MnS Layer Research Articles

Self‐Assembly of MnS Shell on CdTe Nanoparticles Induced by Thermohydrolysis: Synthesis and Characterization

Herein, CdTe/MnS core/shell nanoparticles dispersed in an aqueous solution have been synthesized. The formation of MnS semiconductor shell occurs by spontaneous self‐assembly. This process is activated by thermal hydrolysis that removes the excess of thiol and releases S2− ions. In this process, Mn2+ ions on the surface of the CdTe nanoparticles bind to S2− ions to produce a fine semiconducting layer of MnS. Measurements of Raman spectroscopy, optical absorption, and electrochemical measurements are performed. The Raman spectrum shows CdTe characteristic bands at 141 and 163 cm−1. Bands at 221 and 444 cm−1 are associated with the MnS structure. Cyclic voltammetry and differential pulse voltammetry are used to estimate the electrochemical gap at ≈2.47 eV. Absorption optical measurements show tree absorption bands. A broad band between 460 and 520 nm is associated with the first transition in CdTe nanoparticle. The absorption spectrum reveals an optical gap in the range of 2.41–2.33 eV for all the refluxed samples. These values are consistent with those obtained with the electrochemical measurements. The results evidence the formation of a core–shell semiconducting nanostructure made of CdTe nanoparticles coated with a spontaneously self‐assembled thin layer of MnS nanoparticles.

Effect of Rare‐Earth Cerium on Nonmetallic Inclusions in Fe–Mn–C–Al Twinning‐Induced Plasticity Steel

The effect of Ce treatment on nonmetallic inclusions in Fe–Mn–C–Al twinning‐induced plasticity steel is studied by adding different content of rare‐earth cerium. scanning electron microscopy, energy‐dispersive spectroscopy, and electron probe X‐ray microanalyzer analysis show that the main inclusions in Ce‐treated steel change from Al2O3–MnS to CeAlO3–Ce2S3. With the increase of Ce content, the number, size, and density of inclusions in steel decrease, and the morphology of irregular inclusions is closer to the spindle. In this experiment, the size of inclusions in the test sample with 0.0048% Ce addition is the smallest and the distribution of inclusions is the most uniform. Based on the classical thermodynamics and Factsage thermodynamics software, the evolution rule of Ce addition on inclusions is calculated. The thermodynamic calculation results are in good agreement with the experimental results. In addition, combining the experimental phenomena and thermodynamic calculation results, it is revealed that the transformation path of the main inclusions Al2O3–MnS to CeAlO3–Ce2S3 in the Ce‐treated steel is as follows: the outer layer of MnS → CeS → Ce3S4 → Ce2S3; inner layer Al2O3 → CeAlO3 +Ce2O2S. The anisotropy difference between inclusions and iron matrix after Ce treatment is reduced, which reduces the damage of inclusions to steel.

Efficient and stable all-inorganic Sb2(S, Se)3 solar cells via manipulating energy levels in MnS hole transporting layers

The use of organic hole transport layer (HTL) Spiro-OMeTAD in various solar cells imposes serious stability and cost problems, and thus calls for inorganic substitute materials. In this work, a novel inorganic MnS film prepared by thermal evaporation has been demonstrated to serve as a decent HTL in high-performance Sb2(S, Se)3 solar cells, providing a cost-effective all-inorganic solution. A low-temperature air-annealing process for the evaporated MnS layer was found to result in a significant positive effect on the power conversion efficiency (PCE) of Sb2(S, Se)3 solar cells, due to its better-matched energy band alignment after partial oxidation. Impressively, the device with the optimized MnS HTL has achieved an excellent PCE of about 9.24%, which is the highest efficiency among all-inorganic Sb2(S, Se)3 solar cells. Our result has revealed that MnS is a feasible substitute for organic HTL in Sb-based solar cells to achieve high PCE, low cost, and high stability.

Effects of Zn x Mn1−x S buffer layer on nonpolar AlN growth on Si (100) substrate

Thin film growth of Zn x Mn1−x S on a Si (100) substrate by sputtering was investigated for nonpolar AlN film growth on Si (100) substrate. The Zn x Mn1−x S buffer layer reduces the large differences in thermal expansion coefficient and lattice constants between AlN and Si. Although the solubility of ZnS in MnS is less than 5% at 800 °C in bulk form, the insertion of a room-temperature MnS layer between Zn x Mn1−x S and Si enabled (100)-oriented cubic-Zn x Mn1−x S film growth even at x = 9.5%, which is a metastable phase and a phase separation region in bulk form. On the (100)-oriented cubic Zn x Mn1−x S film, nonpolar AlN growth was achieved by sputtering. Furthermore, X-ray photoelectron spectroscopy measurements revealed that the Zn x Mn1−x S film improved the stability of the AlN/Zn x Mn1−x S interface. Zn x Mn1−x S has the potential to enable nonpolar AlN growth on large-diameter Si (100) substrates.

