TiN/O′-Sialon原位复合材料的抗氧化性能

通过对不同条件下原位复合制备的各种TiN/O′-Sialon材料在空气中的氧化行为研究,考查了氧化温度、气孔率和TiN含量对材料抗氧化性能的影响.结果表明:当氧化温度升高到一定值时,通常材料表层会形成致密的"保护膜",阻碍材料的进一步氧化;材料的气孔率和TiN含量越低,越易形成"保护膜",反之,越不易形成"保护膜".当材料的气孔率为30%以上,TiO2添加量为30wt%以上时,即使在更高的氧化温度下也不能形成"保护膜".     

TiN／O‘—Sialon源位复合材料的抗氧化性能

通过对不同条件下原位复合制备的种种上ＴｉＮ／Ｏ‘－Ｓｉａｌｏｎ材料避的氧化行为研究，考查了氧化温度、气孔率和ＴｉＮ含量对材料抗氧性能的影响。结果表明：当氧化温度升高到一定值时，通常材料表层会形成致密的“保护膜”，阻碍材料的进一步氧化：材料的气孔率和ＴｉＮ含量越低，赵易形成“保护膜”，反之，赵不易形成“保护膜”。当材料的气孔率为。当材料的气孔率为３０％以上，ＴｉＯ２添加量为３０ｗｔ％以上时，即使在更     

原位复合TiN/O'-sialon在空气中的氧化行为

通过对不同气孔率和TiN含量的原位复合TiN/O′-sialon材料在空气中的氧化行为研究 ,得出了不同材料在不同温度下的氧化结果 ,提出了不同材料在不同温度下的氧化机理和模型 .     

原位复合TiN/O′-sialon在空气中的氧化行为

通过对不同气孔率和TiN含量的原位复合TiN/O′-sialon材料在空气中的氧化行为研究,得出了不同材料在不同温度下的氧化结果,提出了不同材料在不同温度下的氧化机理和模型.     

ZrB2-SiC复合材料抗氧化性能研究

通过变温氧化增重试验和恒温氧化增重试验，研究了烧结温度对热压烧结制备的ZrB2-SiC复合材料的抗氧化性能的影响。结果表明：当烧结温度为1750℃时，ZrB2-SiC复合材料的抗氧化性能最好，且该材料的抗氧化性能明显高于单相ZrB2材料。这归结于高温下ZrB2-SiC复合材料表层被氧化形成SiO2和ZrO2保护膜，阻止了材料的进一步氧化，从而提高了ZrB2复合材料的抗氧化性能。     

原位复TiN／O‘—sialon在空气中的氧化行为

通过对不同气孔率和ＴｉＮ含量的原位复合ＴｉＮ／Ｏ’－ｓｉａｌｏｎ材料在空气中的氧化行为研究，得出了不同材料的不同温度下的氧化结果，提出了不同材料在不同温度下的氧化机理和模。     

碳相含量对C—SiC—TiC—TiB2复合材料结构和性能的影响

本文研究了碳相含量在１０～４０ｖｏｌ％范围内变动时对原位合成的碳／陶复合材料（Ｃ－ＳｉＣ－ＴｉＣ－ＴｉＢ２）的结构和性能的影响。结果表明：随着碳含量的增加，材料的抗弯强度下降。当碳相含量小于２０ｖｏｌ％时，材料的抗弯强度可达到４００Ｍｐａ以上。随着碳相含量的增加，应相应提高烧结温度。对材料在６００°Ｃ、８００°Ｃ、１０００°Ｃ、１２００°Ｃ下的抗氧化性能进行了研究。研究发现了在试验温度下，材料表现出优良的抗氧化能力。碳含量较少的试样表现为氧化增重，碳含量较多的试样表现为氧化失重。     

