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1.
采用碳酸盐法测定钢渣中活性氧化镁含量。研究了碳酸盐法测定钢渣中活性氧化镁反应的可行性和测定的准确性。结果表明:二氧化碳在水中可以将氧化镁和氢氧化镁转化成可溶性镁离子,然后用EDTA标准溶液滴定其含量,氧化镁、氢氧化镁与二氧化碳的反应率均达到97%以上;二氧化碳与钢渣反应时间应大于105min,新余热焖钢渣中活性氧化镁质量分数为1.44%;压蒸后钢渣中氢氧化镁质量分数为1.86%,与原钢渣中活性氧化镁测定结果保持一致,相对误差小于1%。 相似文献
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选用不同可溶性镁盐(MgCl_2·6H_2O和MgSO_4·7H_2O)和沉淀剂(NH_3·H_2O、NaHCO_3、NH_4HCO_3和K_2CO_3)为原料,采用水热法制备氧化镁前驱体,之后经过600℃煅烧获得微纳米级活性氧化镁,通过改变物料比例制备系列氧化镁。产品采用FI-IR,XRD和SEM进行表征,并对活性进行检测。结果表明:氧化镁主要呈片状晶体,适当比例硫酸镁和氯化镁与氨水及碳酸氢钠可以制备出活性和产率都较高的微纳米级活性氧化镁,当MgCl_2·6H_2O和NaHCO_3摩尔比为1:1时,制得的氧化镁具有更好活性,对应柠檬酸法中酚酞变红时间为15sec。 相似文献
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钢渣中游离氧化镁含量的测定 总被引:1,自引:0,他引:1
研究和提出了以硝酸铵-乙醇作为提取剂提取活性氧化镁(即游离氧化镁)的分析方法。通过正交实验,选取了最佳的提取条件。样品平行测定的相对标准偏差在0.51%~2.13%之间,回收率实验结果为98.2%~99.0%,表明该实验的精密度和准确度均较好。采用硝酸铵-乙醇作为提取剂提取游离氧化镁的分析方法,实现了钢渣中游离氧化镁的快速、准确测定,为钢渣的回收再利用提供了依据。 相似文献
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简单介绍了生物柴油的生产原料,综述了用废弃油脂生产生物柴油的现状和方法。废弃油脂生产生物柴油的方法主要有物理法和化学法,物理法主要有掺和法和微乳法,化学法主要有热裂解法和酯交换法。目前生产中采用化学法的酯交换法、以酸碱两步催化法的工艺为主,而生物酶法和超临界法是研究热点。 相似文献
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主要依托物理化学中的热力学基本原理,浅议热力学方法、简介化工热力学方法和工程热力学方法及应用等。热力学方法主要有循环法、特性函数法、变量变换法、标准状态法、平衡法及极值法、微元法等,并归纳了各种方法的特点、作用及意义。对于学生学习物理化学中的热力学,具有一定的指导意义,拓展了热力学的基本知识。 相似文献
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S. Feliu Jr M. C. Merino R. Arrabal A. E. Coy E. Matykina 《Surface and interface analysis : SIA》2009,41(3):143-150
The surface characteristics and corrosion behaviour of the AZ31 magnesium alloy exposed to a high relative humidity (RH) atmosphere were investigated. During the first 15 days of humidity test at 98% RH and 50 °C, a significant increase of magnesium carbonate and a decrease of magnesium oxide were detected on the surface film by XPS; after this stage, increased exposure times did not produce substantial changes on the relative amounts of these compounds. The surface film of commercially pure magnesium, also examined for comparison purposes, revealed more magnesium carbonate and less magnesium oxide compared with the AZ31 alloy. Unlike the AZ31 alloy, the surface of pure Mg disclosed almost complete substitution of MgO by magnesium carbonate after 30 days of exposure time. Mass gain values of tested specimens and scanning electron microscope characterisation of corroded surfaces indicated lower corrosion susceptibility of the AZ31 alloy compared with the commercially pure Mg, suggesting superior chemical stability of the oxide/hydroxide film formed over the magnesium–aluminium alloy surface. XPS and energy dispersive X‐ray (EDX) analyses did not revealed any substantial enrichment of aluminium in the corrosion products film on the AZ31 alloy after 30 days of testing. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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F. J. Garcia‐Garcia E. V. Koroleva G. E. Thompson G. C. Smith 《Surface and interface analysis : SIA》2010,42(4):258-263
Nitric acid is commonly used for surface treatments of aluminium alloys. It is used to clean the surfaces after alkaline etching; it has application in chemical polishing and is also used for electrograining. The majority of these treatments undergo the application of anodic polarisation that results in formation of anodic oxide film. However, little is known about the behaviour of aluminium containing magnesium or titanium in solid solution under such conditions. To reveal the effects of magnesium and titanium alloying additions on anodic film formation in nitric acid, Al‐1800 ppm Mg and Al‐800 ppm Ti alloys were investigated. It was found that porous alumina film developed on the surfaces with reduced efficiency of 40%, due to the reactive nature of nitric acid to alumina. The presence of magnesium and titanium in aluminium had little influence on the efficiency of film growth, as confirmed by the relatively similar thicknesses of oxide formed on binary alloys and aluminium. However, incorporation of magnesium ions into the alumina film led to development of a high‐population density of localised voids near the alloy/film interface. An increased titanium content was found in the film regions close to the alloy/film interface, indicating its oxidation. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Yang Guo Wei Zhang Xing Zhou Tong Bao 《Journal of Thermal Analysis and Calorimetry》2013,113(2):787-791
