Experimental Study on Titanium Alloy Cutting Property and Wear Mechanism with Circular-arc Milling Cutters

Titanium alloy has been applied in the field of aerospace manufacturing for its high specific strength and hardness.Nonetheless,these properties also cause general problems in the machining,such as processing inefficiency,serious wear,poor workpiece face quality,etc.Aiming at the above problems,this paper carried out a comparative experimental study on titanium alloy milling based on the CAMCand BEMC.The variation law of cutting force and wear morphology of the two tools were obtained,and the wear mechanism and the effect of wear on machining quality were analyzed.The conclusion is that in contrast with BEMC,under the action of cutting thickness thinning mechanism,the force of CAMC was less,and its fluctuation was more stable.The flank wear was uniform and near the cutting edge,and the wear rate was slower.In the early period,the wear mechanism of CAMC was mainly adhesion.Gradually,oxidative wear also occurred with milling.Furthermore,the surface residual height of CAMC was lower.There is no obvious peak and trough accompanied by fewer surface defects.

一种简易的硫辅助方法制备多孔蜂窝状的铁超小原子簇和单原子Fe/g-C3N4

超小原子簇和单原子分散的活性位点(USCAD)催化剂由于其高原子利用率、高活性、高稳定性等优点,成为多相催化领域一个新兴的研究热点.USCAD通常由载体缺陷、配体和分子筛或金属有机框架的孔道和笼锚定.而制备高密度的USCAD催化剂需要载体上有足够的锚定位点.石墨相氮化碳(g-C3N4)具有高稳定性、高密度且均匀分散的氮原子,是制备USCAD催化剂的理想载体.但是传统热解法制备的金属/g-C3N4催化剂通常为块体结构,会导致金属物种被严重包覆,进而导致催化活性下降.加入固体模板可以制备得到多孔金属g-C3N4催化剂,但是后续复杂的除模板过程制约了其实际应用.因此,开发一种简易的无模板方法制备USCAD金属/g-C3N4催化剂具有重要意义.本工作开发了一种简易的硫辅助热解法制备得到蜂窝状结构的高密度(Fe载量为17.7wt%)USCADFe/g-C3N4催化剂.其多孔蜂窝状结构使催化剂能够暴露更多的USCADFe活性位点,增加了活性位点与反应物的可接近性.通过球差电镜和同步辐射X射线吸收技术证明了Fe物种的分散形式.硫辅助热解法只需要在热解铁盐/三聚氰胺前驱体中加入适量的硫源即可得到蜂窝状的USCAD Fe/g-C3N4催化剂.硫元素作为一种"牺牲载体"通过与铁离子配位促进铁物种在前驱体混合物中分散,经过高温煅烧后以SO2的形式释放而不残留在催化剂中,免除了后续的除模板过程.通过TG-MS,XPS和IR等手段证明了硫元素在热解过程中的状态变化.这种硫辅助热解法表现出非常好的普适性,改变硫源种类(硫脲、硫粉、硫氰酸铵)和铁盐种类都可以得到具有蜂窝状孔道结构的USCADFe/g-C3N4催化剂.将催化剂应用于高级氧化过程可以高效降解各种有机污染物(苯酚、亚甲基蓝、亚甲基橙、罗丹明B),催化剂性能远远优于文献报道的其它Fe基催化剂和传统热解法制备的Fe/g-C3N4催化剂.该硫辅助热解法为无模板法制备纳米多孔USCAD金属/g-C3N4催化剂开辟了一条简易可行的途径.

Nonsurgical orthodontic treatment for an adult with skeletal open bite, class III malocclusion and posterior crossbite: A case report

Class III malocclusion associated with skeletal anterior open bite pattern in adults can be a challenging orthodontic problem, especially for the nonsurgical treatment. Conventionally, several treatment alternatives are available such as tooth extraction, molar intrusion, and absolute anchorage system or orthognathic surgical correction. Although correction with surgery may be the most effective and stable way, many patients refused surgical treatment plan because of the costs and traumas it may bring. We reported a nonsurgical orthopedic treatment of 22-year-old male with severe skeletal anterior open bite, dental Class III malocclusion, posterior crossbite and a high mandibular plane angle. The patient refused surgery and extraction. So we formulated a treatment plan consisting of using rapid palatal expansion appliance to expand the maxilla, standard edgewise brackets to align the teeth, Class III elastics to correct the canines, premolars, and molars relationship, reverse curve of the nickel-titanium wire combined with anterior vertical elastics to intrude molars and correct open bite. In this case, without suffering of surgery, the posterior crossbite was ideally corrected, and ideal overjet and overbite relationships and functional occlusion were all achieved. The patient obtained satisfactory occlusal as well as functional and stable results.

