Corrosion behavior of T24, T92, VM12, and AISI 304 steels exposed to KCl–NaCl–K2SO4–Na2SO4 salt mixtures

The corrosion mechanisms of T24, T92, VM12, and AISI 304 steels are studied under the influence of NaCl–KCl, NaCl–Na₂SO₄, and KCl–K₂SO₄ salt mixtures in a dry air atmosphere at 650°C for 15 days. NaCl–KCl was the most aggressive deposit and AISI 304 stainless steel exhibited the highest corrosion resistance. There was no relation between the Cr content of the ferritic steels and their corrosion resistance in NaCl–KCl. In contrast, the resistance of high-Cr steels was better when exposed to NaCl–Na₂SO₄ and KCl–K₂SO₄. The high-Cr and the low-Cr steels were more susceptible to NaCl–Na₂SO₄ and to KCl–K₂SO₄, respectively.     

Formation mechanism of Ti(C,N) solid solution in Al-brown fused alumina refractory at 1973 K in flowing N2

Brown fused alumina is a cost-effective alumina material, and the state of Ti in alumina has a great influence on its high-temperature performance. In this paper, the Ti-containing phases in brown fused alumina particles and Al-brown fused alumina refractory were successfully transformed into Ti(C,N) at 1973 K in flowing N₂. The evolution of the Ti-containing phases in brown fused alumina under high temperature and nitrogen conditions was investigated by XRD, SEM and EDS. The results show that the Ti-containing phases in brown fused alumina include Ti₂O₃, Ti(C,N,O), TiFeSi₂, Ca_0·95Mg_0·9Al_10·1(Ti)O₁₇ and a low-melting point Ca₃Al₂Si₃(Mg,Ti)O₁₂ phase. Under high temperature and nitrogen conditions, the TiO_2[liquid], MgO_[liquid] and SiO_2[liquid] in the low-melting point phase are transformed into Ti(C,N), Mg(g) and SiO(g), while they are supplemented from Ti₂O₃, Ti(C,N,O) and Ca_0·95Mg_0·9Al_10·1(Ti)O₁₇. After heat treatment at 1973 K for 3 h, Ti₂O₃ and Ti(C,N,O) disappear, Ca_0·95Mg_0·9Al_10·1(Ti)O₁₇ is transformed into plate-like Ca_0·55Al₁₁O_17.05, and Ti(C,N) is formed on the surface of the corundum particles. The formation of Ti(C,N) reduces the porosity of the brown fused alumina particles and increases their strength.     

Microstructure and mechanical performance examination of 3D printed acrylonitrile butadiene styrene thermoplastic parts

Fused filament fabrication (FFF) is a process where thermoplastic materials are heated to its melting point and then extruded, layer by layer, to create a three dimensional printed part. Printing occurs in a layered manner, which leads to creation of voids (air gaps) in the 3D printed parts. These voids act as centers for crack initiation, propagation and therefore resulting bulk mechanical properties are lower. This paper focuses on microstructural characterization and analysis of fused filament fabricated tensile test coupons made from acrylonitrile butadiene styrene polymer, at various design conditions. Comparable tensile modulus with injection molded specimens was obtained for FFF design condition that is, slice height (0.1778 mm), raster width (0.4064 mm), raster to raster air gap (−0.0015 mm), contour to raster air gap (−0.0508 mm) and raster angle (0°). Scanning electron microscope studies provided an understanding as to why FFF processed specimens yielded lower failure strain and an insight into the presence of intralayer voids in specimens having lower tensile modulus. The study confirmed that though bulk mechanicals were affected by the combined effect of inter, intra and interfacial voids, intravoids had a predominant influence.     

偶联剂对PLA/PBAT/WF复合材料3D打印性能的影响

以聚乳酸（PLA）和聚己二酸/对苯二甲酸丁二酯（PBAT）为基体，杨木粉（WF）为填充增强材料，使用混炼机熔融共混制备PLA/PBAT/WF复合材料，采用熔融沉积成型（FDM）技术制备标准实验试样，通过扫描电子显微镜、红外光谱分析、旋转流变测试以及力学试验等方法，研究不同含量的硅烷偶联剂KH550对PLA/PBAT共混物以及PLA/PBAT/WF的相容性、流变性及力学性能的影响。结果表明，在偶联剂用量为3 %（质量分数，下同）时，拉伸强度提高了136 %；偶联剂KH550与 PLA和PBAT共价键偶联生成接枝聚合物，二者相容性得到提高；同时偶联剂与WF表面羟基发生缩聚反应有效的改善了其与PLA/PBAT的基体相容性，PLA/PBAT/WF复合材料的FDM的制件力学性能得到较大提升；复合材料的黏度随偶联剂含量的增加呈下降的趋势，含量为3 %时线材的综合打印性能及制品质量最佳。     

打印层厚度对FDM薄板固有特性的影响

针对不同打印层厚度对熔融沉积成型(fused deposition modeling,简称FDM)薄板固有特性的影响规律及相应的机理进行了研究。首先,以悬臂边界条件下的FDM薄板为研究对象,创建了固有特性理论模型;其次,完成了薄板样件的制备,同时搭建了样件的动力学测试系统,实验研究了样件的固有特性参数;最后,对比分析理论与实验结果,以验证理论模型的正确性。研究结果表明,所建模型可以准确预测FDM薄板结构的固有特征参数;打印层越厚,样件的固有频率越高,但其模态振型不会随着打印层厚度的变化而变化。该研究为提高FDM产品动力学性能提供了理论基础和技术支持。     

