注射成形制备多孔钛及其性能

以氯化钠作为造孔剂,利用金属注射成形(MIM)工艺制备多孔钛。研究烧结温度、造孔剂粒度和含量对多孔钛孔隙度、微观形貌和力学性能的影响。结果表明,随着烧结温度的升高,多孔钛的孔隙度逐渐下降而抗压强度和弹性模量逐渐升高;随着造孔剂粒度的减小,多孔钛的孔径也随之减小;随着造孔剂含量的增多,多孔钛的孔隙度逐渐增大;MIM多孔钛植入体的最佳烧结温度为1100～1200℃,NaCl的最优粒度为150～250μm。     

SLM制备径向梯度多孔钛/钽及其表征研究

利用增材制造技术制作仿天然骨的径向梯度多孔钛/钽骨科植入物具有广阔的前景。基于三周期极小曲面（triply minimal surfaces,TPMS）建模法建立了平均孔隙率为70%的圆柱型径向梯度孔隙结构,孔隙率由中轴线（90%）向圆周面（30%）逐渐降低。利用激光选区熔化(Selected Laser Melting, SLM)工艺制作径向梯度多孔钛/钽。光学显微镜,扫描电镜,Micro-CT检测结果共同显示,SLM径向梯度多孔钛/钽的孔隙结构与设计特征一致。SLM工艺制作的径向梯度多孔钛/钽的孔隙率分别为73.18%与68.18%。力学测试结果表明,梯度多孔钛/钽的弹性模量分别为3.96±0.19GPa与3.47±0.25GPa,抗压强度分别为90.83±3.35MPa与93.27±1.24MPa。梯度多孔钛/钽的弹性模量与抗压强度分别显著高于均匀多孔钛/钽（孔隙率为70.11%的均匀多孔钛弹性模量为2.34±0.48GPa,抗压强度为67.63±1.33MPa,孔隙率为65.39%的均匀多孔钽弹性模量为1.69±0.49GPa,抗压强度为68.56±0.41MPa）。体外细胞相容性实验证明,径向梯度多孔钛/钽均具有良好的生物相容性,适合间充质干细胞与肌肉细胞的粘附生长。SLM工艺制作的径向梯度多孔钛/钽比均匀多孔钛/钽具有与天然骨组织更相近的结构与性能,是理想的骨缺损修复替代物。     

钛合金变形Gyroid单元梯度多孔结构设计与分析

研究一种具有径向和轴向孔径梯度的变形Gyroid单元多孔结构参数化设计方法,采用激光选区熔化成形(selective laser melting, SLM)技术,制备出孔隙率为60%和75%的钛合金变形Gyroid单元梯度多孔结构样件。使用有限元法(finiteelementmethod,FEM)对4组梯度多孔支架模型及2组均质模型进行静力学仿真分析,对制备的钛合金梯度多孔样件进行力学性能测试,并与已测试过的均质样件进行力学性能对比分析。有限元计算结果与力学性能试验结果共同表明：变形Gyroid单元多孔结构力学性能随孔隙率的升高而降低,孔隙率相同时,径向梯度多孔支架力学性能优于均质多孔支架,更适用于皮质骨的骨缺损修复,轴向梯度多孔支架力学性能相比均质多孔支架有所减弱,更适用于松质骨。     

稀土CeO2增强型多孔钛的制备与性能

孔隙率对多孔钛的成骨性能影响较大,高的孔隙率更有利于骨组织的长入。但随着孔隙率的升高,其力学性能必然会急剧下降。因此,如何在保证多孔钛高孔隙率的前提下提高其力学性能,成为当前势必解决的难题。本研究采用浆料发泡法,通过在钛粉中加入不同含量的氧化铈,制备出高孔隙率的多孔钛。结果表明,多孔钛孔隙呈三维网络状,孔隙率为71.6%～73.5%,孔径主要分布在100～700μm,且孔壁上分布着微米级的微孔。当氧化铈的加入量为0.2%(质量分数,下同)时,多孔钛表现出最优的生物力学相容性,其杨氏模量为2.08GPa,抗压强度为60.19MPa。     

