Fabrication and characterizations of Cr3+-doped ZnGa2O4 transparent ceramics with persistent luminescence

0.5 at.% Cr:ZnGa₂O₄ precursor was synthesized by the co-precipitation method with nitrates as raw materials, using ammonium carbonate as the precipitant. Low-agglomerated Cr:ZnGa₂O₄ powders with an average particle size of 43 nm were obtained by calcining the precursor at 900℃ for 4 h. Using the powders as starting materials, 0.5 at.% Cr:ZnGa₂O₄ ceramics with an average grain size of about 515 nm were prepared by presintering at 1150℃ for 5 h in air and HIP post-treatment at 1100℃ for 3 h under 200 MPa Ar. The in-line transmittance of 0.5 at.% Cr:ZnGa₂O₄ ceramics with a thickness of 1.3 mm reaches 59.5% at the wavelength of 700 nm. The Cr:ZnGa₂O₄ ceramics can be effectively excited by visible light and produce persistent luminescence at 700 nm. For Cr:ZnGa₂O₄ transparent ceramics, the brightness of afterglow was larger than 0.32 mcd/m² after 30 min, which is far superior to that of Cr:ZnGa₂O₄ persistent luminescence powders.     

不同方法制备K2MnAl11O19六铝酸盐催化剂及其甲烷的燃烧活性

介绍了共沉淀法和异丙醇盐水解法制备了六铝酸盐催化剂K2MnAl11O19,用XRD、BET、SEM和TG-DTA技术及甲烷燃烧活性对催化剂进行了表征和活性验证。结果表明,两种方法所制备的催化剂经1200℃焙烧4h后均可以形成完整的六铝酸盐晶型,同时都具有高的催化性能和高温稳定性,其中异丙醇盐水解法制备的K2MnAl11O19催化剂具有较高的比表面积和甲烷催化燃烧活性。     

光催化剂SrTiO3的制备及其性能的研究

论述用化学液相共沉淀法制备SrTiO_3的最佳条件,及在不同的活化条件下对SrTiO_3光催化性能的影响。此外还研究了掺入过渡金属氧化物对SrTiO_3催化性能的改善。     

Au/ZnO and Au/Fe2O3 catalysts for CO oxidation at ambient temperature: comments on the effect of synthesis conditions on the preparation of high activity catalysts prepared by coprecipitation

The preparation of Au/ZnO and Au/Fe₂O₃ catalysts using two coprecipitation methods is investigated to determine the important factors that control the synthesis of high activity catalysts for the oxidation of carbon monoxide at ambient temperature. In particular, the factors involved in the preparation of catalysts that are active without the need for a calcination step are evaluated. The two preparation methods differ in the manner in which the pH is controlled during the precipitation, either constant pH throughout or variable pH in which the pH is raised from an initial low value to a defined end point. Non-calcined Au/ZnO catalysts prepared using both methods are very sensitive to pH and ageing time, and catalysts prepared at a maximum pH = 5 with a short ageing time (ca. 0–3 h) exhibit high activity. Catalysts prepared at higher pH give lower activity. However, all catalysts require a short operation period during which the oxidation activity increases. In contrast, the calcined catalysts are not particularly sensitive to the preparation conditions. Non-calcined Au/Fe₂O₃ catalysts exhibit high activity when prepared at pH ≥ 5. Calcined Au/Fe₂O₃ prepared using the controlled pH method retain high activity, whereas calcined catalysts prepared using the variable pH method are inactive. The study shows the immense sensitivity of the catalyst performance to the preparation methods. It is therefore not surprising that marked differences in the performance of supported Au catalysts for CO oxidation that are apparent in the extensive literature on this subject, particularly the effect of calcination, can be expected if the preparation parameters are not carefully controlled and reported.     

