由白云石制备特种硅钢级氧化镁工艺研究

研究了由白云制备特种硅钢级氧化镁的原理及工艺条件，讨论了各工艺参数对产品性能的影响，制出了粒径细小，粒度分布均匀、分散性好，水化率低的氧化镁。     

The influence of hydrating agents on the hydration of industrial magnesium oxide

BACKGROUND: The influence of different hydrating agents on the pH of the hydrating solutions, rate of hydration of MgO to Mg(OH)₂ and product surface area was studied as a function of temperature of hydration. Hydrating agents used were aqueous solutions of ammonium chloride, magnesium acetate, magnesium nitrate, nitric acid, acetic acid, magnesium chloride, sodium acetate and hydrochloric acid and distilled water as control. These were chosen to determine either the effect of addition of a common ion, the effect of changing the solution pH or due to the presence of an acetate ion, found earlier to have a beneficial effect on the hydration of MgO. RESULTS: There was no significant difference in the hydration behaviour of the hydrating agents up to 50 °C, where less than 10% of magnesium hydroxide was formed. The amount of hydroxide increased at temperatures above 60 °C. When compared with the hydration in water, all the hydrating agents, with the exception of sodium acetate, showed a significant increase in the degree of hydration. Sodium acetate formed the lowest amount of magnesium hydroxide, ranging between 1.2 and 12.2% magnesium hydroxide. The largest percentage (56.7%) of magnesium hydroxide was formed from hydration in magnesium acetate. CONCLUSION: It seems that MgO hydration is a dissolution‐precipitation process controlled by the dissolution of MgO. The increased degree of hydration in magnesium acetate is possibly due to the presence of acetate and Mg²⁺ ions. Copyright © 2010 Society of Chemical Industry     

用氯化镁生产氢氧化镁和氧化镁的方法

采用一种精制原料和两次煅烧工艺克服在Aman法分步精制原料和三次煅烧等现有工艺路线长、能耗高、生产成本高等不足，将煅烧温度分为：600－800℃轻烧，800－1200℃重烧，1200－1800℃死烧3个温度段，可以分别制得高纯的轻质、重质氧化镁和镁砂。大幅度缩短了工艺路线和生产周期并降低生产成本，成功解决了从原料直接生产氧化镁的技术难题，创造了氧化镁生产的又一方法。     

磷资源加工研究进展：2．从高镁低品位磷矿中回收镁化学品

介绍对高镁低品位磷矿采用选择性化学反应进行脱镁并回收镁的新方法,磷损失约2%,获得的阻燃剂氢氧化镁产品w(Mg(OH)2)可达95%以上。该工艺既解决了磷矿脱镁的问题,又具有较好的经济价值。     

氢氧化镁和氧化镁中酸不溶物的研究

产硝后的高镁卤水和硫氢化钡溶液进行反应，生成氢氧化镁，酸不溶物在0．3％（质量分数）左右，但将其煅烧成氧化镁后，酸不溶物高达1．2％-2．5％（质量分数），二者酸不溶物远不成比例关系。通过对样品在分析中穿滤对比、硫酸法测定酸不溶物、碘量法测定硫化物试验，确定在生产过程中，硫氢化钡被氢氧化镁吸附，经过高温煅烧，硫氢化钡被氧化成硫酸钡，成为氧化镁中的酸不溶物，这就是氧化镁和氢氧化镁中酸不溶物不成比例的主要原因。     

从卤水制备耐火级高活性氧化镁影响因素探讨

特种耐火级氧化镁不但要有高的纯度,也要有很高的活性,但目前中国尚不能生产这样的优质产品。以卤水为原料,经过氢氧化镁途径制备高纯高活性氧化镁,重点考察了卤水浓度、反应时间等因素对中间体氢氧化镁粒径、分散状态、纯度的影响,并通过添加表面活性剂,得到了制备高纯度高分散中间体氢氧化镁的最佳工艺条件为：氯化镁的浓度为1-1.5 mol/L,反应时间为2-2.5 h。该工艺条件下可以得到粒径小、分散性好、纯度达99%以上的氢氧化镁,为高活性氧化镁的制备奠定了基础,具有重要的实际应用意义。     

Improved Hydration Resistance of Synthesized Magnesia–Calcia Clinker by Surface Modification

Hydration resistance of synthesized MgO–CaO clinker was improved by surface modification using oleic acid, stearic acid, or complex acids as modifiers, with phosphoric acid as a reference. Unmodified and modified samples were evaluated using a powdering resistance test, weight change test, and flowability test. The remarkable effects of the modifiers on the hydration resistance and flowability of the clinker were manifested, and the complex modifier caused the most significant effect. The mechanism involved the formation of calcium-containing films on the surfaces of the clinker particles, which protected them from hydration. The flowability of the clinker also increased with improved hydration resistance because of the decreased bonded-moisture content. Comparison of infrared spectra between unmodified and modified samples confirmed the formation of surface films.     