A Function‐Separated Design of Electrode for Realizing High‐Performance Hybrid Zinc Battery

AbstractA rechargeable hybrid zinc battery is developed for reaching high power density and high energy density simultaneously by introducing an alkaline Zn–transition metal compound (Zn–MX) battery function into a Zn–air battery. However, the conventional single‐layer electrode design cannot satisfy the requirements of both a hydrophilic interface for facilitating ionic transfer to maximize the Zn–MX battery function and a hydrophobic interface for promoting gas diffusion to maximize the Zn–air battery function. Here, a function‐separated design is proposed, which allocates the two battery functions to the two faces of the cathode. The electrode is composed of a hydrophobic MnS layer decorated with Ni–Co–S nanoclusters that allows for smooth gas diffusion and efficient oxygen electrocatalysis and a hydrophilic NixCo1−xS2 layer that favors fast ionic transfer and superior performance for energy storage. The battery with the function‐separated electrode shows a high short‐term discharge voltage of ≈1.7 V, an excellent high‐rate galvanostatic discharge–charge with a power density up to 153 mW cm−2 at 100 mA cm−2, a good round‐trip efficiency of 75% at 5 mA cm−2, and a robust cycling stability for 330 h with an excellent voltage gap of ≈0.7 V at 5 mA cm−2.

Formation mechanism of alumina layer in protecting cubic boron nitride inserts in turning cast irons

Among many cast irons, compacted graphite iron (CGI) has recently been gaining more attention due to its superior mechanical properties over the currently more popular flake graphite iron (FGI), aka gray cast iron. However, the poor machinability has prevented CGI to be used in a wider range of potential applications. The resulting tool life difference between FGI and CGI is staggeringly different to be simply explained by the difference in their physical properties. In particular, the excellent machinability of FGI is claimed to be due to the presence of the MnS layer at the interface between cubic boron nitride (cBN) inserts and FGI at high cutting speed. This paper presents the results of our experimental investigation in an attempt to explain the tool wear difference between FGI and CGI while reexamining the formation of such layers. Straight turning experiments were performed with both FGI and CGI with various cBN inserts in dry condition at high cutting speeds (mostly >400 m/min). The flank and crater surfaces of the inserts during turning experiments were investigated and the difference in both flank and crater wear among various cBN inserts are reported as a function of cutting speed. When turning FGI, speckles of MnS, not as a layer, were present based on our EDS/SEM measurement on the cBN inserts, mainly from the MnS inclusions in FGI smearing on the cBN inserts. However, the total area of MnS speckles did not increase as the turning process continues, questioning the formation of the extensive MnS layer protecting the inserts. When turning CGIs, both Mn and S were present individually, not as MnS, on the cBN inserts. Intriguingly, instead of MnS layer, the extensive Al2O3 layer is formed on the rake side on the certain grades of cBN inserts with the Al2O3 binder phase when cutting at high cutting speeds, which functions as the solubility barrier for certain grades of cBN inserts. The crucial difference between FGI and CGI is that the Al2O3 layer is not only larger in coverage but also significantly more stable after turning FGI. Therefore, the tool wear difference between FGI and CGI mainly comes from the formation of the stable Al2O3 layer on the cBN inserts with Al2O3 binder phase when turning FGI. A few additional mechanisms are introduced to make the complete argument behind the remarkable difference in tool wear.