异丁烯两段催化氧化制甲基丙烯酸催化剂研究 Ⅰ．异丁烯气相氧化制甲基丙烯醛多元复合氧化物催化剂的研究

本文报导用于异丁烯（叔丁醇）选择氧化制ＭＡＬ（甲基丙烯醛）的多元复合氧化物催化剂的研究结果。同共沉淀法制备的催化剂的活性主要决定于其化学组成，同时受到制备条件的影响。最佳催化剂的主要物相组成为ＰｂＯ３，Ｂｉ２ＭｏＯ３．３、ＮｉＭｏＯ４、Ｓｂ２Ｏ３及ａ－Ｆｅ２Ｏ３小颗粒。在３５５℃，１０００～２５００ｈ－１空速范围，叔丁醇：水：空气＝１：３．３：７（摩尔比）的条件下可获得异丁烯转化率达９６％，ＭＡＬ选择性达８９％的结果。     

废旧锂电池中有价金属回收及三元正极材料的再制备

探讨了磷酸体系下不同因素对废旧锂电池正极材料中有价金属浸出效率的影响，结果表明：在浸出时间60min，反应温度60℃，磷酸浓度2mol/L，液固比20mL/g，还原剂(H₂O₂)体积分数为4%时，可得最佳浸出效果，Co、Li、Mn、Ni浸出效率分别可达96.3%、100%、98.8%和99.5%；浸出液添加相应比例金属离子，采用草酸共沉淀法制备前体材料(Ni_1/3Co_1/3Mn_1/3)C₂O₄，并得到相应再生磷酸溶液。再生磷酸进行循环浸出实验，实验研究结果表明：循环浸出5次之后Li的浸出率仍可保持在90.1%，而Co、Mn和Ni的浸出率在75.0%以上。前体添加锂源Li₂CO₃煅烧合成Li(Ni_1/3Co_1/3Mn_1/3)O₂材料，考察了不同温度对Li(Ni_1/3Co_1/3Mn_1/3)O₂材料合成的影响，结果显示，当合成温度为800℃时，得到的材料性能最优良，初次放电容量可达136.4mA·h/g。在0.2C下经过50圈循环后容量保持率为97.2%。     

3Y-ZrO2/Al2O3复合粉体制备工艺研究

以Al(NO3)3·9H2O和ZrOCl2·8H2O为主要原料,采用醇-水溶液加热结合共沉淀法制备出前驱体。利用DTA-TG和X射线衍射(XRD)分析研究了前驱体的煅烧过程。结果显示,275℃时前驱体已完全分解为非晶态氧化物,800℃时t-ZrO2开始结晶,至1150℃时出现α-A12O3晶体,获得3Y-ZrO2/A12O3复合粉体。该复合粉体在1400℃下常压烧结,可得到相对密度达90.4%的ZTA陶瓷。     

钯负载锰氧化物基双金属复合氧化物催化氧化羰基化合成碳酸二苯酯

采用共沉淀法分别制备锰掺杂钨、钒、铋3种双金属复合氧化物载体,以氯化钯为活性组分制备负载型催化剂,并用于苯酚氧化羰基化合成碳酸二苯酯（DPC）。通过气相色谱（GC）、X射线衍射（XRD）、氢气程序升温还原（H₂-TPR）、X射线光电子能谱（XPS）等表征手段,对催化剂结构和性能进行表征。结果表明:钨-锰载体随掺杂比例和焙烧温度升高,逐步形成四氧化三锰晶粒,同时钨渗入锰氧化物晶格中,在掺杂比（物质的量比）为1:1、焙烧温度为600 ℃条件下制备的催化剂性能最佳,DPC收率为5.20%;钒-锰载体在焙烧温度为400 ℃、掺杂比为1:5条件下形成二氧化锰晶相,催化剂性能明显提高,DPC收率为10.46%,而较高的焙烧温度会破坏晶型的完整;铋-锰载体在掺杂比为1:5、焙烧温度为400 ℃条件下制备的催化剂催化效果最好,DPC单程收率可达到13.13%。     

激光焊接金刚石工具过渡层预合金粉末的试验研究

目前可以用于制备激光焊接金刚石工具过渡层粉末的方法主要有机械混合法、雾化法和化学共沉淀法。化学共沉淀法生产的粉末成分均匀,实现了粉末的预合金化,并且设备简单,生产成本低。此次试验采用草酸盐化学共沉淀法,成功制备了3种不同成分的激光焊接金刚石工具过渡层预合金粉末。焊接强度测试表明,3种粉末的焊接强度均满足欧盟EN13236安全标准,其中2#粉末的焊缝强度最高。X射线物相分析结果表明,3种粉末的主相都是Co3Fe7和CoFe。此外,固定Fe与Co的质量比,加入2wt.%的铜可以有效提高预合金粉末过渡层的焊接强度和稳定性。这是因为,Cu原子完全溶入到Co3Fe7或CoFe晶胞中并形成固溶体,产生了固溶强化。