退火温度对新型锆合金薄板带材析出相和织构的影响

采用扫描电镜和超高分辨透射电镜,对具有良好冲制性能的新型锆合金薄板成品带材进行含晶粒、第二相粒子等在内的显微组织研究,并探索真空退火处理条件下温度对带材显微组织的影响。结果显示:新型锆合金薄板成品带材晶粒平均尺寸2.17 μm,存在{0001}<1010>和{0001}<1120>两种织构,大部分晶粒<1120>平行带材RD方向,较少晶粒<1010>平行带材RD方向;第二相粒子分布在晶粒内部及晶界,平均尺寸114 nm,尺寸较大的为不规则椭圆形的Zr-Nb-Fe相,尺寸较小的为圆形的β-Nb相;热处理退火温度降低,带材晶粒尺寸减小,第二相粒子细小弥散分布;新型锆合金薄板成品带材良好冲制性能主要源于轧制积累应变诱发再结晶过程进行充分,导致晶粒细小及孪晶发生破碎;相对轧制变形,退火对带材冲制性能影响不显著。     

不同方法发酵的酸豆角品质对比分析

本文将研究不同方法发酵的酸豆角品质对比分析。选取质地嫩脆、条形均匀、无病虫害的新鲜豆角为泡制原料。采用自然干法发酵、自然湿法发酵与纯种湿法发酵的发酵方法制作酸豆角。检测发酵过程中，pH值、还原糖含量、总酸含量、总糖含量、亚硝酸盐含量以及氨基酸态氮含量，分析纯种湿法发酵与自然湿法发酵对酸豆角品质的影响。结果表明：纯种湿法发酵25 d后，其pH值和还原糖含量分别为3.92、0.03%，均高于自然湿法发酵；总酸、总糖、亚硝酸盐含量、氨基酸态氮含量分别为0.25%、0.04%、0.01 mg/kg和0.01%，均低于自然湿法发酵。另外，纯种湿法发酵酸豆角的甲氧基乙酸含量为0.37%，乙酸乙酯为0.51%，含水量为81.15%，感官评分为45.52，均高于自然干法发酵。纯种湿法发酵对酸豆角品质的效果最好，亚硝酸盐的含量在发酵后期显著降低，感官评分较高，对豆角工业化生产提供了较好的参考价值。     

再加工工艺对N18锆合金板残余应力的影响

采用“热轧+冷轧+退火”工艺对N18锆合金板进行再加工,通过X射线法分析板的表面残余应力,采用EBSD技术分析晶界取向差角分布和大小角度晶界。结果表明,热轧后N18锆合金板的表面残余应力呈现无规律分布状态;冷轧后板的表面残余应力均为压应力,其大小随着冷轧变形量的增加而增加;退火后板的表面残余应力值处于较低水平,当退火制度为500 ℃×2 h时,残余应力处于最低水平;退火后,板的微观结构以小角度晶界为主,且随着退火温度的升高,小角度晶界的密度先增加后趋于稳定。     

New empirical correlation for estimation of vaporization enthalpy of algerian saharan blend petroleum fractions

A Real-coded Genetic Algorithm has been used to develop a new correlation to estimate the enthalpy of vaporization for pure compounds and petroleum fractions as a function of the normal boiling point and specific gravity. In developing the correlation 80% of the data was used and the remaining are used for validation. The results of the proposed correlations are compared to others in literature. The comparison indicates that the proposed model is simple to use and more accurate than the most common correlations for predicting the enthalpy of vaporization of pure compounds and petroleum fractions.     

Adaptive neural network command filtered backstepping control of pure‐feedback systems in presence of full state constraints

An adaptive neural network (NN) command filtered backstepping control is proposed for the pure‐feedback system subjected to time‐varying output/stated constraints. By introducing a one‐to‐one nonlinear mapping, the obstacle caused by full stated constraints is conquered. The adaptive control law is constructed by command filtered backstepping technology and radial basis function NNs, where only one learning parameter needs to be updated online. The stability analysis via nonlinear small‐gain theorem shows that all the signals in closed‐loop system are semiglobal uniformly ultimately bounded. The simulation examples demonstrate the effectiveness of the proposed control scheme.     

Metal–Organic Frameworks Based on Group 3 and 4 Metals

Metal–organic frameworks (MOFs) based on group 3 and 4 metals are considered as the most promising MOFs for varying practical applications including water adsorption, carbon conversion, and biomedical applications. The relatively strong coordination bonds and versatile coordination modes within these MOFs endow the framework with high chemical stability, diverse structures and topologies, and interesting properties and functions. Herein, the significant progress made on this series of MOFs since 2018 is summarized and an update on the current status and future trends on the structural design of robust MOFs with high connectivity is provided. Cluster chemistry involving Y, lanthanides (Ln, from La to Lu), actinides (An, from Ac to Lr), Ti, and Zr is initially introduced. This is followed by a review of recently developed MOFs based on group 3 and 4 metals with their structures discussed based on the types of inorganic or organic building blocks. The novel properties and arising applications of these MOFs in catalysis, adsorption and separation, delivery, and sensing are highlighted. Overall, this review is expected to provide a timely summary on MOFs based on group 3 and 4 metals, which shall guide the future discovery and development of stable and functional MOFs for practical applications.     

