钙长石系尾矿微晶玻璃的制备及发光性能

以钼尾矿、铁尾矿和铜尾矿等为主要原料,采用烧结法制备了钙长石系微晶玻璃。采用X射线衍射仪(XRD)、差热扫描量热仪(DTA)表征了结构和性能,研究了Eu~(3+)在微晶玻璃中的发光性能。结果表明,采用一步法制备钙长石微晶玻璃:较佳熔制温度为1450℃,Eu_2O_3在掺杂浓度0.1%时荧光强度最好,当晶化温度到1050℃时荧光强度最强,Eu~(3+)的有效激发波长为415 nm,发射波长为591 nm的橙-红光。     

氩气中1000℃下热处理对碳钢Q235工件表面金属铝粉涂层性能影响

为了增强承重普碳钢件的耐海水腐蚀性能和耐500℃高温性能,将两种没有气味的环保型水性纯铝粉涂料在室温下喷涂至Q235普碳钢片表面,制得单层和双层两种铝粉涂层.将涂层试样浸泡在室温质量分数为3.5%的NaCl的模拟海水中,考察涂层的抗腐蚀性能.为提高单层涂层的耐腐蚀性和双层涂层的粘接强度,研究了1000℃氩气处理对涂层性能的影响.实验结果表明:原始单层铝粉涂层试样泡在盐水中2天后就开始生锈,而经过1000℃氩气加热处理10 min后,涂层在10天内都没有生锈,同时涂层的粘接强度由11.6 MPa增加到14.0 MPa;原始双层铝粉涂层试样泡在盐水中10天内没有生锈,经过1000℃氩气加热处理10 min后,涂层防腐蚀性能没有降低,而涂层的粘接强度由9.9 MPa增加到11.3 MPa.XRD表征结果表明,原始双层铝粉涂层表面只有金属铝,经过1000℃氩气加热处理10 min后,涂层表面也出现了极少量Al_2O_3.SEM表征表明:经过1000℃氩气加热处理10 min后,单层涂层中球形铝粉颗粒熔化形成了片状颗粒,片状颗粒层在垂直于涂层方向的间隙明显减少,这可能是单层铝粉涂层经1000℃氩气加热10 min后防腐性能明显提高的原因;球形铝粉颗粒熔化也导致了涂层粘接强度的增加.     

Microwave dielectric properties of SrLa[Ga1−x(Mg0.5Ti0.5)x]O4 and SrLa[Ga1−x(Zn0.5Ti0.5)x]O4 (x = 0.2-0.8) ceramics

SrLa[Ga_1−x(R_0.5Ti_0.5)_x]O₄ (R = Mg, Zn) ceramics were prepared by a standard solid state sintering method. The single-phase ceramics with K₂NiF₄-type layered perovskite structure and I4/mmm space group were obtained, indicating that SrLa(R_0.5Ti_0.5) and SrLaGaO₄ can form the unlimited solid solutions. With increasing x for R = Mg and Zn, ε_r increases monotonously, the Qf value first increases and then decreases, while τ_f increases from a negative to a positive value. The optimized microwave dielectric properties were obtained as following: ε_r = 23.3, Qf = 89 400 GHz, τ_f = −0.8 ppm/°C for SrLa[Ga_0.6(Mg_0.5Ti_0.5)_0.4]O₄ and ε_r = 23.3, Qf = 76 200 GHz, τ_f = 0.2 ppm/°C for SrLa[Ga_0.7(Zn_0.5Ti_0.5)_0.3]O₄, indicating that the present solid solution ceramics are the promising candidates as microwave resonator materials for the telecommunication applications.     

机床结构轻量化设计研究进展

对机床进行优化的结构构型设计,使得材料在机床结构空间内更加合理地分布和有效地利用,一直都是机床设计工作者追求探索的目标。论述机床构型和结构件轻量化设计的研究历程和技术发展,对机床结构轻量化设计中常用的现代设计方法:参数优化、结构拓扑优化、多方法综合结构设计、仿生优化设计方法进行具体技术介绍和综合评述,并对近年兴起的仿生优化设计方法进行从方法、实现手段和轻量化效果等方面重点分析和评述,对机床构型和结构件轻量化设计研究的未来发展提出展望。     

煤制天然气中氢对X80钢螺旋焊管力学性能的影响

近年来,我国多项煤制天然气示范工程投入运行,X80钢螺旋焊管常用于天然气长输管道建设,其与煤制天然气的相容性直接影响了长输管道的服役寿命和安全可靠性。为研究煤制天然气对国产X80钢螺旋焊管的力学性能影响,分别从埋弧螺旋焊管的母材和螺旋焊缝处取样,在总压为12 MPa,氢气分数为0,1vol%,2.2vol%,5vol%的模拟环境中分别进行慢应变速率拉伸试验和疲劳裂纹扩展速率试验。试验结果表明:含氢量5vol%以下时,煤制天然气对国产X80管线钢强度性能影响很小,但对塑性性能有一定影响,对疲劳裂纹扩展性能影响很大,煤制天然气中氢对母材的疲劳裂纹扩展性能劣化影响比螺旋焊缝严重。     

Physicochemical characteristics,antioxidant capacity and thermodynamic properties of purple-fleshed potatos dried by radio frequency energy

Abstract

The impacts of using radio frequency (RF) energy to dry purple-fleshed potatoes were investigated and compared to infrared radiation (IR) and microwave (MW) drying techniques. The gelatinization rate, color, flavor, morphological, and structural characteristics, thermodynamic properties, as well as antioxidant capacity were examined. The results indicated that the drying time of RF (70?min) and MW (21?min) were shorter than IR (105?min). The gelatinization ratio of MW, RF, and IR were 94.4?±?2.0, 88.3?±?1.4, and 64.5?±?1.1%, respectively. The degree of crystallization of purple-fleshed potato powder decreased with all three drying methods. RF-dried potatoes were able to retain higher polyphenols (loss rate: 4.3%), total anthocyanin (3.7%), and total flavonoid content (35.1%), whereas IR showed the lowest retention. The content of polyphenols also decreased significantly. Furthermore, after RF heating, the scavenging of free radicals was higher compared to MW and IR.     

Toward an understanding of how red phosphorus and expandable graphite enhance the fire resistance of expandable polystyrene foams

Flame retardant expandable polystyrene (EPS) foams were prepared by coating method. Red phosphorus (RP) and expandable graphite (EG) were chosen as the flame retardants to be coated on the surface of expanded PS beads. By the presence of 33 phr RP/EG with a mass ratio of 1:1, the limiting oxygen index of EPS foam could reach up to 26.9%, with V-0 rating obtained in UL-94 test. The peak heat release rate could also decrease to 180.67 kW/m², which was 72.9% lower than that of neat EPS sample. Thermogravimetric analysis revealed an obvious increase of thermal stability and residue char amount by the presence of RP and EG. From the observation and analysis of char residue, it could be proposed that there existed a significant synergistic effect between RP and EG. RP could be oxidized and further react with graphite by the presence of oxygen at high temperature, forming isolated char layer and releasing nonflammable gases. Moreover, P radicals were generated at high temperature and could capture the radicals formed during the combustion of polystyrene and eliminate the burning chain reactions.