Effects of nano TiN addition on the microstructure and mechanical properties of TiC based steel bonded carbides

TiC based steel bonded carbides with the addition of nano TiN were prepared by vacuum sintering techniques.The microstructure was investigated using scanning electron microscopy（SEM） and transmission electron microscopy（TEM）,and the mechanical properties,such as bending strength,impact toughness,hardness,and density,were measured.The results indicate that the grain size becomes small and there is uniformity in the steel bonded carbide with nano addition;several smaller carbide particles are also found to be inlaid in the rim of the larger carbide grains and prevent the coalescence of TiC grains.The smaller and larger carbide grains joint firmly,and then the reduction of the average size of the grains leads to the increase in the mechanical properties of the steel bonded carbides with nano addition.But the mechanical properties do not increase monotonously with an increase in nano addition.When the nano TiN addition accounts for 6-8 wt.% of the amount of steel bonded carbides,the mechanical properties reach the maximum values and then decrease with further increase in nano TiN addition.

Diffusion Bonding of Ti_3Al Base Alloy

: The effects of diffusion bonding temperature and holding time on the joint strength of Ti3Al base alloy has been investigated in this paper. The shear strength of Ti-14Al-21Nb-3Mo-V alloy diffusion bonding joint under pressure of 12 MPa at 990℃ for 70 min was obtained to 797.6 MPa which approaches the base material strength. In addition, a short-time diffosion bonding process was studied in order to decrease the bonding cost. With the deformation of the specimens of 2.5% and the bonding temperature of 990℃ for 15 min, the bonding strength could reach 801 MPa.

Microstructures and properties of transient liquid phase diffusion bonded joints of Ni_3Al-base superalloy

An investigation of transient liquid phase (TLP) diffusion bonding of a Ni 3Al base directionally solidified superalloy, IC6 alloy, was presented. The interlayer alloy employed was Ni Mo Cr B powder alloy. The results show that the microstructure of the TLP diffusion bonded joints is a combination of γ solid solution (or a γ+γ′ structure) and borides. With the bonding time increasing, the quantity of the borides both in bonding seam and adjacent zones is gradually reduced, and the joint stress rupture property is improved. The obtained stress rupture property of the TLP bonded joints is on a level with the transverse property of IC6 base materials. [

A Single Mode Hybrid Ⅲ-Ⅴ/Silicon On-Chip Laser Based on Flip-Chip Bonding Technology for Optical Interconnection

A single mode hybrid Ⅲ-Ⅴ/silicon on-chip laser based on the flip-chip bonding technology for on-chip optical interconnection is demonstrated. A single mode Fabry-Perot laser structure with micro-structures on an InP ridge waveguide is designed and fabricated on an InP/AIGaInAs multiple quantum well epitaxial layer structure wafer by using i-line lithography. Then, a silicon waveguide platform including a laser mounting stage is designed and fabricated on a silicon-on-insulator substrate. The single mode laser is flip-chip bonded on the laser mounting stage. The lasing light is butt-coupling to the silicon waveguide. The laser power output from a silicon waveguide is 1.3roW, and the threshold is 37mA at room temperature and continuous wave operation.

Adhesive Bonding and Self-Curing Characteristics of α-Starch Based Composite Binder for Green Sand Mould/Core

Interactions between different components in α-starch based composite binder for green sand mould/core were investigated by using XRD, IR spectra, 1H NMR spectra and SEM. Several adhesive hardening structures and theories of the binder at room temperature were proposed according to the interactions between various compositions. Thus, the reasons for the binder to have excellent combination properties and unique adhesive bonding and self-curing characteristics were explained by these theories successfully. And the theories are of great directive importance to design and development of composite binder for green sand mould/core.

Features of microstructure and fracture in the transient liquid phase bonded aluminium-based metal matrix composite joints

Transient liquid phase (TLP) bonded aluminium based metal matrix composite (MMC) joints can be classified into three distinct regions, i.e. the particulate segregation region, the denuded particulate region and the base material region. The microstructure of the particulate segregation region consists of alumina particulate and Al alloy matrix with the Al 2Cu and MgAl 2O 4. It contains more and smaller alumina particulates compared with the base material region. The TLP bonded joints have the tensile strength of 150 MPa ～200 MPa and the shear strength of 70 MPa ～100 MPa . With increasing tensile stress, cracks initiate in the particulate segregation region, especially in the particulate/particulate interface and the particulate/matrix interface, and propagate along particulate/matrix interface, througth thin matrix metal and by linking up the close cracks. The particulate segregation region is the weakest during tensile testing and shear testing due to obviously increased proportion of weak bonds (particulate particulate bond and particulate matrix bond).

