High Pressure Temperature Research Articles

Experimental Investigation of Inclusion of Various Nanocarbon Black Concentrations on Mechanical Characteristics of Oil-Well Cement Slurries in High-Pressure High-Temperature Conditions

This study investigates the impact of adding nanocarbon black (NCB) to wellbore cement under high-pressure, high-temperature (HPHT) conditions to enhance its properties for long-term zonal isolation. Four cementitious slurries were prepared in the laboratory using the wet-mixing method, following the American Petroleum Institute standards (API 10B-2 and API 10A). NCB was incorporated as a reinforced nanomaterial in cementitious composites at varying concentrations of 0.05%, 0.1%, and 0.2% by weight of cement (BWOC) into the slurry mix fluid following a specific mixing sequence before the addition of Class-G wellbore Portland cement, which is manufactured via the dry process and commonly used in the oil and gas industry. The study evaluated parameters, such as density, rheology, free fluid (FF), fluid loss (FL), thickening time (TT), compressive strength (CS), tensile strength (TS), porosity, and permeability, following API standards. The results demonstrated that NCB additions slightly increased slurry density and significantly improved rheological properties, with low yield stress at bottomhole circulating temperatures. NCB concentrations of 0.05% and 0.1% reduced free fluid, fluid loss, and thickening time while enhancing the cement sheath's compressive and tensile strength, simultaneously reducing its porosity and permeability. Moreover, the improved early compressive strength development indicated accelerated cement hydration reactions due to incorporating NCB. The study found that 0.1% NCB was the optimal concentration, enhancing mechanical properties and operational efficiency by reducing wait-on-cement time and costs while improving wellbore integrity. However, higher NCB concentrations required careful dispersion to prevent nanoparticle agglomeration. Overall, NCB significantly enhanced cement sheath characteristics under HPHT conditions.

Nanofiltration-based purification process for whole-cell transformed prebiotic galactooligosaccharides.

The enrichment of galactooligosaccharides (GOS), synthesized by whole cells of Kluyveromyces marxianus 3551 in a 5.0-L bioreactor, was investigated in this study. The synthesized sugar mixture containing 17.89% (w/w of total carbohydrates) of GOS with 15.57% (w/w of total carbohydrates) of lactose, and 66.54% (w/w of total carbohydrates) monosaccharides as impurities, was subjected to nanofiltration for enrichment of GOS. Three distinct spiral wound membranes, namely, NFPS-01(polysulfone), NFCA-02 (cellulose acetate), and NFPES-03 (polyethersulfone) were tested out of which the NFPES-03 performed the best for fractionation of the GOS mixture. The polyethersulphone membrane (cut-off 400-1000Da) was evaluated at 30℃ and 50℃, at different transmembrane pressures or TMP (15, 20, 25bar) and a combination of high temperature (50℃) and low pressure (15bar) gave the greatest difference in the trisaccharide and disaccharide/monosaccharide rejection percentages, resulting in enrichment of GOS. An analysis of the sugar concentrations in the retentate samples by high-performance liquid chromatography indicated the percentage recovery of GOS in the integrated process to be 88.8%. Measurement of the growth profile of several microbes on the nano-filtered GOS demonstrated its effectiveness as a prebiotic source.

A Novel Optical Instrument for On-Line Measurement of Particle Size Distribution—Application to Clean Coal Technologies

A flow cell is a critical measurement interface for many optical instruments. However, the flows are often sampled under harsh conditions, such as under high pressure and/or high temperature, in the presence of particles, moisture, vapors with high dew points or corrosive gases. Therefore, obtaining a high-optical-quality flow cell that does not perturb the measurement is a significant challenge. To address this challenge, we proposed a new flow cell that employs a unique laminar coaxial flow field (for the purge and sample flows). A test system was built to conduct particle size distribution (PSD) measurements with no sampling bias using a state-of-the-art analyzer (Malvern Panalytical Insitec). The results revealed that the measurement zone is well defined solely by the sample flow, and the optical windows are well protected by the purge flow, with minimal risk of any depositions from the sample flow. Using this flow cell, the Insitec can successfully measure PSD under high pressure and temperature under moist, corrosive conditions without generating any sampling bias. Importantly, we successfully applied this flow cell for on-line PSD measurement for the flue gas of a 100 kWth pressurized oxy-coal combustor operating at 15 bara.