Single molecule sequencing reveals response of manganese-oxidizing microbiome to different biofilter media in drinking water systems

Rapid sand biofiltration (RSBF) is widely used for the removal of contaminants from drinking water treatment systems. Biofilm microbiomes in the biofilter media play essential roles in biotransformation of contaminants, but is not comprehensively understood. This study reports on Mn(II) oxidation and the core microbiomes in magnetite sand RSBF (MagS–RSBF) and manganese sand RSBF (MnS–RSBF). MnS–RSBF showed a relatively higher Mn(II) removal rate (40–91.2%) than MagS–RSBF during the start-up. MagS–RSBF and MnS–RSBF had similar Mn(II) removal rates (94.13% and 99.16%) over stable operation for 80 days. Mn(II) removal rates at different depths in the MnS–RSBF reactor significantly changed with operation time, and the filter in the upper layer of MnS–RSBF made the largest contribution to Mn(II) oxidation once operation had stabilized. PacBio single molecule sequencing of full-length 16S rRNA gene indicated that biofilter medium had a significant impact on the core microbiomes of the biofilms from the two biofilters. The magnetite sand biofilter facilitated the enrichment of Mn(II)-oxidizing biofilms. The dominant populations consisted of Pedomicrobium, Pseudomonas, and Hyphomicrobium in the RSBF, which have been affiliated with putative manganese-oxidizing bacteria (MnOB). The relative abundance of Pedomicrobium manganicum increased with operation time in both RSBF reactors. In addition, Nordella oligomobilis and Derxia gummosa were statistically correlated with Mn(II) oxidation. Species-species co-occurrence networks indicated that the microbiome of MnS–RSBF had more complex correlations than that of MagS–RSBF, implying that biofilter medium substantially shaped the microbial community in the RSBF. Hyphomicrobium and nitrite-oxidizing Nitrospira moscoviensis were positively correlated. The core microbiomes’ composition of both RSBF reactors converged over operation time. A hybrid biofilter medium with magnetite sand and manganese sand may therefore be best in rapid sand filtration for Mn(II) oxidation.

Introducing of MnS passivation layer on TiO2 mesoporous film for improving performance of quantum dot sensitized solar cells

Despite great efforts to improve the power conversion efficiency of quantum dot-sensitized solar cells, the cell performances are still far from the maximum theoretical value. Coating a passivation layer on the surface of quantum dot sensitizers has been proven an effective method to enhance cell performance. Herein, a MnS passivation layer is introduced between mesoporous TiO2 and quantum dot sensitizers, rather than being coated on the surface of the quantum dot sensitizers as is generally done. Two kinds of photoanodes, based on TiO2 nanoparticles and {001}-faceted TiO2 nanosheets, are investigated in this work. The results show that introducing a MnS layer induces larger charge transfer resistance and longer carrier lifetime, thus improving cell performance. The photoanode based on {001}-faceted TiO2 nanosheets achieves better power conversion efficiency than that of the TiO2 nanoparticle-based photoanode. A maximum efficiency of 5.01% is acquired, representing a 27.8% relative increase compared with that of the cell without a deposited passivation layer (3.92%). This improvement is attributed to the formation of a cascaded band structure among quantum dots/MnS/TiO2 nanosheets. The present MnS passivation layer achieves the highest improvement in cell efficiency among the limited reports thus far on the surface passivation of TiO2.

Crystal growth of a MnS buffer layer for non-polar AlN on Si (100) deposited by radio frequency magnetron sputtering

The growth conditions of MnS thin film on a Si (100) substrate deposited by the RF-magnetron sputtering method were investigated. The MnS is a buffer layer for the epitaxial growth of non-polar AlN thin film on the Si (100) substrate. The 4°-off-Si (100) substrate and the insertion of MnS film grown at room temperature (RT-MnS) improved the crystallinity and the surface roughness of the MnS film. In particular, the 20 nm thick RT-MnS showed a reduction of surface roughness of the MnS layer deposited at 550 °C. The root mean square value of the MnS layer was 0.23 nm, which is in the same range as that of the Si substrate. X-ray photoelectron spectroscopy measurements revealed that RT-MnS insertion with a thickness over 10 nm reduced the sulfur vacancy formation in the MnS film deposited on RT-MnS, and the MnS was thermally stable at the growth temperature of AlN.

Improve the performance of the quantum dot sensitized ZnO nanotube solar cells with inserting ZnS-MnS composites layers

Interface passivation layer deposited onto photoanodes has been proven to be an available way to suppress charge recombination and enhance the power conversion efficiency in quantum dot-sensitized solar cells. In this work, the ZnS-MnS composites layers inserted in ZnO/CdS nanotubes photoanodes interface is firstly fabricated via ion-exchange and chemical bath deposition methods, simultaneously. By inserting the ZnS-MnS composites, electron back transfer is efficiently hindered. In addition, the uniform ZnS-MnS layer effectively blocks the direct contact between the polysulfide electrolyte and ZnO nanotubes, which inhabits the recombination of electron-hole pairs occurred at the interface. Besides, the MnS layer is in favour of the CdS quantum dots in higher load, profiting the light absorption intensity in the visible light region. Thus ZnO/ZnS-MnS/CdS nanotubes quantum dot-sensitized solar cells have efficiency of 3.62%, which is much higher than that of the solar cell with ZnS passivation layer (2.33%). This work demonstrates that constructing ZnS-MnS interface passivation layer with a proper band gap structure is a promising approach to enhance the performance of quantum dot-sensitized solar cells.

