Isaac Asempah

Dr. Isaac Asempah


Research Focus & Metrics

Academic Career Length

9Years (2018-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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29 January 2018 in Coatings
Verified
Journal Article
Open access
PDF file
WFWu Fanjing
Wu Fanjing
YLyu lihua
yu lihua
HJHongbo Ju
Hongbo Ju
IAIsaac Asempah
Isaac Asempah
JXJunhua Xu
Junhua Xu
In this study, reactive magnetron sputtering was applied for preparing NbCN-Ag films with different Ag additions. Ag contents in the as-deposited NbCN-Ag films were achieved by adjusting Ag target power. The composition, microstructure, mechanical properties, and tribological properties were characterized using energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscopy (HRTEM), Raman spectrometry, nano-indentation, and high-temperature sliding wear tests. Results indicated that face-centered cubic (fcc) NbN, hexagonal close-packed (hcp) NbN and fcc Ag, amorphous C and amorphous CNx phase co-existed in the as-deposited NbCN-Ag films. After doping with 2.0 at.% Ag, the hardness and elastic modulus reached a maximum value of 33 GPa and 340 GPa, respectively. Tribological properties were enhanced by adding Ag in NbCN-Ag films at room temperature. When the test temperature rose from 300 to 500 °C, the addition of Ag was found beneficial for the friction properties, showing a lowest friction coefficient of ~0.35 for NbCN-12.9 at.% Ag films at 500 °C. This was mainly attributed to the existence of AgOx, NbOx, and AgNbOx lubrication phases that acted as solid lubricants to modify the wear mechanism.


1 September 2019 in Journal of Alloys and Compounds
Verified
Journal Article
Closed access
IAIsaac Asempah
Isaac Asempah
JXJunhua Xu
Junhua Xu
LYLihua Yu
Lihua Yu
HLHuang Luo
Huang Luo
JLJinLin Liu
JinLin Liu
NDNing Ding
Ning Ding

1 October 2020 in Surface and Coatings Technology
Verified
Journal Article
Closed access
DYDian Yu
Dian Yu
LYLihua Yu
Lihua Yu
IAIsaac Asempah
Isaac Asempah
HJHongbo Ju
Hongbo Ju
JXJunhua Xu
Junhua Xu
YGYin Gao
Yin Gao

11 December 2018 in Surface Engineering
Verified
Journal Article
Closed access
IAIsaac Asempah
Isaac Asempah
LYLihua Yu
Lihua Yu
HJHongbo Ju
Hongbo Ju
DYDian Yu
Dian Yu
JXJunhua Xu
Junhua Xu
RMRan Miao
Ran Miao
Ti–B–N (nc-TiN/ a-BN) composite coatings with various boron contents were deposited by magnetron sputtering. nano-indentation, ball-on-disc dry sliding X-ray diffraction, and, Raman spectroscopy was used in evaluating the compositional, mechanical and tribological properties of these coatings. The corrosion behaviour of the Ti–B–N coatings was assessed by the electrochemical potentiodynamic polarisation method in a 3 mol-% of NaCl solution. The coefficient of friction (CoF) of the coatings initially increased to 1.0 when the test temperature was 200°C, but a further increase in temperature to 700°C resulted in a decrease in the CoF value to ∼0.18 which was due to the presence of Magneli-type Ti nO2 n−1 oxides. In contrast to the CoF, there was a consistent increase in wear rate when the temperature was increased; the highest wear rate was obtained at 700°C. The B incorporated coatings exhibited improvement in both oxidation and corrosion resistance properties.

29 April 2022 in Coatings
Verified
Journal Article
Open access
PDF file
BCBin Cheng
Bin Cheng
HCHongmei Chen
Hongmei Chen
IAIsaac Asempah
Isaac Asempah
JWJiheng Wang
Jiheng Wang
YZYilin Zhu
Yilin Zhu
Yanxin QiaoYanxin Qiao
Yanxin Qiao
The barrier properties and diffusion behavior of Cu(Re) alloy films were studied. The films were deposited onto barrierless SiO2/Si by magnetron sputtering. X-ray diffraction patterns and electric resistivity results proved that the Cu(Re) alloy films without a barrier layer were thermally stable up to 550 °C. Transmission electron microscopy images and energy-dispersive spectrometry employing scanning transmission electron microscopy provided evidence for a self-formed Re-enriched diffusion layer between the Cu(Re) alloy and SiO2/Si substrate. Furthermore, the chemical states of Re atoms at the Cu(Re)/SiO2 interface were analyzed by X-ray photoemission spectroscopy. The self-formed diffusion layer was found to be composed of Re metal, ReO, ReO2 and ReO3. At 650 °C, the Cu(Re) layer was completely destroyed due to atom diffusion. The low electrical resistivity in combination with the high thermal stability suggests that the Cu(Re) alloy could be the ultimate Cu interconnect diffusion barrier.