Theoretical Study on the Structures, Vibrational Spectra, and the Nature of the Intermediate Hydrogen Bond of Schiff Bases

Semi-empirical method PM3 was used to study the geometry and vibrational spectrum of N-(2-hydroxy-l-naphthyl-methylene)-l-pyrenamine (NPY) with the intermediate hydrogen bond. Results are comparable to experimentations. Based on results of both NPY and its model, N-(2-hydroxy-l-naphthyl-methylene)aniline, it was found that the N-(2-hydroxy-l-naphthyl-methylene) group is principally responsible for the special hydrogen bonding through conjugation effect.

Interface structure and formation mechanism of diffusion-bonded joints of TiAl-based alloy to titanium alloy

Vacuum diffusion bonding of a TiAl based alloy (TAD) to a titanium alloy (TC2) was carried out at 1 273 K for 15～120 min under a pressure of 25 MPa . The kinds of the reaction products and the interface structures of the joints were investigated by SEM, EPMA and XRD. Based on this, a formation mechanism of the interface structure was elucidated. Experimental and analytical results show that two reaction layers have formed during the diffusion bonding of TAD to TC2. One is Al rich α(Ti)layer adjacent to TC2,and the other is (Ti 3Al+TiAl)layer adjacent to TAD,thus the interface structure of the TAD/TC2 joints is TAD/(Ti 3Al+TiAl)/α(Ti)/TC2.This interface structure forms according to a three stage mechanism,namely(a)the occurrence of a single phase α(Ti)layer;(b)the occurrence of a duplex phase(Ti 3Al+TiAl)layer;and(c)the growth of the α(Ti)and (Ti 3Al+TiAl)layers.

High Temperature Oxidation Behavior of Nitride Bonded SiC Based Refractories

High temperature oxidation behavior of two kinds of nitride bonded SiC based refractories wtls bwestigated at I 100-1 .500℃ by means of X-ray di[fractometer, scanning electronic microscopy and thermogravimetry. The results show that ： （1） with the temperature im＇reasing, the oxidation mass increment rote of the specimen increases.first and then. decreases, and oxidation passi＇va tion occttrs; （2） the oxidation resistance of SiAION bonded SiC refractories is superior to that of Si3N4 botlded SiC refractories ; （3） high temperature oxidtttion resuits itt the increase of compressive strength at room temperature of SiC based refractoviesiaes comlmred with specimen before oxidatiotl; the compressive strength of SIMON bonded SiC specimens oxidized at high temperatures decreases with the increase of the temperature as a result of formation amt burst of surfhce bubble, while the decrease of compressive strength of Sign4 bonded SiC specimens oxidized at high temperatures is owitng to the bwrease of the consistency of netlike crack assoeiated with cristobalite transfornuttion during cooling.

Synthesis, Characterization and Crystal Structure of a New Schiff Base Ligand from a Bis(Thiazoline) Template and Hydrolytic Cleavage of the Imine Bond Induced by a Co(II) Cation

The reaction of bis-[2-amino-4-pheny1-5-thiazolyl] disulfide with 5-nitro-salicylaldehyde in absolute ethanol resulted in the formation of a new Schiff base ligand H2L (1). Characterization of the ligand was performed by FT-IR, 1H NMR, 13C NMR, UV-Vis, elemental analysis and single crystal X-ray diffraction. The ligand, (1), possesses a disulfide –S–S– bridge of 2.1121 (3) ? length, and the molecule adopts a cis-conformation around this bond. In the crystal structure of (1), an intramolecular O–H···N hydrogen bond with D… A distance of 2.69 (3) ? was present. The reaction of (1) with Co(NO3)2·6H2O and CuCl2·2H2O in methanol afforded the corresponding metal complexes. The obtained solids were further investigated by elemental analysis and UV-Vis titration that confirmed the formation of [CoL] and [ClCuHL] complexes. However, recrystallizaion of the Co(II) complex in dimethylsulfoxide caused the complete hydrolysis of the imine bond and afforded a Co(II) complex in which two 5-nitro-salicylaldehyde and two DMSO molecules were coordinated to the central metal in an octahedral fashion. This structure (2) was also confirmed by single crystal X-ray analysis.

