工业炭黑加入量对复相结合碳化硅耐火材料性能的影响

为研究工业炭黑对复相结合碳化硅耐火材料性能的影响,以碳化硅颗粒(3~1、1~0.088 mm)与细粉(<0.088 mm)、硅粉(<0.088 mm)、工业炭黑(牌号N990)、SiO2微粉(d_(50)=0.26μm)和ρ-Al_(2)O_(3)微粉(d_(50)=6.0μm)等为主要原料,采用预制浇注成型,在氮气气氛中于1400℃热处理,制备了复相结合碳化硅试样。研究了N990加入量(w)分别为2.5%、3.0%、3.5%时试样的物理性能、物相组成与显微结构。结果表明:1)随N990加入量的增加,泥料的流动性改善,脱模强度及干燥强度提高。2)随N990加入量的增加,氮化后试样的显气孔率升高,体积密度和抗折强度均有下降,试样中游离C含量升高,α-Si_(3)N_(4)减少。3)随N990加入量的增加,因炭黑颗粒团聚的概率增加,氮化处理后试样显微结构的均匀性变差。Si-C和Si-N发生反应烧结,除连续的絮状基质外,局部还出现了致密孤岛状的β-SiC或O′-SiAlON相。综合分析认为,炭黑加入量(w)为3.0%的试样更能满足材料制备和性能的需要。

ρ-Al_(2)O_(3)复合铝酸钙水泥烧结助剂对多孔碳化硅陶瓷性能的影响

为了提高多孔碳化硅陶瓷的性能,以绿碳化硅为主原料,石墨为造孔剂,用铝酸钙水泥(CAC)和水合氧化铝(ρ-Al_(2)O_(3))配制成复合烧结助剂(ρ-Al_(2)O_(3)-CAC),经1450℃保温3 h,制备多孔碳化硅陶瓷。研究了ρ-Al_(2)O_(3)-CAC加入量(加入质量分数为2.5%~20%)对多孔碳化硅陶瓷物相组成、显微结构和性能的影响。结果表明:1)ρ-Al_(2)O_(3)-CAC能促进碳化硅的氧化,并与碳化硅氧化生成的SiO_(2)发生原位反应,形成玻璃-莫来石复相结合,同时还在结合相中引入气泡,气泡会随ρ-Al_(2)O_(3)-CAC加入量的增加而长大;2)当ρ-Al_(2)O_(3)-CAC的加入量为12.5%(w)时,制得的多孔碳化硅陶瓷综合性能最佳,其显气孔率为39.1%,室温弯曲强度为39.3 MPa,透气度为26.74 m^(3)·h^(-1)·kPa^(-1)·m^(-2),抗热震性最优。

Sialon结合SiC复相材料的高温氧化行为

利用X射线衍射仪、扫描电子显微镜、压汞仪和热重分析仪等方法,在1100～1500℃范围内研究了Sialon结合SiC复相材料的高温抗氧化行为。结果表明:(1)随氧化温度升高,由于氧化致密层的形成,试样氧化增重速率降低,在1500℃氧化试样由于气泡破裂严重,氧化面积增大使氧化增重率有所提高;(2)随氧化温度升高出现氧化钝化现象,使得Sialon结合SiC复相材料表现出很好的高温抗氧化性能;(3)高温氧化使得Sialon结合SiC复相材料常温抗压强度比氧化前提高;随氧化温度升高,氧化膜表面形成较多气泡和开口空洞,使耐压强度呈下降趋势。

添加多晶硅废料制备SiC/Si_3N_4复相结合SiC耐火材料

以碳化硅、多晶硅废料、金属硅粉为原料,纸浆废液为结合剂,采用反应烧结工艺制备SiC/Si3N4复相结合SiC耐火材料。运用热力学分析了利用多晶硅废料代替部分工业金属硅粉和碳化硅细粉制备SiC/Si3N4复相结合SiC耐火材料的理论可行性。系统地分析了单质硅氮化机理,提出Si首先与N2中的微量氧反应形成气态SiO,至体系氧分压降至P(O2)/Pθ<1×10-18.9,Si直接氮化。研究了多晶硅废料对材料物相组成和微观结构的影响。结果表明:利用多晶硅废料制备的SiC/Si3N4复相结合SiC耐火材料性能优异;多晶硅废料的添加使反应生成的结合相由原先单一的Si3N4变为Si3N4和β-SiC,两结合相发挥各自的性能优势;多晶硅废料中的硅粉粒径小,活性大,与工业金属硅粉共存时能发生逐级氮化作用,增加了纤维状Si3N4含量,优化了材料结构。

