Advanced Nitride Research Articles

Highly active manganese nitride-europium nitride catalyst for ammonia synthesis

The development of efficient catalysts for ammonia synthesis under mild conditions is critical for establishing a carbon-neutral society powered by renewable ammonia. While significant effort has been focused on Fe and Ru-based catalysts, there have been very limited studies on manganese-based catalysts for ammonia synthesis because of their low intrinsic catalytic activity. Herein, we report that the synergy between manganese nitride (Mn4N) and europium nitride (EuN) yields an ammonia synthesis rate that is 41 and 25 times higher than that of neat Mn4N and EuN, respectively. Detailed studies suggest that a [Eu-N-Mn] species at the interface of Mn4N and EuN plays a pivotal role in ammonia synthesis. Compositing of Mn4N with other rare earth metal nitrides such as LaN, PrN, and CeN also leads to a significant enhancement in catalytic activity. This work broadens the scope of advanced nitride catalysts for ammonia synthesis.

Unification of the BN-1200 reactor core designs with MOX and MNUP fuel

Two types of mixed uranium-plutonium fuel are considered for BN-1200 reactor (Matveev and Khomyakov, 2012) within the framework of Proryv Project: conventional, well-mastered MOX fuel and advanced nitride fuel (MNUP fuel) having higher density. Decision about the expediency of use of this or that type of fuel in the first BN-1200 reactors at the initial stage of their operation will be made taking into account the results of MNUP fuel pins tests carried out in BOR-60 and BN-600 reactors. In this report the information on basic engineering decisions taken in the design of BN-1200 reactor core (Vasiliev et al., 2010; Shepelev et al., 2013; Vasiliev et al., 2017) is given, features of cores with MOX and MNUP fuels are analyzed, possible variants of cores with unified design of fuel pins and FSA are presented, estimates of core characteristic change with increased fuel burnup are given, problems of transition from MOX fuel to MNUP fuel are considered.

RETRACTED: Core design and analysis of a lead-bismuth cooled small modular reactor

Abstract Small modular reactors (SMR) are in great demands in the near future and the lead-based fast reactor is one of the most important directions in the development of SMR. In this paper, core design and analysis of a LEad-bismuth Small MOdular Reactor (LESMOR) was developed and examined to realize the notion of “LESS is MORE”. LESMOR is a 300 MWt pool-type reactor where all facilities are mounted in a reactor vessel. Advanced nitride fuel is adopted, and the spent-plutonium is used as the driven fuel and thorium is used as the fertile fuel. Sub-channel analysis was performed in the assembly design using an in-house sub-channel code SUBAS, and the 11 × 11 scheme with a pitch-to-diameter (P/D) ratio of 1.4 was adopted. The full core neutronic performance was studied and evaluated in this paper. Results show that the reactor can be maintained critical for 20 years and the maximum radial power factor is 1.28. The steady-state thermal-hydraulic performance of the core was analyzed, including the characteristics of the mass flow distribution and the hottest assembly. The peaking fuel cladding temperature is 519.2 °C, and the maximum fuel center temperature is 723.4 °C, both within the temperature limit. This paper provides valuable information in the neutronic and thermal-hydraulic design and analysis of LBE nuclear reactor.

Investigating the effects of hybrid reinforcement particles on the microstructural, mechanical and tribological properties of friction stir processed copper surface composites

Friction Stir Processing (FSP) technique was employed in this research to fabricate copper surface composites through incorporating a hybrid mixture of reinforcement particles. Hybrid combination of advanced nitride based ceramic particles (25% AlN + 75% BN) was dispersed onto the surface of copper matrix at varying volume fractions through FSP technique. Results demonstrated an increase in mechanical properties with respect to increase in the amount of particle dispersion. Mechanism of fracture for developed set of surface composites was studied with the aid of fractography. A tremendous increase in wear resistance was observed with respect to increase in hybrid particle dispersion owing to the hardness and self-lubricating characteristics of dispersed ceramic particles.

