Liesegang图案实验的开发和教学实践

在无机与分析化学实验教学中引入Liesegang图案实验，并对实验不断改进，将实验操作、数值模拟与理论分析相结合，使学生认识沉淀反应中与树年轮、玛瑙石纹理和结石图案等类似的有序现象，初步了解非平衡自组织的基本现象和理论。     

制备方法对复合氧化物Bi_2WO_6-ZrO_2-TiO_2光催化性能的影响

采用一积沉淀法和两积沉淀法分别制备了Bi2WO6-ZrO2-TiO2复合催化剂。利用X射线衍射(XRD),N2吸附(BET),傅里叶变换(FT-IR)光谱技术,X光电子能谱(XPS),紫外-可见(UV-Vis)漫反射光谱等分析技术对样品进行了表征。结果显示,两积沉淀法的Bi、W离子存在于催化剂表面,而一积沉淀法是进入催化剂晶格。利用气相苯进行催化剂的紫外和可见光活性实验,结果表明,两积沉淀法制备的复合催化剂活性最高。     

虚拟仿真技术在大学分析化学实验教学中的应用*

针对传统分析化学实验教学中的不足,介绍了大学分析化学实验虚拟仿真线上教学项目的建设内容及其应用实效,并对虚拟仿真实验技术下一步的发展方向进行了设想。通过近2个学年的教学实践,发现以虚拟仿真实验辅助现场教学,可有效弥补传统分析化学实验教学中学生预习效果差、试剂废液产生量大、安全隐患频发等方面的缺陷;同时,虚拟仿真实验系统的考核评价、分析统计功能为教师在开展现场实验教学过程中,针对学生知识点掌握的薄弱环节开展针对性强化指导训练提供了有效手段。本虚拟仿真实验系统为虚拟仿真技术在大学分析化学实验教学领域的推广应用提供了有益借鉴。     

基于微课的翻转课堂教学模式在分析化学实验教学中的探索

分析化学实验是大学化学实验的重要内容,是分析化学课程学习中不可缺少的组成部分。为了提高分析化学实验教学质量,提升学生动手能力、分析问题和解决问题的能力以及创新能力,解决传统教学模式存在的主要问题,对分析化学实验教学模式进行了改革探索。将以微课为基础的翻转课堂教学模式引入到分析化学实验中,激发学生的实验热情,提高学生综合实验技能,巩固基础理论知识,培养了科学研究思维,真正实现创新性人才培养目标。     

纳米级Mgo粉体的合成

采用化学沉淀法制备了薄片形氧化镁超微粉末，讨论了原始原料，浓度和温度对产物粒径的影响，通过ＸＲＤ及ＴＥＭ等实验手段对超微粉进行了表征。     

纳米硫化银离子敏感材料的研制

采用均相沉淀法研制了硫化银纳米粒子，并用扫描电子显微镜(SEM)对粒子进行表征，确定了制备硫化银纳米粒子的最佳工艺路线；用硫化银纳米粒子研制了PVC膜银离子选择性电极，试验表明，此种电极具有良好的性能。     

酸-碱交替沉淀法铜基甲醇合成催化剂的优化制备与表征

采用酸-碱交替沉淀法制备了Cu基甲醇合成催化剂放大样(500 g), 并用X射线衍射、低温N2吸附和扫描电子显微镜等对催化剂进行了表征,系统考察了制备条件(搅拌速度、溶液滴加速度、盐和碱溶液浓度等)对催化剂性能的影响. 结果表明,采用酸-碱交替沉淀法制备的Cu基甲醇合成催化剂中, Cu和Zn组分以无定形的CuO-ZnO固溶体存在,使得CuO和ZnO的晶粒减小,导致催化剂的晶粒度较小,粒径尺寸分布较均匀,结晶度相对较低,有利于提高催化剂的比表面积. 采用酸-碱交替沉淀法制备的Cu基甲醇合成催化剂具有较高的Cu分散度和较大的Cu比表面积. 在优化条件下制备的催化剂的活性和耐热性均比国内外工业催化剂高.     

