For the southern area of the Shahe Zhongguan Iron Mine of Hebei Iron and Steel Group in the study, a stability calculation model for the drifting chamber pillars was constructed based on Platts theory of ground pressure and the Kastner Formula. The influence of various factors on the roof stability of the drifting chamber during sublevel open stoping with backfill was discussed, and the roof stability in two options: no pillars retained in the drifting chamber (Option 1) and pillars initially retained and subsequently caved along with the orebody (Option 2) were analyzed by numerical simulations. The results show that when the stope length ranges from 27 m to 45 m, the drifting chamber roof in Option 2 faces a higher risk of instability. With a stope length over 45 m, the roofs in both options are at risk of instability. Option 2 leads to stress concentration within the drifting chamber, with accelerated stress release observed in the roof and side walls. In contrast, Option 1 demonstrates more stable stress release and distribution in the drifting chamber, with a relatively delayed failure time. When the ore rock exhibits poor stability, Option 1 is more conducive to maintaining roof stability.

As for the current situation of component segregation and significant brittleness tendency in laser cladded coating of austenitic stainless steel, an austenitic cladded coating was prepared by adopting laser cladding technology, and then effects of preheating and annealing treatment on the microstructure, mechanical properties and service performance (corrosion and corrosive wear) of the cladded coating and heat-affected zone (HAZ) were investigated. The results show that the phase composition of the austenitic coating after preheating or annealing process remains predominantly austenitic, exhibiting only grain growth and a preferential orientation shift towards the (111) crystal plane. Both the cladded coating and HAZ have decreased hardness, but significant improvement in the tensile strength and elongation. This is because that the heat treatment not only reduces the intergranular fracture tendency of the cladded coating but also improves the ductile fracture tendency of the HAZ. Furthermore, preheating or annealing process can enhance the corrosion resistance and wear resistance of the austenitic cladded coating, among which annealing process can bring a significant effect. These improvements are attributed to the synergistic effect of reduced component segregation and enhanced plasticity and toughness in both cladded coating and HAZ.

To address the issues of low purity and high consumption of alkali and acid during chemical purification of graphite, Luobei spherical graphite was taken to explore the occurrence state of impurities therein and to perform tests on its purification by alkali-acid method. A novel alkali-acid method was developed, which consists of stirring with alkali under negative-positive pressure and pressure acid leaching. This purification process is conducted in the following steps with the optimized conditions: firstly leave graphite in a vacuum for 35 min with vacuum degree of -0.15 MPa, and then stir for 40 min under pressure of 0.19 MPa at 120 ℃ by adding NaOH at a concentration of 40%, with NaOH solution and spherical graphite in a liquid-to-solid ratio of 1.0 mL/g；after 120 min roasting at 550 ℃, acid leaching with HCl at a concentration of 2.5 mol/L is performed under pressure of 0.16 MPa at 118 ℃ for 90 min, with HCl solution and graphite in a liquid-to-solid ratio of 1.0 mL/g. As a result, the fixed carbon content in the purified graphite is up from 95.35% to 99.96%.

A stockpile of hazardous waste aluminum ash generated during aluminum smelting has posed serious environmental pollution risks. In order to solve this, a novel approach is proposed, in which the nitrogen-enriched aluminum ash is used in the steelmaking process to promote microalloying with vanadium and nitrogen. Aluminum ash is heated and stir-fried in a nitrogen atmosphere, resulting in its reaction with nitrogen gas, thereby increasing the nitrogen level therein. The effects of reaction temperature, aluminum content and particle size on the nitrogen enrichment of aluminum ash were investigated, and the nitrogen-enriched aluminum ash was characterized by XRD and SEM-EDS. The results show that under the suitable conditions for nitrogen enrichment, including reaction temperature of 880 ℃, initial aluminum content of 45% (aluminum powder), and nitrogen flow rate at 4 L/min, the nitrogen content in the aluminum ash can be improved from 1.18% to 11.90%. During this process, metallic aluminum in the ash reacts with nitrogen gas to form AlN on the surface of alumina particles.

To address the issue of volumetric locking encountered in the slope stability analysis with three-node triangular elements in upper bound finite element method (UBFEM), a six-directional triangular mesh (P6) with weak velocity discontinuity line characteristics was proposed based on the mechanical equivalence effect between velocity discontinuity lines and conjugate triangular elements located in the same position. The P6 is utilized in conjunction with a six-node triangular (T6) element in UBFEM for slope stability analysis. The results show that the potential slip surface of the slope obtained using the P6 combined with T6 elements is clearly defined, with a smooth transition in dissipated energy density. As the mesh density increases, the effect of weak velocity discontinuity lines strengthens, leading to an improved accuracy in the upper bound solution of the slope stability coefficient (N_s). With the combined influences of factors such as the internal friction angle and slope gradient into consideration, the upper bound solutions of N_s obtained with P6 outperform those from three-directional triangular meshes and Delaunay triangular meshes. The uniform mesh generated by the P6 UBFEM in a single computational framework yields favorable results, facilitating batch processing operations such as strength reduction upper bound analysis. Additionally, its application scope can be extended by integrating it with adaptive mesh refinement techniques.