Study of metal injection molding of highly porous titanium by physical modeling and direct experiments

The prospects of metal injection molding (MIM) technique for manufacturing of highly porous titanium parts was studied by physical modeling, based on feedstock warm compaction experiments. The space holder method and typical MIM binder were used in all cases of the study. The influence of the starting powder (dehydrided and atomized) in feedstock on resulting properties of porous titanium was investigated. The size of space holder particles and space holder amount were adjusted to obtain porosity and pore size desired for medical implants application. NaCl and KCl were studied and compared as prospective space holder materials. The porous samples were characterized regarding their microstructure, uptake of interstitial contents and mechanical properties. For comparison, same investigations have been conducted on samples, which were prepared by established space holder technology based on cold isostatic pressing (CIP) and sintering. Finally, first direct MIM experiments and attempts of feedstock optimization were carried out. The peculiarities and problems of metal injection molding of highly porous titanium have been discussed.     

多孔钛合金拓扑优化设计及性能研究

为了得到良好力学性能和高渗透性的钛合金多孔结构,需要在多孔结构的孔隙率与其强度之间保持权衡。以人体膝关节胫骨假体为研究对象,首先,根据胫骨受力状态,采用拓扑优化设计并重构不同载荷工况下的抗压、抗剪单胞结构(TO-P1、TO-P2、TO-S1、TO-S2),与几种常见的基本单胞结构(BCC、FCC、RDC、DCC)进行研究比较;其次,通过对不同类型多孔钛合金进行压缩、剪切性能仿真,研究不同拓扑形态的多孔钛合金关于抗压、抗剪的力学性能,并采用SLM技术成型多孔钛合金压缩试件,验证了仿真分析的有效性;最后,选择力学性能较优的4种多孔钛合金进行渗透性分析。结果表明,TO-S2结构的抗压、抗剪力学性能和渗透性能最为出色,适合作为压剪载荷类植入物的多孔结构。     

Preparation and characterization of porous titanium using space-holder technique

Titanium-based porous materials can be used in structural applications and medical implants because of their excellent mechanical properties at elevated temperatures, good corrosion resistance and wonderful biocompatibility. However, most of the methods used to produce the po-rous metal can only give limited porosity and uncontrollable pore morphologies. In the present study, a newly developed method of powder metallurgy using the space-holder technique was used to fabricate porous titanium with controllable porosity. The morphological features and mechanical properties of the products were fully investigated. The results show that the porosity is in the range of 55%-75%, and the mean pore size, with an average sphericity of～0.72, is 600 μm The plateau stresses vary between 10 MPa and 35 MPa. As predicted by the Gibson-Ashby model, the plateau stress decreases with increasing porosity.     

钛合金变形Gyroid单元多孔结构设计与分析

三周期极小曲面（triply periodic minimal surfaces, TPMS）多孔结构研究广泛,但变形TPMS多孔结构研究较少,而变形TPMS多孔结构在一定方向上的力学性能存在潜在优势。研究Gyroid单元多孔结构的参数化设计方法,采用激光选区熔化（selective laser melting, SLM）技术制备出孔隙率为60%和75%的常规和变形Gyroid单元多孔钛合金样件。通过Micro-CT观察样件的形貌特征,内部连通性良好,未发现有明显的结构断裂和孔隙堵塞。采用Instron电子万能材料试验机进行力学压缩试验,结果表明：孔隙率为60%的变形Gyroid单元多孔结构的抗压强度相比常规Gyroid单元多孔结构增加49.3%,弹性模量增加63.5%;孔隙率为75%时抗压强度增加40.5%,弹性模量增加70.5%。研究结果表明,在相同孔隙率的情况下,长轴在压缩方向上的变形Gyroid单元结构具有更优的力学性能。     

