柠檬酸凝胶法制备Er,Tm∶Yb3Al5O12纳米粉体及发光性能

以柠檬酸为燃烧剂,采用柠檬酸凝胶法制备了Er,Tm∶Yb3Al5O12(Er,Tm:YbAG)纳米粉体,其最佳的制备工艺条件:Er3+和Tm3+掺杂的摩尔分数分别为2%和1%,柠檬酸与金属硝酸盐原子总数的摩尔比为1.7∶1,煅烧温度和时间分别为950℃和2h。制备的粉体颗粒为规则球形,粒径均匀、分散性好,平均粒径约为45nm。研究了样品的发光性能,结果表明:2%Er,1%Tm∶YbAG样品的发光性能最好,在1 587、1 658和1 711nm处有较强发射峰,分别对应Er3+的4 I13/2→4 I15/2跃迁和Tm3+的3 F4→3 H6跃迁。样品的上转换光谱表明,上转换荧光峰包括了蓝光、绿光和红光。     

沥青对水泥沥青砂浆力学性能的影响

采用微机控制电子万能试验机对水泥沥青砂浆(CA砂浆)进行了应力--应变压缩试验,分析了试验过程中CA砂浆的弹性能和耗散能随沥青含量的变化规律。结果表明:随着沥青含量的增加,CA砂浆的强度逐渐降低,脆性逐渐减弱,象征强度弱化区域的有机物--无机物界面的增多是强度降低的主要原因,沥青含量的增加使CA砂浆内释放的弹性能只有小部分用于缺陷的扩展,加之沥青网络结构的横向约束作用导致脆性逐渐减弱。外力功随应变的增加逐渐增大,随沥青含量的增加逐渐减小;弹性能开始向耗散能转化发生在屈服变形阶段,峰值应力后,弹性能向耗散能的转化速率加快,能量迅速释放。能量释放系数随应变的增加逐渐增大,能量释放加快;能量释放系数随沥青含量的增加逐渐增大,表明CA砂浆的阻尼性能提高,减振作用增强。     

Mathematical Modeling the Drying of Poplar Wood Particles in a Closed-Loop Triple Pass Rotary Dryer

Closed-loop drying systems are an attractive alternative to conventional drying systems because they provide a wide range of potential advantages. Consequently, type of drying process is attracting increased interest. Rotary drying of wood particles can be assumed as an incorporated process involving fluid–solid interactions and simultaneous heat and mass transfer within and between the particles. Understanding these mechanisms during rotary drying processes may result in determination of the optimum drying parameters and improved dryer design. In this study, due to the complexity and nonlinearity of the momentum, heat, and mass transfer equations, a computerized mathematical model of a closed-loop triple-pass concurrent rotary dryer was developed to simulate the drying behavior of poplar wood particles within the dryer drums. Wood particle moisture content and temperature, drying air temperature, and drying air humidity ratio along the drums lengths can be simulated using this model. The model presented in this work has been shown to successfully predict the steady-state behavior of a concurrent rotary dryer and can be used to analyze the effects of various drying process parameters on the performance of the closed-loop triple-pass rotary dryer to determine the optimum drying parameters. The model was also used to simulate the performance of industrial closed-loop rotary dryers under various operating conditions.     

Kiln-, Solar-, and Air-Drying Behavior of Lumber of Tectona grandis and Gmelina arborea from Fast-Grown Plantations: Moisture Content,Wood Color,and Drying Defects

Tectona grandis and Gmelina arborea are common in commercial reforestation in the tropics. However, color variations, moisture content, and drying defects are also present in dried lumber. Moisture content variations, drying defects, and color changes were evaluated in the present work for three drying methods (kiln, solar, and air drying) during three seasons (dry, rainy, and transition season) in Costa Rica. According to the results, kiln drying had the fastest drying times, regardless of the season. On the other hand, air drying had slower drying time and higher final moisture content. With regard to defects, kiln drying produced the highest number and magnitude of defects in both species, whereas air drying showed the lowest quantity and severity of defects. No variations due to the drying methods or the season were observed in check and split, though solar drying presented intermediate values in all drying defects. The seasons of the year did not present any effect on drying defects. Finally, T. grandis dried lumber is darker than green lumber, and dried G. arborea wood is clearer. In addition, there is an increase in red ( a ^* ) and yellow ( L ^* ) tonalities, and color changes (Δ E ^* ) are considered perceptible or very perceptible in both species. No differences were found among the three drying methods in Δ E ^* , although the season of the year affected dif L ^* and dif C ^* significantly.     