Forced degradation of AEEA under full CO2 loading, high temperature and high O2 partial pressure conditions: Degradation reaction pathway and degradation inhibitor studies

Forced degradation of AEEA under full CO2 loading, high temperature and high O2 partial pressure conditions: Degradation reaction pathway and degradation inhibitor studies

A novel model for the thermoelastic hydrodynamic lubrication characteristics of the slipper pair in radial piston pumps

Relying on heat conduction and thermoelastic mechanics theories and Takeuti's research, a novel TEHL (thermoelastic hydrodynamic lubrication) model considering thermal effect-induced thermoelastic deformation was developed. The impact of the radial piston pump's slipper pair's working and structural parameters on lubrication under heavy oscillating load was studied. The model was shown to be valid and superior in simulating oil film changes in TEHL, EHL (elastic hydrodynamic lubrication), and HL (hydrodynamic lubrication). It was first used to analyze how different conditions and parameters affect slipper pair lubrication. Thermoelastic deformation simulations were more accurate than previous elastic ones, making results more comprehensive. Friction experiments gave a coefficient of about 0.25 at 400–600 r/min and 0.23 at 600–1000 r/min, while the simulation result was 0.215. The HL model had a thin film, high temperature, and asymmetric pressure at x1 during suction, and increased thickness, decreased temperature, and uniform pressure at y1 during high pressure. In the HL model without deformations, the film was 12.9–14.0 μm thick and 345.7–354.0 K in temperature. In the EHL model with elastic deformation (0.6–2.6 μm), the thickness was 13.6–15.9 μm. In the TEHL model with thermoelastic deformation (0.5–2.1 μm), the thickness was 13.2–15.6 μm and the temperature was 344.4–354.0 K. Also, film thickness, speed, pressure, angle, radius, and ratio significantly affect slipper pair TEHL. This series of simulations proved the proposed model's feasibility for studying TEHL under heavy, variable loads and different structures. The model can optimize pump design parameters, boosting efficiency, and extending service life, and also enables fault prediction and prevention and maintenance strategy optimization, enhancing equipment reliability and production efficiency.

High pressure and high temperature synthesis of a new boron carbide phase

The dense boron carbide (B-C) phases with diamond structure are predicted to be superhard, with hardness close to that of a cubic boron nitride (c-BN). At ambient conditions, graphite-like BC3 is well characterized, firstly reported by Kouvetakis et al. In this work, we have synthesized a new B-C phase from the graphite-like BC3 in a laser-heated diamond anvil cell. Interestingly, this phase could be recoverable to ambient pressure due to dynamic stabilities. The Raman spectrum and X-ray diffraction patterns give the possible structure of this new phase.

Microwave synthesis of molybdenum disulfide quantum dots and the application in bilirubin sensing

Molybdenum disulfide quantum dots (MoS2QDs) is a new type of graphite like nanomaterial, which exhibited well chemical stability, unique fluorescence characteristics, and excellent biocompatibility. The conventional hydrothermal synthesis of MoS2generally requires a long-term reaction at high temperature and high pressure. Herein, we have developed a simple and fast MoS2QDs synthesis scheme using microwave heating, and further modified the surface of MoS2QDs using 3-aminophenylboronic acid. The 3- aminophenylboronic acid modified MoS2QDs (B-MoS2QDs) were further coated by a zinc-based metal-organic backbone (ZIF-8) in a solution containing zinc ions and 2-methylimidazolium. The constructed nanohybrid B-MoS2@ZIF-8 were successfully applied to the visualization and rapid detection of bilirubin based on the ratiometric fluorescence changes. The linear range for bilirubin detection is 0.2-75 μmol·l-1, and detection limit is 0.017 μmol·l-1.

The Influence of the Binder Phase on the Properties of High-Pressure Sintered Diamond Polycrystals or Composites for Cutting Tool Applications

A review of binder phases used for sintering diamond powders under high pressure and high temperature conditions along with an outline of the properties of polycrystalline diamonds or composite materials intended for cutting tools, wire drawing dies, and drilling rocks are presented. The interaction of diamond with metals from group VIII of the periodic table, carbon-forming metals, carbides, MAX phases and with silicides, borides, and alkali carbonates is presented. The interaction of the bonding phases with diamond was determined. The influences of sintering process parameters, amounts, and methods of introducing of these phases on the basic mechanical properties and thermal resistance of diamond materials are analyzed. The investigated material properties are compared with the properties of commercial PCD with a cobalt and the SiC binder phase.

