Scanning Auger and Xps Studies of Fracture Surfaces of B4C Hot Pressed with Excess Carbon

AbstractA series of boron carbide materials was hot pressed with 0-7% excess carbon. The strength of each material was determined by four point bending, and found to decrease from about 600MPa to 300MPa as the carbon content increased from 0% to 7%. Diamond indentation yielded hardness values that decreased from 28.3 to 25.OGPa and toughness values that increased from 3.5 to 4.5 MPa√mover the same carbon range. Each sample was fractured in situ in ultrahigh vacuum (UHV) and examined by scanning Auger microanalysis (SAM) and XPS to determine both the elemental and chemical state distributions. For the samples with excess carbon, localized carbonrich regions are observed on fracture surfaces by SAM. XPS reveals a 50% enhancement of excess carbon on the fracture surface compared to the bulk for the sample with 7% excess carbon. A correlation was observed between surface carbon composition and the bulk toughness and hardness. The C(ls) XPS spectra were utilized to determine the nature of carbon in B4C on freshly fractured and Ne+ bombarded surfaces. Two distinct peaks were observed in the C(ls) region. Low dose ion bombardment resulted in a single broad C(ls) peak at the midpoint of the two initial peaks. It can be inferred from this data that there are C-C-C intericosahedral linkages in B4C.

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Outcome of Percutaneous Nephrostomy in Children With Ureteropelvic Junction Obstruction

Bangladesh Journal of Urology ◽

10.3329/bju.v20i2.49654 ◽

2020 ◽

Vol 20 (2) ◽

pp. 61-64

Author(s):

Mohammad Mahfuzur Rahman Chowdhury ◽

Rifat Zaman ◽

Md Amanur Rasul ◽

Akm Shahadat Hossain ◽

Shafiqul Alam Chowdhury ◽

...

Keyword(s):

Renal Function ◽

Low Dose ◽

Ureteropelvic Junction Obstruction ◽

Percutaneous Nephrostomy ◽

Ureteropelvic Junction ◽

College Hospital ◽

Medical College ◽

Split Renal Function

Introduction and objectives: Congenital ureteropelvic junction obstruction (UPJO) is the most common cause of hydronephrosis. Management protocols are based on the presence of symptoms and when the patient is asymptomatic the function of the affected kidney determines the line of treatment. Percutaneous nephrostomy (PCN) became a widely accepted procedure in children in the 1990s. The aim of the study was to evaluate the results of performing percutaneous nephrostomy (PCN) in all patients with UPJO and split renal function (SRF) of less than 10% in the affected kidney, because the management of such cases is still under debate. Methods:This prospective clinical trial was carried out at Dhaka Medical College Hospital from January 2014 to December 2016. Eighteen consecutive patients who underwent PCN for the treatment of unilateral UPJO were evaluated prospectively. In these children, ultrasonography was used for puncture and catheter insertion. Local anesthesia with sedation or general anesthesia was used for puncture. Pig tail catheters were employed. The PCN remained in situ for at least 4 weeks, during which patients received low-dose cephalosporin prophylaxis. Repeat renography was done after 4 weeks. When there was no significant improvement in split renal function (10% or greater) and PCN drainage (greater than 200 ml per day) then nephrectomies were performed otherwise pyeloplasties were performed. The patients were followed up after pyeloplasty with renograms at 3 months and 6 months post operatively. Results: All the patients had severe hydronephrosis during diagnosis and 14 patients with unilateral UPJO were improved after PCN drainage and underwent pyeloplasty. The rest four patients that did not show improvement in the SRF and total volume of urine output underwent nephrectomy. In the patients with unilateral UPJO who improved after PCN drainage, the SRF was increased to 26.4% ±8.6% (mean± SD) after four weeks and pyeloplasty was performed. At three and six months follow-up, SRF value was 29.2% ±8.5% and 30.8.2% ±8.8% respectively. Conclusion: Before planning of nephrectomy in poorly functioning kidneys (SRF < 10%) due to congenital UPJO, PCN drainage should be done to asses improvement of renal function. Bangladesh Journal of Urology, Vol. 20, No. 2, July 2017 p.61-64

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In-Situ Synchrotron X-ray Diffraction Investigation of Microstructural Evolutions During Low-Pressure Carburizing

Metallurgical and Materials Transactions A ◽

10.1007/s11661-021-06171-2 ◽

2021 ◽

Author(s):