高温气体净化用纤维过滤材料的性能

采用真空抽滤的方法制备以多晶莫来石和硅酸铝两种纤维为原料的纤维过滤材料,研究了材料中两种纤维比例和加热温度对材料性能的影响.利用SEM表征材料中纤维之间的相互粘结及成孔情况,同时采用压汞仪和热膨胀仪分别分析了材料的孔体积和孔径分布、热膨胀情况.结果表明:当多晶莫来石纤维含量在90％时材料的抗弯强度达到最大值为8.65 MPa;经过800℃加热处理后,纤维材料的抗弯强度、在1m/min的风速下过滤阻力和气孔率分别为8.65 MPa、92.21 Pa和72.35％;材料中纤维彼此交错连接,形成相互贯通的气孔,孔径主要分布在30～100岬之间,其中孔径为30～80 μm之间的孔占总孔体积的57.05％;材料的平均热膨胀系数为1.81×10-6K～1.     

基于分形理论对轻质材料微孔结构与物理性能关系的研究

本文以NaCl为熔盐介质、镁橄榄石为原料制备了多孔镁橄榄石轻质材料,采用分形理论研究材料的微孔结构与材料物理性能的关系.对图像数据在预处理后用Image-Pro Plus软件进行二值化处理.利用分形理论确定线性关系式的相关系数R,以及用数学的方式来研究分形维数D.在烧成温度相同的条件下(1050℃,1100℃和1150℃),随试样中盐含量的增加,孔分形维数略有增加,当试样的烧成温度为1100℃,盐的含量为50％时,分形维数达到最大,即D=2.7.而在同一配比下,试样在1100℃时,孔分形维数较大,试样的孔结构趋于三维规则,烧成后试样的体积密度、显气孔率和常温耐压强度出现拐点.从而揭示了材料结构与性能之间的关系,即材料的分形维数越大,孔结构越趋于三维结构,材料的性能越优.     

耐酸材料气孔率结构的研究

研究结果表明,向配料中加入长石精矿时在1000～1300℃区间陶瓷坯体发生最显著的致密化,此时由配料3(以重选尼矿中的粘土为原料)制成的试样的开口气孔率为2％～3％,由配料4(以札纳道尔矿高岭土为原料)制成的试样的开口气孔率为4％～5％。当烧成温度提高至1400℃时,在由配料3制成的试样中形成 55％以上的液相,由配料4制成的试样中液相量达50％以上,致使耐酸材料板的开口气孔率提高,并发生变形扭曲。在1250℃时,在由配料3制成的试样中观察到均匀的气孔,不同的气孔图谱及lg(Φ2)关系的小角度射线图谱的曲率缩小便可证明上述情况。     

A novel approach to prepare reticulated porous TiN ceramics with high strength and high porosity by in-situ synthesis

Titanium nitride (TiN) with high porosity (90%) was successfully in-situ prepared by a novel approach with the combination of carbothermic reduction nitriding method and replication template method. The microstructure of porous TiN prepared with different temperature and phenolic resin (PF) content were revealed by XRD, Raman spectrum, SEM, TEM, respectively. The results show that when the mass ratio of PF and TiO₂ is 1:2 and the sintering temperature is 1850 ℃, porous TiN with high purity and ideal strength could be synthesized. In addition, the synthesis path and thermodynamic mechanism of porous TiN were analyzed by TG-DSC and Gibbs free energy calculation. The mechanical properties and corrosion resistance were preliminarily explored.     

