Permeable resin applied to surface of sealed demineralized enamel

The self-made demineralized teeth samples treated with preamble resin to seal or not were observed under electron microscopy and tested microhardness value to show surface structure and hardness of demineralized enamel.The experimental results showed that the permeable resin formed longer resin tags on the surface of the enamel and a lot of cracks in the deep part which has a higher microhardness value than ordinary enamel.     

Permeable Resin Applied to Surface of Sealed Demineralized Enamel

The self-made demineralized teeth samples treated with preamble resin to seal or not were observed under electron microscopy and tested microhardness value to show surface structure and hardness of demineralized enamel.The experimental results showed that the permeable resin formed longer resin tags on the surface of the enamel and a lot of cracks in the deep part which has a higher microhardness value than ordinary enamel.     

Formation and mechanical properties of ductile Fe-based amorphous alloys using a cast iron with minor addition of B and Al

Fe-based amorphous alloys with ductility were synthesized using the commercial cast iron QT50 (denoted as QT) with the combining minor addition of B and Al by single roller melt-spinning. The melt-spun (QT_1-xB_x)₉₉Al₁ (x is from 0.006wt% to 0.01wt%) amorphous alloys exhibit onset crystallization temperatures and Curie temperatures of 759–780 and 629–642 K respectively, and which increase with B content. The amorphous ribbons are ductile and can be bent 180° without breaking. With the increase in B content from 0.006wt% to 0.01wt%, the Vickers microhardness of the amorphous alloys increases from Hv 830 to Hv 1110. The effects of the additional B and Al elements on the glass forming ability and mechanical properties were also discussed.     

Zn ~(2 ) Release Performance in Simulated Uterine Solution and Surface Characteristics of ZnO/LDPE Nanocomposites

1Introduction Intrauterinedevices(IUDs)areeffectivedevicesfor contraceptionandarewidelyusedintheworld[1,2].Espe ciallyinChina,thenumberofwomenadoptingIUDshas beenthehighestofallthoseadoptingcontraceptive measures[3].Asaneffectivecontraceptive,copper bear …     

Microstructure and thermal physical parameters of Ni60-Cr3C2 composite coating by laser cladding

To satisfy performance and long life requirements for hot forging die, Ni60-Cr₃C₂ composite coatings were prepared on the high-speed steel W₆Mo₅Cr₄V₂ using laser cladding technology. Laser clad coatings with different ratios of Ni60:Cr₃C₂ were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX) and microhardness tester, respectively. Specific heat capacity and thermal conductivity were measured by Laser Thermal Constant Meter. Thermal expansion coefficient and elastic modulus were measured by Dynamic Mechanical Thermal Analyzer and Electro-Hydraulic Servocontrolled Testing System, respectively. The results indicated that Ni60+50wt% Cr₃C₂ composite coating had dense and homogeneous structure, as well as a metallurgical bonding with the substrate. With the increase of Cr₃C₂ content, volume of chromium-containing compounds in the composite coating increased, microhardness increased and microstructure refined. The thermal physical parameters results showed that Ni60+ 50wt% Cr₃C₂ composite coating was overall worse than W₆Mo₅Cr₄V₂, but had a higher hot yield strength to alleviate hot fatigue and surface hot wear of hot forging die during hot forging and thus improve the service life of hot forging die.     

Controlled Deposition of HAp Mimicking Tooth Enamel

1Introduction Dentalenamelistheoutermostlayeroftheteeth.Thematureenamelcrystalsofthemammaliantoothhave someuniquecharacteristics:enamelcrystalsareextremely elongatedinthec axialdirection,havehighcrystallinityandarehighlyorientedparalleltoeachother[1].Them…     

Wear Properties of Plasma Transferred Arc Fe-based Coatings Reinforced by Spherical WC Particles