硝酸法处理中低品位高镁胶磷矿技术研究

通过5因素5水平正交实验获得了高镁胶磷矿脱镁的最优工艺条件：液固质量比为3.0、硝酸用量为0.207 g（以1 g磷矿计）、磷矿细度为150~180 μm、温度为45 ℃、反应时间为2.5 h。以磷精矿中镁磷比为参数进行回归分析并得到数学模型,该模型的相关系数为0.926,能够较好地预测高镁胶磷矿的脱镁结果。在最优工艺条件下进行重复实验,结果表明镁脱除率达到了96.1%,磷损失率仅有0.303%,得到磷精矿的镁磷质量比为0.594%、磷精矿五氧化二磷质量分数达31.0%、氧化镁质量分数仅为0.184%,完全达到磷矿湿法加工一等品的要求。研究结果对工业化应用中低品位高镁胶磷矿具有重要的参考与指导意义。     

宜昌中低品位磷矿生产钙镁磷肥的可行性

宜昌地区磷矿储量较大而富矿很少．目前年生产约400万t，均为P2O528％以上的富矿，资源浪费严重。建议采用荆襄磷化公司的经验用P2O524～27％的矿石生产钙镁磷肥，技术可行，经济合理，各项指标较好。     

A study of sintering of magnesium oxide obtained from sea-water

The process of sintering of magnesium oxide obtained from sea-water is studied. The sample thickening stage in the isothermal sintering is determined to establish the manner of pore elimination in the process. The process of isothermal sintering of magnesium oxide is described mathematically to obtain a better insight into the process, in terms of a function giving the best possible correspondence between theoretical and experimental data.     

氧化镁的制备及其杀菌性能研究

采用溶胶-凝胶法和液相沉淀法制备氧化镁粉体。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、能谱(EDS)对氧化镁颗粒的结构、形貌和元素含量分析进行表征。采用抑菌圈法,将不同方法制备的氧化镁对大肠杆菌进行抗菌性能测试。结果表明:溶胶-凝胶法制备的氧化镁具有更好的杀菌效果,抑菌圈直径达14.2 mm。     

超细氧化镁粉体的制备方法探讨

超细氧化镁粉体属于新型高功能精细无机材料。着重介绍了超细氧化镁粉体的制备方法(包括气相法、金属醇盐水解法、液相法、固相法、硬脂酸法)，对各方法的原理及优缺点作了详细的阐述。最后提出了硬脂酸法这一有前景的新工艺。     

Synthesis and properties of a novel bio‐based benzoxazine resin with excellent low‐temperature curing ability

A novel bio‐based benzoxazine resin (diphenolic acid/furfurylamine benzoxazine resin, PDPA‐F‐Boz) was prepared by using bio‐based diphenolic acid, furfurylamine and paraformaldehyde as raw materials. The structure of DPA‐F‐Boz monomer was characterized by Fourier transform infrared spectroscopy, ¹H NMR and ¹³C NMR, and then its curing reaction and the thermal stability of the cured PDPA‐F‐Boz were analyzed. Compared with the traditional fossil‐based benzoxazine (bisphenol A/aniline benzoxazine, BPA‐A‐Boz) and the bio‐based benzoxazine (diphenolic acid/aniline benzoxazine, DPA‐A‐Boz), DPA‐F‐Boz monomer showed the lowest curing temperature, and PDPA‐F‐Boz had the highest residual char ratio at 800 °C and the lowest degradation rate at the peak temperature. Meanwhile, the total heat release, peak heat release rate and heat release capacity of PDPA‐F‐Boz were much lower than those of PBPA‐A‐Boz and PDPA‐A‐Boz. Thus, PDPA‐F‐Boz showed excellent low‐temperature curing ability and thermal stability. © 2019 Society of Chemical Industry     