Boron was chosen as fuel owing to its excellent thermodynamic values for combustion. The difficulty of the boron in combustion is the formation of a surface oxide layer, which postpones the combustion process, reducing the performance of the rocket engine. In this paper, magnesium boride was sintered as high-energy fuel as a substitute for boron. The combustion heat and efficiency of magnesium boride and boron were determined using oxygen bomb calorimeter. The combustion characteristics of magnesium boride were investigated by thermal analysis, chemical analysis, XRD, and EDS. Results show that the combustion performance of magnesium boride are better than that of amorphous boron in oxygenated environments. The evaporation of magnesium in magnesium boride combustion process prevent the formation of a closed oxide layer, leading to higher combustion efficiency. 相似文献
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It has been shown that an existing procedure to differentiate calcium oxide from the carbonate and silicate of calcium can be used in the presence of the phosphate, fluoride and sulphate of calcium, and of the carbonate and oxide of magnesium. It is based on the reaction in aqueous solution of calcium oxide with sucrose to form calcium saccharate, and subsequent titration with oxalic acid solution. The method has application for a direct chemical determination of calcium oxide in phosphate rock where calcination of accompanying carbonate is necessary in beneficiation processes. 相似文献
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Composite films of magnesium oxide embedding metals such as gold, iron and chromium are prepared by the simultaneous deposition technique onto cleavage surfaces of sodium chloride and characterized by high resolution electron microscopy. These metals grow epitaxially and uniformly inside magnesium oxide films as crystallites of a few nm in size. The thickness of the crystallites is estimated to be a few atomic layers. The observation of isolated single atoms or atomic clusters is attempted under an off-Bragg condition. For composite films of iron and magnesium oxide, a heat treatment at 500°C for two hours brings about the growth ofγ-iron crystallites. A strain field at the periphery of theγ-iron crystallites is analysed. For composite films of chromium and magnesium oxide, chromium crystallites of around 1 nm in size grow epitaxially inside magnesium oxide films with two kinds of orientation. 相似文献
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The results of studies on the synthesis of defect magnesium oxides by MgO hydration in salt solutions are summarized. The incorporation of oxygen-containing salt anions into the anionic hydroxide/oxide framework is described. In this case, the anion residue whose oxygen atoms belong to the oxygen framework of the oxide is incorporated in the octahedral oxygen cell of the oxide to occupy the place of a virtual magnesium cation. A portion of cationic vacancies remains free, whereas a portion is occupied by the transformed anion residue with a positive charge other than 2+. As a result, defect magnesium oxides are formed as substitutional solid solutions. The structure and charge heterogeneity of defect oxides is responsible for their high catalytic activity. 相似文献
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L. M. Plyasova N. A. Vasil’eva T. A. Kriger A. N. Shmakov G. S. Litvak 《Kinetics and Catalysis》2000,41(4):557-560
The structure of magnesium oxide prepared by hydration in lithium nitrate and magnesium nitrate solutions and further thermal
treatment is examined by X-ray analysis on a precision diffractometer using synchrotron irradiation. Magnesium oxide with
a distorted lattice is formed when this preparation procedure is used, and the symmetry is reduced from cubic to rhombohedral.
