The effect of heat treatment on colemanite processing: a ceramics application

Boron oxide (B₂O₃), water content, particle size, and specific surface area are important parameters in colemanite (2CaO3B₂O₃5H₂O) in the production of glasses especially of E-glass, boron carbide (B₄C) and borides (CaB₆, LaB₆, SiB₆, LiB₆, MgB₂, TiB₂, and TaB₂ etc.) which are used in ceramics applications. Calcination, a thermal treatment method, is known to affect these parameters significantly. In this study, differential thermal analysis (DTA)-TG, X-ray diffraction (XRD), SEM, BET and chemical analysis were performed on Turkish colemanites before and after calcination. The results are compared in order to elucidate the influence of calcination on processing. An application in the ceramic industry for the production of CaB₆ is demonstrated. Results indicate that the raw colemanite could be processed through calcination in the temperature range of 400 and 600 °C without milling. Calcination is shown to have a significant impact on colemanite similar to that of the milling process. As a result, colemanite was upgraded to ∼58 wt.% B₂O₃ for <250 μm yielding a specific surface area of 2.8 m²/g. This is higher than that of milled colemanite. Because of the crystal water of colemanite, CaB₆ is not produced from uncalcined colemanite, but easily produced from colemanite calcined at 600 °C.     

New cadmium and rare earth metal tungstates with the scheelite type structure

New cadmium and rare earth metal tungstates with the formula Cd_0.25RE_0.50□_0.25WO₄ (RE=Nd, Sm, Eu, Gd, □-statistical distributed vacancies in cation sublattice) were synthesized by the solid-state reaction between CdWO₄ and corresponding RE₂W₂O₉. The obtained phases crystallize in the scheelite type structure. The Cd_0.25RE_0.50□_0.25WO₄ compounds were characterized by X-ray diffractometer (XRD), (DTA-TG), infrared (IR) and EPR methods.     

高能球磨Al-Y2O3粉体固相反应制备YAG陶瓷的研究

用高纯Al粉体和Y₂O₃粉体(Al-Y₂O₃粉体)为原料采用固相反应法制备了YAG陶瓷. Al-Y₂O₃粉体高能经过球磨, 煅烧生成YAG粉体, 再真空烧结制备高致密YAG陶瓷. 采用DTA-TG对球磨Al-Y₂O₃粉体进行分析, 采用XRD、SEM对球磨的Al-Y₂O₃粉体、YAG粉体及YAG陶瓷进行了表征. 实验表明: Al-Y₂O₃粉体在～569℃时, Al粉强烈氧化, 并与Y₂O₃粉反应, 600℃煅烧出现YAM相, 随煅烧温度升高出现YAP相, 1200℃煅烧生成YAG粉体. 成型YAG素坯在1750℃保温2h真空烧结出YAG相陶瓷, YAG陶瓷相对密度可达98.6%, 晶粒生长均匀, 晶粒尺寸为810μm.     

高能球磨Al-Y2O3粉体固相反应制备YAG陶瓷的研究

用高纯Al粉体和Y₂O₃粉体(Al-Y₂O₃粉体)为原料采用固相反应法制备了YAG陶瓷. Al-Y₂O₃粉体高能经过球磨, 煅烧生成YAG粉体, 再真空烧结制备高致密YAG陶瓷. 采用DTA-TG对球磨Al-Y₂O₃粉体进行分析, 采用XRD、SEM对球磨的Al-Y₂O₃粉体、YAG粉体及YAG陶瓷进行了表征. 实验表明: Al-Y₂O₃粉体在～569℃时, Al粉强烈氧化, 并与Y₂O₃粉反应, 600℃煅烧出现YAM相, 随煅烧温度升高出现YAP相, 1200℃煅烧生成YAG粉体. 成型YAG素坯在1750℃保温2h真空烧结出YAG相陶瓷, YAG陶瓷相对密度可达98.6%, 晶粒生长均匀, 晶粒尺寸为810μm.     

烧结干法脱硫灰激发高炉矿粉活性及其机理研究

针对烧结干法脱硫灰资源化利用和高炉矿粉早期活性不高的问题,采用烧结干法脱硫灰激发高炉矿粉活性,测试了不同烧结干法脱硫灰掺量下高炉矿粉-水泥体系的强度、干缩、浸水自由膨胀性能;采用X射线衍射、扫描电镜、差示扫描量热-热重法研究了烧结干法脱硫灰激发高炉矿粉-水泥体系的水化产物、微观形貌及其火山灰放热行为机理。结果表明,采用烧结干法脱硫灰激发高炉矿粉能显著提高高炉矿粉3d、7d、28d抗压强度,其原因是高炉矿粉在烧结干法脱硫灰形成的SO42-、CO32-、SO32-环境下,生成了3CaO·Al2O3·CaSO4·32H2O、2CaSiO3·CaCO3·CaSO4·15H2O和3CaO·Al2O3·CaSO3·11H2O等水化产物;烧结干法脱硫灰的掺入使得高炉矿粉-水泥体系出现第三个放热峰,虽峰值相差不大,但出现时间明显滞后,有效减缓了高炉矿粉-水泥体系的水化放热。     