Phase evolution and microstructure of new Sr0.5Zr2(PO4)3-NdPO4 composite ceramics prepared by one-step microwave sintering

Sodium Zirconium Phosphate (NaZr₂(PO₄)₃, hereinafter NZP) and monazite are both potential materials for immobilization of nuclear waste. In this work, novel (1-x)Sr_0.5Zr₂(PO₄)₃-xNdPO₄ composite ceramics (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) for simultaneously immobilizing the simulated fission product (FP) Sr and trivalent minor actinide (MA) Nd were prepared by one-step microwave sintering technique, in which Sr and Nd were immobilized into NZP and monazite type structures, respectively. The phase evolution and microstructure of the samples were investigated by X-ray diffraction (XRD), Raman, and backscattering scanning electron microscopy (BSE). The results showed that the expected composite ceramics were successfully obtained by one-step microwave sintering at 1050 °C for 2 h. The as-prepared samples consisted of Sr_0.5Zr₂(PO₄)₃ and NdPO₄ phases, and the content of the two phases varied regularly as x changed, generally conforming to the designed nominal chemical composition. Importantly, the composite ceramics presented the homogenous and dense microstructure. The relative density of the composite ceramics was more than 95%, meanwhile, the Vickers-hardness of the samples was higher than 600 MPa. It was indicated that NZP-monazite type composite ceramics could be a potential matrix for the simultaneous immobilization of actinide and fission product.     

超细晶纯钛的微动疲劳特性

利用自行设计的微动疲劳实验夹具装置研究超细晶纯钛在柱面-平面接触下的微动疲劳特性,分析循环应力对其微动疲劳寿命的影响,通过观察接触区磨损和断口形貌,分析其微动损伤机制。结果表明,当法向载荷不变时,超细晶纯钛的微动疲劳寿命随着循环应力的增加而减小,比常规疲劳寿命更小。微动疲劳裂纹于接触区边缘萌生,磨损区破裂严重且附着有磨粒,在磨粒磨损作用下加速了试样的疲劳失效。断口同时呈现出疲劳形貌和微动形貌,形貌从平滑转向粗糙直至断裂,裂纹由小变大,裂纹扩展速率也逐渐增加,且在裂纹扩展区存在二次裂纹；由于受力不均在裂纹扩展区与断裂区之间存在山脊状形貌。     

Pure and mixed gas permeation study of silica incorporated polyurethane-urea membrane modified by MOCA chain extender

Polyurethane-urea (PUU) nanocomposite membranes have been prepared using various loadings of silica (SiO₂) nanoparticles. A Novel PU was fabricated by a two-step bulk polymerization technique based on polycaprolactone (PCL), hexamethylene diisocyanate (HDI), and diamine chain extender, 4,4-methylenebis(2-chloroaniline) (MOCA). The FTIR spectra indicated that the extent of phase separation reduces with increasing SiO₂ content. The presence of crystal regions in the soft and hard segments was confirmed by DSC and XRD analyses. The obtained results illustrated a decrement in the gases' permeation in the presence of SiO₂ particles. By increasing the filler content up to 15 wt% and pressure of 8 bar, the gas permeation value of the CO₂, O₂, and N₂ decreased 36%, 54%, and 59%, respectively. However, the permselectivity of the CO₂/N₂ and O₂/N₂ increased considerably, 55% and 13% respectively. On the contrary, by raising the temperature, a dramatic augmentation in the permeability of all gases with a simultaneous reduction in the selectivity values of both gas pairs was revealed. Increasing the pressure led to a decrease in the permeability values of all membranes for O₂ and N₂, whereas the permeability for CO₂ increased with the pressure. Nevertheless, the selectivity values for the pair of gases increased (at a pressure of 10 bar, 1.66 and 1.17 times the neat PU for CO₂/N₂ and O₂/N₂, respectively). Furthermore, the permeability of the CO₂, O₂, and N₂ for the mixed gases was smaller than for pure ones at the same gas upstream pressure. Nonetheless, like the pure gas, the selectivity of both pair gases increased.     

纯镁表面硅烷/透明质酸钠复合涂层的结构及腐蚀性能研究

纯镁因较快的腐蚀速率使其用于手术移植材料成为了一个障碍。为了控制其降解速率,本研究采用BTSE(1,2-(三乙氧基硅基)乙烷)硅烷化处理和共键嫁接1-(3-二甲氨基丙基)-3-乙基碳二亚胺盐酸盐(EDC)/N-羟基丁二酰亚胺(NHS)交联改性的透明质酸钠涂层的两步制备工艺在纯镁上制备复合涂层。同时使用红外光谱(FTIR)、X射线光电子能谱(XPS)、原子力显微镜(AFM)和静态接触角方法(CA)分析涂层的物化性能,通过电化学行为分析涂层在模拟体液中的耐腐蚀性能。FTIR和XPS结果表明在纯镁表面上成功的制备出复合涂层;其他结果显示,交联透明质酸钠涂层表面较裸镁、硅烷表面更平整、光滑,且呈现出亲水性,提高了其生物活性;与未改性的纯镁相比,复合涂层的腐蚀电流密度减小了2个数量级,阻抗值提高3个数量级,表现出很好的耐腐蚀性能。表明这种复合涂层作为手术移植材料在医学上具有很大的应用前景。