A novel Temperature–Humidity–Time defrosting control method based on a frosting map for air-source heat pumps

To improve the defrosting accuracy and the energy efficiency of the air-source heat pump (ASHP) under frosting and defrosting conditions, a novel Temperature–Humidity–Time (T–H–T) defrosting control method, based on a frosting map for the ASHP unit, is proposed in this paper. A field test was conducted for two heating seasons, to verify the feasibility and applicability of the T–H–T method. The advantages of the T–H–T method, compared to the conventional Temperature–Time (T–T) defrosting control method, are presented. In total, eight cases are shown in this paper. Cases 1 to 4 were chosen to reveal the T–H–T performance under different frosting conditions. It was found that no matter what kind of frosting conditions, defrosting was always initiated in a similar situation: ∼90% of the outdoor coil surface was covered by frost; the temperature difference between the compressor suction and discharge increased by ∼20%; and the heating capacity decreased by ∼30%. These results indicate that the T–H–T method can make an accurate decision under different frosting conditions. Cases 5a, 5b and Cases 6a, 6b were two groups of cases to compare the advantages of the T–H–T method against the conventional T–T method. Cases 5a and 5b were chosen for the non-frosting condition. It was found that the T–T method initiated the defrosting operation 31 times within 24 h. However, none of the defrosting operations was conducted for the T–H–T method. Cases 6a and 6b were chosen to compare these two methods under consecutive and variable frosting conditions. For the T–T method, 63% of the defrosting processes were found to be executed under conditions where defrosting was not necessary. However, for the T–H–T method, all the defrosting controls were found to be accurate and reasonable. These results indicated that the novel T–H–T method is suitable for the defrosting control of the ASHP, and has a more competitive performance than the conventional T–T method.     

Studies on solvent extraction of La(III) using [A336][NO3–] and modeling by statistical analysis and neural network

Solvent extraction of La(III) from acidic nitrate medium has been studied with [A336][NO₃^–] in kerosene. The factors affecting the extraction of La(III) like equilibration time, nitrate ion, extractant and La(III) concentrations, aqueous acidity, O/A ratio variation, nature of diluent, and temperature have been investigated. McCabe-Thiele diagram has been plotted to find out the actual number of theoretical stages needed for complete extraction of lanthanum. The solvent has been successfully regenerated for further use after stripping of the metal. IR studies of [A336][NO₃^–] and La(III) loaded [A336][NO₃^–] have been carried out. Modeling of extraction data has been done using Multiple linear regression analysis and Artificial Neural Network, and the performances have been compared. Error in each case was evaluated in terms of R² and Root mean squared error (RMSE). Maximum extraction of La(III) was 82% when 0.6 M [A336][NO₃^–] was used for extraction. About 98% of the metal has been recovered using 0.2 M HNO₃ as stripping agent. Extractive separation of La(III) and Sm(III) was maximum (β = 65.2) using 0.1 M [A336][NO₃^–]. IR studies revealed formation of lanthanum complex in the extraction process. Artificial Neural Network proved to be better over Multiple linear regression in data prediction.     

利用固相反应法制备的石榴石结构的Li7La3Zr2O12粉体的形成机制

The formation mechanisms of garnet-like Li7La3Zr2O12 (LLZO) phase using LiOH?H2O as raw materials are investigated symmetrically by XRD and DTA/TG measurements. It was found that reaction mechanisms of the LLZO formation are as follows: 7Li2O 3La2O3 4ZrO2=2Li7La3Zr2O12 The production of LLZO phase takes place at about 680oC observed from the XRD patterns, in agreement with the thermic peak at 700oC in DTA/TG curves, which arises from the formation of LZZO phase. The stable existence temperature range of LLZO phase is wide, from 720 to 1000oC. However, LLZO is thermally unstable at the high temperatures (>1000oC) due to a serious loss of lithium element, and it discomposes into pyrochlore phase La2Zr2O7. And the amount of the decomposed products increased, and LLZO decreased gradually with the increase of the calcination temperature. When the reactant mixture was calcined at the low temperature, the produced phases were identified to be lanthanum compounds because La2O3 absorbs moisture and CO2 very easily. The chemical reactions at lower temperature are mainly related with the reactions among lanthanum compounds. LLZO powder was synthesized by solid state reaction at 800℃. It is found that the LLZO crystal belongs to the tetragonal symmetry. SEM observations show that the obtained LLZO powder was nano-sized.     