Fe-based coatings reinforced by spherical WC particles were produced on the 304 stainless steel by plasma transferred arc(PTA) to enhance the surface wear properties. Three different Fe/WC composite powder mixtures containing 0 wt%, 30 wt%, and 60 wt% of WC were investigated. The microstructure and phase composition of the Fe/WC composite PTA coatings were evaluated systemically by using scanning electron microscope(SEM) and X-ray diffraction(XRD). The wear properties of the three fabricated PTA coatings were investigated on a BRUKER UMT TriboLab. The morphologies of the worn tracks and wear debris were characterized by using SEM and 3 D non-contract profiler. The experimental results reveal that the microhardness on the cross-section and the wear resistance of the fabricated coatings increase dramatically with the increasing adding WC contents. The coating containing 60 wt% of WC possesses excellent wear resistance validated by the lower coefficients of friction(COF), narrower and shallower wear tracks and smaller wear rate. In the pure Fe-based coating, the main wear mechanism is the combination of adhesion and oxidative wear. Adhesive and two-body abrasive wear are predominated in the coating containing 30 wt% of WC, whereas threebody abrasion wear mechanism is predominated in the coating containing 60 wt% of WC.     

Effects of Rare Earth Pr/Ce on Tribological Behavior of ADC12 Alloy

The microstructure and microhardness of ADC12 alloy that was mixed with 0,0.3,0.6,and 0.9 wt.% rare earth praseodymium/cerium (Pr/Ce) were studied.The addition of Pr/Ce improved the microhardness of the alloys.The ADC12+0.6 wt% Pr/Ce alloy displayed the smallest grain size and maximal microhardness.The tribological behavior of the alloys was tested by the pin-on-disc dry sliding friction pair with a sliding velocity of 0.21 m/s under various loads (20,40,60,80 N).The wear morphology was observed by a scanning electron microscope (SEM) and the wear mechanism was discussed.The result indicated that the wear resistance of ADC12+0.6 wt% Pr/Ce alloy was the most optimal.The wear rate relative to the matrix is reduced by 67.5% under a load of 20 N.The wear mechanism is adhesive wear.     

Metallurgical quality of CSP thin slabs

The casting structure, chemical composition segregation, dendrite arm space, inclusiona and during the CSP (compact strip production) rolling process were investigated. The results show that the CSP thin slab has a feature of uniform fine grains, more columnar crystals, less central porosity and segregation etc. There is no great difference in macrostructure between the CSP thin slab and conventional slab; however, the fine dendrite structure of the CSP slab is more uniform. Moreover, the central porosity and segregation are obviously improved after the first pass; and the dendrite is bent along the rolling direction rather than broken into pieces.Small inclusions with the diameter less than 10 p.m in the CSP slab are dominantly consisted of aluminates formed by A1 deoxidation and Ca treatment and not floating out of the melt. The large size inclusions found in the continuous casting slab are very few.     

Microstructural characterizations and mechanical properties of Mg-8Sn-1Al-1Zn-xCu alloys

Microstructural characterization and mechanical properties of as-cast Mg-8Sn-1Al-1Zn-xCu（x=0wt%, 1wt%, 1.5wt% and 2.0wt%） alloys were studied by OM, Pandat software, XRD, SEM, DSC and a standard universal testing machine. The experimental results indicate that adding Cu to TAZ811 alloy leads to the formation of the AlMgCu and Cu3 Sn phases. Tensile tests indicate that yield strength increases fi rstly and then decreases with increasing Cu content. The alloy with the addition of 1.5wt% Cu exhibits optimal mechanical properties among the studied alloys. The improved mechanical properties can be ascribed to the second phase strengthening and fi ne-grain strengthening mechanisms resulting from the more dispersed second phases and smaller grain size, respectively. The decrease in ultimate tensile strength and elongation of TAZ811-2.0wt% Cu alloy at room temperature is ascribed to the formation of continuous AlMgCu and coarse Mg2 Sn phases in the liquid state.     

Pulsed Nd：YAG laser cladding of high silicon content coating on low silicon steel

A pulsed Nd:YAG (yttrium aluminum garnet) laser-based technique was employed to clad low silicon steel with preplaced Si and Fe mixed powders for high Si content. The surface morphology, microstructural evolution, phase composition, and Si distribution, within the obtained cladding coatings, were characterized by optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), with associated energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The microhardness was also measured along the depth direction of the specimens. A crack-and pore-free cladding coating through excellent metallurgical bonding with the substrate was successfully prepared on low silicon steel by means of optimized sin-gle-track and multi-track laser cladding. The phases of the coating are α-Fe, γ-Fe, and FeSi. The high microhardness of the la-ser-cladding zone is considered as an increase in Si content and as the refined microstructure produced by the laser treatment. The Si contents of the cladding coatings were about 5.8wt/ in the single-track cladding and 6.5wt/ in the multi-track cladding, respectively.     