纳氏试剂比色法测定水中氨氮的干扰分析

就实验过程中的各种干扰来源及带来的误差进行了分析,并着重对絮凝沉淀法带来的误差及误差消除进行了研究。     

碳铵沉淀法制备纳米氧化钇过程中氯离子的行为

研究了碳酸氢铵沉淀法制备纳米氧化钇过程中氯离子的行为及去除方法,认为沉淀物的组成为Y(OH)0.1Cl0.1(CO3)1.4·2H2O。讨论了氯离子的存在形式,氯离子主要以氯化铵吸附或夹带和碳酸钇复合物的形式存在,其中碳酸钇复合物和颗粒内部夹带的氯离子是影响最终纳米氧化钇中氯含量的关键。通过实验研究证明采用洗涤和提高煅烧温度和延长保温时间可以有效减少氯离子的含量,制得了氯离子含量为0.054%的纳米氧化钇粉体。     

理科分析化学教材编审小组会议在武汉举行(1985.11)

会议的任务是:一、修订综合性大学化学系“分析化学和分析化学实验”、“仪器分析和仪器分析实验”教学大纲;二、讨论分析化学1986—1990年教材规划。对于“分析化学”课程,会议建议将定性分析并入无机化学课程中,任教学中适当增加分离方法方面的内容;在有条件的学校中,应注意增加将电子计算机用于离子平衡、数据处理等的内容。     

A DSC study of precipitation hardening in a WE43 Mg alloy

The phase transformations leading to hardening a Mg-Y-Nd-Zr (WE43) alloy submitted to thermal treatments are followed by calorimetric and microhardness measurements. A double-stage thermal treatment is adopted, the first at 210°C for 8 h and the second at 150°C, on samples quenched from a temperature higher than the conventional one. A secondary precipitation of the metastable phase β″ in the second stage makes the hardness increase with respect to the primary precipitation.     

银氨溶液配制过程中的沉淀现象探析

通过一系列实验发现,新制的氨水与硝酸银溶液反应只能看到暗棕色的氧化银沉淀生成与溶解的实验现象;氨水与空气接触时间较长时,部分氨水吸收了空气中的二氧化碳生成碳酸铵,这样的氨水与硝酸银溶液反应,便有白色的碳酸银沉淀生成。     

两步沉淀法制备耐高温和优异还原性能CeO2材料

分别采用两种沉淀方法制备了CeO2:以传统的氨水为沉淀剂,在氨水沉淀法前引入碳铵沉淀步骤(两步沉淀法)。采用热重-差热(TG-DTA)、傅里叶变换红外(FTIR)、X光电子能谱(XPS)等手段对沉淀及其分解过程进行了研究。结果表明,在两步沉淀法中的第一步,碳酸物种为主要沉淀物种,而在第二步中被氢氧根取代。X射线衍射(XRD)和透射电子显微镜(TEM)结果表明,两步沉淀法生成的沉淀颗粒粒径更大。通过两步沉淀法制备的CeO2与氨水沉淀相比具有更好的抗高温老化性能和还原性能。经过900℃焙烧3 h后,仍然具有25 m2.g-1和0.11 cm3.g-1的比表面和孔容。     

Tannin Content in Vitis Species Red Wines Quantified Using Three Analytical Methods

Tannin content in red wines is positively correlated with astringency perception and wine grade; however, tannin quantification is one of the main challenges. In this study, tannin content was quantified using three analytical methods in commercial red wines from Vitis vinifera and interspecific cold-hardy hybrids including Marquette, Frontenac, and Petite pearl cultivars. Protein (PP) and methylcellulose precipitation (MCP) methods were compared to a HPLC-DAD method, which is based on the interaction between tannins and a hydrophobic surface (RPC). Frontenac wines were the poorest in tannins and Cabernet sauvignon wines were the richest regardless of the method used. In cold-hardy red wines, the tannin content was higher in Marquette with high alcohol content, which suggested that the tannins were extracted from seeds rather than skins. The high limit of quantification of the PP method and the presence of anthocyanin di-glucosides in cold-hardy wines were parameters suggesting that protein and methylcellulose precipitation methods were neither suitable nor reliable for the quantification of tannins in cold-hardy red wines. The tannin content quantified by RPC was positively correlated to tannin quantified by MCP, suggesting that the RPC method would be relevant for the quantification of tannins in red wines.     

Effect of secondary polymer on self‐precipitation of pH‐sensitive polymethylmethacrylate derivatives Eudragit E100 and Eudragit L100

