respectively. When sintered at 1450 °C, Si3N4 fibres grow further and reach a diameter of 342.5 nm, the nitriding rate is 92.43%, the fibres tend to form a full network structure, and the mechanical properties of Si3N4-bonded SiC products are the best. 相似文献
2.
P(N-phenylmaleimide-alt-styrene) (PNS) was synthesized, and nylon 6 (PA6)/PNS blends were prepared by melt blending. The heat resistant and crystallographic properties of PA6/PNS blends with different contents were investigated and analyzed. The results showed that the heat deflection temperature (HDT), relative crystallinity (Xn), and dynamic viscosity (η) increased with increasing PNS. The results of differential scanning calorimetry proved that PNS had played a positive role in nucleating PA6. Scanning electron microscosopy showed that the PNS domains were between 0.2 and 4 μm in diameter. The experimental results indicated that the addition of PNS improved the rigidity of PA6/PNS blends, thereby improving the heat-resistant properties of these blends. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47689. 相似文献
3.
《Journal of the European Ceramic Society》2022,42(11):4456-4464
A series of 3 C-SiC coatings were prepared by organometallic chemical vapor deposition (MOCVD) using precursor solution containing a varying proportion of commercial-grade hexamethyldisiloxane (HMDSO) and n-hexane. The phase composition, bonding state, and microstructure of 3 C-SiC coatings were studied in detail by grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The microstructure and mechanical properties of the optimal 3 C-SiC coating were characterized by scanning transmission electron microscopy (STEM) and nanoindentation, respectively. Our results revealed that the amount of undesired graphite phase can be significantly reduced in the 3 C-SiC coating by introducing hydrogen gas in the reaction chamber alongside increasing the ratio of HMDSO/n-hexane in the precursor mixture. The STEM results revealed that the optimal coating was predominantly composed of nano-crystalline 3 C-SiC grains alongside a small amount of amorphous graphite. The hardness and elastic modulus of the optimal coating were 38.19 GPa and 363.2 GPa, respectively. 相似文献
4.
Garnet-type Ta-doped Li7La3Zr2O12 (LLZTO) electrolyte suffers from unstable chemical passivation under air exposure, responsible for the poor interfacial wettability and conductivity with Li metal. Instead of conventional methods to remove surface contaminants by mechanical polishing, acid etching and high temperature reduction, herein we propose a simple strategy of interfacial gas release and detergency to smartly convert Li2CO3 passivation layer into ion-conductive Li3PO4 domains at mild temperature (∼200 ℃). The in-situ formation of PH3 vapor and its phosphorization enables a dramatic decrease of Li/garnet interfacial resistance down to 2 Ω cm2 at room temperature (RT). The improved interfacial wettability and conductivity endow the symmetric cells with ultra-stable galvanostatic cycling over 1500 h and high critical current density of 2.6 mA/cm2. The high coulombic efficiency of Li plating enables a high reversibility of solid-state NCM811/Li cells even under a low N/P ratio (∼4) and high cut-off voltage of 4.5 V at RT. The prototype of fluoride-garnet solid-state batteries are successfully driven as rechargeable system (rather than widely known primary battery) with high conversion capacity (400 ∼ 500 mAh/g) and high-rate performance (251.2 mAh/g at 3 C). This interface infiltration-detergency approach provides a practical solution to the achievement of high-energy solid-state Li metal batteries. 相似文献
5.
《Ceramics International》2017,43(8):6472-6476
Spherical-like Tb3+ and Eu3+ co-doped Gd2O3 nanoparticles with a particle size around 5.5 nm were synthesized by a polyol route. The optimized luminescence property was obtained when 5 mol% Tb3+ and 2 mol% Eu3+ were co-doped. The influence of different polyalcohol solvents (DEG/PEG) on particle size and luminescence properties was investigated. The results show that the nanoparticles Gd2O3:5%Tb3+ prepared in PEG presented greater particle size (around 79 nm) and higher luminescence intensity. 相似文献
6.