Siliconizing formation mechanism and its property by slurry pack cementation on electro-deposited nickel layer into copper matrix

Silicide coating was prepared on electro-deposited nickel layer by the slurry pack cementation process on copper matrix at 1173 K for 12 h using SiO₂ as Si source, pure Al powder as reducer, a dual activator of NaF+NH₄Cl and albumen (egg white) as cohesive agent. Microstructure, properties and siliconizing mechanism of silicide coating were discussed. The experimental results show that the silicide coating with 220 μm thickness is mainly composed of a Ni₂Si phase and a small amount of Ni₃₁Si₁₂ phase. Its mean microhardness (HV 790) is ten times than that of copper substrate (HV 70). The coefficient of friction decreases from 0.8 of pure copper to about 0.3 of the siliconzed sample. SiF₂, SiCl₂ and SiCl₃ are responsible for the transportation and deposition of Si during the slurry pack cementation process.     

不同Ca/P比粉末对宽带激光熔覆梯度生物陶瓷涂层组织结构的影响

采用梯度设计思想,利用宽带激光熔覆技术,在TC4合金表面分别熔覆Ca/P为1.4和1.5的CaH-PO4.2H2O+CaCO3混合粉末制备含羟基磷灰石[Ca10(PO4)6(OH2),简称HA]、β-磷酸三钙[β-Ca3(PO42),简称β-TCP]的度生物陶瓷涂层.采用XRD、SEM等表征手段,研究不同Ca/P粉末配比对生物陶瓷涂层组织结构的影响.研究表明:由于P在激光条件下存在烧损现象,当Ca/P为1.5的粉末经激光熔覆后所生成的陶瓷组织较Ca/P较1.4结晶状态更好.不同Ca/P粉末以及CeO2的添加量对催化合成HA+β-TCP有着深刻的影响.当Ca/P=1.4,CeO2的添加量为0.4wt%时,催化合成HA+β-TCP的数量最多;而当Ca/P=1.5,CeO2的添加量在0.2～0.4wt%范围内,催化合成HA+β-TCP的量最多.     

薄板坯连铸连轧工艺生产的低碳钢冷轧基板力学特性

以采用薄板坯连铸连轧工艺生产的低碳钢作为冷轧基板,在实验室二辊可逆轧机上进行不同程度的冷变形,对不同变形后的冷轧板进行室温拉伸试验和显微硬度值测定,分析了其加工硬化情况,并对不同冷变形后试验钢的显微组织进行分析。结果表明:低碳钢经冷变形后,屈服强度和抗拉强度增大,加工硬化显著;试验钢的显微组织为铁素体和少量的珠光体,晶粒随着变形量的增大而拉长细化。     

Effect of the addition of Al-Ti-C master alloy on the microstructure and microhardness of a cast Al-10Mg alloy

The microstructure and microhardness of a cast Al-10wt%Mg （henceforth Al-10Mg） alloy with 0.2wt% addition of Al- 5Ti-0.25C master alloy were compared with those of a refiner-free alloy of similar chemical composition. It was found that this level of the master alloy addition not only caused an effective grain refinement, but also caused a significant increase in the microhardness of the Al-10Mg alloy. Microchemical analysis revealed that TiC particles existed in the grain center. The relationship between the holding time and grain size was also studied. It shows that the grain refining efficiency is faded observably with the holding time. This is explained in terms of the instability of TiC particles.     

TC4钛合金低磷化学镀工艺研究

针对TC4钛合金低磷化学镀,在浸锌活化和乳酸-乙酸络合条件下,对镍磷质量浓度比、温度、pH值、乙酸、乳酸等工艺因素对镀速和镀层磷含量的影响进行系列实验研究。用扫描电镜、能谱仪、显微硬度仪、X射线衍射仪对镀层的表面形貌、硬度和物相进行表征。研究结果表明：提高镍磷质量浓度比、温度、pH值,控制络合剂乳酸在20g/L～22g/L,乙酸在19g/L～20g/L范围内,均有利于低磷镀层的形成,平均镀速为25.6μm/h;镀层为晶态的Ni-P过饱和固溶体,平均粒径10μm,磷含量为2.56wt%,硬度为750.2HV.     