Ogün Baris Tapar ◽

Jérémy Epp ◽

Matthias Steinbacher ◽

Jens Gibmeier

Keyword(s):

Carbon Content ◽

Carbon Diffusion ◽

Low Pressure ◽

Carbon Accumulation ◽

Experimental Chamber ◽

Carbide Formation ◽

X Ray Diffraction ◽

X Ray ◽

Carbon Supply

AbstractAn experimental heat treatment chamber and control system were developed to perform in-situ X-ray diffraction experiments during low-pressure carburizing (LPC) processes. Results from the experimental chamber and industrial furnace were compared, and it was proven that the built system is reliable for LPC experiments. In-situ X-ray diffraction investigations during LPC treatment were conducted at the German Electron Synchrotron Facility in Hamburg Germany. During the boost steps, carbon accumulation and carbide formation was observed at the surface. These accumulation and carbide formation decelerated the further carbon diffusion from atmosphere to the sample. In the early minutes of the diffusion steps, it is observed that cementite content continue to increase although there is no presence of gas. This effect is attributed to the high carbon accumulation at the surface during boost steps which acts as a carbon supply. During quenching, martensite at higher temperature had a lower c/a ratio than later formed ones. This difference is credited to the early transformation of austenite regions having lower carbon content. Also, it was noticed that the final carbon content dissolved in martensite reduced compared to carbon in austenite before quenching. This reduction was attributed to the auto-tempering effect.

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Carbon Particle In-Situ Alloying of the Case-Hardening Steel 16MnCr5 in Laser Powder Bed Fusion

Metals ◽

10.3390/met11060896 ◽

2021 ◽

Vol 11 (6) ◽

pp. 896

Author(s):

Matthias Schmitt ◽

Albin Gottwalt ◽

Jakob Winkler ◽

Thomas Tobie ◽

Georg Schlick ◽

...

Keyword(s):

Laser Beam ◽

Mechanical Strength ◽

Carbon Content ◽

Metal Powder ◽

Case Hardening ◽

Powder Bed Fusion ◽

Powder Bed ◽

Carbon Particles ◽

Case Hardening Steel

The carbon content of steel affects many of its essential properties, e.g., hardness and mechanical strength. In the powder bed fusion process of metals using a laser beam (PBF-LB/M), usually, pre-alloyed metal powder is solidified layer-by-layer using a laser beam to create parts. A reduction of the carbon content in steels is observed during this process. This study examines adding carbon particles to the metal powder and in situ alloying in the PBF-LB/M process as a countermeasure. Suitable carbon particles are selected and their effect on the particle size distribution and homogeneity of the mixtures is analysed. The workability in PBF-LB is then shown. This is followed by an evaluation of the resulting mechanical properties (hardness and mechanical strength) and microstructure in the as-built state and the state after heat treatment. Furthermore, potential use cases like multi-material or functionally graded parts are discussed.

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Peridotite dissolution and carbonation rates at fracture surfaces under conditions relevant for in situ mineralization of CO2

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2012.12.001 ◽

2013 ◽

Vol 106 ◽

pp. 1-24 ◽

Cited By ~ 26

Author(s):

R. van Noort ◽

C.J. Spiers ◽

M.R. Drury ◽

M.T. Kandianis

Keyword(s):

Fracture Surfaces

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Research on Anisotropic Fracture Mechanical Behavior of Cortical Bone with Combined Method of Fractal and Gray Level Co-Occurrence Matrix

Journal of Biomaterials and Tissue Engineering ◽

10.1166/jbt.2021.2569 ◽

2021 ◽

Vol 11 (1) ◽

pp. 67-75

Author(s):

Dagang Yin ◽

Bin Chen ◽

Huifen Zhou

Keyword(s):

Mechanical Properties ◽

Fracture Surface ◽

Cortical Bone ◽

Fracture Mechanisms ◽

Gray Level ◽

Combined Method ◽

Characteristic Parameters ◽

Fracture Surfaces ◽

Anisotropic Fracture ◽

Occurrence Matrix

The irregular fracture surface of cortical bone, which is caused by complex multilevel micro-nanostructure, reflects the mechanical properties and fracture mechanisms. It is of great significance to characterize some characteristic parameters from the fracture surfaces of bone. In this research, anisotropic fracture mechanical properties of bovine femoral cortical bone along transverse, longitudinal and radial direction are firstly obtained by three-point bend experiment. Then the fracture routes and fracture surfaces are observed by scanning electron microscope. The observation shows that the formed fracture surfaces, which are caused by different crack routes, are extremely rough and have complex textures. Lastly, the combined method of fractal and gray level co-occurrence matrix are adopted to describe the morphology of fracture surface of cortical bone objectively and quantitatively. It is shown that the fracture surface of cortical bone has obvious fractal characteristics and four statistical texture feature parameters (contrast,angular second moment, correlation and entropy) of GLCM of fracture surfaces can describe a certain fracture texture character. The relationship between the characteristic parameters and macroscopic mechanical properties are established. The quantitative analysis and automatic class identification for the fracture surfaces of cortical bone can be achieved.