Neutronic/thermal‐hydraulic design features of an improved lead‐bismuth cooled small modular fast reactor

Lead-based fast reactors (LFRs) have unique advantages in the development of a SMR, which has attracted a lot of attention in recent years. In this paper, an optimized design for a lead-bismuth small modular reactor was studied on the basis of the design of SUPERSTAR. This paper aims to propose an improved LFR core scheme to enhance the neutronic performance as well as the thermal-hydraulic safety of the reference reactor. Advanced nitride fuel is adopted in which the plutonium is used as the driven fuel, while thorium is used as the fertile fuel. Subchannel analysis was performed in the assembly design using an in-house subchannel code, SUBAS, and an 11 × 11 scheme with a pitch-to-diameter (P/D) ratio of 1.4 was chosen. Using the modified assembly, the core was redesigned using the coupled code MCORE. The active core was divided into four zones with different enrichment of 239Pu to extend the core lifetime and flatten the power distribution. The main kinetic parameters and reactivity coefficients were obtained. Neutronic performance at different operation times was also studied. The maximum radial power peak factor was 1.28, while the maximum total power peak factor was 1.737. During the whole lifetime, the reactivity swing was 0.926$, which was below the limit of 1$. The subchannel study of the core flow distribution showed that a flow distributor is needed to further improve the flow distribution capability. The peaking cladding temperature was 508.7°C, and the maximum fuel center temperature was 723.4°C, both of which do not exceed the limit temperature. Compared with features of SUPERSTAR, the peaking cladding temperature was well improved and the lifetime extended.

Load sensitivity in repetitive nano-impact testing of TiN and AlTiN coatings

A key step in optimisation of coating behaviour is to understand the relationship between a range of parameters that can easily be obtained in the repetitive nano-impact test and ultimate coating performance in demanding applications. In this study we have performed a statistical analysis of multiple repetitive impact tests on advanced nitride coating systems and have identified the key parameters that can be used to assess durability and wear resistance. At lower load the coating mechanical properties and microstructure are beneficial in providing improved impact resistance. At higher load the initial impact resistance is also enhanced in non-columnar coatings with higher resistance to plastic deformation but their limited ductility can affect their damage tolerance under continued impact.

Physical characteristics of large fast-neutron sodium-cooled reactors with advanced nitride and metallic fuels

Mixed nitride uranium–plutonium fuel is the most attractive and advanced type of fuel for fast-neutron sodium-cooled reactors, and is considered as the base fuel for future commercial fast-neutron power reactors. However, a substantial increase in breeding achieved thanks to the use of this fuel instead of oxide fuel is not enough to meet new requirements the major of which, minimization of the burn-up reactivity margin, is defined by the reactor core breeding. This paper presents the results of computational studies aimed at choosing the best possible layout for the core of a large fast-neutron sodium-cooled reactor meeting modern requirements.Metallic fuel has been considered as the fuel for fast-neutron reactors since their early designs due to high density and heat conductivity and the smallest possible number of the diluent nuclei which provides for the highest possible breeding efficiency. The paper presents the features of the fuel under consideration and the results of computational studies into its application in large fast-neutron sodium-cooled reactors as compared to nitride fuel. A conclusion is made that, with the same design of the reactor core, metallic fuel is inferior to nitride fuel from the point of view of ensuring the safety of the reactor facility.Most of the calculations were performed in a diffusive approximation based on the TRIGEX software package.

Физические характеристики быстрых натриевых реакторов большой мощности на перспективных видах топлива – нитридном и металлическом

Физические характеристики быстрых натриевых реакторов большой мощности на перспективных видах топлива – нитридном и металлическом

In situ characterization of the nitridation of dysprosium during mechanochemical processing

Processing of advanced nitride ceramics traditionally requires long durations at high temperatures and, in some cases, in hazardous atmospheres. In this study, dysprosium mononitride (DyN) was rapidly formed from elemental dysprosium in a closed system at ambient temperatures. An experimental procedure was developed to quantify the progress of the nitridation reaction during mechanochemical processing in a high energy planetary ball mill (HEBM) as a function of milling time and intensity using in situ temperature and pressure measurements, SEM, XRD, and particle size analysis. No intermediate phases were formed. It was found that the creation of fresh dysprosium surfaces dictates the rate of the nitridation reaction, which is a function of milling intensity and the number of milling media. These results show clearly that high purity nitrides can be synthesized with short processing times at low temperatures in a closed system requiring a relatively small processing footprint.