Synthesis of a linear low‐density polyethylene/MgO@Mg(OH)2 nanocomposite using modified in situ polymerization

Composites of linear low‐density polyethylene were obtained in toluene slurry by in situ copolymerization of ethylene and 1‐octene in the presence of untreated magnesium oxide–hydroxide nanoparticles (MgO@Mg(OH)₂) of ±50 nm and such treated with dibutylmagnesium (DBM) as support for a bis(n‐butylcyclopentadienyl)zirconium dichloride–methylaluminoxane (MAO) catalyst system. Treatment of the nanoparticles with DBM (0.5–6 mmol g^?1 MgO@Mg(OH)₂) allows one to decrease the amount of MAO by 1.2 mmol Al g^?1 MgO@Mg(OH)₂, while reaching the same average catalyst activity and a finer distribution of the particles. Energy‐dispersive X‐ray mapping shows that the MAO is mainly associated with the filler. The crystallinity of the matrix polymer decreases with filler content. © 2018 Society of Chemical Industry     

Flame‐retardant action of red phosphorus/magnesium oxide and red phosphorus/iron oxide compositions in recycled PET

Red phosphorus was combined with metallic oxides Fe₂O₃ and MgO to improve the fire properties of recycled PET. Both Fe₂O₃ and MgO act as co‐synergist agents at a total loading of 5 wt%. The analysis by diffraction X of the char formed during combustion shows that transformation of Fe₂O₃ to Fe₃O₄ occurs. Fe₂O₃ favours the oxidation and improves the effectiveness of red phosphorus. It is suggested that MgO interacts with acidic end groups of PET and forms a thermal stable residue. The thermal decomposition of recycled PET containing red phosphorus combined with Fe and Mg oxides was studied by thermal analysis and leads to an increase in char formation. While the incorporation of Fe₂O₃ in this ternary blend maintains the mechanical properties of PET, the reactivity of MgO leads to a brittle material. The use of reinforcements (talc and glass fibres) to mechanically stabilize the char formed during combustion of ternary blend with Fe₂O₃ entails a further decrease in heat release rate, nevertheless impact resistance of the material decreases dramatically. Copyright © 2005 John Wiley & Sons, Ltd.     

Thermodynamic and kinetic studies of the MgCl2‐NH4Cl‐NH3‐H2O system for the production of high purity MgO from calcined low‐grade magnesite

To improve the overall sustainability of MgO‐based refractory production, a novel process to produce high purity MgO from calcined low‐grade magnesite in ammonium chloride solution was developed. The process was designed on the basis of the phase equilibria of the NH₄Cl‐MgCl₂‐NH₃‐H₂O system obtained using the Mixed Solvent Electrolyte model embedded in OLI software. The optimum calcination temperature of low‐grade magnesite was determined to be 650°C in terms of the conversion ratio of magnesium and calcium in the leaching experiments. An apparent activation energy of Mg extraction was 30.98 kJ/mol, which is slightly lower than that of Ca leaching. An empirical kinetic model of magnesium extraction was also developed to describe the effects of NH₄Cl concentration, particle size of calcined magnesite, and solid‐to‐liquid ratio on the extent of extraction of magnesium. At leaching time of 10 min, the leachate with high Mg/Ca molar ratio was obtained. Then, MgO with a purity of 99.09% was produced through the decomposition of intermediate 4MgCO₃·Mg(OH)₂·4H₂O. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1933–1946, 2015     

TGA analysis of γ‐irradiated linear low‐density polyethylene

Linear low‐density polyethylene (LLDPE), based on butene‐1 or hexene‐1, was irradiated with γ‐rays under vacuum or in the presence of air. The study focused on the influence of the dose rate and the γ‐dose on the thermal properties of LLDPE. Differential scanning calorimetry, thermogravimetric analysis (TGA), and TGA/FTIR techniques were used to address the thermal behavior as a result of γ‐irradiation. During this irradiation, competition between crosslinking and scission reactions, subsequent to oxidation reactions, occurred in the polymeric material, which strongly depends on the experimental conditions. A decrease of the crystallinity for γ‐irradiated samples was observed in particular for samples irradiated under vacuum. This observation may be explained by increased hindrance of segment mobility due to crosslinking reactions that prevent crystal growth. TGA investigations revealed an enhancement of the thermal stability for samples irradiated under vacuum but not for those irradiated in air. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2790–2795, 2006