Distortions were more pronounced in the case of a sample treated with magnesium nitrate. The distortions are due to NO3 groups incorporated into the oxygen framework of the oxide. Such a structure is stable up to 1000°C. The defects formed lead
to the structure and charge inhomogeneity of the crystalline lattice. It is likely that these defects are responsible for
the high catalytic activity of the samples. 相似文献
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Nanocrystalline metal oxides, MgO, CuO, ZnO, TiO2 as catalysts or catalyst supports have been received much attention in the recent years, especially nanocrystalline magnesium
oxide (NAP-MgO) has been used as a recyclable catalyst for Wittig, Wadsworth–Emmons, aza-Michael, Baylis–Hillman, Strecker,
Aldol, Claisen-Schmidt condensation and other useful organic reactions. In general, it is reported that nanocrystalline magnesium
oxide shows better activity in many organic reactions. These high reactivities are due to high surface areas combined with
unusually reactive morphologies. The nanomaterials were also explored as supports to make supported metal catalysts for the
organic reactions. The higher activity of these catalysts was studied partly to understand the mechanism of the reaction,
the putative reaction pathways were preliminarily presented with the help of spectroscopic support, XPS, silicon, and phosphorus
NMR spectroscopy. The catalysts are recovered and reused for several cycles. These catalytic systems are expected to contribute
to the development of benign chemical processes. 相似文献
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Ishizaki T Okido M Masuda Y Saito N Sakamoto M 《Langmuir : the ACS journal of surfaces and colloids》2011,27(10):6009-6017
Alkanoic and phosphonic acid derived self-assembled monolayers (SAMs) were formed on magnesium alloy by the vapor phase method. AFM and XPS studies showed that SAMs were formed on Mg alloy. The chemical and anticorrosive properties of the SAMs prepared on magnesium alloys were characterized using contact angle measurements, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. Water contact angle measurements revealed that, although SA and ISA have the same headgroup to anchor to the magnesium alloy surface, the packing density on the magnesium alloy surface could be considerably different. The contact angle hysteresis of SAMs with a carboxylate headgroup is much larger than that of SAMs with a phosphonic acid group. The XPS O 1s peaks indicated more likely a mix of mono-, bi-, or tridentate binding of phosphonic acid SAM to the oxide or hydroxide surface of the Mg alloy. The electrochemical measurements showed that the phosphonic acid derived SAM had better corrosion resistance compared to alkanoic acid derived SAM. The chemical stability of SAMs modified magnesium alloy was investigated using water contact angle and XPS measurements. The water contact angle and XPS measurements revealed that the molecular density of OP and PFEP on magnesium alloy would be higher than those of SA and ISA on magnesium alloy. 相似文献
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The magnesium isotope effects were investigated by chemical ion exchange with a hydrous manganese(IV) oxide. The capacity of manganese(IV) oxide was 0.5 meq g(-1). The distribution coefficient of magnesium ions on the MnO(2) was determined by a batch method. The heavier isotopes of magnesium were enriched in the solution phase, while the lighter isotopes were enriched in the hydrous MnO(2) phase. The separation factor was determined according to the method of Glueckauf from the elution curve and isotopic assays. The separation factors of (24)Mg(2+)-(25)Mg(2+), (24)Mg(2+)-(26)Mg(2+), and (25)Mg(2+)-(26)Mg(2+) isotope pair fractionations were 1.011, 1.021, and 1.011, respectively. 相似文献