碳纤维增强超高温陶瓷基复合材料的多相反应制备与抗烧蚀性能

为提高C/C复合材料在2000℃以上有氧环境中的抗氧化烧蚀性能,本研究采用ZrB_(2)浆料浸渍、ZrC-SiC前驱体浸渍裂解与Si-Zr10共晶合金反应熔渗复合工艺制备了C/C-SiC-ZrB_(2)-ZrC复合材料,细致研究了复合材料在熔渗过程中的基体微观结构演变机理及其力学性能和抗烧蚀性能。结果表明,在反应熔渗结束后的降温阶段,部分ZrC陶瓷与残余Si熔体通过原位固-液反应转化为ZrSi_(2)和SiC,生成的亚微米级SiC颗粒均匀镶嵌于ZrC-ZrSi_(2)二元混合物中,最终形成ZrC-ZrSi_(2)-SiC三相混合微区。制备的C/C-SiC-ZrB_(2)-ZrC复合材料密度为3.18 g/cm^(3),开孔率为2.77%,其弯曲强度和弯曲模量分别为121.46±13.77 MPa和21.78±5.56 GPa。在其断口处能观察到较长且较多的单丝纤维拔出以及明显的界面脱黏,这表明复合材料的失效方式为韧性断裂。经2000℃,300 s的大气等离子体烧蚀,复合材料表现出优良的抗超高温烧蚀性能(质量烧蚀率和线烧蚀率分别为1.37×10^(-3)g/s和3.43×10^(-3)mm/s)。分析发现,烧蚀中心形成了独特的双层梯度氧化物结构,底部的ZrO2层可阻挡外部热量向材料内部基体的传递,表面由固相ZrO2颗粒和液相富SiO2的SiO2-ZrO2熔体组成的复合氧化层既能抵御高速气流的机械冲刷,又能抑制氧气向内部基体的扩散。

Effects of Xinfeng capsule on pulmonary function based on treg-mediated notch pathway in a rat model of adjuvant arthritis

OBJECTIVE:To observe the impact of xinfeng xapsule(XFC) on pulmonary function in a rat model of adjuvant arthritis(AA) and to investigate the mechanism of action.METHODS:Forty rats were randomly divided into four groups of ten:normal control(NC);model control(MC);tripterygium glycosides tablet(TPT);and xinfeng capsule(XFC).Except for the NC group,AA was induced in all rats by intracutaneous injection of 0.1 mL Freund's complete adjuvant in the right paw on the 19th day.NC and MC groups were given(0.9%) physiological saline.The TPT and XFC groups were given TPT(10 mg/kg) and XFC(1.2 g/kg),respectively.Thirty days after administration,changes in paw edema(E),the arthritis index(AI),pulmonary function,levels of regulatory T-cells(Treg),ultrastructure of lung tissue,and expression of Notch receptors and ligands in lung tissue were observed.RESULTS:In the MC group,E and the AI were increased and pulmonary function significantly decreased;the structure of alveolar type-II cells was damaged;ratios of Treg in peripheral blood were reduced;and expression of Notch receptors such as Notch3 and Notch4 and ligands such as Delta1 in lung tissue were significantly increased whereas expression of Notch1,Jagged1 and Jagged2 were significantly decreased.After intervention with XFC,E and the AI were decreased;pulmonary function was enhanced;the structure of alveolar type-II cells was improved;and expression of Treg,Notch1,Jagged1,Jagged2 was elevated,whereas that of Notch3,Notch4 and Delta1 was reduced.CONCLUSION:XFC can not only inhibit E and the AI and improve joint symptoms,it can also improve pulmonary function and reduce inflammation in lung tissue.These actions could be carried out through increases in the expression of Treg,Notch receptors(Notch1) and ligands(Jagged1,Jagged2),and reductions in the expression of Notch3,Notch4 and Delta1.These phenomena would reduce the deposition of immune complexes and the inflammatory response in lung tissue,thereby improving joint symptoms and pulmonary function.

Use of Xinfeng capsule to treat abarticular pathologic changes in patients with rheumatoid arthritis

OBJECTIVE: To observe the influence of Xinfengcapsule(XFC) on abarticular pathologic changes(APCs) and other indices of patients with rheumatoid arthritis(RA) and explore the mechanism of action of XFC in improving such changes.METHODS: Three-hundred RA patients were divided randomly into a treatment group(n=150) and control group(n=150). A normal control(NC)group(n=90) was also created. Changes in cardiac function, pulmonary function, anemia indices and platelet parameters of RA patients were measured.Curative effects of the two groups were compared,and comparison carried out with the NC group.RESULTS: In 300 RA patients, late diastolic peak flow velocity(A peak) was much higher(P<0.01)and early diastolic peak flow velocity(E peak), E/A,and left ventricular fraction shortening much lower(P<0.01) than those in the NC group. Vital capacity(VC), forced vital capacity in one second, forced vital capacity(FVC), maximal voluntary ventilation(MVV), maximal expiratory flow in 50% of VC(FEF50) and FEF75 were lowered remarkably(P<0.05 or P<0.01). Platelet count(PLT), plateletcrit(PCT) and mean platelet volume(MPV) increased markedly(P<0.05 or P<0.01), and hemoglobin(Hb)level decreased significantly(P<0.05). After XFC treatment, the A peak and PLT and PCT were much lower(P<0.05), and E/A and the number of red blood cells as well as Hb level were much higher(P<0.05), as were FVC, MVV and FEF50(P<0.05 or P<0.01), in the treatment group than those in the NC group. Total score of pain and swelling in joints,uric-acid level and high-sensitivity C-reactive protein level were much lower, and superoxide dismutase level as well as the number of CD4 +CD25+ regulation T cells(Treg) and CD4+CD25+CD127- Treg were much higher(P<0.05 or P<0.01)in the treatment group than those in the NC group.CONCLUSION: RA patients with pathologic changes in joints also suffer from lower cardiac and pulmonary functions and from parameters of anemia and platelet factors. XFC can improve the symptoms of RA patients, ameliorate their cardiac and pulmonary functions and reduce the parameters of anemia and platelet factors. XFC lowers the immune inflammatory reaction to improve APCs in RA patients.

