Influence of operational parameters on the TiO2 photocatalytic degradation of Methylene blue

Thin films of titanium oxide were obtained by dip-coating, using the sol–gel method. TiO₂ powder (Degussa, P25) and polyethylene glycol (PEG) were added to enhance the photocatalytic properties of resulting films. Effects of experimental variables on the photocatalytic properties of the coatings were evaluated based on the degradation efficiency of the reference dye (Methylene blue). The photocatalytic activity of resulting TiO₂ coatings was improved with the loading of TiO₂ powder (Degussa, P25) and PEG in the sols. The electron-hole pair photogeneration increases with the energy of irradiation and improves photocatalytic efficiency. Increasing coating thickness leads to a rough surface with more reaction sites. Photodegradation conversion of Methylene blue (Mb) decreases with an increase in the initial concentration of Mb.     

Sol–gel preparation and properties of Ag–TiO2 films on surface roughened Ti–6Al–4V alloy

Ag–TiO₂ films (Ag/Ti?=?3·3, 9·1 at-%) were sol–gel coated on Ti–6Al–4V alloy that had been surface roughened by the NaOH–HCl treatment for antibacterial applications. Scanning electron microscopy observation showed that pore size of the surface layer of NaOH–HCl treated Ti–6Al–4V alloy increased with the NaOH concentration. Ag–TiO₂ films on the surface roughened substrate were adherent and crack-free. X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses indicated that Ag existed in metallic state, and the films completely covered the roughened substrate. X-ray diffraction peaks of the substrate and anatase TiO₂ were detected. The Ag–TiO₂ films on the roughened substrate exhibited good adhesion quality and high cohesion strength in the indentation test. The potentiodynamic polarisation test showed that the TiO₂ and Ag–TiO₂ films improved corrosion resistance of the substrate.     

Cu调控的TiN-Cu纳米复合膜包覆钛合金的抗菌性研究

利用磁控共溅射技术在钛合金(Ti6Al4V)表面包覆氮化钛-铜纳米(TiN-Cu)复合膜,并通过控制Cu靶溅射功率实现对TiN-Cu薄膜中Cu含量的调节,进而实现对材料耐蚀性和抗菌性的协同调控。采用扫描电子显微镜、原子力显微镜、X射线衍射仪、能谱仪分析了包覆TiN-Cu纳米复合膜的钛合金的表面形貌、相结构、元素成分及价态,并在模拟体液条件下测试了该材料的耐腐蚀性能,通过体外抗菌实验评价了Cu含量对材料抗菌性的影响。结果表明:通过在Ti6Al4V表面包覆TiN-Cu纳米复合薄膜显著增强了材料的抗菌性;并抑制了有毒性的V⁴⁺、Al³⁺离子在体液中的释放。Cu靶溅射功率升高在提高TiN-Cu薄膜中Cu含量和薄膜沉积速率的同时,也导致了薄膜中大量柱状晶体结构的生成,加速了薄膜的腐蚀,但提高了抗菌性。综上,合理调控Cu的含量是协同提升TiN-Cu薄膜的耐腐蚀性及抗菌性的关键。     

Corrosion and Wear Resistance Characterization of Environmentally Friendly Sol-gel Hybrid Nanocomposite Coating on AA5083

Environmentally friendly organic-inorganic hybrid nanocomposite films have been developed by sol-gel method for corrosion protection of AA5083 alloy.The hybrid nanocomposite coatings have been synthesized from tetraethylorthosilicate(TEOS) and 3-glycidoxypropyltrimethoxysilane(GPTMS) precursors.The multilayer coatings were prepared by dip-coating technique.Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was carried out to show the formation of the Si-O-Si structural backbone of the hybrid coatings.Structure and surface morphology of the coatings were studied by optical microscopy(OM), scanning electron microscopy(SEM) and atomic force microscopy(AFM).Characterization of the coatings with respect to pencil scratch hardness,adhesive and abrasion resistance was performed.The corrosion protection performance of these coatings was examined by using cyclic potentiodynamic polarization technique in Persian Gulf water.The results revealed that crack-free films with smooth surface were obtained. With increasing the number of sol—gel coated layers,corrosion resistance increased from 81 to 419 kΩcm~2, while the abrasion wear resistance did not change significantly.However,the triple sol-gel coated layer offered excellent protection against corrosion.     