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In situ TEM observations of ion irradiation damage in boron carbide

Journal of the European Ceramic Society ◽

10.1016/j.jeurceramsoc.2018.11.011 ◽

2019 ◽

Vol 39 (4) ◽

pp. 726-734 ◽

Cited By ~ 4

Author(s):

Guillaume Victor ◽

Yves Pipon ◽

Nathalie Moncoffre ◽

Nicolas Bérerd ◽

Claude Esnouf ◽

...

Keyword(s):

Boron Carbide ◽

Ion Irradiation ◽

Irradiation Damage ◽

In Situ Tem

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Periodic corrugation on fracture surface of Zr-based bulk metallic glass composite with in situ precipitated nanocrystalloids

10.1063/1.4794656 ◽

2013 ◽

Cited By ~ 1

Author(s):

Shengli Zhu ◽

Guoqiang Xie ◽

Hao Wang ◽

Fengxiang Qin

Keyword(s):

Fracture Surface ◽

Metallic Glass ◽

Bulk Metallic Glass ◽

Glass Composite ◽

Bulk Metallic Glass Composite

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29Si NMR and XPS Investigation of the Structure of Silicon Oxycarbide Glasses Derived from Polysiloxane Precursors

MRS Proceedings ◽

10.1557/proc-346-351 ◽

1994 ◽

Vol 346 ◽

Cited By ~ 8

Author(s):

R.J.P. Corriu ◽

D. Leclercq ◽

P.H. Mutin ◽

A. Vioux

Keyword(s):

Solid State ◽

Photoelectron Spectroscopy ◽

Solid State Nmr ◽

Random Distribution ◽

Silicon Oxycarbide ◽

29Si Nmr ◽

Xps Spectra ◽

Excess Carbon ◽

X Ray ◽

Silicon Oxycarbide Glasses

ABSTRACTTwo silicon oxycarbide glasses with different compositions (O/Si ratio 1.2 and 1.8) were prepared by pyrolysis at moderate temperature (900 °C) of polysiloxane precursors. Their structure was investigated using quantitative 29Si solid-state NMR and X-ray photoelectron spectroscopy (XPS). The environment of the silicon atoms in the oxycarbide phase corresponded to a purely random distribution of Si-O and Si-C bonds depending on the O/Si ratio of the glass only and not on the structure of the precursors. At the light of the NMR results, the Si2p XPS spectra of the glasses may be interpreted using the contribution of the five possible SiOxC4-x tetrahedra. The Cls spectra of these glasses indicated the presence of oxycarbide carbon in CSi4 tetrahedra, similar to carbide carbon, and graphitic-like excess carbon.

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Pressureless Sintering of Boron Carbide-Based Superhard Materials

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.159.145 ◽

2010 ◽

Vol 159 ◽

pp. 145-148 ◽

Cited By ~ 7

Author(s):

Dimitar D. Radev

Keyword(s):

Transition Metal ◽

Boron Carbide ◽

Sintering Temperature ◽

Liquid Phase Sintering ◽

Vacuum Furnace ◽

Pressureless Sintering ◽

Metal Carbides ◽

Sintering Aids ◽

Transition Metal Carbides

Boron carbide-based materials B4C-MexBy were densified by pressureless sintering in a vacuum furnace. Some transition metal carbides (TiC, ZrC, HfC, Cr3C2 and WC) from groups IV-VI were used as sintering aids. The optimal sintering temperature in the range 2220-2250oC was used for any composition. Here we show the possibilities to activate the mass transport of the B4C by the mechanism of liquid phase sintering. The method of reactive sintering of B4C in the presence of additives of some transition metal carbides allows in situ synthesis of dense B4C-MexBy materials. Structural properties and fracture toughness of the B4C-based composite materials were discussed. The properties of some of these materials and the possibilities for their application are also discussed.

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