天然针铁矿热处理产物的结构特征

采用X射线粉末衍射仪、热重分析仪、透射电子显微镜、比表面积分析仪等研究空气中热处理铜陵新桥天然针铁矿的结构演化。热分析结果表明:针铁矿在154.5℃开始脱羟基向赤铁矿转变,在300℃时相转变完全。煅烧温度250~700℃之间,虽然产物都是赤铁矿,但都保持针铁矿原有的形貌特征,且产物的比表面积和孔结构随煅烧温度变化有明显差异。300℃煅烧产物由于脱羟基水,针铁矿假象颗粒内部出现1~5μm大小的孔,且具有最大的比表面积(107.8m2/g);随着煅烧温度升高,由于赤铁矿晶体生长变大,赤铁矿晶体间空隙变大,比表面积逐步降低;煅烧温度大于700℃时,由于赤铁矿晶粒生长开始出现颗粒间烧结现象,针铁矿假象颗粒内部和外部空隙进一步减少,当煅烧温度达到900℃时,针状形貌变成粗短圆柱状,此时比表面积降至最小值为4.8m2/g。结果表明:铜陵新桥针铁矿可以在300~400℃空气中煅烧获得高比表面积的纳米孔材料,在环境保护领域具有很大的潜在应用价值。     

氢气还原针铁矿去除水中的亚硝酸盐

采用氢气还原天然针铁矿和合成针铁矿制备铁粉,研究了反应时间、反应pH值、初始亚硝酸盐浓度等对两种还原铁粉去除亚硝酸盐的影响。结果表明：反应3 h、低亚硝酸盐初始浓度（〈16 mg/L）、低铁粉与亚硝酸盐质量比（〈33：1）情况下,由合成针铁矿制备的还原铁粉对亚硝酸盐的去除率均高于由天然针铁矿制备出的铁粉,但随着反应时间的延长（〉3 h）、亚硝酸盐初始浓度的增加（〉16 mg/L）、铁粉与亚硝酸盐质量比的增加（〉33：1）,由天然针铁矿制备的还原铁粉对亚硝酸盐的去除率均高于由合成针铁矿制备出的铁粉。Al部分替代天然针铁矿中Fe阻碍了铁粉表面钝化膜的形成,从而增加了还原铁粉还原亚硝酸盐的稳定性,提高了亚硝酸盐的去除率。     

黄铁矿-针铁矿混合无氧焙烧产物物相演变和特性

通过将针铁矿和黄铁矿混合无氧焙烧,制备了可用于水处理的材料,研究了氮气气氛下500~700℃焙烧针铁矿与黄铁矿混合物产物中物相的演变过程、微结构和特性。结果表明:针铁矿与黄铁矿无氧混合焙烧,在500℃时,针铁矿脱羟基转变为赤铁矿,黄铁矿未分解,黄铁矿和针铁矿之间未发生化学反应,在550~600℃时,上述赤铁矿与黄铁矿分解产生的单质硫发生氧化还原反应首先形成磁铁矿,磁铁矿再与单质硫发生歧化反应形成磁黄铁矿和二氧化硫;550℃温度区域针铁矿相变产物主要是磁铁矿,固体产物磁化率最高,达204×10--6 m3/kg。针铁矿转变为赤铁矿、磁铁矿的过程中继承了针铁矿的形貌特征,但转变为磁黄铁矿后其形貌为粒状,并且随着焙烧温度升高形成磁黄铁矿的粒径增大。针铁矿与黄铁矿无氧混合焙烧可以使针铁矿转变为磁黄铁矿材料,该方式制备的磁黄铁矿比黄铁矿热分解形成的磁黄铁矿除磷效果好,在废水深度脱氮除磷处理领域具有潜在应用价值。     