Effect of calcium-ion implantation on the corrosion resistance and bioactivity of the Ti6Al4V alloy

The corrosion resistance and bioactivity of Ti6Al4V alloy after calcium-ion implantation were examined. Polished samples were implanted with a dose of 10¹⁷ Na⁺/cm² at a beam energy of 25 keV. The chemical composition of the surface layer formed during the implantation was determined by XPS and SIMS. The bioactivity of the samples was evaluated by soaking them in a simulated body fluid (SBF) at 37 °C for 168 and 720 h. The corrosion resistance in SBF at 37 °C was determined by electrochemical methods after exposure in SBF for various times. The surfaces of the samples before and after examinations were observed by optical microscopy, SEM-EDS and AFM.The results of the corrosion examinations indicated that under stationary conditions and after short-term exposures, the calcium-ion implanted titanium alloy had an increased corrosion resistance, but during the anodic polarization, calcium-implanted samples underwent pitting corrosion. The microscopic observations show that the precipitations of calcium phosphates are present on the surface, but they do not form a continuous layer.     

High Microwave Absorption of Nano-Fe3O4 Deposited Electrophoretically on Carbon Fiber

Production of magnetite (nano-Fe₃O₄)-coated carbon fibers (MCCFs) composites using the electrophoretic deposition (EPD) technique has been investigated in the present research. Fe₃O₄ nano-powder was synthesized by the reduction of Fe (III)-tri-ethanolamine (TEA) in an aqueous alkaline solution. By the deposition of nano-Fe₃O₄ particles distributed stably in a suspension on the surface, a uniform and compact Fe₃O₄ thin-film was fabricated on nitric acid-treated carbon fiber. According to the results, the strongest reflection loss (RL) of MCCFs was recognized to be ?11 dB at 10.37 and 11.4 GHz for a layer of 1.7 mm in thickness. EPD was introduced as a suitable method for the production of MCCFs due to its low cost, easy productivity and time efficiency as well as the high absorption properties of the resulting MCCFs compared with the previous reported works.     

Ti6Al4V磁控溅射沉积Ti-Ag-(N)薄膜及其抗菌性的研究

利用磁控溅射法在医用钛合金Ti6Al4V表面制备Ti-Ag、Ti-Ag-N薄膜。采用扫描电子显微镜、X射线衍射、X射线能量色散谱、X射线光电子能谱分析薄膜的表面形貌、微观结构、化学成分和化学价态。采用平板计数法测试薄膜对大肠杆菌的抗菌性。研究结果表明:薄膜主要由Ti、Ag、(N)组成,且Ag是以Ag~0形式存在;与基材相比,两种薄膜对大肠杆菌(E.coli)均有抗菌性,且Ti-Ag-N薄膜表现出更优越的抗菌性能。     

Cryogenic Drilling of Ti–6Al–4V Alloy Under Liquid Nitrogen Cooling

This article is focused on experimental study of the effects of cryogenic liquid nitrogen (LN₂) coolant during drilling of Ti–6Al–4V alloy material with three different levels of cutting speed (V_c) and feed rate (f) at a constant depth. Cutting temperature (T), thrust force (F_z), torque (M_z), surface roughness (R_a), and hole quality are the output responses investigated by using cryogenic LN₂ coolant compared with a wet coolant. Tool wear and chip morphology were examined with the changes in cryogenic LN₂ coolant. It is found that cryogenic LN₂ coolant results in lowering cutting zone temperature which helps more removal of heat from the cutting zone. Lower thrust forces and surface roughness were observed due to less friction and better chip breaking in cryogenic LN₂ condition. Also better chipping results in improvement in hole quality, viz., circularity and cylindricity in cryogenic LN₂ condition. Less serration and uniform segmentation results in better chip morphology and no damage to the cutting inserts resulted in improved tool life in cryogenic LN₂ condition. The main application of cryogenic LN₂ coolant in the cutting zone provides better lubrication and is more effective than wet coolant. The effects of this investigation show that cryogenic LN₂ coolant is an alternative approach for a wet coolant in the drilling process.     

Metallurgical and Corrosion Properties of Explosively Welded Ti6Al4V/Low Carbon Steel Clad

Titanium alloy (Ti6Al4V) and Iow carbon steel (LCS) were joined by explosive welding method using different ratios of explosive. Some metallurgical properties of joined samples were investigated. Joined samples were examined by means of optical microscope, scanning electron microscope (SEM) and tensile-shearing tests. Bending, tensile, hardness and corrosion behaviour of the samples were investigated. Separation was not occurred on the joining interface after tensile-shearing and bending tests. It is seen that hardness of both plates were increased with increasing explosive.It is found that increasing explosive ratio leads to an increase in corrosion. It is also found that corrosion rate was high at the beginning of the experiment but the rate of the corrosion decreased subsequently during the experiment.     