Particle and microstructural characteristics in the coarse-grained heat-affected zone of Al–Ti–Ca complex deoxidized steels

Abstract The particles and microstructures in the coarse-grained heat-affected zones of Al–Ti–Ca complex deoxidized steels with different Al content were investigated by in-situ observation, various analytical techniques and calculations. The results show that the inclusions in high Al steel consist of Al–Ca oxides containing small amounts of TiO x surrounded by an outer layer of MnS. In low Al steel, the inclusions consist of Al–Ca–Ti oxides with high TiO x content covered by an outer layer of MnS, and the high TiO x content in the inclusions can remarkably enhance the ability of the inclusions to promote acicular ferrite nucleation. The fine-grained microstructure obtained in the coarse-grained heat-affected zones of low Al steel is attributed to the pinning effect of the finer particles and the formation of a high density of acicular ferrite.

Optimization of the MBE growth of metastable zinc blende MnS on GaAs (1 0 0) substrates using ZnS as sulphur source

MnS has been grown by molecular beam epitaxy in the metastable zinc blende (ZB) crystal structure on GaAs (1 0 0) substrates using ZnS as a sulphur source. MnS layers were grown over a wide range of growth conditions by varying the growth temperature from 220 °C to 300 °C and ZnS:Mn flux ratio from 5 to 20. Double-crystal X-ray rocking curves were used to determine the crystallinity and residual zinc content in the layers. This allowed a phase diagram to be produced for ZB MnS giving zinc incorporation as function of the growth temperature and the ZnS:Mn beam flux ratio. In turn, this allowed an optimum growth region to be identified at a growth temperature 240 °C and ZnS:Mn flux ratio 6 where ZB MnS with less than 1% residual zinc incorporation were obtained. Under these optimum growth conditions the maximum ZB MnS layer thickness obtained was double that obtained in previous studies, with layers up to 250 nm thick produced.

Grain refinement in coarse-grained heat-affected zone of Al–Ti–Mg complex deoxidised steel

ABSTRACTThe particles and microstructure characteristics of coarse-grained heat-affected zone (CGHAZ) in Al–Ti–Mg killed steels with different Al contents were investigated. The results show that inclusion in high Al steel consists of Al–Mg oxide surrounded with a layer of MnS. However, inclusion in low Al steel is Al–Ti–Mg oxide covered with a layer of MnS, effectively promoting the formation of acicular ferrite. The precipitates of both steels are (Ti, Nb)N, the finer and more dispersed inclusions and precipitates in low Al steel can effectively inhibit austenite grain growth by grain boundary pinning during the thermal cycle. The fine-grained microstructure is obtained in CGHAZ of the low Al steel due to the pinning effect of finer particles and the high density of acicular ferrite.

Quantitative analysis of microstructure and impact toughness in the simulated coarse-grained heat-affected zone of Cu-bearing steels

ABSTRACTBecause of 0.32% Cu addition, the inclusion is modified from Al-Ti oxide covered with layer of MnS in Cu-free steel to Al-Ti oxide with shell of (Mn,Cu)S in Cu-bearing steel. The quantitative result reveals that the frequency of inclusion effectively for acicular ferrite nucleation, fraction of acicular ferrite and high angle grain boundary in the simulated coarse-grained heat-affected zone (CGHAZ) of Cu-bearing steel are higher than that of Cu-free steel, respectively. Therefore, the high density of acicular ferrite microstructures in CGHAZ of Cu-bearing steel with smaller crystallographic grain size has superior impact toughness than that in Cu-free steel.