Yuanyuan Zhang Lefu Mei Haikun Liu Sergey M.Aksenov Dina V.Deyneko Deliang Chen 《中国稀土学报(英文版)》2023,41(5):673-681
A series of Dy3+-activated phosphors with the general formula LiGd9(SiO4)6-x(GeO4)xO2:Dy3+(0 ≤ x≤ 3)characterized by an apatite-type structure were successfully synthesized via a simple solid-state technique involving a partial substitution of [SiO4]4-with [GeO4]4- species.The effects of homovalent[GeO4]4--[SiO4]4- substit... 相似文献
7.
采用拜耳法利用高硫铝土矿生产氧化铝时,矿石中的硫在溶出后主要以S2-和S2O2-3等形式进入生产过程中的铝酸钠溶液,对生产造成一系列的危害。实验通过设计的特殊装置,在含硫的铝酸钠溶液中添加氯化亚锡的盐酸溶液,以氮气为保护气体和载体,生成的硫化氢气体与醋酸镉溶液反应生成硫化镉沉淀,再采用间接碘量法测定S2-含量;加入硝酸银溶液生成硫代硫酸银、亚硫酸银和硫酸银沉淀,再添加氨水溶解亚硫酸银和硫酸银沉淀,根据硫代硫酸银水解后的硫化银沉淀量计算S2O2-3含量。试验研究了氮气流速、氨水加入量和淀粉指示剂加入量对测定结果的影响。实验方法用于测定3种模拟铝酸钠溶液中S2-和S2O2-3,S2-和S2O2-3的回收率均为95%,S2-和S2O2-3测定结果的相对标准偏差(RSD,n=5)分别为0.12%~0.34%和0.27%~0.57%。按照实验方法对3份贵州某铝厂拜耳法生产氧化铝过程铝酸钠溶液中S2-和S2O2-3进行测定,S2-和S2O2-3测定结果的RSD(n=5)分别为0.28%~0.35%和0.32%~0.46%,加标回收率为94%~95%。 相似文献
8.
《中国稀土学报(英文版)》2020,38(9):951-960
Ceria nanoparticles were facilely synthesized by a molten NaOH-KOH hydroxide flux method with the precursor of Ce(NO_3)_3·6H_2O under different conditions in alumina crucibles or Teflon-lined stainless steel autoclave.The XRD patterns and TEM images show that both the crystal and particle sizes of synthesized nanoceria are around 10 nm.XPS results reveal that the nanoceria obtained in alumina crucible has a Ce~(3+) fraction of 17.1% which is higher than that of ceria synthesized in the Teflon vessel,the FTIR spectra of nanoceria prepared in alumina crucible show a stronger intensity of O-H stretching mode.UV-DRS and PL spectra results show that the nanoceria synthesized in alumina crucible with a calculated band gap of 2.9 eV has a wider responding light wavelength and a lower photogene rated electron-hole recombination rate,due to a higher concentration of oxygen vacancies(Ce~(3+)%).The photocatalytic results show that the degradation ratio and rate of the Rhodamine B(RhB) solution with the nanoceria synthesized in alumina crucible are 98.39% and 0.02919 min~(-1),both of which are larger than those of the ceria obtained from Teflon vessel.This method proves to be a simple and scalable way to synthesize nanoceria with rich oxygen vacancies and high photocatalytic activity. 相似文献
9.
《Catalysis communications》2007,8(5):773-776
The effects of acetic acid pretreatment for dried catalysts prepared from cobalt nitrate were investigated. Cobalt catalyst prepared from cobalt nitrate, followed by treatment of 2.2 M acetic acid, namely CoN/2.2Ac catalyst, showed the highest CO conversion as well as the lowest CO2 and CH4 selectivities in liquid-phase Fischer–Tropsch synthesis. On the contrary, cobalt catalyst prepared from cobalt acetate exhibited poor catalytic activity due to very low reduction degree of supported cobalt. The higher catalytic activity for CoN/2.2Ac catalyst could be ascribed to the formation of the mixture of cobalt nitrate and cobalt acetate with suitable ratio between them during acetic acid treatment, which led to an optimum balance between the dispersion and reduction degree of supported cobalt, eventually realizing the higher catalytic activity. Various catalysts were characterized by XRD, TPR and H2 chemisorption. 相似文献
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