Si_3N_4结合SiC复相材料的高温氧化行为

利用X-射线衍射仪、扫描电子显微镜、压汞仪和热重分析仪等手段,在1 100～1 500℃范围内研究Si3N4结合SiC复相材料的高温抗氧化行为。结果表明:随氧化温度升高,由于氧化致密层的形成,试样氧化质量增加速率降低;随氧化温度升高出现氧化钝化现象,使Si3N4结合SiC复相材料表现出很好的高温抗氧化性能;高温氧化使Si3N4结合SiC复相材料显气孔率降低,常温抗压强度升高,由于氧化层表面裂纹形成使氧化后试样的常温耐压强度随氧化温度升高而降低。

复元胶囊对兔膝骨关节炎软骨中胰岛素样生长因子-I及胰岛素样生长因子结合蛋白3表达的影响

目的观察复元胶囊对兔膝骨关节炎软骨中胰岛素样生长因子-I(IGF-I)、胰岛素样生长因子结合蛋白3(IGFBP3)表达的影响。方法采用右后肢伸直石膏固定法造模,将44只雌雄各半新西兰大白兔随机分为正常组、模型组、盐酸氨基葡萄糖组、复元胶囊低、中、高剂量组。正常组4只,其余各组8只。各药物组每天灌胃1次,持续6 w。免疫组织化学法检测IGF-I、IGFBP3表达。结果模型组IGF-I、IGFBP3表达积分明显高于正常组(P<0.01);复元胶囊各剂量组与模型组比较,IGF-I表达积分不同程度升高(P<0.05),而IGFBP3表达积分不同程度降低(P<0.01),高剂量组显著。结论复元胶囊具有防治膝骨关节炎作用,其机制可能与调节IGF-I、IGFBP3表达水平有关。

Al2O3-SiO2陶瓷纤维对堇青石结合碳化硅复相材料性能的影响

以碳化硅颗粒为骨料,以滑石粉、苏州土和α-Al_2O_3粉为基质并适量加入Al_2O_3-SiO_2陶瓷纤维,通过原位反应合成法制备了堇青石结合碳化硅复相材料,研究了纤维加入量(质量分数0~10%)对该复相材料性能的影响。结果表明:该复相材料的主晶相为碳化硅和堇青石,当Al_2O_3-SiO_2陶瓷纤维质量分数小于8%时,纤维与基体结合紧密,分散较好;随纤维加入量的增加,复相材料的抗折强度先增大后降低,抗热震性能则逐渐提高;当纤维质量分数为8%时,复相材料的抗折强度最大,达33 MPa,其综合性能良好。

腹针结合胃复春片治疗脾胃虚弱型慢性萎缩性胃炎30例

目的观察腹针结合胃复春片治疗脾胃虚弱型慢性萎缩性胃炎的临床疗效。方法将符合参与本次研究的60例患者按随机数字表法随机的分为对照组30例(单纯的予以胃复春片口服治疗方案)、治疗组30例(单纯的予以胃复春片口服治疗方案基础上给予腹针治疗方案),治疗8周后(共治疗4个疗程),观察两组主要症状积分及两组临床疗效比较。结果两组治疗后主要症状积分比较:治疗前,两组主要症状积分比较,差异无统计学意义(P>0.05);治疗后,治疗组主要症状积分低于对照组,差异有统计学意义(P<0.05)。两组临床疗效比较:治疗组总有效率(93.33%)明显高于对照组治疗总有效率(63.33%),且两组比较差异有统计学意义(P<0.05)。腹针结合胃复春片治疗脾胃虚弱型慢性萎缩性胃炎的临床疗效明显优于单纯的予以胃复春片治疗方案。结论腹针结合胃复春片治疗脾胃虚弱型慢性萎缩性胃炎的临床疗效显著、确切,值得在临床进一步推广应用。

Design and evaluation of UHPP steel bridge deck pavement for high-temperature and rainy regions

To enhance the serviceability of steel bridge deck pavement(SBDP)in high-temperature and rainy regions,a concept of rigid bottom and flexible top was summarized using engineering practices,which led to the proposal of a three-layer ultra-high-performance pavement(UHPP).The high-temperature rutting resistance and wet-weather skid resistance of UHPP were evaluated through composite structure tests.The internal temperature distribution within the pavement under typical high-temperature conditions was analyzed using a temperature field model.Additionally,a temperature-stress coupling model was employed to investigate the key load positions and stress response characteristics of the UHPP.The results indicate that compared with the traditional guss asphalt+stone mastic asphalt structure,the dynamic stability of the UHPP composite structure can be improved by up to 20.4%.Even under cyclic loading,UHPP still exhibits superior surface skid resistance compared to two traditional SBDPs.The thickness composition of UHPP significantly impacts its rutting resistance and skid resistance.UHPP exhibits relatively low tensile stress but higher shear stress levels,with the highest shear stress occurring between the UHPP and the steel plate.This suggests that the potential risk of damage for UHPP primarily lies within the interlayer of the pavement.Based on engineering examples,introducing interlayer gravel and optimizing the amount of bonding layer are advised to ensure that UHPP possesses sufficient interlayer shear resistance.