Tool Wear Mechanisms of pcBN tooling during High-Speed Machining of Gray Cast Iron

The presence of graphite particles in gray cast iron commonly implies a good machinability, especially if compared to common steels. However, increasing industrial demands have resulted in a new interest for high-speed machining of these materials with higher performing tool materials than the traditionally used. Thus, the research presented in this paper focuses on evaluating the active tool wear mechanisms while high-speed machining EN-GJL-250 gray cast iron with pcBN tools with different composition, geometries and edge preparations. In addition to the expected flank and notch wear, formation of MnS, SiO2, and Al2O3 tool protection layers was found on the worn surfaces. Non-chamfered tools exhibited higher tendency towards notching. In general, the tools were found to have a rather small wear land but large edged radius indicating edge rounding being a more accurate wear criterion.

Enhancement in efficiency of CdS/CdSe quantum dots-sensitized solar cells based on ZnO nanostructures by introduction of MnS layer

In this study, the formation of a MnS layer on the surface of ZnO films was investigated for improving the power conversion efficiency of CdS/CdSe co-sensitized quantum dot solar cells. The results showed that the MnS layer had a remarkable effect on the light-absorption characteristics and short-circuit current density of the solar cells by ensuring that a greater number of quantum dots were adsorbed and by reducing the charge-recombination rate. As a result, the CdS/CdSe/ZnS electrode based on the ZnO film modified with the MnS layer exhibited a power conversion efficiency of 3.45%, which was much higher than for the solar cells without a MnS layer (2.27%).

The role of Cu and Al addition on the microstructure and fracture characteristics in the simulated coarse-grained heat-affected zone of high-strength low-alloy steels with superior toughness

ABSTRACTThe effects of Cu and Al addition on the microstructure and fracture in the coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steels with superior toughness were studied and compared with the X70 pipeline base steel counterpart. The microstructure in base steel was dominated by a small fraction of acicular ferrite and predominantly bainite. However, acicular ferrite microstructure was obtained in Cu-bearing steel, which nucleated on complex oxide with outer layer of MnS and CuS because of Cu addition. The microstructure in Al-bearing steel consisted of bainite with ultrafine martensite–austenite constituent, which was refined by Al addition. CGHAZ in Cu-bearing and Al-bearing steels had superior impact toughness and ductile fracture, which were attributed to acicular ferrite and ultrafine martensite–austenite constituent, respectively.

Effect of Cu addition on microstructure and impact toughness in the simulated coarse-grained heat-affected zone of high-strength low-alloy steels

The effects of Cu content on microstructure and impact toughness in the simulated coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steels were investigated. It has been observed that the microstructure in the simulated CGHAZ of Cu-free steel is dominated by a small proportion of acicular ferrite and predominantly bainite with martensite–austenite constituent. Whereas, in the 0.45 and 1.01% Cu-containing steels, the acicular ferrite increased significantly due to the effective nucleation on intragranular inclusions with outer layer of MnS and CuS. The formation of acicular ferrite is attributed to superior high heat-affected zone impact toughness in the 0.45% Cu-containing steel. Furthermore, the increasing martensite–austenite constituent and ε-Cu precipitates in the simulated CGHAZ of 1.01% Cu-containing steel caused degradation in impact toughness.

Atomic scale understanding of the interaction between alloying copper and MnS inclusions in stainless steels in NaCl electrolyte

The effect of alloying copper on the dissolution of manganese sulphide which triggers the pitting corrosion of stainless steels was studied by in-situ ex-environment transmission electron microscopy (TEM) with an atomic resolution. It was found that the benefits of Cu addition act in two ways: Cu ions replace the Mn ions in the surface layer of MnS and insoluble copper sulphide compound forms; on the other hand, Cu ions could stabilize harmful surphur species released from dissolved MnS. The two processes are supposed to be helpful to reduce the detrimental effect of MnS on the corrosion resistance of stainless steels.

Toughness improvement by Cu addition in the simulated coarse-grained heat-affected zone of high-strength low-alloy steels

The effect of microstructure and Cu addition in a simulated coarse-grained heat-affected zone (CGHAZ) of a high-strength low-alloy (HSLA) steel subjected to 100 kJ cm−1 heat input welding was studied. It has been observed that the primary microstructure in Cu-free HSLA steels is dominated by bainite, whereas, in Cu-bearing HSLA steels, the predominant microstructure is acicular ferrite. The acicular ferrite nucleated at intragranular complex inclusions consisting of Al and Ti oxides, covered with layer of MnS and CuS. The presence of high intensity of acicular ferrite and hard impingements between acicular ferrite laths or plates has contributed to the fine-grained and interlocked microstructure. The enhanced toughness in CGHAZ of Cu-bearing HSLA steel is attributed to the fine-grained interlocked microstructure of acicular ferrite.