Mechanical and thermo-physical properties of rapidly solidified Al-50Si-Cu(Mg) alloys for thermal management application

Al-high Si alloys were designed by the addition of Cu or Mg alloying elements to improve the mechanical properties. It is found that the addition of 1 wt.% Cu or 1 wt.% Mg as strengthening elements significantly improves the tensile strength by 27.2% and 24.5%, respectively. This phenomenon is attributed to the formation of uniformly dispersed fine particles(Al2Cu and Mg2Si secondary phases) in the Al matrix during hot press sintering of the rapidly solidified(gas atomization) powder. The thermal conductivity of the Al-50 Si alloys is reduced with the addition of Cu or Mg, by only 7.3% and 6.8%, respectively. Therefore, the strength of the Al-50 Si alloys is enhanced while maintaining their excellent thermo-physical properties by adding 1% Cu(Mg).

NEW REGULATIONS ON IMPORT AND EXPORT MANAGEMENT RIGHTS GRANTED TO COMMERCIAL AND MATERIAL SUPPLY ENTERPRISES

With the approval of the State Council, State Economicand Trade Commission, Ministry of Foreign Trade and EconomicCooperation and Ministry of Internal Trade recently issued theCircular Regarding Some Relevant Issues in Granting Import andExport Management Rights to Commercial and Material SupplyEnterprises. It means that work ofgranting import and exportmanagement rights has from a trial been led onto the right path ofexamination and approval. The principle of examination and ap-proval, conditions, and the procedure of reporting to a higher in-stitution shall still be in conformity with the relevant regulationsprescribed in Decree No.76 (1993) of the State Council.In November 1993, the State Council approved and trans-mitted Opinions on Experiment of Granting Import and ExportManagement Rights to Some Commercial and Material Enterprisesby State Economic and Trade Commision, Ministry of ForeignTrade and Economic Cooperation and Ministry of Internal Trade.Totaling 206 commercial (including grain and supply and sale)and material supply enterprises are put to trial and granted

Self-Modifying Nanointerface Driving Ultrahigh Bidirectional Thermal Conductivity Boron Nitride-Based Composite Flexible Films

While boron nitride(BN) is widely recognized as the most promising thermally conductive filler for rapidly developing high-power electronic devices due to its excellent thermal conductivity and dielectric properties,a great challenge is the poor vertical thermal conductivity when embedded in composites owing to the poor interracial interaction causing severe phonon scattering.Here,we report a novel surface modification strategy called the "self-modified nanointerface" using BN nanocrystals(BNNCs) to efficiently link the interface between BN and the polymer matrix.Combining with ice-press assembly method,an only 25 wt% BNembedded composite film can not only possess an in-plane thermal conductivity of 20.3 W m-1K-1but also,more importantly,achieve a through-plane thermal conductivity as high as 21.3 W m-1K-1,which is more than twice the reported maximum due to the ideal phonon spectrum matching between BNNCs and BN fillers,the strong interaction between the self-modified fillers and polymer matrix,as well as ladder-structured BN skeleton.The excellent thermal conductivity has been verified by theoretical calculations and the heat dissipation of a CPU.This study provides an innovative design principle to tailor composite interfaces and opens up a new path to develop high-performance composites.

A FEASIBILITY STUDY OF IMPLEMENTING MATERIAL MANAGEMENT IN CONSTRUCTION: UNITED KINGDOM AND HONG KONG EMPIRICAL STUDIES

Construction organizations have a common practice to purchase and to deliver required materials to construction sitesabout one month before activities start. This leads to uneconomical inventory on site and contractors’ warehouses. Thispaper investigates the feasibility in implementing material management in construction. United Kingdom and HongKong are selected for the investigation as one has a long implementation period and another one is just implementingmaterial management as noted by interviewed contractors. Questionnaires and structured interviews are conducted.It is found that United Kingdom construction industry benefi ts are more signifi cant than that in Hong Kong. Thiscan stimulate interests in implementing material management in Hong Kong. Respondents from Hong Kong claimedthat their companies will be willing to implement material management where practicable. This study can also helpcountries currently implementing material management. From that, waste generation can be reduced and a greenconstruction environment can be achieved. Recommendations to improve the implementation are also discussed.

Research on the Logistics Model of Agricultural Material

The paper states something about the characteristic of agricultural material, product and agricultural material market, and searches for the new agricultural material logistics model. In .addition, some proper strategies are provided for logistic companies.