喷砂酸蚀处理促进Ti6Al7Nb表面钙磷沉积

研究了Ti、Ti6Al4V和Ti6Al7Nb 3种钛基材料在喷砂酸蚀处理后成骨细胞在其表面生长的生物活性。通过Al2O3喷砂和盐酸、硫酸混合物酸蚀的表面改性方法,在Ti、Ti6Al4V和Ti6Al7Nb3种钛基材料表面进行喷砂酸蚀处理,通过SEM观察样品的表面形貌,样品的表面呈现出微米级多孔形貌;将样品浸入模拟体液(simulated body fluid,SBF)中浸泡7,14和21 d后通过SEM、X射线衍射仪(XRD)分析样品表面沉积物的形貌、物相,样品浸入SBF 14 d后,Ti6Al7Nb表面最先观察到表面覆盖的羟基磷灰石涂层;样品浸入SBF 21 d后,Ti、Ti6Al4V和Ti6Al7Nb表面都观察到羟基磷灰石涂层。羟基磷灰石涂层有利于促进钛基植入体与体内骨组织的骨结合,喷砂酸蚀处理的Ti6Al7Nb表现出良好的生物活性。     

Fabrication and characterization of self-organized mixed oxide nanotube arrays by electrochemical anodization of Ti-6Al-4V alloy

Self-organized mixed oxide nanotube arrays were fabricated by anodization of Ti-6Al-4V alloy in H₃PO₄/NH₄F aqueous solution. The nanotubes of 90-180 nm in diameter and 10-20 nm in wall thicknesses could be tuned by changing anodization voltages. Whereas, the as-prepared nanotube arrays were amorphous; to induce crystallinity, the products were annealed at 400 °C, 500 °C and 600 °C, respectively. The UV-Vis spectra of samples annealed at 600 °C gives the maximum absorption in the visible spectra range. Various characterization techniques (viz., FESEM, XPS, XRD, and UV-Vis) were used to study the morphology, composition, phase and band gap of the films.     

钛合金表面激光熔覆Ni基梯度涂层的研究

为了改善Ti6Al4V钛合金表面耐磨性能和抗高温氧化性能,采用CO2激光在Ti6Al4V钛合金表面进行激光熔覆Ni基梯度涂层试验.利用扫描电镜和显微硬度计等手段分析了熔覆层组织,测试了基体和熔覆层的显微硬度.结果表明,采用适当的工艺参数,可以在钛合金表面获得连续、均匀、无裂纹和气孔的熔覆层.熔覆层组织由树枝晶和晶间共晶组织构成,并与基体形成牢固的冶金结合.由基体到表面,显微硬度过渡平稳,呈明显梯度渐变特征.     

烧结NdFeB永磁体表面TiO2/聚氨酯基复合涂层的制备及耐蚀性研究

采用阴极电泳沉积在烧结NdFeB永磁体表面制备了TiO_2纳米颗粒增强的聚氨酯涂层,研究了电泳沉积过程中电流密度的变化趋势和电泳液中二氧化钛颗粒浓度对复合涂层的表面形貌、粗糙度、接触角、显微硬度和耐蚀性的影响。结果表明,电泳沉积过程中电流密度随着时间的延长而降低,大致可分为3个阶段;二氧化钛颗粒可均匀弥散地分布在聚氨酯基体中,随着电泳液中二氧化钛浓度的增加,复合涂层中镶嵌的颗粒越多,导致表面粗糙度和硬度增大,而接触角降低;复合涂层可大幅度降低NdFeB试样在H_2SO_4溶液中浸泡的质量损失,且二氧化钛浓度越大,质量损失越小,即纳米二氧化钛颗粒的掺入进一步提高了NdFeB永磁体的耐蚀性。     

纳米TiO2微粒对2214铝合金微弧氧化膜微观结构及耐磨性能的影响

在含有不同浓度纳米TiO_2微粒的硅酸盐体系电解液中对2214铝合金进行微弧氧化处理,以在2214铝合金表面制备包含TiO_2的复合陶瓷膜。分别使用SEM、EDS、激光共聚焦显微镜、XRD、维氏硬度计、划痕仪和球盘式摩擦磨损试验机对复合陶瓷膜的微观结构、表面粗糙度、相成分、硬度、粘结强度、耐磨性能进行分析。结果表明:复合陶瓷膜主要由γ-Al_2O_3、α-Al_2O_3、莫来石、锐钛矿型TiO_2和金红石型TiO_2组成,且随着电解液中TiO_2微粒浓度的增加,复合陶瓷膜表面的微孔数量显著减少,微孔尺寸显著减小。与不含TiO_2成分的微弧氧化陶瓷膜相比,复合陶瓷膜通过更低的摩擦系数和更小的磨损率展示了更好的耐磨性能。     