Environmentally benign supercritical CO2 extraction of galanthamine from floricultural crop waste of Narcissus pseudonarcissus

The influence of diverse factors on the supercritical fluid extraction (SFE) with supercritical CO₂ (scCO₂) of galanthamine from bulbs of Narcissus pseudonarcissus cv. Carlton was investigated. The parameters that were studied were CO₂ density (temperature and pressure), flow rate and plant material particle size and pre-treatment. The highest yield (303 μg/g) was achieved by extracting 53–1000 μm particle-size powdered dried bulb material moistened with NH₄OH (25%, v/v) at 70 °C, 220 bar (690 kg/m³) for 3 h. Other N. pseudonarcissus alkaloids such as O-methyllycorenine and haemanthamine were also obtained. N. pseudonarcissus alkaloids as free bases are highly soluble in CO₂ at a high pH as opposed to the slightly soluble salt form in which they are generally found in plants. Therefore, plant material pre-treatment with a base is an essential step for galanthamine extraction. Scanning electron microscope (SEM) results also revealed that the desorption of N. pseudonarcissus alkaloids from the plant material rather than the solubility of the alkaloids in the scCO₂ plays a major role in this scCO₂ extraction. This extraction method has a good potential for industrial application.     

Design of high productivity sequential multi-column chromatography for antibody capture

An integrated experimental and modeling approach for the design of sequential multi-column chromatography (SMCC) is presented to maximize productivity in bioprocessing. The approach consists of three steps: (1) single-column model development and validation, (2) multi-column model development and validation, and (3) productivity optimization. The integrated use of process experimentation and modeling enables sufficient process understanding to be gained during process development such that the optimal SMCC design is found even with limited time and materials. The application of the approach is demonstrated by determining the optimal SMCC design that maximizes the capture of human IgG by a silica-based protein A adsorbent named AbSolute. For this example, the optimum productivity was found to increase from 2.9 kg L⁻¹ day⁻¹ for batch operation to 4.0 kg L⁻¹ day⁻¹ for SMCC operation with three columns. A second case study considering a hypothetical adsorbent of larger particle size and slower mass transfer is also presented, to further demonstrate the applicability of the integrated approach. The case studies clearly illustrate the capabilities of the integrated approach in quickly determining the optimal design and operation for an SMCC arrangement and with minimal, carefully targeted, experimentation.     

Microstructure and properties of diamond/SiC composites prepared by tape-casting and chemical vapor infiltration process

This article reported a novel method for preparing diamond/SiC composites by tape-casting and chemical vapor infiltration (CVI) process, and the advantages of this method were discussed. The diamond particle was proved to be thermally stable under CVI conditions and the CVI diamond/SiC composites only contained diamond and CVI-SiC phases. The SEM and TEM results showed a strong interfacial bonding existed between diamond and CVI-SiC matrix. Due to the strong bonding, the surface HRA hardness could reach up to 98.4 (HV 50 ± 5 GPa) and the thermal conductivity (TC) of composites was five times higher than that of pure CVI-SiC matrix. Additionally, the effects of diamond particle size on microstructure and properties of composites were also investigated. With the increasing of particle size, the density and TC of composites with the size 27 μm reached 2.940 g/cm³ and 82 W/(m K), respectively.     

基于CDIO工程教育理念的化学工程与工艺专业培养模式研究与探索

我们针对现阶段国内工科院校教育现状,借助国际先进的CDIO工程教育模式,对合肥工业大学化学工程与工艺专业的教学体系、教学内容、教学方法及学生的考核制度等进行了改革。教改注重课程理论与实践环节的连接,引导学生主动探索,全面培养学生的CDIO工程能力,以培养合格的化学工程与工艺专业人才为目标。     

工程材料及机械制造基础课程立体化教学与改革的探讨

本文阐述了工程材料及机械制造基础课程整合与课程教学改革的原因、改革的措施。从结果上看,激发和提高了学生的学习兴趣,加强了理论联系实际和工程应用能力培养,这一课程整合与教学改革达到了目标,取得了良好的实践效果,探索了该课程立体化教学和教学实践改革的思路与方法。