有机絮凝剂对铁矿相沉降性能影响及其吸附机理

通过模拟拜耳法赤泥沉降过程研究了聚丙烯酸铵(PAAA)、阴离子聚丙烯酰胺(APAM)和氧肟酸絮凝剂(HPAM/HCPAM)对赤铁矿和针铁矿沉降性能的影响规律和絮凝后絮体的粒径分布及分形维数,并利用傅里叶变换红外光谱探讨了絮凝剂与铁矿相的吸附机理。在不同类型絮凝剂中,添加氧肟酸絮凝剂铁矿相沉降速度最快,且氧肟酸含量越高,沉降性能越好;聚丙烯酸铵和阴离子聚丙烯酰胺絮凝剂对铁矿相沉降性能影响较小;同等条件下赤铁矿沉降速度要远高于针铁矿,增加絮凝剂添加量有助于提高针铁矿沉降速度。在赤铁矿絮体中,添加PAAA絮体粒径最大,HPAM絮体分形维数最大、致密性最好;在针铁矿絮体中,添加APAM絮体粒径最大,HCPAM絮体分形维数最大、致密性最好。氧肟酸絮凝剂与铁矿相形成结构稳定、吸附能力强的五元环状螯合物,增强了赤铁矿和针铁矿的絮凝效果;PAAA通过双齿桥接配位与赤铁矿表面发生吸附,通过单齿配位与针铁矿表面发生吸附,其吸附能力弱于五元环;APAM与赤铁矿和针铁矿表面发生化学吸附,沉降性能差。     

有机负荷对针铁矿厌氧消化产甲烷体系的影响

厌氧产甲烷是有机废弃物资源化的有效途径之一,已经被广泛应用于处理工业废水、城市生活垃圾、农业废弃物、禽畜粪便等。但目前存在产甲烷效率低、转化速率较慢等缺点。本研究尝试利用自然界中广泛存在的针铁矿为添加剂强化废水产甲烷过程。以乙酸钠和葡萄糖和为碳源模拟有机废水,研究了针铁矿对有机废水厌氧产甲烷的作用,考察了不同水力负荷条件下对连续流厌氧产甲烷反应器消化体系甲烷产量及产甲烷速率的作用。     

有机絮凝剂对铁矿相沉降性能影响及其吸附机理

通过模拟拜耳法赤泥沉降过程研究了聚丙烯酸铵(PAAA)、阴离子聚丙烯酰胺(APAM)和氧肟酸絮凝剂(HPAM/HCPAM)对赤铁矿和针铁矿沉降性能的影响规律和絮凝后絮体的粒径分布及分形维数,并利用傅里叶变换红外光谱探讨了絮凝剂与铁矿相的吸附机理。在不同类型絮凝剂中,添加氧肟酸絮凝剂铁矿相沉降速度最快,且氧肟酸含量越高,沉降性能越好;聚丙烯酸铵和阴离子聚丙烯酰胺絮凝剂对铁矿相沉降性能影响较小;同等条件下赤铁矿沉降速度要远高于针铁矿,增加絮凝剂添加量有助于提高针铁矿沉降速度。在赤铁矿絮体中,添加PAAA絮体粒径最大,HPAM絮体分形维数最大、致密性最好;在针铁矿絮体中,添加APAM絮体粒径最大,HCPAM絮体分形维数最大、致密性最好。氧肟酸絮凝剂与铁矿相形成结构稳定、吸附能力强的五元环状螯合物,增强了赤铁矿和针铁矿的絮凝效果;PAAA通过双齿桥接配位与赤铁矿表面发生吸附,通过单齿配位与针铁矿表面发生吸附,其吸附能力弱于五元环;APAM与赤铁矿和针铁矿表面发生化学吸附,沉降性能差。     

人工合成针铁矿与颗粒活性炭、石英砂作为反硝化生物滤池填料的比较

本文研究了颗粒活性碳、石英砂和人工合成针铁矿作为填料时的反硝化生物滤池的反硝化脱氮性能。结果表明,维持反硝化生物滤池的运行条件在pH 7.30±0.10和温度25±2℃,人工合成针铁矿为填料的反硝化生物滤池达到稳定状态的去除率比其他两种填料高,COD去除率可达68.32%,NO_3~-去除率为65.86%。实验结果表明人工合成针铁矿是一种良好的反硝化生物滤池填料。     

海水中主要无机阴离子对针铁矿吸附磷的影响

采用水解中和法制备了针铁矿,研究了海水中的无机阴离子Cl-、Br-、F-、SO42-和HCO3-对针铁矿吸附磷的影响。结果表明:当存在SO42-、Cl-、Br-和F-时,针铁矿吸附低浓度磷酸盐受到抑制,吸附高浓度磷酸盐时得到促进;而HCO3-对针铁矿吸附磷有着很强的抑制能力;全部组分的主要无机阴离子共同存在时,针铁矿吸附磷受到抑制,酸性条件下的吸附量高于碱性条件。     