Microwave-Assisted Synthesis of Carbon Nanospheres and Their Application as Plugging Agents for Oil-Based Drilling Fluids

Wellbore instability caused by the invasion of drilling fluids into formations remains a significant challenge in the application of oil-based drilling fluids (ODFs). In this study, carbon nanospheres (CNSs) were synthesized using glucose as the carbon source through a microwave-assisted method. The effects of the reaction temperature, carbon source concentration, and reaction time on the particle size of CNSs were systematically investigated. The results revealed that under optimal conditions, CNSs with an average particle size of 670 nm were successfully synthesized, exhibiting high sphericity and excellent dispersibility. CNSs demonstrated stable dispersion in mineral oil when lecithin was used as a dispersant. The plugging performance of CNSs in ODFs was evaluated through low-pressure filtration and high-temperature, high-pressure (HTHP) filtration tests. After aging at 180 °C for 16 h, the addition of 2% CNSs reduced the filtration volume from 10.6 mL to 2.5 mL on standard filter paper (average pore size: 3 μm) and from 8.5 mL to 1.6 mL on microporous membranes (average pore size: 0.5 μm). Additionally, the HTHP filtration volume decreased from 73 mL to 18 mL, and the permeability of the filter cake formed during HTHP filtration was reduced from 26.5 × 10−3 mD to 1.2 × 10−3 mD. Furthermore, CNSs improved the rheological properties and emulsion stability of ODFs. With excellent compatibility and applicability, CNSs offer a promising solution for enhancing the performance of oil-based drilling fluids.

From Powders to Performance-A Comprehensive Study of Two Advanced Cutting Tool Materials Sintered with Pressure Assisted Methods.

This paper presents a comprehensive study of two tool materials designed for the machining of Inconel 718 superalloy, produced through two distinct sintering techniques: High Pressure-High Temperature (HPHT) sintering and Spark Plasma Sintering (SPS). The first composite (marked as BNT), composed of 65 vol% cubic boron nitride (cBN), was sintered from the cBN-TiN-Ti3SiC2 system using the HPHT technique at a pressure of 7.7 GPa. The second composite (marked as AZW) was fabricated from the Al2O3-ZrO2-WC system using SPS at a pressure of 63 MPa. The final phase composition of BNT material differed significantly from the initial composition due to reactions occurred during sintering. In contrast, the phase composition of the AZW ceramic composite before and after sintering was similar. The materials exhibited high quality, as evidenced by a Young's modulus of 580 GPa for BNT and 470 GPa for AZW, along with hardness of 26 GPa for BNT and 21 GPa for AZW. Both composites were used to prepare cutting inserts that were evaluated for their performance in machining Inconel 718 alloy. While both inserts showed durability comparable to their respective reference commercial inserts, they differed in performance and price relative to one another.

Ultrasonic backscattering model of lamellar duplex phase microstructures in polycrystalline materials.

Carbon steel and low alloy steel are pearlitic heat-resistant steels with a lamellar microstructure. There are good mechanical properties and are widely used in crucial components of high-temperature pressure. However, long-term service in high-temperature environments can easily lead to material degradation, including spheroidization, graphitization, and thermal aging. This study proposes a theoretical model of ultrasonic backscattering with a lamellar structure in pearlite areas. It analyzes the effects of different pearlite area ratios and interlamellar spacing on ultrasonic backscattering signals. A Voronoi diagram is used to constructs a two-dimensional finite element (FE) model of the lamellar structure, and the effects of different pearlite area ratio and interlamellar spacing on the backscattering signals are analyzed to verify the correctness of the theoretical model. By preparing spheroidization samples of various grades, the change values of pearlite area ratio and interlamellar spacing are measured. The backscattering signals of different spheroidization samples are collected through the ultrasonic testing experimental platform, and the root-mean-square (RMS) maximum values of the ultrasonic backscattering are extracted. The observed trend is consistent with the theoretical model, finite element method (FEM), and experimental. Compared with the experimental results, the model results have some errors, but can be used to evaluate the performance degradation of metallic materials with lamellar pearlite structure.