The fundamental principles of stereolithography (SLA), digital light processing (DLP), and two-photon polymerization (TPP) in photo-curing technique for ceramic were reviewed. Based on systematical introduction and analysis of the research status, application fields of SLA, DLP, and TPP technologies, as well as the existing challenges, a comprehensive review was provided of ceramic slurries and their performance optimization, photo-curing mechanisms, and subsequent debinding and sintering processes. Finally, prospects for obtaining ceramic slurries with high performance, finished products with superior mechanical properties and translating research outcomes into practical applications were discussed. Furthermore, several recommendations were proposed, including increasing the types of ceramic slurries, accelerating the development of composite ceramic materials, and making more efforts in research of large-size ceramic components.

Based on experimental studies on separation and quality improvement for a boron-bearing iron ore, a scheme for boron extraction and sulfur reduction was proposed, and a metallurgical process combined with mineral processing was determined, which consists of activation roasting, grinding, alkali leaching and magnetic separation. After activation roasting at 650 ℃ for 90 min in a neutral atmosphere, the obtained roasted ore was ground to a fineness of -0.075 mm 83.28%, and then leached for 60 min at 100 ℃, with liquid-to-solid ratio of 3∶1, leaching reagent of NaOH at a concentration of 15%, and stirring speed of 180 r/min. A boron-bearing mother liquor was obtained, with leaching rate of B₂O₃ at 94.62%. The leaching residue was subjected to conventional magnetic separation, resulting in an iron concentrate grading 54.94% TFe, containing 0.24% B₂O₃ and 0.077% S. It is concluded that boron can be fully recovered and the quality of iron concentrate can be also improved by adopting this processing scheme.

The effects of common depressants, including calcium oxide and calcium polysulfide, on the surface zeta potential of marmatite were studied by using dry grinding, and the influence of active ions such as Cu²⁺, Pb²⁺ and Ag⁺ on the surface atomic composition and chemical state of marcasite was explored by using XPS. It is found that after depression by calcium oxide and calcium polysulfide, the marmatite has its surface zeta potential shifted to varying degrees. After the marmatite interacts with calcium oxide, its surface zeta potential shifts positively, with point of zero charge at pH of 6.43；after the marmatite interacts with calcium polysulfide, its surface zeta potential shifts negatively at low amplitude. Both calcium oxide and calcium polysulfide exhibit weak depression for marmatite. After activation by ions like Cu²⁺, Pb²⁺ and Ag⁺, the marmatite has sulfur atoms and metallic atoms on the surface at a ratio of 2.07, 1.34 and 1.07, respectively, all higher than the theoretical value (1.0) of sphalerite. Due to Cu²⁺ with its ionic radius similar to Zn²⁺ and Fe²⁺, facilitating strong ion substitution, marmatite presents a metal-deficient mineral phase on the surface, being bound to the surface S^2-；while Pb²⁺ and Ag⁺ have their ionic radius quite different from Zn²⁺ and Fe²⁺, which can alter the surface phase composition of marmatite by adsorption and precipitation, but bring less impact to the ratio of sulfur and metallic atoms. As a result, polysulfides and sulfates exist on the surface of marmatite.

Effects of roasting temperature and heating rate on the crystalline form evolution of calcium arsenate during heat treatment were investigated. The heat-treated calcium arsenate was leached by strong acids (sulfuric acid, nitric acid, hydrochloric acid, aqua regia), and the relationship between the crystalline form of calcium arsenate and arsenic concentration in leaching solution was investigated. The results show that calcium arsenate undergoes significant crystalline form transition during roasting process, and higher roasting temperature can result in higher degree of crystallization. The heat-treated calcium arsenate is leached with acids and it is shown that less arsenic is leached out as the roasting temperature rises. After calcium arsenate is subjected to roasting at 500 ℃, the concentration of arsenic in the leaching solution can meet GB 5085.3—2007. After calcium arsenate is subjected to a roasting process at 900 ℃ and above, the concentration of arsenic in the leaching solution satisfied GB 3838—2002.

A refractory ore characterized by ultra-fine gold particles disseminated therein was taken for flotation test. A technique of re-grinding and re-flotation of the middlings, together with the self-developed collector of ZHS-3, was adopted to enhance the collection of fine-grained gold, resulting in a gold concentrate grading 43.70 g/t Au at 74.29% recovery, and a secondary concentrate grading 15.60 g/t Au at 4.28% recovery. Two obtained products had a total gold grade of 39.79 g/t and recovery of 78.57%. It is shown that both gold grade and recovery are improved compared with conventional flotation processes. This processing technique can achieve efficient recovery of fine-grained gold, thus improving resource utilization.