生物可降解梯度多孔Fe-3Ag/HA复合材料的制备与性能研究

采用粉末冶金技术制备梯度多孔Fe-3Ag/HA复合材料,研究了造孔剂分布、烧结温度、HA含量对梯度多孔Fe-3Ag/HA复合材料的孔隙度和力学性能的影响。观察了梯度多孔Fe-3Ag/HA复合材料的显微组织及腐蚀后的微观形貌,测量了梯度多孔Fe-3Ag/HA复合材料的物相组成和耐腐蚀性能。结果表明,随着造孔剂和HA含量增加,烧结产物的孔隙度增加,抗压强度减少。提高造孔剂含量,梯度多孔Fe-3Ag/HA复合材料的耐腐蚀性能明显降低;提高HA含量,该复合物的耐腐蚀性能比梯度多孔Fe-3Ag略有增加,但是其腐蚀速率明显高于梯度多孔纯Fe试样。在模拟人工体液中浸泡3天后,梯度多孔Fe-3Ag/HA复合材料比梯度多孔Fe-3Ag合金表面沉积了更多的HA,这表明HA相有诱导模拟人工体液中Ca和P离子沉积的能力,与Fe基合金相比该复合材料具有更好的生物相容性。     

Fabrication of Entangled Tough Titanium Wires Materials and Influence on Three-Dimensional Structure and Properties

Pure titanium (Ti) TA1 fibers/wires with 0.08 and 0.15 mm diameters were processed by a novel method that combined press forming, vacuum sintering (≥10^?2 Pa), and heat treatment to fabricate entangled Ti wire materials (ETWMs). The ETWMs exhibited a total porosity ranging from 44.2 ± 0.1 to 81.2 ± 0.1% and an open porosity ranging from 43.5 ± 0.1 to 80.9 ± 0.1%. The processing parameters of fiber diameter, formation pressure, sintering temperature, and sintering time were applied to examine porous ETWM morphology, porosity, pore size, and mechanical properties. The importance of primary factors controlling porous structure and porosity in ETWMs were found to be fiber/wire diameter > formation pressure > sintering temperature > sintering time. Furthermore, Ti fiber diameter was shown to directly impact pore size. High formation pressure resulted in a fine, uniform porous structure with low porosity. Sintering at high temperature for long-time periods promoted sintering point formation, resulting in neck coarsening. This effect contributed to the characteristic mechanical properties observed in these ETWMs. If the sintering effect is considered in isolation, ETWMs fabricated with 0.08 mm diameter Ti fibers/wires and sintered at 1300 °C for 90 min achieved smaller, more uniform porous structures that further exhibited improved connections among fibers/wires and excellent mechanical properties.     

Nanospike surface-modified bionic porous titanium implant and in vitro osteogenic performance

This work aimed to prepare the nanospike surface-modified bionic porous titanium implants that feature favorable osteointegration performance and anti-bacterial functions. The implant was prepared using freeze casting, and nanospike surface-modification of the implant was performed using thermal oxidation. The pore morphology and size, mechanical properties, and osteogenic performance of the implants were analyzed and discussed. The results showed that when the volume ratio of titanium powder in slurry was set to be 10%, the porosity, pore diameter, compressive strength, and elastic modulus of the porous samples were (58.32±1.08)%, (126.17±18.64) μm, (58.51±20.38) MPa and (1.70±0.52) GPa, respectively. When the porous sample was sintered at a temperature of 1200 °C for 1 h, these values were (58.24±1.50)%, (124.16±13.64) μm, (54.77±27.55) MPa and (1.63±0.30) GPa, respectively. The nanospike surface-modified bionic porous titanium implants had favorable pore morphology and size, mechanical properties and osteointegration performance through technology optimization, and showed significant clinical application prospect.     