2024铝合金氟铝酸盐转化膜的制备及其防腐蚀性能

为了寻找替代传统铬酸盐转化的处理工艺,采用由NaF,(NH4)2SiF6,(NaPO3)6和钛盐促进剂组成的转化液,在2024铝合金表面制备了一种氟铝酸盐化学转化膜,优化了转化液组分及转化工艺条件。结果表明:最优工艺为5.0 g/L NaF,5.0 g/L(NH4)2SiF6,0.9 g/L(NaPO3)6,0.5 g/L钛盐促进剂,pH值为4.7,室温,20 min;最优工艺所得氟铝酸盐转化膜由排列紧密且形状规则的晶体颗粒组成,表面覆盖有胶状物,膜层连续而致密、呈亚光,组成(质量分数)为7.53%O,48.87%F,19.11%Na,20.78%Al,0.79%Si,1.66%P,1.26%Cu;氟铝酸盐转化膜耐蚀性优良,最优工艺所得转化膜耐盐雾腐蚀达285 h,其使铝合金在3.5%NaCl溶液中的腐蚀电位增加了58 mV,腐蚀电流密度降为钝化前的1/9。     

Obtaining of Ni–P–TiO2 Composite Coatings with TiO2 Sol and Surfactants and Their Properties

The influence of surfactants and TiO₂ sol on mechanical, catalytic, and corrosive properties of electroless Ni–P coatings was investigated. Additives of the surfactants caused the decrease of internal stresses in the Ni–P coatings and smoothing of their surfaces. Incorporation of the TiO₂ particles facilitated the rise of microhardness of the Ni–P coatings from 545 ± 11 Hv up to 614 ± 17 Hv. Additives of the surfactants accelerated hydrogen evolution reaction on the composite Ni–P–TiO₂ coatings in acid and alkaline media, and increased photocatalytic activity in methylene blue decomposition. Incorporation of the TiO₂ particles and application of the surfactants resulted in an improvement in the corrosion resistance of original Ni–P coatings in 0.5 M H₂SO₄.     

An investigation of super-hydrophilic properties of TiO2/SnO2 nano composite thin films

A sol-gel dip coating technique was used to fabricate TiO₂/SnO₂ nano composite thin films on soda-lime glass. The solutions of SnO₂ and TiO₂ were mixed with different molar ratios of SnO₂:TiO₂ as 0, 3, 4, 6, 8, 9, 10.5, 13, 15, 19.5, 25 and 28 mol.% then the films were prepared by dip coating of the glasses. The effects of SnO₂ concentration, number of coating cycles and annealing temperature on the hydrophilicity of films were studied using contact angle measurement. The films were characterized by means of scanning electron microscopy, X-ray diffraction and atomic force microscopy measurements. The nano composite thin films fabricated with 8 mol.% of SnO₂, four dip coating cycles and annealing temperature of 500 °C showed super-hydrophilicity.     

The seeding effect on the microstructure and photocatalytic properties of ZnO nano powders

Nano sized ZnO powders, with suitable amount of TiO₂ (P25), have been successfully synthesized via a novel modified hydrothermal method by using zinc acetate. Titania nano powder plays an important role in fabrication of ZnO nano structure. The structure and morphology of the product were characterized by X-ray diffraction and scanning electron microscopy, which show different morphologies and particle sizes. Photocatalytical properties of the product exhibit strong improvement in the reactivity of seeded powders. These powders have better properties because of coupling effect of semiconductors, small powder size and reduced recombination of electron-hole in the surface of a catalyst.     

Constitutive modeling and the effects of strain-rate and temperature on the formability of Ti–6Al–4V alloy sheet

The constitutive model considering the strain-rate and temperature effects was presented by fitting the true stress–strain curves of Ti–6Al–4V alloy over a wide range of strain-rates (0.0005–0.05 s⁻¹) and temperatures (923–1023 K). The Forming Limit Curve (FLC) of Ti–6Al–4V alloy at 973 K was measured by conducting the hemispherical dome test with specimens of different widths. The forming limit prediction model of Ti–6Al–4V alloy, which takes strain-rate and temperature sensitivity into account, was predicted based on Marciniak and Kuczynski (M–K) theory along with Von Mises yield criterion. The comparison shows that the limit strain decreases with temperature lowering but strain-rate increasing. The comparison between theoretical analysis and experiment of FLC verifies the accuracy and reliability of the proposed methodology, which considers the strain-rate and temperature effects, to predict limit strains in the positive minor strain region of Forming Limit Diagram (FLD).     

Ti6Al4V基体及其改性试样的冲击磨损行为分析

在Ti6Al4V合金基表面制备了N+注入与氮化层、TiN膜及DLC膜,进行小载荷反复冲击,分析不同冲击周次下磨痕形貌及磨坑深度,比较磨损性能。结果表明疲劳磨损是反复冲击条件下实验试样的共同失效机制,主要表现为疲劳剥落。改性后试样的抗冲击磨损能力较基体材料均有提高,其中N+注入与氮化的"长程强化效应"使试样在较高冲击周次保持良好的抗磨性能;晶态结构TiN膜层由于较高的表层硬度,提高了试样的耐磨性,尤其是较低的冲击周次下;DLC膜的特殊非晶态结构,使其在整个冲击过程中具有小的磨损深度,高的失效周次。