Stability of edible oils and fats to fluorescent light irradiation

Butter, butterfat, and corn, coconut, rapeseed, and soybean oils were exposed to 500 ft-c of fluorescent light at varying time-temperature conditions. Oxidation rates were measured by the peroxide values. Vitamin A and β-carotene content of butterfat were estimated. The effect of wavelength on the relative rates of oxidation was determined. The light transmitting properties of the samples at 15 and 30 C over a spectral range of 380–750 nm were measured. It was observed that there was no increase in oxidation rate when the light was switched off. The stability of the oils as shown by the oxidation rates did not correlate well with the ratios of C18:2 to C18:1 or C18:3 to C18:2 nor with the degree of unsaturation. Increase in temperature alone had minimal effect; however, in the presence of light the rate of oxidation increased considerably with a corresponding decrease in the content of Vitamin A and β-carotene. β-Carotene provided strong protective properties. After the photobleaching of β-carotene in butterfat, there was a rapid increase in peroxide values. With coconut oil, the oxidation rate was greater at 15 C than at 30 C due to greater light absorption at 15 C over the entire spectrum. The rate of oxidation decreased at higher wavelengths, and this effect was more pronounced in the vegetable oils than in butterfat, where the β-carotene was considered to serve as a filter for light of low wavelength. Presented at the AOCS meeting, Dallas, April 1975.     

An isothermal oxidation behaviour of atmospheric plasma and high-velocity oxy-fuel sprayed nickel based coating

This paper describes the isothermal oxidation behaviour of NiCrBSiFe coatings on SS 316 L deposited by the atmospheric plasma (APS) and high-velocity oxy-fuel (HVOF) processes. As-sprayed coatings were oxidised isothermally in the air at 900 °C temperature for 1000 h. The thermogravimetric analysis was performed to measure the oxidation rate. The coating and oxide scale characterisation was carried out using SEM, EDAX, XRD, porosity analysis, and nanoindentation. The HVOF sprayed NiCrBSiFe coating shows better oxidation resistance than the APS coating, due to high density, less porosity, and formation of more protective oxide scale.     

Optical Waveguides Fabricated from Oxidised Porous Silicon

Further results on the optical properties of oxidised porous silicon as a function of porosity and oxidation conditions are presented in this paper. The refractive index varies logarithmically with the oxidation time irrespective of the porosity of the sample and the oxidation temperature. Burried waveguides have been realised from as-prepared and oxidised porous silicon. Optical losses of 18 dB cm^–1 at = 1.3 m have been obtained after oxidation at 800°C for 35 min.     

镀膜温度对30CrMnSiNi2A表面多弧离子镀氮化钛薄膜力学性能的影响

针对30CrMnSiNi2A材料表面多弧离子镀氮化钛薄膜后,材料力学性能出现波动的问题,研究了镀膜温度对材料力学性能的影响规律,优化了镀膜温度控制范围。结果表明,控制镀膜θ为200℃可保证制备得到的氮化钛薄膜的纵向冲击力不低于47 J,当镀膜θ高于260℃后,温度进入二次回火区间,材料脆性会上升。     

The Model for Oxidation Kinetics of Titanium Nitride Coatings

The oxidation kinetics of titanium nitride (TiN) film has been studied based on the experimental data summarized in the literature. The analysis shows that the diffusion process is the rate-controlling step. Based on the experimental data, a new model for predicting the oxidation process is used. In this paper, the effects of factors, such as temperature and heating rate, on the oxidation behavior are discussed not only qualitatively but also quantitatively. The results obtained show that our new model can fit the oxidation data very well. Compared with the previous oxidation studies of TiN coatings, the new model can provide a clear physical meaning of all parameters and therefore it will be useful for a theoretical discussion. The new model can also perform a simple calculation. Most importantly, the new model will lead to a more accurate calculation result; therefore, it can be used to predict the oxidation behavior of TiN materials based on limited experimental information.     

连续玻纤增强聚丙烯混纤纱织物层压成型工艺研究

采用两种不同形式的混纤纱机织物为原料,利用层压成型的方法制备了连续玻璃纤维(GF)增强的聚丙烯(PP)板材。研究了层压温度、压力、保压时间和混纤纱机织物形式对层压板材的弯曲性能和层间剪切强度(ILSS)的影响。结果表明,当层压温度为230℃,层压压力为8.5 MPa,保压时间为30 min,降温过程冷却速度为0.5℃/min时,层压板材的力学性能最佳。弯曲强度和模量分别达到352.58 MPa、23.09 GPa,ILSS达到27.37 MPa。此时,纤维含量和空隙率分别为72.25%、2.03%。在最优工艺条件下制备的两种不同织物形式层压板材弯曲强度和弯曲模量以及ILSS:2/2斜纹织物平纹织物。两种织物层压板材的空隙率:2/2斜纹织物平纹织物。     