Porous nickel–titanium alloy prepared by gel-casting

To explore the preparation of porous nickel–titanium alloy with excellent properties, larger size and complex shape, the premixed powder of Ni and Ti with atomic ratio of 1:1 was shaped by gel-casting. The effects of solids loading and the content of dispersant on flow ability of nickel–titanium slurry and the mechanical properties of nickel–titanium sintered body were studied. The drying models under different solids loading were also discussed.The results show that the viscosity of slurries significantly increases with an increase in solids loading. After a proper process of drying, the green body with complex shape is obtained. The sintered body with porosity rate reaching up to49.5 % and compression strength reaching to 364.74 MPa could meet the basic demands of implant materials.     

多孔钛骨组织工程支架设计及孔结构表征

针对目前骨组织工程支架微孔结构难以准确设计制备的问题,提出了一种基于点云的参数化建模+3D打印新方法。通过提取cube(C)、diamond(D)、gyroid(G)3种结构的型面函数点云数据,完成对不同孔结构特征的参数化建模。通过对模型有限元力学分析,对不同孔结构特征的多孔钛骨组织支架进行力学设计与订制。借助激光选区熔融(SLM)3D打印技术,完成对不同孔特征的骨组织支架快速成型。对多孔钛骨组织支架进行了相关材料学表征,包括孔结构表征与力学性能测试。结果表明:参数化模型的快速成型制造,能够有效地设计制备钛合金骨组织工程支架的孔结构特性,且可有效设计订制支架的力学性能,从仿生的角度实现多孔钛合金骨组织工程支架生物学功能的设计优化。     

凝胶注模工艺制备医用多孔Ti-Co合金的性能

采用凝胶注模工艺制备含8%和12%Co(质量分数,下同)的多孔Ti-Co合金,研究获得均匀悬浮稳定浆料的分散剂加入量。采用扫描电子显微镜、X射线衍射、压缩和三点弯曲试验分别对多孔Ti-Co合金的显微结构和力学性能进行了测试和分析。结果表明,加入1%分散剂可获得分散效果最佳的悬浮浆料,所制备多孔Ti-Co合金的孔隙率在50%左右,孔隙呈三维通孔结构。与多孔纯钛相比,添加Co元素明显提高了多孔Ti的力学性能,其中压缩强度在68～378MPa之间,抗弯曲强度在53.68～169.17MPa之间,弹性模量在7～21GPa之间。固相体积分数为33%,在1100℃下烧结的多孔Ti-8%Co合金由于与成人骨的力学相容性最好,适合作为医用植入材料。     

NaCl-induced accelerated oxidation of a titanium alloy

The effect of a surface deposit of NaCl on the oxidation characteristics of a high-temperature titanium alloy was studied in the temperature range of 400–600°C. The influence of the water vapor content in the oxidizing environment was examined in the light of an existing electrochemical mechanism proposed for the hot-salt stress-corrosion-cracking phenomenon found in titanium alloys. It was established that the NaCl deposit increased the oxidation rate by a factor of 100 for hygrometry levels of 10 ppm or higher. Further, there exists a hygrometry threshold between 10 and 5×10^–3 ppm below which the NaCl-induced accelerated oxidation decreases with decreasing hygrometry level. Electron microprobe analysis suggests that the titanium matrix reacts with chlorine before forming rutile.The authors are indebted to the Société Nationale d'Etudes et de Construction de Moteurs d'Aviation (S.N.E.C.M.A.) for its financial support of this study.     

凝胶注模成型制备微多孔氮化硅陶瓷

采用凝胶注模法,在无其它添加剂的条件下,通过提高单体含量,成功制备出高性能微多孔氮化硅陶瓷,陶瓷抗弯强度高达137 MPa以上,气孔率高达50%以上,孔中径小于1 μm.结果表明:随着有机单体含量的增加,氮化硅微多孔陶瓷气孔率单调增加;随着固含量的增大,氮化硅微多孔陶瓷气孔率单调下降,抗弯强度先上升然后又下降,固含量有一优化值,此时陶瓷体抗弯强度最大;随着烧结温度的增加,氮化硅陶瓷强度单调增加,而气孔率单调下降.     