针铁矿对模拟废水中磷的吸附实验研究

采用水解中和法制备了针铁矿,并进行了其吸附模拟废水中磷的实验研究。结果表明,时间对针铁矿吸附磷有很大影响,210 min达到吸附平衡;向50 mL 5 mg/L的含磷废水中投加1.0 g吸附剂,可去除磷90%;溶液初始酸碱性对吸附效果有显著影响,酸性溶液有利于吸附,当pH值为3时,去除率达到最高;针铁矿对磷的吸附受温度影响较小;可以用Langmuir吸附等温式描述针铁矿对磷的吸附行为,吸附动力学可以用准二级动力学方程来描述。     

针铁矿对模拟废水中磷的吸附实验研究

采用水解中和法制备了针铁矿,并进行了其吸附模拟废水中磷的实验研究。结果表明,时间对针铁矿吸附磷有很大影响,210 min达到吸附平衡;向50 mL 5 mg/L的含磷废水中投加1.0 g吸附剂,可去除磷90%;溶液初始酸碱性对吸附效果有显著影响,酸性溶液有利于吸附,当pH值为3时,去除率达到最高;针铁矿对磷的吸附受温度影响较小;可以用Langmuir吸附等温式描述针铁矿对磷的吸附行为,吸附动力学可以用准二级动力学方程来描述。     

Structural and Textural Modifications of Ternary Phosphate Glasses by Thermal Treatment

Phosphate-based glasses of composition xNa₂O−(45+(10−x))CaO−45P₂O₅ with different Na₂O, CaO (x = 1, 5, 10, 15, and 20 mol%), and invariable P₂O₅ (45 mol%) contents were prepared using the rapid melt quench technique. The obtained thermal data from differential thermal analysis revealed a decline in glass transition (T_g) and crystallization (T_c) temperatures of glasses against the compositional changes. The inclusion of Na₂O at the cost of CaO in the glass network led to a reduction in its thermal stability. The thermal treatment carried out on glasses helped to derive their glass-ceramic counterparts. The amorphous and crystalline features of samples were characterized using X-ray diffraction patterns. The crystalline species that emerged out of the calcium phosphate phases confirmed the dominance of Q¹ and Q² structural distributions in the investigated glass-ceramics. The obtained scanning electron micrographs and atomic force microscopic images confirmed the surface crystallization and textural modification of the samples after thermal treatment. The N₂-adsorption–desorption studies explored the reduction of porous structures due to thermal treatment on the melt-driven glass surface. The measured elastic moduli and Vicker's hardness values of the glasses showed an increase after thermal treatment, which were reduced against the inclusion of alkali content in both glass and glass-ceramics.     

Structural Defect Evolution of TATB‐Based Compounds Induced by Processing Operations and Thermal Treatments

2,4,6‐Triamino‐1,3,5‐trinitrobenzene (TATB) compounds are commonly used in high performance explosives because of their thermal stability and high detonation velocities compared to other materials. The insensitivity and mechanical properties are related to the stability of their crystalline structure. Crystallographic structure and structural defects evolution of TATB and TATB‐based compounds were studied by X‐ray diffraction for powders, molding powders, and pressed compounds, using Rietveld refinement. The effects of synthesis conditions, thermal treatments, coating and pressing operations on the structure of TATB compounds were evaluated. The results show that the pressing operation results in anisotropic crystallite size, leading to an increase of the structural defects density. It could be due to the anisotropic mechanical response of the TATB crystal under pressure, possibly plasticity. Finally, it is shown that increasing thermal treatment temperature on TATB powders decreases the structural defects density.     

不同热处理条件下聚丙烯腈的结构演变

采用傅里叶变换红外光谱(FTIR)和广角X射线衍射(WAXD)研究了处理温度、处理时间、气体氛围对聚丙烯腈(PAN)均聚物及其共聚物P[丙烯腈(AN)/甲基丙烯酸甲酯(MMA)/衣康酸(IA)]热处理过程中结构演变的影响。FTIR结果表明,在氮气中,环化反应可以大量出现,但脱氢反应较少;而在空气氛围中,环化反应和脱氢反应都可以大量发生。氧气对PAN均聚物的环化反应有抑制作用,而对P(AN/MMA/IA)的环化反应有促进作用。WAXD结果表明,PAN均聚物的预氧化反应首先发生在非晶区,而后发生在晶区。在240℃时,t=1 h,环化反应主要发生在非晶区;t≥1.5 h,主要发生在晶区。     