Effects of Ca（Y）-Si modifier on interface morphology and solute segregation during directional solidification of an austenite medium Mn steel

The austenite medium Mn steel modified with controlled additions of Ca, Y, Si were directionally solidified using the vertical Bridgman method to study the effects of Ca（Y）-Si modifier on the solid-liquid （S-L） interface morphology and solute segregation. The interface morphology and the C and Mn segregation of the steel directionally solidified at 6.9 μtrn/s were investigated with an image analysis and a scanning electron microscope equipped with energy dispersive X-ray analysis. The 0.5wt% Ca-Si modified steel is solidified with a planar S-L interface. The interface of the 1.0wt% Ca-Si modified steel is similar to that of the 0.5wt% Ca-Si modified steel, but with larger nodes. The 1.5wt% Ca-Si modified steel displays a cellular growth parttern. The S-L interface morphology of the 0.5wt% Ca-Si＋1.0wt% Y-Si modified Mn steel appears as dendritic interface, and primary austenite dendrites reveal developed lateral branching at the quenched liquid. In the meantime, the independent austenite colonies are formed ahead of the S-L interface. A mechanism involving constitutional supercooling explains the S-L interface evolution. It depends mainly on the difference in the contents of Ca, Y, and Si ahead of the S-L interface. The segregation of C and Mn ahead of the S-L interface enhanced by the modifiers is observed.     

Si和Al对机械合金化合成Ti3SiC2的影响

采用3Ti／Si／2C单质粉体为原料,进行机械合金化,以合成Ti3SiC2粉体。研究了Al和过量Si对机械合金化合成Ti3SiC2的影响。研究结果表明,机械合金化单质混合粉体,会诱发自蔓延反应。反应后产生大量坚硬的颗粒状产物。机械合金化3Ti／Si／2C粉体,会产生组成相为TiC、Ti3SiC2、TiSi2和Ti5Si3的粉体与颗粒产物。添过量Si并不会促进机械合金化反应合成Ti3SiC2。添适量Al可消除硅化物,明显促进反应合成Ti3SiC2。采用3Ti／Si／2C／0．15Al粉体作原料时,颗粒产物中Ti3SiC2含量最高,为92．8wt％;而采用3Ti／Si／2C／0．20Al粉体作原料时,粉体产物中Ti3SiC2含量最高,为61．9wt％。     

Characteristics and composition of particulate matter from coal-fired power plants

Measurements of the characteristics of particulate matter(PM)were performed at the inlet and outlet of the electrostatic precipitators(ESP)of four boilers in two full-scale pulverized coal power plants.PM was collected with a 13-stages low-pressure-impactor(LPI)having aerodynamic cut-off diameter ranging from 10.0 to 0.03μm for a size-segregated collection.The properties of PM including its con-centration,mass size distribution,emission characteristics,percent penetration of PM through ESP and elemental com...     

Effect of trace La addition on the microstructure and mechanical property of as-cast ADC12 Al-Alloy

The effects of addition of La on the microstructure of as-cast ADC12 Al-Alloy were investigated by using optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), and energy disperse spectroscopy (EDS). The experimental results showed that the a-Al and eutectic Si crystals were modified with the addition of 0.3 wt% La. The eutectic Si crystals showed a granular distribution. At the same time, the alloy possessed the best mechanical property. When more than 0.3 wt% La was added to ADC12 aluminum alloy, the microstructure of as-cast alloy was coarsening gradually with the increase of the content of La and the mechanical property decreased. The effect of rare earth La which was added in ADC12 Al-Alloy for up to 0.9 wt% had been investigated in this study. The dendrites of ADC12 Al-alloy was refined obviously and the morphology of Si crystals showed a particle structure when the addition of La reached 0.3 wt%. Besides, the acicular La-rich intermetallics in the alloy deteriorated the mechanical property of alloy. To avoid this unwanted phase, the amount of added rare earth La must be less than 0.6 wt%.