Lianqi Wei

Preparation and Characterization of Integral Hollow Microspheres of Nickel Hydroxide and Nickel Oxide

Hollow microspheres of nickel hydroxide and nickel oxide were prepared with as-synthesized PS/Ni(OH)2 composite particles by sacrificing core method, respectively. The composite particles were synthesized by deposition of the Ni(OH)2 nanoflakelets formed by the hydrolysis of nickel nitrate onto the surfaces of polystyrene (PS) particles. The effects of different concentrations of nickel salt and urea on the deposition of the nanoflakelets of nickel hydroxide were studied. It was found that the uniform nanoflakelets were deposited on the polystyrene particles under the conditions of the 4╳10-3 M nickel salt and 0.667M urea. Compared with the directly calcinating of composite particles, Integral hollow microspheres of nickel hydroxide were attained by removal of cores of polystyrene in composite particles with toluene and NiO hollow microspheres by calcinating of these Ni(OH)2 hollow spheres in oven at 600°C for 2h.

Influence of Protective Coating at High Temperature on Surface Quality of Stainless Steel

A ceramic matrix coating for minimzing steel loss of stainless steel at high temperatures was prepared by handled air-spraying technique, and the influence of coating on surface quality of stainless steel was mainly investigated in laboratory. Experimental results showed that the protective coating reduced the oxidation of stainless steel by more than 91% and minimized high-temperature scaling and also enhanced steel surface quality. The scales of coated specimen were removed completely and the scales of uncoated specimen were partly residual on the surface after cooling process. Mn-rich and Fe-rich zones were found in the oxides. The Cr2O3 found in scales came from the underlying stainless steel and formed a Cr-rich layer along the spalled surface.

Hydrothermal synthesis of β-FeOOH with different morphologies using NaH2PO4 as structural modifier

Different morphologies of β-FeOOH were prepared by hydrothermal synthesis using NaH2PO4 as structural modifier. The rod-shaped, straw-like and flower-like products could be controllably obtained. The as-obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Ultraviolet-visible (UV-Vis) absorption spectroscopy. The experimental results show that the morphology manipulation could be achieved by adding different amounts of NaH2PO4. XRD pattern indicates that the asprepared sample is the pure tetragonal phase of β-FeOOH. UV-Vis absorption spectra of the products are affected by their morphologies, which shows that both the rod-shaped and straw-like β-FeOOH have outstanding absorption ability on the whole UV area (200–400 nm), which will have vast application prospects in UV protection.

Influence of a Protective Coating Slurry on Enhancing the Descaling Ability and Oxidation Resistance of 9% Nickel Steel

A kind of ceramic slurry was prepared and sprayed onto the surface of 9Ni steel at room temperature. The coating layer will not only reduce the depth of the formed Ni-enriched entanglement at high temperature but also have an excellent ability to resist oxidation of the 9Ni steel. Compared to bare specimen, the depths of the entanglement of the coated 9Ni specimen could be successfully reduced by 74.1% and the oxidation loss be decreased by 62.3% by heating at 1 250 °C for 60min. In addition, the coated specimen indicates no trace of oxide pegs. It proves that the coating has outstanding improvement to internal oxidation resistance. Some characterization methods such as metalloscopy, XRD, XPS, SEM and EDX have been used to reveal a possible protective mechanism. The result shows that the coating layer reacts with the iron oxide to form MgFe2O4 on the surface of the coated specimen, which could provide a smaller diffusion coefficient rate of Fe ion. The coating with a low cost and easy implementation is promisingly applicable in the slab-reheating process of the 9Ni steel.

Preparation and Characterization of Low-melting Glasses Used as Binder for Protective Coating of Steel Slab

The low-melting phosphate glass was prepared for production of glass binders for protective coating of steel slab. Effects of different O/P ratios on glass structures and properties were analyzed. Differential thermal analysis (DTA) and infrared spectroscopy (IR) techniques were applied for low-melting glass binder. It was found that the glass transition temperature(Tg) was about 300 °C and softening temperature(Tf) was about 480 °C. The choice of O/P ratio was very important to the glass transition and softening temperatures. When more P=O bonds existed in the glass networks, P-O-P bond angle was deformed with decreasing of the ratio of O/P. The coatings could adhere to the substrates instantaneously at 800 °C when the content of binder exceeded 3wt%. The optimal content of glass binder was 5wt%.

Preparation and Characterization of the Decarbonization Preventing Nano-Coating Applied in Spring Steel Protection

Surface decarburization is one of important issues in spring steel production. The novel decarbonization-resistant nano-coating has been successfully fabricated, by using a low-cost, and easily accessible bauxite minerals and other additional components, including magnesia, silicon carbide，glass powder and agglomerant, which is used to prevent spring steels from being decarburized during the hot-rolling process. The microstructure of the protective nano-coating is observed by means of X-ray diffraction, TG-DTA, metalloscope and so on. It is found that even if some glass ceramic exists within the coating in the initial lower temperature (950°C~1000°C) the decarbonization-preventing coating still presents decarburization resistance up to 72.2%. Furthermore, the protective ration reaches to 100% when the heating temperature rises to range (1050°C~1100°C). The excellent decarbonization preventing properties are attributed to the formation of glass ceramic and pleonaste, which hinders the second interdiffusion of oxygen and carbon.

Mechanical properties of SiC/FexSiy composites

The SiC/FexSiy composites were synthesized by reaction sintering process with iron tailings as raw material and carbon as reductant. The room and high temperature flexural strengths and fracture toughness of composites were studied in this paper. Fracture surfaces were observed by means of a scanning electron microscope (SEM). The results showed that the room temperature flexural strength of SiC/FexSiy composites changed along with the different contents of FexSiy and sintering temperature. The flexural strength of composites reaches the maximum at 900°C. The correlation between flexural strength and temperature is consistent with curveⅠ.The fracture toughness of composites is related to the content of FexSiy. The fracture behavior of composites is mainly transcrystalline in room temperature and intercrystalline in high temperature.

Preparation and Property of Ceramic Matrix Coating of Anti-Oxidation for Stainless Steel at High Temperature by Slurry Method

In this paper, the new high temperature ceramic matrix coating of anti-oxidation for stainless steel was prepared by slurry method. With the research about oxidation resistance of ceramic matrix coating formed on stainless steel, the effect of initial melting temperature, melting temperature range and thermal expansion coefficients of ceramic sintering change on protective properties of high temperature coating prepared at 1250°C is investigated, and then high temperature sintering ceramic with high-performance is gained through optimization. Through the test of TG-DTA and XRD to the coating, study on high temperature oxidation resistance of ceramic coating and the structure changing of the scale with coating from SEM images and photos, it is shown that the ceramic coating has excellent oxidation resistant properties, the weight loss with coating decrease more than 85%.