Effect of Spraying Power on Oxidation Resistance of MoSi2-ZrB2 Coating for Nb-Si Based Alloy Prepared by Atmospheric Plasma

The MoSi₂-ZrB₂ coatings were prepared on Nb-Si based alloy by atmospheric plasma spraying with the spraying power 40, 43 and 45 kW. The effect of spraying power on the microstructure and oxidation resistance of MoSi₂-ZrB₂ coating at 1250 °C were studied. The results showed that the main constituent phases of coatings were MoSi₂ at all spraying power. The coating became more compact as the spraying power increased. The coating prepared at 45 kW was dense and uniform, which exhibited the best oxidation resistance due to the formation of a dense and uniform glass layer consisting of SiO₂ and ZrSiO₄.     

Effect of SiO2–Al2O3 Glass Composite Coating on the Oxidation Behavior of Ti60 Alloy

A SiO₂–Al₂O₃ glass composite coating was prepared on Ti60 alloy via air spraying slurry and then a suitable baking process. It was composed of potassium silicate glass, alumina and quartz powders. The high temperature oxidation performance of the alloy with and without coating was evaluated in static air at both 800 °C and 900 °C. The results show that catastrophic oxidation occurs for Ti60 bare alloy. It had a mass gain of about 2 mg/cm² after oxidation at 800 °C and 17 mg/cm² at 900 °C for 100 h. On the contrary, the oxidation resistance of alloy coated with composite coating was much improved with the mass gain about 0.36 mg/cm² and 0.95 mg/cm² at 800 °C and at 900 °C, respectively. The microstructure evolution of the composite coating and the alloy was analyzed by scanning electron microscope and electron probe microanalyzer. The effect of the composite coating on the oxidation performance of the alloy is discussed especially in terms of oxygen diffusion and interfacial reaction.     

Characterization of W–Cr Metal Matrix Composite Coatings Reinforced with WC Particles Produced on Low-Carbon Steel Using Laser Processing of Precoat

The paper presents the study results of laser processing of precoat applied on C30 steel. The precoat consisted of powder mixtures with a binder in the form of water glass. Tungsten powder, chromium, and tungsten carbide (WC) were used to produce the precoat. The laser processing was carried out using a Yb:YAG disc laser with a rated power of 1 kW. Constant producing parameters (power of laser beam, 600 W; laser beam scanning rate, 400 mm/min) were applied. Chemical composition of the precoat was a variable parameter in coating production. A mixture consisting of 50% W and 50% Cr as a metal matrix was prepared. Subsequently, WC particles in weight ratios of 25%, 50%, and 75% were added to matrix. As a result, W–Cr metal matrix composite coatings reinforced with WC particles were formed. This study focused on investigation of microstructure, microhardness, phase, and chemical composition as well as corrosion and wear resistance, of the newly formed W–Cr/WC coatings. An instrumented nanoindentation test was also used in this study. As a result of laser beam action, the newly formed coatings had an interesting microstructure and good properties which were improved in comparison to substrate material. It is anticipated that the resulting coatings, depending on the treatment parameters (e.g., W–Cr/WC powder mixture) used, can be successfully applied to metal forming or foundry tools.     