Temperature compensation study of pressure sensors after leadless packaging

Purpose The purpose of this paper is to reduce the problem of temperature drift causing output errors in such sensors, three hardware compensation schemes are proposed in this paper, and three compensation schemes are designed and implemented. Design/methodology/approach In response to the problem of temperature drift causing output errors in this type of sensor, this paper proposes three hardware compensation schemes and carries out the design and implementation of the three compensation schemes. Finally, the advantages and disadvantages of the three compensation schemes are discussed through the analysis of the experimental results. The three hardware compensation methods are series-parallel resistance network compensation, digital signal processor (DSP) compensation and the joint compensation of resistance network and DSP. Series parallel resistance network compensation is to connect the low-temperature drift resistance and the sensor in series and parallel; DSP compensation is based on the combination of cubic spline interpolation and linear fitting algorithm, which uses DSP to process the data. Joint compensation is a new compensation method composed of the above two compensation methods. Findings The experimental results show that the relative error of the output is reduced to a certain extent after the three compensation methods, and the relative error of the output after the joint compensation is reduced to about 0.2%, which proves that the three compensation methods are feasible. Originality/value This paper presents three novel hardware compensation methods to reduce temperature drift in silicon on insulator (SOI) high-temperature pressure sensors. The joint compensation method, combining resistance network and DSP compensation, is particularly innovative and significantly improves output accuracy, reducing relative error to about 0.2%.

Research on Application of diamond MOSFET in DCDC converter

This paper focuses on the industrial application of diamond power devices and DCDC converters, carries out the application research of diamond MOSFET in DCDC converters, analyzes the limitations of current silicon-based DCDC converters and how diamond MOSFET should make up for this limitation. This paper summarizes the research on the practical application of diamond power devices at home and abroad and points out that there is a gap in the application of diamond MOSFETs in DCDC converters. Diamond has the advantages of a large band gap, high carrier mobility, high temperature and high pressure resistance, so the application of diamond MOSFET in a DCDC converter can improve its operating frequency, input and output voltage and efficiency. This paper also discusses the difficulties encountered by diamond semiconductor materials and diamond power devices in the research and industrial fields, as well as the research status of diamond semiconductor materials at home and abroad, and gives the research method for the future application of diamond MOSFET in DCDC converters. The study can use the analogy of applying SiC or GaN to DCDC converters improving their performance, and redesigning the drive circuit to match the limiting performance of diamond power devices. By applying diamond MOSFET into the DCDC converter, its operating voltage, operating frequency, output power and efficiency will be greatly improved.

Numerical Simulation of Gas–Liquid–Solid Erosive Wear in Gas Storage Columns

Gas reservoirs play an increasingly important role in oil and gas consumption and safety in China. To study the problem of erosion and wear caused by gas-carrying particles in the process of gas extraction from gas storage reservoirs, a mathematical model of gas–liquid–solid three-phase erosion of gas storage reservoir columns was established through theories of multiphase flow and particle motion. Based on this model, the effects of the water volume fraction, gas extraction rate, particle mass flow rate, particle size, and bending angle on the erosion location and rate of the pipe columns were investigated. The findings indicate that when the water content volume fraction is low, the water production volume minimally affects the maximum erosion rate of pipe columns. Conversely, the gas extraction rate exerted the most significant influence on the column erosion, showing a power function relationship between the two. When gas extraction volume exceeds 60 × 104 m3/d, the maximum erosion rate surpasses the critical erosion rate of 0.076 mm/a. This coincided with the increased sand mass flow rate, although the maximum erosion rate of the pipe columns remained relatively steady. The salt mass flow rate demonstrated a linear relationship with the erosion rate, with the maximum erosion rate exceeding the critical erosion rate of 0.076 mm/a. The maximum erosion rate of the pipe columns increased, stabilized with larger sand and salt particle sizes, and exhibited an increasing trend with the bending angle. For gas extraction volumes exceeding 46.4 × 104 m3/d and salt mass flow rates exceeding 22 kg/d, the maximum erosion rate of pipe columns exceeds the critical erosion rate of 0.076 mm/a. The conclusions of this study are of some importance for the clarification of the influencing law of pipe column erosion under high temperature and high pressure in gas storage reservoirs and for the formulation of measures for the prevention and control of pipe column erosion in gas storage reservoirs.