Microstructure and bonding strength of Ni-based alloy coating

A Ni-Cr-B-Si coating technique was developed and successfully applied on austenite grey iron substrate in a conventional resistance furnace under graphite powder protection. The microstructure, phase distribution, chemical composition profile and microhardness along the coating layer depth were investigated. Shear strength of the coating was also tested. Microanalysis shows that the coating is consist of γ-Ni solution and γ-Ni+Ni3B lamellar eutectic, as well as small amount of Cr5B3 particles. Diffusion induced metallurgical bonding occurs at the coating/substrate interfaces, and the higher the temperature, the more sufficient elements diffused, the broader interfusion region and the larger bonding strength, but it has an optimum value. And the bonding strength at the interface can be enable to reach 250-270 MPa, which is nearly the same as that of processed by flame spray. The microhardness along the coating layer depth shows a gradient distribution manner.

A High-Precision Calculation of Bond Length and Spectroscopic Constants of Hg2 Based on the Coupled-Cluster Theory with Spin-Orbit Coupling

Based on the two-component relativistic effective core potential and matched basis sets cc-pwcvnz-pp （n=Q, 5）, combining the completed basis-set extrapolation of electronic correlation energy and the fourth-order polynomial fitting technique, the bond length and spectroscopic constants of Hg2 are studied by the coupled cluster theory with spin-orbit coupling. Spin-orbit coupling is included in the post Hartree-Fock procedure, i.e., in the coupled- cluster iteration, to obtain more reliable theoretical results. The results show that our theoretical values agree with the experimental values very well and will be helpful to understand the spectral character of Hg2.

Reinforcement of Lignin-Based Phenol-Formaldehyde Adhesive with Nano-Crystalline Cellulose (NCC): Curing Behavior and Bonding Property of Plywood

The curing behavior of lignin-based phenol-formaldehyde (LPF) resin with different contents of nano-crystalline cellulose (NCC) was studied by differential scanning calorimetry (DSC) at different heating rates (5, 10 and 20&degC/min) and the bonding property was evaluated by the wet shear strength and wood failure of two-ply plywood panels after soaking in water (48 hours at room temperature and followed by 1-hour boiling). The test results indicated that the NCC content had little influence on the peak temperature, activation energy and the total heat of reaction of LPF resin at 5 and 10&degC/min. But at 20&degC/min, LPF0.00% (LPF resin without NCC) showed the highest total heat of reaction, while LPF0.25% (LPF resin containing 0.25% NCC content) and LPF0.50% (LPF resin containing 0.50% NCC content) gave the lowest value. The wet shear strength was affected by the NCC content to a certain extent. With regard to the results of one-way analysis of variance, the bonding quality could be improved by NCC and the optimum NCC content ranged from 0.25% to 0.50%. The wood failure was also affected by the NCC content, but the trend with respect to NCC content was not clear.

一种抗超高温配位键合型低聚物降黏剂

针对高密度水基钻井液高温增稠引发的滤失量大、ECD与内耗高、流动性下降甚至完全丧失难题,在AAAMPS聚有机酸降黏剂分子中引入富含大量邻苯二酚基团的单宁酸,采用自由基聚合法研制了一种抗超高温配位键合型低聚物降黏剂AA-AMPS-TA,并通过正交实验明确了PAAT的最优合成条件。表征并评价了PAAT的降黏性能,结果表明:引入TA后,PAAT的红外光谱出现了源于酚羟基的分子内氢键吸收峰,且因其分子结构中引入了大量苯酚基团,显著提升了热稳定性,分解温度接近500℃;PAAT可降低低浓度膨润土浆和7%膨润土+8%高岭土的高浓度混合黏土浆黏度,在高密度水基钻井液体系中降黏率达26.5%,240℃热滚后降黏率达44.4%。采用Zeta电位与粒径分析验证了PAAT的吸附降黏机理,并在蓬深101井中现场应用,控制了井浆高温下黏度、切力增涨,降黏效果良好。