氟涂层镁铝合金的体外生物相容性研究简

目的 研究氟涂层镁铝合金的体外生物相容性。方法实验分为空白对照组（N组）、镁铝合金组（M组）、氟涂层镁铝合金组（F组）和阳性对照组（P组）4组。细胞毒性实验：将L929细胞在各组的DMEM浸提液中培养,光学显微镜下观察细胞生长状况。应用WST-1法测量光密度（OD）值。溶血实验：按GB-T16175-2008《医用有机硅材料生物学评价实验方法》第13部分《溶血试验》进行实验。测量各样本的OD值,计算溶血率。豚鼠最大剂量致敏实验,按照GBJ16886.10-2005（（医疗器械生物学评价》第10部分《刺激与迟发型超敏反应试验》进行实验。观察激发阶段去除贴附片后24、48、72h豚鼠皮肤致敏情况。结果各观察期F组的形态分级为0级,M组为4级。各组各观察期内OD值差异均有统计学意义（F=312.96,P=0.000）。第3天,实验组OD值均高于P组（1.050±0.065 vs 0.292±0.010）（P〈0.05）。第5天、第7天,F组与N组OD值（1.429±0.096 vs 1.622±0.156,0.928±0.040 vs 50.995±0.070）处于同一水平（P〉0.05）,均高于P组（0.270±0.015,0.281±0.006）（P〈0.05）。M组溶血率为68.3％,F组为0.8％。24h、48h和72h后N组、M组、F组皮肤均无红斑。结论氟涂层镁铝合金体外实验显示具有良好的生物相容性。     

Influence of Zeolite Coating on the Corrosion Resistance of AZ91D Magnesium Alloy

The protective performance of zeolite coating on AZ91D magnesium alloy was evaluated using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) in 0.1 M sodium chloride solution (NaCl). Electrical equivalent circuit (EEC) was developed based upon hypothetical corrosion mechanisms and simulated to correspond to the experimental data. The morphology and the chemical nature of the coating were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Post corrosion morphologies of the zeolite coated and the uncoated AZ91D alloy were investigated using SEM. The corrosion resistance of the zeolite coated specimen was at least one order of magnitude higher than the uncoated specimen.     

Hot Corrosion Behavior of Sputtered Nanocrystalline Coating with Yttrium Addition at 900 °C

The high temperature corrosion behavior of sputtered nanocrystalline K38 coating with and without yttrium addition under mixed molten salt film in air was investigated. Accelerated corrosion occurred on the coating without yttrium (Y) addition locally after 60 h exposure at 900°C, which resulted in negative weight gain in kinetics. A uniform and protective alumina scale formed on surface of the coating containing yttrium in comparison. Y enriched particle as corrosion product was observed on the top of alumina scale. The results indicated the beneficial influence of Y on the chemical stability of the protective scale in the presence of chloride. The mechanism was discussed.     

X线平片与多层螺旋CT在四肢骨关节骨折中的诊断价值

目的探讨X线平片与多层螺旋CT(MSCT)后处理技术在诊断四肢骨关节骨折中的应用价值。方法回顾性分析我院就诊治疗的62例四肢骨关节骨折患者的临床资料进行回顾性整理分析,以手术诊断为标准,总结不同检查方法对四肢骨关节骨折的诊断正确性,分析不同骨关节骨折在不同影像学检查中的图像特征。结果整理临床病例资料可知,X线平片和MSCT后技术处理检查对四肢骨关节骨折检出率分别为83.87%和96.77%,比较差异间无统计学意义(P>0.05),但MSCT后技术处理对四肢骨关节骨折的诊断符合率显著高于X线平片检查,比较差异间具有统计学意义(P<0.05);由资料可知,经X线平片检查符合诊断48例,其余14例显示为可疑及未见异常但是实际上存在着隐匿性骨折,而X线检查中,多数均表现为骨皮质不连续,呈现中断。由于X线平片检查中对于髋臼、髌骨、踝关节后踝、肱骨内上髁、第4、5掌骨基底部中细小骨折线因影像的重叠未能明显显示,故易发生误诊,而在MSCT后处理技术检查中,行MSCT扫描后,再经MPR SSD VRT多方面重建,其中MPR轴位可明显见掌骨基底存在细小骨折线,且对于肱骨内上髁游离的细小骨碎片也可清晰显示。结论 MSCT后处理技术诊断四肢骨关节骨折的正确符合率更高,对于实际在但未能明显表现的隐匿性骨折、骨折部位、位置以及与周围组织关系更能清晰立体的显现,进而更有利于临床医生进行观察和诊断。     