In-situ Micro-CT analysis of deformation behavior in sandwich-structured meta-stable beta Ti−35Nb alloy

Beta Ti−35Nb sandwich-structured composites with various reinforcing layers were designed and produced using additive manufacturing(AM)to achieve a balance between light weight and high strength.The impact of reinforcing layers on the compressive deformation behavior of porous composites was investigated through micro-computed tomography(Micro-CT)and finite element method(FEM)analyses.The results indicate that the addition of reinforcement layers to sandwich structures can significantly enhance the compressive yield strength and energy absorption capacity of porous metal structures;Micro-CT in-situ observation shows that the strain of the porous structure without the reinforcing layer is concentrated in the middle region,while the strain of the porous structure with the reinforcing layer is uniformly distributed;FEM analysis reveals that the reinforcing layers can alter stress distribution and reduce stress concentration,thereby promoting uniform deformation of the porous structure.The addition of reinforcing layer increases the compressive yield strength of sandwich-structured composite materials by 124%under the condition of limited reduction of porosity,and the yield strength increases from 4.6 to 10.3 MPa.

低潮气量通气结合肺复张对妇科腹腔镜手术患者的肺氧合功能恢复影响研究

随着医学科技的发展,在妇科领域应用腹腔镜手术日益增多。然而,手术过程中由于人工气腹的建立和特殊体位的影响,患者可能会出现一系列呼吸生理变化,如潮气量降低、肺不张和肺内分流增加等,这些变化可能影响患者的肺氧合功能,导致术后并发症的发生。低潮气量通气是一种针对急性呼吸窘迫综合征(ARDS)的通气策略,其主要目的是减少肺损伤。而肺复张是一种通过增加胸腔压力来增加肺容积的方法,可以改善肺不张和肺内分流,提高肺氧合功能。在妇科腹腔镜手术中,单独应用低潮气量通气或肺复张的研究已有报道,但两者联合应用的研究尚不多见。因此,本研究旨在探讨低潮气量通气结合肺复张对妇科腹腔镜手术患者肺氧合功能恢复的影响。从2022年7月~2023年7月收集70例经腹腔镜行妇科手术的病人,用随机数字表将其分成两组,分别为低潮气组(L,n=35)和对照组(C,n=35)。治疗组在插管后采用低潮气量通气,在术中用手控式肺复张;C组采用常规换气法。分别测定两组病人进入手术室时、气腹后10分钟(T1)、气腹后30分钟(T2)、气腹后60分钟(T3)和气腹结束后10分钟(T4)的动脉血气;T0~T4期间,两组病人的平均动脉压(MAP),心率(MAP),呼末二氧化碳分压(PETCO2),气道峰压(Ppeak),气道平台压(Pplat),肺顺应性(Pplat),以及与术后通气有关的副作用,并分别计算了氧合指数(OI)和肺内分流率(Qs/Qt)。最终得到的结论是L组通气结合肺复张在妇科腹腔镜手术下可以显著提高肺氧合功能,减少肺部分流,使得内环境保持稳定状态。

催化氮化反应Si_3N_4增强SiC基复相耐高温材料的研究

为解决Si_3N_4结合SiC复相材料氮化不完全产生"黑心"/"夹心"以及强度有待提高的问题,本文在探讨Fe、Co、Ni等催化剂对Si粉催化氮化过程的基础上,研究了催化剂Co的加入对原位催化Si粉氮化反应形成Si_3N_4结合SiC复相耐高温材料的物理性能与显微结构特征的影响。结果表明:催化剂Fe、Co、Ni能够有效促进Si粉的氮化以及Si_3N_4纤维的形成,同时能够降低氮化反应的温度。1400℃氮化烧结后,当Co加入量为0.5wt.%时催化氮化制备的Si_3N_4结合SiC复相材料的强度达到最大60.2 MPa,比未添加Co的提高了88.7%,可能是由于形成了大量的纤维网络结构强化了SiC基质。

Effects of Fe-Al intermetallic compounds on interfacial bonding of clad materials

The growth of intermetallic compounds at the interface between solid Al and Fe and the effects of intermetallic compound layers on the interfacial bonding of clad materials were investigated. The results showed that the interface between the solid Fe and Al formed by heat-treatment consisted of Fe2Al5 and FeAl3 intermetallic compound layers, which deteriorated the interfacial bonding strength. Fractures occurred in the intermetallic compound layer during the shear testing. The location of the fracture depended on the defects of microcracks or voids in the intermetallic compound layers. The microcracks in the intermetallic compound layer were caused by the mismatch of thermal expansion coefficients of materials during cooling, and the voids were consistent with the Kirkendall effect. The work will lay an important foundation for welding and joining of aluminum and steel, especially for fabrication of Al-Fe clad materials.