Sc,La对Al-Mg焊料中杂质元素偏聚的调控作用

采用金相显微镜、扫描电镜、能谱分析和X射线衍射仪,研究了添加微量钪、镧对铝镁焊料中杂质元素偏聚的调控作用. 结果表明,在铝镁焊料合金凝固过程中,铁、硅等杂质元素在晶界有偏聚效应,添加微量钪、镧可以降低铁、硅杂质在晶界的偏聚浓度. 钪与镧减轻杂质元素在晶界偏聚的效果存在差别,添加钪的合金比添加镧的合金晶界处杂质元素偏聚强度明显减弱. 造成这种差别的原因是,钪、镧对杂质元素偏聚的调控机制不同.     

On comparison of luminescence properties of La2Zr2O7 and La2Hf2O7 nanoparticles

Unveiling the underlying mechanisms of properties of functional materials, including the luminescence differences among similar pyrochlores A₂B₂O₇, opens new gateways to select proper hosts for various optoelectronic applications by scientists and engineers. For example, although La₂Zr₂O₇ (LZO) and La₂Hf₂O₇ (LHO) pyrochlores have similar chemical compositional and crystallographic structural features, they demonstrate different luminescence properties both before and after doped with Eu³⁺ ions. Based on our earlier work, LHO-based nanophosphors display higher photo- and radioluminescence intensity, higher quantum efficiency, and longer excited state lifetime compared to LZO-based nanophosphors. Moreover, under electronic O²⁻→Zr⁴⁺/Hf⁴⁺ transition excitation at 306 nm, undoped LHO nanoparticles (NPs) have only violet blue emission, whereas LZO NPs show violet blue and red emissions. In this study, we have combined experimental and density functional theory (DFT) based theoretical calculation to explain the observed results. First, we calculated the density of state (DOS) based on DFT and studied the energetics of ionized oxygen vacancies in the band gaps of LZO and LHO theoretically, which explain their underlying luminescence difference. For Eu³⁺-doped NPs, we performed emission intensity and lifetime calculations and found that the LHOE NPs have higher host to dopant energy transfer efficiency than the LZOE NPs (59.3% vs 24.6%), which accounts for the optical performance superiority of the former over the latter. Moreover, by corroborating our experimental data with the DFT calculations, we suggest that the Eu³⁺ doping states in LHO present at exact energy position (both in majority and minority spin components) where oxygen defect states are located unlike those in LZO. Lastly, both the NPs show negligible photobleaching highlighting their potential for bioimaging applications. This current report provides a deeper understanding of the advantages of LHO over LZO as an advanced host for phosphors, scintillators, and fluoroimmunoassays.     

扩渗时间对镁合金表面扩渗Zn+La2O3组织与性能的影响

在390℃温度下对AZ31镁合金进行固态扩渗Zn+La2O3（扩渗剂中的质量分数为0.4%）处理,扩渗时间分别为0、2、4、6h。研究了不同扩渗时间下镁合金表面渗层组织的变化,并测试了镁合金表面扩渗层的硬度和耐腐蚀性能。结果表明：当扩渗时间为2h时,未出现渗层;当扩渗时间为4h时,扩渗层中出现了Mg0.97Zn0.03固溶体和Mg-Zn化合物(MgZn+Mg2Zn3+MgZn2+ Mg2Zn11)。随着扩渗时间的延长,使得Zn原子的扩渗能力增强,Mg和Zn反应扩散形成了多种化合物,在AZ31镁合金表面得到了渗层。当扩渗时间为6h时,Mg7Zn3作为一种新相出现在了渗层中,同时,渗层组织粗化。扩渗试样的硬度随扩渗时间的增加而增加,而耐腐蚀性能在扩渗时间为4 h时为最佳。     