Designing a performance measurement system to support materials management in engineer-to-order:a case study

There are many different production situations that can be employed to meet demand. In the engineer-to- order （ETO） production situation, products are manufac- tured to meet specific customer needs by unique engineering or significant customization. In such an environment, failing to supply the required materials in the right quantities and at the right time increases the risk of breaching due date agreements and thereby losing customer satisfaction. As such, materials management is one of the most important and critical processes within production planning and control in ETO. To bring attention and improvement to this area, ETO companies may benefit from a performance measurement system （PMS） that systematically monitors how well mate- rials management is carried out. The design of a company＇s PMS varies with its production situation. Within the large body of literature on performance management and mea- surement, limited literature specifically addressing perfor- mance measurement in ETO has been identified. After being approached by a Norwegian ETO company requesting a PMS for materials management, the authors therefore set out to design the PMS from scratch, using literature on ETO, materials management and performance management and measurement as a starting point. The paper presents the proposed PMS. It provides a basis for further studies on the topic, and could be used by managers in ETO companies to assess and improve their materials management practice.

A Quantitative Description of Complex Adaptive System:The Self-Adaptive Mechanism of the Material Purchasing Management System Towards the Changing Environment

This paper demonstrates a new interpretation of the material purchasing management system(MPMS) from the perspective of complex adaptive systems(CAS).Within the framework of CAS,the authors design the self-adaptive mechanism of the MPMS responding to the changing environment,such as the change of the price,by using risk measurement theory,modern portfolio theory(MPT) and the information of the material's modifying priority.As a bottom-up systems view,CAS focuses on the individual level and studies system's overall complexity by analyzing the mutual competition and adaptation among the individuals.This paper demonstrates a quantitative description of CAS by discussing the MPMS which can be viewed as a kind of CAS,and makes numerical simulations of Daqing oilfield MPMS.Compared to the benchmarks,the authors set the simulations show that the self-adaptive mechanism adapts well to the change of the material's market price.Hence,this paper accomplishes a numerical simulation of CAS's quantitative self-adaptive mechanism responding to the environment's change.

Enhancing the thermal conductivity of nanofibrillated cellulose films with 1D BN belts formed by in-situ generation and sintering of BN nanosheets

The rapid miniaturization and high integration of modern electronic devices have brought an increasing demand for polymer-based thermal management materials with higher thermal conductivity.Boron nitride nanosheets(BNNs)have been widely used as thermally conductive fillers benefiting from the extremely high intrinsic thermal conductivity.However,the small lateral size and weak interface bonding of BNNs enabled them to only form thermally conductive networks through physical overlap,resulting in high interfacial thermal resistance.To address this issue,an innovative strategy based on interface engineering was proposed in this study.High-aspect-ratio boron nitride belts(BNbs)were successfully synthesized by carbon thermal reduction nitridation method through the in-situ generation and sintering of BNNs.The surface of BNb showed the sintering of numerous smaller-sized BNNs,which precisely addresses the issue of weak interfacial bonding between BNNs.On this basis,the as-synthesized BNbs were combined with nano-fibrillated cellulose(NFC)to prepare NFC/BNb composite films through a facile vacuum filtration process.Due to the thermally conductive network formed by the horizontal oriented arrangement of BNb and their particular morphological advantages,the NFC/BNb films demonstrated significantly higher in-plane thermal conductivity than that of NFC/BNNs films,achieving the highest value of 19.119 W·m^(−1)·K^(−1) at a 20 wt%filling fraction.In addition,the NFC/BNb films also exhibited superior thermal stability,mechanical strength,flexibility,and electrical insulation performance,suggesting the significant application potential of the designed BNb fillers in the thermal management field.

A Spiral Graphene Framework Containing Highly Ordered Graphene Microtubes for Polymer Composites with Superior Through-Plane Thermal Conductivity

As the power density of electronic devices increases,there has been an urgent demand to develop highly conductive polymer composites to address the accompanying thermal management issues.Due to the ultra-high intrinsic thermal conductivity,graphene is considered a very promising filler to improve the thermal conductivity of polymers.However,graphene-based polymer composites prepared by the conventional mixing method generally have limited thermal conductivity,even under high graphene loading,due to the failure to construct efficient heat transfer pathways in the polymer matrix.Here,a spiral graphene framework(SGF)containing continuous and highly ordered graphene microtubes was developed based on a modified CVD method.After embedding into the epoxy(EP)matrix,the graphene microtubes can act as efficient heat pathways,endowing the SGF/EP composites with a high through-plane thermal conductivity of 1.35 W·m^(-1)·K^(-1) at an ultralow graphene loading of 0.86 wt%.This result gives a thermal conductivity enhancement per 1 wt%filler loading of 710%,significantly outperforming various graphene structures as fillers.In addition,we demonstrated the practical application of the SGF/EP composite as a thermal interface material for efficient thermal man-agement of the light-emitting diode(LED).