Solid-phase sintering process and forced convective heat transfer performance of porous-structured micro-channels

A solid-phase sintering process for the low-cost fabrication of composite micro-channels was developed. Three kinds of composite micro-channels with metallic porous structures were designed. The sintering process was studied and optimized to obtain porous-structured micro-channels with high porosity. The flow resistance and heat transfer performance in the composite micro-channels were investigated. The composite micro-channels show acceptable flow resistance, significant enhancement of heat transfer and dramatic improvement of flow boiling stability, which indicates a promising prospect for the application in forced convective heat transfer.

Fabrication and ablation property of carbon/carbon composites with novel SiC-ZrB_2 coating

A novel SiC?ZrB2 coating was prepared using a two-step technique by slurry-sintering and chemical vapor reaction on carbon/carbon (C/C) composites. The SiC?ZrB2 coating was composed of the scattered ZrB2 phase and the continuous SiC phase. It was observed that a good adhesion was built between the coating and the C/C composites. The SiC?ZrB2 coating samples exhibited a better ablation resistance in comparison with the uncoated C/C composites. The SiO2?ZrO2 barrier layer, the heat dissipation of the gaseous products and the pinning effect of ZrO2 all contributed to the good ablation resistance of the SiC?ZrB2 coated composites.

Properties of W/DLC/W-S-C composite films fabricated by magnetron sputtering

A kind of W/DLC/W-S-C composite film was fabricated by magnetron sputtering method.Effects of WSx content on the structure and the adhesion of the composite films were investigated.In addition,tribological behavior of the composite films was studied in the conditions of the ambient air and N2 gas atmosphere by ball-on-disk tester.The results indicate that the composite films show dense and amorphous microstructure.The WCx and WSx compounds are found in amorphous diamond like carbon matrix in the top layers of W-S-C.A proper WSx content is beneficial for improving the adhesion of the composite films.In air atmosphere,the composite films with high C content have better wear resistance and the friction coefficients range from 0.15 to 0.25.In N2 condition,high WSx content is benefit for the wear resistance and the friction coefficients of the composite films range from 0.03 to 0.1.

Preparation and Fluorescence Properties of Co-doped Nanocomposite Film Based on Supra Molecular Structure

A novel materials design procedure based on the co-doping of metal nanoparticle and azo dye compound （MNPADC） is developed to improve the properties of functional molecules. The synthesized materials were characterized by transmission electron micrograph （TEM）, ultraviolet-visible absorption spectra （UV-Vis） and fluorescence spectra （FS）. It was found that the fluorescence intensity of methyl orange （MO） was enhanced by 5 times in the aqueous composite system doped with silver nanoparticles whereas it was reduced by 15% and 20% in composite films with co-mixing and coating structures, respectively. The results indicate that the properties of functional molecules can be greatly improved in composite film with supra molecular structure and that the procedure presented here is effective.

一种新的预测铣刀刀尖频响函数的方法

为准确快速地预测铣刀刀尖点频响函数,提出一种基于逆响应耦合子结构分析(IRCSA)法辨识刀柄-刀具结合面参数的刀尖点频响函数预测方法。该方法通过建立计算刀柄末端频响函数矩阵和刀尖点频响函数矩阵的数学模型,利用逆响应耦合子结构分析法求取随频率变化的刀柄-刀具结合面参数。通过Cuckoo search算法及有限元分析确定刀尖点频响函数中对刀柄-刀具结合面复刚度矩阵变化最为敏感的固有频率,取该频率对应的结合面参数为刀柄-刀具结合面复刚度矩阵的辨识结果,由此计算出刀尖点频响函数。通过硬质合金圆柱棒、2刃铣刀和4刃铣刀进行验证,对比了所提预测方法、Cuckoo search优化算法预测的刀尖点频响函数与实测值三者之间的差异,实验结果表明该预测方法预测的刀尖点频响函数的固有频率和实测固有频率的误差在5%以内,所用时间约为Cuckoo search优化算法的1%,达到了较高的预测精度,并且更加省时、简便。

Compound structure analysis of a new chaotic system

This paper analyzes the compound attractor structure of a new three-dimensional autonomous chaotic system. First, it is found that there exist five equilibria in the chaotic system, and the stabilities of these equilibria are discussed under a constant scalar control input parameter m. Secondly, the trajectories of the attractors on a y-z plane are examined, the reasons why these trajectories can exist or disappear are also described. Finally, the forming procedure of the different scrolls chaotic attractor is explored by computer simulations when the parameter m is varied. It is shown that the new chaotic attractor has a compound structure, it can evolve to other three-dimensional autonomous chaotic systems. The results of theoretical analysis and simulation are helpful for better understanding of other similar chaotic systems.