Interpolyelectrolyte complexes or polyplexes can be seen as interesting alternatives in the purpose of active ingredients encapsulation. Working on polymethylmethacrylate derivatives with special focus on controlled oral drug delivery, the influence of charged polyelectrolytes (polyacrylic acid, polyethylenimine, and amino‐dextran) and noncharged ones (polyvinyl alcohol, dextran 40, and Pluronic F68) has been investigated on the precipitation of two pH‐sensitive Eudragit polymers, namely, L100 and E100. Moreover, the possibility of preparing polyplexes involving the two polymethylmethacrylate derivatives with different charged and noncharged secondary polyelectrolytes has been studied. The obtained dispersions have been characterized in terms of mean particle size, size distribution, zeta potential, and morphology. Direct precipitation of Eudragit L100 by medium acidification in a batch process and in the presence of polyethylenimine allowed the production of particles with a narrow size distribution. The mean size was around 200 nm. In this case, the zeta potential was found to be +45 mV at pH = 7 in 1mM aqueous NaCl solution, and the produced suspension was stable in time since no aggregation and sedimentation have been observed. A precipitation pH of 8.16 allows us to suggest the preparation of a polyplex based on Eudragit L100 and polyethylenimine. In contrary, polyvinyl alcohol has shown ability to induce an increase in particle mean size whereas other polyelectrolytes showed no significant effect. Moreover, it was observed that polyethylenimine and polyacrylic acid solutions were able to directly induce Eudragit E100 precipitation whereas amino‐dextran and noncharged polyelectrolytes showed no effect on its precipitation and on particle size distribution.     

Homogeneous precipitation of mullite precursors

The synthesis of mullite powders or gels from an aqueous precursor solution has been studied. The starting solution is made by hydrolyzing TEOS into an aqueous solution of aluminium nitrate. When this solution is sprayed into a solution of ammonia in isopropanol, a nearly monophasic mullite precursor is obtained, whereas if this precipitation is made into an aqueous solution of ammonia, or ammonium carbonate, a diphasic colloidal precipitate is formed. By a slow and homogeneous precipitation in aqueous solution, induced by in-situ generation of ammonia by thermal hydrolysis of urea, a monophasic gel is also obtained. The samples have been studied by DTA, DSC, TGA, XRD and dilatometry.     

沉淀滴定法测定碘

提出沉淀滴定Ｉ－的新方法，以聚乙烯醇（ＰＶＡ）作为沉淀的胶体保护剂，（Ｉ）－３（碘钅翁离子）作为吸附指示剂，用ＡｇＮＯ３标准溶液直接测定Ｉ－；讨论了滴定机理。检测范围为０．０１～０．１ｍｏｌ／Ｌ，相对误差小于０．２％。本法已用于鸡饲料添加剂中Ｉ－的测定。     

用硝酸银溶液沉淀及分步沉淀卤素离子的数字化实验研究*

卤化银难溶电解质的沉淀溶解平衡是中学化学教学的重要知识点。应用本项目组研制的MXLab21先进数字化实验系统,结合银硫离子电极,测定AgNO₃溶液沉淀Cl^-,Br^-,I^-及其混合离子的沉淀曲线,即电动势(E)随AgNO₃溶液体积(V)变化的关系曲线。3种单一离子的沉淀曲线可以直观体现出滴定的电动势突跃范围与相应沉淀的溶度积大小的关系及其规律性变化。通过混合离子的沉淀曲线分析3种离子两两混合或3者混合时分步沉淀的可行性。Cl^-,Br^-,I^-的沉淀及分步沉淀的动态E-V曲线的建立,对中学化学教学具有重要作用,对化学学科核心素养的发展和培养具有重要价值。     

α-Co(OH)_2的制备及其超级电容特性

以氯化钴为原料,聚乙烯吡咯烷酮(PVP)为分散剂,采用化学沉淀的方法制备出由纳米粒子组成的片状α-Co(OH)2.用红外光谱对所制样品的组分进行分析,用X射线衍射和场发射扫描电子显微镜表征产物的结构和形貌,用循环伏安和恒电流充放电等测试方法对其电化学性能进行研究.研究结果表明,由纳米粒子组成的片状α-Co(OH)2表现出优良的电化学性能,单电极比电容高达1220 F/g.     

萃取Fe3+和氨水-乙醇反萃沉淀法制备α-Fe2O3

以磷酸二异辛基酯(P204)为萃取剂,CCl4为溶剂,从Fe(NO3)2水溶液中萃取铁离子,以氨的乙醇溶液反萃含铁的有机相,通过优化控制相间传质过程,获得了Fe(OH)3前驱体,经煅烧后得α-Fe2O3粉体,采用TEM、FTIR、XRD等测试技术对α-Fe2O3进行表征。 研究表明,在油水相比为1∶1,水相c(Fe3+)=0.10 mol/L(pH=3.0)、油相P204为V(P204)∶V(CCl4)=1∶3、平衡时间为20 min,Fe3+萃取率达98.44%;反萃取溶液V(氨水)∶V(乙醇)=1∶7、陈化温度约10.0 ℃,制备纳米α-Fe2O3的煅烧温度为600 ℃较宜。