高粗糙度NiCrB打底层对陶瓷颗粒增强聚合物基复合涂层性能的影响

目的提高水电装备过流部件表面聚合物基复合抗空蚀涂层与碳钢基材的结合强度,解决因聚合物涂层局部分层,使得水进入聚合物涂层与碳钢界面,引起碳钢快速氧化膨胀,导致涂层快速剥落的难题。方法采用电弧喷涂技术在碳钢基材表面制备NiCrB高粗糙度耐腐蚀打底层,然后在其上涂覆聚氨酯基复合涂层。通过激光共聚焦显微镜、扫描电镜,以及结合强度测试、电化学测试和中性盐雾测试,分别表征打底层的表面形貌、致密度,并评价打底层对聚氨酯基复合结合强度和防腐蚀性能的影响。结果通过调控参数,在NiCrB打底层表面形成由熔滴气化后沉积形成的规则排布凸起颗粒,涂层的表面粗糙度相较于常规热喷涂涂层得到显著提高,在Ra 10.95~37.24μm内可有效调控,且涂层的孔隙率均低于1.5%。添加高粗糙度致密NiCrB打底层后,聚氨酯基复合涂层的结合强度由13.6 MPa升至30.5 MPa。在基体添加NiCrB打底层后,其开路电位由−0.73 V升至−0.54 V,腐蚀电位(vs.SCE)由−0.76 V升至−0.58 V,电荷转移电阻由1729Ω·cm^(2)升至8425Ω·cm^(2)。在上层聚合物涂层破损的情况下,带有NiCrB打底层的样品在接受300 h中性盐雾测试后无明显锈点,相较于无打底层样品,其盐雾腐蚀寿命提高了11倍以上。结论通过电弧喷涂NiCrB打底层可以在较大范围内实现表面粗糙度的调控,打底层的高粗糙度显著提升了聚合物基复合涂层的结合强度,打底层优异的耐腐蚀性能显著提升了聚合物基复合涂层的长效耐腐蚀性能,保障了水力过流部件的长效服役。

动态席夫碱交联的壳聚糖基水凝胶的合成与性能研究

壳聚糖基水凝胶机械性能往往较差,为提高其机械性能通常进行戊二醛交联,但是戊二醛会对水凝胶的生物安全性造成影响。为在提高壳聚糖基水凝胶的机械性能时充分保障其生物安全性,本研究制备了一款完全基于壳聚糖及其衍生物的水凝胶。羧甲基壳聚糖(CMC)与双醛壳聚糖(DACS)通过席夫碱键共价交联,形成壳聚糖基水凝胶(CBH),通过流变学实验、拉伸实验、黏附实验对CBH的自愈合性能、机械性能进行评价。通过抗菌实验、活/死细胞实验、细胞毒性、溶血实验、抗炎实验对CBH的抗菌性能、生物相容性以及抗炎性能进行了全面评估。研究发现,CBH可拉伸至原长的2倍,在4 h后的愈合效率可达72%,这证明席夫碱键交联赋予了CBH良好的自愈合性能并提高了其机械性能。CBH的平衡溶胀率可达4 500%,且具有pH响应性。CBH对大肠杆菌(Escherichia coli)和金黄色葡萄球菌(Staphylococcus aureus)的抑制效率分别为80.95%和79.79%。与CBH共用培养的细胞可随时间正常增殖,无明显细胞死亡,且溶血率仅为3%,这证明CBH具有优异的生物相容性。同时,CBH还可以抑制一氧化氮和TNF-α、IL-1β、IL-6等促炎因子的分泌,增加IL-10等抗炎因子的分泌,具有良好的抗炎活性。研究结果表明,利用CMC和DACS制备的CBH,具有良好的自愈合性能、机械性能、抗菌、抗炎性能以及高度生物相容性,其在生物医学领域有广阔的应用潜力。

