Ultrasonic Nanocrystal Surface Modification Assisted Nitriding: An Experimental Study

A powerful surface severe plastic deformation (SSPD) technique, ultrasonic nanocrystal surface modification (UNSM) has been used to treat pure iron to induce surface nanocrystallization. Transmission electron microscopy and surface profiler were used to study the microstructure and surface roughness after UNSM. Results indicate that the surface nanocrystallization with the controllable surface roughness was obtained. After that, gas nitriding of the nanocrystalline and microcrystalline iron was carried out and compared. X-ray diffraction, micro hardness testing and energy dispersive spectroscopy were applied to investigate the phase, micro hardness and distribution of nitrogen atoms in the iron sample after nitriding. It has been found that nitriding efficiency has been significantly improved in UNSM-processed samples than that in the non-processed samples as manifested by higher hardness and higher volume fraction of the nitride phase. With appropriate nanocrystallization, nitriding can occur efficiently at temperature as low as 300 °C.

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TEM Study of High-Temperature Precipitation of Delta Phase in Inconel 718 Alloy

Advances in Materials Science and Engineering ◽

10.1155/2011/940634 ◽

2011 ◽

Vol 2011 ◽

pp. 1-9 ◽

Cited By ~ 47

Author(s):

Moukrane Dehmas ◽

Jacques Lacaze ◽

Aliou Niang ◽

Bernard Viguier

Keyword(s):

Inconel 718 ◽

Volume Fraction ◽

Alloy 718 ◽

Double Diffraction ◽

X Ray Diffraction ◽

Inconel 718 Alloy ◽

X Ray ◽

Delta Phase ◽

Transmission Electron ◽

Matrix Free

Inconel 718 is widely used because of its ability to retain strength at up to 650∘C for long periods of time through coherent metastable Ni3Nb precipitation associated with a smaller volume fraction of Ni3Al precipitates. At very long ageing times at service temperature, decomposes to the stable Ni3Nb phase. This latter phase is also present above the solvus and is used for grain control during forging of alloy 718. While most works available on precipitation have been performed at temperatures below the solvus, it appeared of interest to also investigate the case where phase precipitates directly from the fcc matrix free of precipitates. This was studied by X-ray diffraction and transmission electron microscopy (TEM). TEM observations confirmed the presence of rotation-ordered domains in plates, and some unexpected contrast could be explained by double diffraction due to overlapping phases.

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Preparation and Property of Al87Ce3Ni8.5Mn1.5 Nanophase Amorphous Composites

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.412.263 ◽

2011 ◽

Vol 412 ◽

pp. 263-266

Author(s):

Hong Wei Zhang ◽

Li Li Zhang ◽

Feng Rui Zhai ◽

Jia Jin Tian ◽

Can Bang Zhang

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Single Phase ◽

Volume Fraction ◽

Material Structure ◽

X Ray Diffraction ◽

Scanning Calorimetry ◽

X Ray ◽

Transmission Electron ◽

Different Temperatures

The higher mechanical strength of Al87Ce3Ni8.5Mn1.5 nanophase amorphous composites has been obtained with two methods. The first nanophase amorphous composites are directly produced by the single roller spin quenching technology. The method taken for the second nanophase amorphous composites is at first to obtain amorphous single-phase alloy, followed by annealed at different temperatures .The formative condition, the microstructure, the particle size, the volume fraction of α-Al phase and microhardness of nanophase amorphous composites etc have been investigated and compared by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The microstructure of composites produced by the second method is higher than the former, the fabricated material structure of the system is more uniform and the process is easier to control.

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Hardness evolution of Al–Cr–N coatings under thermal load

Journal of Materials Research ◽

10.1557/jmr.2008.0366 ◽

2008 ◽

Vol 23 (11) ◽

pp. 2880-2885 ◽

Cited By ~ 32

Author(s):

Herbert Willmann ◽

Paul H. Mayrhofer ◽

Lars Hultman ◽

Christian Mitterer

Keyword(s):

Thermal Load ◽

Structural Changes ◽

Single Phase ◽

Volume Fraction ◽

X Ray Diffraction ◽

Scanning Calorimetry ◽

X Ray ◽

Al Content ◽

Annealing Temperatures ◽

Transmission Electron

Microstructure and hardness evolution of arc-evaporated single-phase cubic Al0.56Cr0.44N and Al0.68Cr0.32N coatings have been investigated after thermal treatment in Ar atmosphere. Based on a combination of differential scanning calorimetry and x-ray diffraction studies, we can conclude that Al0.56Cr0.44N undergoes only small structural changes without any decomposition for annealing temperatures Ta ⩽ 900 °C. Consequently, the hardness decreases only marginally from the as-deposited value of 30.0 ± 1.1 GPa to 29.4 ± 0.9 GPa with Ta increasing to 900 °C, respectively. The film with higher Al content (Al0.68Cr0.32N) exhibits formation of hexagonal (h) AlN at Ta ⩾ 700 °C, which occurs preferably at grain boundaries as identified by analytical transmission electron microscopy. Hence, the hardness increases from the as-deposited value of 30.1 ± 1.3 GPa to 31.6 ± 1.4 GPa with Ta = 725 °C. At higher temperatures, where the size and volume fraction of the h-AlN phase increases, the hardness decreases to 27.5 ± 1.0 GPa with Ta = 900 °C.