Microwave synthesis of molybdenum disulfide quantum dots and the application in bilirubin sensing.

Molybdenum disulfide quantum dots (MoS2 QDs) is a new type of graphite like nanomaterial, which exhibited well chemical stability, unique fluorescence characteristics, and excellent biocompatibility. The conventional hydrothermal synthesis of MoS2 generally requires a long-term reaction at high temperature and high pressure. Herein, we have developed a simple and fast MoS2 QDs synthesis scheme using microwave heating, and further modified the surface of MoS2 QDs using 3-aminophenylboronic acid. The 3- aminophenylboronic acid modified MoS2 QDs (B-MoS2 QDs) were further coated by a zinc-based metal-organic backbone (ZIF-8) in a solution containing zinc ions and 2-methylimidazolium. The constructed nanohybrid B-MoS2@ZIF-8 were successfully applied to the visualization and rapid detection of bilirubin based on the ratiometric fluorescence changes. The linear range for bilirubin detection is 0.2-75 μmol•L-1, and detection limit is 0.017 μmol•L-1.

An investigation into the impact of diapir structures on formation pressure systems: a case study of the Yinggehai Basin, China

Under the influence of diapir structure, the formation pressure system is complicated. The characteristics of high temperature and high pressure are obvious, the prediction is difficult, and complex accidents such as well kick and leakage are frequent, which seriously restrict the efficient development of oil and gas resources. Therefore, taking Yinggehai Basin in China as an example, combined with the evolution characteristics of diapir structure, the influence of diapir structure on abnormal high-pressure, wellhole collapse and fracture is analyzed. Three pressure calculation methods are selected, and the distribution rules of pressures and safety density window are analyzed, too. The results show that the diapir structure and its associated fault not only constitute the fluid transport system, but also make the deep overpressure transfer upward and accumulate into high pressure in the shallow formation, and the development of the associated fault destroy the integrity of the formation rock and reduce the strength of the rock. The upwelling of hot fluid changes the local geothermal conditions, reduces the hydrocarbon generation threshold of shallow source rocks, promotes the evolution of clay minerals, causes hydrothermal expansion, and enhances the shallow high pressure. In high-temperature environment, the cooling effect of drilling fluid will produce heating stress, change the stress distribution around the wellhole, and increase the risk of wellbore instability. Additionally, under the influence of diapir structures, the pore pressure in deep formations increases, while the fracture pressure decreases, resulting in a significantly narrowed safe density window. The safety density window width generally presents a half-spindle shape, and with the increase of depth, the window width increases first and then decreases.

Numerical simulation of cementing seal integrity during electric heating of oil shale

Electric heating technology is a vital method for in-situ modification and exploitation of oil shale. This process subjects the wellbore and cement sheath to prolonged exposure to high temperature and pressure environments, posing significant challenges to the integrity of the cementing seal. To investigate the thermally induced changes during the electric heating process of cement sheath and oil shale, a combined model of cement sheath and oil shale was established using the discrete element method. The combined model was calibrated based on macroscopic mechanical experiments of cement sheath and oil shale. Subsequently, the thermal-mechanical coupling problem and thermal cracking phenomenon of the combined model under high temperature and high pressure environments were examined. The results revealed that thermal cracks begin to emerge at the onset of heating at around 150 °C, leading to a decrease in compressive strength and elastic modulus of the combined body. As the temperature reaches 400 °C to 500 °C, the number of thermal cracks peaks. The underground high-pressure environment impedes the thermal expansion of combined body particles, thereby inhibiting the development of thermally induced cracks. The addition of steel fibers to the cement sheath significantly reduces thermal cracking and effectively enhances the sealing performance of the cement sheath.

Structural and transport properties of (Mg,Fe)SiO3 at high temperature and high pressure

