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- Ben Hassine, Mohamed, 1985, et al.
(författare)
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Growth model for high-Al containing CVD TiAlN coatings on cemented carbides using intermediate layers of TiN
- 2021
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Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 421
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Tidskriftsartikel (refereegranskat)abstract
- This work concerns high Al-containing TixAl1-xN coatings prepared using low pressure-chemical vapour deposition (LP-CVD). The coatings were examined using electron microscopy techniques, such as scanning transmission electron microscopy (STEM), energy dispersive X-ray analysis (EDX) and transmission Kikuchi diffraction (TKD). An intermediate TiN-layer with a 〈211〉 texture consisting of twinned, needle-shaped grains influences the subsequent growth of the TiAlN layer. The TiAlN grains were columnar with a texture of 〈211〉. As the grains grow along 〈111〉, with {001} facets, this led to a tilted pyramid surface morphology. The grains developed an internal periodic epitaxial nanolamella structure. The thicknesses were 2 nm for the low (x = 0.6) and 6 nm for the high (x = 0.9) Al-containing lamellae. The TiAlN layer growth could be described by a “two-wing” model, where two TiAlN grains with a twin-related orientation grow on a twinned TiN grain, where the two TiAlN grains gradually switch sides, making the appearance of two wings of columnar grains. In general, this work shows that it should be possible to control the growth of TiAlN layers by controlling the texture and morphology of an intermediate layer, such as TiN.
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| 2. |
- Bill-Axelson, Anna, et al.
(författare)
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Radical Prostatectomy or Watchful Waiting in Early Prostate Cancer
- 2014
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Ingår i: New England Journal of Medicine. - Waltham : Massachusetts Medical Society. - 0028-4793 .- 1533-4406. ; 370:10, s. 932-942
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundRadical prostatectomy reduces mortality among men with localized prostate cancer; however, important questions regarding long-term benefit remain. MethodsBetween 1989 and 1999, we randomly assigned 695 men with early prostate cancer to watchful waiting or radical prostatectomy and followed them through the end of 2012. The primary end points in the Scandinavian Prostate Cancer Group Study Number 4 (SPCG-4) were death from any cause, death from prostate cancer, and the risk of metastases. Secondary end points included the initiation of androgen-deprivation therapy. ResultsDuring 23.2 years of follow-up, 200 of 347 men in the surgery group and 247 of the 348 men in the watchful-waiting group died. Of the deaths, 63 in the surgery group and 99 in the watchful-waiting group were due to prostate cancer; the relative risk was 0.56 (95% confidence interval [CI], 0.41 to 0.77; P=0.001), and the absolute difference was 11.0 percentage points (95% CI, 4.5 to 17.5). The number needed to treat to prevent one death was 8. One man died after surgery in the radical-prostatectomy group. Androgen-deprivation therapy was used in fewer patients who underwent prostatectomy (a difference of 25.0 percentage points; 95% CI, 17.7 to 32.3). The benefit of surgery with respect to death from prostate cancer was largest in men younger than 65 years of age (relative risk, 0.45) and in those with intermediate-risk prostate cancer (relative risk, 0.38). However, radical prostatectomy was associated with a reduced risk of metastases among older men (relative risk, 0.68; P=0.04). ConclusionsExtended follow-up confirmed a substantial reduction in mortality after radical prostatectomy; the number needed to treat to prevent one death continued to decrease when the treatment was modified according to age at diagnosis and tumor risk. A large proportion of long-term survivors in the watchful-waiting group have not required any palliative treatment. (Funded by the Swedish Cancer Society and others.) The randomized Swedish trial of prostatectomy versus watchful waiting in disease detected mainly clinically (not by PSA screening) continues to show a benefit for early prostatectomy. The number of men younger than 65 needed to treat to prevent one death is now four. The Scandinavian Prostate Cancer Group Study Number 4 (SPCG-4), a randomized trial of radical prostatectomy versus watchful waiting in men with localized prostate cancer diagnosed before the era of prostate-specific antigen (PSA) testing, showed a survival benefit of radical prostatectomy as compared with observation at 15 years of follow-up.(1) By contrast, the Prostate Cancer Intervention versus Observation Trial (PIVOT), initiated in the early era of PSA testing, showed that radical prostatectomy did not significantly reduce prostate cancer-specific or overall mortality after 12 years.(2) PSA screening profoundly changes the clinical domain of study. Among other considerations, the substantial additional lead time ...
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| 8. |
- Qiu, Ren, 1993, et al.