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Surface Modification and Preparation of High Purity Nanometer Magnesium Hydroxide Using Impinging Stream

Materials Science Forum ◽

10.4028/www.scientific.net/msf.675-677.847 ◽

2011 ◽

Vol 675-677 ◽

pp. 847-851

Author(s):

Jian Hai Zhao ◽

Yan Ping Lai

Keyword(s):

Surface Modification ◽

Magnesium Hydroxide ◽

High Purity ◽

X Ray Diffraction ◽

Control Factors ◽

Operation Conditions ◽

Crystallization Method ◽

Transmission Electron ◽

Mean Size ◽

The Mean

High purity nanometer magnesium hydroxide is produced by impinging stream reaction crystallization method using bischofite as feedstock. Effects of operation conditions on the impinging stream of Mg (OH)2 are reported and the control factors of purity are confirmed. The morphology of the powder was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Result shows that purity of Mg (OH)2 can reach 99% and the mean size of crystal is 13.5nm. Surface modification of nano-sized magnesium hydroxide using four surface modifiers such as sodium steatite, sodium laurylsulfonate, sodium oleate and sodium silicate were investigated in this paper. The modified magnesium hydroxide has smaller particle size, larger powder contact angle, slower sedimentation velocity, the less in-oil capacity than unmodified sample

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Sol-gel derived Ba(Mg1/3Ta2/3)O3 thin films: Preparation and structure

Journal of Materials Research ◽

10.1557/jmr.1997.0087 ◽

1997 ◽

Vol 12 (3) ◽

pp. 596-599 ◽

Cited By ~ 6

Author(s):

Ji Zhou ◽

Qing-Xin Su ◽

K. M. Moulding ◽

D. J. Barber

Keyword(s):

Thin Films ◽

Annealing Temperature ◽

Volume Fraction ◽

Sol Gel ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

Sol Gel Process ◽

Small Grains

Ba(Mg1/3Ta2/3)O3 thin films were prepared by a sol-gel process involving the reaction of barium isopropoxide, tantalum ethoxide, and magnesium acetate in 2-methoxyethanol and subsequently hydrolysis, spin-coating, and heat treatment. Transmission electron microscopy, x-ray diffraction, and Raman spectroscopy were used for the characterization of the thin films. It was shown that the thin films tend to crystallize with small grains sized below 100 nm. Crystalline phase with cubic (disordered) perovskite structure was formed in the samples annealed at a very low temperature (below 500 °C), and well-crystallized thin films were obtained at 700 °C. Although disordered perovskite is dominant in the thin films annealed below 1000 °C, a low volume fraction of 1 : 2 ordering domains was found in the samples and grows with an increase of annealing temperature.

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Microstructure and Creep Behaviors of As-Cast Mg-Zn-Er Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.898.305 ◽

2017 ◽

Vol 898 ◽

pp. 305-310

Author(s):

Rui Jing Li ◽

Shu Bo Li ◽

Ke Liu ◽

Zhao Hui Wang ◽

Xian Du ◽

...

Keyword(s):

Electron Microscope ◽

Creep Strain ◽

Volume Fraction ◽

Cast Alloy ◽

Optical Microscope ◽

Quasicrystalline Phase ◽

X Ray Diffraction ◽

Creep Tests ◽

Transmission Electron ◽

Icosahedral Quasicrystalline

The microstructure and creep behaviors of cast Mg-xZn-yEr (x=3,6,9 wt.%, x/y=6) alloys were investigated by X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). XRD results indicated that the main phase compositions of as-cast Mg-xZn-yEr alloys were the icosahedral quasicrystalline phase (I-phase) and α-Mg solid solution. The I-phase mainly distributed in the dendritic and staccato strips. The creep tests were conducted under the condition of 448 K, 70 MPa for 100 h. As the addition of Er increased from 0.5 wt.% to 1.5 wt.%, the total creep strain decreased from 0.962% to 0.512%, and the steady state creep rate decreased from 1.411×10-8s-1 to 4.917×10-9s-1. The I-phase had a tendency to be bulky and continuous, as the volume fraction of Er element increased. Ascribed to the I-phase, the creep strain happened and effectively blocked the movement of dislocations, resulting in the strengthened as-cast Mg-Zn-Er alloys and improved creep resistance. Based on the investigation of creep behaviors, the creep mechanism of the as-cast alloy was mainly grain boundary slipping.