Effect of Xinfeng capsule on pulmonary function in a adjuvant arthritis rat model

OBjECTIVE:To observe the relationship between reduced pulmonary function and regulatory T cells(Tregs)and helper T cells(Th)1/Th2 drift in a rat model of adjuvant arthritis(AA),and to study the impact of Xinfeng capsule(XFC)on pulmonary function and investigate the mechanism of action.METHODS:Forty rats were randomly divided into normal control group(NC),model control group(MC),Tripterygium glycosides tablet group(TPT),and XFC group,with 10 in each.Except for the NCgroup,AA was induced in all rats by intracutaneous injection of 0.1 mL Freund's complete adjuvant in the right paw.On the 19th day after modeling,the NC and MC groups were given physiological saline(0.9%),while the TPT and XFC groups were given TPT(10 mg/kg)and XFC(2.4 g/kg),once daily,respectively.Thirty days after administration,changes in paw swelling,arthritis index(AI),pulmonary function,levels of serumγ-interferon(IFN-γ)and interleukin(IL)-4,Tregs in peripheral blood,and IFN-γ,IL-4,Forkhead box transcription factor 3(FoxP3)in lung tissue were observed by enzyme-linked immunosorbent assay,flow cytometry,polymerase chain reaction,and western blot.RESULTS:Compared with the NC group,paw swelling,AI,IFN-γ,and Th1/Th2 were increased,and pulmonary function parameters,IL-4,FoxP3 were decreased significantly in the MC group(P<0.05 or P<0.01).Pulmonary function parameters,Treg,IL-4,FoxP3(and mRNA)were higher,and paw swelling,AI,and IFN-γ(and mRNA)were lower in the XFC group than those in the MC group.The XFC group was also much better than theTPT group in improving pulmonary function,FoxP3 mRNA,IFN-γ,IL-4,Th1/Th2,and IL-10(P<0.05 or P<0.01).CONCLUSION:Xinfeng capsule can improve pulmonary function by regulating the levels of Tregs,inhibiting the activation of Th1 to Th2 cells,inducing drift,maintaining cell immune suppression,correcting the imbalance of Th1/Th2,and reducing inflammatory mediators.

Corrosion Resistance of Ti_3Al/BN Abradable Seal Coating

Ti–Al mixed powder（Ti：Al = 3：1 in atomic ratio） and Ti3 Al intermetallic alloy powder mechanically clad hexagonal BN to fabricate Ti Al/BN and Ti3Al/BN composite powders. The corresponding porous abradable seal coatings（named as TAC-1 and TAC-2, respectively） were deposited using vacuum plasma spray（VPS） technology, and their corrosion behavior was studied via salt spray corrosion and electrochemical tests. Phase compositions and microstructures of these coatings before and after corrosion were characterized by X-ray diffraction（XRD） and scanning electron microscopy（SEM） facilitated with energy dispersive X-ray spectrometer（EDS）. The results showed that spontaneous passivation of TAC-1 and TAC-2 granted the coatings excellent corrosion resistance than that of commercial Al/BN coating. Additionally, TAC-2 exhibited higher corrosion potential（Ecorr） and breakdown potential（Ebp） but a lower corrosion current density（icorr） than TAC-1. A small quantity of the corrosion product（Al（OH）3and Al O） could be detected on the surface of TAC-1, while no corrosion product appeared in TAC-2. The non-uniform elements distribution in the metal matrix of TAC-1 resulted in localized corrosion and relatively poor corrosion resistance compared to TAC-2.

Wear Behavior of a NiCr/AgVO_3 Self-Lubricating Composite

NiCr/AgVO3 self-lubricating composite was prepared by powder cold-pressed method with the NiCr alloy as the matrix and 10 wt.% additive of AgVO3 as solid lubricant. The AgVO3 additive powder was synthesized by the precipitation method which exhibits a melting point of 460℃. Microstructure, phase composition and thermal properties of the AgVO3 powder, as well as the composite of NiCr/AgVO3 were analyzed using scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and differential scanning calorimeter （DSC）. The friction and wear behavior of the specimens from room temperature （R.T.） to 800℃ was evaluated using a ball-on-disk tribometer and 3D white light interference （WLI）. The results showed that the friction coefficient of this material under atmosphere decreases with temperature increasing from R.T. to 800 ~C. However, the wear rate firstly increases from R.T. to 200℃, almost remains stable from 200℃ to 600℃, and then decreases with further increasing the temperature up to 800 ℃. It is also found that the prepared composite materials show a better frictional behavior than NiCr alloy over the whole range of temperatures, which is mainly attributed to solid lubrication of AgVO3 exhibiting a lamella-slip structure at temperatures below 460℃ and forms liquid-film at elevated temperatures above the melting point.