(författare)
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Atom probe tomography investigation of 3D nanoscale compositional variations in CVD TiAlN nanolamella coatings
- 2021
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Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 426
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Tidskriftsartikel (refereegranskat)abstract
- The cubic (Ti1−xAlx)Ny (TiAlN) phase with a nanolamella structure, synthesized via low pressure chemical vapour deposition (LPCVD), has been widely used in wear-resistant coatings during the latest years. The nanolamella structured TiAlN coatings contain periodic and epitaxially grown Ti-rich [denoted as Ti(Al)N] and Al-rich [denoted as Al(Ti)N] lamellae. However, the chemical compositions of these nano-structures have not been fully revealed. In this study, the microstructure of the nanolamella TiAlN coating was studied using scanning and transmission electron microscopy (SEM and TEM), and the chemical content was investigated using atom probe tomography (APT) that provides three-dimensional composition data with good accuracy and a spatial resolution down to the nanometer scale. It was found that over- and under-stoichiometries of N exist for the Ti(Al)N and the Al(Ti)N lamellae, respectively. According to the previous simulation results, such over- and under-stoichiometries are due to metal (Al and Ti) and N vacancies, respectively. The Al(Ti)N lamellae have a chemical formula of (Ti0.12Al0.88)N0.90, and have 10% N vacancies. The Ti(Al)N lamellae have a chemical formula of (Ti0.70Al0.30)0.97N, and have 3% metal (Al and Ti) vacancies. In addition to the nanolamella structure, compositional variations on a scale of a few nm were found in both types of lamellae. In the Ti-richest volumes, the composition corresponds to (Ti0.72Al0.28)0.88N so a maximum of 12% of metal vacancies exists. In the Al-richest volumes, the composition corresponds to (Ti0.07Al0.93)N0.64 so a maximum of 36% N vacancies exists. In addition, a small amount of Cl (around 0.1 at.%) was found in the coating, which could originate from the incomplete dissociation of chloride precursors during the CVD surface reaction.
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| 9. |
- Qiu, Ren, 1993, et al.
(författare)
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CVD TiAlN coatings with tunable nanolamella architectures
- 2021
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Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 413
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Tidskriftsartikel (refereegranskat)abstract
- In this work, Ti1-xAlxN (TiAlN) coatings were synthesized by low pressure chemical vapour deposition (LPCVD), and the influence of a rotational precursor gas supply on the coating microstructure was studied. The microstructure of the TiAlN coatings were characterized using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and electron backscattered diffraction (EBSD). It is shown that a rotational precursor gas supply induces an oscillatory surface reaction, which causes a nanolamella architecture. When the gas beam directly hits the sample, the local gas flow velocity is high, which increases the deposition rate of Ti and a Ti(Al)N lamella is formed. When the gas beam rotates away, the local gas velocity is low, so the deposition rate of Ti decreases, and an Al(Ti)N lamella is formed. As this is repeated a periodic nanolamella architecture is formed. The nanolamellae grow epitaxially on three {001} facets of the 111 textured grains, which leads to a pyramidal surface morphology. Without gas supply rotation, a high Al content cubic phase was still obtained, but no nanolamella was formed. This indicates that Ti-rich lamellae are not necessary to stabilize an Al-rich cubic TiAlN phase. In addition, spinodal decomposition is not likely to be the driving force behind the nanolamella formation in LPCVD TiAlN, as this would also have happened in the sample without a rotational gas supply. Finally, the nanolamella periodicity is found to be tunable via controlling the rotation speed of the precursor supply relative to the coating growth rate.
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| 10. |
- Qiu, Ren, 1993, et al.
(författare)
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Effects of gas flow on detailed microstructure inhomogeneities in LPCVD TiAlN nanolamella coatings
- 2020
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Ingår i: Materialia. - : Elsevier BV. - 2589-1529. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Depositing homogeneous TiAlN coatings with a high Al content on cutting tool inserts is a challenging task. In this work, high-Al cubic Ti1-xAlxN coatings (average x = 0.8) with periodic Ti(Al)N (x = 0.5) and Al(Ti)N (x = 0.9) nanolamellae structure were synthesized by low pressure chemical vapour deposition (LPCVD) with different gas flow velocities, and the detailed microstructure was investigated by electron microscopy and simulations. Using a high gas flow rate, the columnar TiAlN grains with regular periodic nanolamella structures disappeared, the coating became enriched in Ti and hexagonal AlN (h-AlN) formed in the coating. The high Ti content is suggested to be caused by the high gas flow rate that increases the mass transport of the reactants. However, this does not influence the Al-deposition much as it is mainly limited by the surface kinetics due to the relatively low deposition temperature. Density functional theory (DFT) modelling and electron microscopy showed that h-AlN tends to form on the Ti(Al)N phase with a specific crystallographic orientation relationship. The Ti enrichment due to high gas flow rate promotes the formation of h-AlN, which therefore deteriorates the nanolamella structure and causes the disappearance of the columnar TiAlN grains. Thus, by designing the CVD process conditions to avoid too high gas flow rates, homogenous TiAlN coatings with high Al content and nanolamella structures can be deposited, which should yield superior cutting performance.
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