Influence of additives content on the high temperature oxidation of silicon nitride based composites

A life prediction tool for mechanical and electrical applications of electroconductive structural ceramics is essential in order to know the limit for engineering uses. The aim of this work was to study the influence of additives content on the oxidation behaviour, in pure oxygen between 900 and 1400 °C, of two fully dense Si₃N₄–35 vol.% TiN composites. For this purpose, a hot pressed material (HP), containing 3.7 wt.% of Y₂O₃ and Al₂O₃ as sintering aids, was compared to an hipped material (HIP), containing 0.4 wt.% of the same additives. Up to a temperature T<∼1200 °C, where the oxidation of the composite is mainly governed by the preferential oxidation of TiN, the two materials exhibit paralinear kinetics with very close oxidation resistance. Contrarily, the hipped material shows a better oxidation resistance at T>∼1200 °C, when the oxidation of the Si₃N₄ matrix takes place. The formation of a compact silica sub-scale acts as an efficient diffusion barrier leading to asymptotic kinetics, with final weight gains exhibiting a negative temperature dependence. In the case of the HP material, i.e. in presence of a higher content of additives, a deterioration of the protective nature of the scale is provoked by the increased mobility of the impurity cations (Y³⁺, Al³⁺) linked to a decrease of the viscosity of the secondary glassy phase. The kinetics have a paralinear shape up to 1400 °C, with final weight gains increasing as a function of temperature. Therefore, this study confirms the deleterious influence on oxidation resistance of additives used for a better sintering of powders and the beneficial effect of hot isostatic pressing for which lower amounts of aids are necessary in comparison with hot pressing.     

A study of semiconducting oxide-glass coatings on mild steel

Preliminary attempts to develop inexpensive, protective conducting coatings on mild steel for use as insoluble anodes are described. From the consideration that a mixture of acid resistant semiconducting oxide and glass might form a satisfactory coating when heated on a steel substrate, Sb-SnO₂ and Ti-Fe₂O₃ were selected as conducting oxide materials for evaluation. With 3–30 wt.% glass added to the oxides, Sb-SnO₂ was found to be unsuitable as pellets of the glass-oxide mixture did not densify on heating up to 1400° C. 3% Ti-Fe₂O₃ plus 20% glass pellets fired at 1250° C showed low resistivity and porosity. An oxide-glass mixture of this composition fired on a mild steel substrate at 1250° C gave a coating with a porosity of 0.5%, on which chlorine could be evolved in HCl solution. The Ti-Fe₂O₃ oxides were very acid resistant under conditions of chlorine evolution. A reduction in the porosity of the coating, or the use of an acid resistant metal substrate, would be required to make the oxide-glass coating a practicable proposition.     

Properties and behavior of periclase-carbon systems during the firing-process under oxidizing conditions

Conclusions It is not advisable to introduce more than 20% graphite into the composition of the periclase-carbon refractories because, in this case, the strength of the products decreases significantly and their porosity increases.The temperature corresponding to the beginning of carbon depletion (burn off) does not depend on its content in the body and amounts to 550–560°C.Caustic periclase introduced for achieving additional low-temperature densification of the strucutre with reduced degree of carbon depletion did not give the expected effect: the temperature at which carbon depletion begins does not depend on its content in the body.When fired under oxidizing conditions, a reducing atmosphere is created within the periclase-carbon products which actively reacts with periclase; at and above 1650°C, one observes reduction of MgO up to Mg vapor with its subsequent oxidation and redeposition in the form of a dense layer of secondary MgO; a relict polygonized grain structure of MgO forms in the products and is accompanied by the development of a layered texture exhibiting cyclic recurrence.Translated from Ogneupory, No. 6, pp. 8–12, June, 1987.