nHA/BG涂层与Bio-Oss骨粉修复种植体骨缺损的实验研究

目的:评价生物玻璃/纳米羟基磷灰石(nHA/BG)涂层与Bio-Oss骨粉在种植体骨缺损中引导骨再生的效果。方法:选取6只Beagle犬,拔除两侧下颌前磨牙。3个月后预备种植窝,同时颊侧制造裂隙状骨缺损(2.25 mm×3 mm×4 mm)。按照分组植入种植体和骨粉,A组为nHA/BG+Bio-Oss,B组为nHA/BG+血凝块愈合,C组为微米级HA+Bio-Oss。术后2周、处死前2周和3 d分别进行四环素、钙黄绿素和茜素红荧光标记。术后8周和16周处死动物,行大体观察和组织学测量。采用SPSS13.0软件包对数据进行统计学分析。结果:3组骨-种植体结合率(BIC)在8周时分别为30%、18%、21%,16周时分别为61%、53%、46%;缺损区新骨面积(RA)在8周时分别为(2.1±0.6)mm3、(1.4±1.0)mm3、(0.6±0.1)mm3,16周时分别为(4.2±0.7)mm3、(2.2±1.2)mm3、(1.2±0.6)mm3。各组8周与16周的BIC和RA相比均有显著差异(P<0.05);8周时,A、C 2组的BIC和RA相比有显著差异(P<0.05),16周时,A、B 2组的RA相比有显著差异(P<0.05)。结论:在种植体周围2.25 mm骨缺损区,nHA/BG涂层能促进种植体-Bio-Oss替代骨-骨的骨结合。     

Bio-inspired stable antimicrobial peptide coatings for dental applications

We developed a novel titanium coating that has applications for preventing infection-related implant failures in dentistry and orthopedics. The coating incorporates an antimicrobial peptide, GL13K, derived from parotid secretory protein, which has been previously shown to be bactericidal and bacteriostatic in solution. We characterized the resulting physicochemical properties, resistance to degradation, activity against Porphyromonas gingivalis and in vitro cytocompatibility. Porphyromonas gingivalis is a pathogen associated with dental peri-implantitis, an inflammatory response to bacteria resulting in bone loss and implant failure. Our surface modifications obtained a homogeneous, highly hydrophobic and strongly anchored GL13K coating that was resistant to mechanical, thermochemical and enzymatic degradation. The GL13K coatings had a bactericidal effect and thus significantly reduced the number of viable bacteria compared to control surfaces. Finally, adequate proliferation of osteoblasts and human gingival fibroblasts demonstrated the GL13K coating’s cytocompatibility. The robustness, antimicrobial activity and cytocompatibility of GL13K-biofunctionalized titanium make it a promising candidate for sustained inhibition of bacterial biofilm growth. This surface chemistry provides a basis for development of multifunctional bioactive surfaces to reduce patient morbidities and improve long-term clinical efficacy of metallic dental and orthopedic implants.     

NiTi根管器械表面耐磨镀层的制备和性能研究

目的：研究镍钛合金表面耐磨镀层的制备工艺和性能,提高镍钛根管器械的表面硬度和耐磨性。方法：采用直流电镀法在NiTi合金表面制备了Ni—W合金镀层,通过能谱分析和X射线衍射技术（XRD）研究电镀工艺对Ni—W耐磨镀层成分和结构的影响。采用销一盘式摩擦试验机对耐磨Ni—W合金镀层的耐磨性进行测试,通过磨损失重和磨痕形貌观察评价和分析了Ni—W合金镀层的耐磨性和耐磨机理。结果：在NiTi合金表面所制备的Ni—W合金耐磨镀层的W含量在15．2．20．2wt％范围内,且镀层致密,无微观裂纹。Ni—W合金镀层的结构是W在Ni中的固溶体。与Ni—Ti合金基体相比,镀有Ni—W合金镀层的Ni—B合金试样的磨损失重大幅度降低,耐磨性显著提高;Ni—W合金镀层的硬度和耐磨性随镀层中W含量的增加而增大。结论：直流电镀技术对镍钛合金根管器械进行表面改性可显著提高其耐磨忡．