Abstract (Mg,Fe)SiO3 is primarily located in the mantle and has a substantial impact on geophysical and geochemical processes. Here, we employ molecular dynamics simulations to investigate the structural and transport properties of (Mg,Fe)SiO3 with varying iron contents at temperatures up to 5000 K and pressures up to 135 GPa. We thoroughly examine the effects of pressure, temperature, and iron content on the bond lengths, coordination numbers, viscosities, and electrical conductivities of (Mg,Fe)SiO3. Our calculations indicate that the increase of pressure leads to the shortening of the O-O and Mg-O bond lengths, while the Si-O bond lengths exhibit the initial increase with pressure up to 40 GPa, after which it is almost unchanged. The coordination numbers of Si transition from four-fold to six-fold and eventually reaching eight-fold coordination at 135 GPa. The enhanced pressure causes the decrease of the diffusion coefficients and the increases of viscosities of (Mg,Fe)SiO3. The increased temperatures slightly decrease coordination numbers and viscosities, as well as obviously increase diffusion coefficients and electrical conductivities of (Mg,Fe)SiO3. Additionally, iron doping facilitates the diffusion of Si and O, reduces viscosities, and enhances electrical conductivities of (Mg,Fe)SiO3. These findings advance fundamental understanding of the structural and transport properties of (Mg,Fe)SiO3 under high temperature and high pressure, which provide novel insights for unraveling the complexities of geological processes within the Earth's mantle.

Research on carbon dioxide treatment and utilization technology

This paper summarizes the various types of carbon dioxide treatment technology, the current situation, and the development trend, and describes the progress and challenges in the application of carbon dioxide treatment technology at the present stage. It is found that the focus of research and development should be on improving carbon capture efficiency and reducing carbon capture costs. CO2 utilization technology is currently in the industrial demonstration stage, and breaking through the bottleneck of high temperature and high pressure environment, and searching for suitable catalysts to improve the carbon utilization efficiency are the key research directions in the next stage of CO2 utilization technology. CO2 treatment technology needs to overcome the challenges of economic profitability, technological innovation, cost reduction and efficiency enhancement, and policy subsidies and incentives. CO2 bioprocessing technology will become a new mode of CO2 treatment promotion in the future. This study is of reference significance for accurately grasping the research direction of CO2 treatment technology, promoting the progress and innovation of CO2 treatment technology, and accelerating the leapfrog development of CO2 treatment technology.

Study on the growth of Li<sub>3</sub>N doped diamond single crystals under HPHT

In the paper, under 5.8 GPa and 1300℃, the Li<sub>3</sub>N doped diamond single crystals were synthesized in a cubic anvil high pressure and high temperature apparatus. Firstly, Fe<sub>59</sub>Ni<sub>25</sub>Co<sub>16</sub> alloy was used as the catalyst, high-purity Li<sub>3</sub>N powder was used as the additive, industrial high-purity graphite powder was used as the carbon source, and the (100) crystal orientation of industrial grade diamond single crystal with good crystalline quality was used as the growth direction of diamond single crystal, the effect of Li<sub>3</sub>N addition ratio on the growth of diamond single crystals was systematically investigated with a growth time of 20 hours. The research results indicate that with the increase of Li<sub>3</sub>N addition ratio, the color of diamond single crystals gradually transitions from yellow green, green, and dark green to dark green, and their morphology gradually transitions from hexahedron, hexahedron to octahedron. Moreover, the growth rate of single crystals decreases with the gradual increase of Li<sub>3</sub>N addition ratio, which can be attributed to the phenomenon of upward movement in the “V-shaped region” of diamond single crystal growth with the gradual increase of Li<sub>3</sub>N addition ratio in the P-T phase diagram of carbon. Secondly, using Fourier transform infrared (FTIR) spectroscopy, it was revealed that the nitrogen content of diamond single crystals increases with the increase of Li<sub>3</sub>N addition ratio, and increasing the diamond growth pressure can achieve the increase in the nitrogen content of diamond single crystals. Fig. 5 shows FTIR spectra of diamond crystals synthesized under different Li<sub>3</sub>N addition ratios. When the amount of Li<sub>3</sub>N added to the catalyst is 0.55 wt.%, the nitrogen content of the grown diamond single crystal is 892 ppm. Thirdly, Raman spectroscopy testing revealed that the Raman characteristic peak of diamond single crystals gradually shifts towards the low-energy end with the increase of Li<sub>3</sub>N addition ratio, which is related to the increase of internal stress in diamond single crystals. Finally, the PL spectroscopy test results showed that this study achieved high temperature and high pressure preparation of diamond single crystals with NV<sup>-</sup> color centers, and the zero phonon line intensity of NV<sup>-</sup> color centers in the single crystals significantly decreased with the increase of crystal nitrogen content. Fig. 7 shows PL spectra of diamond crystals synthesized under different Li<sub>3</sub>N addition ratios.