Porosity and mechanical properties of porous titanium fabricated by gelcasting

Porous Ti compacts with large size and complex shape for biomedical applications were fabricated in the porosity range from 40.5% to 53.8% by controlling gelcasting parameters and sintering conditions. The experimental results show that the total porosity and open porosity of porous titanium compacts gelcast from the Ti slurry with 34 vol.% solid loading and sintered at 1100℃ for 1.5 h are 46.5% and 40.7%, respectively, and the mechanical properties are as follows： compressive strength 158.6 MPa and Young＇s modulus 8.5 GPa, which are similar to those of human cortical bone and appropriate for implanting purpose.     

Highly porous open cellular TiAl-based intermetallics fabricated by thermal explosion with space holder process

High porosity TiAl-based intermetallics were prepared through thermal explosion (TE) from Ti–50Al at.% powders with NaCl as soluble template. The results showed that the space holder particles of NaCl were removed completely in green compacts, and porous Ti–Al materials were synthesized via a low-energy consumption method of TE at a temperature of 600 °C. TiAl was evolved as dominant phase in sintered materials at 1100 °C. With adding 80 vol.% NaCl to Ti–50Al at.% powders, the open porosity was significantly elevated up to 84%. Moreover, the porous materials exhibited a bimodal pore size distribution: large pores (200–500 μm) replicating NaCl particles and small pores (<50 μm) embedded in pore walls. The interconnected small and large pores make open cellular porous TiAl materials, which prescribe them promising for a wide range of applications in separation, heat insulation and catalysis.     

Processing and characterization of porous Ti2AlC with controlled porosity and pore size

In this work, we demonstrate a simple and inexpensive way to fabricate porous Ti₂AlC, one of the best studied materials from the MAX phase family, with controlled porosity and pore size. This was achieved by using NaCl as the pore former, which was dissolved after cold pressing but before pressureless sintering at 1400 °C. Porous Ti₂AlC with samples a volume fraction of porosity ranging from ～10 to ～71 vol.% and different pore size ranges, i.e. 42–83, 77–276 and 167–545 μm, were successfully fabricated. Fabricated samples were systematically characterized to determine their phase composition, morphology and porosity. Room temperature elastic moduli, compressive strength and thermal conductivity were determined as a function of porosity and/or pore size. For comparison, several samples pressureless-sintered without NaCl pore former, or fabricated by spark plasma sintering, were also characterized. The effects of porosity and/or pore size on the room temperature elastic moduli, compressive strength and thermal conductivity of porous Ti₂AlC are reported and discussed in this work. It follows that porosity can be a useful microstructural parameter to tune mechanical and thermal properties of Ti₂AlC.     

基于TPMS结构的多孔钛制备与表征

多孔钛因具有与人体骨组织相近的弹性模量和允许骨长入的孔隙结构而备受关注。其孔隙结构特征不仅影响骨长入效果,而且决定了多孔钛的力学性能。通过三周期极小曲面(triply periodic minimal surfaces,TPMS)隐函数参数的精确调控可以构建出理想的孔隙结构模型。本实验针对TPMS模型中常用的G单元模型,研究了G单元模型隐函数参数对孔隙率、孔径、杆径等孔隙结构特征的影响规律,设计出了孔隙率约为77%,孔径分别为300(G300)、500(G500)微米的均质孔隙结构;模仿自然长骨径向梯度结构模型,构建了相应的G单元仿生梯度孔隙结构。采用选区激光熔化(SLM)增材制造技术制备了相应的多孔钛样件,利用数字显微镜和扫描电镜观测多孔钛的孔隙结构特征,发现SLM多孔钛实测孔隙率低于设计孔隙率,实测孔径小于设计值,实测杆径大于设计值。力学性能检测结果显示,G300和G500多孔钛弹性模量分别为2.04和3.12GPa,其最大抗压强度分别为63.5和103.5MPa,梯度孔隙结构多孔钛弹性模量和最大抗压强度分别为6.3 GPa和186.9 MPa。研究结果表明,G单元梯度孔隙结构多孔钛是一种理想的承重部位骨缺损修复体。