La的掺杂方式对CeO2-MnOx催化氧化氯苯性能的影响

采用共沉淀法制备CeO₂-MnO_x和La₂O₃-CeO₂-MnO_x催化剂,再用沉积-沉淀法制备La₂O₃/CeO₂-MnO_x催化剂,并对催化剂的氯苯催化氧化反应活性进行检测。结果表明,La的加入可以显著提高催化剂催化氧化氯苯的活性。XRD和TPR表征结果表明,La的加入抑制CeO₂晶粒尺寸的长大,增强CeO₂的晶格应变,并促进Mn进入CeO₂的晶相,形成较好的MnCeO_x固溶体。催化剂的热稳定性评价结果表明,La的加入有效提高CeO₂-MnO_x催化剂的热稳定性。     

La/Al基累托石矿物材料的研究

在室温条件下,用取代法和共聚法配制稳定的La/A l二元聚合阳离子,用该聚合阳离子柱撑累托石,其柱撑材料的热稳定性达到500℃以上。柱化剂的制备方法和La/A l的摩尔比对La/A l基柱撑粘土矿物材料的热稳定性均有影响。在La/A l的比例为1∶9时,通过共聚法和取代法制备的La/A l柱化剂其结构最稳定。根据探针成分分析,探讨La/A l基柱撑粘土矿物材料的微结构特征。     

Adsorption of hydrocarbons by ZSM-5 zeolites with different SiO2/Al2O3 ratios: a combined FTIR and gravimetric study

In metal-free ZSM-5, the decrease in the concentration of Bronsted and Lewis acid sites parallels the increase in the SiO₂/Al₂O₃ ratio. In the presence of residual moisture, the adsorption of small alkanes does not markedly depend on the SiO₂/Al₂O₃ ratio in the range from 30 to 150. The acidity is more important for the adsorption of alkenes (propene) which oligomerize following adsorption. The addition of 5 wt.% of La does not significantly affect the strength of the surface acid sites but does decrease their concentration. It causes a transformation, in a part, of the Bronsted acid sites. These new centers could perhaps be assigned to LaO(OH) or La(OH)₂⁺ species which may be formed on the surface in La-containing ZSM-5. La could exchange only the strongest acidic sites without inducing large changes in their total concentration. La addition has a very small effect on the adsorption of small hydrocarbons. The exchange of the protons by Cu²⁺ decreases the concentration of Bronsted acid sites. At a sufficient loading of the ZSM-5 by Cu²⁺, i.e. at an atomic ratio Cu/Al > 1.0, the exchange can almost totally suppress the Bronsted acidity. Another effect of the ion exchange is the suppression of the adsorption capacity of small hydrocarbons due to lowered surface area and internal pore volume. The lowered available internal pore volume also limits the extent of the oligomerization of propene.     

硫化镉插层制备K2La2Ti3-xCexO10 复合催化剂及其活性研究

采用硬脂酸法制备K2La2Ti3-xCexO10本体。分别采用微波辅助法和水浴法对K2La2Ti3-xCexO10进行质子交换、胺柱撑和硫化镉插层,制备了硫化镉插层K2La2Ti3-xCexO10催化剂。用X射线衍射（XRD）、扫描电镜（SEM）和紫外-可见漫反射（UV-vis）等手段对复合催化剂的晶型、粒径、表面形貌等进行表征,考察催化剂的可见光催化分解有机物活性。结果表明：在K2La2Ti3-xCexO10层间插入硫化镉可以将催化剂的光谱响应范围拓展到可见光区,提高了光催化降解有机物活性。水浴法制备的CdS-K2La2Ti3-xCexO10降解罗丹明B的降解率可以达到17.68%,而采用微波法制备的CdS-K2La2Ti3-xCexO10降解罗丹明B的降解率可以达到33.66%。