新型偶氮苯共轭席夫碱化合物的合成与表征

以对苯二甲醛与偶氮苯胺基化合物进行缩合反应合成系列新型具有不同取代基的含有偶氮苯共轭基团的席夫碱化合物。利用紫外光谱、红外光谱以及荧光光谱研究了目标产物的取代基效应,并用差热-热重分析方法对其热稳定性能进行测定。实验数据表明,对于分子内取代基团、共轭体系等因素的调控,可以得到性能迥异的席夫碱化合物,在功能材料等领域具有广泛的应用价值。     

Synthesis and Energetic Properties of Imidazolium and 2‐Methylimidazolium Salts of 3‐Nitro‐1,2,4‐Triazol‐5‐One

Two new energetic salts of 3‐nitro‐1,2,4‐triazol‐5‐one (NTO) were described. Imidazole and 2‐methylimidazole salt of NTO decomposes exothermically at 217 and 258 °C respectively. Detonation parameters calculated for 2‐methylimidazole salt are significantly smaller than that of 2,4,6‐trinitrotoluene (TNT) but these parameters estimated for imidazole salt are comparable with that of TNT. Structure of new compounds were investigated with NMR and IR spectroscopy. Impact and friction sensitivity determined for new compounds are smaller than for pure NTO, so they are more safe during handling.     

两种间位芳纶浆粕结晶性能的比较

芳纶浆粕的结晶性能对芳纶纸基材料的结构和重要性质有重大影响,采用差示扫描量热仪(DSC)对两种间位芳纶浆粕(F1和F2)进行测试,得到F1和F2无定型部分的玻璃化转变温度在283℃左右处出现,F1和F2在370℃以上出现了冷结晶放热峰,且F2的冷结晶能力强于F1。用DTA-TG对F1和F2进行了等温结晶性能分析,结果表明,F1的玻璃化转变温度较F2的低,冷结晶峰顶温度较F2高;并对热压后F1和F2的结晶性能进行了研究。     

高能球磨Al-Y203粉体固相反应制备YAG陶瓷的研究

用高纯Al粉体和Y2O3粉体(Al-Y2O3粉体)为原料采用固相反应法制备了YAG陶瓷. Al-Y2O3粉体高能经过球磨,煅烧生成YAG粉体,再真空烧结制备高致密YAG陶瓷.采用DTA-TG对球磨Al-Y2O3粉体进行分析,采用XRD、SEM对球磨的Al-Y2O3粉体、YAG粉体及YAG陶瓷进行了表征.实验表明:Al-Y2O3粉体在～569℃时,Al粉强烈氧化,并与Y2O3粉反应,600℃煅烧出现YAM相,随煅烧温度升高出现YAP相,1200℃煅烧生成YAG粉体.成型YAG素坯在1750℃保温2h真空烧结出YAG相陶瓷,YAG陶瓷相对密度可达98.6%,晶粒生长均匀,晶粒尺寸为8～10μm.     

基于BaO-CaO-Al2O3-B2O3-SiO2体系探究BaCO3的残余量及其对玻璃热性能的影响

采用中温固体氧化物燃料电池(IT-SOFC, Intermediate Temperature-Solid Oxide of Fuel Cell)封接玻璃BaO-CaO-Al₂O₃-B₂O₃-SiO₂体系探究三种熔制工艺(1300℃保温1 h; 1400℃保温1 h; 1400℃保温3 h)对玻璃原料BaCO₃的残余量及玻璃热性能的影响。利用差热-热重分析(DTA-TG)对配方粉体和不同熔制工艺获得玻璃的热性能进行表征, 根据DTA-TG数据进行了计算并验证BaCO₃的残余量。通过傅里叶红外光谱、XRD和热膨胀系数测定仪对样品进行了表征。结果表明: 采取1300℃保温1 h制备的玻璃中仍有59wt% BaCO₃未分解, 并且析出的单斜BaAl₂Si₂O₈晶体降低了玻璃的膨胀系数; 1400℃保温3 h制备的玻璃由于Al₂O₃含量增加, 玻璃软化点(T_s)明显升高(>800℃), 1400℃保温1 h制备的玻璃在室温到玻璃温度转变点范围内的膨胀系数为10.3×10^-6 K^-1。因此对于本实验玻璃配方, 1400℃保温1 h是最为合适的熔制工艺, 可以用于SOFC电堆的封接。