Corrosion Resistance of CrSiN Coatings by Cathodic Arc Deposition with Different Arc Currents

Bipolar plate with multiple functions is one of the essential components of the PEMFC (Proton Exchange Membrane Fuel Cells) stacks. Recently, metallic bipolar plates, particularly different grades of stainless steels, have been increasingly considered due to relatively low cost, good corrosion resistance, sufficient stiffness and excellent flexibility in thin forms, and easy manufacturability [1-3]. However, the major concerns with the use of stainless steel alloys as bipolar plates are their corrosion resistance and interfacial electrical resistance under long operation conditions. Development of advanced ternary nitride coatings such as chromium silicon nitride (CrSiN) has attracted significant industrial interest in recent years [4-11]. Si addition of CrN to form CrSiN films were prepared by cathode arc ion deposition technique and magnetron sputter technique, in order to improve the characterizations of the coatings from structure to corrosion behaviors. It is reported that with the additional element of Si, the hardness and corrosion resistance of the CrSiN coatings can be greatly improved compared to that of the CrN coating. A direct link between the microstructure and mechanical properties of CrSiN coatings with varying Si contents was established [8]. With increasing Si content, the structure of CrSiN coating exhibited the transformation from a columnar-grained structure to a nanocomposite structure, consisting of CrN nanocrystallites embedded in an amorphous matrix. A maximum hardness of 26.6 GPa was found for CrSiN coating with Si content of about 6.7 at.%, while that of pure CrN was 19.4 GPa [6]. Up to now, the CrSiN is yet thoroughly investigated.

A Technology Overview of the PowerChip Development Program

The PowerChip research program is developing technologies to radically improve the size, integration, and performance of power electronics operating at up to grid-scale voltages (e.g., up to 200V) and low-to-moderate power levels (e.g., up to 50W) and demonstrating the technologies in a high-efficiency light-emitting diode driver, as an example application. This paper presents an overview of the program and of the progress toward meeting the program goals. Key program aspects and progress in advanced nitride power devices and device reliability, integrated high-frequency magnetics and magnetic materials, and high-frequency converter architectures are summarized.

Experimental investigations of advanced ceramics in high efficiency deep grinding

In order to improve machining efficiency and grinding surface integrality of advanced ceramics, the effect of different grinding conditions (different wheel speed, different depth of cut or different feed rate) on surface characteristics, grinding force, specific grinding energy and material remove modes of advanced ceramics, including alumina, nitride silicon and yttria partially stabilized zirconia, are studied under high efficiency deep grinding condition. Special grinding efficiency and depth of cut arrive at 120 mm/(mm·s) and 6 mm respectively. Experiments indicate that the increase in wheel speed and decrease in depth of cut, i.e., decrease in maximum undeformed chip thickness, result in decrease in specific grinding force, increase in specific grinding energy and plough striations. It is shown that the grinding efficiency increases and the surface integrality does not become worse under grinding condition of great depth of cut.