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Effects of Combined Surface Modification on Adhesion Strength of CrN Coatings for STS420

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.297-301.1334 ◽

2010 ◽

Vol 297-301 ◽

pp. 1334-1339

Author(s):

G.C. Jeong ◽

H.J. Choi ◽

Yong Ho Sohn ◽

S.I. Kwun

Keyword(s):

Surface Modification ◽

Adhesion Strength ◽

Intermediate Layer ◽

Scratch Test ◽

X Ray Diffraction ◽

Ion Nitriding ◽

Transmission Electron ◽

Nitrogen Ion ◽

And Performance ◽

Crn Coatings

In order to improve the durability and performance of molds and tools, diverse methods of surface modification are used where the adhesion strength between a substrate and coating plays an important role. To improve adhesion strength, a combined surface modification method is often utilized. In this study, adhesion strength and microstructure of various combined surface modifications (i.e., ion-nitriding, Cr intermediate layer, CrN layer and nitrogen ion- implantation) were examined on STS420. Phase constituents, microstructure, adhesion strength and hardness of coating-substrate system with combined surface modification were examined by using optical microscopy, X-ray diffraction, transmission electron microscopy, scratch test, and nano-indentation. The highest adhesion strength was observed when CrN coating was formed by nitrogen implantation on ion-nitrided substrate with a Cr-intermediate layer. Influence of processing sequence and combination is related to microstructural observations and adhesion strength.

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Synthesis of nanostructured metal (Fe, Al)-C60 composites

MRS Proceedings ◽

10.1557/proc-1276-14 ◽

2010 ◽

Vol 1276 ◽

Author(s):

I. I. Santana García ◽

V. Garibay Febles ◽

H. A. Calderon

Keyword(s):

Raman Spectroscopy ◽

Mechanical Milling ◽

Volume Fraction ◽

High Volume ◽

X Ray Diffraction ◽

Nanostructured Composite ◽

Plasma Sintering ◽

Transmission Electron ◽

Show Evidence ◽

Spark Plasma

AbstractComposites of M-2.5 mol. % Fullerene C60 composites (where M= Fe or Al) are prepared by mechanical milling and Spark Plasma Sintering (SPS). The SPS technique has been used to consolidate the resulting powders and preserve the massive nanostructure. Results of X-Ray Diffraction and Raman Spectroscopy show that larger milling balls (9.6 mm in diameter) produce transformation of the fullerene phase during mechanical milling. Alternatively smaller milling balls (4.9 mm in diameter) allow retention of the fullerene phase. SEM shows homogeneous powders with different particle sizes depending on milling times. Sintering produces nanostructured composite materials with different reinforcing phases including C60 fullerenes, diamonds and metal carbides. The presence of each phase depends characteristically on the energy input during milling. Transmission Electron Microscopy (TEM) and Raman Spectroscopy show evidence of the spatial distribution and nature of phases. Diamonds and carbides can be identified for the sintered Fe containing composites with a relatively high volume fraction.

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On the Study of PbTe-Based Nanocomposite Thermoelectric Materials

Journal of Nano Research ◽

10.4028/www.scientific.net/jnanor.17.165 ◽

2012 ◽

Vol 17 ◽

pp. 165-174 ◽

Cited By ~ 4

Author(s):

Th. C. Hasapis ◽

S. N. Girard ◽

Euripides Hatzikraniotis ◽

Konstantinos M. Paraskevopoulos ◽

M. G. Kanatzidis

Keyword(s):

Volume Fraction ◽

Vibrational Properties ◽

Effective Medium Approximation ◽

Bilayer Thickness ◽

Phonon Confinement ◽

X Ray Diffraction ◽

X Ray ◽

New Class ◽

Transmission Electron ◽

Form Features

We Report on the Structural and Vibrational Properties of the X = 0.11 and X = 0.33 Compositions of a New Class of Nanostructured Thermoelectric System (PbTe)1-X(PbSnS2)x by Means of X-Ray Diffraction, Scanning and Transmission Electron Microscopy and Infrared Reflectivity. both Compositions Are Phase Separated, where Pbsns2 Self-Segregates from Pbte to Form Features with Dimensions Ranging from Tens of Micrometers to Tens of Nanometers. Effective Medium Approximation Was Used in Order to Determine the Volume Fraction and the Dielectric Function of the Nanoscale Pbsns2 Embedded in Pbte. by Comparing the Phonon Parameters of the Nanoscale Pbsns2 and Bulk Pbsns2 Single Crystals, we Concluded that Phonon Confinement Effects and Bilayer Thickness Anisotropy within the Pbsns2 Nanostructures Embedded within Pbte Are Responsible for the Observed Variations in the Frequencies of the Shear and the Compression Modes Not Observed in Pure Crystals of Pbsns2.

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