中间层对GH5188高温合金TLP扩散焊接头的影响

通过自主研发制备了三种不同W含量KCo7、KCo8、KCo9中间层,采用X射线衍射仪(XRD)、差示扫描量热仪(DSC)对中间层进行表征,并在1180℃保温60 min的条件下进行GH5188高温合金真空瞬间液相扩散焊试验验证;分别研究了中间层厚度以及不同中间层接头显微结构及力学性能的影响。结果表明:当KCo7中间层厚度为20μm时,接头存在大量未焊合缺陷,室温抗拉强度仅有568 MPa;当KCo7中间层厚度增加至40μm时,焊缝填充良好,室温抗拉强度达到941.3 MPa。此外,随着中间层中W含量由0增加至8%(质量分数)时,焊缝中心富W的M_6C析出量明显增加,室温抗拉强度先上升后下降。其中,采用厚度为40μm的KCo8中间层获得的接头具有最高的室温抗拉强度1033 MPa,且断裂发生在母材区。

个性化机加工底板托槽的抗剪切强度研究

目的:采用两种临床常用粘接剂,对个性化机加工底板托槽、新型网底托槽、双向倒钩底板托槽和传统网底托槽的抗剪切强度(shear bond strength,SBS)进行比较研究,为临床个性化机加工托槽的粘接提供参考。方法:收集48颗新鲜人类前磨牙,随机分为8组。A、B组选用个性化机加工底板托槽,C、D组选用新型网底托槽,E、F组选用双向倒钩底板托槽,G、H组选用传统网底托槽;A、C、E、G组使用化学固化粘接剂,B、D、F、H组使用光固化粘接剂。在粘接实验前,在所有托槽中,每种托槽随机选1颗,对其底板在放大40倍、100倍的扫描电镜下进行观察并拍照。使用万能材料实验机,对每组托槽进行SBS的测定,并进行粘接剂残留量(adhesive remnant index,ARI)计分。结果:使用化学固化粘接剂时,其他3种托槽相比,双向倒钩底板托槽粘接强度较低,差异有统计学意义(P<0.05)。使用光固化粘接剂时,双向倒钩底板托槽粘接强度最低,新型网底托槽较低,传统网底托槽和个性化机加工底板托槽粘接强度最高,差异有统计学意义(P<0.05),传统网底托槽和个性化机加工底板托槽之间粘接强度无明显差异(P>0.05)。各组ARI计分差异有统计学意义(P<0.05),进一步比较可得:H组ARI计分最小,且H组与A组和E组的差异有统计学意义(P<0.05)。结论:个性化机加工底板托槽使用光固化粘接剂或使用化学固化粘接剂对其粘接强度无明显影响,粘接强度均能满足正畸临床粘接的要求。H组脱粘接断裂部位相对更接近牙釉质,其余各组牙釉质在脱粘接过程中损伤的风险较小。

SiC功率模块封装材料的研究进展

随着SiC功率模块的高频高速、高压大电流、高温、高散热和高可靠发展趋势,基于封装结构和封装材料的SiC功率模块封装技术也在不断地更新换代。与封装结构相比,SiC功率模块封装材料的相关研究报道较少。该文从封装材料角度出发,综述近年来陶瓷覆铜基板、散热底板、黏结材料、互连材料及灌封材料的研究进展,同时引出相关封装材料的研究重点,以满足SiC功率模块的应用需求。

高压作用下水泥基粉末材料的接触硬化研究综述

在高压作用下,一些具有无定型相的水泥基粉末材料会发生接触硬化现象,粉末颗粒在压力作用下发生缩聚运动,并在粉末颗粒间形成结构键,进而快速形成具有一定强度及耐水性的人造石材。本文综述了压力作用下水泥基粉末材料接触硬化的成键机理以及粉末水分含量、干燥条件、钙硅比、压制过程对其接触硬化性能影响的研究进展。相关研究结果表明,压力作用下粉末颗粒间会形成氢键、范德华力、固体桥键等结构键;粉末水分含量是影响接触硬化性能的重要因素,在压力作用下,水分可以改变粉末颗粒的表面性质并影响颗粒之间的结合,进而改变压制成品的力学性能;钙硅比对接触硬化性能的影响显著,不同粉末材料在压制时的最佳钙硅比亦是不同;摩擦力的存在降低了压制效率,造成压制成品密度、强度分布不均匀,润滑剂的加入可以有效降低摩擦力的影响;此外,降低压制模具高径比并使用双面压制可有效提升压制成品的质量。