科创中国

研究了模拟日光照射下草酸协同黄铁矿对Cr(Ⅵ)的还原作用机理及其影响因素.结果表明,加入草酸后,反应体系中生成了光化学活性高的草酸铁(Ⅲ)配合物,同时还可能阻止了黄铁矿表面Fe(Ⅲ)水解产物Fe(OH)3和CrxFe1-x(OH)3的生成,从而使黄铁矿还原Cr(Ⅵ)的速率明显得到提高.增加溶液酸度、草酸浓度和黄铁矿质量浓度,有利于Cr(Ⅵ)的还原.

对比分析了所研制的高Cr铸铁风帽与耐热钢(ZG40Cr24Ni9Si2N RE)风帽的高温耐磨性能.高Cr铸铁的碳化物为黑色细条杆状并且呈点状分布,有利于高温耐磨性能的提高;而现用的耐热钢w(C)量低,合金碳化物少,不利于高温耐磨性.对比试验、理论分析和生产验证,所研制的高Cr铸铁风帽在生产成本和使用寿命方面均优于厂家现用的耐热钢风帽.

介绍了溜槽衬板的使用工况条件及技术要求,研究开发了新型Cr22MoWVTiNbRE钢铁高炉溜槽衬板,其化学成分为:w(C) 2.6%~3.2%,w(Si)0.4~0.8%,w(Mn)0.5%~1.0%,w(Cr) 21.0%~23.0%,w(Mo)0.9%~1.1%,w(W)1.1%~1.8%,w(Cu)0.4%~0.6%,w(V)0.3%~0.5%,w(Ti) 0.06%~0.2%,w(Nb)o.1%~0.5%,w(RE) 0.04%~0.08%,w(S)≤0.06%,w(P)≤0.06%.热处理工艺为980~1 050℃淬火+280~520℃回火,得到的硬度超过63.6 HRC,冲击值超过24.66 J/cm2;450~520 ℃二次回火,金相组织为回火马氏体=共晶碳化物(M7C3)+二次碳化物+少量残余奥氏体,得到的铸件硬度超过64 HRC.

研究了75SiFe孕育和REMg变质对金属型铸造高Ni-Cr铸铁铸态和回火态的组织与硬度的影响.结果表明,75SiFe孕育处理使石墨析出数量增多,增加了奥氏体+石墨的共晶体数量,石墨片长度增加,而板条状碳化物数量减少.REMg变质促进点球状石墨析出,石墨析出数量减少,碳化物转变为断网分布,即呈岛状和骨骼状,高冷却速度弱化REMg的变质作用.75SiFe孕育回火处理促进奥氏体分解,回火后残余奥氏体较多.75SiFe孕育降低高Ni-Cr铸铁的铸态和回火态硬度,而REMg变质可略提高高Ni-Cr铸铁的铸态和回火态硬度.

The porcelain fracture caused by low metal-ceramic bond strength is a critical issue in porcelain fused to metal(PFM)restorations.Surface roughening methods,such as sand blasting,acid etching and alkaline degreasing for the metal matrix are used to increase bond strength.However,the metal matrix of PFM processed by selective laser melting(SLM)has natural rough surface.To explore the effect of the original roughness on metal-ceramic bond strength,two groups of specimen are fabricated by SLM.One group of specimen surface is polished smooth while another group remains the original rough surface.The dental porcelain is fused to the specimens'surfaces according to the ISO 9693:1999 standard.To gain the bond strength,a three-point bending test is carried out and X ray energy spectrum analysis(EDS),scanning electron microscope(SEM)are used to show fracture mode.The results show that the mean bond strength is 116.5±16 MPa of the group with rough surface(Ra=17.2),and the fracture mode is cohesive.However,when the surface is smooth(Ra=3.8),the mean bond strength is 74.5 MPa 5 MPa and the fracture mode is mixed.The original surface with prominent structures formed by the partly melted powder particles,not only increases surface roughness but also significantly improves the bond strength by forming strong mechanical lock effect.Statistical analysis(Student's t-test)demonstrates a significant difference(p<0.05)of the mean value of bond strength between the two groups.The experiments indicate the natural rough surface can enhance the metal-ceramic bond strength to over four times the minimum value(25 MPa)of the ISO 9693:1999 standard.It is found that the natural rough surface of SLM-made PFM can eliminate the porcelain collapse defect produced by traditional casting method in PFM restorations.

目的 探讨应用降纤酶治疗非ST段抬高心肌梗死的临床疗效及其对预后的影响.方法 选取住院非ST段抬高心肌梗死患者86例,随机分为对照组和治疗组,均给予规范化方案治疗,而治疗组在此基础上加用降纤酶.结果 治疗组临床有效率明显高于对照组;心肌酶、高敏C反应蛋白水平明显低于对照组(P<0.05).结论 在规范治疗的基础上加用降纤酶更有利于改善患者的临床症状、减少并发症的发生,并对心肌梗死后心肌重构有一定抑制作用.

采用75SiFe孕育与REMg变质处理金属型铸造高Ni-Cr铸铁,研究了微观组织对高Ni-Cr铸铁热疲劳和热磨损性能的影响,结果表明:(1)550℃的高温磨损试验中,75SiFe孕育、REMg变质高Ni-Cr铸铁的磨损失重量随载荷的增大呈线性增长,在载荷相同的条件下,REMg变质试样的磨损失重小于75SiFe孕育试样,表现出较好的抗高温磨损性能,高Ni-Cr铸铁的高温磨损机制为氧化粘着磨损和接触疲劳磨损.(2)75SiFe孕育试样热裂纹垂直长度为15.49 mm,优于REMg变质试样热裂纹垂直长度17.69 mm,抗热裂性能较好.75SiFe孕育试样热裂纹在片状石墨尖端处基体组织内萌发,沿奥氏体和莱氏体界面扩展;REMg变质试样热裂纹在碳化物内萌生,并在碳化物内传播,造成碳化物破碎.