Chemical and Structural Evolution of Sol-Gel-Derived Hydroxyapatite Thin Films under Rapid Thermal Processing

Chemical and structural evolution of hydroxyapatite thin films produced by sol-gel synthesis is characterized by ion beam analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. Formation of the hydroxyapatite structure began at 500°C; no other phases were observed at higher temperatures. Elimination of residual organics was observed in the form of the disappearance of excess oxygen, hydrogen and carbon. Crystal size increases with increasing anneal temperature; spectroscopy indicates the formation of highly crystalline films. The analytical methods chosen provide insight into subtle chemical and structural changes which occur in films produced by this synthetic route.     

Evolution of Extractive Composition During Thermal Treatment of Jack Pine

Abstract

The thermal treatment of wood has many benefits such as better dimensional stability and attractive dark color and does not use toxic chemicals. The resistance against biological decay can be improved when wood is not in contact with ground. On the other hand, after thermal transformation, wood becomes more fragile. The changes of the wood properties are related to the modification of the wood composition. During the thermal treatment, the evaporation of the moisture content is not the only event. Volatile extractives are evacuated from the wood, while new products and by-products of different chemical reactions appear. The comparison of the extracts obtained from untreated and treated wood can help to identify thermo-chemical reactions, taking place during the heat treatment. This article presents the analysis by Gas Chromatography–Mass Spectroscopy (GC-MS), High Performance Liquid Chromatography (HPLC), and Thin Layer Chromatography (TLC) of polar and non-polar extracts of untreated and heat-treated North American Jack pine (Pinus banksiana). The study of the impact of maximum heat treatment temperature on the composition of the Jack pine extracts showed that the major part of extractives leaves the wood under 200°C whereas most of the new products appear only above 200°C. While the extractives of the untreated Jack pine are dominated by non-polar components, the thermo-transformation seems to generate mainly polar compounds. However, presence of water vapor increases the portion of polar extractives in wood. Interestingly, an important decrease of concentration of phenolic compounds (such as pinosylvin, pinosylvin monomethyl ether, and pinobanksin) in Jack pine wood was observed between 160–200°C. On the other hand, 4-hydroxy-methylfurfural and vanillin have been identified as compounds generated by the heat treatment above 200°C. The identification of other by-products will be presented in a later paper.     

杂化介孔二氧化硅陈化过程中结构的演变及其SAXS表征

运用小角X-射线散射(SAXS)技术,定量地分析了杂化介孔二氧化硅产物SiO2骨架、介观孔洞以及纳米结构整体的分形维数在陈化处理过程中的演变过程。结果表明,SiO2骨架电子不平均区尺度(E)、孔洞回旋半径(Rg)和整体质量分形(DM)尺度数目都呈逐渐减少的趋势,标志着在陈化处理过程中产物整体结构规整程度逐步得到提高。     

Evolution in Structural and Optical Properties of Stannic Oxide Xerogel upon Heat Treatment

Upon consecutive heat treatments at increasing temperatures, the microstructure of solution–sol–gel-derived stannic oxide (SnO₂) xerogel evolves in three stages: (I) below 300°C, characterized by extensive dehydroxylation and gel shrinkage with little grain growth and surface loss; (II) between 300° and 500°C, by extensive crystallization, leading to dramatic surface loss (by 70%); and (III) above 500°C, by grain growth. Concurrently, the UV-absorption edge shows red shifts during stages I and II and blue shifts during stage III, resulting in distinct color variations. The edge displacement bears a close correlation with a Raman "defect band" at ∼305–328 cm⁻¹.     

胺处理聚甲醛的热稳定化研究

针对聚甲醛由于合成中残留催化剂及不稳定端基导致其热稳定较差的问题,采用胺对聚甲醛进行处理,并考察了胺种类、胺处理工艺及水用量对聚甲醛热稳定性能影响;采用等温热质量损失率、等温热质量损失速率、甲醛释放量分析等方法对三乙醇胺对POM的热稳定作用进行了进一步研究。结果表明：以三乙醇胺为胺处理剂、采用熔融后处理法可有效提高聚甲醛热稳定性能,三乙醇胺最佳用量为0.2％。