Core-shell nanostructure of single-wall carbon nanotubes and covalent organic frameworks for supercapacitors

Covalent organic frameworks （COFs） were nano-coated onto single-walled carbon nanotubes （SWCNTs） by in situ polymerization of TpPa-COFs together with SWCNTs under solvotherma] conditions. At the molecular level, the COF/SWCNT interface can be efficiently controlled. Thus, the TpPa-COF-SWCNTs nano-hybrid wire, which combines the excellent conductivity of SWCNTs and the high porosity and good redox activity of TpPa-COFs, was employed as active electrode materials for supercapacitors. The strategy reported in this work can give guidance for the design of other similar COF-based electrodes, and hold a great potential in energy storages

A comparative study of the osteogenic performance between the hierarchical micro/submicro-textured 3D-printed Ti6Al4V surface and the SLA surface

Three-dimensional(3D)printed titanium and its alloys have broad application prospect in the field of biomedical implant materials,although the biological performance of the original surface should be improved.Learning from the development experience of conventional titanium implants,to construct a hierarchical hybrid topological surface is the future direction of efforts.Since the original 3D-printed(3D hereafter)Ti6Al4V surface inherently has micron-scale features,in the present study,we introduced submicron-scale pits on the original surface by acid etching to obtain a hierarchical micro/submicro-textured surface.The characteristic and biological performance of the 3D-printed and acid-etched(3DA hereafter)surface were evaluated in vitro and in vivo,compared with the conventional sandblasted,large-grit,acid-etched(SLA hereafter)surface.Our results suggested the adhesion,proliferation and osteogenic differentiation of bone marrow derived mesenchymal stromal cells(BMSCs),as well as the in vivo osseointegration on 3DA surfaces were significantly improved.However,the overall osteogenic performance of the 3DA surface was not as good as the conventional SLA surface.

The synergistic effect of 3D-printed microscale roughness surface and nanoscale feature on enhancing osteogenic differentiation and rapid osseointegration

Personalized precision therapy and rapid osseointegration are the main development directions of dental implants.3 D printing is a vital advanced manufacturing technology for personalized precision therapy.However,the osteogenesis of the 3 D printed Ti6 Al4 V implants is unsatisfactory.From the bionic perspective,the hierarchical micro/nano-topography can mimic the microenvironment of the multilevel structure of natural bone tissue and may endow the implant surface with superior bioactivity.In the present study,the hierarchical micro/nano-topography was successfully fabricated by construction the nanoscale feature on 3 D printed microscale roughness surface of 3 D-printed Ti6 Al4 V implants by alkali-heat treatment and hydrothermal treatment.Then the cell biological responses in vitro and osseointegration performance in vivo were systematically evaluated.The hierarchical micro/nano-topography evidently increased the roughness,improved the hydrophilicity and accelerated the hydroxyapatite deposition and mineralization,which significantly enhanced the adhesion,differentiation and extracellular matrix mineralization of bone marrow derived mesenchymal stromal cells(BMSCs).Most importantly,the hierarchical micro/nano-topography on 3 D-printed implants facilitated the new bone formation and rapid osseointegration in vivo.Our study suggested that 3 D-printed implant with micro/nano-topography may be a promising candidate to be applied in orthopedic field to meet the need of customized therapy and rapid osseointegration.

Calcium silicate bioactive ceramics induce osteogenesis through oncostatin M

Immune reactions are a key factor in determining the destiny of bone substitute materials after implantation.Macrophages,the most vital factor in the immune response affecting implants,are critical in bone formation,as well as bone biomaterial-mediated bone repair.Therefore,it is critical to design materials with osteoimmunomodulatory properties to reduce host-to-material inflammatory responses by inducing macrophage polarization.Our previous study showed that calcium silicate(CS)bioceramics could significantly promote osteogenesis.Herein,we further investigated the effects of CS on the behavior of macrophages and how macrophages regulated osteogenesis.Under CS extract stimulation,the macrophage phenotype was converted to the M2 extreme.Stimulation by a macrophage-conditioned medium that was pretreated by CS extracts resulted in a significant enhancement of osteogenic differentiation of bone marrow mesenchymal stem cells(BMSCs),indicating the important role of macrophage polarization in biomaterial-induced osteogenesis.Mechanistically,oncostatin M(OSM)in the macrophage-conditioned medium promoted osteogenic differentiation of BMSCs through the ERK1/2 and JAK3 pathways.This in vivo study further demonstrated that CS bioceramics could stimulate osteogenesis better thanβ-TCP implants by accelerating new bone formation at defective sites in the femur.These findings improve our understanding of immune modulation of CS bioactive ceramics and facilitate strategies to improve the in vitro osteogenesis capability of bone substitute materials.

A novel channel-wall engineering strategy for two-dimensional cationic covalent organic frameworks:Microwave-assisted anion exchange and enhanced carbon dioxide capture

A novel channel-wall engineering strategy of the porous materials cationic covalent organic frameworks(COFs)is established based on rapid microwave-assisted anion exchange reaction and utilized to prepare a set of new COFs.Due to the interaction between the carbon dioxide(C02)and the acetate anion,the resulting SJTU-COF-AcO shows greatly enhanced carbon dioxide capacity up to 1.7 times of the pristine COF.The effect of the counteranions to CO2 capacity in the cationic COFs is investigated for the first time,which demonstrates that our channel-wall engineering strategy is a promising way to tailor the property of COFs for high CO2 capacity.