Structural Refinement in High Temperature Annealing of Magnetron Sputtered Titanium Vanadium Nitride Coatings

Development of advanced ternary nitride coatings such as titanium aluminium nitride and titanium vanadium nitride has attracted significant industrial interest in recent years. Titanium vanadium nitride is considered one of the advanced ternary nitride coatings of great commercial potential. It is believed with the additional element, the oxidation resistance of the coatings can be greatly improved at elevated temperatures. Furthermore, the type of elements selected can produce unique coating properties that can be beneficial to machining of different materials. This paper is to report a study on the structural stability of nanostructured titanium vanadium nitride coatings in high temperature annealing. Nanostructured titanium vanadium nitride coatings were produced by reactive magnetron co-sputtering on AISI H13 tool steel substrates at 240oC. Heat treatment was applied to the coatings at temperatures up to 1000oC. It was found that an unexpected grain refinement of the coatings occurred in the heat treatment process. Grain size of the coatings was found to decrease from ~200-300 nm to ~150 nm after the heat treatments. A strong TiN/TiVN (200) component was found to exist at temperatures up to 700oC but was depleted at higher annealing temperatures. With a finer and densified grain structure, the hardness of the coatings substantially increased from ~800 HV to ~1700 HV.

Pulsed laser deposition of advanced titanium nitride thin layers

Pulsed laser deposition of advanced titanium nitride thin layers

The chemistry and physics of modelling nitride fuels for transmutation

Against the background of increased interest in nitride fuel for transmutation of minor actinides, this paper presents the current status of UK modelling of nitride fuel pins. A new equilibrium chemistry model for nitride fuel, suitable for inclusion in fuel pin modelling codes, is described. High-temperature experiments on (U,Zr)N in a sealed capsule indicate that actinide nitrides in a nitrogen atmosphere are stable up to their melting point. The paper also recommends a set of physical and chemical properties for advanced nitride fuels, highlighting the areas where data are presently missing.

Front-end, single-wafer diffusion processing for advanced 300-mm fabrication lines

Single-wafer, diffusion processing offers the possibility to significantly reduce cycle times, provide ‘greener’ processes and fulfil key technology requirements of ever-reducing thermal budgets and improving critical thin-film interface control. This paper will discuss the cycle time and other potential gains of a transition to 300-mm single-wafer diffusion processing and go on to describe work carried out on such processing for advanced nitride CMOS gate and SiGe applications. Multi-product, multi-process ASIC/SOC 300-mm processing will require aggressive cycle times to ensure early time-to-market, rapid time-to-volume and accelerated development of new technologies and functionality. One of the key cycle time detractors in current multi-process facilities is the batching requirement in diffusion. The advantages of a transition to single-wafer diffusion processing will be presented. A nitrided CMOS gate application has been studied on a 300-mm single-wafer tool featuring a module for RTA/RTO/RTN, a module for mono-Si/poly-Si and SiGe CVD deposition and a cool-down chamber equipped with optical metrology to allow direct control of different steps. Different pre- and post-nitridation steps on oxide or oxide-free silicon surface will be reported that demonstrates the advantages of such an integrated single-wafer tool.

Enhancing materials design capability through understanding multicomponent phase relationships

Abstract

Material chemistry studies - their role for the development of advanced nitride materials

Abstract

A 96 kHz 16 bit dual channel A/D converter LSI for digital audio applications

A low-cost, 96-kHz, 16-bit dual-channel A/D (analog/digital) converter LSI has been developed. Its S/N (signal/noise) ratio is 93 dB, and the THD (total harmonic distortion) is 0.003%. When the converter is used in combination with an antialiasing digital filter, it is possible to reduce the order of the analog filter preceding the A/D converter, which might be harmful to the sound quality. To realize low cost, this LSI is fabricated by a conventional bipolar process, A-NSA (advanced nitride self-aligned process). The discussion covers the features of A-NSA, the A/D conversion principle, the method used to achieve high-speed conversion, the DC offset compensation circuit, and the performance of the converter. >

Fully integrated FM demodualator circuits for satellite TV receivers

Two kinds of integrated circuit are described for use in FM demodulators of satellite TV receivers. The ICs, an automatic gain control amplifier (AGC AMP) and a phase-locked demodulator, include a signal level amplifier, a driver for the first AGC circuit, an automatic frequency tuning amplifier, and a voltage regulator. The ICs were fabricated using an advanced nitride self-aligned process with 2-μm design rules. The threshold level, the differential gain, and differential phase of the FM demodulator using those ICs are 6 db, 1%, and 1°, respectively.