中国无机盐工业发展现状及展望

建国70 a以来中国无机盐工业发展迅猛,取得了巨大成就,中国已成为世界上最大的无机盐生产、出口和消费国。分析了中国无机盐工业生产现状和进出口情况,指出行业存在大宗产品产能过剩、产品精细化率偏低、产业集中度和资源配置率偏低、矿产资源保障能力不足、节能减排任务重、自主创新能力弱等问题,并提出未来发展建议及发展方向。新能源用无机材料、无机粉体功能材料、5G通迅用无机材料、电子化学品和电镀化学品等专用化学品将是未来无机盐工业发展的热点。随着产业链现代化水平的不断提升,将会逐渐实现行业规模化、绿色发展与安全生产。     

FDM用PETG系列耗材的改性研究

对市售聚对苯二甲酸乙二醇酯-1，4-环己烷二甲醇酯（PETG）丝材及原材料进行研究，选用PETG 2012作为制备熔融堆积成型技术（FDM）用PETG丝材的基体树脂。选用聚碳酸酯（PC）对基体PETG进行增韧增强改性，并制成3D打印高分子丝材进行打印测试，探讨了PC含量对PETG耗材及制件性能的影响。结果表明，在低PC含量下，PETG与PC的相容性较好，PETG与PC制件未出现明显的分层，分布比较均匀；共混物的流动性随着PC含量的增加而降低，且打印件的维卡软化温度和热变形温度随着PC用量的增加而增加；此外，PC材料的加入使得PETG打印件的力学性能得到较大改善：打印件的拉伸强度随着PC用量的增加而增大，缺口冲击强度却随着PC用量的增加呈现先增加后减小的趋势； PETG/PC的配比为1∶1时，可制得力学性能优异的3D打印耗材。     

Enhanced hydrogen generation from Al-water reaction mediated by metal salts

Hydrogen generation by the reaction of micrometer-aluminum powder with water at room temperature is hard to proceed due to the inhibition of alumina layer. In this study, a novel strategy of metal salts mediated Al-water reaction was proposed for more efficient and practical hydrogen generation. The effects of metal salt composition and dosage, and water injection rate and volume on hydrogen generation were investigated. The hydrogen yield of 230.0 mL was achieved in the Al/Ni/Cu/H₂O system within 600 s under the following conditions: 0.24 g aluminum with the molar ratio of Al, Ni and Cu at 10:1:1 and 2 mL water at the injection rate of 2 mL/min, which was equivalent to 70.4% of the theoretical hydrogen yield. Based on the morphology, element composition, crystal structure and electrochemical test results of the obtained composites after reaction, the mechanism of hydrogen production by metal salts mediated Al-water reaction was proposed.     

氟锆酸钾盐混合物对Mg-3Y-3.5Sm-2Zn合金组织和性能的影响

制备了三种氟锆酸钾(K2ZrF6)盐混合物(M),分别在三个温度下将三种盐混合物加入到铸态Mg-3Y-3.5Sm-2Zn合金中。通过差热分析(DSC),X射线衍射(XRD),光学显微镜(OM),扫描电子显微镜(SEM),能量色散谱(EDS)和拉伸试验研究了合金的显微组织和力学性能,讨论了K2ZrF6盐混合物在合金中的晶粒细化机理。结果表明,铸态Mg-3Y-3.5Sm-2Zn合金由α-Mg,Mg12(Y,Sm)Zn 和 (Mg,Zn)3(Y,Sm)三种相组成。SEM和XRD检测发现,添加K2ZrF6盐混合物不会在合金中产生新的相。在780°C下加入M3盐(60wt% K2ZrF6-20wt% NaCl-20wt% KCl)时,合金的晶粒细化效果最佳。通过在780℃下加入三种盐,铸态Mg-3Y-3.5Sm-2Zn合金的力学性能得到提高,由M3盐细化后的合金具有最佳的力学性能。K2ZrF6盐混合物可细化铸态Mg-3Y-3.5Sm-2Zn合金,这是由于Mg和K2ZrF6之间还原反应得到的细Zr质点和富锆区在合金中起到的晶粒细化作用。     

Experimental investigation of high-temperature corrosion properties in simulated reducing-sulphidizing atmospheres of the waterwall fireside in the boiler

The presence of reducing atmospheres of the waterwall fireside in the boiler due to extensive use of low-NOx combustion mode caused severe high-temperature corrosion problems. In this study, high-temperature sulphur corrosion properties of two types of low alloyed waterwall steel (15CrMoG and 12Cr1MoVG) in two kinds of reducing-sulphidizing atmospheres were investigated by lab-scale experiments. The experimental atmospheres and temperature were simulated according to field measurements in the boiler of a thermal power plant. The experimental results showed that the reducing-sulphidizing atmosphere with CO was more corrosive, and the CO accelerated the corrosion of H₂S and worsened the corrosion. The CO inhibited the formation of oxide scales, provided some corrosion resistance, and produced the intensely corrosive COS. The corrosivity of the alkali metal chlorides was limited in the reducing-sulphidizing atmosphere without CO, while the corrosion was strongly hindered in the reducing-sulphidizing atmosphere with CO.